This paper studies the influence of Ni3Al intermetallic particles on the fracture behaviour of aluminium matrix (2014) composite materials. Intermetallics were obtained by mechanical alloying and by atomisation. The composite materials were manufactured by mixing, uniaxial compacting of a preform, and subsequent extrusion without canning or degassing. The study considered materials in extruded state and after T6 heat treatment. Assessments were made from the viewpoint of microstructure (by means of optical and scanning electron microscopy), and studying the reactions between the matrix and the reinforcement. These reactions produce a highly copper-enriched interphase. The influence of the reinforcement and state of the alloy on the fracture behaviour of the composite materials was studied through scanning electron microscopy. (C) 2003 Kluwer Academic Publishers.