Fretting wear and fatigue performance of solid self-piercing riveted magnesium alloy/steel joints

Solid self-piercing riveting (SSPR) is a cold joining technology that has developed rapidly in recent years. Owing to its advantages of simple process operation and high joining strength for dissimilar metals (e.g., magnesium alloy/steel), it has attracted considerable attention in the field of lightweight manufacturing. In this study, the fatigue performance of solid self-piercing riveted joints between magnesium alloy and steel was systematically investigated. The results showed that fatigue cracks were mainly concentrated near the edge of the rivet hole in the upper sheet. Scanning electron microscope (SEM) observations revealed a large quantity of fretting wear debris at the rivet neck, while energy-dispersive spectroscopy (EDS) analysis confirmed that the wear debris mainly consisted of Mg and MgO. According to the contact interface characteristics, the fretting wear regions were classified into the upper sheet–rivet neck contact area (Area A) and the lower sheet–rivet neck contact area (Area B). Further analysis indicated that cyclic loading induced micro-slip at the contact interface, leading to oxidation and detachment of magnesium alloy wear debris. The presence of hard wear debris intensified friction and accelerated crack initiation. These results demonstrate that fretting wear is the dominant mechanism governing fatigue failure in such joints.