中文摘要：

应用透射电镜研究了快速凝固,常规凝固以及热处理后Mg97Zn1Y2合金中长周期堆垛结构（LPS）的形成、结构和变化特征。结果表明,快速凝固带状材料中,18R类型的LPS首先在网状第二相中形成,573K时效20h后,18R有向6H转变的趋势。铸态合金中LPS主要为6层堆垛结构,这种结构在573K时效50h后仍然保持稳定。铸态合金在823K热处理10h后,LPS趋于溶解,但镁基体中仍可观察到6层堆垛的LPS的存在。通过不同的凝固和热处理过程,可以获得不同结构和分布状态的LPS。

英文摘要：

　Electron microcopy has been applied to study formation,structures and structural changes of long period stacking structures（LPSs）in as-spun,as-solidified and heat-treated Mg_ 97Zn_1Y_2 alloys.The results show that the LPS structure of 18R type can form from second phases with a network distribution in the as-spun alloy.It appears that a 18R-to-6H structural transition occured when annealing the as-spun alloy at 573 K for 20 hrs.The LPS formed in the as-solidified alloy has a 6-layer periodic structure;it remained stable at 573 K for 50 hrs.When annealing at 823 K for 10 h,LPSs with 6-layer stacking structure still remained even though dissolution of LPS already taken place at this stage.It is believed that structural types and distribution for LPSs in Mg-Zn-Y alloys are controllable through changing of solidification conditions and subsequent heat treatments.