2009 Volume 81 Issue 10 Pages 475-481
Usually, aluminum die-cast alloys are used with casting surface, therefore it can be assumed that defects exist in the sub-surface regions. These defects are largely neglected in conventional evaluations as these regions are removed before testing. In the present study, fatigue tests were performed using specimens with casting surface. Fatigue life was statistically analyzed, and synchrotron radiation X-ray microtomography was also applied to visualize surface defects in 3D together with the in-situ observation of crack initiation. The results revealed that specimens with shorter fatigue lives exhibit aligned micropores of approximately 10μm in diameter in a sub-surface region, which inevitably cause premature fatigue crack initiation. The in-situ observation clearly revealed fatigue crack initiation at agglomerated micropores.
