Achieving excellent strength-ductility synergy via cold rolling-annealing in Al-containing refractory high-entropy alloys

Abstract

Most refractory high-entropy alloys (RHEAs) with Al possess excellent strength but low elongation. Low ductility is generally induced by the formation of brittle phases after long-term heat treatment. Here, we demonstrate a new strategy to optimize strength-ductility in RHEAs through cold rolling-annealing treatments. The Zr35Ti30Nb20Al10Ta5 RHEA was cold rolled followed by annealing. A high tensile yield strength of ∼997 MPa with an elongation of ∼20% was obtained. Several factors together optimize the mechanical properties. First, the high-density dislocation entanglements introduced by cold rolling and short-time annealing are beneficial to uniform strain hardening and ductility. Second, short-term annealing can prevent the generation of the brittle LAVES phase in Al-containing RHEAs. Third, the B2 nanoprecipitates are dispersed in the BCC matrix phase, strengthening the alloys. Fourth, the fine grain size induced by cold rolling and short annealing times contributes to the strength.