Cui Zhenjie

This study systematically investigated the regulatory mechanisms of the Mg/Si ratio and natural aging treatment on the characteristics of intergranular precipitates and the intergranular corrosion resistance of 6082 aluminum alloy. Key findings reveal that the alloy with an atomic Mg/Si ratio of 2.0 promoted the coarsening of intergranular precipitates and the formation of continuous chain‐like structures due to solute enrichment, resulting in a broad precipitate‐free zone (PFZ) and a significant electrochemical gradient, which exacerbated intergranular corrosion. The alloy with an atomic Mg/Si ratio of 0.8 utilized the intragranular stable clusters formed during natural aging to preferentially capture solutes, effectively inhibiting the continuity of intergranular precipitates and significantly reducing the PFZ, thereby synergistically optimizing strength and corrosion resistance. The alloy with an atomic Mg/Si ratio of 1.4 avoided continuous nucleation and significant coarsening, forming a discontinuous precipitate distribution, and exhibited relatively excellent corrosion resistance. The research clarifies the cross‐scale mechanism, where the Mg/Si ratio drives the competitive evolution of intragranular and intergranular precipitates through the regulation of solute diffusion kinetics, providing a key theoretical basis for the composition and process design of high‐strength, corrosion‐resistant aluminum alloys.

Natural aging (NA) is unavoidable in Al-Mg-Si alloys during actual manufacturing. Revealing the reasons for the alloy strength reduction caused by the negative NA effect is of great significance to research and practice. In this work, atom probe tomography (APT) and transmission electron microscopy (TEM) were employed simultaneously to study the effect of NA on precipitates and their contributions to the strength of Al-Mg-Si alloys. It was found that the numerous clusters formed after significant NA are unstable and will dissolve into the matrix during initial AA. However, a few stable clusters are undissolved and will result in abnormal growth of β″, which then transforms to β′. Due to the decrease of nucleation sites resulting from the abnormal growth of precipitates, more solute atoms remain in the matrix. The calculation results show that the strengthening of the solid solution atoms is much smaller than that of large-sized β′, which is much less than that of fine β″. Therefore, lengthy NA causes a significant reduction in AA strength of the Al-Mg-Si alloy.