Making a coherent L12-nano-precipitates-reinforced Ni-based alloy ultrastrong and ductile by constructing dual heterogeneous structures

It is known that inhibiting rapid decline of strain hardening is crucial in enhancing uniform ductility under uniaxial tension stress for metallic materials with high yield stress. In this study, a high-mechanical-response Ni-based alloy was introduced by fabricating a dual-heterogeneous structure allowing to provide improved strain-hardening capability at both ambient and cryogenic temperatures. Especially at cryogenic temperature, an exceptional strength-ductility synergy with yield strength of 1.85 GPa and ductility of 24% can be achieved, accompanied by a distinctive five-stage strain-hardening response. In such a case, deformation twinning behavior was activated successfully to assist the strain hardening in the Ni base alloy although precipitation-hardening effect was available. Our work sheds light on the strain hardening effect assisted by twinning previously unexpected in coherent precipitation-hardened Ni base alloys, and hence represents a promising route for improving uniform ductility of Ni base alloys with high yield strength.