Effect of SiC content on microstructure, mechanical and electrical properties of sintered Al-20Si-xSiC nanocomposites fabricated by mechanical alloying

SiC is considered as an interesting material for reinforcement of composites for structural applications. Al-20Si- x SiC nanocomposites ( x = 0, 5, 10, 15 and 20 wt%), were fabricated by mechanical alloying technique. X-ray analysis and transmission electron microscope were utilized to examine the phase identification, morphology and size of prepared powders. In order to examine the sinterability, the prepared powder was uniaxially pressed and sintered at 450 and 550 °C. The relative density and apparent porosity of solidified composites were tested by water displacement methods. Microstructure of sintered composites was examined by scanning electron microscope. The mechanical properties in terms of microhardness, compressive strength, elastic, longitudinal, shear, and bulk moduli as well as Poisson's ratio were measured by suitable techniques. Furthermore, electrical conductivity was also determined. The results revealed that a homogeneous dispersion of SiC grains in Al-Si matrix was accomplished. Also, the crystal and particles sizes of prepared powders were reduced after increasing the amount of added SiC. For the sintered composites, the apparent porosity and mechanical properties were increased with increasing SiC contents. On the other side, the relative density and electrical conductivity were reduced significantly. The density, mechanical properties and electrical conductivity of composites sintered at 550 °C were higher than that sintered at 450 °C.