中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 27 No. 1 January 2017 |
（1. College of Mechanics and Materials, Hohai University, Nanjing 211100, China;
2. Ocean and Coastal Engineering Research Institute, Hohai University, Nantong 226300, China;
3. College of Mechanical Engineering, Yangzhou University, Yangzhou 225009, China;
4. College of Materials Science and Engineering, Southeast University, Nanjing 211189, China）
Abstract: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.
Key words: Mg-Y-Zn alloy; 18R LPSO phase; 14H LPSO phase; high-temperature annealing; microstructure evolution
