Correlative synchrotron absorption edge tomography and microtomography provide insights into the effect of element distribution within intermetallic phases on the fracture behaviour of cast Al-Si alloys

A combined 3D investigation of elemental distribution and tensile fracture behaviour was carried out using synchrotron x-ray micro-tomography and absorption edge tomography for two near eutectic cast Al-Si-Cu-Ni alloys. Absorption edge tomography allowed the identification of intermetallics three-dimensionally based on the Cu/Ni distribution and morphology of the phases. In addition, inhomogeneities in the distributions, especially on the surface of intermetallics, were revealed by this technique. A correlation of the post-mortem state with the 3D Cu and Ni distributions showed that the main crack tends to propagate along interfaces between different types of intermetallics, while local inhomogeneities in element distribution within intermetallics acted as crack deflection sites.