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首页> 外文会议>Symposium Proceedings vol.842; Symposium on Integrative and Interdisciplinary Aspects of Intermetallics; 20041129-1201; Boston,MA(US) >Creep Behavior and Microstructural Stability of Ti-46Al-9Nb with Different Microstructures
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Creep Behavior and Microstructural Stability of Ti-46Al-9Nb with Different Microstructures

机译：不同组织Ti-46Al-9Nb的蠕变行为和组织稳定性

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摘要

In this paper the creep behavior and the microstructural stability of Ti-46Al-9Nb (in at.%) sheet material were investigated in the temperature range of 700℃ to 815℃. The study involves three different types of microstructure, namely fully lamellar with narrow lamellar spacing, duplex and massively transformed. Short-term creep experiments conducted at 700℃ and 225 MPa confirmed that the lamellar microstructure with narrow lamellar spacing exhibits a much higher creep resistance when compared to the massively transformed and duplex ones. During long-term creep tests up to 1500 hours stress exponents (in the range of 4.4 to 5.8) and apparent activation energies (of about 4 eV) have been estimated by means of load and temperature changes, respectively. Both, stress exponents and activation energies suggest that under the applied conditions diffusion-assisted climb of dislocations is the dominant creep mechanism. The thermal stability of the different microstructures under various creep conditions has been analyzed by electron microscopy and X-ray diffraction. Our investigations revealed considerable ' stress and temperature induced microstructural changes which are reflected in the dissolution of the α_2 phase accompanied by precipitation of a Ti/Nb - rich phase situated at grain boundaries. This phase was identified as a ω-related phase with B8_2-type structure. It was shown, that in particular the duplex microstructure is prone to such microstructural instabilities.
机译：本文研究了Ti-46Al-9Nb（原子％）片材在700℃至815℃温度范围内的蠕变行为和显微组织稳定性。该研究涉及三种不同类型的微观结构，即具有层状间距窄的全层状结构，双相结构和大量转变的结构。在700℃和225 MPa下进行的短期蠕变实验证实，与大规模转化和双相转变相比，具有窄层间距的层状微观结构具有更高的抗蠕变性。在长期蠕变测试中，分别通过负载和温度变化估算了长达1500小时的应力指数（在4.4至5.8范围内）和表观活化能（约4 eV）。应力指数和活化能都表明，在应用条件下，位错的扩散辅助爬升是主要的蠕变机制。通过电子显微镜和X射线衍射分析了不同微观结构在各种蠕变条件下的热稳定性。我们的研究表明，相当大的'应力和温度引起的微观结构变化反映在α_2相的溶解过程中，伴随着位于晶界处的富Ti / Nb相的析出。该相被确定为具有B8_2型结构的ω相关相。结果表明，特别是双相微结构易于出现这种微结构不稳定性。

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