Sun Jiapeng, Han Jing, Yang Zhenquan, Liu Huan, Song Dan, Ma Aibin, Fang Liang
College of Mechanics and Materials, Hohai University, Nanjing 210098, China.
School of Mechanical and Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, China.
Nanomaterials (Basel). 2018 Oct 18;8(10):848. doi: 10.3390/nano8100848.
Metallic nanowires usually exhibit ultrahigh strength but low tensile ductility, owing to their limited strain hardening capability. Here, our larger scale molecular dynamics simulations demonstrated that we could rebuild the highly desirable strain hardening behavior at a large strain (0.21 to 0.31) in twinned Au nanowires by changing twin orientation, which strongly contrasts with the strain hardening at the incipient plastic deformation in low stacking-fault energy metals nanowires. Because of this strain hardening, an improved ductility is achieved. With the change of twin orientation, a competing effect between partial dislocation propagation and twin migration is observed in nanowires with slant twin boundaries. When twin migration gains the upper hand, the strain hardening occurs. Otherwise, the strain softening occurs. As the twin orientation increases from 0° to 90°, the dominating deformation mechanism shifts from slip-twin boundary interaction to dislocation slip, twin migration, and slip transmission in sequence. Our work could not only deepen our understanding of the mechanical behavior and deformation mechanism of twinned Au nanowires, but also provide new insights into enhancing the strength and ductility of nanowires by engineering the nanoscale twins.
金属纳米线通常表现出超高强度，但拉伸延展性较低，这是由于其有限的应变硬化能力。在此，我们通过更大规模的分子动力学模拟表明，通过改变孪晶取向，我们可以在孪晶金纳米线中在大应变（0.21至0.31）下重建非常理想的应变硬化行为，这与低堆垛层错能金属纳米线初始塑性变形时的应变硬化形成强烈对比。由于这种应变硬化，实现了延展性的提高。随着孪晶取向的变化，在具有倾斜孪晶界的纳米线中观察到部分位错传播和孪晶迁移之间的竞争效应。当孪晶迁移占上风时，会发生应变硬化。否则，会发生应变软化。随着孪晶取向从0°增加到90°，主导变形机制依次从滑移 - 孪晶界相互作用转变为位错滑移、孪晶迁移和滑移传递。我们的工作不仅可以加深我们对孪晶金纳米线力学行为和变形机制的理解，还可以为通过设计纳米尺度孪晶来提高纳米线的强度和延展性提供新的见解。
