| Weld bonding technology was a hybrid join method, combining the welding and adhesive bonding process. It took the advantages of the welding and adhesive bonding technique. The combined connections ensured better the carrying power and the peel performance. However, the welding source used in weld bonding process was few, which only contained resistance spot welding and laser welding at present. At the same time, the effect of adhesive on the welding source was almost not investigated. It limited the development of the weld bonding technology greatly. Therefore, "plasma arc weld bonding" (PAWB) and "laser-Tungsten Inert Gas (TIG) weld bonding" (LTWB) technology, two new weld bonding method, were presented in this paper. Through PAWB and LTWB process of Mg to Al alloy, the effect of adhesive on different welding source and structure of Mg/Al joint was investigated. The main research contents and results were as follow:1. PAWB process of Mg/Mg alloy was conducted, and the welding characteristic and weldability were investigated. The variety of welding process due to the addition of adhesive was observed and tested, including the welding plasma, welding current, welding voltage, temperature distribution on the surface of weldment, macrostructure, microstructure and mechanical property of joints. The results showed that the the welding problem, such as non-shape and pores, could be avoided by the adjustment of technics parameters, as a result a better PAWB joint was obtained. Besides, it was found that in PAWB process of Mg alloy, because of the addition of adhesive, the welding plasma contracted in alternating current electrode positive stage. The welding current was not changed, and the welding voltage was increased. The melton pool grain was refined. The heat-transfer rate between sheets was enhanced, leading to increment of cooling velocity of melton pool. PAWB joint showed higher tensile shear failure load comparing with plasma arc weld joint and adhesive bonding joint.2. PAWB process of Mg/Al alloy was conducted. The effect of adhesive on the plasma behaviors and structure and mechanical property of Mg/Al joint was investigated. The results showed that due to the addition of adhesive, the welding plasma contracted in PAWB process of Mg to Al alloy. More Mg atom entered the ionization atmosphere of plasma arc, and then ionized. The spectrum intensity of Mg and Mg+ increased. The electron temperature of the plasma arc reduced, and the electron density of the plasma arc increased. The welding current was not changed, and the welding voltage increased. At the same time, because the addition of adhesive, the joint structure was changed to non-uniform, the transitional zone between fusion zone and lower base metal was changed from smooth to wavily, as a result the connect area between Al3Mg2 layer and a-Al increased. Besides, the tensile shear failure load of PAWB joint was higher than plasma arc welding joint, and was lower than adhesive bonding joint. Based on investigation, it was concluded that increasing the carrying power of joint and dereasing the failure area of adhesive at the same time was the ultimate method to improve the carrying power of Mg/Al weld bonding joint.3. LTWB process of Mg/Al alloy was conducted. The welding weldability and the effect of adhesive on the welding source and structure and mechanical property of Mg/Al joint were investigated. The results showed that because of the addition of adhesive, the welding plasma expanded, and the brightness of which enhanced during the LTWB process of Mg to Al alloy. The spectrum intensity of Mg and Mg+increased, and the spectrum intensity of Ar and Ar+ dereased. The distribution of Mg atom increased, and the distribution of Ar atom dereased. The electron temperature of the arc plasma reduced, and the electron density of the arc plasma increased. The welding current was not changed, and the welding voltage increased. At the same time, the joint structure was changed to non-uniform. Transitional zone between fusion zone and lower base metal was changed to wavily and disordered. The connect area between Al3Mg2 layer and a-Al layer increased. Besides, LTWB joint showed higher tensile shear and peel failure load than laser-TIG welding joint.4. Through the investigation of PAWB and LTWB process of Mg to Al alloy, the effect mechanism of adhesive on the different welding source and Mg/Al joint structure was investigated. The results indicated that during PAWB process, the addition of adhesive casued more Mg atom to enter the ionization atmosphere of plasma arc, leading to the thermal contraction effect. The electric path contracted and the energy density of plasma arc increased, which was helpful to get a deeper penetration depth. During LTWB process, the adhesive decomposed and producted a lot of gases by the welding source, which increased the pressure inside the laser keyhole. It not only accelerated the escape of the metal plasma inside laser keyhole, but also reduce the the thickness of liquid metal layer around the laser keyhole. It casued that the absorption and the defocus effect of metal plasma on laser inside the laser keyhole decreased, and the absorb speed of solid metal for laser energy increased. The penetration power of laser beam was enhanced, thus the deeper penetration depth was obtained. Besides, more Mg atom entered the arc plasma and ionized instead of Ar atom. By the thermal contraction effect, the energy density of arc was also increased. For Mg/Al joint structure, because of the decomposition and gasitication of adhesive, the flow of molten pool metal was accelerated. The transitional zone between fusion zone and lower base metal was changed from smooth to wavily. The connect area between Al3Mg2 layer and a-Al layer was increased, which was helpful to increase the carry power of the joint.
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