Showing papers on "Laves phase published in 2000"
TL;DR: A comprehensive review of the phase stability, point defects, and fracture toughness of AB 2 Laves phases, and on the alloy design of dual-phase alloys based on a soft Cr solid solution reinforced with hard X Cr 2 second phases (where X = Nb, Ta and Zr) is provided in this paper.
192 citations
TL;DR: In this article, the effect of additional softening phases on deformability and toughness of NiAl alloys with disordered Fe-Al phase and partially transformed martensitic NiAl phase is investigated.
151 citations
TL;DR: A new intermetallic compound MgYNi4 with C15b(AuBe5)-type Laves phase structure was successfully synthesized by both mechanical milling and casting methods.
100 citations
15 Dec 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, microstructural results in as-cast and annealed samples are discussed, and the dominant equilibrium phases identified are the C 14 -like Laves phase, a Ti 2 Ni-like phase, α(Ti/Zr), the b.c. 1/1 W-phase and the i-phase.
Abstract: Equilibrium phase formation is reported for ternary Ti–Zr–Ni alloys near the i-phase-forming composition, for temperature slices between 500 and 700°C. Selected microstructural results in as-cast and annealed samples are discussed. Dominant equilibrium phases identified are the C 14 -like Laves phase, a Ti 2 Ni-like phase, α(Ti/Zr), the b.c.c. 1/1 W-phase and the i-phase. The i-phase forms over a small compositional range from a high-temperature equilibrium phase mixture of the Laves and α(Ti/Zr) solid solution phases. Lower annealing treatments have not been found to transform the i-phase, suggesting that in this alloy, the quasicrystal phase might be the ground state phase. Additions of small amounts of Pb and Pd, 1–2 at.%, are demonstrated to substantially effect the equilibrium phase formation for the i-phase and the W-phase. The addition of 1 at.% of Pb significantly orders the i-phase structure.
67 citations
TL;DR: In this paper, the effect of non-stoechiometry was first studied and the maximum hydrogen storage capacity was obtained for the slightly under stoechiometric Ti 0.95Zr0.95.
62 citations
TL;DR: In this paper, a cyclic oxidation screening test was used to evaluate potential for high-temperature oxidation resistance of several two-phase Cr(X)-Cr2X in-situ composites.
55 citations
TL;DR: In this article, microstructural analysis of a two-phase alloy of composition Cr-9.8.% Ta and lying in the Cr-Cr2Ta region of the Cr−Ta binary system confirmed that the existing phase diagram is inaccurate.
50 citations
TL;DR: In this paper, the evolution of the microstructure, tensile and impact properties of Fe-7.5/11CrWVTa reduced activation martensitic (RAM) steels after thermal aging performed at relevant temperatures for fusion applications (250-550°C).
37 citations
34 citations
TL;DR: In this article, microprobe analysis and X-ray powder diffraction were performed for a series of intermetallic compounds Ti095Zr005Mn145M05 where M=V, Cr, Mn, Co, Ni and Al.
33 citations
TL;DR: In this paper, the lattice parameter of the ZrCo2 Laves phase remains constant for the alloys with Zr content higher than 333 at%, indicating that the solubility range of Zr in Zr-Co2 on the zr-rich side is essentially zero.
TL;DR: The magnetization and magnetostriction of a variety of Laves phase rods of TbxDyyHo1−x−yFe1.95 grown in the form of [112] oriented dendritic platelets were measured as a function of magnetic field H(−2200
Abstract: The magnetization and magnetostriction of a variety of Laves phase rods of TbxDyyHo1−x−yFe1.95 grown in the form of [112] oriented dendritic platelets were measured as a function of magnetic field H(−2200
TL;DR: In this article, a tensile and charpy impact test was conducted on OPTIFER steel grades and F82H mod. The steels show little difference in tensile properties, but pronounced differences in charpy impacts.
TL;DR: In this paper, it has been found that Fe excess increases and rare earth excess decreases the crystallization temperature, whereas the addition of Zr leaves the crystallisation temperature unaffected, and that the Fe 2 RE (Tb, Dy) Laves phase can be obtained by subsequent heat treatment for all compositions investigated here.
TL;DR: In this paper, the phase stability of the C15 and C14 structures based on a consideration of atomic size factor and the average electron concentration was discussed, and the orientation relationship between the C14 and C15 structures was determined to be (111)[110]C15//(0001)[1120]C14.
TL;DR: In this paper, a semiquantitative model describing the properties of the magnetic twister is presented and discussed, where the authors show that the magnetic response of DyFe2/YFe2 structure and that of the YFe2 seed layer are not completely independent of one another.
Abstract: Laves phase DyFe2/YFe2 multilayers have been grown epitaxially on a YFe2 seed layer, with a (110) growth direction. Magnetic measurements taken in applied fields of up to 12 T, and from 5 K to room temperature, show that short period multilayers (∼100 A) behave, collectively, as a single magnetic entity. As a result, it is possible to engineer magnetic compensation points, in a digital manner, by adjusting the thicknesses of the alternate DyFe2 and YFe2 layers. Nevertheless, the magnetic response of the DyFe2/YFe2 structure and that of the YFe2 seed layer are not completely independent of one another. Because of a mismatch in the Fe–Fe magnetic exchange at the multilayer/seed interface, a 180° magnetic soliton-like domain (“magnetic twister”) is set up in the top of the YFe2 seed layer. A semiquantitative model describing the properties of the magnetic twister is presented and discussed.
TL;DR: In this paper, the effect of the M/Cr substitution with regards to the alloys and hydrides stability and the maximum hydrogen content was studied with respect to the m/cr substitution.
TL;DR: In this paper, thermal aging of low-activation F82H-modified steel has been performed at temperatures in the range 300-600°C during periods up to 5000 h. The results show a decrease of the impact properties after aging at 600°C that has been related to the precipitation of the Laves phase.
TL;DR: In this paper, a hypo-stoichiometric Zr-based Laves phase alloys were prepared and studied from a viewpoint of discharge capacity for electrochemical application, which reveals relatively good properties with regard to hydrogen storage capacity, hydrogen equilibrium pressure and electrochemical discharge capacity.
TL;DR: In this paper, the charge density distribution of the intermetallic compound MgCu2 is obtained by the maximum entropy method (MEM) from the synchrotron powder diffraction data.
Abstract: The charge density distribution of the intermetallic compound MgCu2 is obtained by the maximum entropy method (MEM) from the synchrotron powder diffraction data. In the MEM charge density map, the overlap of electron densities was clearly observed between the neighbouring Cu atoms. This clearly shows that there is a rather strong covalent bond between Cu-Cu atoms. It is also found that the Cu-Cu bonding is along the very well known kagome net, which characterizes the Laves phase structure. At least, in the case of MgCu2 , the kagome network is the electronic network in reality rather than a geometrical concept to represent structural characteristics of Laves phase compounds.
TL;DR: In this paper, the phase stability of precipitates in 12Cr-2W-Cu-V-Nb steel tubes after one-year and three-year service exposure tests in a Japanese practical boiler has been investigated from a standpoint of phase stability, and it is concluded that the morphology and compositions of MX have been stable under the present service conditions, thereby the creep strength as well as tensile strength has kept high after long-term service exposure.
Abstract: Microstructural evolution of 12Cr-2W-Cu-V-Nb steel tubes (ASME SA213-T122) after one-year and three-year service exposure tests in a Japanese practical boiler has been investigated from a standpoint of the phase stability of precipitates. The test tubes consist of tempered martensite and δ-ferrite, and the main precipitates are MX-type carbonitride, M 23 C 6 carbide and Laves phase. TEM observations on thin films show that the MX has precipitated in a plate-shaped with a coherent or semi-coherent relationship with the matrix inside grains. An estimation of the lattice misfit between MX and the matrix suggests that the coherent strain has been high enough to enhance the shear stress and then strongly interact with dislocations. Another important point is that morphology and compositions of MX have been stable under the present service conditions, thereby the creep strength as well as tensile strength has kept high after long-term service exposure. The long-term exposure to the present service temperature has enhanced the precipitation of Fe 2 (W, Mo) Laves phase inside grains, resulting in a marked reduction in the dissolved W and Mo in matrix. It is found that the kinetics of W-partitioning between matrix and Laves phase can be successfully expressed by the Johnson-Mehl-Avrami type equation and applied to estimate the actual temperatures of the exposed tubes. It is concluded that the kinetics of Laves phase precipitation and morphology of MX have mainly controlled a microstructural stability in the 12Cr-2W-Cu-V-Nb steel, and also give helpful suggestion to increase the creep resistance during the long-term service exposure.
TL;DR: In this paper, it is shown that the measured coercivity is in semiquantitative agreement with a simple theoretical expression, for the nucleation fields in both bilayer and multilayer compounds.
Abstract: Molecular beam epitaxial methods have been used to grow single crystal Laves phase DyFe2–YFe2 superlattice samples with a (110) growth direction. It is shown that it is possible, in principle, to engineer a desired coercivity between the limits KDyFe2⩽K⩽∞. This can be achieved by adjusting the relative thickness of the individual DyFe2 and YFe2 layers, in multilayer films This novel feature is illustrated, using the superlattice films [x A DyFe2/(100-x) A YFe2]×40, with x=80, 60, 50, and 45. It is found that the measured coercivity is in semiquantitative agreement with a simple theoretical expression, for the nucleation fields in both bilayer and multilayer compounds. However, in practice, exchange spring penetration into the DyFe2 layers can set a limit to the maximum coercivity that can be achieved.
TL;DR: In this article, the effects of the addition of BCC former elements such as Nb, Ta, Mo, and W on protium absorbing properties and the phases of Cr-Ti-V-M alloys have been studied.
Abstract: Vanadium-based alloys with BCC structure are known to absorb high content of protium. The reduction of costs of the alloys requires to lower V content and to have higher protium capacity. The decrease of the V content in the alloys appears to form Laves phases, which results in reduced protium capacity. It is expected that BCC former addition to the alloys will form BCC phase with less V content inhibiting formation of Laves phase. The effects of the addition of BCC former elements such as Nb, Ta, Mo, and W on protium absorbing properties and the phases of Cr-Ti-V-M alloys have been studied. It has been found that Nb, Ta, and Mo additions are effective in forming BCC structures with improved homogeneity of the alloys, resulting in flattening the slope of plateau region of their PCT curves.
TL;DR: In this article, the homogeneity ranges of two ternary praseodymium alumogermanides, PrAl 1.55-1.52 and PrAl 0.98 Ge 0.45-0.476, were determined and their crystal structures refined from X-ray single-crystal diffraction data.
TL;DR: In this paper, the authors performed a neutron-diffraction study of hydrogen-disordered and hydrogen-ordered phases in the hexagonal (C14-type) hydrogen solid solution ZrCr 2 D 3.8.
TL;DR: A series of multicomponent Zr0.5Ti0.4V0.6Ni1−xFex alloys are prepared and their crystal structure and P-C-T curves are examined as mentioned in this paper.
TL;DR: In this article, the two-phase Cr(Ta) + Cr2Ta alloys exhibited superior oxidation resistance to either the single-phase (Ta) or the single phase (Ta, Nb) alloys.
Abstract: The oxidation behavior of the Cr(X) solid solution and intermetallic Cr2X Laves phases (X = Nb, Ta) was studied individually and in combination at 1,100°C in humid air. The two-phase Cr(Ta) + Cr2Ta alloys exhibited superior oxidation resistance to either the single-phase Cr(Ta) or the single-phase Cr2Ta alloys. However, the two-phase Cr(Nb) + Cr2Nb alloys exhibited lower oxidation resistance than either the single-phase Cr(Nb) or Cr2Nb alloys. The two-phase Cr(Ta) + Cr2Ta alloys were also found to exhibit superior oxidation resistance to the two-phase Cr(Nb) + Cr2Nb alloys. This was hypothesized to be related to the lower amount of the Cr2X phase in the Cr(Ta)–Cr2Ta eutectic and to the lower solubility of Ta in the Cr(X) phase, relative to the Cr–Nb system. Both of these factors resulted in significantly less oxidation and nitridation in the Cr(Ta) + Cr2Ta alloys.
TL;DR: In this paper, the L1 2 phase field and phase equilibria surrounding the L 1 2 phase in the temperature range of interest were established, and two isothermal sections at 1423 and 1273 K were determined from metallography, X-ray diffraction and electron probe microanalyses.
Abstract: Sintering of elemental powders and conventional arc-melting were used to form temary L1 2 intermetallic compounds in the Al-Ti-Fe system. The L1 2 phase field and phase equilibria surrounding the L1 2 phase in the temperature range of interest were established. Two isothermal sections at 1423 and 1273 K were determined from metallography, X-ray diffraction and electron probe microanalyses. The compositions of L12 phase field, the center compositions of oval-shaped region, were about 28Ti-8Fe-64Al and 27Ti-9Fe-64Al compositions at 1423 and 1273 K, respectively. Thus the L1 2 phases had less ternary and more titanium than those reported in the other Al-Ti-X (X = Mn, Cr) systems. Besides the L1 2 phase, the pertinent second phases were TiAl (L1 0 -type), TiAl 2 (HfGa 2 -type), Ti 2 Al 5 (28 atoms/unit cell-type), Al 3 Ti (D0 22 -type), C14 (Laves phase, MgZn 2 -type), and D8 a (cubic, Mn 23 Th 6 -type). The solubility of iron in TiAl 2 phase was about 2 and 3 mol% at 1423 and 1273 K, respectively. The TiAl 2 phase is more stable at 1273 K and can coexist with L1 2 , TiAl, C14, and D8 a phases in separate phase fields. Thus in the isothermal section at 1273 K, no two-phase equilibrium between the TiAl and L1 2 phases exists. This impedes the development of bonding between TiAl and L1 2 alloys in coating applications.
TL;DR: In this paper, self-diffusion of both constituents in the Laves phase NbCo2 has been explored using the tracer method and the radioisotopes 57Co and 95Nb in combination with sputter and grinder sectioning.
Abstract: Self-diffusion of both constituents in the Laves phase NbCo2 has been explored using the tracer method and the radioisotopes 57Co and 95Nb in combination with sputter and grinder sectioning. The temperature dependences of the Co diffusivity in Nb31Co69 and Nb29Co71 (two compositions inside the phase field of NbCo2) and of the Nb diffusivity in Nb31Co69 are reported. All activation enthalpies are of similar magnitude. Nb diffusion in NbCo2 is significantly slower than Co diffusion. Co diffusion itself is considerably faster in the alloy with higher Co content. The diffusion results are discussed in connection with the structure of and the scarce information available about atomic defects in NbCo2. We propose that diffusion is mediated by thermal vacancies. Furthermore, the results are compared with self-diffusion data for the C14-type Laves compounds MgZn2 and Tife2, with interdiffusion data obtained from multiphase diffusion experiments in our laboratory, and with self-diffusion in the also close...
TL;DR: The single phase of micro-crystalline C14 Laves of Zr 0.7 Ti 0.3 (NiVMnCr) 2.1 alloy was successfully prepared by melt-spinning processing with a certain cooling rate as mentioned in this paper.