Determination of liquid fraction during solidification of aluminium alloys using a single-pan scanning calorimeter

The traditional method of obtaining the fraction liquid from DSC enthalpy data is discussed. It is concluded that accurate values cannot be obtained directly unless an allowance is made for the microsegregation which always occurs during solidification of alloys. A technique is developed, which allows the fraction liquid to be calculated indirectly. ments have been carried out on an Al–4.45 wt.% Cu alloy using a single pan scanning calorimeter. The single pan calorimeter gives accurate data even when significant latent heat is evolved. The results obtained agree well with those predicted using a numerical model of microsegregation. The multi-component microsegregation model is linked with the thermodynamic data programme MTDATA, so that a direct comparison can be made of predicted and measured enthalpy. It is concluded that a direct calculation of fraction liquid from enthalpy data is only possible when there is no change in the average composition in the solid and liquid phases during the transformation.