Multi-Spot Ultrasonic Welding of Aluminum to Steel Sheets: Process and Fracture Analysis

Ultrasonic metal welding is an energy-efficient, fast and clean joining technology without the need of additional filler materials. Single spot ultrasonic aluminum to steel sheets using automotive materials has already been investigated. Up now, further studies close gap application-relevant multi-metal structures with multiple weld spots generated are still missed. In this work, two different arrangements presented, each consisting spots, joined 0.9 mm thick wrought alloy AA6005A-T4 1 galvannealed (galvanized annealed) dual-phase HCT980X. An anvil equipped variable clamping punches was used for first time. The tensile shear forces reached 4076 ± 277 N parallel connection 3888 308 series connection. Temperature measurements by thermocouples at interface through thermal imaging presented peak temperatures above 400 °C interface. Microscopic investigations fractured surfaces identified Zn layer as strength-limiting factor. Energy-dispersive X-ray spectroscopy (EDX) indicated intermetallic phases Fe in border areas well separation zinc from within these areas.