Synthesis and characterisation of Al-Mg-SiO2 particulate composite prepared by nanostructured silica from rice husk ash

Abstract

Liquid metallurgy technique involves the addition of second-phase particles to the melt above the key liquid temperature before solidification, has been developed to produce Metal Matrix Particle Composite. Amorphous nano-silica (>95% SiO2), extracted from rice husk was added to the Al-5%Mg alloy in the proportion of weight% of the alloy. This paper aims to study the evolution of different phases like MgA12O4, Mg2Si, MgO in the MMC using locally available sources of amorphous silica. To improve the wettability of the Al alloy, 5%Mg was used. Experimental results from XRD displayed the presence of MgO2, MgA12O4, and Mg2Si (The spinal structures) which imparts hardness of 250 HV to the Composite. The A15%Mg SiO2 composite was metallographic polished and etched by Keller’s reagent. The microstructure appeared to be typical lamellae “Chinese-script” structure these structures are of phase Mg2Si (hardening phase). This phase has formed along the grain boundary. The solidified form of the microstructure of the alloy will contain three major components white phase surrounding the darker phase it is followed by the poly-phased structure. Furthermore, the darker phase present at its center indicates the dendritic arrangements of the multi-faced (polygonal) arrangements. Those phases present at the alloys are Magnesium (Mg) and Mg2Si.