In situ synchrotron X-ray multimodal experiment to study polycrystal plasticity

The microstructure of polycrystals is known to govern the performance of structural materials. This drives the need for mechanical characterization methods capable of probing large representative volumes at the grain and subgrain scales. In this paper, the use of in situ diffraction contrast tomography (DCT) along with far-field 3D X-ray diffraction (ff-3DXRD) at the Psiche ' beamline of Soleil is presented and applied to study crystal plasticity in commercially pure titanium. A tensile stress rig was modified to comply with the DCT acquisition geometry and used for in situ testing. DCT and ff-3DXRD measurements were carried out during a tensile test of a tomographic Ti specimen up to 1.1% strain. The evolution of the microstructure was analyzed in a central region of interest comprising about 2000 grains. Using the 6DTV algorithm, DCT reconstructions were successfully obtained and allowed the characterization of the evolution of lattice rotation in the entire microstructure. The results are backed up by comparisons with EBSD and DCT maps acquired at ESRF-ID11 that allowed the validation of the orientation field measurements in the bulk. Difficulties at the grain boundaries are highlighted and discussed in line with increasing plastic strain during the tensile test. Finally, a new outlook is provided on the potential of ff-3DXRD to enrich the present dataset with access to average lattice elastic strain data per grain, on the possibility of performing crystal plasticity simulations from DCT reconstructions, and ultimately on comparisons between experiments and simulations at the scale of the grain.

Automated summary

This study presents the use of in situ diffraction contrast tomography (DCT) and far-field 3D X-ray diffraction (ff-3DXRD) to investigate crystal plasticity in commercially pure titanium. The microstructure evolution, particularly lattice rotation, was analyzed using DCT reconstructions and ff-3DXRD measurements. The results were validated with EBSD and DCT maps, and difficulties at the grain boundaries during the tensile test were discussed. The study also discussed the potential of ff-3DXRD for obtaining average lattice elastic strain data per grain and performing crystal plasticity simulations from DCT reconstructions.