Abstract:Newly designed α-type titanium (α-Ti) alloys were proposed based on both electron parameters (bonding time Bo_t and d-orbital energy level Md_t). The newly designed α-Ti alloy Ti-5Al-4Zr-3.6Sn, modified alloy Ti-5Al-3Sn-1.9Zr, and reference alloy Ti-5Al-2.5Sn have the same Bo_t value of 3.847 and different Md_t values of 2.430, 2.426, and 2.422, respectively. The ultimate tensile strength (σ_UTS), fracture strain (?_f), and hot salt corrosion resistance of the three α-Ti alloys were measured. The three α-Ti alloys were produced by the cold crucible levitation melting (CCLM) technique. Results show that homogeneous microstructures can be observed in three α-Ti alloys. The α mono-phase in three α-Ti alloys has the grain size of approximately 600 μm. σ_UTS and ?_f of Ti-5Al-4Zr-3.6Sn alloy are 801 MPa and 16%, respectively; σ_UTS and ?_f of Ti-5Al-3Sn-1.9Zr alloy are 708 MPa and 15%, respectively; σ_UTS and ?_f of Ti-5Al-2.5Sn alloy are 603 MPa and 15%, respectively. After hot salt corrosion tests were conducted for 28.8 ks, the mass loss ratio of Ti-5Al-4Zr-3.6Sn, Ti-5Al-3Sn-1.9Zr, and Ti-5Al-2.5Sn alloys is 2.61%, 2.83%, and 3.10%, respectively. The results of σ_UTS, ?_f, and hot salt corrosion resistance indicate that the newly designed alloy Ti-5Al-4Zr-3.6Sn has great potential for practical applications.

Abstract:Phytic acid, one kind of organic acid, was added into the electrolyte to enhance the corrosion performance and thermal stability of micro-arc oxidation (MAO) coating on TC4 titanium alloy. The effect of phytic acid on the coating formation, morphology, and performance was analyzed by scanning electron microscope, X-ray diffractometer, X-ray photoelectron spectroscope, and thermal shock experiments. Results show that the addition of phytic acid leads to the refinement of discharge microholes and improves the formation efficiency and phase structure of MAO coating. Through potentiodynamic polarization tests, it is found that adding phytic acid can significantly enhance the corrosion resistance of MAO coating. The corrosion current density decreases from 8.406×10^-5 A·cm^-2 to 2.580×10^-6 A·cm^-2 when the phytic acid concentration in electrolyte changes to 12 mL/L (optimal phytic acid concentration). Cyclic high temperature oxidation test results indicate that the thermal shock resistance and high temperature oxidation resistance of TC4 alloy are enhanced.

Abstract:In order to satisfy the requirements of aerospace field for rapid preparation of high strength and toughness complex titanium alloy parts, new Ti-5321 (Ti-5Al-3Mo-3V-2Zr-2Cr-1Nb-1Fe) alloy with high strength and high toughness was prepared by laser cladding forming, which possesses the superiority of rapid prototyping, high efficiency, and good formability. Through single annealing and multiple heat treatment (β-annealing with slow cooling and aging, BASCA) on Ti-5321 alloy, the microstructure evolution was revealed, and the influence of different microstructures on the fracture toughness was explored. Results show that after single annealing, the alloy morphology presents the basket-weave structure consisting of elongated lamellar α phases. Its ultimate tensile strength is 1102 MPa, and fracture toughness is 68.1 MPa·m^1/2. After BASCA heat treatment, the elongated lamellar α phase changes to coarse lamellar α phase and ultrafine needle-like α phase. Thus, the ultimate tensile strength increases to 1309 MPa, whereas the fracture toughness reduces to 45.5 MPa·m^1/2. BASCA heat treatment can enhance the strength but degrade the toughness of alloys. This is because the elongated lamellar α phase in basket-weave structure can greatly increase the crack growth resistance and aggravate the tortuous degree of crack growth path, thus improving the alloy toughness. Coarse lamellar α phase after BASCA heat treatment has a certain degree of directionality, and the cracks only deflect when passing through the coarse lamellar α phase of different β grains. Crack propagation mainly occurs in the ultrafine needle-like α phase. However, due to the extremely small size of ultrafine needle-like α phase, it cannot hinder the development of crack path or deflect the cracks. Thus, the toughness of coarse lamellar structure becomes more inferior after BASCA heat treatment.

Abstract:Hot isostatic pressure diffusion bonding experiments were conducted on the dissimilar alloys of TC4 titanium alloy and Al6061 aluminum alloy. The interface characteristics, formation mechanism, and mechanical properties of the TC4/Al6061 joint were investigated, and the relevant experiment phenomena were explained by thermodynamic analysis. Results show that obvious mutual diffusion of elements occurs on both sides of base material after hot isostatic pressure diffusion bonding and subsequent annealing treatment. The chemical potential driving force leads to the enrichment of Si and Mg elements in the diffusion transition zone and Al side interface, respectively. The intermetallic compounds, including TiAl₃, TiAl, and Ti₃Al, are formed through metallurgical reactions at the joint interface. The calculation results through effective heat formation model indicate the preferential formation of TiAl₃ phase. The hardness test indicates that the Ti-Al intermetallic compounds formed at the interface exhibit higher hardness. The tensile test reveals that the maximum tensile strength of joint reaches 144 MPa.

Abstract:In this paper, the microstructure and mechanical properties of integral bladed titanium alloy Ti60 repaired by laser were studied. The results showed that the heat affected zone structure presents the transition characteristics from the Dual structure of the matrix area to the mesh basket structure of the repair area, and its average width is about 900 μm. The repair zone is mainly composed of columnar crystals growing epitaxially through multiple sedimentary layers, and the columnar crystals are uniformly distributed α phase mesh basket structures. Ti₃(Sn, Al) facet facies of similar size were dispersed in the structure of the three regions, but their morphology and regional content varied significantly due to the solidification speed of the preparation process. The three areas are equally hard. The fracture characteristics of tensile specimens show that the fracture mechanism of laser additive repaired Ti60 titanium alloy is mixed fracture. The average tensile strength and yield strength are 992.4 MPa and 916.6 MPa respectively, which are superior to the strength standard of Ti60 titanium alloy forgings, the average elongation and section shrinkage after fracture are 8.5% and 14.6% , which are similar to the standard of Ti60 titanium alloy forgings and meets the requirements of practical engineering application

Abstract:Gleeble-1500 thermodynamic simulation machine was used to perform thermal compression deformation of pure titanium before and after the phase change point, and the influence of thermal compression on the phase transition was studied. It is found that when the stress is applied near the phase change point, the phase transition first occurs between the slats, and the newly formed β grains are mostly spherical or short rod-shaped. As the amount of compression increases, adjacent β nuclei gradually connect and become strip-like tissues. There is a critical value for phase transition, when the compression temperature is 860 °C, 890 °C and 920 °C, respectively, when the compression amount reaches 40%, 30% and 20%, the phase transition tends to saturate, replaced by a large number of dynamic recrystallization. The higher the temperature, the more obvious the phenomenon of deformation promoting phase change, when the compression temperature is after the phase change point, a small amount of compression can make a large number of phase transitions occur.

Abstract:The adsorption and dissociation of CO and CO₂ molecules on UO₂ (111) slab were investigated by the first-principles calculations based on density functional theory with the addition of Hubbard term for calculation correction. Different static and dynamic adsorption mechanisms under different configurations were analyzed, and the adsorption sites included top, hollow, and bridge sites. In the static calculations, the variation of adsorption parameters, such as adsorption configuration, adsorption energy, and charge transfer, during adsorption process was investigated. ab-initio molecular dynamics (AIMD) was employed to study the dissociation process of CO₂ molecules and the changes in charge density difference. Results show that the adsorption of CO molecules can be categorized into two types: (1) stable adsorption, including chemical and physical adsorptions; (2) unstable adsorption. The adsorption types of CO₂ on UO₂ (111) slab only include the chemical adsorption of stable adsorption and unstable adsorption. No physical adsorption exists. The optimal configuration for the adsorption of both CO and CO₂ molecules is short-bridge vertical (B-short-Ver) adsorption. Additionally, at 0 K, the CO₂ molecules at the configurations related to B-short-Ver adsorption and long-bridge vertical adsorption on UO₂ (111) slab spontaneously dissociate after adsorption. AIMD simulation results show that both configurations dissociate at 300 K.

Abstract:To enhance the dispersibility and photostability of AgCl nanoparticles (NPs), AgCl NPs were firmly anchored on the surface of attapulgite (ATP) to prepare the ATP-AgCl composites. The microstructure, crystal structure, and antibacterial activity of the ATP-AgCl composites were investigated. Results demonstrate that the introducion of ATP not only avoids the agglomeration of AgCl NPs, but also decreases their particle size from 5–10 μm to 3–20 nm. Due to the small size effect of NPs, the antibacterial activity of as-prepared ATP-AgCl composites is comparable to that of pure AgCl. The antibacterial ratios against Escherichia coli and Staphylococcus aureus are 99.98% and 99.88%, respectively. Additionally, the introduction of ATP also improves the photostability of AgCl NPs: the composites remains offwhite after exposure to sunshine for 24 h.

Abstract:According to the spatial distribution pattern of melt pool size features, a prediction method of melt pool width based on edge iterative model was proposed. In order to obtain accurate melt pool width, mathematical morphological method was used to denoise the melt pool image and coarse segmentation was conducted on the melt pool image by manual thresholding method. The Canny algorithm was then employed to extract the melt pool edge. Finally, the edge iterative model was used for edge iteration and the melt pool width after fine segmentation was obtained. Comparison experiment results show that this algorithm has good accuracy and robustness, and it is simple and efficient.

Abstract:The combined method of Navier-Stokes equation and direction simulation Monte-Carlo method was used to simulate the flow in the reaction chamber, and the relationship between gas flow velocity and plasma density was analyzed by the Langmuir probe detection equipment. Results show that the flow uniformity can significantly impact the plasma uniformity. Under the pressure of 6.5 Pa, the plasma density and flow velocity show a positive correlation, which is consistent with the experiment results in atmosphere pressure. This research verifies that improving the flow uniformity can enhance the plasma oxidation uniformity.

Abstract:With copper/steel composite pipe as research object, two-dimensional numerical simulation of explosive welding process was conducted through AUTODYN finite element software with SPH and ALE methods. The dynamic welding process and boundary effect were analyzed, and the explosive welding tests of copper/steel composite pipe were conducted. Results indicate that under the action of detonation waves, the composite pipe obliquely collides with the base pipe. The pressure in the collision zone remains stable at the order of 10⁷ kPa, and a plastic deformation band appears near the collision zone. The shear stresses have opposite directions on the base pipe and composite pipe, and the interface morphology changes from straight line to wavy shape with the propagation of explosion wave. This result is consistent with the actual interface morphology of the T2/316L bimetal composite pipe in experiments, indicating that this finite element model can effectively simulate the explosive welding process of bimetal composite pipe. During the numerical simulation process, the dynamic parameter values at the edges are all smaller than the normal values, leading to boundary effects. Increasing the length of composite pipe and explosive can eliminate the boundary effect.

Abstract:In order to enhance the nano-cutting surface quality of Ni₃Al-based alloy to obtain better service state, the nano-molecule dynamics (MD) simulation and micro-cutting experiment were combined to investigate the effect of loading temperature (300–1050 K) on cutting force and surface morphology. MD simulation results show that the fluctuation of cutting force is the smallest when the loading temperature is 750 K during nano-cutting process of Ni₃Al-based alloy, compared with that at other temperatures. When the loading temperature is 600–750 K, the number of convex atoms affecting the surface morphology is the least, which indicates that Ni₃Al-based alloy can achieve higher surface quality at loading temperature of about 750 K. The micro-cutting experiments of Ni₃Al-based alloy show that higher flatness of the processed surface can be obtained at the loading temperature of 600–750 K, which indirectly verifies the feasibility of MD simulation results of the nano-cutting process of Ni₃Al-based alloy. Results suggest that selecting appropriate loading temperature is an effective method to improve the nano-cutting surface quality of Ni₃Al-based alloy.

Abstract:Gradient lattice structure is now commonly used as energy-absorbing components in aerospace, national defense and medical fields due to its excellent energy absorption ability when compressed. However, with the development of modern industry, the engineering field has put forward higher requirements on its compression properties. To make it further optimized, it is necessary to study the relationship between cell, structural parameters and compression properties. Therefore, in this study, two AlSi10Mg rod-diameter-change gradient body-centered cubic (BCC) and diamond (Diam) structures with different gradient gap were formed by selective laser melting (SLM) to investigate the effect of gradient gap on the compression properties, and to compare the two cells. The results of quasi-static uniaxial compression experiments and finite element analysis (FEA) show that the absorbed energy per unit volume increases significantly with the increase of gradient gap at the same relative density and with the same cell. The compressive modulus, yield strength, compressive strength and peak stress of Diam gradient lattice structure are higher than those of BCC when the gradient gap is the same, and its absorbed energy per unit volume and energy absorption efficiency are also higher than those of BCC.

Abstract:Based on XRD, XPS, H2-TPR and other characterization methods and activity evaluation methods, the physical and chemical properties and catalytic activity of CDPF samples doped with different concentrations of La2O3 under hydrothermal aging condition were studied. The results show that with the increase of La2O3 doping concentration, the diffraction characteristic peak shifts a large angle and crystallinity of CDPF aging samples show a trend of decreasing then increasing. La2O3 doping can better inhibit the sintering and distortion of samples during hydrothermal processing and can effectively inhibit the reduction of active quantity, so that the concentration of Pt atoms on the surface of CDPF remains basically unchanged, and the degradation rate of CO, C3H8 and NO catalytic performance decreases. With the increase of doping concentration, the CDPF tends to reverse the trend of ageing.

Abstract:The microstructure and mechanical properties of a novel Nickel-based powder superalloy FGH4113A under two heat treatment conditions were studied by means of scanning electron microscope (SEM), optical microscope (OM), tensile, creep and fatigue testing, providing the basis for dual microstructure heat treatment (DMHT). The results show that the supsolvus and subsolvus microstructure and mechanical properties have obvious dual-mode. At room temperature, the yield strength of subsolvus sample is 10.6% higher than that of supsolvus samples, and at 800 ℃, the yield strength of supsolvus samples is 11.7% higher correspondingly; The tensile strength of FGH4113A is better than that of ME3 and equivalent to that of LSHR. The creep deformation of FGH4113A alloy at 750°C/450MPa is dominated by the dislocation slip mechanism, and the dispersed small-sized borides conducive to improve the creep performance; FGH4113A has excellent creep properties, which is better than ME3 and equivalent to LSHR; The coarse-grain structure in the supsolvus sample has a longer slip band in crack propagation, resulting in lower cumulative damage under cyclic loading, and the crack growth resistance is better than that of subsolvus sample; The crack propagation fracture of the supersolvus sample is characterized by transgranular fracture. The existence of primary γˊ on the fine grain boundary reduces the crack growth resistance, and the fracture is rough, showing mixed fracture characteristics of intergranular and transgranular.

Abstract:Fe-Ni based alloys are used in high temperature for a long time, so the microstructure stability at high temperature is one of the important indexes of the alloys. The microstructure and properties evolution of a new Fe-Ni based superalloy 21Cr-32Fe-41Ni at 750 ℃ for different aging time were investigated by scanning electron microscopy ( SEM ), transmission electron microscopy ( TEM ), electron probe microanalysis ( EPMA ) and chemical phase analysis. The results show that the precipitates in the alloy after long-term aging were mainly γ′, σ, α-Cr, MC phases. The weight percentage and size of the dispersed spherical γ′ in the matrix increased rapidly within 500 h aging. With the increase of aging time from 500 h to 2000 h, the weight percentage and size increase rate of γ′ gradually decreased. During the long-term aging process, the σ phases were distributed along the grain boundaries in block or strip shape, and within grains in needle or strip shape. The distribution of α-Cr phases in the grains was the same as that of σ phases. With the increase of aging time, the number of σ and α-Cr phases increased and they gradually coarsened. The σ phases with discontinuous distribution along the grain were gradually connected, and there was a tendency to develop into a network distribution. With the increase of aging time to 2000 h, the strengths of the alloy increased first and then decreased. They reached the peak after aging for 500 h. The hardness kept increasing.

Abstract:In order to achieve precise control of the structure and precipitates during the rolling-cooling process of the high V, N micro-alloyed steel, the Gleeble-1500D thermal simulated test machine was used to study the thermal expansion curve and phase transformation rules of the experimental steel at different cooling rates after rolling. Especially, the dynamic continuous cooling transformation curve (dynamic CCT curve) of supercooled austenite, and the microstructure evolution behavior, microhardness and sensitivity of the nano-sized carbonitride precipitation behavior to the cooling rate were studied. The results show that when the cooling rate is lower than 3 °C/s, the microstructure of the experimental steel is composed of ferrite and pearlite. As for the cooling rate is 3 °C/s, bainite transformation occurs, and the matrix structure is composed by ferrite, pearlite and bainite. On the other hand, the pearlite structure is disappeared, and the martensite structure begins to be formed at the cooling rate of 8 ℃/s, and the matrix structure is composed of intergranular ferrite, bainite and martensite. When the cooling rate reaches 20 °C /s, the matrix structure is dominated by martensite and it is mixed with a small amount of proeutectoid ferrite and bainite. Furthermore, the cooling rate also has a significant influence on the precipitation behavior of nano-sized carbonitrides. When the cooling rate is within 1 °C/s, the diameter and number density of the nanoprecipitates in the polygonal ferrite show strong sensitivity to the cooling rate. The diameter of the nanoprecipitates is apparently decreased with the increase of cooling rate, and the it is inverse for the change in number density. When the cooling rate increases from 1 ℃/s to 3 ℃/s, the diameter of the nanoprecipitates further decreases, and the number density tends to be stable. As the cooling rate is further increased from 3 ℃/s to 5 ℃/s, the diameter of the nanoprecipitates keeps constant, and the number density is decreased. It was also found that less nanoprecipitates is contained in the bainite structure and the bainite is not helpful for the precipitation. Based on the above research on the structure evolution and precipitation law, a high V, N micro-alloy steel with a yield strength of more than 700 MPa and meeting seismic requirements has been industrialized and trial-produced.

Abstract:In this paper, the effects of substrate preheating temperature on the microstructure and mechanical properties of AlSi9Mg1ScZr alloy samples prepared by selective laser melting were investigated. SLM samples were prepared at three different substrate preheating temperatures of 35°C, 85°C and 135°C and subjected to microstructure observation and property testing, respectively. The results showed that the substrate preheating temperature set to 135℃ caused the in-situ aging effect of the alloy during the printing process due to the combined effect of the substrate preheating temperature and laser scanning heat input, which promoted the precipitation of elements from the supersaturated solid solution while retaining fine dendrites and Si lattices. Compared to the sample with the substrate preheated at 35 °C, the nanoscale Mg₂Si and Si phases precipitated significantly more in the α-Al matrix and dendrite boundaries, which served to improve the strength; however, the precipitation of the micron-scale Fe-rich phase had a negative effect on plasticity. At a substrate preheating temperature setting of 135°C, the prepared AlSi9Mg1ScZr alloy exhibited a yield strength of 360 MPa, a tensile strength of 502 MPa, and an elongation of 7% in the 0° direction, and a yield strength of 331 MPa, a tensile strength of 511 MPa, and an elongation of 5.4% in the 90° direction. In this study, the microstructure of AlSi9Mg1ScZr alloy prepared by SLM was improved by increasing the substrate preheating temperature and achieving in situ aging of the SLM samples during SLM, which significantly reduced the residual stresses and obtained ultra-high strength AlSi9Mg1ScZr alloy samples without subsequent heat treatment .

Abstract:Ag-Cu-Ti and Ag-Cu-Ti+B4C composite brazing alloys were successfully used to braze the B4C-TiB2-SiC-TiC (BTST) composite ceramic. The effects of brazing temperature and holding time on the interfacial microstructure and mechanical properties of the joints were investigated. The results show that Ag-Cu-Ti brazing alloy had a good wettability with BTST and Ti reacted with BTST to form TiC and TiB. The thickness of reaction layer increased with the increase of brazing temperature or holding time, and Ag-Cu eutectic alloy formed in the brazing seam. The bending strength of the joints increased with the brazing temperature or holding time first and then decreased. The addition of B4C into the Ag-Cu-Ti refined the microstructure of brazing seam and reduced the thickness of reaction layer. The maximum bending strength of the joint achieved was 314 MPa, when the BTST composite ceramic was brazed at 890℃ for 15 min using the Ag-Cu-Ti with 1 wt.% B4C.

Abstract:The Ti/IrO₂-PbO₂ anodes were prepared by thermal decomposition. The effects of sulfuric acid, nitric acid, hydrochloric acid, oxalic acid and hydrochloric acid/oxalic acid etching sequence on the performance of Ti/IrO₂-PbO₂ anodes were studied deeply. Surface morphologies, structure and electrochemical behavior of the titanium substrates with oxide-coated were investigated by field emission scanning electron microscope, X-ray diffraction, cyclic voltammetry, linear scanning voltammetry, electrochemical AC impedance spectroscopy and accelerated lifetime test. The results showed that dual-acid etching can obtain a better corrosion effect with a denser and more uniform surface structure compared to them of single-acid etching. The dual-acid etching achieved a complete TiH_x crystal form. It can be beneficial to increase the coating loading and enhance the bonding force between the active layer and the substrate. The electrochemical properties of the anode were little determined by the order of double acid etching. The Ti/IrO₂-PbO₂ anode treated by oxalic acid followed by hydrochloric acid showed the best electrocatalytic activity and the longest accelerated lifetime.

Abstract:In order to improve the forming quality of W-ring, the ultrasonic vibration rolling process of W-ring was studied in this paper. Based on ABAQUS/Explicit finite element simulation software, a three-dimensional finite element model of W-ring with ultrasonic vibration assisted rolling was established, and the influence of ultrasonic frequency on the non-uniform deformation of the ring was studied. The results show that with the increase of ultrasonic frequency, the stress unevenness of the ring increases first and then decreases. The strain unevenness of the ring component decreases slightly first, then increases sharply, and then decreases again. The non-uniformity of wall thickness decreases first, then increases and then decreases. When the ultrasonic frequency is 30kHz and 40kHz, the unevenness of the ring deformation increases significantly, which is caused by the wrinkle phenomenon of the ring. By analyzing the stress, strain and wall thickness of the section, it is proved that the position of wave crest and trough is the key position in the forming process.

Abstract:Given the high sensitivity of hydrogen porosity in the welding process of AlSi10Mg aluminum alloy formed by selective laser melting, a study was conducted to compare the effect of dehydrogenation treatment on the pore defects of alloy laser welded joints using solid solution dehydrogenation and vacuum solid solution dehydrogenation methods, under different states. The study analyzed pore distribution, microstructure evolution, and mechanical behavior of laser welded seam. The findings reveal that the solution treatment can effectively reduce the porosity of AlSi10Mg aluminum alloy laser welded seam formed by selective laser melting. Vacuum solution treatment has the best effect, reducing porosity from 2.64% of the deposited state laser welding seam to 0.14% of the vacuum solid solution state weld. The study explains the reasons for the appearance of pores, analyzes the evolution of the joint structure, and examines the change of the phase morphology and composition of the substrate. It is revealed that vacuum heat treatment is an effective method for pore formation, solving the problem of hydrogen gas in the weld due to the high content of hydrogen pre-existing in the substrate. After solid solution, the hardness of the base metal decreased significantly, and the average hardness of the welds of each test plate was 80HV, which was relatively consistent. The tensile strength of the welded joint of the solid solution test plate was 143MPa, which was lower than that of the deposited joint, but the elongation increased to 24%, characteristic of ductile fracture.

Abstract:Ni-Go composite coating was prepared on Q235 steel by electrodeposition. The effect of rare earth cerium on the morphology and properties of the composite coating was studied. The results show that when the cerium concentration is 0.8 g . L-1, the deposition rate of the composite coating increases to 7.142 g . dm-2 . h-1, the hardness reaches 608.8 HV, the wear amount is the smallest, the friction coefficient is the lowest, the self-corrosion potential Ecorr ( -0.3993 V ) is corrected, the corrosion current Icorr ( 3.258 . 10-6 A . cm-2 ) is the smallest, the corrosion rate is the lowest, and the corrosion resistance of the composite coating is the best. It was found that after the addition of rare earth cerium, the coral-like micro-sized convex polymer of the Ni-1.0GO composite coating became a small coral-like convex polymer with a smaller size, and the coating structure was significantly refined. When the cerium concentration is 0.8 g . L-1, the Ni-1.0GO-0.8RE composite coating has the best microstructure and the best performance. The main reason is that the rare earth cerium improves the dispersion ability of the particles in the plating solution and the cathodic polarization rate. The effect of increasing the precipitation potential of hydrogen ions at the cathode inhibits the occurrence of hydrogen evolution reaction, which further improves the performance of the composite coating.

Abstract:In order to expand the industrial application of diamond coating tool and improve the adhesive strength of diamond coating tool. In this paper, the “Acid-Murakami-Acid” (AMA) three-step pretreatment process for cemented carbide with different WC grain size of 0.2, 0.4, 1.0μm was systematically studied. The surface morphology of the pretreated substrate, cobalt content and coating morphology were analyzed by scanning electron microscope and EDS spectrometer. The phase structure of the coating was analyzed and characterized by Raman spectroscopy and X-ray diffraction spectroscopy. The scour resistance of the diamond coating was tested by dynamic impact experiments. These results showed that the acid treatment played an important role in removing Co. The smaller the grain size of WC, the longer the acid treatment time was required. The etching capacity of WC by Murakami treatment increased at first and then decreased, and the maximum Co exposure was reached at 3min. Therefore, the best pretreatment process of WC-6%Co (0.2, 0.4, 1.0μm) substates were determined. After the three-step method, the substates obtained uniform and compact diamond coatings with grain orientation of (111), excellent scouring resistance and great adhesion strength.

Abstract:In this paper, porous CoCrNi mesentropic alloys with porosity of 63%~78% and pore size of 1.3~2.2mm were successfully prepared by powder sintering and dissolution method. The pore morphology and phase composition of the samples were analyzed by SEM and XRD, and the axial quasi-static compression experiments were conducted on the samples. The results show that the elastic modulus and yield platform stress of porous CoCrNi alloy decrease with the increase of porosity and pore size. Compared with porosity, the effect of pore size on mechanical properties is low. The energy absorption values per unit volume of porous CoCrNi mesentropy alloys with different porosity range from 34.8 to 14.3MJ/m₃ ^{under d}ense strain, about 3.8 times that of aluminum foam, and the ideal energy absorption efficiency (I) of the five porosity ratios is close to 0.8, indicating that the porous CoCrNi mesentropy alloy has the potential to become an ideal energy absorption material.

Abstract:The strength and elongation of Cu-14Sn-0.3Ti alloy were improved synergistically in this investigation by hot rolling+electric pulse treatment. The elongation of Cu-15Sn-0.3Ti alloy increased from 4.7% to 40%, and the strength increase from 298 MPa to 530 MPa after 70% hot rolling+10 min electric pulse treatment. The influence of deformation energy storage and pulse current on reduction of stacking faults and twin growth was investigated by adjusting hot rolling and electric pulse processing. The results show that the strength and density of Cu-14Sn-0.3Ti alloy increase with the increase of deformation energy storage. The δ phase dissolves, and the deformation-induced stacking faults reduced because of the synergetic effect of Joule heat and electron wind. After electric pulse treatment, the formation of twins provides additional slip systems for the movement of dislocations and improves the elongation of Cu-14Sn-0.3Ti alloy. On the one hand, the appearance of twins has divided and refined the grains. On the other hand, the formation of twin boundaries hinders the movement of dislocations during the deformation of Cu-14Sn-0.3Ti alloy, making the strength of Cu-14Sn-0.3Ti alloy improve.

Abstract:Electrochromic materials have very important application prospects in the fields of intelligent display and military camouflage. In order to improve the long response time and poor cycling stability of NiO film in alkaline electrolyte, strontium doped nano-sheet NiO electrochromic films were prepared by hydrothermal method. The lattice distortion caused by ion doping and the synergy of micro-nano structure make NiO thin films exhibit excellent electrochromic properties. Strontium ion doping improves the electrochemical characteristics of NiO film, thus improving the electrochromic response time (coloring time is about 4.5 s, bleaching time is about 2.7 s), and improving the coloration efficiency (CE, 85.2 cm₂^C_-1). On the other hand, it provides support for the NiO crystal structure, strengthens the stability of the crystal structure in the electrochromic process, and significantly improves the cycle stability of the film (the cycle number exceeds 10000). The research results of this paper have certain reference and guiding significance to promote the engineering application of electrochromic materials.

Abstract:The research progress of the corrosion behavior of magnesium alloy in the marine atmospheric environment was reviewed and summarized in this present literature. The current research progress was concluded, and some perspectives on future research directions were given. In the marine atmospheric environment, the electrochemical reaction of magnesium alloy under the coating of thin electrolyte layer on the surface is prone to localized corrosion, and is also susceptible to the influence of environmental factors. Compared to the inland atmospheric environment, the marine atmosphere is rich in aerosol particles, which promote serious pitting corrosion of magnesium alloys. Higher relative humidity can increase the thickness of thin electrolyte layer, resulting in higher atmospheric corrosion rate of the alloy. Meanwhile, the atmospheric corrosion rate of magnesium alloy increases linearly with the increase of temperature. CO₂ in the air can inhibit the erosion of NaCl on magnesium alloys. Future research in this field may focus on the revelation of corrosion mechanism in specific environment and the synergistic effect of various environmental factors on corrosion behavior, so as to guide the design and preparation of marine magnesium alloy materials.

Abstract:The development of miniaturized and multifunctional electronic products makes the devices face problems such as thermal damage and substrate warpage during the packaging and assembly process. In order to reduce the thermal impact of electronic packaging and assembly processes on chips and devices, low melting point interconnect materials need to be researched and developed. Tin-bismuth (Sn-Bi) alloy solder has received considerable attention due to its low melting point, low cost, good wettability and mechanical strength, but the segregation of the brittle Bi phase is detrimental to the long-term service reliability of the devices. By adding alloying elements to the Sn-Bi solder to form a Sn-xBi-yM alloy solder, the service reliability of the Sn-Bi alloy solder and its solder joints can be effectively improved. This paper analyzes and summarizes the effects of different alloying elements on the melting point, wettability, microstructure, mechanical properties, interfacial reaction and reliability of Sn-Bi solder from the perspective of solder alloying. And based on the existing research results, the future development direction of Sn-Bi alloy solder is prospected.

Abstract:The strength-plastic inversion generally exists in the traditional metals with uniform or random microstructure, while the gradient nanostructured metals exhibit excellent comprehensive mechanical properties due to the gradient change of grain size and the coordination of different characteristic sizes during deformation. In recent years, the design theory, preparation method and deformation mechanism of the heterostructures composed of heterogeneous regions with different properties have been gradually improved. In this paper, the classification and preparation methods of heterostructure metals, such as gradient structure, bimodal structure, harmonic structure, heterogeneous layered structure, dispersed nano-domain and layered nano-twin structure, are summarized. Combined with the non-uniform plastic deformation behavior of gradient nanostructured metal during stress loading, the strengthening and toughening mechanisms of gradient nanostructured metal are summarized, including gradient plasticity, geometrically necessary dislocation, mechanically driven grain coarsening, surface residual stress, surface disturbance and shear band behavior, and the challenges faced by its future development are discussed.

Abstract:The precise monitoring of humidity is related to the preservation of some deliquescent materials, the measurement accuracy of electronic instruments and other aspects. High-performance humidity sensors have a wide range of uses in modern industry, agriculture, and medicine. Humidity sensitive materials include dielectric materials, semiconductor materials, metal materials, etc. As a special kind of dielectric material containing spontaneous electrodes, the application of ferroelectric materials in the field of humidity-sensitive sensors is receiving increasing attention. Theoretically, the electrodeposition of ferroelectric materials has a strong adsorption effect on the polar water molecules on the surface, and at the same time, the polar water molecules attached to the surface can in turn affect the ferroelectric polarization, dielectric and electrical impedance properties of ferroelectric materials. Therefore, ferroelectric materials have important application prospects in high-performance wet-sensitive sensor devices, and ferroelectric wet-sensitive materials have the advantages of high sensitivity, fast response, and good stability. This paper reviews the development history and status of ferroelectric moisture-sensitive materials, and summarizes in detail the physical mechanism of humidity sensing by ferroelectric materials. The ferroelectric moisture-sensitive materials are classified into four major parts, namely, ferroelectric nano, ferroelectric ceramic, ferroelectric thin film, and ferroelectric single crystal, according to their categories and properties, and the research progress of their moisture-sensitive properties and various factors affecting the moisture-sensitive performance are reviewed respectively, in order to provide some scientific references for the future research of moisture-sensitive of new ferroelectric materials.

Abstract:In recent years, with the development of refractory metal research, the traditional process can not meet the demand of refractory metal and its complex structure. In view of the high melting point and excellent high temperature mechanical properties of refractory metal materials, combining them with laser additive manufacturing technology will provide greater elasticity and machinability in refractory metal design. In this paper, we summarize the laser additive manufacturing technology of refractory metal materials. According to material classification, tungsten alloy, porous tantalum, molybdenum alloy and refractory high entropy alloy are reviewed. Because refractory metals manufactured by laser additive are sensitive to low melting point elements and processing parameters, we conclude the influences of these factors on process control and final part quality. Finally, including the advantages and disadvantages of the current research are, and the future development trend is prospected.