晶内分布碳纳米管增强铝基复合材料及其强化机制研究

Regarding the problems of low content of singly dispersed carbon nanotubes (CNTs) and poor bonding between Al and CNTs induced by the intergranular dispersion of CNTs in Al matrix composites, a new idea of intragranular distribution of CNTs is proposed. Firstly, the Al-CNTs composite powders after high energy ball milling are annealed and process control agents are added repeatedly to realize multiple cycles of the powder flattening-spheroidization process, which promotes the dispersion of CNTs into Al powders and grains. Then, low-temperature sintering and large-deformation hot extrusion are applied to realize the uniform dispersion of high-content CNTs in the matrix and effective Al-CNTs interface. On this basis, the relationship between the fabrication parameters and microstructure of intragranular-reinforcing typed CNTs/Al composites is systematically studied. The evolution of CNTs distribution, size and matrix grain features during dispersion and consolidation are revealed towards the controllable design of CNTs implantation positions in grains. The deformation behavior and strengthening mechanisms of intragranular reinforced CNTs/Al composites are clarified to provide theoretical and technical support for the preparation and aerospace applications of Al matrix composites with comprehensively excellent mechanical properties of high strength, high modulus and high plasticity.

针对碳纳米管/铝（CNTs/Al）复合材料中CNTs分布在Al晶界导致CNTs单一分散含量低与Al-CNTs界面结合差的问题，提出Al晶粒内部分布CNTs的新思路，即首先通过重复对高能球磨Al-CNTs粉末进行退火处理并添加过程控制剂，实现粉末扁平化-球化过程多次循环，促进CNTs分散并进入Al晶粒内部，随后采用低温烧结与大变形量热挤压实现高含量CNTs在基体晶内均匀分散与Al-CNTs有效界面结合。在此基础上，系统研究晶内增强型CNTs/Al复合材料的制备工艺与微观组织关系，揭示分散与成形过程中CNTs分布与尺寸、基体晶粒结构的演化规律，实现CNTs植入晶粒内部位置的可控设计，阐明晶内增强型CNTs/Al复合材料的变形行为与强化机制，为具有高强度、高模量、高塑性等优异力学性能Al基复合材料的制备及其在航空航天领域的应用提供理论支持与技术支撑。

碳纳米管增强铝基复合材料因其优异的综合力学性能有望成为下一代轻质高强结构材料，在空天领域具有重要的应用前景。高含量CNTs的均匀分散是制备高性能CNTs/Al复合材料性能的关键，针对碳纳米管/铝（CNTs/Al）复合材料中CNTs分布在Al晶界导致CNTs单一分散含量低与Al-CNTs界面结合差的问题，本项目提出Al晶粒内部分布CNTs的新思路，即首先采用高能球磨法通过控制粉末变形及冷焊过程，促进CNTs分散并进入Al晶粒内部，随后采用低温烧结与大变形量热挤压实现高含量CNTs在基体晶内均匀分散与Al-CNTs有效界面结合。研究发现，球磨过程中复合材料粉末在磨球的压应力和剪切应力下扁平化，CNTs在这一过程中逐渐嵌入铝粉内部，并随着冷焊过程的进行裹入颗粒粉末内部，且扁平状粉末态持续时间长有利于CNTs进入基体晶粒内部。制备的晶内分散2wt.%CNTs/Al复合材料相比晶界2wt.%CNTs/Al复合材料，强度提升5.7%，延伸率提升36.4%。制备的6wt.%CNTs/Al复合材料强度达542MPa，断裂应变为10.2%，大幅度提升了现有CNTs/Al复合材料的强塑匹配性。通过增强机制计算发现奥罗万增强机制起主导增强作用，载荷传递机制贡献随CNTs长径比降低而逐渐减弱。最后结合分子动力学模拟揭示了晶内CNTs可以有效阻碍Al基体内全位错的移动，从而提升复合材料整体的位错密度来进一步提高力学性能。基于研究结果，在Carbon、Compos Part A、Compos Part B、MRL、JMST等国内外知名期刊发表论文11篇，包括中科院分区一区论文8篇，授权国家发明专利2件。本项目的实施为具有优异综合力学性能铝基复合材料的制备及其在航空航天领域的应用提供理论支持与技术支撑。