片状黒鉛鋳鉄の共晶凝固界面の形状と過冷度について

抄録

  The shape and undercooling of the eutectic solidification front in flake graphite cast iron solidified unidirectionally were investigated by interrupting the solidification. At low growth rates in which graphite flakes were arranged to the overall growth direction, the undercooling at the solidification front increased nearly linearly with the growth rate. At high growth rates, the undercooling deviated from the linearity to a lower value and graphite flakes were curved to be a irregularly arranged structure. The average spacing of graphite flakes λ was expressed by the equation of λ=8.3×10⁻⁵R^−0.53cm, where R was the growth rate in cm/sec. The graphite flakes were sheathed with austenite at the solidification front and the shape of the sheaths was found to be parabolic. The true radius of curvature at the tip of a sheath was independent of the undercooling and most of the radii fell in the range of 3−6μm. The parabolic shape of the sheath was attributed to the thickening growth controlled by carbon diffusion through austenite from the grooved liquid to the graphite flake in the center of austenite sheath.