The application of the bifurcation theory to the microstructure changes and its stability.

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Several interesting phenomena for the formation of microstructure have recently been observed when the alloys, ceramics and semiconductors are elastically constrained. Particularly, the extraordinary behavior in the precipitate coarsening ; deceleration of particle coarsening, stopping the particle coarsening and splitting of a particle into plural small particles are typical examples. These phenomena have theoretically supported by "bifurcation diagram", proposed by us. In the practical point of view. This phenomena imply an existence of non-over ageing work is to get even if heated at high temperature for atom to diffuse. The purpose of the present work is to get a more wide range of experimental examinations and also to give more accurate theoretical back ground.The results obtained for this academic years are as follows.(1)Hitherto the splitting of a particle was recognized in Ni-base and Iron-base alloys such as Ni-A1, Ni-Si, Fe-A1-Co and so on. However, the splitting behavior bet … More ween the Ni-base alloys and Iron-base ones was different. The shape changing rate of splitted particles was remarkably fast in Iron base alloys.(2)In the Fe-Si-V system which has a large eigenstrain, the uniformalization of particle size, the deceleration of particle coarsening and particle alignment to <100> direction were experimentally recognized. Especially these behaviors become dominant as the volume fraction of precipitates increase. Inevitability of such the characteristic coarsening is theoretically discussed on the bifurcation diagram.(3) Kinetic path calculated for the precipitate nucleation process was consistent with minimum-energy path predicted by the theory of the system free energy proposed by us. This result indicates that the energy analysis is very useful even for the early stage of the phase decomposition. Therefore we calculated the time developmence of particle coarsening on the base of the energetic estimation. As the calculation results, more accurate behavior of the particle coarsening in elastically constrained systems is obtained. Less