Metal matrix composites are engineered materials with a combination of two or more dissimilar materials, (at least one of which is a metal) to obtain enhanced properties. In the present investigation Al-4.5% Cu alloy was used as the matrix and fly ash and silicon carbide (SiC) as reinforcements. The hybrid metal matrix composite was produced using conventional foundry techniques. The fly ash and SiC were added in 5%, 10%, and 15% by weight (equal proportion) to the molten metal. The hybrid composite was tested for fluidity, hardness, density, mechanical properties, impact strength, dry sliding wear, slurry erosive wear, and corrosion. The microstructure examination was done using scanning electron microscope to assess the distribution of particulates in the aluminum matrix. The results show that there is an increase in hardness with increase in the particulates content. The density decreases with increase in fly ash and SiC content. The tensile strength, compression strength, and impact strength increases with increase in fly ash and SiC. The resistances to dry wear and slurry erosive wear increases with increase in fly ash and SiC content. Corrosion increases with increase in fly ash and SiC content. This material can be used as bearing material.
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.
Aluminium alloy based metal matrix composites (MMCs) have attracted attention in the automobile sector owing to ease of manufacturing, high specific strength properties, and better wear resistance. The stir casting or liquid metallurgy technique is the most economic and direct route for producing near-net-shape MMC components. In the present investigation, an Al-4.5%Cu alloy MMC with fly ash particles has been cast by the stir casting technique. Properties such as density, hardness, wear, and tensile and compression strength of the MMC have been evaluated. Further, to test the applicability of this composite as a bearing, a bush was prepared from the composite and tested under lubricated conditions for 200 h. The bush made from the composite showed more resistance to wear than the base alloy. A cylinder liner was cast from the composite and then tested in a two-stroke petrol engine. No seizure was observed even after 400 h of testing.
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