An interpretation of tracer diffusion in β-CuZn

In this paper, two models which are solved with analytical and computer simulation methods are used to interpret the tracer diffusion and isotope effect data in beta-CuZn. The first model is a four-frequency one in which the atom-vacancy exchange frequencies are assumed to be independent of environment apart from sublattice. The second is the Ising, i.e. nearest neighbour atomic interaction, model. For the first model it is found that the correlation factors contribute roughly a half and one third of the activation energies for tracer diffusion of Zn and Cu, respectively. The correlation factors for the more realistic Ising model on the other hand contribute about a quarter and an eighth of the activation energies for tracer diffusion of Zn and Cu, respectively. The correlation factors in beta-CuZn as determined from the isotope effect must be analysed with the impurity-form of the correlation factors. This turned out to be possible using the analytical approach (both models) and a special computer simulation method. Our best estimate of the correlation factor for Zn diffusion at 683 K is 0.4 while our best estimate for the correlation factor for Cu diffusion is 0.59. (C) 1998 Acta Metallurgica Inc.