IRON NICKEL AND COBALT DIFFUSION IN TRANSITION METALS OF IRON GROUP

The heterodiffusion coefficients of iron in nickel and cobalt, cobalt in nickel and iron, and nickel in cobalt and iron have been determined by electronic gauge microanalysis between 1136°C and 1370°C, at infinite dilution. The validity of this method is justified compared with some results obtained by radioactive tracers. The values obtained for frequency factors D0 and activation energies Q are found in table 8. The difference, ΔQ, between the heterodiffusion activation energies of transition impurity for a transition metal and the activation energy of matrix self-diffusion increases linearly with the atomic number of the impurity. ΔQ = αΔZ where α > 0 and ΔZ = Zsolute - Zsolvent. The analysis of the temperature dependence of correlation factor leads to a better determination for the vacancy-transition impurity interaction in a transition metal 1. (i). if Zsolute > Zsolvent; ΔQ > 0 (it is the case for DCo(Fe), DNi(Fe), DNi(Co)), then there is an impurity-vacancy repulsion and the correlation factor contribution can be neglected 2. (ii). if Zsolute < Zsolvent; ΔQ < 0 (it is the case for DFe(Co), DFe(Ni), DNi(CO)), then there is an impurity-vacancy attraction. © 1969.