Instabilities during coupled growth of hypermonotectics

The production of aligned fibrous microstructures in hypermonotectic (immiscible) alloys by directional solidification requires control of several instabilities including maintaining a macroscopically planar solidification front. However, even when the conditions for a macroscopically planar interface are used when processing a sample of hypermonotectic composition, difficulties often arise due to convective instabilities. Examples are shown of samples processed under one-g conditions where convective instability causes continuous flow during processing and of samples processed under alternating gravity level conditions.