Development of a recovered/recrystallized multilayered microstructure in Al alloys by accumulative roll bonding

A high-purity Al alloy and a supersaturated Al–0.3 wt.% Sc alloy (Al(Sc)) were accumulative roll bonded at 200 °C to generate sheet material consisting of alternating layers of Al and Al(Sc). The deformation structure within these layers consisted of lamellar bands aligned parallel to the rolling direction. Compared with those bands in Al(Sc), the bands in the Al layers were less refined but contained a larger fraction of high angle grain boundaries (HAGBs). Subsequent annealing at 350 °C generated alternating layers of coarse grains (Al layers) and a recovered substructure (Al(Sc) layers); the latter were stabilized by the precipitation of Al3Sc particles. Within the Al layers, annealing did not significantly alter the rolling texture (β-fibre), although the strong Brass component was largely eliminated; this behaviour has been explained using the “ReNuc” model of recrystallization whereby nucleation is deemed to occur on HAGBs between the β-fibre components of the lamellar bands in conjunction with orientation dependent recovery.