Abstract
Cast aluminum alloys are promising from the perspective of its high specific strength and high cost effectiveness. However, cast aluminum alloys inevitably contain casting defects which degrade its fatigue strength, and it leads to the low reliability. It was observed in the experiments that the cracking was initiated by the fracture of Si particles or debonding of Al-Si interface. In this study, the image-based finite element analyses were carried out by using synchrotron X-ray CT images to elucidate the crack initiation mechanism of cast aluminum alloy under low-cycle fatigue. To examine the difference of mechanisms between fracture of Si particle and debonding of Al-Si interface, the finite element elastic-plastic analyses of five models for the fractured or debonded particles were performed under ten cycles of fatigue loading. From the numerical results, the Si particle with large volume was fractured because of high stress concentration, while the Si particle neighboring closely to intermitallics was debonded since the large plastic deformation of the aluminum matrix between Si and IMC particles.
