Nanostructured metals are usually strong because the ultrahigh density of internal boundaries restricts the mean free path of dislocations. Usually, they are also more brittle because of their diminished work-hardening ability. Nanotwinned materials, with coherent interfaces of mirror symmetry, can overcome this inherent trade-off. We show a bulk nanostructuring method that produces a multiscale, hierarchical twin architecture in a hexagonal closed-packed, solute-free, and coarse-grained titanium (Ti), with a substantial enhancement of tensile strength and ductility. Pure Ti achieved an ultimate tensile strength of almost 2 gigapascals and a true failure strain close to 100% at 77 kelvin. The multiscale twin structures are thermally stable up to 873 kelvin, which is above the critical temperature for many applications in extreme environments. Our results demonstrate a practical route to achieve attractive mechanical properties in Ti without involving exotic and often expensive alloying elements.

中文翻译：

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具有超高强度和延展性的低温锻造纳米孪晶钛

纳米结构金属通常很坚固，因为超高密度的内部边界限制了位错的平均自由程。通常，由于加工硬化能力降低，它们也更脆。具有镜像对称相干界面的纳米孪晶材料可以克服这种固有的折衷。我们展示了一种块状纳米结构方法，该方法在六方密堆积、无溶质和粗晶钛 (Ti) 中产生多尺度、分层的孪生结构，并显着提高了拉伸强度和延展性。纯钛在 77 开尔文下实现了近 2 吉帕斯卡的极限抗拉强度和接近 100% 的真实失效应变。多尺度孪晶结构的热稳定性高达 873 开尔文，高于极端环境中许多应用的临界温度。