Flow curve and microstructure of Ni–30Cu alloy were studied after hot compression at 1150 °C and strain rate of 0.01 s. The stress-strain and work hardening rate curves showed a weak peak at strain of 0.32, followed by a slight dynamic softening. The dominant microstructural mechanisms in low (0.1–0.23) and medium strains (0.23–0.32) were dynamic recovery and dynamic recrystallization, respectively. Microstructural characterizations by electron back scattered diffraction (EBSD) showed that continuous dynamic recrystallization brings about after the peak strain (ε = 0.32) and leads to grain refinement. It was found that the twin boundaries help to activate a grain dissociation mechanism which works as a new variant of continuous dynamic recrystallization. The grain boundary maps developed by EBSD showed that new twin boundaries form through the evolution of low angle grain boundaries. This step, named as “recovery twinning”, was identified as the origin for the observed twinning-assisted continuous dynamic recrystallization (TCDRX). The Kocks-Mecking dislocation evolution model was modified in order to take the dynamic softening by TCDRX into account and describe the variation in the frequency of high angle grain boundaries with strain. Model predictions were validated and confirmed by the experimental results.

中文翻译：

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Ni-Cu合金热变形过程中的显微组织表征及动态再结晶行为

研究了 Ni-30Cu 合金在 1150 °C 和 0.01 s 应变速率下热压缩后的流动曲线和显微组织。应力-应变和加工硬化率曲线在应变为 0.32 时出现弱峰，随后出现轻微的动态软化。低应变（0.1-0.23）和中应变（0.23-0.32）的主要微观结构机制分别是动态回复和动态再结晶。电子背散射衍射 (EBSD) 显微结构表征表明，在峰值应变 (ε = 0.32) 之后发生连续动态再结晶，导致晶粒细化。研究发现，孪晶界有助于激活晶粒解离机制，该机制是连续动态再结晶的新变体。 EBSD 开发的晶界图表明，新的孪晶界是通过小角度晶界的演化而形成的。这一步骤被称为“恢复孪晶”，被认为是观察到的孪晶辅助连续动态再结晶（TCDRX）的起源。为了考虑TCDRX的动态软化并描述大角度晶界频率随应变的变化，对Kocks-Mecking位错演化模型进行了修改。模型预测得到了实验结果的验证和证实。