通过在表面生成纳米晶层，有可能使得材料的整体性能提高而不改变其化学成分，表面机械研磨处理（SMAT）是近年来发展起来的非常有效的材料表面纳米化处理方法。本项目以高强度稀土镁合金Mg-Gd系作为研究对象，通过SMAT工艺对材料进行表面纳米化处理，研究稀土元素含量、初始晶粒尺寸及SMAT工艺参数对合金表面微观组织的演变规律；采用高分辨透射电镜对合金表面形成的具有梯度结构的组织进行表征，并将其与SMAT变形过程中的应力-应变关系相对照，深入研究合金在SMAT过程中的晶粒细化机制；最后测试合金的室温低周疲劳性能，研究疲劳裂纹萌生和扩展特征，理解SMAT处理后合金的疲劳强化机制，用以指导稀土镁合金表面纳米化处理工艺参数的优化。

By generating nano-crystalline layer on the surface, it may make to improve the overall performance of the materials without changing its chemical composition; surface mechanical attrition treatment (SMAT) is a very effective nano-material surface treatment methods developed recently. This project is focused on a high strength magnesium alloy Mg-Gd system and investigates the effect of RE contents, initial grain size and SMAT processing parameters on the microstructure evolution during SMAT treatments; by using HRTEM to characterize the gradient structure formed on the surface of the alloy, and also study the stress-strain relationship during deformation process, the grain refinement mechanism of SMAT process will be clarified through combination of microstructure investigation and deformation mechanisms studying; finally the low cycle fatigue properties at room temperature will be tested, and the fatigue crack initiation and propagation will be also characterized, in order to understanding the strengthening mechanism of fatigue in the Mg-Gd alloy after SMAT treated. The research results should be a fundamental knowledge for optimizing the process parameters to generate a nano-crystalline layer in the surface of magnesium alloys.