Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 30    No. 6    June 2020

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Evolution of precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy with fine plate-like 14H-LPSO structures aged at 240 °C
Yong-gang PENG1,2,3,4, Zhi-wei DU1,2,3,4, Wei LIU5, Yong-jun LI6, Ting LI1,2,3,4, Xiao-lei HAN1,2, Ming-long MA6, Zheng PANG1,2,3,4, Jia-wei YUAN6, Guo-liang SHI6

1. National Center of Analysis and Testing for Nonferrous Metals and Electronic Materials, GRINM Group Co., Ltd., Beijing 100088, China;
2. Guobiao (Beijing) Testing & Certification Co., Ltd., Beijing 100088, China;
3. Beijing General Research Institute for Non-ferrous Metals, Beijing 100088, China;
4. China United Test & Certification Co., Ltd., Beijing 100088, China;
5. Beijing Chunlizhengda Medical Instruments Co., Ltd., Beijing 101100, China;
6. State Key Laboratory of Non-ferrous Metals & Processes, GRIMAT Engineering Institute Co., Ltd., Beijing 101407, China

Abstract:The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr (wt.%) alloy with fine plate-like 14H-LPSO structures aged at 240 °C were investigated using transmission electron microscopy (TEM) and high-angle annular dark-?eld scanning transmission electron microscopy (HAADF-STEM). Fine plate-like 14H-LPSO structures precipitate after heat treatment at 500 °C for 2 h, and β-type phases precipitate after the alloy is aged at 240 °C. The long-period atomic stacking sequence of 14H-LPSO structures along the [0001]α direction is ABABCACACACBABA. After being aged at 240 °C for 2 h, the β-type phases are the ordered solution clusters, zig-zag GP zones, and a small number of β′ phases. The peak hardness is obtained at 240 °C for 18 h with a Brinell hardness of 112, the β-type phases are β'''' phases and local RE-rich structures. After being aged at 240 °C for 100 h, the β-type phases are β'''', β1 and β''''F phases. β′ phases nucleate from the zig-zag GP zones directly without β″ phases, and then transform into β1 phase by β''''→β''''F→β1 transformations. The Zn not only can form LPSO structure, but also is the constituent element of β1 phases. LPSO structures have a certain hindrance to the coarsening of β'''' and β1 along á0001?α.

 

Key words: magnesium alloy; ageing; precipitates; long-period stacking ordered (LPSO) structures; HAADF-STEM

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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