Implementing and evaluating far-field 3D X-ray diffraction at the I12 JEEP beamline, Diamond Light Source

Abstract

Three-dimensional X-ray diffraction (3DXRD) is shown to be feasible at the I12 Joint Engineering, Environmental and Processing (JEEP) beamline of Diamond Light Source. As a demonstration, a microstructually simple low-carbon ferritic steel was studied in a highly textured and annealed state. A processing pipeline suited to this beamline was created, using software already established in the 3DXRD user community, enabling grain centre-of-mass positions, orientations and strain tensor elements to be determined. Orientations, with texture measurements independently validated from electron backscatter diffraction (EBSD) data, possessed a ∼0.1° uncertainty, comparable with other 3DXRD instruments. The spatial resolution was limited by the far-field detector pixel size; the average of the grain centre of mass position errors was determined as ±∼80 µm. An average per-grain error of ∼1 × 10−3 for the elastic strains was also measured; this could be reduced in future experiments by improving sample preparation, geometry calibration, data collection and analysis techniques. Application of 3DXRD onto I12 shows great potential, where its implementation is highly desirable due to the flexible, open architecture of the beamline. User-owned or designed sample environments can be used, thus 3DXRD could be applied to previously unexplored scientific areas.

A dislocation density-based crystal plasticity constitutive model: comparison of VPSC effective medium predictions with ρ-CP finite element predictions

“…The distribution becomes broader with increasing applied strain for all stress components. Moreover, recent experimental 3D x-ray diffraction (XRD) measurements of residual stresses in DX-54 steel show a similar distribution (see figure7inBall et al 2023). In fact, the peak values at the respective means from our ρ-CP predictions are comparable with the experimental counterparts inBall et al (2023), i.e.…”

“…For example, the value of f used in our simulations ranges from 0.01 to 0.04 and describes dispersion of intragranular stresses with respect to the mean in each grain. On the other hand, the value of the normalized standard deviation of combined inter and intragranular stresses is in the range 0.2 to 0.3 both, for finite element simulations and for experimental 3D-XRD measurements reported recently in Ball et al (2023). The latter is much larger because grains with different crystallographic orientations have a larger dispersion in their mean stress, which is the magnitude captured by diffraction measurements.…”