Microstructure evolution and deformation texture during rolling of TIMETALⓇ 407

Abstract

TIMETALⓇ 407 is a new titanium alloy primarily developed for combining high formability with improved strength compared to commercially pure titanium. In this study, the evolution of microstructure, spherodization behavior of α laths, macro and micro textures during rolling of TIMETALⓇ 407 are examined. For this purpose, TIMETALⓇ 407 with transformed β microstructure was rolled at 650 and 820 °C to 50 and 75% reduction ratios followed by recrystallization heat treatment at 820 °C. The material was characterized focusing on microstructure morphology and texture evolution. The material rolled at 650 °C displayed strong basal pole concentrations towards the normal direction (ND)/30° towards transverse direction (TD) together with a weak transverse component. When the material was rolled at higher temperature 820 °C, the texture only showed a weak transverse type texture. Complete spherodization of the α laths occurred only when the material was rolled to 75% reduction at 650 °C. At other rolling temperature and reduction ratios, the extent of spherodization per se was limited. Our results clearly show that activation of deformation twinning in the material rolled at 650 °C to 75% reduction played a key role in the break-up of α laths and significant texture change involving formation of strong 30° basal texture component. The spherodization behavior of α laths in TIMETALⓇ 407 is compared with Ti-6Al-4V rolled to equivalent temperatures relative to the β-transus based on classical boundary splitting and termination migration mechanisms.