2007 Volume 79 Issue 12 Pages 738-744
In the case of aluminum, for example, iron impurities form coarse columnar intermetallic compounds during solidification, which hamper the recycling process. To control the compound morphology, a series of experiments were designed to apply ultrasonic vibration during solidification. Al-Si alloy systems with different iron contents were heated to their molten state. In the alloy systems, the primary crystals formed from the liquidus temperature were intermetallic compounds identified as Al3Fe, α-AlSiFe (Al7.4SiFe2) or β-AlSiFe (Al9Si2Fe2).
In Al-6Si-4Fe, Al-12Si-4Fe and Al-18Si-4Fe alloys, coarse plate-like intermetallic compounds appeared when solidified normally, however, distinctive fine granular structure was achieved with the application of ultrasonic vibration.
Almost all of the iron in Al-Si-Fe alloys are crystallized as intermetallic compounds. As a result, the density of the intermetallic compound became higher and showed gravitational segregation. Thus it is possible to produce castings where the intermetallic compounds are accumulated towards the bottom by gravitational segregation.
