Abstract
An external magnetic field was applied during the TIG welding-brazing of Mg/steel plates, which both has the thickness of 1.5 mm. The effects of magnetic field on the weld microstructure, micro hardness and tensile strength were studied by scanning electron microscope, Vickers hardness tester and tensile testing machine. The following conclusions can be drawn. The applying of magnetic field could lower the thickness of Mg–Zn reaction layer of brazed joint. With the continuous increase of coil current, the thickness value of IMC layer decreased gradually. Besides, electromagnetic force induced by magnetic field can promote the flow of molten pool and tend to break initial dendrite to pieces, which could turn into the new nucleation point. Hence noteworthy grain refinement was achieved by the applying of external magnetic field. For the magnetic field treated joint, the microhardness of welding seam enlarged from 49.9 HV to 56.8 HV and the maximum welding strength of 246 N mm−1 was obtained with coil current of 1.5 A.
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