CNT-induced microstructural evolution in Al matrix composite made by additive manufacturing and studying the effect of CNT presence on mechanical and tribological properties

Abstract

This study investigates the microstructural behaviour and mechanical properties of carbon nanotube (CNT)-reinforced AA2024 aluminum matrix composites fabricated via Selective Laser Melting (SLM), with varying CNT contents of 1, 3, and 5 wt%. As the CNT content increased, the quality of single-track deposits improved, leading to more consistent and continuous weld beads, particularly at 5 wt% CNT. The results demonstrate that CNT reinforcement significantly influences microstructural evolution and enhances the mechanical performance of SLM-processed nanocomposites. Specifically, the 5 wt% CNT/AA2024 composite exhibited refined microstructures, uniform CNT dispersion, improved mechanical properties, and the formation of the Al₄C₃ phase during the SLM process. Wear analysis revealed that increasing sliding speed led to a reduction in wear rate and a transition in wear mechanism—from abrasive to delamination—due to the formation of a stable mechanically mixed layer (MML) that reduced contact between the composite surface and the counter body. Additionally, at higher normal loads, a combined oxidation and delamination wear mechanism became dominant in the CNT-reinforced composites.

Keywords

• Selective laser melting
• Nanocomposite
• CNTs
• Wear mechanism
• Microstructure