Abstract
In the case of aluminum, for example, iron impurities form coarse columnar intermetallic compounds during solidification, which hamper the recycling process. To control the morphology of the material microstructure, an experiment was designed to apply ultrasonic vibration to the material during solidification. Four mass% Fe (hereinafter eliminated mass%) was added to an Al-Si alloy and melted. In this alloy, the primary crystals formed from the liquidus were intermetallic compounds identified as Al3Fe, α-AlSiFe (Al7.4SiFe2) or β-AlSiFe (Al9Si2Fe2). Assuming that application of ultrasonic vibration would have a larger effect on grain refinement if applied at the liquidus line, preliminary work was carried out to determine with accuracy the liquidus temperature. The liquidus temperatures for Al-6～15Si-4Fe alloys are concentrated in the range from 945 to 955K regardless of the composition. That of Al-18Si-4Fe alloy is 977.2K.
In Al-6Si-4Fe and Al-12Si-4Fe alloys, coarse columnar intermetallic compounds were formed, but some fine grain structures were achieved with the application of ultrasonic vibration. For Al-18Si-4Fe alloy, it was possible to modify the structure from a coarse columnar structure into a fine grain structure.
