The measurement of volume diffusion by the method of autoradiography

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Abstract
The application of autoradiography to the measurement of volume diffusion is limited because of the difficulty in interpreting the effects of the energy of the radiations, the scattering and absorption properties of the specimen and other complicating factors. A general method of interpretation is described in which the effects of these factors are suitably combined into a single function that is determined by one experiment. The method is applied by matching the experimental density trace of the diffusion zone, with a density curve which is computed from a derived expression. As a trial of this treatment, the diffusion of 124Sb into single crystals of copper has been studied over the penetration range 10 μ < (Dt)½ < 150 μ and in the temperature range 560°c to 896°c with specimens mounted singly and in a double sandwich-type arrangement. The results that have been produced show good agreement with the results obtained from mechanical sectioning and the accuracies of the two methods are comparable. In the case of small penetrations at low temperatures, anomalously low values of the diffusion coefficient are noted. The additional studies that have been made with 110Ag as the tracer element, are also used to discuss the application and the limitation of the method.