多尺度第二相颗粒对Mg-Zn-Gd-Zr合金力学性能的耦合影响及过程模拟

As a lightweight structural material, the quantitative relationships between microstructures and mechanical properties of aged magnesium alloys has attracted wide attention. In particular, the process simulation of mechanical behavior during the aging process is helpful to guide artificial control of heat treatment parameters, and achieve the best match of strength and ductility. However, current researches are mostly limited to the simple hypothesis of single aging precipitation, which can not truly reflect the coupling effects of coexistence of multiple second-phase particles and their evolutions during the aging process on the mechanical properties. In this project, Mg-Zn-Gd-Zr alloys with dual precipitates are taken as the research object. By adjusting the alloy composition and heat treatment process, a series of microstructural parameters are obtained. The quantitative relationships between the multi-scale second-phase particles and yield strength, fracture strain are systematically studied. Dual precipitation strengthening model and multi-scale fracture strain model are established to simulate the dynamic aging process. The coupling effects of multi-scale second-phase particles on mechanical properties are clarified, and the strengthening mechanism and deformation fracture mechanism are analyzed in depth. Improving the quantitative simulation studies on the composition/heat treatment process-microstructures-mechanical properties of the aged magnesium alloys could provide key theoretical guidance and experimental basis for the design and preparation of magnesium alloys with specific mechanical properties.

作为一种轻质结构材料，时效镁合金微观组织与力学性能之间的量化关系一直以来受到广泛关注，尤其是时效过程中力学行为的动态模拟，有助于指导热处理工艺参数的人为调控，实现强度和延性的最佳匹配。但目前研究多限于单一时效析出的简单假设，不能真实反映多种第二相颗粒共存及其在时效过程中演变对力学性能的耦合影响。本项目以含有双重析出相的Mg-Zn-Gd-Zr合金为研究对象，通过调整合金成分及热处理工艺，获得微观组织特征参数的系列组合。系统研究多尺度第二相颗粒与屈服强度、断裂应变之间的量化关系，建立双重析出强化模型及多尺度断裂应变模型，进行动态时效过程模拟，阐明多尺度第二相颗粒对力学性能的耦合影响，深入分析强化机制和变形断裂机理。通过完善时效镁合金成分/热处理工艺—微观组织—力学性能的量化模拟研究工作，为设计制备具有特定力学性能的镁合金提供关键理论指导及实验依据。

作为一种轻质金属结构材料，镁合金在国防军工、航空航天、轨道交通、电子产品等领域具有极为广泛的应用前景。工业用时效镁合金由于组元多且制备工艺复杂，微观组织中常含有多种不同尺度的第二相颗粒，对材料的强度和延性具有显著影响。阐明多尺度第二相颗粒与力学性能的量化关系，对高强高延镁合金的成分设计及其力学性能调控具有重要意义。. 本项目以Mg-Zn-Gd-Zr合金为研究对象，通过微观组织精细表征，与屈服强度、断裂应变相联系，分析了多尺度第二相参数与准静态力学性能之间的对应关系，并建立了相应的强化模型和断裂应变模型。结果表明，多尺度第二相颗粒的强化效果依赖于杆状、基面盘片状、球状三种多重析出相颗粒相对含量；多重时效析出相对断裂应变的耦合影响遵循加权叠加方式，且同样依赖于多重析出相之间的相对体积含量。所构建的复合强化模型、多尺度断裂应变模型较好地动态模拟了屈服强度及断裂应变随时效时间的演变。此外，项目研究了镁合金中产生吕德斯带屈服平台的充要条件是细晶晶粒组织和高密度可动位错，而且析出相可以减小吕德斯带应变。同时，制备出了异质纤维层状结构镁合金，实现了强度和延性的协同提高，并对其高强高延性机制进行了初步探索性研究。研究了多尺度第二相颗粒对镁合金腐蚀行为的影响，高密度且细小的纳米杆状析出相，对腐蚀产物膜层具有强烈的钉扎作用，阻碍腐蚀进程，有助于提高镁合金的耐腐蚀性。. 本项目对阐明多尺度第二相颗粒微观组织与强韧化变形断裂行为和腐蚀行为的构效关系提供了重要支撑，对设计和制备高性能镁合金材料具有重要的指导意义。