Improving the mechanical properties of carbon nanotubes reinforced pure aluminum matrix composites by achieving non-equilibrium interface

Highlights: • Pure Al powder and CNTs were used to fabricate CNTs reinforced Al matrix composites. • A non-equilibrium interface was obtained through SPS sintering and hot extrusion. • The new interface keeps the non-equilibrium state prior to the formation of Al₄C₃. • The new interface can greatly improve the tensile properties of the composite. • The fine Al powder is preferred to achieve a high performance of the composites. The weak interfacial bonding between carbon nanotubes (CNTs) and Al matrix is a critical issue for the achievement of high strength and good ductility of Al/CNTs composites, and thus hinders the wide application of the composites. Here we obtained a non-equilibrium interface that can provide tight interfacial bonding between the CNTs and Al matrix in the Al/CNTs composites fabricated through spark plasma sintering (SPS) and subsequently hot extrusion. This special interface, accompanied by small grain size, the uniform dispersion and the integrity of the CNTs, can significantly improve the mechanical properties of the Al/CNTs composite. Additionally, the effect of initial Al matrix powder size on the mechanical properties of the composites were investigated. The results indicate that the size of the initial matrix powder affected the dispersion of the CNTs and the interface between the CNTs and Al matrix, and thus influenced the mechanical properties. This work provides a new designation for the high performance of metal based composites with excellent interfacial bonding strength.