金属再结晶织构的相场模拟与择优取向机制

This project aims to develop a model for texture evolution in recrystallization annealing of metals based on phase field kinetics. For this purpose, we investigate the expression of order parameters for factors such as crystalligraphic orientations and strain stored energy and the construction of corresponding phase field equations. A method for including the calculation of grain boundary energy and grain boundary mobility from molecular dynamics into the phase field framework is established. A energy principle for the determination of preferential grain orientations during nucleation is proposed. As validations, face-centered cubic metals with different stacking fault energies are subjected to plastic deformation up to various strain levels along various strain paths. The recrystallization behavior and the corrsponding texture and microstructure developments are investigated. A method to determine the initial conditions needed for the simulations from electron-back scattering diffraction and X-ray diffraction is established.The formation mechanisms of preferred orientations during nucleation and growth and the underlying physics are investigated by comparing the experimental and modeling results. The theoretical and experimental results can bring insight into the effect of structural characteristics, processing state, and annealing conditions on the recrystallization behavior and the underlying mechanisms. These results are also expected to enrich and extend the theory as well as the modeling and simulations techniques about recrystallization, and to provide important theories and methods to aid the control of texture, microstructure and properties of metals during annealing treatment.

：本项目基于相场动力学研究晶体学取向和应变储能等因素的序参量表示方式及相应相场方程的构建，引入晶界能和晶界迁移率的分子动力学计算，提出再结晶形核择优取向的能量原则，建立再结晶退火织构与组织演变的相场模型，以更好反映再结晶过程中的物理行为、定量预测再结晶织构的演变；选取具有不同层错能的面心立方金属，进行多种变形路径和变形程度的塑性加工，研究退火过程中的再结晶行为和织构及组织演变，确立通过电子背散射衍射和X 射线衍射相结合以确定模拟所需初始条件的方法；结合实验和模拟结果，深入探讨晶粒在形核和长大阶段的择优取向机制及其物理本质、层错能的影响。相关理论和实验成果的取得将进一步揭示材料结构特性与状态及退火条件对再结晶行为的影响规律和机理，丰富和发展金属材料再结晶理论和建模与仿真技术，为有效控制材料的退火织构、组织及性能提供重要的理论依据和方法。

本项目采用以纯铝和紫铜为代表的层错能不同的典型面心立方金属，开展了冷轧、等通道转角挤压(ECAE)、累积叠轧焊(ARB)三类塑性加工和退火试验，定量测试和表征了形变和退火过程中微观组织和晶体学织构的演变规律；在理论方面，发展了合成驱动力分子动力学晶界迁移计算方法、截断球形分子动力学晶界能计算方法，构建了纯铝晶界特性大型数据库；提出有效网格追踪相场计算方法，提出了最小晶界能形核准则、晶核吞噬基体晶粒长大的最大迁移速率准则以及再结晶晶粒间竞争长大的局部能量最小化准则，确立了充分考虑形变材料微结构特征、形核和长大动力学的再结晶退火行为与组织及织构演变的相场和蒙特卡罗模型；结合模拟和实验结果，开展了冷轧纯铝再结晶退火过程中晶粒形核及长大微观组织与织构的模拟计算，验证了模型的精度和计算效率，深入探讨了定向形核和择优长大对退火织构演变的影响及其机理，获得了关于再结晶织构形成纳观-微观物理本质的新认识。相关理论和实验成果的取得进一步揭示了材料结构特性与状态及退火条件对再结晶行为的影响规律和机理，丰富和发展金属材料再结晶理论和建模与仿真技术，为有效控制材料的退火织构、组织及性能提供了理论依据和方法。