Showing papers on "Laves phase published in 1985"
TL;DR: In this paper, the dissociation plateau pressure at 20°C was obtained in a range from 0.01 MPa (for Ti 0.9 Zr 0.4 V 0.2 Cr 0.1 Mn 1.4 -H).
104 citations
TL;DR: In this article, the electronic structures of d electrons in the intermetallic compounds ScCo2, TiCo2 and ZrCo2 with cubic Laves phase structure are calculated in the tight-binding approximation.
Abstract: Electronic structures of d electrons in the intermetallic compounds ScCo2, TiCo2, ZrCo2, LuCo2, HfCo2 and ScNi2 with cubic Laves phase structure are calculated in the tight-binding approximation. By using the calculated density-of-states curves and taking the effect of spin fluctuations into account, the temperature dependences of the paramagnetic spin susceptibility in these compounds are calculated. The magnetic field dependence of the induced magnetic moment in LuCo2 at 0K is also calculated. Good agreement between the calculated and observed results is obtained. As observed in ZrCo2 and HfCo2, moreover, an excess Co atom in the Co-rich non-stoichiometric compounds is shown to have a local magnetic moment.
62 citations
TL;DR: In this article, the electronic structure of d electrons in the cubic Laves phase of the intermetallic compound YCo2 under an external magnetic field is calculated in the tight-binding approximation.
Abstract: The electronic structure of d electrons in the cubic Laves phase of the intermetallic compound YCo2 under an external magnetic field is calculated in the tight-binding approximation. The magnetic-field dependence of the induced moment is obtained at 0K and it is shown that the metamagnetic transition from the paramagnetic to ferromagnetic state occurs at about 90 T. It is also shown that the different hybridisations between the 3d band of Co and the 4d band of Y or the 5d band of R (where R is a rare earth) with majority and minority spins play an important role in the appearance of the local moment on Co in the magnetised state of the compounds YCo2 or RCo2.
55 citations
TL;DR: In this paper, the densites of states (DOS's) of the C14 Laves phase compounds AB 2 are characterized by the atoms B(2a) and B(6h) around the Fermi level, which play an important role in investigating their magnetism.
Abstract: The electronic structures were calculated by the KKR and the local-spin-density methods for ZrMn 2 , TiFe 2 and NbFe 2 . The densites-of-states (DOS's) of the C14 Laves phase compounds AB 2 are characterized by the DOS's of the atoms B(2a) and B(6h) around the Fermi level which play an important role in investigating their magnetism. We can guess from the structures of the DOS's and the number of valence electrons whether or not a compound is magnetic.
53 citations
TL;DR: In this paper, the effect of iron additions in the range 5 to 15 wt % iron inclusive on the microstructure and properties of two Co-Mn-Cr-Si wear resistant alloys (Tribaloys” T400 and T800) has been investigated.
Abstract: The effect of iron additions in the range 5 to 15 wt % iron inclusive on the microstructure and properties of two Co-Mn-Cr-Si wear resistant alloys (“Tribaloys” T400 and T800) has been investigated. Iron additions were found to stabilize the f c c form of the cobalt solid solution, to give a fully eutectic matrix and to decrease the volume fraction of the primary Laves phase. These microstructural modifications have little effect on the plane strain fracture toughness but result in a significant increase in the modulus of rupture. The addition of iron induces only minor changes in the corrosion and oxidation resistance of T800, whereas the performance of T400 deteriorates.
39 citations
TL;DR: The structure of the domain boundaries has been studied by HREM and no disorder has been found as discussed by the authors, and the domain boundary structure has been discussed from the point of view of the intergrowth of various tetrahedrally close-packed structures with juxtaposed pentagonal antiprisms.
Abstract: Planar faults occur abundantly on (001), (110) and (11 1) planes in the C14 Laves phase precipitated in a Fe-based superalloy, and these faults will divide the latter into many parallel domains. The structure of the domain boundaries has been studied by HREM and no disorder has been found. Pentagonal antiprisms are reorganized at these boundaries, forming other tetrahedrally close-packed phases, such as differently oriented μ or C phases on (110) and (11 1) boundaries. The domain boundary structure has been discussed from the point of view of the intergrowth of various tetrahedrally close-packed structures with juxtaposed pentagonal antiprisms.
37 citations
TL;DR: In this article, the electronic structures of paramagnetic and ferromagnetic ScFe 2 are calculated self-consistently using the KKR method in the framework of the local-spin density approximation for the exchange-correlation potential.
Abstract: The electronic structures of paramagnetic and ferromagnetic ScFe 2 are calculated self-consistently using the KKR method in the framework of the local-spin-density approximation for the exchange-correlation potential. The general electronic structures are similar for both of the atom Fe(2 a ) at the 2 a sites and the atom Fe(6 h ) at the 6 h sites. However the difference is seen near the Fermi level in the densities-of-state of d bands between Fe(2 a ) and Fe(6 h ). This difference induces a small difference in the magnetic moments between the two Fe; the values are 1.40 µ B /Fe(2 a ) and 1.46 µ B /Fe(6 h ). The atom Sc also carries a magnetic moment of 0.27 µ B /Sc with the direction opposit to the moment of Fe.
26 citations
TL;DR: In this article, the influence of the atom A on the electronic structures and the magnetic properties of C14 compounds was examined and it was shown that the hybridization between d states of A and Fe becomes stronger with increasing the number of valence electrons.
Abstract: The band structures of AFe 2 (A=Mo, Hf, Ta, W) were calculated to examine the influence of the atom A on the electronic structures and the magnetic properties. The band structures are essentially unaffected by the difference in the kind of d bands of the atom A. The hybridization between d states of A and Fe becomes stronger with increasing the number of valence electrons of the atom A and affects the DOS curves of Fe(2 a ) and Fe(6 h ) around the Fermi level which are closely related with the magnetic properties for the C14 compounds. However, since the variation of the electronic structure with the change of the atom A is not so drastic, we can roughly guess the magnetic properties of the C14 compounds with the rigid-band-model.
24 citations
TL;DR: In this paper, the general properties of rare earth-manganese alloys are described and reviewed using differential thermal analysis, X-ray examination, metallography and microprobe analysis.
Abstract: The general properties of rare earth-manganese alloys are described and reviewed. The Pr-Mn system was studied using differential thermal analysis, X-ray examination, metallography and microprobe analysis. Both the stable phase diagram and information on the metastable equilibria were obtained. Evidence of the peritectic formation (790 °C) of Pr 6 Mn 23 (Th 6 Mn 23 -type structure) and the decomposition (about 650 °C) of the same phase appears in the stable diagram. A eutectic (660 °C, 25 at.% Mn) was also observed. The peritectic formation (740 °C) of PrMn 2 (hexagonal Laves phase) took place under metastable conditions. The various methods of preparing these alloys are discussed and their strong reactivity with alumina is studied. Finally it is shown that the Pr-Mn diagram fits well in the sequence of the known diagrams of manganese with the rare earths and the basic metals. The relation between the ratio of the atomic dimensions, the valence electron number and the mutual reactivity is emphasized.
21 citations
TL;DR: In this article, the authors examined the possibility of obtaining complete solid solutions in dependence with the dimensions of M, M′ atoms and their valence, and investigated the effect of the "chemical pressure" on the valence state of solid solutions of Ce, Eu, and Yb compounds by magnetic measurements.
Abstract: Pseudobinary systems (M,M′)Al2 where M Ca, La, Ce, Eu or Yb, and M′ Ca, Sc, Y, La, Sm, Dy, Er or Lu, have been studied in order: 1. (a) to examine the possibility of obtaining complete solid solutions in dependence with the dimensions of M, M′ atoms and their valence; 2. (b) to investigate the effect of the “chemical pressure” on the valence state of solid solutions of Ce, Eu, and Yb compounds by magnetic measurements .
20 citations
Patent•
30 Dec 1985
TL;DR: In this article, a nickel base superalloy composition useful in the cast+HIP+heat treated condition is described, which has properties comparable to similarly processed IN718 articles and is substantially free from Laves phase, even at slow solidification rates.
Abstract: A nickel base superalloy composition useful in the cast+HIP+heat treated condition is described. Articles having the invention composition have properties which are comparable to similarly processed IN718 articles. The invention alloys have an as-cast microstructure which is substantially free from Laves phase, even at slow solidification rates. As a result, the alloys are significantly more weldable than IN718. This desirable microstructure is achieved by modifications of the chromium, molybdenum, iron, and nickel contents compared to the typical IN718 composition.
TL;DR: In this paper, superconducting properties have been studied for newly developed V2(Hf, Zr) multifilamentary wires and the overall J c of these wires are twice as large as that of the bronze processed Nb3Sn multifilamary wire.
TL;DR: In this article, the authors present experimental results for the low-temperature specific heat, electrical resistivity, elastic constants, ultrasonic attenuation and thermal conductivity of the C 15 Laves phase HfV2 for both polycrystalline and single crystal samples.
Abstract: We present experimental results for the low-temperature specific heat, electrical resistivity, elastic constants, ultrasonic attenuation and thermal conductivity of theC 15 Laves phase HfV2 for both polycrystalline and single crystal samples. BelowTc=9 K, the temperature dependence of the specific heat can roughly be approximated by aT3 law over a large temperature range. This may be explained with strong coupling effects in consistence with the high value for ΔC/γTc=1.9. Heat transport appears dominated by the known phonon contribution also belowTc. There is no electronic contribution to the ultrasonic attenuation in HfV2.
TL;DR: In this article, new phases were detected in alloys of the R-Fe series which were obtained by quenching from the melt at a constant pressure of 7.7 GPa.
Abstract: New phases were detected in alloys of the R-Fe series which were obtained by quenching from the melt at a constant pressure of 7.7 GPa. These compounds have the following imperfect disordered Laves phase structures: MgZn2 type (C14) for R≡Tb, Ho, Er, Tm, Yb, Lu, and MgCu2 type (C15) for R≡Pr, Sm, Dy. The connection between the structures of the new phases and the structure of metallic RFe2 glasses is discussed.
TL;DR: In this article, the crystal structure of the cubic Laves phase UMn2 at 295 K and 12 K was refined using Rietveld profile analysis, and structural data and interatomic distances were given.
Abstract: We refined the crystal structure of the cubic Laves phase UMn2 at 295 K and 12 K using the method of Rietveld profile analysis. Structural data and interatomic distances are given.
TL;DR: In this article, the changes of the ferromagnetic moment and the longitudinal stiffness constant are explained as transitions between the two states with the different temperature variation of the local amplitude of spin fluctuations.
Abstract: (Sc 0.35 Ti 0.65 )Fe 2 having the hexagonal Laves phase structure is a ferromagnet with the Curie temperature of 360 K. The ferromagnetic moment changes from 1.3 to 0.9 µ B around 70 K with increasing temperature. The transition is of the first order. The longitudinal stiffness constant for spin fluctuations changes around 500 K. The magnetic state below 70 K seems to be the same state as that above 500 K and is more localized than the state between 70 and 500 K. The changes of the ferromagnetic moment and the longitudinal stiffness constant are explained as transitions between the two states with the different temperature variation of the local amplitude of spin fluctuations.
TL;DR: In this paper, the intermetallic precipitates in Zircaloy-4 have been identified as the C15 type Zr(CrFe)2 Laves phase using high order Laue zones and series diffraction patterns from the transmission electron microscope.
TL;DR: In contrast to the other magnetic rare Earth (RE) ions for which the cubic Laves REIr 2 compound is ferromagnetic, YbIr 2 and TmIr 2 are antiferromagnetic below 0.40 and 0.05 K, respectively.
TL;DR: In this article, a very rapid reaction takes place between the Nb sublayers and molten Sn. This phase transforms into orthorhombic NbSn 2 which then reacts with the remaining Nb to form Al5 Nb 3 Sn.
Abstract: Thin films of A15 Nb 3 Sn have been prepared by reactive diffusion of sputter-deposited Nb/Sn multilayers. The layer thicknesses were arranged in such a way as to produce Nb 3 Sn and desired off-stoichiometry samples. The reaction was studied by means of in situ temperature-dependent X-ray analysis in the range 50°C-950°C. It was observed that, prior to the formation of the Al5 phase, a very rapid reaction takes place between the Nb sublayers and molten Sn. In this reaction a new phase was observed which could be interpreted as a hexagonal Laves phase NbSn 2 . This phase transforms into orthorhombic NbSn 2 which then reacts with the remaining Nb to form Al5 Nb 3 Sn. The fact that the reaction occurs at the Nb/liquid Sn interface with the formation of the most Sn-rich phase indicates that the reaction takes place by diffusion of Nb into liquid Sn. The highest superconducting transition temperature was found to be 17.45°K. The values of the Al5 cell parameters indicated that the diffusion reaction of both on-and off - stoichiometry Nb 3 Sn multilayers is driven towards the Sn-rich side of Nb 3 Sn, with a maximum composition range of 24-28 at% Sn.
TL;DR: The dependence of the hyperfine field on the lattice constant suggests that lattice expansion plays an important role in the magnetic ordering of Mn 2 as discussed by the authors, and the NMR of 159 Tb in Tb 0.75 Lu 0.63 A has a satellite line in the frequency range from 50 MHz to 80 MHz.
Abstract: 55 Mn NMR measurements have been done in magnetically ordered state of the Laves phase compounds RMn 2 and R 1- x R x ′ Mn 2 (R=rare earth; R'=rare earth or yttrium). The abrupt change in the Mn hyperfine field as a function of the cubic lattice constant occurs at around 7.62 A. For example, the Mn hyperfine field changes from 30.5 kOe in Er 0.5 Gd 0.5 Mn 2 with the lattice constant of 7.62 A to 100 kOe in Er 0.4 Gd 0.6 Mn 2 with 7.63 A. In addition, the NMR spectrum in the compound which has a cubic lattice constant in the critical region from 7.58 A to 7.63 A has a satellite line in the frequency range from 50 MHz to 80 MHz. The dependence of the hyperfine field on the lattice constant suggests that the lattice expansion plays an important role in the magnetic ordering of Mn. The NMR of 159 Tb in Tb 0.75 Lu 0.25 Mn 2 was also investigated under zero and 18 kOe external fields.
TL;DR: In this paper, the paramagnetic Curie temperature and paramagnetic effective moment were measured for the pseudobinary compounds Gd(Al1−xSnx)2, where the Me metals used in the systems under investigation differ in the number of conduction electrons per Me atom.
Abstract: The paramagnetic Curie temperature and the paramagnetic effective moment were measured for the pseudobinary compounds Gd(Al1−xSnx)2. The results are compared with those for similar systems of the type Gd(Al1−x)2, where Me Cu, Ag, Pd, In. In no case, except for the highly concentrated samples with Me Cu and Ag, were remarkable changes of the paramagnetic effective moment observed. However, a dramatic decrease of the paramagnetic Curie temperature (Θp) was observed for all systems. The Me metals used in the systems under investigation differ in the number of conduction electrons per Me atom. This number can be assumed to be 0 for Pd, 1 for Cu and Ag, 3 for In and Al atoms, and 4 in the case of Sn. The very sharp decrease of the paramagnetic Curie temperature, observed in all cases, is explained on the basis of band structure calculations. The crucial change of the density of states at the Fermi level as a function of concentration for Me ions with different numbers of conduction electrons seems to be responsible for the effects observed.
TL;DR: In this paper, the Laves phase pseudo-binary system Ce(Fe 1-x Al x ) 2 for x ≤ 0.20 has been studied by means of electrical resistivity measurements from 1.5 to 300 K.
Patent•
03 Dec 1985
TL;DR: In this article, the authors proposed to replace vanadium which is an ingredient raw material with ferrovanadium (V-Fe alloy) represented by formula I as a starting raw material, and an alloy whose alloy phase is Laves phase of intermetallic compound and crystal structure is C14 type of hexagonal symmetry and/or C15 type of cubic symmetry, or hydride of this alloy is manufactured.
Abstract: PURPOSE:To reduce raw material cost and manufacturing cost, to heighten safety, to improve workability, and to increase reliability by replacing vanadium which is an ingredient raw material with ferrovanadium (V-Fe alloy). CONSTITUTION:At least ferrovanadium (V-Fe alloy) represented by formula I is used as a starting raw material, and an alloy whose alloy phase is Laves phase of intermetallic compound and crystal structure is C14 type of hexagonal symmetry and/or C15 type of cubic symmetry, or hydride of this alloy is manufactured. For C14 type hexagonal symmetry, crystal lattice constant a is 4.8-5.2Angstrom and c is 7.9-8.3Angstrom . For C15 type of cubic symmetry, crystal lattice constant a is 6.92-7.70Angstrom .
TL;DR: Magnetic hysteresis losses in V2Zr and V2Hf Laves phase compounds are investigated in this article, where the influence of the geometrical shape, first penetration field and that of the flux creep phenomenon is considered.
Abstract: Magnetic hysteresis losses in V2Zr and V2Hf Laves phase compounds are investigated. The influence of the geometrical shape, first penetration field and that of the flux creep phenomenon is considered. The hysteresis at static magnetization is calculated for a set of values of the parameter γ describing magnetic induction profile and compared with observed data. The best fit value depends on the ordering state of the sample.
Nous avons etudie les pertes d'energie par hysteresis magnetique des phases de Laves de V2Zr et V2Hf. L'influence de l'amplitude du champ de penetration et du phenomene de reptation de flux a ete mise en evidence. L'aimantation statique calculee pour un ensemble de valeurs du parametre y caracteristique du profil de l'induction magnetique est comparee aux resultats experimentaux. La valeur du parametre donnant le meilleur accord depend de l'etat d'ordre de l'echantillon.
TL;DR: Magnetic, 57Fe Mossbauer and neutron diffraction measurements are reported for the cubic Laves phase compounds Ho(FexAl1−x)2, x≤0.3 as discussed by the authors.
Abstract: Magnetic, 57Fe Mossbauer and neutron diffraction measurements are reported for the cubic Laves phase compounds Ho(FexAl1−x)2, x≤0.3. The ordering temperatures, which coincide with the vanishing of the 57Fe hyperfine splitting, are nearly constant, indicating the dominance of the HoHo exchange interaction. From the Mossbauer spectra recorded at 5 K it can be deduced that all Fe atoms carry a magnetic moment. In addition to the coherent scattered intensities a diffuse contribution, which increases with increasing Fe content, is observable in the neutron diffraction patterns.
TL;DR: Using the arc-furnace hammer-and-anvil method, metastable alloys in the Al-rich portions of four Al-RE systems (10−30 at. pet. RE; Re = Gd, Ho, Er and Y) were prepared and examined by XRD as discussed by the authors.
Abstract: Using the arc-furnace hammer-and-anvil method, metastable alloys in the Al-rich portions of four Al-RE systems (10–30 at. pet. RE; Re = Gd, Ho, Er and Y) were prepared and examined by XRD. The principal results are: all equilibrium alloy phases [Al4RE (T phase), Al3RE (CN12 close-packed phases) and Al2RE (Laves phase)] have substantial metastable solid solubilities for excess Al; e.g., in the Al-Y system, L phase is extended from 66.7 up to 86 at. pet. Al, suppressing any formation of the Al3RE phase in that system. For early RE elements up to and including Gd, T phase is favored; for alloy chemically intermediate RE elements such as Y, L phase is dominant and for late RE elements (after Ho), the CP phases are extended most. DSC work indicates the formation of additional metastable phases occurring during equilibration.
TL;DR: In this paper, the magnetic excitations in a large single crystal at low temperatures using neutron inelastic scattering were measured and two relatively dispersionless branches were observed centred near 2.5 and 7.0 meV.
Abstract: The cubic Laves phase compound ErAl2 is ferromagnetic below 12.5 K. We have measured the magnetic excitations in a large single crystal at low temperatures using neutron inelastic scattering. Two relatively dispersionless branches were observed centred near 2.5 and 7.0 meV. An analysis of the energies and intensities using the RPA dynamical susceptibility has allowed a refinement of the crystal field parameters estimated from bulk magnetisation measurements.
TL;DR: In this paper, a comparative study of crystalline and amorphous DyAg using161Dy Mossbauer spectroscopy is presented as a way to gain insight into the changes in electronic structure and spin dynamical properties of the rare-earth ion when its local surrounding is randomly distorted.
Abstract: A comparative study of crystalline and amorphous DyAg using161Dy Mossbauer spectroscopy is presented as a way to gain insight into the changes in electronic structure and spin dynamical properties of the rare-earth ion when its local surrounding is randomly distorted. It can be seen, especially in the paramagnetic regime, that the influence of the lowering of local symmetry is significant in both the electronic ground state of Dy3+ and the fluctuation rate of the local magnetic moment. At high-spin fluctuation rates, Mossbauer spectroscopy rapidly becomes insensitive, while muon spin relaxation (μSR) has still a high power of resolution. μSR measurements on Laves phase intermetallics are used to demonstrate the presence of paramegnetic spin correlations far above the Curie temperature. First measurements of this kind on crystalline and amorphous DyAg will also be discussed.
TL;DR: In this article, a Fe-9Cr-2Mo-1NiVNb ferritic/martensitic steel designated JFMS has been selected as a reference material for future fusion reactor applications by the Japanese fusion reactor materials research group.
TL;DR: In this article, pressure dependence of the Young's and shear moduli of RFe2 (R = Sm, Gd, Tb, Dy, Ho and Er) has been determined at room temperature in the pressure range between 0 and 1 GPa.