Investigation of three-dimensional morphology changes of the eutectic Si particles affected by trace P and Sr in Al-7%Si cast alloys by means of synchrotron nano-tomography

The difference of the three-dimensional morphology of eutectic Si particles has been investigated in Al-7mass%Si cast alloys changing trace P and Sr contents by means of synchrotron radiation nano-tomography with Zernike phase plate. Fibrous Si morphology aligning in the same direction is observed in Al-7mass%Si-2ppmP alloy. Si particles in Al-7mass%Si-8ppmP-42ppmSr are not only of a plate-like morphology but also a coral-like and a fibrous morphology. All of the Si particles have either a fibrous morphology or a coral-like morphology in Al-7mass%Si-9ppmP-277ppmSr. It is realized that a solidification sequence affected by trace P and Sr contents changes the three-dimensional morphology of Si particles.