Abstract The paper describes the microstructure evolution by high-temperature compression of a high Nb-containing TiAl alloy. The paper extends a previous publication [Song, et al. Intermetallics 109 (2019) 91–96], in which a unique twin-like morphology in the α2 (Ti3Al) phase was reported. However, the origin of these structures could not be clarified without doubt. The present study is focused on phase transformations that in this multiphase alloy can be associated with deformation. Particular attention is paid to local transformations of the α2 phase into O phase or ω-related phases, which, because of structural and chemical similarity of these phases with α2, can easily occur and could mistakenly be considered as a twin structure. The details of the atomic processes involved are elucidated by electron microscopy. Given the large shufflings and the atomic site interchanges required for the operation of this twinning system, it is concluded that twinning of the α2 phase is a diffusive-displacive process. Within the α2 phase, ωo is heterogeneously nucleated. The nucleation sites are defect-rich areas, which are subjected to high local stresses. The study strongly emphasizes the close relationship between high-temperature deformation and phase transformations in multiphase titanium aluminide alloys.

中文翻译：

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高含铌 TiAl 合金层状结构高温变形和相变机制的新见解

摘要 本文描述了一种高含 Nb TiAl 合金在高温压缩下的显微组织演变。该论文扩展了之前的出版物 [Song, et al. 金属间化合物 109 (2019) 91-96]，其中报道了 α2 (Ti3Al) 相中独特的孪晶形貌。然而，这些结构的起源不能毫无疑问地澄清。本研究的重点是在这种多相合金中可能与变形相关的相变。特别注意 α2 相向 O 相或 ω 相关相的局部转变，由于这些相与 α2 的结构和化学相似，很容易发生并可能被错误地认为是孪晶结构。所涉及的原子过程的细节由电子显微镜阐明。鉴于此孪生系统运行所需的大改组和原子位点互换，可以得出结论，α2 相的孪生是一个扩散位移过程。在 α2 相内，ωo 是异相成核的。成核位置是缺陷丰富的区域，受到高局部应力。该研究强烈强调了多相铝化钛合金的高温变形与相变之间的密切关系。