CONCENTRATION DEPENDENCE OF INTERDIFFUSION COEFFICIENT IN BINARY METALLIC SOLID SOLUTION

In binary alloys the interdiffusion coefficient DAB experimentally determined from Fick's second law, is the product of an activity-corrected diffusion coefficient DAB and a thermodynamic factor which represents the departure from ideality of the solution AB = DABαAB = DAB(1 + (dlnαA dlnNA) Analyses of all the available experimental results concerning solid binary alloys, where solubility is unlimited, leads to the following general empirical correlation DAB = (DA(B)0)NB(DB(A)0)NAexp - (16ΔTsAB RT) where D0A(B) and D0B(A) are the limiting values of the interdiffusion coefficient at infinite dilution and ΔTsAB represents the difference between the solidus temperature of the phase diagram TsAB and the temperature which would be computed if the solidus line varied linearly with composition (See Fig. 2). This correlation is justified by previously successful empirical correlations between diffusivity and physical properties. © 1968.