T–x–y Diagram of MgO–SiO2–Al2O3 System: Microstructure Design

Abstract

A computer model of the T–x–y diagram of MgO–SiO₂–Al₂O₃ system is used to show the possibility of analysis of its microstructure constitution in terms of competition between primary and eutectic crystals by means of vertical mass balance diagrams calculated for a given centroid over the whole temperature range. The usefulness of horizontal mass balance diagrams is considered for studying phase relations at a fixed temperature along the chosen isopleth. Mass balances were used to determine the crystallization path at the quasi-peritectic liquidus point with the invariant reaction L + Al₂O₃ = 3Al₂O₃ · 2SiO₂ + MgO · Al₂O₃, whose composition was taken into account in giving a rationale to corundum armor element technology.