将常规多晶材料的粗晶粒尺寸缩小到纳米尺度时,这些纳米晶体材料会呈现出与其对应的粗晶材料迥异的物理现象.与材料力学行为最相关的是强度及塑形变形机理这两个方面.考虑到晶界的变形与破坏可能是纳米晶体材料低塑性的根源,克服纳米晶体材料中强度与韧性之间存在的“熊掌和鱼不可兼得”的问题,也通常称为晶界工程.在众多的晶界中,孪晶界面被发现可同时保持材料的强度和韧性.本文主要就纳米金属材料中界面的力学行为做一个简要述,包含晶界的强化力学机理以及新型孪晶界面的力学行为与揭示内在尺度效应的模型研究。

When grain sizes of crystals are down to nano-scale, the so-called nanocrystalline materials exhibit distinct physical properties in contrast to their conventional counterparts. The strength and plastic deformation mechanisms were among the most broadly investigated properties from mechanical society. Since deformation and pre-mature failure in interfaces (including grain boundaries, twin boundaries, and interfaces between different media) could be the origin of lov'r ductility in nanocrystalline materials, the effort to evade the strength-ductility tradeoff dilemma in nanocrystalline materials, by tuning their interfacial structures/properties, is usually called as interfacial engineering. Twin boundaries stand out among all possible boundary structures for their capability to enhance strength and retain ductility of crystalline metals. In this paper, current understanding about the mechanical behavior associated with interfaces in nanostructured metals is reviewed, with a focus on the strengthening mechanisms played by twin/grain boundaries and current physical models to shed light on the size-effect induced by grain sizes and twin thicknesses.