汽车用高成形性铝合金内多尺度原生相梯度分布的过程关联与耦合调控机制

In view of the great requirement of car lightweight on the wrought Al alloys with low cost and high comprehensive performance, and the aggregation of iron-rich phases during melt and casting process and their adverse effects, based on process correlation and coupling control on the formation, dispersion and graded distribution of primary iron-rich phases, it has been put forward a new method to greatly improve the formability of advanced Al alloys in this proposal. After process correlation and coupling control on micro-alloying, multi physical field in melting and casting, and thermomechanical processing, not only the graded distribution of multi-sized primary phases, but also the graded microstructure and random orientation features can be formed in the final alloy sheets due to the positive effects of multi-sized primary phases on the evolution of microstructure and texture. These features finally could make the formability of alloy sheets greatly improved. The following topics, the formation, dispersion, graded distribution of multi-sized primary iron-rich phases, and the evolution, influence and reappearance of the distributed multi-sized primary phases during thermomechanical processing all will be deeply studied by EBSD, XRD, TEM, neutron diffraction, numerical simulation and mechanical property measurements. Accordingly, the quantitative relationship between composition, processing, microstructure and properties can be established, and then, the process correlation and coupling control mechanism of graded distribution of multi-sized primary iron-rich phases can be put forward based on it. The systematical researches in this project will not only benefit the further development, fabrication, characterization and applications of the advanced Al alloys, but also provide an important theoretical support for better controlling the microstructure of many other alloys and studying the related key scientific issues in them.

针对汽车轻量化对低成本高综合性能变形铝合金的迫切需求，以及传统熔铸易使富铁相偏聚长大而产生不利影响等问题，本项目提出基于多尺度原生富铁相形成、离散和梯度分布的过程关联与耦合调控大幅提高新型铝合金板材成形性能的研究思路。通过微合金化、熔铸时多物理场和热加工等多过程关联与耦合调控，不仅可使多尺度原生富铁相梯度分布，而且可利用其对组织和织构演化的积极影响，使终态合金呈梯度组织和随机取向特征，成形性能获突破性提高。本项目拟采用EBSD、XRD、TEM、中子衍射、数值模拟和性能测量等手段，对多尺度原生富铁相形成、离散、梯度分布及其热加工时的演化、影响和再现进行深入研究。据此建立成分-工艺-组织-性能间定量关系，进而提出多尺度原生富铁相梯度分布的过程关联与耦合调控机制。本研究不仅为该系合金进一步开发、加工、表征和应用提供重要指导，而且也为其它合金组织调控及其相关机制等共性关键科学问题研究提供理论支撑。

针对汽车轻量化对低成本高综合性能变形铝合金的迫切需求，以及传统熔铸易使富铁相偏聚长大而产生不利影响等问题，本项目打破传统铝合金组织调控思路，开展了基于多尺度原生富铁相形成、离散和梯度分布的过程关联与耦合调控创新性研究，最终使得新型铝合金板材成形性能获大幅提高。具体包括：（1）促进原生富铁相形核的微合金化元素设计原则及其作用机制研究：通过建立微合金化元素种类（Ni和P）、含量与原生富铁相尺寸、形态、构成和分布间关系，掌握了有效促进原生富铁相形核的Ni和P微合金化元素设计原则及作用机制。（2）多尺度原生富铁相形成、离散和梯度分布的多场耦合调控方法及其作用机制研究：系统研究了复合物理场处理条件对原生富铁相尺寸、形态以及分布状态的影响规律，掌握了调控工艺参数对组织的影响规律以及最佳调控工艺，同时通过建立合金成分、富铁相凝固行为、物理场处理条件、原生富铁相尺寸、形态以及分布状态等之间的关系，并结合模型图创建，研究清楚了多尺度原生富铁相形成、离散和梯度分布的多场耦合调控作用机制。（3）热加工时多尺度原生富铁相梯度分布合理演化、影响和再现的多过程耦合调控方法及其作用机制研究：完成了热加工多过程对多尺度原生富铁相梯度分布在合金内进一步演化、影响以及再现的多过程调控研究，掌握了工艺参数对合金组织和性能的影响规律以及最佳调控工艺，同时，通过建立各因素间关系，揭示了热加工多过程耦合调控作用机制。（4）高成形性合金内多尺度原生富铁相梯度分布的过程关联与耦合作用机制研究：根据所制备高成形性合金板材组织特征及其协调变形行为，建立了各因素间关系，提出了高成形性铝合金内多尺度原生富铁相梯度分布的过程关联与耦合作用机制。本研究不仅对于低成本高性能新型Al-Mg-Si-Cu-Zn系合金进一步开发、加工和应用具有重要推动作用，且对于汽车轻量化用新型铝合金及其他特殊领域用新型铝合金的组织设计、调控以及相关作用机制研究也有重要的指导和启迪作用。