Interaction of AZ91 Magnesium Alloy with Ceramic Shell during Investment Casting

The investment casting into a ceramic shell of magnesium alloys brings several difficulties, one of which is the high reactivity of some magnesium alloys with the often-used ceramic shells. In the group of these potentially problematic alloys belong the AZ91 magnesium alloy too. This paper aims to describe the interaction of magnesium melt with ceramic shell, especially from the point of view of manufacturing problems on the surface of emerging defects with reduced corrosion resistance. Samples of AZ91 magnesium alloy castings in as-cast and heat-treated were microstructurally evaluated. Surface defects were analysed using light and scanning electron microscopy, including their EDX chemical microanalysis.