Abstract:An high temperature quasistatic compression test (0.01 s-1) and a dynamic shearing experiment (103 s-1) on TC6 titanium alloy were performed by the gleeble-1500-type thermal simulation testing machine and a split Hopkinson bar process, respectively. Microstructure evolution of TC6 titanium alloy deformed under the condition of high temperature and high strain rate were contrastively investigated by means of optical microscope and transmission electron microscopy. Results show that the microstructure evolution of TC6 titanium alloy deformed at high temperatures is observably different from that at high strain-rate. The former includes four stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, breakdown of lath-shape α phase and simultaneous appearing and growth of dynamically recrystallized grains and phase transformation of α/β. The later goes through three stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, and then to lathy α phase due to rapid movement of dislocation, breakdown of lathy α phase and appearing of a few dynamically recrystallized grains. Under the two conditions of deforming, there is dynamically recrystallized grains occurring without exception, but there is a greater amount of dynamically recrystallized grains under the condition of high temperature and the dynamically recrystallized grains have grown up with sizes of 3-5 μm approximately. Whenas there are a few dynamically recrystallized grains that never grow up at high strain-rate with sizes of 0.1-0.2 μm approximately