The Effect of Milling Time on Aluminum- Silicon Carbide Composites Fabricated by Powder Metallurgy

Abstract — To fabricate aluminum- silicon carbide composites, 10 vol % of the silicon carbide powders at size of 20 µm mixed with aluminum powders, Those mixtures were ball-milled for 0, 40, 80, and 120 minute in a planetary ball mill at speed of 200 rpm using zirconia balls.The ball- to powder mass ratio 10:1. The mixed powders are die-pressed at room temperature under a pressure of 10 ton in a 12.7 mm internal diameter cylindrical stainless steel die. The aim of this study is to develop Al – 10 vol %SiC composite by mechanical alloying; the main steps in mechanical alloying are milling, compacting and sintering. Aluminum and silicon carbide powder are mixed by ball milling and it was then sintered at 550 ° C for 5 hours. The parameter to control the microstructure of the composites is milling time. Microstructure and hardness of the composite were investigated. The results are showed that hardness of the composites has increased as the time of the milling increased. The maximum value of hardness can be obtained at 80 minute milling time. After 80 minute milling time, the hardness starts to drop for Al- silicon carbide composite. Microstructure plays important role in controlling the hardness of the composites. Index Terms—; Milling time; particles size reduction; reinforcement dispersion; mechanical properties XRD; SEM; EDX