Fe-Mo系における相互拡散および反応拡散

Abstract

Interdiffusion and reaction diffusion in the Fe-Mo system were studied in the temperature range between 800 and 1400°C with diffusion couples of pure Fe/pure Mo and pure Fe/Mo alloy.Formation of three intermediate phases, ∈, R, and σ, were observed in the diffusion zone. However, the Laves phase, λ, could not be found. The layers of three intermediate phases were found to grow according to the parabolic law showing that the growth was by a diffusion process. The interdiffusion coefficients in the intermediate phases were also determined applying Heumann's method. Quantitative correlation between the activation energy for the layer growth determined by the temperature dependence of the rate constant and that of the interdiffusion was found in each phase.The interdiffusion coefficient in the α phase determined by the Matano analysis was found to decrease with increasing Mo content, at each temperature. The interdiffusion coefficient in the γ phase, Dγ, could be estimated from the interdiffusion coefficient in the α phase and the growth rate of the α phase and it was found that the temperature dependence of Dγ showed the Arrhenius relationship.The Kirkendall effect was observed in the diffusion couple of Fe-3.0at%Mo and Fe-7.0at%Mo alloys in the temperature range between 1100 and 1300°C, and it was found that the markers moved toward the Mo rich side. Deviation of the γ-loop determined by the concentration distribution in the diffusion couple from that in the equilibrium phase diagram was observed and turned out difficult to be quantitatively investigated at the present stage.