Abstract:Eight shape parameters were selected to qualitatively and quantitatively characterize the particle shape of superalloy powders using field emission scanning electron microscopy (FE-SEM) and dynamic image analysis (DIA) technique. The results show that Krumbein sphericity (SPHT_K), aspect ratio (AR), compactness (Compct) and Krumbein roundness (RDNS_C) demonstrate a significant distinction degree of superalloy powder particle shape, and can be used as critical parameters for the characterization of particle shape.In addition, the distinction degree of circularity (C), sphericity (SPHT) and SPHT_K increases gradually. In particular, the SPHT_K has the highest distinction degree among the three shape parameters. By comparing the difference in distinction degree among eight shape parameters, it is found that the distinction degree of circularity (C), sphericity (SPHT), convexity (Conv_A) and solidity (Solid) is not significant.Therefore, the SPHT_K, AR, Compct and RDNS_C are selected as the shape parameter combination to quantitatively characterize the particle shape. The combination of these four shape parameters can be used to quantitatively characterize the change of superalloy powder particle shape. Meanwhile, it provides a data basis to effectively optimize the atomization processing parameters. The promotion of the development of additive manufacturing and advanced powder metallurgy technology in future was discussed in the end.

Abstract:Hot deformation behavior of powder metallurgical high tungsten alloy steel was investigated by Gleeble thermal simulator in a temperature range of 900~1100 °C and a strain rate range of 0.001~1 s^-1. The results show that the flow stress decreases with the decrease of strain rate and the increase of deformation temperature. A constitutive equation is derived with Arrhenius hyperbolic sine function, and a processing map is constructed. The activation energy is 377 kJ/mol. The suitable processing regions are 1000~1100 °C/0.001~0.01 s^-1. The precipitation of tungsten-rich μ phase occurs during hot deformation process. Microvoids and micro-cracks form in the bulging region of the specimen. The amount of microvoid increases with the increase of strain rate and the decrease of temperature. The μ phase precipitation improves the high temperature strength of the steel.

Abstract:The effects of rotational speed on the intermetallic compounds and low melting point eutectic of Al/Mg friction stir welded joints were investigated. The interfacial microstructures of both Al and Mg sides were characterized by electron backscatter diffraction. The results show that when the low rotational speed of 375 r/min is used, the eutectic layer (Mg+Al₁₂Mg₁₇), with an average thickness of 38.83 μm, appears at the upper of the Mg side interface. A continuous columnar Al₃Mg₂ layer with a thickness of 12.3 μm, perpendicular to the boundary between the Al₃Mg₂ layer and eutectic layer, is also found at the upper of the Mg side interface. At the middle and bottom of the Mg side interface, there are merely Al₃Mg₂ layer and Al₁₂Mg₁₇ layer, the thickness of which decreases sequentially from the upper to the bottom along the thickness direction. In addition, the Al₃Mg₂ layer with high kernel average misorientation at the Al and Mg side interface provides a path for the diffusion of Al and Mg atoms. When the high rotational speed of 600 r/min is used, the eutectic layer composed of Mg solid solution and Al₁₂Mg₁₇ phase is distributed across the Mg side interface along the thickness direction, and the thickness of the eutectic layer increases significantly compared with that at the low rotational speed of 375 r/min. The average thickness of the Al₃Mg₂ layer and eutectic layer on the upper of the Mg side interface is 32.89 and 68.92 μm, respectively. Finally, the strain rate caused by rotational speed plays an important role in the growth of intermetallic compounds.

Abstract:The hot deformation behavior of explosive welded titanium-aluminum (Ti-Al) clad plate was studied by isothermal compression tests at 300~500 °C with strain rates of 0.1~10 s^-1 on Gleeble 3500 simulated machine. The hot processing map was developed on the basis of experimental data using the principles of dynamic materials model, and the verification experiment of hot rolling process of Ti-Al clad plate was carried out based on the hot processing map. The results show that Ti-Al clad plate is a kind of positive strain rate sensitive material. The efficiency of power dissipation of 0.64~0.72 can be observed at 420~460 °C with strain rate of 1.6~6.3 s^-1 in the hot processing map, and the process parameters of this region are suitable for the hot rolling of Ti-Al clad plate. After hot rolling, the interfaces of the Ti-Al clad plates are well bonded, and the plates have excellent mechanical property and good sheet metal forming property. The deformation mechanism of Ti-Al clad plate in the hot rolling process is as follows: the Al layer with low deformation resistance and fast flow can produce plastic deformation, and at the same time it can pull the Ti layer together to produce plastic deformation; in this process, the Al layer is hot deformation while the Ti layer is cold deformation.

Abstract:Aiming at solving the problem of poor strength, low conductivity and thermal conductivity of Cu-W alloys, high pressure aging treatment was conducted to reinforce Cu-51.15W-0.24Cr alloy. The microstructure, hardness, thermal conductivity and conductivity of the alloy after high pressure aging treatment and normal pressure aging treatment were compared. The results show that high pressure aging treatment can increase the compactness of Cu48.61W51.15Cr0.24 alloy, eventually resulting in more dispersed distribution and finer grain size of Cr phase during the aging treatment, and improving the hardness and thermal conductivity of the alloy. After solution treatment at 960 °C for 1 h and aging at 500 °C for 1 h under a pressure of 3 GPa, the hardness, thermal diffusivity and resistivity are determined to be 1540 MPa, 0.5236 cm²·s^-1 and 4.458×10^-8 Ω·m, respectively, which are 17.56% and 10.74% higher than and 4.85% lower than those of alloy under normal pressure, respectively. Therefore, high pressure aging treatment can be an effective way to improve mechanical properties and to reduce resistivity of Cu-51.15W-0.24Cr alloy.

Abstract:A high-efficiency and green physical method was proposed to clean the surface of NdFeB waste magnets for recycling. NdFeB regenerated magnets were fabricated by adding low-melting point Ho_63.3Fe_36.7 alloy to grain boundaries. Results show that in magnets without Ho_63.3Fe_36.7, there are insufficient Nd-rich phases to isolate the Nd₂Fe₁₄B phase, leading to poor magnet performance. With the addition of Ho_63.3Fe_36.7 alloy, the grain boundary phases become clear and concatenated. Optimal magnetic energy [(BH) _max+H_cj=1756.07] can be obtained by adding 2wt% Ho_63.3Fe_36.7 to the magnet. Further, the coercivity increases by 123 kA/m (approximately 9.1%), the maximum magnetic energy product decreases from 290.94 kJ/m³ to 281.07 kJ/m³, and remanence decreases slightly. Through analysis of the microstructure and composition, it can be seen that the (Nd, Pr, Ho)₂Fe₁₄B shell layers form at the grain boundary, which enhances the coercivity of the magnet. X-ray diffraction analysis suggests that the diffraction peak intensity ratio of magnet I₍₀₀₆₎/I₍₁₀₅₎ increases from 0.92 to 1.32, which indicates that the alignment degree is improved and the influence on remanence is weakened. Therefore, regenerated magnets can possess improved coercivity while maintaining magnetic remanence.

Abstract:CaF₂, NaF and Na₂SiF₆ were chosen as activating fluxes for laser welding of Ti6Al4V (TC4) alloy. During the welding process, the laser-induced plasma images above the weldment were captured with a high-speed camera. After welding, the weld penetration and the width of the weld were measured and the microstructure was observed by an optical microscope. Then, the morphology of acicular martensite in the weld was studied by EBSD, and the element composition of the weld was determined by energy spectrometer. The hardness and tensile strength of the joints were tested. The results show that the activating fluxes change the surface state of the weldment and compress the laser-induced plasma area, thereby increasing the laser absorptivity and the area of the weld melting zone. Besides, all the activating fluxes can increase the penetration depth and reduce the top weld width of the partial penetration weld, and reduce the top weld width while increase the middle and bottom weld widths of the penetration weld. It is also found that for the welds coated with CaF₂, NaF and without activating fluxes, the β columnar crystals on the upper part of the welds all grow towards the weld surface, while for the welds coated with Na₂SiF₆, the β columnar crystals on the upper part of the welds grow towards the weld center. The activating fluxes have no obvious effect on the growing direction of the β columnar crystals of the lower part of the weld. Na₂SiF₆ can significantly refine the acicular α′ in the β columnar crystals of the upper part of the welds in the laser welding of TC4 alloy. The tensile strength of the welded joint coated with Na₂SiF₆ is increased by 12.5%. Compared with other activating fluxes, Na₂SiF₆ has the most prominent effect on the weld formation and mechanical property of the laser welded TC4 titanium alloy, and thus it can be used as the most preferred activating flux.

Abstract:The effect of vanadium (V) content on the microstructure, phase transformation behavior, and microhardness of the as-cast equiatomic NiTi shape memory alloy was investigated by optical microscope (OM), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Vickers microhardness tester. Results indicate that the as-cast Ni_50-x/2Ti_50-x/2V_x alloys with equiaxed grains consist mainly of B19' and Ti₂Ni phases when V content is 0.5at%, above which Ni_50-x/2Ti_50-x/2V_x (x=1.5~3.5, at%) alloys exhibit a three-phase structure consisting of B19', Ti₂Ni and V-rich phases, and the V-rich phases are more segregated at grain boundaries with the increase of V content. Further analysis reveals that both Ni_49.75Ti_49.75V_0.5 and Ni_49.25Ti_49.25V_1.5 alloys show a one-stage B2?B19' transformation. However, a two-stage B2?R?B19' transformation occurs in Ni_48.75Ti_48.75V_2.5 and Ni_48.25Ti_48.25V_3.5 alloys although R-phase transformation partially overlaps B19' martensitic transformation upon cooling. The transformation temperatures drop down with increasing the V content, which is attributed to the increase of Ni/Ti ratio in the matrix. In addition, as V element increases from 0.5at% to 3.5at%, the microhardness of the alloys first decreases and then remains almost unchanged.

Abstract:The formation of weld seams in the rectangular section of continuously extruded copper tubes with unequal wall thickness was investigated via optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and universal electronic tensile testing machine. Results show that the weld seams are formed by the confluence of two fine grain belts with a grain size of 13.1~53.4 μm. As the continuous extrusion proceeds, the fine grains gradually grow to the similar grain size (100~200 μm) of the base material. Secondary grain refinement occurs as the fine grains pass through the compression zone of the die. Afterward, micropores in the welded interface disappear. Dynamic recrystallization occurs during continuous extrusion welding. The interface between the two metal is broken through dislocation migration, and new grains form. The bonding strength of the weld seams dramatically increases along the flow direction of the metal. The bonding strength increases from 63 MPa in the initial confluence area to 212 MPa at the outlet of the die, which achieves 98.1% of that of the weld seam-free zone. The number and size of dimples in the fracture of the weld seams gradually and simultaneously increase. The elongation increases from 0.5% to 35%, reaching 70% of that of the weld seam-free zone.

Abstract:Mn-La catalysts were prepared by solid-state reaction (SSR) and co-precipitation methods (CPM). The effects of preparation methods on denitration and SO₂/H₂O resistance of the catalysts were investigated. The structure and physicochemical properties of the catalysts were characterized by XRD, BET, H₂-TPR, NH₃-TPD and XPS. The results show that La doping decreases the crystallinity of MnO_x and increases the specific surface area and pore volume of MnO_x. The bond cooperation of Mn-O-La promotes the dispersion of Mn on the catalyst surface, while the highly dispersed Mn are easier to be reduced. The reduction temperature of the catalyst moves to lower temperature, and the redox ability is improved. After La doping, the amount of Br?nsted acid and total acid increase on the catalyst surface, and the concentration of Mn⁴⁺ and the surface chemisorption oxygen also increase. Therefore, La doping is beneficial to the denitration activity of the catalyst. The results of reaction evaluation show that MnLa-CPM catalyst exhibits the best denitration efficiency, which is close to 100% at 80 °C. In the presence of H₂O and SO₂, the denitration efficiency of MnLa-CPM catalyst can still reach 80%, showing good SO₂/H₂O resistance performance.

Abstract:To extract vanadium efficiently from the acidic leachate of vanadium slag, a thermodynamic analysis of phosphorus-sulfur-vanadium-water acidic systems was established at 298 K. Results show that in the P(V)-V(V)-H₂O acidic system, VO₂⁺ is first conver-ted to phosphovanadic heteropolyacid ions when pH=1~4 and then converted to vanadium isopolyacid ions when pH=4~7. In the S(VI)-V(V)-H₂O acidic system, VO₂⁺ and VO₂SO₄^- are the main existing chemical forms when pH=0~1 and gradually converted to vanadium isopolyacid ions when pH=2~6. In the P(V)-S(VI)-V(V)-H₂O acidic system, when pH=1~3, VO₂⁺ and VO₂SO₄^- are gradua-lly converted to phosphovanadic heteropolyacid ions. The optimum molar fraction of ΣPV₁₄ (total sum of phosphovanadic heteropolyacid ions) reaches 88.55% at pH=2. As the pH value increases to 4~6, phosphovanadic heteropolyacid ion gradually disappears and is converted to vanadium isopolyacid anions, and the optimum molar fraction of ΣV₁₀ (total sum of vanadium isopolyacid ions containing ten vanadium) is 100.00% at pH=5.

Abstract:Ti(C_x,N_1-x)-based cermets are fabricated with different ratios of carbon to nitrogen. The effect of C/N ratio on the core-rim structures and properties of cermets was studied. The results indicate that Ti(C_0.5,N_0.5)-based cermets possess poor properties due to too many pores. With the increase of C/N ratio, the formation rate of white-core/gray-rims decreases, and the homogeneity of the microstructure is enhanced. Consequently, the Ti(C_0.7,N_0.3)-based cermets show excellent mechanical properties, but a spot of voids and low relative density. TiC-based cermets with excellent relative density and non-porosity can be achieved in the absence of N element, which have coarser grain compared with Ti(C_0.7,N_0.3)-based cermets. In order to achieve fine grains and high density microstructure, 0.25wt%Cr₃C₂-0.75wt%VC is introduced into the TiC-based cermets. Superior hardness, transverse rupture strength and toughness are achieved. In addition, 0.25wt%Cr₃C₂-0.75wt%VC is also added into the Ti(C_0.7,N_0.3)-based cermets, but its mechanical properties are lower than that of the Ti(C_0.7,N_0.3)-based cermets without 0.25wt%Cr₃C₂-0.75wt%VC addition, which is due to acute solid solution reaction of finer and reactive particles with Ti(C,N). The cutting and friction performances of Ti(C_x,N_1-x)-based cermets with different C/N ratios were also investigated. The results show that the TiC-based cermets with 0.25wt%Cr₃C₂-0.75wt%VC exhibit the lowest coefficient of friction which is 0.15 at the room temperature, and the longest service life during high speed cutting at 1000 r/min.

Abstract:The microstructure, immersion corrosion behaviour in simulated body fluid and mechanical properties of Zn-1.2Cu-1.2Mg-xGd (x=0, 0.1, 0.25, 0.5, wt%) alloys were studied. The results show that the microstructure of zinc alloy is mainly composed of Zn solid solution and Mg₂Zn₁₁ intermetallic compound. When Gd addition content is 0.5wt%, the GdZn₁₂ intermetallic compound appears. The microhardness of zinc alloy increases with the increase of Gd addition content, and when the addition content of Gd is 0.5wt%, the microhardness reaches maximum, 1530 MPa. The tensile strength increases first and decreases afterwards, and when the Gd addition content is 0.25wt%, the zinc alloy has high tensile strength. Zinc alloy with 0.1wt% Gd addition content has the lowest corrosion rate.

Abstract:Microstructure evolution of Ni-based superalloy GH202 after oxidation from 800 °C to 1100 °C was investigated. The results show that the hardness of GH202 decreases with the increase of oxidation temperature, and the hardness is decreased by 43.5% after oxidation at 1100 °C for 100 h. The growth rate of the grains after oxidation at 800 and 900 °C is slower and the grains increase slightly at 900 °C. The grain size increases significantly after oxidation at 1000 and 1100 °C, and many fine grains are annexed to form large grains due to grain boundary migration and elemental diffusion during the recrystallization at high temperatures for above 100 h. The big block carbides (MC) decompose into a large number of carbon atoms which combine with Cr atoms to form a few Cr-rich granular M₂₃C₆. After oxidation at 900 °C for 150 h, the M₂₃C₆ evolves into Ti-rich M₆C. With the increase of oxidation temperature, the carbides almost melt into γ phase. Moreover, the γ' phase gradually grows up after oxidation at 800, 900 and 1000 °C, and it is completely dissolved into the γ phase after oxidation at 1100 °C for 100 h.

Abstract:The equiaxed and lamellar microstructures of T-55511 alloy were obtained by different heat treatment routes. Microstructure evolution and mechanical properties of Ti-55511 alloy with equiaxed and lamellar microstructures during hot rolling and annealing were investigated by SEM, EBSD, TEM and tensile tests. The results show that equiaxed α phases are slightly deformed and β phase experiences dynamic recovery and dynamic recrystallization during 750 oC rolling; whereas lamellar α phase is nearly distributed in parallel, some of which are partly fragmentized, and β phase merely undergoes dynamic recovery. Texture intensity of α phase increases remarkably in lamellar structure but slightly in equiaxed structure, while texture intensity of β phase decreases both in equiaxed and lamellar structure. In addition, the anisotropy of equiaxed structure is small while that of lamellar structure is obvious. When the rolled lamellar structure is annealed at 600 °C, texture intensities of α and β phase both decrease and the anisotropy of mechanical properties significantly decreases.

Abstract:Corrosion resistance of rare earth permanent magnet material NdFeB was achieved by electrodeposited Cu-graphene (Cu-GR) composite films. The impact of the films on corrosion performances was studied by examining the morphology, water contact angle, and surface microhardness. The results show that the hydrophobicity and the hardness are enhanced as the concentration of graphene in the plating solution increases from 0 g·L^-1 to 0.9 g·L^-1. The characterization through SEM/EDS and XPS verifies the uniform dispersion of graphene sheets in the electrodeposited coating and the composition of Cu-GR composites. The electrochemical performance of the Cu-GR composite coating was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS), and it is demonstrated that the electrochemical performance becomes more stable and the corrosion resistance is improved with the addition of graphene in the composites. For the sintered NdFeB samples coated with Cu-GR composite films with different graphene concentrations the best protective effect is obtained for the film prepared from the plating solution with a graphene concentration of 0.3 g·L^-1.

Abstract:The evolution of microstructures of ZL201 sub-frame during casting was investigated. The processes of casting and cooling solidification were calculated by finite element and thermodynamic theory. The phase compositions were characterized by X-ray diffraction (XRD), and the microstructures were detected by optical microscope (OM) and scanning electron microscopy (SEM). The results show that the simulated results of casting and cooling process are consistent with the experiment. When the pressure is 0.4 MPa, the filling rate of ZL201 sub-frame is 98% and the filling time is 10 s. After heat treatment, the θ phases (Al₂Cu) dissolve into the Al matrix, and form homogeneous solid solution, which increases the grain size.

Abstract:The characteristics of (Re+Ir)-rich Re-Ir-Ni alloy films electroplated galvanostatically from citrate aqueous solutions with low pH of 2.0~2.5 were investigated. The effects of electroplating variables and bath chemistry on surface morphology, chemical composition and crystallographic structure of the films were studied. The morphology, composition and phase of the alloy films were characterized by environmental scanning electron microscopy, X-ray energy dispersive spectroscopy and X-ray diffraction, respectively. The results show that a dense and bright Re-Ir alloy file is obtained under the conditions of current density of 60 mA·cm^-2 and pH=2.0. Increasing temperature results in good quality of the alloys at pH=2.5, but at pH=2.0 the result is opposite. The films deposited at bath temperatures of 60~70 °C and pH=2.0 consist of amorphous phase. At bath temperature of 80 °C, the films consist of ReO₃ phase. At current density of 60 mA·cm^-2, the crystallographic structure of the film changes from an amorphous phase to a mixture of crystalline and amorphous phases when pH is increased from 2.0 to 2.5. The phases of crystalline are hcp-Ir_0.4Re_0.6 and hcp-Ni.

Abstract:The lamellar structure of Ti-15Mo alloy was obtained by solution aging treatment. The effect of strain rate on deformation mechanism was studied by split Hopkinson pressure bar (SHPB). Combined with adiabatic temperature rise, microstructure and hardness analysis, it was shown that the flow stress curve fluctuated due to the interaction between dislocation and the second phase. Increasing the strain rate, on the one hand, causes the strain rate to strengthen; On the other hand, it promotes adiabatic heating and softening. When the alloy temperature reaches 379k, the thermal softening effect exceeds the strain hardening effect, and the deformation mode changes from uniform plastic deformation to adiabatic shear deformation. The width of adiabatic shear band increases with the increase of shear strain, and equiaxed grains are produced by subcrystalline rotation recrystallization mechanism. The interface strengthening of recrystallization leads to the hardness from high to low: mixed tissue>strip tissue>matrix tissue. Aging treatment inhibits the twinning induced plasticity (TWIP) effect, resulting in lower strain hardening ability of the alloy and deteriorating the dynamic mechanical properties of the material.

Abstract:Explosively driven fragmentation of ductile metals cylinders is a highly complex phenomenon, which is involved to many kinds of competition and coupling of fracture modes and was of interest to researchers. In this paper, the fragmentation experiments of TA2 industrial pure titanium cylindrical shell with varying charge were carried out. Through the analysis of macroscopic fracture and microscopic metallographic for the recovered fragments, the fracture mode and mechanism explosively fragmentation of TA2 metal are discussed. As the results shown that: (1) Though all of the TA2 alloy fragments failure with shear mode in explosive-driven cylinders expansion tests, the failure mechanisms of shear mode is different for tests with different explosion pressures. It is observed that the shear failure caused by the evolution of micro-voids in tests with relatively low pressure but controlled by multiple adiabatic shear localization in tests with relatively high pressure. (2) The microscopic metallography shows that the dynamic phase transition of α→β may occur during the high-speed deformation of the TA2. It is shown that the microstructure of the inner surface is converted to lath martensite with a specific orientation and the resulted grain size is apparently larger than the as-received. Thus, it is necessary to consider the influence of the dynamic phase transition of material under shock waves when analyze the fracture characteristics and mechanisms of external explosive experiments. This work can provide a significant reference to the analysis of multiple failure modes of cylinders under external explosion loading conditions.

Abstract:Pure tungsten and solid solution strengthened W-Nb alloy were fabricated by selective electron beam melting (SEBM). The microstructure and crack were analyzed. Results showed that columnar crystal structure along the building direction of SEBM formed both in the pure tungsten and W-Nb alloy. The addition of Nb reduced the average size of columnar crystals from 109.78μm to 25.10μm. No significant cracks formed in the pure tungsten, but microcracks along the grain boundaries were found in W-Nb alloys. The rapid solidification, rapid cooling and holding at elevated temperature process in SEBM caused recovery and recrystallization of W and W-Nb alloys, so that the accumulated stress during the forming process was released. The cracking of W-Nb alloy is mainly formed during solidification, that is, because the liquid metal cannot feed the dendrite in a very short time during the solidification process, nanopores formed and gathered at the grain boundaries, and caused cracks along the grain boundary under little stress.

Abstract:The research on the dynamic mechanical behavior and deformation localization of metals under high-speed impact, that is, the adiabatic shear deformation, is of great significance to the scientific application of materials under impact environments. J-C constitutive equation is an effective method to deal with the problems of large strain, high strain rate and high temperature of engineering materials. The software " J-C constitutive parameter and damage model parameter measurement system of materails -C dynamic constitutive parameters of a near α Ti alloy by clustering global optimization method, which avoids the large amount of calculation and complexity of traditional measurement methods and even can not reflect the shortcomings such as parameter relevance. Through the anti-elasticity test of the titanium alloy target plate, using the J-C constitutive parameters, the commercial dynamics calculation software AUTODYN was used to complete the simulation of the shooting test. The simulation results are in good agreement with the test data, which verifies accuracy and precision of the accuracy of the J-C dynamic parameters. Bullet hole microstructure analysis shows that adiabatic shear bands can be observed at the ends of the cracks, which proves that the initiation of cracks is caused by adiabatic shear bands, indicating that the failure mode under high-speed impact dynamic environment is mainly adiabatic shear.

Abstract:Freckles are presently one of the main casting defects in the single crystal(SC)components made of superalloys. In the present work,a series of SC components with complex geometry, including turbine blades, were directionally solidified. It was found that the casting shape has more significant influence on the freckle formation than the local thermal condition. On the transverse sections of the components with curved contour, freckles were exclusively found on the outward curving surfaces having positive curvature, because the surface effect zones of the neighboring sides are overlapped, providing more favorable convection condition. In comparision, the surfaces with negative curvature remained freckle free, because the surface effect of the neighboring sides is divergent from each other. In the longitudinal direction, the freckle formation can be promoted by contracting contour and suppressed by expanding one, respectively.

Abstract:Aluminum foam is used as filling material to improve the load bearing efficiency of metallic sandwich beam with corrugated cores. After filling of aluminum foam prims into the space of corrugated cores which were cut firstly and gluing process, aluminum foam-filled corrugated sandwich beam is formed. Considering the anisotropy of the corrugated structure, both transverse and longitudinal bending response and failure modes are studied by three-point bending loads experimentally. The result shows that aluminum foam filling can effectively change the bending failure mode of corrugated sandwich beam, and lead to a significant increase of bending stiffness and peak bending load. Compared with transverse bending, the enhancement effect of aluminum foam filling on longitudinal bending is more significant. The bending loads presents a long plateau region and with no notable decline after its peak, showing a stronger post-buckling bearing capacity.

Abstract:In this paper, large-area EBSD splicing technology was used to study the crystal grain morphology and size, preferred orientation, and grain boundary feature distribution of the electrolytic nickel plate in the growth direction, and the microstructure of the nickel plate is observed by SEM. The results show that the nickel crystal grains change from small equiaxed crystal grains to coarse columnar crystals with the size of micro-nano scale as the deposition progresses; the crystal orientation does not have a strong preferred orientation at the beginning of the deposition, and finally changes to the <001> orientation. In the initial stage of deposition, the large-angle grain boundaries accounted for more than 80%; as the deposition progresses, the proportions of large and small grain boundaries vary in different positions of the deposition layer; a large number of adjacent grains in the nickel deposition layer are separated by ∑3, ∑9, ∑27 twin boundaries, and the ∑3 grain boundary frequency reaches more than 65%. The nickel deposition layer formed on the different surfaces of the starting sheet grows in different ways. The surface of the fine grains grows in the nucleation and growth way, and the nickel atoms on the free-growing surface are directly incorporated into the crystal lattice without undergoing the nucleation process.

Abstract:Mechanical relaxation behavior of high-entropy metallic glasses is not only crucial for understanding the glass transition phenomenon, plastic deformation and relaxation mechanism but also help for extending their application in engineering. The mechanical relaxation behavior of Ti₂₀Zr₂₀Hf₂₀Cu₂₀Be₂₀ high-entropy metallic glass (HE-MG) was investigated by static stress relaxation analysis in the current research. With a constant strain, the stress relaxation process was analyzed in a wide time window and temperature range. A decoupling of the relaxation into a two-step (slow relaxation and fast relaxation) was found in the glass state below T_g. The slow relaxation process exhibits a stretched decay and a significant Arrhenius dependence on the temperature. The relaxation time decreases sharply with the increase of temperature, which may relate to the long-range atomic rearrangements at larger scales. The fast relaxation relates to the atomic scale internal stress dissipation. In addition, the strain has no distinct influence on the stress relaxation process, whether high-entropy metallic glass is deformed at the elastic stage or yields. This study reveals the decoupling phenomenon and the related unique dynamics relaxation mechanism in high-entropy metallic glass, which will enhance our understanding of the mechanical relaxation behavior and intrinsic characteristics of high-entropy metallic glasses.

Abstract:The thermal deformation behavior of 2060-T8E30 aluminum-lithium alloy at deformation temperature of 425 ~ 500 ℃ and strain rate of 0.001 ~ 0.1 s_^-1 was studied by using SansCMT4104 electronic universal experimental machine.The results show that the peak stress of 2060-T8E30 aluminum-lithium alloy decreases with the increase of temperature and the decrease of strain rate during thermal deformation.The average deformation activation energy of the alloy was 240.502kJ/mol, and the average strain rate sensitivity index was 0.28.Based on the true stress-true strain curve of the thermal tensile test, the Arrhenius constitutive equation with strain compensation was established. The average relative error between the predicted value and the experimental value of the model was 5.89%, showing a good accuracy of the model.

Abstract:_{:To improve the straightening accuracy of magnesium alloy plates, the neutral layer offset pattern of magnesium plates needs to be analyzed. At room temperature, the plasticity of magnesium alloy is poor and the tensile asymmetry is also large. And when the magnesium plate is straightened at room temperature, improper control of the amount of pressure will cause the straightening effect of the plate to be seriously affected. Therefore, the magnesium plate is often used to improve the straightening accuracy and the temperature is an important factor affecting the pulling and pressing asymmetry of magnesium plate. In this paper, based on the CaBa2004 tensile-compression asymmetry yield criterion and using the basic theory of elastoplastic mechanics, the formula for calculating the neutral layer offset in the straightening process of AZ31B magnesium plate is derived. A thermodynamically coupled straightening model was established using ABAQUS finite elements to derive the neutral layer offset law at different temperatures, and using experiments, the neutral layer offset theory was experimentally verified.}

Abstract:The mesoporous TiN powder was prepared by non-hydrolyzed sol-gel method combined with ammonia gas reduction nitrification method using ethanol as oxygen donor, titanium tetrachloride (TiCl4) as titanium source and P123 as pore-forming agent. The effect of reduction nitride temperature on the phase, pore structure and electrochemical performance of mesoporous TiN powder was test by XRD, SEM, BET, XPS, CV, GDC and EIS. The results showed that as the reduction nitrification temperature increased, TiO2 was reduced TiO in the powder and then turned into TiN, and Ti-O bond was gradually replaced by Ti-N bond. In addition, the phase purity and particle size increased, and the pore diameter of the intermediate hole first increased and then decreased. When the reduction nitrification temperature is 800℃, the specific surface area of the powder is 41 m2/g, the pore structure is developed, and the average pore diameter is 24nm, which is conducive to ion transfer and electrochemical performance improvement. At this point, the internal impedance is 0.9 Ω. As the current density is 20 mA/g, the specific capacitance is 130 F/g. It is worth mentioning that after 1000 cycle also can keep the initial specific capacitance of nearly 90% under the 50 mA/g.

Abstract:In this paper, TC21 titanium alloy with high strength and toughness was selected, and the heat treatment process of "Step quenching" was used to regulate and optimize the multi-scale lamellar microstructure and its mechanical properties. The microstructure morphology, fracture morphology and cross-section crack propagation morphology of multi-scale lamellar microstructure were investigated by SEM and TEM. The results show that the isothermal quenching temperature has a strong influence on the α phase precipitation behavior and the mechanical properties of the alloy. The samples were solution treated at 930 ℃ for 1h, and then step-quenched with temperature from 0 ℃ to 600 ℃. With the increasing of temperature, the width of secondary α lath phase gradually increased, and the hardness first increased and then decreased slightly, among which the hardness at 400 ℃ being the highest. The samples were solution treated from 880 ℃ to 960 ℃ for 1h and aged at 400 ℃ for 2h with water cooling to room temperature. Thus, coarse lamellar, multi-scale lamellar and fine lamellar microstructure were obtained respectively, and the hardness and strength of the alloy increased successively. However, due to its tortuous crack propagation path and crack deflection characteristics, the multi-scale lamellar microstructure showed excellent crack propagation resistance (KQ=104 MPa?m1/2) which was significantly higher than the coarse lamellar (KQ=67 MPa?m1/2) and the fine lamellar microstructure (KQ=33 MPa?m1/2).

Abstract:In this investigation, NiTi alloys with different Ni contents were fabricated by mechanical alloy and spark plasma sintering (SPS) at 1000℃. Microhardness, mechanical and tribological properties of the NiTi alloys with different Ni contents were evaluated by the microhardness tester, universal testing machine and friction and wear tester. The wear volumes and wear rates were calculated by three-dimensional white light profilometer. The wear morphologies of NiTi alloys were analyzed by scanning electron microscopy (SEM) with energy disperse spectroscopy (EDS). The experimental results showed that the microstructures of NiTi alloy were uniformed in general. When the content of Ni was lower than 50 wt. %, the NiTi phase and NiTi₂ phase were presented in the microstructures. While the NiTi phase and Ni₃Ti phase were presented in the microstructures with more than 50 wt. % Ni contents. When the nickel content is 50 wt. %, the microhardness of the alloys were significantly improved. For the compressive strengths, these of NiTi were decreased as the Ni contents increased. When the nickel content is 55 wt. %, the tribological properties of the alloy can be significantly improved, because the E/H value of the NiTi alloy is the lowest. The wear mechanisms of NiTi alloy are abrasive wear and fatigue wear through the wear surfaces examined by SEM and EDS.

Abstract:It is of significant importance to understand the influence of defects on the fatigue property of Ti6Al4V alloy prepared by selective laser melting for breaking through the limitation of this material in industrial applications. As the defects cannot be completely avoided, with the help of metallographic microscope, electron backscatter diffraction, X-ray tomography, fatigue testing machine, scanning electron microscope and laser confocal microscope, the microstructure and defect characterizations, high cycle fatigue performance and failure mechanism of the material were studied. The results show that, the microstructure of the alloy exhibits the unique process characteristics of additive manufacturing materials. Specifically, the density of the material is 99.99%, and the overall defect size is less than 60 μm. The fatigue limit of the material is 398 MPa, fatigue cracks are formed in the lack of fusion defects of the fracture specimens and the cycles are less than 106. Most of the effective stress intensity factors at the defects of the fractured samples are distributed above the threshold value of short crack fatigue crack growth, which determines the low cycle life of the material. Finally, the K-T model is also introduced to establish an evaluation method for the safe service of the material.

Abstract:In order to further study the corrosion behavior of β-Nb second phase particles (SPPs) in zirconium alloys, a bulk 90Nb-10Zr alloy was prepared using vacuum non-consumable arc furnace based on the chemical composition and crystal structure of β-Nb SPPs. The 90Nb-10Zr alloy was corroded in 500 ℃ and 10.3 MPa super-heated steam in a static autoclave for 1 h and 7 h. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the microstructure of the oxide film formed on the alloy. The results revealed that the monoclinic Nb2O5 was formed directly when 90Nb-10Zr alloy was corroded for 1 h, because the corrosion medium was directly contact with the outer surface of the alloy. When 90Nb-10Zr alloy was corroded for 7 h, the oxide film on the alloy was double-layer structure: the outer layer was monoclinic Nb2O5 and the inner layer was tetragonal NbO2 since the occurrence of further corrosion required the internal diffusion of the oxidizing substances in the corrosion medium. No single oxide of Zr was detected in this study. This oxidation process can reasonably explain the relationship between the Nb content and the corrosion behavior of Nb-containing zirconium alloy in super-heated steam.

Abstract:The structure evolution and magnetic properties of melt-spun Fe_90-xPt₁₀B_x (x = 20–40) alloys before and after annealing have been investigated. The increase of x from 15 to 25–30 changes the melt-spun structure from a composite composed of amorphous and fcc-FePt phases to a single amorphous phase. Further increasing x to 35 and 40 results in the formation of fcc-FePt + Fe₂B + FeB and L1₀-FePt + FeB phases, respectively. After appropriate annealing, dual phases of fcc-FePt + Fe₂B are formed for the alloys with x = 15–20, which have soft magnetic properties, while the nanocomposite structure consisting of L1₀-FePt together with Fe₂B and /or FeB phases are obtained for the alloys with x = 25–40, which exhibit the characteristics of the nanocomposite magnets. The best hard magnetic properties are obtained for the alloy with x = 30 annealed at 823 K for 900 s, of which the coercivity, remanence, and maximum energy product are 173.2 kA/m, 1.20 T, and 88.3 kJ/m^₃, respectively. The good hard magnetic performance is due to the formation of a more fine and homogeneous L10-FePt /Fe₂B nanocomposite structure with an average grain size of about 15 nm.

Abstract:ZrO₂ ceramic and GH3536 alloy were successfully reactive air brazed (RAB) at 1050℃ for 30min with Ag-CuO-Al₂TiO₅ composite filler. The interface structure and formation mechanism of the brazing joint were analyzed. Meanwhile, the influence of the exposure test at 800 ℃ on the microstructure and properties of joints were systematically analyzed. The results showed that Al₂TiO₅ particles were decomposed into Al₂O₃ and TiO₂ particles, and TiO₂ reacted with ZrO₂ ceramic to form the ZrTiO₄ phase. The oxidation reaction occurred on the metal elements from GH3536, which reacted with Al₂O₃ and CuO in the brazing seam respectively to generate NiAl₂O₄ phase with fine distribution in the brazing seam and massive NiCuO₂ phase adjacent to the spinel layer. After the ZrO₂/GH3536 joint was oxidized above 1000 h at 800 ℃, NiAl₂O₄ in the brazing joint was distributed in blocks and while the thin layer of Cr₂O₃ remained stable. The elements inside the spinel layer were homogenized, the thickness of which increased significantly. The strength of the joint first decreased and then stabilized at 20 MPa with the extension of oxidation time.

Abstract:Using irregular tungsten powder as the raw material, spherical tungsten powder was prepared by radio frequency plasma spheroidization technique in this study. It mainly focused on the pure tungsten parts fabricated by the selective laser melting. The study systematically investigated the impact of process parameters (including laser power and scanning speed) on the densification, microstructure, microhardness and compressive properties of the pure tungsten samples. Results showed that after being spheroidized, the tungsten powder had regular shape and its spheroidization rate reached more than 98%. Besides, the tap density and loose density of the tungsten powder were increased and its flowability was also improved. Meanwhile, the spheroidized tungsten powder was well-adapted to selective laser melting, with the density of printed samples between 84% to 95.6%. The study also found that with the increase of laser power, the density, microhardness and compressive strength of printed samples increased first and then decreased, while their cracks and holes decreased. Furthermore, with the increase in the scanning speed, the density and hardness of the printed samples reduced while the amount of cracks increased. Therefore, it is of great significance for the selective laser melting of tungsten powder to explore the appropriate printing parameters.

Abstract:A series of Zr-xFe (x=0.05, 0.2, 1.0, wt.%) alloys were designed to investigate the effect of Fe on the microstructure and corrosion behavior in 400 ℃/10.3 MPa superheated steam of zirconium alloys. The microstructures of alloy matrix and oxide layer were characterized using scanning electron microscope and transmission electron microscope. The results showed that the grain size of α-Zr matrix was obviously decreased by adding 0.05 wt.% Fe but remined nearly unchanged with a further increase in Fe content from 0.2 wt.% to 1.0 wt.%. Most of the Fe atoms in the zirconium alloys was found to precipitate as Zr₃Fe secondary phase precipitates (SPPs). The SPP size was increased with the increase in Fe content, whereas its structure remained unchanged. Fe not only promoted the growth of columnar crystals in the oxide layer, but inhibited the columnar-to-equiaxed transformation, giving rise to a good corrosion performance of Zr-xFe alloys. Additionally, the corrosion resistance of Zr-xFe alloys was increased by increasing the Fe content. The stress accumulated at the oxide/metal (O/M) interface played a key role in the formation of sub-oxides in Zr-1.0Fe alloy during corrosion process, which can relieve the stress at the O/M interface, and thus largely improve the corrosion resistance by impeding the columnar-to-equiaxed transformation.

Abstract:The electrowinning process plays a substantial role in zinc hydrometallurgy, and its oxygen evolving potential on anode is critical for energy saving and high-quality metallic zinc. Based on the electro-catalysis of carbon nano-materials for oxygen evolving reaction (OER), 6 typical 0-dimensional, 1-dimensional, and 2-dimensional carbon nanomaterials were used as the catalytic enhanced phase to prepare lead-based composite anodes. The electrochemical behavior of the composite anode was studied by cyclic voltammetry, anodic polarization, EIS and corrosion resistant test under zinc electrowinning conditions. Nano-carbon materials enhanced Pb composite anodes show excellent electrocatalysis for OER and their stable overpotetntial are lower than pure Pb anode by more than 96mV under current density of 500A/m2. The electrochemical catalytic performance of 2-dimensional carbon materials is not as well as that of 0-dimensional carbon materials, and the 1-dimensional ones have the best performance among them. After modified with functional groups or decorated with functional particles on the surface of 1-dimensional carbon materials, the increase of electrochemical catalytic performance was significant.

Abstract:Bi₂Te₃/Bi₂Se₃ multi-layered nanowire arrays with the spring morphology were firstly fabricated by pulsed current electrodeposition. Also, the deposition course was monitored by electrochemical workstation connecting with a computer. In addition, the phase structure and morphology were characterized by XRD, FE-SEM and TEM, inspectively. The results showed that the pulsed current electrodeposition method could be used to prepare multi-layered nanowire arrays. According to investigation, the whole resistance of the three-electrode electrochemical system gradually increased. But the increasing degree of the resistance became smaller and smaller. Besides, the results of XRD analysis showed that the as-deposited multi-layed nanowire arrays were Bi₂Te₃/Bi₂Se₃ nanowires. Meanwhile, there were some “satellite peaks” appeared in the XRD pattern. This also conformed the as-fabricated materials were multi-layered nanowires. What’s more, the morphology of the as-prepared materials was spring-like morphology. The two phases could be distinguished by their own color. In order to investigate the effect of pulsed time on the length of each periodical segment, we change the pulsed time and prepared another sample. According to the results of TEM, the length of each segment could be tuned.

Abstract:The microstructure, mechanical properties and corrosion resistance of Al-Mg-Si-Mn alloy with different contents of rare earth element La were studied by SEM, OM, tensile test (normal temperature/high temperature), bending test and intergranular corrosion test, and the effects of rare earth element La on the mechanical and corrosion properties of the alloy were analyzed. The results show that with the addition of La element, the as-cast microstructure of the alloy is gradually refined, the morphology of the second phase is improved, the thickness of the coarse grain zone of the profiles is reduced, and the mechanical properties and corrosion resistance of Al-Mg-Si-Mn alloy are improved. When La content is 0.2 wt. %, the grain refinement effect is the best, and the coarse grain zone is the thinest. When La content is greater than 0.2wt. %, the primary phase formed by excessive La interacts with the grain refiner Ti in the alloy, which reduces the number of heterogeneous nucleation cores, leads to grain coarsening phenomenon, and degrades the mechanical properties and corrosion resistance of the alloy.

Abstract:In this paper, the high entropy alloy CrFeNiAlSiCux (x=0.2-1.2) is prepared by laser self-propagating sintering by adding non-equimolar ratio Cu element into Cr, Fe, Ni, Al and Si pure powder and then pressed into blank. It is characterized by OM, XRD, SEM and EDS, Vickers microhardness tester, abrasive wear machine and electrochemical workstation, and its phase structure, microstructure, density and porosity, hardness, wear resistance and corrosion resistance are analyzed. The results show that the sintered alloy always coexists with BCC and FCC phase. With the addition of Cu element, FCC phase increases, but BCC phase is still more than FCC phase. The alloy is a typical dendrite structure accompanied by many chrysanthemum like structures, which mainly contain Cr, Fe, Si and Ni elements, and interdendritic structure mainly contains Cu element. CrFeNiAlSiCu0.4 has the best comprehensive performance, the maximum microhardness is 908.68HV, the minimum wear per unit area is 48 mg·cm-2, the minimum corrosion current is 0.4100 A/cm-2, and the maximum corrosion potential is -149.264 mV.

Abstract:Silicified graphite was prepared by liquid-phase siliconizing method and in-situ reaction method. The influence of graphite matrix density and siliconizing method on the mechanical properties and friction properties of siliconized graphite was discussed. The results show that the two methods can significantly improve the flexural strength of graphite. The surface of the siliconized graphite prepared by the liquid-phase siliconizing method has a SiC layer with a concentration gradient, which can significantly improve the wear resistance of the matrix. Considering the comprehensive mechanical properties and friction properties, choosing low-density graphite through graphitization treatment and adopting the liquid phase siliconizing method can prepare silicified graphite with better performance.

Abstract:The effects of Nd and Er elements on the friction and wear behavior of Mg-6.0Zn-0.5Mn alloy were studied. More types and quantities of intermetallic compounds can hinder the migration and slip of the grain boundary, and the volume fraction of dynamic precipitates β_1^" with a smaller average length increased, which increases the hardness of the matrix and leads to reduce the wear rate of Mg-6.0Zn-0.5Mn-0.6Nd-0.3Er alloy. The wear mechanism of Mg-6.0Zn-0.5Mn alloy under a lower load of 5N is mainly abrasive wear, accompanied by oxidative wear; when the load increased to 20N, abrasive wear is weakened obviously and oxidative wear increases in Mg-6.0Zn-0.5Mn alloy. The wear mechanism of Mg-6.0Zn-0.5Mn-0.6Nd-0.3Er alloy under 5N is mainly abrasive wear, accompanied by oxidative wear and adhesion wear; due to the improved wear resistance, when the load increases to 20N, the wear mechanism of Mg-6.0Zn-0.5Mn-0.6Nd-0.3Er alloy is still mainly abrasive wear, accompanied by oxidative wear and weakened adhesion wear.

Abstract:The cathode material of single-crystal polyhedral LiAl0.08Ni0.03Mn1.89O4(LANMO) was rapidly synthesized by a solid-phase combustion method. The exposed surfaces of the single-crystal particles include {111}, {110} and {100} crystal faces. The results show that, LANMO material is a single-phase spinel structure, belonging to the space group Fd3m and exhibits a good crystallinity, the particle size is between 200 to 300 nm. The initial discharge specific capacity of LANMO is 110.6 and 96 mAh·g-1 at 1 C and 5 C, respectively, and the capacity retention rate reaches more than 70% after 1000 cycles. Under the elevated temperature (55 ℃) 1 C condition, the LANMO material also has an initial discharge specific capacity of 114.2 mAh·g-1, showing an excellent electrochemical performance. The kinetic performance test shows that the LANMO sample has a higher Li+ ion diffusion coefficient of 1.58×10-11 cm2 s-1 and a lower apparent activation energy of 23.89 kJ·mol-1. The Al-Ni synergistic modification improves the crystal structure stability of single crystal polyhedral spinel LiMn2O4 material, inhibits the Jahn-Teller effect effectively, reduces Mn dissolution, increases Li+ diffusion channels, Li+ diffusion rate and electrode reversibility as well as improves the rate performance and cycle life.

Abstract:High magnetic fields (HMF) can pass high intensity energies to the atomic scale of materials without contact to change the thermodynamic state of materials, and affect the arrangement, matching and migration of atoms and molecules. Therefore, in this work, HMF was introduced into wet-chemical synthesis to prepared FePtCu nanoparticles (NPs). The results show that the FePtCu NPs with L10 structure, uniform morphology, and good dispersibility were successfully prepared under HMF. The HMF increased the size, ordering degree s and the coercivity of the FePtCu NPs. The L10-FePtCu NPs with sizes of about 11 nm and ordering degree of 0.8985 were obtained under the HMF of 6 T. The HMF might magnetize the NPs and cause lattice distortions, which facilitates formation of vacancies or defects in the FePt NPs. A lot of vacancies are effectively accelerate the orderly diffusion of Fe and Pt atoms, and promoted the disordered-ordered transformation of the FePt NPs. Therefore, HMF assistance can accomplish the regulation of ordered structure. This method offers a new path for the direct synthesis of L10 structured nanomaterials.

Abstract:HVOF ( high velocity oxygen fuel) sprayed WC cermet coating possess high hardness, high bonding strength and nearly full-density, which are the candidates of EHC(electrolytic hard chromium). In the present paper, the research status quo of the influence of HVOF sprayed WC coating on the fatigue life of the substrate was summarized and the reasons of crack invitation and fatigue life decrease were also analyzed. The factors affecting the fatigue life are as follows: the difference between the coating and the substrate in properties, the defects introduced by grit blasting, residual stress and coating gradient design, shot peening replacing grit blasting and could be adopted in order to improve or increase the fatigue life of substrate.

Abstract:To meet the development trend of functionalization and miniaturization of electronic products in recent decades, aluminum electrolytic capacitors are facing the same trend to achieve miniaturization and high electrical properties.SOne of the most effective ways to make it actualize is the preparation of high specific capacitance anode foil. By depositing a thin film that has high relative permittivity on aluminum foil, the permittivity of abode composite film as well as the specific capacitance of aluminum electrolytic capacity will both be largely enhanced.SIn this review, we systematically introduce the deposition techniques for the preparation of valve metal compounds for aluminum electrolytic capacitors. From the perspective of the film quality prepared by different deposition techniques, we expound the advantages and disadvantages of the various deposition techniques when preparing the anode composite foil for aluminum electrolytic capacitors. Further, we analyze the research progress of increasing the electric performance of anode foil by composite a valve metal thin film. Accordingly, several outlooks for promoting the practical applications of high specific capacitance aluminum electrolytic capacitors are proposed.

Abstract:Hydrogen energy is an ideal energy carrier. Hydrogen production from activated metal splitting water has the characteristics of solid-state containing energy, in-situ hydrogen production, supplied hydrogen on demand, and lower requirements for water quality. In this paper, the common problems of activated aluminum alloy are reviewed from the thermodynamics and the kinetics of Al/H2O reaction, and the feasible methods of engineering applied are summarized from the internal factors and the external factors affecting Al/H2O reaction. The key issue of activated aluminum is to adopt multi-element alloying and suitable fabrication processing, and the potential and outbreak of the engineering application of Al/H2O reaction is extreme environment. Moreover, it is pointed out that the predictive investigation and the quantitative investigation of Al/H2O spontaneous reaction, the recycling of Al/H2O reaction products in industrialization are the further development direction. Finally, the industrial application of hydrogen produced by activated aluminum splitting water is low-cost, environment-friendly, safe and reliable.

Abstract:A new type of high entropy amorphous alloy (denoted as HEAA) ribbons Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅ was prepared by injection in copper mould with arc melting. The effect of Cu content on corrosion resistance of the Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅ HEAA was studied mainly by adding Cu element into the alloy. The glass-forming ability and hardness of the alloy were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and microhardness tester, respectively. The corrosion resistance of these ribbons in 3.5 wt.% NaCl corrosive solution at room temperature were investigated by potentiodynamic polarization curves (Tafel) and Nyquist plots. The results show that four kinds of (AlNiZrCo)_75-xCu_xY₂₀Si₅(x=0, 10, 14, 15) near equiatomic HEAA ribbons present typical amorphous diffraction peaks. The Cu content has little effect on the glass-forming ability of the AlNiZrCoYSi HEAA ribbons, but it will reduce the corrosion resistance. The Vickers microhardness of the above alloys is over 470 HV_0.1. The corrosion resistance of the Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅ HEAA ribbons is the finest. The corrosion potential (E_corr) is -0.248 V, the corrosion-current density (i_corr) is 1.63 μA / cm^₂, and the polarization resistance (R_P) is 24.56 kΩ.cm^₂. This material has demanding application potential to solve the problem of anti-corrosion and wear resistance in harsh marine environment.

Abstract:In this paper, CuSe/ZnSe nanoparticles with core-shell structure with CuSe as the core and ZnSe as the shell were successfully prepared were prepared. First, CuSe nanoparticles (NPs) were prepared by reflux condensation. Then, a simple and rapid photochemical method, namely ultraviolet illumination, was used to grow ZnSe shells on CuSe nanoparticles at room temperature. Finally, CuSe/ZnSe core-shell nanoparticles were obtained. The synthesized CuSe/ZnSe core-shell NPs was characterized by different analyses methods such as X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and Photoluminescence Spectroscopy (PL). The results show that the synthesized CuSe nanoparticles have hexagonal phase structure with an average particle size of 12 nm. The core-shell structure of CuSe/ZnSe nanoparticles is clear, and the ZnSe shell is of cubic sphalerite structure with a particle size of about 15~45 nm. The blue light emission at 475 nm was induced by the coating of ZnSe shell, and the fluorescence intensity was significantly enhanced.