Studies on the kinetics of β → α phase transformation in 47Zr–45Ti–5Al–3V alloy under isothermal conditions by X-ray diffraction

Abstract

The kinetics of the β→α phase transformation in the 47Zr–45Ti–5Al–3V (wt.%) alloy with different initial β grain sizes under isothermal conditions was investigated by X-ray diffraction. The results showed that the volume fraction of α phase first increased with increasing aging time, and then reached an equilibrium value. The equilibrium value of α phase decreased with increased aging temperature. At the same aging temperature and time, the volume fraction of α phase in the 47Zr–45Ti–5Al–3V alloy solution-treated at 850°C was higher than at 1050°C, and the size of α phase in the 47Zr–45Ti–5Al–3V alloy solution-treated at 850°C was larger than that at 1050°C. The kinetics of the β→α phase transformation was modeled under isothermal conditions in the theoretical frame of the Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory. The Avrami index (n) increased with increasing aging temperature, while the reaction rate constant (k) decreased.