Observation of Bulk Plasticity in a Polycrystalline Titanium Alloy by Diffraction Contrast Tomography and Topotomography

TL;DR

This study demonstrates the use of combined X-ray diffraction contrast tomography and topotomography to observe and analyze bulk slip events in a polycrystalline titanium alloy, revealing heterogeneity in deformation.

Contribution

It introduces a novel correlative imaging approach for in situ 3D observation of plasticity in polycrystalline metals, expanding the ability to study slip transmission in bulk microstructures.

Findings

Larger grain neighborhoods were mapped than before, enabling detailed slip transmission analysis.

Significant differences between surface and bulk grain deformation were observed.

3D imaging is essential for understanding polycrystalline deformation mechanisms.

Abstract

The mechanical properties of polycrystalline metals are governed by the interaction of defects that are generated by deformation within the 3D microstructure. In materials that deform by slip, the plasticity is usually highly heterogeneous within the microstructure. Many experimental tools can be used to observe the results of slip events at the free surface of a sample; however, there are only a few methods for imaging these events in the bulk. In this article, the imaging of bulk slip events within the 3D microstructure are enabled by the combined use of X-ray diffraction contrast tomography and topotomography. Correlative measurements between high-resolution digital image correlation, X-ray diffraction contrast tomography, topotomography and phase contrast tomography are performed during deformation of Ti-7Al to investigate the sensitivity of the X-ray topotomography method for the observation of slip events in the bulk. Much larger neighborhoods of grains were able to be mapped than in previous studies, enabling quantitative measurements of slip transmission. Significant differences were observed between surface and bulk grains, indicating the need for 3D observations of plasticity to better understand deformation in polycrystalline materials.