Effect of field shaper structure on microstructure and properties of magnetic pulse assisted semi-solid brazing joint

The magnetic pulse assisted semi-solid brazing process of Cu/Al tubes with constant diameter field shaper and cone angle field shaper was analyzed by adopting the method of multi-physics coupling simulation of electromagnetic, structure and flow fields. The deformation behavior of outer tube and the shear flow behavior of semi-solid solder were investigated. The results shown that, the shear stress and corresponding shear flow velocity of solder were the highest at the top, followed by the bottom and the weakest in the middle by using constant diameter field shaper, which leads to the difference in removal of oxide film in overlap area, and even affects metallurgical bonding at the interface. The cone angle field shaper can more reasonably meet the requirements of the coordination between the deformation of outer tube and the shear rheology of solder without flux brazing, effectively improve the rheology behavior of solder and make the shear stress, shear flow velocity, removal effect of oxide film relatively uniform in the whole overlap area, which is beneficial to improve the quality of interface connection. Based on the analysis results, an improved field shaper was manufactured, and the brazing experiment and related tests were carried out. The results shown that, compared with constant diameter field shaper, the cone angle field shaper can effectively improve the interfacial bonding quality of Cu/Al joint, refine the grain of brazing seam, and finally improve the shear strength of brazing joint.