Interlock Formation, Mechanical Performance and Interfacial Characteristics of Dissimilar AA5182–22MnB5 Clinched Joints

The increasing use of multi-material automotive structures has intensified the demand for reliable joining technologies capable of integrating lightweight aluminum alloys with ultra-high-strength steels. This study investigated the formation mechanisms, geometrical characteristics, mechanical performance, and interfacial behavior of dissimilar AA5182 aluminum alloy and 22MnB5 press-hardened steel joints produced by clinching. Cross-sectional metallography, mechanical testing, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were employed for characterization. The analyzed joint cross-section exhibited well-developed mechanical interlocking, with left and right interlock lengths of 0.175 and 0.191 mm, respectively. Severe localized deformation during clinching produced thickness reductions of approximately 75% in AA5182 and 67% in 22MnB5. Mechanical testing showed a higher peak load under lap-shear loading (1210 ± 130 N) than under cross-tension loading (900 ± 40 N). SEM observations revealed extensive interfacial contact without major discontinuities, while EDS indicated localized redistribution of Al, Fe, and Si associated with deformation of the Al–Si-coated interface. No clear evidence of diffusion-controlled metallurgical bonding was identified. The results indicate that joint integrity was governed primarily by mechanical interlocking, with interfacial friction considered a possible secondary contribution to load transfer, demonstrating the technical feasibility of clinching for AA5182–22MnB5 multi-material structures.