中文摘要：

利用摩擦搅拌加工技术，对AZ31镁合金进行表面组织细化、表面复合化。通过金相显微镜和扫描电镜观察研究搅拌摩擦加工后的加工显微组织及退火显微组织，并测试加工区的硬度，发现摩擦搅拌区晶粒明显细化，晶粒尺寸可降至几微米，且复合化表面即使高温长时间退火，组织依然稳定；摩擦搅拌加工制备复合材料，分别添加纳米Si3N4粒子和SiO2粒子复合于AZ31镁合金表面，纳米粒子均匀分布于合金表面，与未添加任何粒子的样品相比，晶粒细化效果明显提高，且由于复合粒子在基体中产生大量新界面，抑制了晶界迁移，使搅拌摩擦加工后的组织具有很高的热稳定性。

英文摘要：

The surface structure refinement and compounding of AZ31 alloy by friction stir processing （FSP） were studied. Metallographic microscope and scanning electronic microscope were used to observe the microstructure of FSPed and annealed samples, and the hardness of the stirred area was measured. The results show that an obvious refinement of grain size within the FSPed region can be observed with grain size reduced to micrometers, and the structure of composited surface remains stable even after long-time annealing at high temperature. Particulate-reinforced composites were prepared by compounding nano-scaled particles such as Si3 N4 and SiO2 respectively into AZ31 matrix by FSP. Due to particles distributed homogeneously at the surface, grain Furthermore, the migration of the grain boundary is restrained FSPed structure presents a high degree of thermal stability. size is finer than that of the by the new boundaries created uncompounded samples. by those particles, so the