The orientation between twin boundary (TB) and loading direction may play an intriguing role in the deformation behaviors of twinned metallic materials. In this aspect, its essential effect on the high-entropy alloy (HEA) nanocrystals is elusive. Attention herein is focused on the atomic-scaled deformation mechanisms and fracture behaviors of HEA nanocrystals containing twins of even smaller spacings via a combined approach of in situ tensile tests inside a high-resolution transmission electron microscope and molecular dynamics simulations. The results indicate that the deformation mechanisms (especially dislocation activities) of HEA nanocrystals depend on the load orientation with respect to TBs. Because of the low activation energy and uneven local composition of HEA, the surface acts as an effective dislocation source and, together with Schmid factor, dominate the activated dislocation slip system. The load orientation-dependent TB-dislocation interactions may transform the type of fracture from semi-brittle to ductile. Our results indicate that the deformation mechanisms and the types of fracture in HEA nanocrystals can be controlled by changing the orientation.

孪晶边界（TB）和加载方向之间的取向可能在孪生金属材料的变形行为中起着有趣的作用。在这方面，它对高熵合金（HEA）纳米晶体的本质作用难以捉摸。本文关注的是通过原位结合方法包含间距更小的孪晶的HEA纳米晶体的原子尺度形变机理和断裂行为高分辨率透射电子显微镜内的拉伸试验和分子动力学模拟。结果表明，HEA纳米晶体的变形机制（尤其是位错活性）取决于相对于TB的载荷方向。由于活化能低，HEA的局部组成不均匀，因此表面可作为有效的位错源，并与Schmid因子一起主导活化的位错滑移系统。与载荷方向相关的结核-位错相互作用可能会将裂缝的类型从半脆性转变为韧性。我们的结果表明，HEA纳米晶体的变形机理和断裂类型可以通过改变取向来控制。