Papers by Keyword: Electron Channeling Contrast (ECC)

Abstract: A sliding wear test was conducted in a copper single crystal having (001) surface. Microstructures induced by the sliding wear were investigated by means of the electron channelling contrast (ECC) imaging and electron backscattered diffraction (EBSD) analysis. The microstructures below the worn surface consisted of the stack of dislocation cell structure, layered structure and equiaxed fine-grained structure. At the dislocation cell structure, there was no significant change in crystallographic orientation. On the other hand, the crystal at the layered structure rotated continuously around the axis which was perpendicular to sliding wear direction. In the fine-grained structure, preferential orientations no longer existed. The authors attempted to explain grain boundary formation in terms of a rotation angle gradient which is proportional to density of geometrically-necessary dislocations.

Abstract: The dependence on the grain orientation of the alignment of planar dislocation boundaries in plastically deformed metals has been investigated by examining grains of S orientation ({123}<63-4>) in cold-rolled polycrystalline aluminum. For the ideal S orientation the {111} slip plane associated with the highest resolved shear stress lies either at +40° or -40° to the rolling direction in the longitudinal section, with two S variants corresponding to each case. Boundary traces in S orientation grains in the rolled sample were examined by the combined use of electron channeling contrast imaging and electron backscatter diffraction orientation mapping. In each case the +/- sense of the observed planar boundary traces matched that of the {111} slip plane with the highest resolved shear stress showing that the alignment of the boundaries is predominantly controlled by crystallographic rather than macroscopic considerations.

Abstract: Non-destructive tests using impact echo (IE) and pulse velocity measurements (PVM) were conducted to evaluate degradation of elastic properties of cement-based materials during uniaxial compression. Prismatic specimens (100
100
200 mm) made of ECC (engineered cementitious composites) mixture, were used for the test. The specimens were subjected to monotonic axial loading until failure while resonance frequency and travel time were recorded. Changes in the amplitude, velocity, and frequency were correlated to the increasing damage levels and the feasibility of IE and PVM techniques to evaluate the damage level in ECC was preliminarily assessed.