Exploring the effect of bio-silica on the mechanical, microstructural, and corrosion properties of aluminium metal matrix composites

Abstract

The role of silica in the aluminium alloy is to enhance its mechanical properties. Silica is an eco-friendly material that lowers the melting temperature which in turn enhances the fluidity of alloys. Low-cost synthesis, abundant natural resources, and mass production are other merits of silicon. In this investigation, plant-based bio-silica particles were incorporated in aluminium 7075 hybrid composites. The rice husk is rich in silica, and when it is burned or processed, it turns into ash, known as rice husk ash (RHA). After purification, the silica in RHA can be extracted using alkali fusion. Stir casting processes were used to fabricate hybrid composite material. Aluminium 7075 hybrid composites reinforced with different wt.% (0, 3, 6, and 9) of bio-silica extracted from rice husk were fabricated. Mechanical properties such as tensile, hardness, and impact were evaluated. Also, corrosion resistance was studied for the fabricated composites. The samples with different proportional values such as AlB (Al7075), AlBS1 (97 wt. % Al7075 + 3 wt. % bio-silica), AlBS2 (94% Al7075 + 6 wt. % bio-silica), and AlBS3 (91 wt. % Al7075 + 9 wt. % bio-silica) were fabricated by the stir casting process. Detailed microstructure characterization has been investigated using scanning electron microscopy (SEM). AlBS3 hybrid composites demonstrate a notable enhancement of 303.66 Mpa tensile strength and we observed a remarkable 10% increase in ductility compared to other composites. It was noticed that the sample AlBS3 shows an increased hardness of 162.4 HV and an impact energy of 26.67 kJ/mm2 due to the increased number of bio-silica particles. SEM-based fractography analysis of tensile and impact test specimens revealed the presence of dimples, cleavage facets, and intergranular cracks offering valuable insights into the failure mode.