Prediction of hot cracking susceptibility in resistance spot welding of aluminum alloys

Hot cracking is a persistent problem in the resistance spot welding (RSW) of high-strength 7xxx aluminum alloys. Existing hot cracking susceptibility (HCS) models, such as KOU, RDG, and SKK, were originally developed for fusion welding, and their applicability to RSW remains unclear. In this work, the RDG and SKK models were applied and optimized for the RSW of AA7075, with AA6061 introduced for comparison. A combined framework of electro-thermo-mechanical finite element simulation, experimental data, and CALPHAD-derived material properties was employed to evaluate predictive accuracy. To address RSW-specific conditions, a hybrid prediction criterion was proposed, incorporating coalescence temperature, weld nugget pressure, and strain rate. Experiments revealed that AA7075 welds are highly susceptible to hot cracking, while AA6061 exhibits much lower HCS. The refined RDG and SKK criteria successfully predicted HCS distributions, with RDG showing stronger agreement with experiments and SKK performing better in the equiaxed grain zone. Sensitivity analysis identified longitudinal temperature gradient and grain size as key controlling factors, consistent with AA6061's finer grains and higher gradient values. This study represents the first comprehensive integration and optimization of RDG and SKK models for RSW and introduces a hybrid HCS prediction approach, providing a new tool for predicting and mitigating hot cracking in RSW. • This integration of hot cracking susceptibility (HCS) criteria (RDG/SKK) with the resistance spot welding (RSW) process and assesses their predictive accuracy for RSW. • A hybrid criterion is developed to map HCS distribution across the entire weld nugget, and confirms AA7075 exhibits higher HCS than AA6061. • Governing parameters are identified, suggesting grain refinement and thermal control as mitigation pathways.