The Deformation of Nial Bicrystals
Abstract
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1990
- Accession Number
- ADA263139
Entities
People
- Daniel B. Miracle
Organizations
- Wright Laboratory