Microstructure evolution and mechanical properties of CNT/Al composite joints via friction stir welding

Abstract

The traditional fusion welding of carbon nanotubes (CNTs) reinforcement aluminium matrix composites has serious welding defects due to the violent interfacial reaction and the brittle secondary phase. In this paper, friction stir welding (FSW), a solid-phase welding technique, was applied to join the CNT/Al matrix composites. The result shows that the tensile strength of the FSW joint fabricated at 800 rev min^–1 and 100 mm min^–1 is 511 MPa, reaching 92.1% of the CNT/Al composites. After FSW, the original CNTs were damaged and formed the nano Al₄C₃ phase. Orowan strengthening of the Al₄C₃ phase, dislocation strengthening and grain refinement of FSW are the predominant strengthening mechanism for the joints. The great interfacial bonding between nano Al₄C₃ and matrix benefits the joint mechanical properties as well.