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

Abstract

X-ray diffraction patterns from bulk specimens of nickel deformed by compression have been measured with a Geiger-counter spectrometer. A composite specimen has been used to overcome the effects of preferred orientations. The results indicate that during the annealing there is no change in the background intensity. No evidence has been found for stacking faults or changes in lattice parameter. The integrated intensities of all lines remain constant up to a temperature of annealing of about 480[ddot]c. A large decrease (30–75%) in the integrated intensity of all lines occurs on annealing to 600[ddot]c and this is attributed to extinction; an estimate of 2–4 μ is obtained for the size of the 'perfect' regions required to produce this effect. The diffraction profiles are analysed by a number of methods. The broadening produced by the particle size effect is small. The stored energies derived from the various methods of analysis range from 0.04-2-4cal/g. Best agreement is obtained between values of stored energy measured using a calorimetric method (0.28 cal/g) and those derived from x-ray measurements if it is assumed that the distribution of strain is Gaussian.