针对高强超细晶镁合金塑性差的问题，本项目提出通过粉末冶金工艺进行混晶结构(超细晶和微米晶)组织构型，实现Ti颗粒增强超细晶镁合金增韧的目的。采用实验和理论分析相结合的方法，开展机械球磨制备Ti颗粒增强混晶结构镁合金粉末工艺研究，构建球磨过程镁合金混晶组织演化模型；研究混晶结构粉末挤压固结成形工艺，结合第二相颗粒的钉扎效应分析热力耦合作用下混晶组织演化热力学与动力学问题；阐明Ti颗粒增强混晶结构镁合金塑性变形机制，构建混晶结构增韧的细观力学模型，揭示Ti颗粒增强镁合金混晶结构增韧机理。本项目研究工艺参数对混晶组织的影响和交互作用，实现Ti颗粒增强混晶结构镁合金可控组织构型，通过本项目的实施，确定有效增韧的混晶结构材料参数“窗口”，为高强超细晶镁合金混晶结构增韧提供必要的理论依据和设计指导。

In view of poor plasticity of ultrafine grained magnesium alloys with high strength, a process to obtain bimodal-grained microstructure (ultrafine grains mixed with micron grains) by powder metallurgy is proposed to improve the plasticity of Ti particles strengthened ultrafine grained magnesium alloys. Both the experimental and theoretical analysis will be adopted during this study. Mechanical milling will be carried out to prepare Ti particles strengthened magnesium alloys powders with bimodal-grained microstructure, and the corresponding evolution model of microstructure will be built. The milled powders with bimodal-grained microstructure will be extruded to billets and the processing parameters will be analyzed. In consideration of thermo-mechanical coupling effects together with the pinning effect of second phase particles, thermodynamics and kinetics of microstructure evolution will be investigated. The plastic deformation mechanism of Ti particles strengthened magnesium alloys with bimodal-grained microstructure will be made clear, and the micro-mechanics model about improving the plasticity of bimodal-grained microstructure will be built. Ultimately, toughening mechanism about bimodal-grained microstructure of magnesium alloys Ti particles strengthened magnesium alloys will be clarified. In this study, the influence and interaction of processing parameters will be investigated to realize the designed microstructure architecture of Ti particles strengthened magnesium alloys with bimodal-grained microstructure. Meanwhile, the window of bimodal-grained microstructure to toughen will be confirmed, which will provide the necessary theoretical basis and designing guidance for toughening ultrafine grained magnesium alloys with high strength.