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Anomalous high-temperature strengthening in alpha Ti-Al solid-solution alloys

α Ti-Al 固溶合金的异常高温强化

基本信息

批准号：
07455252
负责人：
KOIKE Jun-ichi
金额：
$ 4.35万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455252/
关键词：
titanium alpha titanium high-temperature strength mechanical properties shrot range order

项目摘要

Tensile tests were performed in Ti- (7-13) at.%Al alloys. Temperature dependence and strain-rate dependence on deformation behavior were investigated. The possibility of the strength anomaly athigh temperatures was examined and its reason was discussed, based on the obtained results and the reported results for alloys with low Al concentrations.In the case of low-aluminum alloys containing less than 5mol%Al, the stress-strain rate relationship showed transition of the stress exponent from 3.5 to 4.6. The concentration dependence of flow stress was found to agree with theroreticaly predicted behavior by an ordinarly solid-solution herdening theory. In the case of concentrated alloys containing more than 5%Al, no transition was observed and the stress exponent was found to be a constant value of 3.5. The concentration dependence of flow stress was more than twice as large as the theoretically predicted calues, indicating the anomalous high-temperature strengthening in concentrated alpha Ti-Al solid-solution alloys.Structural analysis by X-day diffraction and transmission electron microscopy suggested the presence of a short-range ordered (SRO) structure. The possibility of the SRO formation was investigated by Monte Carlo calculation. It was found that the SRO structure became noticeable for a concetration of more than 5 mol%. The SRO tedency was also found to increase with increasing the aluminum concentration. Since the presence of the ordered structure increases flow stress, the anomalous strengthening in the Ti-Al alloy was found to be caused by the formation of the SRO structure.

在Ti-（7-13）at.%铝合金。温度依赖性和应变速率依赖性的变形行为进行了研究。根据实验结果和文献报道的低铝含量合金的实验结果，分析了高温强度异常的可能性，并讨论了其原因，当低铝含量低于5mol%Al时，应力-应变速率关系出现应力指数从3.5到4.6的转变。流动应力的浓度依赖性被发现同意理论预测的行为由普通的固溶体放牧理论。在含有超过5%Al的浓缩合金的情况下，没有观察到转变，并且发现应力指数为3.5的恒定值。流变应力的浓度依赖性是理论预测值的2倍以上，表明α Ti-Al固溶体合金在高温下具有反常的强化作用，X射线衍射和透射电子显微镜的结构分析表明存在短程有序（SRO）结构。通过Monte Carlo计算研究了SRO形成的可能性。结果表明，当浓度大于5mol%时，SRO结构变得明显。随着铝浓度的增加，SRO趋势也增加。由于有序结构的存在增加了流动应力，因此Ti-Al合金的异常强化是由SRO结构的形成引起的。