F. Gesmundo
,
Y Niu
,
F. Vianiand D.L. Douglass(Universita di Genova
,
Fiera del Mare
,
Pad. D
,
16129 Genova
,
Italy)(State Key Lab. for Corrosion and Protection
,
Institute of Corrosion and Protection of Metals
,
theChinese Academy of Sciences
,
Shenyang 110015
,
China)(University of Arizona
,
4715 East Fort Lowell Road
,
TUcson
,
AZ 85712
,
USA)
金属学报(英文版)
The cormsion in air of a two-phase Cu-75Cr alloy was studied at 700-900℃. Thealloy cormded nearly parabolically at 700-800℃, but at 900℃ its instantaneousparabolic mte constant decreased with time. The scales were complex and consistedof an outermost layer of copper oxide generally followed bg a layer of the double ox-ide Cu2 Cr2 O4 sometimes containing particles of unoxidized chromium surmunded bya chromia layer. An innermost layer of chromia was also observed in some cases.Finally metallic copper was al8o frequently mixed with chromia particles. No Cr de-pletion was observed in the alloy close to the inteffoce with the scale. In any case,this alloy was not able to form an exclusive continuous protective chromia layer. Thespecial cormsion behavior Of this alloy is typical of two-phase binary systems with alange solubility gaP in which the outwaof dthesion fiux of the most-reactive componentin the alloy is strongly reduced and may be inswncient to fOrm a protective externallayer of the cormsponding oxide. In paTticular, the presence of particles of Cr withina double oxide layer is very unusual and is allowed only for the kinetic reason.
关键词:
copper-chromium
,
null
,
null
,
null
D.Eylon
,
S.R.Seagle
材料科学技术（英文）
The state of Ti research, development and industry is reviewed in this article. The fifty-year anniversary of Ti technology commercialization in the USA provides an opportunity for a historical perspective. Incorporation of "information-age" tools into alloy development, processing, and production invigorates the technology. Consolidation, diversification and globalization have been transforming the Ti industry in the recent years.
关键词:
HSU Shuen
,
YANG Sycherng
,
HON Weipirn
,
WANG Chienyi LEE Tsangsheau (Chung-Shan Institute of Science and Technology
,
Lung-Tan
,
Taiwan
,
China) HSU Ichung(National Taiwan University
,
Taipei
,
Taiwan
,
China) CHIN Stephen
,
ANTON Donald L.(United Technologies Research Center
,
East Hartford. CT
,
USA)
金属学报(英文版)
The compressive and tensile strain rate sensitivities of polycrystalline and single crystal NiAl have been evaluated at 877 ℃ which is well above DBTT. Samples were prepared to specific sizes by hot press consolidation of appropriate powder sizes and minimizing past consolidation thermal exposures. NiAl single crystals were grown in the [100]orientation using a modified Bridgeman technique. The yield and tensile strength of polycrystalline NiAl as a function of grain size generally follows a Hall-Petch type relationship . A tensile strain rate effect was found at strain rate of 1 to 10-4 sec-1. The strain rate sensitivity coefficient, m,in the equation of σ = Kε is in the range of 0. 10 to 0. 13. The highest strain rate (1 sec-1) resulted in significantly higher strengths and little or no observed ductility. Compressive strain rate testing al strain rate of 10-5to 10-2 sec-1 and at temperature of 1050°to 1250°K was conducted both for polycrystalline and for single crystal NiAl. The calculated stress exponents and the activation energy for creep were compared with the reference data.
关键词:
:strain rate sensitivity polycrystalline NiAl
,
null
Q.B. Yang
,
G.J Shifietand E.A. Starke
,
Jr(Department of Physics
,
Xiangtan University
,
Xiangtan 411105
,
China)(Depedment of Materials Science and Engineering
,
University of Virginia
,
Charlottesvil1e
,
VA22903
,
USA)
金属学报(英文版)
A clear understanding of the structure of the S precipitates which are present in Al-Li-X alloys is verp imporiant because the S -phase decreases the localization of strainand promotes less anisotropic properties during deformation. The close structural re-lationship between the S-phase and the Al matrix and their possible intedece bound-ary strvcture are described in detail. The proposed model is in good agreement with::::rimental obserwations. The dynamics Of the phase trunWrmation and possiblermation mechani8ms for the S,-phase are alSo proposed.
关键词:
Al-Li alloy
,
null
,
null
D M DIMIDUK(Wright-Laboratory
,
Materials Directorate
,
WL/MLLM
,
Wright-Patterson AFB
,
OH45433-7817
,
USA)P R SUBRAMANIAN and M G MENDIRATTA (UES
,
Inc.
,
Dayton
,
OH 45432
,
USA)
金属学报(英文版)
Since the late 1980's there have been a number of research efforts aimed at exploring and developing the refractory intermetalllic materials for service at temperatures which compete with the nickel-based superalloys in structural applications. These efforts have documented the physical and mechanical properties of a broad set of compositions. However, only in the last three years have these efforts yielded sufficient experimental results on single selected systems to suggest that damage tolerance, creep resistance and oxidation resistance may be obtained and controlled simultaneously. These findings led to alloy development concepts and approaches which are currently under investigation and are expected to lead to research focused on a smaller set of alloys. An overview of selected alloy development strategies and resulting structural properties is presented herein.
关键词:
: refractory intermetallics
,
null
,
null
Campbell Laird(Dept. of Materials Science & Engineering
,
University of Pennsylvania
,
Philadelphia
,
PA 19104-6272
,
USA)Pedro Peralta(Center for Materials Science
,
Los Alamos National Laboratory
,
MaU Stop K765
,
Los Alamos
,
NM 87545-0001
,
USA)
材料科学技术（英文）
The mechanisms of fatigue crack propagation are breifly reviewed in relation to Professor McClintock's contributions to the early development of the field. The most securely established understanding has been obtained for those mechanisms of propagation involving plasticity-inducedgeometrical changes to the crack tip during tensile and compressive straining (the plastic blunting process). The roles of more complex factors in controlling the kinetics of crack propagation,which cause the magnitude of the Paris exponent to exceed 2, remain to be elucidated. Recentlyobtained results revealing the interconnection between the slip behaviour at the crack tip, theplastic blunting process and the dislocation structures present in the material before the crackencounters them are reported.
关键词:
M.B.Peterson(Wear Sciences Corporation
,
Arnold
,
Maryland
,
USA)Shizhuo LI(Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)S.F.Murray(Rensselaer Polytechnic Institute
,
Thoy
,
New York
,
USA)
材料科学技术（英文）
A study was conducted to develop low-friction, wear-resistant surfaces on high temperature alloys for the temperature range from 26℃ to 900℃. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological properties. Improvement is needed at low temperatures where the oxide film, previously formed at high temperature, spalls due to stresses induced by sliding. Experiments with Ti, W and Ta additions show a beneficial effect when added to Ni and Ni-base alloys. Low friction can be maintained down to 100℃ from 900℃. For unalloyed Ni friction and surface damage increases at 400℃ to 500℃. Two new alloys were perpared based on the beneficial results of binary alloys and ZrO2 diffusion in Ni.Low friction at temperature above 500℃ and reasonable values (0.32~0.42) at low temperature are obtained.
关键词:
Qiqing ZHANG
,
Lei REN and Lingrong LIU(Institute of Biomedical Engineering
,
Chinese Academy of Medical Sciences
,
Tianjin 300192
,
China)Chun WANG(CCCD
,
University of Utah
,
Salt Lake City
,
UT84112
,
USA)
材料科学技术（英文）
Naturally derived collagen protein was mixed thoroughly with medical grade poly (vinyl alcohol)(PVA) at the ratio of 90:10 (w/w) and was crosslinked by formaldehyde to form a homogeneous composite membrane. The buIk structure of the membrane was characterized ly means of Xray diffraction (XRD) and transmission electron microscoor (TEM). The membrane surface Structure was investigated using Fourier transform-infrared spectroscopy (attenuated totalrefraction) (FTIR-ATR), electron spectroscopy for chemical analysis (ESCA) and contact angle measurement. lt was found that collagen and PVA can remain Stable. This was supported by the fact that no sign of phase separation had been observed. The use of crosslinking agent can Substantially influence the Structure of the composite. It is suggested that this new compositedeserves further investigation and is potentially usable as a biomedical material.
关键词:
Yanchun ZHOU(Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang
,
110015
,
China)M.N.Rahaman (Ceramic Engineering Department
,
University of Missouri-Rolla
,
Rolla
,
MO 65401
,
USA)
材料科学技术（英文）
Nanocrystalline CeO2 powders (particle size ≈10-15 nm), doped with up to 20 at.-% of Mg,Ca or Y were prepared by chemical precipitation under hydrothermal conditions. The particle size and shape of the powders change slightly with the dopant concentrations. The the of the dopants on the sintering of the compacted powders was investigated during heating at a constant rate of 10℃/min. The elemental composition and the concentration of the dopant has significant efFect on the densification and grain growth. Compared to undoped CeO2, the dopants produce a shift in the densification curve to higher temperatures. For the same dopant concentration and under identical sintering conditions, the Ca doped samples reach nearly full density with the smallest grain size (≈50 nm), however, the Mg doped sample has the lowest density (≈95% of the theoretical) with the largest grain size (≈1 μm)
关键词:
