Microstructures, properties and high-temp oxidation behaviors of Ti-45Al-8Nb-xHf alloys
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摘要: 采用氩气保护真空感应熔炼工艺制备了Ti-45Al-8Nb-xHf (x=0.5、1.0、1.5、2) 合金,利用金相显微镜(OM)、扫描电镜(SEM)、能谱仪 (EDS)、X射线衍射仪(XRD)、万能试验机等研究了合金显微组织、压缩性能和抗氧化性能。结果表明,Hf元素含量的增加能够保持和细化合金显微组织,延缓高温下组织的转变,使合金抗压强度和压缩率分别提高到1923 MPa和25.7%,升幅30%以上,具有显著强化效应。合金在
1000 ℃氧化时具有稳定TiO2+Nb2O5的氧化亚层,以平直界面氧化生长,氧化扩散层尺寸稳定小于85 μm,氧化质量呈线性变化,氧化速率曲线下降并最终达到稳定氧化阶段。适量Hf的添加有利于强化合金的力学性能和高温抗氧化性能。-
关键词:
- Ti-45Al-8Nb-xHf /
- 力学性能 /
- 显微组织 /
- 抗氧化性
Abstract: Ti-45Al-8Nb-xHf (x=0.5, 1.0, 1.5, 2) alloys were prepared by argon-protected vacuum induction melting process, and the microstructure, compressive properties and antioxidant properties of the alloys were investigated by using optical microscope (OM), scanning electron microscope (SEM), energy spectrum spectrometry (EDS), X-ray diffraction (XRD) and universal testing machine. The results show that the increase of Hf element content can maintain and refine the microstructure of the alloys, delay the transformation of the tissue at high temperature, and increase the compressive strength and compression ratio of the alloys to1923 MPa and 25.7%, respectively, with an increase of more than 30%, which has a significant strengthening effect. The alloys have a stable TiO2+Nb2O5 oxide sublayer when oxidized at1000 ℃, which grows by oxidation at a flat interface, the size of the oxide diffusion layer is stable less than 85 μm, the oxidized quality changes linearly, and the oxidation rate curve decreases and finally reaches the stable oxidation stage. The addition of appropriate amount of Hf is conducive to strengthening the mechanical properties of the alloys and high-temperature oxidation resistance.-
Key words:
- Ti-45Al-8Nb-xHf /
- mechanical properties /
- microstructure /
- oxidation resistance
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表 1 TiAl基多元合金铸锭化学成分
Table 1. Chemical composition of test alloys with different Hf contents
% Al Nb xHf Ti 45.0 8.0 0.5、1.0、1.5、2.0 Bal. 表 2 合金
1000 ℃氧化动力学参数Table 2. Kinetic parameters of oxidation at
1000 ℃合金 n kn R2 t/h Ti-45Al-8Nb-0.5Hf 1.659 0.602 0.9963 0~100 Ti-45Al-8Nb-1.0Hf 1.640 0.609 0.9772 0~100 Ti-45Al-8Nb-1.5Hf 1.944 0.522 0.9947 0~100 Ti-45Al-8Nb-2.0Hf 1.914 0.514 0.9985 0~100 -
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