Friction Stir Processing (FSP) of As-Cast AA5083 for Grain Refinement and Superplasticity

Abstract

Multi-pass FSP was conducted on continuously-cast (CC) AA5083 materials in the ascast condition. Stir zone grains were refined to ~1.0 – 3.5μm in size and highly superplastic response was obtained during tension testing of the as-processed materials at 450°C (>1200 pct. elongation at 10-1 s-1). Current models of recrystallization do not predict adequately the highly refined grains and predominantly random textures that are observed in stir zones. Grain refinement during FSP is accompanied by refinement and redistribution of non-deforming constituents in the absence of particle fracture. 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.