Locking in nanoscale strength Metals with nanometer-sized crystal grains are super strong, but they do not generally retain their structure at higher temperatures. This property undermines their high strength and makes their use in applications challenging. Li et al. found a minimum-interface structure in copper with 10-nanometer-sized grains that, when combined with a nanograin crystallographic twinning network, retains high strength to temperatures just below the melting point. This discovery suggests a different path forward for stabilizing nanograined metals. Science, this issue p. 831 A minimum interface structure in nanograined copper allows retention of high strength at high temperatures. Metals usually exist in the form of polycrystalline solids, which are thermodynamically unstable because of the presence of disordered grain boundaries. Grain boundaries tend to be eliminated through coarsening when heated or by transforming into metastable amorphous states when the grains are small enough. Through experiments and molecular dynamics simulations, we discovered a different type of metastable state for extremely fine-grained polycrystalline pure copper. After we reduced grain sizes to a few nanometers with straining, the grain boundaries in the polycrystals evolved into three-dimensional minimal-interface structures constrained by twin boundary networks. This polycrystalline structure that underlies what we call a Schwarz crystal is stable against grain coarsening, even when close to the equilibrium melting point. The polycrystalline samples also exhibit a strength in the vicinity of the theoretical value.

中文翻译：

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具有极细晶粒的多晶铜中受约束的最小界面结构

锁定纳米级强度具有纳米级晶粒的金属非常坚固，但它们在较高温度下通常不会保持其结构。这种特性削弱了它们的高强度，并使它们在应用中的使用具有挑战性。李等人。发现铜中的最小界面结构具有 10 纳米尺寸的晶粒，当与纳米晶粒晶体孪晶网络结合时，在略低于熔点的温度下仍保持高强度。这一发现表明了稳定纳米颗粒金属的不同途径。科学，这个问题 p。831 纳米晶粒铜的最小界面结构允许在高温下保持高强度。金属通常以多晶固体的形式存在，由于存在无序的晶界，因此在热力学上是不稳定的。晶界趋于通过加热时粗化或当晶粒足够小时转变为亚稳态非晶态而消除。通过实验和分子动力学模拟，我们发现了极细晶粒多晶纯铜的一种不同类型的亚稳态。在我们通过应变将晶粒尺寸减小到几纳米后，多晶中的晶界演变为受双晶界网络约束的三维最小界面结构。这种多晶结构是我们所说的 Schwarz 晶体的基础，即使在接近平衡熔点时，它也能稳定防止晶粒粗化。多晶样品的强度也接近理论值。