Hot deformation behavior and microstructural characterization of CoCrFeNiNb0.45 eutectic high entropy alloy

Abstract

In recent years, several multicomponent alloys of near equiatomic composition (also known as high-entropy alloys) with excellent mechanical properties have been developed. In this study, a eutectic high entropy alloy, CoCrFeNiNb0.45, was chosen for a hot deformation study. The alloy consists of a primary face-centered cubic (FCC) phase (CoCrFeNi rich) and a eutectic region between the FCC and Laves phase (Co2Nb type). The combination of FCC and eutectic region is expected to provide better strength and ductility. Hot compression tests were carried out at different strain rates of 0.001, 0.1, 1, and 10 s−1 with varying temperatures of 1,073, 1,173, 1,273, and 1,323 K. The optimum processing window was identified by plotting processing maps, and the instability region was verified using multiple parameters. Constitutive equation relating stress, strain rate, and temperature is established. The optimum processing condition was correlated with the microstructural characterization, and instability was characterized with cracks on the specimen. Finite element simulation was carried out, taking the flow curve as input and correlating the strain field distribution with the microhardness variation. These studies are intended to contribute to an integrated computational materials engineering approach to developing these alloys toward a product. © 2019 by ASTM International