Crystal-melt coexistence in fcc and bcc metals: a molecular-dynamics study of kinetic coefficients

摘要

As a sequel to the previous paper on the calculation of the crystal-melt interface free energy (2021 Materialia 15 100962), here we report the results on the kinetic coefficients using molecular dynamics simulations performed on six fcc metals and four bcc metals with the intention to compare the crystal structural influence. We found that the calculated kinetic coefficients are well described by the model by Broughton, Gilmer and Jackson (1982 Phys. Rev. Lett. 49 1496), and in particular, they exhibit varying degrees of anisotropy. We reveal that the anisotropies are related to the fluctuation of the crystal-melt interfaces, which causes the increase of the actual interface area in melting or solidification. The kinetic coefficients always display asymmetry between the solidification and melting process, and the difference is much more pronounced for the (111) interfaces in fcc metals which have the highest anisotropy. We found that the atomic mechanisms of the kinetic behaviors of these interfaces are closely related to the formation of twin-crystal domains during solidification, which delays the solidification process and consequently causes a decrease in the calculated kinetic coefficients.