<i>In-situ</i> Observation of Inclusion Formation Behaviors during Solidification Process Using Model Alloy

The formation of secondary inclusions during the solidification process of molten steel is a complex phenomenon triggered by microsegregation. Controlling the dispersion of secondary inclusions in solidified steel is an important issue that significantly affects the properties of steel; however, the distribution of inclusions after solidification does not always coincide with the locations of inclusion formation. Therefore, estimating when, where, and at what supersaturation level the inclusions crystallize in the liquid phase is difficult; therefore, clarifying their formation behavior is desired to control the dispersion of inclusions. In this study, we investigated the formation process of inclusions using a ternary model material of succinonitrile-water-Lumogen Yellow by in-situ observation, where the formation of oversaturated Lumogen Yellow can be regarded as inclusion formation. The frequency of inclusion formation was confirmed to increase markedly when the solution was held at lower temperatures, that is, when a large supersaturation ratio was applied. The results of the formation frequency indicated that the formation of inclusions occurred in the liquid phase according to classical nucleation theory.