Powder Metallurgy Fabrication and Characterization of Copper-Fly Ash Composites

Copper matrix composites containing 0-16 wt% fly ash with or with out copper coating were prepared using powder metallurgy. The copper coating of fly ash particles was carried out using an electroless process. Small cylindrical specimens were fabricated at 300 MPa using single action die compaction at ambient temperature. These compacts were sintered in argon atmosphere for a period of 45 min at 850, 890, and 930° C, respectively. The density, porosity, hardness, compressive yield strength and wear resistance of the sintered compacts were determined as a function of fly ash weight percent. Density and compressive yield strength of the composites were found to decrease with increasing weight percent of fly ash. The addition of fly ash resulted in increase in porosity and hardness of both coated and uncoated fly ash composites. The wear resistance of coated and uncoated composites was found to increase up to 8 wt% fly ash addition, beyond which a marginal decrease is observed. Coated fly ash composites possessed better combination of density, porosity, hardness, yield strength and wear resistance than uncoated composites. At high volume fractions, the use of copper coated fly ash was found to yield superior composites than the use of a mixture of uncoated fly ash and copper powder.