Thermal analysis during solidification of cast Al-Si alloys

Solidification of a series of aluminium alloys was studied by means of thermal analysis; the study was centred on the effect that silicon and iron exert on the temperatures for the onset of different microstructural characteristics. The alloys were prepared in a gas fired furnace and were poured into graphite moulds instrumented with a type K thermocouple. The cooling curve was registered with the aid of a computer-driven data logging system and was derived to determine the temperatures for the onset of the formation of pre-eutectic aluminium dendrites, and those for the Al-Si eutectic and for a complex Al-Si-Cu-Mg eutectic. It was found that silicon exerts a strong influence on the two former temperatures, whereas the third one is independent of the content of silicon or iron.