Aluminum alloy automotive parts produced by the Lost Foam Casting (LFC) process have coarser microstructure and porosity defects than parts produced with conventional casting processes at faster cooling rates. This coarse microstructure has a major influence on the fatigue properties and crack initiation. In order to study its influence upon the mechanical behaviour, an experimental protocol has been set up using X-ray tomography and 3D Digital Volume Correlation (DVC). The present work focuses on the use of this protocol to study the influence of the casting microstructure upon the tensile behaviour. The 3D cracks were observed to initiate at large pores and microshrinkage cavities and then to propagate along the hard inclusions towards the free surface when cracks originate from a subsurface pore. The validated experimental protocol is presently applied to in-situ fatigue tests realized with synchrotron tomography and a newly developed DVC platform in order to analyze the damage micromechanisms of this alloy subjected to low cycle fatigue test.