The estimation of dislocation densities in metals from X-ray data

Abstract

Recent work has shown that substructures are formed within the grains of a cold-worked polycrystalline metal. In this paper, methods are described by which the density of the excess dislocations of one sign in the boundaries between the particles can be found from data obtained from X-ray diffraction photographs. The methods may be extended to give estimates of the excess and total dislocation densities within the particles and the densities in annealed metals. The results for both cold-worked and annealed metals show that the present estimates are less than the usually accepted values. The discrepancy in the case of the cold-worked metals could be due to a different distribution of dislocations in the boundaries which may not be detected by the existing X-ray methods; however a strict comparison cannot be made until more reliable data are available from other physical measurements. It is shown that the usually accepted figure for the dislocation density in annealed metals has no theoretical or experimental support and that the dislocation density in some metal crystals may be very much less.