深冷镁合金纳米准晶相析出动力学及强化机制

纳米准晶相具有特殊的高硬度和低界面能等优点，能够弱化镁合金的织构和改善变形行为，是一种提高镁合金综合性能的优良增强相。因此，寻找一种合适的工艺，使镁基体中能够形成大量的纳米准晶相，是提高镁合金性能的一个关键。 本项目拟选择准晶增强Mg-Zn-Gd合金系，对其进行深冷处理，促使镁合金基体内部形成大量的纳米准晶相，并研究其析出动力学及强化机制。本项目研究镁合金纳米准晶相在深冷条件下的析出动力学条件，揭示纳米准晶相的形成机理和析出动力学模型。研究深冷条件下镁合金成分对纳米准晶相形成的热力学条件。研究深冷条件对镁合金组织结构的变化(包括晶粒大小、晶粒转动和织构)和力学性能的影响，阐明纳米准晶相对镁合金的强化机制。揭示深冷处理工艺-组织结构-性能之间的本质关系。 本项目研究将揭示深冷条件下纳米准晶相的形成机制及其对镁合金的强化机制等基础理论，对我国高性能镁合金材料研究具有重要的学术价值和应用前景。

Quasicrystalline phase with nanoscale (nano I-phase) has fantastic physical properties, such as high hardness and low interface energy. This kind of nano I-phase is one excellent strengthening phase of magnesium alloy, since nano I-phase could weaken largely basal texture of Mg alloy and then improve its deformation behavior. Thus, the key point is to design a process, which could form large volume fraction of nano I-phase in the Mg matrix. The present project is plan to study the precipitation kinetics of nano I-phase and its strengthening mechanism in Mg-Zn-Gd alloy by using the cryogenic treatment. Cryogenic treatment (CT) is a technique that materials are going to be processed at about liquid nitrogen temperatures (77K). The formation condition of nano I-phase under cryogenic environment will be focused. The model of precipitation kinetics of nano I-phase will be constructed. The thermodynamic of I-phase will be investivaged through varing the component of Mg alloy under the cryogenic condition. The effect of CT on microstructures (including grain size, grain rotation and texture) and mechanical properties of Mg alloy under ambient and elevated temperature will be investigated intensely. The strengthening mechanism of nano I-phase will be illustrated by discussing the relationship among CT, microstructure and properties. This project has significant scientific value for the development of Mg alloy with high performance and promotes its application.