Thermodynamic interdiffusion coefficient in binary systems with intermediate phases

A new form of diffusion coefficient, termed the thermodynamic interdiffusion coefficient has been introduced in this investigation; it is related to the conventional chemical interdiffusion coefficient and thermodynamic properties of the system. Three main advantages in using the thermodynamic interdiffusion coefficient are described by applying this alternative approach of diffusion analysis, as an example, to the Al-Ni system. These include (1) a better interpretation of the relative diffusivities in the different phases of the same system, (2) estimation of appropriate values of the activation energy of the diffusion process and (3) determination of the thermodynamic intrinsic diffusion coefficient (also known as the tracer diffusion coefficient) in an intermediate phase with narrow homogeneity range, which otherwise is not possible without tracer diffusion experiments. (C) 1999 Elsevier Science Ltd. All rights reserved.