Effects of Sn Addition on Clustering and Age-Hardening Behavior in a Pre-aged Al-Mg-Si Alloy

摘要

The effects of Sn addition on clustering and age-hardening behavior in an Al-0.6Mg-l.0Si (mass %) alloy were investigated. Addition of Sn delayed the age-hardening in single aging at 170°C. On the other hand, Sn promoted the age-hardening response in 3-step aging process which comprises a pre-aging (PA) at 90°C for 18ks followed by natural aging (NA) for 604.8ks and artificial aging (AA) at 170°C. The characteristics of clusters formed during PA and NA were evaluated by differential scanning calorimetry (DSC) analysis and atom probe tomography (APT). The DSC results show that the endothermic peak at around 160°C to 200°C was observed in the Sn-free alloy. On the other hand, in the Sn-added alloy, endothermic peak was not observed. It is suggested that Sn addition suppresses the formation of the clusters formed during NA. The APT results show that the Sn addition decreases the number density of clusters, especially smaller clusters. No Sn precipitates were found in Mg-Si precipitates formed during AA at 170°C for 3.6ks. It is speculated that suppression of smaller cluster formation by addition of Sn promotes the age-hardening response.