C.B. Xiao
,
Y.F. Had and X.A. Zhang (Cast Superalloys Lab.
,
Beijing Institute of Aeronautical Materials (BIAM)
,
Beijing 100095
,
China)
金属学报(英文版)
The effect of different amounts of silicon on the microstructure of the yttrium modified Ni3Al base alloy IC6 was studied with transmission electron microscope (TEM). The chemical compositions of phases formed due to the presence of silicon and yttrium were analyzed with energy dispersive spectrum(EDS) technique of electron probe microstructural analysis (EPMA). The results showed that a bulk shape phase rich in Mo and Si was formed in the alloys with addition of 0.10-0.20wt%Si and 0.12wt%Y, and that a needle like phase named Y-NiMo was precipitated in the interdendritic area in the alloy with addition of 0.30wt%Si and 0.12wt%Y besides the formation of the bulk shape phase mentioned above. The stress rupture properties under 1100℃/80MPa and the thermal fatigue properties at 1100℃ were improved by adding 0. 12wt%Y but decreased by adding 0.10-0.30wt%Si and 0.12wt%Y. The addition of 0. 10-0.20wt%Si and 0.12wt%Y has no obvious influence on the tensile properties of alloy IC6 at room temperature (R. T.), 760, and 900℃, respectively.
关键词:
silicon
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null
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null
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null
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null
QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
,
Beijing
,
China
金属学报(英文版)
The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.
关键词:
stress corrosion cracking
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null
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null
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G.Q. Zhang
金属学报(英文版)
The status of research, development of superalloys and materials processing & fabrication technologies for aero-engine applications in China Aviation Industry, with an emphasis on recent achievements at BIAM including directionally solidified and single crystal superalloys for blade and vane applications, wrought superalloys for aero-engine disks and rings, and powder metallurgy (PM) superalloys for high performance disk applications were described. It was also reviewed the development of new class of high temperature structural materials, such as structural intermetallics, and advanced material processing technologies including rapid solidification, spray forming and so on. The trends of research and development of the above mentioned superalloys and processing technologies are outlined. Cast, wrought and PM superalloys are the workhorse materials for the hot section of current aero-engines. New high temperature materials and advanced processing technologies have been and will be the subject of study. It is speculated that high performance, high purity and low cost superalloys and technologies will play key roles in aero-engines.
关键词:
superalloy
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null
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null
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
The terminology of materials study inspired by biological systems or phenomena is analyzed at first. It is pointed that the term "bio-inspired" may be better than the terms "bionic" or "biomimetic", since the former is relatively easy to be accepted. The new trends of bio-inspired study of structural materials are analyzed in short. Some progress in bio-inspired design and processing of materials in this institute (IMRCAS) are summarized briefly in this talk, such as biomimetic design of worst bonding interface for composites; dumbell-like whiskers simulating animal bone; fractal tree reinforcement by mimicry of branched roots in soil; etc. The possibility of modification and recovery of materials by nonequilibrium bio-inspired treatment are further explored, including the nonequilibrium process under transient heating, dissipative structure and self-organization process of open system, inspiration by living process, influence of high intensive electropulsing on the working Life of materials, a possible way of fatigue recovery of materials and the healing effect of electropulsing in metals. Some tentative practice in biomaterial modification are also studied such as the reformed bamboo reinforced aluminium laminates, etc. A discussion on the methodology of bio-inspired study of materials consists briefly in the last part of the talk. (C) 2000 Elsevier Science S.A. All rights reserved.
关键词:
bio-inspired;bionic;biomimetic;structural materials;composites
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
