Utilizing molecular dynamics simulations, the authors investigate the notion of bimodal nanotwinned (NT) microstructure in strength-ductility trade-off. Using a coarse circular grain with twins embedded in a sea of nano-grains (without twins) as a surrogate, the paper explores three scenarios pertaining to the strength and failure strain mapping: (i) the effect of twin boundary (TB) inclination; (ii) the effect of coarse-grain size; (ii) the effect of twin boundaries spacings (TBSs). The central result is that there exists an optimum grain size at which the strength and failure strain are simultaneously improved. Meanwhile, the fracture mechanisms of bimodal NT microstructure are demonstrated by analyzing dislocation-TB interactions, which involve TB migration, deformation twinning, void generation, etc.

利用分子动力学模拟，作者研究了双峰纳米孪晶（NT）微观结构在强度-延展性之间进行权衡的概念。本文使用具有双胞胎的纳米颗粒（没有双胞胎）的粗大圆形晶粒作为替代，探讨了三种与强度和破坏应变映射有关的方案：（i）孪晶边界（TB）倾角的影响；（ii）粗粒度的影响；（ii）孪生边界间距（TBS）的影响。中心结果是存在最佳晶粒尺寸，同时强度和破坏应变得到改善。同时，通过分析位错-TB相互作用，包括TB迁移，变形孪生，空洞产生等，证明了双峰NT微结构的断裂机理。