On Vacancy Concentrations in Dilute FCC Alloys

Abstract

Berces and Kovacs [1] have estimated the vacancy concentrations cv(x) in dilute alloys taking into account V-iX complexes with i impurity atoms X in nearest-neighbour (NN) distance of the vacancy V and NN X-X interactions. The obtained approximation is based on the statistical arrangement of the impurity atoms in NN distance of the vacancy. In thermodynamical equilibrium a redistribution of the impurity atoms has to be taken into consideration. This means that e.g. for attractive V-X interaction and repulsive X-X interaction arrangements with smaller numbers of impurity atoms in NN distance are preferred. In the present study the correct solution for the Gibbs free energy of vacancy formation for V-iX complexes is derived. The improved model is compared with experimental data of cv(x) obtained with the aid of differential dilatometric investigations on dilute fcc alloys [2].