Decomposition of the βo phase to the P63/mcm, hP18 structure in Nb–(24–36)Ti–40Al alloys
Decomposition of the βo phase to the P63/mcm, hP18 structure in Nb–(24–36)Ti–40Al alloys
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DOI：
10.1016/j.actamat.2009.06.006
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发表时间：
2009-09
期刊：
影响因子：
9.4
通讯作者：
K. Leonard;R. Tewari;A. Arya;J. C. Mishurda;G. Dey;V. Vasudevan
中科院分区：
文献类型：
--
作者：
K. Leonard;R. Tewari;A. Arya;J. C. Mishurda;G. Dey;V. Vasudevan
在研究Nb-Ti-Al体系相平衡的过程中，在三个Nb-（24-36）Ti-40 Al（at.%）中观察到有序B2/β相分解为有序ω型产物。合金在700°C下老化和高温淬火后。使用透射电子显微镜和X射线衍射技术，该相被确定为P63/mcm结构的hP 18变体，晶格参数ao= 7.96 Å和co= 5.57 Å，ao≈aβ6和co≈aβ3与母相β相的关系。进行从头计算以估计各种相的形成能量，并且还建立Nb在hP 18相的稳定中的作用。这种结构的演变和稳定性的结果，并进行了讨论。
During the course of investigation of the phase equilibria in the Nb–Ti–Al system, decomposition of the ordered B2/βophase to an ordered ω-type product was observed in three Nb–(24–36)Ti–40Al (at.%) alloys following aging at 700°C and on quenching from high-temperatures. Using transmission electron microscopy and X-ray diffraction techniques, this phase was determined as the hP18 variant of the P63/mcm structure, with lattice parameters ao=7.96Å and co=5.57Å, and an ao≈aβ6 and co≈aβ3 relationship with the parent βophase. Ab initio calculations were carried out to estimate the energy of formation of various phases and to also establish the role of Nb in the stabilization of the hP18 phase. The results of the evolution and stability of this structure are presented and discussed.