1997 Volume 69 Issue 10 Pages 815-821
To study the formation mechanism of banded segregation in centrifugal casting, molten Al-4.4%Cu alloys were poured into a stainless drum, and the casting was tilted from 10 to 30 degree to cause the shear deformation in the solid-liquid coexisting region. Banded segregation formed for the equiaxed structure but not for the columnar structure. The fraction solid of the place where banded segregation formed was between 0.2 and 0.3 at the start of tilting. The banded segregation formed when the fraction solid gradient was above 0.05mm-1 and tilting speed of the drum above 50mm/s. Copper concentration was 5.1 to 5.5% in the banded segregation, which is larger than that in the neighboring fine equiaxed zone (4.1 to 4.8%). The development of dendrite structures was observed in the banded segregation. The boundary between the banded segregation and neighboring zone was not clear. It has been concluded that slip developed due to the shear deformation in the solid-liquid coexisting region from gravity force, and the slip region was filled with solute rich liquid, thus resulting in the banded segregation. A similar phenomenon can be expected in centrifugal casting.
