Microstructure and excess free volume of severely cold shape rolled CoCrFeNiMn high entropy alloy

A CoCrFeNiMn high-entropy alloy (HEA) was subjected to shape rolling through equivalent strain of 0.5, 1.1, 1.4, 2.5, 3.7 and 4.2 at room temperature to study the microstructural evolution and formation of excess free volume during severe plastic deformation. The microstructure of the processed sample through the equivalent strain of 4.2 revealed a single fcc phase with an average grain size of similar to 50 nm and an excess free volume of similar to 0.96% due to formation of nano voids and defects after severe shape rolling. Microhardness measurements showed a saturation level but no nano voids were observed in the processed samples with equivalent strains of lower than 4.2. The results show precipitation and then dissolution of precipitates and also annihilation of defects due to recrystallization during heating between 700 and 900 degrees C. Density of processed samples reached to the initial condition after heating up to 1000 degrees C except the processed sample at the equivalent strain of 4.2 due to existence of stable nano voids in this sample. (c) 2020 Elsevier B.V. All rights reserved.