In metal matrix particulate composites, factors such as the volume fraction of the particulate phase, particle size and interfacial bonding on influence the crack propagation behavior. In this study, the effects of the volume fraction of the particulate phase and heat treatment on the relationships between crack propagation rate da/dN and the stress intensity factor range ΔK, crack pass profiles and crack opening displacement COD are examined using two kinds of Al₂O₃/Al alloy composites and Al alloy. At the low ΔK level, da/dN decreases with the increase of the volume fraction, but with increasing ΔK level, the tendency disappears. This is mainly due to crack deflection and roughness-induced crack closure due to the presence of particles. A unique relationship is obtained between da/dN and CTOD irrespective of heat treatment and volume fraction. Thus, it can be concluded that the main factor which controls da/dN is CTOD.