Achieving remarkable enhancement of yield strength ensuring large ductility in a metastable Fe₅₀Mn₃₀Cr₁₀Co₁₀ high-entropy alloy via warm rolling treatment

Abstract

The metastable Fe₅₀Mn₃₀Cr₁₀Co₁₀ (at. %) high-entropy alloy (HEA) integrates the principles of HEA and transformation-induced plasticity (TRIP), resulting in an exceptional combination of tensile strength and ductility. However, the inherently low yield strength restricts its application as a structural material. In this study, 50% warm rolling at 573 K was employed as a straightforward and cost-effective thermomechanical processing strategy to fabricate metastable Fe₅₀Mn₃₀Cr₁₀Co₁₀ HEA with enhanced yield strength while retaining large ductility. The mechanical responses and deformation behaviors of the metastable HEA were examined using room temperature tensile tests, along with postmortem X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) analyses. Compared to the fully recrystallized counterparts, the warm-rolled specimens exhibited a threefold increase in yield strength while retaining substantial uniform elongation. The warm rolling treatment increased the mechanical stability of the austenitic phase against stress-assisted γ-ε martensitic transformation, shifting the yielding mechanism from martensitic transformation to dislocation slip, thereby enhancing the yield strength. Moreover, warm rolling completely suppressed the athermal γ-ε martensitic transformation even at 77 K, while the strain-induced γ-ε martensitic transformation remained pronounced at room temperature, contributing to the alloy's high strength and large ductility.