抄録
The self-diffusion coefficients of nickel in the austenitic phase of steels containing 2.5, 3.5, 7 and 9 wt% of nickel were investigated in the temperature range from 900° to 1300°C by the auto-radiographic method with 63Ni as the tracer. Because of the difficulty of grain growth treatment in these commercial steels, the grain size of specimens was only 0.1 to 0.3 mm. Then the volume diffusion coefficient and the grain boundary diffusion coefficient were determined by Suzuoka’s self-consistent method based on the instantaneous source model.
For volume diffusion, the frequency factors were (This article is not displayable. Please see full text pdf.), and the activation energies were 56.8±1.4, 54.9±2.3, 49.4±3.1 and 46.7±1.4 kcal/mole for steels containing 2.5, 3.5, 7 and 9 wt% of nickel, respectively. From these data, the relation between the activation energies and the logarithm of the frequency factors was considered to be linear.
For grain boundary diffusion, neither activation energies nor frequency factors could be correlated with the nickel content. Therefore, the average grain boundary diffusion coefficients for these steels could be represented by (This article is not displayable. Please see full text pdf.) for the frequency factor and 30.9±1.8 kcal/mole for the activation energy, respectively.
