层状铝合金复合铸坯连续铸造的基础研究

Laminated composite possesses the properties of high strength, high hardness, high stiffness, low density and good fracture toughness. It has become one of the most potential applications of light weight high-performance materials in the field of aerospace, protective armor etc...A new continuous casting method is proposed to produce laminated aluminum alloy slab with different materials and performances between its inner and outer layer in this project. molten aluminium alloy and the mixture of boron carbide and aluminum powder are injected into a same mold. They are isolated with each other in the upper part of the mold and bond together at the bottom by a semi-solid nucleation baffle inserted in the mold. A series of studies are performed, including wettability between molten aluminum alloy and boron carbide mixture, the heat transfer and mass transfer law between the melt and mold and the heat transfer and mass transfer law between melt and boron carbide mixture. The formation and evolution law of complex layer slab interface structure will be investigated, and corresponding mathematical, physical model will be built. In addition, thermodynamics and kinetics mechanisms of the boron carbide mixture in the process of curing and rheology are studied to explore how the process parameter, the size of boron carbide particle and volume fraction affect the mechanical and physical properties of stratified slab. Finally, a new method with independent intellectual property rights for continuous casting of aluminum alloy - boron carbide mixture - aluminum alloy multi-layer stratified slab is developed. It can provide high-quality, low-cost light weight complex layer material for the near-space vehicle and equipment of the military-industrial manufacturing in China.

层状复合材料具有高强度、高硬度、高刚度和低的密度以及较好的断裂韧性，已成为航空航天、防护装甲等最有应用潜力的轻质高性能复合材料之一。.本项目提出向同一结晶器内同时注入铝合金液和碳化硼与铝粉的混合体，通过插入半固态形核挡板，将二者在结晶器上部隔离，并在结晶器下部使铝合金液与碳化硼混合体熔合在一起，连续得到内外层材质和性能不同的层状铝合金复合铸坯。通过研究碳化硼混合体与铝合金液的润湿性、连铸过程中金属熔体与结晶器、金属熔体与碳化硼混合体之间的传热、传质规律，把握复层铸坯界面结构的形成与演化规律，建立相对应的数学、物理模型。研究碳化硼混合体的固化与流变过程的热力学和动力学机制，探索工艺参数、碳化硼颗粒尺寸和体积分数对复层铸坯力学、物理性能的影响，研究出具有自主知识产权的连续铸造铝合金-碳化硼混合体-铝合金多层复合铸坯新方法。为我国近空间飞行器以及军事工业装备的制造提供优质、低价的轻质复层材料

碳化硼是一种理想的增强相材料，它具有重量轻、高强度、熔点高、热胀系数低、高温力学性能优异、良好的中子吸收能力、二次放射污染少等诸多特点，碳化硼增强铝基复合材料被认为是世界各国争夺高技术优势的热点材料之一。在未来极有可能在航天航空、军事装备、核电材料等多个重要领域得到广泛应用。本项目经过几年研究，取得以下结果：.1、自行设计了一套垂直半连续铸造设备及半连铸-热轧工艺，可通过半连续铸造方法制备大尺寸层状碳化硼增强铝基复合材料，中间层碳化硼颗粒含量高达40%，碳化硼与铝基体之间、中间层与边界层之间的具有良好的结合，界面处无缺陷，界面平直完整，力学性能优异。该方法工艺简单，成本低，生产效率高。.2、自行设计轧制工艺，将压力加工的工作温度降低至450℃。大大降低了轧制工艺的能耗，缩短了轧制工艺流程，提高生产效率。.3、通过真空座滴法研究碳化硼和铝合金的润湿性问题。发现铝合金与Al/B4C金属陶瓷复合材料润湿行为的驱动力为表面张力及毛细作用力，并深入研究了B4C颗粒质量分数、分布、表面粗糙度、合金化元素、接触时间等对二者润湿性的影响，为铸造法制备高含量碳化硼的铝基复合材料提供了重要的理论依据。.4、根据不同的应用要求，设计了不同碳化硼含量、粒径、不同层结构的层状复合材料。例如Al/Al-40wt.%B4C/Al层状复合材料板材（B4C的粒径50-75μm）因碳化硼拥有优异的热中子吸收性能，可应用在核工业乏燃料的储运中；Al/7075-40wt.%B4C/Al层状复合材料板材、7075/7075-40wt.%B4C/7075层状复合材料板材（B4C的粒径1-3mm，前板和背板材料具有厚度差）可作为轻型军用装备披挂装甲。