Abstract: Ti-6Al-4V compacts were fabricated by metal injection molding(MIM). Influence of vacuum sintering time on mechanical properties and microstructure of the sintered compacts at 1260℃ were investigated. The experimental results show that the compacts sintered at 1260℃ for 3-6h,  which was made from hydrogenation dehydrogenation(HDH) powder (average particles size is 45μm),  have a relative density of 95.6%-96.7%,  ultimate tensile strength of 648-686MPa and 0.2% yield strength of 526-615MPa; but a lower elongation(＜4%) and that the compacts sintered at 1260℃ for 2-6h,  which was made from 90% gas-atomized powder (average particles size is 32.5μm) and 10% HDH powder,  have higher relative density(＞95%), ultimate tensile strength of 800-848MPa, 0.2% yield strength of 712-762MPa and high elongation (7.4%-9.5%). When the sintering time is increased,  porosity decreases and microstructure of sintered products changes from equiaxed to typical Widmanstatten,  the average sizes of prior β grains, α colonies and α phase thickness in the β grains increase accordingly. After HIP treatment, pores obviously become less, microstructure of alloy is refined and mechanical properties are greatly improved.

Key words:  metal injection molding;Ti-6Al-4V; sintering time; properties;microstructure