High power fiber laser arc hybrid welding of AZ31B magnesium alloy

摘要

High power fiber laser-metal inert gas arc hybrid welding of AZ31B magnesium alloy was studied. The fusion zone consisted of hexagonal dendrites, where the secondary particle of Al_8Mn_5 was found at the center of dendrite as a nucleus. Within hybrid weld, the arc zone had coarser grain size and wider partial melted zone compared with the laser zone. The tensile results showed the maximum strength efficiency of 5 mm thick welds was up to 109%, while that of 8 mm thick welds was only 88%. The fracture surface represented a ductile-brittle mixed pattern characterized by dimples and quasi-cleavages. On the frac ture surface some metallurgical defects of porosity and MgO inclusions around with secondary cracks were observed. Meanwhile, a strong link between the joint strength and weld porosity were demon strated by experimental results, whose relevant mechanism was discussed by the laser-arc interaction during hybrid welding.