Microstructure and mechanical properties of 2219 aluminum alloy refilling friction stir welded joints

The 2219 aluminum alloy sheets were welded with refilling friction stir welding technology. The microstructure and mechanical properties of the welded joints were characterized, and the effects of retraction speed of the stir-pin on the mechanical properties of the joints were analyzed. The results show that,for the upper part of the joints obtained in stable welding stage,the fracture during tension test occurred in the thermalmechanically affected zone (TMAZ) on advancing side; while for the lower part,the specimen fractured in the zone A3. The joints in the retraction part fractured in the heat-affected-zone (HAZ) on retreating side. The tensile strength and elongation of the bead were 70% and 80% of the base metal,respectively. The retraction speed of stir-pin had remarkable effect on the mechanical properties of the joints,and when the retraction speed was 6 mm/min,the elongation of the joints reached the maximum. The lowest microhardness located in the boundary between TMAZ and HAZ.