Papers by Keyword: Dislocation Tensor

Abstract: Significant advances are reported in the application of HR-EBSD to the imaging of the dislocation structure of polycrystalline materials. The central assumption of the method is the compatibility of the total displacement field, which relates the (Nye) dislocation tensor to the (partially measurable) curl of the elastic displacement field. Two key challenges must be addressed, including: a) the fundamental limitation imposed by the electron-opacity of typical materials, which limits the measurement of gradients in the displacement field in the direction normal to the sample surface; and b) the inability of HR-EBSD to recover the spherical (elastic) distortions of the lattice. This second challenge can be overcome if a traction free boundary condition is applied. It is illustrated that consideration of the familiar stress equilibrium relations gives additional information, which may enable estimates of the missing components of the Nye tensor. An example of application of HR-EBSD to a Mg-Ce sample is presented.

Abstract: Recent advances in high-resolution electron backscatter diffraction (EBSD)-based microscopy are applied to the characterization of incompatibility structures near the grain boundaries (GBs) in polycrystals. The principal interest described here is recovery of geometrically-necessary dislocation (density) tensors, of the 2- and 3-D type, described by Nye and Kröner. These developments are presented in the context of the continuum dislocation theory. High resolution data obtained near a single grain boundary in well-annealed, low content steel suggests that it may be possible to measure the intrinsic elastic properties of GBs.