A novel diffraction contrast tomography (DCT) acquisition strategy for capturing the 3D crystallographic structure of pure titanium

Abstract

The acquisition of high-fidelity 3D grain maps is essential for advancing our understanding of the micromechanical behavior of polycrystalline materials. Grain orientations, grain boundary misorientations, and grain shapes play a significant role in slip transfer mechanisms and grain growth phenomena. The past few years have seen considerable advances in the acquisition of high-reliability grain maps using laboratory-based Diffraction Contrast Tomography (LabDCT). Additionally, the microstructures of challenging sample geometries have become more accessible at the lab scale with recent developments in advanced Lab DCT acquisition strategies, such as helical phyllotaxis Lab DCT (HP-DCT). Unlike a conventional Lab DCT (C-DCT) scan, in which an elongated sample is scanned in multiple sections, a helical phyllotaxis motion is employed in an HP-DCT scan to illuminate the different parts of the sample in a single scan. This strategy can theoretically allow to scan and reconstruct challenging sample geometries, such as elongated and high aspect ratio samples, in a single process with fewer diffraction projections and reduced scan and analyses times. In this study, a detailed analysis of the grain maps for a pure Ti sample obtained from C-DCT and HP-DCT scan data is carried out. The DCT grain maps are compared with the surface grain maps obtained from ground-truth EBSD and SEM scans. Furthermore, the quality of grain reconstructions, grain orientations, grain boundary misorientations, grain shapes and morphology is quantitatively assessed, and the differences in accuracy of grain maps obtained from the conventional and helical phyllotaxis scans are highlighted. These results indicate that the grain reconstructions from HP-DCT scans have comparable grain fidelity to those obtained from C-DCT scan, with the conventional scans performing marginally better in terms of grain shape and orientation but at a higher time cost.