A study of flow behavior and fracture modes of alclad 2A12 aluminum alloy FSLW joints at different rotational speeds

Friction stir lap welding (FSLW) technology was utilized to join 2 mm-thick 2A12-T42 aluminum alloy plates in the current study. Experimental findings demonstrated successful plate joining without welding defects across rotational speeds ranging from 400 to 600 rpm. Higher rotational speeds facilitated ample material flow, resulting in joints that are free of hole defects. The presence of a step can be attributed to a non-synergistic material flow caused by the shoulder and pin. The fracture behavior of the joint is primarily influenced by joint formation factors, such as the distribution of the aluminum cladding (alclad) layer and effective lap width (ELW), as well as the microstructure. The continuous distribution of the alclad layer promotes crack propagation into the nugget zone (NZ). In cases where the ELW is inadequate (at 400 rpm), shear fracture occurs due to crack propagation along the NZ. With an increase in ELW (at 600 rpm), crack propagation is hindered by grain refinement in the NZ, causing the crack to propagate along the weaker thermomechanically affected zone (TMAZ) leading to tensile fracture.