Douxing LI and Hengqiang YE (Laboratory of Atomic imaging of Solids
,
Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang
,
110015
,
China)
材料科学技术（英）
The present paper summarizes the current status of high resolution electron microscopy (HREM)and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction,subnanometer level analysis, image simulation and image processing.
关键词:
LIU Guoquan Department of Materials Science and Engineering
,
University of Science and Technology Beijing
,
100083
,
China.
材料科学技术（英）
Quantitative analysis of populations having a geometric structure,which has developed into a special scientific subject called microstructology or stereology,is of great importance to the characterization and evaluation of microstructures and their evolution in various processes.This paper, besides a brief discussion on those topics such as the recent developments of computer assisted image analysis,mathematical morphology,and fractal analysis,will mainly focus on the scope,fundamen- tals,present status,and perspectives of classical stereology.Several case examples of its application to materials science will also be given.
关键词:
stereology
,
null
,
null
,
null
Journal of Applied Physics
The dependence of yield strength, uniform elongation, and toughness on grain size in metallic structural materials was discussed. The toughness is defined as the product of yield strength and uniform elongation. The yield strength versus grain size can be well described by the Hall-Petch relation; however, the uniform elongation versus grain size is not well understood yet. A simple model involving the densities of geometrically necessary dislocations and statistically stored dislocations was proposed to estimate the uniform elongation versus grain size. Existing data for low carbon steels and aluminum indicate that, in the grain size less than 1 mu m, the materials usually exhibit high strength and low uniform elongation and, in the grain size greater than 10 mu m, the materials usually exhibit low strength and high elongation; in either case the toughness is low. However, in the grain size of several micrometers, the toughness is the highest. It is suggested that we should pay more attention to develop the metallic materials with grain size of several micrometers for structural applications. (c) 2007 American Institute of Physics.
关键词:
nanocrystalline copper;nanostructured metal;steels;deformation;ductility;law
Fatigue & Fracture of Engineering Materials & Structures
Fatigue data for welded joints subjected to an explosion treatment (ET) were obtained using rotary bending fatigue specimens. The fatigue fracture surfaces were observed by SEM and the dislocation morphologies by TEM. Mechanical properties have been quantitively studied by considering elastic and plastic shock wave characteristics. The test results indicate that the fatigue strength of welded joints subjected to ET is apparently improved due to the action of elastic or plastic stress waves while the ductility of the welded joints, i.e., reduction in area, is greatly increased.
关键词:
Transactions of Nonferrous Metals Society of China
Based on the simplified structure model of high porosity materials, the formulas for approximately evaluating the tensile strength of these materials have been derived from the corresponding deductions taken by means of the relative theories about geometry and mechanics. The results show that, the tensile strength of these materials not only associates with the material sort and production method, but do further have a direct value relationship with the porosity, theta. This value relationship can be specifically expressed by the power of the item (1 - theta), and it makes the tensile strength variation display a complicated nonlinear law with the porosity. In addition, the application of those formulas has been investigated with the corresponding experiment on a nickel foam.
关键词:
high porosity material;tensile strength;evaluation
N.V.Ch
,
ra Shekar
,
P.Ch.Sahu
,
K.Govinda Rajan
材料科学技术（英）
Laser-heated diamond-anvil cell (LHDAC) is emerging as the most suitable, economical and versatile tool for the measurement of a large spectrum of physical properties of materials under extreme pressure and temperature conditions. In this review, the recent developments in the instrumentation, pressure and temperature measurement techniques, results of experimental investigations from the literature were discussed. Also, the future scope of the technique in various avenues of science was explored.
关键词:
Laser heating
,
null
,
null
,
null
Applied Physics Letters
We report high strength reliability under tension of a bulk metallic glass (BMG), demonstrated by its high uniformity in strength found over a statistically significant number of specimens, despite the fact that the samples all showed no macroscopic plasticity. Weibull statistical analysis showed that the Weibull modulus of the material is 36.5, which is much higher than the values of more typical brittle materials, further confirming BMGs' high reliability [Appl. Mech. Rev. 5, 449 (1952)]. (c) 2008 American Institute of Physics.
关键词:
plasticity;alloys;temperature;brittleness;estimators;fracture;stress
