Room-Temperature Superformability in Novel As-Cast High-Entropy Alloy During Compressive Loading

Conventional alloys show low compressive strength and strain accommodation due to their propensity for limited strengthening mechanisms and rapid compressive instability. High-entropy alloys (HEA) may overcome this limitation by metastability engineering. Inspired by this, herein, a dual-phase Fe44Mn20Cr15Ni7.5Co6Si7.5 HEA (M-HEA) which shows maximum engineering strength of ≈4.4 GPa at true compressive strain of ≈2.2 (engineering strain of 90%) in as-cast condition due to controlled hardening and sustained softening response during deformation is presented. The controlled hardening phenomenon (up to 60% strain) is attributed to transformation-induced plasticity in γ-phase and nanotwinning in untransformed γ-phase. The sustained softening is a result of extensive strain accommodation by both γ- and β-phases via dynamic recovery in γ-phase and shearing of β-phase during deformation. Hence, this superformability in M-HEA makes it an excellent material for structural applications in comparison with other conventional alloys and HEAs.