3D In Situ Imaging of Aluminium Alloys During Solidification

X-ray tomography has become a widely used 3D characterisation technique in materials science either using laboratory tomographs or large X-rays facilities. The advantage of large X-rays facilities is the high photon flux which allows fast tomography to be performed. With fast acquisition CCD cameras, it is possible to obtain a 3D image of the material in less than 30 s with a spatial resolution of the order of 1 or 2 mu m. We will show that this allows to study the influence of copper addition on the formation of intermetallics formation in Al-Si-Fe-Cu alloys: we will show that copper seems to have beneficial effects. With CMOS cameras it is possible to reduce acquisition times down to values of about 0.15 s. We will show that this allows to obtain in situ 3D information on the early stage of solidification in aluminium alloys, only accessible up to now using radiography : the solidification front rate was measured on several individual dendrites an Al-20wt%Cu alloy and estimated to be around 10 mu m/s.