Microstructure and properties of in situ Si and Fe-rich particles reinforced Al matrix composites assisted with ultrasonic vibration

Abstract

In this research, the in situ Si and Fe-rich particles reinforced Al matrix composites were fabricated by rheocasting (RC) process assisted with ultrasonic vibration (USV). After USV treatment, the polygonal primary Si crystals were refined into particles with average diameter of about 15-23 μm, and the fraction of primary Si declined to about 5.4-6.5 vol%. The coarse plate-like δ-Al4(Fe,Mn)Si2 phase was transformed into fine particles with average diameter of about 17-20 μm, and the fraction of particle-like Fe-bearing particles is about 3.6-5.3 vol%. The ultimate tensile strength of the RC composites increases with the increase of Fe content at 350 °C. The increase of the elevated temperature strength of the composites is mainly attributed to the refinement of δ-Al4(Fe,Mn)Si2 phase and the increase of the volume fraction of the Fe-bearing compounds. Compared with the composites without USV, the RC composites assisted with USV have thinner mechanical mixing layer in wear test, which corresponds to smaller wear rate.