Weibull statistics for evaluating failure behaviors and joining reliability of friction stir spot welded 5052 aluminum alloy

Friction stir spot welding (FSSW) was applied to make lap-joints of 5052 rolled (5052-R) aluminum alloys. The resulting microstructural observation, microhardness, tensile shear failure load and failure morphologies are reported, including a brief look into failure behaviors in the present study. The metallurgical bonded TMAZ region with a plastic metal flow is obviously created around the probe, and the microhardness is significantly increased at the TMAZ region for FSSW-joined 5052 aluminum alloys. The FSSW lap-joints with an obvious metallurgical bonded TMAZ region generally display a higher failure load and ductile failure morphologies with dimples fracture. In addition, the failure load of FSSW lap-joints was increased with increasing the probe penetration depth and the welding time. Based on the data fluctuation of tensile shear failure load, the Weibull model provided a statistical analysis method for assessing the minimum failure, the failure mechanism and the joining reliability for the FSSW lap-joints. Through the statistical analysis of the Weibull distribution function, FSSW-joined aluminum alloys with a wear-out failure model are recognized as reliable lap-joints for further engineering application.