Effect of anisotropic microstructure on high-temperature compression deformation of CoCrFeNi based complex concentrated alloy

Abstract

The effect of anisotropic as-cast microstructure on high-temperature compression deformation of multiphase Co24Cr19Fe24Ni19Al8(Ti,Si,C)6 (at.%) complex concentrated alloy (CCA) derived from a single phase CoCrFeNi based high entropy alloy (HEA) was studied at temperatures ranging from 750 to 900°C. The highly anisotropic microstructure composed of several columnar grains with [100] crystallographic direction parallel or nearly parallel to the load axis leads to asymmetric barrelled shapes of the compression specimens with multiple protuberances on the barrelled surfaces. The experimental barrelled shapes differ from the numerically calculated ones. The deformation curves exhibit strain hardening stage which is followed by a deformation at a constant flow stress at all studied temperatures. The work hardening rate (WHR) first increases with increasing strain. After achieving a peak value, the WHR decreases and achieves values around zero corresponding to the steady-state deformation. The finite element analysis (FEA) of 3D distribution of local equivalent strains and stresses corresponds qualitatively quite well to the observed structural changes within the barrelled specimens.