The behavior of a VTI-4 (Ti–22Al–25Nb) alloy during hot compression at a strain rate of ~2.5 s^–1 is studied. Hot compression to a strain of 65% is carried out in the temperature range 850–1020°C, covering two phase regions β + Ο and β + α₂. Hot compression results in the dissolution and spheroidization of lamellar O and α₂ phases in the severe deformation zone. X-ray diffraction analysis does not reveal any qualitative changes in the phase composition after deformation. Energy dispersive X-ray spectroscopy (EDS) analysis conducted on a transmission electron microscope indicates niobium depletion of the O phase when the hot compression temperature increases or during compression. Niobium-depleted zones form near interphase boundaries during the dissolution and spheroidization of lamellar-shaped O and α₂ phases. The dissolution and spheroidization process includes two stages. The first stage involves defect accumulation in the O-phase and α₂-phase lattices, and it is accompanied by a simultaneous increase in the temperature due to deformation-induced heating. The second stage icludes niobium redistribution between the β matrix and the phase in defective sites, which leads to phase dissolution and spheroidization.

中文翻译：

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高速热压缩过程中VTI-4（Ti–22Al–25Nb）合金的相变和结构转变

研究了VTI-4（Ti–22Al–25Nb）合金在热变形过程中的应变速率为〜2.5 s ^–1的行为。热压缩到65％的应变的温度范围内850-1020℃下进行，覆盖两个相区域β+Ο和β+α ₂。热压缩结果，在溶解和片状的O球化和α ₂严重变形区的相。X射线衍射分析未显示出变形后相组成的任何质变。在透射电子显微镜上进行的能量色散X射线光谱（EDS）分析表明，当热压缩温度升高或压缩过程中，O相的铌耗尽。铌耗尽区形成的层状形澳溶解和球化过程中和α附近相间边界_2个相。溶解和球化过程包括两个阶段。第一阶段涉及在O形相和α缺陷积累₂相晶格，并伴随着由于变形引起的加热而使温度同时升高。第二阶段包括在缺陷部位的β基体和相之间的铌重新分布，这导致相溶解和球化。