Abstract Microstructural evolution of a Nb–Si based ultrahigh temperature alloy during hot compression at different temperatures and strain rates has been investigated. The results show that the fraction of Nbss recrystallized grains is larger at higher temperatures or lower strain rates. The variation of Nbss grain size (d) with deformation temperatures (T) and strain rates ( e ˙ ) in steady-state flow conforms to a relation: ln d = 4.41 − 0.06 ( ln e ˙ + 577420 R T ) . Cracking has been significantly exacerbated and continuous dynamic recrystallization (CDRX) has been substantially restrained in Nb5Si3 when deformation temperature decreases from 1350 to 1250 °C or strain rate increases from 0.001 to 0.1 s−1. Nb5Si3 flakes have broken up into smaller particles via boundary splitting during hot deformation. Both the fragmentation of Nb5Si3 flakes and the composition homogenization in Nbss/Nb5Si3 eutectics have been accelerated with increase in deformation temperature from 1250 to 1350–1410 °C at 0.001 s−1, but slowed down at a higher temperature of 1500 °C and restrained at higher strain rates of 0.01–0.1 s−1. The correlation between microstructural evolution and the strain rate sensitivity has been discussed.

中文翻译：

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变形温度和应变速率对热压缩 Nb-Si 基超高温合金组织演变的影响

摘要 研究了 Nb-Si 基超高温合金在不同温度和应变速率下热压缩过程中的显微组织演变。结果表明，在较高温度或较低应变速率下，Nbss 再结晶晶粒的比例较大。Nbss 晶粒尺寸 (d) 随变形温度 (T) 和应变速率 (e·) 在稳态流动中的变化符合以下关系：ln d = 4.41 − 0.06 (ln e ˙ + 577420 RT)。当变形温度从 1350 °C 降低到 1250 °C 或应变速率从 0.001 增加到 0.1 s-1 时，Nb5Si3 的开裂显着加剧并且连续动态再结晶 (CDRX) 得到显着抑制。Nb5Si3 薄片在热变形过程中通过边界分裂分解成更小的颗粒。Nb5Si3 薄片的破碎和 Nbss/Nb5Si3 共晶中的成分均匀化都随着变形温度在 0.001 s-1 时从 1250 到 1350-1410 °C 的增加而加速，但在 1500 °C 的较高温度下减慢并受到抑制在 0.01–0.1 s-1 的较高应变率下。已经讨论了微观结构演变和应变率敏感性之间的相关性。