Molecular dynamics simulation of the critical and subcritical nuclei during solidification of nickel melt

ZY Jian and AH Gao and FE Chang and BB Tang and L Zhang and N Li, ACTA PHYSICA SINICA, 62, 056102 (2013).

DOI: 10.7498/aps.62.056102

The microstructures of nickel solidified at different cooling rates are studied by using molecular dynamics simulation and the critical condition for nickel melt to form ideal metallic glass is calculated. The simulation results show that the crystal structure is obtained after the nickel melt has been solidified at a cooling rate that is lower than 10(11) K/s; while a mixture is composed of crystal structure and amorphous structure when the cooling rate is in a region from 10(11) K/s to 10(14.5) K/s. The solidified crystal of nickel is of fcc structure when the cooling rate is lower than 10(10) K/s, while it changes into crystal structure composed of fcc and hcp when the cooling rate is between 10(10) K/s and 10(14.5) K/s. By analyzing the calculation and simulation results, it is determined that the critical cooling rate for nickel melt to form ideal metallic glass is 10(14.5) K/s. Moreover, it is found that the structures of the subcritical nuclei (the cooling rate is higher than 10(14.5) K/s), critical nuclei (the cooling rate is 10(14.5) K/s), and the growing crystal (the cooling rate is lower than 10(14.5) K/s) are the lamellar structures composed of fcc and hcp atoms, which indicates that the subcritical nuclei, critical nuclei and the growing crystal have the same structures.

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