Mo中のFeの不純物拡散

Abstract

The residual activity technique was employed to determine the impurity diffusion coefficients of Fe59 in Mo in the temperature range of 1000 to 1350°C. The diffusion coefficient at 1350°C was 1.2×10−12 cm2/sec, which was larger than the value for the impurity diffusion coefficient of Co in Mo obtained by Peart et al., but smaller than any value for the impurity diffusion coefficient of Fe in refractory metals as Nb, Ta and W at the corresponding temperature. It was found that the temperature dependence of Fe59 diffusivity in Mo showed the Arrhenius relationship, DFe→Mo=(0.15+0.09−0.06)exp(−82.7±1.9⁄RT) cm2/sec, and no anomaly as in the impurity diffusion of Fe in β-Ti was observed. The activation energy for the diffusion of Fe in Mo was found to be smaller than that for the self-diffusion in Mo by about 10 kcal/mol. This trend holds in case of the impurity diffusion of Fe in the refractory metals such as Nb, Ta and W. The size effect appears to be important for the impurity diffusion of Fe in those metals, and the above trend may be tentatively explained by the small atomic radius of Fe with respect to those of such other elements. Using Swalin’s model, the activation energy for the impurity diffusion of Fe in Mo was calculated to be 84.4 kcal/mol, which was in good agreement with the experimental value. The empirical equation, lnD0=0.12Q−11.6, was obtained by the data on the self-diffusion of Mo, Nb, Ta and W the impurity diffusion of Fe and the other elements in these metals.