A study on the thermodynamics of in situ MgAl2O4/Al MMC formation using amorphous silica sources

MgAl₂O₄ (spinel) is considered as a commercially important ceramic reinforcement in MMC fabrication because of the possible tailorable properties imparted with Al for many applications. Generally, any oxygen source, i.e., the dissolved oxygen, or pure oxygen atmosphere or atmospheric oxygen is sufficient for the formation of MgAl₂O₄ in Al–Mg alloy. Among all the reactive oxygen sources, the reactivity of SiO₂ with Al alloy is found to be higher. Amorphous silica is highly reactive in nature compared to crystalline silica. The present study has examined the thermodynamics of MgAl₂O₄ formation in Al–Mg alloy by amorphous silica sources with the aid of differential thermal analyzer (DTA) and the simulated experiments. The dissolution of Si and the formation of MgAl₂O₄ are detected as the endothermic peak and the immediate exothermic peak respectively in DTA curves and the presence of MgAl₂O₄ is confirmed by the XRD of the simulated sample. The MgO formed due to the oxidation of Mg in Al–Mg alloy has been found to influence the MgAl₂O₄ formation.