Effect of type-C liquid metal embrittlement on mechanical properties of spot-welded TRIP steel

Abstract

Type-C liquid metal embrittlement (LME) crack refers to an internal crack in the heat-affected zone near the notch area. In contrast to type-A and type-B LME, the type-C LME has rarely been studied for its effect on the mechanical properties of the metal. This study investigates the effects of type-C LME on uniaxial tension and high-cycle fatigue behaviors of transformation-induced plasticity (TRIP) steel joined using resistance spot welding (RSW). The mechanical properties of the steel sample were evaluated in two deformation modes of tensile shear (TS) and cross-tension (CT). Type-C LME cracks barely affected the tensile behavior in both deformation modes. In case of cyclic loading, their influence varied based on the deformation mode. Pre-cracks in a corona bond exhibited a higher contribution to fatigue fracture than did the LME cracks in the TS mode. However, the contribution of LME cracks increased in the CT mode owing to an increase in the local stress concentration. Consequently, unlike type-A and type-B LMEs, type-C LME affected the high-cycle fatigue resistance of the RSW-processed TRIP steel.

Keywords

• Resistance spot welding
• Liquid metal embrittlement
• Tension
• High-cycle fatigue
• TRIP steel