碳化硼颗粒增强铝基复合材料热处理过程中多相多尺度组织结构的演变规律及强韧化机理

AA7075-B4C复合材料一直是高比强度材料领域的研究热点，但其室温塑性较差，在保证材料强度的基础上通过多尺度结构设计有望提高铝基复合材料的塑性/韧性，然而，针对可热处理强化AA7075-B4C复合材料，其热处理(固溶-时效处理)过程中多相多尺度组织结构的演变规律及其强韧化机理尚不明确。本项目基于热稳定性差异诱导部分晶粒长大的多尺度结构设计方法，采用粉末冶金实现粗晶粒在纳米/超细晶基体中的均匀分布。构建三维MC Potts模型研究热处理对不同尺度Al晶粒空间分布的影响规律，研究时效阶段不同尺度Al晶粒内纳米析出相的形成与分布规律，建立热处理工艺-多相多尺度结构-综合力学性能的内在关联，基于Mori-Tanaka两“相”模型，结合背应力强化理论阐明多相多尺度组织结构的协同强韧化机理。预期研究成果将为AA7075-B4C复合材料的热处理工艺参数优化和可控结构设计提供理论指导。

AA7075-B4C composites have been widely studied in the field of materials with high specific strength, however, this type of composites show limited plasticity at ambient temperature. The multi-modal design are able to enhance the plasticity/toughness of Al-based metal matrix composites without sacrifice of the strength, but for the heat treatable AA7075-B4C composites, the scientific puzzle of the multi-modal structural evolution and strengthening-toughening mechanisms during heat treatment processing is still unclear. Based on the multi-modal design of the local grain growth caused by the thermal stability difference, the coarse grains are able to distribute uniformly in the nanocrystalline/ultra-fined grains via Powder Metallurgy. This project is going to study the influence of heat treatment on the spatial distribution of multi-scaled Al grains by creating the three-dimensional MC Potts model; to study the formation and distribution of the precipitates in multi-scaled Al grain interior during aging; to establish the correlation of the heat treatment processing, multi-modal structure and comprehensive mechanical properties; to clarify the synergetic strengthening-toughening mechanisms by combination of two phases Mori-Tanaka modal and back-stress strengthening. The expected research results can provide the AA7075-B4C composite with theoretical basis including the optimization of the heat treatment processing, and controllable structure design.