两级网状结构(TiBw+Ti5Si3)/TC4复合材料设计与强化机理

受自然界多级多尺度结构启发，为提高钛基复合材料综合性能，通过低能球磨在TC4颗粒周围同时镶嵌细小TiB2粉与Si粉，在热压烧结过程中TiB2与Ti反应形成微米TiB晶须(TiBw)，分布在TC4颗粒周围形成一级网状结构(约150μm)。Si通过固溶和脱溶，在一级网状结构内部的α相周围析出纳米针状Ti5Si3，形成二级网状结构(约10μm)，其结构参数与组织特征可通过热处理得到调控。通过对复合材料结构参数、制备参数与热处理参数的设计与优化，实现(TiBw+Ti5Si3)/TC4复合材料两级网状结构精确设计与综合性能宏观调控，阐明复合材料微观结构与性能的内在关系，揭示两级网状结构与纳米针状Ti5Si3形成与演变机制。结合断裂与原位拉伸分析，揭示两级网状结构(TiBw+Ti5Si3)/TC4复合材料强化机理。为金属基复合材料多级多尺度结构设计与复合材料强韧化理论研究提供试验与理论指导。

Inspired by natural multi-scale hierarchical structures, in order to further improve combination property of titanium matrix composites, fine TiB2 powders and Si powders are simultaneously adhered onto the surface of TC4 particles by low-energy milling process. Micro TiB whiskers (TiBw) are in-situ synthesized by the reaction between TiB2 and Ti in the process of hot pressing sintering, and distributed around TC4 particles, which forms the first-scale network structure with about 150μm diameter. Subsequently, nano Ti5Si3 needles are formed by Si solid solution and precipitation, and distributed around α grains in the interior of the first-scale network structure, which forms the second-scale network structure with about 10μm diameter. The parameters of the second-scale network structure and microstructure characteristics of Ti5Si3 can be controlled by subsequent heat treatment. The delicate design of two-scale network structures and macro control of mechanical property of (TiBw+Ti5Si3)/TC4 composites will be achieved by designing and optimizing the composite structure parameters, fabrication parameters and heat treatment parameters. The relationships between microstructure and property of the composites will be clarified. The formation and evolution mechanisms of two-scale network structure and Ti5Si3 reinforcement will be further revealed. Combining with analysis on fracture and in-situ tensile observation, the strengthening mechanisms of (TiBw+Ti5Si3n)/TC4 composites with two-scale network microstructure can be finally revealed. Therefore, the present work will provide experimental and theoretical guides for multi-scale hierarchical structure design of metal matrix composites and toughening mechanisms investigation on composites.