FLAKE POWDER METALLURGY APPROACH FOR PRODUCTION OF Al–Al2O3 COMPOSITES WITH ENHANCED PROPERTIES

Flake Powder Metallurgy (FPM) is utilized for the processing of Al–Al2O3 composites. The effects of contents of 1-μm-sized alumina (0, 3, 6 and 9 vol.%) on the microstructure, hardness, porosity and wear behavior of these composites are investigated. The as-received aluminum powder particles are milled in a planetary ball mill for different time durations (0.5, 1, 1.5 and 2 h), and the resultant flake powders are characterized by sieving, SEM, optical microscopy and XRD to determine their particle size, morphology and grain size. Al flakes and different amounts of Al2O3 powders are stacked into the mold cavity using a floating column filled with alcohol. Then the compacts are cold pressed at 750 MPa and sintered in a tube furnace at 655∘C for 60min. For comparison, reference samples from as-received aluminum powders are also fabricated. SEM studies showed a uniform distribution of alumina particles within the matrix of FPM-processed composites. These composites, despite their higher porosity, exhibited higher hardness levels and improved wear properties in comparison with the conventionally produced powder metallurgy (PM) counterparts. This is due to: (i) the special morphology of the flake powders that contributed to a more uniform distribution of alumina within the matrix and (ii) their smaller grain size due to work hardening that occurred during milling, which resulted in higher hardness values.