In situ melting and solidification assessment of AZ91D granules by computer-aided thermal analysis during investment casting process

Computer-aided thermal analysis was carried out to precisely measure the thermal characteristics of AZ91D magnesium alloy granules during in situ melting and solidification in investment casting process. Ceramic shell moulds of two different thicknesses equipped with highly sensitive thermocouples at three different locations were prepared to provide a range of heating and cooling rates during in situ melting and solidification. The results revealed that dissimilar thermal regimes were experienced by the granules at different locations of the mould during heating, which led to asynchronous melting of the granules. It was found that both melting commencement and completion were increased with increasing heating rate; in contrast inverse behaviour was observed during cooling. The onset and the end of solidification temperatures and duration decreased with increasing cooling and solidification rates. The information from this approach is very crucial for suppressing mould-metal reaction especially during cooling in casting of magnesium alloys by investment casting process.

► AZ91D granule was used for the assessment during investment casting process.
► Different range of heating and cooling rates was used for thermal analysis.
► Onset and completion of melting were increased with increasing heating rate.
► Increased cooling rate decreased nucleation and end of solidification temperatures.
► Suppressing mould-metal reaction can be met by increasing heating and cooling rate.