Concentration dependence of ternary interdiffusion coefficients in Ni3Al/Ni3Al-X couples with X = Cr, Fe, Nb and Ti

The gamma' single phase interdiffusion in Ni3Al-X (X = Cr, Fe, Nb and Ti) was studied in temperature interval 1173-1533 K. Elements of diffusion matrix, (D) over tilde ((Ni))(ij), were estimated by a modification of Dayananda's method which enables evaluation of their concentration dependence using one couple only. It was found that activation enthalpy, Q(XX)((Ni)), and frequency factor, D-o(XX)(Ni), decrease with increasing concentration of element X. In the limit c(x)-->0, the values of (D) over tilde ((Ni))(XX) approach the literature values of tracer diffusion coefficients of X in Ni3Al. An estimation of Al "tracer" diffusion coefficient in Ni3Al was obtained that is in reasonable agreement with other estimations in the literature. With decreasing concentration of X in Ni3Al, the difference between Arrhenius parameters Q(XX)((Ni)), D-o(XX)(Ni) and respective values of Q(AlAl)((Ni)) and D-oAlAl((Ni)) decreases, Q(XX)((Ni)), D-o(Ni)(XX) agree with values reported in the literature for very diluted solution of X in Ni3Al. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.