The tracer diffusion coefficient of Fe (table 244) and the chemical diffusion coefficient (table 245) in L12-ordered Pt3Fe were measured at temperatures below the order-disorder transition. The diffusion of Fe could be described by:

23.3mol%Fe:     D (m2/s) = 4.21 x 100 exp[-454(kJ/mol)/RT]

25.2mol%Fe:     D (m2/s) = 2.10 x 10-1 exp[-418(kJ/mol)/RT]

26.4mol%Fe:     D (m2/s) = 2.68 x 10-3 exp[-369(kJ/mol)/RT]

and the chemical diffusion could be described by:

D (m2/s) = 1.86 x 10-5 exp[-293(kJ/mol)/RT]

The tracer diffusion coefficient of Fe in a nearly stoichiometric alloy curved upwards, in the Arrhenius plot, upon approaching the order-disorder transition temperature. The chemical diffusion coefficient was some 10 to 30 times higher than the diffusion coefficient of Fe. The tracer diffusion coefficient was affected by the composition: it increased with increasing Fe concentration through the stoichiometric composition, but this trend almost vanished at higher temperatures. The chemical diffusion coefficient was essentially independent of composition. The tracer diffusion coefficient of Pt was estimated from the Darken-Manning relationship. At 1223K, it was between the chemical diffusion coefficient and the tracer diffusion coefficient of Fe.

Y.Nosé, T.Ikeda, H.Nakajima, H.Numakura: Materials Transactions, 2003, 44[1], 34-9

Table 244

Tracer Diffusivity of Fe in Pt3Fe

Table 245

Chemical Diffusivity of Fe in Pt3Fe