CAS Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Acadamy of Sciences, 62 Wencui Road, Shenyang 110016, China.
Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China.
Sci Rep. 2017 Jan 5;7:40078. doi: 10.1038/srep40078.
Natural ageing responses of duplex structured Mg-6%Li and Mg-6%Li-6%Zn-1.2%Y alloys have been investigated. Microstructural analyses revealed that the precipitation and coarsening process of α-Mg particles could occur in β-Li phases of both two alloys during ageing process. Since a certain amount of Mg atoms in β-Li phases were consumed for the precipitation of abundant tiny MgLiZn particles, the size of α-Mg precipitates in Mg-6%Li-6%Zn-1.2%Y alloy was relatively smaller than that in Mg-6%Li alloy. Micro hardness measurements demonstrated that with the ageing time increasing, the α-Mg phases in Mg-6%Li alloy could have a constant hardness value of 41 HV, but the contained β-Li phases exhibited a slight age-softening response. Compared with the Mg-6%Li alloy, the age-softening response of β-Li phases in Mg-6%Li-6%Zn-1.2%Y alloy was much more profound. Meanwhile, a normal age-hardening response of α-Mg phases was maintained. Tensile results indicated that obvious ageing-softening phenomenon in terms of macro tensile strength occurred in both two alloys. Failure analysis demonstrated that for the Mg-6%Li alloy, cracks were preferentially initiated at α-Mg/β-Li interfaces. For the Mg-6%Li-6%Zn-1.2%Y alloy, cracks occurred at both α-Mg/β-Li interfaces and slip bands in α-Mg and β-Li phases.
对双相结构 Mg-6%Li 和 Mg-6%Li-6%Zn-1.2%Y 合金的自然老化响应进行了研究。微观结构分析表明，在时效过程中，两种合金的β-Li 相中都可能发生α-Mg 颗粒的析出和粗化过程。由于β-Li 相中一定数量的 Mg 原子用于析出大量细小的 MgLiZn 颗粒，因此 Mg-6%Li-6%Zn-1.2%Y 合金中α-Mg 析出物的尺寸相对较小Mg-6%Li 合金。显微硬度测试表明，随着时效时间的增加，Mg-6%Li 合金中的α-Mg 相可以具有 41 HV 的恒定硬度值，但所含的β-Li 相表现出轻微的时效软化响应。与 Mg-6%Li 合金相比，Mg-6%Li-6%Zn-1.2%Y 合金中β-Li 相的时效软化响应更为明显。同时，α-Mg 相保持正常的时效硬化响应。拉伸结果表明，两种合金的宏观拉伸强度都出现了明显的时效软化现象。失效分析表明，对于 Mg-6%Li 合金，裂纹优先在α-Mg/β-Li 界面处萌生。对于 Mg-6%Li-6%Zn-1.2%Y 合金，裂纹发生在α-Mg/β-Li 界面和α-Mg 和β-Li 相中滑移带处。
