共查询到20条相似文献,搜索用时 11 毫秒
1.
Three two-phase Fe-Mn-Al alloys with nominal compositions, Fe-24Mn-9Al, Fe-27Mn-9Al-3Cr,. and Fe-27Mn-9Al-6Cr, were prepared
in the solution-treated and cold-rolled conditions. The fractions of ferrite in the solution-treated condition were controlled
at 46 to 60 pct, mainly by adjusting the carbon content and the relative amounts of Mn and Al. The ferrite fractions were
reduced to 30 to 37 pct after 75 pct deformation by cold-rolling. Specimens were tensile tested at open circuit in aerated
3.5 pct NaCl solution at slow strain rates ranging from 4 × 10-7 to 4 × 10-5 s-1 at room temperature. All of the alloys were quite susceptible to environmentally assisted cracking (EAC). The deformed specimens
showed less susceptibility, presumably because the plasticity was already too limited. The EAC appeared to occur at or after
the onset of plastic deformation. In this alloy system, the ferritic phase was less resistant to EAC than the austenitic phase,
in contrast to the Fe-Cr-Ni stainless steels. The crack propagated preferentially through the ferrite grains or along the
ferrite/austenite grain boundaries. The addition of up to 6 pct Cr did not improve the EAC resistance.
Formerly Graduate Student, Department of Materials Science and Engineering, National Tsing Hua University 相似文献
2.
M. Bobby Kannan V. S. Raja A. K. Mukhopadhyay P. Schmuki 《Metallurgical and Materials Transactions A》2005,36(11):3257-3262
The 7010 Al alloy with and without addition of 0.25 wt pct Sc in peak-aged condition was examined for its environmentally
assisted cracking (EAC) behavior. Slow strain rate testing (SSRT) per ASTM standard G129-00 was employed to investigate EAC.
The base 7010 Al alloy showed 10 pct elongation, 9.9 pct reduction in area, and 561 MPa ultimate tensile strength (UTS), when
tested in air. The ductility of the base alloy dropped to 3 and 3.3 pct in terms of elongation and reduction in area, respectively,
when tested in 3.5 pct NaCl solution, showing its high susceptibility to EAC. On the other hand, the 0.25 wt pct Sc containing
alloy showed a significant improvement in ductility not only in air but also in 3.5 pct NaCl solution, without any loss in
the UTS. Thus, the 0.25 wt pct Sc containing alloy exhibited 13.4 pct elongation, 15.8 pct reduction in area, and 560 MPa
UTS in air and 12.5 pct elongation, 16.4 pct reduction in area and 560 MPa UTS in 3.5 pct NaCl solution. The study for the
first time shows that the high resistance to EAC of 7010 alloy can be imparted even in peak-aged condition by the addition
of 0.25 wt pct Sc. 相似文献
3.
C. L. Briant 《Metallurgical and Materials Transactions A》1979,10(2):181-189
This paper reports a study of hydrogen assisted cracking in type 304 stainless steel. It shows that the most detrimental effect
in increasing the susceptibility of the material to hydrogen cracking is the formation of martensite upon deformation. This
is particularly damaging if the martensite is localized at the grain boundaries. With martensite present intergranular impurities
such as phosphorus play a secondary role. As martensite becomes more difficult to form, the importance of impurities increases. 相似文献
4.
5.
Hans Hoffmeister 《国际钢铁研究》1986,57(7):344-347
The self restraining Instrumented Restraint Cracking (IRC)-test enables the determination of weld joint reaction forces and -moments responsible for hydrogen assisted cracking. With help of continuous measurements during cooling of the weld, the effects of crack inducing parameters can be detected in detail. The IRC-test can be applied to procedure development and procedure qualification welding, making use of current fabrication practice at restraint intensities of the to-be-fabricated structure. It is easy to carry out and the results are quickly at hand. 相似文献
6.
Most academic psychologists do not yet accept the existence of psi, anomalous processes of information or energy transfer (e.g., telepathy or other forms of extrasensory perception) that are currently unexplained in terms of known physical or biological mechanisms. It is believed that the replication rates and effect sizes achieved by 1 particular experimental method, the ganzfeld procedure, are now sufficient to warrant bringing this body of data to the attention of the wider psychological community. Competing meta-analysis of the ganzfeld database are reviewed, one by R. Hyman (see record 1986-05166-001), a skeptical critic of psi research, and the other by C. Honorton (see record 1986-05165-001), a parapsychologist and major contributor to the ganzfeld database. Next the results of 11 new ganzfeld studies that comply with guidelines jointly authored by R. Hyman and C. Honorton (see record 1987-12537-001) are summarized. Issues of replication and theoretical explanation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
8.
In mammalian cells, membrane uptake of long-chain fatty acids is mediated by two separate components; a passive component that is a linear function of the concentration of free fatty acid in the extracellular medium and a saturable component that exhibits the characteristics of a protein-facilitated process. This review summarizes the body of work that has accumulated related to the mechanism of fatty acid transport. Evidence in support of a facilitated uptake process is presented with relation to the different cell types or membrane systems where it was collected. The evidence includes saturation kinetics, competition between different substrates, and sensitivity to a variety of inhibitors. Recent knowledge related to membrane proteins thought to be implicated in the uptake process is reviewed. Factors that may modulate uptake or alter the relative contribution of passive versus facilitated components are briefly discussed. These include the molar ratio of fatty acid to its physiological carrier, plasma albumin and the metabolic or hormonal milieu. 相似文献
9.
《粉末冶金学》2013,56(3):343-353
AbstractA process based on powder metallurgy approach was developed to produce open celled aluminium foam. In the preparation of foam specimens, the Al powder and the NaCl (leaching agent) were dry mixed together in order to prepare a homogeneous mixture. The blended mixture was then subjected to pressure assisted sintering in which a pressure beyond atmospheric level is externally applied to the specimen during high frequency induction heated sintering. The embedded leaching agent was then dissolved in order to leave behind an open celled Al with the same chemical composition as that of the original Al powder. The final material is highly porous and has an interconnected porosity network. The structure of the resulting material has three levels of porosity (i.e. main cells, windows and microporosity). The X-ray diffraction analysis shows that, as the content of NaCl is increased to the volume fraction of 60%, no traces of NaCl presents in the foam. 相似文献
10.
Reviewed a database sponsored by the National Institutes of Health (NIH) that lists all clinical trials currently underway indicated that there are at least 400 investigational drugs in various stages of development for central nervous system (CNS) disorders, such as major depression, schizophrenia, Alzheimer's disease, and social anxiety disorder (NIH, 2002). Of the 65 new drugs approved in 2001, 10 were drugs for (CNS indications (S. Briggs et al., 2002). Given this level of activity, psychologists might benefit from an overview of the drug development process that would further their understanding of the dynamics involved in bringing a drug into the market. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
11.
Rats were conditioned to fear a tone paired with shock to the feet. Retention tests 4 days later showed that consolidation had occurred. Other animals were not tested for retention at 4 days, but the tone was presented in order to reactivate their memories of the conditioning. An amnesia gradient was generated by low-intensity electrical stimulation of the amygdaloid complex at different intervals after the tone, but stimulation was without effect either when given to rats not previously conditioned or when given to conditioned rats without preceding memory reactivation. Thus, stimulation of the amygdaloid complex can can affect memory retrieval. Moreover, the data call into question the assumption that an amnesia gradient indicates that the memory consolidation process has been modified. 相似文献
12.
13.
14.
Stress corrosion cracking of an Al-Li alloy 总被引:1,自引:0,他引:1
Z. F. Wang Z. Y. Zhu Y. Zhang W. Ke 《Metallurgical and Materials Transactions A》1992,23(12):3337-3341
Stress corrosion cracking (SCC) has been studied in an Al-Li alloy with variables of orientation of specimen, heat treatment,
and applied potentials. The distribution of the electrochemical potential resulting from precipitate clusters was measured,
and the hydrogen content on the specimen surface was detected. The results showed that the SCC susceptibility under the peakaged
(PA) condition was higher than that under the natural (NA) and overaged (OA) conditions. The transverse (TL) specimen was
more susceptible to SCC propagation than the longitudinal (LT) specimen. The SCC susceptibility and the hydrogen content on
the specimen surface were dependent on the applied potentials. The hydrogen content increased when the applied potential changed
to positive or negative directions. There was a critical hydrogen content, below which local anodic dissolution (LAD) plays
an important role, above which hydrogen embrittlement (HE) plays an important role. 相似文献
15.
Wang Z. F. Zhu Z. Y. Zhang Y. Ke W. 《Metallurgical and Materials Transactions A》1992,23(1):3337-3341
Stress corrosion cracking (SCC) has been studied in an Al-Li alloy with variables of orientation of specimen, heat treatment, and applied potentials. The distribution of the electrochemical potential resulting from precipitate clusters was measured, and the hydrogen content on the specimen surface was detected. The results showed that the SCC susceptibility under the peak- aged (PA) condition was higher than that under the natural (NA) and overaged (OA) conditions. The transverse (TL) specimen was more susceptible to SCC propagation than the longitudinal (LT) specimen. The SCC susceptibility and the hydrogen content on the specimen surface were dependent on the applied potentials. The hydrogen content increased when the applied potential changed to positive or negative directions. There was a critical hydrogen content, below which local anodic dissolution (LAD) plays an important role, above which hydrogen embrittlement (HE) plays an important role. 相似文献
16.
Substantial correlational evidence supports a causal (mediational) interpretation of alcohol expectancy operation, but definitive support requires a true experimental test. Thus, moderately to heavily drinking male college students were randomly assigned to 1 of 3 conditions in a pre–post design: expectancy challenge (designed to manipulate expectancy levels), "traditional" information, and assessment-only control. Expectancy challenge produced significant drinking decreases, compared with the other 2 groups. Decreases in measured expectancies paralleled drinking decreases in the challenge condition. Significant increases in alcohol knowledge in the traditional program were not associated with decreased drinking. These experimental findings support a causal (mediational) interpretation of expectancy operation. The implications for a cognitive (memory) model of expectancies and for prevention and intervention programs for problem drinking and alcoholism are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
17.
Jaffee Sara R.; Caspi Avshalom; Moffitt Terrie E.; Taylor Alan 《Canadian Metallurgical Quarterly》2004,113(1):44
The well-documented finding that child physical maltreatment predicts later antisocial behavior has at least 2 explanations: (a) Physical maltreatment causes antisocial behavior, and (b) genetic factors transmitted from parents to children influence the likelihood that parents will be abusive and that children will engage in antisocial behavior. The authors tested these hypotheses in the representative Environmental-Risk cohort of 1,116 twin pairs and their families, who were assessed when the twins were 5 and 7 years old. Mothers reported on children's experience of physical maltreatment, and mothers and teachers reported on children's antisocial behavior. The findings support the hypothesis that physical maltreatment plays a causal role in the development of children's antisocial behavior and that preventing maltreatment can prevent its violent sequelae. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
R Foust NN Tran C Cox TF Miller JS Greenspan MR Wolfson TH Shaffer 《Canadian Metallurgical Quarterly》1996,21(5):316-322
Evidence of surfactant inactivation by meconium has led to the use of exogenous surfactant therapy in the management of meconium aspiration syndrome (MAS). Liquid assisted ventilation has been shown to improve the cardiopulmonary function in lungs with high surface tension. We compared exogenous surfactant therapy with liquid assisted ventilation in the management of experimental acute meconium aspiration injury. Thirty-two newborn lambs were ventilated at peak inspiratory pressures of 13-16 cm H2O, positive end expiratory pressure of 3-4 cm H2O, fractional inspired oxygen concentration (FiO2) of 1.0, and a respiratory frequency range between 30 and 35 breaths/min. Baseline arterial blood gases, pulmonary function, and arterial blood pressure measurements were taken. All lambs were given 2-3 ml/kg of an unfiltered 25% meconium solution. Lambs were then randomized into either gas-ventilated meconium control, or one of three treatment groups: 1) surfactant; 2) partial liquid ventilation (PLV); or 3) total liquid ventilation (TLV) for 4 hours after meconium injury. All treated groups demonstrated a significant increase in arterial oxygenation (P < 0.05); surfactant and PLV-treated lambs demonstrated significantly decreased arterial PCO2 (P < 0.05). Compliance in all groups increased compared with injury values; compliance of the TLV group increased more than in all other treatment groups (P < 0.05). In addition, lung histology of the TLV group demonstrated clear, intact alveolar epithelium and homogeneously expanded alveoli, while no such improvement was evident in the other groups. These data suggest roles for both exogenous surfactant therapy and liquid assisted ventilation techniques in the management of MAS. 相似文献
19.
20.
以秸秆热解产生的焦油为原料,在固定床反应器实验台上进行了催化裂解实验,研究了反应温度和催化剂种类对生物质焦油的裂解反应产物——二次焦油成分的影响规律.在高铝砖作为催化剂作用下,随着温度的升高,二次焦油构成有芳香化的趋势,多环芳烃的种类和含量都在增加.反应温度的提高有利于焦油的深度转化,二次焦油产率降低;但是高温下生成的二次焦油芳化程度更高,更容易引起催化剂积炭失活.当反应温度为900℃时,碱性催化剂白云石和石灰岩作用下二次焦油成分相似,以复杂的大分子环烃为主,而且焦油成分种类减少到10种左右;酸性催化剂高铝砖作用下焦油成分仍然很复杂,有将近30种,除了含有大分子环烃外,还含有部分石蜡烃,芳香族种类很多,多以双环、三环以及四环的形式存在. 相似文献