Dependence of Competitive Grain Growth on Secondary Dendrite Orientation During Directional Solidification of a Ni-based Superalloy

The competitive grain growth in bicrystal samples during unidirectional solidification of a Ni-based superalloy was found to depend on secondary dendrites perpendicular to the grain boundary of bicrystal samples, rather than primary dendrites parallel to the thermal gradient as generally recognized. The primary dendrite orientation, however, had significance for the dendrite blocking in overgrowth processes and the resultant overgrowth rate during competitive grain growth.