Mechanical and wear properties of SiCp/CNT/Al6061 hybrid metal matrix composites

6061 aluminum (Al6061) alloy matrix composites with hybrid reinforcements composed of both carbon nano tubes (CNTs) and silicon carbide particles (SiCp) were prepared by spark plasma sintering technique. SiCp, CNTs and Al6061 powder were firstly mixed by a tip-sonication mixing, then frozen the suspension in liquid N-2, and finally freeze-dried in a vacuum to obtain the uniform dispersion of SiCp and CNTs. The SiCp/CNT/Al6061 hybrid composites containing homogenously dispersed SiCp and CNTs exhibited significantly improvements in hardness, tensile strength and yield strength values of 37%, 38%, and 49%, respectively, compared with those of SiCp/Al6061 composites without CNTs. The improvements in the mechanical properties were attributed to the synergistic strengthening effects of the CNTs and SiC particulates. The coefficient of friction and specific wear rates of the hybrid composites were decreased by the addition of low-friction CNTs due to the self-lubrication effect. The CNTs did not reduce the friction coefficient and specific wear rate of the specimens as significantly with the increase of the applied load. This could be resulted from the transformation of carbonaceous structures of CNTs during the tribological testing process.