Multi-pass FSP has been conducted on continuously-cast (CC) AA5083 materials in the as-cast condition. Stir zone grains were refined to ~1.0 µm in size and highly superplastic response was obtained during tension testing of the as-processed material at 450°C (>1200 pct. elongation at 10-1 s-1). Post-FSP anneals were employed to vary both microstructure and superplastic response. Microstructure analysis used orientation imaging microscopy to assess microtextures, grain boundary and grain size distributions, and also employed optical and transmission electron microscopy methods. Current models of recrystallization do not predict adequately the highly refined grains and predominantly random textures that are observed in stir zones, and alternative models will be discussed. Grain refinement during FSP is accompanied by refinement and redistribution of non-deforming constituents in the absence of particle fracture. However, the mechanics of the homogenization process remain to be established and requirements for redistribution mechanisms will be summarized. Comparison reveals that results from FSP of the as-cast material are superior to those attained in conventional processing.
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