Mechanical properties and microstructure analysis of refilling friction stir welding on 2219 aluminum alloy

Peilin LI 1), Zhongfeng XU 1), Chun YU 1,2), Hao LU 1,2) Junshan YAO 3) and Guoyu CHEN 3)( 1) School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China 2) Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai 200240, China 3) Shanghai Aerospace Equipments Manufacture, Shanghai 200240, China)

摘 要：The 2219 aluminum alloy under refilling friction stir welding （RF-FSW） was investigated. The micrographs showed that the bead could be divided into six zones, and the grain size and shape were greatly different in these zones. According to the microstructure analysis, the weld nugget zone and the shoulder stirring zone consisted of equiaxed grains, while the grains in the heat affected zone were seriously coarsened. It was obvious that bending deformation occurred in the thermo-mechanically affected zone. According to the microhardness analysis, the lowest hardness of the weld was at the thermo-mechanically affected zone, and the microhardness increased with the retraction of the stir-pin. The tensile strength and elongation of the bead were 70% and 80% of the base metal, respectively. The tensile strength was slightly different for the stable stage and the retraction stage, while the elongation decreased in the retraction stage. The mechanical properties and microstructure responded to different retraction speed were analyzed, and it showed that the elongation decreased with increasing retraction speed.

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