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Fabrication of Al-4.5% Cu alloy with fly ash metal matrix composites and its characterization

Mahendra K. V., Radhakrishna K.

Materials Science Poland

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2007

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Vol. 25, No. 1

57--68

EN

Metal matrix composites (MMCs) are engineered materials, formed by the combination of two or more dissimilar materials (at least one of which is a metal) to obtain enhanced properties. In the present investigation, an Al-4.5% Cu alloy was used as the matrix and fly ash as the filler material. The composite was produced using conventional foundry techniques. The fly ash was added in 5%, 10%, and 15 wt. % to the molten metal. The composite was tested for fluidity, hardness, density, mechanical properties, impact strength, dry sliding wear, slurry erosive wear, and corrosion. Microstructure examination was done using a scanning electron microscope to obtain the distribution of fly ash in the aluminium matrix, The results show an increase in hardness, tensile strength, compression strength, and impact strength with increasing the fly ash content. The density decreases with increasing fly ash content. Resistance to dry wear and slurry erosive wear increases with increasing fly ash content. Corrosion increases with increasing fly ash content.

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Sliding wear, slurry erosive wear and corrosive wear behavior of aluminium/SiC composite

Ramachandra M., Radhakrishna K.

Materials Science Poland

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2006

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Vol. 24, No. 2/1

333--349

EN

In this study, an aluminium based metal matrix was reinforced with silicon carbide (SiC) particulates using a conventional casting technique, Vortex method. Macro and microstructural studies conducted on the samples revealed a near uniform distribution of SiC particulates. Sliding wear, slurry erosive wear and corrosive wear of the as cast metal matrix composite (MMC) were studied and found that sliding wear and slurry erosive wear resistance improved considerably with the addition of SiC. Whereas corrosion resistance has decreased with addition of SiC particles. The microscopic examination of the worn surfaces, wear debris and subsurface shows that the base alloy wears primarily because of micro cutting. But the MMC's wear because of micro cutting, oxidation, plastic deformation and thermal softening. In slurry erosive wear the formation of passive layer has retarded the wear of the material. It is observed that pitting corrosion was the dominant corrosion mechanism. The bulk hardness has increased with the increase in percentage of SiC particulates. There was no much change in the density of MMC's compared to base metal.

3

Evaluation of metal / mould interfacial heat transfer during solidification of aluminium-4.5% copper alloy castings cast in CO2-sand moulds

Kulkarni S.N., Radhakrishna K.

Materials Science Poland

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2005

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Vol. 23, No. 3

821--838

EN

In this study, two methods were employed to measure the heat transfer coefficient, h, at the metal-mould interface during casting. The first method is to measure the size of gap formed between metal and mould during the casting process and estimate the value, h, based on the gap size. The second method is to measure temperature at certain locations of metal and mould, and by using reverse method, h, at the gap, can be derived. A procedure is also developed to make use of temperature measurement data to obtain the h as the function of casting temperature near the interference. This form of h data is very useful for mathematical modeling of solidification for casting. In the present study, the casting material is Al-4.5% Cu alloy and the mould material is CO2-Sand. The results of the measurements show that the value of h is not a constant, but varies with time/temperature during casting. With the gap size measurement, h is very large in the beginning and keeps dropping afterwards. As the gap is fully developed, h approaches a constant value between 130 and 40W/(m0-2C). By the inverse method, along with the temperature measurement, the value of h increase in the beginning stage and reaches a peak value of approximately 710W/(m0-2C), then h drops rapidly approximately to solidification temperature and rises again until the end of solidification. After that, h keeps dropping until the end of casting.