Abstract A pre-cold-deformation process was applied for commercially pure titanium at cryogenic temperature to activate high-density deformation twins, and subsequent hot-deformation was used to induce dynamic recrystallization (DRX). Three major types of twins were effectively activated during cryogenic deformation, including { 11 2 ¯ 2 } contraction twins, { 11 2 ¯ 1 } extension twins, and { 10 1 ¯ 2 } extension twins. A special type of slipped { 11 2 ¯ 1 } “twins” was also activated by a sequential effect of twinning and slip. Selection of twinning variants followed Schmid's law well, where only the twinning systems with a Schmid factor of m ≥ 0.4 could be activated. The pre-activated twinning led to a remarkably stable flow stress at 500 °C up to a true strain of 1.0, due to the attainment of dynamic equilibrium between strain hardening and high-temperature softening. Two DRX stages occurred: (1) twin-active DRX stage, and (2) discontinuous dynamic recrystallization (DDRX) stage. The DRX mechanisms identified were twinning-induced DRX (or TDRX) and DDRX. While the low-temperature slip alone had little influence on DRX, the pre-activated { 11 2 ¯ 2 } twins, { 11 2 ¯ 1 } twins, { 10 1 ¯ 2 } twins and slipped { 11 2 ¯ 1 } “twins” contributed effectively to DRX in the form of spheroidization of twin lamellae due to twin-dislocation interactions, leading to a substantial grain refinement from ∼41 to ∼1 μm during subsequent hot-deformation.

中文翻译：

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钛的动态再结晶：低温下预活化孪晶的影响

摘要 商业纯钛在低温下采用预冷变形工艺激活高密度变形孪晶，随后通过热变形诱导动态再结晶（DRX）。低温变形过程中有效激活了三种主要类型的孪晶，包括{ 11 2¯ 2 }收缩孪晶、{ 11 2¯ 1}拉伸孪晶和{ 10 1 ¯ 2 }拉伸孪晶。一种特殊类型的滑移 { 11 2 ¯ 1 } “孪生”也被孪生和滑移的顺序效应激活。孪生变体的选择很好地遵循施密德定律，其中只有施密德因子 m ≥ 0.4 的孪生系统才能被激活。预激活孪晶在 500 °C 下产生非常稳定的流动应力，真实应变为 1.0，由于在应变硬化和高温软化之间达到动态平衡。发生了两个 DRX 阶段：(1) 双活性 DRX 阶段，和 (2) 不连续动态再结晶 (DDRX) 阶段。确定的 DRX 机制是孪生诱导的 DRX（或 TDRX）和 DDRX。虽然单独的低温滑移对 DRX 影响不大，但预激活的 { 11 2¯ 2 } 孪晶、{ 11 2¯ 1 } 孪晶、{ 10 1 ¯ 2 } 孪晶和滑移 { 11 2 ¯ 1 } “孪晶由于双位错相互作用，以双片晶球化的形式有效地促进了 DRX，导致在随后的热变形过程中晶粒从 ~41 到 ~1 μm 显着细化。确定的 DRX 机制是孪生诱导的 DRX（或 TDRX）和 DDRX。虽然单独的低温滑移对 DRX 影响不大，但预激活的 { 11 2¯ 2 } 孪晶、{ 11 2¯ 1 } 孪晶、{ 10 1 ¯ 2 } 孪晶和滑移 { 11 2 ¯ 1 } “孪晶由于双位错相互作用，以双片晶球化的形式有效地促进了 DRX，导致在随后的热变形过程中晶粒从 ~41 到 ~1 μm 显着细化。确定的 DRX 机制是孪生诱导的 DRX（或 TDRX）和 DDRX。虽然单独的低温滑移对 DRX 影响不大，但预激活的 { 11 2¯ 2 } 孪晶、{ 11 2¯ 1 } 孪晶、{ 10 1 ¯ 2 } 孪晶和滑移 { 11 2 ¯ 1 } “孪晶由于双位错相互作用，以双片晶球化的形式有效地促进了 DRX，导致在随后的热变形过程中晶粒从 ~41 到 ~1 μm 显着细化。