析出相对第三代铝锂合金热机械加工组织织构演变的作用规律及影响机制研究

The third generation aluminum-lithium alloys, the key structural materials for the C919 aircraft, have not been completely commercialized in China. At present, many scientific issues including microstructure/texture evolution, structure-property relationship and associated influential mechanism during thermomechanical processing are still not clear for the academia, seriously hindering the optimization of processing technologies, alloy microstructure and final performance. In this project, the effect of precipitate characteristics and plastic deformation parameters on dislocation structure and microstructure/texture evolution process and mechanism will be investigated systematically, based on the AA2099 aluminum-lithium alloy, using advanced analytic techniques and equipment. Crystal plasticity constitutive models simulating the interaction between precipitates and dislocations will be built to reveal the associated rules existing between dislocation slip and microstructure/texture evolution, and consequently, to discover how precipitate characteristics affect the microstructure/texture evolution during the plastic deformation process. In addition, the effect of precipitate characteristics and annealing parameters on microstructure/texture evolution will be studied to unveil the mechanism for the effect of precipitates on recrystallization nucleation and grain boundary migration. Then the effect of precipitates on microstructure/texture evolution during the annealing process will be elucidated. The outcomes of the project will enrich and advance the theories associated with microstructure/texture evolution of aluminum-lithium alloys during thermomechanical process from the perspective of precipitates, which will eventually provide important theoretical guidance for adjusting the microstructure/texture and properties of aluminum-lithium alloys through controlling precipitate characteristics.

第三代铝锂合金是C919客机的关键结构材料，尚未实现国产化替代。目前学术界对铝锂合金加工过程组织织构演变规律、构性关系及影响机制等科学问题的研究尚不明晰，严重制约了铝锂合金加工工艺和组织性能的优化。本申请拟以第三代铝锂合金AA2099为研究对象，采用先进显微分析手段，系统研究轧制过程析出相特征与变形参数对位错结构演化的影响机制及对组织织构演变的作用规律；构建耦合析出相-位错相互作用的晶体塑性本构模型，采用晶体塑性有限元模拟阐明位错滑移机制与变形组织织构的关联规律，揭示析出相特征对变形组织织构演变的影响机制。系统研究不同析出相特征和退火参数条件下组织织构的演变行为，揭示析出相对再结晶形核及晶界迁移的影响机制，阐释析出相对退火组织织构演变的作用规律。项目研究成果将丰富和发展基于析出相作用的铝锂合金热机械加工过程组织织构演变规律与机制理论体系，为利用析出相调控铝锂合金组织织构和性能提供理论指导。

项目以第三代铝锂合金AA2099为研究对象，针对δ’、T1、T2等析出相在热机械加工过程中对变形及退火微观组织织构的影响规律与机制开展了系统深入的研究，对变形协调机制、轧制织构演变、再结晶形核机制、再结晶组织织构控制、构性关系等关键点进行了重点剖析，取得的主要研究结论和科学意义如下：.1）δ’相可显著增强平面滑移，促进剪切带形成；平面滑移增强导致基体易开动滑移系个数降低，变形协调机制更接近Relax Constrain模型。T1与T2相对平面滑移具有抑制作用，使基体易开动滑移系个数上升，变形协调机制更接近Full Constrain模型。上述变形协调机制差异将导致β-fiber取向管在ODF空间中的位置发生移动，并对后续退火组织织构产生遗传效应。.2）基于1）中δ’ 、T1和T2相对位错滑移的影响规律，建立了δ’ 、T1和T2相影响下的晶体塑性模型，实现了变形织构和几何必须位错分布的精确预测，揭示了上述析出相对AA2099合金变形组织织构演变的影响机制。.3）AA2099合金的再结晶形核机制主要为粒子激发形核机制，β-fiber取向管的移动将影响40°<111>高可动界面的形成几率，进而影响退火组织织构。T1相可以通过缓解粗大颗粒附近非均匀应变的方式，抑制粒子激发形核，可从源头指导解决铝锂合金固溶过程易发生异常晶粒长大的技术难题。.4）探明了异步轧制在AA2099合金板厚方向组织均匀性方面的工艺优势，理清了AA2099合金异步轧制的微观组织演变规律，为铝锂合金薄板制造新工艺开发提供了理论指导。.5）阐明了预拉伸时效板材的力学各向异性与基体内的无T1相析出带间的关联机制，基于定量实验结果和Hall-Petch公式，建立了力学各向异性预测模型，深化了学术界对AA2099合金构性关系的认识。.项目研究工作在国内外高水平期刊发表论文11篇，其中SCI一区论文6篇，二区论文4篇，EI收录论文1篇；授权国家发明专利3项；获省部级科技进步二等奖1项；组织学术会议2次；培养研究生12人。研究成果作为第三代铝锂合金微观组织织构精细调控的理论基础，将为我国研发高端铝锂合金材料自主制备技术提供重要支撑。