Abstract Modern aluminum industries need an in-depth understanding and a more accurate prediction of the flow stress and microstructure evolution during multi-stage thermomechanical processing. The underlying mechanisms of Al alloys are distinct from that of other metallic materials (e.g., steels and copper) owing to the very high stacking fault energy. In the hot forming process of ultra-high strength Al-Zn-Mg-Cu alloys, the high alloying element additions have a more complex effect on multiple static softening mechanisms during post-deformation, i.e. the coupled recovery, recrystallization, precipitation and their interactions, which have not been well revealed and included in the existing plasticity models. In the present work, an integrated physically based model based on the observed microstructural characteristics and static softening behavior was developed to unravel the multiple static softening mechanisms following multi-stage hot deformation of Al-Zn-Mg-Cu alloys. By incorporating the multicomponent effects, i.e. process variables and chemical compositions, into static recovery, static recrystallization and precipitate coarsening models, the evolutions of stress, microstructure and static softening fraction could be accounted reasonably during post-deformation holding. A special attention was paid to model the functions of various alloy solute contents (i.e. Zn, Mg, Cu and Zr) on the precipitation thermodynamic, recovery and recrystallization kinetics in Al-Zn-Mg-Cu alloys. After validating by experimental data, the integrated physically based model could predict the effects of alloying elements on microstructural evolution, recrystallization and static softening kinetics of Al-Zn-Mg-Cu alloys. It was found that the different precipitation behaviors due to the addition of various alloying elements have a considerable influence on recovery, recrystallization and coupled static softening process. The solid solution atoms remaining in the matrix basically contributed to grain boundaries mobility and then slow recrystallization process, which depended on the interaction parameter, binding energy and diffusion rates of various alloying elements. This work offers an in-depth understanding of static softening mechanisms and provides a potential way for future development of advanced models and design strategies for multi-stage thermomechanical processes in Al-Zn-Mg-Cu alloys.

中文翻译：

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铝-锌-镁-铜合金多阶段热变形后多重静态软化机制的综合物理建模

摘要 现代铝工业需要深入了解和更准确地预测多阶段热机械加工过程中的流动应力和微观结构演变。由于非常高的堆垛层错能，铝合金的基本机理不同于其他金属材料（例如钢和铜）的机理。在超高强度Al-Zn-Mg-Cu合金的热成型过程中，高合金元素的添加对后变形过程中的多种静态软化机制，即耦合恢复、再结晶、析出及其相互作用具有更为复杂的影响。 ，尚未很好地揭示并包含在现有的可塑性模型中。在目前的工作中，基于观察到的微观结构特征和静态软化行为，开发了一个基于物理的综合模型，以揭示 Al-Zn-Mg-Cu 合金多阶段热变形后的多种静态软化机制。通过将多组分效应，即工艺变量和化学成分，纳入静态恢复、静态再结晶和沉淀粗化模型，可以合理地考虑变形后保持过程中应力、微观结构和静态软化率的演变。特别注意模拟各种合金溶质含量（即 Zn、Mg、Cu 和 Zr）对 Al-Zn-Mg-Cu 合金的析出热力学、回复和再结晶动力学的影响。经实验数据验证后，基于物理的综合模型可以预测合金元素对 Al-Zn-Mg-Cu 合金显微组织演变、再结晶和静态软化动力学的影响。结果表明，由于加入各种合金元素而产生的不同析出行为对回复、再结晶和耦合静态软化过程有相当大的影响。残留在基体中的固溶原子主要促成晶界迁移，然后减缓再结晶过程，这取决于各种合金元素的相互作用参数、结合能和扩散速率。