The main preparation technologies are introduced for ultrafine/nano WC-Co composite powders, such as liquid phase reduction method,oxidation-reduction method, sol-gel method, coprecipitation method and spray conversion method. The current research on spray conversion is expounded based on the research results of the authors, and its advantages are pointed out, such as short process, uniform distribution of powder components and nano-crystallization. However, some deeper theoretical researches are to be conducted ina spects of control of particle size and morphology,component migration and in-situ low-temperature reduction carbonization.

Molybdenum alloys with different Zr dosage were prepared by powder metallurgy,and the influences were studied of Zr dosage on the microstructure and properties of molybdenum alloy. The results show that the strengthening effects of Zr element on the molybdenum alloy are mainly reflected in two aspects：one is the second phase strengthening from the second phase oxide generated after Zr element added to Mo matrix,and the other is solution reinforcement and grain refinement both from Zr dissolved into Mo matrix. The tensile strength of all the Zr-doped molybdenum alloys is higher than pure molybdenum at room temperature,while their elongation is the opposite. Under the condition of Zr dosage 0.08%-0. 15%,the tensile strength of molybdenum alloy increases with the increase of Zr dosage,while the elongation increases at first and then decreases and reaches the maximum when Zr dosage is 0.19,%.

Fe-36Ni invar alloys with different Zr content were prepared by smelting in a carbon tube furnace. The effects of Zr addition and solidification conditions on alloy solidification mierostrueture were investigated by SEM and EDS,and then the mechanism of solidification microstructure improvement was analyzed. The results show that alloy solidification microstructure is obviously refined after Zr addition. With the increase of Zr content, refinement effect of the solidification microstructure becomes better. A large number of high-melting-point compound ZrO2 is formed and dispersed in the alloy after Zr addition. The lattice misfit between ZrO2 （0001） surface and Fe-36Ni （100） surface is low,so ZrO2 can serve as effective heterogeneous nucleation core to refine the solidification microstructure of the invar alloy. Under the condition of adding the same content of rare earth element Y, the solidification microstructure is remarkably re- fined with decreased casting temperature and increased cooling speed. When casting temperature exceeds 1 500℃, the effect of Y2O2 S as heterogeneous nucleation core disappears, and the solidification microstructure of the alloy is composed of complete columnar grains.

Eu3＋-doped YPO4 phosphors were synthesized via citric acid-assisted sol-gel process, and their crystal structure and fluorescence properties were investigated. The results show that both heat treatment temperature and heat treatment time have direct influence on phase structure of the products. During the heat treatment,the hexagonal YPO4 · 0.8H20 crystal is generated from xerogel before tetragonal YPO4 crystal is developed from the dehydration of YPO4 · 0.8H2O crystal. Emission spectra of the samples show that the synthesized Eu3＋-doped YPO4 can be effectively excited with 222 nm wavelength light, emittng intense orange-red light at 595 nm and 621 nm. Concentration quenching phenomenon occurs when Eu3＋ dosage is over 8% （molar fraction）. Furthermore,fluorescence properties can be effectively improved by in- creasing heat treatment temperature or prolonging heat treatment time.

The different types （Pb-Pr,Pb-Sm,Pb-Nd） and different RE contents （0.1%、0.5%、1.0%、1.5%、2.0%） of Pb-RE alloys were prepared by two-stage remelting,and the study was made on the influence rule of the content and type of rare earth element on the tensile strength and microstructure of the alloy. The results show that addition of Pr,Sm,Nd can improve the strength of the alloy in different level, and with the increase of content of rare earth elements the strength of the alloy can improve in different degree. The extent of the effect of RE elements on improving the tensile strength of the alloy goes as follows： Pr〉Sm〉Nd. Nd,Sm and Pb generate intermetaliic compound and precipitate on the grain interface,bene- ficial for the alloy strength improvement. Besides generating intermetallic compound,Pr can also refine alloy grains and prevent grain slip, as is also one of the most important factors to improve the tensile strength of the alloy.

The creeping behavior of Mg-5Y-3Sm-0.8Ca-0.5Sb alloy at 200℃ and 50 MPa or 70 MPa was investigated by creeping tests, microstructure observation and theoretic calculation. The results show that the alloy has similar creeping resistance at 200 ℃ compared with that of commercial heat resistant magnesium alloy WE43. With the increase of creeping stress,the grain size of the alloy has no change,but the grain boundary is unobvious. The calculation result of stress exponent indicates that the creeping behavior is controlled by diffusion and grain boundary sliding.

Single-crystal nickel-based superalloys DD90 with different boron contents were prepared by seed growth technique, and the influences were researched of B element on dendritic structure, eutectic structure and carbide morphology. The results show that with boron content increasing, the secondary dendrites gradually become thicker, the third dendrites become more distinct, and meanwhile, the carbides increase while the eutectic microstructure obviously decreases.

The cathode material LiNi1/3Co1/3Mn1/3O2 for lithium-ion battery was successfully synthesized with the spray drying method and its crystal structure, morphology and electrochemical performance were characterized by SEM,XRD and charge-discharge experiments. The results show that the cathode material LiNi1/3Co1/3Mn1/3O2 with spherical and evenly distributed particles can be synthesized at 750 ℃ for 12 h. And the cathode material exhibits excellent electrochemical performance for that its initial discharge specific capacity is 154 mA ·h/g under the conditions of 2.8~4.3 V and 0.1C and its discharge specific capacity is maintained at 94.7 % after 25 cycles.

In view of increased product consumption and scrap accumulation in domestic cemented carbide field and decreased reserves and exploitation of tungsten resources, recycled materials from cemented carbide scrap were chosen as the research subjects. Crystal morphology, chemical composition and phase structure of recycled cobalt powder and tungsten carbide powder were characterized by SEM, EDS and XRD. Hardness of recycled W-Co alloy was tested by Rockwell apparatus. Based on the analysis for the above results,the existing problems in recycled cemented carbide are determined, providing some theoretical support for improvement of recycling technology and process control technology of cemented carbide scrap.

Heat treatment was done on the steel-bonded carbide DGJW30 prepared by electro-slag melting and casting. The mierostructure of steel-bonded carbide DGJW30 was studied by metallographic analysis, scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD） focusing on the microhardness change rule of steel substrate, ledeburite and undissolved WC of the steelbonded carbide in its heat treatment process.