Investigation of the annealing of deformed nickel powder by X-ray and stored energy measurements

Abstract

Abstract The stored energy was measured by a calorimetric method. The measured value of 3.6 cal/g and the manner of its release suggests that a wide range of deformations is present, both the maximum and average deformations being considerably greater than those present in heavily deformed solid specimens of nickel. The diffraction patterns, measured with a Geiger counter spectrometer, show that during annealing there is no change in the background intensity. The integrated intensities of the high angle lines remain constant and small changes in the low angle lines are attributed to changes in extinction. Only small changes occur in the tails of the lines at temperatures of annealing up to 400°C. No evidence has been found for stacking faults or changes in lattice parameter. The diffraction profiles are analysed by a number of methods, the broadening in each case being attributed partly to strain and partly to small particle size. The results indicate two stages in the relief of strain. The first occurs m...