†Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
‡Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States.
Nano Lett. 2015 Jun 10;15(6):4037-44. doi: 10.1021/acs.nanolett.5b01015. Epub 2015 May 15.
Metallic nanowires usually exhibit ultrahigh strength but low tensile ductility owing to their limited strain hardening capability. Here we study the unique strain hardening behavior of the five-fold twinned Ag nanowires by nanomechanical testing and atomistic modeling. In situ tensile tests within a scanning electron microscope revealed strong strain hardening behavior of the five-fold twinned Ag nanowires. Molecular dynamics simulations showed that such strain hardening was critically controlled by twin boundaries and pre-existing defects. Strain hardening was size dependent; thinner nanowires achieved more hardening and higher ductility. The size-dependent strain hardening was found to be caused by the obstruction of surface-nucleated dislocations by twin boundaries. Our work provides mechanistic insights into enhancing the tensile ductility of metallic nanostructures by engineering the internal interfaces and defects.
金属纳米线通常由于其应变硬化能力有限而表现出超高强度和低拉伸延展性。在这里，我们通过纳米力学测试和原子模拟研究了五重孪晶 Ag 纳米线的独特应变硬化行为。在扫描电子显微镜内进行的原位拉伸测试揭示了五重孪晶 Ag 纳米线的强应变硬化行为。分子动力学模拟表明，这种应变硬化受到孪晶界和预先存在的缺陷的严格控制。应变硬化与尺寸有关；更细的纳米线实现了更多的硬化和更高的延展性。发现尺寸相关的应变硬化是由孪晶界阻碍表面形核位错引起的。我们的工作为通过工程内部界面和缺陷来提高金属纳米结构的拉伸延展性提供了机械方面的见解。
