中文摘要：

添加适量稀土元素钇后,镁铝合金高温力学性能会得以改善。本文利用光学显微镜（OM）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）,对693 K保温24 h的Mg-9.0wt.%Al-2.2 wt.%Zn-6.1wt.%Y铸态合金样品的微结构进行了研究。实验结果表明,显微组织相组成是基体α-Mg、晶界处γ-Mg17Al12、晶胞内的Al2Y、τ-Mg32（Al,Zn）49及-Al5Mg11Zn4相。确定了-Al5Mg11Zn4相与α-Mg基体间的取向关系是（10 10）α//（106）,[51053]α//[010]。

英文摘要：

The addition of rare earth elements（RE） into the magnesium-aluminum based alloy can improve its mechanical performance, especially the performance under the condition of higher temperature, beeause of the refinement of the grains and the emerge of the intermediate compounds. In this article, the microstructure of a magnesium-aluminum based alloy with nominal chemical composition of Mg-9. 0wt. % A1-2. 2wt. % Zn-6. 1 wt. % Y after heat-treated at higher temperature was investigated by optical microscope （OM） , X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） methods. The cast ingots of Mg-9.0wt. % A1-2. 2wt. % Zn-6. lwt. % Y alloy were thermal treated at the temperature 693 K for 24 hours then quenched into water at room temperature. The experimental results showed that the mierostrueture was constituted by a-Mg, T-Mg17Al12 phase, a little amount of the A12Y phase and two ternary phases, including τ-Mg32 （Al,Zn）49 phase and 6-A15 Mg11 Zn4 phase. Besides, the crystallographic orientation relationship （OR） between the Ф-Al5 MgH Zn4 phase and the matrix was determined as （10 ^-10）a//（106）Ф, [ ^-510^-53 ]a//[010]Ф.