Designing an ultrahigh-strength and ductile Ni-based alloy with a partially recrystallized structure

Abstract

Despite having excellent mechanical properties, the applications of many Ni-based alloys are limited owing to their modest yield strengths. Grain refinement has provided the opportunity for further strengthening, while also requiring significant and undesirable compromises in ductility. In this work, a novel Ni-based alloy with a heterogeneous, partially recrystallized structure was designed by controlling the thermomechanical process after cold-rolling. The alloy exhibits a superior combination of ~ 2 GPa yield strength and ~ 9% tensile uniform elongation, surpassing the room-temperature mechanical performance of most Ni-based alloys reported in recent years. The ultrahigh strength originates from the synergistic strengthening effects of grain boundaries, high-density dislocations, and γ' nanoparticles. Meanwhile, the considerable ductility is primarily ascribed to the improved strain hardening ability and delayed necking induced by two mechanisms: (i) the formation of high-density stacking faults, Lomer-Cottrell locks, and deformation twins in the recrystallized grains; (ii) the abundant dislocations pile-up at the interface between the γ' nanoparticles and matrix. These findings suggest that the design of partially recrystallized structures has great potential to solve the strength-ductility trade-off in Ni-based alloys.