Showing papers on "Alloy published in 2000"
TL;DR: In this article, the authors investigated the stabilization properties of the supercooled liquid for a number of alloys in the Mg-, lanthanide-, Zr-, Ti-, Fe-, Co-, Pd-Cu- and Ni-based systems.
5,173 citations
TL;DR: Under unconstrained mechanical loading organized shear band patterns develop throughout the sample, which results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass.
Abstract: Results are presented for a ductile metal reinforced bulk metallic glass matrix composite based on glass forming compositions in the Zr-Ti-Cu-Ni-Be system. Primary dendrite growth and solute partitioning in the molten state yields a microstructure consisting of a ductile crystalline Ti-Zr-Nb b phase, with bcc structure, in a Zr-Ti-Nb-Cu-Ni-Be bulk metallic glass matrix. Under unconstrained mechanical loading organized shear band patterns develop throughout the sample. This results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass. PACS numbers: 81.40. – z, 81.05.Kf Zr41.2Ti13.8Cu12.5Ni10Be22.5 (V1) exhibits an exceptional bulk metallic glass (BMG) forming ability that has motivated investigations of its mechanical behavior [1– 3]. This alloy exhibits a 1.9 GPa tensile yield strength, and a 2% elastic strain prior to failure under tensile or compressive loading. However, as in all metallic glasses, V1 specimens loaded in a state of uniaxial or plane stress fail catastrophically on one dominant shear band and show little global plasticity. Specimens loaded under constrained geometries (plane strain) fail in an elastic, perfectly plastic manner by the generation of multiple shear bands. Multiple shear bands are observed when the catastrophic instability is avoided via mechanical constraint, e.g., in uniaxial compression, bending, rolling, and under localized indentation. This behavior under deformation has limited the application of bulk metallic glasses as an engineering material. This Letter presents results for a new class of ductile metal reinforced BMG matrix composites prepared via in situ processing. Under loading, the two-phase microstructure leads to spatial variations in elastic properties as well as the conditions for yielding, the ductile phase having a lower yield strain. The initiation and propagation of shear bands is controlled by the scale and geometry of the ductile phase dispersion with the result that deformation occurs through the development of highly organized patterns of regularly spaced shear bands distributed uniformly throughout the sample. The compositions in the Zr-Ti-Cu-Ni-Be system are compactly written in terms of a pseudoternary Zr-Ti-X phase diagram, where X represents the moiety Be9Cu5Ni4, characteristic of Zr41.2Ti13.8Cu12.5Ni10Be22.5. Results presented here are for alloys of the form Zr1002x2zTixMz1002yXy, where M is an element that stabilizes the crystalline b phase in Ti- or Zr-based alloys. The inset in Fig. 1 shows the x-ray diffraction pattern for the nominal composition Zr75Ti18.34Nb6.6675X25; i.e., an alloy with M Nb, z 6.66, x 18.34, and y 25. The diffraction pattern was obtained with an INEL diffractometer (Co-Ka radiation) on the cross sectioned surface of a 25 g arc melted rod of roughly cylindrical diameter, f 1 cm. The peaks shown [with (hkl) values labeled] are due to the bcc phase. A Nelson-Riley extrapolation yields a lattice parameter a 3.496 A [4]. Upon cooling from the high temperature melt, the alloy undergoes partial crystallization by nucleation and subsequent dendritic growth of the b phase in the remaining liquid. The remaining liquid subsequently freezes to the glassy state producing a twophase microstructure containing b-phase dendrites in a glass matrix. The final microstructure of a chemically etched specimen is shown in the scanning electron microscopy (SEM) image of Fig. 1. SEM electron microprobe analysis gives the average composition for the b-phase dendrites (light phase in Fig. 1) to be Zr 71Ti16.3Nb10Cu1.8Ni0.9. Under the assumption that all of the Be in the alloy is partitioned into the matrix we estimate that the average composition of the amorphous matrix (dark phase) is Zr47Ti12.9Nb2.8Cu11Ni9.6Be16.7. Both are quoted
1,365 citations
TL;DR: In this article, a review of the metallurgy of zinc-coated steel from a scientific standpoint to develop relationships to practical applications is presented. And the effect of the microstructures of these coatings on the important properties of corrosion, formability, weldability and paintability is discussed.
1,194 citations
TL;DR: In this article, the properties of oxide films formed on a Ti-6Al-4V alloy by AC plasma electrolytic oxidation (PEO) in aqueous solutions containing aluminate, phosphate, silicate and sulfate anions and some of their combinations are studied by SEM, XRD and microhardness analyses, and by scratch, impact, pin-on-disc friction and potentiodynamic corrosion testing.
Abstract: The paper discusses processing and property aspects of oxide films formed on a Ti–6Al–4V alloy by AC plasma electrolytic oxidation (PEO) in aqueous solutions containing aluminate, phosphate, silicate and sulfate anions and some of their combinations. Structure, composition, mechanical tribological and corrosion resistant characteristics of the films formed are studied by SEM, XRD and microhardness analyses, and by scratch, impact, pin-on-disc friction and potentiodynamic corrosion testing. It is found that the films produced from the aluminate–phosphate electrolyte are dense and uniform and are composed mainly of Al 2 TiO 5 and TiO 2 phases of the rutile form. The films possess a beneficial combination of 50–60 μm thickness, 575 kg/mm 2 hardness and high adhesion and provide a low wear rate (3.4×10 −8 mm 3 /Nm) but a relatively high friction coefficient of μ=0.6–0.7 against steel, caused by material transfer from the counterface. A minimum friction coefficient of μ=0.18 is recorded during the testing of softer rutile–anatase films, 7 μm thick, produced from a phosphate electrolyte. Both of these types of film show good corrosion resistance in NaCl and physiological solutions, where the corrosion current is approximately 1.5 orders of magnitude lower than that of the uncoated substrate. SiO 2 /TiO 2 -based films with 70–90 μm thickness and high bulk porosity produced from silicate and silicate–aluminate electrolytes demonstrate better corrosion behaviour in H 2 SO 4 solution, due to the greater chemical stability of the film phase components in this environment.
586 citations
TL;DR: In this paper, the effect of microconstituents on the corrosion and electrochemical behaviour of AZ91D alloy prepared by die-casting and ingot casting route has been investigated in 3.5% NaCl solution at pH 7.25.
584 citations
TL;DR: In this paper, the percolation of the carbon nanotubes was studied and discussed in relation to the nature of the matrix, the electrical conductivity, the fracture strength and the fracture toughness.
530 citations
TL;DR: In this article, the hydrogen storage properties of the new ternary system alloys, La2MgNi9, La5Mg2Ni23, La3mgNi14, and La0.7Mg0.8Co0.5, were investigated.
516 citations
TL;DR: In this article, carbon-supported Pt-based binary alloy electrocatalysts (Pt-Co, Pt-Cr and Pt-Ni) were prepared by incipient wetness method to investigate the origin of the enhanced activity of the oxygen reduction reaction in fuel cells.
515 citations
TL;DR: In this article, the structure and catalytic activity of Cu/ZnO methanol synthesis catalysts have been investigated by a further developed in situ method, which combines X-ray diffraction (XRD), Xray absorption fine structure spectroscopy (XAFS), and on-line catalytic measurements by mass spectrometry.
508 citations
15 May 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the deformed microstructures were investigated at various strains using X-ray diffraction, optical microscopy, scanning electron microscopy and electron back-scattered diffraction.
Abstract: Discontinuous dynamic recrystallization (involving nucleation and grain growth) is rarely observed in metals with high stacking fault energies, such as aluminium. In this metal, two other types of recrystallization have been observed: continuous dynamic recrystallization (CDRX, i.e. the transformation of subgrains into grains); and geometric dynamic recrystallization (due to the evolution of the initial grains). The main purpose of this work was to bring clearly into evidence and to better characterize CDRX. Uniaxial compression tests were carried out at 0.7 T m and 10 −2 s −1 on three types of polycrystalline aluminium: a pure aluminium (1199), a commercial purity aluminium (1200) and an Al-2.5wt.%Mg alloy (5052), and also on single crystals of pure aluminium. In addition, 1200 aluminium specimens were strained in torsion. The deformed microstructures were investigated at various strains using X-ray diffraction, optical microscopy, scanning electron microscopy and electron back-scattered diffraction. Observations of the single crystalline samples confirm that subgrain boundaries can effectively transform into grain boundaries, especially when the initial orientation is unstable. In the case of polycrystalline specimens, after separating the effects of the initial and new grain boundaries, it turns out that CDRX operates faster in the 1200 aluminium compared to the two other grades. Moreover, it appears that the strain path does not alter noticeably the CDRX kinetics.
470 citations
TL;DR: In this paper, the conduction band minimum formation of GaAs{sub 0.5{minus}y}P{sub 2y} is investigated for small nitrogen compositions (0.1% < 2y < 1.0%), using a pseudopotential technique.
Abstract: The conduction band minimum formation of GaAs{sub 0.5{minus}y}P{sub 0.5{minus}y}N{sub 2y} is investigated for small nitrogen compositions (0.1% < 2y < 1.0%), by using a pseudopotential technique. This formation is caused by two unusual processes both involving the deep-gap impurity level existing in the dilute alloy limit y {r_arrow} 0. The first process is an anticrossing with the {Gamma}{sub Ic}-like extended state of GaAs{sub 0.5}P{sub 0.5}. The second process is an interaction with other impurity levels forming a subband. These two processes are expected to occur in any alloys exhibiting a deep-gap impurity level at one of its dilute limit.
TL;DR: The binary quasicrystal offers a new opportunity to investigate the relation between thermodynamic stability and quasiperiodic structure, as well as providing a basis for the construction of crystallographic models.
Abstract: All stable quasicrystals known so far are composed of at least three metallic elements1,2,3,4. Sixteen years after the discovery of the quasicrystal5, we describe a stable binary quasicrystalline alloy in a cadmium–ytterbium (Cd–Yb) system. The structure of this alloy represents a new class of packing of 66-atom icosahedral clusters whose internal structure breaks the icosahedral symmetry. The binary quasicrystal offers a new opportunity to investigate the relation between thermodynamic stability and quasiperiodic structure, as well as providing a basis for the construction of crystallographic models.
TL;DR: In this article, three stainless steel alloys, 310, 316 and 904L, have been evaluated in terms of the electrical resistance of their surface oxide film and showed that ohmic losses exhibited in fuel cell performance varied depending on the elemental composition of the stainless steel alloy.
TL;DR: In this article, the active catalyst formed a phase-separated hydrons oxide-on-metal structure that retains the Pt metal−RuOxHy boundaries required to oxidize methanol fully to carbon dioxide and water.
Abstract: Contrary to the current understanding of Pt−Ru electrocatalyzed oxidation of methanol, the bimetallic alloy is not the most desired form of the catalyst. In the nanoscale Pt−Ru blacks used to electrooxidize methanol in direct methanol fuel cells, Pt0Ru0 has orders of magnitude less activity for methanol oxidation than does a mixed-phase electrocatalyst containing Pt metal and hydrous ruthenium oxides (RuOxHy). Bulk, rather than near-surface, quantities of electron−proton conducting RuOxHy are required to achieve high activity for methanol oxidation. The active catalyst forms a nanoscopic, phase-separated hydrons oxide-on-metal structure that retains the Pt metal−RuOxHy boundaries required to oxidize methanol fully to carbon dioxide and water.
TL;DR: In this article, the sliding friction and wear behavior of Al, Al-7075 and SiC particulate reinforced aluminium matrix composites (Al-SiC) were investigated under dry sliding wear conditions.
Book•
01 Jan 2000
TL;DR: The ASM Handbook as discussed by the authors provides a comprehensive guide to the compositions, properties, processing, performance and applications of nickel, cobalt, and their alloys, including new or updated coverage in the following areas: Expanded corrosion coverage including guidelines for selecting the best alloy for specific environments or applications Data sheets covering the compositions and specifications, applications and properties for dozens of the most commercially important heat, corrosion and wear-resistant nickel and cobalt alloys.
Abstract: This book is a comprehensive guide to the compositions, properties, processing, performance and applications of nickel, cobalt, and their alloys. It includes all of the essential information contained in the 20-volume ASM Handbook series. Includes new or updated coverage in the following areas: Expanded corrosion coverage including guidelines for selecting the best alloy for specific environments or applications Data sheets covering the compositions, specifications, applications and properties for dozens of the most commercially important heat, corrosion and wear-resistant nickel and cobalt alloys Recent advances in superalloy development, including coatings to extend high-temperature service life Unique characteristics of nickel and cobalt which allow them to be used in special-purpose applications, e.g., magnets, controlled-expansion devices, electronics, and implants for the human body Engineering applications for nickel and cobalt coatings produced by electroplating, electroforming, electroless coating, thermal spraying, and weld surfacing. Contents include: Nickel and Its Alloys: The Nickel Industry, occurrence, recovery and consumption Uses of nickel Wrought and Cast Corrosion-Resistant Alloys Cast Heat-Resistant Ni-Cr and Ni-Cr-Fe alloys Superalloys Special-Purpose Alloys Nickel Coatings Corrosion Behavior, including performance in specific environments, Stress-Corrosion Cracking and Hydrogen Embrittlement, and High-Temperature Corrosion Fabrication and Finishing, including forming, forging, powder metallurgy, heat treating, machining, welding and brazing, cleaning and finishing, and high-temperature coatings for superalloys Metallography, Microstructures, and Phase Diagrams Cobalt and Its Alloys: The Cobalt Industry, occurrence, recovery and consumption Uses of cobalt Cobalt-base alloys Wear behavior Corrosion Behavior Fabrication Characteristics Metallography, Microstructures and Phase Diagrams.
TL;DR: In this paper, a monolayer-protected Au, Ag, and Au:Ag alloy nanoclusters have been synthesized using octanethiol and octadecanethiol as capping agents.
Abstract: Monolayer-protected Au, Ag, and Au:Ag alloy nanoclusters have been synthesized using octanethiol and octadecanethiol as capping agents. The particle-size distribution is narrow with an average core size of 3--4 nm. Optical nonlinearity induced by 35 ps pulses at 532 nm has been investigated in these samples using the Z-scan technique. It is found that in general, they behave either as saturable absorbers or reverse saturable absorbers depending on the intensity of excitation. Au and Ag clusters show nearly the same efficiency for optical limiting, but the alloy clusters are found to be less efficient in limiting and are less photostable. The observed effects are explained in terms of the electron dynamics of the excited-state species.
TL;DR: Based on the theory of Pilling-Bedworth ratio (PBR) for metals, PBR for oxidation of alloys is suggested as in this paper, where PBR is used for alloys.
Abstract: Based on the theory of Pilling-Bedworth ratio (PBR) for metals, PBR for oxidation of alloys is suggested as
TL;DR: In this article, the corrosion behavior of Fe, Cr, Ni, the ferritic alloys Fe 15Cr and Fe 35Cr and the austenitic alloys Alloy 800, Alloy 825 and Alloy 600 at temperatures between 400 and 700°C using discontinuous exposures and thermogravimetric experiments.
15 Feb 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the influence of rear earths (RE) on the microstructure of AZ91 and Mg-6Al-xRE magnesium alloys was investigated, where x is 0, 1, 2 and 3% (in weight percent, wt%), respectively.
Abstract: AZ91–xRE and Mg–6Al–xRE magnesium alloys were studied, where x is 0, 1, 2 and 3% (in weight percent, wt.%), respectively. Influence of rear earths (RE) on the microstructure was investigated. Fine morphology could be achieved by high cooling rate. By casting fluidity spiral specimens, fluidities of the alloys were achieved. The hardness and microhardness of the alloys was tested. RE improved fluidity and hardness. By casting specimens in permanent mold, tensile properties of the alloys with different RE additions at ambient and elevated temperatures were studied. RE had little effect on ambient temperature tensile strength of AZ91 alloy but greatly improved that of Mg–6Al alloy and high temperature tensile properties of both alloys. The fracture behavior of the alloys, which was changed by RE and high temperature, was examined by scanning electron microscopy (SEM) and optical microscopy. Fracture of the alloys is predominantly brittle cleavage or/and quasi-cleavage failure.
TL;DR: In this article, the current knowledge of the properties of ultrathin, well-ordered oxide, nitride and oxynitride films grown on metal and metal alloy surfaces is reviewed.
[...]
15 Mar 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors presented data on new wrought weldable alloys based on the Al-Mg-Sc system, namely, 01515, 01523, 01535, 01545, 01570 and 01571, which differ from each other mainly by magnesium content and belong to the family of non-heat-treatable Alloy alloys.
Abstract: Data on new 01515, 01523, 01535, 01545, 01570 and 01571 wrought weldable alloys based on the Al–Mg–Sc system are presented. These alloys differ from each other, mainly, by magnesium content and belong to the family of non-heat-treatable alloys. Wrought Al–Mg–Sc alloy semiproducts as-hot worked or as-annealed show much higher properties (especially yield strength) than those made from conventional Al–Mg alloys with the same magnesium content. Strengthening relates to both direct strengthening effect of the secondary Al3Sc particles and development of a stable nonrecrystallized structure. Of Al–Mg–Sc alloys, 01570 alloy containing about 6% Mg has found the widest application. Yield strength of hot worked or annealed 01570 alloy semiproducts is at a level of 300 MPa, while yield strength of semiproducts made from a similar scandium-free alloy is about 180 MPa. Prospects of the usage of the new alloys for production of various structures are discussed.
TL;DR: In this article, bipolar plate materials for the Solid Polymer Fuel Cell (SPFC), alternative to the presently used graphite, should satisfy the following requirements in order to be applicable: low-cost, easy to machine or to shape, lightweight and low volume, mechanically and sufficiently chemically stable, and having a low contact resistance.
TL;DR: In this article, a wear mapping approach, consisting of identification of micromechanisms of wear leading to the generation of loose debris and surface damage and determination of the range of applicability of each mechanism as a function of load and speed, was adopted.
TL;DR: In this paper, the authors investigated the oxidation kinetics and electrical properties of oxide scales thermally grown on the surface of a commercial ferritic alloy, as functions of temperature and time under oxidizing atmospheres with four different electrodes.
TL;DR: In this paper, the precipitation of three new types of metastable phases, i.e., TYPE-A, TYPE-B and TYPE-C, with different crystal structures from the β′ phase is proposed from a research on the change in crystal structures and formation sequence during the aging of the Al-1.0mass% Mg2Si-0.4mass% Si alloy by a combination of analytical high resolution electron microscopy and energy dispersive X-ray spectroscopy.
Abstract: The precipitation of three new types of metastable phases, i.e., TYPE-A, TYPE-B and TYPE-C, with different crystal structures from the β′ phase is proposed from our research on the change in crystal structures and formation sequence of metastable phases during the aging of the Al-1.0mass% Mg2Si-0.4mass% Si alloy by a combination of analytical high resolution electron microscopy and energy dispersive X-ray spectroscopy. The sequence of their formation is explained as follows. First, precipitation of the β′ phase and TYPE-B precipitate, then β′ dissolution into the matrix and degradation of the TYPE-B precipitate. Finally, predominant precipitation of the metastable TYPE-A precipitate. The TYPE-C precipitate appeared heterogeneously in the over-aged condition.
15 Mar 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a series of Al-Mg-based alloy plates with thickness of 4 mm containing minor Sc and Zr were prepared and tensile properties and microstructures of the alloys were studied.
Abstract: A series of Al–Mg based alloy plates with thickness of 4 mm containing minor Sc and Zr were prepared. Tensile properties and microstructures of the alloys were studied. The results show that adding 0.2% Sc and 0.1% Zr to Al–5Mg alloy, the strength of the alloy increased by 150 MPa. Strengthening effect is the most outstanding among all minor alloying elements in aluminum alloys. Strength increment caused by adding minor Sc and Zr is attributed mainly to fine grain strengthening, precipitation strengthening of Al3(Sc, Zr) and substructure strengthening.
TL;DR: In this article, magnetic properties and magnetic-field-induced strains (MFIS) have been investigated for off-stoichiometric Ni-Mn-Al Heusler alloys with an ordered L21 structure.
Abstract: Magnetic properties and magnetic-field-induced strains (MFIS) have been investigated for off-stoichiometric Ni–Mn–Al Heusler alloys with an ordered L21 structure. A clear martensitic transformation in Ni53Mn25Al22 alloy was revealed below the Curie temperature. In the polycrystalline specimen, an irreversible relative change due to the MFIS was confirmed between the martensite start and finish temperatures Ms and Mf, and a maximum relative length change ΔL/L|7T of about −100 ppm was observed at just above Mf. On the other hand, a large irreversible relative length change of about 1000 ppm has been demonstrated in the magnetic field of 7 T for a single crystal cut from the polycrystalline specimen. A delay of the response of strains against the magnetic field was also confirmed.
TL;DR: In this paper, the authors describe the preparation and characterization of new PtRu alloy colloids that are suitable as precursors for fuel cell catalysts, which can be easily modified to show hydrophilic properties.
TL;DR: A series of single crystal nickel-based superalloys containing additions of rhenium and ruthenium were designed with the aid of time-saving formulae allowing to predict some of their physical characteristics as mentioned in this paper.
Abstract: A series of single crystal nickel-based superalloys containing additions of rhenium and ruthenium were designed with the aid of time-saving formulae allowing to predict some of their physical characteristics. This alloy design programme succeeded in identifying the new generation single crystal alloy MC-NG suited for gas turbine blade and vane applications. This alloy exhibited a density-corrected high temperature creep strength comparable to that of high-rhenium containing alloys, but with a lower density and no propensity to form deleterious TCP phases.