Effects of the volume fraction, solidification structure and particle distribution on fatigue crack growth properties in SiC particulate-reinforced cast aluminum alloy composites have been investigated. Comparing with the un-reinforced matrix alloys, fatigue crack growth resistance of the cast composites is found to be improved at the low ΔK region, deteriorated at the high ΔK region, and comparable at the Paris region. These correspond to the crack growth behaviour of the powder metallurgy-processed composites which exhibit fine matrix microstructure and homogeneous particle distribution. However, fatigue crack growth characteristics of the cast composites are influenced by the solidification structure. The dendritic solidification structure including non-uniform particle distribution results in complicated crack growth path, and such the particle segregation provides both positive and negative effects for the fatigue crack growth properties. It improves fatigue crack growth resistance at the low ΔK region due to the remarkable crack deflection and the resultant roughness-induced crack closure. While, it deteriorates the high ΔK region fatigue crack growth properties due to the enhanced monotonic fracture mode contribution.
