Microstructural Evolution During Zinc-Assisted Liquid Metal Embrittlement Cracking in Third-Generation Trip Steel

Third-generation medium Mn transformation-induced plasticity (M-Mn TRIP) steel offers superior mechanical properties and is being utilized in the automotive industry for the development of lightweight and safe vehicles. However, M-Mn TRIP steel is susceptible to zinc-induced liquid metal embrittlement cracking during thermomechanical processing, which hinders its application in the automotive sector. This study presents the microstructural evolution during high-temperature tensile tests at 700°C and 800°C to investigate how changes in microstructure can affect LME cracking propagation. It was observed that increasing temperature leads to a rise in LME susceptibility. Additionally, retained austenite was detected near the fracture surface, with a slightly higher volume fraction in samples tested at 800°C compared to those at 700°C, indicating minimal plastic deformation during LME-induced cracking. This suggests that as the susceptibility to LME cracking increases with temperature, less plastic deformation is needed for LME crack propagation.