Effects of hot extrusion through a curved die on the mechanical propertiesof SiCp/Al composites fabricated by melt-stirring

Metal-matrix composites (MMCs) of particulate-SiC-reinforced 6061 aluminium alloy were fabricated by the melt-stirring method. The primary MMC billets were prepared with volume fractions ranging from 0.05 to 0.20 and particle sizes ranging from 13 to 22 mu m. The microstructure and mechanical proper ties were investigated. The MMC billets were extruded at 500 degrees C at a constant extrusion velocity of V-e = 2 mm/min through a curved die. Extrus ion force, particle rearrangement, microstructure and mechanical properties were examined. The mechanical properties of the primary billets were compa red with those of extruded specimens. The effects of volume fraction and pa rticle size were studied. The increase in uniformity of particle dispersion is the major reason for the improvement in reliability resulting from hot extrusion through an optimally shaped die. Young's modulus and 0.2% offset yield strength of the extruded MMCs were compared with theoretical values c alculated by the Eshelby method. (C) 1999 Elsevier Science Ltd. All rights reserved.