Powder hot pressing and front pad extrusion method for aluminum-lithium based metal matrix composites

A simple powder metallurgy (P/M) route was adopted to fabricate aluminium-lithium based metal matrix composites (MMCs) reinforced by submicron SiC particulate by directly hot pressing mixed powders and extrusion. The consolidation behavior of the as-mixed MMC powder and matrix powder during the hot pressing were investigated. In order to avoid fir-tree cracking on the extrudate's surface, a soft metal pad (A16061) was put between the die and the billet: By this method, the MMCs were successfully extruded without any surface cracking, and all the extrudates were found to be covered by a thin layer of the pad material. This is illustrated by the flow pattern of the extrudate and pad material in the dead zone during extrusion. This method, termed as Front Pad Extrusion Method by the authors, is presented here and found to be effective in solving the extrusion problem of P/M aluminum-lithium based MMCs.