Ni-V Alloys Research Articles

Mixing Enthalpies of Liquid Ni-V, Ni-Nb and Ni-Ta Alloys Measured by Levitation Alloying Calorimetry

Mixing Enthalpies of Liquid Ni-V, Ni-Nb and Ni-Ta Alloys Measured by Levitation Alloying Calorimetry

組成傾斜を利用したNi-VおよびNi-Mo整合相境界の決定

The composition gradient method recently proposed is applied to determine the coherent phase boundaries of the Ni-V and Ni-Mo alloy systems by utilizing the alloys having the macroscopic composition gradient. The result, obtained are as follows:(1) The coherent phase boundaries of Ni/(Ni+Ni3V) were experimentally determined to be a line connecting 15.5 at%V at 873 K and 18.0 at%V at 1173 K, which was consistent with Moreen’s empirical results obtained from the metallographic examinations.(2) The phase boundaries of Ni/(Ni+Ni4Mo) and (Ni+Ni4Mo)/Ni4Mo were also obtained, which were almost coincident with those in the equilibrium phase diagram of Ni-Mo proposed by Massalski. The new method is recognized to be very powerful for a metallographic determination of the coherent phase boundary.

First-principles theory of short-range order, electronic excitations, and spin polarization in Ni-V and Pd-V alloys.

The short-range order (SRO) and long-range order (LRO) of Ni-V and Pd-V alloys are studied theoretically by a combination of first-principles calculations of Ising-like interaction energies (${\mathit{J}}_{\mathit{f}}$) with a Monte Carlo solution of the Ising Hamiltonian. We find the following: (i) There are several compositions in these alloys for which the dominant wave vectors of LRO and those of SRO do not coincide, indicating that the low-temperature (T) LRO may not always be inferred from the high-T SRO. (ii) In ${\mathrm{Ni}}_{3}$V and ${\mathrm{Pd}}_{3}$V, the density of states at the Fermi level, n(${\mathrm{\ensuremath{\epsilon}}}_{\mathit{F}}$), is much larger in L${1}_{2}$ than in the stable D${0}_{22}$ structure. This has two consequences: (a) thermal electron-hole excitations across ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{F}}$ are energetically more favorable in the L${1}_{2}$ structure and lead to a T dependence of ${\mathit{J}}_{\mathit{f}}$, and (b) magnetization stabilization is larger in L${1}_{2}$, so spin polarization affects structural stability. As a result, (iii) calculations using T-dependent ${\mathit{J}}_{\mathit{f}}$'s are needed to obtain quantitative agreement with experimental measurements of LRO, SRO, and transition temperatures in ${\mathrm{Ni}}_{0.75}$${\mathrm{V}}_{0.25}$, ${\mathrm{Ni}}_{0.67}$${\mathrm{V}}_{0.33}$, and ${\mathrm{Pd}}_{0.75}$${\mathrm{V}}_{0.25}$.(iv) We provide predictions of the SRO patterns where there is currently no experimental evidence for ${\mathrm{Pd}}_{0.67}$${\mathrm{V}}_{0.33}$, ${\mathrm{Ni}}_{0.6}$${\mathrm{V}}_{0.4}$, ${\mathrm{Pd}}_{0.6}$${\mathrm{V}}_{0.4}$, and ${\mathrm{Pd}}_{0.5}$${\mathrm{V}}_{0.5}$. (v) For ${\mathrm{Ni}}_{3}$V and ${\mathrm{Pd}}_{3}$V, discrepancies are found between the total-energy differences of the L${1}_{2}$ and D${0}_{22}$ structures as determined by T=0 first-principles calculations and those inferred from diffuse neutron scattering measurements at high T. By performing temperature-dependent self-consistent local-density-approximation calculations, we find that electronic excitations are responsible for reducing the discrepancy by \ensuremath{\sim}25% and the combination of spin polarization and electronic excitations reduce the discrepancy by \ensuremath{\sim}30--50 %. Thus, electronic excitations and spin polarization are not fully responsible for the T dependence of ${\mathit{J}}_{\mathit{f}}$ used in the SRO calculations.

First Principles Calculation of Phase Stability of High Temperature Intermetallic Alloys

ABSTRACTOne way to calculate the coherent phase diagram of an alloy based on first principles methods is to compute the ground state total energy for various ordered configurations, from which many-body interactions can be calculated and employed in a thermodynamic model. If the Connolly and Williams method (CWM) is used to extract the many-body interactions from the calculated total energies, the resulting many-body interactions can exhibit a strong dependence on the choice of ordered configurations and multi-site clusters, and the accuracy and convergence of the CWM energy expansion is not assured. To overcome this difficulty, a successful systematic method for implementing the CWM is proposed. This approach is applied to a study of the fcc-based Ni-V and Pd-V substitutional alloys and these interaction parameters together with the cluster variation method (CVM) are used to calculate phase diagrams.

Spin-density asymmetry in NiV alloy at various temperatures

Polarised neutron diffraction has been used to determine the neutron magnetic form factors of a Ni0.959V0.041 random alloy at 4.2, 290 and 378 K. From the analysis of the form factors it is concluded that within experimental accuracy the spatial distribution of the spin density remains unaltered up to 0.9 Tc for this alloy.

Magnetic moment distribution in FeNiV and FeCoV alloys

Abstract Magnetization and neutron scattering measurements were made on the alloys Fe 0.375 Ni 0.375 V 0.25 and Fe 0.165 Co 0.585 V 0.25 in both the atomically ordered and disordered state. Individual atomic magnetic moment assignments were made based on these data and the known systematic behaviour of fcc Ni-V and Co-V alloys. Fe moments of 1.14μ B /Fe (ordered) and 0.95μ B /Fe (disordered) were obtained for the ferromagnetic FeNiV alloys at 4.2 K. Much smaller moments were found for the FeCoV alloys which are not spontaneously ferromagnetic and far from saturation under the experimental conditions. The V moments are small and oppositely aligned to the net magnetization.

Neutron magnetic form factors of Ni-rich NiV alloys

The magnetic form factors of Ni1-xVx (x=0.014, 0.041 and 0.046) have been measured at room temperature. A new determination of the form factor of pure Ni has also been performed. The Ni1-xVx form factors and the form factors of Ni0.95Cr0.05 and Ni0.98Ti0.02 are compared with the Ni form factor. It is concluded that in these alloys the long-range disturbance of the magnitude of the Ni moments, caused by the presence of the solute atoms, does not change the distribution of the unpaired electrons within the Wigner-Seitz cell.

Nitrogen solubility in liquid Fe-V and Fe-Cr-Ni-V alloys

Nitrogen solubility in liquid Fe, Fe-V, Fe-Cr-V, Fe-Ni-V and Fe-18 pct Cr-8 pet Ni-V alloys has been measured using the Sieverts’ method for vanadium contents up to 15 wt pct and over the temperature range from 1775 to 2040 K. Nitrogen solution obeyed Sieverts’ law for all alloys investigated. Nitride formation was observed in Fe-13 pet V, Fe-15 pet V and Fe-18 pet Cr-8 pet Ni-10 pet V alloys at lower temperatures. The nitrogen solubility increases with increasing vanadium content and for a given composition decreases with increasing temperature. In Fe-V alloys, the nitrogen solubility at 1 atm N2 pressure is 0.72 wt pet at 1863 K and 15 pct V. The heat and entropy of solution of nitrogen in Fe-V alloys were determined as functions of vanadium content. The first and second order interaction parameters were determined as functions of temperature as: $$e_N^V = \frac{{ - 463.6}}{T} + 0.148 and e_N^{VV} = \frac{{17.72}}{T} - 0.0069$$ The effects of alloying elements on the activity coefficient of nitrogen were measured in Fe-5 pet and 10 pet Cr-V, Fe-5 pet and 10 pet Ni-V and Fe-18 pet Cr-8 pct Ni-V alloys. In Fe-18 pet Cr-8 pet Ni-10 pet V, the nitrogen solubility at 1 atm N2 pressure is 0.97 wt pet at 1873 K. The second order cross interaction parameters, eNCr,V and eNNi,V, were determined at 1873 K as 0.00129 and − 0.00038 respectively.

The oxidation behavior of dilute Ni-V alloys at 1200�C

The oxidation behavior of nickel and dilute Ni-V alloys has been studied in flowing oxygen at 1 atm pressure, using various kinetic and electron-optical techniques. The oxidation rate rises progressively as the alloy vanadium content is increased from 0 to 0.8% and then to 1.7%. However, further additions to 4.2% cause only a slight further increase. These increases in oxidation rate are largely controlled by the extent of doping of the NiO, particularly for the two more dilute alloys, although internal oxidation, spinel blocking effects in the oxide, and dissociation of the NiO affect the weight gains to some extent, particularly for the case of the Ni-4.2% V alloy.

Low temperature specific heats of NiCr and NiV alloys near the ferromagnetic-paramagnetic transition

The magnetic field dependence of the low temperature specific heats of critical concentration alloys of NiCr and NiV has been measured in the range 1−4 K at fields up to 45 kOe. The observed reduction in specific heat with applied field is characteristic of superparamagnetic clusters.

Temperature and concentration dependence of the magnetocrystalline anisotropy of NiV alloys

Measurements of the first anisotropy constant K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> have been made for a series of NiV alloys containing up to 6.72 at.% V. Electrical resistivities have been determined on the same alloys and on a NiMo alloy. It has been shown that K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> depends exponentially on both temperature and concentration of V in agreement with a suggestion by Franse et al. [1] that the electron mean free path is an important factor. Resistivity measurements have been analysed so as to seperate the impurity resistivity contributions due to the majority and minority d-bands. These along with the measurements of other workers have been used to demonstrate a correlation between variations of the minority resistivity and of the first anisotrophy constant in alloys of the form NiMe where Me may be Ti, V, Cr, Mn, Fe, Co, or Cu.

Itinerant magnetism in NiV alloys around the critical concentration for ferromagnetism

After subtraction of a contribution due to magnetic clusters, the magnetization of NiV alloys, as a function of the field, temperature and concentration, follows fairly well the itinerant model, on both sides of the critical concentration. In a critical alloy ( approximately 89 at% Ni) the percentage of Ni atoms in magnetic clusters probably does not exceed 10%. Special attention is focussed on the temperature dependence of the magnetization in high fields.

Transport properties, giant moments and nearly magnetic impurities in some nickel alloys near the magnetic transition

The authors present a systematic study of the magnetic transition from the paramagnetic to the ferromagnetic state in some nickel concentrated alloys NicT1-c (T=V, Cr, Mo, Ru, Cu). The magnetic measurements between 4K and 300K show that this transition occurs from the coupling between giant moments whose concentration increases when the nickel concentration increases up to the critical concentration ccr; their magnitude is the largest critical composition. A detailed study of NiV, NiMo and NiCu alloys shows that the magnetization results from giant moments whose magnitude increases when c to ccr and from nearly magnetic impurities in the vicinity of these moments. The existence of this nearly magnetic term is consistent with the temperature dependence of the resistivity in all the investigated alloys and with the magnetoresistance measurements in NiT alloys (T=V, Mo, Cu).

Precipitation in ternary Ni-V-Nb alloys

A transition from a continuous ordering reaction to nucleation and growth has been identified by means of transmission electron microscopy in aged Ni-V-Nb alloys. The substitution of 2.5 a/o Nb for V is sufficient to suppress the continuous ordering reaction observed in binary Ni-V alloys. This effect has been attributed to the additional strain energy associated with the presence of niobium atoms in the fcc matrix. The equilibrium precipitate near the Ni 3(V, Nb) composition is a DO 22 structure for compositions below 5 a/o Nb and an orthorhombic Ni 3Nb type structure for alloys containing in excess of 5 a/o Nb.

Effects of Hydrostatic Pressure on the Curie Temperature of Ni-V Alloys

Effects of Hydrostatic Pressure on the Curie Temperature of Ni-V Alloys

TRANSPORT PROPERTIES, GIANT MOMENTS AND NEARLY MAGNETIC IMPURITIES IN SOME NICKEL ALLOYS NEAR THE MAGNETIC TRANSITION

The authors present a systematic study of the magnetic transition from the paramagnetic to the ferromagnetic state in some nickel concentrated alloys NicT1-c (T=V, Cr, Mo, Ru, Cu). The magnetic measurements between 4K and 300K show that this transition occurs from the coupling between giant moments whose concentration increases when the nickel concentration increases up to the critical concentration ccr; their magnitude is the largest critical composition. A detailed study of NiV, NiMo and NiCu alloys shows that the magnetization results from giant moments whose magnitude increases when c to ccr and from nearly magnetic impurities in the vicinity of these moments. The existence of this nearly magnetic term is consistent with the temperature dependence of the resistivity in all the investigated alloys and with the magnetoresistance measurements in NiT alloys (T=V, Mo, Cu).

The formation of modulated structures in Ni-V alloys

The precipitation of the ordered Ni3V phase in binary Ni-V alloys has been studied by employing transmission electron microscopy, X-ray analysis, electrical resistivity and mechanical property measurements. The reaction consists of two stages, the first of which involves the formation of domain wave composition modulations manifested by a tweed microstructure and an accompanying strain field. The second stage is an amplification of the long-range order waves and is manifested by the formation of the ordered Ni3V phase. The strain fields produced by the domain waves interact with the strain field of the Ni3V nuclei leading to the formation of a single variant of tetragonal Ni3V in a given region of the matrix. The strength of the continuously ordered alloys is controlled by the strain in the lattice in agreement with the Mott and Nabarro theory of strengthening.

Environment effects in NiV alloys near the magnetic transition critical concentration

We show the existence of environment effects on the V51 NMR line in the critical range of concentration. These effects are interpreted by a simple model which assumes that the V51 resonance spectra result from the superposition of several lines corresponding to the resonance of isolated vanadium atoms, pairs and larger statistical clusters of vanadium atoms surrounded by nickel atoms. Nous montrons l'existence d'effects d'environnement sur la résonance du V51 dans la région critique de concentration: Nous interprétons ces effets selon un modéle simple qui suppose que le spectre de résonance du vanadium résulte de la superposition de plusieurs raies correspondant à la résonance d'atomes isolés de vanadium, de paires et de groupes plus importants d'atomes de vanadium entourés de nickel.

Magnetic Properties of σ-Phase of Some 3d-Transition Alloys

Magnetic susceptibility measurement has been made on the σ-phase of Fe-V, Co-V, Ni-V and Co-Cr binary alloys. The Fe-V system only is ferromagnetic. The temperature dependent parts of the susceptibility of Fe-V alloys obey the Curie-Weiss law. The paramagnetic moment µ per iron atom in Fe-V varies with vanadium concentration C v following an empirical relationship, µ/µ B =-2.62+173/ C v , where C v is atomic-% of vanadium. The Curie temperature is sensitive to heat treatments of the specimens, but the magnetic moment is not affected. The susceptibility of the other alloys is found to be nearly temperature independent. The magnitude of the magnetic moment localized on magnetic atoms at different kinds of sites in these σ-phase is suggested.

The electrical resistivity of nickel and its alloys

The electrical resistivity has been measured over the temperature range 1 °K to 120 °K in dilute alloys of nickel with Pd, Cu, Co, Fe, Mn, Cr, V and Ti. The impurity (residual) resistivity is very small for alloys of nickel with its near neighbours in the periodic table, Pd, Cu, Co, Fe and Mn, but is an order of magnitude greater for alloys containing Cr, V and Ti. The ice-point values of the deviations from Matthiessen's rule are unusually large in the Ni-Co, Ni-Fe, Ni-Mn, and Ni-Cr alloys, somewhat smaller in the Ni-Cu, Ni-V and Ni-Ti alloys, and negligible in Ni-Pd.