Three-dimensional maps of grain boundaries and the stress state of individual grains in polycrystals and powders

Abstract

A fast and non-destructive method for generating three-dimensional maps of the grain boundaries in undeformed polycrystals is presented. The method relies on tracking of micro-focused high-energy X-rays. It is veri®ed by comparing an electron microscopy map of the orientations on the 2.5 Â 2.5 mm surface of an aluminium polycrystal with tracking data produced at the 3DXRD microscope at the European Synchrotron Radiation Facility. The average difference in grain boundary position between the two techniques is 26 mm, comparable with the spatial resolution of the 3DXRD microscope. As another extension of the tracking concept, algorithms for determining the stress state of the individual grains are derived. As a case study, 3DXRD results are presented for the tensile deformation of a copper specimen. The strain tensor for one embedded grain is determined as a function of load. The accuracy on the strain is Á4 9 10 À4 .

On the mechanistic basis of fatigue crack nucleation in Ni superalloy containing inclusions using high resolution electron backscatter diffraction

“…These modelling efforts have focused at a range of length and timescales, using approaches such as molecular dynamic simulations [8,9] up to the grain level using crystal plasticity finite element techniques [10][11][12][13][14][15]. This range of approaches necessitates ever increasing fidelity of experimental studies that span length and timescales, such as X-ray synchrotron [16] [17,18] and high energy neutron diffraction [19]; as well as electron microscopy [20,21] microstructurally-sensitive and physically based modelling approaches necessitate local measurements of defect content and residual stresses to improve the prediction of fatigue crack nucleation and short crack growth.…”

Strain tensor determination of compressed individual silica sand particles using high-energy synchrotron diffraction

“…It is based on transmission geometry that can be applied in both layered and bulk materials [23][24][25][26][27]. It allows nondestructive 3D mapping of polycrystalline materials and monitors in situ dynamic processes of the bulk specimens.…”

Microstructural Characterization of Hard Ceramics

“…There are, however, a number of emerging high--energy X--ray techniques that allow orientation maps to be determined from transmitted X--ray beams. (Hefferan et al, 2009, Larson et al, 2002, Poulsen et al, 2001 This makes it possible to create a three--dimensional orientation map, subject the sample to external stimulus (mechanical, chemical, thermal, or electrical) and map the structure again.…”

“…(Barnard et al, 2006, Batenburg et al, 2009, Mobus and Inkson, 2001, Weyland et al, 2006 The Dual Beam, Focused Ion Beam Scanning Electron Microscope (DB--FIB SEM) makes three--dimensional imaging and crystallography mapping possible at the submicron level. (Dillon and Rohrer, 2009b At larger length scales, X--ray tomography (Chen et al, 2010, Chino andDunand, 2008) and high energy X--ray diffraction microscopy (HEDM) (Hefferan et al, 2009, Larson et al, 2002, Poulsen et al, 2001) allow phase mapping and crystallographic mapping, respectively. Finally, at the largest length scale, "RoboMet" robotic polishing and metallography allows the three--dimensional imaging of samples with sizes up to the cm size range.…”