Microstructural analysis of sand and gravity die cast aluminium scraps

: Scraps of locally sourced aluminium pistons and of aluminium pots, were separately melted and casted using Sand and gravity die casting methods. The cast specimens were machined to standard testing dimensions grounded and polished on B.G-20 belt grinder having abrasive papers lubricated by a gentle flow of water, polished, etched by immersing in a chemical reagent of 0.5% hydrofluoric acid. The microstructural examinations showed that in unetched condition the main structure contains large quantity of relatively coarse silicon crystals (clearly visible in the polished state) set in an aluminium matrix; that the main structure contains large quantity of silicon magnesium crystal in an aluminium matrix, and that the microstruture of the material greatly affects its mechanical properties as seen on the responses of the materials to applied loads; that scraps from aluminium pistons and pots when recycled can be re-used for Engineering applications that require lesser strength and hardness. The grain size measurement shows that specimen from permanent mould casting process either etched or unetched are made up of closely packed grains 43mm2, 38mm2 and 40mm2 respectively (larger than sand cast specimen), hence better mechanical properties and good surface finish of the specimen compared with sand cast samples.