镁/钢异种金属磁脉冲焊接接头组织和性能

Microstructure and Properties of Mg/Fe Dissimilar Metal Joints Fabricated by Magnetic Pulse Welding

摘要:

采用磁脉冲焊接技术对AZ31B镁合金/DC56D钢异种不相容金属进行了焊接。对比研究了一次焊和二次焊对被焊界面的影响。通过扫描电子显微镜、能谱仪和X射线衍射仪等对焊接接头的宏观形貌、微观组织及界面结构进行了研究。结果表明，铝中间层通过变形和扩散作为桥梁，实现了镁/钢异种不相容金属的磁脉冲焊接。AZ31B/AA1060界面呈现出典型的波形界面，在接头界面中存在过渡区，过渡层中可能生成了非常复杂的微观组织结构，其组织明显不同于两侧的AZ31镁合金和1060铝组织，可能是Al₃Mg₂和Al_l2Mg₁₇的脆性金属间化合物。过渡区主要存在于铝侧，最厚处约为13.53 μm。在二次焊过渡区中发现微米级孔洞缺陷，一次焊界面出现不同厚度的不完全熔化层。AA1060/DC56D界面主要是平直界面，在接头界面中只有少量过渡区断续分布在界面上，过渡区存在FeAl₃脆性金属间化合物，最厚处约为4 μm。

Abstract:

Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding. The effects of primary and secondary welding processes on the welded interface were comparatively investigated. Macroscopic morphology, microstructure, and interfacial structure of the joints were analyzed using scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer (XRD). The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer, which acts as a bridge for deformation and diffusion. Specifically, the AZ31B/AA1060 interface exhibits a typical wavy morphology, and a transition zone exists at the joint interface, which may result in an extremely complex microstructure. The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys, and it is identified as brittle intermetallic compounds (IMCs) Al₃Mg₂ and Al_l2Mg₁₇. The transition zone is mainly distributed on the Al side, with the maximum thickness of Al-side transition layer reaching approximately 13.53 μm. Incomplete melting layers with varying thicknesses are observed at the primary weld interface, while micron-sized hole defects appear in the transition zone of the secondary weld interface. The AA1060/DC56D interface is mainly straight, with only a small number of discontinuous transition zones distributed intermittently along the interface. These transition zones are characterized by the presence of the brittle IMC FeAl₃, with a maximum thickness of about 4 μm.