Al-Si合金の凝固界面形態におよぼす遠心力の影響

Abstract

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, Ctip, 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.