Effect of hot extrusion on the microstructure of a particulate reinforced magnesium matrix composite

A particulate reinforced magnesium matrix composite fabricated by stir casting was extruded at 250 °C with an extrusion ratio of 12:1 and constant RAM speed of 15 mm/s. Extrusion of the composite causes large scale dynamic recrystallization resulting in a fine matrix microstructure. The reinforcing particles stimulate dynamic recrystallization, and dynamic recrystallization in the composite is sensitive to the particle content on a local scale. The particle distribution of the composite before and after extrusion was studied using a window technique. It is found that the segregation of particles in the as-cast composite is largely eliminated by extrusion and the particle distribution is significantly improved. Extrusion-induced damage to the reinforcement is observed in the extruded composites, and the particle fracture induced by extrusion is also sensitive to the particle content on a local scale.