The Influence of Fluid Flow on Intermetallic Phases in Al-Cast Alloys

Technical Al-Si alloys always contain sufficient amounts of Fe and Mn, especially alloys made from scrap. During casting, Fe-containing intermetallics, such as Al-Fe, Al-Fe-Si and Al-Fe- Mn-Si phases, are formed between the aluminum dendrites. Fe and Mn-rich intermetallic phases are well known to be strongly influential on mechanical properties in Al-Si alloys. In the present work the influence of controlled fluid flow conditions on the morphology and spatial arrangement on intermetallic phases in cast Al-Si alloys is characterized. A binary Al-7wt.%Si and a ternary Al- 7wt.%Si-1wt.%Fe alloy was solidified under and without the influence of a rotating magnetic field (3mT at 50Hz) over a range of solidification velocities (0.015- 0.18mm/s) at a constant temperature gradient G of 3K/mm. The scientific results reached so far indicate a strong influence of the electromagnetic stirring on the primary dendrite and secondary dendrite arm spacings.