Comparative Assessment of GI and GA Coated AHSS LME Sensitivity During Spot Welding

Liquid Metal Embrittlement (LME) is a complex phenomenon which may occur during spot welding of zinc-coated Advanced High Strength Steels (AHSS) developed for the Automotive market. Zn or Zn-rich alloy in liquid state penetrates along the steel grain boundaries and may cause, depending on conditions, grains’ decohesion and cracks’ initiation and propagation under given mechanical stresses. LME sensitivity depends on the steel microstructure and mechanical properties, its bulk and surface composition, the coating composition and the spot welding process itself. In this study, a comparative assessment of conventional GalvanIzed (GI) and GalvAnnealed (GA) coatings in terms of LME behaviour has been done on the same sensitive AHSS material with the same welding process configuration and parameters. The intrinsic effect of the type of coating (GI vs GA) on the LME performance during spot welding could therefore be properly evaluated. It has been observed that no significant difference exists between both coatings.