关键词： 纤维增强水泥   材料性能   界面微结构  

关键词： 反应生成   陶瓷基复合材料   显微结构  

关键词： Materials  

摘要： Ultrasonic imaging techniques for portraying and evaluating cumulative internal microstructural damage in engineering materials are described. A quantitative delineation of the damage is made in terms of acoustic attenuation obtained from computer analyses of digitized ultrasonic images. Acoustic attenuation data are a basic ingredient in previously developed models of damage processes in materials. The ultrasonic imaging methodology has been developed using filled polymer (inert solid rocket-propellant) samples subjected to progressive uniaxial tensile strain. Successive ultrasonic images taken at various levels of applied strain display dewetting and the evolving microvoid formation/growth which occurs. Both initially intact material and that with pre-existing cracks are of interest. Changes in acoustic attenuation with strain, derived from the processing of digital images, have provided results as to the degree of preferential damage accumulation at sites of filler particle agglomerations appearing on the ultrasonic images. Also, the quantitative extent of an asymmetry in the damage-field distribution near the tips of an extending crack was determined in precracked material. Iso-attenuation type contours generated by computer reveal that kidney-shaped damage zones occur in the neighborhood of the propagating crack tips, reminiscent of the plastic-zone shapes near crack tips in ductile metals under strain. Ultrasonic images of precracked samples show that before crack extension begins, the material damage in the neighborhood of the crack already extends over a relatively large volume of the specimen.

关键词： 水稻抗白叶枯病   超微结构观察   抗病品种   病原菌   抗性品种   白叶枯病菌   育种材料  

摘要： 自1884年发现水稻白叶枯病至今,已有近百年历史,并由亚洲传播到大洋洲、非洲和中南美洲等地区。在我国也几乎传播到所有水稻产区。由于发生地区广泛、为害严重,所以世界各国对此病予以高度重视,并进行了大量科学研究。实践证明选育抗病品种是防治水稻白叶枯病一个经济、省工、收效大的重要措施。

关键词： 微结构损伤   局部化变形   M—K模型   韧性断裂  

摘要： 本文从连续介质损伤力学的基本原理出发,基于新近提出的微孔洞损伤模型和修正的M—K模型,分析了轴对称变形和平面应力变形情况下材料内部微结构损伤对局部化变形的影响,同时也探讨了由于内部损伤引起的材质劣化程度以及试件外截面不均匀度的影响。结果表明材料内部损伤、材质劣化和外截面不均匀在材料局部化变形过程中起着重大的作用。这些因素使极限应变大大降低,断裂过程加速,是导致材料破坏的直接原因。

关键词： 氧化错   单斜相   四方相   氧化铝复合材料   微裂纹   显微结构  

摘要： 近年来,氧化锆增靱的氧化铝材料（ZTA）因其强度和靱性都得到改善而引起广泛重视。对于 ZTA 材料的增靭性能通常认为有二种机理:材料中四方相氧化锆受应力后产生应力诱导相变;已相变的单斜相氧化锆在其周围产生微裂纹增靱;。因此认为最佳的 ZTA 材料是单斜相和四方相氧化锆的混合体;,其目的是利用不同增靱机理来使材料增靱。我们曾研究团聚体氧化锆对陶瓷材料靱性的影响;。

关键词： 沉淀相   离子   Ni   化学成份   Cu   AP-FIM   磁性材料   电工材料   FIM   微结构   土壤结构  

摘要： 场离子显微镜（FIM）是一种具有高分辨高放大倍数且能直接观察到固体表面单个原子的技术,将FIM与飞行时间质谱计配合构成原子探针——场离子显微镜（AP-F;M）可鉴别极微区域（几nm）的化学成份,因此是研究材料微结构的有力工具。本文用AP-FIM研究了Al-Ni-Co永磁材料的微结构。用场离子显微镜观察了合金中沉淀相的形貌并用原子探针测定了不同沉淀相的化学成份及数量合金元素在沉淀相中分布。结果表明,合金中存在富铝相,富镍-钴相铁-钴-镍桐,少量Ce及Cu分布在富镍-钴相中。

关键词： 显微结构   气孔   晶界   晶粒间界   晶体点阵   晶粒   颗粒  

摘要： 对于用烧结方法制备的陶瓷超导体来说,烧结体内部显微结构的控制,是获得稳定性能的关键。为此,日本东京工业大学的水谷惟恭撰文介绍了晶粒直径控制、晶界设计等新的陶瓷制造技术他认为:烧结陶瓷的性能是由四个要素决定的,即构成显微结构的晶粒,晶界、气孔和二次相。晶粒直径控制是显微结构控制之一。若改变烧结体的晶粒尺寸,则很多性能会同时发生变化,如磁性,光学性能,热性能

关键词： METALLOGRAPHY  

摘要： A new experimental set-up combining X-ray topography and microbeam diffraction has been designed for the investigation of heterogeneous microstructures with features in the size range of more than 50μm. Built around a four-circle goniometer of 5/1000° angular resolution, this apparatus offers similar facilities to those obtained by TEM but at a different scale. In the Berg-Barrett position, grain and subgrain boundaries can be observed over large surface areas (typically 100 mm²). Based on topography observations, areas of interest of typically 100μm diameter can be precisely selected for microdiffraction measurements. A laser beam directed through the pinhole system of the X-ray microbeam collimating system permits one to directly visualize the irradiated zone. The divergence of the X-ray microbeam is typically 0.034° (full width at half maximum) and permits the measurement of lattice spacing variations (Δa/a) of the order of 10^?4. While TEM permits one to examine very localized areas, this new device is appropriate to detect long-distance effects and phase interactions in materials with coarse distributed heterogeneities. In order to demonstrate the versatility of this new device, the orientation distribution, variation of lattice spacing and mosaic structure of dendrites in directionally solidified nickel-base alloys are analysed.