Improvement of ductility by reversion heat treatment on FSW jointed Al-Mg-Si alloy T4 sheet

The improvement of the ductility in the friction stir-welded Al-1.0Si-0.5Mg-0.1Mn (mass%) alloy sheet in T4 temper was investigated to develop a tailored blank that has superior press-formability. The fracture position during the tensile test shifted from the HAZ to the base metal, and the elongation increased by the reversion heat treatment at 523K for 0 seconds immediately following FSW. Additionally, the maximum forming height in the cup-drawing test improved. If the temperature during natural aging between FSW and reversion heat treatment was 293 K, the aging time of up to 2 hours was acceptable for the ductility improvement. Moreover, the ductility improvement was maintained for over 30 days at 293 K and within 15 days at 313 K after reversion, however, the fracture position during the tensile test shifted to the stir zone after 30 days at 313 K. Improvement in ductility was also achieved by applying reversion heat treatment before FSW. These improvements were considered to the result of differences in the natural aging properties at the stir zone, HAZ, and base metal.