Study On Laser Weld Bonding Of Magnesium Alloy To Aluminum Alloy

Increased application of lightweight materials puts forward to a new require towards joining technique and accelerates originality innovation of joining technique to adapt the demand on industrial development. At the present time, welding is widely applied in commercial run, but has restriction in some fields. For badly welding materials, due to metallurgy, it is hard to join them only by welding technology, such as magnesium alloy and aluminum alloy.This thesis draws lessons from the application of spot-weld bonding in metals' joining, for the first time adhesive bonding is combined with laser continuous welding to join magnesium alloy and aluminum alloy (namely laser weld bonding, LWB). This paper selects AZ31B magnesium ally and 6061 aluminum ally as research objects to study process characteristics and mechanism of LWB similar metals and dissimilar metals with the same and different adhesive thicknesses, and profoundly discusses the selection of welding parameters, the analysis of microstructures, distribution of elements, mechanical properties, welding defects, and so on.The results show that adhesive in the LWB weld was heated and escaped in the form of gas, which would not affect the microstructures of weld. Adhesive near the LWB weld was oxidized and carbonized, leading to the formation of a failure zone, but this failure zone had little influence on load bearing capability of the LWB joints. Besides, in tensile shear test and T-peel test, compared with laser welded samples and adhesive bonded samples, LWB samples gave both the highest shear resistance and the highest peel resistance.The LWB Mg/Al weld was characterized by complex vortex flow at the bottom, and there existed intermetallic compound layer between weld pool and lower sheet metal, which was composed of the brittle phases of Al₃Mg₂ and Al₁₂Mg₁₇, resulting in the formation of weld cracking. Meanwhile, it was also found that the penetration of LWB Mg/Al joints was greater than that of laser welded joints alone.It is indispensable to weld twice in adhesive bonded Mg/Al samples with thicker adhesive layer under proper technological parameters. In comparison with transverse section of joints, the weld penetration depth decreases with increment of adhesive thickness. The shear force of LWB Mg/Al joints with thicker adhesive layer was much greater than that with thinner adhesive layer.The study reveals in the practical production of LWB Mg/Al, we should use thicker adhesive layer on the condition that not making technological conditions complex.