On the measurement of dislocations and dislocation substructures using EBSD and HRSD techniques

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 (rho(T)) measured via HRSD is approximately 1E13 m(-2), while the minimum GND density (rho(G)) 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 rho(G) 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 rho(G) from HRSD-measured size of CSDs. The measured evolution of rho(T), and rho(G) is compared with plasticity theory models - the current results suggest that Ashby's single-slip model underestimates the amount of ONDs (rho(G)), while Taylor's model is correctly predicting the total amount of dislocation (rho(T)) present in the material as a function of imparted plastic strain. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.