Deformation behavior and microstructure evolution in multistage hot working of TA15 titanium alloy: on the role of recrystallization

Interrupted compression tests of TA15 titanium alloy with initially equiaxed microstructure were carried out at deformation temperatures between 1173 to 1273 K and strain rates between 0.001 to 0.1 s(-1) to investigate the deformation behavior and microstructure evolution under multistage deformation. The TA15 alloy exhibits significant flow softening in both beta and (alpha + beta) working. It is found that the flow softening relates to dynamic recrystallization of beta phases under current experimental conditions. In multistage beta working, metadynamic recrystallization is the main softening mechanism during inter-pass holding. The grain refinement by metadynamic recrystallization leads to the decrease in peak stress upon reloading. In multistage (alpha + beta) working, static recrystallization is the main softening mechanism during inter-pass holding. The static recrystallization kinetics increases with temperature and strain rate. The inter-pass holding has little influence on the morphology of the primary alpha phases. The beta grain size is determined by spacing of primary alpha phases, which is more affected by working temperature but less dependent on strain rate and inter-pass holding time.