关键词： Fiber reinforced plastics  

摘要： This work deals with the AC electrical properties measurements under large strain of composites strongly contrasted in the viewpoint of their electrical and mechanical properties. First, the possibility to model a strongly heterogeneous material (from the viewpoint of electrical properties) using an improvement of a RC-type model is explored;this model relates the R and C values to the geometrical characteristics of the network of reinforcing fibres. Secondly, a powerful method is developed to characterize the filler rearrangement by measuring the electrical properties. It is concluded that the evolution of the real part of the conductivity is related to the damage of the percolating network, whereas the imaginary part of the conductivity reflects the global rearrangement of the filler in the matrix under large strain.

关键词： Plates (structural components)  

摘要： Based on the thin laminate plate theory, new material parameters introduced in the coupled stress theory are investigated. The constitutive relations for the coupled stress theory are discussed and its special form with a transverse symmetry are applied to describe the constitutive relations of a thin plate element. Their relations with microstructural parameters are provided through a micro-macro homogenization in a thin plate element, representative volume element (RVE).

关键词： 原位反应   SiC   TiSi2   纳米复合材料   显微结构  

摘要： 采用Si粉和TiC为原料，通过反应热压可制得纳米SiC粒子复合的TiSi2材料，生成的纳米SiC粒子聚集分布在TiSi2基体中，SiC粒子与TiSi2的界面没有晶界相存在．但由于残余应力的作用．TiSi2晶格发生扭曲并有位错出现。

关键词： 蠕变行为   显微结构   活化能   耐火材料  

摘要： 本文论述了蠕变行为和相应粘结相的显微结构特征之间的关系,并分析了蠕变机理同时列出各种耐火材料的蠕变活化能。

关键词： 二硅化钼   碳化硼   显微结构   力学性能   复合材料  

摘要： 研究了在热压过程中ＭｏＳｉ２ 与Ｂ４Ｃ反应合成的硅化物与硼化物复合材料的显微结构及力学性能．结果表明，得到的复合材料以ＭｏＳｉ２，Ｍｏ２Ｂ５ 为主要组成相．复合材料的力学性能较纯ＭｏＳｉ２ 有较大改进．当Ｂ４Ｃ 添加量ｗ ＝ １０％ 时，σｂ 及ＫＩＣ均达到最大值，分别为３８０ＭＰａ 和３．９ＭＰａ·ｍ １／２，复合材料的硬度值则随添加量增加而增加．

关键词： Metallographic microstructure  

摘要： A certain degree of cold working is advantageous in developing a fine microstructure with minute silicon crystals for eutectic and/or hypereutectic Al-Si cast alloys. A novel process, repeated thermomechanical treatment (RTMT), was applied to an Al-12.6 wt pet Si cast alloy. The process involves multiple-pass cold working (less than a 20 pet reduction in section area) and heat treatment at 793 K for 3.6 ks. Cold-work annealing was repeated up to about an 80 pet reduction in section from the beginning. The RTMT material showed a refined microstructure with high ductility. Most silicon crystals were fragmented to only a few micrometers and were spheroidized. The RTMT material showed such marked plasticity that it could be wrought up to a 99 pet reduction in section at room temperature. The Cold-worked RTMT materials exhibited an excellent balance between tensile strength and elongation and a higher strain hardening than the cast material.

关键词： Crystal microstructure  

摘要： Upon extrusion of SiO2-B2O3-Al2O3-MgO-Na2O-K2O-F- glasses, mullite-aluminium berate solid-solution crystals become aligned with their elongated axes parallel to the extrusion direction. During subsequent heat treatments, fluorophlogopite platelets crystallize in part epitaxially on these solid-solution crystals. As shown by texture goniometry and electron microscopy, an orientation of mica basal planes either parallel or perpendicular to the extrusion direction is indicated. Using selected-area electron diffraction in a transmission electron microscope, epitaxial orientation relationships between the lattices of the fluorophlogopite and the solid-solution crystal are determined. The combination of texture formation and epitaxial growth opens new ways of microstructural design in extruded glass-ceramics. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Lid. All rights reserved.

关键词： GaN   蓝色发光材料   电子显微结构  

摘要： 该论文主要是对分子束外延(MBE),低压金属有机化学气相外延(LPMOVPE),金属有机化学气相沉积(MOCVD)生长的GaN/Al<,2>O<,3>(0001)薄膜进行了透射电子显微学研究.

关键词： permanent magnet materials   Lorentz microscopy   transmision electron microscopy  

摘要： Transmission electron microscopy has been used to study the physical and magnetic microstructures of thinned sections of four different NdFeB-type alloys. Three of the materials were prepared by the solid-HDDR process and differed in that one was a simple ternary alloy, another contained Co & Ga additions and a third was appreciably richer in Nd than stoichiometric Nd2Fe14B1. For the fourth material HDDR powder had been hot-pressed into a fully dense compact prior to die-upsetting. Isotropic grains with a mean size approximate to 300 nm were found for the first three materials whilst the die-upset material had an average grain size of approximate to 300 x 700 nm(2). All materials other than the simple ternary alloy showed strong alignment of the c-axis, the clustering of grains with similar alignment being most pronounced in the sample with Co & Ga additions. The sample with the largest region of alignment was the die-upset material, the c-axis orientation being approximately parallel to the pressing direction throughout. It was in this sample that magnetic alignment was found to be most extensive, the domains lying parallel to the mean c-axis across the whole of the visible area. Significant magnetic alignment was also found in the sample with Co & Ga whilst the Nd-rich material had relatively small areas of magnetic alignment. In the three samples with good crystallographic alignment local variations in domain wall orientation between neighbouring grains within an aligned region showed maximum variations that corresponded with the angular spread of spots in the selected area diffraction patterns. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： 微型电子机械系统   微型机械   纳米机械   尺寸范围   小型机械   微型化   机械工程   微小   划分   广义  

摘要： 在微小尺寸范围内,将机械可划分为1～10mm的小型机械,1μm～1mm的微型机械,以及1nm～1μm的纳米机械。所谓微型电子机械系统(Micro Electro Mechanical System,MEMS),从广义上包含小型、微型和纳米机械,但并非机械的单纯微小化,它集微型机械、