Manufacturing of cast A356 matrix composite reinforced with nano- to micrometer-sized SiC particles

In this study, large micron-sized SiC particles were fragmented via ball-milling process in the presence of iron and nickel powders, separately, to fabricate composite powders of Fe–SiC and Ni–SiC. Continuous fracturing of brittle SiC powders leads to the formation of multi-modal-sized SiC powders with size of from 50 nm to slightly higher than 10 µm after 36-h ball milling. The milled powders were then incorporated into the semisolid melt of A356 aluminum alloy to ease the incorporation of fine SiC particles by using iron and nickel as their carrier agents. The final as-cast composites were then extruded at 500 °C with a reduction ratio of 9:1. Lower-sized composite powders with slight agglomeration are obtained for the 36-h milled Ni–SiC mixture compared to that of Fe–SiC powders, leading to incorporation of SiC particles into the melt with a lower size and suitable distribution for the Ni–SiC mixture. It is found that lower-sized composite particles could release the fine SiC particles into the melt more easily, while large agglomerated composite particles almost remain in its initial form, resulting in sites of stress concentration and low-strength aluminum matrix composites. Ultimate tensile strength (UTS) and yield strength (YS) values of 243 and 135 MPa, respectively, are obtained for the aluminum matrix composite in which nickel acts as the carrier of fine ceramic particles.