Investigating the influence of electrode surface morphology on aluminum alloy resistance spot welding

Abstract

Electrode pitting is a significant challenge that restricts wide applications of resistance spot welding for aluminum alloys in the automotive manufacturing industry. To address this issue, a new electrode was developed and the effects of gradual changes in electrode morphology were systematically studied, which included varying the number of convex rings, ranging from zero to four, to alter the electrode morphology. Microstructural analysis, mechanical property testing, and comparisons of electrode life were investigated. It was found that as the quantity of convex rings increases, the associated crystal defects within the nugget also increase. However, when the number of convex rings surpasses four, the associated crystal defects within the nugget begin to diminish. Moreover, the presence of convex rings plays a pivotal role in regulating current distribution. Properly distributing the quantity of these rings can enhance current utilization, facilitating increased heat input during nucleation process and yielding larger nugget sizes. During the welding process, the puncturing of the oxide film by the convex rings of the electrode enhances current distribution, potentially redirecting pitting corrosion away from the electrode and consequently prolonging its service life.