Al-Cu-Mg alloys, as the most widely used lightweight structural materials, have been recognized as promising candidates in the transportation field for a low-carbon economy. However, the tensile strength and plasticity of alloys cannot be simultaneously improved to satisfy the requirements of continuously upgraded transportation vehicles. In this work, inspired by high-tensile strength and high plasticity of cobweb structure, a novel cobweb-like sub-grain structure was developed in Al-Cu-Mg alloys by a successive solution, high-strain-rate rolling (4.4 s-1), cryogenic treatment (–196 °C) and aging process (SRCA). Notably, the tensile strength and plasticity of this alloy were superior to those reported in the current study. An ultrahigh Vickers hardness and tensile strength value of 206.2 Hv and 619.6 MPa, which were 39.8 % and 31.8 % higher than those of traditional T6 heat-treated Al-Cu-Mg alloys, were obtained after SRCA. Meanwhile, an increase in the elongation of this alloy from 4.31 % to 8.23 % (increase of 90.9 %) was also achieved. More importantly, the high strength-plasticity (“double high”) Al-Cu-Mg alloy was attributed to a cobweb-like sub-grain structure, which was proposed for the first time by utilizing reverse thinking to enhance plasticity through elevating dislocations, due to the formation of high-density dislocations from high-strain-rate rolling and rearrangement effect of dislocations from cryogenic treatment. Furthermore, the strength-plasticity mechanism was verified using in-situ tensile electron back scatter diffraction (EBSD), molecular dynamics (MD) simulations, and crystal plasticity (CP) models. The results indicated that the cobweb-like sub-grain structure, resembling countless walls, formed barriers that hindered dislocation migration towards high-angle grain boundaries (HAGBs) and absorbed them, thereby reducing the occurrence of stress concentration zones, i.e., the dislocation absorption and stress-strain sharing mechanisms. Additionally, the strengthening mechanism was associated with synergistic strengthening by multiscale microstructures, including micron-sized grains, micron-sized high-density dislocation lattices, and nanosized Al2CuMg phases, which were activated by successive deformation processes. Consequently, the concept of biomimetic structure design, which may serve as an effective method for achieving structural materials with high strength-plasticity synergy, can be extended to transportation fields, such as railway tracks and body structure design.

中文翻译：

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一种新型蜘蛛网状亚晶粒结构 Al-Cu-Mg 合金，具有高强度-塑性协同作用


Al-Cu-Mg 合金作为应用最广泛的轻质结构材料，已被公认为低碳经济交通领域有前途的候选者。然而，合金的抗拉强度和塑性不能同时提高以满足不断升级的运输车辆的要求。在这项工作中，受蜘蛛网结构的高拉伸强度和高可塑性的启发，通过连续固溶、高应变率轧制 （4.4 s-1）、低温处理 （-196 °C） 和时效工艺 （SRCA） 在 Al-Cu-Mg 合金中开发了一种新型的蜘蛛网状亚晶粒结构。值得注意的是，这种合金的拉伸强度和塑性优于当前研究中报道的那些。SRCA后获得了206.2 Hv和619.6 MPa的超高维氏硬度和抗拉强度值，比传统的T6热处理Al-Cu-Mg合金分别提高了39.8%和31.8 %。同时，该合金的伸长率也从 4.31 % 增加到 8.23 %（增加了 90.9 %）。更重要的是，高强度塑性（“双高”）Al-Cu-Mg 合金归因于蜘蛛网状亚晶结构，这是首次通过利用逆向思维通过提升位错来提高塑性而提出的，这是由于高应变率轧制形成高密度位错和低温处理位错的重排效应。此外，使用原位拉伸电子背散射衍射 （EBSD） 、分子动力学 （MD） 模拟和晶体塑性 （CP） 模型验证了强度-塑性机制。 结果表明，类似于无数壁的蜘蛛网状亚晶结构形成了阻碍位错向高角度晶界 （HAGBs） 迁移的屏障并吸收它们，从而减少了应力集中区的发生，即位错吸收和应力-应变共享机制。此外，强化机制与多尺度微结构的协同强化有关，包括微米级晶粒、微米级高密度位错晶格和纳米级 Al2CuMg 相，这些相由连续的变形过程激活。因此，仿生结构设计的概念可以作为实现高强度-可塑性协同结构材料的有效方法，可以扩展到铁路轨道和车身结构设计等交通领域。