The mechanism of columnar-to-equiaxed transition during electromagnetic centrifugal solidification

Abstract

Abstract A series of Hastelloy C tubes were solidified under a centrifugal field with various conditions of bulk liquid flow obtained with a controllable electromagnetic field. Their macrostructures show that the columnar-to-equiaxed transition was promoted both by increasing electromagnetic stirring and by increasing the superheat, and the application of electromagnetic stirring at different times can also influence the percentage of the total area occupied by the equiaxed region. Mechanical damage of dendrites is the most probable mechanism for the promotion of the columnar-to-equiaxed transition with high velocity flows. The detachment of the nuclei originated in the chill zone can also promote the columnar-to-equiaxed transition.