Characterisation of 3D strain heterogeneity at the microstructure scale during low cycle fatigue of an AlSi7Cu3Mg alloy at 250 °C

3D tomographic images of a cast AlSi7Cu3Mg alloy were obtained using synchrotron X-ray tomography during in-situ Low Cycle Fatigue tests at 250 °C. While image analysis highlights the role of eutectic Si particles close to pores in damage mechanisms, high resolution digital volume correlation reveals the relationship between strain heterogeneity at the microstructural scale and hard particles failure or cracks. Monitoring strains evolution with cycles within hard particles, i.e. eutectic Si and Fe or Cu intermetallics, allows measuring their local failure strains and drawing a hierarchy of the deformation to failure. Then, a local Manson-Coffin curve per hard phase is proposed.