Output Predictions for Iron Castings and Aluminum Castings in 2006 and 2008 in China

China will continue expanding its in the castings market all over the world.According to statistics,the global castings of     

Creep and microstructure of Nextel™ 720 fiber at elevated temperature in air and in steam

Creep of Nextel? 720 alumina–mullite fiber tows was investigated at 1100 and 1200 °C for tensile stresses of 100–400 MPa in air and in steam. Fiber microstructures were characterized after creep by transmission electron microscopy. At low stresses steam increased creep rates by up to an order of magnitude and reduced creep lifetimes. At high stresses creep rates in steam and air were similar. Cavitation was prevalent in steam but not in air. The creep-rupture data obtained at 1200 °C were analyzed in terms of a Monkman–Grant (MG) relationship. The MG parameters were independent of the test environment. Results reveal that the MG relationship can be used to predict creep rupture for Nextel? 720 fibers and composites reinforced with these fibers at 1200 °C in air and in steam. In steam the mullite in the Nextel? 720 fibers decomposed to porous alumina. Decomposition kinetics were linear and had an activation energy of ～200 kJ mol^?1. Intergranular films were not observed on alumina grain boundaries or alumina–mullite interphase boundaries after creep in steam. Creep mechanisms are discussed.     

Observation and theoretic analysis of gas-bubble formation and growth in water-model

The behavior of bubbles is observed with high-speed digital camera in water-model. It is found that each bubble has three processes： bubble formation, bubble coalescence and bubble division. Bubble shape is spherical firstly, then elliptical and spherical crown after coalescence, and spherical again after division. These phenomena are explained theoretically. And the bubble size is defined newly. The so-defined bubble size is measured through digital camera and LECO graphical analyzer. And the measured results are compared with those in literatures.     

Macro—and microstructural changes in hydrogenated TiMn2 and Ta

Binary TiMn2 alloys with various compositions were arc melted in an Ar atmosphere.These alloys consist of TiMn2 and a small amount of TiMn depending on alloy composition.Annealed Ti-59.4%Mn exhibits the greatest capacity for hydrogen absorption and the smallest degradation of capacity during repeated hydrogen absorption and desorption.No apparent macro-and microstructural chanes are observed in Ti-59.4%Mn by repeated hydrogenation of 30cycles.At Mn content higher than 59.4%Mn,the formation of nano-sized Ti-hydride and the lattice expansion due to retained interstitial hydrogen were confirmed in repeatedly hydrogenated alloys.Pulverized powders were refined in all the alloys with increasing the number of repeated hydrogenation cycles.Many onion-like cracks are introduced in annealed pure Ta with 100℃m equi-axed grains by holding at 1473K followed by furnace cooling to room temperature in a hydrogen atmosphere,but no crack is observed after holding at 1473K in a hydrogen atmosphere followed by furnace cooling in an Ar atmosphere.It is concluded that the surface activation is attained in a hydrogen atmosphere at 1473K and multiple cracking occurs by absorbing a large amount of hydrogen at lower temperature.Volume expansion and dislocations generated by hydrogenation and hydride formation are responsible for multiple cracking.Hydrogen-induced multiple cracking in Ta occurs in the following sequence:hydrogen absorption,lattice expansion,hydride formation,and crack nucleation and propagation.Powder fabrication of Ta by hydrogenation is discussed in comparison with the hydrogen pulverization of intermetallic alloys.     

Development of welding technique in architectural and construction industry in China

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Timescales and contribution of heating and helicity effect in helicity-dependent all-optical switching

The heating and helicity effects induced by circularly polarized laser excitation are entangled in the helicity-dependent all-optical switching(HD-AOS),which hinders understanding the magnetization dynamics involved.Here,applying a dual-pump laser excitation,first with a linearly polarized(LP) laser pulse followed by a circularly polarized(CP) laser pulse,the timescales and contribution from heating and helicity effects in HD-AOS were identified with a Pt/Co/Pt triple-layer.When the LP laser pul...     

Anomalous scattering in structural chemistry and biology¶

The uses of X-ray anomalous scattering in crystal structure analysis have undergone a major expansion due to the refinement and ease of availability of the necessary X-ray instrumentation and methods. The structural chemistry and biology fields span a similar suite of technical needs but with widely differing molecular systems. The innate synergies between the two research fields brought two of the authors (JRH and VK) together at an Erice Summer School on Synchrotron Radiation in Crystallography in 1985 and took them into a collaboration spanning already 20 years. The authors’ wide perspectives are therefore, if not unique, perhaps rather rare. Thus the breadth of coverage of this review is unusual. However, there are two excellent books on anomalous scattering and its uses that have been published covering the periods up to 1975 and 1994 [S. Ramaseshan, S.C. Abrahams (Eds). Anomalous Scattering, Munksgaard, Copenhagen (1975); G. Materlik, C.J. Sparks, K. Fischer (Eds). Resonant Anomalous X-ray Scattering: Theory and Applications, North Holland, Amsterdam (1994)]. As the number of examples of applications in structural biology are now so many it has only been possible to select some illustrative examples but with surveys of trends. In addition though, the development of the methodologies is described in more detail. The structural chemistry applications in, for example, microporous materials, superconductors and magnetic materials is expanding fast but still at a stage where we could attempt to provide a detailed coverage of results, which we have done. Anomalous scattering results on locating metal atoms can also be compared with other technique results and so sections on X-ray Absorption Spectroscopy (XAS), Diffraction Anomalous Fine Structure (DAFS), neutron diffraction and Nuclear Magnetic Resonance (NMR) applications are described where they relate to metal atom location and local structure. Finally anomalous scattering has also been very useful to help develop the modern synchrotron Laue method for quantitative crystal structure analysis, which is also briefly described.

Anomalous scattering in structural chemistry and biology¶ ¶Dedicated to Professor Durward W. J. Cruickshank, FRS, Emeritus Professor of Chemistry, The University of Manchester, on the occasion of his 82nd Birthday, 7 March 2006. Durward is an inspiration to us all as a scientist with many fine contributions spanning nearly 60 years, as well as a friend, mentor and colleague to several of us for many years.

All authors

M. Cianci, J. R. Helliwell, M. Helliwell, V. Kaucic, N. Z. Logar, G. Mali & N. N. Tusar

https://doi.org/10.1080/08893110500421268

Published online:

25 January 2007

Table     

Development of electroslag metallurgy and casting in China

The electroslag metallurgy has been developed since 1958. At present, all special steel plants have constructed electroslag metallurgical workshops. There are 86 Electroslag Remetting (ESR) furnaces in these steel plants with annual capacity of 100 000 tons. The products by ESR include 243 designations of steel and superalloy. The Chinese metallurgists have made significant achievements in the type and structure of electroslag remelting furnaces, eletroslag remelting technology, shaped castings by Electroslag Remelting Casting (ESRC), the manufacture of large-size ingots by ESR and the study of ESR mechanism. These achievements have already been recognized by foreign metallurgists.     

Corrosion and fatigue in micro-sized Ni cantilever beams

The Ni microcantilevers were fabricated by femtosecond laser. The corrosion behavior of the micro-sized Ni cantilever beams was studied by electrochemical noise and a newly developed fatigue testing method. The results show that the micro-sized specimens exhibit general corrosion behavior under the studied corrosion condition, whereas the ordinary-sized plates exhibit the localized corrosion behavior. The critical load amplitude of the micro-sized Ni specimens under corrosion fatigue status was determined to be 15 mN. The maximum bending loads, which were measured by fatigue tests, decrease gradually prior to final fracture. Corrosion fracture first occurs in the range of notch with a higher tensile bending stress, and exhibits clear evidence of trans-columnar fracture. The variation of maximum bending loads with time agrees with that creep deformation of the micro-sized Ni specimens can easily occur at room temperature, which implies that the micro-sized Ni specimens appear to have an improved resistance towards total crack as compared with the ordinary-sized Ni specimens.     

Electrical and thermal conductivities in quenched and aged high-purity Cu–Ti alloys

Electrical resistivity and thermal diffusivity at room temperature have been measured in quenched and aged high-purity copper–titanium alloys. The results show that the electrical and thermal conductivities increase as aging time at 720 K increases, which indicates that precipitation takes place in these alloys.     

Microstructural evolution in adiabatic shear bands in Ta and Ta–W alloys

Microstructural evolution of adiabatic shear bands originated due to high strain, high strain rate deformation in Ta and Ta–W alloys has been examined. Tests were performed using a specially designed stepped specimen in a Hopkinson bar. Upon completion of the deformation, the region is cooled to below one half of the temperature achieved during adiabatic heating in less than one millisecond. Microstructural characterization of the shear bands was performed using optical microscopy as well as scanning and transmission electron microscopy. No evidence of recrystallization within the shear bands could be found. This is in contradiction with several recent reports, which claim that recrystallization may take place at these stringent time and temperature conditions. These studies, however, do not take into account the kinetics of boundary refinement processes, which are a distinctive characteristic of a recrystallized microstructure. It will be shown that the absence of recrystallization in Ta and Ta–W adiabatic shear bands can be predicted by a progressive subgrain misorientation (PriSM) recrystallization model, applied successfully in previous studies to predict the microstructure evolution in copper adiabatic shear bands.     

Adsorption difference of Pb2＋ and Zn2＋ in sandstone and breccia

The adsorption difference of Pb2 and Zn2 in sandstone and breccia of Pb-Zn Mine of Yunnan Province was studied by using modem instrument analysis method and fractal geometry theory. The results show that the adsorption capacity (Q) of Pb2 in this two rocks is bigger than that of Zn2 , and Q in various initial concentration solutions obeysv Freundlich experiential formula. The value of l/n on the adsorption Pb2 and Zn2 in sandstone hardly has any difference, but the value ofk differs observably. The adsorption process ofZn2 or Pb2 in sandstone or breccia from solution is fractal-like. The kinetic equation of adsorption is lgp = k - alg t or Q = abt( 1 bt)-1, and the values oflg k, a, and D of brecciaare bigger than those of sandstone at 30 and 50 ℃. These parameters decrease basically with the increase of temperature.The adsorption capacity of Pb2 is almost equal in sandstone and breccia, but the adsorption ability of Zn2 in breccia is stronger than that in sandstone.     

The transformation of narrow dislocation dipoles in selected fcc metals and in γ-TiAl

Transformations of vacancy dipoles of dissociated edge dislocations are analyzed in Cu, Ni and γ-TiAl by molecular dynamics. Dipole heights up to 20 {1 1 1} interplanar distances are investigated at temperatures ranging from 0 K to near the melting points of Cu and Ni and slightly below the upper boundary of the single phase γ-TiAl domain. Three model configurations, hollows, vertical compact and inclined dipoles, are considered and their relative stabilities compared. Except for dipoles one interplanar distance high, hollows are either metastable or unstable and they are never formed by mutually approaching dipolar dislocations. The three configurations transform into a variety of height- and temperature-dependent layouts including cores containing ordered free volumes, zigzagged faulted dipoles and agglomerated stacking-fault tetrahedra (SFT). At the highest temperatures, small individual SFTs are formed by short-range pipe-diffusion along the dipole cores. There is no critical height below which small-height dipoles or their debris would just simply disappear.     

Microstructural and Textural Differences Induced by Water and Furnace Cooling in Commercially Pure Zr Annealed in the α + β Region

In this work, a commercially pure Zr sheet with a typical bimodal basal texture was annealed in an α?+?β region and then subjected to different coolings (in water and furnace). Microstructures and textures of both the as-received and the heat-treated specimens were investigated by electron channeling contrast imaging and electron backscatter diffraction techniques. Results show that a duplex microstructure consisting of untransformed bulk α grains and twinned martensitic plates is produced in the water-cooled specimen, which possesses a weakened texture compared to the initial one. For the specimen cooled in furnace, however, a uniform microstructure fully comprised of coarser equiaxed grains with a strengthened texture is obtained. Analyses reveal that the rapid cooling in water could suppress variant selection behaviors during β?→?α transformation and allow α plates with scattered orientations to be nucleated inside β phases, contributing to the weakened texture. In contrast, during slow cooling in furnace, β boundaries would act as preferred nucleation sites of α embryos, resulting in a strong variant selection that accounts for the intensified texture.     

Flow Pattern and Temperature Distribution in HMCZ Silicon Melt

The axial and radial convective flow,temperature fluctuation and distribution in the HMCZ silicon meltare studied tentatively.The experimental results show that the axial and radial convective speeds,the tempera-ture variation and the radial temperature gradient,parallel to magnetic field and near melt surface,alldecrease,but the axisymmetry of temperature distribution no longer exists when the magnetic field is applied.     

Fatigue threshold and crack propagation in γ-TiAl sheets

The fatigue crack propagation behaviour of two different microstructures — a coarse-grained designed fully lamellar (DFL), and a fine-grained near γ (FG) — of a Ti–46.5 at.% Al–4 at.% (Cr, Nb, Ta, B) alloy was studied. Both the threshold of stress intensity range and standard long crack growth behavior were determined. A special technique was applied to separate the different mechanisms — intrinsic and extrinsic effects — and their changes with crack length. The fatigue crack propagation rate of long cracks is much smaller in the DFL microstructure than in the FG microstructure at the same stress intensity range. The effective threshold of stress intensity range of both microstructures is about 1.7 MPa√m. The threshold of stress intensity range shows a strong R-curve behavior. In other words the propagation–non-propagation conditions of cracks are significantly influenced by the crack extension. The long crack thresholds of stress intensity range at the stress ratio 0.1 are relatively large; they are about 4.5 and 8 MPa√m in the DFL and the FG microstructure, respectively. The differences in the crack growth behavior between the two microstructures are mainly induced by extrinsic resistance mechanisms.     

Damping capacity and compressive characteristic in some aluminum foams

1　INTRODUCTIONMetallicfoams ,especiallyaluminumalloyfoamsaresuper lightmetalsexhibitingunique propertiessuchashighenergyabsorptionandhighdampingca pacity .So ,theyarebelievedtohavegreatpotentialforapplicationsinmanyaspects ,forexample ,theap plicationinenergyabsorptionandvibrationdamping .Therefore ,theirmechanicalpropertieshaveattractedaconsiderableattentioninrecentyears .Anumberofworksonthecompressivebehavioroffoamedalu minumanditsalloyhaverevealedthatthedeforma tionbehaviorofaluminumf…     

Be Diffusion and Suppression in HBT StructureMaterials Grown by

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Liquid Ni–Fe penetration and recrystallisation in tungsten

Melt penetration in grain boundaries of solid tungsten has been investigated.Solid tungsten rods have been exposed to a nickel–iron melt saturated with tungsten and the penetration depth and the shape of the liquid channels have been examined. The solid tungsten samples have been treated in different ways like cold working, annealing and recrystallisation, before melt exposure. Important parameters for the penetration process are stresses, surface tensions, solution and kinetic effects. A new theoretical model for the penetration mechanism in cold worked samples is proposed.Rapid recovery of the grains in the penetrated areas of the cold worked samples was observed. This is discussed, as well.