Cusp instability in cellular growth

Abstract
During directional solidification of alloys, a cellular structure can be observed above a critical pulling speed. Under certain conditions, the cusps behind the cells can present a secondary instability characterized by a periodic emission of liquid droplets. These droplets are transported by the solid, but also migrate towards the solid-liquid interface by temperature gradient zone migration. We study the conditions of appearance of the droplet instability and discuss the information concerning growth mechanisms that can be deduced from a study of the migration