DISLOCATION DENSITIES AND CHARACTER EVOLUTION IN COPPER DEFORMED BY ROLLING UNDER LIQUID NITROGEN FROM X-RAY PEAK PROFILE ANALYSIS

摘要

The microstructure evolution in pure copper deformed by rolling at liquid nitrogen temperaturernwas determined by using X-ray diffraction peak profile analysis. The crystallite size distributionrnand defects evolution were determined as a function of different reduction levels (e.g. 67%, 74%,rn87%, and 97%). By using the Multiple Whole-Profile (MWP) fitting procedure the Fourierrntransforms of the experimental X-ray peak profiles were fitted all at once by theoreticalrncalculated functions. Here it is assumed that the crystallites are spherical shape and have a lognormalrnsize distribution. It is also supposed that the strain broadening of the profiles is caused byrn<110>{111}-type dislocations. The results show that the median and the variance of therncrystallite size distribution decreases as the deformation reduction increases. The dislocationrndensity has a minim value at 74% reduction. The increase of the dislocation density at higherrndeformation levels is due to the nucleation of new generation of dislocations from the crystalliterngrain boundaries. It was found that the edge dislocation type is predominating the dislocationrnnetwork formed during the deformation process.