Effect Of Nb Addition Research Articles

Effect of Nb addition on the microstructure and properties of AlCoCrFeNi high-entropy alloy

Abstract The microstructures and properties of the AlCoCrFeNbxNi high-entropy alloys (HEAs) were investigated. Two phases were found in the prepared AlCoCrFeNbxNi HEAs: one is body-centered-cubic (BCC) solid solution phase; the other is the Laves phase of (CoCr)Nb type. The microstructures of the alloy series vary from hypoeutectic to hypereutectic, and the compressive yield strength and Vickers hardness have an approximately linear increase with increasing Nb content. The residual magnetization (Mr) reaches a maximum for AlCoCrFeNb0.1Ni alloy, which is 6.106 emu/g. The factor of Ω, which is defined as entropy of mixing times 1000 over enthalpy of mixing, well predicts the phase formation for the multicomponents alloys.

Effect of Nb addition on the structure and soft magnetic properties of melt-spun Co 69Fe 7Si 14B 10 alloy

Melt-spun ribbons of Co 69Fe 7Si 14− x Nb x B 10 alloys with x=0, 2 and 4 have been prepared and characterized for structure and soft magnetic properties. Ribbons with x=0 and x=2 are found to be completely amorphous whereas the ribbon with x=4 contains irregular shaped faulted Co 2Si orthorhombic phase with grain size of about 100 nm. Nb addition is found to decrease the degree of amorphicity and induce perpendicular anisotropy, deteriorating the soft magnetic and magnetoimpedance properties.

Effect of Nb addition on corrosion behavior of Fe-based metallic glasses in Ringer's solution for biomedical applications

The corrosion behavior of Fe 55 − x Cr 18Mo 7B 16C 4Nb x (x = 0, 3, and 4 at.%) amorphous ribbons in Ringer's solution with pH value 6.5, open to air at 37 °C, was investigated by linear polarization and electrochemical impedance spectroscopy (EIS) methods, aiming to estimate the feasibility of Fe-based metallic glasses as potential biomaterials. It was shown that the corrosion resistance in Ringer's solution significantly increases with an increase in Nb content. The linear polarization and EIS measurements indicated that the Fe 51Cr 18Mo 7B 16C 4Nb 4 possesses larger polarization resistance value than that of 316L stainless steel and Ti–6Al–4V which are used in the human body in biomedical applications. In addition, the ICP test was carried out to measure the concentrations of ions which had dissolved into the electrolyte. It was seen that amorphous alloys do not release any significant ions into the Ringer's solution, implying good biocompatibility of these alloys.

Effects of Nb Content on Young’s Modulus and Tensile Property of Ti-30Ta Alloy for Biomedical Applications

The effects of Nb addition on microstructures, Young’s moduli, tensile properties of Ti-30Ta-xNb (x = 21, 24, 27, 30, wt. %) alloys were investigated in this study. The results show that dual phases containing β phase and a little α" martensite were observed when x = 21 and 24, whereas single β phase is present when x = 27 and 30. A minimum Young’s modulus of 52.13 GPa was obtained in Ti-30Ta-21Nb alloy. Ti-30Ta-xNb alloys exhibit high strength-to-modulus ratios, showing their great potentials to develop as new candidates for biomedical applications.

Effect of Nb Addition on the Structural and Mechanical Properties of Cu<sub>46</sub>Zr<sub>42</sub>Al<sub>7</sub>Y<sub>5</sub> Bulk Metallic Glass

In this work, the Cu46Zr42-xAl7Y5Nbx alloys with different Nb contents were prepared by water-cooled copper mold casting. The effects of Nb addition on the structural and mechanical properties were studied. It was found that the structure remains in amorphous state at low Nb concentration (x =1, 2). However, some crystalline phases appear in the high Nb content alloy (x > 2), showing a composite structure, that is, the second phase particles dispersed in an amorphous matrix. The effects of Nb on the glass-forming ability of Cu46Zr42Al7Y5 were studied by differential scanning calorimetric (DSC). The compressive mechanical properties of Cu46Zr42-xAl7Y5Nbx alloys were studied. It was found that the compressive strength can be improved by introducing Nb. However, the ductile of the alloys were not improved by the introduction of Nb.

Effect of Nb additions on the microstructure, thermal stability and mechanical behavior of high pressure Zr phases under ambient conditions

This paper analyzes the influence of Nb on the shear-induced α→ω→β transformation taking place when processing Zr by high pressure torsion (HPT) under suitable conditions of pressure and shear. With that purpose, pure Zr and Zr–2.5%Nb were processed by HPT at room temperature and at pressures ranging from 0.25 to 6GPa using 5 anvil turns. Nb causes a further reduction of the transition pressures, which are already lower when applying shear besides pressure. Thus, the transition pressure to the β phase is reduced at least 100 times in the Zr–Nb alloy. Alloying with Nb decreases the grain size of the transformed phases, significantly enhances their thermal stability and increases their UTS and elongation to failure. Selected post-HPT annealing treatments lead to the development of very tough, multiphase Zr and Zr–Nb with bimodal grain size distributions. The retention of the high pressure phases under ambient conditions is explained by the development of a high internal stress during processing. This stress is measured by synchrotron radiation diffraction at HZB-BESSY II. It is proposed that the presence of Nb reduces the internal stress level required for the retention of the high pressure phases.

The Effect of Nb Addition on Phase Equilibria in the Ni-Rich Ni-Al-V Ternary System

ABSTRACTThe effect of Nb addition on phase equilibria among Ni (A1), Ni3Al (L12) and Ni3V (D022) phases was investigated in the Ni-rich Ni-Al-V ternary system. The addition of Nb to the Ni-Al-V ternary system shifts the three-phase coexisting region of A1 + L12 + D022 towards the Ni-rich side at 950 ºC. Nb is partitioned into the D022 phase more strongly than the A1 and L12 phases. These results suggest that the addition of Nb stabilizes the D022 phase against the A1 and L12 phases in the systems. The alloying element raises the temperature of a eutectoid-like reaction (A1→L12+D022) by ~30 ºC in the vertical section of Ni-Al-V ternary system at 75 at. % Ni.

Suppression of Coarse Columnar Grain Formation in As-cast Austenite Structure of a Hyperperitectic Carbon Steel by Nb Addition

Effects of Nb addition on as-cast γ-austenite grain structure in 0.2 mass% carbon steel are investigated by means of furnace cooling and permanent mold casting experiments. In the furnace-cooled samples with Nb addition, Nb(C,N) particles crystallize from the last-solidifying liquid in non-equilibrium solidification condition and they act as pinning particles for γ grain growth just after the solidification completion. The Nb addition produces a strong pinning effect on the as-cast γ grain structure. In the permanent mold casting experiment, Coarse Columnar Grains (CCG) structure develops from the mold wall in the sample without Nb. The increase in Nb concentration gradually decreases the fraction of CCG region and increases the fraction of Fine Columnar Grains (FCG), thus leading to the grain refinement. This refinement could be ascribed to the pinning effect of Nb(C,N) particles.

Microstructure and Electrical Properties of Niobium Doped Barium Titanate Ceramics

The effects of Nb addition on phase, microstructure and electrical properties of barium titanate ceramics were investigated. Nb-doped barium titanate ceramics (BaTi1-xNbx)O3, x = 0 to 0.02) were prepared by conventional mixed-oxide method. All barium titanate compositions show tetragonal perovskite structure. Low Nb concentration (x = 0.005) results in abnormal grain growth in barium titanate. However, the grain size becomes uniform and decreases as Nb content increases, suggesting Nb inhibits grain growth in the studied composition range. The dielectric constant increases as the amount of Nb increases. The temperature of tetragonal to cubic phase transition shifts to lower temperature and the temperature curves become broadening with increasing of Nb content. Measurement of ferroelectric P-E hysteresis loop at 50 Hz and applied electric field of 15 kV shows that the remanent polarization of barium titanate ceramics tends to decrease as Nb content increases. Change in dielectric properties and the P-E hysteresis loop did not show large aging effect in the Nb-doped barium titanate ceramics.

Significant changes in crystallization kinetics of Nd2Fe14B/α-Fe nanocomposites induced by Nb addition

The effects of Nb addition on the crystallization kinetics, microstructure and magnetic properties of melt-spun Nd2Fe14B/α-Fe nanocomposite magnets have been studied. The analysis of crystallization kinetics for the alloys indicates that the growth of crystallites in the Nb-doped alloy needs more activation energy than that in the Nb-free alloy. This crystallization behaviour contributes to the formation of a finer and more homogeneous microstructure in the Nb-doped alloy than in the Nb-free alloy. And the Nb addition makes the grains more equiaxed shape. The intrinsic coercivity and the maximum energy product increase from 600 kA/m, 105 kJ/m3 for Nd10Fe84B6 alloy to 750 kA/m, 120 kJ/m3 for Nd10Fe83Nb1B6 alloy, respectively.

Effect of Nb Addition on Cu Precipitation in Ferritic Stainless Steel

Formations of Cu-rich precipitate in 18%Cr-1.5%Cu stainless steels without and with 0.5%Nb have been examined mainly using transmission electron microscopy. The specimens solution-treated at 1250°C were isothermally transformed at various temperatures between 500 and 850°C. Fine spherical Cu-rich solute zones were nucleated in the steels in the beginning of aging. These Cu-rich zones exhibited bcc structure and then transformed into 9R structure with twins during aging. The spherical 9R-Cu particles changed into rod-shaped fcc-Cu particles after prolonged aging. Laves phase of Fe 2 Nb type started to form in the Nb-added steel almost after finishing nucleation and growth of Cu particles. Addition of Nb in the steel delayed the nucleation of the Cu-rich zones due to slow diffusion of Nb atoms in ferrite.

Microstructure of TiC/Nb-Ni Cermets Cladding Layer

This paper reports an investigation of the effect of Nb additions on the microstructure of TiC–Ni cermets, which is prepared by plasma cladding technique. The composition of the cermets cladding layer was observed by scanning electron microscope (SEM) in combination with energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis was carried out for phase identification. The microstructure has a trend to become finer with the increase of Nb additions, however, when the Nb addition goes to 15 wt%, the ceramic particles become much bigger and cause large amounts of cracks. Then the component variation of different parts of the ceramic particle was analyzed using the EDS, and explained the reason of the variation and why the rim structure wasn't formed.

Thermodynamics and liquid phase separation in the Cu–Co–Nb ternary alloys

This work first deals with the effect of Nb addition on the liquid phase separation in the Cu–Co system, which displays a metastable liquid miscibility gap. The isothermal sections at 800, 900, 1000, 1100, and 1200 °C in the Cu–Co–Nb system have been experimentally determined by optical microscopy, electron probe microanalysis, and x-ray diffraction on the equilibrated alloys, and the phase equilibria in the Cu–Co–Nb ternary system were thermodynamically assessed by using CALPHAD (Calculation of Phase Diagrams) method on the basis of the presently determined experimental data. Nb additions can stabilize the metastable liquid phase separation in the Cu–Co binary system and significantly increase its critical temperature. The solidified Cu–Co–Nb alloys appearing on the top-bottom separated microstructural morphology under low cooling rate while forming core-type macrostructural morphology under high cooling rate have been confirmed.

Effects of Niobium Addition on Microstructures and Formability in Si‐Al‐Mn TRIP Cold‐rolled Steels

AbstractThe effects of Nb addition on microstructures and formability in Si‐Al‐Mn TRIP cold‐rolled steels were investigated. These steels were intercritical annealed at 770 °C for 5 min, and isothermally treated at 400 °C for 3 min. Microstructural observation, tensile tests and forming limit diagram (FLD) tests were conducted, and the changes of retained austenite volume fraction as a function of tensile strain were measured by using an X‐ray diffractometer. The results showed that Nb addition makes grain size refined, the volume fraction of ferrite increase and that of bainite decrease, however, obviously it does not affect the volume fraction and carbon content of retained austenite. The Nb addition increased the stability of retained austenite owing to grain refinement. With Nb addition, increase in strength, ductility, strain hardening exponent and formability could be achieved simultaneously. These findings indicate that Nb addition can be a new direction of microalloying design for the low carbon TRIP steels with excellent formability and high stability of retained austenite.

Study on crystallization behavior and microstructure of melt-spun Nd2(Fe,Nb)14B/α-Fe alloys

The effects of Nb addition on the crystallization behavior, microstructure, and magnetic properties of melt-spun Nd2Fe14B/α-Fe nanocomposite magnets have been studied. The addition of Nb can significantly improve the thermal stability of amorphous phase in as-spun alloys, narrow the range between the onset crystallization temperature and the optimal annealing temperature, restrain the initial formation and growth of α-Fe and Nd2Fe14B. A finer and more homogeneous microstructure can be obtained in the Nb-doped alloy than in the Nb-free alloy. And the Nb addition makes the grains more equiaxed shape. The Nd10Fe83Nb1B6 alloy annealed at 715 °C for 10 min exhibits the improved magnetic properties, Br = 0.90 T, iHc = 750 kA/m, (BH)max = 120 kJ/m3, the intrinsic coercivity and the maximum energy product increase by 25% and 14%, compared with the Nd10Fe84B6 alloy.

Effect of Nb addition on the glass-forming ability, mechanical and soft-magnetic properties in (Co 0.942Fe 0.058) 72− xNb xB 22.4Si 5.6 bulk glassy alloys

The effect of Nb addition on the glass-forming ability (GFA), mechanical and soft-magnetic properties in (Co 0.942Fe 0.058) 72− x Nb x B 22.4Si 5.6 alloys system was investigated. In addition to the increase of glass-forming ability, the increase of Nb content was found to be effective for the improvement of mechanical and soft-magnetic properties. By copper mold casting, Co-based bulk glassy alloys with diameters up to 4 mm were formed in (Co 0.942Fe 0.058) 67Nb 5B 22.4Si 5.6 glassy alloy. The bulk glassy alloys exhibit a superhigh fracture strength of 2980–3600 MPa and Young's modulus of 121–166 GPa. The bulk glassy alloys also exhibit excellent soft-magnetic properties, i.e., high saturation magnetization of 0.6 T, low coercive force within 0.2–0.5 A/m, high permeability of 47165 at 1 KHz and zero magnetostriction.

Effect of Nb on Transformation Kinetics and Mechanical Properties in Zr-Al-Ni-Cu Metallic Glasses

The effect of Nb addition on the nucleation and grain growth behaviors has been investigated in the monolithic Zr65Al7.5Ni10Cu12.5Nb5 metallic glass. Nb has been well-known as an element for icosahedral quasicrystalline (QC) phase formation in the primary crystallization stage as well as for improving mechanical properties and corrosion resistance. The grain growth rate of the QC phase at near the crystallization temperature is 1.2×10−9 m/s, which is approximately 10 times smaller than that of the primary fcc Zr2Ni phase in the Zr65Al7.5Ni10Cu17.5 metallic glass. In contrast, nucleation rate increases drastically by Nb addition. It can be calculated as 1.2×1021/m3 s, which is approximately 105 times larger than that of the Zr65Al7.5Ni10Cu17.5 alloy. The results indicate that Nb is a very effective element for controlling grain growth and nucleation rates. Good plasticity is exhibited in the as-cast alloy, however, it is lost drastically even after the structural relaxation as well as the QC precipitation. Such significant change may be attributed to the local ordering and/or phase separating tendencies by a positive chemical affinity of the Zr-Nb pair.

The effect of annealing on single-layer CoCrPtNb thin films

The effect of Nb addition on grain size segregation and intergranular coupling of ternary CoCrPt alloys prepared by annealing of crystalline samples and crystallization of the Nb-rich (more than 4.6 at.%) amorphous films is investigated. Mean surface roughness as a function of Nb addition decreased for Nb contents of up to 2.7 at.% and then increased. The size and distribution of magnetic clusters were significantly affected by Nb addition. Vacuum annealing of the ternary and quaternary films (2.7 at.% Nb) increased the coercivity of the films from 53.71 kA/m and 52.09 kA/m to about 61.14 kA/m and 105 kA/m, respectively. Film with 12.1 at.% Nb was also produced and then annealed at different times and temperatures. Increasing the temperature to 700 °C caused the recrystallization of the 12.1 at.% Nb amorphous film. The observed magnetic properties are discussed in terms of composition, crystallographic orientation of deposited layer and oxidation of elements during annealing.

Effect of Nb addition on the subsurface deformation behavior in Cu 47Ti 34Zr 11Ni 8 bulk metallic glasses through Vickers indentation

In this paper, 3 mm diameter (Cu 47Ti 34Zr 11Ni 8) 100− x Nb x ( x = 0,1,2) glass forming alloys were fabricated by water-cooled copper mould cast. Microstructural characterization reveals that the monolithic Cu 47Ti 34Zr 11Ni 8 bulk metallic glass exhibits homogenous amorphous structure. While the alloys with Nb addition exhibit a composite structure. For alloys with x = 1, micro-scaled crystalline particles were found to distribute in the glassy matrix. For alloys with x = 2, the microstructure is dominated by a high density of dendritic phase embedded in the glassy matrix. Bonded interface technique was adopted to study the deformation behavior of the alloys underneath the Vickers indentation. It reveals that the subsurface shear patterns are significantly affected by the precipitated phases. The different deformation mechanism of the alloys resulted from the minor Nb addition was put forward and discussed.

Effect of Nb addition on the Microstructure and the Magnetic Properties of Nd-Fe-B-Based Nanocomposites

Effect of Nb addition on the Microstructure and the Magnetic Properties of Nd-Fe-B-Based Nanocomposites