Formation of low angle boundaries in Ni-based superalloys

The evolution of misorientation accompanying branching and growth of dendrite stems advancing into an increasingly undercooled liquid at a geometrical discontinuity in cross section (platform of a turbine blade) during solidification of a Ni-base superalloy has been experimentally investigated. The misorientation generated is cumulative in nature with a systematic rotation of the principal 〈 0   0   1 〉 -crystal axes. It is proposed that the misorientation arises from plastic deformation of the dendrite stems during growth. Low angle boundaries are subsequently produced across impinging dendrite fronts.