Abstract
The addition of Sn in Al-Mg-Si alloys has drawn widely attention due to its strong interaction with the vacancies. In the present work, the effect of different amount of Sn addition on natural aging and precipitation hardening in Al-Mg-Si alloys are investigated. During natural aging (NA), the Sn addition can effectively suppress the clustering by capturing vacancies, and the NA hardness is gradually decreased with increasing Sn content. However, during artificial aging (AA) at 170 °C after NA, it is found that the positive effect of Sn addition is highly dependent on the Sn content. A Sn content ≤0.1 wt% can facilitate the precipitation of β″ phase due to the release of vacancies at high aging temperature. While a Sn content >0.1 wt% can result in a decrease of AA hardness. This is mainly due to the coarser and sparser distribution of β″ phases in the α-Al matrix. Besides, the excess Sn atoms preferentially form coarse primary Sn particles and Mg2Sn particles instead of being solute atoms in the α-Al matrix, which can deteriorate the mechanical properties of this alloy. Some Sn particles are formed at the interface of Fe-rich intermetallic particle, which probably refine the Fe-intermetallic phases in the high-Sn alloys. These results indicate that the Sn content should be accurately controlled for the Al-Mg-Si-Sn alloys with increased properties.
Published Version
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