Enhancement of microstructure and mechanical properties of hypereutectic Al-16%Si alloy by ZnO nanocrystallites

This study was carried out to examine the mechanical properties of hypereutectic Al-16% Si alloy with the introduction of zinc oxide (ZnO) nanoparticles (NPs) synthesized by simple sol-gel method. The microstructure of the synthesized ZnO NPs was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The microstructure of the synthesized ZnO NPs reflects the formation of the wurtzite-type ZnO and the average crystallite sizes around 35nm. Hypereutectic Al-16% Si with varies concentration of ZnO NPs (0.5, 1, 1.5 and 3%) was synthesized utilizing permanent mold casting technique. Energy-dispersive spectrometer (EDS) and scanning electron microscopy (SEM) of hypereutectic Al-16 wt% Si alloys after the dispersion of these nanoparticles were analyzed. The results revealed that an addition of ZnO nanoparticle to hypereutectic Al-16wt % Si alloy enhanced the tensile strength, impact energy and the hardness. The maximum tensile strength, impact energy and hardness of this alloy was 200MPa, 5.38J, 60 BHN, respectively, which occurred at 3 wt% of ZnO NPs. This enhancement in mechanical properties can attributed to the decomposition and dissolution of the nano-oxide particles in aluminum alloy melt and grain growth restriction.