Recrystallization and texture evolution in friction stir welded 7050-T7451 aluminum alloy

Abstract

Friction stir welding was performed on 7050-T7451 alloy of the Al-Zn-Mg-Cu system. Sound welds without defects were produced using a rotation rate of 600 rpm and a traverse speed of 100 mm/min. The as-received base material (BM) displayed overaged microstructures with coarse, elongated grains and fine, partially recrystallized grains. In the stir zone (SZ), fine equiaxed dynamically recrystallized (DRXed) grains with a high fraction of high-angle boundaries (HABs) were generated via continuous dynamic recrystallization (CDRX). The SZ primarily comprised recrystallized and deformed microstructures, with the proportion of recrystallized features being significantly higher than that in the BM. The rolling texture present in the as-received BM did not notably affect the preferred orientation of recrystallized grains in the SZ; instead, it was replaced by a recrystallization texture in the friction stir-welded (FSW) joints. Furthermore, dynamic recovery was identified as the dominant mechanism governing the DRX process occurring in the SZ.