Simultaneously improving strength and ductility of carbon nanotube (CNT)-reinforced aluminum matrix composites by embedding CNTs inside matrix grains

The inadequate ductility of high-strength aluminum (Al) matrix composites (AMCs) reinforced with carbon nanotubes (CNTs) greatly limits their engineering applications. Here, we report a strategy to improve the ductility of CNTs/Al composites with increased tensile strength by embedding CNTs into matrix grains. Through a modified-ball-milling-involved powder metallurgy process, two kinds of AMCs were fabricated, one with most CNTs dispersed inside grains (IG) and the other one with most CNTs at boundaries between grains (BG). A reference composite with more randomly dispersed CNTs was also fabricated by conventional ball milling. Results showed that the IG-structured composites with different CNT contents had both higher tensile strength and ductility compared with the BG composites and the reference composite. This phenomenon was associated to the different interaction behaviors between matrix dislocations and the CNTs with IG or BG distribution as revealed by transmission electron microscopy. Molecular dynamic simulation clarified the microscopic interaction mechanisms between dislocations and CNTs in IG and BG structures during deformation. This study provides a new strategy for fabricating high-strength and ductile CNT-reinforced metal matrix composites.