Step growth of a primary silicon crystal observed by decantation during centrifugal casting

Abstract

A new method of decantation during centrifugal casting has been used to study crystal growth. The shape of a primary silicon crystal grown from a hypereutectic Al–Si alloy was obtained by means of this method and a growth mechanism depending on the use of dislocation steps was found to apply for primary silicon crystals. Furthermore a mechanism for the branching of primary silicon crystals and the development of a structure of α-Al–Si eutectic encapsulated in primary silicon crystal was successfully explained by the growth mechanism of the primary silicon crystal. A growth process leading to the α-Al–Si eutectic surrounding the primary silicon crystal was also observed.