Microstructure of dissimilar metal joint with magnesium alloy AZ31B and steel 304 for laser-tungsten inert gas lap welding

The lap welding of magnesium alloy AZ31B and steel 304 dissimilar joint by laser-tungsten inert gas(TIG)welding was investigated, and the microstructure was analyzed by SEM, EPMA etc.The resultsshowed thatMg andFe can be joined effectively due to the new phase forming in transition zone of the joint.It also found the new phases were different because the extent to oxidation was different.One was "bamboo" MgO phase, another was consecutive Mg_xFe_yO_z phase.During the latter phase forming, the phenomenon of Mg diffusion can be found.