The effects of the disposition of SiC particles on the forgeability and mechanical properties of co-sprayed aluminium-based MMCs

An investigation of the forgeability and mechanical properties of unworked and extruded co-sprayed metal matrix composites (MMCs) is reported in this paper. The materials investigated are mainly co-sprayed particulate SiC reinforced 2014 and 2618 aluminium-based MMCs. A similar powder metallurgy (PM) MMC and a co-sprayed monolithic aluminium alloy which is used as the matrix of one of the MMCs are investigated also for base-line comparisons. Forgeability tests were performed on a mechanical press with cylindrical test billets at temperatures ranging from 250 to 450 degrees C. Tensile tests were performed at room temperature. The forgeability and some tensile properties of co-sprayed MMCs were found to be affected greatly by a unique metallurgical pattern designated the tree ring structure (TRS). Metallurgical examination showed that the TRS comprises bands with high and low concentrations of SIC particles. Forged and tensile test specimens show that these bands are easy paths for fractures to propagate along. The more homogeneous distribution of the SIC particles in the PM MMC resulted in a forgeability superior to that of the co-sprayed material. (C) 1997 Elsevier Science S.A.