Precipitation behavior of 14H LPSO structure in single 18R phase Mg-Y-Zn alloy during annealing at 773 K

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• 作者：Huan LIU^a ; ^b ; ^{liuhuanseu@hhu.edu.cn} ; Kai YAN^c ; Jing-li YAN^d ; Feng XUE^d ; Jia-peng SUN^a ; Jing-hua JIANG^a ; ^b ; Ai-bin MA^a ; ^b
• 关键词：Mg&ndash ; Y&ndash ; Zn alloy ; 18R LPSO phase ; 14H LPSO phase ; high-temperature annealing ; microstructure evolution
• 刊名：Transactions of Nonferrous Metals Society of China
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：27
• 期：1
• 页码：63-72
• 全文大小：3581 K
• 卷排序：27

文摘

The microstructural evolution of a 18R single phase (S18) alloy during annealing at 773 K for 100 h was investigated in order to reveal the formation mechanism of 14H phase. The results showed that the as-cast S18 alloy was composed of 18R phase (its volume fraction exceeds 93%), W particles and α–Mg phase. The 18R phase in S18 alloy was thermally stable and was not transformed into 14H long period stacking ordered (LPSO) phase during annealing. However, 14H lamellas formed within tiny α–Mg slices, and their average size and volume fraction increased with prolonging annealing time. Moreover, the 14H phase is nucleated within α–Mg independently on the basis of basal stacking faults (SFs). The broadening growth of 14H lamellas is an interface-controlled process which involves ledges on basal planes, while the lengthening growth is a diffusion-controlled process and is associated with diffusion of solute atoms. The formation mechanism of 14H phase in this alloy could be explained as α–Mg'→ α–Mg+14H.