Sn microalloying can depress the adverse effect of natural aging after quenching(i.e., room-temperature storage) of Al-Mg-Si alloys. However, the other effect of Sc micro-addition to the Al-Mg-Si-Sn alloys remains elu...Sn microalloying can depress the adverse effect of natural aging after quenching(i.e., room-temperature storage) of Al-Mg-Si alloys. However, the other effect of Sc micro-addition to the Al-Mg-Si-Sn alloys remains elusive. Here, the optimal room-temperature storage time,properties and micromechanisms of Al-0.43 Mg-1.2Si-0.1Sn-0.1Sc(wt%) alloy are investigated by atomic-resolution scanning transmission electron microscopy(STEM),microhardness and corrosion resistance tests. The results show that the peak-aging Al-Mg-Si-Sn-Sc alloy exhibits vastly shortened peak hardening time, increased thermal stability and corrosion resistance compared with its Sc-free counterpart after a long room-temperature storage time of 1 week. Under such a designed double-stage aging regime(1-week room-temperature storage + artificial aging at 180℃), the addition of Sc to Al-Mg-Si-Sn alloy induces a decrease in diameter but an increase in length of peakhardening β″-based precipitates. In addition, a suppressed over-aging phase transition from Sc/Sn-containing β″ to β′ is identified in the Al-Mg-Si-Sn-Sc alloy. The Sn tends to segregate to the Si site in the low-density cylinder of β″ and the central site of sub-B′ in the precipitate can be occupied by Sn/Sc. Further study reveals that Sc and Sn coexist in the precursors of β″. Both reduced width of precipitation free zones and protective corrosion product film easily formed on the material contribute to the improved corrosion resistance of Al-Mg-Si-Sn-Sc alloy.The results provide important insight into the development of high-performance Al alloys.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 52061003 and U20A20274)the Natural Science Foundation of Guangxi (No.2018GXNSFAA050012)Guangxi Science and Technology Project (Nos. AA17204036-1, AA18118030 and AA17204100)。
文摘Sn microalloying can depress the adverse effect of natural aging after quenching(i.e., room-temperature storage) of Al-Mg-Si alloys. However, the other effect of Sc micro-addition to the Al-Mg-Si-Sn alloys remains elusive. Here, the optimal room-temperature storage time,properties and micromechanisms of Al-0.43 Mg-1.2Si-0.1Sn-0.1Sc(wt%) alloy are investigated by atomic-resolution scanning transmission electron microscopy(STEM),microhardness and corrosion resistance tests. The results show that the peak-aging Al-Mg-Si-Sn-Sc alloy exhibits vastly shortened peak hardening time, increased thermal stability and corrosion resistance compared with its Sc-free counterpart after a long room-temperature storage time of 1 week. Under such a designed double-stage aging regime(1-week room-temperature storage + artificial aging at 180℃), the addition of Sc to Al-Mg-Si-Sn alloy induces a decrease in diameter but an increase in length of peakhardening β″-based precipitates. In addition, a suppressed over-aging phase transition from Sc/Sn-containing β″ to β′ is identified in the Al-Mg-Si-Sn-Sc alloy. The Sn tends to segregate to the Si site in the low-density cylinder of β″ and the central site of sub-B′ in the precipitate can be occupied by Sn/Sc. Further study reveals that Sc and Sn coexist in the precursors of β″. Both reduced width of precipitation free zones and protective corrosion product film easily formed on the material contribute to the improved corrosion resistance of Al-Mg-Si-Sn-Sc alloy.The results provide important insight into the development of high-performance Al alloys.
