Viscoplastic lattice strain during repeated relaxation of age-hardened Al alloy

We examined the repetitive stress relaxation behavior of extruded AA7075 subjected to different heat-treatments (solid-solutionized (SS), under-aged (UA), peak-aged (PA)). Compared to SS and UA, the PA showed the highest stress drop (Δσs), plastic strain change (Δεp) and re-yielding (Δσr), in conjunction with the largest reduction in mobile dislocation density right after stress relaxation. As stress relaxation cycles repeated, the stress drop...