The relationship between flow behavior and initial microstructure of Ti-10V-2Fe-3Al alloy during subtransus deformation

Abstract

The morphology of alpha phase has a significant effect on the deformation and flow softening of near-β titanium alloys. This study investigated the deformation behavior of Ti-10V-2Fe-3Al alloy with equiaxed and lamellar microstructures by isothermal compression test in α + β region. The results show that lamellar microstructure presented higher peak stresses as well as intenser flow softening than equiaxed microstructure. Constitutive analysis including the flow softening index is consistent with the observed phenomenon. Microstructure characterization was employed to investigate the effect of deformation parameters on microstructural evolution. Then softening mechanisms for equiaxed and lamellar morphologies were summarized comprehensively. The softening mode for beta matrix is dominated by continuous dynamic recrystallization (CDRX) and it can be enhanced by alpha phase particles. With the increase of strain rate and decrease of temperature, the subgrain network in beta phase became denser due to dispersed alpha particles. Alpha lamellar evolutions, including globularization, kinking and rotation, were very sensitive to plastic strain and they all contributed to the flow softening of lamellar microstructure. Since the globularization fraction was generally very limited, the loss the Hall-Petch strengthening resulted from lamellae rotation and kinking was inferred as the main softening mechanism for Ti-10V-2Fe-3Al with colony lamellar alpha phase.