X-ray diffraction line broadening under elastic deformation of a polycrystalline sample: An elastic-anisotropy effect

Abstract

A homogeneous stress field imposed on a polycrystalline sample containing elastically anisotropic crystallites produces an inhomogeneous strain field. The average strain causes a shift of the diffraction-line position, and the variance of the strain is a measure of line broadening. Though the shift of the line is commonly observed, earlier attempts to measure the broadening caused by elastic anisotropy were not conclusive. In the article, expressions have been derived for the average strain and variance of strain for a polycrystalline sample (cubic system) subjected to uniaxial elastic stress. The (310) and (222) lines of beta brass under an uniaxial load have been recorded using Co Kα and Cu Kα radiations, respectively. The average strain and variance of strain derived from the measured diffraction line profiles are in good agreement with those predicted by the theory. The present measurements provide conclusive evidence for the diffraction line broadening caused purely by elastic anisotropy.