B. Z. Bai X.J.Sun and L.Y.Yang 1) Department of Materials Science and Engineering
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Tsinghua University
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Beijing 100084
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China 2) Beijing Research Institute of Mechanical and Electrical Technology
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Beijing 100083
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China
金属学报(英文版)
Gleeble1500 thermo-mechanical simulation machine is considered to be the first grade equipment in materials' research. However, it is seldom used in superplastic research. Perhaps this is because its specimen's heating method is not suitable to get large elongation. Elongation is an important parameter to evaluate superplasticity, but some other parameters such as the relationship between stress and strain rate are more important than elongation-it is an essential property to superplasticity. The stress-strain rate relationship can be very easily and very accu- rately got with Gleeble machine than with some other simlar equipment, and the relationship between microstructure and superplastic deformation is more easily examined with Gleeble. Present authors have got some new achievement in anisotropy, heterogeneity of superplastic deformation, and first put forward the regulation of dynamic equilibrium in microstructural evolution during superplastic deformation. All of these have been concluded from the experimental results mainly through Gleeble as well as the microstructural examination.The research work has got the support of National Natural Science Foundation and some international cooperation. Some theoretic and experimental results have been used in the practice of superplastic forming. Obvious effect of reducing cost and improving quality of formed parts has been achieved.
关键词:
thermo-mechanical simulation
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null
Applied Physics a-Materials Science & Processing
The Pr(1+x)Ba(2-x)Cu(3)O(7+/-delta) solid solution was investigated by means of X-ray powder diffraction combined with Rietveld analysis. A Pr123 single phase could be synthesized under Pr-rich conditions by sintering at 950 degreesC in air. The solubility range of Pr(1+x)Ba(2-x)Cu(3)O(7+/-delta) solid solution is 0.08 less than or equal to x less than or equal to 0.80. The structure of Pr(1+x)Ba(2-x)Cu(3)O(7+/-delta) for 0.08 less than or equal to x less than or equal to 0.30 is orthorhombic. The structure transforms into tetragonal for 0.30 less than or equal to x less than or equal to 0.80. To form the Pr123 single phase, the Ba sites in the Pr123 structure must have partial Pr ions, and the least amount is x = 0.08. Ba ions cannot occupy the sites of Pr ions. In the Pr123 structure, Ca ions can replace Pr ions; the highest value is x = 0.4 in the PrBa(2-x)Ca(x)Cu(3)O(7+/-delta) system under our experimental conditions. However, Ca ions cannot replace B a ions. The ionic radius plays a more important role than the chemical properties in the substitution between Pr, Ba and Ca ions in the Pr123 structure.
关键词:
cu-o system;approximately 950-degrees-c;superconductivity;diagram;pr;growth;nd;prba2cu3o7-delta;praseodymium;property
Andrej Atrens
材料科学技术（英文）
Corrosion research by Atrens and co-workers has made significant contributions to the understanding of the service performance of engineering materials. This includes: (1) elucidated corrosion mechanisms of Mg alloys, stainless steels and Cu alloys, (2) developed an improved understanding of passivity in stainless steels and binary alloys such as Fe-Cr, Ni-Cr, Co-Cr, Fe-Ti, and Fe-Si, (3) developed an improved understanding of the melt spinning of Cu alloys, and (4) elucidated mechanisms of environment assisted fracture (EAF) of steels and Zr alloys. This paper summarises contributions in the following: (1) intergranular stress corrosion cracking of pipeline steels, (2) atmospheric corrosion and patination of Cu, (3) corrosion of Mg alloys, and (4) transgranular stress corrosion cracking of rock bolts.
关键词:
Stress corrosion cracking
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null
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null
LIU Guoquan Department of Materials Science and Engineering
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University of Science and Technology Beijing
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100083
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China.
材料科学技术（英文）
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
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null
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null
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null
Ieee Transactions on Magnetics
The spin orientation and spontaneous magnetostriction of multicomponent TbxDy1-x-yPry(Fe0.9B0.1)(1.93) (0.10 less than or equal to x less than or equal to 0.25, 0.30 less than or equal to y less than or equal to 0.60) Laves phases were studied by step-scanning their (440) X-ray diffraction lines. The easy magnetization direction (EMD) of the Laves phases changed from the (100) to (111) axis when x was increased from 0.10 to 0.25. With increasing y, the EMD of Tb0.15Dy0.85-yPry(Fe0.9B0.1)(1.93) and Tb0.2Dy0.8-yPry(Fe0.9B0.1)(1.93) Laves phases reoriented from the (100) to (111) axis. The magnetostriction coefficient lambda(111) of TbxDy1-x-yPry(Fe0.9B0.1)(1.93) Laves phases increased with increasing x (or y) when y (or x) was kept constant.
关键词:
Laves phases;magnetostriction;spin orientation;X-ray diffraction;anisotropy compensation;alloys
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element, composed of two layers of helically wound fiber, was suggested. To detect the structural characteristics of such a microstructure, four types of macro fiber specimens made of engineering composites were employed: axially aligned solid and hollow cylinders, and single- and double-helical hollow cylinders. These specimens were subjected to several possible loadings, and the experimental results reveal that only the double-helical structural unit possesses the optimum comprehensive mechanical properties. An interlaminar transition zone model imitating bamboo bast fiber was proposed and was verified by engineering composite materials. In our work, the transition zone can increase the interlaminar shear strength of the composite materials by about 15%. These biomimetic structural models can be applied in the design and manufacture of engineering composite materials.
关键词:
bamboo;bast fiber;biomimetics;engineering composites
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
