한국주조공학회

The effect of wheel surface condition on solidification behavior of Al-Cu ribbon was investigated in order to establish extreme levels of heat extraction. The condition of wheel surface was changed either by heating the wheel surface up to 200℃ or by coating boron nitride(BN) onto the the rim of a wheel. Heating the wheel surface up to 200℃ improved the wetting behavior between the molten metal and the rotating wheel, leading to an increase in the ratio of columnar structure to the entire thickness of Al-4.3wt%Cu and Al-33.2wt%Cu ribbons. For Al-4.3wt%Cu ribbon, assuming one grain as a single heterogeneous nucleation event at the contact point, the nucleation density with the wheel surface heated to 200℃, was 4X10^6/mm^2, and in the cases of BN coating with thin and thick layers, 10^5/mm^2 and 5X10^4/mm^2, respectively. The largest cooling capacity of the wheel corresponded to the heated wheel surface, and as the thickness of BN coating layer increased, the cooling capacity of the wheel gradually decreased.