Journal articles on the topic 'Nb-Si based alloys'
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Yang, Jianyong, Guanqun Zhuo, Kaiyong Jiang, Xinghan Zhu, and Linfen Su. "The Oxidation Resistance of Nb-Si-Based Alloys at Intermediate and High Temperatures." Materials 13, no. 5 (March 9, 2020): 1229. http://dx.doi.org/10.3390/ma13051229.
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The oxidation behavior of three Nb-Si-based alloys were evaluated at intermediate (800 °C) and high (1250 °C) temperatures for 100 h in air. At 800 °C, the Nb-24Ti-15Si-13Cr-2Al-2Hf (at. %) alloy suffered from catastrophic pest oxidation. This pest phenomenon was suppressed by the addition of Sn. However, Ta addition protected the Nb-Si-based alloys from pest oxidation for a short time. At 1250 °C, Sn could enhance the oxidation resistance of Nb-Si-based alloys due to the formation of a Sn-rich layer. In addition, the oxidation mechanisms of Nb-Si-based alloys at intermediate and high temperatures were discussed.
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Qu, Shi Yu, Ya Fang Han, and Liguo Song. "Microstructures and Properties of Refractory Niobium-Silicide-Based Composites." Materials Science Forum 475-479 (January 2005): 737–40. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.737.
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The microstructures, mechanical properties and oxidation resistance of the refractory Nb-silicide-based composites have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), compression tests and high-temperature oxidation experiments. The results showed that 1773K/100h heat-treatment was an optimum processing for acquiring equilibrium Nb solid solution and silicides microstructure. In the binary Nb-Si system, the microstructure consisted of continuous Nb5Si3 equilibrium matrix and dispersed Nb particles, while in the the Nb-Ti-Cr-Al-Si-(Hf) multicomponent system, there are two typical microstructures, i.e., a two-phase structure of β (Nb solid solution)+D81 Nb5Si3-type silicide in the alloys with the Si+Al content (15at.% and 6at.%, respectively), and a three-phase structure of β+D81 Nb5Si3-type + D88 Ti5Si3-type silicides in the alloys with lower Si+Al content (10at.% and 8at.%, respectively). The results of compression tests showed that all alloys display high strength at both room and high temperatures, only a slight decrease in compression properties occured for Nb-Ti-Cr-Al-Si alloys, comparing to the binary Nb-Si in-situ composites. This type of alloys possesses good high temperature strengths up to at least 1473K. The results of high-temperature oxidation experiments showed that the oxidation rates of the alloys with Ti, Cr, Al and Hf addition were at least one order of magnitude lower than those of the Nb-Si binary alloys.
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Kim, Won Yong. "Microstructure and Pseudoelasticity of Ti-Nb-Si Based Alloys with Biocompatible Alloying Elements." Materials Science Forum 546-549 (May 2007): 2151–56. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.2151.
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We have newly designed a metastable β Ti-Nb-Si based alloy with biocompatible alloying elements without containing toxic V or Al for orthodontic applications. Microstructures and pseudoelastic behavior of β Ti-Nb-Si alloys were investigated in order to correlate the pseudoelasticity and microstructure together with martensite transformation. Nb and Si alloying to the present alloy make β phase to be stable. It is found that metastable β phase is favorable to display pseudoelastic behavior than stable or unstable β phase. Optical microscope (OM) revealed that stress-induced martensitic transformation takes place during room temperature deformation in the present alloys. Within the alloys having β (bcc) phase studied the alloy with low content of Si appeared to exhibit a dominant behavior for stress-induced martensitic transformation than that with high content of Si. After recrystallization heat treatment pseudoelasticity of the present alloy appeared to be prominent. The pseudoelastic behavior of this alloy was correlated to the stress-induced martensite transformation. Pseudoelasticity of the present alloys is hindered by the development of {001}<110> rotated cube component.
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Hagisawa, Takehito, Hirokazu Madarame, Shinji Tanaka, Yasuyuki Kaneno, and Takayuki Takasugi. "High Temperature Compression Properties of Ni3(Si,Ti) Based Intermetallic Compounds." Materials Science Forum 783-786 (May 2014): 1129–35. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1129.
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High temperature compression properties of Al-, Cr-or Nb-added Ni3(Si,Ti) based intermetallic compounds were investigated by uni-axial compression test and microstructural observation. The Al-or Cr-added Ni3(Si,Ti) alloys after homogenization heat treatment exhibited a two-phase microstructure consisting of L12and Ni-solid solution phases. The Nb-added Ni3(Si,Ti) alloy after homogenization heat treatment exhibited a triple-phase microstructure consisting of G-phase with D8a structure and Ni-solid solution phase in the L12matrix. The volume fraction of Ni-solid solution phase increased in order of Cr-, Nb-and Al-added Ni3(Si,Ti) alloys. The Cr-added Ni3(Si,Ti) alloy was deformable at high strain rate, while the Nb-added one was deformable at low strain rate. It can be considered that the deformability of Ni3(Si,Ti) at high temperature is closely correlated with volume fraction of Ni-solid solution phase and recrystallization behavior.
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Miura, Seiji, Tatsuichi Tanahashi, Yoshinao Mishima, and Tetsuo Mohri. "Alloy Design of Nb-Si Based High Temperature Alloys by Phase Stability Control." Materials Science Forum 654-656 (June 2010): 444–47. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.444.
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In order to spheroidize -Nb5Si3 strengthening phase embedded in Nb matrix for attaining a good room temperature toughness of Nb-Si alloy, the authors have proposed a microstructure control technique by combining eutectic and eutectoid reactions. Nb3Si intermetallic compound formed during solidification is a key phase for the microstructure control, but its stability is very sensitive to the alloying elements. Nb3Si disappears by adding as small as 3 at% of W and Mo, while these elements are very effective for the solid solution strengthening of Nb phase. For a further alloy development, establishment of an alloy design concept based on the control of phase stability of Nb3Si is needed. Similarly to ferrous alloys such as stainless steels where Cr and Ni are added to control the stability of bcc phase and fcc phase, two alloying elements (one is a stabilizing element and the other is a destabilizing element for Nb3Si phase) are added to a Nb-Si binary master alloy and their microstructure is investigated using SEM. The stabilizing element Ta is found to enlarge the composition area where Nb3Si exists even with the destabilizing element Mo, and it is confirmed that the phase stability concept is useful for designing Nb-Si based alloys.
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Shen, Fuqiang, Yingyi Zhang, Laihao Yu, Tao Fu, Jie Wang, Hong Wang, and Kunkun Cui. "Microstructure and Oxidation Behavior of Nb-Si-Based Alloys for Ultrahigh Temperature Applications: A Comprehensive Review." Coatings 11, no. 11 (November 9, 2021): 1373. http://dx.doi.org/10.3390/coatings11111373.
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Nb-Si-based superalloys are considered as the most promising high-temperature structural material to replace the Ni-based superalloys. Unfortunately, the poor oxidation resistance is still a major obstacle to the application of Nb-Si-based alloys. Alloying is a promising method to overcome this problem. In this work, the effects of Hf, Cr, Zr, B, and V on the oxidation resistance of Nb-Si-based superalloys were discussed. Furthermore, the microstructure, phase composition, and oxidation characteristics of Nb-Si series alloys were analyzed. The oxidation reaction and failure mechanism of Nb-Si-based alloys were summarized. The significance of this work is to provide some references for further research on high-temperature niobium alloys.
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Ghadyani, Mohammad, Claire Utton, and Panos Tsakiropoulos. "Microstructures and Isothermal Oxidation of the Alumina Scale Forming Nb1.45Si2.7Ti2.25Al3.25Hf0.35 and Nb1.35Si2.3Ti2.3Al3.7Hf0.35 Alloys." Materials 12, no. 5 (March 5, 2019): 759. http://dx.doi.org/10.3390/ma12050759.
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Coating system(s) will be required for Nb-silicide based alloys. Alumina forming alloys that are chemically compatible with the Nb-silicide based alloy substrate could be components of such systems. The intermetallic alloys Nb1.45Si2.7Ti2.25Al3.25Hf0.35 (MG5) and Nb1.35Si2.3Ti2.3Al3.7Hf0.35 (MG6) were studied in the cast, heat treated and isothermally oxidised conditions at 800 and 1200 °C to find out if they are αAl2O3 scale formers. A (Al/Si)alloy versus Nb/(Ti + Hf)alloy map, which can be considered to be a map for Multi-Principle Element or Complex Concentrated Nb-Ti-Si-Al-Hf alloys, and a [Nb/(Ti + Hf)]Nb5Si3 versus [Nb/(Ti + Hf)]alloy map were constructed making use of the alloy design methodology NICE and data from a previously studied alloy, and were used to select the alloys MG5 and MG6 that were expected (i) not to pest, (ii) to form αAl2O3 scale at 1200 °C, (iii) to have no solid solution, (iv) to form only hexagonal Nb5Si3 and (v) to have microstructures consisting of hexagonal Nb5Si3, Ti5Si3, Ti5Si4, TiSi silicides, and tri-aluminides and Al rich TiAl. Both alloys met the requirements (i) to (v). The alumina scale was able to self-heal at 1200 °C. Liquation in the alloy MG6 at 1200 °C was linked with the formation of a eutectic like structure and the TiAl aluminide in the cast alloy. Key to the oxidation of the alloys was the formation (i) of “composite” silicide grains in which the Nb5Si3 core was surrounded by the Ti5Si4 and TiSi silicides, and (ii) of tri-aluminides with high Al/Si ratio, particularly at 1200 °C and very low Nb/Ti ratio forming in-between the “composite” silicide grains. Both alloys met the “standard definition” of high entropy alloys (HEAs). Compared with HEAs with bcc solid solution and intermetallics, the VEC values of both the alloys were outside the range of reported values. The parameters VEC, and of Nb-Ti-Si-Al-Hf coating alloys and non-pesting Nb-silicide based alloys were compared and trends were established. Selection of coating alloys with possible “layered” structures was discussed and alloy compositions were proposed.
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Wang, Q., C. L. Zhu, Y. H. Li, X. Cheng, W. R. Chen, J. Wu, J. B. Qiang, Y. M. Wang, and C. Dong. "Co- and Fe-based multicomponent bulk metallic glasses designed by cluster line and minor alloying." Journal of Materials Research 23, no. 6 (June 2008): 1543–50. http://dx.doi.org/10.1557/jmr.2008.0210.
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Bulk metallic glass (BMG) formations in Co- and Fe-based alloy systems are investigated by using our cluster line approach in combination with minor alloying principle. Basic ternary alloy compositions in Co–B–Si, Fe–B–Y, and Fe–B–Si systems are first determined by cluster lines defined by linking special binary clusters to third elements. Then the basic ternary alloys are further minor alloyed with 3 to 5 at.% Nb to improve glass-forming abilities (GFAs) and ϕ3 mm BMGs are formed in (Co8B3–Si)–Nb and (Fe8B3–Y)–Nb but not in (Fe8B3–Si)–Nb, TM8B3 (TM = Fe, Co) being the most compact binary cluster. The BMGs are expressed approximately with a unified simple composition formula: (TM8B3)1M1, M = (Si, Nb) or (Y, Nb). Finally, mutual Fe and Co substitutions further improve the GFAs as well as the soft magnetic properties, e.g., Is reaching 0.98 T and Hc < 6 A/m for the Co–Fe–B–Si–Nb BMGs. Using the (cluster)1(glue atom)1 model, a new ternary BMG Fe8B3Nb1 is obtained.
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Wang, Jin San, Yong Wang Kang, and Chang Rong Li. "Phase Diagram and Phase Equilibrium Studies on Ultra High Temperature Alloys of Nb-Si-Ti." Materials Science Forum 849 (March 2016): 618–25. http://dx.doi.org/10.4028/www.scientific.net/msf.849.618.
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Due to their high melting temperatures, low densities and excellent high-temperature strengths, Nb-Si-Ti-based ultra high temperature alloys shows great potential for vane materials on the next generation of high thrust-weight ratio aero-engines. In the present paper, the Nb-Si-Ti ternary system was studied, the phase diagram of Nb-Si-Ti and the phase fraction calculated, and the curve of solidification process established. The calculated results provide primary guidance for developing Nb-Si-Ti-X ultrahigh temperature alloys. Moreover, it is very useful as a guide for alloy design and processing development.
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Goto, Daisuke, Ken-ichi Ikeda, and Seiji Miura. "Phase equilibrium and mechanical properties of Cr-Mo-Nb-Si-B alloys Composed of BCC and T2-silicide phase." MRS Advances 4, no. 25-26 (2019): 1491–96. http://dx.doi.org/10.1557/adv.2019.110.
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ABSTRACTA new class of high-temperature materials based on refractory elements was investigated with an aim to improve the energy efficiency of thermal power plants. Alloys based on Nb and Mo composed of BCC solid solution (BCCss) (Nb-Mo) and T2-silicide (Nb,Mo)5(Si,B)3 are promising candidates as high-temperature materials. Further investigation on the alloy phase equilibria of this system is required to improve the mechanical properties and oxidation resistance through optimization of the phase compositions. Cr is one candidate to modify the properties of the alloy because Cr is expected to stabilize the T2 compound phase along with B. Here, the phase equilibria among BCCss and the T2 compound are widely investigated in the Cr-Mo-Nb-Si-B system, and a BCCss-T2 two-phase microstructure is found in Mo-rich alloys. The B/Si ratio in the T2 phase increases with the Cr content, while almost no B solubility was found in BCCss. As the Si content increases in alloys, the A15 silicide phase ((Cr, Mo, Nb)3Si) and/or Laves phase appear.Nanoindentation tests were conducted to investigate the mechanical properties of the BCCss phase of the alloys in the Cr-Mo-Nb-Si-B system. The nanohardness and reduced elastic modulus of these alloys tended to be higher with an increase in Cr.
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Hernández-Negrete, Ofelia, and Panos Tsakiropoulos. "On the Microstructure and Isothermal Ooxidation of Silica and Alumina Scale Forming Si-23Fe-15Cr-15Ti-1Nb and Si-25Nb-5Al-5Cr-5Ti (at.%) Silicide Alloys." Materials 12, no. 7 (April 2, 2019): 1091. http://dx.doi.org/10.3390/ma12071091.
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An Nb-silicide based alloy will require some kind of coating system. Alumina and/or SiO2 forming alloys that are chemically compatible with the substrate could be components of such systems. In this work, the microstructures, and isothermal oxidation at 800 °C and 1200 °C of the alloys (at.%) Si-23Fe-15Cr-15Ti-1Nb (OHC1) and Si-25Nb-5Al-5Cr-5Ti (OHC5) were studied. The cast microstructures consisted of the (TM)6Si5, FeSi2Ti and (Fe,Cr)Si (OHC1), and the (Nb,Ti)(Si,Al)2, (Nb,Cr,Ti)6Si5, (Cr,Ti,Nb)(Si,Al)2 (Si)ss and (Al)ss (OHC5) phases. The same compounds were present in OHC1 at 1200 °C and the (Nb,Ti)(Si,Al)2 and (Nb,Cr,Ti)6Si5 in OHC5 at 1400 °C. In OHC1 the (TM)6Si5 was the primary phase, and the FeSi and FeSi2Ti formed a binary eutectic. In OHC5 the (Nb,Ti)(Si,Al)2 was the primary phase. At 800 °C both alloys did not pest. The scale of OHC1 was composed of SiO2, TiO2 and (Cr,Fe)2O3. The OHC5 formed a very thin and adherent scale composed of Al2O3, SiO2 and (Ti(1−x−y),Crx,Nby)O2. The scale on (Cr,Ti,Nb)(Si,Al)2 had an outer layer of SiO2 and Al2O3 and an inner layer of Al2O3. The scale on the (Nb,Cr,Ti)6Si5 was thin, and consisted of (Ti(1−x−y),Crx,Nby)O2 and SiO2 and some Al2O3 near the edges. In (Nb,Ti)(Si,Al)2 the critical Al concentration for the formation of Al2O3 scale was 3 at.%. For Al < 3 at.% there was internal oxidation. At 1200 °C the scale of OHC1 was composed of a SiO2 inner layer and outer layers of Cr2O3 and TiO2, and there was internal oxidation. It is most likely that a eutectic reaction had occurred in the scale. The scale of OHC5 was α-Al2O3. Both alloys exhibited good correlations with alumina forming Nb-Ti-Si-Al-Hf alloys and with non-pesting and oxidation resistant B containing Nb-silicide based alloys in maps of the parameters δ, Δχ and VEC.
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Kim, Han Sol, and Won Yong Kim. "Microstructures and Mechanical Properties of Biologically-Inspired Ti-Nb Based Alloys with Ternary Element Additions." Materials Science Forum 539-543 (March 2007): 647–52. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.647.
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Microstructures and mechanical properties including elastic modulus were investigated in terms of ternary alloying elements Si addition, Nb content variations and tensile test. Martensite structure with α'(hcp) or α"(orthorhombic) was observed in Ti-xNb-1.5at.%Si, where x=10-20at.%. The crystal structure of martensite formed from water quenching process was largely dependent upon Nb content but does not on Si content. On the basis of experimental results obtained, it is suggested that Si has an effective role to suppress the precipitation of ω phase leading to reduction in elastic modulus in the metastable β phase region. Metastable β phase region was superior to reduce the elastic modulus than stable β phase region in the present alloy system. The minimum value of elastic modulus was measured to 48GPa. We have found that stress-induced martensitic transformation takes place during the deformation in the present alloys. Within the alloys having β(bcc) phase studied Nb-poor region appeared to exhibit a dominant behavior for stress-induced martensitic transformation than Nb-rich region. This result suggests that metastable β phase is superior to stable β phase for the occurrence of stress-induced martensitic transformation in the present alloy system.
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Zhao, Jiang, Claire Utton, and Panos Tsakiropoulos. "On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)." Materials 13, no. 20 (October 13, 2020): 4548. http://dx.doi.org/10.3390/ma13204548.
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We studied the microstructures and isothermal oxidation of the Nb-silicide-based alloys Nb-11.5Ti-18Si-5Mo-2W-4.9Sn-4.6Ge-4.5Cr-4.7Al-1Hf (JZ4) and Nb-21Ti-18Si-6.7Mo-1.2W-4.4Sn-4.2Ge-4Cr-3.7Al-0.8Hf (JZ5), calculated their average creep rate for the creep goal conditions of T = 1200 °C and σ = 170 MPa, and compared properties of the two alloys with those of other refractory metal (RM) complex concentrated alloys (RCCAs). Both alloys had a density less than 7.3 g/cm3 and lower than the density of multiphase bcc solid solution + M5Si3 silicide RCCAs. There was macrosegregation of Si in both alloys, which had the same phases in their as-cast microstructures, namely βNb5Si3, αNb5Si3, A15-Nb3X (X = Al, Ge, Si, Sn), TM5Sn2X (X = Al, Ge, Si), C14-Cr2Nb, but no solid solution. After heat treatment at 1500 °C for 100 h, a low volume fraction of a W-rich (Nb, W)ss solid solution was observed in both alloys together with βNb5Si3, αNb5Si3 and A15-Nb3X but not the TM5Sn2X, whereas the Laves phase was observed only in JZ4. At 800 °C, both alloys did not pest, and there was no spallation of their scales at 1200 °C. At both temperatures, both alloys followed parabolic oxidation kinetics and their weight changes were lower than those of Ti-rich Nb-silicide-based alloys. The oxidation of both alloys was superior to that of other RCCAs studied to date. For each alloy the Si macrosegregation, volume fraction of solid solution, chemical composition of solid solution and Nb5Si3, and weight changes in isothermal oxidation at 800 and 1200 °C that were calculated using the alloy design methodology NICE agreed well with the experimental results.
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Tyagi, Megha, B. Vishwanadh, Subir Kumar Ghosh, and R. Tewari. "Synthesis and Characterization of Silicide Coating on Niobium Alloy Produced Using Molten Salt Method." Materials Science Forum 830-831 (September 2015): 683–86. http://dx.doi.org/10.4028/www.scientific.net/msf.830-831.683.
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The main aim of the present work is to develop an oxidation resistant Nb-Si coating on Nb alloys. For this purpose electroless molten salt - method was used, where a selective reaction occurs between NaCl–KCl–NaF–Na2SiF6and the Si powder. Due to this reaction, oxidation resistant Nb-Si phases forms on the surface of substrate. This paper reports the thickness variation of Nb-Si coating as a function of deposition time. The surface morphology was studied by using scanning electron microscopy (SEM). The various Nb-Si based phases formed on the Nb substrate have been identified using X-ray diffraction (XRD) analysis, supplemented with energy dispersive X-ray spectroscopy results. Based on these results mechanism of silicide coating on Nb alloys has been discussed in detail.
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Inoue, Akihisa, Bao Long Shen, and Akira Takeuchi. "Syntheses and Applications of Fe-, Co-, Ni- and Cu-Based Bulk Glassy Alloys." Materials Science Forum 539-543 (March 2007): 92–99. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.92.
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This paper reviews our recent results of the formation, fundamental properties, workability and applications of late transition metal (LTM) base bulk glassy alloys (BGAs) developed since 1995. The BGAs were obtained in Fe-(Al,Ga)-(P,C,B,Si), Fe-(Cr,Mo)-(C,B), Fe-(Zr,Hf,Nb,Ta)-B, Fe-Ln-B(Ln=lanthanide metal), Fe-B-Si-Nb and Fe-Nd-Al for Fe-based alloys, Co-(Ta,Mo)-B and Co-B-Si-Nb for Co-based alloys, Ni-Nb-(Ti,Zr)-(Co,Ni) for Ni-based alloys, and Cu-Ti-(Zr,Hf), Cu-Al-(Zr,Hf), Cu-Ti-(Zr,Hf)-(Ni,Co) and Cu-Al-(Zr,Hf)-(Ag,Pd) for Cu-based alloys. These BGAs exhibit useful properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based glassy alloys have good soft magnetic properties which cannot be obtained for amorphous and crystalline type magnetic alloys. The Feand Ni-based BGAs have already been used in some application fields. These LTM base BGAs are promising as new metallic engineering materials.
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Amancherla, Sundar, Sujoy Kar, Bernard Bewlay, Yang Ying, and Austin Chang. "Thermodynamic and Microstructural Modeling of Nb-Si Based Alloys." Journal of Phase Equilibria and Diffusion 28, no. 1 (April 6, 2007): 2–8. http://dx.doi.org/10.1007/s11669-006-9015-4.
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Kim, DaeJin, Dongyi Seo, Seong-Woong Kim, SeungEon Kim, DongYeop Keum, and JaeKeun Hong. "Cyclic Oxidation Behaviors of TiAl–Nb–Si-Based Alloys." Oxidation of Metals 86, no. 5-6 (August 19, 2016): 417–30. http://dx.doi.org/10.1007/s11085-016-9644-x.
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Yang, Tao, and Xiping Guo. "Effects of Nb Content on the Mechanical Alloying Behavior and Sintered Microstructure of Mo-Nb-Si-B Alloys." Metals 9, no. 6 (June 4, 2019): 653. http://dx.doi.org/10.3390/met9060653.
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Different from conventional Mo-Si-B-based alloys consisting of Moss, Mo3Si, and Mo5SiB2, Mo3Si-free Mo-Si-B-based alloys (Moss+Mo5Si3+Mo5SiB2 or Moss+Mo5SiB2) show great potentials for more excellent oxidation resistance and elevated temperature strength. In the present work, alloying element Nb was added to Mo-12Si-10B (at.%)-based alloy to suppress the formation of the Mo3Si phase. Mo-12Si-10B-xNb (x = 10, 20, 22, 24, 26, 28, 30, and 40) bulk alloys were fabricated using mechanical alloying followed by cold pressing and then sintering at 1773 K for 2 h. Effects of Nb content on the mechanical alloying behavior and then sintered microstructure were studied. The addition of Nb with an amount less than 30 at.% accelerated the mechanical alloying process, but 40 at.% Nb addition decreased the process due to excessive cold welding and high powder volume. For the sintered bulk alloy prepared from the mechanically alloyed powders milled for 30 h, a critical Nb content between 24 and 26 at.% was found to suppress Mo3Si production and γNb5Si3 phase formed in the alloys with the addition of Nb content more than 26 at.%. Prolongation of a prior milling process could facilitate the suppression of Mo3Si and delay the formation of niobium silicides.
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Park, Sang Kyu, Tae Hyuk Lee, Moon Soo Sim, Jae Soo Noh, Soo Haeng Cho, and Jong Hyeon Lee. "Alloy Design of New Ni-Based Structural Materials for Electrolytic Reduction and its Corrosion Behavior in Lithium Molten Salt." Advanced Materials Research 886 (January 2014): 41–44. http://dx.doi.org/10.4028/www.scientific.net/amr.886.41.
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In this study, the corrosion behavior of new Ni-based structural materials was studied for electrolytic reduction after exposure to LiCl-Li2O molten salt at 650°C for 24-216h under an oxidizing atmosphere. The new alloys with Ni, Cr, Al, Si, and Nb as the major components were melted at 1700°C under inert atmosphere. The corrosion products and fine structures of the corroded specimens were characterized by SEM, EDS, and XRD. The corrosion rate of 12wt% Cr-2wt% Si alloys and 12wt% Cr-5wt% Si alloys are below 0.3mm/year. However, the corrosion rate of 20wt% Cr-5wt% Si is 0.6mm/year. Also, the corrosion products of 12wt% Cr alloys were Cr2O3, NiCr2O4, Ni, and NiO; those of 20wt% Cr alloys were Cr2O3, LiAl2Cr3O8, and NiO. The higher corrosion rate of 20wt% Cr-5wt% Si could be the higher solute concentration which leads to an unstable alloy formation. As confirmed by the pseudo binary phase diagram of (Ni-Cr-Al-Nb)-Si, the solubility of the silicon with 20 wt% of Cr decreased to 4 wt% from 5 wt% with 12 wt% of Cr.
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Yang, Wonchul, Choong-Heui Chung, Sangyeob Lee, Jong Won Lee, and Joon Sik Park. "Microstructures and Oxidation Behavior According to Nb:Mo Ratio in a Nb–Mo–Si System with Si Pack Cementation Coatings." Coatings 9, no. 12 (November 20, 2019): 772. http://dx.doi.org/10.3390/coatings9120772.
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Research is being conducted on Mo- and Nb-based alloys that are used in the aerospace sector, including those used for advanced gas turbines and aircraft engines. There is a limit to using Mo, which has a high density among refractory metals, and a few studies exist describing the addition of Nb to Mo–silicide alloys. There is a lack of guidance research on the basic Nb:Mo ratio of alloys, and it is necessary to study how to improve oxidation resistance. Therefore, this study aims to improve oxidation resistance by controlling the ratio of Nb and Mo in (Nbx, Moy)Si2 coating layers with Si pack cementation coatings on Nb–Mo alloys. Static oxidation tests were carried out at 1200 °C for 6 h to confirm the oxidation characteristics. As a result, a SiO2 or SiO2 + Nb2O5 ceramic protective layer was formed on the surface. After the oxidation tests, alloys with a Nb content of less than 35 at.% were found to protect the surface. The ratios of Nb and Mo in the Nb–Mo alloy and silicide coating layer were compared, and the improvement of oxidation resistance is discussed in terms of microstructural evolution.
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Wang, Qing, Chun Lei Zhu, Yan Hui Li, Jiang Wu, Chuang Dong, Jian Bing Qiang, Wei Zhang, and Akihisa Inoue. "Cluster-Based Bulk Metallic Glass Formation in Co (-Fe)-Si-B-Nb Alloy Systems." Materials Science Forum 561-565 (October 2007): 1275–78. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.1275.
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The present paper investigates the bulk metallic glass formation in Co-based alloy systems with the guidance of the cluster line and minor-alloying principles. The selected basic ternary Co-B-Si alloy compositions are intersecting points of cluster lines, defined by linking special binary clusters to the third element. Then these basic ternary alloys are further minor-alloyed with Nb and quaternary bulk metallic glasses are obtained only by 4-5 at. % Nb minor-alloying of the basic composition Co68.6B25.7Si5.7 that is developed from dense-packed cluster Co8B3. The bulk metallic glasses are expressed approximately with a unified simple composition formula: (Co8B3)1(Si,Nb)1. In addition, a quantity of Fe substitution for Co further improves the glass-forming abilities.
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Jiang, Y., F. Li, S. R. Li, K. Xu, L. L. Chen, X.-Z. Deng, Y. Y. Huang, and K. Chang. "Thermodynamic assessment of the Fe-Nb-Si system." Journal of Mining and Metallurgy, Section B: Metallurgy, no. 00 (2021): 29. http://dx.doi.org/10.2298/jmmb191220029j.
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Nb-Si based alloys have drawn continuously increasing attention due to their excellent high-temperature mechanical properties. The addition of element Fe could improve their poor high-temperature oxidation resistance which largely restricts their applications. With the aim to study the effect of Fe addition on the Nb-Si system and to design appropriate alloy composition, the Fe-Nb-Si ternary system has been thermodynamically investigated using the CALPHAD (CALculation of PHAse Diagrams) approach aided with the formation enthalpies for ternary compounds at 0 K computed via ab initio calculations. A self-consistent thermodynamic description of the Fe-Nb-Si system was obtained in this work. Key isothermal sections and liquidus projection were presented, and the calculation results show a good agreement with available experimental data.
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Ma, Xiao, Xiping Guo, and Maosen Fu. "Precipitation of γNb5Si3 in Nb-Si based ultrahigh temperature alloys." Intermetallics 98 (July 2018): 11–17. http://dx.doi.org/10.1016/j.intermet.2018.04.007.
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Kim, Han Sol, and Won Yong Kim. "Mechanical Property and Elastic Modulus of Metastable Ti-Nb Based Alloys with Si Addition." Materials Science Forum 546-549 (May 2007): 1427–30. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.1427.
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Mechanical Property and elastic modulus of Ti-Nb based alloys with various Si content, prepared by water quenching from high temperature β phase field, cold rolling and recrystallization heat treatment followed by water quenching, were investigated in terms of tensile test and resonance vibration method. TEM observations revealed that in addition to orthorhombic structured α" phase and bcc structured β phase, an intermediate ω phase is characterized in the microstructure. The volume fraction ratio of constituent phases was dependent upon Nb and Si contents. In as-quenched samples yield strength increased with increasing Si content. This propensity was similar to the cold rolled alloys. In recrystallized samples however, yield strength decreased slightly with increasing Si content even though the alloy containing higher Si content showed smaller grain size. From these results, it is found that strength of the present alloy influences largely on solid solution hardening and phase stability but does weakly on grain size. Yield strength of cold rolled sample was higher than as-quenched and recrystallized samples. Elastic modulus values were measured to 55GPa, 63GPa and 44GPa for as-quenched, cold rolled and recrystallized samples, respectively. The variations of yield strength and elastic modulus values were interpreted in terms of changes in microstructure as well as grain size and phase stability.
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Wang and Guo. "Re-Melting Nb–Si-Based Ultrahigh-Temperature Alloys in Ceramic Mold Shells." Metals 9, no. 7 (June 26, 2019): 721. http://dx.doi.org/10.3390/met9070721.
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In furnaces with different heating elements, Nb–Si based ultrahigh-temperature alloy rods were re-melted in pure yttria mold shells and zirconia face-coat mold shells at 1850 °C for 30 min. The results evidenced that in the furnace with a tungsten heating element, the microstructure of the re-melted alloy became coarser, and the composition varied depending on the type of mold shell. Although the interface reaction layer between the re-melted alloy and the zirconia face-coat mold shell was much thicker, the deformability of the mold shell and the sand burning phenomenon of the alloy inside it were improved and ameliorated, respectively. However, after being re-melted in the furnace with a graphite heating element, the misrun phenomenon occurred in both specimens. Both re-melted alloys inside the mold shells were divided by a gap into an internal and an external part, with totally different microstructures and compositions. No reaction layer emerged at the interface between the re-melted alloy and the mold shells. Instead, infiltration zones arose in the mold shells adjacent to the interface.
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Zhao, Jiang, Claire Utton, and Panos Tsakiropoulos. "On the Microstructure and Properties of Nb-12Ti-18Si-6Ta-2.5W-1Hf (at.%) Silicide-Based Alloys with Ge and Sn Additions." Materials 13, no. 7 (April 10, 2020): 1778. http://dx.doi.org/10.3390/ma13071778.
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In this paper two Nb-silicide-based alloys with nominal compositions (at.%) Nb-12Ti-18Si-6Ta-2.5W-1Hf-2Sn-2Ge (JZ1) and Nb-12Ti-18Si-6Ta-2.5W-1Hf-5Sn-5Ge (JZ2) were studied. The alloys were designed using the alloy design methodology NICE to meet specific research objectives. The cast microstructures of both alloys were sensitive to solidification conditions. There was macro-segregation of Si in JZ1 and JZ2. In both alloys the βNb5Si3 was the primary phase and the Nbss was stable. The A15-Nb3X (X = Ge,Si,Sn) was stable only in JZ2. The Nbss+βNb5Si3 eutectic in both alloys was not stable as was the Nb3Si silicide that formed only in JZ1. At 800 °C both alloys followed linear oxidation kinetics and were vulnerable to pesting. At 1200 °C both alloys exhibited parabolic oxidation kinetics in the early stages and linear kinetics at longer times. The adhesion of the scale that formed on JZ2 at 1200 °C and consisted of Nb and Ti-rich oxides, silica and HfO2 was better than that of JZ1. The microstructure of JZ2 was contaminated by oxygen to a depth of about 200 μm. There was no Ge or Sn present in the scale. The substrate below the scale was richer in Ge and Sn where the NbGe2, Nb5(Si1-xGex)3, W-rich Nb5(Si1-xGex)3, and A15-Nb3X compounds (X = Ge,Si,Sn) were formed in JZ2. The better oxidation behavior of JZ2 compared with JZ1 correlated well with the decrease in VEC and increase in δ parameter values, in agreement with NICE. For both alloys the experimental data for Si macrosegregation, vol.% Nbss, chemical composition of Nbss and Nb5Si3, and weight gains at 800 and 1200 °C was compared with the calculations (predictions) of NICE. The agreement was very good. The calculated creep rates of both alloys at 1200 °C and 170 MPa were lower than that of the Ni-based superalloy CMSX-4 for the same conditions but higher than 10−7 s−1.
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Xu, Zhen, Claire Utton, and Panos Tsakiropoulos. "A Study of the Effect of 2 at.% Sn on the Microstructure and Isothermal Oxidation at 800 and 1200 °C of Nb-24Ti-18Si-Based Alloys with Al and/or Cr Additions." Materials 11, no. 10 (September 25, 2018): 1826. http://dx.doi.org/10.3390/ma11101826.
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Alloying with Al, Cr, Sn, and Ti significantly improves the oxidation of Nb silicide-based alloys at intermediate and high temperatures. There is no agreement about what the concentration of Sn in the alloys should be. It has been suggested that with Sn ≤ 3 at.% the oxidation is improved and formation of the brittle A15-Nb3Sn compound is suppressed. Definite improvements in oxidation behaviour have been observed with 5 at.% Sn or even higher concentrations, up to 8 at.% Sn. The research reported in this paper is about three model alloys with low Sn concentration and nominal compositions Nb-24Ti-18Si-5Cr-2Sn (ZX3), Nb-24Ti-18Si-5Al-2Sn (ZX5), and Nb-24Ti-18Si-5Al-5Cr-2Sn (ZX7) that were studied to understand the effect of the 2 at.% Sn addition on as-cast and heat-treated microstructures and isothermal oxidation in air at 800 and 1200 °C for 100 h. There was macrosegregation of Si and Ti in the alloys ZX3 and ZX5 and only of Si in the alloy ZX7. The Nbss was stable in all alloys. Tin and Ti exhibited opposite partitioning behaviour in the Nbss. The βNb5Si3 was the primary phase in all three cast alloys and had partially transformed to αNb5Si3 in the alloy ZX3. Aluminium in synergy with Sn increased the sluggishness of the βNb5Si3 to αNb5Si3 transformation during solidification. After the heat treatment the transformation of βNb5Si3 to αNb5Si3 had been completed in all three alloys. Fine precipitates were observed inside some αNb5Si3 grains in the alloys ZX5 and ZX7. In the latter alloys the A15-Nb3X (X = Al, Si, and Sn) formed after the heat treatment, i.e., the synergy of Al and Sn promoted the stability of A15-Nb3X intermetallic in these Nb-silicide-based alloys even at this low Sn concentration. A Nbss + Nb5Si3 eutectic formed in all three alloys and there was evidence of anomalous eutectic in the parts of the alloys ZX3 and ZX7 that had solidified under high cooling rate and/or high melt undercooling. A very fine ternary Nbss + Nb5Si3 + NbCr2 eutectic was also observed in parts of the alloy ZX3 that had solidified under high cooling rate. At 800 °C none of the alloys suffered from catastrophic pest oxidation; ZX7 had a smaller oxidation rate constant. A thin Sn-rich layer formed continuously between the scale and Nbss in the alloys ZX3 and ZX5. At 1200 °C the scales formed on all three alloys spalled off, the alloys exhibited parabolic oxidation in the early stages followed by linear oxidation; the alloy ZX5 gave the smallest rate constant values. A thicker continuous Sn-rich zone formed between the scale and substrate in all three alloys. This Sn-rich zone was noticeably thicker near the corners of the specimen of the alloy ZX7 and continuous around the whole specimen. The Nb3Sn, Nb5Sn2Si, and NbSn2 compounds were observed in the Sn-rich zone. At both temperatures the scales formed on all three alloys consisted of Nb-rich and Nb and Si-rich oxides, and Ti-rich oxide also was formed in the scales of the alloys ZX3 and ZX7 at 1200 °C. The formation of a Sn-rich layer/zone did not prevent the contamination of the bulk of the specimens by oxygen, as both Nbss and Nb5Si3 were contaminated by oxygen, the former more severely than the latter.
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Zhao, Jiang, Claire Utton, and Panos Tsakiropoulos. "On the Microstructure and Properties of Nb-12Ti-18Si-6Ta-5Al-5Cr-2.5W-1Hf (at.%) Silicide-Based Alloys with Ge and Sn Additions." Materials 13, no. 17 (August 22, 2020): 3719. http://dx.doi.org/10.3390/ma13173719.
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The microstructures and properties of the alloys JZ3 (Nb-12.4Ti-17.7Si-6Ta-2.7W-3.7Sn-4.8Ge-1Hf-4.7Al-5.2Cr) and JZ3+(Nb-12.4Ti-19.7Si-5.7Ta-2.3W-5.7Sn-4.9Ge-0.8Hf-4.6Al-5.2Cr) were studied. The densities of both alloys were lower than the densities of Ni-based superalloys and many of the refractory metal complex concentrated alloys (RCCAs) studied to date. Both alloys had Si macrosegregation and the same phases in their as cast and heat treated microstructures, namely βNb5Si3, αNb5Si3, A15-Nb3X (X = Al, Ge, Si, Sn), C14-Cr2Nb and solid solution. W-rich solid solutions were stable in both alloys. At 800 °C only the alloy JZ3 did not show pest oxidation, and at 1200 °C a thin and well adhering scale formed only on JZ3+. The alloy JZ3+ followed parabolic oxidation with rate constant one order of magnitude higher than the single crystal Ni-superalloy CMSX-4 for the first 14 h of oxidation. The oxidation of both alloys was superior to that of RCCAs. Both alloys were predicted to have better creep at the creep goal condition compared with the superalloy CMSX-4. Calculated Si macrosegregation, solid solution volume fractions, chemical compositions of solid solution and Nb5Si3, weight changes in isothermal oxidation at 800 and 1200 °C using the alloy design methodology NICE agreed well with the experimental results.
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Thandorn, Tophan, and Panos Tsakiropoulos. "The Effect of Boron on the Microstructure and Properties of Refractory Metal Intermetallic Composites (RM(Nb)ICs) Based on Nb-24Ti-xSi (x = 16, 17 or 18 at.%) with Additions of Al, Cr or Mo." Materials 14, no. 20 (October 15, 2021): 6101. http://dx.doi.org/10.3390/ma14206101.
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This paper is about metallic ultra-high temperature materials, in particular, refractory metal intermetallic composites based on Nb, i.e., RM(Nb)ICs, with the addition of boron, which are compared with refractory metal high entropy alloys (RHEAs) or refractory metal complex concentrated alloys (RCCAs). We studied the effect of B addition on the density, macrosegregation, microstructure, hardness and oxidation of four RM(Nb)IC alloys, namely the alloys TT2, TT3, TT4 and TT8 with nominal compositions (at.%) Nb-24Ti-16Si-5Cr-7B, Nb-24Ti-16Si-5Al-7B, Nb-24Ti-18Si-5Al-5Cr-8B and Nb-24Ti-17Si-3.5Al-5Cr-6B-2Mo, respectively. The alloys made it possible to compare the effect of B addition on density, hardness or oxidation with that of Ge or Sn addition. The alloys were made using arc melting and their microstructures were characterised in the as cast and heat-treated conditions. The B macrosegregation was highest in TT8. The macrosegregation of Si or Ti increased with the addition of B and was lowest in TT8. The alloy TT8 had the lowest density of 6.41 g/cm3 and the highest specific strength at room temperature, which was also higher than that of RCCAs and RHEAs. The Nbss and T2 silicide were stable in the alloys TT2 and TT3, whereas in TT4 and TT8 the stable phases were the Nbss and the T2 and D88 silicides. Compared with the Ge or Sn addition in the same reference alloy, the B and Ge addition was the least and most effective at 800 °C (i.e., in the pest regime), when no other RM was present in the alloy. Like Ge or Sn, the B addition in TT2, TT3 and TT4 did not suppress scale spallation at 1200 °C. Only the alloy TT8 did not pest and its scales did not spall off at 800 and 1200 °C. The macrosegregation of Si and Ti, the chemical composition of Nbss and T2, the microhardness of Nbss and the hardness of alloys, and the oxidation of the alloys at 800 and 1200 °C were also viewed from the perspective of the alloy design methodology NICE and relationships with the alloy or phase parameters VEC, δ and Δχ. The trends of these parameters and the location of alloys and phases in parameter maps were found to be in agreement with NICE.
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Yang, Xiu Xia, Jiang Bo Sha, and Hu Zhang. "Property Responses in Nb-Si-Hf-Ti-Al-W-B-Cr Alloys for High-Temperature Applications." Materials Science Forum 654-656 (June 2010): 468–71. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.468.
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Multi-component Nb-(11,15)Si-5Hf-30Ti-4Al-4W-2B-(8,16)Cr alloys have been proposed, attempting to obtain the Nb-Si based alloys with a comprehensive property. The results show that three phases of NbSS, Nb5Si3 and Laves Cr2Nb exist in the alloys with a Cr content of 16 at%. With increasing Si and Cr contents the fracture toughness KQ decreases, while the oxidation resistance at 1250°C and strength at 1250°C and 1350°C exhibit an increasing tendency. The 15Si-16Cr alloy shows the highest strength and oxidation resistance, and the lowest toughness; they are 385MPa at 1350°C, 215mg/cm2 at 1250°C for 100 h, and 5.45 MPa•m1/2 at room temperature, respectively. The 11Si-8Cr alloy with an NbSS/Nb5Si3 microstructure only has the highest toughness of 11.87 MPa•m1/2, its strength and oxidation resistance are the lowest.
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Nelson, Jack, Mohammad Ghadyani, Claire Utton, and Panos Tsakiropoulos. "A Study of the Effects of Al, Cr, Hf, and Ti Additions on the Microstructure and Oxidation of Nb-24Ti-18Si Silicide Based Alloys." Materials 11, no. 9 (September 1, 2018): 1579. http://dx.doi.org/10.3390/ma11091579.
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In Nb-silicide based alloys Al, Cr, Hf, and Ti additions are crucial for achieving balance of properties. It is not known how the simultaneous addition of Hf with Al and Ti, or Hf with Al, Cr, and Ti affects macrosegregation, and how the alloying affects hardness, Young’s modulus and bulk alloy oxidation, and contamination of the solid solution Nbss and the Nb5Si3 compound by oxygen. Two alloys with nominal compositions (at.%) Nb-24Ti-18Si-5Al-5Hf (alloy NbSiTiHf-5Al) and Nb-24Ti-18Si-5Al-5Cr-5Hf (alloy NbSiTiHf-5Al-5Cr) were studied in the as-cast and heat-treated conditions and after isothermal oxidation at 800 and 1200 °C and were compared with similar alloys without Hf. In both alloys there was macrosegregation of Si and Ti, which was more severe in NbSiTiHf-5Al. Both alloys formed Nbss+βNb5Si3 eutectic. The Nbss was stable and its Al and Cr concentrations increased with increasing Ti concentration. In both conditions the βNb5Si3 was observed in the alloys NbSiTiHf-5Al and NbSiTiHf-5Al-5Cr, and the γNb5Si3 only in the alloy NbSiTiHf-5Al. In both heat-treated alloys, separate Hf-rich Nb5Si3 grains were formed. The Si and Al concentrations in Nb5Si3 respectively decreased and increased with increasing Ti concentration. Al and Cr had a stronger hardening effect in the Nbss than Al, Cr, and Hf. Al, Cr, and Ti had a stronger negative effect on the Young’s modulus of the Nbss compared with Al, Cr, Hf, and Ti. When Nb was substituted by Ti, Cr, and Hf, and Si by Al in the βNb5Si3, the Young’s modulus was reduced compared with the unalloyed silicide. At 800 °C both alloys did not exhibit catastrophic pest-oxidation after 100 h. The Nbss and Nb5Si3 were contaminated by oxygen in both alloys, the former more severely. At 1200 °C the scales spalled-off, more severely in the alloy NbSiTiHf-5Al, where substrate that was heavily contaminated by oxygen below the scale also spalled-off. In both alloys the contamination of Nb5Si3 and Nbss by oxygen was more severe compared with 800 °C, but the silicides were not contaminated by oxygen in their bulk. The Nbss was not contaminated by oxygen only in the bulk of the alloy NbSiTiHf-5Al-5Cr.
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Menon, E. Sarath K., and Madan G. Mendiratta. "High Temperature Oxidation in Multicomponent Nb Alloys." Materials Science Forum 475-479 (January 2005): 717–20. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.717.
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Niobium-Silicon alloys offer potential as a new generation of refractory material system that could meet the high-temperature capability envisaged to exceed the application temperatures of Ni base superalloys. A serious concern in the application of Nb based alloys is their poor oxidation resistance at elevated temperatures. The ternary diagram Nb-Ti-Si system exhibits eutectic groves nearly parallel to the Nb-Ti binary and terminate in a Class II invariant reaction, L+(Nb,Ti)3Si → β+ (Ti,Nb)5Si3. A peretectic ridge from the reaction, L+(Nb,Ti)5Si3 →(Nb,Ti)3Si also exists and these reactions control the microstructures resulting from solidification of these Nb alloys. The microstructures associated with these alloys comprise a distribution of Nb5Si3 in β matrix. The effect of various alloying elements on the resulting microstructures are illustrated The effect of microstructural distribution on oxidation resistance of multiphase alloys are also discussed.
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Zhao, Zhao, Anne Denquin, Stefan Drawin, and Jonathan Barreau. "Microstructure and Mechanical Behaviour of NbTiAl Based Alloys Doped with Low Additions of Silicon." Materials Science Forum 783-786 (May 2014): 1207–12. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1207.
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Nb-base refractory intermetallic materials have potential interest for high temperature applications thanks to their low density and high temperature strength. While advanced intermetallics in monolithic form have limited prospects for providing the required balance of properties for use at high temperatures, two-phase or multicomponent intermetallic systems composed of a ductile, Nb-base refractory phase in equilibrium with one or more silicide intermetallics show promise for further development as structural materials. In the present paper, Nb-base refractory alloys based on Nb-35Ti-15Al (at.%) were doped with small amount of Si (1 and 2 at% of silicon) addition to improve its high temperature strength by keeping an acceptable ductility at room temperature. The samples were prepared by arc-melting starting from pure elements (99.99%). The silicon addition effects on the microstructural features were investigated by using X Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) techniques. Its effects on the mechanical properties were assessed by compression tests at ambient and high temperatures. Compression tests show the beneficial effect of the Si addition on strength.
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Gao, Juan, Jing Ying Ye, Wen Chun Zhang, Hui Juan Wang, and Wen Deng. "Influence of Nb and Sn on d Electrons of TiAl Alloys Studied by Coincidence Positron Annihilation Spectroscopy." Advanced Materials Research 415-417 (December 2011): 1132–35. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.1132.
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The coincidence Doppler broadening spectra of single crystals of Si, Al, polycrystals of Ti, Nb and Sn, and TiAl-based alloys (TiAl, Ti50Al48Nb2and Ti50Al48Sn2) have been measured and analyzed. It has been found that the 3d electron signal for binary TiAl alloy is lower than expected due to the Ti 3d-Al 3p interactions. The addition of Nb atoms to TiAl alloy leads to the enhancement of d-d interactions and thus the d electron signal in the spectrum. The d electron signal in the spectrum of Ti50Al48Nb2alloy is higher than that of Ti50Al48Sn2alloy. The influence of Nb and Sn on d electrons of TiAl alloys has been discussed.
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Hernández-Negrete, Ofelia, and Panos Tsakiropoulos. "On the Microstructure and Isothermal Oxidation of the Si-22Fe-12Cr-12Al-10Ti-5Nb (at.%) Alloy." Materials 12, no. 11 (June 3, 2019): 1806. http://dx.doi.org/10.3390/ma12111806.
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Nb-silicide based alloys are new ultra-high temperature materials that could replace Ni-based superalloys. Environmentally resistant coating system (s) with αAl2O3 or SiO2 forming bond coat alloys that are chemically compatible with the Nb-silicide based alloy substrates are needed. This paper makes a contribution to the search for non-pesting bond coat alloys. The microstructure and isothermal oxidation at 800 °C of the silicide-based alloy Si-22Fe-12Cr-12Al-10Ti-5Nb (OHC2) were studied. The cast alloy exhibited macrosegregation of all elements. The microstructures in the cast alloy and after the heat treatment at 800 °C consisted of the same phases, namely TM6Si5, TM5Si3 (TM = transition metal), FeSi2Ti, Fe3Al2Si3, (Fe,Cr)(Si,Al), and an unknown phase of dark contrast. The latter two phases were not stable at 950 °C, where the TMSi2 was formed. There was evidence of endothermic reaction(s) below 1200 °C and liquation at 1200 °C. The alloy followed parabolic oxidation kinetics after the first hour of isothermal oxidation at 800 °C, did not pest, and formed a self-healing scale, in which the dominant oxide was Al2O3. The alloy was compared with other alumina or silica scale-forming intermetallic alloys and approaches to the design of bond coat alloys were suggested.
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Drawin, Stefan, J. P. Monchoux, J. L. Raviart, and Alain Couret. "Microstructural Properties of Nb-Si Based Alloys Manufactured by Powder Metallurgy." Advanced Materials Research 278 (July 2011): 533–38. http://dx.doi.org/10.4028/www.scientific.net/amr.278.533.
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An NbTiHfCrAlSi niobium silicide based atomized powder has been compacted by a conventional technique (hot extrusion) and by spark plasma sintering to nearly fully dense alloys. Both materials exhibit a metastable fine micrometer-sized microstructure that has been coarsened by a subsequent heat treatment. The densification of the SPS sample takes place between ca. 800°C and 1300°C.
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Wang, Na, Lina Jia, Bin Kong, Yueling Guo, Huarui Zhang, and Hu Zhang. "Eutectic evolution of directionally solidified Nb-Si based ultrahigh temperature alloys." International Journal of Refractory Metals and Hard Materials 71 (February 2018): 273–79. http://dx.doi.org/10.1016/j.ijrmhm.2017.11.001.
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Inoue, A., B. L. Shen, A. R. Yavari, and A. L. Greer. "Mechanical properties of Fe-based bulk glassy alloys in Fe–B–Si–Nb and Fe–Ga–P–C–B–Si systems." Journal of Materials Research 18, no. 6 (June 2003): 1487–92. http://dx.doi.org/10.1557/jmr.2003.0205.
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Mechanical properties of cast Fe-based bulk glassy alloy rods with compositions of (Fe0.75B0.15Si0.1)96Nb4 and Fe77Ga3P9.5C4B4Si2.5 were examined by compression and Vickers hardness tests. The Young's modulus (E), yield strength (σy), fracture strength (σf), elastic strain (εe), fracture strain (εf), and Vickers hardness (Hv) were 175 GPa, 3165 MPa, 3250 MPa, 1.8%, 2.2%, and 1060, respectively, for the former alloy and 182 GPa, 2980 MPa, 3160 MPa, 1.9%, 2.2%, and 870, respectively, for the latter alloy. The εf /E and Hv/3E were 0.019–0.017 and 0.020–0.016, respectively, for the alloys, in agreement with the previous data for a number of bulk glassy alloys. The agreement suggests that these Fe-based bulk glassy alloys have an elastic–plastic deformation mode. The syntheses of high-strength Fe-based bulk glassy alloys with distinct compressive plastic strain and elastic–plastic deformation mode are encouraging for future development of Fe-based bulk glassy alloys as structural and soft magnetic materials.
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Zacharis, Eleftherios, Claire Utton, and Panos Tsakiropoulos. "A Study of the Effects of Hf and Sn on the Microstructure, Hardness and Oxidation of Nb-18Si Silicide Based Alloys without Ti Addition." Materials 11, no. 12 (December 3, 2018): 2447. http://dx.doi.org/10.3390/ma11122447.
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The paper presents the results of an experimental study of large (≈0.6 kg) arc melted buttons of four Ti free Nb-silicide based alloys with Sn addition with nominal compositions (at.%) Nb-18Si-5Hf-5Sn (EZ1), Nb-18Si-5Al-5Sn (EZ7), Nb-18Si-5Cr-5Hf-5Sn (EZ3) and Nb-18Si-5Al-5Hf-5Sn (EZ4). The alloys were studied in the as-cast and heat treated conditions. In all the alloys there was macrosegregation of Si (MACSi). Among the single element additions Hf had the weakest and Sn the strongest effect on MACSi. The simultaneous presence of Cr and Hf in the alloy EZ3 had the strongest effect on MACSi. In all the alloys the βNb5Si3 was the primary phase and was present after the heat treatment(s), the Nb3Si silicide was suppressed and the A15-Nb3Sn intermetallic was stable. The Nbss was not stable in the alloys EZ7 and EZ4 and the C14-NbCr2 Laves phase was stable in the alloy EZ3. Very Hf-rich Nb5Si3 was stable in the alloy EZ4 after prolonged heat treatments. Eutectics were observed in all the alloys. These were binary eutectics in the alloys EZ1 and EZ7, where respectively they consisted of the Nbss and βNb5Si3, and βNb5Si3 and A15-Nb3Sn phases. Most likely ternary eutectics consisting of the Nbss, C14-NbCr2 and βNb5Si3, and Nbss, βNb5Si3 and A15-Nb3Sn phases were observed, respectively in the alloys EZ3 and EZ4. The addition of Al increased the vol% of the Nb5Si3 and A15-Nb3Sn phases, particularly after the heat treatment(s). The lattice parameter of Nb respectively increased and decreased with the addition of Hf, and Al or Cr and the latter element had the stronger negative effect. Pest oxidation was not suppressed in the alloys of this study.
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Mitra, Rahul. "Oxidation Behavior of Silicides." Diffusion Foundations 21 (March 2019): 127–56. http://dx.doi.org/10.4028/www.scientific.net/df.21.127.
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The oxidation behavior of Mo, Nb, and Ti-silicides has received significant attention in past few decades for their potential to be used as high temperature structural materials. These Si-bearing intermetallic alloys have the ability to form an oxide scale containing SiO2, which is protective if formed as a continuous and impervious layer, so that the ingress of oxygen from atmosphere to the underneath alloy is restricted. To form a continuous and stable SiO2scale, it is important to have sufficient activity of Si along with thermodynamic and kinetic conditions favoring its growth in comparison to that of oxides of other alloying elements. MoSi2has superior oxidation resistance compared to that of Mo3Si or Mo5Si3, because of its higher Si content. Furthermore, a continuous film of SiO2is able to form at temperatures in the range of 800-1700oC on MoSi2due to vaporization of MoO3, but not on NbSi2or TiSi2due to competitive growth of Nb2O5or TiO2, respectively. During past two decades, a significant effort has been devoted to development of Mo-Si-B alloys containing Mo-rich solid solution, Mo3Si and Mo5SiB2as constituent phases, due to their ability to form a protective borosilicate scale. The presence of B2O3contributes to fluidity of borosilicate scale, thereby contributing to closure of porosities. Efforts have been also made to develop multicomponent Nb-silicide based alloys with optimum combination of mechanical properties and high temperature oxidation resistance with limited success. There have been efforts to develop silicide based coatings for protection oxidation for Mo-rich Mo-Si-B alloys and Nb-Si based ternary or multicomponent alloys with inadequate oxidation resistance. Oxidation behavior of selected silicides with potential for structural application, along with mechanisms for protection against oxidation has been reviewed and discussed.
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Kanunnikova, Olga M., O. Yu Goncharov, and V. I. Ladyanov. "Assessment of the Structural State of the Amorphous Alloys Thin Surface Layers." Materials Science Forum 946 (February 2019): 174–80. http://dx.doi.org/10.4028/www.scientific.net/msf.946.174.
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The complex approach based on the combination of methods of equilibrium thermodynamics and x-ray electron spectroscopy for layer-by-layer analysis of the composition of surface layers of amorphous alloys is described on the example of Fe-Si-B-Nb-Cu alloy.
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Zacharis, Eleftherios, Claire Utton, and Panos Tsakiropoulos. "A Study of the Effects of Hf and Sn on the Microstructure, Hardness and Oxidation of Nb-18Si Silicide-Based Alloys-RM(Nb)ICs with Ti Addition and Comparison with Refractory Complex Concentrated Alloys (RCCAs)." Materials 15, no. 13 (June 30, 2022): 4596. http://dx.doi.org/10.3390/ma15134596.
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In this paper, we present a systematic study of the as-cast and heat-treated microstructures of three refractory metal intermetallic composites based on Nb (i.e., RM(Nb)ICs), namely the alloys EZ2, EZ5, and EZ6, and one RM(Nb)IC/RCCA (refractory complex concentrated alloy), namely the alloy EZ8. We also examine the hardness and phases of these alloys. The nominal compositions (at.%) of the alloys were Nb-24Ti-18Si-5Hf-5Sn (EZ2), Nb-24Ti-18Si-5Al-5Hf-5Sn (EZ5), Nb-24Ti-18Si-5Cr-5Hf-5Sn (EZ6), and Nb-24Ti-18Si-5Al-5Cr-5Hf-5Sn (EZ8). All four alloys had density less than 7.3 g/cm3. The Nbss was stable in EZ2 and EZ6 and the C14-NbCr2 Laves phase in EZ6 and EZ8. In all four alloys, the A15-Nb3X (X = Al,Si,Sn) and the tetragonal and hexagonal Nb5Si3 were stable. Eutectics of Nbss + Nb5Si3 and Nbss + C14-NbCr2 formed in the cast alloys without and with Cr addition, respectively. In all four alloys, Nb3Si was not formed. In the heat-treated alloys EZ5 and EZ8, A15-Nb3X precipitated in the Nb5Si3 grains. The chemical compositions of Nbss + C14-NbCr2 eutectics and some Nb5Si3 silicides and lamellar microstructures corresponded to high-entropy or complex concentrated phases (compositionally complex phases). Microstructures and properties were considered from the perspective of the alloy design methodology NICE. The vol.% Nbss increased with increasing ΔχNbss. The hardness of the alloys respectively increased and decreased with increasing vol.% of A15-Nb3X and Nbss. The hardness of the A15-Nb3X increased with its parameter Δχ, and the hardness of the Nbss increased with its parameters δ and Δχ. The room-temperature-specific strength of the alloys was in the range 271.7 to 416.5 MPa cm3g−1. The effect of the synergy of Hf and Sn, or Hf and B, or Hf and Ge on the macrosegregation of solutes, microstructures, and properties of RM(Nb)ICs/RCCAs from this study and others is compared. Phase transformations involving compositionally complex phases are discussed.
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Bondarenko, Yu A., M. Yu Kolodyazhnyy, and V. A. V. A. "Creation of high-temperature heat-resistant alloys based on refractory matrices and natural composites." Perspektivnye Materialy 2 (2021): 5–15. http://dx.doi.org/10.30791/1028-978x-2021-2-5-16.
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The scientific, technical and technological aspects in the field of creating new high-temperature materials for the hot tract parts of gas turbine engines (GTE) with operating temperatures exceeding those existing in the GTE are considered. Investigated more refractory metal materials to create new high-temperature alloys used in the manufacture of working and nozzle blades and other parts of promising gas turbine engines based on Co – Cr, Pt – Al, Nb – Si, Mo – Si – B systems. In Co – Cr alloys, heat resistance is mainly ensured by hardening the Co matrix, including dispersed precipitates of the carbide phase (TaC) and the boride phase Cr2B. In alloys of the Pt – Al system, due to the doping of Cr, Al, Ti, Re ... and precipitates of the coherently embedded Pt3Al phase. In eutectic alloys of the Nb-Si system, this is due to complex hardening of the Nb solid solution and Nb5Si3 silicide, as well as the natural compositional structure. In Mo – Si – B alloys, high strength is achieved by doping a-Mo solid solution and the formation of intermetallic phases Mo3Si, Mo5SiB2, carbides Mo2C, TiC. Compositions were selected, analysis of their smelting methods was carried out, including directed crystallization, which provides a natural compositional structure, mechanical properties at room and high temperatures, oxidation resistance were evaluated, structural features were investigated, information was provided on technological equipment and the possibility of obtaining parts in various ways. It is shown that, depending on the composition of the selected matrix, the working temperature of heat-resistant alloys can increase to 1300 – 1500 °C, which significantly exceeds the existing nickel heat-resistant alloys. It is concluded that the materials under study are promising for use in aircraft engine building and the aerospace industry.
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Thandorn, Tophan, and Panos Tsakiropoulos. "On the Microstructure and Properties of Nb-Ti-Cr-Al-B-Si-X (X = Hf, Sn, Ta) Refractory Complex Concentrated Alloys." Materials 14, no. 24 (December 10, 2021): 7615. http://dx.doi.org/10.3390/ma14247615.
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We studied the effect of the addition of Hf, Sn, or Ta on the density, macrosegregation, microstructure, hardness and oxidation of three refractory metal intermetallic composites based on Nb (RM(Nb)ICs) that were also complex concentrated alloys (i.e., RM(Nb)ICs/RCCAs), namely, the alloys TT5, TT6, and TT7, which had the nominal compositions (at.%) Nb-24Ti-18Si-5Al-5B-5Cr-6Ta, Nb-24Ti-18Si-4Al-6B-5Cr-4Sn and Nb-24Ti-17Si-5Al-6B-5Cr-5Hf, respectively. The alloys were compared with B containing and B free RM(Nb)ICs. The macrosegregation of B, Ti, and Si was reduced with the addition, respectively of Hf, Sn or Ta, Sn or Ta, and Hf or Sn. All three alloys had densities less than 7 g/cm3. The alloy TT6 had the highest specific strength in the as cast and heat-treated conditions, which was also higher than that of RCCAs and refractory metal high entropy alloys (RHEAs). The bcc solid solution Nbss and the tetragonal T2 and hexagonal D88 silicides were stable in the alloys TT5 and TT7, whereas in TT6 the stable phases were the A15-Nb3Sn and the T2 and D88 silicides. All three alloys did not pest at 800 °C, where only the scale that was formed on TT5 spalled off. At 1200 °C, the scale of TT5 spalled off, but not the scales of TT6 and TT7. Compared with the B free alloys, the synergy of B with Ta was the least effective regarding oxidation at 800 and 1200 °C. Macrosegregation of solutes, the chemical composition of phases, the hardness of the Nbss and the alloys, and the oxidation of the alloys at 800 and 1200 °C were considered from the perspective of the Niobium Intermetallic Composite Elaboration (NICE) alloy design methodology. Relationships between properties and the parameters VEC, δ, and Δχ of alloy or phase and between parameters were discussed. The trends of parameters and the location of alloys and phases in parameter maps were in agreement with NICE.
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Bewlay, B. P., M. R. Jackson, J. C. Zhao, P. R. Subramanian, M. G. Mendiratta, and J. J. Lewandowski. "Ultrahigh-Temperature Nb-Silicide-Based Composites." MRS Bulletin 28, no. 9 (September 2003): 646–53. http://dx.doi.org/10.1557/mrs2003.192.
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AbstractThis article reviews the most recent progress in the development of Nb-silicide-based in situ composites for potential applications in turbine engines with service temperatures of up to 1350°C. These composites contain high-strength Nb silicides that are toughened by a ductile Nb solid solution. Preliminary composites were derived from binary Nb-Si alloys, while more recent systems are complex and are alloyed with Ti, Hf, W, B, Ge, Cr, and Al. Alloying schemes have been developed to achieve an excellent balance of room-temperature toughness, fatigue-crack-growth behavior, high-temperature creep performance, and oxidation resistance over a broad range of temperatures. Nb-silicide-based composites are described with emphasis on processing, microstructure, and performance. Nb silicide composites have been produced using a range of processing routes, including induction skull melting, investment casting, hot extrusion, and powder metallurgy methods. Nb silicide composite properties are also compared with those of Ni-based superalloys.
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Miura, Seiji, Toru Hatabata, Takuya Okawa, and Tetsuo Mohri. "Effect of Alloying Elements on Nb-Rich Portion of Nb-Si-X Ternary Systems and In Situ Crack Observation of Nb-Si-Based Alloys." Metallurgical and Materials Transactions A 45, no. 3 (January 3, 2014): 1136–47. http://dx.doi.org/10.1007/s11661-013-2118-8.
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Kim, Won Yong, Han Sol Kim, Shae K. Kim, Tae Yeub Ra, and Mok Soon Kim. "Effect of Ternary Alloying Elements on Microstructure and Mechanical Property of Nb-Si Based Refractory Intermetallic Alloy." Materials Science Forum 486-487 (June 2005): 342–45. http://dx.doi.org/10.4028/www.scientific.net/msf.486-487.342.
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Microstructure and mechanical property at room temperature and at 1773 K of Nb-Si based refractory intermetallic alloys were investigated in terms of compression and fracture toughness test. Mo and V were chosen as ternary alloying elements because of their high melting points, atomic sizes smaller than Nb. Both ternary alloying elements were found to have a significant role in modifying the microstructure from dispersed structure to eutectic-like structure in Nb solid solution/Nb5Si3 intermetallic composites. The 0.2% offset yield strength at room temperature increased with increasing content of ternary elements in Nb solid solution and volume fraction of Nb5Si3. At 1773 K, Mo addition has a positive role in increasing the yield strength. On the other hand, V addition has a role in decreasing the yield strength. The fracture toughness of ternary alloys was superior to binary alloys. Details will be discussed in correlation with ternary alloying, volume fraction of constituent phase, and the microstructure.
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Guo, Yueling, Lina Jia, Huarui Zhang, Fengxiang Zhang, and Hu Zhang. "Enhancing the oxidation resistance of Nb-Si based alloys by yttrium addition." Intermetallics 101 (October 2018): 165–72. http://dx.doi.org/10.1016/j.intermet.2018.08.004.
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Larimian, T., V. Chaudhary, M. U. F. Khan, R. V. Ramanujan, R. K. Gupta, and T. Borkar. "Spark plasma sintering of Fe–Si–B–Cu–Nb / Finemet based alloys." Intermetallics 129 (February 2021): 107035. http://dx.doi.org/10.1016/j.intermet.2020.107035.
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Bolzoni, L., and N. Hari Babu. "Heterogeneous Nb-Based Nuclei for the Grain Refinement of Al-Si Alloys." JOM 68, no. 5 (April 1, 2016): 1301–6. http://dx.doi.org/10.1007/s11837-016-1855-8.
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