Hiromasa Takeuchi1 and Naomi Nishi2
1Department of Materials Science, Faculty of Engineering, Tokai University, Tokyo
Droplets of Al-0~5.7 mass%Cu alloys were dropped on a chill block made of pure copper, cast iron and stainless steel. The heat transfer during solidification of droplets was calculated using the heat balance equation. The external surfaces of droplets solidified were examined by optical microscope.
The degree of supercooling of droplets decreased with increasing solute content and superheat of molten metal. The number of discs increased with increasing solute content and superheat. The degree of supercooling and the number of discs became large in order of stainless steel, cast iron and pure copper. The concentration of copper in the disc increased with increasing degree of supercooling. The effective distribution coefficients of Al-4.5 mass%Cu alloy varied from 0.20 to 0.40 with changing degree of supercooling from 7 K to 32 K. The relation between the growth rate of disc (R) and the degree of supercooling (Δ TC) was expressed as R∝ (Δ TC)1.5.
aluminum-copper alloys, predendrite, disc, supercooling of melt, growth rate of disc, heat transfer during solidification, chill cast, crystallization
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