dislocation density
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By: Divya Kohli
Dislocation Density Measurement by XRD
Effect of Lattice Strain
B.D. Cullity, S.R. Stock, Elements of X-Ray Diffraction ,third edition
Pre-processing XRD data
Raghavan.R, Estimation of dislocation density and its character for Zr 2.5% Nb alloy using X-Ray Diffraction and Transmission Electron Microscopy, 2010
Ungar's Method
Ungar has introduced a factor C, called contrast factor
Raghavan.R, Estimation of dislocation density and its character for Zr 2.5% Nb alloy using X-Ray Diffraction and Transmission Electron Microscopy, 2010
/)sin(2 bK
Or logAL = ax2 + bx + c where x stands for K2C.
)(log)()( 2
iL
RiBLib e
)(log
)(
)(2 iL
RB
iL
ib e
Raghavan.R, Estimation of dislocation density and its character for Zr 2.5% Nb alloy using X-Ray Diffraction and Transmission Electron Microscopy, 2010
Williamson Hall plot
Indicative of the amount of strain in the material. More steep the curve, more the amount of strain.Raghavan.R, Estimation of dislocation density and its character for Zr 2.5% Nb alloy using X-
Ray Diffraction and Transmission Electron Microscopy, 2010
Direct method : Variance Method
The Variance method, proposed by Groma considers an individual peak for estimating DD.
The local intensities of the peak are transformed corresponding to the parameter q defined as
The kth order moments of I(q) dened as
FIG. 1. High-resolution x-ray Bragg peaks which show pure strain (AlMg at RT), pure size (nano Fe), and combined broadening (AlMg at 400 °) areshown.A. Borbe´ ly and I. Groma, Appl. Phys. Lett., Vol. 79, No. 12, 17 September 2001
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