The diffusion of 63Ni and 114mIn in the intermetallic L12 phase Ni3Al is measured in the temperature range from 900 to 1200 °C and for compositions between 73.5 and 77 at% Ni in steps of 0.5 at%. The In isotope serves as a substitute for 26Al. The usual serial sectioning method is applied using a precision parallel grinder. There is only a weak concentration dependence of the diffusion coefficient at temperatures > 950 °C but it gets stronger with decreasing temperature. There is a minimum of the diffusion coefficient at 76 and not at 75 at% Ni as may be expected. The diffusion of 63Ni in Ni3Al and in pure Ni is comparable. The same is true for the diffusion of 114mIn in Ni3Al. Very likely the diffusion of 63Ni is by a normal vacancy mechanism and the diffusion of 114mIn by In antisite atoms in the Ni sublattice. The D 0*‐values are for In (and probably for Al as well) considerably higher than for Ni. This could be due to a higher entropy term. As a consequence of the considerably larger D 0*‐values of In an intersection of the two linear Arrhenius plots for Ni and Al is observed at about 950 °C for all concentrations except Ni76Al24. This fits well to interdiffusion investigations where at higher temperatures Al is found to be the faster component, and Ni at lower temperatures.

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Once again an attempt is made to quench‐in vacancies in very pure iron (< 0. 5 at ppm C). This is achieved with a quenching rate of 1.5 × 104 K/s and an iron wire with a diameter of 100 μm. The recovery begins at 380 K and continues up to stage IV. An annihilation in stage III cannot be observed. This result can be interpreted with vacancy–C pairs — formed above 380 K with the residual content of carbon — and a following dissociation of the pairs and an annihilation of the vacancies at sinks up to temperatures of 600 K. Such an interpretation assumes the validity of the “two interstitial model” (TIM) and a formation enthalpy of the V–C pairs of ≧4 eV. The possibility of precipitation of the residual carbon in the form of graphite is discussed.

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