The uniform distribution of carbon nanotubes (CNTs) can lead to severe grain refinement to ultrafine-grained (UFG) regime of Al matrix, resulting in low strain hardening ability, thereby low ductility in CNT/Al composites. To evade this dilemma, CNT/Al-Mg composites with bimodal microstructures were prepared by a powder assembly process in this study. The effects of weight/volume fraction of coarse grains on microstructure evolution, plastic deformation behavior and micro-strain distribution were investigated. The elongation improved from 4.2% of the uniform microstructure to 5.2% for the bimodal CNT/Al-Mg composites with 25wt.% (CG25) coarse grains. The compression stress relaxation test revealed the enhanced effective stress and activation of multiple dislocation-mediated mechanisms during plastic deformation in the CG25 sample, which lead to sustainably higher strain hardening ability. The uniform micro-strain distribution was revealed in the CG25 sample by Kernel average misorientation analysis, attributed to the constrained deformation of soft coarse-grain phase by hard CNT-enriched UFG Al-Mg phase.

碳纳米管（CNT）的均匀分布会导致严重的晶粒细化到Al基体的超细晶粒（UFG）态，导致应变硬化能力低，从而降低CNT / Al复合材料的延展性。为避免这一难题，本研究通过粉末组装工艺制备了具有双峰微结构的CNT / Al-Mg复合材料。研究了粗粒重量/体积分数对组织演变，塑性变形行为和微应变分布的影响。对于具有25wt。％（CG25）粗晶粒的双峰CNT / Al-Mg复合材料，伸长率从均匀微观结构的4.2％提高到5.2％。压缩应力松弛测试揭示了CG25样品塑性变形过程中有效应力的增强和多种位错介导机制的激活，从而持续提高应变硬化能力。通过核平均取向差分析，在CG25样品中发现了均匀的微应变分布，这归因于硬质CNT富集的UFG Al-Mg相限制了软质粗晶相的形变。