Towards heterogeneous AlxCoCrFeNi high entropy alloy via friction stir processing

A heterogeneous bimodal-grained AlxCoCrFeNi high entropy alloy was realized through friction stir processing (FSP) with the addition of Al powders. With the bimodal-grained structure and second phases, strength was increased and ductility was retained as compared with the friction stir processed base alloy. Face-centered cubic grains in the matrix were refined from similar to 500 mu m to similar to 15 mu m by FSP and subsequent recrystallization. With addition of Al powders, localized Al-rich regions facilitated the formation of body-centered cubic phase (Al, Ni-rich) and Al rich precipitates, which further refined grain size to similar to 5 mu m and enhanced local strength. (C) 2018 Elsevier B.V. All rights reserved.