Effect of Deformation and Subsequent Heat Treatment on SigmaPhase Precipitation and Mechanical Property of CoCrFeMnNi High Entropy Alloy

In this study, we focused on the effects of various deformation amounts and subsequent heat treatment on sigma -phase precipitation in CoCrFeMnNi high entropy alloy, known as Cantor alloy. Homogenized specimens with an initial FCC single-phase structure were deformed to various shear strains (1.1-25.8) using high-pressure torsion (HPT). This process resulted in a variety of deformation microstructures, with low to medium shear strains leading to the formation of twin -matrix lamellae intersected by shear bands, while high shear strains resulted in nanocrystalline structures. After deformation, the specimens were heat -treated at 700 degrees C for up to 5 h, which led to recrystallization of the FCC matrix accompanied by precipitation of sigma phase. The kinetics of recrystallization and precipitation and their interactions during the heat treatment were greatly different among the specimens with different degrees of pre -deformation. Notably, the precipitation of sigma phase was accelerated in the specimens subjected to higher shear strains, particularly in those with nanocrystalline structures. The increased rate of precipitation was beneficial for grain refinement since the presence of numerous precipitates within the recrystallized microstructures inhibited their grain growth. Tensile testing of the heat -treated specimens displayed various combinations of strength and ductility, with specimens subjected to higher pre -deformation exhibiting enhanced strength due to finer recrystallized grain sizes and larger fractions of precipitates. Our findings offer valuable insights into fabrication processing of HEAs, aiming to optimize microstructure and mechanical properties for potential engineering applications.