Weld profile, microstructure, and mechanical property of laser-welded butt joints of 5A06 Al alloy with static magnetic field support

The magnetic support technology has been widely recognized to be an ideal way of improving the welding quality. In current work, the 7-mm 5A06 Al plates are laser welded with an external static magnetic field aligned vertically to the welding direction. The bead formation, grain configuration, alloying element distribution, and weld hardness are experimentally analyzed to reveal the magnetically dominated flow behavior within the weld pool. The results indicate that, under the function of the magnetostatic field, the continuity and stability of the aluminum welds are improved and the weld width especially on the bead surface diminishes obviously with increasing magnetic flux density from 0 to similar to 238 mT. The evolutions on weld profile are caused by the induced electromagnetic suppression on the molten convection, especially the Marangoni. The grain enlargement, remarkable grain-boundary segregation, and chemical heterogeneity are found in the seams with magnetic field applied since the blocked melt flow restrains the thermal transfer and decreases the nucleation rate and supercooling degree. The weld hardness achieves lower in fusion zone but higher in HAZ compared with the control case, which is consistent with the microstructure characteristics.