High Resolution Mapping of Orientation and Strain Gradients in Metals by Synchrotron 3D X-ray Laue Microdiffraction

Abstract

Synchrotron 3D X-ray Laue microdiffraction, available at beamline 34-ID-E at Advanced Photon Source in Argonne National Laboratory, is a powerful tool for 3D non-destructive mapping of local orientations and strains at sub-micron scale in the bulk. With this technique, it is possible to study local residual stresses developed during manufacturing or while in service due to interactions between, for example, different phases and/or grains with different orientations in materials containing multiple or single phase(s). Such information is essential for understanding mechanical properties and designing advanced materials, but is largely non-existent in the current generation of materials models. In the present paper, the principle and experimental set-up of the 3D microdiffraction are introduced, followed by a description of a method for quantification of the local plastic deformation based on high-angular-resolution orientation maps. The quantification of local residual stresses in two model materials, ductile cast iron (two phases) and partially recrystallized pure nickel (single phase), using 3D microdiffraction will then be presented. The results show that 3D microdiffraction is important for understanding the origin of local residual stresses and to relate them to the microstructural evolution. Finally, the limitations of the 3D microdiffraction on the current generation synchrotron source and new possibilities after the synchrotron upgrade are discussed.

Recovery of small orientation gradients in a recrystallized grain observed in 3D during ex-situ annealing

“…Concerning residual stresses, which have not been mapped in the present work, they may as well be of high importance. Other works have reported very large residual stress even within recrystallizing grains [11,12]. It is thus suggested to include strain mapping in future studies of recrystallization, as residual strains are likely a missing link in identifying nucleation sites and understanding local migration phenomena.…”

“…Recent developments of advanced synchrotron Xray techniques have enabled 3D non-destructive mapping of both crystallographic orientations and residual strains with very high angular resolution as well as good spatial and strain resolutions [5][6][7][8][9]. By such synchrotron measurements, it was revealed that a network of very low angle (<0.1°) dislocation boundaries and local residual strains as large as 1×10 -3 may exist within recrystallizing grains [10][11][12]. It is thus of interest to study interior misorientations and strains in recrystallizing grains in more detail using these advanced experimental methods, to understand effects hereof on 1249 (2022) 012050 IOP Publishing doi:10.1088/1757-899X/1249/1/012050 2 the nucleation and growth of recrystallizing grains, and to follow the evolution during the recrystallization anneal.…”

In Situ Synchrotron X-ray Micro-Diffraction Investigation of Elastic Strains in Laminated Ti-Al Composites

“…From the energy scans at the chosen sample position, the intensity distribution of the diffracted beam as a function of the diffraction vector was determined for each depth, and this distribution was fitted using a Gaussian function (see Figures S3 and S4 in the Supplementary Materials). The center of the Gaussian function was used to determine the spacing of the diffraction planes [17,20]. By comparing to the unstrained plane spacing (here taking the theoretical lattice constants a = 4.0495 Å for Al [21] and a = 2.9508 Å and c = 4.6855 Å for Ti [22]), the lattice strain along the plane normal was determined and termed ε ND , as the plane normal is very close to the ND of the tensile sample.…”

Recent trends in X‐ray‐based characterization of nodular cast iron

“…Over the past two decades, significant effort has been devoted to the development of synchrotron techniques for characterizing 3D grain structure and local stresses, including 3D X‐ray Laue microdiffraction (3DμXRD) 30–32 and 3D X‐ray diffraction (3DXRD) 33,34 and its variants: high‐energy X‐ray diffraction microscopy, 35,36 diffraction contrast tomography, 37,38 dark field X‐ray microscopy, 39,40 and scanning 3DXRD 41 . Among these techniques, 3DμXRD is in particular suitable for mapping microstructure and strain/stress state in bulk samples, as it can provide a spatial resolution of submicrometer, angular resolution of 0.01°, and a strain resolution of 1 × 10 −4 32,42 …”