The isothermal compression test of Ti-25 Al-15 Nb-1 Mo alloy melted in vacuum was carried out with Gleeble-3800 thermal simulation tester.The high temperature rheological curve,microstructure evolution and hardness change trend in different regions of the alloy at temperature of 1100~1200℃and strain rate of 0.1~0.5 s^-1 were studied.The results show that in the process of high temperature deformation,the true stress-strain curve of the alloy appears a single peak,and the flow stress of the alloy decreases with the decrease of strain rate or the increase of temperature.Thermal deformation changes the microstructure from mixed structure of coarse O-lath and original B2 phase to single B2 recrystallization structure.The main reason for the rheological softening and microstructure evolution of the alloy is the dynamic recrystallization of B2 structure.The minimum hardness of recrystallization zone is 350 HV,which is related to dynamic recrystallization.

Mo-12Si-8.5B and Mo-12Si-8.5B-8Ti alloys were prepared by spark plasma sintering at different sintering temperatures,and their microstructure and mechanical properties at room temperature were compared.The results show that Mo-12Si-8.5B alloy consists of Moss,Mo3Si and Mo5SiB2,while Mo-12Si-8.5B-8Ti alloy consists of(Mo,Ti)ss,(Mo,Ti)3Si and(Mo,Ti)5SiB2,and solid solution of Ti occurs in the three phases.The density,Vickers hardness and bending strength of the two alloys increase rapidly at the sintering temperatures of 1400~1600℃,and that have no significant change at the sintering temperatures of 1600~1700℃.Compared with the Mo-12Si-8.5B alloy,the hardness and bending strength of the Mo-12 Si-8.5 B-8 Ti alloy sintered at 1700℃ increase by 10.2% and 15.1%,respectively.Therefore,the addition of Ti can improve the mechanical properties of Mo-12Si-8.5B alloy at room temperature,which is attributed to the decrease of micropores in Mo-12 Si-8.5B-8Ti alloy and the solution strengthening effect of Ti in(Mo,Ti)ss,(Mo,Ti)3Si and(Mo,Ti)5SiB2.

Al/Ni dual doped lithium manganate thin film electrode materials were prepared by electrostatic spray deposition,and XRD,SEM,cyclic voltammetry and constant current charge-discharge technique were employed to characterize phase,morphology and electrochemical performance of the materials.The results show that the electrostatic spray deposition technology can prepare doped modified lithium manganate thin film electrode materials with high crystallinity,compact morphology and excellent electrochemical performance.Al/Ni dual doping can significantly improve cycle performance and rate performance of lithium manganate materials.

Three contact materials of AgSnO2,AgSnO2/Bi2O3 and AgSnO2/TiO2 were prepared by powder metallurgy.The electrical contact performance of the prepared contact materials was tested at different current levels and DC 14 V,and the contact resistance and arc energy parameters were obtained.The electrical contact performance of doped AgSnO2 contact materials at DC 14 V and different current levels was analyzed.Combined with the results of microstructure analysis,the most suitable current range for doped AgSnO2 contact materials at DC14 V voltage was determined.The results show that the contact resistance of AgSnO2/Bi2O3 and AgSnO2 materials increases firstly and then decreases with the increase of current level.The contact resistance of AgSnO2/TiO2 material shows a trend of decreasing in volatility.The arc energy of the material is continuously increasing.The addition of additives has a certain improvement on the electrical contact performance of AgSnO2 contact materials.AgSnO2/Bi2O3 material in the three materials has better comprehensive performance and reaches the best comprehensive performance at 20 A.

Several solid solutions including(W,Ti)C,(Ta,Nb)C,(W,Ti,Ta)C and(W,Ti,Ta,Nb)C were synthesized via one-step reduction method.Ti,Ta and Nb were added to WC-7%Co cemented carbides in the forms of single carbide and solid solution,respectively.The effect of carbide addition methods on the microstructure and mechanical properties of WC-7%Co cemented carbides was investigated.The results show that the mechanical properties of WC-7%Co cemented carbides can be improved by adding the solid solution of(W,Ti,Ta,Nb)C,and bending strength,Vickers hardness and fracture toughness are 2289.9 MPa,1683 HV and 9.67 MPa·m^1/2,respectively.

The effects of five factors of alkali types,pelletization water addition,alkali addition,roasting temperature and time on porosity and vanadium extraction rate of the roasted pellets from vanadium slag were studied.The results show that the surface of roasted pellets with NaOH addition has many large pores with a diameter of about 0.5 mm,while the surface of roasted pellets with Na2CO3 addition has no such macropores.Moreover,the porosity of the two pellets with NaOH and Na2CO3 addition is 32% and 6%,and the vanadium extraction rate is 92% and 52%,respectively.When water addition is 3%,the porosity of roasted pellets with NaOH addition reaches a maximum of 36.7%,while the vanadium extraction rate reaches a maximum of 97% with 4.5% water addition.When NaOH addition is 35.5%,the porosity of roasted pellets reaches a maximum of 38% and the vanadium extraction rate also reaches a maximum of 98%.When the roasting temperature is 740 ℃,the porosity of roasted pellets with NaOH addition reaches a maximum of 40%,while the vanadium extraction rate reaches a maximum of 97% at the roasting temperature of 680 ℃.When the roasting time is 60 min at 800 ℃,the porosity of roasted pellets with NaOH addition reaches a maximum of 40% and the vanadium extraction rate also reaches a maximum of 96%.There is a positive correlation between the porosity and the vanadium extraction rate of roasted pellets.

Tungsten carbide layers with a certain thickness were in-situ synthesized on the surface of sintered tungsten products by high temperature heat treatment in carbon atmosphere protected by hydrogen gas to prepare WC/W surface composites.The effects of heat treatment temperature and tungsten matrix density on microstructure and properties of in-situ synthesized WC/W surface composites were studied by density and hardness test and metallographic microscope.The element composition and phase composition of tungsten carbide layers were analyzed by SEM/EDS and XRD.The results show that high temperature heat treatment temperature has significant influence on the growth thickness and quality of tungsten carbide layer,while tungsten matrix density has no obvious influence on the growth of tungsten carbide layer.When the temperature is lower than 1 800 ℃,the thickness of the tungsten carbide layer is relatively thin and its strength is poor.However,too high temperature will lead to an increase in defects of the tungsten carbide layer.The tungsten carbide layer in-situ synthesized on the surface of tungsten matrix has columnar crystal microstructure and single phase composition,closely combining with tungsten matrix,and the interface is clean and free of impurities.The surface composites can fully exhibit the excellent properties of the two materials at high temperature.

To study the influence of cone angle on the morphology of WC/Co coating prepared by shaped charge explosive spraying,the numerical simulation about motion state of the powder particles under different cone angles was carried out with smoothed particle hydrodynamics(SPH) method based on ANSYS/LS-DYNA software,and the simulation results were experimentally verified.The simulation results reveal that when the cone angle of charge is 60°,the uniformity of particle flow is much higher than that of other angles,and the velocity is generally maintained at 2~2.75 km/s.The experimental results show that when the cone angle of charge is 60°,the coating area increases by 164.88% and 39.37%,respectively compared with the cone angle of 40° and 50°,and its uniformity is the best.

93W-Ni-Cu/ABS composite filaments with a diameter of about 1.70 mm were prepared by using industrial tungsten powder,nickel powder,copper powder and ABS powder as raw materials.Then,using the filaments as raw material,the green billets with complex structure were printed by FDM(fused deposition molding) technology.The properties of 93W-Ni-Cu/ABS composite filaments prepared under different conditions and the effects of solid volume fraction on the compactness and mechanical properties of green billets were studied.The results show that the addition of surfactants can enhance the cohesion between ABS and 93W-Ni-Cu particles and reduce the porosity of the composites.With the increase of solid volume fraction,the tensile fracture load and elongation at break of the filaments gradually decrease.The highest solid volume fraction of the composite filaments is 45%.When the solid volume fraction of the green billets is 40%,the elastic modulus of the composite filaments reaches the maximum value of 1 390 MPa,which is 55.3% higher than that of ABS.

TiC-based cermets with different contents of Mo substitute for Ni were prepared by powder metallurgy,the mass fraction of TiC matrix and cohesive phase Co is 75% and 5%,and the total massfraction Mo and Ni is 20%.The microstructure,flexural strength,density and electrical properties of the cermets were investigated.The results show that when the content of Mo substitute for Ni in TiC-based cermets changes,the properties of cermets also change.When the mass fraction of Mo is 4%,the composite properties of TiC-based cermets are the best,its bending strength is 149.18 MPa,resistivity is 1.45×10^-5Ω·m,and density is 94%.