High-temperature oxidation behavior of directionally solidified(DS) Nb-Si-based alloys with Re additions was investigated at 1200 and 1250℃,respectively.Microstructures and high-temperature oxidation behavior of the ...High-temperature oxidation behavior of directionally solidified(DS) Nb-Si-based alloys with Re additions was investigated at 1200 and 1250℃,respectively.Microstructures and high-temperature oxidation behavior of the alloys were characterized.Results show that the microstructures in vertical section of Nb-24Ti-15Si-4Cr-2Al-2Hf-xRe(x=0,1,3;at%) alloys grow parallel to the withdrawal direction and the cross section exhibits bud-like structures.The bud-like structures become finer with more Re additions.The weight gain of the Nb-24Ti-15Si-4Cr-2Al-2Hf-3Re alloy after oxidation at 1200℃ for 100 h is 198.1 mg·cm^(-2),and it is a bit higher at 1250℃.The other two alloys perform somewhat worse.The influence of Re addition on the oxidation resistance at 1250℃ is more significant than that at 1200 ℃.Although Re addition does not benefit obviously the high-temperature oxidation resistance of the DS samples,it does not compromise the oxidation resistance with a certain amount of Re additions in contrast with the alloy without Re addition.展开更多
Microstructures and oxidation behaviors of four Dy-doped Nb-Si-based alloys at 1250 ℃ were investigated. The nominal compositions of the four alloys are Nb-15Si-24Ti-4Cr-2Al-2Hf-xDy （at.%）, where x = 0, 0.05, 0.10 ...Microstructures and oxidation behaviors of four Dy-doped Nb-Si-based alloys at 1250 ℃ were investigated. The nominal compositions of the four alloys are Nb-15Si-24Ti-4Cr-2Al-2Hf-xDy （at.%）, where x = 0, 0.05, 0.10 and 0.15, respectively. Results showed that the four alloys all consisted of Nbss, αNbsSi3 and γNbsSi3, and the addition of Dy produced no obvious effect on the phase constitution and the microstructures of Nb-Si-based alloys. After oxidation at 1250 ℃ for 58 h, it was found that the addition of Dy accelerated the oxidation rate of Nb-Si-based alloys and caused a larger weight gain, accompanied by the formation of a more porous and less protective oxide scale. The oxides of Nb2O5, Ti2Nb10O29, TiNb2O7, Ti0.4Cr0.3Nb0.302 and glassy SiO2 were formed on Dy-doped Nb-Si-based alloys. The high- temperature oxidation mechanism of Dy-doped Nb-Si-based alloys was discussed.展开更多
The microstructure and oxidation behavior of directionally solidified(DS) Nb-15 Si-24 Ti-4 Cr-2 Al-2 Hf alloys with separate vanadium,tantalum,tungsten and zirconium additions were investigated by X-ray diffraction(XR...The microstructure and oxidation behavior of directionally solidified(DS) Nb-15 Si-24 Ti-4 Cr-2 Al-2 Hf alloys with separate vanadium,tantalum,tungsten and zirconium additions were investigated by X-ray diffraction(XRD),electron probe microanalyzer(EPMA) equipped with wave-dispersive spectroscopy(WDS),scanning electron microscopy(SEM) and transmission electron microscopy(TEM) equipped with an energy-dispersive spectroscopy(EDS).Results show that the five alloys are all composed of primary(Nb,Ti) solid solution((Nb,Ti)ss)phase and eutectic(Nb,Ti)ss/(Nb,Ti)_(5) S_(3) structure.After oxidation at 1250℃ for 100 h in air,the surfaces of the five alloys are covered by the oxides of Nb_(2)O_(5),TiNb_(2) O_(7),Ti_(2) Nb10O29,TiO_(2) and amorphous SiO_(2).It is found that the alloying elements of V and W are detrimental for oxidation resistance and the addition of Ta has no obvious effect.Zr addition obviously benefits the oxidation resistance at high temperature,by decreasing the weight gain from 242.75 to184.83 mg·cm^(-2).The oxidation mechanism of Nb-Sibased alloys and the effects of different alloying elements on the oxidation resistance of Nb-Si-based alloys were discussed.展开更多
基金financially supported by the National Nature Science Foundation of China (No.51471013)。
文摘High-temperature oxidation behavior of directionally solidified(DS) Nb-Si-based alloys with Re additions was investigated at 1200 and 1250℃,respectively.Microstructures and high-temperature oxidation behavior of the alloys were characterized.Results show that the microstructures in vertical section of Nb-24Ti-15Si-4Cr-2Al-2Hf-xRe(x=0,1,3;at%) alloys grow parallel to the withdrawal direction and the cross section exhibits bud-like structures.The bud-like structures become finer with more Re additions.The weight gain of the Nb-24Ti-15Si-4Cr-2Al-2Hf-3Re alloy after oxidation at 1200℃ for 100 h is 198.1 mg·cm^(-2),and it is a bit higher at 1250℃.The other two alloys perform somewhat worse.The influence of Re addition on the oxidation resistance at 1250℃ is more significant than that at 1200 ℃.Although Re addition does not benefit obviously the high-temperature oxidation resistance of the DS samples,it does not compromise the oxidation resistance with a certain amount of Re additions in contrast with the alloy without Re addition.
基金financially supported by the National Natural Science Foundation of China (Nos. 51471013, 51571004 and 51404017)
文摘Microstructures and oxidation behaviors of four Dy-doped Nb-Si-based alloys at 1250 ℃ were investigated. The nominal compositions of the four alloys are Nb-15Si-24Ti-4Cr-2Al-2Hf-xDy （at.%）, where x = 0, 0.05, 0.10 and 0.15, respectively. Results showed that the four alloys all consisted of Nbss, αNbsSi3 and γNbsSi3, and the addition of Dy produced no obvious effect on the phase constitution and the microstructures of Nb-Si-based alloys. After oxidation at 1250 ℃ for 58 h, it was found that the addition of Dy accelerated the oxidation rate of Nb-Si-based alloys and caused a larger weight gain, accompanied by the formation of a more porous and less protective oxide scale. The oxides of Nb2O5, Ti2Nb10O29, TiNb2O7, Ti0.4Cr0.3Nb0.302 and glassy SiO2 were formed on Dy-doped Nb-Si-based alloys. The high- temperature oxidation mechanism of Dy-doped Nb-Si-based alloys was discussed.
基金financially supported by the National Nature Science Foundation of China(Nos.51471013 and51571004)。
文摘The microstructure and oxidation behavior of directionally solidified(DS) Nb-15 Si-24 Ti-4 Cr-2 Al-2 Hf alloys with separate vanadium,tantalum,tungsten and zirconium additions were investigated by X-ray diffraction(XRD),electron probe microanalyzer(EPMA) equipped with wave-dispersive spectroscopy(WDS),scanning electron microscopy(SEM) and transmission electron microscopy(TEM) equipped with an energy-dispersive spectroscopy(EDS).Results show that the five alloys are all composed of primary(Nb,Ti) solid solution((Nb,Ti)ss)phase and eutectic(Nb,Ti)ss/(Nb,Ti)_(5) S_(3) structure.After oxidation at 1250℃ for 100 h in air,the surfaces of the five alloys are covered by the oxides of Nb_(2)O_(5),TiNb_(2) O_(7),Ti_(2) Nb10O29,TiO_(2) and amorphous SiO_(2).It is found that the alloying elements of V and W are detrimental for oxidation resistance and the addition of Ta has no obvious effect.Zr addition obviously benefits the oxidation resistance at high temperature,by decreasing the weight gain from 242.75 to184.83 mg·cm^(-2).The oxidation mechanism of Nb-Sibased alloys and the effects of different alloying elements on the oxidation resistance of Nb-Si-based alloys were discussed.
