X-ray line broadening from metals deformed at low temperatures

Abstract

Comparative measurements of the X-ray line broadening in copper, aluminium and nickel, plastically deformed by various amounts at room temperature and at liquid air temperature, have been made and the behaviour at room temperature of specimens previously deformed at the low temperature studied. Also, some measurements have been made of the effects of change of temperature or of direction of straining during the deformation. It appears that recovery or self-annealing does not, in general, limit the line broadening, but support is given to the hypothesis that the broadening is due to internal stresses which cannot exceed the yield stress of the cold-worked metal. Stress-strain tests on specimens similar to the line-broadening specimens show that the course of the line-broadening with increasing plastic deformation is roughly parallel to the yield stress versus strain curve, and the internal stresses estimated from the observed line broadening are of the same order of magnitude as the macroscopic yield stress. The influence of the temperature of deformation is practically the same on both the line broadening and the yield stress at large plastic strains. Finally, the origin of the internal stresses mainly responsible for X-ray line broadening is discussed briefly and it is suggested that the major contribution to the broadening arises from elastic distortion of the glide lamellae.