Effect Of Nb Addition Research Articles

Effect of Nb Addition on the Deformation Behavior of TiC Matrix Solid Solution at High Temperature

Effect of Nb Addition on the Deformation Behavior of TiC Matrix Solid Solution at High Temperature

Effect of Nb Addition on Martensitic Transformation Behavior of AuTi-15Co Based Biomedical Shape Memory Alloys

The effect of quaternary addition of Nb being from 0 to 2mol% on the phase constitution, phase transformation behavior and shape memory behavior of Au-50mol%Ti-15mol%Co (AuTiCo) alloys is studied. X-ray diffraction analysis shows that, with increasing Nb concentration, the primary phase appeared at room temperature changes from B19 orthorhombic martensite phase to B2 cubic parent phase, and that all the lattice parameters are not largely changed by Nb addition. The maximum transformation strain evaluated in 2mol%Nb-added AuTiCo is 7.4%. Differential scanning calorimetry revealed that the reverse martensitic transformation finish temperature (Af ) decreases from 414K in Nb-free AuTiCo to 303K by 2mol%Nb addition. The ratio of Af change by Nb addition is evaluated to be 155K/mol%Nb, that is comparably larger than 131K/mol%Nb in NiTi. These results indicate that Nb addition is effective to stabilize B2 parent phase. AuTiCo alloy containing less than 2mol%Nb exhibits shape memory effect with 90% shape recovery ratio. Besides, AuTiCo containing 2mol%Nb exhibits 2.8% superelastic shape recovery at room temperature as well as 7.4% maximum transformation strain. Therefore, Nb addition to AuTiCo is effective to decrease the martensitic transformation temperature and to improve superelasticity, although the transformation temperature hysteresis increases by Nb addition, similar to Nb-added NiTi. [doi:10.2320/matertrans.M2014418]

Effect of Nb on hydrogen-induced delayed fracture in high strength hot stamping steels

The effect of Nb addition (0.022, 0.053, 0.078wt%) on the hydrogen-induced delayed fracture resistance of 22MnB5 was studied by constant load test and electrochemical hydrogen permeation method. It is shown that the appropriate addition of Nb is beneficial to the improvement of the delayed fracture resistance of tested steel, especially when the steel contains high concentration of hydrogen, and the maximum delayed fracture resistance is obtained at a Nb content of 0.053%.The result of hydrogen permeation test shows that the diffusion coefficient of hydrogen in the steel containing niobium is lower than that in steel without niobium, which indicates that it is harder for hydrogen in the steels containing niobium to diffuse and aggregate. In addition, the reason for Nb improving the delayed fracture resistance of steels is discussed from two aspects: hydrogen trap effect and grain refinement effect. The analysis shows that the main reason leading to the improvement of the delayed fracture resistance is the hydrogen trapping effect of NbC while the grain refinement effect of Nb(C,N) secondary.

Effect of Nb addition on the microstructure and mechanical properties of an 1800MPa ultrahigh strength steel

Abstract The microstructure–property relationship of Nb-free and Nb-bearing ultrahigh strength steels were studied in this work. Martensitic steels with 1800 MPa tensile strength were obtained by conducting reheated quenching and tempering after thermomechanical rolling. The microstructures of the steels were investigated by scanning electron microscopy, transmission electron microscopy electron backscattering diffraction technique. The results show that with the addition of Nb, the prior austenite grain growth was impeded, which leaded to the further refinement of final martensite microstructure. Randomly distributed Nb-rich (Nb,Ti)C in Nb bearing steel played an important role in the strengthening of the steel. As revealed by dilatometry and differential scanning calorimetry, with the increase of tempering temperature the decrease of mechanical properties mainly initiated by the decomposition of retained austenite during low temperature tempering, and the formation of harmful iron carbides was retarded when the steel microalloyed with 0.021% Nb.

Effect of Nb addition on the microstructure of BNT ceramics

This research studied the fabrication of bismuth-sodium-titanate (BNT) powders and the effect of Nb2O5 addition on the structure and the properties of BNT ceramics. The powders were synthesized via high-energy ball milling by using a mixed-oxide process. The results show that the perovskite structure was obtained in BNT powders at a calcination temperature of 800 °C. Particle sizes below 200 nm were observed. For the study, BNT/xNb ceramics were prepared using x = 0.01, 0.02, 0.03 and 0.05. The ceramics were sintered at a temperature of 1200 °C for 2 hours. The results showed that the relative density increased with increasing Nb2O5 from 0 to 0.03 whereas the grain size decreased with increasing Nb2O5 from 0.01 to 0.05. In addition, the dielectric constant increased with increasing Nb2O5 content.

Effects of Nb Addition on Glass-Forming Ability, Thermal Stability and Mechanical Properties of Ti-Based Bulk Metallic Glasses

Abstract Ti-based bulk metallic glasses (BMGs) alloy of (Ti 40 Zr 25 Cu 9 Ni 8 Be 18 ) 100- x Nb x with x =0, 1, 3, 4 and 5 at% were prepared by copper mould casting. Cylindrical rods of more than 6 mm in diameter consisting of fully glassy single phase were obtained. The effects of Nb addition on the glass-forming ability (GFA) and thermal stability of the (Ti 40 Zr 25 Cu 9 Ni 8 Be 18 ) 100- x Nb x alloy were studied by X-ray diffraction (XRD), transmission electron microscope (TEM) and differential scanning calorimeter (DSC). Mechanical properties were measured on a MTS810-type machine at room temperature under a compressive mode with a strain rate of 2 × 10 −4 s −1 . It is found that the GFA is not influenced and the thermal stability is increased by Nb addition. With the increase of Nb content, the alloys exhibit high fracture strength. When Nb content x =4, the (Ti 40 Zr 25 Cu 9 Ni 8 Be 18 ) 96 Nb 4 rod of fully glassy single phase exhibits the highest compressive strength of 1945 MPa and plastic elongation of about 7.0%, showing significant plasticity improvement. The large ductility of (Ti 40 Zr 25 Cu 9 Ni 8 Be 18 ) 96 Nb 4 is due to the development of the large density shear bands proved by scanning electron micrographs (SEM).

Effect of Nb addition on anodic behavior of Ti alloy in electrolyte containing calcium and phosphorus

The surface characteristics of the anodic oxide film (AOF) before and after dielectric breakdown on a Ti–30Nb–1Fe–1Hf alloy anodized in the electrolyte containing Ca and P were investigated. The AOF comprises an almost amorphous structure with local bubbles. The electrolyte-derived species are incorporated into the outer part of the AOF and stabilize the amorphous structure. Dielectric breakdown hardly affects the AOF composition, but it reduces the hydroxyl groups on the surface. Furthermore, Nb oxide can effectively hinder AOF rupture and increase the dielectric breakdown voltage of the AOF on Ti–30Nb–1Fe–1Hf compared with that of the AOF on pure Ti.

Effects of Nb addition on microstructure and mechanical properties of TiNiNb alloys fabricated by elemental powder sintering

Porous TiNi binary and TiNiNb ternary alloys of four compositions (Ti50Ni47.5Nb2.5, Ti50Ni45Nb5, Ti50Ni42.5Nb7.5, and Ti50Ni40Nb10) were fabricated by the elemental powder sintering process. The effects of Nb addition on microstructure and mechanical properties of TiNi(Nb) alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and tensile tests, respectively. With the increase of Nb contents, the TiNi matrix as the main phase is always retained, while the intensity of its diffraction peak gradually became weak with the appearance of β-Nb and TiNb phases. Most Nb particles are well-distributed in the TiNi matrix and (Ti,Nb)2Ni phase is found in the binding domain between Nb phase and TiNi phase. The tensile strength and elastic modulus of TiNiNb alloys increase with the increase of Nb contents, due to the solid solution strengthening effect of Nb-rich particles, the enlarged sintering neck and the strengthened bond between particles. Consequently, Nb plays a crucial role in adjusting composition and improving microstructure and mechanical properties of TiNiNb alloys.

Effects of Nb on Microstructural Evolution and Mechanical Properties of Low-Carbon Cold-Rolled Dual-Phase Steels

The effects of Nb additions, up to 0.06%, on the microstructure and properties of dual-phase (DP) steels containing 0.08% C and 2.2% Mn, were evaluated after hot rolling at different coiling temperatures, and after intercritical annealing of cold-rolled steels. During hot rolling, Nb precipitation was promoted by higher coiling temperature. During annealing of cold-rolled steels, microstructural characterization revealed that recovery and recrystallization processes overlapped with austenite formation. The addition of Nb increased the ferrite recrystallization start temperature, but had no significant effect on the start temperature of austenite formation during heating. Nb additions accelerated austenite formation once the transformation started, and also resulted in the formation of a finer and more homogeneous microstructure after annealing. In comparison with the steel without Nb, the ultimate tensile strength increased with the addition of up to 0.04% Nb, whereas addition of 0.06% Nb did not further increase the strength level of cold-rolled DP steels. Hot rolling at lower coiling temperatures improved both the strength and the ductility of the Nb-containing DP steels after annealing.

Effects of Nb addition on glass-forming ability and magnetization behaviors of nanocomposite Nd–Fe–B–Nb strip flakes

The influences of Niobium doping on the glass-forming ability (GFA) and magnetization properties of Nd–Fe–B–Nb alloys were investigated. It is found that the GFA of Nd–Fe–B–Nb alloys are improved by the Nb addition. It is also revealed that the GFA of the samples increases with the Nb content. Rapidly solidified Nd4.5Fe77−xNbxB18.5 (x = 0, 0.25, 0.5, 0.75, 1) nanocomposite strip flakes were successfully prepared by using strip casting technique with a higher production efficiency and a lower cooling rate compared to melt spinning method. The coercivity of nanocomposite Nd–Fe–B–Nb alloy strip flakes can be dramatically enhanced by 0.5 at. % Nb addition, attributing to grain refinement. The best magnetic properties with Hcj = 278.9 kA/m, (BH)max = 41.06 kJ/m3 have been obtained in Nd4.5Fe76.5Nb0.5B18.5 nanocomposite strip flake, which can be used for bonded magnets. The recoil loss of Nd4.5Fe76.5Nb0.5B18.5 alloy is also reduced by the Nb addition.

Role of Nb in glass formation of Fe–Cr–Mo–C–B–Nb BMGs

A new Fe-based bulk metallic glass with superior glass-forming ability (GFA), Fe46Cr15Mo14C15B6Nb4, was developed based on the Fe–Cr–Mo–C–B alloy system by minor addition of Nb. The effects of Nb addition on glass formation of the Fe50−xCr15Mo14C15B6Nbx (x=0, 2, 4 and 6at.%) alloys were investigated. The optimum addition content of Nb was determined as 4at.% by X-ray diffraction and differential scanning calorimeter analysis. A fully amorphous rod sample with 3mm in diameter was produced by using commercial-grade raw materials and a copper mold casting technique. This alloy shows an ultimate compressive strength of 1920MPa and Vicker’s hardness 1360HV, which is two to three times that of conventional high strength steel and suggests a promising potential for applications combining outstanding corrosion and wear resistance properties. The crystallization kinetics studies found that the activation energies for glass transition, onset of crystallization and crystallization peak were higher than those of other reported Fe-based bulk metallic glasses. The value of the fragility parameter m for the Fe46Cr15Mo14C15B6Nb4 alloy was calculated to be 34, indicating that the Fe–Cr–Mo–C–B–Nb alloy system is a strong glass former according to the Angell’s classification scheme. It is inferred that the more sequential change in the atomic size, the generation of new atomic pairs with large negative heats of mixing and the amount of oxygen in the molten liquid neutralized into Nb oxides provide a synergetic effect for the remarkably improved GFA and thermal stability.

Magnetic properties and microstructure of nanocomposite (Nd,Pr)–Fe–B ribbons by doping Nb element

Effects of Nb addition and annealing treatment on magnetic properties and microstructure of (Nd0.4Pr0.6)9Fe76–xNbxB15 (x = 0–4) ribbons were systematically investigated by means of vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). The extra phases with nonmagnetic (Nd,Pr)1.1Fe4B4 phase and metastable compound (Nd,Pr)2Fe23B3 crystallized during quenching the Nb-free alloy. Moreover, the nonmagnetic (Nd,Pr)1.1Fe4B4 phase does not diminish during the following annealing treatment. The addition of Nb to (Nd,Pr)–Fe–B alloy suppresses metastable (Nd,Pr)2Fe23B3 and nonmagnetic (Nd,Pr)1.1Fe4B4 phases. The intrinsic coercivity increases from 397 kA·m−1 for the Nb-free sample to 1,091 kA·m−1 for the 4 at% Nb-doped sample optimally annealed. The Nb-free sample has the magnetic properties with Js = 1.04 T, Jr = 0.66 T, and (BH)max = 43.5 kJ·m−3. By comparison, the magnetic properties of the 4 at% Nb-doped sample were 0.97 T, 0.68 T, and 65.7 kJ·m−3, respectively. The significant improvement of magnetic properties mainly originates from the finer grains of the ribbons by introducing Nb.

Effect of Nb Addition on the Growth and Coarsening of Cu-particles in Ferritic Stainless Steel

Effect of Nb Addition on the Growth and Coarsening of Cu-particles in Ferritic Stainless Steel

Effect of Nb addition on the structure and mechanical behaviors of CoCrCuFeNi high-entropy alloy coatings

The microstructure and mechanical properties of the CoCrCuFeNiNb high-entropy alloy coating prepared by plasma transferred arc cladding process were investigated. Two phases are found in the prepared coating with Nb: one is face-centered-cubic solid solution phase; the other is the Laves phase of (CoCr) Nb type. The nano-indentation testing indicates that the microhardness (H), elastic modulus (E), the hardness/modulus of elasticity ratio (H/E ratio) and high resistance to plastic deformation (H3/E2) of the coating with Nb are 6.13GPa, 221GPa, 0.028 and 4.7×10−3 respectively. The CoCrCuFeNiNb coating displays excellent wear and corrosion resistance. The wear resistance of the coating with Nb is about 1.5 times higher than that of the coating without Nb under the same wet sand rubber wheel abrasion testing conditions. Compared with the coating without Nb and as-cast 304 stainless steel, the coating with Nb shows the lowest icorr values in polarization curves and the highest fitted Rf values in EIS plots in 6N hydrochloric acid solution.

Effect of Nb addition on microstructure evolution and nanomechanical properties of a glass-forming Ti–Zr–Si alloy

The glass-forming Ti75Zr10Si15 alloy is regarded as a potential material for implant applications due to its composition of non-toxic, biocompatible elements and some interesting mechanical properties. The effects of partial substitution of 15 at.% Ti by Nb on the microstructure and the mechanical behaviour have been investigated by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analysis, transmission electron microscopy and nanoindentation techniques. Copper mold casting and melt-spinning methods have been applied to study the influence of the cooling rate on the properties of both alloys, Ti75Zr10Si15 and Ti60Zr10Nb15Si15. As a result of different cooling rates, significant microstructural variations from multiphase crystalline states in cast rods to nanocomposite structures in ribbons were observed. The limited glass-forming ability (GFA) of the Ti75Zr10Si15 alloy results for melt-spun ribbons mainly in nanocomposite structures with β-type nanocrystals being embedded in a glassy matrix. Addition of Nb increases the glass-forming ability. Raising the overheating temperature of the melt prior to melt-spinning from 1923 K to 2053 K yields for both alloys a higher amorphous phase fraction. The mechanical properties were investigated using compression tests (bulk samples) and the nano-indentation technique. A decrease of hardness (H), ultimate stress and reduced Young's modulus (Er) is observed for Ti60Zr10Nb15Si15 rods as compared to Ti75Zr10Si15 ones. This is attributed to an increase of the fraction of the β-type phase. The melt-spun ribbons show an interesting combination of very high hardness values (H) and moderate reduced elastic modulus values (Er). This results in comparatively very high H/Er ratios of >0.075 which suggests these new materials for applications demanding high wear resistance.

Effect of Nb addition on Fe-Ni-B-Si amorphous and crystalline composite coatings by laser processing

The effect of Nb addition on Fe–Ni–B–Si amorphous and crystalline composite coatings was studied. Firstly, the coatings with different forms of Nb were investigated by X-ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM) tests. It was found that ferroniobium can increase the glass forming ability (GFA) of the coatings and large negative mixing enthalpies of elements are helpful to form an amorphous phase in coatings. A precipitation phase with complex structure in supercooled liquid is helpful to form an amorphous phase. Secondly, the coatings with different amounts of Nb were investigated, too. It was found that one stage crystallization reaction happened in Fe31Ni31Si18B18Nb2 coating with low Nb content and two stage crystallization reactions in Fe30Ni30Si18B18Nb4 and Fe28Ni28Si18B18Nb8 coatings by laser processing. The thickness of amorphous and crystalline composite layer of coatings is about 0.4mm. The hardness of composite layer is higher than that in the clad layer. Breaking off of hard phases in high Nb content coatings will increase the mass loss in wear tests.

Thermal stability and phase transformations of martensitic Ti–Nb alloys

Aiming at understanding the governing microstructural phenomena during heat treatments of Ni-free Ti-based shape memory materials for biomedical applications, a series of Ti–Nb alloys with Nb concentrations up to 29 wt% was produced by cold-crucible casting, followed by homogenization treatment and water quenching. Despite the large amount of literature available concerning the thermal stability and ageing behavior of Ti–Nb alloys, only few studies were performed dealing with the isochronal transformation behavior of initially martensitic Ti–Nb alloys. In this work, the formation of martensites (α′ and α″) and their stability under different thermal processing conditions were investigated by a combination of x-ray diffraction, differential scanning calorimetry, dilatometry and electron microscopy. The effect of Nb additions on the structural competition in correlation with stable and metastable phase diagrams was also studied. Alloys with 24 wt% Nb or less undergo a transformation sequence on heating from room temperature to 1155 K. In alloys containing >24 wt% Nb α″ martensitically reverts back to β0, which is highly unstable against chemical demixing by formation of isothermal ωiso. During slow cooling from the single phase β domain α precipitates and only very limited amounts of α″ martensite form.

Effect of Nb Addition on the Corrosion Behavior of Porous TiAl Based Alloys in Aqueous Environments

The corrosion behavior of porous Nb-containing TiAl based alloys in HCl, NaOH and NH3H2O aqueous solutions with various concentrations has been studied simultaneously at room temperature. The results indicate that the porous alloys have good acidic resistance which is probably based on the combined work of Ti-Ti metallic bond and covalent bond. And pitting corrosion is the main corrosion behavior of Nb-free TiAl alloys during the first 40 hours, while intergranular corrosion is the main corrosion behavior later. Nb-containing alloys have better acid corrosion resistance due to inhibiting intergranular corrosion by Nb element. In addition, the porous TiAl based alloys are much more resistant to corrosion in alkaline solutions than in acidic solutions, owing to the different oxide films formed in alkalis solutions.

Effect of Nb Addition on the Glass-Forming Ability, Soft-Magnetic Properties and Mechanical Properties of CoFeNiBSiNb Bulk Glassy Alloys

The effect of Nb addition on the glass-forming ability (GFA), soft-magnetic properties and mechanical properties of [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx(x=36) alloy system were investigated. The results showed that by adjusting the content of Nb, the thermal stability of the supercooled liquid and the GFA increased effectively. With increasing the amount of Nb, the supercooled liquid region (ΔTx) increased from 45 to 65 K and the reduced glass transition temperature (Trg=Tg/Tl) was located in the range of 0.5840.644. As a result, the [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx bulk glassy alloys (BGAs) with diameters up to 5.0 mm were produced by copper mold casting. In addition to the high GFA, the Co-based glassy alloys exhibited excellent soft-magnetic properties, i.e., saturation magnetization of 0.530.81 T, low coercive force of 0.511.75 A/m, and high effective permeability of (1.522.53)×104 at 1 kHz under a field of 1 A/m. Besides, the Co-based BGAs also exhibited super high fracture strength of 42704490 MPa and vickers hardness of 11271182.

Suzuki segregation in Co–Ni-based superalloy at 973 K: An experimental and computational study by phase-field simulation

Suzuki segregation in Co–Ni-based superalloys is of longstanding interest. In this study, the development of widely extended stacking fault (SF) ribbons was confirmed in a Co–Ni-based superalloy aged at 973K after deformation at room temperature, which supports the decrease in stacking fault energy (SFE) due to Suzuki segregation. In addition, the plastic deformation behaviors of Co–Ni-based superalloys with various Nb contents up to 3wt.% were investigated focusing on the effect of Nb addition on dynamic strain-aging by Suzuki segregation. The negative strain-rate dependence of flow stress due to dynamic strain-aging became more significant with increasing Nb content; however, attempts to detect segregating elements by scanning transmission electron microscopy and energy-dispersive spectroscopy analysis were not successful. A phase-field simulation of Suzuki segregation suggested strong Ni depletion with segregation of Cr and Mo atoms at the SF, and the SFE can become negative as a consequence of the segregation. This agrees with the experimentally observed formation of wide SFs by the aging at 973K after cold deformation. It is also suggested that Nb atoms are strongly depleted at SFs, and a small amount of Nb addition dramatically enhances Cr segregation, resulting in further decreases in the SFE, which is probably responsible for the observed enhancement of dynamic strain-aging by Nb addition. In addition, the local structural changes, such as short-range ordering and/or an in-plane ordering, accompanying the segregation were discussed as possible additional mechanisms for strain-aging enhancement.