In this work, a new Al–Mg–Zn alloy was designed based on thermodynamic calculations combined with the concept of cooperative strengthening and toughening. The influence of different aging processes on microstructure and mechanical properties of the designed Al–Mg–Zn alloy was studied using experimental techniques including hardness testing, room-temperature tensile testing, EBSD, and HRTEM. The results indicate that after four different aging heat treatments, fine and uniformly distributed nano T-Mg(Al, Zn) phases have precipitated within the grains. Compared to single-stage aging (140 °C/36 h, 180 °C/7 h), two-stage aging (90 °C/24 h + 140 °C/18 h, 90 °C/24 h + 180 °C/5 h) resulted in a smaller size and an increased number density of precipitated phases within the grains. After the aging process of 90 °C/24 h + 140 °C/18 h, the grains exhibited the smallest precipitated phases, being of 2.77 nm in size and a number density of 1.06 × 10 #/m³. Additionally, TEM diffraction spot analysis identified the presence of Al(Sc, Zr) precipitates within α-Al matrix. Under the aging process of 90 °C/24 h + 140 °C/18 h, the alloy exhibited superior mechanical properties with a tensile strength of 566 MPa, yield strength of 477 MPa, and elongation of 16.5%. The primary strengthening mechanisms of the presently investigated Al–Mg–Zn alloy include precipitation strengthening, solid solution strengthening, and grain boundary strengthening. A yield strength model considering various strengthening mechanisms is used to predict the yield strength based on thermodynamic calculations and experimental data. The research findings will offer theoretical insights guiding the design of compositions and heat treatment schedule for aluminum alloys.

中文翻译：

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热处理对添加Sc和Zr的Zn改性Al-Mg合金显微组织演变、强化机制和力学性能的影响

在这项工作中，基于热力学计算并结合协同强化和增韧的概念，设计了一种新型Al-Mg-Zn合金。利用硬度测试、室温拉伸测试、EBSD 和 HRTEM 等实验技术研究了不同时效工艺对所设计的 Al-Mg-Zn 合金显微组织和力学性能的影响。结果表明，经过四种不同的时效热处理后，晶粒内析出细小且均匀分布的纳米T-Mg(Al,Zn)相。与单阶段老化（140℃/36小时、180℃/7小时）相比，两阶段老化（90℃/24小时+140℃/18小时、90℃/24小时+180℃） C/5 h)导致晶粒内析出相的尺寸更小并且数量密度增加。经过90℃/24h+140℃/18h的时效处理后，晶粒呈现出最小的析出相，尺寸为2.77nm，数密度为1.06×10#/m3。此外，TEM 衍射点分析发现 α-Al 基体中存在 Al(Sc, Zr) 沉淀物。在90℃/24h+140℃/18h的时效工艺下，合金表现出优异的力学性能，抗拉强度为566MPa，屈服强度为477MPa，伸长率为16.5%。目前研究的Al-Mg-Zn合金的主要强化机制包括沉淀强化、固溶强化和晶界强化。考虑各种强化机制的屈服强度模型用于根据热力学计算和实验数据来预测屈服强度。研究结果将为指导铝合金成分和热处理方案的设计提供理论见解。