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Structure and Deformation of Intermetallic Beryllides

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Journal of Materials Science & Technology 1994年第6期10卷 391-405页

作者： TG.Nieh(Lawrence livermore National Laboratory, P.O.Box 808, L-350, livermore, CA 94551, USA ) Lawrence livermore Natl Lab Livermore United States

Intermetallic beryllides are potential light-weight, high-temperature structural materials. In this paper. the processing techniques, microstructure. deformation, and oxidation properties of intermetallic beryllides are described. In addition to nickel beryllides (NiBe). which is treated as a model *** high beryllium-containing refractory beryllides, such as Nb2 Be17. VBe12. are also *** room temperature deformation and high-temperature creep properties of these beryllides are repor4ed. At room temperature. NiBe exhibits certain tensile ductility (~ 1 .3%). but all other beryllides are essentially brittle. Nonetheless, these beryllides become ductile at temperatures above approximately 1000℃. Their creep properties are presented. The creep properties are compared with those of intermetallic aluminides. Also. a comparison is made between the ductile-to-brittle transition behaviour of intermetallic beryllides and that of aluminides. Although beryllides are generally oxidation resistant at high temperatures, some beryllides, e.g., ZrBe13, suffer the pest reaction during oxidation at intermediate tem peratures. The pest mechanisms are proposed

关键词： BeO Res AIME Structure and Deformation of Intermetallic Beryllides MPa

Deformation of metallic glasses with special emphasis in supercooled liquid region

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中国有色金属学会会刊：英文版 2002年第4期12卷 726-733页

作者： T.G.Nieh (Lawrence livermore National Laboratory, L 350, PO Box 808, livermore, CA 94551, USA) Lawrence livermore National Laboratory 美国 Livermore CA 94551

Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous deformation begins to take place. A bulk amorphous Zr 10Al 5Ti 17.9Cu 14.6Ni alloy was observed to exhibit the Newtonian behavior at low strain rates but becomes non Newtonian at high strain rates in the supercooled liquid region. Structures of the amorphous material, both before and after deformation, were examined using X ray diffraction and high resolution electron microscopy. Results showed the presence of nanocrystallites in the deformed samples. Thus, the non Newtonian behavior is attributable to the concurrent crystallization of the amorphous structure during deformation. A mechanistic model is presented to interpret the observed non Newtonian result. A phenomenological approach is also used to develop the deformation map for bulk metallic glasses in the supercooled liquid region.

关键词：非晶合金金属玻璃超塑性过度冷却液体层

ATOMISTIC SIMULATIONS FOR Ni/Al INTERMETALLICS

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Acta Metallurgica Sinica(English Letters) 1995年第Z1期8卷 287-298页

作者： BASKES M. I.(Sandia National Laboratories, livermore, Califormia) Sandia National Lab Livermore California United States

A large number of Embedded Atom Method (EAM) potentials have been developed for the Ni/Al system. These potentials are compared to a common data base. It is found that there is significant difference in quality in these potentials. One of the potentials has also been extended to represent the properties of hydrogen in Ni/Al intermetallics. This potential describes the solution and migration behavior of hydrogen in both Ni and Al.A number of calculations using the Ni/Al/H potential have been performed. It is found that hydrogen strongly prefers sites in Mi3AI that are surrounded by 6 Ni atoms. Calculations of trapping of hydrogen to a number of grain boundaries in Ni3Al have been performed as a function of hydrogen chemical potential at room temperature. The failure of these bicrystals under tensile stress has been examined and will be compared to the failure of pure Mi3AI *** order to investigate the potential embrittlement of γ/γ'alloys, trapping of hydrogen to a spherical Hi3Al precipitate in Ni as a function of chemical potential at room temperature has been calculated. It appears that the boundary is not a strong trap for hydrogen, hence embrittlement in these alloys is not primarily due to interactions of hydrogen with the γ/γ'interface. (Supported by the U. S. DOE through Contract DE-AC04-94AL85000.)

关键词： intermetallics atomistic calculations,hydrogen embrittlement

A two-configuration study on the photodetachment cross-section for the 3σ_u channel of F_2^-

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Science China Mathematics 1997年第4期40卷 432-435页

作者：孙卫国 R.M. Pitzer C.W. McCurdyLawrence livermore National Laboratory P.O.Box 5509 L-561 livermore CA 94550 U.S.A. Department of Applied Chemistry Sichuan Union University Chengdu 610065 China Department of Chemistry Ohio State University Columbus Ohio 43210 U.S.A.

An unusual resonance feature of the photodetachment cross-section for the 3σu channel of F2- observed in the early static-exchange study is confirmed by using correlated target (F2) wavefunctions determined by configuration interaction (CI). The magnitude of the cross-sections is lowered from that in earlier calculation by the potential of the correlated target.

关键词： resonance cross-section photodetachment configuration-interaction.x

THE CHANGING ROLE OF THE NATIONAL LABORATORIES IN MATERIALS RESEARCH

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Acta Metallurgica Sinica(English Letters) 1995年第Z1期8卷 245-259页

作者： WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate,Lawrence livermore National Laboratory, livermore, CA 94551)

The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.

关键词： U.S. Materials Science. U.S. National Laboratories and Facilities International Partnerships

The Specimen Data Refinery:A Canonical Workflow Framework and FAIR Digital Object Approach to Speeding up Digital Mobilisation of Natural History Collections

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Data Intelligence 2022年第2期4卷 320-341页

作者： Alex Hardisty Paul Brack Carole Goble Laurence livermore Ben Scott Quentin Groom Stuart Owen Stian Soiland-Reyes School of Computer Science and Informatics Cardiff UniversityCardiff CF243AAUK The Department of Computer Science The University of ManchesterManchester M139PLUK The Natural History Museum London SW75BDUK Meise Botanic Garden 1860 MeiseBelgium Informatics Institute Faculty of ScienceUniversity of Amsterdam1090 GH AmsterdamThe Netherlands

A key limiting factor in organising and using information from physical specimens curated in natural science collections is making that information computable,with institutional digitization tending to focus more on imaging the specimens themselves than on efficiently capturing computable data about *** data are traditionally manually transcribed today with high cost and low throughput,rendering such a task constrained for many collection-holding institutions at current funding *** show how computer vision,optical character recognition,handwriting recognition,named entity recognition and language translation technologies can be implemented into canonical workflow component libraries with findable,accessible,interoperable,and reusable(FAIR)*** libraries are being developed in a cloudbased workflow plaform-the Specimen Data Refinery'(SDR)-founded on Galaxy workflow engine,Common Workflow Language,Research Object Crates(RO-Crate)and WorkflowHub *** SDR can be applied to specimens'labels and other artefacts,offering the prospect of greatly accelerated and more accurate data capture in computable *** kinds of FAIR Digital Objects(FDO)are created by packaging outputs of SDR workflows and workflow components as digital objects with metadata,a persistent identifier,and a specific type *** first kind of FDO are computable Digital Specimen(DS)objects that can be consumed/produced by workflows,and other applications.A single DS is the input data structure submitted to a workflow that is modified by each workflow component in turn to produce a refined DS at the *** Specimen Data Refinery provides a library of such components that can be used individually,or in *** cofunction,each library component describes the fields it requires from the DS and the fields it will in turn populate or *** second kind of FDO,RO-Crates gather and archive the diverse set of digital and real-world resources,configurations,a

关键词： Digital Specimen Workflow FAIR Digital Object RO-Crate

CONTROLLING HIGHTEMPERATURE DEFORMATION BY VARYING MICROSTRUCTURE IN A Ti47Al2Cr2Nb ALLOY

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中国有色金属学会会刊：英文版 1999年第S1期9卷 254-262页

作者： T.G.Nieh and J.Wadsworth Lawrence livermore National Laboratory, L-369, P.O.Box 808, livermore, CA 94550, U.S.A.

A Ti 47Al 2Cr 2Nb alloy was made by powder extrusion methods. By varying extrusion temperature, different microstructures were produced. At an extrusion temperature of 1 400 ℃ (above α transus), a uniform, fully lamellar structure was observed. In contrast, when powders were extruded at 1 150 ℃, an inhomogeneous microstructure consisting of γ,α 2 and metastable β phases was obtained. It was demonstrated that, while alloy extruded at 1 400 ℃ exhibited an excellent creep resistance, alloy with the same composition extruded at 1 150 ℃ exhibited superplasticity. The good creep resistance was resulted from the presence of fine lamellae which restrict dislocation slip within γ grains. These fine lamellae also promote the nucleation of deformation twins which impede dislocation glide along the interfaces ( γ/γ and γ/α 2) and, thus, reduces creep rate. In the case of low temperature extrusion, an elongation value of over 300% was obtained at a strain rate of 2×10 -5 s -1 and at a temperature as low as 800 ℃, which is close to the ductile to brittle transition temperature. This is in contrast to the prior major observations of superplastic behaviors in TiAl in which typical temperatures of 1 000 ℃ have usually been required for superplasticity. It was proposed that the occurrence of superplasticity at 800 ℃ is caused by the presence of a B2 phase which, during superplastic deformation (grain boundary sliding), accommodates sliding strains to reduce the propensity for cavitation at grain triple junctions and, thus, delays the fracture process.

关键词： Ti 47Al 2Cr 2Nb alloy microstructures high temperature deformation

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2016年

作者： Jesse livermore原

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