Volume 49,Issue 11,2020 Table of Contents
2020, 49(11):3653-3661.
DOI: 10.12442/j.issn.1002-185X.20200136
Abstract:
The hot deformation behavior of as-cast Ti-5553 (Ti-5Al-5Mo-5V-3Cr) alloy with coarse grain was investigated at the temperature range of 700 °C-1100 °C and strain rate range of 0.001 s-1-10 s-1 by Gleeble-3800 thermal physical simulator. The results show that the flow stress is sensitive to both temperature and strain rate, and the flow curves display various softening modes at different conditions. The activation energy map and constitutive relationship are constructed for the alloy, and the average deformation activation energy is calculated as 447.2 kJ/mol. The hot processing map is successfully established based on the dynamic materials model with the identification of underlying mechanisms at various processing regions. Two peak domains are identified in the hot processing map, which are: 800 °C-975 °C/0.001 s-1-0.01 s-1 and 1000 °C-1100 °C /0.01 s-1-0.1 s-1, and the flow instability region locates at the region with strain rate higher than 1 s-1. External cracking, adiabatic shear banding and/or flow localization are observed at low-temperature deformation and in the flow instability region, and these conditions should be avoided for actual processing. The mechanism at the peak efficiency domains are DRV or the combination of DRV and DRX, among which the region with the occurrence of extensive DRX is recommended as the optimal processing window for the alloy at high temperature about 1100 °C and medium-low strain rate about 0.01 s-1.
The hot deformation behavior of as-cast Ti-5553 (Ti-5Al-5Mo-5V-3Cr) alloy with coarse grain was investigated at the temperature range of 700 °C-1100 °C and strain rate range of 0.001 s-1-10 s-1 by Gleeble-3800 thermal physical simulator. The results show that the flow stress is sensitive to both temperature and strain rate, and the flow curves display various softening modes at different conditions. The activation energy map and constitutive relationship are constructed for the alloy, and the average deformation activation energy is calculated as 447.2 kJ/mol. The hot processing map is successfully established based on the dynamic materials model with the identification of underlying mechanisms at various processing regions. Two peak domains are identified in the hot processing map, which are: 800 °C-975 °C/0.001 s-1-0.01 s-1 and 1000 °C-1100 °C /0.01 s-1-0.1 s-1, and the flow instability region locates at the region with strain rate higher than 1 s-1. External cracking, adiabatic shear banding and/or flow localization are observed at low-temperature deformation and in the flow instability region, and these conditions should be avoided for actual processing. The mechanism at the peak efficiency domains are DRV or the combination of DRV and DRX, among which the region with the occurrence of extensive DRX is recommended as the optimal processing window for the alloy at high temperature about 1100 °C and medium-low strain rate about 0.01 s-1.
2 Influencing Factors of Micro Deformation Behavior of Constituent Phases in Ti-6Al-4V Titanium Alloy
2020, 49(11):3662-3668.
DOI: 10.12442/j.issn.1002-185X.20190848
Abstract:
In this paper, A micro-mechanics finite element model is established based on the realistic microstructure of Ti-6Al-4V alloy. And considering the dual-phase characteristic, the micro deformation behaviors during the uniaxial tension at ambient temperature are studied. The results show that the hard transformed β matrix (βt) in Ti-6Al-4V alloy bears most external loading force, while the external load deformation is mainly carried out by the soft primary α phase (αp). The strain and stress distribution in different regions within the same phase are also strongly asymmetrical. With the increase of the macro-strain, the strain ratio of αp to βt and the stress ratio of βt to αp are basically unchanged at first, then increase rapidly, and finally maintain stability. The volume fraction and grain size of αp have a significant effect on the strain and stress distribution in the constituent phases. With the increases of volume fraction or the decreases of grain size, the strain ratio and the stress ratio increases and decreases, respectively.
In this paper, A micro-mechanics finite element model is established based on the realistic microstructure of Ti-6Al-4V alloy. And considering the dual-phase characteristic, the micro deformation behaviors during the uniaxial tension at ambient temperature are studied. The results show that the hard transformed β matrix (βt) in Ti-6Al-4V alloy bears most external loading force, while the external load deformation is mainly carried out by the soft primary α phase (αp). The strain and stress distribution in different regions within the same phase are also strongly asymmetrical. With the increase of the macro-strain, the strain ratio of αp to βt and the stress ratio of βt to αp are basically unchanged at first, then increase rapidly, and finally maintain stability. The volume fraction and grain size of αp have a significant effect on the strain and stress distribution in the constituent phases. With the increases of volume fraction or the decreases of grain size, the strain ratio and the stress ratio increases and decreases, respectively.
wangcuiping
,
wudan
,
lilingling
,
zhangjinbin
,
yangshuiyuan
,
yangmujin
,
hanjiajia
,
luyong
,
liuxingjun
2020, 49(11):3669-3675.
DOI: 10.12442/j.issn.1002-185X.20190632
Abstract:
In this study, the isothermal sections of the Mo-Ru-Ti ternary system at 1100 and 1300 °C have been established using electron probe microanalysis and X-ray diffraction techniques. The results indicated that: (1) There were three three-phase regions at 1100 °C isothermal section and two three-phase regions at 1300 °C isothermal section; (2) the σ-Mo5Ru3 phase was stabilized to 1100 °C and formed a small single-phase region with the addition of Ti. (3) the (βTi, Mo) phase extended from Mo-rich side to Ti-rich side and dissolved a lot of Ru at 1100 and 1300 °C. The phase relationship of Mo-Ru-Ti system will provide the basic experimental data for the thermodynamic database of titanium alloys.
In this study, the isothermal sections of the Mo-Ru-Ti ternary system at 1100 and 1300 °C have been established using electron probe microanalysis and X-ray diffraction techniques. The results indicated that: (1) There were three three-phase regions at 1100 °C isothermal section and two three-phase regions at 1300 °C isothermal section; (2) the σ-Mo5Ru3 phase was stabilized to 1100 °C and formed a small single-phase region with the addition of Ti. (3) the (βTi, Mo) phase extended from Mo-rich side to Ti-rich side and dissolved a lot of Ru at 1100 and 1300 °C. The phase relationship of Mo-Ru-Ti system will provide the basic experimental data for the thermodynamic database of titanium alloys.
2020, 49(11):3676-3682.
DOI: 10.12442/j.issn.1002-185X.20200276
Abstract:
The effect of TiO2 on viscosity of low-fluoride CaF2-CaO-Al2O3-MgO-Li2O slag for electroslag remelting was investigated under the continuous cooling conditions and the FTIR and the Raman spectroscopy were employed to analyze the correction between the quenched slags and the corresponding structure in the study. It can be found that the slag viscosity lowers as gradually increasing TiO2 content, and when TiO2 content up to 13.1%, the corresponding viscosity values slowly decrease from 0.067 Pa?s, 0.059 Pa?s, 0.056 Pa?s to 0.054 Pa?s with the temperature increases from 1743 K, 1793 K, 1843 K to 1893 K and at higher temperature of 1843 K and above, TiO2 addition has only a relatively small effect on lowering the slag viscosity. The calculated activation energy of viscous flow decreases from 58.0 kJ/mol, 47.7 kJ/mol, 42.8 kJ/mol to 38.6 kJ/mol as increasing TiO2 content from 0, 4.3%, 8.7% to 13.1%. Additionally, the FTIR results reveal that with the addition of TiO2, [AlOnF4-n]-tetrahedral complexes and [AlO4]-tetrahedra network structures depolymerized, but [AlO6]-octahedra is not found in the slag. Simultaneously, it can be seen by Raman analysis that with the addition of TiO2, leading to the depolymerization of the Al-O-Al linkage in the [AlO4]-tetrahedra network structures, the transformation of part Q4 units to Q2 units, and the forms of O-Ti-O and Ti-O-Ti chains. These results suggest that polymerization degree of these slags decreases as increasing TiO2 content, which is beneficial to simplify slag structure. Finally, the changed slag structure is in good agreement with the slag corresponding to the varying viscosity.
The effect of TiO2 on viscosity of low-fluoride CaF2-CaO-Al2O3-MgO-Li2O slag for electroslag remelting was investigated under the continuous cooling conditions and the FTIR and the Raman spectroscopy were employed to analyze the correction between the quenched slags and the corresponding structure in the study. It can be found that the slag viscosity lowers as gradually increasing TiO2 content, and when TiO2 content up to 13.1%, the corresponding viscosity values slowly decrease from 0.067 Pa?s, 0.059 Pa?s, 0.056 Pa?s to 0.054 Pa?s with the temperature increases from 1743 K, 1793 K, 1843 K to 1893 K and at higher temperature of 1843 K and above, TiO2 addition has only a relatively small effect on lowering the slag viscosity. The calculated activation energy of viscous flow decreases from 58.0 kJ/mol, 47.7 kJ/mol, 42.8 kJ/mol to 38.6 kJ/mol as increasing TiO2 content from 0, 4.3%, 8.7% to 13.1%. Additionally, the FTIR results reveal that with the addition of TiO2, [AlOnF4-n]-tetrahedral complexes and [AlO4]-tetrahedra network structures depolymerized, but [AlO6]-octahedra is not found in the slag. Simultaneously, it can be seen by Raman analysis that with the addition of TiO2, leading to the depolymerization of the Al-O-Al linkage in the [AlO4]-tetrahedra network structures, the transformation of part Q4 units to Q2 units, and the forms of O-Ti-O and Ti-O-Ti chains. These results suggest that polymerization degree of these slags decreases as increasing TiO2 content, which is beneficial to simplify slag structure. Finally, the changed slag structure is in good agreement with the slag corresponding to the varying viscosity.
Hongbin Zhang
,
Chengcai Zhang
,
Baokun Han
,
Kuidong Gao
,
Huiping Li
,
Shengxue Qin
,
Jie Liu
,
Yan Wang
,
Peng Zhang
,
Haiping Zhou
2020, 49(11):3683-3691.
DOI: 10.12442/j.issn.1002-185X.E20200007
Abstract:
The influence of thermal-mechanical processing (TMP) parameters on the grain boundary character distribution evolution in a cold-rolled Ni-based superalloy was studied. During annealing treatment, growth accident model was considered to be the main mechanism for the formation of new Σ3 boundaries in the SRX grains. With the increasing annealing time and temperature, there was more time for grain boundary migration and the grain boundary migration was faster at the higher annealing temperature, which could stimulate the formation of Σ3 boundaries by increasing the frequency of growth accidents. In addition, the fraction of Σ3 boundaries decreased firstly with the increasing strain, and then increased again. At the strains of 0.1 and 0.7, the fractions of Σ3 boundaries reached around 60%, which was related to the well development of large grain-clusters. Besides that, the evolution of Σ1 boundaries, coherent Σ3 boundaries, incoherent Σ3 boundaries, Σ9 boundaries, Σ27 boundaries, and random boundaries were also analyzed in detail.
The influence of thermal-mechanical processing (TMP) parameters on the grain boundary character distribution evolution in a cold-rolled Ni-based superalloy was studied. During annealing treatment, growth accident model was considered to be the main mechanism for the formation of new Σ3 boundaries in the SRX grains. With the increasing annealing time and temperature, there was more time for grain boundary migration and the grain boundary migration was faster at the higher annealing temperature, which could stimulate the formation of Σ3 boundaries by increasing the frequency of growth accidents. In addition, the fraction of Σ3 boundaries decreased firstly with the increasing strain, and then increased again. At the strains of 0.1 and 0.7, the fractions of Σ3 boundaries reached around 60%, which was related to the well development of large grain-clusters. Besides that, the evolution of Σ1 boundaries, coherent Σ3 boundaries, incoherent Σ3 boundaries, Σ9 boundaries, Σ27 boundaries, and random boundaries were also analyzed in detail.
Zhen Xu
,
Wei Zhang
,
Hongbin Wang
,
Xinyu Zhang
,
Hua Song
,
Shengli Li
,
Can Wu
,
Yingyu Huo
,
Long Zhao
2020, 49(11):3692-3701.
DOI: 10.12442/j.issn.1002-185X.20191011
Abstract:
The effect of different warm rolling temperature and cumulative reduction on microstructure and mechanical properties of a 6061 aluminum alloy sheet rolled by twin roll casting was studied. Multi-scale characterization techniques were employed to study the microstructures of cast-rolled and warm-rolled sheets. The mechanical properties such as hardness, strength and elongation were also measured. The results show that the cast-rolled 6061 alloy mainly contains heat-resistant phase e.g. Al0.7Fe3Si0.3, and Al9Fe0.84Mn2.16Si, and a small amount of strengthening phase Mg2Si.With increasing rolling passes, the shape of second phases gradually changes from mesh and sheet shape to line shape along the rolling direction, and finally to fine granular shape. After warm rolling, the amount of a new precipitate Al0.5Fe3Si0.5 and Mg2Si increases. Additionally, the hardness linearly increases with increasing reduction, and the maximum slope (2.42114) of hardness curves is found at the warm rolling temperature of 370℃. At this temperature, fine AlFeSi precipitates and Mg2Si phases are uniformly dispersed in the alloy. The highest hardness of 84.28HV is obtained for plate. The tensile strength, yield strength and elongation are 29.34MPa, 79.09MPa and 20.11% respectively.
The effect of different warm rolling temperature and cumulative reduction on microstructure and mechanical properties of a 6061 aluminum alloy sheet rolled by twin roll casting was studied. Multi-scale characterization techniques were employed to study the microstructures of cast-rolled and warm-rolled sheets. The mechanical properties such as hardness, strength and elongation were also measured. The results show that the cast-rolled 6061 alloy mainly contains heat-resistant phase e.g. Al0.7Fe3Si0.3, and Al9Fe0.84Mn2.16Si, and a small amount of strengthening phase Mg2Si.With increasing rolling passes, the shape of second phases gradually changes from mesh and sheet shape to line shape along the rolling direction, and finally to fine granular shape. After warm rolling, the amount of a new precipitate Al0.5Fe3Si0.5 and Mg2Si increases. Additionally, the hardness linearly increases with increasing reduction, and the maximum slope (2.42114) of hardness curves is found at the warm rolling temperature of 370℃. At this temperature, fine AlFeSi precipitates and Mg2Si phases are uniformly dispersed in the alloy. The highest hardness of 84.28HV is obtained for plate. The tensile strength, yield strength and elongation are 29.34MPa, 79.09MPa and 20.11% respectively.
2020, 49(11):3702-3708.
DOI: 10.12442/j.issn.1002-185X.20191065
Abstract:
In this study, tungsten particle (Wp) reinforced 6061Al matrix composites with different volume fractions (1～7%) were fabricated by spark plasma sintering (SPS) followed by hot-rolling. The effects of Wp content on the microstructure, mechanical properties and electrical resistivity of the as-rolled composites were investigated. The results show that the W particles were homogeneously distributed in the metal matrix, achieving excellent metallurgical bonding. At the interface of Wp/6061Al, element solid solution and WAl12 intermetallics were formed during the fabrication process. The mechanical test results show that, with the increase of W volume fraction, relative density and ductility of the as-rolled composites decreased while the tensile strength first increased and then decreased. It is noteworthy that both high tensile strength and ductility were obtained by the composites with 1 and 3 vol.% Wp, being 192.85 MPa ,16.84% and 315.18 MPa ,11.93%, respectively. Besides, the fabricated Wp reinforced 6061Al matrix composites had excellent electrical conductivity and the increase of Wp content had a little influence on the electrical conductivity.
In this study, tungsten particle (Wp) reinforced 6061Al matrix composites with different volume fractions (1～7%) were fabricated by spark plasma sintering (SPS) followed by hot-rolling. The effects of Wp content on the microstructure, mechanical properties and electrical resistivity of the as-rolled composites were investigated. The results show that the W particles were homogeneously distributed in the metal matrix, achieving excellent metallurgical bonding. At the interface of Wp/6061Al, element solid solution and WAl12 intermetallics were formed during the fabrication process. The mechanical test results show that, with the increase of W volume fraction, relative density and ductility of the as-rolled composites decreased while the tensile strength first increased and then decreased. It is noteworthy that both high tensile strength and ductility were obtained by the composites with 1 and 3 vol.% Wp, being 192.85 MPa ,16.84% and 315.18 MPa ,11.93%, respectively. Besides, the fabricated Wp reinforced 6061Al matrix composites had excellent electrical conductivity and the increase of Wp content had a little influence on the electrical conductivity.
Zhao Xueting
,
Shang Shan
,
Zhang Tianxiang
,
Zhang Ruijie
,
Wang Xianfei
,
Li Zhongquan
,
Han Zhiqiang
2020, 49(11):3709-3717.
DOI: 10.12442/j.issn.1002-185X.20190858
Abstract:
A phase-field model of ternary Mg-Gd-Y magnesium alloy was developed by coupling with the thermodynamics of Mg-Gd-Y system and considering cooling rate for the first time. It was applied to simulate the solidification microstructure and concentration distribution of GW103 (Mg-1.69mol%Gd-1.32mol%Y) alloy at different cooling rates both in one-grain and multigrain simulation cases. Then GW103 alloys were prepared via gravity casting method and characterized to verify the model. Results give new understanding that the GW103 alloy exhibits thick sixfold primary dendrite, a few protuberance-like secondary arms and even no higher-order arms, instead of developed dendrite. The ascending cooling rate results in refinement of microstructure of GW103, which exhibits smaller grain size, slimmer primary dendrite and less secondary arms in multigrain simulation case. Besides, higher cooling rate aggravates the solute enrichment and inhomogeneous distribution of Gd and Y in interdendritic area. The simulation and the experimental results are matched well.
A phase-field model of ternary Mg-Gd-Y magnesium alloy was developed by coupling with the thermodynamics of Mg-Gd-Y system and considering cooling rate for the first time. It was applied to simulate the solidification microstructure and concentration distribution of GW103 (Mg-1.69mol%Gd-1.32mol%Y) alloy at different cooling rates both in one-grain and multigrain simulation cases. Then GW103 alloys were prepared via gravity casting method and characterized to verify the model. Results give new understanding that the GW103 alloy exhibits thick sixfold primary dendrite, a few protuberance-like secondary arms and even no higher-order arms, instead of developed dendrite. The ascending cooling rate results in refinement of microstructure of GW103, which exhibits smaller grain size, slimmer primary dendrite and less secondary arms in multigrain simulation case. Besides, higher cooling rate aggravates the solute enrichment and inhomogeneous distribution of Gd and Y in interdendritic area. The simulation and the experimental results are matched well.
Renguo Guan
,
Xiang Wang
,
Di Tie
,
Haobo Ren
,
Yuxiang Wang
,
Haifeng Liu
,
Lufei Yan
,
Minfang Chen
2020, 49(11):3718-3723.
DOI: 10.12442/j.issn.1002-185X.20190878
Abstract:
The evolution of microstructure and mechanical properties of the continuous rheo-rolled AZ91 magnesium alloy during heat treatment was revealed in the present study. Two kinds of Mg17Al12 phases precipitated from the supersaturated magnesium matrix were observed: most of which distributed discretely at grain boundary while the rest precipitated in alloy matrix in small size. With higher aging temperature, atom diffusion velocity increased and more precipitates formed. As a result, the hardness and the tensile strength peaked at 16h, whilst the elongation decreased with increasing time and temperature. The optimal comprehensive mechanical properties were obtained after solution treatment at 415 °C for 20 h and aging treatment at 220 °C for 16 h. The tailored hardness, tensile strength and elongation of the rheo-rolled alloy after heat treatment reached 99 HV, 251 MPa and 4.5%, respectively, which were significantly higher than that of the untreated alloy. Compared with traditional processing methods, rheo-rolling followed by heat treatment demonstrates its effectiveness on tailoring and obtaining balanced mechanical properties of AZ91 alloy.
The evolution of microstructure and mechanical properties of the continuous rheo-rolled AZ91 magnesium alloy during heat treatment was revealed in the present study. Two kinds of Mg17Al12 phases precipitated from the supersaturated magnesium matrix were observed: most of which distributed discretely at grain boundary while the rest precipitated in alloy matrix in small size. With higher aging temperature, atom diffusion velocity increased and more precipitates formed. As a result, the hardness and the tensile strength peaked at 16h, whilst the elongation decreased with increasing time and temperature. The optimal comprehensive mechanical properties were obtained after solution treatment at 415 °C for 20 h and aging treatment at 220 °C for 16 h. The tailored hardness, tensile strength and elongation of the rheo-rolled alloy after heat treatment reached 99 HV, 251 MPa and 4.5%, respectively, which were significantly higher than that of the untreated alloy. Compared with traditional processing methods, rheo-rolling followed by heat treatment demonstrates its effectiveness on tailoring and obtaining balanced mechanical properties of AZ91 alloy.
2020, 49(11):3724-3733.
DOI: 10.12442/j.issn.1002-185X.20190873
Abstract:
In this paper, numerical simulation technique and experimental study were used, and the effects of different process parameters on the properties of the products of unidirectional asynchronous rolling of magnesium alloy plate are analyzed. We also used ANSYS/LS-DYNA finite element software to complete the numerical simulation and carried out the experimental study of unidirectional asynchronous rolling under different rolling conditions. Besides, the internal structure was observed by metallographic microscope, and the yield, tensile and hardness properties of magnesium alloy plate were tested by tensile testing machine and micro vickers hardness tester.
In this paper, numerical simulation technique and experimental study were used, and the effects of different process parameters on the properties of the products of unidirectional asynchronous rolling of magnesium alloy plate are analyzed. We also used ANSYS/LS-DYNA finite element software to complete the numerical simulation and carried out the experimental study of unidirectional asynchronous rolling under different rolling conditions. Besides, the internal structure was observed by metallographic microscope, and the yield, tensile and hardness properties of magnesium alloy plate were tested by tensile testing machine and micro vickers hardness tester.
2020, 49(11):3734-3740.
DOI: 10.12442/j.issn.1002-185X.20190879
Abstract:
In this study, the effects of hydrogen concentration on hydrogen permeation and stress corrosion cracking behavior in 80SS low-alloy tubing steels in a saturated CO2 simulated produced water environment was explored by electrochemical hydrogen permeation, slow strain rate tension and stereo microscope, SEM methods. The results show that the acidity and the hydrogen permeation parameters i^∞, D and C_0^H were both increasing with the raise of the concentration of H+, which contributes to the diffusion behavior of hydrogen atoms. Since the synergistic effect of tensile stress and hydrogen atom, the fracture time of 80SS low alloy steel is reduced by nearly 50% compared with the tensile in air, and the change is occurred to ductile fracture to brittle fracture. As the hydrogen concentration of the solution increases, the mechanical damage of the steel and the stress corrosion sensitivity strengthen. Before and after pre-charged hydrogen the index Iδ changed from 3.16 to 8.49 when 80SS steel is stretched in a medium containing saturated CO2. Pre-charged hydrogen promoted the stress corrosion cracking sensitivity of the sample. When stretched in saturated CO2 produced water containing 1% HAc, the microscopic morphology before pre-charged hydrogen showed a river pattern with quasi-cleavage fracture characteristics. Discontinuous cracks and small pores are distributed with fiber area of 80SS steel of the pre-charged hydrogen. Compared with before pre-charged sample, pre-charged hydrogen improved the plastic properties of the steel and reduced the stress corrosion cracking sensitivity of the steel.
In this study, the effects of hydrogen concentration on hydrogen permeation and stress corrosion cracking behavior in 80SS low-alloy tubing steels in a saturated CO2 simulated produced water environment was explored by electrochemical hydrogen permeation, slow strain rate tension and stereo microscope, SEM methods. The results show that the acidity and the hydrogen permeation parameters i^∞, D and C_0^H were both increasing with the raise of the concentration of H+, which contributes to the diffusion behavior of hydrogen atoms. Since the synergistic effect of tensile stress and hydrogen atom, the fracture time of 80SS low alloy steel is reduced by nearly 50% compared with the tensile in air, and the change is occurred to ductile fracture to brittle fracture. As the hydrogen concentration of the solution increases, the mechanical damage of the steel and the stress corrosion sensitivity strengthen. Before and after pre-charged hydrogen the index Iδ changed from 3.16 to 8.49 when 80SS steel is stretched in a medium containing saturated CO2. Pre-charged hydrogen promoted the stress corrosion cracking sensitivity of the sample. When stretched in saturated CO2 produced water containing 1% HAc, the microscopic morphology before pre-charged hydrogen showed a river pattern with quasi-cleavage fracture characteristics. Discontinuous cracks and small pores are distributed with fiber area of 80SS steel of the pre-charged hydrogen. Compared with before pre-charged sample, pre-charged hydrogen improved the plastic properties of the steel and reduced the stress corrosion cracking sensitivity of the steel.
2020, 49(11):3741-3747.
DOI: 10.12442/j.issn.1002-185X.20190896
Abstract:
ZL205A alloy-infiltrated SiC foam ceramic composites are prepared through extrusion infiltration process. The effect of different porosity of SiC foam ceramic on the properties of composites is investigated. The SiC foam ceramics are tightly combined with the ZL205A matrix material, and there are few cracks and other defects can be observed. The SiC foam ceramic as the reinforcing phase refines the grains of the ZL205A matrix phase. The pore structure and the grain size are finer and smaller with decreasing of the reinforcing phase porosity. The mechanical properties of the ZL205A alloy-infiltrated SiC foam ceramic composites are investigated. The hardness and flexural strength of the composites are 127.6HV and 415MPa, respectively. The wear resistance of the composites is also investigated, the results demonstrate that the addition of ceramic reinforcing phase can effectively transform the severe adhesive wear and spalling wear of the matrix phase into lighter abrasive wear, which greatly improves the friction and wear properties of the composite.
ZL205A alloy-infiltrated SiC foam ceramic composites are prepared through extrusion infiltration process. The effect of different porosity of SiC foam ceramic on the properties of composites is investigated. The SiC foam ceramics are tightly combined with the ZL205A matrix material, and there are few cracks and other defects can be observed. The SiC foam ceramic as the reinforcing phase refines the grains of the ZL205A matrix phase. The pore structure and the grain size are finer and smaller with decreasing of the reinforcing phase porosity. The mechanical properties of the ZL205A alloy-infiltrated SiC foam ceramic composites are investigated. The hardness and flexural strength of the composites are 127.6HV and 415MPa, respectively. The wear resistance of the composites is also investigated, the results demonstrate that the addition of ceramic reinforcing phase can effectively transform the severe adhesive wear and spalling wear of the matrix phase into lighter abrasive wear, which greatly improves the friction and wear properties of the composite.
2020, 49(11):3748-3760.
DOI: 10.12442/j.issn.1002-185X.E20190104
Abstract:
ZrO2 films were deposited on 304 stainless-steel substrates by a sol-gel spin coating method. Electrochemical testing technology and a to-and-fro wear test apparatus were used to study the electrochemical corrosion and tribocorrosion properties of the films in different NaCl solutions. According to the results, the coated specimens were better than the bare substrate regarding resistance to corrosion and tribocorrosion. In the NaCl solutions, increasing either the solution temperature or concentration decreased the protective effects of the ZrO2 films; study of the solution temperature factor showed that serious pitting corrosion and obvious cracking occurred on the surface of the coated specimens; study of the solution concentration factor showed pitting corrosion on the sample surfaces. Regarding the tribocorrosion of the coated specimens, as the NaCl concentration increased from 2% to 6.5%, the abrasive wear was more obvious, and the corrosive wear was aggravated.
ZrO2 films were deposited on 304 stainless-steel substrates by a sol-gel spin coating method. Electrochemical testing technology and a to-and-fro wear test apparatus were used to study the electrochemical corrosion and tribocorrosion properties of the films in different NaCl solutions. According to the results, the coated specimens were better than the bare substrate regarding resistance to corrosion and tribocorrosion. In the NaCl solutions, increasing either the solution temperature or concentration decreased the protective effects of the ZrO2 films; study of the solution temperature factor showed that serious pitting corrosion and obvious cracking occurred on the surface of the coated specimens; study of the solution concentration factor showed pitting corrosion on the sample surfaces. Regarding the tribocorrosion of the coated specimens, as the NaCl concentration increased from 2% to 6.5%, the abrasive wear was more obvious, and the corrosive wear was aggravated.
2020, 49(11):3761-3768.
DOI: 10.12442/j.issn.1002-185X.20190899
Abstract:
Fluid flow in the solidifying pool plays an important role for the casting quality in Electron Beam Cold Hearth Re-melting (EBCHR or EB Re-melting) process. A three-dimensional unsteady state model has been built to describe the fluid flow and the sump evolution during the EBCHR process of titanium slab casting. The Mixed Lagrange and Euler (MiLE) approach was employed to investigate the unsteady state casting process. A set of asymmetrical EB power input was tested in the model to demonstrate the characteristic of the fluid flow, temperature distribution and sump profile. The results showed that the asymmetrical sump is induced by the coupling of fluid flow and heat transfer within the asymmetrical mold. Part of the inlet fluid infiltrates the solidifying shell, and part of the inlet fluid rebounds to the melt surface. The infiltration of downward inlet flow reduces the solidifying shell, while the rebound of upward inlet flow enforces the heat absorption along the melt surface. The sump asymmetry can be adjusted with optimization of the EB power density.
Fluid flow in the solidifying pool plays an important role for the casting quality in Electron Beam Cold Hearth Re-melting (EBCHR or EB Re-melting) process. A three-dimensional unsteady state model has been built to describe the fluid flow and the sump evolution during the EBCHR process of titanium slab casting. The Mixed Lagrange and Euler (MiLE) approach was employed to investigate the unsteady state casting process. A set of asymmetrical EB power input was tested in the model to demonstrate the characteristic of the fluid flow, temperature distribution and sump profile. The results showed that the asymmetrical sump is induced by the coupling of fluid flow and heat transfer within the asymmetrical mold. Part of the inlet fluid infiltrates the solidifying shell, and part of the inlet fluid rebounds to the melt surface. The infiltration of downward inlet flow reduces the solidifying shell, while the rebound of upward inlet flow enforces the heat absorption along the melt surface. The sump asymmetry can be adjusted with optimization of the EB power density.
2020, 49(11):3769-3775.
DOI: 10.12442/j.issn.1002-185X.E20190105
Abstract:
Ti-6Al-4V alloy (TC4) is widely used in the field of marine and aviation, and its severe service environment is easy to lead to hydrogen embrittlement (HE) which can cause the degradation of mechanical properties and a sudden catastrophic fracture for the material. To investigate the HE behavior and mechanisms, mechanical properties of the TC4 alloy after different electrochemical hydrogen charging (EHC) time were measured by small punch test (SPT) first. Then, hydrogen distribution and the phase transition of the TC4 alloy with different EHC time were discussed in detail based on the atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The strength and elongation obtained by SPT fitting data show obvious deterioration with increasing EHC time while the macroscopic fracture morphology of the TC4 alloy exhibits a transformation from ductile mode to brittle mode. At the same time, the generation of hydride after EHC is proved a main contributor to the HE of the TC4 alloy. The results in this paper provide an effective and convenient method to assess the HE behavior of TC4 alloy in service.
Ti-6Al-4V alloy (TC4) is widely used in the field of marine and aviation, and its severe service environment is easy to lead to hydrogen embrittlement (HE) which can cause the degradation of mechanical properties and a sudden catastrophic fracture for the material. To investigate the HE behavior and mechanisms, mechanical properties of the TC4 alloy after different electrochemical hydrogen charging (EHC) time were measured by small punch test (SPT) first. Then, hydrogen distribution and the phase transition of the TC4 alloy with different EHC time were discussed in detail based on the atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The strength and elongation obtained by SPT fitting data show obvious deterioration with increasing EHC time while the macroscopic fracture morphology of the TC4 alloy exhibits a transformation from ductile mode to brittle mode. At the same time, the generation of hydride after EHC is proved a main contributor to the HE of the TC4 alloy. The results in this paper provide an effective and convenient method to assess the HE behavior of TC4 alloy in service.
2020, 49(11):3776-3781.
DOI: 10.12442/j.issn.1002-185X.20190908
Abstract:
Hot compression tests of as-cast TB6 titanium alloy were performed at the temperature of 800-1150°C and the strain rate range of 0.001-10s?1 to examine microstructure evolution associated with stress induced martensite (SIM). The results reveal the occurrence of the SIM with the dendritic morphology in present alloy during hot compression process. The orthorhombic structure of SIM was confirmed for the alloy. It was found that the SIM nucleates both in the β grain interior and at grain boundary. TheSalloy composition uniformity and internal stress are strongly dominated by strain rate and deformation temperature, which is responsible for the amounts of SIM. The content of SIM at different strain rate is related to the temperature ranges. More contents of SIM appear at the strain rate of 0.1s-1 for the temperature of 800℃~900℃, at 0.01s-1 and 1s-1 for the temperature of 900℃~1000℃, at the strain rate of 1s-1 for the temperature of above 1000℃. 50% martensite can be obtained at an optimal combination of the temperature of 925℃ and the strain rate range of 1s-1.
Hot compression tests of as-cast TB6 titanium alloy were performed at the temperature of 800-1150°C and the strain rate range of 0.001-10s?1 to examine microstructure evolution associated with stress induced martensite (SIM). The results reveal the occurrence of the SIM with the dendritic morphology in present alloy during hot compression process. The orthorhombic structure of SIM was confirmed for the alloy. It was found that the SIM nucleates both in the β grain interior and at grain boundary. TheSalloy composition uniformity and internal stress are strongly dominated by strain rate and deformation temperature, which is responsible for the amounts of SIM. The content of SIM at different strain rate is related to the temperature ranges. More contents of SIM appear at the strain rate of 0.1s-1 for the temperature of 800℃~900℃, at 0.01s-1 and 1s-1 for the temperature of 900℃~1000℃, at the strain rate of 1s-1 for the temperature of above 1000℃. 50% martensite can be obtained at an optimal combination of the temperature of 925℃ and the strain rate range of 1s-1.
2020, 49(11):3782-3789.
DOI: 10.12442/j.issn.1002-185X.20190910
Abstract:
In this paper, a sandwich composite with broad-band wave-absorbing properties in C-Band was designed and prepared , and the electromagnetic parameters and reflectivity of the composite board were analyzed by a coaxial cable method and a vector network analyzer. The thickness of the composite laminate is 5 mm, and the surface layer of the board and the bottom layer are the glass fiber/ epoxy resin composite material, and the Fe50Ni50 powders/ butyl rubber nanocomposite is the interlayer. A spherical Fe50Ni50 powders with a particle size of about 100 nm were prepared by a liquid-phase reduction method, and a two-step blending method was used to prepare the Fe50Ni50/ butyl rubber nanocomposite. The result shows that the wave-absorbed mechanism of the interlayer is the magnetic loss in the frequency band of 2-18 GHz . The matching of the surface layer and the interlayer is the key to obtain the broad-band wave-absorbing properties, and the good wave-absorbing properties can be obtained by adjusting the thickness of the surface layer and the interlayer. When the thickness of the composite laminate is 5 mm and the thickness of the interlayer is 2 mm, the wave-absorbing frequency band for R being less than -10 dB, is in the range of5.6 GHz -7.6 GHz and 16.8 GHz -18 GHz, and the width of wave-absorbing band reaches 3.2 GHz, and the wave-absorbing bandwidth in the C-band is 2 GHz, which has achieved a breakthrough.
In this paper, a sandwich composite with broad-band wave-absorbing properties in C-Band was designed and prepared , and the electromagnetic parameters and reflectivity of the composite board were analyzed by a coaxial cable method and a vector network analyzer. The thickness of the composite laminate is 5 mm, and the surface layer of the board and the bottom layer are the glass fiber/ epoxy resin composite material, and the Fe50Ni50 powders/ butyl rubber nanocomposite is the interlayer. A spherical Fe50Ni50 powders with a particle size of about 100 nm were prepared by a liquid-phase reduction method, and a two-step blending method was used to prepare the Fe50Ni50/ butyl rubber nanocomposite. The result shows that the wave-absorbed mechanism of the interlayer is the magnetic loss in the frequency band of 2-18 GHz . The matching of the surface layer and the interlayer is the key to obtain the broad-band wave-absorbing properties, and the good wave-absorbing properties can be obtained by adjusting the thickness of the surface layer and the interlayer. When the thickness of the composite laminate is 5 mm and the thickness of the interlayer is 2 mm, the wave-absorbing frequency band for R being less than -10 dB, is in the range of5.6 GHz -7.6 GHz and 16.8 GHz -18 GHz, and the width of wave-absorbing band reaches 3.2 GHz, and the wave-absorbing bandwidth in the C-band is 2 GHz, which has achieved a breakthrough.
2020, 49(11):3790-3795.
DOI: 10.12442/j.issn.1002-185X.20191056
Abstract:
The interdigital transducer (IDT), developed from surface acoustic wave devices, has been gradually applied to structural health monitoring systems due to its operating frequency, adjustable frequency bandwidth and low loss. Therefore, it has a wide application prospect in smart materials and structures. In this paper, the wideband trapezoidal interdigital transducer (TIDT) is studied for the shortage, narrow bandwidth, of the existing rectangular IDT. The finite element analysis method was used to optimize the TIDT structure, and the TIDT performance was tested. The preliminary application of TIDT for structural damage detection was studied through experiments. The experimental results show that TIDT improves damage recognition accuracy in practical applications and has broad application prospects.
The interdigital transducer (IDT), developed from surface acoustic wave devices, has been gradually applied to structural health monitoring systems due to its operating frequency, adjustable frequency bandwidth and low loss. Therefore, it has a wide application prospect in smart materials and structures. In this paper, the wideband trapezoidal interdigital transducer (TIDT) is studied for the shortage, narrow bandwidth, of the existing rectangular IDT. The finite element analysis method was used to optimize the TIDT structure, and the TIDT performance was tested. The preliminary application of TIDT for structural damage detection was studied through experiments. The experimental results show that TIDT improves damage recognition accuracy in practical applications and has broad application prospects.
2020, 49(11):3796-3802.
DOI: 10.12442/j.issn.1002-185X.20190855
Abstract:
The effects of the quenching speed on the phase composition and morphology of the Sm-Fe alloy ribbons are measured and analyzed by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (HRTEM). It was found that the size of alloy ribbons decrease along the width and thickness direction firstly with the increasing of quenching speed and maintain stability in the thickness direction even increasing the speed sequentially. The size of agglomeration also decreases in the free surface,about 0.5~3μm as the quenching speed is up to 36m/s. The XRD and EDS results show that there are three different phases in the ribbons: Sm2Fe17, α-Fe and Sm-rich phase,the main phase grain size of the ribbons is on the sub-micron scale (daver≈340nm, 36m/s), which is restricted not only by the wheel speed but also by the bare two element type. It is the first time to characterize the grain morphology by different methods.
The effects of the quenching speed on the phase composition and morphology of the Sm-Fe alloy ribbons are measured and analyzed by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (HRTEM). It was found that the size of alloy ribbons decrease along the width and thickness direction firstly with the increasing of quenching speed and maintain stability in the thickness direction even increasing the speed sequentially. The size of agglomeration also decreases in the free surface,about 0.5~3μm as the quenching speed is up to 36m/s. The XRD and EDS results show that there are three different phases in the ribbons: Sm2Fe17, α-Fe and Sm-rich phase,the main phase grain size of the ribbons is on the sub-micron scale (daver≈340nm, 36m/s), which is restricted not only by the wheel speed but also by the bare two element type. It is the first time to characterize the grain morphology by different methods.
2020, 49(11):3803-3808.
DOI: 10.12442/j.issn.1002-185X.20190984
Abstract:
Nitrogen is one of the undesirable impurity elements of superalloys and it can induce the precipitation of nitrides and the formation of microporosity to worsen the mechanical properties of material. With the increasingly high demands in superalloy component quality, nowadays the nitrogen content in superalloy has been recommended to be no higher than 10×10-6 wt.%. Chromium is an important beneficial alloying element widely employed in superalloys (with an addition up to 20 wt.%) for it can enhance the anti-corrosion performance of alloys at elevated temperature. However, chromium has a high affinity to nitrogen that it could be very hard to achieve a low nitrogen content in high-Cr alloys. Therefore, it is necessary to study the features of the nitrogen-removing process of high-Cr alloys. In this work, the nitrogen-removing process during the vacuum induction melting of a high-Cr nickel based alloy was investigated through thermodynamic calculation and kinetic experiments. Results show that high-Cr nickel based alloy had a high thermodynamic equilibrium solubility of nitrogen, and it was mainly dominated by the vacuum pressure. In order to achieve the goal of [N]≤10 ppm, the melting vacuum pressure should be no higher than 0.1 Pa. To study the kinetic characteristics of nitrogen-removing process, the melted metal was held at 1500, 1550 and 1600 ℃, and sampled at 0, 30, 60, 120, 180 and 240 min at 0.1 Pa after the complete melting of alloy, respectively. Results indicate that nitrogen content dramatically decreased at the beginning of melt holding, but in the medium and later stage it took a much longer period of time to get close to the equilibrium solubility of nitrogen. Kinetic data analysis shows that the nitrogen-removing process of high-Cr nickel based alloy can be classified as the second-order reaction, which reflects that the process was controlled by the chemical reaction on melt surface. The apparent rate constants of nitrogen-removing process at 1500, 1550 and 1600 ℃ were calculated to be 0.0184, 0.0233 and 0.0397 m?s-1 , respectively, and the apparent activation energy was determined to be 211.4 kJ?mol-1.
Nitrogen is one of the undesirable impurity elements of superalloys and it can induce the precipitation of nitrides and the formation of microporosity to worsen the mechanical properties of material. With the increasingly high demands in superalloy component quality, nowadays the nitrogen content in superalloy has been recommended to be no higher than 10×10-6 wt.%. Chromium is an important beneficial alloying element widely employed in superalloys (with an addition up to 20 wt.%) for it can enhance the anti-corrosion performance of alloys at elevated temperature. However, chromium has a high affinity to nitrogen that it could be very hard to achieve a low nitrogen content in high-Cr alloys. Therefore, it is necessary to study the features of the nitrogen-removing process of high-Cr alloys. In this work, the nitrogen-removing process during the vacuum induction melting of a high-Cr nickel based alloy was investigated through thermodynamic calculation and kinetic experiments. Results show that high-Cr nickel based alloy had a high thermodynamic equilibrium solubility of nitrogen, and it was mainly dominated by the vacuum pressure. In order to achieve the goal of [N]≤10 ppm, the melting vacuum pressure should be no higher than 0.1 Pa. To study the kinetic characteristics of nitrogen-removing process, the melted metal was held at 1500, 1550 and 1600 ℃, and sampled at 0, 30, 60, 120, 180 and 240 min at 0.1 Pa after the complete melting of alloy, respectively. Results indicate that nitrogen content dramatically decreased at the beginning of melt holding, but in the medium and later stage it took a much longer period of time to get close to the equilibrium solubility of nitrogen. Kinetic data analysis shows that the nitrogen-removing process of high-Cr nickel based alloy can be classified as the second-order reaction, which reflects that the process was controlled by the chemical reaction on melt surface. The apparent rate constants of nitrogen-removing process at 1500, 1550 and 1600 ℃ were calculated to be 0.0184, 0.0233 and 0.0397 m?s-1 , respectively, and the apparent activation energy was determined to be 211.4 kJ?mol-1.
2020, 49(11):3809-3815.
DOI: 10.12442/j.issn.1002-185X.20200149
Abstract:
The melting and solidification behaviors of Ni-based superalloy U720Li were investigated by means of high temperature confocal laser scanning microscopy (HT-CLSM) and differential thermal analysis (DTA) in this study. The in-situ HT-CLSM observation of melting process shows that incipient melting takes place at the front of some eutectic (γ + γ′) particles at about 1122 ℃. But the molten pools cannot expand rapidly until the temperature is increased above 1173 ℃. Discrete spotted molten pools occurs on localized region of the dendrite area at around 1195 ℃, and the radius of these molten pools increases slowly with raising temperature. The eutectic (γ + γ′) particles precipitated in the interdendritic region begin to melt at about 1235 ℃ and the molten pools rapidly expand towards the dendrite area as the temperature increases. Finally, the dendrites are completely melted at 1333 ℃. The in-situ HT-CLSM observation of solidification process shows that the melt starts to solidify at about 1315 ℃ and the solidification ends at around 1180 ℃. As the temperature decreases the transformation rate of the solid phase initially increases slowly and then increases rapidly until a maximum value, afterwards it quickly decreases and at the final solidification stage it is about zero. The DTA analysis indicates that the onset temperature of γ′ dissolution in the ingot is about 1047 ℃, and the ingot is completely melted at 1362 ℃. By comparison, it is clear that the results of HT-CLSM in-situ observations are about 30 ℃ lower than those of DTA analysis.
The melting and solidification behaviors of Ni-based superalloy U720Li were investigated by means of high temperature confocal laser scanning microscopy (HT-CLSM) and differential thermal analysis (DTA) in this study. The in-situ HT-CLSM observation of melting process shows that incipient melting takes place at the front of some eutectic (γ + γ′) particles at about 1122 ℃. But the molten pools cannot expand rapidly until the temperature is increased above 1173 ℃. Discrete spotted molten pools occurs on localized region of the dendrite area at around 1195 ℃, and the radius of these molten pools increases slowly with raising temperature. The eutectic (γ + γ′) particles precipitated in the interdendritic region begin to melt at about 1235 ℃ and the molten pools rapidly expand towards the dendrite area as the temperature increases. Finally, the dendrites are completely melted at 1333 ℃. The in-situ HT-CLSM observation of solidification process shows that the melt starts to solidify at about 1315 ℃ and the solidification ends at around 1180 ℃. As the temperature decreases the transformation rate of the solid phase initially increases slowly and then increases rapidly until a maximum value, afterwards it quickly decreases and at the final solidification stage it is about zero. The DTA analysis indicates that the onset temperature of γ′ dissolution in the ingot is about 1047 ℃, and the ingot is completely melted at 1362 ℃. By comparison, it is clear that the results of HT-CLSM in-situ observations are about 30 ℃ lower than those of DTA analysis.
2020, 49(11):3816-3821.
DOI: 10.12442/j.issn.1002-185X.20200264
Abstract:
Based on the empirical electron theory of solids and molecules, the valence electron structures of S phase and the S/a interface were calculated, then the relationships between their VESs and precipitation strength and interface properties were analyzed in Al-Cu-Mg alloys in this paper. It is shown the covalent bond distribution of S phase is uniform and its main bond network is built by four stronger covalent bonds connected by Cu atoms. The nature of precipitation strength of S phase lies in its binding force of the strongest covalent bond is bigger 135.14% than that of the matrix a-Al and causes the stronger inhibition to the dislocation movement. The covalent electron density difference of (100)S//(100)a, (010)S// aand (001)S//(021)ais 0.003%, 3.564%and 5.811% respectively, while the covalent electron density of (100)S//(100)ais 10.3915 nm-2 and 10.3918 nm-2 , and that of (010)S// ais 0.0486 nm-2 and 0.0469 nm-2, and that of (001)S//(021)ais 0.0486 nm-2 and 0.0459 nm-2. Compared with (001)S//(021)a和(010)S// a, the binding force and covalent electron density of (100)S//(100)a is the biggest while its covalent electron density difference is the smallest, so that the interface continuity is the best and the interface stress is the smallest.
Based on the empirical electron theory of solids and molecules, the valence electron structures of S phase and the S/a interface were calculated, then the relationships between their VESs and precipitation strength and interface properties were analyzed in Al-Cu-Mg alloys in this paper. It is shown the covalent bond distribution of S phase is uniform and its main bond network is built by four stronger covalent bonds connected by Cu atoms. The nature of precipitation strength of S phase lies in its binding force of the strongest covalent bond is bigger 135.14% than that of the matrix a-Al and causes the stronger inhibition to the dislocation movement. The covalent electron density difference of (100)S//(100)a, (010)S// aand (001)S//(021)ais 0.003%, 3.564%and 5.811% respectively, while the covalent electron density of (100)S//(100)ais 10.3915 nm-2 and 10.3918 nm-2 , and that of (010)S// ais 0.0486 nm-2 and 0.0469 nm-2, and that of (001)S//(021)ais 0.0486 nm-2 and 0.0459 nm-2. Compared with (001)S//(021)a和(010)S// a, the binding force and covalent electron density of (100)S//(100)a is the biggest while its covalent electron density difference is the smallest, so that the interface continuity is the best and the interface stress is the smallest.
2020, 49(11):3822-3827.
DOI: 10.12442/j.issn.1002-185X.20190971
Abstract:
The Ni/ solder /Cu sandwich solder joints were prepared with four kinds of mixed soldering alloys with different Pb contents (0, 4.67%, 22.46%, 37%), and the effects of Pb content and aging time on the microstructure, the evolution of intermetallic compounds (IMC), and mechanical properties were investigated by putting the solders into the -196℃ liquid nitrogen with different times of 10 days, 20 days and 30 days, respectively. The results indicate that Pb element accumulates gradually with the increase of Pb content in solder, moreover, the Pb-rich phase continuously coarsens with the increase of aging time. The nominal chemical composition in IMC layer does not alter during ultra-low temperature aging treatment, while some microcracks and holes will occur gradually by accompanied with the transformation of the scallop-like IMC into lamellar IMC. At the same time, the Pb element accumulates alone the IMC interface near the solder, and a Pb-rich layer will be formed, even some Pb-rich phases extend inside the IMC layer. With the prolongation of aging time, the fracture mode of the solder joint is transformed from ductile fracture to ductile-brittle mixed fracture. The shear strength will be improved with appropriate increased of Pb element, however, it will be decreased as exceeding to 22.46% of Pb content.
The Ni/ solder /Cu sandwich solder joints were prepared with four kinds of mixed soldering alloys with different Pb contents (0, 4.67%, 22.46%, 37%), and the effects of Pb content and aging time on the microstructure, the evolution of intermetallic compounds (IMC), and mechanical properties were investigated by putting the solders into the -196℃ liquid nitrogen with different times of 10 days, 20 days and 30 days, respectively. The results indicate that Pb element accumulates gradually with the increase of Pb content in solder, moreover, the Pb-rich phase continuously coarsens with the increase of aging time. The nominal chemical composition in IMC layer does not alter during ultra-low temperature aging treatment, while some microcracks and holes will occur gradually by accompanied with the transformation of the scallop-like IMC into lamellar IMC. At the same time, the Pb element accumulates alone the IMC interface near the solder, and a Pb-rich layer will be formed, even some Pb-rich phases extend inside the IMC layer. With the prolongation of aging time, the fracture mode of the solder joint is transformed from ductile fracture to ductile-brittle mixed fracture. The shear strength will be improved with appropriate increased of Pb element, however, it will be decreased as exceeding to 22.46% of Pb content.
2020, 49(11):3828-3834.
DOI: 10.12442/j.issn.1002-185X.20190988
Abstract:
Two kinds of aluminum-based abradable seal coatings (AlSi-hBN and AlSi-PHB) were prepared by atmospheric plasma spraying. XRD, OM, SEM, quasi-static and dynamic compression tests were utilized to research the microstructure, compressive properties under different strain rates and relevant damage characteristics of the seal coatings. The results indicated that AlSi-hBN and AlSi-PHB seal coatings were mainly composed of α-Al solid solution phase, eutectic Si phase, abradable second phase (hBN/PHB) and pores. No obvious yield platform was observed on compressive true stress-true strain curves of two coatings under both quasi-static and dynamic loading conditions. The dynamic compressive strength of AlSi-hBN coating was higher than that of AlSi-PHB coating. Particles inside the coatings were severely deformed under dynamic loading. The main damage forms were debonding and cracking at the interparticle interface as well as initiation and propagation of cracks at the internal defects.
Two kinds of aluminum-based abradable seal coatings (AlSi-hBN and AlSi-PHB) were prepared by atmospheric plasma spraying. XRD, OM, SEM, quasi-static and dynamic compression tests were utilized to research the microstructure, compressive properties under different strain rates and relevant damage characteristics of the seal coatings. The results indicated that AlSi-hBN and AlSi-PHB seal coatings were mainly composed of α-Al solid solution phase, eutectic Si phase, abradable second phase (hBN/PHB) and pores. No obvious yield platform was observed on compressive true stress-true strain curves of two coatings under both quasi-static and dynamic loading conditions. The dynamic compressive strength of AlSi-hBN coating was higher than that of AlSi-PHB coating. Particles inside the coatings were severely deformed under dynamic loading. The main damage forms were debonding and cracking at the interparticle interface as well as initiation and propagation of cracks at the internal defects.
Zhang Xuewei
,
Kang Shidong
,
Wang Zhaosong
,
Dong Qing
,
Liu Wei
,
Dong Qiushi
,
Qiao Shuai
,
Yang Zhiyuan
,
Liu Zhihua
,
Chen Lianzhong
2020, 49(11):3835-3840.
DOI: 10.12442/j.issn.1002-185X.20191047
Abstract:
U-Mo alloy is with great development potential as a kind of dispersive fuel in research and test reactors. Improving the efficiency of powder obtention via hydride-dehydride process is a prerequisite for efficient powder metallurgy preparation of U-Mo alloy dispersion fuels. Optimizing parameters such as homogenization temperature, isothermal aging temperature, isothermal aging time, and Mo content is beneficial to increase the α-phase content of U-Mo alloys, thereby improving the efficiency of the power obtention of U-Mo alloy. Machine learning aided design of materials can greatly reduce the trials of expensive and time-consuming experiments and improve the efficiency of material development. In this paper, a machine learning method is applied to the rapid design of isothermal decomposition parameters of U-Mo alloys. With the hardness of the alloy as a design index, a machine learning support vector machine (SVM) model between the alloy hardness and the above parameters is established based on a small amount of data. Based on the prediction of hardness, the differences in optimization efficiency between the two types of experimental design algorithms based on predicted values and based on expected improvement are compared. The results show that the experimental design algorithm based on the expected improvement can significantly improve the hardness through a small number of iterative experiments, while the design algorithm based on the predicted value does not significantly improve the hardness. Using the above-mentioned machine learning aided design method, the optimal parameter combination for isothermal decomposition of the alloy was successfully determined through 4 experiments. When the aging temperature is 565 °C, the aging time is more than 20 h, the homogenization temperature is 900~950 °C, and the Mo content is 6wt.%, the hardness of the alloy processed is the highest, and the powder obtention rate is the highest. This study made a preliminary attempt to use machine learning methods to quickly optimize U-based alloy process parameters. Such data-based methods can effectively improve the efficiency of material development.
U-Mo alloy is with great development potential as a kind of dispersive fuel in research and test reactors. Improving the efficiency of powder obtention via hydride-dehydride process is a prerequisite for efficient powder metallurgy preparation of U-Mo alloy dispersion fuels. Optimizing parameters such as homogenization temperature, isothermal aging temperature, isothermal aging time, and Mo content is beneficial to increase the α-phase content of U-Mo alloys, thereby improving the efficiency of the power obtention of U-Mo alloy. Machine learning aided design of materials can greatly reduce the trials of expensive and time-consuming experiments and improve the efficiency of material development. In this paper, a machine learning method is applied to the rapid design of isothermal decomposition parameters of U-Mo alloys. With the hardness of the alloy as a design index, a machine learning support vector machine (SVM) model between the alloy hardness and the above parameters is established based on a small amount of data. Based on the prediction of hardness, the differences in optimization efficiency between the two types of experimental design algorithms based on predicted values and based on expected improvement are compared. The results show that the experimental design algorithm based on the expected improvement can significantly improve the hardness through a small number of iterative experiments, while the design algorithm based on the predicted value does not significantly improve the hardness. Using the above-mentioned machine learning aided design method, the optimal parameter combination for isothermal decomposition of the alloy was successfully determined through 4 experiments. When the aging temperature is 565 °C, the aging time is more than 20 h, the homogenization temperature is 900~950 °C, and the Mo content is 6wt.%, the hardness of the alloy processed is the highest, and the powder obtention rate is the highest. This study made a preliminary attempt to use machine learning methods to quickly optimize U-based alloy process parameters. Such data-based methods can effectively improve the efficiency of material development.
2020, 49(11):3890-3895.
DOI: 10.12442/j.issn.1002-185X.20190980
Abstract:
The chloroplatinic acid, nickel chloride and cobalt nitrate, as raw materials, are used to synthesize PtCoNi alloy nanoparticles with well dispersion loaded on xc-72 carbon black by spray drying method combined with calcination reduction. The influence of the surface of the carbon black on the formation and dispersion alloy nanoparticles was studied, and the effects of PtCoNi with the same atomic ratio and PtCoNi with different atomic ratio on methanol catalytic oxidation activity and CO poisoning resistance and durability were investigated in detail. The results showed that PtCoNi catalyst loaded on surface modified carbon black is alloy nanoparticles, and the nanoparticles are dispersed evenly on the surface of carbon black with particle size distribution of 1-4nm and average particle size of 2.3nm. Compared with commercial Pt/C catalysts, PtCoNi/C with the same atomic ratio has higher catalytic methanol oxidation activity, durability and CO poisoning resistance. The order of activity of PtCoNi catalysts with different atomic ratio in catalytic methanol oxidation reaction is :PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C, and the sequence of CO poisoning resistance is PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C.
The chloroplatinic acid, nickel chloride and cobalt nitrate, as raw materials, are used to synthesize PtCoNi alloy nanoparticles with well dispersion loaded on xc-72 carbon black by spray drying method combined with calcination reduction. The influence of the surface of the carbon black on the formation and dispersion alloy nanoparticles was studied, and the effects of PtCoNi with the same atomic ratio and PtCoNi with different atomic ratio on methanol catalytic oxidation activity and CO poisoning resistance and durability were investigated in detail. The results showed that PtCoNi catalyst loaded on surface modified carbon black is alloy nanoparticles, and the nanoparticles are dispersed evenly on the surface of carbon black with particle size distribution of 1-4nm and average particle size of 2.3nm. Compared with commercial Pt/C catalysts, PtCoNi/C with the same atomic ratio has higher catalytic methanol oxidation activity, durability and CO poisoning resistance. The order of activity of PtCoNi catalysts with different atomic ratio in catalytic methanol oxidation reaction is :PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C, and the sequence of CO poisoning resistance is PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C.
2020, 49(11):3841-3846.
DOI: 10.12442/j.issn.1002-185X.20190954
Abstract:
The Ultrafine-grained CoCrFeMnNiGd0.15 high-entropy alloy (HEA) was prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and mechanical properties of CoCrFeMnNi Gd0.15 high-entropy alloy was investigated. It was found that the sintered CoCrFeMnNiGd0.15 alloy showed a multi-phase microstructure including the FCC matrix, a rare earth oxide (Gd2O3) and a tetragonal phase rich in Gd, Ni and Mn element. As the sintering temperature increased, the content and size of the precipitated phase increased continuously, the compressive yield strength of the alloy decreased while the plasticity showed the opposite trend. The sintered alloy achieved the best comprehensive mechanical properties at the sintering temperature of 900 °C, with a compressive yield strength of 1662 MPa, compressive strength of 2518 MPa, plastic strain of 30.6% and Vickers hardness of 458 Hv. With the increase of temperature, the fracture morphology of compressive specimens consisted of fine equiaxed dimples, the diameter and depth of the dimples increased continuously and some tearing ridges were observed.
The Ultrafine-grained CoCrFeMnNiGd0.15 high-entropy alloy (HEA) was prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and mechanical properties of CoCrFeMnNi Gd0.15 high-entropy alloy was investigated. It was found that the sintered CoCrFeMnNiGd0.15 alloy showed a multi-phase microstructure including the FCC matrix, a rare earth oxide (Gd2O3) and a tetragonal phase rich in Gd, Ni and Mn element. As the sintering temperature increased, the content and size of the precipitated phase increased continuously, the compressive yield strength of the alloy decreased while the plasticity showed the opposite trend. The sintered alloy achieved the best comprehensive mechanical properties at the sintering temperature of 900 °C, with a compressive yield strength of 1662 MPa, compressive strength of 2518 MPa, plastic strain of 30.6% and Vickers hardness of 458 Hv. With the increase of temperature, the fracture morphology of compressive specimens consisted of fine equiaxed dimples, the diameter and depth of the dimples increased continuously and some tearing ridges were observed.
28 Preparation and sintering properties of nano WC powder by Pt catalyzed hydrogen-free carbonization
2020, 49(11):3847-3853.
DOI: 10.12442/j.issn.1002-185X.20190953
Abstract:
In order to solve the problem of slow reaction rate and particle growth in hydrogen-free carbonization, a amount of Pt (0.01 wt%) was added as catalyst in the carbonization process to improve the reaction rate and prepare nano WC powder.The binderless tungsten carbide was produced by hot press sintering (HPS) at 1400-1800 ℃ with an applied pressure of 40 MPa.The effects of Pt addition on the sintering performance and microstructure WC powder and the effects of Pt addition and the sintering temperature on the densification, microstructure and mechanical properties of the sintered sample were investigated.The results show that a amount of Pt (0.01 wt%) can significantly reduce the temperature of hydrogen-free carbonization, and the prepared WC powder has a fine and uniform particle size.As the sintering temperature increases, the density of binderless tungsten carbide increases, the grain size increases, and the hardness and fracture toughness increase. However, when the sintering temperature is too high, resulting in abnormal growth grains and W2C phase, which leads to a serious decline in the fracture toughness of binderless tungsten carbide. When the sintering tempertuare was 1700 ℃, the hardness and fracture toughness reached the maximum walues of 2887 kg.mm-2 and 7.1 MPa.mm1/2, respectively.
In order to solve the problem of slow reaction rate and particle growth in hydrogen-free carbonization, a amount of Pt (0.01 wt%) was added as catalyst in the carbonization process to improve the reaction rate and prepare nano WC powder.The binderless tungsten carbide was produced by hot press sintering (HPS) at 1400-1800 ℃ with an applied pressure of 40 MPa.The effects of Pt addition on the sintering performance and microstructure WC powder and the effects of Pt addition and the sintering temperature on the densification, microstructure and mechanical properties of the sintered sample were investigated.The results show that a amount of Pt (0.01 wt%) can significantly reduce the temperature of hydrogen-free carbonization, and the prepared WC powder has a fine and uniform particle size.As the sintering temperature increases, the density of binderless tungsten carbide increases, the grain size increases, and the hardness and fracture toughness increase. However, when the sintering temperature is too high, resulting in abnormal growth grains and W2C phase, which leads to a serious decline in the fracture toughness of binderless tungsten carbide. When the sintering tempertuare was 1700 ℃, the hardness and fracture toughness reached the maximum walues of 2887 kg.mm-2 and 7.1 MPa.mm1/2, respectively.
2020, 49(11):3854-3860.
DOI: 10.12442/j.issn.1002-185X.20190963
Abstract:
The p-type SnxBi0.5-xSb1.5Te3 thermoelectric materials with high ZT values have been prepared by vacuum melting, ball milling, cold-pressing and ambient pressure sintering. The effect of Sn content on the crystal structure, microscopic appearance, thermoelectric properties for SnxBi0.5-xSb1.5Te3 materials was investigated. As a result, the crystal structure of SnxBi0.5-xSb1.5Te3 thermoelectric materials is the rhombohedral structure; Bi0.5Sb1.5Te3 based thermoelectric materials contain more nanostructure defects with adding alloying element Sn. The addition of the alloying element Sn can increase carrier concentration and DOS effective mass to improve the electrical conductivity and power factor (PF). While, the reduction in lattice thermal conductivity is attributed to the enhanced phonon scattering. Eventually, the power factor reaches 3.10 mW·m-1·K-2, the lattice thermal conductivity is 0.358 W·m-1·K-1 and the ZT value is 1.25 at 300 K for Sn0.015Bi0.485Sb1.5Te3. And，in the temperature range of 300～400K，the ZT values for the Sn0.015Bi0.485Sb1.5Te3 are 1.25～1.33.
The p-type SnxBi0.5-xSb1.5Te3 thermoelectric materials with high ZT values have been prepared by vacuum melting, ball milling, cold-pressing and ambient pressure sintering. The effect of Sn content on the crystal structure, microscopic appearance, thermoelectric properties for SnxBi0.5-xSb1.5Te3 materials was investigated. As a result, the crystal structure of SnxBi0.5-xSb1.5Te3 thermoelectric materials is the rhombohedral structure; Bi0.5Sb1.5Te3 based thermoelectric materials contain more nanostructure defects with adding alloying element Sn. The addition of the alloying element Sn can increase carrier concentration and DOS effective mass to improve the electrical conductivity and power factor (PF). While, the reduction in lattice thermal conductivity is attributed to the enhanced phonon scattering. Eventually, the power factor reaches 3.10 mW·m-1·K-2, the lattice thermal conductivity is 0.358 W·m-1·K-1 and the ZT value is 1.25 at 300 K for Sn0.015Bi0.485Sb1.5Te3. And，in the temperature range of 300～400K，the ZT values for the Sn0.015Bi0.485Sb1.5Te3 are 1.25～1.33.
2020, 49(11):3861-3864.
DOI: 10.12442/j.issn.1002-185X.20190968
Abstract:
In this paper, focusing on the exigent requirement of ultra-thin sound absorption structure in the limited space for noise treatment, the raw material was stainless steel fiber felt, the complex film materials composed with stainless steel fiber porous material and metal film were prepared by low temperature sintering technology. The sound absorption coefficient of complex film materials was tested by B&K acoustic test platform at the frequency range from 50 Hz to 1000 Hz, and the effect of structural parameters on the sound absorption performance of complex film materials is analyzed. The results shown as follows: the effects of pore structure of metal fiber porous materials (pore diameter, wire diameter, sintering node) and number of metal film layers on the sound absorption performance of complex film materials were studied. It is found that in the frequency range of 50 Hz to 1000 Hz, the optimal structure of ultra-thin complex film materials is that the arranged order of the porous metal fiber material is fine wire diameter, small pore facing to sound source, thick wire diameter and large pore in the back. Complex copper-film inside the materials can effectively improve the sound absorption performance at low frequency.
In this paper, focusing on the exigent requirement of ultra-thin sound absorption structure in the limited space for noise treatment, the raw material was stainless steel fiber felt, the complex film materials composed with stainless steel fiber porous material and metal film were prepared by low temperature sintering technology. The sound absorption coefficient of complex film materials was tested by B&K acoustic test platform at the frequency range from 50 Hz to 1000 Hz, and the effect of structural parameters on the sound absorption performance of complex film materials is analyzed. The results shown as follows: the effects of pore structure of metal fiber porous materials (pore diameter, wire diameter, sintering node) and number of metal film layers on the sound absorption performance of complex film materials were studied. It is found that in the frequency range of 50 Hz to 1000 Hz, the optimal structure of ultra-thin complex film materials is that the arranged order of the porous metal fiber material is fine wire diameter, small pore facing to sound source, thick wire diameter and large pore in the back. Complex copper-film inside the materials can effectively improve the sound absorption performance at low frequency.
31 Research on W-Ni-Fe-Co alloys fabricated by Selective electron beam melting from pre-alloyed powder
Yang Guangyu
,
Chen Jinghai
,
Liu Nan
,
Yang Kun
,
Jia Liang
,
Jian Wenpeng
,
Wang Jian
,
Tang Huiping
2020, 49(11):3865-3869.
DOI: 10.12442/j.issn.1002-185X.20200235
Abstract:
W-Ni-Fe-Co pre-alloyed powder was prepared by plasma rotating electrode process, and then fabricated by selective electron beam melting (SEBM). W-Ni-Fe-Co pre-alloy powder consists of spherical powders and irregular powders with the microstructure of tungsten particles coated by γ- (Ni-Fe) phase, which contains supersaturated tungsten. Microstructure of the W-Ni-Fe-Co alloy shows a certain heredity from powder to SEBMed sample. The molten pool will be subjected to recoil pressure, hot capillary force and Marangoni convection during SEBM, the instantaneous flow of the molten pool promoted the rearrangement of tungsten particles, leading a higher uniformity in the SEBM sample than the powder. Densification process during SEBM is mainly the rearrangement of W particles, and there is no significant dissolution-precipitation process of W. The tensile strength of SEBMed W-Ni-Fe-Co alloy was measured to be 1098MPa together with a poor ductility. Fracture mode is brittle transgranular fracture and ductile tearing of γ- (Ni-Fe) bonding phase.
W-Ni-Fe-Co pre-alloyed powder was prepared by plasma rotating electrode process, and then fabricated by selective electron beam melting (SEBM). W-Ni-Fe-Co pre-alloy powder consists of spherical powders and irregular powders with the microstructure of tungsten particles coated by γ- (Ni-Fe) phase, which contains supersaturated tungsten. Microstructure of the W-Ni-Fe-Co alloy shows a certain heredity from powder to SEBMed sample. The molten pool will be subjected to recoil pressure, hot capillary force and Marangoni convection during SEBM, the instantaneous flow of the molten pool promoted the rearrangement of tungsten particles, leading a higher uniformity in the SEBM sample than the powder. Densification process during SEBM is mainly the rearrangement of W particles, and there is no significant dissolution-precipitation process of W. The tensile strength of SEBMed W-Ni-Fe-Co alloy was measured to be 1098MPa together with a poor ductility. Fracture mode is brittle transgranular fracture and ductile tearing of γ- (Ni-Fe) bonding phase.
2020, 49(11):3870-3874.
DOI: 10.12442/j.issn.1002-185X.20190974
Abstract:
In order to investigate the mechanical extension property of high-temperature superconducting(HTS) cable at room temperature and 77 K, we have respectively studied the mechanical extension properties of 10 m HTS cable and 10 m copper core at room temperature and 77 K. The stress-stain curves and Young modulus of the samples at corresponding temperature have been obtained by experiments. Meanwhile, we have investigated the contraction of 10 m HTS cable and 10 m copper core in a cooling process from room temperature to 77 K with tensile load of 2000 kg. The experimental results obtained in this paper could provide references to the determination of margin of cable-laying.
In order to investigate the mechanical extension property of high-temperature superconducting(HTS) cable at room temperature and 77 K, we have respectively studied the mechanical extension properties of 10 m HTS cable and 10 m copper core at room temperature and 77 K. The stress-stain curves and Young modulus of the samples at corresponding temperature have been obtained by experiments. Meanwhile, we have investigated the contraction of 10 m HTS cable and 10 m copper core in a cooling process from room temperature to 77 K with tensile load of 2000 kg. The experimental results obtained in this paper could provide references to the determination of margin of cable-laying.
2020, 49(11):3875-3881.
DOI: 10.12442/j.issn.1002-185X.20190976
Abstract:
Low density AlTiCrNiCu high-entropy alloy (HEAs) powder particles and bulk HEAs were prepared by mechanical alloying and spark plasma sintering. The effects of ball milling time on the alloying process of various elemental powders and the sintering temperature (950 ~ 1050 °C) on the microstructure and mechanical properties of high-entropy alloys were investigated. The results show that the high-entropy alloy powder is a single-phase BCC structure. As the ball milling time increases, the powder particle size first becomes larger and then smaller, and the final powder particle size is about 20 μm. The phase structure of the bulk high-entropy alloy is BCC1 (matrix phase) + BCC2 (Cr-rich phase) + FCC (Cu-rich phase), and the density was between 6.22 ~ 6.30 g/cm3. As the sintering temperature increases, the metallurgical bonding of the high-entropy alloy powder is more complete and the microstructure is more dense, which is related to increasing the sintering temperature so that there is enough energy between the atoms of the elements for sufficient diffusion. The increase of sintering temperature is beneficial to the metallurgical combination of high-entropy alloy powder and promotes the densification of the bulk high-entropy alloy materials. When the sintering temperature is 1050 °C, the AlTiCrNiCu high-entropy alloy has good comprehensive mechanical properties, and its yield strength, compressive strength, plasticity and microhardness are 1410 MPa, 2000 MPa, 9.13% and 524 HV, respectively. The analysis considers that a high sintering temperature provides sufficient energy for sufficient diffusion between the atoms of the elements. However, TEM analysis indicates that a high sintering temperature also promotes the aggregation of the dispersed FCC-rich Cu phase at the grain boundaries.
Low density AlTiCrNiCu high-entropy alloy (HEAs) powder particles and bulk HEAs were prepared by mechanical alloying and spark plasma sintering. The effects of ball milling time on the alloying process of various elemental powders and the sintering temperature (950 ~ 1050 °C) on the microstructure and mechanical properties of high-entropy alloys were investigated. The results show that the high-entropy alloy powder is a single-phase BCC structure. As the ball milling time increases, the powder particle size first becomes larger and then smaller, and the final powder particle size is about 20 μm. The phase structure of the bulk high-entropy alloy is BCC1 (matrix phase) + BCC2 (Cr-rich phase) + FCC (Cu-rich phase), and the density was between 6.22 ~ 6.30 g/cm3. As the sintering temperature increases, the metallurgical bonding of the high-entropy alloy powder is more complete and the microstructure is more dense, which is related to increasing the sintering temperature so that there is enough energy between the atoms of the elements for sufficient diffusion. The increase of sintering temperature is beneficial to the metallurgical combination of high-entropy alloy powder and promotes the densification of the bulk high-entropy alloy materials. When the sintering temperature is 1050 °C, the AlTiCrNiCu high-entropy alloy has good comprehensive mechanical properties, and its yield strength, compressive strength, plasticity and microhardness are 1410 MPa, 2000 MPa, 9.13% and 524 HV, respectively. The analysis considers that a high sintering temperature provides sufficient energy for sufficient diffusion between the atoms of the elements. However, TEM analysis indicates that a high sintering temperature also promotes the aggregation of the dispersed FCC-rich Cu phase at the grain boundaries.
2020, 49(11):3882-3889.
DOI: 10.12442/j.issn.1002-185X.20190975
Abstract:
In this study, Al-Mg-Sc-Zr aluminum alloy was prepared by selective laser melting (SLM). The effects of different processing parameters on the formation and different aging conditions on mechanical properties of SLM-formed samples were investigated. The results show that the high density samples can be obtained at a high laser power and a low laser scanning speed. The layer by layer stacking of the molten pool can be observed along the deposition direction of the sample. The nanoparticles are observed at both the inside and boundary of molten pool. After aging treatment at different temperatures, the hardness and compressive yield strength of the sample first increase and then decrease. The maximum yield strength ~469 ± 4 MPa is achieved after aged the sample at 400 ° C for 3 h.
In this study, Al-Mg-Sc-Zr aluminum alloy was prepared by selective laser melting (SLM). The effects of different processing parameters on the formation and different aging conditions on mechanical properties of SLM-formed samples were investigated. The results show that the high density samples can be obtained at a high laser power and a low laser scanning speed. The layer by layer stacking of the molten pool can be observed along the deposition direction of the sample. The nanoparticles are observed at both the inside and boundary of molten pool. After aging treatment at different temperatures, the hardness and compressive yield strength of the sample first increase and then decrease. The maximum yield strength ~469 ± 4 MPa is achieved after aged the sample at 400 ° C for 3 h.
2020, 49(11):3896-3901.
DOI: 10.12442/j.issn.1002-185X.20190986
Abstract:
The Ti3C2Tx MXene was successfully etched in situ HF method and modification of glass fiber fabric with dopamine. The Ti3C2Tx / glass fiber Composites composites were prepared by the vacuum filtration, the EMI SE of the samples with different Ti3C2Tx loading were studied in frequency range of 2–18 GHz. The results show that the Ti3C2Tx nanosheets are successfully attached to the surface of the glass fiber, which improves the conductive network of the glass fiber. After the etching by in-situ HF method, the 002 peak position was moved from 9.5 ° to 6.1 °, and 104 peaks of Ti3AlC2 disappeared, and the Ti3C2Tx etching was successful; Due to the high conductivity of Ti3C2Tx and a large amount of electrons on the surface, which induces that contribute to ohmic losses with electromagnetic waves, thereby reducing electromagnetic wave energy and achieving electromagnetic shielding effect. In the frequency range of 2~18 GHz, the electromagnetic shielding performance of the Ti3C2Tx loading of 2.55 mg/cm2 is 55.1 dB, and the surface resistance was 0.95 Ω/sq; the average electromagnetic shielding showed that the absorption loss in the sample played a major role.
The Ti3C2Tx MXene was successfully etched in situ HF method and modification of glass fiber fabric with dopamine. The Ti3C2Tx / glass fiber Composites composites were prepared by the vacuum filtration, the EMI SE of the samples with different Ti3C2Tx loading were studied in frequency range of 2–18 GHz. The results show that the Ti3C2Tx nanosheets are successfully attached to the surface of the glass fiber, which improves the conductive network of the glass fiber. After the etching by in-situ HF method, the 002 peak position was moved from 9.5 ° to 6.1 °, and 104 peaks of Ti3AlC2 disappeared, and the Ti3C2Tx etching was successful; Due to the high conductivity of Ti3C2Tx and a large amount of electrons on the surface, which induces that contribute to ohmic losses with electromagnetic waves, thereby reducing electromagnetic wave energy and achieving electromagnetic shielding effect. In the frequency range of 2~18 GHz, the electromagnetic shielding performance of the Ti3C2Tx loading of 2.55 mg/cm2 is 55.1 dB, and the surface resistance was 0.95 Ω/sq; the average electromagnetic shielding showed that the absorption loss in the sample played a major role.
2020, 49(11):3902-3908.
DOI: 10.12442/j.issn.1002-185X.20190991
Abstract:
Ti2AlNb-based alloy is a kind of intermetallic compound. It is expected to replace Ni-based superalloys for high-temperature structural applications with a temperature range of 650-800 ℃. In this work, a Ti2AlNb based alloy with a nominal composition of Ti-22Al-25Nb is prepared by water-cooled copper crucible induction floating melting method. The structural features of the as-cast Ti-22Al-25Nb alloy are characterized by XRD and SEM. It is found that the main phase of the as-cast Ti-22Al-25Nb alloy can be B2/? phase or O phase, depending on its melting and casting process parameters. The grain size of the as-cast Ti-22Al-25Nb alloy reaches several hundred microns. The mechanical properties of the as-cast Ti-22Al-25Nb alloy are investigated by tensile, compressive and nanoindentation tests at room temperature. The ultimate tensile strength of the as-cast Ti-22Al-25Nb O phase alloy and B2/? alloy reaches 1125 MPa and 1031 MPa respectively, with the elongation of 1.32% and 1.82%. The nanoindentation hardness of the as-cast Ti-22Al-25Nb O phase alloy is slightly higher than that of the as-cast B2/? phase alloy. The tensile fracture and compression fracture of as-cast Ti-22Al-25Nb alloy show obvious cleavage fracture characteristics. In addition, the tensile fracture is mainly intergranular, while the compression fracture is mainly transgranular.
Ti2AlNb-based alloy is a kind of intermetallic compound. It is expected to replace Ni-based superalloys for high-temperature structural applications with a temperature range of 650-800 ℃. In this work, a Ti2AlNb based alloy with a nominal composition of Ti-22Al-25Nb is prepared by water-cooled copper crucible induction floating melting method. The structural features of the as-cast Ti-22Al-25Nb alloy are characterized by XRD and SEM. It is found that the main phase of the as-cast Ti-22Al-25Nb alloy can be B2/? phase or O phase, depending on its melting and casting process parameters. The grain size of the as-cast Ti-22Al-25Nb alloy reaches several hundred microns. The mechanical properties of the as-cast Ti-22Al-25Nb alloy are investigated by tensile, compressive and nanoindentation tests at room temperature. The ultimate tensile strength of the as-cast Ti-22Al-25Nb O phase alloy and B2/? alloy reaches 1125 MPa and 1031 MPa respectively, with the elongation of 1.32% and 1.82%. The nanoindentation hardness of the as-cast Ti-22Al-25Nb O phase alloy is slightly higher than that of the as-cast B2/? phase alloy. The tensile fracture and compression fracture of as-cast Ti-22Al-25Nb alloy show obvious cleavage fracture characteristics. In addition, the tensile fracture is mainly intergranular, while the compression fracture is mainly transgranular.
2020, 49(11):3909-3913.
DOI: 10.12442/j.issn.1002-185X.20190994
Abstract:
The design, processing and fabrication of high energy density and power density solid tantalum capacitor anode blocks are the hotspots and difficulties in current research.In the experiment, the anode block of tantalum capacitor with gradient structure was fabricated by using the direct writing 3D printing technology of multi-material slurry.The preparation technology of anode block printing was studied, and the influences of size ratio, extrusion amount, layer spacing and printing speed on the forming effect were analyzed.The results showed that the slurry prepared with tantalum powder, binder PVA (polyvinyl alcohol) and solvent water (ratio: 7.5:1:5) had a printing speed of 3 mm/s, a gas pressure of 765 KPa, and a print pinhole inner diameter of 0.84. Mm, layer spacing of 0.5mm, through the model design, print slurry configuration, dual nozzle printing, wire insertion (welding), orthopedic, sintering and chemical conversion processes, the anode block shape with gradient structure is regular and uniform The shrinkage rate is between 9.7% and 14.5%, and the CV per unit mass is 53200μF.V/g, which is 15.6% higher than that of similar products, which basically meets the industrial production demand. This technology is a beneficial supplement to the existing processing and preparation technology, and is a useful exploration of the high power density and energy density electrolytic capacitor anode block preparation technology.
The design, processing and fabrication of high energy density and power density solid tantalum capacitor anode blocks are the hotspots and difficulties in current research.In the experiment, the anode block of tantalum capacitor with gradient structure was fabricated by using the direct writing 3D printing technology of multi-material slurry.The preparation technology of anode block printing was studied, and the influences of size ratio, extrusion amount, layer spacing and printing speed on the forming effect were analyzed.The results showed that the slurry prepared with tantalum powder, binder PVA (polyvinyl alcohol) and solvent water (ratio: 7.5:1:5) had a printing speed of 3 mm/s, a gas pressure of 765 KPa, and a print pinhole inner diameter of 0.84. Mm, layer spacing of 0.5mm, through the model design, print slurry configuration, dual nozzle printing, wire insertion (welding), orthopedic, sintering and chemical conversion processes, the anode block shape with gradient structure is regular and uniform The shrinkage rate is between 9.7% and 14.5%, and the CV per unit mass is 53200μF.V/g, which is 15.6% higher than that of similar products, which basically meets the industrial production demand. This technology is a beneficial supplement to the existing processing and preparation technology, and is a useful exploration of the high power density and energy density electrolytic capacitor anode block preparation technology.
2020, 49(11):3914-3918.
DOI: 10.12442/j.issn.1002-185X.20190998
Abstract:
One-dimensional multi-segment Co-CdSe metal-semiconductor heterojunction nanowires were alternately deposited by direct current electrodeposition in a two-cell system of Co electrolyte and CdSe electrolyte using porous anodized aluminum template assisted method. The morphology, structure, magnetic and optical properties of the heterojunction nanowires were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), vibrating sample magnetometer (VSM), UV-visible spectrophotometer (UV-Vis) and photoluminescence spectroscopy (PL). The results show that the Co-CdSe heterojunction nanowires are well layered and exist in a face-centered cubic structure. The Co-CdSe heterojunction nanowires have the same magnetic coercivity as the elemental metal Co nanowires, and simultaneously, the heterojunction nanowires exhibit the excellent optical properties.
One-dimensional multi-segment Co-CdSe metal-semiconductor heterojunction nanowires were alternately deposited by direct current electrodeposition in a two-cell system of Co electrolyte and CdSe electrolyte using porous anodized aluminum template assisted method. The morphology, structure, magnetic and optical properties of the heterojunction nanowires were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), vibrating sample magnetometer (VSM), UV-visible spectrophotometer (UV-Vis) and photoluminescence spectroscopy (PL). The results show that the Co-CdSe heterojunction nanowires are well layered and exist in a face-centered cubic structure. The Co-CdSe heterojunction nanowires have the same magnetic coercivity as the elemental metal Co nanowires, and simultaneously, the heterojunction nanowires exhibit the excellent optical properties.
2020, 49(11):3919-3924.
DOI: 10.12442/j.issn.1002-185X.20191001
Abstract:
Ti-48Al and Ti-48Al-2Cr-2Nb alloys were fabricated by in-situ alloying assisted double-wire arc additive manufacturing. The microstructure and properties of the two alloys were characterized by XRD, OM, SEM, micro mechanical tensile test and high temperature oxidation test. The results showed that both of these two deposited alloys showed quite uniform components and composed of γ-TiAl and α2-Ti3Al. The addition of tracing Cr and Nb showed no significant effect on microstructure. Micro tensile testing showed that ultimate strength elevated after the addition of Cr and Nb yet no significant effect to plasticity. High temperature oxidation resistance test confirmed that Ti-48Al-2Cr-2Nb has a good resistance to oxidation compared to Ti-48Al. The final weight gain of the sample decreased from 5.26mg /cm2 to 1.95mg /cm2.
Ti-48Al and Ti-48Al-2Cr-2Nb alloys were fabricated by in-situ alloying assisted double-wire arc additive manufacturing. The microstructure and properties of the two alloys were characterized by XRD, OM, SEM, micro mechanical tensile test and high temperature oxidation test. The results showed that both of these two deposited alloys showed quite uniform components and composed of γ-TiAl and α2-Ti3Al. The addition of tracing Cr and Nb showed no significant effect on microstructure. Micro tensile testing showed that ultimate strength elevated after the addition of Cr and Nb yet no significant effect to plasticity. High temperature oxidation resistance test confirmed that Ti-48Al-2Cr-2Nb has a good resistance to oxidation compared to Ti-48Al. The final weight gain of the sample decreased from 5.26mg /cm2 to 1.95mg /cm2.
2020, 49(11):3925-3931.
DOI: 10.12442/j.issn.1002-185X.20191004
Abstract:
Biomedical Ti-25Ta-3Ag alloys were prepared via spark plasma sintering (SPS). The microstructure, morphology and phases of the alloy were characterized by XRD and SEM. The effects of sintering temperature on the electrochemical corrosion properties were investigated in artificial simulated body fluid (Hank"s solution) by open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that there are α phase (irregular polygon), martensite α" phase (needle) and β phase (platelets) in the sinter of Ti-25Ta-3Ag, and the elemental Ag (white particle) precipitation at the grain boundary. Electrochemical experiments show that the corrosion resistance of the alloy is improved with the increasing of sintering temperature. The main factors of the excellent corrosion resistance of the alloy in artificial simulated body fluids was owing to Ag addition in the alloy which improves the corrosion potential as well as Ag precipitates at the grain boundary due to the high corrosion resistance of Ag, so that the grain boundary was less prone to corrosion. On the other hand, the passivation film formed on the surface of the alloy which consists of TiO2 and Ta2O5 oxides and low ionic oxides of Ti and Ta as well as metal Ag precipitations, the stability and protection of were enforced.
Biomedical Ti-25Ta-3Ag alloys were prepared via spark plasma sintering (SPS). The microstructure, morphology and phases of the alloy were characterized by XRD and SEM. The effects of sintering temperature on the electrochemical corrosion properties were investigated in artificial simulated body fluid (Hank"s solution) by open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that there are α phase (irregular polygon), martensite α" phase (needle) and β phase (platelets) in the sinter of Ti-25Ta-3Ag, and the elemental Ag (white particle) precipitation at the grain boundary. Electrochemical experiments show that the corrosion resistance of the alloy is improved with the increasing of sintering temperature. The main factors of the excellent corrosion resistance of the alloy in artificial simulated body fluids was owing to Ag addition in the alloy which improves the corrosion potential as well as Ag precipitates at the grain boundary due to the high corrosion resistance of Ag, so that the grain boundary was less prone to corrosion. On the other hand, the passivation film formed on the surface of the alloy which consists of TiO2 and Ta2O5 oxides and low ionic oxides of Ti and Ta as well as metal Ag precipitations, the stability and protection of were enforced.
YU Wenzhen
,
HUANG He
,
WANG Zhanlei
,
YAN Jun
,
YE Xiaoqiu
,
WANG Xuefeng
,
Luo Linling
,
FENG Chunrong
,
LI Bingqing
,
RAO Yongchu
,
XIAO Yao
2020, 49(11):3932-3937.
DOI: 10.12442/j.issn.1002-185X.20191006
Abstract:
Tungsten is the material of choice for the first wall of magnetically constrained thermonuclear fusion reactors. The retention and effective removal of hydrogen isotopes in tungsten-based materials is of great significance for the damage assessment of materials under the conditions of fusion reactors and the placement of hydrogen isotope fuels. In order to eliminate the influence of the geometrical factors of bulk tungsten in the study of hydrogen isotope retention and effective removal, the work of hydrogen isotope retention and effective removal was carried out in this work, using thermal desorption and isotope exchange. By using these two methods, the deuterium retained in powder tungsten has been removed, and the residual amount, desorption characteristic peak and solid solubility of the tungsten powder in the two methods were obtained. The results show that the two removal methods have obvious removal effects on the three types of lanthanum residing in tungsten powder; the time and conditions for the two removal methods to reach equilibrium are different; the isotope exchange is more effective than the thermal desorption. However, its operation is more difficult, and the thermal desorption method has a greater advantage.
Tungsten is the material of choice for the first wall of magnetically constrained thermonuclear fusion reactors. The retention and effective removal of hydrogen isotopes in tungsten-based materials is of great significance for the damage assessment of materials under the conditions of fusion reactors and the placement of hydrogen isotope fuels. In order to eliminate the influence of the geometrical factors of bulk tungsten in the study of hydrogen isotope retention and effective removal, the work of hydrogen isotope retention and effective removal was carried out in this work, using thermal desorption and isotope exchange. By using these two methods, the deuterium retained in powder tungsten has been removed, and the residual amount, desorption characteristic peak and solid solubility of the tungsten powder in the two methods were obtained. The results show that the two removal methods have obvious removal effects on the three types of lanthanum residing in tungsten powder; the time and conditions for the two removal methods to reach equilibrium are different; the isotope exchange is more effective than the thermal desorption. However, its operation is more difficult, and the thermal desorption method has a greater advantage.
Li Zhiping
,
Luo Liangshun
,
Sun Xiongkai
,
Yang Huimin
,
Liu Tong
,
Wang Liang
,
Zhang Donghui
,
Su Yanqing
,
Guo Jingjie
,
Fu Hengzhi
2020, 49(11):3938-3942.
DOI: 10.12442/j.issn.1002-185X.20191007
Abstract:
In this paper, the ingots of TNM alloy(Ti-44Al-4Nb-1Mo-0.1B at.%) were obtained using a non-consumable electric arc melting furnace. As-cast microstructure of TNM alloy was investigated. Liquid metal cooling Bridgman-type apparatus was employed in the heat stabilization experiment of TNM alloy and the effect of thermal stabilization time on the mushy zone of TNM alloy during directional solidification has been investigated. The results show the as-cast microstructure of TNM alloy consists of a major of (α2+γ) lamellar colonies, network-like B2 phase, small γ phase and boride located at the interface of colonies. With the thermal stabilization time increasing, the solid/liquid interface will come to a planar one and the field of temperature and solute in the melt in front of solid/liquid interface will become more homogenous in thermal stabilization test. However, overmuch thermal stabilization time will make the melt contaminated by the crucible. The study shows the thermal stabilization time of 30~60 min is sufficient to provide a planar starting interface for directional solidification. Thermal stabilization affects the distribution of Al in solid and liquid phases near the solid/liquid interface of TNM alloy, and further affects the distribution of borides.
In this paper, the ingots of TNM alloy(Ti-44Al-4Nb-1Mo-0.1B at.%) were obtained using a non-consumable electric arc melting furnace. As-cast microstructure of TNM alloy was investigated. Liquid metal cooling Bridgman-type apparatus was employed in the heat stabilization experiment of TNM alloy and the effect of thermal stabilization time on the mushy zone of TNM alloy during directional solidification has been investigated. The results show the as-cast microstructure of TNM alloy consists of a major of (α2+γ) lamellar colonies, network-like B2 phase, small γ phase and boride located at the interface of colonies. With the thermal stabilization time increasing, the solid/liquid interface will come to a planar one and the field of temperature and solute in the melt in front of solid/liquid interface will become more homogenous in thermal stabilization test. However, overmuch thermal stabilization time will make the melt contaminated by the crucible. The study shows the thermal stabilization time of 30~60 min is sufficient to provide a planar starting interface for directional solidification. Thermal stabilization affects the distribution of Al in solid and liquid phases near the solid/liquid interface of TNM alloy, and further affects the distribution of borides.
2020, 49(11):3943-3949.
DOI: 10.12442/j.issn.1002-185X.20191013
Abstract:
A high Mg-content Al-Si-Mg3 aluminium alloy was designed for SLM based on the technical characteristics of the liquid quenching in SLM. The effect of the process parameters and aging treatment on the microstructure and the hardness of the SLM-formed AlSiMg1.5 alloy were systematically studied. The results show that all SLM-formed samples are composed of α-Al, Si and Mg2Si phases. High laser energy density is beneficial to increase the formability of the samples. The minimum porosity ~ 0.07% is obtained for the sample fabrication at a laser power of 160 W with a scanning speed of 200 mm/s. The Mg element dissolved in α-Al and the proportion of Si-rich microstructures increases with the increase of the scanning speed, as a result, the hardness of the SLM-formed samples increases gradually. The maximum hardness of the SLM-formed sample reaches 194±3 HV. The hardness increases obviously after aging treatment the SLM-formed samples at 150 ℃ for different times due to the precipitation of nanoparticles. The maximum hardness of the samples is 210 ± 2 HV, which is much higher than the reported SLM-formed Al-Si and Al-Si-Mg alloys. A special Al-Si-Mg alloy for SLM with excellent formability and mechanical properties was reported in this paper.
A high Mg-content Al-Si-Mg3 aluminium alloy was designed for SLM based on the technical characteristics of the liquid quenching in SLM. The effect of the process parameters and aging treatment on the microstructure and the hardness of the SLM-formed AlSiMg1.5 alloy were systematically studied. The results show that all SLM-formed samples are composed of α-Al, Si and Mg2Si phases. High laser energy density is beneficial to increase the formability of the samples. The minimum porosity ~ 0.07% is obtained for the sample fabrication at a laser power of 160 W with a scanning speed of 200 mm/s. The Mg element dissolved in α-Al and the proportion of Si-rich microstructures increases with the increase of the scanning speed, as a result, the hardness of the SLM-formed samples increases gradually. The maximum hardness of the SLM-formed sample reaches 194±3 HV. The hardness increases obviously after aging treatment the SLM-formed samples at 150 ℃ for different times due to the precipitation of nanoparticles. The maximum hardness of the samples is 210 ± 2 HV, which is much higher than the reported SLM-formed Al-Si and Al-Si-Mg alloys. A special Al-Si-Mg alloy for SLM with excellent formability and mechanical properties was reported in this paper.
2020, 49(11):3950-3956.
DOI: 10.12442/j.issn.1002-185X.20191023
Abstract:
WC–Ni–Fe–Mo cemented carbides with fine properties were prepared by low pressure sintering. The effects of Mo content on the microstructure and properties of WC–Ni–Fe–Mo cemented carbides were analyzed in detail. The results show that the addition of Mo has obvious influence on WC–Ni–Fe cemented carbides. The addition of Mo can refine WC grains to a certain extent by inhibiting the dissolution and precipitation of WC grains in WC–Ni–Fe cemented carbides. With the increase of the of Mo content, the porosity of the alloys decrease gradually. The density of alloys first decreased and then increased, while the bending strength had the opposite trend. When a trace amount of Mo was added, the hardness of alloys was relatively stable, ?the bending strength increased obviously，the fracture toughness had a gradually decreased. When the addition of Mo contents further increased, the hardness and bending strength were both decreased, and the fracture toughness increased. WC–Ni–Fe–Mo cemented carbide with 0.5 wt% Mo had the optimum properties, which can comparable to those of WC–Co cemented carbides with the identical binder ratio. The maximum value of its hardness, bending strength and fracture toughness were HV 1460, 4245 MPa, 17.01 MPa·m1/2, respectively.
WC–Ni–Fe–Mo cemented carbides with fine properties were prepared by low pressure sintering. The effects of Mo content on the microstructure and properties of WC–Ni–Fe–Mo cemented carbides were analyzed in detail. The results show that the addition of Mo has obvious influence on WC–Ni–Fe cemented carbides. The addition of Mo can refine WC grains to a certain extent by inhibiting the dissolution and precipitation of WC grains in WC–Ni–Fe cemented carbides. With the increase of the of Mo content, the porosity of the alloys decrease gradually. The density of alloys first decreased and then increased, while the bending strength had the opposite trend. When a trace amount of Mo was added, the hardness of alloys was relatively stable, ?the bending strength increased obviously，the fracture toughness had a gradually decreased. When the addition of Mo contents further increased, the hardness and bending strength were both decreased, and the fracture toughness increased. WC–Ni–Fe–Mo cemented carbide with 0.5 wt% Mo had the optimum properties, which can comparable to those of WC–Co cemented carbides with the identical binder ratio. The maximum value of its hardness, bending strength and fracture toughness were HV 1460, 4245 MPa, 17.01 MPa·m1/2, respectively.
2020, 49(11):3957-3961.
DOI: 10.12442/j.issn.1002-185X.20191024
Abstract:
The study focuses on preparation technology of tungsten based heavy alloy (WHA). By adding trace element into traditional raw material, carrying out compositon explonation of large-scaled WHA product. 93WNiFe was chosen and multi-step sintering was adopted for the alloy preparation. By means of surpervisor control product size in sintering process and sampling for mechanical performance analysis, internal organization evolution law was investigated. The final part is weight 4 tons, with maximum diameter 700 mm and maximum height of 1400 mm, and sampling for each part, the product tensile strength is greater than 920 Mpa, elongation more than 20%.
The study focuses on preparation technology of tungsten based heavy alloy (WHA). By adding trace element into traditional raw material, carrying out compositon explonation of large-scaled WHA product. 93WNiFe was chosen and multi-step sintering was adopted for the alloy preparation. By means of surpervisor control product size in sintering process and sampling for mechanical performance analysis, internal organization evolution law was investigated. The final part is weight 4 tons, with maximum diameter 700 mm and maximum height of 1400 mm, and sampling for each part, the product tensile strength is greater than 920 Mpa, elongation more than 20%.
2020, 49(11):3962-3968.
DOI: 10.12442/j.issn.1002-185X.20191031
Abstract:
In this paper, hollow ammonium paramolybdate precursor microspheres were prepared from ammonium paramolybdate solution by spray drying, and they were calcined and reduced to square or spherical molybdenum. It was characterized that the morphology of the ammonium paramolybdate precursor microspheres, and the morphology and composition were studied after calcination and reduction of ammonium paramolybdate precursor microspheres. The effects of reduction temperature, heating process and atmosphere on the reduction of ammonium paramolybdate precursor microspheres were also investigated. Consequently, as the concentratione of solution increase, the particle size range of microspheres become bigger, pits in the surface increase, and the agglomeration phenomenon becomes more obvious; with the increase of feed rate, the particle size range of microspheres decreased a little, and pits in the surface decrease; with the increase of spray drying temperature, the particle size range first increase and then decrease, while pits in the surface increase evidently; at the temperature of 800℃，the square or near spherical molybdenum can be obtained by hydrogen-argon mixer reduction, while the spherical molybdenum can be obtained by pure hydrogen reduction.
In this paper, hollow ammonium paramolybdate precursor microspheres were prepared from ammonium paramolybdate solution by spray drying, and they were calcined and reduced to square or spherical molybdenum. It was characterized that the morphology of the ammonium paramolybdate precursor microspheres, and the morphology and composition were studied after calcination and reduction of ammonium paramolybdate precursor microspheres. The effects of reduction temperature, heating process and atmosphere on the reduction of ammonium paramolybdate precursor microspheres were also investigated. Consequently, as the concentratione of solution increase, the particle size range of microspheres become bigger, pits in the surface increase, and the agglomeration phenomenon becomes more obvious; with the increase of feed rate, the particle size range of microspheres decreased a little, and pits in the surface decrease; with the increase of spray drying temperature, the particle size range first increase and then decrease, while pits in the surface increase evidently; at the temperature of 800℃，the square or near spherical molybdenum can be obtained by hydrogen-argon mixer reduction, while the spherical molybdenum can be obtained by pure hydrogen reduction.
2020, 49(11):3969-3976.
DOI: 10.12442/j.issn.1002-185X.20191041
Abstract:
Wire and Arc Additive manufacturing (WAAM) of 2219 aluminum alloy parts is a prospective manufacturing technology in the aerospace industry. In this study, the single wall specimens of 2219 aluminum alloy were built by WAAM technology using CMT welding process. The microstructure characteristics in as deposited state, solid solution state and artificial aging state were systematically investigated. It was found that the weakness strip with more micro porosities, θ(Al2Cu) phases and iron rich phases in the interlayer region resulted in the anisotrpic mechanical properties of the WAAM specimens. When the specimens were tensioned in the vertical direction, cracks formed easily in the interlayer region, and deteriorated the tensile strength and plasticity. In order to increase the mechanical properties of the WAAM 2219 aluminum alloy in the vertical direction, the composition of Fe and Si in the wire should be as low as possible.
Wire and Arc Additive manufacturing (WAAM) of 2219 aluminum alloy parts is a prospective manufacturing technology in the aerospace industry. In this study, the single wall specimens of 2219 aluminum alloy were built by WAAM technology using CMT welding process. The microstructure characteristics in as deposited state, solid solution state and artificial aging state were systematically investigated. It was found that the weakness strip with more micro porosities, θ(Al2Cu) phases and iron rich phases in the interlayer region resulted in the anisotrpic mechanical properties of the WAAM specimens. When the specimens were tensioned in the vertical direction, cracks formed easily in the interlayer region, and deteriorated the tensile strength and plasticity. In order to increase the mechanical properties of the WAAM 2219 aluminum alloy in the vertical direction, the composition of Fe and Si in the wire should be as low as possible.
2020, 49(11):3977-3986.
DOI: 10.12442/j.issn.1002-185X.20190990
Abstract:
The design and preparation of ORR electrocatalysts with low cost, high catalytic activity and high stability are of crucial importance to the practical application of fuel cells. Carbon aerogels (CAs) have the advantages of controllable pore structure, high specific surface area, high conductivity and large pore volume, and these characters allow it a potential candidate for fuel cell ORR electrocatalyst carrier. In this review, the recent progress on CAs as fuel cell catalyst carrier were reviewed. Firstly, the species of carbon aerogels and methods of supporting catalysts were simplely introduced, and then the research progress on precious metal catalysts supported on CA, especially Pt, the non-noble metal catalysts supported on CA and non-metal doping CA catalysts were discussed. In addition, the challenges and development direction in the future were summarized.
The design and preparation of ORR electrocatalysts with low cost, high catalytic activity and high stability are of crucial importance to the practical application of fuel cells. Carbon aerogels (CAs) have the advantages of controllable pore structure, high specific surface area, high conductivity and large pore volume, and these characters allow it a potential candidate for fuel cell ORR electrocatalyst carrier. In this review, the recent progress on CAs as fuel cell catalyst carrier were reviewed. Firstly, the species of carbon aerogels and methods of supporting catalysts were simplely introduced, and then the research progress on precious metal catalysts supported on CA, especially Pt, the non-noble metal catalysts supported on CA and non-metal doping CA catalysts were discussed. In addition, the challenges and development direction in the future were summarized.
2020, 49(11):3987-3997.
DOI: 10.12442/j.issn.1002-185X.20200241
Abstract:
Graphene, a one-atom-thick layer of carbon with sp2 hybrid orbital bonding and two-dimensional structure material ，has excellent electrical, mechanical, and optical properties. With its extraordinary structure and excellent properties，graphene has great application potential in many fields such as semiconductors, electronics, optics, and sensors. While graphene can be prepared by direct exfoliation from mother materials or growth on transition metals, the uncontrolled production or the additional complex transfer process has been challenging for graphene applications, therefore the direct preparation of graphene on the dielectric substrate by CVD has become an interesting research direction. This paper reviews the research progress of direct preparation of graphene by CVD on dielectric substrates surface at home and abroad, systematically introduces the main methods of direct preparation of graphene on dielectric material surface, and expounds that the catalytic conditions and growth parameters during the growth process are the key to the preparation of graphene on dielectric substrates. In addition, due to the weak catalysis on the surface of dielectric materials, the direct preparation of graphene on the surface has small domain size and poor electrical properties. Therefore, the realization of high quality and controllable preparation of graphene on the surface of dielectric materials is the future research direction.
Graphene, a one-atom-thick layer of carbon with sp2 hybrid orbital bonding and two-dimensional structure material ，has excellent electrical, mechanical, and optical properties. With its extraordinary structure and excellent properties，graphene has great application potential in many fields such as semiconductors, electronics, optics, and sensors. While graphene can be prepared by direct exfoliation from mother materials or growth on transition metals, the uncontrolled production or the additional complex transfer process has been challenging for graphene applications, therefore the direct preparation of graphene on the dielectric substrate by CVD has become an interesting research direction. This paper reviews the research progress of direct preparation of graphene by CVD on dielectric substrates surface at home and abroad, systematically introduces the main methods of direct preparation of graphene on dielectric material surface, and expounds that the catalytic conditions and growth parameters during the growth process are the key to the preparation of graphene on dielectric substrates. In addition, due to the weak catalysis on the surface of dielectric materials, the direct preparation of graphene on the surface has small domain size and poor electrical properties. Therefore, the realization of high quality and controllable preparation of graphene on the surface of dielectric materials is the future research direction.
2020, 49(11):3998-4004.
DOI: 10.12442/j.issn.1002-185X.20190959
Abstract:
With the rapid development of electric vehicle industry, the safety and fast charging of lithium ion batteries have attracted more and more attention. Graphite, as commercial anode material for lithium-ion batteries, has a great potential safety hazard of internal short-circuit caused by the lithium plating due to the low intercalationSpotential (~0 V), and is not suitable for fast charging batteries. LiEuTiO4 with a layered perovskite structure has intercalationSpotential of about 0.8 V and actual capacity of over 200 mAh/g, which can avoid the occurrence of lithium plating and will keep high energy density and rate performance, thus hopefully become the ideal anode for safe fast-charging power battery for electric vehicles. In this paper, the current research status of LiEuTiO4 is summarized, including molecular structure, lithium-storage mechanism, preparation method and problems to be solved, etc.
With the rapid development of electric vehicle industry, the safety and fast charging of lithium ion batteries have attracted more and more attention. Graphite, as commercial anode material for lithium-ion batteries, has a great potential safety hazard of internal short-circuit caused by the lithium plating due to the low intercalationSpotential (~0 V), and is not suitable for fast charging batteries. LiEuTiO4 with a layered perovskite structure has intercalationSpotential of about 0.8 V and actual capacity of over 200 mAh/g, which can avoid the occurrence of lithium plating and will keep high energy density and rate performance, thus hopefully become the ideal anode for safe fast-charging power battery for electric vehicles. In this paper, the current research status of LiEuTiO4 is summarized, including molecular structure, lithium-storage mechanism, preparation method and problems to be solved, etc.
