合金元素对Nb性能的影响
合金元素 密度 高温强度 蠕变抗力 室温塑性 室温韧性 抗氧化性 Si(2.33) W(19.3) Mo(10.2) Hf(13.1) Ti(4.5) Cr(7.19) Zr(6.49) Ge(5.32) B(2.34)
C
（一）航空领域中使用的Nb-Si合金
1、 Nb5Si3 High melting point: 2520 ºC Moderate density: 6.1 g·cm-3 Toughness: KIC= 1~3 MPa·m1/2
PJhUasTe EMI and TNObSHS/UNbK5USi3Uni. In Japan)
Target Appl. TNebm5Sip3>e5r0a%ture: 1500°C KAQlloyed with <h1i0ghMPWama1/n2 d Mo
DHucitgilhitystrengthze:ro
Good strength and oxidation resistance at HT; Brittle, difficult to process
➢Cnsity, good strength at HT; Poor oxidation resistance & Difficult to process
Nb及合金的特点
2、 韧化 合金化-------Hf、Ti元素对NbSS韧化 减少Si含量-----Si减少， Nb5Si3减少，塑韧性上升 改变组织形态----Mo，W等元素倾向形成片状组 织改善NbSS和Nb5Si3形态
3、抗氧化：基体抗氧化+涂层 Cr------NbCr2有利于抗氧化 Si-------SiO2有利于抗氧化，Ti有利于抗氧化
NbSS Good ductility at RT
NbSS + Nb5Si3
Nb-Si binary diagram
Alloys with NbSS and Nb5Si3: Can be stable up to very high
temperature ( 1670ºC)
国内外研究现状
Compositions
S6tr5en0gMthPa at 15~90500°MCPa at 1400°C
for creep resistance 6.5~8 g/cm3
for oxidation resistance 6.5~7.5 g/cm3
NbSS/Nb3Si(Nb5Si3) Nb3Si(Nb5Si3)>50% 6~20MPam1/2
材料科学与工程前沿
航空航天高温结构材料
High-Temperature Structural Materials in Aerospace
北京航空航天大学 材料学院
六、Nb-Si基高温合金
Superalloy can not meet design requirements of aeroengines
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OHxiidg. hRedsiesntasnictey:
Behaviors
Nb-Si-Mo-W-Ti (AIST in Japan)[1N] b-Si-Ti-Hf-Mo (GE)[2]
Nb-Si-Ti-Cr-Hf -B-Ge(GE)[3]
for high temperature strength
DNenbsi-t1y 8Si-15W9~1-01g0/Mcm3o-10Ti (AIST,
What materials could be qualified？
Temperature℃
1650
1450
1320℃
T/W ratio 20
1250 1050
Single-cystal superalloy DS- superalloy
T/W ratio 15
Wrought superalloy
T/W ratio 10
Nb及合金的特点
固溶强化— Mo, W, Hf, Cr, Al, Si 等能与Nb形成置 换固溶体，W、Mo最强
金属间化合物—NbSS/Nb3Al (Nb-Al二元合金)和 NbSS/Nb5Si3（Nb-Si二元合金)，
NbSS 提供韧性而Nb3Al和Nb5Si3提供高温强度 韧/脆两相结构，NbSS：Solid solution，固溶体 特殊热加工—定向凝固（DS: directional solidification），热等静压(HIP: hot isostatic pressing), 热挤出（HE: hot extrusion), 粉末冶金等
NbSS/Nb5Si3/Cr2Nb Nb5Si3>40%, Cr2Nb>25%
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Typical alloy, 370MPa at 1200°C
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Poor toughne~s6s5,0MduPcataitli1t5y0a0°nCd
Moixni.dcaretieopnratrees~is1t.a4×n1c0e-7 at 1400°C & 200MPa 5~1.2×10-8 at 1200°C & 140MPa
元素周期表
Nb及合金的特点
➢Nb具有良好的室温塑韧性，机械加工性和高 的熔点（2447ºC，超过Ni约1000ºC)，以及热 传导率大, 热膨胀系数小, 弹性系数大, 密度小, 到熔点都保持稳定b.c.c. ➢承温能力：1200~1700ºC. ➢可以采用多种方式强化、韧化和改善抗氧化
性: 1、强化
➢Nb/Si based intermetallics (composites)
Good formability, and Comprehensive advantage in mechanical performance at HT Poor ductility and oxidation resistance
850
Cast superalloy
650
T/W ratio 8
1940
1960 1980
2000 2020
T/W :Thrust to Weight Ratio for Aero-Engine
Potential candidates are as follows
➢Ceramics matrix composites