Effect of cold rolling on the phase transformation kinetics of an Al_0.5CoCrFeNi high-entropy alloy

The solid state phase transformation kinetics of as-cast and cold rolling deformed Al_0.5CoCrFeNi high-entropy alloys have been investigated by the thermal expansion method. The phase transformed volume fractions are determined from the thermal expansion curve using the lever rule method, and the deformed sample exhibits a much higher transformation rate. Two kinetic parameters, activation energy (E) and kinetic exponent (n) are determined using Kissinger- Akahira-Sunose (KAS) and Johnson-Mehl-Avrami (JMA) method, respectively. Results show that a pre-deformed sample shows a much lower activation energy and higher kinetic exponent compared with the as-cast sample, which are interpreted based on the deformation induced defects that can promote the nucleation and growth process during phase transformation.