In order to ensure the corrosion resistance of the hard seal surface of titanium alloy earth-penetration valve, and improve the hardness, wear resistance and compressive fatigue properties of the valve, laser cladding of pure tantalum was carried out on the surface of TA2 titanium alloy by YAG laser. The metallurgical binding degree, microstructure, component and hardness distribution of layer-cladding Ta coat were analyzed by OM, SEM, EDS and microhardness tester. The results indicate that direct laser cladding of pure Ta powder on TA2 titanium alloy surface is feasible, and there is well metallurgical binding between Ti-Ta alloy coat and the substrate. The dilution of Ti element in laser cladding layer is large,and the dilution decreases with increased distance away from the binding surface. The binding region of laser cladding layer and the substrate is composed mainly of dendrites, and the middle region in the cladding layer is composed of dendrites and partial massive microstructure. The microhardness HV0.2 of the cladding layer is 190- 200, more than 40 higher than that of Ti substrate. The microhardness HV0.2 of the binding region is 200- 220 ,and therefore the hardness gradient is relatively obvious.

The microstructure and mechanical properties of Ti600 high temperature titanium alloy for engine were researched by optical microscope,X-ray diffractometer and mechanical property test. The results show that Ti600 plate is mainly composed of equiaxed primary a grains and a small amount of lamellar α＋β eutectic tissue. Ti600 alloy has small grains and uniform microstructure,and its average gain size is about 2- 4 μm. Ti600 alloy plate has high strength and plasticity at room temperature. With the increase of temperature,tensile strength and yield strength show a weak increasing trend, while elongation rate significantly increases. Ti600 titanium alloy plate is characterized by ductile fracture,with a dimple fracture.

The effect of rare earth Ce on microstructure and mechanical properties of A356 alloy was studied by using OM, SEM, EDS, XRD and universal electronic tensile testing machine. The results indicate that rare earth Ce is an excellent modifier for A356 alloy. Ce is helpful not only for refining the grains of primary α-Al phase,but also for forming small,round and uniform eutectic Si. Rare earth Ce in A356 alloy exists mainly in the form of rare earth intermetallic compound Al11Ce3. When 0.04% Ce is added into A356 alloy,its tensile strength,yield strength and elongation respectively reach 307.5 MPa,239 MPa and 7.72%, increased by 7.89% ,24.48% and 108.09% compared with the alloy without Ce.

The effects of key parameters on forming performance of 7A60 aluminum alloy cup during isothermal pressure torsion were investigated by technological experiments and finite element simulation. The results show that the effect of height to diameter ratio of the blank on cumulative deformation is mainly in upsetting deformation stage. As lower mould torsion speed increases, the forming load is reduced and the torque increases. When lower mould torsion speed is too large, the damage value of transition fillet area of the torsional disk would be greater than 1, and the edge is easy to fracture. The influence is significant of forming temperature on forming load and torque. The continuity of the alloy cannot be destroyed with a torsional shear deformation of less than one ring during forming process,and its strength is improved corn pared with the alloy obtained by conventional extrusion.

Wafer surface was activated with Ar plasma, and then Ni-Si wafer bonding was carried out. The effects of gas flow and reactive ion etching power during surface activation on wafer bonding were investigated. The images of scanning acoustic microscopy were applied for assessing the quality of wafer bonding. The results show that holes and bubbles on the bonding interface can be reduced by surface plasma activation to efficiently improve the quality of wafer bonding.

Stabilization methods of cemented carbide performance prepared in hydrogen dewaxing sintering furnace were discussed. The results show that all the following factors can result in unstable performance of sintered cemented carbide.actual dewaxing temperature fluctuation, dewaxing carrier gas turbulence,inaccurate dewaxing time control,underdeveloped WC raw material and ball milling time fluctuation during material mixing. Cemented carbide with more stable performance can be obtained by taking certain measures to control these factors.

WC-gCo （containing 0.8 % Cr3 C2/VC） ultrafine cemented carbides were prepared at different sintering temperature by using mixture with different total carbon content of 5.66% and 5.70%. Change with ball milling time in the oxygen content of the mixture,size and internal strain of WC grains was measured, and the change of magnetic properties in the wc-gCo cemented carbides sintered at different temperatures with ball milling time was also investigated. The results show that the nano-size WC grains cannot be crushed by rolling ball milling. With the increase of ball milling time, the oxygen content of mixture with different carbon contents linearly increases,and the increase rate is slower with higher carbon content. Corn value of the ultrafine cemented carbides is a main factor affecting Hc value. Hc value increases at first and then decreases with the increase of Corn value showing a parabolic law, and the maximum Hc value is reached at a certain Corn value. It can be deduced that the carbon content affects the precipitation of V and Cr on the WC/Co interface and the formation of （W,Cr）Cx and （W,V）Cx interphases which can inhibit the growth of WC grains,and therefore affects the inhibition effect.

To study impact fatigue fracture mechanism of WC-Co cemented carbides and effects of microstructure parameters on their low cycle impact fatigue performance, impact fatigue tests were carried out for six kinds of cemented carbides with different WC grain size and Co content. And the impact fatigue fracture was observed by scanning electron microscopy. The results show that the cracks in the cemented carbides with impact loading are initiated from the powder metallurgy defects, the initiated cracks are interconnected with the holes to form the main cracks, and the rapid propagation of the main cracks leads to fatigue and failure of cemented carbides. The cemented carbide with higher Co content has greater fatigue sensitivity and shorter impact fatigue lifetime. The cemented carbide with larger WC grain size has longer impact fatigue life.

The new-type cemented carbide tool material was prepared by adding graphene into WC-6Co cemented carbide with the methods of stepwise vacuum ball milling and hot pressing sintering. Its phase composition,microstructure, mechanical properties and wear resistance were analyzed. The results show that surface hardness, mechanical properties and wear resistance of the new-type tool material increase at first and then decrease with the increase of graphene content. The optimized graphene content is 2 % ,and surface HV hardness reaches 2 842. Compared with commercial WC-6Co tool material,the new-type tool material has increased transverse rupture strength by 143% and decreased wear volume by 71%.

Research progress is reviewed on saponification process of rare earth extraction separation in re- cent years, focusing on the principles and characteristics of ammonia saponification technology, sodium sa- ponification technology, calcium saponification technology, magnesium saponification technology and so on. And future development direction of the saponification process is proposed.