Enhancing mechanical properties of FSW joints in 6061 aluminum alloy through post-weld shot peening treatment

Mechanical Engineering Department, Faculty of Engineering and Planning, Institut Teknologi Nasional Yogyakarta, Yogyakarta, Indonesia

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Abstract

This study investigated the effects of post-weld shot peening treatment on friction stir welded (FSW) joints in 6061 aluminum alloy. It is well known that FSW joints experience softening and a reduction in mechanical properties compared to the base material. Shot peening was applied to the weld metal surface to improve its mechanical performance. The FSW process was performed on 3 mm thick 6061 aluminum alloy plates in a butt joint configuration, using a travel speed of 18 mm/min and a spindle rotation of 910 rpm. Three types of shot peening media were used: steel shot (S230), and aluminum oxide (Al24 and Al54). Microstructural analysis revealed that shot peening produced plastic deformation up to a depth of approximately 700 μm from the surface. Tensile tests showed that shot peening with Al54 particles achieved the highest tensile strength of 208 MPa, while impact tests demonstrated the best impact toughness of 0.57 J/mm² with S230 particles. Vickers hardness testing revealed an increase in hardness in the weld metal area, especially with the S230 steel shot, which outperformed the Al24 and Al54 media. These findings suggest that shot peening, particularly with steel shot, effectively enhances the surface hardness and overall mechanical properties of FSW joints.