MICRO-MACRO MODELLING OF SOLIDIFICATION WITH EXPERIMENTAL VALIDATION IN SELECTED EUTECTIC BINARY ALUMINIUM ALLOYS

Experimental and numerical studies of solidification phenomena have continued to complement each other in the quest for advanced knowledge during component manufacture. The dynamics of engineering designs coupled with the desire for lightweight and improved materials have sustained the progress achieved in recent decades on the modelling of casting systems. The current study presents the simulation of solidification conditions for different aluminium-based eutectic binary alloys and validation with an experimental investigation. The effect of mould material was analysed for the solidification of Al-4.5% Cu using metallic, sand, quartz and Plaster of Paris (POP) moulds respectively. Simulation of the eutectic alloys was carried out using micro-macro model previously developed by the current authors. The effect of mould size and transient evolution of structure during solidification in static casting process were successfully simulated. The results of the experimental investigation showed that although the cooling curves for the different mould materials are qualitatively similar, they respond differently to the presence of the liquid metal leading to significantly different rates of latent heat evolution. The simulated cooling curves for the four eutectic alloys solidified inside sand mould showed that Al-4.5% Cu and Al-3.0% Si have the fastest transformations while Al-6.0% Mg and Al-3.0% Zn have the slowest rate of cooling. Mould size has significant influence on thermal distribution during solidification as temperature tends to reach steady-state and homogenize faster in smaller moulds than bigger ones. For all the alloys compared, nucleation period is very small relative to the total solidification time. The results showed that transient evolution of volumetric grain density and grain radius varied significantly.