多相拡散対における中間相の層成長速度の律速因子と近似式

Abstract

Kidson’s simultaneous equations describing positions of phase boundaries in a multi-phase diffusion couple were numerically solved for various diffusion conditions. Based on the calculated results, the relation between layer growth rates of intermediate phases and the three controlling factors pointed out by Seith, i.e., interdiffusion coefficient, solubility range of each phase and miscibility gap between adjacent phases, was examined in detail.There exists an obvious quantitative relation between the layer growth rates of intermediate phases and the interdiffusion coefficients \ ildeD or the solubility ranges ΔN. Between the layer growth rates and miscibility gaps, however, such a distinct relation can not be found. If the miscibility gap is excluded from the factors controlling the layer growth rates of intermediate phases, the average composition within each phase N may be regarded as an alternative factor.Effect of these factors including the average phase composition on the layer growth rates of intermediate phases should be evaluated synthetically. It is concluded that any intermediate phase formed in a multi-phase diffusion couple grows more rapidly as the value of ΔN\ ildeD⁄{N(1−N)}2⁄3 becomes greater. The ratio of layer growth rates between the two given intermediate phases can be approximately expressed in terms of the ratio of the above value.