Aluminum is a remarkable material that contributes to the sustainability of society due to its lightness and good recyclability. However, since the production process of primary aluminum is highly energy intensive, it is essential to increase the use of secondary aluminum alloys, i.e., recycled aluminum, in order to realize the environmental edge of aluminum. Based on this viewpoint, casting aluminum alloy is becoming increasingly important. Aluminum is considered a material with no fatigue limit, unlike common steel materials. In addition, cast materials inherently contain a lot of defects such as shrinkage porosity. For these reasons, it is necessary to clarify the relationship between fatigue properties and defects to ensure the reliability of casting aluminum alloy. In this study, high-cycle rotating bending fatigue tests were carried out using specimens with an artificial small defect, and the effect of defect geometry (size and shape) on the fatigue strength properties of Al-Si-Mg casting aluminum alloy was discussed.

The S-N data showed a knee point although it was not as clear as in common steels. In other words, there was a stress level such that the fatigue life drastically increased as the applied cyclic stress decreased. The fatigue crack growth behaviour was observed by replica method in the specimen that endured up to 108 cycles without failure, and it was found out that the crack did not grow after 107 cycles, that is the crack non-propagation occurred.