| High density tungsten based alloys possess an unique combination of physical and mechanical properties, such as high density, strength and ductility, which are used extensively as kinetic energy penetrators, counterbalance weights, radiation shields and electrical contacts. They cannot be replaced in the field, such as national defence, military industry, aviation and spaceflight. With the quick development of science and technology, higher demand for material properties is put forward and preparation of tungsten based alloys with high properties is one of the hotspot in the world. But the cores of preparation of tungsten based alloys with high properties are preparation of nanometer powder and study for properties of alloy. Preparation of nanometer W-Ni-Fe composite powder and properties of alloy were systemic studied according to the cores.Electrochemistry characters of (W,Ni,Fe) solution colloid system were studied deeply. Influence of Zeta potential, pH value and surfactants added on particle dispersity and stability of colloid solution system were investigated. The roles of cetyl trimethyl ammonium bromide (CTAB), N,N-dimethylformampe and polyethylene glycol-1000 (PEG-1000) on electrostatic hindrance, steric hindrance and electrostatic-steric hindrance cooperation function of particle surface were studied in detail. (W,Ni,Fe) precursor composite oxide powders were first synthesized by preparation of solution colloid and spray drying. Action mechanism of surfactants in spray drying process was discussed deeply and schematics of capillary action force during particle drying was established.Reduction mechanism was studied deeply during reduction of (W,Ni,Fe) composite oxide powder. Results showed: influence of reduction temperature and time on properties of W-Ni-Fe composite powder was remarkable, and the best reduction condition was 700℃ for 90min. Nanometer W-Ni-Fe composite powder, average Fsss of which was smaller than 0.61 μm, BET sizes smaller than 100nm, crystalline size smaller than 30nm, oxide content of reduced powder smaller than 0.23%, homogeneous disperse and spherical morphology, was fabricated at 700℃ for 90min. Air phase transfer which mainly resulted in growth of particles during reduction was put forward. With the increasing of vapour produced during reduction, volatility WO2(OH)2 was easy synthesized by tungsten oxide and vapour. WO2(OH)2 deposited in surface of oxide tungsten with lower chemistry value or metal tungsten powder and resulted in growth of particles. Then two-stage reduction method and adding rare earth La or Y were put forward in order to inhibit growth of particles in this paper. When adding rare earth elements La or Y, new phase La(Ni0.75W0.25)O3 or Y(Ni0.75W0.25)O3 produced and adsorbed on surface of metal tungsten particles or tungsten oxide particles. Producing speed of volatility WO2(OH)2 was prevented from synthesizing of tungsten oxide and vapour, then air phase transfer was decreased. Growth of powderparticles were hold back. When the rare earth element content was below 0.8 wt%, with the increasing of the rare earth elements content, the properties of the composite powder improved distinctly. When same content of rare earth elements were added, the effect degree on powder properties was Y>La-Y(mixing rare earth)>La.Coexistence field of solid and liquid is in the temperature range of 1341.2°C to 1365.8 °C by means of DTA apparatus. The field is lower about 70-90 °C than conventional 90W-Ni-Fe powder. Influence of sintering temperature and time on sintering properties of nanometer powder 90W-7Ni-3Fe alloy were studied according to this viewpoint. Low-temperature sintering mechanism of nanometer powder 90W-7Ni-3Fe alloy was investigated.Influence of adding rare earth elements La or Y on properties and microstructure of 90W-Ni-Fe alloy were investigated deeply and three-layer microstructure model images of W particle in alloy was established. Relation between adding La or Y and properties or microstructure of alloy was explained commendably by three-layer microstructure model images of W particle.It was not evident that W crystal was prevented from growing and properties of alloys improved by adding rare earth La. Transgranular cleavage fracture of W crystal and ductile avulsion of matrix phase are main fracture modes in the samples when adding Y. Inhibiting function from growing of W crystal was distinct and W crystal sizes decreased from 20-25 u m to 12 u m by adding 0.4% Y. Emergence chance of cavities and vapour reduced during liquid sintering in dry-tb atmosphere was decreased, and properties of alloys improved prominently by adding some Y. Relative density, tensile strength and elongation of samples was 99.6%, 1027.5MPa and 18.6% by adding 0.4% Y, respectively. When adding 0.6% Y, relative density, tensile strength and elongation of samples was 99.3%, HOOMPa and 16.3%, respectively. The properties of alloys are enhanced 25-30% than conventional 90W-Ni-Fe alloys. But W crystal morphology changed by adding some Y, W crystal morphology was nearly spherical by adding 0.4% Y or polyhedron by adding 0.8% Y. When same content of rare earth elements were added, the effect degree on properties of alloys was Y>La-Y(mixing rare earth)>La.When adding some rare earth elements, diffuse speed and solubility of tungsten in matrix phase descended, and solubility of tungsten in matrix phase decreased from 58.65 wt%(without rare earth) to 29.86 wt%(adding 0.4% La-Y). Therefore, deformation adjustability of matrix phase enhanced greatly.
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