Rice Husk Ash as Pore Former and Reinforcement on the Porosity, Microstructure, and Tensile Strength of Aluminum MMC Fabricated via the Powder Metallurgy Method

Abstract

The handling of rice husk ash (RHA) has been raising environmental concerns, which led to the consideration of incorporating RHA in aluminum metal matrix composite fabrication. Due to the high silicon dioxide content of RHA, it can assist in enhancing both the properties and functionality of pure aluminum. In this research, the fabrication of aluminum metal matrix composite was carried out by utilizing different compositions of RHA, including weight fractions of 10 wt.%, 15 wt.%, and 20 wt.% via a powder metallurgy approach. The element powders, including aluminum and RHA, and magnesium stearate as a binder, were mixed, compacted, and sintered to attain a composite sample in the form of a pellet. The pellet was then characterized using field emission scanning electron microscopy (FESEM-EDX) to identify the pore structure and size for each RHA composition. The samples were also mechanically tested via Archimedes’ Principle and Brazilian Testing to identify their density, porosity, and tensile strength, respectively. The total porosity of RHA-15 wt.% was found to be the highest at 19.19%, yet with the highest tensile strength at 5.19 MPa due to its low open porosity at 4.65%. In contrast, the total porosity of RHA-20 wt.% was found to be slightly lower at 15.38%, with the highest open porosity at 6.95%, which reduced its tensile strength to 5.10 MPa, therefore indicating that reducing open porosity through controlling the composition of reinforcement tends to enhance the mechanical strength of aluminum metal matrix composites.