Induction plasma spheroidization process was applied to deal with irregularly shaped W and Cr powders,and the effect of powder-feed rate on powder spheroidization was investigated. The morphology, phase composition, particle size distribution and apparent density of the powders before and after sphe- roidization were characterized by scanning electron microscopy （SEM）,X-ray diffraction （XRD）,laser par- ticle size analyzer and Hall flow meter. The results show that the spherical W and Cr powders with single phase can be prepared by induction plasma spheroidization, and their apparent density and powder flow-ability are greatly improved. The spheroidization ratio of W and Cr powders increases with the decrease of powder-feed rate,and the maximum spheroidization ratio is higher than 98%. The particle size and particle size distribution of the sphericized powders are affected by the dispersion of the raw powders.

W-Cu blanks with complex shape were prepared by non-aqueous gel-casting. The effect of disper- sant content and solid content on slurry viscosity was investigated. The blank drying curve was drawn and the drying system was established. Microstructure and bending strength of the blank were characterized. The results show that when the dosage of dispersant is 0.15%（ mass fraction and based on the quality of the metal powder）,slurry viscosity reaches the minimum and the slurry can obtain 45% （volume fraction） solid to meet the requirement of gel-casting. The blank is dried firstly at room temperature for 10 h and then placed in a constant temperature drying oven at 100℃ for 8 h to obtain W-Cu blank without deforma- tion and cracking on its surface. With the increase of solid content, both the density and uniformity of the blank increase. The blank has good surface quality and its bending strength can be up to 26.9 MPa.

Based on the Hall-Petch formula,the quantitative model of grain size and yield strength of niobium sheet was developed by quantitative metallography and mechanical property tests. By experimental ver- ification, the relative error between the calculated value and the experimental value is less than 8 %, indica- ting that the model has a high prediction accuracy.

The evaporation behavior of metal cerium was analyzed and proper evaporation temperature was determined. And then design of the electromagnetic induction evaporation device and research of evapora- tion technology were carried out. Evaporation rate of metal cerium was measured, vapor density distribu- tion was analyzed with film thickness method, and vapor density was measured with weighing method. The results show that evaporation rate of metal cerium at 2 000 ℃ is about 99-135 g/h,and the measured val- ue is slightly lower than the theoretical value. The density distribution of cerium vapor approximately fol- lows the relationship of high order power of cosine function,and atomic vapor density magnitude is about 1011 atom/cm3. The application of electromagnetic induction heating evaporation for cerium film deposition is feasible.

. LiFe1-xCex PO4/C （x= 0,0. 01,0. 03,0. 05） cathode material doped with rare earth Ce was syn- thesized with hydrothermal method. The electrochemical properties of the prepared material were studied by a series of systematic tests. XRD results show that the olivine crystal structure of LiFePO4 stays the same after doping 1 %- 5 % Ce, but cell volume is extended, which is favorable for the Li＋ extraction-inser- tion. The SEM images further demonstrate that doping rare earth Ce can refine the grain size,and then ef- fectively reduce Li＋ diffusion and migration pathway. In the potential range of 2. 044.0 V,the initial dis- charge specific capacity of LiFe1-xCexPO4/C at the discharge rate of 0.1C firstly increases and then decrea- ses with Ce dosage increasing,and it reaches the maximum value of 144.1 mA /g at x= 0. 03 , increased by 17.4% compared with the undoped LiFePO4/C. And its capacity retention ratio is 95.0% after 50 cy- cles. CV and EIS measurements show that LiFe1-xCexPO4/C （x=0.03） has the lowest charge transfer re- sistance,and the redox peak of the sample remains visible after 50 cycles at the charge and discharge rate of 0.1C,demonstrating that the sample has stable structure and good reversible reaction performance.

The semi-solid A356-0.5Ce （mass fraction） alloy ingots with ideal tensile properties and solidifi- cation microstructure were prepared by the combined process of intermittent reversible electromagnetic stirring and low superheat casting. The effects of melt stirring methods （without stirring, 30 Hz single-way continuous electromagnetic stirring, 30 Hz intermittent reversible electromagnetic stirring） on grain size and morphology of primary a phase were investigated by OM. The results show that with 30 Hz intermit- tent reversible electromagnetic stirring, the primary grains are well refined and spheroidized with average equal-area circle diameter of 35.9 ~m and shape factor of 0.79. In addition,the tensile properties and frac- ture morphology of the alloy ingots with three stirring methods were studied by SEM. The experimental results show that compared with the conventional casting, the tensile strength of the alloys obtained by 30 Hz single-way continuous electromagnetic stirring and 30 Hz intermittent reversible electromagnetic stir- ring increases from 125 MPa to 143 MPa and 176 MPa,the elongation increases from 4.2% to 5.4% and 7.8% ,and the fracture mechanism is changed from brittle cleavage fracture to ductile fracture.

The magnetic properties, microstructure and bending strength of the sintered NdFeB magnets with different rare earth content were studied. The results show that the bending strength, coercivity and demagnetization curve rectangularity of the sintered NdFeB magnets can be effectively enhanced by increas- ing rare earth content,but the remanence will be reduced. SEM images show that increasing rare earth con- tent can effectively improve the microstructure of casting strips and sintered NdFeB magnets, resulting in more uniform and continuous distribution of rare earth-rich phase and enhanced bending strength and coer- civity of sintered NdFeB magnets.

Isothermal compression tests of near-α TA15 titanium alloy were carried out on Gleeble 3500 thermal simulation machine. The influence was investigated of heating institution on microstructure and grain boundary or grain orientation of the deformed TA15 titanium alloy. The results show that when the alloy is deformed in the two-phase region （900 ℃）,its microstructure with ordinary heating institution consists of primary equiaxed a phase, recrystallized a phase and martensite α＇ phase, and its grain boundary ratio exhibits a peak value at the grain boundary misorientation of 40°, 60° and 90°. However, its micro- structure with β phase zone heating institution consists of lamellar martensite α＇ phase,β phase and interg- ranular a phase,and its grain boundary ratio exhibits a peak value at the grain boundary misorientation of 60° and 90° with enhanced grain preferred orientation. When the alloy is deformed in β single phase region （1 050 ℃）, its microstructure with ordinary heating institution has clear β grain boundaries and obvious cluster characteristics. However,its microstructure with βphase zone heating institution mainly consists of α＇ phase with greater length to width ratio, the original β grains disappear, and grain boundary ratio exhibits a peak value at the grain boundary misorientation of 60° and 90° with weakened grain preferred orientation and enhanced isotropics.

With Bi2Tea7Se0.3 as basic composition ratio and 99.99% high -purity Te,Bi ＆ Se as raw materi- als,bulk n-type Bi2Te3 based thermoelectric material was prepared by vacuum melting alloying,oxygen- free environment mechanical crushing, precision sieving of powder, and rapid hot pressing with original hot pressing device. The particle size and oxygen content of the alloy powder were determined by particle size analyzer, scanning electron microscope and oxygen nitrogen analyzer. The phase composition of the alloy powder was characterized by X-ray diffractometer,and the bending strength of hot pressed bulk samples was measured. The results of thermoelectric property test show that Seebeck coefficient and ZT value （thermoelectric figure of merit） of hot pressed bulk sample are almost isotropic, but its resistivity and thermal conductivity have strong anisotropy with obviously decreased orientation degree compared with the commercially available zone-melting products. The relative density of the hot pressed bulk sample is as high as 99% ,its bending strength is 87 MPa and the maximum ZT value is about 0.7. The above process has the advantages of simple equipment,low cost and high efficiency, suitable for industrialization.

Pure tantalum ingot blanks were prepared by powder metallurgy, and tantalum sheets with a thickness of 0. 28 mm were produced through forging and rolling of the ingot blanks. The effects were studied of different particle size proportion, intermediate annealing temperature and product annealing tem- perature on the physical properties of tantalum sheets. The results show that the properties of pure tanta- lum sheets obtained by powder metallurgy such as tensile strength, elongation and microhardness can be controlled to a certain extent through different particle size proportion,intermediate annealing temperature and product annealing temperature, and the properties of the produced tantalum sheets reach the require- ments of customers.