Advanced Materials and Processes Research Institute
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Microstructure and wear of cast (Al-Si alloy)-graphite composites
No full textGraphite-particle-dispersed Al-Si alloys have potential for a variety of antifriction applications. In the present investigation, two Al-Si alloys (LM13 of near eutectic and LM30 of hypereutectic composition) were chosen as matrix alloys and composites were prepared by casting. Composites and matrix alloys were heat treated to produce different morphologies of silicon ranging from plate-like in die-cast alloys to near spherical in heattreated alloys.\ud
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Wear tests were conducted, under both dry and partially lubricated conditions, with SAE30 oil on a pin-on-disc wear test apparatus, against a rotating steel (EN25) counterface. In partially lubricated wear tests, the sliding velocity V was varied from 1.4 to 4.6 m s−1 and the applied pressure P from 1.0 to 5.0 MPa. P-V limits of all matrix alloys and composites with different microstructures were evaluated. Heat-treated composites were found to possess superior wear properties (wear rate, seizure resistance and P-V limits) as compared with those of die-cast composites and matrix alloys. Worn surfaces of heat-treated composites showed the presence of a graphite film while those of die-cast alloys and composites showed surface fracture. The role of graphite particle dispersion and the morphology of silicon on the sliding wear behaviour is discussed
Sintered 6061 Al-alloy solid Lubricant Particle Composites: sliding wear & Mechanisms of Lubrication
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Sintered 6061 aluminium alloy—solid lubricant particle composites: sliding wear and mechanisms of lubrication
No full textAluminium alloy (6061) matrix composites containing up to 14 vol.% natural graphite particle dispersions were prepared by a powder metallurgy route. Dry sliding wear rates of composites were evaluated against a rotating EN25 steel disc using a pin-on-disc apparatus. Worn surfaces and debris were examined in the scanning electron microscope. Model experiments were conducted on the etched surfaces of a 6061 aluminium alloy-14 vol.% graphite composite with graphite particle protrusions.\ud
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Wear rates of composites increased linearly with the graphite volume fraction. Worn surfaces did not reveal the presence of a graphite film and the majority of debris were flaky in nature. This anomalous behaviour with graphite was attributed to the increased porosity (interconnected and interfacial) in the composites. Wear rates of composites in the etched condition showed a substantial decrease over that of the matrix alloy. Worn surfaces of composites in this case showed patches of graphite layers adhering to them
Microstructure of rapidly solidified Al-Si graphite composite.
No full textALUMINA WAS ADDED TO 6061 ALUMINUM POWDER TO YIELD COMPACTS CONTAINING 0, 4, 7, 10, AND 14 VOLUME PERCENT ALUMINA. THE COMPACTS WERE SINTERED FOLLOWED BY REPRESSING-RESINTERING. THE INFLUENCE OF ALUMINA VOLUME FRACTION ON DENSIFICATION PARAMETER, DENSITY, DIMENSIONAL CHANGE, POROSITY, HARDNESS AND ELECTRICAL RESISTIVITY IS ILLUSTRATED. TERMS: INDIA, SINTERING, ALUMINA ADDITION, 6061, ALUMINUM ALLOYS, PARTICULATE COMPOSITES, DIMENSIONAL STABILITY, POROSITY, DENSITY, DENSIFICATION, VOLUME FRACTION, ELECTRICAL RESISTIVITY, HARDNESS.
