Short-time stress aging: Tailoring γ″ precipitation for superior strength-ductility synergy in Inconel 625 alloy

The sluggish aging response of Inconel 625 alloy has long limited its precipitation strengthening potential, restricting its application in high-demand environments. Conventional γ″ precipitation requires hundreds of hours of thermal exposure, making the process highly time-inefficient. To address this challenge, short-time stress aging was employed to accelerate precipitation kinetics and enhance mechanical performance. Stress-free and stress aging treatments were conducted at 650°C for 50-200 h, and the γ″ precipitation behavior was examined using TEM, EBSD, and first-principles calculations. Stress aging promoted rapid γ″ nucleation, producing a high precipitate number density and fine morphology. Compared with 200 h of stress-free aging, stress aging for only 50 h and 150 h increased the yield strength by 105.8 MPa (16.0%) and 175.9 MPa (26.6%), respectively, while maintaining comparable ductility. The refined γ″ precipitates restricted dislocation slip and promoted the activation of low-Schmid-factor slip systems, stacking faults, and deformation twinning, thereby achieving a superior strength-ductility synergy. These results demonstrate that short-time stress aging is a precise and time-efficient strategy for tailoring γ″ precipitation, providing new insights into microstructure design and performance optimization of Ni-based superalloys.