Homogeneous dispersion of graphite in a 6061 aluminum alloy by ball milling

A composite of rapidly solidified Al-6061 alloy powder with graphite particle reinforcements was prepared by ball milling and subsequent hot extrusion. Proper choice of the processing parameters ensured a homogeneous distribution of the graphite particles in the aluminum alloy matrix. The microstructure and mechanical properties of these composites were investigated as a function of milling time. With increasing milling time, the spherical powder became elongated and acicular, which subsequently became spherical with a lamellar structure inside it. The shape change and intermixing process of the two constituent powders, and consequently the microstructure of the milled powder and extruded bars, were dependent on the milling time. The best compression and wear properties were obtained in the powder milled for 70 h, associated with the increased fine and homogeneous distribution of graphite particles in the aluminum alloy matrix.