The Deformation of Nial Bicrystals
Final rept. 1 Jun 85-30 Jun 90,
WRIGHT LAB WRIGHT-PATTERSON AFB OH
Pagination or Media Count:
The glide of non-100 dislocations at NiAl grain boundaries is proposed to account for the observed ductility of this compound near the brittle-to-ductile transition temperature. Two bicrystal orientations have been produced to investigate the activation of 111 dislocations due to the concentrated local stress at the bicrystal interface arising from elastic and plastic incompatibility. Observations of surface slip markings and TEM characterization of the dislocations responsible for bicrystal deformation have been made. The glide of 110 dislocations on 110 planes is the dominant mode of deformation in the vicinity of the oriented bicrystal interfaces investigated. It is concluded that the glide of non-100 dislocations may contribute to the plasticity of polycrystalline NiAl in a general sense, and not just in cube-oriented single crystals where 100 slip is geometrically restricted. The dominant mode of 110 dislocation generation is the nucleation of 110 loops away from the grain boundary. The macroscopic stress required to activate these 110 dislocations, in the presence of a stress concentration such as that produced by a dislocation pile-up at a grain boundary, is the same as that required to nucleate 100 dislocations. The statistical relevance of this phenomenon as it pertains to the general deformation of NiAl polycrystals has not been established.... Nial, Nickel aluminide, Bicrystal, Deformation, Dislocation structures, Stress concentration.
- Inorganic Chemistry