Morphological determination of forced shear flow rate during directional solidification of succinonitrile-1%salol alloy

Interface morphologies during directional solidification of SCN based alloy in the presence of shear flow are investigated. Microstructure map of wide pulling rate and shear flow rate is summarized. With pulling rate increasing, there exist three distinct regions in the map: planar, transitional and dendritic regions. It is shown that shear flow elevates the critical velocities of both steady planar and dendritic growth. Although the stable cellular interface occupies most area of the transitional region, extraordinary patterns of planar-cellular oscillation and irregular cells are observed on the two sides of the region, respectively. The mechanism of the self-excited oscillatory interface induced by shear flow is discussed.