On the Microstructure and Properties of the Nb-23Ti-5Si-5Al-5Hf-5V-2Cr-2Sn (at.%) Silicide-Based Alloy—RM(Nb)IC

Vellios, Nikos; Keating, Paul; Tsakiropoulos, P.

doi:10.3390/met11111868

Cited by 13 publications

(50 citation statements)

References 53 publications

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“…Microstructure and properties of RM(Nb)ICs containing these elements have been studied by different groups [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. With the exception of one systematic study on the effect of the concentration of Sn (2 to 8 at.%) on the microstructure of as-cast and heat-treated (1200 • C/120 h) MASCbased Nb-25Ti-16Si-8Hf-2Al-2Cr-xSn alloys and their oxidation [16], all other studies and patents have been of Sn-free alloys (e.g., [17][18][19][20]), Hf-free alloys (e.g., [21][22][23]), Al-, Cr-, and Sn-free alloys (e.g., [24,25]), Ti-free alloys [26], or alloys where the elements Al, Cr, Hf, Si, Sn and Ti were in synergy with other TMs or RMs or REs (e.g., [27][28][29][30][31]). (MASC is the RM(Nb)IC Nb-25Ti-16Si-8Hf-2Al-2Cr developed by General Electric [32].)…”

Section: Introductionmentioning

confidence: 99%

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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)

2022

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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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Section: Introductionmentioning

confidence: 99%

“…Furthermore, the chemical inhomogeneity can be important vis-à-vis the contamination of RM(Nb)ICs with interstitials [20,22,23]. The contamination of the aforementioned phases with interstitials differs (for example, it is more severe for Nb ss than Nb 5 Si 3 ) and depends on their chemical composition (e.g., [20,22,23,31]).…”

Section: Introductionmentioning

confidence: 99%

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)

2022

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“…Moreover, note that with the exception of TT8, the Δχ Nbss in the other alloys is less than 0.105 ( Figure 8 c). Note that (a) above is not uncommon in RM(Nb)ICs, for example, see [ 47 ].…”

Section: Discussionmentioning

confidence: 99%

On the Microstructure and Properties of Nb-Ti-Cr-Al-B-Si-X (X = Hf, Sn, Ta) Refractory Complex Concentrated Alloys

Thandorn

Tsakiropoulos

2021

Materials

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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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“…In reported RHEAs, WMoTaNb is famous for retaining high strength above 400 MPa at temperatures up to 1600 • C and has a great potential for high temperature applications; however, its compressive plastic strain at room temperature (RT) is inferior at 3%, severely limiting its processing formation performance [4]. The microstructure and performance of RHEAs can be changed dramatically by alloying other elements [5][6][7]. It is reported that alloying with V effectively improves the strength of WMoTaNb alloys to approximately 200 MPa at elevated temperatures of 600 • C-1200 • C [4].…”

Section: Introductionmentioning

confidence: 99%

Effect of V and Ti on the Oxidation Resistance of WMoTaNb Refractory High-Entropy Alloy at High Temperatures

Liang

et al. 2021

Metals

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Alloying with V and Ti elements effectively improves the strength of WMoTaNb refractory high entropy alloys (RHEAs) at elevated temperatures. However, their effects on the oxidation resistance of WMoTaNb RHEAs are unknown, which is vitally important to their application at high temperatures. In this work, the effect of V and Ti on the oxidation behavior of WMoTaNb RHEA at 1000 °C was investigated using a thermogravimetric system, X-ray diffraction and scanning electron microscopy. The oxidation of all alloys was found to obey a power law passivating oxidation at the early stage. The addition of V aggravates the volatility of V2O5, MoO3 and WO3, and leads to disastrous internal oxidation. The addition of Ti reduces the mass gain in forming the full coverage of passivating scale and prolongs the passivation duration of alloys.

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On the Microstructure and Properties of the Nb-23Ti-5Si-5Al-5Hf-5V-2Cr-2Sn (at.%) Silicide-Based Alloy—RM(Nb)IC

Cited by 13 publications

References 53 publications

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)

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)

On the Microstructure and Properties of Nb-Ti-Cr-Al-B-Si-X (X = Hf, Sn, Ta) Refractory Complex Concentrated Alloys

Effect of V and Ti on the Oxidation Resistance of WMoTaNb Refractory High-Entropy Alloy at High Temperatures

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