The influence of SiC particles on the compressive properties of metal matrix composites

Room temperature compressive tests have been carried out on three metal matrix composites (MMCs), all based on the Al alloy CW67 and on monolithic material. The composites, CW67 alloy reinforced with homogeneously distributed SiC particles in three nominal sizes 0.7, 15 and 33 mum, were produced by hot pressing up to the theoretical density. The addition of the SiC particles increased the yield strength and elastic modulus while decreasing the ultimate compressive strength and ductility of the CW67 alloy in both the peak-aged and under-aged conditions. The greatest strengthening effects were achieved with the CW67-15 mum SiC composite material. Both the presence of agglomerations of small (0.7 pm) SiC particles and the cracking of large (33 mum) SiC particles had detrimental effects on CW67 alloy strengthening. The higher compressive strength and lower ductility were achieved with the peak-aged matrix compared with the under-aged matrix. The presence of SiC particles causes the aging process to be accelerated due to an increase in dislocation density, which provides more sites for the nucleation of precipitates. (C) 2001 Elsevier Science Inc. All rights reserved.