纳米TiB2-Sc协同作用下铸造铝锂合金晶界PFZ与析出相调控机制

铸造铝锂合金因轻量化显著、各向同性且易于成形大型复杂零件等特点在航空航天领域具有广阔的应用前景。然而，铸造铝锂合金在时效热处理过程中易形成晶界无析出带(PFZ)且δ'相(Al3Li)粗化严重，导致材料强韧性差而限制其应用，亟需开发有效的时效析出强化方法。本项目提出将少量纳米TiB2与微量Sc相配合对铸造铝锂合金时效析出行为进行协同调控的新方法，实现沉淀析出相/纳米颗粒在合金中均匀分布而大幅缩小晶界PFZ宽度，在显著提高合金强韧性的同时大幅度缩短峰时效时间。研究内容包括：1)纳米TiB2-Sc协同作用下凝固组织演变与TiB2颗粒分布控制方法；2)凝固组织、时效条件对晶界PFZ和析出相特征的影响规律及调控机制；3)纳米TiB2-Sc协同作用下铸造铝锂合金力学性能变化规律及强韧化机理。研究成果对于开发低密度、高强韧铸造铝锂合金强化及快速时效响应新技术，扩大铝锂合金的应用范围具有重要意义。

Cast Al-Li alloys have broad application prospects in the aerospace field due to their remarkable light weight, isotropy and feasibility in large and complex parts. However, in the process of aging heat treatment, cast Al-Li alloys are prone to form precipitation free zone (PFZ) at grain boundaries and δ'(Al3Li) phase is severely coarsened, resulting in poor strength and toughness of cast Al-Li alloys, which limits their industrial applications. Therefore, it is urgent to develop an effective aging precipitation strengthening method for cast Al-Li alloys. This project proposes a novel method to synergistically control the aging precipitation behavior of cast Al-Li alloys by introducing a small amount of TiB2 nanoparticles with minor Sc elements, so as to achieve the uniform distribution of precipitates/ nanoparticles in the alloy and greatly reduce the width of grain boundary PFZ, which not only significantly improves the strength and toughness of the alloy, but also greatly shortens the peak aging time. The research contents include: 1) The evolution of solidification microstructure and the control method of TiB2 particle distribution under the synergistic effect of nano-TiB2-Sc; 2) The influence of solidification microstructure and aging conditions on the characteristics of grain boundary PFZ and precipitates and their regulation mechanism; 3) Variation in mechanical properties, and strengthening & toughening mechanism of cast Al-Li alloys under the synergistic effect of nano-TiB2-Sc. The research results have important significance for developing new technologies of strengthening and rapid aging response of low-density, high strength and toughness cast Al-Li alloys, and expanding the application range of Al-Li alloys.