Recovery and Recrystallization during Thermo-Mechanical Processing of Ti-6.5Al-1.5Zr-3.5Mo-0.3Si Alloy

Abstract

In this investigation, microstructure evolution of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy during thermo-mechanical processing at temperatures in beta single-phase and alpha+beta two-phase fields was studied. Microstructure analyses indicate that: (1) in the beta single-phase field, dynamic recovery accompanied by geometric dynamic recrystallization at large strains takes place dominantly within elongated large prior beta grains with serrate grain boundaries during deformation at higher temperatures and lower strain rates; and discontinuous dynamic recrystallization occurs along elongated small prior beta grain boundaries during deformation at lower temperatures and higher strain rates. During discontinuous dynamic recrystallization, recrystallized grain size is a function of Zener–Hollomon parameter, and a modified Avrami recrystallized kinetic model was established. (2) In the alpha+beta two-phase field, the globularization process is a thermally activated process controlled by parameters of temperature and strain rate. A modified Avrami globularized kinetic model was established. The primary alpha grain size is a function of Z on a ln-ln scale.