Influence of Supercooling on the Formation of Primary Phase during Solidification

Abstract

It is reported actual volume fraction of the primary phase in alloys is larger than the equilibrium value. Larger volume fraction of the primary phase may cause shrinkage cavities and surface or internal cracks. Although control of the solidified structure is important for the quality of cast products, this problem has not been fully elucidated. Taking these results into account, this study has been carried out in order to comprehend the phenomenon of larger volume fraction of primary phase. The Sn-Pb alloy has been used as a test alloy to examine the relation between supercooling for nucleation and the volume fraction of primary phase. Actually, the volume fraction of the primary phase in Sn-Pb alloy is larger than that of the lever rule. It was also observed that the volume fraction of β-Sn decreases with decreasing the supercooling in the early stage of solidification. In the final stage of solidification, however, the effect of supercooling on volume fraction of primary phase is small. Futhermore, when the supercooling was low, the volume fraction of primary phase slowly increased.