Observation of instabilities leading to side-branch formation in the dendritic growth of cubic (F.C.C.) ⁴He

Abstract

Observation of the dendritic growth of f.c.c. ⁴He shows that side-branch formation is a two-step process. The first instability of a dendrite growing in the preferred <100> direction takes the form of four thin lateral wings at 90° to each other. At low supercooling, no other instability develops. At larger supercooling, the lateral wings develop a cellular Mullins–Sekerka type instability. These cells, through further growth, develop into the dendritic side-branches. Side-branch formation has not been observed in dendrites that did not undergo the initial development of lateral wings. Dendrites growing at very low supercooling do not develop lateral wings, and show no side-branch formation.