Study on microstructure evolution of Ti–6Al–3Nb–2Zr–1Mo alloy with bimodal structure during hot compression in the near β region

Abstract

Hot compression tests were performed different reductions on Ti–6Al–3Nb–2Zr–1Mo alloy with bimodal structure in the near β phase region to investigate the microstructure evolution. The stress–strain curves showed obvious flow softening. With the increase of deformation strain, the alloy gradually undergoes dynamic recrystallization (DRX). Simultaneously, the thickness of lamellar αs grains significantly decreases. The high-density dislocation area provides a suitable place for β grains nucleation. Subsequently, β grains grow in lamellar α grains and become approximately 60° with the lamellar α grains under the driving force of the dislocation. The calculated DRX critical true strain of the alloy deformed at 0.01 s−1 and 980 °C is 0.095. Discontinuous dynamic recrystallization (DDRX) is the main DRX mechanism, while continuous dynamic recrystallization (CDRX) is the assistant DRX mechanism. In addition, the twin boundaries provides opportune locations for the nucleation of DRX grains, thereby promoting the DRX of the alloy. Moreover, the initial texture disappears, and different new texture components appear during hot deformation. The texture density first increases with increased deformation strain. With the further increase of deformation strain, the texture density gradually decreases, due to the combined action of sufficient DRX and dynamic phase transformation.

Keywords

• Ti–6Al–3Nb–2Zr–1Mo alloy
• Microstructure
• Dynamic recrystallization
• Texture