Periodic layer formation in the growth of dilute binary alloys

The oscillatory growth of a dilute binary alloy in rapid directional solidification has recently been described by a nonlinear oscillator equation, assuming a uniform diffusion constant of the solute component in both phases. In a more realistic model with a vanishing diffusion coefficient in the solid phase this leads to the formation of durable layers of alternating solute concentrations. Due to the Mullins–Sekerka instability, the high-concentration layers commonly feature a dendritic microstructure. We conjecture that the mechanism behind this so-called banded-structure effect also applies to some of the quite independently discussed striation phenomena in a large number of general crystal-growth processes.