Morphological evolution of the solid-liquid interface near grain boundaries during directional solidification

Abstract

Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that the grain boundary provides the starting point of morphological instability of the solid-liquid interface. The initial perturbation near the grain boundary is significantly larger than other perturbations on the interface. The initial shape of the interface and the competition between the thermal direction and preferred crystalline orientations determine the subsequent growth pattern selections. The temporal variations of the curvature radius of cell/ridge tips near the grain boundary have also been studied when the instability occurs. This process is divided into three parts. As the pulling velocity increases, dendrites at the grain boundary grow in two different directions to form a bicrystal microstructure. Side branches on either side of the dendrite exhibit different growth patterns. grain boundary, solid-liquid interface, directional solidification, growth directions