The role of the partial melting zone in the nugget growth process of unequal-thickness dissimilar aluminum alloy 2219/5A06 resistance spot welding

The effect of the partial melting zone on nugget growth in aluminum alloys' resistance spot welding (RSW) process was investigated in this study by exerting same welding schedule on dissimilar 2219/5A06 aluminum alloys' combination (of unequal-thickness) and commercial pure aluminum 1060 with the same gauge. A two-dimensional symmetrical finite model of unequal thickness RSW of which considering the coupling of the thermal, electrical and mechanical fields was exerted to reveal the dynamic nugget evolution under dissimilar 2219/5A06 aluminum alloys' combination. Calculation of phase diagram (CALPHAD) technique was used to simulate the dynamic evolution of physical properties regarding the different phase portion at different local temperature. Between the solidus and the liquidus, both 2219 (548-645 degrees C) and 5A06 (449-626 degrees C) aluminum alloy exhibits a marked decrease in thermal and electrical conductivity. This leads to nugget shape evolution of dissimilar 2219/5A06 aluminum alloys' combination (the peak diameter is not located at the workpiece/workpiece interface) differed from that of the commercial pure aluminum ones (the peak diameter is located at the workpiece/workpiece interface). Finally, by comparing the experimental and the calculated data, the model developed in this study provides a more reliable method to predict the size of the load-bearing plane when the effect of the partial melting zone is pronounced.