The application of the bifurcation theory to the microstructure change 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-overaging materials 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 experimental results obtained for this academic year are written below.(1) Hitherto the splitting of particle was recognized in Ni-base alloys such as Ni-Al, Ni-Si and so on. However, the splitting has first been observed in I … More ron base Fe-Al-Co ternary alloys. This examination fact clearly shows that the splitting of particles is not special but common in the elastically constrained system.(2) In the Fe-Al-Ge system which has a small eigenstrain the precipitates increase their sizes L with aging time t in accordance with LSW theory, that is L=k ・t^<1/3>. In the Fe-Al-V system having a large eigenstrain, however, the uniformalization of particle size and the deceleration of particle coarsening were experimentally recognized. Inevitability of such the characteristic coarsening is theoretically discussed on the basis of the bifurcation diagram.(3) New parameters showing the 3-dimensional distribution of particles are introduced to classify the microstructures(4) In the conventional bifurcation disgrain the microstructure consisting two particles vas adopted as the most simple case of the many body microstructure. In this research, the many body microstructure is taken into the calculation of bifurcation diagram so as to analyze more accurate behavior of the particle coarsening. Less