Department of Mechanical Engineering, Northwestern University, Evanston IL 60208, USA.
Small. 2012 Oct 8;8(19):2986-93. doi: 10.1002/smll.201200522. Epub 2012 Jul 25.
A unique size-dependent strain hardening mechanism, that achieves both high strength and ductility, is demonstrated for penta-twinned Ag nanowires (NWs) through a combined experimental-computational approach. Thin Ag NWs are found to deform via the surface nucleation of stacking fault decahedrons (SFDs) in multiple plastic zones distributed along the NW. Twin boundaries lead to the formation of SFD chains that locally harden the NW and promote subsequent nucleation of SFDs at other locations. Due to surface undulations, chain reactions of SFD arrays are activated at stress concentrations and terminated as local stress decreases, revealing insensitivity to defects imparted by the twin structures. Thick NWs exhibit lower flow stress and number of distributed plastic zones due to the onset of necking accompanied by more complex dislocation structures.
通过实验-计算相结合的方法，展示了一种独特的尺寸相关应变硬化机制，该机制可使五孪晶 Ag 纳米线（NWs）同时具有高强度和延展性。发现薄的 AgNW 通过在沿 NW 分布的多个塑性区中表面形核堆垛层错十面体（SFD）来变形。孪晶界导致 SFD 链的形成，从而局部使 NW 硬化，并促进 SFD 在其他位置的随后形核。由于表面起伏，SFD 阵列的链式反应在应力集中处被激活，并在局部应力降低时终止，显示出对孪晶结构赋予的缺陷不敏感。由于伴随颈缩的开始，厚 NWs 的流动应力和分布的塑性区数量较低，并且具有更复杂的位错结构。
