A Study on the Thermodynamics of in Situ MgAl2O4/Al MMC Formation Using Amorphous Silica Sources

Abstract

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. © 2007 Elsevier B.V. All rights reserved