Ni-Nb Alloys Research Articles

Effect of Zr addition on the glass-forming ability and mechanical properties of Ni–Nb alloy

The effect of zirconium (Zr) addition on the glass-forming ability (GFA) and mechanical properties of the Ni61.5Nb38.5 alloy has been studied. The addition of Zr improves the GFA. When x = 5 for Ni61.5Nb38.5−xZrx (in at.%) alloys, the alloy exhibits the best GFA and can be cast into 3-mm-diameter amorphous samples by using the copper mold injection-casting method. Differential scanning calorimetry measurements indicated that the thermal parameters, such as Trg and γ, have not a good correlation with the GFA in the Ni–Nb–Zr alloys. Compression tests reveal that the addition of Zr just decreases the fracture strength slightly from 3.4 to 3 GPa and that all of the tested samples exhibit a little compressive plasticity of about 2%. When x = 9, the feature of the fracture surface indicates that the alloy has a tendency for transition from the ductile to the brittle. And delicate “dimple” and microscale vein pattern structures have been observed on it.

The effect of Zr addition in glass forming ability of Ni–Nb alloy system

The effect of Zr addition on glass forming ability (GFA) of Ni–Nb alloys has been investigated. Ni 60Nb 40− x Zr x ( x = 0–40) alloys were prepared by melt-spinning and injection-casting. Crystallization behavior of the alloys was studied by differential scanning calorimetry (DSC), differential thermal analyzer (DTA) and X-ray diffractometry (XRD). The GFA increased with the addition of Zr, thus, a rod with the diameter of 2 mm was obtained in Ni 60Nb 30Zr 10 which has the highest reduced glass transition T rg value of 0.619 among the alloys investigated. When Zr content is more than 10 at.%, the GFA deteriorated significantly. The atomic structure of Ni–Nb–Zr alloys investigated by means of extended X-ray absorption fine structure (EXAFS), indicated presence of chemical inhomogeneity in the amorphous structure due to the positive mixing enthalpy between Zr and Nb.

Fabrication of Binary Ni‐Nb Bulk Metallic Glass with High Strength and Compressive Plasticity

Off‐eutectic Ni61.5Nb38.5 alloy, exhibiting the highest glass‐forming ability in the binary Ni‐Nb system, can be cast into the 1.5mm‐diameter fully amorphous rods by using copper mold injection casting method. Room temperature uniaxial compression tests yield for the high fracture strength and compressive plastic strain values of about 3.4GPa and 2%, respectively. The successful fabrication of the bulk metallic glassy samples in the binary Ni‐Nb alloy is of great interest to prepare large dimension Ni‐based bulk metallic glasses as structural materials.

Binary Ni–Nb bulk metallic glasses

We studied the glass forming ability of Ni–Nb binary alloys and found that some of the alloys can be prepared into bulk metallic glasses by a conventional Cu-mold casting. The best glass former within the compositional range studied is off-eutectic Ni62Nb38 alloy, which is markedly different from those predicted by the multicomponent and deep eutectic rules. The glass formation mechanism for binary Ni–Nb alloys was studied from the thermodynamic point of view and a parameter γ* was proposed to approach the ability of glass formation against crystallization.

Appearance of Two-Way Strain in Shape Memory Effect of Ti–Ni–Nb Alloy —Influence of Applied Strain on Two-Way Strain—

A promising field for applications of shape memory alloys (SMAs) in the near future is the micro-actuator technology. Especially, two-way shape memory effect (TWSME) is the most suitable to apply in actuators, because a pre-determined response can be obtained very easily by thermal changes against shape memory elements.In this paper, the TWSME in Ti–Ni–Nb alloy was investigated quantitatively by applying various levels of pre-deformation. The deformation in a complete martensite phase was applied by a thermo-mechanical treatment in order to obtain the two-way memory strain. The experimental results indicated that the deformation mechanism in a martensite phase was just the martensite reorientation accompanied by the dislocation slip. The dislocation due to the slip deformation is the origin of the internal stress field that is necessary to generate the two-way memory strain. However, excessive introduction of the dislocation decreases the two-way memory strain. The maximum two-way memory strain observed in this experiment was 2.1% at an applied strain of 18%. In addition, pre-deformation increases the temperature of reverse transformation, but decreases the temperature of martensitic transformation. These experimental results can be explained by using the series-parallel combined model that has been suggested in our previous work.

Effect of prestrain on martensitic transformation in a Ti46.4Ni47.6Nb6.0 superelastic alloy and its application to medical stents

The effect of applied strain on martensitic transformation in a superelastic Ti(46.4)Ni(47.6)Nb(6.0) alloy at room temperature was investigated by tensile tests, differential scanning calorimetry measurements, and X-ray diffraction. Reverse transformation starting (A(s)) and finishing (A(f)) temperatures increased with the application of tensile-strain over 13%, the undeformed specimen showing A(s) = -29.2 degrees C and A(f) = 17.9 degrees C, while the 13% predeformed alloy exhibited A(s) = 37.1 degrees C and A(f) = 40.2 degrees C. Furthermore, the values of the A(s) and A(f) for the predeformed alloy almost recovered to those of the undeformed alloy when heated to about 42 degrees C and then showed superelasticity again at room temperature. This characteristic is significant for application in sensors, actuators, and medical devices. Especially, medical stents with such qualities show promise as a new class of self-expandable stents with both excellent mountability and deliverability.

Computer Simulation of Amorphous Ni–Nb Alloys from Diffraction Data

Diffraction data are used to develop 300-K models of the amorphous Ni62Nb38 and Ni44Nb56 alloys using a “hybridization” algorithm, in which the force functions for each atomic pair are linear combinations of those generating the structure of the alloy at 0 and 300 K. These force functions are found using the Schommers algorithm at 300 K and the “coordination number comparison algorithm” (proposed in this work) at 0 K. The pair correlation functions thus found agree well with the diffraction data. The calculated vibrational densities of states for the Ni and Nb atoms in the amorphous alloys studied are in reasonable agreement with inelastic neutron scattering data. The calculated heat capacity of Ni62Nb38 agrees well with experiment, while that of Ni44Nb56 is lower than the reported values.

TiNiNb wide hysteresis shape memory alloy with low niobium content

Abstract Low niobium content dependence of the shape memory characteristic and transformation behavior in Ti–Ni–Nb alloy was studied in this paper. Ti 46.9 Ni 50.1 Nb 3 alloy has excellent shape memory effect, and it can also exhibit enough wide transformation temperature hysteresis after deformation at M s +30 °C.

Strain field due to transition metal impurities in Ni and Pd

The strain field due to body centered substitutional transition metal impurities in Ni and Pd metals are investigated. The calculations are carried out in the discrete lattice model of the metal using Kanzaki lattice static method. The effective ion-ion interaction potential due to Wills and Harrison is used to evaluate dynamical matrix and the impurity-induced forces. The results for atomic displacements due to 3d, 4d and 5d impurities (Fe, Co, Cu, Nb, Mo, Pd, Pt and Au) in Ni and (Fe, Co, Cu, Ni, Nb, Mo, Pt and Au) impurities in Pd are given up to 25 NN’s of impurity and these are compared with the available experimental data. The maximum displacements of 4.6% and 3.8% of 1NN distance are found for NiNb and PdNb alloys respectively, while the minimum displacements of 0.63% and 0.23% of 1NN distance are found for NiFe and PdFe alloys respectively. Except for Cu, the atomic displacements are found to be proportional to the core radii and d state radius. The relaxation energies for 3d impurities are found less than those for 4d and 5d impurities in Ni and Pd metals. Therefore, 3d impurities may easily be solvable in these metals.

Analysis of nickel–niobium alloys by inductively coupled plasma optical emission spectrometry

Inductively coupled plasma optical emission spectrometry (ICP-OES) was applied to the analysis of major and minor elements of Ni–Nb alloys obtained by aluminothermic reduction process. Digestion of samples was made using a mixture of HF+HNO 3. Minor and trace elements were determined without matrix separation. The precision for all constituents was <3%. Recoveries for the analyte-spiked samples were 95%.

Triggered Nucleation in Ni60Nb40 Using an Electrostatic Levitator

External triggering of nucleation in an undercooled liquid metal has been performed for the first time in an electrostatically levitated sample of undercooled eutectic Ni60Nb40. With the Electrostatic Levitator (ESL) facility at NASA/MSFC, NiNb alloys were externally nucleated at various undercooling increments. Observation of the resulting microstructure indicates that only one nucleation site is initiated with a trigger if the undercooling is sufficiently high. Well-defined transition zones exist in all the samples. An "anomalous" fine structured eutectic is initially grown from the nucleation point into the undercooled liquid followed by an unexpected variable width transition zone leading to a coarse structured region of dendrites. Our study tends to corroborate the findings of other studies on highly undercooled eutectics regarding a coupled growth zone within which the lamellar structure is formed and outside of which the anomalous is found.

Microstructural development inside the stress induced martensite variant in a Ti–Ni–Nb shape memory alloy

The microstructural development inside the stress induced martensite (SIM) variants in Ti–Ni–Nb alloy with various degrees of deformation have been revealed by electron microscopic observations. The orientation relationship between the SIM and the parent phase has been found: [1 1 ̄ 0] M //[11 1 ̄ ] B2 , (001) M 5° away from (101) B2. The lattice invariant shear of the SIM variants at the slightly deformed stage is dominantly (11 1 ̄ ) Type I twin. Besides the ordinary slip, the adjustment and development of the internal secondary twinning from (11 1 ̄ ) Type I twin to 〈011〉 Type II/or (011) Type I twin, (001) compound twin and (111) Type I twin happen concurrently or in combination inside the SIM variants with the further deformation. The corresponding deformation mechanisms include stress induced reorientation of SIM substructural bands by the most favorably oriented twin system, stress induced migration of the SIM substructural boundary through internal twinning and stress induced injection of foreign SIM variant to the preexisting substructural bands.

Ni-65wt%Nb alloy by aluminothermic reduction process

Ni–Nb alloys have been used as master-alloy in the production of Ni-based superalloys containing niobium. In the case of INCONEL 718, the most used superalloy, the niobium content is in the range 5.0–5.5 wt%. The aim of this work is to present results related to the production of Ni-65wt%Nb alloy by aluminothermic reduction process. Two different reactant mixtures were used: Nb 2O 5 + Ni + Al and Nb 2O 5 + NiO + Al. For each type of mixture the Al excess was varied from 0% to 15% over the stoichiometric amount. All the alloys were produced in a bulk form with Nb and Ni composition according to specifications. The best results came from the experiments involving mixtures of Nb 2O 5 + NiO + Al, where an overall metallic yield of 86% was obtained. The alloys produced from Nb 2O 5 + Ni + Al mixtures showed low metallic yields and high oxygen contents associated to the presence of a niobium oxide-phase in the microstructure.

Electrochemical and XPS studies of the corrosion behavior of sputter-deposited amorphous Fe–Cr–Ni–Nb alloys in 6 M HCl

Amorphous Fe–Cr–Ni–Nb alloys containing 9–68 at.% niobium were successfully prepared by the D.C. magnetron sputtering method using targets consisting of a commercial Type 304 stainless steel disc and high purity niobium discs. The corrosion rate of the sputter-deposited Fe–Cr–Ni–Nb alloys containing more than 19 at.% niobium in 6 M HCl at 30°C was more than four orders of magnitude lower than that of bulk Type 304 stainless steel and almost the same as that of sputter-deposited niobium metal, although the corrosion rate of the alloys was higher than that of the binary Cr–Nb alloys. The corrosion potential of the alloys was higher than that of niobium and all the Fe–Cr–Ni–Nb alloys were spontaneously passivated in 6 M HCl at 30°C. XPS analysis revealed that the spontaneous passive films formed on the alloys after immersion in 6 M HCl for 48 h were rich in chromium and niobium cations and deficient in iron cation. The formation of the homogeneous double oxyhydroxide films containing chromium, niobium and iron cations is responsible for the high corrosion resistance of the alloys.

Effect of Nb addition to Ni and Fe on electronic structure and magnetic properties

The electronic structure and magnetic properties of fcc NiNb and bcc FeNb alloys within the Nb concentration of 20 at% are studied by band structure calculations based on the Korringa-Kohn-Rostoker coherent-potential approximation method. The results show that niobium has a magnetic moment in Ni and Fe with antiparallel coupling. The density of states of Nb in fcc NiNb and bcc FeNb calculated in the paramagnetic state shows a minimum at the Fermi energy which leads to the antiparallel coupling of Nb. The local magnetic moments of Nb and Ni drop abruptly in fcc NiNb alloy as the Nb concentration increases, although the local magnetic moment of the Nb hardly decreases in bcc FeNb alloy.

Mechanical Alloying of Ni-Nb Alloys

Mechanical Alloying of Ni-Nb Alloys

Mixing enthalpies of liquid Ni-V, Ni-Nb and Ni-Ta alloys measured by levitation alloying calorimetry

Mixing enthalpies have been determined by levitation alloying calorimetry (the LAC method) for the liquid systems Ni-V in the Ni rich range up to x v = 0.48 at 1927 and 2020 K and in the V rich range up to x Ni = 0.4 at 2320 K, for Ni-Nb up to x Nb = 0.4 at 2000 K and for Ni-Ta up to x Ta = 0.31 at 2000 K. The experimental results are successfully described by means of the quasichemical model. A temperature dependence of the mixing enthalpy cannot be found. The location of the minima corroborates the glass forming ability of the systems. The values of the mixing enthalpy have been compared with the available formation enthalpies for the solid compounds of the systems. The comparison shows a good agreement.

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

Mixing enthalpies have been determined by levitation alloying calorimetry (the LAC method) for the liquid systems Ni-V in the Ni rich range up to Xv = 0.48 at 1927and 2020 K and in the V rich range up to XNi = 0.4 at 2320 K, for Ni-Nb up to XNb = 0.4 at 2000 K and for Ni- Ta up to XTa = 0.31 at 2000 K. The experimental results are successfully described by means of the quasichemical model. A temperature dependence of the mixing enthalpy cannot be found. The location of the minima corroborates the glass forming ability of the systems. The values of the mixing enthalpy have been compared with the available formation enthalpies for the solid compounds of the systems. The comparison shows a good agreement. Résumé Les enthalpies de mélange ont été déterminées par calorimétrie pour alliage par lévitation (la méthode “LAC”) pour les systèmes liquides Ni-V dans le domaine riche en Ni jusqu'à Xv = 0.48 à 1927K et Ré 2020 K et dans le domaine riche en V jusqu'à XNi = 0.4 à 2320 K, pour le Ni-Nb jusqu'à XNb = 0.4 à 2000 K et pour le Ni-Ta jusqu'à XTa = 0.31 à 2000 K. Les résultats expérimentaux sont décrits avec succès par le modele quasi-chimique. On n'a pas trouvé de dépendance sur la température de l'enthalpie de melange. L'emplacement des minima corrobore l'habilité des systèmes à former du verre. Les valeurs de l'enthalpie de mélange ont été comparées avec les enthalpies de formation disponibles pour les composés solides des systémes. La comparaison montre une bonne corrélation.

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

The corrosion of two NiNb alloys under 1 atm O 2 at 600–800 °C

The oxidation of two NiNb alloys containing 15 and 30 wt% Nb has been studied at 600–800 °C in pure oxygen under 1 atm O 2 at 600–800 °C. The scales formed on both alloys under all conditions show an external scale, generally duplex, containing an outermost layer of nearly pure NiO and an innermost region of NiO mixed with the double NiNb oxide NiNb 2O 6. Moreover, the samples corroded at all temperatures also show a region of internal oxidation composed of a mixture of alpha nickel and niobium oxides (Nb 2O 5 or/and NbO 2), which formed from both alloy phases Ni 8Nb and Ni 3Nb. No important depletion of niobium was observed in the alloy close to the interface with the zone of internal oxidation, while the depth of this region is generally much higher than measured for the corrosion of the same alloys under low oxygen pressures at the same temperatures. The corrosion mechanism of these alloys is examined with special reference to the effects of the low solubility of niobium in nickel.