DIFFUSION IN ALUMINUM ALLOYS BY ACTIVATION ANALYSIS

Abstract

This work was undertaken to determine the effect of manganese on the rate of diffusion of copper in aluminum in anticipation of possible effects on the precipitation rate of CuAl2 in Al-Cu-Mn alloys. Toward this end, (a) the theory has been developed for the analysis of concentration-dependent diffusion in multi-component systems, (b) a method is given for designing experiments to determine the diffusion coefficients for a given system most efficiently, (c) the method of composition analysis by neutron activation and subsequent measurement of gamma radiation is outlined, its scope and limitations given, and (d) six different couples of alloys in the Al- Cu-Mn system were diffused, analysed by neutron activation analysis, and the diffusion coefficients calculated. Activation analysis was used for composition determination for two reasons: first, the samples obtainable from a diffusion couple are small (of the order of ten milligrams); second, the method of activation analysis is relatively new and it was thought desireable to explore the scope and precision of this method. The use of activation analysis seemed particularly appropriate at McMaster University, where Canada’s first university experimental reactor has been built. Actually, the main irradiations for this work were made at Brookhaven National Laboratories in Upton N.Y., U.S.A. since the McMaster reactor was not yet fully operational.