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[en] Studies dealing with TRIP-assisted multiphase steels have emphasized the crucial role of the bainite transformation of silicon-rich intercritical austenite in the achievement of a good combination of strength and ductility. The present work deals with the bainite transformation in two steels differing in their silicon content. It is shown that both carbon enrichment of residual austenite and cementite precipitation influences the kinetics of the bainite transformation. A minimum silicon content is found to be necessary in order to prevent cementite precipitation from austenite during the formation of bainitic ferrite in such a way as to allow stabilisation of austenite by carbon enrichment. (orig.)
[en] Many crystalline materials of interest to the Canadian Nuclear Program have the potential to undergo phase transitions in their range of application. During such phase transitions, a representation of the space group of the higher symmetry polymorph softens to induce the transition. This report is the first in a series of reports concerned with the group-theoretic properties of phase transitions in crystalline materials. The object of the research is to identify all spectroscopically-active soft modes for the 230 three-dimensional space groups. Identification of these soft modes will enable a detailed examination of phase transitions in materials of interest to the Canadian Nuclear Program and aid in the optimization of material properties. In this report, the group-theoretic properties of crystal structures and phase transitions are reviewed. It is demonstrated that the problem of extending a group reduces to that of determining its automorphisms. The automorphism groups of the crystallographic and icosahedral point groups are derived using a consistent presentation
[en] Soon after the innovation of the magnetic fluid (Mf), it was found that needle like agglomerates (macro-clusters) were generated in some kind of MFs under an external magnetic field by optical microscope observation. However, the macro-clusters disappeared when the external field was removed. Therefore, many theories were proposed whether or not macro-clusters were simple precipitants of the colloidal particles, or one phase of the two-phase separation, or etc. On the other hand, MFs under an external magnetic field show many peculiar and interesting phenomena in acoustics and magneto optics In order to interpret these peculiar phenomena, an assumption that submicron-order agglomerates of the colloidal particles elongated along the field direction (micro-clusters) was necessary. However, this assumption contradicted the MF's phase transition of second order between the particles monodispersed phase and the phase in which the agglomerates were generated (Landau criterion). In this paper, first, the macro-cluster's nature is explained. The experimental results of the time dependence of the Mf shaft seal's burst pressure, the MF's acoustic properties and magneto-optical effects are explained followed by explaining the necessity of micro-cluster assumption. Proton-NMR experiment of the water-solvent Mf and the latent heat measurement of the Mf phase transition by differential scanning calorimetry are explained. The conventional Mf and 1000-fold diluted Mf were used for the magnetization curve measurement, temperature and Ac magnetic field frequency dependence experiment of the initial complex spastically measurement and frozen MF's magnetic aftereffect experiment. From these experiments, the magnetic colloidal particles interaction in the Mf is discussed. Finally, we show a physical model that the excess surfactant molecules which are isolated and freely dissolved in the MF's solvent make special micelles when the temperature is decreased or the external magnetic field is applied. The magnetic colloidal particles stick to the suffice of the micelles and this applied. The magnetic colloidal particles stick to the surface of the micelles and this micelle with the colloidal particles is the actual micro-cluster. We show that this special micelle model explains all the MF's peculiar phenomena without any contradictions, especially the contradiction between the anisotropic al agglomeration and Landau criterion with respect to the phase transition of second order. (author).