Numerical simulation of the effects of a Phase Change Material (PCM) on solidification path of gravity sand cast Al-Cu alloy

Solidification structure has a significant effect on mechanical and physical properties of metallic materials and its control is a main direction in the research for the improvement of materials performance. Various methods, such as control of cooling rate, inoculation, imposing vibration and pressure, are traditionally used to control the solidification structure during casting and solidification processes. In this paper, the preliminary results of a new method for controlling the solidification structure during casting using Phase Change Materials (PCMs) are presented. The evolution of the solidification structure of a directionally chilled Al-Cu alloy poured in a silica sand mould with and without the use of pure zinc as a PCM was examined using experimental and simulation methods. It was shown that the PCM temperature could reach about 510 degrees C during the solidification of the aluminium alloy, therefore, absorbing its melting latent heat from the solidifying aluminium alloy melt which affects its local solidification cooling rate. Therefore, the solidification structure of the sample cast in the PCM fitted mould differed from that of the sample without PCM. While macrostructures of both samples showed the transition from columnar to equiaxed grains, the columnar zone in the PCM sample was larger than in the sample without PCM. In other words, columnar to equiaxed transition (CET) for the sample without PCM occurred sooner than that for the sample with PCM. In addition, the average size of the equiaxed grains at the Chill sample is smaller than the PCM sample.