Phase transformation and decomposition mechanisms of the βo(ω) phase in cast high Nb containing TiAl alloy
Phase transformation and decomposition mechanisms of the βo(ω) phase in cast high Nb containing TiAl alloy
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DOI：
10.1016/j.jallcom.2014.07.130
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发表时间：
2014-12
影响因子：
6.2
通讯作者：
Lin Song;X. J. Xu;L. You;Yongfeng Liang;J. Lin
中科院分区：
文献类型：
--
作者：
Lin Song;X. J. Xu;L. You;Yongfeng Liang;J. Lin
High Nb containing TiAl (Nb–TiAl) alloys are thought to be used at higher temperatures than the conventional TiAl alloys, typically up to 900 °C. However, the βoand ω-related phases are usually induced by Nb-segregation in cast alloys. It is important to reveal the transformation mechanisms of the βoand ω-related phases at elevated temperatures for better design of the alloy and optimizing the heat treatment process. In this study, the interconversion mechanism between the ordered ω and βophases and the decomposition process of the βophase in the as-cast Ti–45Al–8.5Nb–0.2W–0.2B–0.02Y (at.%) alloy are studied. The ωoparticles grow up by richening Nb and rejecting W to the surrounding βomatrix. The βoand ωophase are separated after annealing at 900 °C, whereas the ωophase dissolves into the βomatrix after annealing at 950 °C. The βoand ωophases undergo βo→ γ and ωo(B82structure) → D88-ω (D88structure) → γ transformation respectively during annealing, and the βo→ γ transformation can be achieved in several ways. The ωoparticles with a high Nb content act as pinning points at the βo/γ boundaries during the βo→ γ transformation. The corresponding mechanisms of the transformations mentioned above are discussed.
