Interface formation between liquid and solid Mg alloys—An approach to continuously metallurgic joining of magnesium parts

In this project we describe a process where a magnesium melt (pure Mg or AJ62) is cast onto a solid magnesium substrate (AZ31). The natural oxide/hydroxide layer on magnesium alloys usually prevents metallurgical joining via casting. Therefore, a pre-treatment was applied to the AZ31 substrate to replace the oxide layer with a Zn/MgZn2 coating. This procedure comprises a combined pickling/redox-reaction and galvanization/heat-treatment procedure, which drastically changes the substrateʹs surface wetting properties. We depict the process parameters that allow for the formation of a continuous metallurgic joint, which is free of oxides, micro-cavities or other imperfections, and discuss the interface formation from a metal-physical view. In such a way the surface modification creates the preconditions that are necessary to join wrought and cast magnesium components by means of compound casting.