CoCrFeNiMn high entropy alloy microstructure and mechanical properties after severe cold shape rolling and annealing

Abstract

A CoCrFeNiMn high entropy alloy (HEA) was processed by Severe Cold Shape Rolling (SCSR) to equivalent strain of 3.7 at room temperature. The processed alloy shows a single-phase CoCrFeNiMn HEA with an average grain size of ~50 nm and dislocation density of 2.1 × 1015 m−2. Heat treatment at 723–1223 K for up to 30 min was conducted to study microstructural evolution during short term post-deformation annealing (PDA). The results showed the maximum hardness of 527 Hv after PDA at 773 K due to formation of Cr-rich precipitates. PDA at 1223 K led to significant drop of the hardness value due to dissolution of precipitates, recrystallization and grain growth in the microstructure. The results suggested that formation of precipitates increased strength but reduced ductility significantly. Remarkable mechanical properties achieved after short-term PDA at 1023 K with an ultimate tensile strength of 1000 MPa, yield stress of 920 MPa and an elongation to failure of 20%.