Phase Equilibria in the System “MnO”–CaO–MgO–SiO₂–Al₂O₃ with Al₂O₃/SiO₂ Weight Ratio of 0.17 and MgO/CaO Weight Ratio of 0.25 at Mn–Si Alloy Saturation

Abstract

Liquidus isotherms and phase equilibria have been determined experimentally for a pseudo-ternary section of the form “MnO”–(CaO+MgO)–(SiO₂+Al₂O₃) with a fixed Al₂O₃/SiO₂ weight ratio of 0.17 and MgO/CaO weight ratio of 0.25 for temperatures in the range 1 393–1 673 K.
The primary phase fields found in the investigated section include manganosite (Mn, Mg, Ca)O; dicalcium silicate α-2(Ca, Mg, Mn)O·SiO₂; merwinite 3CaO·(Mg, Mn)O·2SiO₂; melilite [2CaO·(MgO, MnO, Al₂O₃)·2(SiO₂, Al₂O₃)]; wollastonite [(Ca, Mg, Mn)O·SiO₂]; diopside [(CaO, MgO, MnO, Al₂O₃)·SiO₂]; tridymite (SiO₂); rhodonite [(Mn, Mg, Ca)O·SiO₂]; anorthite (CaO·Al₂O₃·2SiO₂) and tephroite [2(Mn, Mg, Ca)O·SiO₂].
The liquidus temperatures and primary phase fields are significantly different to those in the ternary system “MnO”–CaO–SiO₂, but are close to those previously reported pseudo-ternary section “MnO”–(CaO+MgO)–(SiO₂+Al₂O₃) for Al₂O₃/SiO₂ weight ratio of 0.17 and MgO/CaO weight ratio of 0.17.
The partitioning of CaO, MgO and MnO between liquid and solid phases was measured using EPMA, and the extents of solid solutions for a range of bulk compositions and temperatures were characterised.