Quantitative analysis of influences of defects on mechanical properties in refill friction stir spot welding Al–Mg-Li alloy joints

This research significantly extends the previous studies by providing a quantitative analysis of the impact of defect size on the mechanical integrity of 5A90-T3S Al–Mg–Li alloy joints via refill friction stir spot welding (RFSSW). It particularly elucidates the pronounced effects of the defects at both vertical and horizontal interfaces on the mechanical properties (such as shear and tensile strengths). Notably, larger defects at the vertical interface are found to critically undermine the tensile strength, whereas the defects at the horizontal interface primarily diminish the shear strength. Moreover, the presence of cavity defects at the interface junctures is identified as a pivotal factor severely compromising joint performance. Comprehensive mechanical testing coupled with detailed statistical analysis underscores the critical importance of precise control over welding parameters and the implementation of rigorous inspection protocols to minimize defect impacts, thereby bolstering the structural integrity of aerospace components.