A new transformation-induced plasticity-assisted dual-phase medium-entropy alloy with ultra-high cryogenic mechanical properties

Abstract

A novel maraging Fe68Ni10Mn10Co10Ti1.5Si0.5 (at%) medium-entropy alloy (MEA) was designed and microstructurally engineered to obtain a superior combination of tensile strength and uniform elongation at liquid nitrogen temperature. To this end, short-time martensite-to-austenite reversion treatment was conducted on an aged specimen to gain a dual-phase microstructure decorated by needle-like (NiMn)3−xTix and the elliptical-shaped Ni2SiTi nano-precipitates. The alloy exhibited an ultra-high yield strength of 1.41 GPa and ultimate tensile strength of 1.88 GPa, with a uniform elongation of ∼14% in the reverted condition. These superior properties are attributed to the transformation-induced plasticity (TRIP)-assisted heterogeneous dual-phase microstructure strengthened by well-distributed nano-precipitates. The metastability-engineering approach to achieve TRIP-assisted maraging MEA can usefully guide design to overcome the strength–ductility trade-off in extreme environments. © 2023 Acta Materialia Inc.