Comparison between prediction of liquid fraction versus temperature and experimental results from DSC and SPSC

The processing window is important for the semisolid processability of alloys. This study focusses on the kinetics of diffusion. It compares prediction of fraction liquid versus temperature taking into account both thermodynamic and kinetics, with experimental results from Differential Scanning Calorimetry (DSC) and Single Pan Scanning Calorimetry (SPSC). SPSC is a novel technique with an order of magnitude higher accuracy than DSC. A range of Al-Si binary alloys has been investigated. The studies reveal that the simulation results predicted by DICTRA (DIffusion-Controlled TRAnsformations) show the same pattern with experimental results in the relationship of fraction liquid-temperature. However, the SPSC results are closer to the prediction results than DSC curves even with the relatively large sample size associated with SPSC. This is potentially a significant result as conventionally one of the difficulties is predicting the liquid fraction versus temperature for the heating of a billet for semi-solid processing. DSC results are known to be unrepresentative because the heating rates which can be achieved in DSC are much lower than those in induction heating. In addition, the DSC results are dependent on sample size and heating rate. The long term aim is to gain confidence in prediction with software packages which will reduce trial and error.