Phase formation, texture evolutions, and mechanical behaviors of Al0.5CoCr0.8FeNi2.5V0.2 high-entropy alloys upon cold rolling

Abstract

The cold rolling (CR) reduction dependence of microstructure evolutions and mechanical properties for Al0.5CoCr0.8FeNi2.5V0.2 high-entropy alloy (HEA) were investigated. The HEA remains FCC structures consisting of nanoscale ordered L12 phase, confirming the phase formation prediction. With increasing CR reduction, the textures transform from random ones to FCC rolling ones accompanied by dense slip bands and deformation twins. Under a 50% CR reduction, the deformation textures started to become evident and were governed by typical {111}<112>F, {110}<100>Goss and {112}<111>Cu texture components. When the CR reduction approached 90%, the deformation textures mainly contained the {110}<111>A, {114}<110>X, and {112}<111>Cu texture components. As a result, both Vickers hardness and ultimate strength increased, but the ductility decreased roughly. The enhanced strength should be attributed to the anisotropy and work hardening behavior from textures. The plastic deformation for the samples under low CR reductions was dominated by deformation twins and slip bands. However, under high CR reductions, the textures severely impeded the further propagation of pre-existing slip bands, leading to the rapid decrease of ductility. Therefore, the CR reduction should be carefully designed before optimal heat treatments to enhance the strength and ductility synergy.