梯度双模结构碳纳米管/铝复合材料的组织构建和强韧化机理研究

Due to excellent comprehensive performance, Carbon nanotube (CNT) reinforced Al matrix composites (CNT/Al) have wide application prospects in aerospace, military equipment and transportation areas. Despite the high strength of CNT/Al due to CNT incorporation, the low ductility of CNT/Al restricts its application scope. Thus, it is urged to achieve high strength-ductility CNT/Al through microstructure design. In previous study we found that, by constructing bimodal structure of “hard zone” with CNT-rich zone but fine grains, and “soft zone” with CNT-free zone but coarse grains, the strength-ductility of the CNT/Al was enhanced. However, the huge differences between “hard zone” and “soft zone” were not benefit for further improving the strength-ductility. By forming gradient of CNT content and grain size in “hard zone” could not only relieve the huge differences between “hard zone” and “soft zone”, but also improve the ability of hardening in “hard zone”, which was beneficial to strength-ductility enhancement. Based on this, this project is proposed to take CNT/2009Al composite materials as the research object and form the gradient-bimodal structure consisted of “gradient hard zone” and “soft zone” by combination of milling in the style of adding Al alloy powders step by step and powder metallurgy. By analyzing the effect of structural parameters of “soft zone” and “gradient hard zone” on the hardening ability and strength-ductility of the CNT/2009Al composites, the mechanism of coordination deformation and toughening should be revealed to provide the basis for the industrial application of CNT/Al composites.

碳纳米管增强铝基复合材料（CNT/Al）因其优异的综合性能，具有广阔的应用前景。但CNT/Al在获得高强度的同时，韧性下降明显，这限制了其工程应用范围。通过结构设计实现其强韧化的研究亟需开展。申请人发现，在CNT/Al中构建富集CNT的细晶“硬区”与不含CNT的粗晶“软区”的双模结构可以提高强韧性，但“硬区”与“软区”巨大的性能差异不利于进一步强韧化。申请人认为CNT含量、晶粒尺寸呈梯度的“梯度硬区”可以缓解“硬区”－“软区”的巨大差异，并提高“硬区”的加工硬化能力，从而实现进一步强韧化。基于此，本项目拟以CNT/2009Al为研究对象，通过球磨中分步添加原始铝合金粉末，结合后续粉末成型，构建出“梯度硬区”－“软区”的梯度双模结构。通过分析“梯度硬区”、“软区”结构参数变化对复合材料的加工硬化能力和强韧性的影响规律，阐明各区域的协调变形机制和强韧化机理，为CNT/Al的工业化应用提供依据。

碳纳米管增强铝基复合材料（CNT/Al）因其优异的综合性能，具有广阔的应用前景。但CNT/Al在获得高强度的同时，韧性下降明显，这限制了其工程应用范围。通过结构设计实现其强韧化的研究亟需开展。申请人发现，在CNT/Al中构建富集CNT的细晶“硬区”与不含CNT的粗晶“软区”的双模结构可以在不降低抗拉强度的同时提高塑韧性，而其塑韧化来源于双模结构极大的抑制应变局域化和微裂纹扩展。但“软区”在受载后的提前变形会极大降低复合材料的屈服强度，不利于强韧化。申请人提出细化”软区“晶粒尺寸，以缓解”软区”的优先变形和“硬区”－“软区”巨大差异的思路。基于该思路，通过对原始铝合金粉末进行不同程度的球磨，结合后续添加到球磨的CNT/Al粉末中，构建出“富集CNT的超细晶硬区”－“无CNT的超细晶软区”的改进双模结构，不仅实现抗拉强度和延伸率的进一步提升，而且大幅改善屈服强度软化的现象。以上研究不仅为CNT/Al的工业化应用提供依据，而且为其它复合材料的强韧化提供了借鉴参考。