Deformation-induced phase transformation in Zircaloy-4 below the beta transus

Abstract Dynamic transformation is shown to take place in steels and titanium alloys at temperatures above and below the beta transus, respectively. Here the hard phase transforms into a softer phase during deformation. This unusual metallurgical phenomenon has previously been explained in terms of transformation softening (Ghosh et al., 2016). In the present work, compression tests were performed on samples of Zircaloy-4 at temperatures below the beta transus. The microstructures and microhardness measurements indicate that alpha transforms displacively into beta during deformation at temperatures down to about 75 °C below the transus.