Effect of Nb Addition on Oxide Formation on Ti-xNb Alloys
Effect of Nb Addition on Oxide Formation on Ti-xNb Alloys
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DOI：
10.2320/matertrans.mt-m2019136
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发表时间：
2019-01-01
影响因子：
1.2
通讯作者：
Miura-Fujiwara, Eri
中科院分区：
文献类型：
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作者：
Ogawa, Yuya;Miura-Fujiwara, Eri
据报道，Ti-29Nb-13Ta-4.6Zr(TNTZ)合金在高温氧化过程中形成致密的氧化层，而Cp Ti则形成由金红石单分子层和空泡层组成的多层氧化物。由于TNTZ致密的氧化层由多个氧化相组成，至少有金红石型的TiO2O7和TiNb2O7，这种形态变化可能主要是由于Nb的加入引起的。本文研究了Ti-xNb合金(x=1，5，7，10，13，15，18，20，23，26，28，30和32mol%)在1273K下3.6K的高温氧化行为，探讨了Nb对其高氧化行为和氧化物组织的影响。从扫描电子显微镜的观察结果可以看出，从1%Nb到10%Nb，在Ti-xNb衬底上形成了一层具有空洞层的氧化层。然而，在Ti-13Nb上证实了氧化层的致密化。当Nb含量达到32mol%时，形成致密的氧化层。X射线衍射结果表明，从1%Nb到10%Nb，只有金红石型的TiO2O2生成；从13mo%Nb到32mo%Nb，TiNb2O7和TiNb2O7都形成了金红石型的二氧化钛。这些结果表明，致密氧化层的形成归因于从TiO2O7到TiNb2O7的相分离。在10mol%Nb之前，Nb的加入抑制了氧化层的厚度，但从13mol%Nb开始，随着Nb含量的增加，氧化层的厚度增加。当Nb含量为20mol%时，氧化层的抗剥落性能最好。各种Ti-xNb合金的氧化物生长速率的结果表明，Nb在钛中的扩散可能是致密氧化层形成的决定过程。
It had been reported that Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy forms a dense oxide layer by high-temperature oxidation whereas CP Ti forms a multilayered oxide consisted of rutile monolayers and void layer. This morphological change is supposed to be mainly caused by Nb addition in Ti since the dense oxide layer of TNTZ consists of multiple oxide phases, at least with rutile TiO2 and TiNb2O7. In this study, high-temperature oxidation at 1273 K for 3.6 ks in the air of Ti-xNb alloys (x = 1, 5, 7, 10, 13, 15, 18, 20, 23, 26, 28, 30 and 32 mol%) was investigated to discuss the effect of Nb addition to Ti on its high-oxidation behavior, and on its oxide microstructure. From the results of the SEM observation, an oxide layer with a void layer was formed on Ti-xNb substrate from 1 mol%Nb up to 10 mol%Nb. However, densification of the oxide layer was confirmed at Ti-13Nb. Then, the dense oxide layer was formed up to 32 mol%Nb. XRD results indicated that only rutile-type TiO2 was identified from 1 mol%Nb up to 10 mol%Nb, then both TiO2 and TiNb2O7 were formed from 13 mol%Nb to 32 mol%Nb. These results indicate that dense oxide layer formation attributes to phase separation from TiO2 to TiNb2O7. Until 10 mol%Nb, the thickness of oxide layer was suppressed by Nb addition, whereas the layer thickness increased with increasing Nb content from 13 mol%Nb. The maximum exfoliation resistance of the oxide layer was obtained at 20 mol%Nb. The results of oxide growth rate at each Ti-xNb alloys suggested that Nb diffusion in Ti may rate-determining process of the dense oxide layer formation.