Growth rates and microstructures of reacted layers between molten Al–Fe alloy and SiO2

Fabrication of composite materials consisting of Al2O3 and Al–Fe alloy was attempted by means of an in-situ reaction between SiO2 and molten Al–Fe alloys. In this study, SiO2 rods were immersed into the molten alloy at various conditions. Growth rate of the reacted layer was measured and its microstructure was observed by using various techniques. The growth rate decreased as an increase of Fe content in the molten alloys, and microstructures of the reaction layer became fine, comparing with that of Al/Al2O3 (reaction product between pure Al and SiO2). Concentration gradients of Fe and Si existed in the reacted layer, namely, Si and Fe contents were higher at the reaction interface than in the edge. Si was segregated in the metal area having higher Fe content. Reasons for the decreases in growth rate were discussed considering the observed microstructures. Judging from the growth rate dependence on the Fe content, it is impossible to fabricate FeAl (intermetallic compound)/Al2O3 composite materials in-situ by simple immersion of SiO2 into the molten Al–Fe alloy. The alternative two-stage immersion process was proposed.