Mechanism of continuous dynamic recrystallization in a 50Ti-47Ni-3Fe shape memory alloy during hot compressive deformation

Abstract

The mechanisms of dynamic recrystallization (DRX) in a 50Ti-47Ni-3Fe alloy are studied using compression tests at temperatures of 1023–1323 K with strain rates of 0.01–10 s−1, and the resulting stress-strain curves are used to construct an Arrhenius equation with a Zener-Hollomon parameter (Z). The relationship between this Z parameter and stress, and its effect on the subgrain size are discussed. With the help of electron backscatter diffraction (EBSD), the development of recrystallizing grain boundaries is tracked in deformed grains with different grain orientation spread (GOS) values. Continuous dynamic recrystallization (CDRX) is subsequently confirmed by evidence of the conversion of low-angle boundaries (LAGBs) into high-angle boundaries (HAGBs). Grain boundary sliding (GBS) and HAGB migration are therefore considered secondary mechanisms under high-Z (ln Z > 29) and low-Z (ln Z < 23.5) conditions, but CDRX is confirmed as the dominant DRX mechanism.