Effect Of Niobium Content Research Articles

Effect of niobium content on microstructure and wear and corrosion resistance of laser-clad FeCo0.5CrNi1.5B0.5Nbx coatings on ductile iron

Ductile iron with a high carbon content is highly susceptible to the precipitation of brittle carbides during the cladding process, which makes it challenging to achieve the desired formability of the coating. In this study, FeCo0.5CrNi1.5B0.5Nbx (x = 0.1, 0.2, 0.3, and 0.4) high-entropy alloy coatings were designed using theoretical calculations and prepared on ductile iron through laser cladding. The effect of niobium (Nb) content on the microstructure evolution and phase composition of the coating was explored to determine the alloy component with the highest wear and corrosion resistance. All of the prepared coatings consisted of face-centered cubic (FCC) phases, along with Nb(C, B2) and Laves phases. With the increase in Nb content, the intensity of the diffraction peaks of NbC significantly increased compared to those of the other precipitates due to element diffusion. Nb0.3 coatings, which had the highest hardness, H/E, and H3/E2 values due to the most suitable percentage of FCC and hard phases, presented the lowest average friction coefficients of 0.48, 0.49, and 0.50, as well as the minimum wear volume of 0.64 × 108, 2.06 × 108, and 5.04 × 108 μm3 under loads of 10, 30, and 50 N, respectively. The wear mechanism of all the coatings was dominated by adhesive wear and oxidation wear under loads of 10 N and 30 N, while it changed to abrasive wear under a load of 50 N. Furthermore, Nb0.3 coatings also showed superior corrosion resistance due to the positive influence of the optimal Nb content on the oxide film. The Ecorr values were − 395 mV and − 337 mV, and the Icorr values were 0.21 × 10−6 A/cm2 and 1.10 × 10−6 A/cm2 in NaCl (3.5 wt%) and HCl (0.5 mol/L) solutions, respectively.

Effect of Niobium Content on the Microstructure and Mechanical Properties of Simulated Coarse-Grained Heat-Affected Zone (CGHAZ) of High-Strength Low-Alloy (HSLA) Steels.

The effect of Nb-content and heat input rate on the mechanical properties and microstructure of simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steel (HSLA) was investigated. While using a low heat input (20 kJ/cm), the toughness of simulated CGHAZ was improved by increasing the Nb-content. The maximum toughness was obtained when the Nb-content was 0.110 wt.% and the heat input was 20 kJ/cm. The samples made at this condition had fine martensite/austenite (M/A-constituent), acicular ferrite and refined austenite grains. As the heat input was increased to 200 kJ/cm, the toughness of simulated CGHAZ was significantly decreased irrespective of the Nb-content because of the formation of coarse austenite grains, low angle grain boundaries, and massive M/A-constituents.

Effect of niobium content on irradiation microstructure and hardening in FeCrAl-based alloys

• The evolution of dislocation loop with niobium content in FeCrAl alloys was discussed. • The formation of laves phase resulted in the decrease of Mo content and the increase of Cr content in the matrix of the FeCrAl alloys. • Nb addition increased nanoindentation hardness and reduced irradiation hardening in the FeCrAl alloys . Iron-chromium-aluminum (FeCrAl) alloys with different content of niobium (Nb)—0, 0.4 wt%, 0.8 wt%, and 1.2 wt%—were designed and prepared. All samples were then irradiated with 2.4 MeV Fe 2+ ion to the dose of 1 and 15 displacements per atom (dpa) at 400 °C. The formations of dislocation loops induced by self-ion irradiation in these alloys were investigated by transmission electron microscopy (TEM). Nano-indentation tests were used to assess the hardness and irradiation hardening of samples. For the samples before irradiation, the (Fe, Cr) 2 (Nb, Mo) Laves phases density and the nano-indentation hardness increased with increasing Nb content of the samples. After irradiation to 1 and 15 dpa, both of a /2<111> and a <100> dislocation loops were produced but no voids or αˊ phase were found in all samples. With increasing Nb content of the samples, the size of dislocation loops increased first and then decreased, while the total volume number density decreased and then increased. The fraction of a <100> dislocation loops increased first and then decreased with increasing Nb content, and increased with increasing irradiation dose. Dislocation networks and the amorphization of the Laves phases were observed in the samples with irradiation dose of 15 dpa. Irradiation hardening of Nb free samples was two to four times that of Nb containing samples, and the irradiation hardening increased with increasing Nb content of Nb containing samples. The experimental results indicate that the increase of Nb content in FeCrAl alloys can increase the density of Laves phases, leading to the decrease of Mo content and increase of Cr content in the matrix. The competition between the two types of solutes affects the nucleation and growth of the dislocation loops.

Synthesis of nanostructured biomaterials by high-pressure torsion: Effect of niobium content on microstructure and mechanical properties of Ti-Nb alloys

Titanium-niobium alloys with the bcc structure (β-Ti-Nb) are recently investigated for their potential use in biomedical applications; however, improvement of their mechanical properties (particularly hardness and elastic modulus) is still a challenge. In this study, nanostructured Ti-Nb alloys with different Nb contents were successfully synthesized by mechanical alloying of elemental powders via high-pressure torsion (HPT). The HPT process led to the homogenous mixture of the two elements and the formation of nanograined β phase. Examination of mechanical properties by nanoindentation and microhardness measurements revealed that all synthesized alloys exhibited high hardness and good plasticity; however, the best combination of low elastic modulus and high hardness was obtained for the sample with 25 at% Nb: E = 39 ± 11 GPa (close to the elasticity of human bone) and Hv = 3.7 ± 0.1 GPa (comparable to the hardest Ti-based biomaterials). The current results confirm the potential of HPT to synthesize nanograined Ti-Nb alloys for future biomedical applications.

Effect of niobium content on the microstructure and Young's modulus of Ti-xNb-7Zr alloys for medical implants

New generation titanium alloys with low elastic moduli are promising materials for medical implants, particularly load-bearing orthopaedic implants. In this paper, the effect of niobium content on the microstructure and mechanical properties of new Ti alloys including Ti-23Nb-7Zr, Ti-28Nb-7Zr and Ti-33Nb-7Zr (wt%) is studied. Ti-23Nb-7Zr was found to mainly form α΄ and α″- phases, while both the Ti-28Nb-7Zr and Ti-33Nb-7Zr consisted of α″ and β-phases with an increased amount of β-phase in the alloy with 33 wt% of Nb. X-ray diffraction and microstructural analyses showed that the addition of Nb stabilises the β-phase in the solution treated condition with the depleting amount of α΄ and α″- phases. The hardness and Young's modulus values were highest in Ti-23Nb-7Zr which is attributed to the high fraction of α΄- phase in this alloy. The Young's moduli achieved for the three alloys through nanoindentation were 35.9, 29.1 and 29.0 GPa, respectively. The new alloys are encouraging candidates for orthopaedic implants due to their low elastic modulus which can help inhibit stress shielding, although biocompatibility tests (in-vitro and in-vivo) are suggested for future work.

NIOBIUM EFFECT ON BASE METAL AND HEAT AFFECTED ZONE MICROSTRUCTURE OF GIRTH WELDED JOINTS

The development of steels for line pipes during the last decades has been driven by the need to obtain improved combinations of high strength, toughness, weldability on industrial scale at affordable prices. The effect of niobium content on the heat affected zone (HAZ) microstructure is reported in this paper. Niobium, for its specific thermodynamic and kinetic attitude to form carbide and nitride precipitates, played a key role in the development of modern HSLA steels Results show that niobium addition is able to refine both the bainitic packet and cells size in the heat affected zone during welding. This implies that niobium addition leads to an improvement of both toughness and hardness of welded joints manufactured by Nb micro-alloyed steels.

Thin-Film Transistors Based on Amorphous ZnNbSnO Films With Enhanced Behaviors

Amorphous zinc-niobium-tin-oxide (a-ZNTO), a new amorphous oxide semiconductor, was proposed for fabricating thin-film transistors (TFTs). a-ZNTO thin films were grown by magnetron sputtering and used as channel layers of TFTs. The effects of niobium content on film properties and device behaviors were investigated in detail. Nb could serve as a carrier suppressor by reducing oxygen vacancies in a-ZNTO films and lower the interfacial trap states in a-ZNTO TFTs. The enhanced performances of a-ZNTO TFTs were achieved at an optimized Nb content of $x=0.2$ for a Nb:Zn:Sn atomic ratio of $x$ :4:7. The reduced channel sizes are very effective to improve TFT performances, with an ON/OFF current ratio of $\sim 10^{8}$ and a field-effect mobility of 13.2 cm2/Vs. The indium-free a-ZNTO TFTs may have the potential for applications in next-generation displays.

Effects of niobium content on electrical and mechanical properties of (Na0.85K0.15)0.5Bi0.5Ti(1-x)Nb x O3 thin films

(Na0.85K0.15)0.5Bi0.5Ti(1-x)Nb x O3 (NKBT-N100x) thin films were deposited on Pt/Ti/SiO2/Si(100) substrates by metal–organic decomposition method and annealed in oxygen atmosphere at 750 °C. The effects of niobium concentration on the microstructures, ferroelectric, piezoelectric, leakage current and mechanical properties of the NKBT-N100x (x = 0, 0.01, 0.03, 0.05) thin films have been investigated in detail. The NKBT-3N thin film has the largest remnant polarization (7 μC/cm2) and statistically averaged d 33eff (140 pm/V), the smallest leakage current, elasticity modulus (102.0 Gpa), hardness (5.1 Gpa) and residual stress (297.0 Mpa). The evaluation of residual stresses of these thin films will offer useful guidelines of safe working condition for their potential application in microelectromechanical system.

Microstructure and mechanical behavior of metal injection molded Ti–Nb binary alloys as biomedical material

The application of titanium (Ti) based biomedical materials which are widely used at present, such as commercially pure titanium (CP-Ti) and Ti–6Al–4V, are limited by the mismatch of Young's modulus between the implant and the bones, the high costs of products, and the difficulty of producing complex shapes of materials by conventional methods. Niobium (Nb) is a non-toxic element with strong β stabilizing effect in Ti alloys, which makes Ti–Nb based alloys attractive for implant application. Metal injection molding (MIM) is a cost-efficient near-net shape process. Thus, it attracts growing interest for the processing of Ti and Ti alloys as biomaterial. In this investigation, metal injection molding was applied to the fabrication of a series of Ti–Nb binary alloys with niobium content ranging from 10wt% to 22wt%, and CP-Ti for comparison. Specimens were characterized by melt extraction, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Titanium carbide formation was observed in all the as-sintered Ti–Nb binary alloys but not in the as-sintered CP-Ti. Selected area electron diffraction (SAED) patterns revealed that the carbides are Ti2C. It was found that with increasing niobium content from 0% to 22%, the porosity increased from about 1.6% to 5.8%, and the carbide area fraction increased from 0% to about 1.8% in the as-sintered samples. The effects of niobium content, porosity and titanium carbides on mechanical properties have been discussed. The as-sintered Ti–Nb specimens exhibited an excellent combination of high tensile strength and low Young's modulus, but relatively low ductility.

THe effect of niobium content on the hardness and elastic modulus of heat-treated ti-10mo-xnb alloys

This study has investigated the niobium (Nb) additions effect on both microstructure and heat-treated Ti-10Mo-xNb (x = 3, 6 and 9) alloys mechanical properties. The microstructures were characterized by optical microscopy, X-ray diffraction and transmission electron microscopy. The mechanical characterization was carried out by Vickers microhardness test and Young's modulus measurements. The outcomes show that the addition of Nb in alloys decreased the proportion of ω and α' phases. The Ti-10Mo-3Nb alloy presented the best hardness and elastic modulus combination among the three developed alloys and also with respect to Ti-6Al-4V alloy and commercially pure Ti.

Effect of Niobium Content on Laminar Precipitate and High Temperature Mechanical Properties of 21-2N Valve Steel

Effect of niobium content on laminar precipitate and high temperature mechanical properties of 21-2N vavle steel was systematically studied, using specimens contain 0.26%, 0.43%, 0.65% 0.82% and 1.06% Nb. After different solid solution treatment and 750 °C aging heat treatment, experimental results showed that laminar precipitate was suppressed by niobium addition, and with the increasing of niobium content, laminar precipitate content decreased and size, distribution and morphology of laminar precipitate was meliorated. Then creep rupture strength and fatigue strength of experimental steels are improved with increasing of niobium.

Continuous Cooling Transformation Temperatures and Microstructures of Niobium Bearing Microalloyed Steels

Effects of niobium content and cooling rate on ferrite and bainite start temperatures (Ar3, Bs) and microstructural features have been studied in niobium bearing ultralow carbon microalloyed steels. The Ar3 and Bs temperatures decrease as niobium content or cooling rate is increased. The dependence of Ar3 on cooling rate is greater than that of Bs in all niobium contents. The bainitic ferrite laths become longer and narrower with increasing niobium content and cooling rate, and niobium also shows a tendency to decrease polygonal ferrite grain size.

The effect of niobium content on the magnetic properties and microstructures of PrFECoBNb HDDR magnets and alloys

Praseodymium-based permanent magnets were prepared from cast and annealed alloys using the hydrogenation, disproportionation, desorption and recombination process. The effect of niobium content on the magnetic properties of these bonded magnets was investigated. Niobium has a significant effect on the magnetic behaviour of these hydrogen-processed materials. Best overall magnetic properties were obtained in a Pr14Fe63.9Co16B6Nb0.1 magnet.

Stress/strain dependence of critical current in Nb 3Sn superconducting wires stabilized with Cu–Nb microcomposites – effect of Nb content

The effects of niobium content in the Cu–Nb microcomposite on the mechanical property and the axial tensile or transverse compressive stress/strain characteristics of the critical current I c in a bronze processed Nb 3Sn multifilament superconducting wire with the Cu–Nb microcomposite were evaluated at a temperature of 4.2 K in a magnetic field of 14 T. An increase in niobium content increases the 0.2% proof stress as well as both tensile and transverse compressive stress tolerance of I c of the wire. High yield stress value of the Cu–Nb microcomposite increases the strain at peak I c, ε m, as well as the reversible strain limit of I c, ε irr in the wire as compared to those in the Cu stabilized wire. An increase in niobium content in Cu–Nb microcomposite, however, decreases them due to decrease in the coefficient of thermal expansion.

Effect of niobium content on creep strength of cold-worked 15Cr-15Ni-2.5Mo austenitic steel

Effect of niobium content on creep strength of cold-worked 15Cr-15Ni-2.5Mo austenitic steel