Spreading twins throughout nano metals has been proved to effectively mediate the mechanical behaviors in face-centered-cubic (fcc) metals. However, the experimental investigation concerning the roles of twin boundary (TB) during deformation is rarely reported. Here, with the joint efforts of in-situ nanomechanical testing and theoretical studies, we provide a systematic investigation regarding the effects of TB orientation (θ, the angle between tensile loading direction and the normal of TB) and spacing on deformation mechanisms in Ni nanowires (NWs). As compared with single-crystalline counterparts, it is found that nano-twinned (nt) NWs with θ ∼0° exhibit limited ductility, whereas TB can serve as an effective blockage to the dislocation propagation. In contrast, in nt NWs with θ ∼20° and 55°, TB migration/detwinning induced by TB-dislocation reaction or partial dislocation movement dominates the plasticity, which contributes to enhanced NW ductility. Regarding nt NWs with θ ∼90°, dislocations are found to be able to transmit through the TBs, suggesting the limited effect of TB on the NW stretchability. Furthermore, decreasing TB spacing (λ) can facilitate the detwinning process and thus greatly enhance the ductility of NW with θ ∼55°. This study uncovers the distinct roles that TB can play during mechanical deformations in fcc NWs and provides an atomistic view into the direct linkage between macroscopic mechanical properties and microscopic deformation modes.

已证明在整个纳米金属中扩散孪晶可有效调节面心立方 (fcc) 金属的机械行为。然而，关于变形过程中孪晶界（TB）作用的实验研究很少报道。在这里，通过原位纳米力学测试和理论研究的共同努力，我们系统地研究了 TB 取向（ θ，拉伸加载方向与 TB 法线之间的角度）和间距对镍纳米线变形机制的影响（西北地区）。与单晶对应物相比，发现具有θ的纳米孪晶（nt）NW∼0° 表现出有限的延展性，而 TB 可以作为位错传播的有效阻挡物。相比之下，在θ ~20°和55°的nt NW中，由TB位错反应或部分位错运动引起的TB迁移/去孪晶占主导地位，这有助于增强NW延展性。关于θ ~90°的nt NW，发现位错能够穿过TB，表明TB对NW拉伸性的影响有限。此外，减小 TB 间距 ( λ ) 可以促进去孪晶过程，从而大大提高 NW 的延展性与θ～55°。本研究揭示了 TB 在 fcc NW 的机械变形过程中可以发挥的独特作用，并为宏观力学性能和微观变形模式之间的直接联系提供了原子视角。