| Weld-bonding technology is a new method of joining, which is comprised by welding and bonding technology. With certain parameters, the weld-bonding joint with characteristics of welding and bonding can be obtained. The weld-bonding joint possesses not only the welding advantages of light weight, high static load strength and good reliability, but also the bonding advantages of good fatigue property and leak tightness. The weld-bonding technology has a promotion of the comprehensive properties of the joint, and patentability of connecting similar and dissimilar metal materials which is hard to join in traditional way.In order to enlighten the structure and make well uses of materials, joining of dissimilar materials with high quantity is hot in the modern manufacture. Magnesium alloys, due to the unique traits, have been seen as the promising structure materials, and at the same time steels still keep the major place of structure material rank in the engineering. So it is important to join the Mg alloy to steel in a high quality way. As the poor plasticity traits of Mg alloy, the Mg-steel joint cannot stand enough loads. The application of Mg-steel is limited. To improve the load capacity of Mg-steel joint, a new technology of Mg-steel laser-TIG-adhesive hybrid welding comes out, basing on the prior study of Mg-steel joining and weld-bonding.In this paper, AZ61magnesium alloy and Q235steel are the materials for experimental, the Ni foils as the interlayer, Terokal5087for commercial as the adhesive. The laser-TIG hybrid welding technology is used as the welding method. The technology and theory of Mg-steel laser-TIG-adhesive hybrid welding is majorly reported in the investigation. All the work above provides service basis for Mg-steel joining.It is easy to find that the added adhesive will make the dissimilar Mg-steel hard to join from experiments of Mg-steel laser-TIG-adhesive hybrid welding. The major factor affect the joining is the amount of gas that produced during the welding procedure. The joint of Mg-steel with good surface morphology can be got by the parameters that the heat source order is laser prior and arc posterior,the adhesive thickness0.1mm and the welding speed650mm/min. The mechanical property of Mg-steel laser-TIG-adhesive hybrid weld joint is the best with that welding parameter. The linear load of the Mg-steel laser-TIG-adhesive joint can reach2.90kN/cm and1.460kN/cm with and without the adhesive cured. From its Fracture morphology,it is can be asserted as mixed fracture. The adhesive added can promote the plastic property of the Mg-steel joint better. In the Mg-steel laser-TIG-adhesive hybrid welding procedure, as the adhesive added the temperature and the melting metal quantity of the welding pool would increase. The laser-TIG hybrid heating source heats the steel by a similar thermal conductivity welding way, and this will keep the melting metals of Mg, Ni, Fe a metastable state. In the metastable weld pool, the distribution of elements has an obvious change that element Ni concentrative distribute between element Mg and Fe, element Mg and Ni react and elements Ni and Fe would diffuse into each other to form a Fe-Ni solid solution. The gas that produced by the adhesive will enhance the flow ability of the weld pool. Because of this, a Mg-Fe diffuse transition layer occurred in the boundary of elements Mg and Ni. The Mg-Fe diffuse transition layer is comprised by Mg2Ni, MgNi2and Fe-Ni solid solution. With the Mg-Fe diffuse transition layer, the dissimilar Mg and steel would be joined via a metallurgical combination mode. That is why the Mg-steel laser-TIG-adhesive hybrid welding can get such a high level strength. |
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