This study deals with material flow behaviour during the extrusion process of a metal-matrix composite (MMC), and the effects of this behaviour on the damage to die flat surfaces. AA 6063 aluminium matrix composite billets reinforced with Sic particles (167 mu m) were prepared using the stir-casting method for extrusion. Extrusion of the MMC billets were conducted at 500 degrees C with a ram speed of 2 mm s(-1) and an extrusion ratio of 25:1 under laboratory conditions. The extrusion die with two different channel profiles was manufactured from AISI H13 steel that was hardened, tempered and grounded. The How patterns of the deformed billet during the MMC extrusion determine the positions of the SiC particles in the deformation zone. While some of the SiC particles flow within the deformed material, some flow at the deformed billet surface: these Sic particles play the most important role in the damage mechanism of the die-bearing surface and the geometry of the dead metal zone (DMZ). The possible damage to the die-bearing surfaces is severe at the entrance of the die bearing. On the other hand, some SiC particles are broken in this zone due to the severe deformation stress of the MMC billet. (C) 2009 Elsevier Ltd. All rights reserved.