Discontinuous reinforcements in extruded aluminium-lithium matrix composites

Aluminium-based matrix composites with ceramic reinforcements have received considerable attention because of their improved strength, modulus and increased wear resistance over conventional aluminium alloys. The discontinuous type of reinforcements, in this case SiC and Si₃N₄ particulates, have been especially appealing due to their relative availability and low-cost production. In addition, adding lithium to aluminium alloys has the potential for even better properties with weight reductions, highly attractive for the aerospace industries. This paper discusses both the role of discontinuous reinforcements and extrusion parameters in the development of these improved metal-matrix composites (MMCs). The effects of different reinforcements, varying percentages of reinforcements and the relative sizes of these reinforcements were studied with respect to the microstructural development and the consequent mechanical properties.