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1.
Strengthening mechanisms in Elgiloy   总被引:2,自引:0,他引:2  
The effects of cold-working and age-hardening on the microstructure of Elgiloy (composition in wt %, 40 Co, 20 Cr, 15 Ni, 7 Mo, 2 Mn, 0.1 C, balance Fe) have been established. 36% and 72% cold reduction of the solution treated (ST) alloy (f c c) produced a network of thin f c c deformation twins and h c p-martensite platelets. The subsequent age-hardening of the cold-worked strip noted at 500° C was attributed to the formation of additional e-phase (via the f c c h c p transformation), whereas the ST condition did not harden significantly at this temperature. In contrast, ageing the ST condition at 800° C for periods >1000 h caused an increase in hardness due to the formation of a coarse Mo-Co-Cr intermetallic compound together with a smaller amount of M23C6 carbide, while age softening of the cold-worked strip occurred at this temperature as a result of recovery and dissolution of the deformation induced-phase.  相似文献   

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Acoustic nonlinearity (which is quantified in terms of an absolute material parameter, the acoustic nonlinearity parameter, β) can be caused by several sources, one of which is the elastic-plastic deformation of the material. This paper develops a model to quantify the acoustic nonlinearity parameter due to elastic-plastic deformation. This new model is applicable to general anisotropic elastic-plastic materials with existing microplasticity strains due to either monotonic or cyclic loading. As an example, the developed model is applied to calculate the acoustic nonlinearity parameter of a single crystal copper specimen subjected to cyclic fatigue loading. It is found that the acoustic nonlinearity parameter of this specimen increases monotonically with increasing fatigue cycles.  相似文献   

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Magnetron sputtered Ni thin films on both oxidised Si (100) and α-Al2O3 (0001) substrates of thickness 150–1000 nm were tested thermomechanically with a wafer curvature system, as well as in situ in a transmission electron microscope. The films on oxidised Si have a {111}-textured columnar microstructure with a mean grain size similar to the film thickness. On (0001) α-Al2O3 a near single crystal epitaxy with two growth variants is achieved leading to a significantly larger grain size. The thermomechanical testing was analysed in terms of the room temperature/high temperature flow stresses in the films and the observed thermoelastic slopes. It was found that the room temperature flow stresses increased with decreasing film thickness until a plateau of ∼1100 MPa was reached for films thinner than 400 nm. This plateau is attributed to the present experiments exerting insufficient thermal strain to induce yielding in these thinner films. At 500 °C the compressive flow stresses of the films show a competition between dislocation and diffusion mediated plasticity. A size effect is also observed in the thermoelastic slopes of the films, with thinner films coming closer to the slope predicted by mismatch in thermal expansion coefficients. It is put forward here that this is due to a highly inhomogeneous stress distribution in the films arising from the grain size distribution.  相似文献   

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The tensile microstrain behaviour of a series of magnesium-lithium alloys, with lithium contents up to 12.5 wt %, has been studied. The strain hardening exponents in the microstrain region were found to depend on the lithium content, the increase in which led to a change in crystal structure from hcp to bcc. The onset of cross-slip in the bcc alloys was found to sharply reduce the strain hardening capacity of the materials.  相似文献   

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Single crystals of titanium carbide with a C-to-Ti range of 0.64 to 0.99 were plastically deformed at room temperature with a hardness indenter and a drill. The operating slip systems were determined by hardness anisotropy and transmission electron microscopy. The results were characteristic for bulk material deformation of TiC, below, as well as above, the brittle-to-ductile transition temperature. A typical low temperature behaviour is the formation of cracks and dislocation motion along the slip systems {1 1 0} 〈1 1 0〉 and {1 0 0} 〈1 1 0〉, which are both common in the rock-salt structure. The high temperature deformation is characterized by the slip system {1 1 1} 〈1 1 0〉. The degree of plastic deformation and the importance of the slip system {1 1 1} 〈1 1 0〉 increases as the C-to-Ti ratio decreases from 0.99 to 0.64.  相似文献   

8.
Gender differences in publication productivity in psychology in India   总被引:1,自引:0,他引:1  
An analysis of gender differences in psychology in India provides quantitative and qualitative assessment of R&D output contributed by psychologists with the indication of the trend of growth, skewness, relatedness, co-authorship pattern of productivity.  相似文献   

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The system for Metrology in Chemistry in Germany is described. At the national standards level, a network of high-level chemistry institutes coordinated by the national metrology institute, PTB, provides the primary references for chemical measurements. A dissemination mechanism employs chemical calibration laboratories accredited within the framework of the German Calibration Service (DKD). They act as “multipliers” between the national standards level and the user level by providing the user with calibration means which are traceable to the SI via national standards. Traceability structures in clinical chemistry, electrochemistry, elemental analysis and gas analysis are described  相似文献   

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Natural radioactivity in drinking water was determined in population-based random study of 472 private wells. The mean concentrations of (222)Rn, (226)Ra, (234)U, (238)U, (210)Pb and (210)Po in drilled wells were 460, 0.05, 0.35, 0.26, 0.04 and 0.05 Bq l(-1), and in wells dug in the soil were 50, 0.016, 0.02, 0.015, 0.013 and 0.007 Bq l(-1), respectively. Approximately 10% of the drilled wells exceeded a radon concentration of 1000 Bq l(-1) and 18% a uranium concentration of 15 microg l(-1). The mean annual effective dose from natural radionuclides for a drilled well user was 0.4 mSv and 0.05 mSv for a user of a well dug in the soil. The effective dose arising from (222)Rn was 75% of the total of all natural radionuclides for drilled well users. As regards long-lived radionuclides, (210)Po and (210)Pb caused the largest portion of the effective dose. The dose arising from (238)U, (234)U and (226)Ra was only 8% of the total of all natural radionuclides.  相似文献   

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The results of theoretical and experimental investigation of mass transfer in the case of vaporization in vacuum from a point source onto a substrate of arbitrary form are given.  相似文献   

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This study reports the occupational radiation doses for external exposure received in 1999 by the radiation workers monitored by the Radiological Protection and Nuclear Safety Department (DPRSN) in Portugal. Occupational exposures arise from conventional industry, research laboratories, the health or medical sector, and mining. There are no nuclear power plants in the country. There are two dosimetry systems running simultaneously at DPRSN, one based on film dosimetry and the other on thermoluminescence dosimetry (TLD). In 1999, 8400 persons were monitored, 3100 with film and 5300 with TLD and the data presented in this report were obtained by using both technologies. The annual mean effective doses received from external radiation in the different fields of activity and the distribution of the annual effective dose by dose intervals are presented. The collective annual dose by field of activity is estimated and the contribution to the total annual collective dose is determined.  相似文献   

18.
While a general decreasing trend in the number of persons killed in a traffic crash involving a drinking driver has occurred in Canada since the 1980s, it is evident that much of this decrease occurred in the 1990s. Since 2002, less progress has been made as the number of persons killed in crashes involving drinking drivers remains high. To better understand the current situation, this paper describes trends in drinking and driving in Canada from 1998 to 2011 using multiple indicators based on data collected for the Traffic Injury Research Foundation's (TIRF) Road Safety Monitor (RSM), the National Opinion Poll on Drinking and Driving, and trends in alcohol-related crashes based on data collected for TIRF's national Fatality Database in Canada. There has been a continued and consistent decrease in the number of fatalities involving a drinking driver in Canada. This remains true when looking at the number of fatalities involving a drinking driver per 100,000 population and per 100,000 licensed drivers. This decreasing trend is also still apparent when considering the percentage of persons killed in a traffic crash in Canada involving a drinking driver although less pronounced. Data from the RSM further show that the percentage of those who reported driving after they thought they were over the legal limit has also declined. However, regardless of the apparent decreasing trend in drinking driving fatalities and behaviour, reductions have been relatively modest, and fatalities in crashes involving drivers who have consumed alcohol remain high at unacceptable levels.  相似文献   

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Optical film thickness monitoring is more precise than crystal monitoring. The optical measurement makes use of the fact that the intensity of a monochromatic light beam which is reflected on a film will change periodically with increasing film thickness. The measurement is performed at an exchangeable test glass that is positioned beside the substrates and is therefore coated in the same way as the substrates. The accuracy of cut‐off is achieved by a “fit” of a theoretical curve shape to the measured values. Order filters are used to ensure that, at a certain wavelength, higher deflection orders do not influence the measurement when a monochromator grating is used.  相似文献   

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一、采标工作的主要经验做法和取得的成绩(一)领导重视,机构健全是采标工作的有力组织保证沈阳市在消灭无标生产工作中,先后成立了区、县人民政府消灭无标生产工作领导小组,消灭无标生产工作阶段性完成后,根据国家质检总局要求相继改为标准化工作领导小组,领导小组由主管区长挂帅,各职能部门主要领导参加,为采标工作的开展提供了坚实的组织保证,并纷纷出台了一些保障措施。围绕实施名牌产品战略,市政府明确要求,在评选名牌产品时,产品必须首先采标,然后方可有资格参加名牌产品的评选。我们坚持对申报评选的产品进行跟踪,能够…  相似文献   

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