The formation and evolution of Gd-rich precipitates companying with the matrix structure ordering in a Mg_(97)Gd_(2)Cd_(1)(at.%)solid-solution alloy aged at 200℃have been systemically investigated using high-angle an...The formation and evolution of Gd-rich precipitates companying with the matrix structure ordering in a Mg_(97)Gd_(2)Cd_(1)(at.%)solid-solution alloy aged at 200℃have been systemically investigated using high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).The results show that Gd-rich precipitation dynamics during the aging treatment are noticeably affected by a continuous ordering transformation in the matrix.The ordering transformation process involving mainly re-distribution of Cd atoms was revealed to occur in the following way:random super-saturated solid solution(S.S.S.S.)→B19-type ordered domains→D019-type ordered domains.Four Gd(Cd)-rich precipitates,G.P.Ⅰ zone,G.P.Ⅱ zone,β′andβ_(1)phases,have been observed to be formed in sequence to coexist with the various ordered domains.Based on the HAADF-STEM characterization on the aging microstructures at different aging stages,it can be concluded that the Cd-addition and related matrix structure ordering can play significant roles in modifying the early-stage G.P.zone structure,altering the morphology ofβ′precipitates and promoting the forming ability of theβ_(1)precipitate.展开更多
基金The authors would like to acknowledge the financial supports from the National Natural Science Foundation of China[grant number 11274027]Beijing Municipal Natural Science Foundation[grant number 2092005].
文摘The formation and evolution of Gd-rich precipitates companying with the matrix structure ordering in a Mg_(97)Gd_(2)Cd_(1)(at.%)solid-solution alloy aged at 200℃have been systemically investigated using high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).The results show that Gd-rich precipitation dynamics during the aging treatment are noticeably affected by a continuous ordering transformation in the matrix.The ordering transformation process involving mainly re-distribution of Cd atoms was revealed to occur in the following way:random super-saturated solid solution(S.S.S.S.)→B19-type ordered domains→D019-type ordered domains.Four Gd(Cd)-rich precipitates,G.P.Ⅰ zone,G.P.Ⅱ zone,β′andβ_(1)phases,have been observed to be formed in sequence to coexist with the various ordered domains.Based on the HAADF-STEM characterization on the aging microstructures at different aging stages,it can be concluded that the Cd-addition and related matrix structure ordering can play significant roles in modifying the early-stage G.P.zone structure,altering the morphology ofβ′precipitates and promoting the forming ability of theβ_(1)precipitate.
