Failure mechanisms of friction stir spot welds of AA6061-T6/DP590 steel during tensile-shear testing

摘要

The tensile-shear test was conducted for the evaluation of shear load and failure mechanisms of dissimilar friction stir spot weldments of AA6061-T6/DP590 dual-phase steel sheets. The joints were fabricated using a penetrated pin into the steel sheet (lower member). Such design resulted in the formation of a hook at the joint interface and an intermetallic compound layer (IMC) between the upper part of the hook and Al-side. A maximum tensile-shear load of similar to 2950 N was measured for the joint fabricated using a heat input of similar to 10 kJ; a lower strength was noted by varying the heat input. Partial plug was the failure mechanism in all joints. However, three different types of crack propagation paths were found depending on the heat input: along the interface between 6061 Al and IMC layer, thru 6061 Al near the joint interface, or within the IMC layer using relatively low, moderate, and high heat inputs.