Effect of aspect ratio AlB2 flakes on mechanical and physical properties of aluminium boron alloys

In this study, cast Al-B alloys which have different aspect ratio (length/width) AlB2 flakes were produced. The main objective of this investigation was to explore effect of aspect ratio AlB2 flakes on the mechanical and physical properties of the cast Al-B alloys. Borax powders (Na2B4O7.10H2O) wt. 10% was added to molten aluminium at 1000°C which is the peritectic temperature on Al-B phase diagram by holding in the furnace during 45 minutes to fabricate AlB2 compounds. The cast Al-B alloys were cooled in water, air and furnace. Heat treatment was applied to cast Al-B alloys by heating in the furnace at 550°C with different holding times 5h, 15h, 30h, 50h and 70h to acquire different aspect ratio particles. Microstructures of Al-B alloys were observed and aspect ratios of the flakes were measured by using microscope. All samples were subjected to mechanical and physical tests such as hardness, tensile, impact and electrical conductivity. As a result of heat treatment for 15 hours, an increase of 14.5% on hardness, an increase of 16% on tensile strength, an increase of 19% on impact energy and an increase on electrical conductivity were obtained in comparison with non-heat treated samples. Reinforced AlB2 particles in aluminium matrices were also observed by using Scanning Electron Microscope. Keywords: AlB2 Flakes, Boron, Aspect Ratio, Al-B Alloy, Microstructure