We derive an evolution equation governing the cellular structure of a binary alloy having a small segregation coefficient. This equation, applicable to long-wave instabilities of a planar interface, incorporates coupled morphological instabilities and buoyancy effects. The presence of buoyancy can inhibit the onset of the cellular structure by effectively magnifying the segregation and diffusion.

• Received 9 January 1986

DOI:https://doi.org/10.1103/PhysRevB.34.3388