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 temperature was determined by using X-ray diffraction peak profile analysis. The crystallite size distribution and defects evolution were determined as a function of different reduction levels (e.g., 67%, 74%, 87%, and 97%). By using the Multiple Whole-Profile fitting procedure the Fourier transforms of the experimental X-ray peak profiles were fitted all at once by theoretical calculated functions. Here it is assumed that the crystallites are spherical shape and have a log-normal size distribution. It is also supposed that the strain broadening of the profiles is caused by < 110 > {111}-type dislocations. The results show that the median and the variance of the crystallite size distribution decreases as the deformation reduction increases. The dislocation density has a minimum value at 74% reduction. The increase of the dislocation density at higher deformation levels is due to the nucleation of new generation of dislocations from the crystallite grain boundaries. It was found that the edge dislocation type dominate, the dislocation network formed during the deformation process.