Constrained minimal-interface structures in polycrystalline copper with extremely fine grains
Constrained minimal-interface structures in polycrystalline copper with extremely fine grains
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DOI：
10.1126/science.abe1267
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发表时间：
2020-11-13
期刊：
影响因子：
56.9
通讯作者：
Lu, K.
中科院分区：
文献类型：
--
作者：
Li, X. Y.;Jin, Z. H.;Lu, K.
金属通常以多晶固体的形式存在，由于无序晶界的存在，多晶固体是不稳定的。当晶粒足够小时，晶粒边界倾向于通过加热时的粗化或通过转变成亚稳态非晶态而消除。通过实验和分子动力学模拟，我们发现了一种不同类型的亚稳态的极细晶多晶纯铜。当我们将晶粒尺寸减小到几个纳米时，多晶体中的晶界演变成由孪晶界网络约束的三维最小界面结构。这种多晶结构是我们称之为施瓦茨晶体的基础，即使在接近平衡熔点时，它也能稳定地防止晶粒变粗。多晶样品也表现出理论值附近的强度。
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.