Influence of pulling velocity on microstructure and morphologies of SCN-DC eutectic alloy

Eutectic solidification is very important in the development of new materials in which the periodic multiphase structures may have a remarkable or enhanced functionality. The morphology evolution during eutectic solidification is investigated experimentally using slab-geometry slides of succinonitrile-(D)camphor (SCN-DC) transparent organic eutectic material. By specifically focusing on the effect of pulling velocity on microstructure in directional growth, the temperature gradient and the thickness are kept the same in all the experiments. It is found that eutectic seeds first occur in the grain boundary channel or the specimen side-wall groove. And the growth of eutectic seeds is both parallel to the direction of temperature gradient and along the liquid/solid interface at the same time. At a low pulling velocity (0.064-0.44 μm/s), the macroscopic growth morphology is flat, and the inner microstructure is rod-shaped, which is parallel to the growth direction. It is obvious that the eutectic spacing becomes smaller with the increase of pulling velocity. At a high pulling velocity (0.67-1.56 μm/s), the macroscopic growth morphology becomes cellular. However, the inner microstructure is still rod-shaped, but its distribution is radially outward. And the eutectic spacing decreases as pulling velocity increases.