Toward strength-ductility synergy in trimodal grain structured metal composites by actively tuning coarse domains

Trimodal grain structure was effective to balance the strength-ductility trade-off in ultrafine-grained metals, but the relationship between microstructures and mechanical performance is unclear. Here the dimension of coarse grain (CG) domains was elaborately tuned in the trimodal CNT/2024Al composites, and an excellent strength-ductility combination (Tensile strength: 716 ± 5 MPa, Elongation: 9.1 ± 0.3%) was achieved by optimizing the CG bands (∼4.4 µm in width). We found that the size of CG bands hardly affected strain hardening rate, but caused different crack-blunting behaviors, which was responsible for the superior strength-ductility synergy. This work highlights the importance of CG domains design in heterostructured materials.Trimodal grain structured CNT/2024Al composites with different coarse-grained (CG) bands