2010 Volume 51 Issue 4 Pages 756-761
This research demonstrated simple but effective process to produce Al-4 mass%Cu/Al2O3 composites, by powder metallurgy method. The starting powders were aluminum, copper, and rice husk ash silica. Processing was by sintering at 650°C for 3.6 ks, hot forging of sintered billet at 600°C under 660 MPa pressure, followed by heat treatment. Hot forging of sintered billet induced plastic deformation of the matrix as well as fractured the porous silica, thus created ultimate contact between the two phases. The following heat treatment produced alumina, which was the reinforcement phase, by chemical reaction between fractured rice husk ash silica and aluminum matrix. The fabricated composite contained γ- and κ-alumina, and elemental silicon in matrix of aluminum solid solution. Addition of copper facilitated sintering by formation of liquid phase, as well as yielding a matrix material which can be strengthened by precipitation hardening. Maximum hardness obtained was 44 HRA, for composite material using 15 vol% rice hush ash silica. Peak hardness of the matrix was in range of 130–136 HV, after aging for 28.8 to 43.2 ks.