Mechanisms of Ti, Nb, and Zr in Microstructure Evolution and Mechanical Enhancement of CNTs/Al Composites

The limited enhancement efficiency of carbon nanotube (CNT) additives in aluminum matrix composites (AMCs) remains a critical challenge. In this study, the influence of titanium (Ti), niobium (Nb), and zirconium (Zr) additions on the microstructure and property evolution of CNT-reinforced aluminum composites were systematically investigated. The composites were fabricated by vacuum hot-pressing sintering. Experimental results indicate that these elements significantly improved CNT dispersion and refined the aluminum grain. Among them, Zr-containing composites exhibited the most significant enhancements in both mechanical strength and thermal stability. Specifically, the Zr-doped composite exhibited a 15.5% increase in tensile strength and a 60.2% increase in fracture elongation compared to undoped CNTs/Al, while its coefficient of thermal expansion (CTE) was reduced by 20.9% relative to pure aluminum. These findings highlight the effectiveness of element-assisted microstructure regulation in enhancing the integrated performance of CNT-reinforced AMCs.