Effect of Zn on microstructure evolution of Mg-Gd-Y-Nd-Zn-Zr alloy during heat treatment

2018 6th International Conference on Mechanical Engineering, Materials Science and Civil Engineering

材料科学;机械制造;土木建筑工程

Li, T.^1 ; Chen, D.J.^2 ; Liu, W.^1 ; Yuan, J.W.^2 ; Qu, J.^1

China United Test AndCertification Co. Ltd., Guobiao (Beijing) Testing and Certification Co., Ltd., No.2, Xinjiekouwai Street, Xicheng district, Beijing

100088, China^1

State Key Laboratory of Non-ferrous Metals and Processes, GRIMAT Engineering Institute Co. Ltd., No.11, Xinkedong Street, Huairou district, Beijing

101407, China^2

关键词: Aging process;    As-cast;    Eutectic phase;    Lpso phase;    Micro-structure evolutions;    Zn alloys;    Zn content;    Zr alloys;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/542/1/012040/pdf
DOI  :  10.1088/1757-899X/542/1/012040

来源: IOP

【 摘 要 】

The effect of Zn on the microstructure evolution of Mg-7Gd-3Y-1Nd-xZn-0.5Zr (x=1.0, 2.0) (wt.%) alloys during homogenization and ageing heat treatment has been investigated systemically. The results indicate that as-cast 1 Zn alloy is composed mainly of α-Mg, Mg5(RE, Zn) eutectic phase, (Mg, Zn)3RE eutectic phase, stacking faults and block-like compounds rich in RE. Increasing of Zn content result in the disappearance of Mg5(RE, Zn) eutectic phase, but the volume fraction of 14H-typ LPSO phase is increasing, which has made it even more difficult to dissolve into the matrix during homogenization. After homogenization at 520 °C for 48 h, the 14H LPSO phase remains in the alloys with 2 wt.% Zn, but only compounds rich in RE can be seen in the alloy with 1 wt.%Zn. After ageing at 240°C for 18 h, the coherent β′ phase can be found both in 1Zn and 2Zn alloys, resulting in the increase of mechanical properties. The β′, β1 and stacking faults can be found in 1Zn and 2Zn alloys after ageing at 240°C for 100 h. However, it can be concluded that Zn can suppress the formation of LPSO phases but impede the precipitation of β′ and β1 during the aging process. The as-aged alloy with 1% Zn addition shows the optimal mechanical properties.