Effect of Si on microstructure and properties of carbon nanotubes reinforced aluminum matrix composite foams

For metal matrix composite materials, adding alloying elements is an effective way to improve its comprehensive performance. In the present study, the carbon nanotubes (CNTs) reinforced aluminum matrix (CNTs/Al-Si) composite foams with Si element were prepared by high-energy-ball milling and space holder method. Quasi-static compression test was carried out to study the compression properties and energy absorption performance of CNTs/Al-Si composite foams. The effects of sintering temperature and Si content on the microstructure, compression and energy absorption properties of the CNTs/Al-Si composite foams were further studied. The fracture failure mechanism was analyzed by the compression fracture morphology. The results show that the density and bonding of the CNTs/Al-Si composite foams increase with the increment of sintering temperature. When the sintering temperature is 600℃, mass fraction of Si is 7wt%, the yield strength, plateau stress, and energy absorption performance of CNTs/Al-Si composite foams are 98.4%, 167.7%, and 166.4% higher than that of the sintering temperature of 550℃, respectively. Moreover, the addition of Si element can refine composite powders during ball milling. Both of the strength and plasticity for the CNTs/Al-Si composite foams are improved after alloying. Compared with CNTs/Al composite foams, the yield strength and plateau stress of the CNTs/Al-Si composite foams with Si mass fraction of 7wt% increase by 58.5% and 117.8%, respectively. Meanwhile the energy absorption performance is significantly improved.