Dark-field X-ray microscopy for multiscale structural characterization

Abstract

Many physical and mechanical properties of crystalline materials depend strongly on their internal structure, which is typically organized into grains and domains on several length scales. Here we present dark-field X-ray microscopy; a non-destructive microscopy technique for the three-dimensional mapping of orientations and stresses on lengths scales from 100 nm to 1 mm within embedded sampling volumes. The technique, which allows ‘zooming’ in and out in both direct and angular space, is demonstrated by an annealing study of plastically deformed aluminium. Facilitating the direct study of the interactions between crystalline elements is a key step towards the formulation and validation of multiscale models that account for the entire heterogeneity of a material. Furthermore, dark-field X-ray microscopy is well suited to applied topics, where the structural evolution of internal nanoscale elements (for example, positioned at interfaces) is crucial to the performance and lifetime of macro-scale devices and components thereof.

Direct observation of grain rotations during coarsening of a semisolid Al–Cu alloy

“…From a sequence of such measurements applied to the same sample, we can track its microstructural evolution and determine whether a particular processing protocol [such as a heat treatment (22)(23)(24) or a mechanical deformation (25)(26)(27)] induced grain rotation. Furthermore, we can correlate changes in grain orientation to the morphologies and misorientations of a rotating grain's immediate neighbors.…”

The fractional Fourier transform as a simulation tool for lens-based X-ray microscopy

“…With a numerical aperture of order 1 mrad, CRL-based objectives are well matched to the high brilliance of synchrotron beams. A range of methodologies have been developed: magnified bright-field imaging (Lengeler et al, 1999), Zernike contrast microscopy (Falch et al, 2018), high-resolution microscopy for imaging colloidal aggregates (Bosak et al, 2010) and dark-field microscopy, where orientation and strains of deeply embedded grains or domains are mapped in three dimensions (Simons et al, 2015(Simons et al, , 2016. At the same time, direct space imaging can be complemented by diffraction in the back focal plane (Bosak et al, 2010;Ershov et al, 2013).…”

Boundary migration during recrystallization: experimental observations

“…This technique utilizes an objective (typically consisting of many compound refractive lenses (CRLs)) to magnify a diffracted beam by a factor of typically 10-20. With this technique, 3D maps of orientations within both individual deformed and recrystallized grains with a spatial resolution of ~300 nm have been achieved [52]. The 3DXRM techniques utilize a focused, polychromatic synchrotron X-rays with energy of 5-30 keV [51,53].…”

“…Very recently, based on the 3DXRD techniques, a new concept ─ dark-field X-ray microscopy (DFXRM) ─ has been developed and implemented [52]. This technique utilizes an objective (typically consisting of many compound refractive lenses (CRLs)) to magnify a diffracted beam by a factor of typically 10-20.…”