Crystallographic study on phase transformation and artificial interface in ceramics

由于陶瓷和金属间化合物的性能在很大程度上取决于其微观结构，因此它们的相分解过程和相平衡已被研究。在本研究中，对显微组织的形貌和晶体学进行了广泛的研究，并阐明了显微组织演变的机制。机械合金化Mo-HfC或Mo-TiC复合材料中高温区碳化物和/或氧化物沉淀的机理，杂质对氧掺杂硅中氧化物形成的影响，氧化物沉淀法净化硅的机理，TiAl基金属间化合物的相分解和相平衡机理，添加Cr、Zr或Mo对Ti-Al二元合金中β相稳定性的影响，三元Ti-Al-X合金中β相的分解机理，氮化物和/或碳化物形核对低碳钢中初生铁素体形成的影响，研究了不同元素对高铬钢相分解和相平衡的影响、人体用钛基材料相分解和相平衡的机理、铝合金的时效过程以及各种金属间化合物的形成过程，并对界面结构进行了分析，通过对陶瓷和合金相平衡和相分解的晶体学分析，阐明了析出相是控制析出相尺寸分布和析出相各向异性的主要因素。它的结论是，晶体学分析的相变和平衡是必不可少的，以控制材料的性能。

The phase-decomposition processes and -equilibria in ceramics and intermetallics have been investigated, because their properties depend largely on the microstructures. In the present investigations, the morphology and crystallography of the microstructures have been extensively examined, and the mechanisms for the microstructure evolutions have been clarified.Details in the present investigations are as follows ; the mechanisms of carbide and/or oxide precipitation in mechanically alloyed Mo-HfC or Mo-TiC composite materials in high-temperature regions, the effects of impurities on oxide formation in oxygen-doped silicon, the mechanism of purification of silicon by the oxide-precipitation, the mechanisms of phase-decomposition and -equilibria in TiAl-based intermetallics, the effects of addition of Cr, Zr or Mo to Ti-Al binary alloys on the stability of β phase, the mechanism of the β phase decomposition in the ternary Ti-AI-X alloys, the effects of nitrides and/or carbide nucleation on formation of primary ferrite in low C steels, the effects of addition of various elements on phase-decomposition and -equilibria in high Cr steels, the mechanism of phase-decomposition and -equilibria in Ti-based materials for human being, the aging processes in Al alloys, and the formation processes of various intermetallic compounds.The structures of interphase interfaces have been examined, and clarified to be dominant factor controling size distribution of precipitates and precipitation anisotropy by the crystallographic analyses for phase-equilibria and -decomposition in ceramics and alloys. It is concluded that crystallographic analyses for phase-transformation and -equilibrium are indispensable to control the material properties.