Effect of microstructure and mechanical properties on Al-Cu welding-brazing joint assisted by longitudinal DC magnetic field

TIG welding was used for butt welding of aluminum copper dissimilar materials. By adding Zn-2%Al flux cored wire to control the composition of the weld, and by adding longitudinal DC magnetic field to control the interface structure, the mechanical properties of the joint were improved. The results show that, compared with no magnetic field, the shape, thickness and compound types of IMC layer on the Cu side change under the action of longitudinal DC magnetic field: the average thickness of IMC layer decreases from 32.8 μm to 14.6 μm; the shape changes from straight to curved, which plays a role of “mechanical occlusion”; the appearance of ternary compound Al_4.2Cu_3.2Zn_0.7 in IMC layer on Cu side inhibits the growth of hard and brittle AlCu and Al₂Cu compounds, and improves the joint performance. After adding DC magnetic field, the joint tensile strength is higher than that without magnetic field, and the joint tensile strength increases first and then decreases with the increase of magnetic field strength. When welding current I = 95 A, welding voltage U = 16 V, welding speed v = 140 mm/min and magnetic field strength B = 10 mT, the tensile strength of the joint is the highest, reaching 110.8 MPa, which is about 24% higher than that without magnetic field.