镁合金作为结构轻量化和可生物降解材料，在诸多领域展现出了广阔的应用前景。为了突破镁合金在实际应用中绝对强度低和延展性差的限制，通过热成形精确控制微观组织成为实现强度-延展性协同提升的关键所在。本文针对镁合金热变形中主要的微观组织演变机制——动态再结晶（DRX）和动态析出（DP）及其相互作用机制进行了深入研究，建立了合理的微观组织演变元胞自动机（CA）模型，并将其应用于镁合金实际热成形微观组织演变的预测中。论文的主要研究内容包括：通过镁合金热变形微观组织演变的实验表征和理论分析，揭示了DRX和DP间的相互作用机制，为镁合金热成形微观组织演变建模提供了依据。研究发现，DP通过阻碍晶界迁移减缓DRX进程并细化DRX晶粒；塑性变形和DRX显著促进DP的发生，通过热力学和动力学方面的计算解释了其机理。基于维氏硬度测量和理论计算，阐明了DRX和DP对镁合金力学性能的影响。构建了镁合金DRX的CA模型，实现了对镁合金高温热变形微观组织演变的模拟。提出了DRX的CA并行计算策略，在不牺牲模拟精度的前提下大幅提升了运算速度。模型能够对镁合金DRX进行准确预测，基于模拟结果分析了温度和应变速率对DRX的影响规律并分析其成因。构建了耦合DRX和DP的多级CA模型，实现了对镁合金中低温热变形微观组织演变的模拟。将多级元胞空间的概念引入CA模型，在准确描述DRX和DP微观组织演变跨尺度特征的同时保证了模拟效率；考虑镁合金动态析出相的不均匀分布特点，提出了适用于CA方法的局部钉扎模型，以描述析出相对DRX晶粒的阻碍作用，其合理性和准确性远优于经典Zener-Smith钉扎模型。在镁合金中低温热变形中，DRX和DP被同时激活，此时DRX和DP的耦合CA模型预测精度远高于传统DRX的CA模型。通过集成宏观有限元分析和介观CA模拟，实现了对镁合金在实际热挤压中热、力场及特征区域微观组织演变的预测。分析了应变场、应变速率场和温度场对挤压棒微观组织分布的影响，发现变形不均匀对DRX的影响强于DP；与挤压实验的对比验证了有限元和CA集成模拟的结果。在更广泛的温度范围内（包括析出温度）优化热挤压工艺参数时，所构建集成模拟方案具有显著优势。

Magnesium alloy, as a structural lightweight and biodegradable material, has promising prospects in many fields. However, the application of magnesium alloy is hindered by its low absolute strength and poor ductility. Regulating and optimizing microstructure through thermomechanical processing benefits the high strength-ductility synergy of magnesium alloy. In this work, an in-depth study on dynamic recrystallization (DRX) and dynamic precipitation (DP), the main microstructure evolution mechanisms during hot deformation of magnesium alloy, as well as their interactions, is carried out. A cellular automaton (CA) model for DRX and DP is established, and further applied to predict the microstructure evolution during practical thermomechanical processing of magnesium alloy. The main contents are as follows:By experimental characterization and theoretical analysis, the underlying interactions between plastic deformation, DRX, and DP are revealed, providing a theoretical basis for modeling the microstructure evolution during hot deformation of magnesium alloy. The DRX kinetics is slowed down and the DRXed grains are refined by the pinning effect of DP. Plastic deformation and DRX significantly promote DP, which is explained through thermodynamic and kinetic calculations. Through Vickers hardness tests and theoretical analysis, the influence of DRX and DP on the mechanical properties of magnesium alloy is elucidated.A CA model for DRX is established to simulate the microstructure evolution during hot deformation of magnesium alloy at high temperature. A parallel computing strategy for the CA model is proposed, which significantly improves computational speed without sacrificing accuracy. The DRX process of magnesium alloy is accurately predicted by the established model. The influence of temperature and strain rate on DRX is analyzed.A multilevel CA model coupled DRX and DP by their interactions is developed to simulate microstructure evolution during the hot deformation of magnesium alloy at low-to-medium temperatures. A multilevel cellular space is constructed to capture the multiscale microstructure evolution of DRX and DP, achieving a balance between accuracy and computational efficiency. Considering the inhomogeneous distribution of precipitates in magnesium alloys, a local pinning model for CA method is proposed to describe the retardation of precipitates to grain boundary migration. Its rationality and accuracy significantly surpass the traditional Zener pinning model. When DRX and DP are simultaneously activated in magnesium alloy, the CA model coupled DRX and DP exhibits significantly superior accuracy compared to the traditional CA model for DRX.By integrating macroscopic finite element analysis and mesoscopic CA simulation, the microstructure evolution during practical hot extrusion of magnesium alloy is predicted. The effects of strain field, strain rate field, and temperature field on the microstructure distribution of extruded rods are analyzed. The influence of uneven deformation on DRX is stronger than on DP. The simulated results are in good agreement with the experimental ones. The integrated simulation scheme offers substantial advantages in optimizing the process parameters of hot extrusion across a broad temperature range that spans the precipitation temperature of magnesium alloy.