Morphological evolution during solidification under stirring

Morphological evolution during the solidification of succinonitrile–5 at.% water transparent alloy and Sn–15 wt.% Pb alloy under mechanical stirring was investigated experimentally by in situ observation and quenching, respectively. The results showed that the primary microstructures were solidified with a globular shape when mechanical stirring induced strong shear flow. The formation mechanism of the globular microstructure is discussed, according to morphological stability theory. The analysis indicates that the rotation of primary microstructure in a shear flow induces a stabilizing effect on the morphological instability at the solid–liquid interface and promotes the globular growth of solidification microstructure after it is nucleated in the melt.