In-situ synthesis of CNTs@Al2O3 wrapped structure in aluminum matrix composites with balanced strength and toughness

For nanocarbon reinforced aluminum matrix composites (AMCs), the architecture design of reinforcements is an effective route to obtain superior mechanical performances. In this work, a novel AMC reinforced by CNTs wrapped with γ-Al2O3 (CNTs@Al2O3) reinforcement with balanced strength and toughness was fabricated by powder metallurgy methods. The wrapping structure of γ-Al2O3 was synthesized through the in-situ reactions of Al matrix and boric acid decorated CNTs, thus improving the interface coupling of the composite. The CNTs@Al2O3/Al composite with the addition of 0.5 wt% CNTs and 10 wt% in-situ Al2O3 exhibited a mean ultimate tensile strength of 404 MPa, which is significantly higher than unreinforced pure Al (183 MPa) and those reinforced by individual CNTs (207 MPa) or Al2O3 (289 MPa). An improvement of ductility was also achieved in CNTs@Al2O3/Al composites compared with the Al2O3/Al composites with the same Al2O3 content. The synergistic strengthening and toughening effects are ascribed to the ingenious in-situ CNTs@Al2O3 wrapped structure, which highlights the importance of architecture design of reinforcements in AMCs, and sheds new light on the development of CNT-reinforced AMCs. [Display omitted] •A CNTs wrapped with in-situ γ-Al2O3 reinforcement structure (CNTs@Al2O3) was achieved.•Synergistic strengthening effect between CNTs and Al2O3 was attributed to the unique wrapped structure.•The enhanced interfacial coupling improves load-transfer capability and hinders crack propagation.•The superior mechanical performance with balanced strength-toughness was obtained.