Transformation-enhanced strength and ductility in a FeCoCrNiMn dual phase high-entropy alloy

High-entropy alloys (HEAs) are considered as promising structural materials. Usually, HEAs with face-centered cubic (FCC) structure exhibit excellent ductility but low strength, while HEAs with body-centered cubic (BCC) structure indicate relatively high fracture strength and low ductility. In this paper, a new transformable FeCoCrNiMn HEA with dual FCC and BCC phases is prepared. Under tensile loading, this HEA undergoes strong strain-hardening, exhibiting low yield strength, high ultimate tensile strength and large tensile elongation. This HEA can maintain stable plastic deformation in a wide strain region with a high constant normalized strain hardening rate, which is far different from the continuous decrease of that for the famous Cantor HEA. The strong strain-hardening capability and large tensile ductility of this HEA can be attributed to the strain-induced FCC-BCC transformation.