Effect of applied stress during aging on the precipitates and the mechanical–electrochemical properties of the Al–10Zn–3Mg–3Cu alloy

This study investigated the stress-aging response of the Al–10Zn–3Mg–3Cu alloy, revealing dislocation-driven η′ precipitate growth as the fundamental strengthening mechanism. Under applied stress (135–450MPa, 120°C), dislocation reorganization enhanced solute diffusion along the <111> direction, promoting η′ phase growth on the {111} habit planes. After stress aging at 450MPa for 24h, η′-to-η 2 transformation occurred with dimensional coarsening, yielding the maximum strength (yield strength with 713MPa and ultimate tensile strength with 740MPa) through synergistic dislocation hardening and Orowan strengthening. Furthermore, grain boundary precipitates transitioned to continuous networks because of stress-enhanced vacancy flux, degrading the corrosion resistance despite the initially minimal corrosion current density ( I corr ) (1.417 × 10 −6 A·cm −2 at 135 MPa/6 h). The density of dislocations introduced during stress aging was found to critically govern the strength–corrosion trade-off by mediating the precipitate growth kinetics and grain-boundary solute segregation. Optimal performance was achieved at 270 MPa-120°C/12–24 h, balancing ultimate tensile strength (>700MPa), elongation (>4.5%), and I corr (<5.1 × 10 −6 A·cm −2 ). This study establishes stress-controlled precipitate engineering as a paradigm for overcoming the strength–corrosion trade-off in next-generation ultrahigh-strength aluminum alloys for aerospace applications.