Differential scanning calorimetry of aluminium EN AB-42000 alloy rheocasting semi-solid in different stage heating rates

Abstract

AbstractDifferential scanning calorimetry (DSC) is used to identify the thermal histories of samples to analyse and diagnose production and quality concerns connected to industrial rheocasting semi-solid alloy, that had undergone different tempers of aluminium alloy EN AB-42000 alloy. In this study, the solidus temperatures of several alloy samples are investigated using thermodynamic calculations and DSC observations in this work. The balance of important characteristics, including pseudo-eutectic, thermal sensitivity, heat flow, and enthalpies behaviour, of Al alloys has been investigated using experimental data from DSC and solid fractions. In addition, the choice of heating rates is critical as high rates can blur the two peaks in the mushy zone, while low rates lead to slower measurements. Using smaller sample weights and slower rates is preferable to obtain more accurate results. Analysing the shape of the fs curve, exact composition, and a reference composition without contaminants is essential for understanding complex behaviours, including pseudo-eutectic phenomena. The thermal sensitivity of compositions also plays a crucial role in the analysis. Despite heat flow decreasing with decreased sample weight, the measurement limit can still be exceeded at high heating or cooling rates (20 °C/min) during the eutectic reaction. The eutectic reaction exhibits higher peaks with enthalpies ranging from 360 to 430 mJ/g. However, drawing conclusions regarding trends in heating versus cooling or comparing low-mass and higher-mass samples can be challenging. The non-equilibrium transformation of the eutectic occurs within a more confined temperature range. Increasing rates lead to overlapping reactions, resulting in complex thermal behaviour.