Effect of ultrasonic vibration on Fe-containing intermetallic compounds of hypereutectic Al-Si alloys with high Fe content

The Fe-containing intermetallic compounds with high melting point in hypereutectic Al-Si alloys can improve the heat resistance and wear resistance at elevated temperatures. However, the long needle-like Fe-containing compounds in the alloys produced by conventional casting process are detrimental to the strength of matrix. The effect of ultrasonic vibration (USV) on the morphology change of Fe-containing intermetallic compounds in the hypereutectic Al-17Si-xFe (x=2, 3, 4, 5) alloys was systematically studied. The results show that, the Fe-containing intermetallic compounds are mainly composed of long needle-like beta-Al5FeSi phase with a small amount of plate-like delta-Al4FeSi2 phase in Al-17Si-2Fe alloy produced by conventional casting process. With the increase of Fe content from 2% to 5% in the alloys, the amount of plate-like or coarse needle-like delta-Al4FeSi2 phase increases while the amount of long needle-like beta-Al5FeSi phases decreases. In Al-17Si-5Fe alloy, the Fe-containing intermetallic compounds exist mainly as coarse needle-like delta-Al4FeSi2 phase. After USV treatment, the Fe-containing compounds in the Al-17Si-xFe alloys are refined and exist mainly as delta-Al4FeSi2 particles, with average grain size ranging from 26 mu m to 37 mu m, and only a small amount of beta-Al5FeSi phases remain. The mechanism of USV on the morphology of Fe-containing intermetallic compounds was also discussed.