Effects of SiC particulates on the fatigue behaviour of an Al-alloy matrix composite

In this study, the fatigue behaviour of aluminium matrix–silicon carbide (SiC) particulate reinforced composite specimens was investigated in comparison to the matrix aluminium alloy containing 12 wt% Si. Three different weight percentages of SiC particulates: 5, 10, and 15 in the size range of 40–60 μm were injected into the melt. Mg was also added to improve the wettability of Al-alloy matrix over SiC particulates resulting in better interfacial bonding. Test specimens were machined from squeeze casting billets. Hardness, bending and fatigue tests indicated that reinforcing the Al-alloy matrix with SiC particulates improved the hardness, flexural strength and fatigue resistance with increasing content of SiC particulates. Stress levels yielding less than 107 cycles to fracture were applied. Cracks initiated at the debonded particulate–matrix interface and/or by the cracking of the coarse particulates. SiC particulates improved fatigue resistance mainly by acting as barriers to cracks and/or deflecting the growth plane of cracks resulting in decreased crack propagation rates.