Obtaining superior strength-ductility synergy properties in a medium-entropy alloy via dual heterogeneous and TRIP effects

Activating additional strain-hardening mechanisms is essential to achieve superior strain hardening capacity and strength-ductility synergy in precipitation-hardened alloys. In this work, we introduce a synergistic strategy that combines dual-heterogeneous structures (DHS) with the transformation-induced plasticity (TRIP) effect in a precipitation-hardened medium-entropy alloy (MEA), thereby enabling multiple strain-hardening mechanisms for the exceptional strength-ductility combination. The tailored alloy showcases a high yield strength of ∼ 1290 MPa, an ultimate tensile strength of ∼ 1737 MPa, and an excellent fracture elongation of ∼ 36.9% at ambient temperature, exhibiting a ∼ 162% increase in yield strength without compromising uniform ductility, compared to its single-phase solid solution counterpart. Microstructural analyses reveal that the enhanced yield strength stems primarily from precipitation hardening and extra hetero-deformation induced (HDI) hardening. Furthermore, plastic deformation mechanism investigations demonstrate that the remarkable work-hardening capacity (> 3 GPa) results from the combined effects of dynamically enhanced HDI hardening and the activated TRIP effect during tensile deformation. These multiple and sustained strain-hardening mechanisms underpin the alloy’s exceptional strength-ductility synergy. Our study provides a promising strategy for designing high-performance structural materials.