Influence of microstructures and particle concentrations on the development of extrusion textures in metal matrix composites

Crystallographic textures and microstructures induced by extrusion in aluminium alloys reinforced by silicon carbides are analysed in some detail. It is shown that the crystallographic texture and the morphology of the Al phase vary with the SiC percentage and distribution. When the SiC concentration is low (i.e. less than 10%), the particles are dispersed randomly within the matrix and the texture intensity is greater than that of the Al alloy deformed under the same conditions. For high concentrations (i.e. greater than 10%) the particle distribution is no longer uniform and the Al texture tends towards isotropy. Simultaneously, the Al grains, which are very elongated in the particle-free alloy, break into subgrains during deformation in the composite materials. To interpret these various observations, extrusion textures have been simulated with a viscoplastic self-consistent model, introducing several concentrations of SiC and the specific morphology of the composite material. The experimental trends can thus be quantitatively reproduced and explained: the influence of the Al morphology and the particle distribution on the Al texture is clearly shown.