Temperature Dependence of Self-Diffusivities in B2-Type Intermetallic Compounds

Temperatur dependence of the self-diffusivities in B2-type intermetallic compounds has been investigated. The self-diffusivities plotted against the inverse of temperature normalized by the solidus temperatures, Tf, show that the activation energy, Q, is related to T f by Q = (19 8)RTf B2 J/mol, and the pre-exponential factor, D 0 , is in a certain range, D 0 = " 2 ~ 10" 6 mV. However, the results of CuZn, which have the order-disorder transformation below solidus temperature, are out of range of a large number of data. The hypothetical T 0 temperature between the ordered and liquid phases, T 0 B2 , is evaluated from thermodynamic consideration, which reveals that the temperature dependence of the self-diffusivity of CuZn replotted against T 0 B2 /T shows a tendency similar to that of other B2-type intermetallic compounds. The relationship between the activation energy of self-diffusion and the enthalpy of fusion of the ordered phase is also discussed.