Probing intra-granular deformation by micro-beam Laue diffraction

摘要

Deformation in polycrystalline materials does not occur uniformly in the constituent grains, but shows strong inter- and intra-granular variations. The local deformation response depends on lattice orientation, anisotropic elastic-plastic properties, hardening and damage behaviour and the microstructural neighbourhood. Understanding of these complex interactions is vital for the construction and validation of crystal plasticity models, the introduction of mesoscopic deformation effects into polycrystal models and the fundamental understanding of the material's deformation behaviour. Micro-beam Laue diffraction provides an excellent tool for the study of inter- and intra-granular deformation, allowing, unlike other microscopy methods, measurements within the bulk of the material. A focused "pink" beam is used to probe the interior of individual grains within a polycrystalline sample. The diffracted radiation forms a pattern of Laue spots which is captured by an area detector. From the spot positions, lattice orientation and elastic strains can be deduced. The intensity distribution within individual spots, can be interpreted in terms of the dislocation arrangement within the gauge volume. In this paper we present a novel setup for microbeam Laue diffraction recently developed on the B16 test-beamline at the Diamond Light Source, UK, with the aim of collecting a high quality dataset characterising mesoscopic deformation behaviour within a polycrystal containing a small number of large grains. Such a dataset was collected from a large grained Ni sample in which a number of maps covering several grains were recorded for a sequence of deformation steps. In this paper some first results from this investigation are presented. Ultimately the dataset is intended to allowe a direct comparison between crystal plasticity models and experimental behaviour.