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

Abstract

The γ′ single phase interdiffusion in Ni3Al–X (X=Cr, Fe, Nb and Ti) was studied in temperature interval 1173–1533 K. Elements of diffusion matrix, D̃ij(Ni), 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, QXX(Ni), and frequency factor, Do(Ni)XX, decrease with increasing concentration of element X. In the limit cX→0, the values of D̃XX(Ni) 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 QXX(Ni), Do(Ni)XX and respective values of QAlAl(Ni) and DoAlAl(Ni) decreases. QXX(Ni), Do(Ni)XX agree with values reported in the literature for very diluted solution of X in Ni3Al.