Microstructure evolution and deformation texture during rolling of TIMETAL® 407

TIMETAL (R) 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 alpha laths, macro and micro textures during rolling of TIMETAL (R) 407 are examined. For this purpose, TIMETAL (R) 407 with transformed beta microstructure was rolled at 650 and 820 degrees C to 50 and 75% reduction ratios followed by recrystallization heat treatment at 820 degrees C. The material was characterized focusing on microstructure morphology and texture evolution. The material rolled at 650 degrees C displayed strong basal pole concentrations towards the normal direction (ND)/30 degrees towards transverse direction (TD) together with a weak transverse component. When the material was rolled at higher temperature 820 degrees C, the texture only showed a weak transverse type texture. Complete spherodization of the alpha laths occurred only when the material was rolled to 75% reduction at 650 degrees 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 degrees C to 75% reduction played a key role in the break-up of alpha laths and significant texture change involving formation of strong 30 degrees basal texture component. The spherodization behavior of alpha laths in TIMETAL (R) 407 is compared with Ti-6Al-4V rolled to equivalent temperatures relative to the beta-transus based on classical boundary splitting and termination migration mechanisms.