Abstract Powder metallurgy (PM) Ti–22Al–25Nb (at.%) alloy was prepared by spark plasma sintering under the conditions of 950 °C/80 MPa/10 min. Isothermal unidirectional compression experiments of the PM Ti–22Al–25Nb alloy were completed on the Gleeble-3500 thermal–mechanical simulator at temperature and strain rate ranges of 920 °C–1100 °C and 0.001–10s−1, respectively, and a total height reduction of 50%. The flow characteristics were described by the establishment of constitutive models belonging to the (α2+β/B2+O) three-phase (920 °C–980 °C) and (α2+B2) two-phase (1010 °C–1070 °C) regions. The three-dimensional (3D) hot processing maps regarding temperatures, strain rates and strains were obtained. The optimum processing parameters (temperature and strain rate) were determined. The microstructures of the deformed specimens under various conditions were analyzed to characterize the corresponding deformation mechanisms. Moreover, electron backscattered diffraction (EBSD) measurements were employed to study the mechanisms of DRX. It was determined that the deformation activation energies of the PM alloy corresponding to the (α2+β/B2+O) phase and (α2+B2) phase regions were 763.969 and 685.587 kJ mol−1, respectively. In addition, the results proved that the proposed 3D hot processing maps could reveal the deformation mechanism and microstructural evolution of the PM Ti–22Al–25Nb alloy during hot processing. The main softening mechanisms in the stability regions were dynamic recrystallization (DRX) and lamellar dynamic globularization. The deformation mechanisms of the unstable domains identified from the 3D instability maps were adiabatic shear bands and flow localization.

中文翻译：

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使用 3D 加工图表征粉末冶金 Ti-22Al-25Nb 合金的热变形行为

摘要 通过放电等离子烧结在 950 °C/80 MPa/10 min 条件下制备粉末冶金 (PM) Ti-22Al-25Nb (at.%) 合金。PM Ti-22Al-25Nb 合金的等温单向压缩实验在 Gleeble-3500 热机械模拟器上完成，温度和应变速率范围分别为 920°C-1100°C 和 0.001-10s-1，总共高度降低 50%。通过建立属于 (α2+β/B2+O) 三相 (920 °C–980 °C) 和 (α2+B2) 两相 (1010 °C–1070) 的本构模型来描述流动特性°C) 区域。获得了关于温度、应变率和应变的三维 (3D) 热加工图。确定了最佳加工参数（温度和应变率）。分析了不同条件下变形试样的显微组织，以表征相应的变形机制。此外，采用电子背散射衍射 (EBSD) 测量来研究 DRX 的机制。确定对应于(α2+β/B2+O)相和(α2+B2)相区域的PM合金的变形活化能分别为763.969和685.587 kJ mol-1。此外，结果证明所提出的 3D 热加工图可以揭示 PM Ti-22Al-25Nb 合金在热加工过程中的变形机制和显微组织演变。稳定区的主要软化机制是动态再结晶（DRX）和层状动态球化。