Showing papers on "Laves phase published in 1993"
TL;DR: In this article, a sharp transition from reversible behaviour to irreversible behaviour in the superconducting mixed state of single-crystal samples of CeRu2 is described and the results are discussed in relation to conventional models and those of more novel superconductivity, such as the Fulde-Ferrel state.
Abstract: A sharp transition from reversible behaviour to irreversible behaviour in the superconducting mixed state of single-crystal samples of CeRu2 is described. Magnetization, AC susceptibility, resistivity and specific heat measurements under an applied field are reported. The results are discussed in relation to conventional models and those of more novel superconductivity, such as the Fulde-Ferrel state.
137 citations
TL;DR: In this article, phase chemistry and precipitation reactions in a variety of maraging steels are investigated by comparing the behavior of different steels, and the roles of different phases and alloying elements are investigated.
Abstract: This article summarizes our studies of phase chemistry and precipitation reactions in a variety of maraging steels. The roles of different phases and alloying elements are investigated by comparing the behavior of different steels. The phases considered are Ni3Ti, Fe7Mo6 μ phase, Fe2Mo Laves phase, ω phase, Ti6Si7Ni16 G phase, “Z phase,” austenite, and α matrix. The alloying elements discussed are Ti, AI, Mo, Si, Mn, Ni, Cr, and Co. By comparing the aging behavior of both commercial steels and model alloys, a major role of Co is confirmed to be the lowering of the matrix solubility of Mo. Of the two main hardening elements in maraging steels (namely, Ti and Mo), Ti is much more active than Mo in the very early stage of precipitation. The main Mo-rich precipitate found in this work was Fe7Mo6μ phase instead of Laves phase. The precipitation of Mo is modified by the presence of Ti. ω phase appears only in Ti-free alloys, especially when aged at a low temperature. The quantity of Ni-containing precipitates and the presence of Cr in the steels change the austenite reversion behavior. Other phases, such as G phase and “Z phase,” contribute to age hardening in different types of maraging alloys.
96 citations
TL;DR: The binary phase diagram of He-Ne mixtures has been measured at 296 K in a diamond anvil cell and is of the eutectic type with no fluid-fluid separation of phases.
Abstract: The binary phase diagram of He-Ne mixtures has been measured at 296 K in a diamond anvil cell. It is of the eutectic type with no fluid-fluid separation of phases. A homogeneous solid mixture is shown to be stable for a mole fraction of He equal to 2/3. Single-crystal synchrotron x-ray measurements indicate that this solid is ordered with 12 atoms in the unit cell. Gibbs free energy calculations support the attribution to the ${\mathrm{MgZn}}_{2}$ type structure. It is the first Laves phase observed in a van der Waals molecular compound,
71 citations
TL;DR: In this article, the optimization of the thermodynamic parameters of the various phases existing in the Cr-Ta system was performed taking into account all available thermodynamic and phase diagram data.
Abstract: The optimization of the thermodynamic parameters of the various phases existing in the Cr-Ta system was performed taking into account all available thermodynamic and phase diagram data. The liquid and the two terminal bcc solid solutions were described by a Redlich-Kister equation. The Laves phases, C14 and C15-Cr2Ta, were described by the sublattice model; two different descriptions were used for each of these phases. The set of optimized parameters and the calculated phase diagrams are presented.
63 citations
TL;DR: In this paper, a series of compounds CaLixAl2 − x was synthesized and structurally characterized in order to probe the effect of valence electron concentration on both global and local structural features in main group intermetallics.
61 citations
TL;DR: In this article, the phase transformations during aging in a variety of model maraging steels were investigated using Atom-probe field-ion microscopy (APFIM) techniques.
Abstract: This article describes studies of phase transformations during aging in a variety of model maraging steels. Atom-probe field-ion microscopy (APFIM) was the main research technique employed. Thermochemical calculation was also used during the course of the work. The composition and morphology of precipitates were compared in several maraging systems aged at different temperatures for different times to investigate the aging sequence. The APFIM results are compared with studies by other workers using different experimental techniques. In Fe-Ni(-Co)-Mo model alloys, ω phase and Fe7Mo6 μ phase have been found to contribute to age hardening at different stages of aging; no evidence was found for the existence of Mo-rich clusters in the as-quenched Fe-Ni-Co-Mo alloy. In a high-Si Cr-containing steel, Ti6Si7Ni16 G phase and Ni3Ti have been found to contribute to age hardening; reverted austenite was found after aging for 5 hours at 520 °C. In a Mn-containing steel, Fe2Mo Laves phase and a structurally uncertain phase with a composition of Fe45Mn32Co5Mo19 have been found to contribute to age hardening.
48 citations
TL;DR: In this article, magnetostriction and magnetomechanical coupling coefficient were measured on samples of Tb0.27Dy0.73Fe2−xCox (x=0,0.5,1.2,2.0) and 1.2.
Abstract: X‐ray‐diffraction studies carried out on Tb0.27Dy0.73Fe2−xCox (x=0,0.5,1.2,2.0) revealed that all compositions investigated retained the C‐15 cubic Laves phase structure. Magnetization and electrical resistivity measurements were carried out in the temperature range 77–800 K. Anomalies observed in the resistivity measurements have been identified corresponding to spin reorientation transitions occurring in this system. Some of these transitions have also been observed in the magnetization data. Magnetostriction and magnetomechanical coupling coefficient were measured on samples of x=0, 0.5, and 1.2 prepared by arc melting as well as arc melting followed by zoning using an induction furnace. Magnetostriction and coupling coefficient were found to decrease with increase in cobalt concentration. Magnetostriction data on zoned samples revealed a change in the easy direction of magnetization from [111] to [100] in the case of x=0.5.
47 citations
TL;DR: In this paper, the C-15-type Laves phase structure of intermetallic compounds Zr 1-x Ho x Co 2 (x = 0.4, 0.6 and 0.8) was determined for the intermetall compounds with a temperature range 50-200 °C at pressures up to 40 bar.
36 citations
15 Jan 1993-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The effect of iron additions on the stability of various Laves phases in the NbCr base system has been examined in this paper, showing that the C14→C36 phase transformation takes place in the entire temperature range studied (RT 1473 K).
Abstract: The effect of iron additions on the stability of various Laves phases in the NbCr base system has been examined. In the binary NbCr system a hexagonal (C14) Laves phase exists at temperatures above approximately 1860 K, and undergoes] a shear-like martensitic transformation to a face centered cubic (C15) Laves phase on cooling to room temperature. Addition of iron promotes formation of an additional phase, the dihexagonal (C36) Laves phase. In alloys with a lower iron content (below approximately 5 wt.%), the C36 phase forms at higher temperatures. In addition, the C15 phase begins to form on cooling to room temperature. In sharp contrast, in alloys with a higher iron content, only the C14→C36 phase transformation takes place in the entire temperature range studied (RT 1473 K). These findings were rationalized on the basis of the effects of chemical energy change and elastic strain energy on magnitude of the activation energy for martensitic transformation.
34 citations
TL;DR: The Mossbauer spectra in the paramagnetic state are all very well described by a model that assumes that the isomer shift and quadrupole interaction are linearly dependent on the number of Al first-nearest neighbors to the iron nucleus.
Abstract: Mossbauer-spectroscopy studies of 57 Fe in Zr(Al x Fe 1-x ) 2 (x=0-0.825) at various temperatures, from 90 to 612 K have been performed. For x<0.25 the systems are of cubic Laves phase structure and order magnetically above room temperature. Above x=0.25 the systems have a hexagonal structure and do not order magnetically above 90 K. The Mossbauer spectra in the paramagnetic state are all very well described by a model that assumes that the isomer shift and quadrupole interaction are linearly dependent on the number of Al first-nearest neighbors to the iron nucleus (0.056 mm/s and -7% per Al neighbor, respectively)
26 citations
TL;DR: In this article, high-field magnetization and low-temperature specific heat of the nearly ferromagnetic compounds Lu(Co1-xGax)2 have been investigated and a sharp metamagnetic transition has been observed in these compounds.
Abstract: High-field magnetization and low-temperature specific heat of the nearly ferromagnetic compounds Lu(Co1-xGax)2 have been investigated. A sharp metamagnetic transition has been observed in these compounds. The critical field Hc decreases with increasing x and becomes lower than 1 T at x=0.12. However, no spontaneous magnetization is confirmed even above x=0.15. With increasing x, the electronic specific heat coefficient gamma increases and reaches 36 mJ K-2 mol-1 for x=0.12 in 0 T, being 1.5 times as large as that of LuCo2. Such a mass enhancement is discussed in terms of the spin fluctuation. The gamma value of the ferromagnetic state for the specimen with x=0.12 in a magnetic field of 14.6 T is reduced about 50% compared with that of the paramagnetic state in zero field. This means that the metamagnetic transition results in a drastic reduction of the spin fluctuation in the compound.
TL;DR: In this article, the deformation behavior of Al3Nb alloys has been studied in compression and bending between room temperature and 1400°C to determine yield strength, ductility and toughness.
TL;DR: In this article, a-GdFe2H3.0 and a-gdCo2H2.4 prepared from the less stable compounds showed the strong tendency for the same kinds of metal atoms to cluster and crystallize to GdH2 and Fe(Co).
Abstract: Enthalpy changes ΔH for hydrogen absorption and desorption, hydrogen-induced amorphization (HIA) in C15 Laves phases c-GdM2 (M = Fe, Co, Ni) and crystallization of the resultant amorphous alloys a-GdM2Hx have been measured by differential scanning calorimetry (DSC). Furthermore, structures of a-GdM2Hx have been investigated by X-ray diffractometry (XRD) to correlate their structures with the stabilities of the original compounds. Both a-GdFe2H3.0 and a-GdCo2H3.4 prepared from the less stable compounds show the strong tendency for the same kinds of metal atoms to cluster and crystallize to GdH2 and Fe(Co). Correspondingly, the sum of ΔH for all reactions become equal to that for the formation of GdH2. On the contrary, a-GdNi2H3.5 prepared from the stable compound shows a rather homogeneous structure and crystallizes to GdH2 and GdH2 and GdNi5. As a result, the sum of ΔH shows a large negative value in comparison with that for the formation of GdH2.
TL;DR: In this article, the results of high-temperature compressive deformation tests on a two-phase alloy consisting of Cr2Nb, a C15 Laves phase, and a soft Nb-based solid solution, are presented along with measurements of oxidation kinetics at 1273 K in air.
Abstract: The results of high-temperature compressive deformation tests on a two-phase alloy consisting of Cr2Nb, a C15 Laves phase, and a soft Nb-based solid solution, are presented along with measurements of oxidation kinetics at 1273 K in air. These alloys are deformable only at temperatures above 1273 K. The measured 0.2% yield stress decreases steadily with increasing temperature and is only slightly sensitive to alloy composition. The steady state flow stress decreases steadily with increasing temperature and depends on alloy composition. A constitutive equation was fitted to the experimental data with a composition-independent stress exponent of about 2.7 and an apparent activation energy which ranges between 477 and 391 kJ/mol, also depending on alloy composition. Microstructural examination shows that cracking (cavitation) and interfacial sliding between the two constituent phases, in addition to bulk deformation of the constituent phases, are responsible for the deformation. The oxidation resistance of these alloys is very good.
TL;DR: The high-field magnetization and temperature dependence of the critical field have been investigated for Laves-phase Lu(Co1-xGax)2 compounds in this article.
Abstract: The high-field magnetization and temperature dependence of the critical field have been investigated for Laves-phase Lu(Co1-xGax)2 compounds. A clear itinerant-electron metamagnetic transition is observed and its critical field increases with increasing temperature for x=0.09. The results are discussed on the basis of the Clausius-Clapeyron equation for the magnetic phase transition. This reveals that the magnetic entropy of these compounds decreases above the critical field, suggesting the suppression of the spin fluctuations due to the metamagnetic transition. This is consistent with the recent results on the field dependence of the electronic specific-heat coefficient of these compounds. The Arrott plots for the specimen with x=0.12, which has a very low critical field, have also been investigated. The squared hypothetical spontaneous magnetization Mh2 decreases linearly with increasing T2 and the reduced Mh versus T plot for Lu(Co0.88Ga0.12)2 is very similar to the reduced magnetization for an Invar-type ferromagnetic Lu(Cu0.83Al0.17)2 compound. This result suggests that Lu(Co0.88Ga0.12)2 in the ferromagnetic state is expected to exhibit marked magnetovolume effects.
TL;DR: The influence of nitrogen alloying on sensitization behavior is complex in that it increases the risk of nitride precipitation but may retard the precipitation of intermetallic phases as discussed by the authors, and the effect of various exposure times at 850 C has been investigated for the alloy containing 0.21 wt % nitrogen in order to elucidate the precipitation reactions and equilibrium state.
Abstract: The highly-alloyed austenitic stainless steels, with molybdenum contents typically in excess of 4 wt %, are a group of materials which are undergoing continual development due to increasing harsh user demands. Nitrogen has proved particularly attractive as an alloying element in view of its strong austenite-stabilizing tendency, beneficial effect on localized corrosion resistance and ready availability. The influence of nitrogen alloying on sensitization behavior is complex in that it increases the risk of nitride precipitation but may retard the precipitation of intermetallic phases. This has been illustrated by Thier et al for 21 Cr 25Ni 6Mo. The same has also been demonstrated to be the case for 20Cr 20-30Ni 4.5Mo steels in that the addition of 0.21 wt % nitrogen retarded the first precipitating intermetallics (principally Laves phase) but caused the appearance of Cr[sub 2]N. The present work represents an elaboration of the latter study in which the effect of various exposure times at 850 C has been investigated for the alloy containing 0.21% nitrogen in order to elucidate the precipitation reactions and equilibrium state.
TL;DR: In this article, the intrinsic degradation behavior of Zr-based Laves phase alloy Zr0.9Ti0.1Cr 0.9Fe1.1 was investigated by pressure-composition isotherm measurements, X-ray diffractometry and thermal analysis on the degraded samples.
TL;DR: In this article, the influence of the intersublattice f-d exchange interaction on the magnetic behavior of itinerant metamagnets Y ( Co 1− x Al x ) 2.
TL;DR: In this paper, the influence of boron addition on the giant magnetostriction of an amorphous (SmFe2) (1−x) at. % alloy has been examined.
Abstract: RFe2 laves phase intermetallic compounds are promising materials for magnetostrictive applications. To obtain a larger magnetostriction in a low magnetic field, the influence of boron addition on the giant magnetostriction of an amorphous (SmFe2) (1−x) at. % B (x) at. % alloy has been examined. In the amorphous alloy, the saturation magnetostriction anomalously increases, while the saturation magnetization decreases with the increase in x. The highest saturation magnetostriction of −670×10−6 at 10 kOe and its effective magnetostriction of −490×10−6 at 0.3 kOe can be obtained for amorphous (SmFe2) 99.26 at. % B 0.74 at. % alloy. This effective giant magnetostriction obtained in a low magnetic field is larger than those reported in previous researches. I attribute this anomalous giant magnetostriction in a low magnetic field to the increment of elastic energy in the amorphous (SmFe2) (1−x) at. % B (x) at. % alloy.
TL;DR: In this paper, the precipitation of second phases in Incoloy 909 has been studied using optical microscopy, scanning electron microscopy and transmission electron microscope, and a time-temperature-transformation diagram was constructed.
Abstract: The precipitation of second phases in Incoloy 909 has been studied using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The compositions and crystal structures of several second phases were determined by analytlcal electron microscopy. A time–temperature–transformation diagram was constructed. The Si addition was found to promote the precipitation of an Fe2Nb type Laves phase during casting and thermal processing, and the formation of Si rich orthorhombic phase at high aging temperatures. Both types of precipitate are considered to enhance the rupture properties of the alloy.MST/1748
TL;DR: In this paper, the lattice parameters, evaluated as a function of x at room temperature, show deviation from Vegard's law, attributed to the presence of a magnetovolume effect and charge transfer.
Abstract: Cubic Laves phase alloys of Ho0.85Tb0.15Fe2−xNix (0≤x≤2) were prepared and the lattice parameters, evaluated as a function of x at room temperature, show deviation from Vegard’s law. This was attributed to the presence of a magnetovolume effect and charge transfer. Magnetization measurements were performed in the temperature range 77–700 K. The results suggest that the system undergoes a gradual transition from ferri‐ to ferromagnetic with increasing x. This has been explained based on the 3d band model. Furthermore, a monotonic decrease in Curie temperature with x was observed. Electrical resistivity studies were carried out in the temperature range 16–700 K. An anomaly was found in the vicinity of the Curie temperature for x=2 which has been attributed to the existence of the long‐range nature of the critical fluctuations due to short‐range spin ordering.
TL;DR: In this paper, the magnetic properties of the Al-substituted Nb(Fe 1- x Al x ) 2 system were investigated for x ≦0.5 by NMR and magnetisation measurements.
Abstract: The C-14 Laves phase NbFe 2 is a very weak antiferromagnet with ferromagnetic spin fluctuations. The magnetic properties of the Al-substituted Nb(Fe 1- x Al x ) 2 system were investigated for x ≦0.5 by NMR and magnetisation measurements. It was found that the antiferromagnetism is enhanced by the Al substitution for x ≧0.05, while for x <0.05 very weak ferromagnetism appears. The origin of the ferromagnetism is discussed.
TL;DR: In this paper, a study was performed on a series of model 9Cr-1Mo steel alloys in which the levels of silicon and phosphorus have been varied to separate the formation of the brittle intermetallic (Laves) phase from the segregation of phosphorus during aging.
Abstract: A study is reported of temper embrittlement and hydrogen embrittlement in a series of model 9Cr–1Mo steel alloys in which the levels of silicon and phosphorus have been varied to separate the formation of the brittle intermetallic (Laves) phase from the segregation of phosphorus during aging. Phosphorus segregation was mildly detrimental to ductility properties, Laves phase formation was more detrimental, and their effects combined produced the most severe loss in ductility. Hydrogen effects were additive to those of aging. In unaged material without silicon enrichment, only M23C6 precipitates were detected, with little phosphorus segregation. With silicon enrichment, phosphorus segregation to lath and grain boundaries was enhanced. This enhancement increased the susceptibility of the materials to hydrogen embrittlement, promoting transgranular cleavage and chisel fracture. In aged material, the high phosphorus alloys showed some grain boundary segregation, but only limited interaction with hydrog...
TL;DR: In this article, the short-range structure of metallic atoms and the chemical environment around a deuterium atom during the hydrogen-induced solid state amorphizing process are examined by X-ray and neutron diffraction.
TL;DR: In this article, single crystals of Fe2(Dy, Lb) Laves intermetallic compound with C15 structure were deformed in compression at high temperatures and the activation volume was small and the dislocations were parallel to and.
Abstract: Single crystals of Fe2(Dy, Lb) Laves intermetallic compound with C15 structure were deformed in compression at high temperatures. Above 875[ddot]C they were ductile. The thermal activation parameters were measured and dislocation structures in the deformed specimens were examined by transmission electron microscopy. The activation volume was small and the dislocations were parallel to and . It has been concluded that the high-temperature plasticity of Fe2(Dy, Tb) single crystals is controlled by the Peierls mechanism.
TL;DR: In this paper, the LaIrSi-type structure of CaPtSi has been obtained from a belt apparatus at high pressures (3-4 GPa) and high temperatures (800-1100°C).
TL;DR: In this paper, the interaction of multicomponent TiMn1.5-type Laves phases with hydrogen and deuterium was investigated by means of standard pressure-composition isotherms and a calorimetric method.
TL;DR: The structural changes of the Laves phases Ce(Ru 1− x M x ) 2, where x = 0.05-0.25 and M is the transition elements such as Fe, Co and Ni, during hydrogen absorption are investigated through X-ray diffraction (XRD), transmission electron microscopy and differential scanning calorimetry (DSC).
TL;DR: The cubic Laves phase NdFe 2 was synthesized by melting at the pressure of 8 GPa the constituents with a small admixture of HfFe 2. The hyperfine magnetic field at Ta at the Nd sites was measured by the PAC method in the temperature range 97-635 K.