Abstract The migration behavior of intermetallic compound (IMC) layer with some distance to the interface was observed in twin-spot laser welding-brazing of AA7075-T5 aluminum to DP590 galvanized steel. The microstructure characterization of different types of IMCs was systematically discussed using scanning electron microscopy, focused ion beam and transmission electron microscopy methods. It was found that the dense plate-like IMC layer formed at the interface was η-Fe2Al5 phase and the acicular IMC was θ-FeAl3 phase, while the sparse plate-like IMC layer that migrated into the weld metal was the mixture of the θ-FeAl3 phase and molten Al. A 3D thermo-fluid numerical model was developed to predict the melt flow behavior and analyze the mechanism of the migration behavior of the IMC layer. The simulation results revealed that the downward violent flow under the twin-spot center impacted the sparse IMC layer and entered into the gap between the steel and IMC layer, forming a broken migrated IMC layer. The joint strength increased with maximum migration distance and the maximum joint strength of 133.14 MPa was obtained. Thicker and sparse IMC was formed at the interface when the migration distance increased, which was adverse to the joint strength.

中文翻译：

---

IMC层在铝钢双点激光钎焊中的迁移行为

摘要 在AA7075-T5铝与DP590镀锌钢的双点激光焊接-钎焊中，观察了距界面一定距离的金属间化合物（IMC）层的迁移行为。使用扫描电子显微镜、聚焦离子束和透射电子显微镜方法系统地讨论了不同类型 IMC 的微观结构表征。发现在界面处形成的致密板状IMC层为η-Fe2Al5相，针状IMC为θ-FeAl3相，而迁移到焊缝金属中的稀疏板状IMC层为θ-FeAl3相的混合物。 -FeAl3 相和熔融铝。开发了 3D 热流体数值模型来预测熔体流动行为并分析 IMC 层迁移行为的机制。模拟结果表明，双点中心下方的剧烈向下流动冲击稀疏的IMC层并进入钢与IMC层之间的间隙，形成破碎的迁移IMC层。接头强度随着最大迁移距离的增加而增加，最大接头强度为133.14 MPa。随着迁移距离的增加，界面处形成较厚且稀疏的IMC，不利于接头强度。