Comparison of the dislocation density obtained by HR-EBSD and X-ray profile analysis

Abstract

Based on the cross correlation analysis of the Kikuchi diffraction patterns high-resolution EBSD is a well established method to determine the internal stress in deformed crystalline materials. In many cases, however, the stress values obtained at the different scanning points have a large (in the order of GPa) scatter. As it was first demonstrated by Wilkinson and co-workers this is due to the long tail of the probability distribution of the internal stress ($P(\sigma)$) generated by the dislocations present in the system. According to the theoretical investigations of Groma and co-workers the tail of $P(\sigma)$ is inverse cubic with prefactor proportional to the total dislocation density $<\rho>$. In this paper we present a direct comparison of the X-ray line broadening and $P(\sigma)$ obtained by EBSD on deformed Cu single crystals. It is shown that $<\rho>$ can be determined from $P(\sigma)$. This opens new perspectives for the application of EBSD in determining mesoscale parameters in a heterogeneous sample

Dislocation interactions in olivine control postseismic creep of the upper mantle

“…Unlike conventional EBSD, which struggles to resolve the subtle microstructural changes associated with transient creep at small strains 39 , HR-EBSD provides exceptionally precise estimates of the density of geometrically necessary dislocations (GNDs, the fraction of the total dislocation density that generates net lattice curvature and long-range stress heterogeneity) and, importantly, maps heterogeneity in elastic strain and residual stress stored in the samples after the experiments [40][41][42][43] . We analyse the stress distributions in terms of the theory, established in the materials sciences [44][45][46][47] , for stress fields of a population of dislocations to test the causality between stress heterogeneity and the dislocation content (Methods). In particular, we test whether tails of the probability (P) distributions of shear stress (σ 12 ) follow a P(σ 12 ) ∝ |σ 12 | −3 relationship, as expected of stress fields generated by dislocations [44][45][46][47].…”

Mapping the full lattice strain tensor of a single dislocation by high angular resolution transmission Kikuchi diffraction (HR-TKD)

“…The angular resolution of EBSD is ~1° [8].The cross-correlation based EBSD analysis approach introduced by Wilkinson (HR-EBSD) improves the angular resolution to 0.005° by measuring small shifts of features in the EBSD patterns compared to a reference EBSD pattern [8][9][10][11]. These small shifts can be interpreted in terms of lattice rotations and lattice distortions [1,[8][9][10][11].HR-EBSD has been widely adopted to characterise geometry necessary dislocation (GND) density and residual lattice strains in crystalline materials [1,[12][13][14][15][16][17]. A comparative study…”

Mechanism-based modeling of solute strengthening: Application to thermal creep in Zr alloy

“…Later, the theory proposed by Groma and Bakó (1998) indicates that the tail of the probability distribution of the internal stress decays with the inverse third power of the stress. This theory has been discussed and verified by Groma and Szé kely (2000), Wilkinson et al (2014) and Kalá cska et al (2017). In the constitutive modeling framework of Wang et al (2016Wang et al ( , 2017, the internal stress distribution is assumed to be Gaussian.…”