Characterization of Al-Cu alloy reinforced fly ash metal matrix composites by squeeze casting method
Metal matrix composites (MMCs) are of great interest in industrial applications for lighter materials with high specific strength, stiffness and heat resistance. The processing of MMCs by casting process is a very promising way of manufacturing near net shape composites at relatively low cost. The liquid metallurgy squeeze casting technique has characteristics such as fine microstructure as a result of rapid cooling, low porosity and good bonding between the particles and base alloy. In this study, the effect of hardness, tensile, compression and impact properties as well as density have been investigated. The Al-4.5wt%Cu alloy was chosen as base matrix casted by both stir and squeeze casting. Fly ash is one of the most inexpensive and low density reinforcement available in large quantities as solid waste is used as reinforcement. The Al-4.5wt%Cu reinforced 3, 6, 9 and 12wt%fly ash composite was squeeze casted with an applied pressure of 120MPa. The results showed that hardness tensile compression and impact values were increased by increasing weight percentage of fly ash reinforcements during squeeze casting. Porosity and other casting defects such as shrinkage cavities were minimised due to pressure applied during solidification. Increase in weight percentage of fly ash composites caused to increase porosity even in squeeze casting but lesser than gravity cast matrix alloy. Microstructure shows the absence of micro porosity, and grain refinement interfacial bond between matrix and reinforcement.
Keywords: Metal matrix composite, squeeze casting and fly ash