Tianhao Wang¹, Scott Whalen¹, Woongjo Choi¹; ¹Pacific Northwest National Laboratory

A mechanically robust joining method for Al/Mg and Mg/CFRP enables decreased vehicle weight while offering more flexibility for vehicle designers. However, certain challenges exist for joining Al/Mg and Mg/CFRP. Mechanical joining cannot seal the dissimilar interfaces against corrosion. With solid-state and fusion based welding, rapid formation of brittle intermetallic compounds at the Al/Mg interface lead to interfacial fracture under mechanical loading. Large differences in physical and mechanical properties of metals and polymers make joining Al or Mg/CFRP challenging. In this study, a Rotational Hammer Rivet (RHR) technique was developed to fabricate Mg/CFRP and Al/Mg joints. Through heat generated by plastic deformation of an Mg rivet, RHR creates a metallurgical bond between rivet head and Mg sheet which seals corrosive electrolyte out of the joint. Direct joining between Al/Mg and Mg/CFRP were avoided. RHR tool design and process parameters were optimized based on microstructural and mechanical characterization of the dissimilar joints.