Hot deformation characteristics and mechanism understanding of Ti-6Al-2Sn-4Zr-6Mo titanium alloy

Two-phase titanium alloy Ti-6Al-2Sn-4Zr-6Mo (TC19) has an excellent application prospect in aerospace field. In order to study its hot deformation behavior and the microstructure evolution mechanism of TC19 titanium alloy, hot compression tests were carried out. The flow behavior of this alloy was predicted by the constitutive models. Besides, the hot processing map of TC19 alloy was drawn according to the dynamic material model (DMM) theory. The peak efficiency of energy dissipation region occurred in the temperature range of 850-1000 °C with the strain rate of 0.001-0.1 s-1. The main deformation mechanisms were dynamic recovery (DRV) and dynamic recrystallization (DRX). It seems that the region of deformation instability was concentrated in high strain rate. The main deformation mechanisms in the structure were deformation band (DB), flow localization (FL), and recrystallized grains produced by continuous dynamic recrystallization (CDRX). Deformation mechanism of TC19 alloy was mainly controlled by the deformation rate. When the deformation rate was low, the deformation mechanism was mainly DRV and the strain-induced grain boundary migration, which led to the bulging of the grain boundary and resulted in discontinuous dynamic recrystallization (DDRX) with the increasing deformation rate. Furthermore, the sub-grain rotated continuously to transform from low angle grain boundaries (LAGBs) into high angle grain boundaries (HAGBs) at the high deformation rate continuously. Recrystallized grains packed with HAGBs were observed in the microstructure. The existence of ω phase in the precipitated phase observed by diffraction pattern, which indicated that phase transition was related to the deformation rate.