Magnesium alloys with high strength in combination of good ductility are especially desirable for applications in transportation, aerospace and bio-implants owing to their high stiffness, abundant raw materials, and environmental friendliness. However, the majority of traditional strengthening approaches including grain refining and precipitate strengthening can usually prohibit dislocation movement at the expense of ductility invariably. Herein, we report an effective strategy for simultaneously enhancing yield strength (205 MPa, 2.41 times) and elongation (23%, 1.54 times) in a Mg-0.2Zn-0.6Y (at.%) alloy at room temperature, based on the formation of a nanosized quasi-long period stacking order unit (QLPSO)-twin structure by ultrahigh-pressure treatment followed by annealing. The formation reason and strong-ductile mechanism of the unique QLPSO-twin structure have been clarified by transmission electron microscopy observations and molecule dynamics simulations. The improved strength is mainly associated with the presence of nanosized QLPSO and the modified ∠86.3 QLPSO-twin boundary (TB) interface, effectively pinning dislocation movement. Comparatively, the enhanced ductility is related to the ∠3.7 QLPSO-TB interface and micro-kinks of nanoscale QLPSO, providing some paths for plastic deformation. This strategy on the QLPSO-twin structure might provide an alternative perspective for designing innovative hexagonal close-packed structural materials with superior mechanical properties.

中文翻译：

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纳米准长周期叠序单元与孪晶相互作用制备高强韧性镁合金

具有高强度和良好延展性的镁合金由于其高刚度、丰富的原材料和环境友好性，特别适合交通、航空航天和生物植入等领域的应用。然而，大多数传统的强化方法，包括晶粒细化和沉淀强化，通常都会以牺牲延展性为代价来阻止位错运动。在此，我们报告了一种在室温下同时提高 Mg-0.2Zn-0.6Y (at.%) 合金的屈服强度（205 MPa，2.41 倍）和伸长率（23%，1.54 倍）的有效策略，基于通过超高压处理和退火形成纳米级准长周期堆叠有序单元（QLPSO）孪晶结构。通过透射电子显微镜观察和分子动力学模拟，阐明了独特的QLPSO-孪晶结构的形成原因和强延展机制。强度的提高主要与纳米级QLPSO和改进的∠86.3 QLPSO-孪晶边界（TB）界面的存在有关，有效地钉扎了位错运动。相比之下，延展性的增强与∠3.7 QLPSO-TB界面和纳米级QLPSO的微扭结有关，为塑性变形提供了一些路径。这种 QLPSO 双结构策略可能为设计具有优异机械性能的创新六方密堆积结构材料提供另一种视角。