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On the Measurement of Dislocations and Dislocation Structures Using EBSD and HRSD Techniques

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Document pages: 32 pages

Abstract: The accumulation of the dislocations and development of dislocation structures in plastically deformed Ni201 is examined using dedicated analyses of Electron Back-Scatter Diffraction (EBSD) acquired orientation maps, and High-Resolution Synchrotron Diffraction (HRSD) acquired patterns. The results show that the minimum detectable microstructure-averaged (bulk) total dislocation density (ρT) measured via HRSD is approximately 1E13 m-2, while the minimum GND density (ρG) measured via EBSD is approximately 2E12 m-2 - the EBSD technique being more sensitive at low plastic strain. This highlights complementarity of the two techniques when attempting to quantify amount of plastic deformation (damage) in a material via a measurement of present dislocations and their structures. Furthermore, a relationship between EBSD-measured ρG and the size of HRSD-measured Coherently Scattering Domains (CSDs) has been mathematically derived - this allows for an estimation of the size of CSDs from EBSD-acquired orientation maps, and conversely an estimation of ρG from HRSD-measured size of CSDs. The measured evolution of ρT, and ρG is compared with plasticity theory models - the current results suggest that Ashby s single-slip model underestimates the amount of GNDs (ρG), while Taylor s model is correctly predicting the total amount of dislocation (ρT) present in the material as a function of imparted plastic strain.

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