THE EFFECTS OF GRAIN REFINEMENT ON THE CASTABILITY OF MAGNESIUM PERMANENT MOULD CASTINGS

摘要

A gravity filled permanent mould casting has been designed to simulate the geometry and feeding habits of a typical automotive wheel. The casting geometry reflects the areas of a wheel casting that are most prone to defect formation, that is, the hub and the transition from the spoke to the rim where hot spots are often experienced. Different magnesium alloys were trialed along with various melt additions to facilitate the refinement of the microstructure during solidification. The effect of grain refinement on the castability of the alloys was investigated by measuring the resulting grain sizes, porosity levels, porosity types, as well as levels of hot tearing and surface slumping defects in the castings produced. It is expected that the conclusions drawn from this and future investigations can be applied to the permanent mould casting of magnesium alloy wheels. The aim of this paper is to present and discuss the results of the investigation to date.