DescriptionMonitoring evolving subgrain structures during varying loading conditions by high resolution reciprocal space mapping W. Pantleon1, C. Wejdemann1, B. Jakobsen2, U. Lienert3, and H.F. Poulsen1 1 Center for Fundamental Research: Metal Structures in Four Dimensions, Materials Research Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, Frederiksborgvej 399, 4000 Roskilde, Denmark 2 Center of Fundamental Research: Glass and Time, Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark 3 Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA With high angular resolution three-dimensional X-ray diffraction quantitative information is gained about dislocation structures in individual grains in the bulk of a macroscopic specimen by acquiring reciprocal space maps. In high resolution three-dimensional reciprocal space maps of tensile deformed copper, individual, almost dislocation-free subgrains are identified from highintensity peaks and distinguished by their unique combination of orientation and elastic strain; dislocation walls manifest themselves as a smooth cloud of lower intensity. The elastic strain varies only slightly within each subgrain, but significantly between different subgrains. In average, subgrains experience backward strains, whereas dislocations walls are strained in forward direction. Based on these observations a revision of the classical composite model is formulated in full accordance with the experimental findings. Additionally, subgrain dynamics is followed in-situ during varying loading conditions by high resolution reciprocal space mapping: During uninterrupted tensile deformation, formation of subgrains can be observed concurrently with broadening of Bragg reflections shortly after onset of plastic deformation. The emergence of dislocation-free regions proofs that ordered dislocation structures develop during tensile deformation. When changing the tensile direction after predeformation in tension, two distinct regimes in the mechanical transient can be identified. During the initial stage, the number of the resolved subgrains changes only slightly while their elastic stresses are significantly altered. In case of perpendicular tensile axes, a reversal of the radial profile asymmetry is observed and explained.
Place: Lake Bostal, Germany
|Period||25 Sept 2011 → 28 Sept 2011|