EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

3rd generation advanced high strength steels present a good compromise between strength, ductility and in-service properties in the automotive industry, which allow structural parts to be made from thinner sheets compared to other alternative materials. However, when zinc coated, they are prone to suffer from Liquid Metal Embrittlement (LME) during Resistance Spot Welding process (RSW), as a result of the contact between the liquid zinc and the solid metal under certain conditions of temperature, stress and strain rate.

In the present work, in a first step, severe welding conditions have been sought to increase drastically the occurrence of LME cracks in a two-sheets homogeneous configuration. Then, the special welding parameters outlined as highly prone to produce inner cracking have been used to generate welds with inner LME cracks and evaluate their impact on Cross-Tension Strength (CTS) and Tensile-Shear Strength (TSS) of spot welds.

The results showed that these specific cracks have no effect on cross-tension behavior. Welds containing inner cracks behave in the same way as those which are free of cracks: similar failure modes and failure loads for both. Regarding Tensile-Shear behavior, the impact of LME inner cracks depends on their position with respect to the tensile direction.