Effect of particle size on the microstructure and distribution of fly ash for metal matrix composite applications

Particle size is an important parameter in the processing of reinforcement particles utilized as particulate metal matrix composites. These particulate reinforcements provide advantages such as high stiffness, high strength, wear resistance properties, corrosion and thermal resistance to metal matrix composites (MMCs). This work attempts to study the effects of ball milling on the density, microstructure and morphology of fly ash. The milling times were varied as 0 mins, 15 mins, 30 mins, 45 mins, 60 mins and 180 mins. The density of the fly ash samples was measured as 2.44 g/cm3 using Le Châtelier's principle. The microstructural analysis showed a change in morphology with increasing milling time. The SEM micrographs showed an agglomeration of the fly ash particles due to the dry milling conditions. The EDS analysis showed the presence of oxygen, aluminium, silicon and iron as the major elements common to all the fly ash samples at the different milling times. The XRD analysis identified mullite (3Al2O3SiO2), silica (SiO2), alumina (Al2O3), wustite (FeO) and hematite (Fe2O3) as the major phases. The particle size distribution obtained via wet sieve analysis showed that 16.3%, 3.9%, 1.76%, 0.43%, 0.1%, and 0% were retained for the 0mins, 15 mins, 30 mins, 45 mins, 60 mins and 180 mins milled fly ash samples respectively.