Thermal stability and grain growth kinetics in rotary swaged Al0.35CoCrFeNi complex concentrated alloy

Abstract

A complex concentrated alloy (CCA) with a nominal composition of Al_0.35CoCrFeNi (mol.%) was prepared by vacuum induction melting and tilt casting. The microstructure of the alloy in the as-cast state consists of columnar dendritic grains. The ingots were solution annealed, rotary swaged, and heat treated to obtain a uniform fine-grain structure. To study the behavior of recrystallization and grain growth, heat treatment was carried out at temperatures from 1150 °C to 1300 °C and holding times up to 480 min. The resulting microstructures were analyzed by LM, SEM, TEM, EBSD, and XRD methods followed by a comparison with the results of hardness measurements. The alloy has a thermally stable single-phase face-centered cubic (FCC) structure in the studied temperature range. The grain growth kinetics were analyzed using classical models, and the activation energy was estimated to be ∼458 kJ mol⁻¹ using an Arrhenius-type equation. The greatest resistance to grain growth was observed at a temperature of 1150 °C. Hardness tests demonstrated an almost double increase in hardness after swaging and a sharp drop during the following heat treatment due to the onset of recrystallization. The Hall-Petch hardening coefficient was calculated to be ∼277.5 HV μm^−1/2.