Yasunori Miyata1, Toshio Suzuki1 and Noboru Nagata2
1Faculty of Engineering, The Technological University of Nagaoka, Nagaoka
An Al-1.0 mass%Si alloy was unidirectionally solidified under the gravity force alone and under 5 G, that is, the centrifugal acceleration force together with the gravity force. The dendrite tip radius, ρ , the primary arm spacing, λ 1, the core diameter of primary arm, d0, the first secondary arm spacing, λ 2, and the tip concentration, Ctip, were measured as functions of growth rate for each series of experiments.
Scaling laws were shown to exist between λ 2, d0 and λ 0, and ρ , which were given by equations λ 2=1.0 ρ , d0=3.3 ρ and λ 0=2.3 ρ , respectively. Characteristic dimensions of dendrite decreased by the addition of acceleration force. Under 5 G the values of ρ , λ 1, d0, λ 0 and λ 2 decreased by about 30, 20, 30, 25 and 30%, respectively, from those under 1 G. The tip concentration was little affected by the accelerational force in the dendrite growth, and the gravity segregation was not confirmed. Planar interface under 5 G was also more unstable than that under 1 G. The increase of its instability was comparable to the decrease of the dendrite tip radius under 5 G.
dendrite growth, unidirectional solidification, gravity effect, dendrite tip radius of curvature, aluminum-silicon alloy
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