The effect of Al2O3 content on the microstructure and properties of Al/Al2O3 functionally graded material

Abstract

This study aims to survey effect of Al2O3 content on the microstructure and also the physical and mechanical properties of Al/Al2O3 which functionally graded material (FGM) that are manufactured by the powder metallurgy technique. For this purpose, five-layer Al/Al2O3 green part samples with Al:Al2O3 different weight ratios were fabricated by cold pressed under 620 MPa. After compaction, the samples were sintered for 1 hour in a nitrogen atmosphere at a temperature range between 600 °C and 640 °C. An optical microscope and a field emission scanning electron microscope (FESEM) were used to evaluate the Microstructural characterization. The Archimedes density, Vickers hardness and flexural strength of sintered samples were measured. The highest relative density of 95% was achieved at a sintering temperature of 640 °C on lower Al:Al2O3 weight ration variation on Al/Al2O3 FGM sample. The hardness values gradually changed in cross section of different FGM samples from 31 HV to 65 HV which depend on the sequence of Al2O3 content in different layers. However, the highest flexural bending strength of 70 MPa was obtained at the sample on Al/Al2O3 FGM included the compositions of 35, 25, 15, 5, 0 wt.% Al2O3. By decreasing Al2O3 content along Al/Al2O3 FGM, the changing semi-brittle or brittle to ductile failure mechanism was observed. In some fabricated FGM samples observed a few cracks in the interfacial region between layers with high Al2O3 content.