dislocation density

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