Mechanistic insight into the role of severe plastic deformation and post-deformation annealing in fracture behavior of Al-Mn-Si alloy

Abstract Dual-straining by constrained groove pressing (CGP) (e eff  = 2.32) and cold rolling (CR) (e r  = 0.47, 0.8, and 12.7) under different routes (direct cold rolling (DCR) and cross cold rolling (CCR)) performed on Al-Mn-Si sheets. In the following, thermal treatments (T a  = 150, 250, and 350 °C) conducted as supplementary processing on deformed specimens. Microstructural investigations and mechanical examinations carried out to study straining path effects. It was revealed that further straining through DCR route was more influential in ultimate grain refinement and strength enhancement. Despite DCR, CCR displayed prominent role in elongation deterioration. By post-deformation annealing of dual-strained specimen at T a  = 350 °C through DCR, ductility enhancement more than 1000% was obtained. Fractography implicated fracture-angles ranged θ f  = 44.5–66° which had inverse correlation with contribution of post uniform deformation (PUD) in tensile tests. Diverse fracture morphologies (fibrous, slip, rupture, and shear) examined by SEM while area contribution of each fluctuated by e r and T a . Increase in rupture fraction observed in more brittle fracture. Characterization of size, morphology and chemical composition of second-phase precipitates proved that they were fragmented, nucleated from matrix under dynamic precipitation and also enriched in alloying elements; however, just those had certain minimum size could find chance to contribute in dimple formation.