Thermochemical behaviour, solidification, thermal stability and oxidation of Al-Mg2Si composites: An experimental and thermodynamic study

Effects of Mg and Si (Mg2Si) concentration on the thermochemical behaviour, solidification, thermal stability and oxidation of Al-Mg2Si composites have been investigated. Thermochemical behaviour, solidification characteristics and solid-liquid phase transformation of the composites have been simulated using FactSageTM 7.3 software and differential scanning calorimetry (DSC) heating and cooling curve analysis. The thermal stability of the composites has been investigated through thermogravimetric analysis (TGA) analysis. The oxides formation in Al-Mg2Si composites has been explored by FESEM-EDX analysis. In the hypoeutectic Al-Mg2Si composites, the alpha-Al nucleation temperature decreases with the increase in Mg2Si concentration, but in the hypereutectic composites, it increases with the increase in Mg2Si concentration in the composites. The reaction starting temperature between Mg and Si in molten composite increases with the increase in Mg2Si concentration. The Mg2Si solid-liquid transition initiation temperature decreases with the increase in Mg2Si concentration in the Al-Mg2Si composites. The Mg2Si acts as a barrier for the oxidation of Al up to the melting temperature of the composites which results in an improvement in the thermal stability of Al. Al2O3, MgO, SiO2, MgAl2O4 and AlFeMgOSi are the common oxides of Al-Mg2Si composites. With the increase in Mg2Si concentration, the Al2O3 and MgO oxides formation decreases and SiO2 and MgAl2O4 oxides formation increases in the Al-Mg2Si composites.