Dynamic fragmentation and spheroidization of α phase grains during hot deformation of Ti-6Al-4V alloy

Abstract

AbstractDevelopment of mechanical properties of titanium alloys is usually achieved by the control of their microstructure (globular, lamellar, bimodal). Dynamic fragmentation and spheroidization of elongated α phase grains, formed from martensite laths, in the microstructure of Ti-6Al-4V alloy are considered in the paper. The effects of α phase grain spheroidization was evaluated in tensile tests over a temperature range of 800–900°C and strain rate range of 10−3–10−2 s−1. Completed spheroidization of elongated α phase grains and subsequent growth of equiaxed grains for all deformation modes were found. A low value of apparent activation energy for deformation was calculated – suggesting grain boundary sliding was the main deformation mechanism. The results showed good correlation with the kinetic rate equation based on the Zener–Hollomon parameter.