Achieving high strength and uniform ductility in high-entropy alloys via dynamic-precipitation accelerated transformation-induced plasticity

This study presents a novel approach to fabricating advanced transformation-induced plasticity (TRIP) high-entropy alloys (HEAs) that exhibit an exceptional combination of high strength and uniform ductility, far surpassing the mechanical performance of previously developed TRIP HEAs and non-TRIP multiphase HEAs. The ultrafine-grained Al5Cr20Fe35Co35Ni5 TRIP HEA sample exhibits a yield strength of gigapascal-level, ranging from 1100-1260 MPa, with large uniform elongations that range from 29% to 39%. Simultaneously, the alloy displays outstanding toughness, reaching 47,000±5390 MPa·%. The achievement of this significant breakthrough rests upon two key factors: (1) achieving an ultrafine-grained FCC matrix in a fully recrystallized microstructure with the aid of thermally induced B2 phase, and (2) dynamic precipitation of nanometer-sized B2 phase particles on high-density stacking faults and slip bands created within the interiors of ultrafine grains through the formation of the amorphous phase, serving as a precursor to the B2 crystalline phase. The dynamic precipitation of the B2 phase, a phenomenon uncommon in HEAs at room temperature, significantly enhances the FCC to HCP TRIP, enabling the overcoming of the inherent ductility constraints typically associated with ultrafine-grained metals. The development of TRIP HEAs with an outstanding combination of high strength and high toughness represents a remarkable milestone in the application field of TRIP HEAs.