| Summary: | Since Mg/steel fusion welding methods fail in Fe melting point higher than the Mg boiling point, it is difficult to bond immiscible Mg/steel based on butt fusion welding. Here we use four different types of Mg/steel laser-TIG butt fusion welding methods to identify the forming mechanism. One of the key points to control the forming of Mg/steel butt fusion welding is to compensate the burning loss of Mg alloy, and the other is to promote the interfacial reaction. The interface mismatch degree for the higher strength joint has analyzed, and the molecular dynamics simulation results are consistent with the fracture analysis results. The Fe/AlNi interface exhibits a fully coherent relationship. The mismatch degree of the AlNi/Mg interface before the lattice distortion of AlNi and Mg shows the following relationship: (0 1 1¯)AlNi//(2¯ 1 1 0)Mg＜(2 1 1)AlNi//(0 0 0 2)Mg＜(1 1 0)AlNi//(0 0 0 2)Mg＜(2 0 0)AlNi// (0 0 0 2)Mg＜(1 1 0)AlNi//(0 1 1¯1¯)Mg. A most likely orientation relationship for AlNi/Mg is (0 1 1¯)AlNi//(2¯ 1 1 0)Mg and [1 0 0]AlNi//[0 1 1¯ 0]Mg before lattice distortion. The mismatch degree AlNi/Mg interface decreases after lattice distortion. Lattice distortion occurred on the Mg alloy side by HRTEM, and the (1 0 1¯ 2)Mg and (0 1 1)AlNi planes are fully coherent. The Mg/AlNi interface has the following orientation relations: [1 0 1 0]Mg//[1 1 1¯]AlNi, (1 0 1¯ 2)Mg//(0 1 1)AlNi.
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