Effect of SiC particle size on the microstructure and properties of functionally graded Al-SiC composites produced via powder stacking method

In the present investigation powder stacking method was used for preparation of functionally graded Al-SiC composites. Commercially pure Al powder with the average size of 120 and SiC particels (with three average sizes of 50, 125 and 165) were used as the matrix and reinforcing phases respectively. Specified amounts of SiC and Al powder were mixed with each other via wet mixing using alcohol. Then the powder mixtures containing 0, 10, 15 and 20 vol.% of SiC particles were stacked on each other in a steel die, pressed at 750 Mpa and sintered in a tube furnace at 675 for 60 min. The cylindrical composite samples were sectioned along their height through their center line, grinded, polished and subjected to metallographic studies (via light microscopy) and Brinel hardness testing. Also their densities were quantified via Archemedos method. The results confirmed that by using fine SiC particles, Al-SiC composites with a smooth gradient of SiC concentration and porosity level along the height of the samples was achieved. The decreased size of SiC particles resulted in the decreased overall porosity of the samples which also depended on the concentration of SiC particles. The size of SiC particles affected both the hardness and distribution of particles in the samples.