析出強化型合金における組織粗大化と弾性エネルギ-の関連性の追究

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1. In weakly constrained systems such as gamma^' particles in Ni-Si-Al alloy, precipitate coarsening obeys the theories of Ostwald ripening: the mean particle size is proportional to the cube root of the ageing time t, that is, the so-called t^<1/3> law holds, and the size distribution of particles can be scaled with respect to the mean particle size.2. In strongly constrained systems such as gamma^' particles in Ni-Cu-Si and Ni_4Mo particles in Ni-Mo alloy, unusual coarsening behaviors are observed: coarsening is remarkably decelerated and the particles become uniform in size during the later stage of ageing.3. Such unusual behavior in strongly constrained systems cannot be explained by the conventional theories of Ostwald ripening but can clearly be explained by the new coarsening theory named Bifurcation theory. In the Bifurcation theory, not only the surface energy but also the elastic energies (especially the elastic interaction energy) are taken into consideration as the driving force for coarsening.4. In Feーbase ordering alloys, coarsening behaviors of coherent precipitates are similar to those in the Niーbase alloys: in weakly constrained system, coarsening proceeds obeying the conventional theories of Ostwald ripening; in strongly constrained systems, coarsening is remarkably decelerated and the particle sizes become uniform. These behaviors are explained by the Bifurcation theory.