The 1724PH stainless steel compacts sintered at 1 380 ℃for 90 min have the best me2 chanical properties and the good microstructure with homogeneously distributed pore structure and the moderate2sized grains. Whereas the compacts sintered for 60 min and 120 min show an inadequate and an over2sintered microstructure re2 spectively. The compacts sintered at 1380 ℃for 90 min have the density of 7.70g/cm3, the strength of 1275MPa, the elongation of 5%, and hardness of HRC36. With the increase of sintering temperature, the density, strength and hard2 ness increase, while the elongation decreases. The 1724PH stainless steel has good corrosion resistance, showing an activa2 tion2passivation polarization curve. But the passivation potential range is narrow and the spot corrosion potential is low, in2 dicating a low anti2spot corrosive properties.

The evolution of the microstructure and the dimension of as-molded parts were studied on the basis of the thermogravimetric analysis of wax-based MIM binder. The results show that the binder removal speeds are different in different temperature ranges during binder removal process. The evolution of the microstructure of as-molded parts during binder removal process clearly showed the initiation and formation of connected pore structure , which is the removal chan-nel of the binder. The as-molded parts almost continuously shrank through binder removal process, except an expansion stage during 320～440℃, which is the dissolution expansion effect due to the dissolution of VPW in the polymer melt.

The fundamental rheological properties of metal injection molding (MIM) feedstock and binder are theoretically analysized. The viscosity of MIM binder and feedstock at different temperature and at different shear rate was measured and evaluated. The results indicated that MIM binder and feedstockpossess pseudoplastic rheological behavior. The Fe-Ni MIM feedstock prepared has the lower value of flow activation energy and the higher value of strain sensitivity exponent . Its injection and filling properties are good.

97W-2Ni-1Fe heavy alloy feedstocks with different powder loadings were prepared for injec-tion molding. The rheological behavior of these feedstocks was studied. The mechanical properties of as-sintered parts and the shrinkage during sintering were measured. The results showed that the rheological be-havior of these feedstocks could be described as pseudoplastic fluid. The mechanical properties of the injection molded alloy are superior to those of alloy prepared by conventional press/ sinter process. There is an optimal powder loading 47% (volume fraction) with the best mechanical properties. The shrinkage during sintering is isotropical and the tolerances of products are small.