Reactions at the Interface Between Al2O3–SiO2 Ceramics with Additives of Alkaline-earth Oxides and Liquid Al–Si Alloy

Abstract

The interfacial reactions between aluminosilicate ceramics doped with MgO, CaO, or BaO and Al–7 wt% Si alloy were investigated at 1023, 1173, and 1323 K under vacuum for 4 h. Alkaline-earth oxide additives defined phase formation and microstructure of the sintered ceramics and subsequently controlled the ceramic/metal interfacial reactions, which were always intensive. In general, reaction zones consisted of Al2O3, infiltrated with Al. In the case of CaO- and BaO-doped ceramics, precipitates formed into the metal phase and concentrated the reduced Ca and Ba, respectively. A reaction mechanism is proposed, which anticipates an active role of SiO2.