Molecular Dynamics Simulation of Homogeneous Nucleation and Growth of Supercooled Al Liquid

Abstract

Molecular dynamics simulation is used to study the spontaneous nucleation and solidification of Al liquid. According to the mean first-passage time (MFPT), the critical crystal nucleus size at 31.6% undercooling is 152 atoms, the nucleation rate is [Formula: see text][Formula: see text]m[Formula: see text][Formula: see text]s[Formula: see text]. The nucleation rate obtained by the survival probability (SP) is [Formula: see text][Formula: see text]m[Formula: see text][Formula: see text]s[Formula: see text], which is very consistent with the result obtained by MFPT. Using Johnson–Mehl–Avrami (JMA) law to analyze the growth of the two extreme conditions in the experiment, the system with the smallest average atomic volume (Run38) grows faster than the system with the largest volume (Run73). In terms of microstructure, Run38 is a lamellar (LAM) structure, and Run73 is a complex polycrystalline structure accompanied by five-fold twinning (FFT). The shapes of clusters in a given range (5–10,000 atoms) during solidification in 100 experiments were counted. The results show that no clusters are perfectly spherical, but ellipsoids are of different shapes, and the larger the ellipsoid size, the closer to a spherical shape.