Investigation of the microstructure and hardness of cast Al7068 nanocomposite reinforced with SiC nanoparticles

In this study, microstructure and mechanical properties of AA7068 nanocomposite reinforced with 1, 2, 3 and 5 wt.% SiC nanoparticles (SiCnp) produced by stir casting and ultrasonic treatment have been investigated. Ultrasound device equipped with a cooling system with 2000 W powers was used for mixing alloy and nanoparticles. Also scanning electron microscopy was used for microstructure studies. The microstructure of nanocomposite was investigated by scanning electron microscope.The microstructural studies of the nanocomposite revealed that SiCnp addition reduces the grain size, but adding higher SiCnp content (5 wt.%) does not change the grain size considerably. Further investigations on hardness revealed that the addition of SiCnp increases hardness. At higher SiCnp contents (5 wt.%), the presence of SiCnp agglomerate on grain boundaries was found that causes decrease the hardness. The optimum amount of nanoparticles is 3 wt.% SiCnp that nanocomposite exhibits hardness of 155 BHN. According to the results of hardness for the initial samples and nanocomposites reinforced with 3 wt.% SiC, 24% increase in hardness can be seen.