Effect of Ti addition on the thermal expansion anisotropy of Mo5Si3
Effect of Ti addition on the thermal expansion anisotropy of Mo5Si3
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DOI：
10.1016/j.actamat.2017.02.066
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发表时间：
2017-06
期刊：
影响因子：
9.4
通讯作者：
M. Azim;H. Christ;B. Gorr;T. Kowald;Olena Lenchuk;K. Albe;M. Heilmaier
中科院分区：
文献类型：
--
作者：
M. Azim;H. Christ;B. Gorr;T. Kowald;Olena Lenchuk;K. Albe;M. Heilmaier
(Mo，Ti)5Si3(Tl)是新型Mo-Si-Ti复合材料的关键组元，与目前最先进的镍基高温合金相比，(Mo，Ti)5Si3(T1)具有优异的蠕变性能和较低的密度。然而，纯Mo5Si3表现出两个缺点：(I)在1650℃以下没有抗氧化性；(Ii)异常高的热膨胀各向异性(CTE(C)/CTE(A)=62.2)。通过钛的微合金化，可以缓解抗氧化性的不足。这项研究的目的是为了深入了解不同的钛浓度在热膨胀系数上的变化，以便在低热膨胀系数失配和较好的抗氧化性的T1相中推导出合适的钛含量。因此，主要由全花样Rietveld分析修正的高温X射线衍射法得到的实验结果得到了密度泛函理论计算的证实和解释。对于Ti>；12.5%，注意到明显的16k位置偏好。Mo37.5Si30Ti的CTE各向异性(at.%)可降低到1.34。
(Mo,Ti)5Si3(T1) is a key component of novel Mo-Si-Ti composites which show superior creep resistance and a lower density than state-of-the-art Ni-based superalloys. However, pure Mo5Si3exhibits two shortcomings: (i) no oxidation resistance below 1650 °C and (ii) unusual high thermal expansion anisotropy (CTE(c)/CTE(a) = 2.2). The lack of oxidation resistance could be alleviated by Ti macroalloying. The aim of this study is to develop an in-depth understanding of varying Ti concentrations on the CTE in order to deduce appropriate Ti amounts in the T1 phase with low CTE mismatch and decent oxidation resistance. Therefore, experimental results, primarily obtained from high temperature X-ray diffraction refined by full pattern Rietveld analysis, were confirmed and elucidated by density-functional theory calculations. A clear 16k site preference is noted for Ti>12.5 at.%. The CTE anisotropy for Mo37.5Si30Ti(at.%) can be reduced to 1.34.