Abstract: A simulation study has been performed for the evolutions of microstructures in a liquid metal Ni system during solidification process under different cooling rates by means of molecular dynamics method and EAM model potential. It shows that the cooling rate plays a critical role to the evolution of microstructures. As the cooling rate being 1.0×10¹⁴ K•s^-1 and 4.0×10¹³ K•s^-1, the amorphous structures would be formed in the system with 1551, 1541 and 1431 bond-types as the main body in the system. As the cooling rate being 2.0×10¹³ K•s^-1 and 1.0×10^{12 K•s-1, both kinds of crystal structures would be formed, respectively；the first one possesses the coexist of the fcc and hcp structures with 1421 and 1422 bond-types as the main body；the second one possesses only the fcc structure with 1421 bond-type as the main body；and their crystallization transition temperatures Tc, would be 1073 and 1173 K, respectively. At the same time, it is found that the mean coordination number of atoms (i.e. the nearest neighbor number) in the system is rather sensitive to the variation of temperature and cooling rate, and their sudden transition points, as shown in Fig. 5, just corresponding to the crystallization transition temperatures Tc, this will give us a new way for researching the crystallization transition processes of liquid metals.}

Key words: Liquid metal Ni, Solidification process, MD simulation, EAM model potential, Mean coordination number