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 < 001 >-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. (c) 2005 Elsevier B.V. All rights reserved.