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In situ measurement of elastic and total strains during ambient and high temperature deformation of a polygranular graphite

DOI: 10.1016/j.carbon.2020.03.020 DOI Help

Authors: Dong Liu (University of Bristol; University of Oxford) , Thomas Zillhardt (University of Oxford) , Philip Earp (University of Oxford) , Saurabh Kabra (ISIS Neutron Source) , Thomas Connolley (Diamond Light Source) , James Marrow (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Carbon

State: Published (Approved)
Published: March 2020
Diamond Proposal Number(s): 12585

Abstract: In situ neutron diffraction and synchrotron X-ray diffraction, combined with image correlation analysis of 2D op- tical and 3D X-ray tomography datasets, have been used to investigate the relationship between elastic lattice strain and total strain during deformation of Gilsocarbon (IM1-24) polygranular nuclear grade graphite. The spec- imens were flat-end Brazilian discs under diametral loading, such that a compressive-tensile biaxial stress state was developed in the central region. The X-ray study was at ambient temperature, and the neutron diffraction was conducted at temperatures from ambient to 850 °C. When under compression, there is a temperature-insensitive linear relationship between the total strain and the lattice strain that is measured perpendicular to the graphite basal planes. However, when under tensile stress, the total strain and elastic strain relationship is temperature sensitive: below 600 °C, the lattice tensile strain saturates with increasing total tensile strain; above 600 °C, sig- nificantly higher tensile lattice strains are sustained. The saturation in tensile lattice strain is attributed to micro- cracking in the graphite microstructure. Improved resistance to microcracking and damage tolerance at elevated temperature explains the increase in tensile strength of polygranular graphite.

Journal Keywords: Gilsocarbon graphite; Neutron diffraction; X-ray diffraction; X-ray computed tomography; Digital image correlation; Digital volume correlation

Subject Areas: Materials, Engineering, Energy


Instruments: I12-JEEP: Joint Engineering, Environmental and Processing

Other Facilities: ISIS-EnginX