Effects of Al-Ti-B-RE grain refiner on microstructure and mechanical properties of Al-7.0Si-0.55Mg alloy

To investigate the effects of Al-Ti-B-RE grain refiner on microstructure and mechanical properties of Al-7.0Si-0.55Mg (A357) alloy, some novel Al-7.0Si-0.55Mg alloys added with different amount of Al-5Ti-1B-RE grain refiner with different RE composition were prepared by vacuum-melting. The microstructure and fracture behavior of the Al-7.0Si-0.55Mg alloys with the grain refiners were observed by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and the mechanical properties of the alloys were tested in mechanical testing machine at room temperature. The observation of Al-Ti-B-RE morphology and internal structure of the particles reveals that it exhibits a TiAl3/Ti2Al20RE core-shell structure via heterogeneous TiB2 nuclei. The tensile strength of Al-7.0Si-0.55Mg alloys with Al-5Ti-1B-3.0RE grain refiner reaches the peak value at the same addition (0.2%) of grain refiner.