Dynamic recrystallization of commercially pure titanium during cryogenic compression

Abstract

In this study, a systematic investigation on the twin-induced dynamic recrystallization (DRX) of commercially pure titanium (CP-Ti) was carried out under uniaxial compression at room (RT) and cryogenic temperature (CT, −150 °C). The compression tests were intentionally interrupted at 0.02, 0.05 and 0.1 strain levels at both deformation temperatures and a detailed post-mortem analysis was performed via electron backscattered diffraction (EBSD) to examine the progressive evolution of microstructure. The results revealed that two major types of twins i.e. {10−12} extension twin (ETW) and {11−22} compression twin (CTW) were effectively activated at both deformation temperatures. During RT deformation, increased strain levels resulted in the higher evolution of ETWs and CTWs, where numerous twin lamellas, lateral twin thickening and twin-twin interactions (ETW-ETW, ETW-CTW) were observed. On the other hand, CT deformation led to significant grain refinement with the average grain size reduced by 94% (3.7 μm for CT-10 sample as compared to 63 μm of initial material). The recrystallization kinetics were understood with respect to three region of interests (ROIs). The DRX mechanism was identified as tDRX, where intersectional {10–12} ETWs and {11–22} CTWs network provided the preferential sites for the nucleation of DRXed grains due to high strain energy from the dislocation pile-ups at the TBs.