Enhanced grain refinement due to deformation-induced precipitation during ambient-temperature severe plastic deformation of an Al–7%Si alloy

An Al–7wt%Si alloy was prepared by casting. Billets from the as-cast ingot were annealed at 540 °C and then either quenched or furnace cooled to control the Si concentration in the primary Al constituent. Subsequently, as-cast billets as well as billets in the annealed conditions were subjected to ambient temperature severe plastic deformation (SPD) by equal-channel angular pressing (ECAP). Microstructures were evaluated by optical, scanning electron, and transmission electron microscopy methods and Vickers hardness data were also acquired. Grain refinement and hardening in the primary Al by ambient temperature ECAP processing are influenced by deformation-induced precipitation of Si from a supersaturated solid solution. The finest grain size and highest hardness are associated with the greatest initial supersaturation of Si.