Regulating microstructure of Al matrix composites with nanocarbon architecture design towards prominent strength-ductility combination

Evading the strength-ductility trade-off is essential for engineering application of metal matrix composites. Herein, we propose a novel strategy to achieve the prominent strength-ductility combination of nanocarbon-Al composites. The strategy makes use of the nanocarbon architecture design via longitudinally unfolding the multi -walled carbon nanotubes (CNTs) into graphene nanoribbons (GNRs). It was found that the nano-sized intra-granular and interfacial Al4C3 (length: 64 +/- 23 nm) easily formed in GNR/Al via the "heterogeneous nucleation -growth " pattern, which is contrary to the submicron-sized epitaxial Al4C3 (length: 133 +/- 39 nm) in CNT/Al. Detailed characterizations reveal the specific orientation relationships between Al4C3 and Al in GNR/Al, which benefits the robust interfacial bonding. The intragranular Al4C3 and intergranular GNR with large aspect ratio effectively increase the dislocation storage and hence working hardening ability, which leads to the strength -ductility synergy of GNR/Al. Meanwhile, the GNR anchored by dense interfacial Al4C3 introduces extra tough-ening effect by crack bridging, blunting and deflection.