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

A homogeneous stress field imposed on a polycrystalline sample containing e lastically anisotropic crystallites produces an inhomogeneous strain field. The average strain causes a shift of the diffraction-line position, and th e variance of the strain is a measure of line broadening. Though the shift of the line is commonly observed, earlier attempts to measure the broadenin g caused by elastic anisotropy were not conclusive. In the article, express ions 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 r ecorded using Co K alpha and Cu K alpha radiations, respectively. The avera ge strain and variance of strain derived from the measured diffraction line profiles are in good agreement with those predicted by the theory. The pre sent measurements provide conclusive evidence for the diffraction line broa dening caused purely by elastic anisotropy. (C) 2001 American Institute of Physics.