Microstructural characterisation and corrosion behaviour of microwave-sintered magnesium alloy AZ61/fly ash microspheres syntactic foams

Magnesium alloy AZ61/fly ash microspheres (FAMs) syntactic composite foams were synthesised via powder metallurgy and microwave (MW) sintering techniques. MW sintering was rapidly completed in 20 min and minimized the formation of brittle interfacial products. Effect of FAMs on the density, microstructure, and corrosion resistance of the alloy were investigated. FAMs were intact and fairly distributed in the microstructure of the foams. Corrosion behaviour in 3 wt.% sodium chloride solution showed that Tafel polarization curves shifted to lower current densities as the volume fraction of FAMs increased. This indicated that FAMs generally enhanced the corrosion resistance of the foams due to minimal galvanic interaction and reduction in the surface area of the material exposed to the corrosion medium. These results are significant and outline the enhancement of corrosion resistance of magnesium alloy AZ61 foams by using FAMs.