Hypereutectic Al-Si Matrix Composites Prepared by In Situ Fe₂O₃/Al System

Abstract

Al₂O₃ particles reinforced hypereutectic Al-Si composites were prepared by in situ Fe₂O₃/Al reaction system. The thermodynamic analysis and microstructure evolution were investigated by differential scanning calorimetry, optical microscope, scanning electronic microscopy and transmission electron microscope. Results show that the reaction between Fe₂O₃ and Al is spontaneous which can be separated into two steps at different temperatures. The in situ Al₂O₃ particles in nano size distribute on the Al matrix accompanied with long needle-shaped β Fe-rich intermetallic phase. With different content of Mn addition, β phase can be modified to α-Al₁₅(Mn,Fe)₃Si₂ and δ-Al₄(Fe,Mn)Si₂. Both tensile strength and elongation results at room temperature and 300 °C reveal that the optimal Fe-rich intermetallic phase is finer Chinese-script and polyhedral α phase with a Mn/Fe mass ratio 0.5 for the composites. Both in situ Al₂O₃ particles and α-Fe phases contribute to the properties improvement of the composites

Keywords

hypereutectic Al-Si alloys / particles reinforced composites / Al₂O₃ particles / Fe-rich intermetallic compounds