Liquid metal embrittlement (LME) was observed in the laser lap welds of zinc-coated GEN3 steels. When line energy input ranged from 54 kJ/m to 60 kJ/m, the LME crack initiated from the weld edge at the faying interface, propagated along the growth direction of columnar grains and extended upwards along the weld centerline, exhibiting an inversed Y-shape. Multiple Fe–Zn phases such as α-Fe (Zn), Γ-Fe₃Zn₁₀ and δ-FeZn₁₀ were created by liquid zinc in grain boundaries reacting with the austenite matrix during the cooling stage of the laser welding process. Those hard and brittle Fe–Zn phases, especially Γ-Fe₃Zn₁₀, deteriorated the grain boundary cohesion and led to crack initiation. Simulation results indicate that a weld profile being deep with partial penetration will result in a high stress concentration at the notch root during the LME active temperature range. Therefore, full penetration welding is recommended to reduce the risk of LME by enabling zinc vapor to escape from both the top and bottom of the keyhole.

在镀锌的GEN3钢的激光搭接焊缝中观察到液态金属脆化（LME）。当线能量输入范围为54 kJ / m至60 kJ / m时，LME裂纹在接合界面处从焊缝边缘开始，沿圆柱状晶粒的生长方向扩展，并沿焊缝中心线向上延伸，呈现出反Y形。形状。多个的FeZn相，如α -铁（ZN），Γ -铁₃的Zn ₁₀和δ-的FeZn ₁₀通过液体锌在晶界中的激光焊接过程的冷却阶段，奥氏体基体反应产生。那些硬而脆的Fe-Zn系相，特别是Γ -铁₃的Zn ₁₀，恶化了晶界的内聚力，并导致裂纹萌生。仿真结果表明，在LME有效温度范围内，焊缝轮廓较深且具有部分熔深会在缺口根部产生较高的应力集中。因此，建议使用全熔透焊接，以使锌蒸气从锁孔的顶部和底部逸出，从而降低LME的风险。