Effect of cooling rate on the 3D morphology of the proeutectic Al_3Ni intermetallic compound formed at the Al/Ni interface after solidification

Effect of cooling rate on the 3 D morphology and the growth mechanism of the proeutectic Al_3Ni intermetallic compound(IMC) that forms at the Al/Ni interface after solidification was investigated by synchrotron X-ray microtomography in combination with EBSD analysis. The proeutectic Al_3Ni phase that forms under an average cooling rate of 0.1 Ks~(-1) shows a characteristic faceted growth behavior and presents a typical 3 D morphology as partially hollow quadrangular prisms. On the contrary, that forms under an average cooling rate of 10 Ks~(-1) shows complicated dendritic morphology with asymmetrically distributed arms and faceted V-shape groove at the distal end, indicating a gradual transition of the growth behavior from non-faceted to faceted during the solidification process. These results reveal that the morphology of the proeutectic Al_3Ni is highly sensitive to the solidification condition so that fine control of the desired morphology may be achieved by carefully manipulating the cooling profile.