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Online ISSN : 1347-5320
Print ISSN : 1345-9678
Influence of Temperature Dependence of Solubility on Kinetics for Reactive Diffusion in a Hypothetical Binary System
Masanori Kajihara
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2008 Volume 49 Issue 4 Pages 715-722

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Abstract

Influence of temperature dependence of solubility for each phase on kinetics of reactive diffusion has been theoretically analyzed for a hypothetical binary system consisting of two primary solid-solution phases (α and γ) and one compound phase (β). For the analysis, we consider that the β phase is produced owing to the reactive diffusion between the α and γ phases in a semi-infinite diffusion couple and the growth of the β phase is controlled by volume diffusion. In such a case, the parabolic relationship holds good between the thickness l of the β phase and the annealing time t as follows: l2=Kt. Here, the parabolic coefficient K is mathematically expressed as a function of the interdiffusion coefficients and the solubility ranges of the α, β and γ phases. The temperature dependencies of the parabolic coefficient K, the solubility range Δyθ and the interdiffusion coefficient Dθ of the θ (θ=α,β,γ) phase are described by Arrhenius equations of K=K0exp(−QKRT), Δyθy0θexp(−QθRT) and Dθ=D0θexp(−QDθRT), respectively. The analysis indicates that QK is close to QDβ+Qβ at QDβQDα and QDβQDγ but greater than QDβ+Qβ at QDβ>QDα or QDβ>QDγ. As a consequence, the temperature dependency of the parabolic coefficient is directly related with those of the interdiffusion coefficient and the solubility range of the compound phase in the former case but not in the latter case.

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© 2008 The Japan Institute of Metals and Materials
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