Abstract Phase transformations in near Ti2AlNb alloy occurring on cooling of 10 °C min−1 from 1020 °C were studied in situ using high energy X-ray diffraction and electrical resistivity measurements coupled with simultaneous dilatometric analysis. From Rietveld refinement of X-ray data, it was established that high temperature range from about 870 to 1020 °C contained partially ordered β phase. The degree of long-range order was of 0.6 at 1020 °C and decreased slowly with temperature decrease and fast when O-phase was formed. The formation of O-Ti2AlNb phase started from about 870 °C and consisted of two stages: (i) fast transformation of partially ordered β into O phase at higher temperatures followed by (ii) slow transformation of fully disordered β into O-phase at lower temperatures. The appearance of O-phase was accompanied by important volume decrease of the alloy as recorded using dilatometry as well as by a decrease of electrical resistivity. The transformations temperatures revealed by high energy X-ray diffraction, dilatometry and electrical resistivity were in good agreement. The obtained results were discussed using thermodynamic simulations carried out with Thermo-Calc software and TCTI2 database.

中文翻译：

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Ti2AlNb 合金相变的同步加速器 X 射线衍射、膨胀法和电阻率的联合原位研究

摘要 使用高能 X 射线衍射和电阻率测量以及同步膨胀分析，原位研究了近 Ti2AlNb 合金在从 1020°C 冷却 10°C min-1 时发生的相变。根据 X 射线数据的 Rietveld 精修，确定约 870 至 1020 °C 的高温范围包含部分有序的 β 相。长程有序度在1020°C时为0.6，随温度下降缓慢下降，O相形成时迅速下降。O-Ti2AlNb 相的形成从大约 870 °C 开始，由两个阶段组成：（i）部分有序的 β 在较高温度下快速转变为 O 相，然后（ii）完全无序的 β 在高温下缓慢转变为 O 相较低的温度。O 相的出现伴随着合金的显着体积减小，如使用膨胀测定法记录的那样以及电阻率的减小。高能 X 射线衍射、膨胀法和电阻率显示的转变温度非常一致。使用 Thermo-Calc 软件和 TCTI2 数据库进行的热力学模拟讨论了获得的结果。