Vanadium Alloys Research Articles

Stability of the Transition Zones in a Steel–Vanadium Alloy–Steel Sandwich after Thermomechanical Treatment

A priority in atomic power today is to develop a new material for fuel-rod casings in fast-neutron reactors. A radiation- and corrosion-resistant three-layer composite based on vanadium alloy and stainless steel has been developed. This composite potentially meets the operational requirements on fuel-rod casings in very challenging operating conditions (high temperatures, radiation, and aggressive media). The performance of this material depends on the quality of the joint between the three layers, which is determined by the preliminary deformation and heat treatment. In the present work, the influence of tempering on the chemical composition, structure, and strength of the joint between the vanadium alloy and steel in the sandwich obtained by hot pressing a three-layer pipe blank at 1100°C is studied. The components of the pipe are 20Kh13 (Russian standard) steel for the external layers and V–4Ti–4Cr vanadium alloy in the core. The structure and chemical composition at the interfaces is investigated by optical and electronic microscopy, with X-ray spectral analysis. The strength of the steel–alloy bond is assessed in compressive tests of an annular three-layer sample with a cut; acoustic-emission measurements are employed. Pressing is found to form a transition zone of thickness 10–15 μm between the vanadium alloy and the steel, which is characterized by diffusional interaction and has a variable chemical composition. This zone consists of a series of solid solutions, without the deposition of brittle phases, and consequently the junction between the layers is strong. No pores, peeling, or defect are observed at the steel–alloy junction. However, in compressive tests of semiannular three-layer samples with a cut after hot pressing, a crack is formed in the steel layer at the tip of the cut. Annealing at 800°C improves the transition zone by increasing the thickness corresponding to diffusional interaction. Consequently, in mechanical tests, the sandwich behaves as a monolithic material, without cracking or peeling between the steel and the vanadium alloy.

In vitro and in vivo biological performance of porous Ti alloys prepared by powder metallurgy.

Titanium (Ti) and Ti-6 Aluminium-4 Vanadium alloys are the most common materials in implants composition but β type alloys are promising biomaterials because they present better mechanical properties. Besides the composition of biomaterial, many factors influence the performance of the biomaterial. For example, porous surface may modify the functional cellular response and accelerate osseointegration. This paper presents in vitro and in vivo evaluations of powder metallurgy-processed porous samples composed by different titanium alloys and pure Ti, aiming to show their potential for biomedical applications. The porous surfaces samples were produced with different designs to in vitro and in vivo tests. Samples were characterized with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and elastic modulus analyses. Osteogenic cells from newborn rat calvaria were plated on discs of different materials: G1—commercially pure Ti group (CpTi); G2—Ti-6Al-4V alloy; G3—Ti-13 Niobium-13 Zirconium alloy; G4—Ti-35 Niobium alloy; G5—Ti-35 Niobium-7 Zirconium-5 Tantalum alloy. Cell adhesion and viability, total protein content, alkaline phosphatase activity, mineralization nodules and gene expression (alkaline phosphatase, Runx-2, osteocalcin and osteopontin) were assessed. After 2 and 4 weeks of implantation in rabbit tibia, bone ingrowth was analyzed using micro-computed tomography (μCT). EDS analysis confirmed the material production of each group. Metallographic and SEM analysis revealed interconnected pores, with mean pore size of 99,5μm and mean porosity of 42%, without significant difference among the groups (p>0.05). The elastic modulus values did not exhibit difference among the groups (p>0.05). Experimental alloys demonstrated better results than CpTi and Ti-6Al-4V, in gene expression and cytokines analysis, especially in early experimental periods. In conclusion, our data suggests that the experimental alloys can be used for biomedical application since they contributed to excellent cellular behavior and osseointegration besides presenting lower elastic modulus.

Influence of the fabrication route of tunsgen-2 wt.% vanadium in the microstructure and mechanical properties

This study evaluates the microstructural and mechanical behaviour of two tungsten (W) − 2 wt.% vanadium (V) alloys and compares them with a pure W reference material. All the materials were processed by hot isostatic pressing (HIP). However, some differences were introduced during the fabrication process of the W-2 V alloys: one was processed with mechanical alloying (MA) and the other with only mixing of the powders. For the mechanical characterisation non-standard tree-point bending (TPB) tests were performed in air in both smooth and V-notched specimens. Tests were performed in a temperature range between 77 K, via immersion in liquid nitrogen, to 1073 K to determine the mechanical strength, yield strength and fracture toughness. Other physical and mechanical tests were performed such as measurement of the hardness, density and elastic modulus. The results exhibit significant differences between both alloys and the pure-W reference material and reveal the critical important of the MA during the fabrication process.

Helium Porosity Formation in Vanadium Alloys of V-Ti-Cr, V-W-Zr and V-W-Ta Systems in Comparison with Binary Alloys

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An F82H steel pressurized tube creep capsule for irradiation in HFIR

A novel capsule design has been developed for measurement of irradiation creep in pressurized tubes and is being used to irradiate reduced activation ferritic/martensitic F82H steel creep test specimens. These tests are being conducted in the flux trap of the High Flux Isotope Reactor at the Oak Ridge National Laboratory. The capsule design uses a tight-fitting corrugated aluminum foil placed in the center of a vanadium alloy holder to conduct heat from the centrally located test specimen. The foil acts as a compressible thermal interface between the pressurized tube and holder, maintaining a constant thermal resistance (and thus a constant tube temperature gradient) during irradiation, regardless of differential thermal expansion, creep, and swelling in the test specimen. Mechanical interference with creep deformation of the specimen tube is minimized by using a thin (0.05 mm) foil with sufficient room to crush. Finite element analysis of the contact pressure between the specimen and foil, combined with thermal creep in the foil, showed little interference with specimen stress conditions. Specimens were designed to experience hoop stresses of 380, 300, 150, and 0 MPa at a temperature of 300 °C while being irradiated to a dose of 3.7 dpa. Passive SiC thermometry is located within the pressurized tube and the holder material for confirmation of experiment irradiation target temperatures. This work discusses aspects of the capsule's fabrication and design, including thermal models of the capsule during irradiation.

Structure Formation and Hardening of the Hybrid Material Based on Vanadium and Zirconium Alloys during High-Pressure Torsion

A layered hybrid material is prepared by high-pressure torsion of a three-layer (vanadium alloy–zirconium alloy–vanadium alloy) billet. A mixed nanostructure with a highly uniform distribution of zirconium and vanadium alloy regions forms under the chosen severe plastic deformation conditions in the middle layer of the material. The microhardness of this layer increases by a factor of about 2.5 as compared to the initial state.

Joining of tungsten with low-activation ferritic–martensitic steel and vanadium alloys for demo reactor

The conceptual designs of the blanket and the helium-cooled divertor of the DEMO reactor require joining of reduced activation steel (for example RUSFER EK-181, EUROFER, etc.) and tungsten. Significant differences in their physical properties can lead to the generation of the stresses during cooling and, as a result, to the failure of the joint. In this paper, diffusion brazing of RUSFER EK-181 steel with tungsten using a V–4Ti–4Cr interlayer was obtained. Rapidly-quenched ribbon brazing alloys based on copper of various compositions were used. Brazing was carried out in vacuum furnaces at temperatures in the range of 800–1000 °C. The structural-phase states of the joints obtained were studied, the microhardness was measured, and thermocycling tests were performed in the interval of 700 to 25 °C. FEM simulation was used to calculate the optimal thickness of the interlayer.

Proving the viability of manufacturing of multi-layer steel/vanadium alloy/steel composite tubes by numerical simulations and experiment

Vanadium alloys are promising structural materials for fuel cladding tubes for fast-neutron reactors. However, high solubility of oxygen and nitrogen in vanadium alloys at operating temperatures of 700 °C limits their application. In this work, we present a novel composite structure consisting of vanadium alloy V-4Ti-4Cr (provides high long-term strength of the material) and stainless steel Fe-0.2C-13Cr (as a corrosion resistant protective layer). It is produced by co-extrusion of these materials forming a three-layered tube. Finite element simulations were utilised to explore the influence of the various co-extrusion parameters on manufacturability of multi-layered tubes. Experimental verification of the numerical modelling was performed using co-extrusion with the process parameters suggested by the numerical simulations. Scanning electron microscopy and microhardness measurements revealed a defect-free diffusion layer at the interfaces between both materials indicating a good quality bonding for these co-extrusion conditions.

Effect of Annealing on Microstructures and Hardening of Helium-Hydrogen-Implanted Sequentially Vanadium Alloys

The effect of post-irradiation annealing on the microstructures and mechanical properties of V-4Cr-4Ti alloys was studied. Helium-hydrogen-irradiated sequentially V-4Cr-4Ti alloys at room temperature (RT) were undergone post-irradiation annealing at 450 °C over periods of up to 30 h. These samples were carried out by high-resolution transmission electron microscopy (HRTEM) observation and nanoindentation test. With the holding time, large amounts of point defects produced during irradiation at RT accumulated into large dislocation loops and then dislocation nets which promoted the irradiation hardening. Meanwhile, bubbles appeared. As annealing time extended, these bubbles grew up and merged, and finally broke up. In the process, the size of bubbles increased and the number density decreased. Microstructural changes due to post-irradiation annealing corresponded to the change of hardening. Dislocations and bubbles are co-contributed to irradiation hardening. With the holding time up to 30 h, the recovery of hardening is not obvious. The phenomenon was discussed by dispersed barrier hardening model and Friedel-Kroupa-Hirsch relationship.

Simultaneous Increase of Both Strength and Ductility of Medium Mn Transformation-Induced Plasticity Steel by Vanadium Alloying

In general, microalloying such as vanadium (V) is considered to deteriorate the mechanical stability of austenite grains in medium Mn steel due to the consumption of C content. In this paper, we show that the mechanical stability of austenite grains could be optimized by V-alloying. This is because the V-alloying will refine the austenite grain size and tends to stabilize the austenite grains. The competition between the grain refinement and the reduced C content results in proper mechanical stability of austenite grains, providing continuous transformation-induced plasticity (TRIP) effect. In addition, the V-alloying suppresses the formation of intergranular cracks, leading to a ductile fracture morphology and a large non-uniform elongation.

Development of technology of superconducting multilevel wiring in speed GaAs structures of LSI/VLSI

Technological aspects of the use of superconducting materials are considered and the possibility of making targets for magnetron deposition of films for the formation of cryoconductive wiring in GaAs-based LSI-structures is shown. The technological methods and regimes are determined and high-performance technology of cryoalloys making based on Al, Nb, V with Si, Ge and rare-earth metal admixtures and magnetron formation of superconducting films from aluminum, niobium and vanadium alloys are developed. In particular, technological regimes (ion current, accelerating voltage, deposition rate, plasma composition, uniformity of components per silicon substrate diameter) have been established, which provide a thickness of films at the level of 0.6-1 μm. Insignificant thermomechanical stresses (about 1 kg/cm 2 ) and small grain size (~ 10 nm) will allow for excellent adhesion of deposited films and formation of a topological pattern of submicron sizes using photolithography. The parameters and characteristics of the Schottky field GaAs transistors on homo- and heterostructures (Schottky barrier height 0.75-0.8 eV, non-ideality factor 1.2-2, breakdown voltage of Schottky barrier 15-30 V) are explored and methods for increasing the speed of the LSI-structures are defined. It is shown that increasing the speed of LSI/VLSI-structures on gallium arsenide is achieved by using thermostable cryomaterials as gate electrodes, conductors and contacts of source-drain regions of the Schottky field-effect transistors.

Blistering behavior and deuterium retention in tungsten vanadium alloys exposed to deuterium plasma in the linear plasma device STEP

The behavior of tungsten-vanadium (W-V) alloys fabricated by powder metallurgy as a plasma facing material has been studied. W-V alloys with different vanadium concentrations (5 and 10 wt %) manufactured by hot pressing (HP) were exposed to deuterium plasma (flux ∼4.6 × 1021 m−2s−1, fluence ∼5.6 × 1025 m−2, ion energy ∼60 eV, target temperature ∼450 K) in the linear plasma device STEP at Beihang University. Three typical grains are observed on HP sintered W-V alloys and exhibit a significant effect on its performance under deuterium plasma irradiation. Surface blistering only occurs at W-enriched grains and is significantly mitigated in W-V alloys, especially in W-10 V, blistering is completely suppressed. On the other hand, deuterium retention dramatically increases in the W-V alloys due to vanadium addition. The deuterium retention in W-5 wt. % V is about 6.2 times more than that in rolled pure W, and this factor further increases to 6.9 when the V concentration rises to 10 wt %. We ascribe these phenomena to the changes of microstructures and components caused by vanadium addition.

Short term exposure to titanium, aluminum and vanadium (Ti 6Al 4V) alloy powder drastically affects behavior and antioxidant metabolites in vital organs of male albino mice.

Titanium, Aluminum and Vanadium (Ti 6Al 4V) alloy are frequently used as surgical implant but regarding their compatibility in living systems is limited. Ti 6Al 4V was prepared from high purity constituents and Ti 6Al 4V alloy powder (25 mg/ml solvent/Kg body weight) was gavaged to albino mice for 8 days. A saline treated control group was maintained in parallel. A series of behavioral (rota rod, light and dark box, open field and novel object) test performance, complete blood count, selected serum (HDL cholesterol, LDL cholesterol, creatinine, cholesterol and triglycerides) parameters, antioxidant metabolites from vital organs (superoxide dismutase, catalase and lipid peroxidation) from vital organs and body weight were determined in both treatments. It was observed that rota rod test performance in male (P = 0.05) and novel object recognition capability in female mice (P = 0.04) were significantly reduced as compared to their respective control groups. Body weight, complete blood count and studied serum parameters remained unaffected when compared between two treatments of both genders. Concentration of superoxide dismutase in liver (P = 0.008), heart (P = 0.01) and lungs (P = 0.05) was significantly elevated while catalase concentration in liver (P = 0.001) was significantly decreased in female albino mice that were exposed to 25 mg/ml solvent/kg body weight of Ti 6 A l 4 V alloy powder. In case of male albino mice, superoxide dismutase concentration in lungs was reduced (P = 0.05) in mice exposed to Ti 6 A l 4 V alloy powder. In conclusion, our results indicated that short term exposure to 25 mg/ml solvent/Kg body weight of Ti-6Al-4V alloy powder supplementation had adversely affected selected aspects of behavior of albino mice in a gender specific manner. Analysis of antioxidant parameters in vital organs has demonstrated that the applied dose of Ti-6Al-4V alloy powder can disturb the H₂O₂ associated metabolic pathways in albino mice, especially in female mice. As this alloy is part of surgical implants, so we recommend that their effects in living systems must be extensively explored under variable dose and exposure time conditions to know more about their biocompatibility.

Metallic Membranes for Hydrogen Separation : Palladium Alloys and Vanadium Alloys

Metallic Membranes for Hydrogen Separation : Palladium Alloys and Vanadium Alloys

Structure and phase composition of material based on vanadium alloy V-4.9Ti-4.8Cr and ferrite steel 17Cr-12Ni-Fe

Three-layer materials consisting of the V-4.9Ti-4.8Cr/ferrite steel 17Cr-12Ni-Fe /V-4.9Ti-4.8Cr were obtained in the paper. Phase composition and microstructure of the transition zone of the three-layer material of vanadium alloy V-4.9Ti-4.8Cr and ferrite steel 17Cr-12Ni-Fe were considered. The use of the method of direct laser growing allowed obtaining a three-layer material with qualitative interconnection of layers, as well as decreasing a multistage nature of deformation and thermal operations used when obtaining a three-layer material in earlier works. Additional thermal treatment of a three-layer alloy led to growth of matrix grains up to 100 μm of the vanadium alloy. A uniform distribution of main elements V, Ti, Cr was observed in the transition zone both before and after annealing. A zone of interdiffusion of the metals amounted to 250-350 μm.

バナジウム合金膜を用いた大容量超高純度水素分離デバイスの開発

バナジウム合金膜を用いた大容量超高純度水素分離デバイスの開発

Fabrication and Analysis of Vanadium-Based Metal Powders for Selective Laser Melting

Vanadium Alloy is a type of advanced nuclear material with many ideal properties compared as traditional nuclear materials, which has very wide and important application in first-wall and blanket structural material for fusion power plant applications. So it has attracted increasing attentions, especially on new manufacturing methods, such as selective laser melting and so on. In this paper, the comparative study of the powders obtained by mechanical mixing method, dry grinding method and wet grinding method respectively was performed to evaluate the effect of ball milling process on the microstructure and degree of alloying of the vanadium-based powder mixtures with the nominal composition of V5Cr5Ti vanadium alloy. The powders prepared by dry grinding method exhibits better spherical-like morphology and degree of alloying than those prepared by mechanical mixing method and wet grinding method, which indicates that dry grinding method can be used to prepare the superfine vanadium alloy powders for selective laser melting. This work provides a new method as well as important insights into the preparation of superfine vanadium alloy powders for selective laser melting additive manufacturing technology.

Hydrogen transport through the tubular membranes of V-Pd alloys: Permeation, diffusion, surface processes and WGS mixture test of membrane assembly

The membranes of vanadium alloys can be a more productive and less expensive alternative to the membranes of palladium alloys for the extraction of ultrapure hydrogen. Alloying of V with Pd is very effective for the reduction of excessive hydrogen solubility inherent in pure V while the ductility of substitutional V-Pd alloys remains sufficient for making thin walled tubular membranes for practical applications. The hydrogen transport through the tubular membranes of substitutional V-κPd alloys with Pd coating of inner and outer sides was systematically studied with variation of alloy composition (0 ≤ κ ≤ 13.3at%), temperature (300 – 500°C) and pressure (0.001 – 1.2MPa). The permeation flux density was almost independent of temperature for all investigated alloys. It was found that the main reason for this is the surface processes whose role dramatically increased with decreasing temperature, getting crucial at 300°C. The record hydrogen diffusivity inherent in pure V reduced by alloying with Pd no more than 3 times even at the maximum degree of alloying (13.3%) and lowest temperature (300°C). An assembly of 18 tubular membranes of V-5.2at%Pd with 145µm wall thickness was designed for feeding 1kW PEMFC and demonstrated a highly productive extraction of ultrapure hydrogen from WGS mixture.

Investigation of the interstitial oxygen behaviors in vanadium alloy: A first-principles study

This study aims at characterizing the interstitial Oxygen (O) behaviors in the Vanadium (V) Alloy by means of the first-principles calculations. For this, the interations between vacancy (Vac) and O interstitil atom are studied in detail to obtain the binding energies and stable structures of the complexes. It can be seen that monovacancy binding with two O atoms occupied the opposing octahedral stie are particularly stable, and is liable to form VacO2 cluster in the V alloys. According to the mass action analysis, the predicted temperature dependence of the concentration for VacOn complexes are presented. Apart from monovacancy, we also consider the trapping behavior of vacancy cluster on the O atoms. The results also prove that one vacancy can trap two O atoms in the V alloys. Based the diffusion theory, we obtain the diffusion coefficients as a function of temperature with or without the vacancy effect in the V alloys. The predicted O diffusion coefficients in defect-free V alloys from our first-principles calculations are in excellent ageement with the experimental data, meanings that the vacancy-limited mechanism does not play the key role for O diffusion in V alloys. Regarding the interactions between vacancy, solutes and O atom, combining with the diffusion barriers of O affected by vacancy and solute, we infer the formation mechanism of the precipitates in the V alloys.

The direct correlation between precipitate-size-dependent strain at the interface and the irradiation hardening in V-4Cr-4Ti

V-4Cr-4Ti alloy, one of the promising candidate structural materials for fusion first wall/blanket applications, was annealed in different temperatures (800 °C and 1000 °C) followed by hydrogen and subsequent helium ions irradiation. It is designed for ion irradiations by forming different size of precipitates, intending to investigate the effect of interfacial coherency characteristic on the irradiation damage behavior at an atomic scale. The microstructure was studied by transmission electron microscopy and the effect of irradiation hardening was evaluated by nanoindentation technique. The results show that TiC precipitate with different size and density was formed during the heat treatment. The lattice matching and the resulting strain state at the interface between the precipitate and the matrix were also investigated quantitatively. The samples with large precipitate exhibited a relatively lower irradiation hardening rate than the one with smaller precipitate, which attributes to the distinct aggregation of He atoms at the interface between the larger precipitate and vanadium alloy matrix. It suggests that the strain state at the interface between the precipitate and the matrix plays a key role in determining the distribution state of irradiation defects thus affect the irradiation damage behavior significantly.