We have studied the onset and evolution of instabilities at the solid-liquid interface of tin undergoing directional solidification, as a function of growth velocity, temperature gradients, and impurity content. The initiation of an instability that we identify as "cellular" growth, and its passage to pseudosteady state, have been investigated. Within this steady state a new oscillatory phenomenon has been found, indicative of changes in the interface configuration that are quasiperiodic in time.

• Received 21 September 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.2686