合金のデンドライト組織形態の評価

抄録

Methods for evaluating dendrite structure of an Al-5mass%Si alloy were investigated based on the fractal dimension and dimensionless perimeter. A phase-field simulation was carried out and calculated columnar dendrite showed a self-affine fractal characteristics. However, difference was small between self-affine parameters for x and y directions that mean columnar dendrites can be regarded as a self-similar fractal. Unidirectional and isothermal solidification experiments were carried out and it was shown that the fractal dimension and dimensionless perimeter of dendrites were determined only by local solidification time, and irrespective of solidification manner and dendrite morphology. This result demonstrated the potential of the fractal dimension and dimensionless perimeter as parameters for estimating local solidification time of an ingot. The tensile test showed that the tensile strength increased with increase in fractal dimension or dimensionless perimeter of dendrites in test specimens. Permeability of dendrite arrays were estimated by using the dimensionless perimeter as the tortuosity factor of interdendritic liquid channels. Obtained permeability corresponded to reported values.