Review on nucleation catalysis of tetragonal D022 Al3Ti and L12 modified (Al1−xMex)3Ti intermetallic compounds for solidification of alpha-al grains

Abstract Heterogeneous nucleation could be considered as a surface catalyzed nucleation process. It is known that Al3Ti phase in Al-Ti refiner is an effective catalytic substrate for solidification of alpha-Al. However, since the Al3Ti phase has a tetragonal D022 structure with lattice constants of a =0.3851 nm and c =0.8608 nm, different planes of Al3Ti phase have different lattice misfit between Al. Moreover, it is reported that the shape of Al3Ti in Al-Ti refiner is platelet and wide plane of the platelet has the relatively large lattice misfit between Al. Therefore, the dominant face of Al3Ti platelets in Al-Ti refiner is not the best plane for heterogeneous nucleation. To overcome these shortcomings, in our previous studies, high-symmetry L12 modified (Al1-xMex)3Ti phases with a lattice constant of a =0.3927 nm for Me = Cu, a =0.393 nm for Me = Fe, a = 0.394 nm for Me = Ni were used as catalytic substrate. In this paper, the role of lattice misfit on heterogeneous nucleation of Al will be discussed.