Sn合金を用いた柱状晶組織によるブリッジングに起因して生成するマクロ偏析の解析

抄録

A mold was devised to evaluate the macrosegregation caused by solidification shrinkage and bridging by columnar dendritic structures. Casting experiments and numerical simulations of Sn–30wt.%Bi alloys using the devised mold were conducted to investigate the behavior of macrosegregation formation. Bridging due to columnar dendrites formed in the experimental sample, with minor positive segregation and shrinkage cavities forming below this. Numerical simulations reproduced the measured cooling curves, and the distributions of temperature, liquid flow, and Bi segregation ratio during the alloy solidification were analyzed. Consequently, a Bi-segregation region similar to that in the experiment was formed along the centerlines of the sample. During the formation of this segregation, the liquid flowed across the bridging region and toward the bottom. These results confirm that the mold devised in this study can generate macrosegregation (positive segregation) owing to solidification shrinkage and bridging of the columnar dendritic structure.