Extrusion of mechanically milled composite powders

Mechanical alloying has come to the fore in fields such as the production of intermetallic compounds, supersaturated solid solutions, amorphous materials and metal matrix composites. With this process, composite powders are obtained with characteristics that are impossible to achieve employing conventional powder metallurgy techniques. In this work, aluminium powder AA6061 is mixed with silicon and aluminium nitrides in a conventional mixer and in a high-energy ball mill to obtain composite powders that are subsequently uniaxially cold pressed and hot extruded. The necessary pressure to extrude the composite cold pressed powders varies with the powder condition, being lower for the composite powder conventionally mixed, higher for the composite powder after a short time of milling, and intermediate after a longer time of milling, due to the morphological and structural changes typical of the mechanical alloying process. (C) 2002 Kluwer Academic Publishers.