{10–12} twinning is an important deformation mechanism for hexagonal metals; however, its characteristically low critical stress and resulting high twin activity often lead to rapid strain localization and premature failure. Therefore, this study aims to strategically delay {10–12} twinning at the initial deformation stage to prevent the strain localization, and concurrently seeks to reactivate {10–12} twinning at the large deformation stage to facilitate continuous hardening. Guided by these dual objectives, we selected rolled titanium as the model material and designed the loading direction to minimize the Schmid factor of {10–12} twinning, and then introduced cryogenic temperatures as low as 77 K to apply GPa-grade stress, thereby enabling continuous strengthening until the reactivation of {10–12} twinning. Under these specified conditions, the rolled titanium exhibited markedly enhanced mechanical properties; the ultimate strength increased from 618 MPa to 1634 MPa, while the true strain was increased by approximately 0.15 when the temperature was reduced from 298 K to 77 K. More importantly, an unusual strain hardening behavior was experimentally observed at a true strain of 0.16, at which {10–12} twins started to behave as the predominant twinning mechanism. Quantitative analysis further indicated that the large majority of the strain hardening capacity was attributed to high-density {10–12} twins. The present study therefore highlighted the pivotal role of {10–12} twins and offers a novel viewpoint for designing and achieving distinctive mechanical properties through the manipulation of deformation twinning.

中文翻译：

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在低温下由 {10–12} 个强纹理钛孪晶介导的不寻常硬化


{10–12} 孪晶是六方金属的重要变形机制;然而，其典型的低临界应力和由此产生的高孪生活性通常会导致应变快速定位和过早失效。因此，本研究旨在战略性地在初始变形阶段延迟 {10–12} 双胞胎以防止应变局部化，同时寻求在大变形阶段重新激活 {10–12} 双胞胎以促进连续硬化。在这些双重目标的指导下，我们选择轧制钛作为模型材料，并设计了加载方向以最小化 {10-12} 孪晶的 Schmid 因子，然后引入低至 77 K 的低温以施加 GPa 级应力，从而实现持续强化，直到 {10-12} 孪晶重新激活。在这些规定条件下，轧制钛表现出显着增强的机械性能;极限强度从 618 MPa 增加到 1634 MPa，而当温度从 298 K 降低到 77 K 时，真实应变增加了约 0.15。更重要的是，在实验中观察到了 0.16 的真实应变下不寻常的应变硬化行为，此时 {10-12} 双胞胎开始表现为主要的孪生机制。定量分析进一步表明，大部分应变硬化能力归因于高密度 {10-12} 双胞胎。因此，本研究强调了 {10–12} 双胞胎的关键作用，并为通过操纵变形孪晶设计和实现独特的机械性能提供了一种新的视角。