Mg/Si比对Al-Mg-Si-Zn合金自然时效效应的影响

Mg/Si比对Al-Mg-Si-Zn合金自然时效效应的影响

范 唯，向雪梅，雷潘敏，赖玉香^*，陈江华^*

（1. 湖南大学高分辨电镜中心，湖南长沙410082；2. 海南大学皮米电镜中心，海南海口570228）

摘 要 通过显微硬度测试、导电率测试、差示扫描量热分析和透射电子显微镜，探究了两种不同Mg/Si比的Al-Mg-Si-Zn合金中自然时效对后续180 ℃人工时效的影响。结果表明，在富Si合金中，自然时效对后续人工时效的峰值硬度没有明显的负面效应，而富Mg合金则表现出显著的自然时效负面效应。虽然有少量板条相存在，针状的β"相为两种合金在所有峰值时效状态下的主要析出强化相。富Mg合金的自然时效负面效应主要与β"相尺寸粗化和析出相体积分数减小有关。不同Mg/Si比的Al-Mg-Si-Zn合金中自然时效团簇的特性具有显著差异。富Mg合金中的自然时效团簇有相当一部分在人工时效时是稳定的，同时稳定的团簇大部分不能作为析出相的形核点，导致析出相的形核点数量减少，析出相尺寸粗化。而大量富Si合金中的自然时效团簇在后续人工时效早期发生溶解，来自溶解团簇的溶质原子重新用于β"相的形核生长，因此析出相尺寸粗化不明显。

关键词 Al-Mg-Si合金；微合金元素；自然时效；析出；透射电镜

中图分类号：TG146.21；TG115.21⁺5.3 文献标识码：A   doi:10.3969/j.issn.1000-6281.2023.06.006

Effect of Mg/Si ratio on the natural aging in Al-Mg-Si-Zn alloys

FAN Wei ¹, XIANG Xue-mei ¹, LEI Pan-min¹, LAI Yu-xiang ^2*,CHEN Jiang-hua ^2*

(1. Center for High Resolution Electron Microscopy, College of Materials Science and Engineering, Hunan University, ChangshaHunan 410082; 2. Pico Electron Microscopy Center, College of Materials Science and Engineering, Hainan University, Haikou Hainan 570228，China)

Abstract  The effects of natural aging on subsequent artificial aging at 180 °C in Al-Mg-Si-Zn alloys with different Mg/Si ratios have been investigated by microhardness test,electrical conductivity test, differential scanning calorimetry and transmission electron microscopy. In the Si-rich alloy, there is no significant negative natural aging effect on the maximum hardness achieved during artificial aging, whereas the Mg-rich alloy exhibits a significant negative natural aging effect. Although few lath-like precipitates exist, needle-like β" precipitates are the primary hardening precipitates in all the peak-aged alloys. The negative natural aging effect of the Mg-rich alloy is mainly related to the coarsening of the β" precipitates and the reduction in the volume fraction of the precipitates. The two Al-Mg-Si-Zn alloys with varying Mg/Si ratios exhibit remarkably distinct natural aging cluster natures. A significant proportion of the natural aging clusters in the Mg-rich alloy remain stable during artificial aging, but the majority of the stable clusters are unable to serve as nucleation sites for the precipitates, reducing the number of nucleation sites for the precipitates and causing the precipitates to become coarser. In contrast, during the initial stage of subsequent artificial aging, a significant portion of the natural aging clusters in the Si-rich alloy are dissolved. The solute atoms from the dissolved clusters are reused in the nucleation and growth of the β" precipitates, making the coarsening of the precipitates not as obvious.

Keywords   Al-Mg-Si alloys; trace element; natural aging; precipitation; transmission electron microscopy

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