Abstract:The high temperature thermal compression test was carried out by using Gleeble-1500 thermal simulator for the Ti-6Al-4V alloy prepared by hot isostatic pressing process in the temperature range of 950~1050°C, strain rate range of 0.01~1s-1 and engineering compressive strain of 70%. The effect of deformation temperature and strain rate on the microstructure evolution of the alloy was investigated. The results showed that the microstructure was mainly composed of corase β grains and needle and lath martensite, which exhibited typical microstructure character in β-phase filed hot deformation after water quenching. The β transformed lamellar microstructure in the β grain form basketweave structure with certain craystall misorientation. The microstructure analysis illustrated that dynamic recovery and dynamic recrystallization occtured during thermal compression. When the condition of 950℃,0.01s-1, deformation mechanism was dynamic recrystallization and the uniform equiaxed β grain with β transformed microstructure was obtained. With increasing of strain rate, β grains were elongated to long strip in the direction perpendicular to the compression direction, and the β transformed lamellar microstructure was refined, which was attributed to that the dynamic recovery was the main deformation mechanism. As the temperature increased, the size of β grains and β transformed lamellar microstructure increased. However, the strip shaped β grains were still maintained.