Effect of coating type on microstructure and mechanical behavior of resistance spot welds of thin X626 aluminum sheet to low carbon steel

Resistance spot welds were produced using GM’s patented welding process. The stack-ups consisted of 0.8 mm thick X626 aluminum and 0.9 mm thick low carbon steel (LCS) with three different coating types: hot dipped galvanized (HDG), Zn-Ni coating, and Zn-Ni coating with a passive layer containing trivalent clear chromate (Zn-Ni-Cr). The addition of Ni or Cr to the Zn coating provides a unique microstructure compared to that for welding to HDG …