An evaluation of the production of magnesium base alloy castings by the expendable pattern casting process

Magnesium alloy is a light weight metallic material which offers good engineering properties and environmental advantages. Most cast components in this material are produced by the traditional casting processes, predominantly the die-casting process. The Expendable Pattern Casting Process (EPC process) is a relatively new casting process which provides many design, processing and environmental benefits. However, the process differs significantly from the conventional empty mould sand casting process and there is the need for research to develop an understanding of the process parameters. The research was established to provide a preliminary evaluation of the production of magnesium base alloy castings by the expendable pattern casting process under gravity and counter gravity pouring. The major process parameters investigated were filling pressure, pouring temperature and pattern bead density. The problems experienced in applying this process for this material in the experimental research were defined. Microstructures and mechanical properties of the cast specimens were investigated and reported. The results showed that the quality of test bar specimens produced by the EPC process under counter gravity pouring with optimised process parameters was compatible with the quality of castings produced by the conventional sand casting process. In addition to the experimental research a review was conducted of the modelling of different methods of pouring. The pouring methods considered were bottom gating in gravity pouring, counter gravity pouring in an empty cavity mould process, and expendable pattern casting processes under both gravity and counter gravity pouring. A quasi one dimensional fluid mechanics analysis was conducted to explain the effect of pattern degradation on the delay in mould filling.