High mechanical properties of CNTs/Al composites achieved by second phase refinement and reinforcement dispersion via hot extrusion

Abstract

The carbon nanotubes (CNTs) reinforced 2A70 alloy by the coating of ZrO₂ (ZrO₂@CNTs/2A70) are processed by a hot extrusion process. The microstructure and mechanical properties of ZrO₂@CNTs/2A70 composites were investigated in this study. The results show that the second phase of the composites is broken and uniformly dispersed under the action of shear force and the second phase as well as the ZrO₂@CNTs reinforcement is uniformly distributed along the extrusion direction. The hot extrusion process eliminates the cast defects and improves the reinforcing phase's dispersion and the material's mechanical properties are significantly improved. At the extrusion ratio of 25, the composites exhibited notable enhancements in their mechanical properties, as evidenced by a significant increase in hardness, yield strength (YS), ultimate tensile strength (UTS), and elongation (EL), with respective values of 141.7 HV, 237.4 MPa, 309.7 MPa and 13.9%. These values were higher than those obtained from cast composites by 17.5%, 20.0%, 20.9% and 152.7%, respectively. The fracture characteristics of the composite are mainly ductile fractures. Besides, the extruded composites are strengthened mainly by grain refinement and load transfer mechanism.