Papers by Keyword: Dislocation Boundaries

Abstract: The present work examines the microstructure and texture evolution in a Ni-30wt.%Fe austenitic model alloy deformed in torsion at 1000 °C, with a particular emphasis on the orientation dependence of the substructure characteristics within the deformed original grains. Texture of these grains was principally consistent with that expected for simple shear and comprised the main A, B and C components. The deformation substructure within the main texture component grains was characterised by “organised” arrays of parallel microbands with systematically alternating misorientations, locally accompanied by micro-shear bands within the C grains. With increasing strain, the mean subgrain size gradually decreased and the mean misorientation angle concurrently increased towards the saturation. The stored deformation energy within the main texture component grains was principally consistent with the respective Taylor factor values. The microband boundaries corresponded to the expected single slip {111} plane for the A oriented grains while these boundaries for the C oriented grains represented a variety of planes even for a single grain.

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: Microstructural observations are presented for different metals deformed from low to high strain by both traditional and new metal working processes. It is shown that deformation induced dislocation structures can be interpreted and analyzed within a common framework of grain subdivision on a finer and finer scale down to the nanometer dimension, which can be reached at ultrahigh strains. It is demonstrated that classical materials science and engineering principles apply from the largest to the smallest structural scale but also that new and unexpected structures and properties characterize metals with structures on the scale from about 10 nm to 1 μm.