The disaccommodation technique was used to determine the activation volume of C diffusion, ΔV, in 6 face-centered cubic Fe-Ni alloys (table 131). Measurements were made at 68 to 90C, and pressures of upto 6kbar, using samples having Ni contents of between 31 and 63at%. A maximum activation volume of 3.9cm3/mol was found at 34at%Ni. The compositional dependence of ΔV was satisfactorily explained by a magnetic-energy continuum model in which it was assumed that the activation free energy for diffusion was essentially ferromagnetic in origin.

J.Keiser, M.Wuttig: Physical Review B, 1972, 5[3], 985–90

Table 131

Activation Volume for C Diffusion in Fe-Ni Alloys