ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.1

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractHydrogen attack (HA) is a degradation process occurring in steel exposed to hot, high-pressure hydrogen. It is caused by the nucleation, growth, and ultimate link-up into fissures of small methane bubbles–primarily on grain boundaries. The location and growth kinetics of the submicrometre bubbles during the incubation period before fissure formation has been studied only in the past few years. Growth is limited primarily by grain-boundary diffusion, though creep of the ligaments between bubbles can be limiting under certain conditions. The processes limiting bubble nucleation are unclear though there seems to be a critical stress (methane pressure plus applied stress) above which the bubble density increases greatly. Alloying with Cr enhances the resistance to HA, primarily by reducing the bubble density rather than by reducing the bubble growth rate. The process of bubble growth and link-up is completely analogous to that by which grain-boundary voids link-up to limit the creep ductility of alloys. Simultaneous HA and creep leads to a marked acceleration of failure, though it is unclear whether this is caused primarily by the enhancement of nucleation or by growth.MST/112

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.2

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Abstracthis literature review was prepared in order to determine the state of the art with respect to the vacuum refining of copper. There have been numerous reported laboratory investigations of copper refining by vacuum treatment since the 1940s. Most studies have been carried out with the aim of eliminating deleterious impurities, such as arsenic, antimony, bismuth, lead, sulphur, and oxygen, from copper to levels appropriate to marketable grades, thereby improving the quality of the copper produced. It is interesting to note that the majority of work in this area has been carried out by Japanese and Soviet researchers: Japanese authors have generally tried to explain their results by means of kinetic or thermodynamic analyses, whereas the Soviet ones have merely given experimental results. This review contains three sections. In the first, the theory of vacuum treatment is discussed. The second presents information currently available (to 1980) on vacuum refining and is divided into three subsections, based on the type of copper treated, namely: (i) treatment of blister copper (or crude copper); (ii) treatment of anode copper and/or cathode copper; and (iii) treatment of copper matte. Finally, a patent survey has been carried out, which is reported in the third section.MST/54

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.12

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractAn investigation was carried out on the propagation of cracks in coarse-grained bainitic 0·5 Cr-Mo-V material under both load- and displacement-controlled cyclic loading conditions. All tests were performed at 838 K using cyclic frequencies in the range 10−3–10−5Hz. Crack initiation and propagation were found to occur as a result of the formation, growth, and linkage of grain-boundary creep cavities and wedge cracks, irrespective of cyclic frequency. Notch-tip creep displacements at crack initiation were comparable to those observed in statically loaded specimens, and time-dependent crack propagation rates also agreed well with data obtained in static tests. Time-dependent crack propagation rates were a function of the specimen displacement rates, suggesting that cavity growth occurred by either a plastic or a constrained-diffusion mechanism.MST/56

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.19

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe effect of temperature on fatigue-crack propagation in air for 1·8 Ni–Cr–Mo–V steels over the range 24–400°C has been investigated. The variables examined were: (i) specimen orientation (Y–X and X–Y); (ii) steel preparation route (vacuum or air melted); and (iii) vanadium content. In general increasing the test temperature resulted in increased fatigue-crack growth rates, the same trend being observed for both Y–X and X–Y oriented specimens. The air-melted steel exhibited higher crack growth rates than the vacuum-melted steels. Fractographic studies showed that the crack-propagation mechanism was temperature dependent in the steels studied, but differed for vanadium-bearing and vanadium-free steels.MST/48

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.25

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractAn investigation has been made to develop a simple duplex steel for line-pipe application. Controlled rolling of an Fe–0.06C–1.5 Mn alloy followed by direct quenching produced a duplex ferrite–bainite structure in which the coarse upper bainite regions were uniformly distributed within a fine-grained ferrite matrix. The microstructure and mechanical properties of this duplex structure were strongly influenced by the processing variables. Decreasing the finish-rolling temperature improved both tensile and impact properties. This was due mainly to a refinement of the ferrite grain size. There was an abrupt increase in the yield strength and a small increase in the ductile–brittle transition temperature as a result of cold working (pipe forming) because of the steel's continuous yielding behaviour and high initial work-hardening rate. The mechanical properties attained in this duplex steel are attractive for low-temperature line-pipe applicaiion.MST/155

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.32

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractAn equation for the half-width of an adiabatic shear band is derived. With reference to the equation, the importance of thermal conductivity, temperature, and viscosity in determining the bandwidth are illustrated. It is shown that calculations of shear band width are fairly close approximations to those obtained experimentally. The apparent insensitivity of shear band width to the loading conditions is in agreement with experimental findings of other researchers.MST/156

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.38

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractIn this investigation on thin 0·7 wt-%C steel wire (0·25 mm dia.), the effect of an additional small reduction by drawing on the state of the tensile residual surface stresses in the ferrite was examined. For this purpose X-ray stress analysis was applied. It is shown that an additional reduction in cross-sectional area of 1·2% can change axial tensile stresses into compressive stresses, tangential tensile stresses being reduced in magnitude. The reduction is shown to depend on the orientation of the grains when intergranular microstresses are considered. These microstresses were calculated by means of a‘modified sin2ψmethod’.MST/50

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.41

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractExtrusion has been conducted on five Cu–P alloys. The effects of extrusion temperature, strain rate, and extrusion ratio on the pressure required to initiate the process are considered. Attention is given to the problem of hot shortness to which Cu–1.5P is particularly susceptible. Although the second phase Cu3P is brittle at room temperature, evidence is given that under hot-working conditions it exhibits extreme plasticity and a low deformation resistance. It is shown that for all alloys the maximum pressure can be satisfactorily correlated with a function of extrusion parameters. Based on the established relations and estimates of temperature changes, extrusion limits can be determined.MST/49

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.45

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractDirect evidence for the interstitial analogue of the reverse Kirkendall effect has been found in experiments of carbon diffusion through platinum membranes. The carbon diffusion was accompanied by the formation of protrusions and depressions in the carburized and decarburized surfaces respectively. The magnitude of the counter-flux of platinum atoms suggests that some of the carbon atoms are strongly bound to vacancies. An analysis based on Lomer's equation yields a vacancy–carbon atom binding energy Ev-cB0·5eV.MST/32

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.1.53

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor