On the role of eutectics during recrystallization in a single crystal nickel-base superalloy - CMSX-4

The role of eutectics in recrystallization in a single crystal nickel-base superalloy - CMSX-4 - was studied by electron backscatter diffraction and electron probe micro-analysis techniques. It was shown that eutectics can initiate recrystallization by a particle stimulated nucleation mechanism which operates in interdendritic regions. During grain growth in the course of recrystallization, eutectics were observed to inhibit the motion of the advancing recrystallization grain boundary. Alternatively, a recrystallization grain boundary can migrate through eutectics by forming a large gamma' phase particle behind the advancing front, either with the same crystal orientation as the eutectic the boundary advances into or, in some cases, with completely new orientations, i.e. neither the same as the eutectic it grows into nor the same as the recrystallized grains surrounding it.