The single-pass hot compression test of SP700 titanium alloy was carried out on the Gleeble3800 thermal simulation test machine, and the thermal deformation behavior and microstructure evolution at temperature range of 800-880 °C, strain rate range of 1-10 s-1 and compression deformation of 30% -50% were investigated. The results show that the peak flow stress of SP700 titanium alloy decreases with the increase of deformation temperature, while increases with the increase of the strain rate. At a deformation temperature of 800 ℃, the flow stress curves show obvious dynamic softening characteristics with a rapidly decrease of the flow stress after the peak stress. By the metallographic and scanning electron microstructure observation on the deformed microstructure, the α lamellar is gradually broken and spheroidized, and finally dynamic recrystallization occurs. As the deformation temperature increases to 880 ℃, the flow stress curves illustrate steady flow. The microstructure analysis reflects that the globalized α grain disappears and the strain-induced phase transformation occurs. At this temperature, the dynamic recrystallization mainly take place in β phase during the compression process. When the deformation temperature is constant, the spheroidization degree of α lamellae increases with the increase of strain rate and compression deformation. During the hot deformation process, the α lamellae parallel to the compression axis kinks and the cumulative misorientation is discontinuous inside the α lamellae where the new α/α interface boundary generates. For the α lamellae perpendicular to the compression axis, the interface fluctuates resulting a continuous cumulative misorientation interior the α lamellae. At the interface fluctuation or the new α/α interface, β phase easily wedges into the α lamellae by element diffusion which will finally leads to the fragmentation and spheroidization.
DownLoad: