  In this paper the problem of determination of the diffusion coefficients in a
ternary multiphase system is discussed. In the literature there is a lack of
data concerning the approximation method which allows to determine diffusion
coefficients in such complicated systems. We propose the mass conservation
method (MCA) for calculation the diffusivities in phases where the differences
in composition is linear. Only one experimental results is needed for
determination of the diffusion data. The method is implemented and checked
under ternary Ti-NiAl system - this system characterize occurrence three
intermetallic phases in diffusion couple Ti-NiAl.
