Microstructures and Properties of Functionally Gradient Materials

1.表面涂层的功能梯度材料（FMG）。(1)采用透射电镜（TEM）、电子能谱（EPMA）和x射线衍射（X-ray）研究了C/C复合材料表面TiC/SiC薄膜的结构和界面。通过外延生长，在这些层中存在较强的择优取向。(2)声学显微镜观察到PVD和CVD工艺制备的TiC薄膜在硬质合金WC上的维氏压痕和裂纹形成的差异，SEM断口形貌也能清楚地观察到这些差异。从FGM层的形成改善材料表层性能降解的角度出发，本课题后半段将研究工作集中在超细抛光成品的表面结构上。(1)研究了抛光晶体的各向异性。用透射电镜对铁氧体单晶上的非晶层进行了直接观察。经抛光后产生的单晶铁氧体的表面层深度约为-3mum。(2)分析了不同取向的抛光铁氧体单晶的表面层结构，如非晶层、多晶层和位错结构。(3)目前得到的结果表明，表面层对晶体各向异性的影响可能不利于最有效地利用材料的性能，可以通过覆盖FGM层来消除损伤表面。

1.The functionally gradient materials (FMG) of the surface coating.(1) The structure and interface of TiC/SiC films coated on C/C composite materials were investigated by TEM,EPMA and X-ray diffraction. Strong preferred orientation exists in these layrs by the epitaxial growth.(2) The difference of bonding of TiC films on cemented carbides, WC,fabricated by PVD and CVD processes were clearly observed with the acoustic microscopy of Vickers indentations and cracks initiated from them by the SEM fractography.2.From the viewpoint of the improvement of materials property degradation at the surface layr by the formation of FGM layr, in the later half of the present reseach project, reseach work was concentrated to the surface structure of finished by ultra-fine polishing.(1) The crystal anisotropy for polishing was investigated. The direct observation of the amorphous layr on a ferrite single crystal was succeeded with the TEM.The depth of surface layr of a single crystal ferrite introduced by polishing was estimated about -3mum.(2) The structures of surface layr, such as the amorphous layr, poly crystalline layr and dislocation structures, were analyzed for polished single crystals of ferrite with various orientation.(3) The presently obtained results suggest that the effects from the surface layrs depending on crystal anisotropy, which may be undesireble for the most effective utilization of materials property, may be eliminated by covering the damaged surface with a FGM layr.