Al-Si合金の凝固界面形態におよぼす遠心力の影響

抄録

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, λ₁, the core diameter of primary arm, d₀, the first secondary arm spacing, λ₂, and the tip concentration, C_tip, were measured as functions of growth rate for each series of experiments.
Scaling laws were shown to exist between λ₂, d₀ and λ₀, and ρ, which were given by equations λ₂=1.0ρ, d₀=3.3ρ and λ₀=2.3ρ, respectively. Characteristic dimensions of dendrite decreased by the addition of acceleration force. Under 5 G the values of ρ, λ₁, d₀, λ₀ and λ₂ 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.