Structure of AlCoCrFeNi high-entropy alloy after uniaxial compression and heat treatment

Abstract

In this study, we discuss the structure and properties of high-entropy AlCoCrFeNi alloy after casting, cold deformation, and heat treatment. Ingots of the investigated alloys were obtained by arc melting method in argon atmosphere. In order to ensure a homogeneous chemical composition, ingots were remelted several times. Cylindrical samples of 5 mm in diameter and 8 mm in height were cut from ingots by electrospark method for mechanical tests. Subsequently, samples were subjected to uniaxial compression by 5, 11, and 23 %. During the tests, compression curves were recorded, and limit of proportionality of the analyzed alloys was calculated. High-temperature annealing and thermal studies were performed using thermogravimetric analyzer. Thermal studies were carried out in a cyclic mode (3 cycles, including heating up to 1200 °C at a rate of 20 °C/min and cooling at a rate of 20 °C/min). High-temperature annealing was carried out at a temperature of 1200 °C for 5 hours. Such annealing of cast alloys promotes material homogenization and eliminates dendritic structure. The alloy presents limited plasticity. Grain boundaries are effective barriers preventing crack propagation. The studies indicate that plastic deformation has a significant effect on development of relaxation processes during subsequent heat treatment. An increase in strain during the compression leads to a higher rate of healing processes of defects in crystal structure.