The microstructural evolution and mechanical properties of Nb–10Hf–15W–(0/1/3/5)Si (at.-%) alloys were investigated. The as-cast 0Si and 1Si alloys had a single Nb solid solution (NbSS) phase, while the 3Si and 5Si alloys consisted of NbSS matrix and the eutectic of NbSS plus Nb3Si. After heat treatment, the microstructure contained primary NbSS and NbSS + α-Nb5Si3 eutectoid in 3Si and 5Si alloys. Fracture toughness of as-cast and heat-treated samples at room temperature monolithically decreased with increasing Si content. However, the α-Nb5Si3 phase improved compressive strength of the NbSS alloy at 1250 and 1350°C, with no degradation in the ductility or formability of the NbSS/Nb5Si3 microstructure. Finally, the failure mechanisms of the NbSS/α-Nb5Si3 microstructure at room and high temperatures were discussed.
GergoPSOscarB.Rocket propulsion elements, 8th editions. New York (NY): John Wiley and Sons, Inc; 2010.
2.
BewlayBPJacksonMRSubramanianPRA review of very-high-temperature Nb-silicide-based composites. Metall Mater Trans A. 2003; 34(10):2043–2052. doi:10.1016/j.jnucmat.2004.10.118.
3.
PerepezkoJH.The hotter the engine, the better. Science. 2009; 326(5956):1068–1069. doi:10.1126/science.1179327.
4.
PollockTM.Alloy design for aircraft engines. Nat Mater. 2016; 15(8):809. doi:10.1038/nmat4709.
5.
FujikuraMKasamaATanakaREffect of alloy chemistry on the high temperature strengths and room temperature fracture toughness of advanced Nb-based alloys. Mater Trans. 2004; 45(2):493–501. doi:10.2320/matertrans.45.493.
6.
ZhangSGuoX.Alloying effects on the microstructure and properties of Nb–Si based ultrahigh temperature alloys. Intermetallics. 2016; 70:33–44. doi:10.1016/j.intermet.2015.12.002.
7.
SankarMPhanikumarGSinghVEffect of Zr additions on microstructure evolution and phase formation of Nb−Si based ultrahigh temperature alloys. Intermetallics. 2018; 101:123–132. doi:10.1016/j.intermet.2018.07.010.
8.
KimJTabaruTSakamotoMMechanical properties and fracture behavior of an NbSS/Nb5Si3 in-situ composite modified by Mo and Hf alloying. Mater Sci Eng A. 2004; 372(1–2):137–144. doi:10.1016/j.msea.2003.12.010.
9.
ShaJHiraiHUenoHToughness and strength characteristics of Nb-W-Si ternary alloys prepared by arc melting. Metall Mater Trans A. 2003; 34(12):2861–2871. doi:10.1007/s11661-003-0187-9.
SubramanianPRMendirattaMGDimidukDM.The development of Nb-based advanced intermetallic alloys for structural applications. JOM. 1996; 48(1):33–38. doi:10.1007/BF03221360.
12.
MendirattaMGDimidukDM.Strength and toughness of a Nb/Nb5Si3 composite. Metall Trans A. 1993; 24(2):501–504. doi:10.1007/BF02657338.
13.
MendirattaMGLewandowskiJJDimidukDM.Strength and ductile-phase toughening in the two-phase Nb/Nb5Si3 alloys. Metall Trans A. 1991; 22(7):1573. doi:10.1007/BF02667370.
14.
BewlayBPJacksonMRLipsittHA.The balance of mechanical and environmental properties of a multielement niobium-niobium silicide-based in situ composite. Metall Mater Trans A. 1996; 27(12):3801–3808. doi:10.1007/BF02595629.
15.
ShaJHiraiHUenoHMechanical properties of as-cast and directionally solidified Nb-Mo-W-Ti-Si in-situ composites at high temperatures. Metall Mater Trans A. 2003; 34(1):85–94. doi:10.1007/s11661-003-0210-1.
16.
OkamotoHMassalskiTB. Binary alloy phase diagrams. ASM International, Materials Park, OH, USA. 1990. https://doi.org/10.1002/adma.19910031215.
17.
ShaJYangCLiuJ.Toughening and strengthening behavior of an Nb–8Si–20Ti–6Hf alloy with addition of Cr. Scr Mater. 2010; 62(11):859–862. doi:10.1016/j.scriptamat.2010.02.023.
18.
ZhangSMZhouJRShaJB.Effect of Fe additions on microstructure and mechanical properties of a multi-component Nb–16Si–22Ti–2Hf–2Al–2Cr alloy at room and high temperatures. Intermetallics. 2015; 57:146–155. doi:10.1016/j.intermet.2014.10.013.
19.
GuoHGuoX.Microstructure evolution and room temperature fracture toughness of an integrally directionally solidified Nb–Ti–Si based ultrahigh temperature alloy. Scr Mater. 2011; 64(7):637–640. doi:10.1016/j.scriptamat.2010.12.008.
20.
MaLMYuanSNCuiRJInteractions between Nb-silicide based alloy and yttria mould during directional solidification. Int J Refract Met Hard Mater. 2012; 30(1):96–101. doi:10.1016/j.ijrmhm.2011.07.009.
21.
ChanKS.Alloying effects on fracture mechanisms in Nb-based intermetallic in-situ composites. Mater Sci Eng A. 2002; 329:513–522. doi:10.1016/S0921-5093(01)01502-7.
22.
YangCJiaLZhouCMicrostructural evolution and mechanical behaviors of an Nb-16Si-22Ti-2Al-2Hf alloy with 2 and 17 at. PCT Cr additions at room and/or high temperatures. Metall Mater Trans A. 2014; 45(11):4842–4850. doi:10.1007/s11661-014-2423-x.
23.
DavidsonDLChanKSAntonDL.The effects on fracture toughness of ductile-phase composition and morphology in Nb-Cr-Ti and Nb-Si in situ composites. Metall Mater Trans A. 1996; 27(10):3007–3018. doi:10.1007/BF02663850.
24.
MaCLTanYTanakaHMicrostructures and high-temperature strength of silicide-reinforced Nb alloys. MRS Online Proc Libr Arch. 2000:646. doi:10.1557/PROC-646-N5.39.1.
25.
LiuWShaJ.Effect of Nb and Nb5Si3 powder size on microstructure and fracture behavior of an Nb-16Si alloy fabricated by spark plasma sintering. Metall Mater Trans A. 2014; 45(10):4316–4323. doi:10.1007/s11661-014-2378-y.
26.
JinSMorrisJWZackayVF.Grain refinement through thermal cycling in an Fe-Ni-Ti cryogenic alloy. Metall Trans A. 1975; 6(1):141–149. doi:10.1007/BF02673682.
27.
AshbyMBluntFBannisterM.Flow characteristics of highly constrained metal wires. Acta Metall. 1989; 37(7):1847–1857. doi:10.1016/0001-6160(89)90069-2.
28.
ZhangSSLiuWShaJB.Microstructural evolution and mechanical properties of Nb-Si-Cr ternary alloys with a tri-phase Nb/Nb5Si3/Cr2Nb microstructure fabricated by spark plasma sintering. Prog Nat Sci2018; 28(05):626–634. doi:10.1016/j.pnsc.2018.09.001.
29.
RitchieROThompsonAW.On macroscopic and microscopic analyses for crack initiation and crack growth toughness in ductile alloys. Metall Mater Trans A. 1985; 16(2):233–248. doi:10.1007/BF02815305.
30.
HutchinsonJW.Plastic stress and strain fields at a crack tip. J Mech Phys Solids. 1968; 16(5):337–342. doi:10.1016/0022-5096(68)90021-5.
31.
LinGChanKS.Finite-element method simulation of effects of microstructure, stress state, and interface strength on flow localization and constraint development in Nb/Cr2Nb in situ composites. Metall Mater Trans A. 1999; 30(12):3239–3251. doi:10.1007/s11661-999-0234-2.
32.
ZhangW.Effect of grain refinement and alloying on the microstructure and room temperature fracture toughness of Nb-Si alloy (master degree dissertation). Beijing, China: Beihang University; 2018, p. 12.
