Abstract:In order to obtain the critical thickness of graphite-like carbon coating on 6061 aluminum alloy with the corrosion resistance against proton acid and the reduction value of interfacial contact resistance, a series of graphite-like carbon coatings were deposited on 6061 aluminum alloy plate by a magnetron sputtering system. The microstructure of the deposited coatings was characterized, and the interfacial contact resistance, corrosion resistance, and stability of the coatings were analyzed. Results show that the critical thickness of the graphite-like carbon coating on 6061 aluminum alloy with corrosion resistance against the proton acid in proton exchange membrane fuel cell cathode environment is 0.97 μm. Compared with the ones prepared at low carbon target currents, the coatings prepared at the carbon target current of 4.5 A show a smoother surface. When the carbon target current reaches 4.5 A, the interfacial contact resistance is the lowest, reaching 16 mΩ·cm², which is two times larger than that of the graphite bipolar plate.

Abstract:The multifunctional 7075 aviation aluminum alloy with excellent superhydrophobic property was prepared by a simple, low-cost, and efficient etching process. The impedance results show that charge transfer resistance of prepared superhydrophobic 7075 aluminum alloy increases, and the double-layer capacitance decreases obviously, thus significantly improving the corrosion resistance. This research is of great economic value and practical significance for developing low-cost and efficient anticorrosion technique for aviation materials.

Abstract:The effect of ultrasonic vibration (USV) on solidification microstructure of Al-11.5Si-4Cu-2Ni-1Mg-0.45Fe (wt%) piston alloy was investigated. Results show that the significant refinement and morphology transformation from strip into compact polygon can be observed for the primary Si in the alloys produced by USV. The enhanced heterogeneous nucleation and shortened growth time caused by the large undercooling which is triggered by cavitation are responsible for the refinement of primary Si. The morphology of eutectic Si gradually develops from long plate into a short plate structure with increasing the ultrasonic power. Meanwhile, the morphology of α-Al₅FeSi phases changes from coarsening block shape to half circle. The morphology evolution and refinement of eutectic Si as well as intermetallic particles are mainly due to the fragmentation of solid crystals, homogeneous solute distribution field and temperature field, and shortened eutectic growth time caused by cavitation.

Abstract:The influence of annealing temperature on optical properties and surface structure of Ge films prepared by electron beam evaporation was investigated. Ge films with a thickness of about 850 nm were prepared on silicon substrate and annealed at 350, 400, 450, and 500 °C. The transmittance of the film was measured by infrared spectrometer. The variation of refractive index and extinction coefficient of thin films was obtained by spectral inversion method. The crystal properties and surface morphology of the specimens were analyzed by X-ray diffraction and atomic force microscope. Results show that compared with the properties of films before annealing, the transmittance of films after annealing is increased, while the refractive index and extinction coefficient become decreased. When the annealing temperature increases from 350 °C to 500 °C, the transmittance and refractive index gradually decrease, while the extinction coefficient gradually increases. Crystallization occurs in the films after annealing above 400 °C and the Ge(111) crystal plane is the preferred growth orientation. With increasing the annealing temperature, the grain size becomes larger, the granular particles appear on the film surface, and the surface roughness is increased.

Abstract:TiO₂ was selected as the additive of the contact material, and AgSnO₂ and AgSnO₂/TiO₂ contact materials with six different particle sizes of second phase (SnO₂) were prepared by powder metallurgy. The wettability and electrical contact properties of both contact materials were studied. The wetting angle between Ag and SnO₂ was measured by the sessile drop method, and the wettability was characterized. The JF04C electrical contact material testing system was used to test the electrical contact properties, and the change laws of wettability and electrical contact performance of contact materials with different particle sizes of second phase were analyzed. The results show that the properties of the two contact materials with the particle size of second phase ranging in 100~300 nm are better than those with other particle sizes.

Abstract:The as-cast Al_0.3CoCrFeNi high-entropy alloy (HEA) surface was treated by pulsed laser at four different powers (150, 250, 350, 450 W). According to the positions relative to the laser source, HEA structure could be transformed into three parts: the center of laser-affected zone with the cellular structure, the edge of laser-affected zone with the banded cellular structure along the grain boundary, and the unaffected area with original grains. Attributed to the rapid melting and solidification induced by pulsed laser, the cellular structure can be observed in all specimens processed at different powers. Additionally, the long cellular structures can be observed in the edge of the laser-affected zone. Then the specimens after pulsed laser surface treatment were annealed at 660 and 800 °C for 2 h, which leads to the precipitations along the boundaries of the cellular structure. The hardness test results show that the combined method of pulsed laser surface treatment with heat treatment improves the hardness of Al_0.3CoCrFeNi HEA remarkably.

Abstract:The out-of-plane compressive behavior of the closed-cell aluminum foam plate, 3 types of empty corrugated plates, and the sandwich panels with 3 types of closed-cell-aluminum-foam-filled corrugated aluminum plates bonded by epoxy resin was investigated. The results show that the aluminum-foam-filled corrugated plates can increase the compressive strength and energy absorption capacity significantly, and obtain more stable mechanical properties. Aluminum-foam-filled corrugated plates have an obvious three-dimensional effect in compression. The smaller the strength of sandwich panel, the more obvious the three-dimensional extension deformation. The aluminum-foam-filled corrugated plates made of different aluminum alloy plates with different strengths all show similar mechanical properties. The 3003 aluminum alloy plate with good formability, high corrosion resistance, and good weldability is suitable for face plates and corrugated plates.

Abstract:The deformation and damage behavior of the single crystal Ni-based alloy during elevated temperature creep were investigated through analyzing creep properties and microstructure. The results show that the creep life of Ni alloy under the condition of 1040 °C/137 MPa is 556 h, displaying an excellent creep resistance of Ni alloy. The creep feature of Ni alloy at steady state is the dislocation glide in γ phase and dislocation climb over the γ′ rafts. In the late stage of creep, the deformation feature of Ni alloy is that the γ′ rafts are sheared by the dislocations of cross-slip, which forms the Kear-Wilsdorf (K-W) locks to restrain the dislocation glide and cross-slip dislocation. The cross-slip dislocations cause the distortion of γ/γ′ rafts, thereby promoting the initiation of cracks along the γ′/γ interfaces and the interface fracture, which is the damage and fracture features of Ni alloy. The condition of σ>η/α is considered as the prerequisite for unstable crack propagation.

Abstract:The creep behavior and deformation mechanism of the nickel-based single-crystal superalloy containing 6wt% Re and 5wt% Ru at ultra-high temperatures were studied via microstructure observation and creep property analysis. The results show that under the condition of 1160 °C/120 MPa, the Ni-based superalloy has a creep life of 206 h. During the steady state creep period, the deformation mechanism is dominated by dislocation glide in the γ matrix and dislocation climb over the γ′ raft phases. The refractory elements dissolved in the γ matrix can improve the resistance to dislocation movement. In the late creep stage, the cross-slip occurs from {111} plane to the {100} plane with the dislocations used for shearing the γ′ phase, and then the Kear-Wilsdorf (K-W) dislocation locks are formed. A large number of K-W dislocation locks can inhibit the dislocation glide and cross-slip, thus improving the creep resistance and reducing the strain rate for Ni-based superalloys. In the late creep stage, the cross-slip dislocations are initiated to twist the γ′/γ raft phases, and the crack initiation and propagation occur in the γ′/γ interfaces until fracture. These phenomena are the damage and fracture features of the Ni-based superalloys. The Ru atoms dissolved in the γ′ phase can replace the Al atoms. When Ru, Re, and W atoms react in the Ni-based superalloy, more Re and W atoms can be dissolved into the γ′ phase, which reduces the element diffusion rate and hinders the dislocation movement, thereby retaining more K-W dislocation locks and excellent creep resistance of Ni-based superalloys at ultra-high temperatures.

Abstract:The commercial Fe-Si-B metallic glass (Fe-Si-B^MG) powder and the widely used powder of zero valent iron (ZVI), namely Fe⁰, were used to eliminate the Ni(II) from aqueous solution. Kinetic analysis results indicate that the removal efficiency of Fe-Si-B^MG powder in removing Ni(II) is about 38 times faster than that of the Fe⁰ powder. Morphology observation shows that the product layers on the surface of Fe-Si-B^MG powder are composed of homogeneous and loose whiskers, which peel off more easily from the surface during the agitation process, compared with those of Fe⁰ powder. Chemical composition analysis about the surface of Fe-Si-B^MG powders before and after reaction shows that Fe-Si-B^MG powder can eliminate the Ni(II) through surface adsorption, reduction, and coprecipitation mechanisms; while Fe⁰ powder removes the Ni(II) in solution mainly through surface adsorption and coprecipitation mechanisms.

Abstract:AgCuOIn₂O₃SnO₂ electrical contact materials with different SnO₂ contents were prepared by reaction synthesis coupled with plastic deformation process. The morphology and microstructure of the AgCuOIn₂O₃SnO₂ contact materials were characterized by scanning electron microscopy and optical microscope. The distribution uniformity of the metallographic structure and the reinforcement phase of the materials with different SnO₂ contents was analyzed. The phase structure of the materials was measured by X-ray diffraction, and the tensile strength, hardness, and resistivity of the materials were also measured. Results show that the appropriate SnO₂ addition can significantly decrease the pore size and reduce other defects in the structures. The diffusion of oxides in the silver matrix greatly improves the microstructure uniformity of AgCuOIn₂O₃ contact materials. When the SnO₂ content is fixed, the resistivity of materials is decreased with conducting the plastic deformation; with increasing the SnO₂ content, the resistivity is decreased firstly, then increased, and finally turns to be stable at 2.4 μΩ·cm. The hardness of the materials is increased significantly after SnO₂ addition. The material with 1wt% SnO₂ shows the optimal tensile strength and elongation.

Abstract:AlCrN/AlCrVN multi-layer coatings with different numbers (1, 2, 4, 6) of bilayers were deposited by arc ion plating method. The effects of multi-layer structure on microstructure, mechanical properties, tribological properties, and cutting performance were investigated. The results show that the deposited AlCrN/AlCrVN multi-layer coatings are mainly composed of solid solution (Al,Cr)N with preferred growth orientation of [111] crystal orientation. Compared with other multi-layer coatings, the lowest coefficient of friction (~0.46), the lowest wear rate of 0.15×10^-11 m³/N·m, the highest hardness of HK_0.05=38 000 MPa, and coating-substrate bonding strength of L_C2=53±1 N can be achieved for AlCrN/AlCrVN multi-layer coating with 6 bilayers at high temperature. The improvement in hardness and wear resistance is due to the formation of more interfaces between adjacent layers. Cutting test results reveal that AlCrN/AlCrVN coating with 6 bilayers has the longest cutting length of 7.4 m under the cutting wear standard condition of flank wear VB=0.2 due to its relatively higher hardness and better wear resistance.

Abstract:Stress relaxation tests were performed on Ti-6.5Al-2Zr-1Mo-1V titanium alloys with different initial stresses at 500, 550, and 600 °C. Based on the classical Maxwell exponential decay function, the stress relaxation limit was obtained. The relaxation stability coefficient (C_S) and relaxation rate coefficient (C_R) were proposed to describe the relaxation characteristics and to further guide the residual stress reduction. The stress exponent was calculated according to Norton and Arrhenius equations. Both the stress exponent and microstructure were analyzed to illustrate the stress relaxation mechanism. Under different initial stresses, the dislocation climb and diffusion dominate the stress relaxation procedure at 500 °C; the dislocation slip plays a major role in stress relaxation at 550 °C; the dislocation slip, boundary slip, and grain rotation control the stress relaxation process at 600 °C.

Abstract:Bi₂Sr₂CaCu₂O_8+δ (Bi-2212) precursor powders were prepared by spray pyrolysis (SP) and co-precipitation (CP) processes separately. The intermediate phase evolution of Bi-2212 grains was investigated. Compared with that prepared by CP process, the phase formation rate of Bi-2212 grains prepared by SP process is obviously improved. Furthermore, the residual carbonates in CP powders hinder the formation of Bi-2212 grains, while the nitrates in SP powders only have a weak influence on the growth of Bi-2212 grains. The properties of Bi-2212 wires from SP precursor powder are close to those of the ones from CP precursor powder. Considering the much higher fabrication efficiency, SP process is useful for mass production of Bi-2212 wires.

Abstract:Band electrode submerged arc overlay welding was used to weld welding strip of EQ309L stainless steel on the surface of Q345R matrix. The microstructure of EQ309L side, Q345R side, and their interfaces were observed by electron backscattered diffraction (EBSD) technique. Results show that most grains in Q345R matrix are seriously distorted, and the banded grains along the original rolling direction can be clearly observed. The average grain size of Q345R matrix is 30~40 μm in the overheated coarse-grain region, and the grain coarsening is not severe. The average grain size of the fine-grain region is 10~20 μm in the Q345R matrix. The transition zone is 35~40 μm away from the fusion line of Q345R matrix, and it has body-centered cubic (bcc) structure. The EQ309L layer has coarse grains, showing the microstructure of columnar crystal with obvious <100> texture.

Abstract:The microstructure evolution and surface recrystallization behavior of sandblasted DD483 Ni-based superalloys after heat treatment around the service temperature were investigated. The specimens of DD483 alloy were sandblasted under the pressure of 0.4~0.7 MPa and annealed at 1100 °C for 4 and 16 h. The results show that the surface of the alloy is effectively cleaned and the compressive stress is introduced into the surface by sandblasting within the range of predetermined sandblasting pressure. After annealing for 4 and 16 h, the Ti and Al elements volatilize to the surface in the form of oxides, and the cellular recrystallization structure appears on the specimen subsurface. The topologically close-packed (TCP) phase and TiN are precipitated in the recrystallized region and the original matrix near recrystallized region, respectively. In addition, the thickness of the recrystallized region is increased with increasing the annealing time and the actual stress.

Abstract:The effects of ultrasonic rolling strengthening treatment and polishing on 2D12 aluminum alloys were investigated, and the surface hardening, residual stress, and fatigue life were studied. The residual compressive stress and gradient nano-crystalline structure can reduce the fatigue crack initiation and propagation, which play a critical role in improving fatigue performance of components. The results and analytic predictions indicate that after ultrasonic rolling strengthening treatment, the axial compressive stress and the microhardness of specimens are improved by 55% and 20%, respectively. The strengthening rule provides a guidance for strengthening process and the fatigue behavior improvement of 2D12 alloy.

Abstract:The polycrystalline nano-TiO₂ was synthesized by the gaseous-liquid detonation (GLD) method using H₂, O₂, and TiCl₄ as the mixture precursors. The effects of different molar ratios of precursors and initial reaction pressures on the nano-TiO₂ crystalline structures were studied. The nanocrystal structures, components, particle size, and morphology were characterized by the X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results demonstrate that the nano-TiO₂ consists of pure anatase-TiO₂, pure rutile-TiO₂, and the mixtures of spherical or quasi-spherical morphologies with particle size of 20~150 nm. Furthermore, the formation mechanism of nano-TiO₂ by GLD method was analyzed. The relevant GLD parameters were calculated based on the C-J theory and the related chemical reaction data, which effectively verifies the influence of different molar ratios of precursors and initial pressures on the controllable synthesis of polycrystalline nano-TiO₂.

Abstract:Nickel-platinum (NiPt) alloy sputtering target is an important raw material in semiconductor industry. Its microstructure characterization and adjustment are of great significance to improve the quality of target and sputtering film. The recrystallization behavior of cold rolled NiPt5 alloy during annealing treatment was investigated by Electron backscatter diffraction (EBSD) analysis system. The results showed that, the major orientation of cold rolled 80% NiPt5 alloy is {112}<021> texture. After annealing at 450℃, the grain nucleation occurred firstly at the deformation zone of <110>∥ND with sub-grain coalescence mechanism. For samples annealed between 550 ℃ to 650 ℃, the average grain size of recrystallized grain structure increased from 1.2 μm to 15 μm and the orientation distribution tended to <110>∥ND; the evolution of HABS and LABS dominated the structure evolution of NiPt5 alloy. For sample annealed at 550℃, the main grain growth mechanism is grain rotation and coalescence. For sample annealed at 650℃, the appearance of a large number of sub-crystals and 60°{111} annealing twins suggested the co-existence of grain rotation and grain boundary migration mechanism.

Abstract:To overcome the key scientific issues of poor plasticity of most magnesium alloys at room temperature, this paper reviews the theoretical and experimental basis of using stacking fault energy to improve their room temperature plasticity from three aspects: the dislocation characteristics of magnesium alloy, the influence of stacking fault energy on the deformation mechanism, and the relationship between stacking fault energy and critical shear stress of slip system. On this basis, the calculation model of “stacking fault energy-critical shear stress of magnesium alloy slip system” was established. And the critical shear stress of pure Mg, Mg-Al, Mg-Zn and Mg-Y alloy at base plane, prismatic plane and pyramidal plane was calculated by using this model. The influence of Al, Zn and Y on the plasticity of Mg alloy was analyzed by comparing the critical shear stress difference between the slip system of non-base plane and base plane of Mg alloy and pure Mg, so as to verify the reliability of the model. Finally, we propose to reduce the slip shear stress of non-base plane dislocations (especially the dislocations) as a guideline to select appropriate alloy elements for the design of high plasticity magnesium alloys at room temperature.

Abstract:The adsorption of H₂ on Zr(0001) crystal surfaces is studied by the first-principles plane wave pseudopotential method within the density functional theory. By calculating the preferred adsorption sites, adsorption energy and electronic structure of Z(0001)/H₂ system, the microscopic mechanisms for adsorption of H₂ on Zr(0001) surfaces was clarified. The results show that the favourable adsorption position of H₂ on Zr(0001) surface is the fcc site and its adsorption energy is 0.899 eV belonging to a strong chemical adsorption, and the two H atoms dissociated from H₂ molecules are finally stably adsorbed at the hollow and fcc sites on the surface of Zr(0001). There is a large amount of charge transfer between the adsorbed H atom and Zr (0001) surface, which results in the formation of ionic bond between H and Zr atom, and the typical covalent bonds between H and surface Zr formed through the orbital hybridization of H1s and Zr5s, 4d. As a result, one can see that the chemical bonding between the H atom and the surface Zr atom is a characteristic mixture of the ionic and covalent bonding. In addition, the adsorption energy gradually increases with the coverage. When the coverage increases to a certain value, half of H atoms are adsorbed on the subsurface.

Abstract:Due to the large cooling rate, the workpiece often produces thermal stress during the high-pressure gas quenching process, and even plastic deformation or cracking occurs. Therefore, it is particularly important for industrial production to accurately predict the thermal stress distribution of the workpiece during the high-pressure gas quenching process. In this paper, the numerical heat transfer and turbulence model of an exchange flow type vertical high pressure gas quenching furnace was established using computational fluid dynamics method to simulate the gas quenching of a Ti2AlNb hollow workpiece processed by superplastic forming/diffusion bonding.The mesh of simplified furnace model was built using finite volume method and the boundary conditions are set according to the actual working conditions.The simulation results show that at the beginning of gas quenching, the edges around the Ti2AlNb workpiece cool faster than the core. As time increases, the both sides cool faster than the core. The temperature distribution determines the thermal stress distribution. Ti2AlNb workpiece has a high temperature in the core and low temperature at the edges, which causes the core to be restricted by the edges and cannot expand freely, so the core is under compressive stress. During the gas quenching process, the thermal stress does not exceed the yield strength, which belongs to the elastic range.

Abstract:The molecular dynamics method was used to simulate the atomic diffusion behavior of diamond and titanium during the hot pressing diffusion process. The atomic diffusion process at the interface between diamond and titanium at different diffusion temperatures was simulated, and the atomic concentration distribution, diffusion velocity and simulated diffusion coefficient were obtained. The hot pressing diffusion method was used to coat a titanium layer on the diamond surface and the width of the diffusion band at the interface was measured. The research results show that the diffusion speed of C atoms is greater than that of Ti atoms during the diffusion process. With the increase of the diffusion temperature, there exist two stages of atom diffusion, low speed and fast stages. Data fitting of the simulated diffusion coefficients through the molecular dynamics simulation of hot pressing diffusion can be used to determine the diffusion factors and activation energy values of C and Ti atoms. The formula of atomic diffusion coefficient calculation can be determined through a simple and effective method. The calculated value of diamond and titanium diffusion band width is close to the measured value, which indicates that the formula of atom diffusion coefficient obtained by the molecular dynamics method is feasible.

Abstract:In order to study the load-bearing law of tungsten carbide ceramic-coated screws in the process of high-strength plastic injection molding, ANSYS finite element simulation was used to calculate the load-bearing characteristics of tungsten carbide-coated screws with different screw ridge structures, and the three-section tungsten carbide coating on steel substrate was analyzed The influence law of screw load, simulates the stress/strain change law of tungsten carbide coated screw under torque load, discusses the corresponding relationship between the load torque of tungsten carbide coated screw and the maximum stress and maximum strain, and establishes the critical torque of tungsten carbide coated screw The method of determination. The results show that the base material and the tungsten carbide coating at the smallest position of the screw bottom diameter bear the maximum stress and the maximum strain. Under the same loading torque condition, the smaller the screw bottom diameter, the greater its bearing stress and strain; Tungsten coating fracture strength/elongation simulation calculation method of critical torque of tungsten carbide coating screw, simulation calculation method of critical torque of tungsten carbide coating screw of unknown steel substrate based on material elastic modulus and yield strength, the calculation results of the two methods are basically verified Consistent; on this basis, the critical torques of the Cr12Mo1V1, 9Cr18MoV, and CPM420V steel base NiMoCrFeCo-WC coated screws are simulated to be 330.34, 346.87, and 363.59N·m, respectively.

Abstract:In this paper, Ti-6Al-7Nb titanium alloy was studied. The Gleeble-3500 thermal simulation compression testing machine was used to carry out compression tests at different temperatures and strain rates. The high temperature deformation behavior and hot working characteristics of Ti-6Al-7Nb titanium alloy at deformation temperatures of 1023 K、1073 K、1123 K、1173 K and strain rates of 0.005 s-1, 0.05 s-1, 0.5 s-1, 5 s-1, 10 s-1, and the maximum deformation is 60%. The results show that deformation temperature and strain rate change the flow stress curve of Ti-6Al-7Nb titanium alloy, and have complex effects on work hardening and flow softening during the hot plastic deformation of the alloy. The main phases of Ti-6Al-7Nb titanium alloy after hot plastic deformation are as follows: primary α phase, lamellar α phase, secondary α phase, lamellar β phase and primary α phase with spheroidization. The strain rate has a significant effect on the deformation hardening effect of the alloy. The Arrhenius constitutive equation model is suitable for high temperature deformation of Ti-6Al-7Nb titanium alloy under high strain rate, low temperature and high temperature deformation conditions. The optimum plastic deformation range of Ti-6Al-7Nb alloy is determined by MATLAB construction and calculation: the strain rate is 0.0067 s-1-0.1353 s-1 and the temperature is 1100-1173 K. It is possible to obtain the best plastic deformation process parameters of Ti-6Al-7Nb titanium alloy in this region.

Abstract:Series double-pass hot compression experiments were carried out on the MTS810-25T low-cycle fatigue testing machine for the new type alloy of high-quality GH738. The effects of initial grain size, deformation temperature, holding time between passes and strain rate on the evolution of sub-dynamic recrystallization structure of high-quality GH738 alloy were analyzed. Furthermore, combined with quantitative metallography and nonlinear fitting analysis, the sub-dynamic recrystallization models of high-quality GH738 alloy were established. The experimental results show that the decrease of the initial grain size, the increase of the deformation temperature, the extension of the pass interval, and the increase of the strain rate can promote the progress of sub-dynamic recrystallization, and increase the recrystallization volume fraction. Increase the deformation temperature and strain rate can reduce the difference in grain size after sub-dynamic recrystallization, and further improve the uniformity of the microstructure distribution. Based on the experimental results, by using quantitative metallography and nonlinear fitting analysis, sub-dynamic recrystallization models of high-quality GH738 alloy were obtained. The predicted values of the established models were in good agreement with the experimental values, which could meet the actual needs in engineering applications to a great extent.

Abstract:A high specific surface area Al-based metal organic frameworks (MOFs) material Al-ABTC was prepared by hydrothermal synthesis. Then the Al-ABTC and graphene oxide (GO) were compounded by electrostatic adsorption method, and sulfur was loaded to obtain Al-ABTC/RGO@S composite material for lithium-sulfur battery. The crystal structure of Al-ABTC was analyzed by X-ray diffraction (XRD), the octahedral morphology of Al-ABTC, Al-ABTC/GO and Al-ABTC/RGO@S was characterized by scanning electron microscope (SEM), and the electrochemical performance of the material was tested by constant current charge and discharge. The results show that the initial discharge capacity of the Al-ABTC/RGO@S composite electrode reaches 1345.3 mAh g-1 at 0.2 C rate, decayes to 406.4 mAh g-1 after 200 cycles, and the average coulombic efficiency is 99.1%. In addition, even at 2 C, an initial reversible capacity of 714.7 mAh g-1 was received and a capacity of 331 mAh g-1 after 300 cycles, showing an excellent long-term cycling performance.

Abstract:Tungsten-copper films were prepared on slide glass by magnetron sputtering. The structural analyses show that deposition rate and silver content increase, while grain size and microhardness of the films decreases with the copper target current. Solid solution is formed for the WCu films, and Cu particles are segregated at high Cu content. WCu films are highly hydrophobic, and film wettability, droplet size and ambient temperature/humidity affect the drying time of water droplet and water film. The antibacterial tests by plate counting and spraying of bacterial suspension show that WCu films have good antibacterial activity against E. coli. The WCu films are expected to be used in antimicrobial surface modification of environmental facilities.

Abstract:The thermal deformation behavior of W80-Cu20 composites was investigated by hot compression with Gleeble-1500 thermal simulation system in the temperature range of 810-970℃ and strain rate range of 0.01~ 10s_^-1 up to a true strain of 0.69. Based on modi?ed dynamic materials model (MDMM) and Malas"s criterion, the power dissipation map and processing map were established. Combined with microstructure, the reasonable parameters of hot processing were determined. And the damage formation of W80-Cu20 composite was analyzed. The results show that the stress-strain curves of W80-Cu20 composite are typical dynamic recrystallization (DRX) type curves, and the peak stress increases with the decreasing of deformation temperature and the increasing of strain rate. The preferable processing zones of W80-Cu20 composite were determined as follows: 840-885 ℃, 0.2-1.42 s_^-1 and 885-917℃, 0.83-2.05 s_^-1. The damage modes of W80-Cu20 composites involve Cu phase rupture, W-Cu interfacial separation, W-W grain boundary separation and W-grain crack.

Abstract:Based on ABAQUS finite element software, in view of TC4 titanium alloy L profile, under the conditions of creep temperature of 500℃, 600℃ and 700℃, and creep time of 600s, 1200s, 1800s, the numerical simulation analysis of high temperature bending creep is carried out to study the influence of temperature and time on the springback after high temperature bending creep deformation of TC4 titanium alloy L profile. The numerical simulation results show that the stress relaxation effect of TC4 titanium alloy is significantly affected by temperature, when the temperature is 700℃, the residual stress after stress relaxation is reduced to below 50MPa; when the creep time is 600s, the residual stress after stress relaxation has been reduced to a stable limit value, continue to increase the creep time, the stress relaxation effect is not significant.

Abstract:In this work, a novel near α-type powder metallurgy Ti-Al-V-Zr-Mo-Nb titanium alloy (CT1400) was firstly designed and fabricated. The microsturcture characterization, cryogenic temperature mechanical property and deforamtion behavior were also systematically investigated. Results indicated that the CT1400 mainly consists of lamellar α, equiaxed α and a few of lamellar β. The volume fraction of equiaxed α which results from dynamic recrystallization process increases with the increasing fabrication temperature, and shows diversity crystal orientation characteristic. The fabrication temperature has no significant influence on the ultimate tensile stress of CT1400 under 20 K, however, the sample fabricated with 920 ℃ displays optimal cryogenic temperature failure strain resulting from the most sufficient dynamic recrystallization process. Furthermore, CT1400 shows a mixed dislocation slipping and twinning deformation behavior at cryogenic temperature. The twinning deformation could improve the plastic deformation capacity of CT1400 via coordinating dislocation slipping process, and the dislocation strengthening effect also induces the superior ultimate tensile stress under cryogenic temperature.

Abstract:The construction of surface bioactive coating is an effective way to improve the osseointegration ability of metal-based implants. In this study, bioactive hydroxyapatite (HA) coating was fabricated on the surface of porous tantalum (Ta) scaffolds by electrochemical deposition method. The construction of HA coating significantly enhanced the hydrophilicity of porous Ta and increased its specific surface area. The in vitro bioactivity evaluation via simulated body fluid immersion confirmed that the surface of HA coated scaffold was covered with bone-like apatite layer after 3 days of soaking. The in vitro cell culture using MC3T3-E1 cells showed that all porous tantalum scaffolds had good cytocompatibility. After culturing for 5 days, the proliferation rate of the bioactive porous Ta scaffold was 1.1 and 1.4 fold significantly higher than that of the unmodified porous Ta and control groups, respectively, suggesting greater potential on promoting cell adhesion and proliferation. The bioactive porous tantalum scaffold could rapidly induce the deposition of bone-like apatite and promote the attachment and proliferation of osteoblasts on its surface, suggesting its great clinical application prospect in the fields of bone repair.

Abstract:Selective laser melting (SLM) can directly produce personalized medical implants with complex shapes based on CAD models. The paper presents an investigate on the evolution of microstructure and mechanical properties of biological pure titanium (TA1) from SLM to subsequent heat treatment. The results show that the SLMed TA1 alloy possess needle-like martensite a′ and retained prior-β columnar morphology along the building direction. After heat treatment, recrystallized equiaxed a grains are formed and the reduced porosity was found due to pores volume decrease or pores closure. In addition, the precipitations of fine TiFe and TiO₂ were observed along grain boundary or within grains in the samples treated by vacuum annealing at 800 ℃. They precipitate selectivity along the grain boundaries with different character. The subsequent heat treatments, especially vacuum annealing, significantly improve the mechanical properties of the SLMed TA1 samples, which is ascribed to combined effects of porosity decrease and the precipitation of TiFe/TiO₂ phase upon annealing.

Abstract:In this study, 6063 aluminum alloy (6063 Al alloy) which was anodized using phosphoric acid and polyphenylene sulfide (PPS) were connected successfully by ultrasonic welding method. The results show that the shear strength of untreated 6063 Al alloy / PPS ultrasonic welded joint increases at first and then decreases under the given experimental conditions. The maximum shear strength of joint is 1.41 MPa, when the welding pressure and welding time are 0.5 MPa and 6 s, respectively. Once the surface of 6063 Al alloy was anodized with phosphoric acid, the shear strength of joint can reach 16.92 MPa, which is about 12.6 times of that without anodizing. The primary failure modes of the structure are interface cracking and cohesive fracture of PPS. By observing and analyzing the structures of joint using SEM, a good mechanical interlocking between the 6063 Al alloy and PPS was formed and the intermolecular force at the interface was increased due to the forming porous structure on the 6063 Al alloy surface after anodic oxidation treatment was embedded by PPS under the effect of acoustic streaming which achieve a good combination of 6063 Al alloy /PPS.

Abstract:Hot deformation characteristics of a new-type Ni-Cr-Co based alloy was investigated by isothermal compression tests under the deformation temperature range of 1050~1250 ℃ and strain rate range of 0.001~1 s_^-1. The electron backscatter diffraction (EBSD) technique was employed to investiage the microstructure evolution and nucleation mechanisms of dynamic recrystallization. The result showed that the flow stress decreases with the increasing of deformation temperature and the decreasing of strain rate. The Arrhenius constitutive equation and processing map were established based on the hot deformation data, and the hot deformation activation energy was calculated as 520.03 kJ/mol. The optimum hot working conditions were obtained in the temperature scope of 1175~1250 ℃ and the strain rate range of 0.006~1 s_^-1 with the peak power dissipation efficiency of 45%. The fraction of dynamic recrystallization increases with the increasing of deformation temperature and the decreasing of strain rate. And during dynamic recrystallization, a large number of deformed grains were replaced by fine dynamic recrystallized grains and a high frequency of ∑3 twin boundaries were generated. The dominant dynamic recrystallization nucleation mechanism is grain boundary bulging, which is a typical feature of discontinuous dynamic recrystallization. In the low temperature and high strain rate region, continuous dynamic recrystallization characterized by the rotation of subgrains was detected. However, continuous dynamic recrystallization was just an assistant nucleation mechanism for the alloy.

Abstract:This paper describes the preliminary thermal and stress analyses of a novel coated dual pipe system with microstructure configuration under thermo-mechanical loading using a sequentially coupled simulation procedure. The influence of key parameters on the temperature and stress distribution of the system is also investigated. The results show that the protective coating layer contributes to the effective reduction in the surface temperature of the primary steel pipe, but thermal stresses generated due to the significant temperature gradient have a significant impact on the structural integrity of the system. The hoop stress in the system is much larger than the radial stress, and the maximum hoop stress is located at the peak of the TGO/BC cosine interface near the TGO side. In addition, the thickness of the TC, the thermal expansion coefficient of the TC, the temperature and pressure of the cooling steam determine the temperature and stress distribution of the system.

Abstract:In this paper microstructure, friction and wear behavior under different loads of Mg-Si-RE magnesium alloys fabricated by rapid solidified process were studied. It was found that the microstructure of the fast-solidified state Mg-Si-RE alloy mainly consists of α-Mg matrix, eutectic Mg2Si phases and REMg2Si2 nano phases with 500-800 nm size. The relationship curve of friction coefficient and wear quantity with load of Mg-Si-RE alloy is determined. Results show that the friction and wear performance of Mg-Si-RE alloy is obviously better than that of Mg-1Si matrix alloy. The load of changed from slight wear to serious wear is lower than that of matrix alloy 20 N. And the wear amount is much smaller than that of matrix alloy at high load. The wear mechanism of Mg-Si-RE alloy includes oxidation wear, abrasive wear and delamination wear. The excellent friction and wear performance of RSP Mg-Si-RE alloy is mainly due to that the nano-scale rare earth phases were well dispersed along the grain boundary and within α-Mg matrix. Moreover, the Mg-Si-RE alloys exhibit different frictional wear behaviors after the addition of different types of rare earth elements.

Abstract:Abstract:In this paper, pulsed magnetic field was applied to the aging process of TC4 titanium alloy. The effect of pulsed magnetic field on the mechanical properties and microstructure of TC4 was analyzed.By introducing atomic diffusion theory, the effect of pulsed magnetic field on precipitated phase in aging process was investigated.The results show that,After pulsed magnetic field treatment, the number of precipitates in the microstructure increases obviously, the size becomes smaller, and the distribution is more dispersed.The aging time of 0.5 h with pulsed magnetic field was compared with that of 4 h without magnetic field,The Vickers hardness increased by 35.7 HV5 and the compressive strength raise 30 MPa.Pulsed magnetic field can promote the precipitation of secondary phase, which greatly reduces the aging time.From the heory of diffusion, the pulsed magnetic field can increase the diffusion flux and promote the secondary phase precipitation by coupling the electron wind force and magnetization stress.

Abstract:In order to research the cathodic thermionic emission performance difference between preparation of tungsten matrix used ungraded tungsten powder and graded tungsten powder on the micron scale, and to gain a deeper understanding of the electron emission process of the cathode surface micro-area and the cathode emission mechanism, a newly developed instrument aiming at meeting the special operation requirements of thermal dispenser cathode is used in this paper. This instrument called DUV-PEEM/TEEM combines the functions of deep ultraviolet laser photo-emission electron microscope and thermal-emission electron microscope. Thanks to the powerful functions of DUV-PEEM/TEEM, the photoelectron and thermoelectron image of prepared cathode from two tungsten powders was analyzed. The results showed that compared with the ungraded material tungsten powder, the microstructure of the tungsten matrix prepared by the graded tungsten powder is more uniform, and the closed cell ratio was reduced from 1.44% to 0.47%; the photoelectron and thermionic united imaging accurately showed that the emission of the two cathodes mainly located at the pores and active substances of pores; via thermal electron (TEEM) images, the thermal electron emission micro-area area of the cathode prepared by graded tungsten powder was larger and the distribution was more uniform than the cathode prepared by ungraded tungsten powder; and under the working condition of 1050℃, the pulse current density of the cathode prepared by graded tungsten powder was 30.79A/cm2, and the emission slope was 1.38, comprehensive analysis showed that it had more ideal intrinsic thermionic emission capability and emission uniformity, which has a certain guiding effect on understanding the cathode emission performance and improving the hot cathode preparation process.

Abstract:The explosive welding interface between TA2 and 5083 is prone to produce brittle intermetallic compounds, oxides, continuous melting zone and other defects, the welding window is narrow, and the optimal welding parameters are difficult to obtain accurately.In this paper, the β-Vf model of dynamic bending Angle β and impact velocity Vf is reconstructed. The numerical simulation of TA2/1060/5083 explosive welding with explosive thickness of 10mm, 15mm and 20mm and flyer plate thickness of 1.5mm are carried out for the first time by using the Steinberg-Guinan material constitutive model using SPH and Lagrange coupling algorithm. The parameters obtained from numerical simulation were used to carry out explosive welding experiments.The numerical simulation and experimental results show that TA2/1060 and 1060/5083 interface have high quality straight bond when the explosive thickness is 10mm, and 1060/5083 interface has wavy shape bond when the explosive thickness is 15mm. No brittle intermetallic defect formation is detected at the Ti-Al transition interface under the two explosive thickness conditions;When the thickness of explosive is 20mm, the material is damaged and can not be recombined.In this paper, a large area TA2/1060/5083 composite material has been successfully prepared, and the explosive welding process has been accurately calculated, which provides a reliable algorithm for the dissimilar metal explosive composite problem with great difference in physical and chemical properties.

Abstract:The tensile properties, impact properties, dynamic mechanical property and ballistic performance were tested for four kinds of typical titanium alloys of TA15、Ti-6432、TC21 and Ti-15Mo. The microstructure of the different alloying sheets after penetration test of bullet were analyzed. The results show there is no direct relationship between impact properties and tensile properties for four alloys. For tensile properties and dynamic mechanical property, there is a law that high tensile strength is corresponding to high dynamic compression rheological stress and high elongation is corresponding to high homogeneous plastic strain. However, this law is only a reflection of the trend, and there is no corresponding proportional relationship between the specific values. For dynamic performance and ballistic performance, the order of dynamic properties of the four alloys is TC21＞ TA15＞Ti-15Mo＞Ti-6432, the ones of ballistic performance is TC21＞TA15＞Ti-6432＞Ti-15Mo. From the specific value, the difference of dynamic properties for four alloys is obvious but the ones of penetration depth is not obvious, which is at the same level. Besides, the penetration depth of Ti-15Mo is obviously larger than that of other alloys. Which shows that the dynamic performance can not fully reflect the ballistic performance. The above results are mainly related to different microstructure types and different deformation damage mechanisms in the damage process.

Abstract:Effect of different loading waveform on fatigue damage of TC17 titanium alloy under the high stress level is researched. The results show that the dwell fatigue life is lower than low cycle fatigue life for TC17 titanium alloy under the peak stress and the dwell loading for 120s. Under the condition of the same high load dwell fatigue, the fatigue sensitivity of lamellar organization is lower than that of the equiaxed structure. Fracture analysis shows that the crack source of dwell fatigue appeared on the surface and sub-surface of the sample, while that of low cycle fatigue appeared on the surface of the sample. The fracture surface of dwell fatigue was flatter than that of the conventional low cycle fatigue, and the fracture mode did not change fundamentally under the dwell loading condition.

Abstract:Based on the experimental results, the finite element model was established to study the effect of different preheating temperature on the stress, strain and microstructure of AgCuOSnO2 composites during hot extrusion, and the experimental results were verified by simulation calculations. The results show that the increase of preheating temperature will lead to stress reduction, particle dispersion and metal fluidity enhancement, which is beneficial to reduce the wear depth of the mold, but will weaken the degree of fibrosis of CuO. The temperature gradient appears in both the axial and radial directions, and the temperature change of both shows opposite laws during hot extrusion. The radial temperature difference can be zero by increasing the preheating temperature. At 800 ℃, the billet is heated evenly, the mold wear is small, and cubic CuO can be fully fibrosis. Therefore, it is the ideal preheating temperature for hot extrusion of AgCuOSnO2 composite.

Abstract:The Mn-Ga alloy displays high coercivity and a relatively large magnetic anisotropy. These characteristics suggest that it is a good potential magnetic material for the future. Herein, we prepared Mn-20at%Ga magnetic nanocomposites through mechanical alloying using high-energy ball milling. After ball milling for a total time of 3.5 h, the powder was placed in a cylindrical die with an inner diameter of 10 mm, and was pressed into a bulk specimen of size ? 10×30 mm. The samples were sintered in the temperature range from 300℃ to 415℃, and annealed from 2h to 8h. This paper focused on the formation of magnetic phases and their sizes, magnetic properties under various heat-treatment conditions. The results showed that the main magnetic phases in Mn-20at%Ga alloys were Mn3Ga and Mn0.85Ga0.15, in addition to the MnO2 phase caused by oxidation. Mn3Ga and Mn0.85Ga0.15 were generated respectively from the high Ga content region and low Ga content region caused by the high-energy ball milling. The high Ga content region appeared to be irregular particles, whereas the low Ga content region appeared to be located in the interparticle region. The magnetic properties were measured at room temperature using a vibrating sample magnetometer. To evaluate the magnetic properties quantitatively, the coercivity, remanence, and energy product were deduced from the data of hysteresis curves. The remanence, coercivity, and maximum energy product can be improved by enhancing the annealing temperature into a proper range. Enhancing the annealing time properly also benefited the improvement of remanence and maximum energy product. However, coercivity change due to the annealing time was negligible. The optimal magnetic properties in this research were obtained at an annealing temperature of 385℃ and annealing time of 6h, which showed a remanence of 63.21 emu/cm3, a coercivity of 8.1 kOe, and a maximum energy product of 0.15 MGOe. The size change of Mn3Ga nanophase due to annealing conditions was small. However, the size of Mn0.85Ga0.15 nanophase was decreased due to a proper enhancement of annealing temperature and annealing time, which corresponded to the increase of coercivity. The crystal size decrease of Mn0.85Ga0.15 benefited the enhancement of magnetic properties.

Abstract:In the experiment, Fe76cr12mn12n alloy powder was prepared by mechanical alloying. The mechanical alloying process and mechanism were studied. The results show that the powder can be fully alloyed after 4 hours of rod milling. The diffraction peak widens and the diffraction intensity decreases with the increase of rod milling time,. The morphology of the powder particles gradually became spherical. The non-spherical solid solution powders obtained by mechanical alloying can also be used in laser melting deposition (LMD) additive manufacturing technology, which solves the limitation of LMD to spherical powder. The thick cladding coating obtained by LMD technology has good corrosion resistance, and it shows BCC+ FCC dual phase structure. Meanwhile, Cr2N is generated in the printing process. the Vickers hardness of thick coating could reach up to 456.3 HV.

Abstract:The effects of increasing Al+Ti content on microstructure and mechanical properties of IN 617 alloy before and after long time age heat treat were studied. The results show that increasing Al+Ti content contribute to more γˊphases and bigger size which can evidently influence strength, and we can achieve high tensile strength and stress rupture property. Compared to increasing Al content only, increasing Al+Ti content had better structure stability and long stress rupture life. The results indicated that IN 617mod2 alloy can be chose as one of candidate materials for A-USC rotor.

Abstract:Al/Ti laminated composite features remarkable properties, such as low density, high strength, high stiffness and impact resistance, but its application has been limited because of the brittleness of Al3Ti. Its strength and toughness can be improved by introducing fibers and ceramic particles, which makes it have a broad application prospect in aerospace, weapons and armor. In this paper, the preparation methods of fibers and ceramic particles reinforced Al/Ti laminated composite were reviewed. The merit and dement of different preparation methods were compared. Besides, some feasible methods of boron carbide(B4C) reinforced Al/Ti laminated composite were proposed. The 0.2 mm thick B4C sheets reinforced Al/Ti laminated composite was prepared by vacuum hot pressing method. In this method, B4C sheets strengthen the matrix through directly receiving loads and deflecting crack by hardness gradient. Its impact toughness was 89 J/cm2 and bending strength was 756 MPa, it is increased by 51% and 38% respectively compared with the Al/Ti laminated matrix.

Abstract:_{:Scandatecathodes have excellent electron emission properties, but they also have some problems such as emission non-uniformity and poor repeatability. To improve the performance of the cathodes, a method of depositing a kind of composite film on the surface of scandate cathode by Pulse Laser Deposition technology was proposed. The film was deposited using zirconium and high-active barium aluminate salt target alternately. In the paper, the coated scandate cathode was prepared, and its electron emission performance was tested. The photo/thermal emission electron microscopywasobserved, and auger electron spectroscopy analysis of the composition and its depth distributionof the cathode was also processed. The research results show that more Ba and Sc content were detected on the coated cathode surface after activation. An active layer with thickness of 110} ~ _{130 nm was obtained. The cathode exhibits great emission performance. At the same time, the electron emission uniformity of the cathode is significantly improved.}

Abstract:High-entropy ceramics (HECs) usually refer to multi-principal solid solutions formed by five or more ceramic component, which possess many superior properties, such as extremely high hardness and modulus, low thermal conductivity and good oxidation resistance, and exhibit great potential in aerospace, high-speed cutting tools and other harsh environments. However, the current research on HECs is still in its infancy. The improvement of theoretical criteria and composition design theory, the establishment of solid solution coupling mechanism, the optimization of preparation method and the application of high throughout computation are urgently needed in the future. This paper summarized the research progress of HECs, which mainly introduced material design, preparation technology and performances of HECs, and the future development of HECs was prospected.

Abstract:Ce-based bulk amorphous alloys have the characteristics of low elastic modulus, low glass transition temperature, good glass formation ability, etc. Compared with the traditional Zr-, Ti-, Fe-, Pd-based and other bulk amorphous alloys, Ce-based bulk amorphous alloys require lower temperature conditions for uniform plastic deformation in the supercooled liquid region. Due to low-temperature thermoplastic behavior characteristics similar to plastics, Ce-based bulk amorphous alloys are also called metallic plastics. In this paper, we mainly introduce Ce-Al-M, Ce-Al-Cu-X, Ce-La series and Ce-Ga series bulk amorphous alloys. Different from the traditional amorphous alloys, these Ce-based bulk amorphous alloys exhibit unique microstructure features and performance advantages. Their application prospects in the micro-device manufacturing, data storage and other fields are discussed. The existing problems in present research of Ce-based bulk amorphous alloys and their development directions in the future are analyzed as well.