Nb3Si Phase Research Articles

Additively manufactured Nb-Ti-Si based alloy: As-built and heat-treated conditions

This work aims to fully characterise the Nb-Ti-Si based alloy (Nb-26Ti-16Si-2.2Al-2Cr), processed by the electron-beam powder-bed-fusion in both as-built and heat-treated conditions, to elucidate the microstructure-property relationships. The as-built condition has [001]-oriented columnar grains of the Nb3Si phase with the Nbss phase dispersed throughout the microstructure. The microhardness is 645.2 ± 6.7 HV0.5, and the indentation fracture toughness shows distinct directionality: 7.7 MPa·m1/2 in the horizontal direction compared to 5.3 MPa·m1/2 in the vertical direction. Both properties are comparable to the cast version. The directionality is attributed to the underlying mechanisms such as crack bridging, arrest, and micro-crack formation. By contrast, in the heat-treated condition, the alloy exhibits a dual-phase microstructure (Nbss and Nb5Si3 phases) with near-equiaxed grain shape due to the Nb3Si phase decomposition. The fracture toughness increases to 12.1 MPa·m1/2, at the expense of a reduced microhardness of 564.4 ± 15.0 HV0.5.

Microstructure and Mechanical Properties of the Powder Metallurgy Nb-16Si-24Ti-2Al-2Cr Alloy.

The Nb-16Si-24Ti-2Al-2Cr alloy was prepared by plasma rotating electrode process (PREP) technology and the hot-pressing (HP) method, and the effects of sintering temperature on the microstructure, mechanical properties and fracture behavior were investigated. The HP alloys sintered at temperatures below 1400 °C are composed of Nbss (Nb solid solution), Nb3Si and Nb5Si3 phases. When the sintering temperature reaches 1450 °C, the Nb3Si phase is completely decomposed into Nbss and Nb5Si3 phases. Meanwhile, the microstructure coarsens significantly. Compared with the cast alloy, the HP alloy shows better mechanical properties. The fracture toughness of the alloy sintered at 1400 °C reaches 20.2 MPa·m1/2, which exceeds the application threshold. The main reason for the highest fracture toughness is attributed to the decomposition of large-sized brittle Nb3Si phase and the formation of a fine microstructure, which greatly increases the number of phase interfaces and improves the chance of crack deflection. In addition, the reduction in the size and content of silicides also reduces their plastic constraints on the ductile Nbss phase.

Effects of TaB2 addition on microstructure and mechanical properties of Nb[sbnd]Si based alloys

The effects of TaB2 addition on the Nb-16Si-22Ti-3Al alloy were investigated in this study. The results showed that the Nb-16Si-22Ti-3Al alloy consisted of the Nbss phase, α-Nb5Si3 phase, Nb3Si phase, and Tiss phase. With the addition of TaB2 increased from 0 to 0.25 at. %, the Nb3Si disappeared and the eutectic transformation reaction occurred (Nb3Si → Nbss + α-Nb5Si3), which made the volume fraction of the Nbss phase increased from 38.6% to 50.3%. With the TaB2 addition further increasing to 2.0 at. %, the α-Nb5Si3 became the primary phase, and the microstructure transformed from the Nbss + α-Nb5Si3 eutectic structure to the primary α-Nb5Si3 and (Nbss + γ-Nb5Si3) hypereutectic structure. The alloy with 0.25 at. % TaB2 addition had the highest fracture toughness of 10.2 MPa•m1/2 due to the refinement of microstructure and the increment of ductile Nbss. The maximum compressive strength of TaB2 added alloy at room temperature reached 2587.25 MPa in 2.0TaB2 specimen, owing to the solid solution strengthening of Ta and B, and the increment of the silicides content. Additionally, by comparing the fracture toughness of alloys with TaB2 addition obtained by three-point bending (SENBs) and indentation methods, respectively, the feasibility of estimating the fracture toughness of NbSi based alloys by the indentation method is demonstrated with an error of below 20%, which provided a basis for subsequent rapid performance characterization.

Insights into Nb-silicide-based in-situ composite processed by electron beam powder bed fusion

This is the first report introducing the idea of processing Nb-silicide-based in-situ composite through electron beam powder bed fusion (PBF-EB). A high energy input together with a line order strategy resulted in cracking, whilst a lower energy input without the line order led to microstructural inhomogeneity characterised by alternating dark- and bright-contrast bands. In samples printed using the line order strategy, long cracks initiated close to the melt pool boundary and propagated into the previous layer. These cracks were due to the weak interface between the primary Nb3Si columnar grains and the equiaxed (Nb,Ti) solid solution phase or Nb3Si-(Nb,Ti) solid solution eutectic structure. The porosity level increased from 0.122 % to 0.547 % with the increase of area average energy input from 2.22 J/mm2 to 6.67 J/mm2. The density decreased to 6.80 g/cm³ in the line order strategy samples due to the presence of cracks, compared to 6.84 g/cm³ in samples without employing the line order strategy. The dark-contrast band consisted of (Nb,Ti) solid solution, Nb3Si and Nb5Si3, while the bright-contrast band was composed of (Nb,Ti) solid solution and Nb3Si. Within the bright-contrast band, a recurring layered microstructural inhomogeneity appeared, with columnar grains at the bottom, whilst fine- and coarse-grained eutectic networks in the middle and upper regions. The Nb3Si phase exhibited a pronounced {001} texture, whereas the (Nb,Ti) solid solution phase displayed a weaker texture. The Nb-silicide-based in-situ composite fabricated through PBF-EB had a microhardness of ∼700 HV0.5. This value is higher than that achieved through conventional means but falls within the mid-range for laser-based additive manufacturing counterparts.

Phase equilibria of the Nb–Si-Gd ternary system at 1273 K

The phase equilibria of the Nb–Si-Gd ternary system at 1273 K in all the composition ranges were investigated by X-ray diffraction (XRD), electron probe microanalysis (EPMA), and Scanning electron microscopy (SEM) equipped with Energy dispersive spectroscopy (EDS). The isothermal section comprises 12 single-phase regions, 22 two-phase regions, and 11 three-phase regions. The existing of Nb3Si phase was confirmed at 1273 K by couple diffusion. A new ternary compound Gd2Nb3Si4 was discovered and its crystal structure was analyzed by the Rietveld method with Rwp = 2.11%, Rp = 1.54%, Rexp = 0.75%. It belongs to the space group P41212 (No.92) with the lattice parameter a = b = 6.99048 Å, c = 12.94393 Å, α = β = γ = 90°.

Microstructure and fracture toughness of a Nb–Ti–Si-based in-situ composite fabricated by laser-based directed energy deposition

Laser-based directed energy deposition (LDED), a significant integrated preparation technique combining material design and production, has been progressively used to manufacture Nb–Ti–Si-based in-situ composites. However, it is commonly known that Nb–Si-based in-situ composites have low room-temperature fracture toughness. Herein, we have designed a novel Nb–40Ti–10Si–5Al–2V (at.%) composite, the microstructure of LDED-built composite is made up of Nbss and γ-Nb5Si3, the formation of γ-Nb5Si3 precipitate in the Nbss phase with an orientation relationships (ORs) of [1110]γ//[011]Nbss, (10 1‾ 0)γ//(011)Nbss and (1 2‾ 11)γ//(200)Nbss. The composite has Nbss, Nb3Si and γ-Nb5Si3 phases after heat treatment at 1400 °C for 30 h, and δ-Nb11Si4 precipitate has formed in the Nbss phase with an ORs of [100]Nbss//[010]δ, (010)Nbss//(010)δ. The composite processing Nb–40Ti–10Si–5Al–2V (at.%) has outstanding toughness (21.62 MPa·m1/2). It has ascertained that the room-temperature fracture toughness of Nb–Si-based in-situ composite is positively impacted by the high concentration of Ti.

Improving the mechanical properties and oxidation resistance of Nb-16Si-20Ti alloys with B4C addition

Nb-Si-based alloys, as one of the candidate materials which may replace nickel-based alloys for the next generation aero-engines, its low fracture toughness (KQ) and poor oxidation resistance severely limited their application and development. Research has shown that Nb-Si-based alloys with a refined microstructure usually have good fracture toughness, whereas B and C elements are good microstructure refinement elements. So, the effects of B4C on the microstructure evolution and properties of Nb-16Si-20Ti alloys were studied. The results showed that the microstructure of Nb-16Si-20Ti was composed of Nb-based solid solution (Nbss) and Nb3Si phases. With the addition of B4C, the coarse Nb3Si decomposed and transformed into (α, γ)-Nb5Si3 + Nbss eutectic structure, refining the microstructure of the alloys. The room temperature fracture toughness and compressive strength of Nb-16Si-20Ti alloy were improved by adding B4C, among which the fracture toughness of 0.50B4C alloy was up to 11.5 MPa·m1/2, which increased by 98.3% compared with that of the 0B4C alloy. The improvement of the fracture toughness was mainly due to the increment of the ductile Nbss content in the alloy and the refinement of the microstructure. In addition, the addition of an appropriate amount of B4C (≤0.5 at.%) also improved the oxidation resistance of Nb-Si-based alloys.

TEM characterization and reaction mechanism of composite coating fabricated by plasma spraying Nb–SiC composite powder

Niobium carbide composite coatings with Nb2C, NbC, Nb3Si as the main phases were prepared in situ on the surface of TC4 titanium alloy by plasma spraying Nb–SiC composite powder. The microstructure of the coating was characterized in detail by TEM, and the reaction mechanism of Nb–SiC was revealed. Sub-micron and nano-scale NbC grains dispersed in Nb3Si region, nano-Nb/Nb3Si cellular eutectic region, and equiaxed Nb2C nanograins region were formed in the coating. The research results show that Nb and SiC reacted firstly to form cubic NbC and Nb3Si phases during the plasma spraying process. Then, NbC with a higher melting point took the lead in crystallization during the cooling process of the coating, forming sub-micron and nano-scale NbC granular fine grains. Nb3Si with a lower melting point crystallized around the sub-micron and nano-scale NbC granular fine grains in the subsequent cooling process. In the plasma spraying process, the molten droplets formed Nb/Nb3Si cellular eutectic structure under large temperature gradient and extremely fast cooling rate. The remaining Nb in the raw material powder formed a diffusion couple with NbC to generate fine and dispersed nano-equiaxed Nb2C with cubic structure. The present investigation provides a reference for the reaction synthesis of advanced nanocomposites using Nb–SiC system.

Rapid Eutectic Growth Kinetics of Undercooled Nb-Si Alloys at Electrostatic Levitation State

The rapid eutectic growth kinetics of undercooled Nb-Si alloys was investigated by using electrostatic levitation (ESL) technique combined with triggering method. For eutectic Nb-17.3 at.% Si alloy, the rapidly solidified microstructure was characterized by (Nb) dendrites and (Nb)+Nb3Si eutectics, which was different from the master alloy composed of complete eutectic structures. The transition of primary phase from the faceted Nb3Si phase to non-faceted (Nb) phase and the formation of complete eutectic microstructure were observed within hypereutectic Nb-18.7 at.% Si alloy with the increase of undercooling. Three distinct solidification paths leading to different microstructures and constituent phases were revealed by controlling the melt undercooling. Furthermore, the phase selection mechanism was clarified from the perspective of nucleation kinetics. Based on the experimental and analytical results, the coupled zone of (Nb)+Nb3Si eutectic was qualitatively predicted. The final microstructures solidified at different undercoolings were all composed of the (Nb) phase and Nb3Si phase, whose crystaline structures were both confirmed by transmission electron microscopy analysis. Besides, it was found that the volume fractions of (Nb) and Nb3Si phases could be undercooling control adjusted by. According to the nano-indentation and Vickers micro-indentation tests, the mechanical properties varied significantly with solidification paths. Compared with the master alloy, the hardness of hypereutectic Nb-18.7 at.% Si alloy at 157 and 473 K undercoolings was decreased by 42.7 % and 9.9 %, while the fracture toughness was enhanced remarkably by 593.1 % and 144.8 %, respectively. This may provide a desirable approach for designing Nb-Si alloys with improved performances.

Strengthening and toughening effect of laser melting deposited Nb–16Si–20Ti–3Al with nano-ZrC additions

The phase composition, microstructure, and properties of Laser Melting Deposited (LMD) Nb–16Si–20Ti–3Al alloys with different nano-ZrC (0, 2.5, 5.0, 10.0 wt%) addition were detailed investigated in this study. Results showed that the LMDed Nb–16Si–20Ti–3Al alloy was composed Nb-based solid solution (Nbss) and Nb3Si. The addition of nano-ZrC promoted the decomposition of the Nb3Si phase and the eutectic transformation from Nb3Si to (Nbss+γ-Nb5Si3) eutectic structure. With the content of nano-ZrC increased from 2.5 wt% to 5.0 wt%, the (Nbss+γ-Nb5Si3) eutectic structure was significantly refined. Nb-rich TiC phase precipitated at the grain boundaries of (Nbss+γ-Nb5Si3) eutectic structure by the titanium in the alloy reacted with nano-ZrC additions. With the content of nano-ZrC increased to 10.0 wt%, coarse and irregular primary γ-Nb5Si3 phase and dendritic TiC were observed in the Nb–Si alloy. The fracture toughness was improved from 5.1 MPa m½ to 17.1 MPa m½ by adding an optimized amount of nano-ZrC (5.0 wt%) due to the refinement of (Nbss+γ-Nb5Si3) eutectic structure and dispersion distributed nano-ZrC in the alloys. The Nb–16Si–20Ti–3Al alloy with 5.0 wt% nano-ZrC addition has the maximum compressive strength of 1836 MPa and a compressive strain of 12.6%. The crack deflection seems an important toughening mechanism for Nb–16Si–20Ti–3Al alloys containing nano-ZrC. The fracture mode of each Nb–16Si–20Ti–3Al alloys with (0, 2.5, 5.0, 10.0 wt%) addition exhibited a brittle quasi cleavage fracture.

Structure-property correlation and deformation mechanisms in ductile phase (Nbss) toughened cast Nb–Si alloys

High-temperature alloys based on the Nb–Si system have been considered as potential alternative materials for Ni–based superalloys. The focus of present research is to investigate the effect of Ti and Zr alloying elements and its combined addition on the microstructure, mechanical properties (compression, fracture toughness, hardness and modulus) and fracture behavior of the Nb–Si alloys. The microstructure of Nb–18.7Si and Nb–18.7Si–5Ti alloys composed of Nbss and Nb3Si phases. On the other hand, interestingly the Nb-18.7Si-5Zr and Nb–18.7Si-5Ti-5Zr systems exhibited distinctive microstructure and consisted of Nbss and α–Nb5Si3 phases. The present work reveals that the combined addition of Ti and Zr to Nb–Si (Nb–18.7Si–5Ti–5Zr) system resulted exceptionally high copressive strength (2236 ± 81 MPa), improved strain (10.16 ± 0.59%) and fracture toughness (10.59 ± 0.35 MPa.m1/2). The formation of high strength α-Nb5Si3 phase was attributed to such high strength value. Whereas, the increase in the phase fraction and coarsening of Nbss phase along with the presence of lamellar Nbss phase morphology are the contributing factors for its enhanced fracture toughness. The achievement of good combination of properties with stable microstructure without subjecting the Nb–18.7Si–5Ti–5Zr material to any additional heat treatment process is the promising outcome of this research. Fracture in the alloys started with cracking of the silicide phase (Nb3Si/α–Nb5Si3) and the crack path tortuosity increased by the crack bridging, branching and deflection mechanisms at the Nbss phase. Further, the constraint of the brittle silicide phase on the ductile Nbss phase impeded the ductility or deformation of the Nbss phase which resulted in interface debonding in the alloys.

The effect of Mo on microstructure and mechanical properties of Nb-22Ti-16Si alloy additively manufactured via laser directed energy deposition

Alloying process and processing optimization are most effective methods to modify the microstructure and mechanical properties of Nb-Si based alloys. In this work, Nb-22Ti-16Si-xMo(x = 5–20 at%) alloys were successfully fabricated by a laser directed energy deposition additive manufacture with elemental powder mixtures. The effect of Mo on the microstructure, micro-hardness, nano-hardness and fracture toughness of Nb-22Ti-16Si-xMo alloy were investigated. The results indicated that the addition of Mo in Nb-22Ti-16Si alloy is promoting the formation of Ti(Nb)5Si3 and β-Nb5Si3 phases and inhibiting the formation of Nb3Si phase. Mo was preferentially enriched in the niobium solid solution (Nbss) phase. The volume fraction of Nbss phase first increases then slightly decrease, while Ti(Nb)5Si3 phase was increased with Mo content, especially Nbss matrix also become more continuous. The solidification path of Nb-22Ti-16Si-xMo alloys show a certain deviate from the prediction by the Scheil solidification models. Mo alloying in Nb-22Ti-16Si alloy also lead to the increase in the young’s modulus and nano-hardness of Nbss and β-Nb5Si3 phases. The fracture toughness of Nb-22Ti-16Si-xMo(x = 5–20 at%) alloys first increases to 12.2 MPa m1/2 when Mo content increases to 10 at%, then decreases with further increases in Mo content, while their micro-hardness shows the opposite trend.

Influence of Ti and Zr alloying elements on microstructure and micromechanical properties of near-eutectic Nb-18.7Si alloy

The present study investigates the effect of addition of Ti and Zr alloying elements on the microstructure, phase formation and micro mechanical properties of the phases of a near eutectic Nb-18.7Si cast alloy. The alloys were chracterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalyzer (EPMA), electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). Both the alloys Nb-18.7Si and Nb-18.7Si-5Ti exhibited a two phase microstructure consisting of Nbss and Nb3Si. The Nb3Si is not a stable phase and require further long term heat treatments to form stable and high creep resistant α–Nb5Si3 phase. Interestingly, the alloys added with Zr (Nb-18.7Si-5Zr), and Ti, Zr (Nb-18.7Si-5Ti-5Zr) exhibited Nbss, α–Nb5Si3 phases. This indicates that the addition of Zr alone or together with Ti resulted in the formation of equilibrium α–Nb5Si3 phase in the as cast condition itself. The formation of such phases in these alloys is beneficial in improving the properties and being cost effective. The volume fraction of the Nbss (~22–23%) is almost same in Nb-18.7Si and Nb-18.7Si-5Ti alloys. Whereas, the volume fraction is increased more than double (~53–55%) in Nb-18.7Si-5Zr and Nb-18.7Si-5Ti-5Zr alloys. The coarsening of the Nbss phase is also observed with alloying and is more prominant in Nb-18.7Si-5Zr and Nb-18.7Si-5Ti-5Zr alloys. The nano indentation results showed that the hardness of Nbss phase increased with Ti and decreased with Zr additions. Overall, a drastic increase in the elastic modulus of the silicide phase is observed in Nb-18.7Si-5Zr and Nb-18.7Si-5Ti-5Zr alloys as compared to alloys Nb-18.7Si, Nb-18.7Si-5Ti and is due to the formation of α–Nb5Si3 phase in the former alloys compared to Nb3Si phase in the later alloys. The higher volume fraction of Nbss phase, coarsening and decrease in hardness of Nbss in Nb-18.7Si-5Zr and Nb-18.7Si-5Ti-5Zr alloys resulted in improvement in fracture toughness (10.5 ± 0.35 MPa. m1/2). The formation of equilibrium phase α–Nb5Si3 directly in the cast condition is a significant breakthrough since it eliminates the need for long term vacuum heat treatment at higher temperatures.

Sintering behaviour of Nb–16Si–25Ti–8Hf–2Cr–2Al alloy powder fabricated by a hydrogenation–dehydrogenation method

The present study investigated the sintering behaviour of Nb–16Si–25Ti–8Hf–2Cr–2Al alloy powders. The alloy powders were produced using ahydrogenation–dehydrogenation method and featured an irregular morphology. Powders sintered at 1500°C and 1600°C exhibited pores in their microstructures, while powders sintered at 1700°C for 4 h were fully densified and poreless. The cast ingot and powders were composed of three phases: Nbss, Nb5Si3, and Nb3Si. However, the Nb3Si phase was not observed, while HfO2 oxides formed in the sintered compact. The hafnium and oxygen reacted to form an HfO2 oxide during the high-temperature sintering process. From the result of the thermodynamic calculation, Hf oxide formed after sintering because Hf has the highest driving force for oxidation among the elements constituting the alloy.

The Effect of Aluminizing Nb Refractory Metal Surface on Increasing Oxidation Resistance

In order to increase oxidation resistance of Nb refractory metal, Aluminizing and Aluminizing + Siliconizing with co-deposition were applied to its surface through the method of Halide-activated pack cementation (HAPC). The characterization of diffusion coating was conducted via the analyses of SEM, XRD, and EDS. After that, oxidation tests were conducted, and the effect of coating on oxidation resistance was examined. As a result, according to XRD analysis, it was found that there were Nb5Si3 phase structures in both coatings. In addition to this, Nb5Si3 and Nb3Si phases emerged in co-deposition coating. Protective NbSi2 phase was not observed because an activator with fluoride was used but an activator with chloride was not. Both methods increased the oxidation resistance of Nb. However, it was observed that the target value which was “metal loss of 25μm at 1300°C 100 hours after oxidation” was not obtained only through cementation aluminizing process. We are indebted to TUBITAK for their support. Keywords: Refractory metals, oxidation, pack cementation, co-deposition, aluminizing DOI: 10.7176/JSTR/5-10-12

Microstructures and properties of Nb–Si-based alloys with B addition

The Nb–16Si–18Ti–xB (at%, similarly hereinafter, x = 0, 1, 2, 3) alloys were prepared by arc melting in a water-cooled copper crucible. The influences of B addition on their microstructures and properties were based on the data of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and electronic universal material testing machine. It is found that the addition of B promotes the formation of α-Nb5Si3 phase and suppresses the formation of Nb3Si phase. B addition also tends Nb–16Si–18Ti alloy to form the hypereutectic structures. The content of silicide phases shows a trend of firstly decreasing and then increasing in Nb–16Si–18Ti–xB (x = 0, 1, 2, 3) alloys. The size of Nb solid solution (Nbss) phase increases in Nb–16Si–18Ti–xB (x = 0, 1, 2, 3) alloys after heat treatment at 1523 K for 10 h. The room temperature compression strength of Nb–16Si–18Ti alloy increases firstly and then decreases with B addition. The high-temperature compression strength of Nb–16Si–18Ti alloy decreases firstly and then increases with B addition. It is found that the volume and size of silicide phases have a synergistic effect on the compression strength of Nb–Ti–Si-based alloys.

Effect of Zr additions on microstructure evolution and phase formation of Nb−Si based ultrahigh temperature alloys

In the present work, the role of Zr addition on the microstructure and phase formation of hypoeutectic Nb−16 at. % Si alloy has been investigated. The results showed that both binary and alloy with 2 at. % Zr resulted in two phase microstructures composed of Nbss and Nb3Si phases. In contrast, the alloys with 4 at. % Zr and 6 at. % Zr revealed two phase microstructures composed of Nbss and α−Nb5Si3 phases. The orientation relationship (OR) obtained between eutectoid lamellar structure comprising of Nbss and α−Nb5Si3 phases is (110) Nb//(110) Nb5Si3. The equilibrium microstructures consisting of Nb and α−Nb5Si3 phases were obtained in as cast condition when the Zr concentration is above 2 at.%. The addition of Zr accelerated the dissociation kinetics of Nb3Si phase in to Nbss and α−Nb5Si3 phases during solidification. The formation of α−Nb5Si3 phase in the as cast condition eliminates heat treatment required for decomposition of Nb3Si phase in Nb-Si alloys.

Morphological evolution of primary β-Nb5Si3 phase in Nb-Mo-Si alloys

Nb-20Si–xMo (x = 2,4,6)-based ultrahigh temperature alloys were prepared by high-vacuum non-consumable arc melting in a water-cooled copper crucible. The morphological evolution of the primary β-Nb5Si3 phase in the Nb-Mo-Si-based alloys was discussed in detail based on the data of X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The results indicate that the phase constituents in the studied alloys consist of Nb solid-solution (Nbss) phase and β-Nb5Si3 phase, with Nb3Si phases also appearing in the Nb-20Si-2Mo alloy. The Mo addition does not change the morphology of the primary β-Nb5Si3 phase in the Nb-20Si alloy. The primary β-Nb5Si3 phase in the investigated alloys displays various shapes, such as dendritic, L-like, hollow square and square ones. The morphological evolution of the primary β-Nb5Si3 phase follows two main paths in the Nb-Mo-Si alloys. (I) At a lower cooling rate, the primary β-Nb5Si3 morphology undergoes a transformation from L-like shapes to hollow square shapes before finally forming square shapes, and (II) at a higher cooling rate, the primary β-Nb5Si3 morphology transforms from Y-like shapes to hollow square shapes and ends with forming square shapes.

Insight into the influence of alloying elements on mechanical and thermodynamic properties of Nb3Si: A first-principles calculations

Abstract

The Influence of Annealing Temperature on Microstructure and Magnetic Properties of Fe74Co3Si8B10Al1Nb4 Amorphous Alloy Ribbons

Multi-component alloy ribbons with a composition of Fe74Co3Si8B10Al1Nb4 were prepared by a single roller melt-spinning method. The alloy had a fully amorphous structure, as determined by X-ray diffraction. The alloy ribbons were annealed for 10 min at temperatures of 350, 400, 450, 500, 550 and 600 oC, respectively. Differential scanning calorimetry curves indicated that the glass transition temperature (Tg) and the supercooled liquid range (ΔTx) of the amorphous alloy ribbon were about 494 oC and 43 oC, respectively. The ribbons showed soft magnetic properties, with a Curie temperature (Tc) at 284 oC, high saturation magnetization (Ms) of 1.18 T, and coercive force (Hc) of 33.66 A/m. In the present study, both saturation magnetization and coercive force of amorphous alloy ribbons increased with increasing the annealing temperature, due to precipitations and growth of α–Fe phase nanocrystals in the amorphous matrix. On the other hand, it was found that the coercive force of alloy ribbons reduced as a consequence of precipitations of Nb3Si phase if the annealing temperature reached 600 oC.