Atomic structure evolutions and mechanisms of the crystallization pathway of liquid Al during rapid cooling

LL Zhou and JM Pan and L Lang and ZA Tian and YF Mo and KJ Dong, RSC ADVANCES, 11, 39829-39837 (2021).

DOI: 10.1039/d1ra06777j

The solidification of pure aluminum has been studied by a large-scale molecular dynamic simulation. The potential energy, position D, height H, and width W of the first peak and valley of PDF curves, and the local structures were investigated. It was found that the FCC-crystallization ability of pure Al is so strong that still local crystal regions exist in the amorphized solid. As the temperature decreases, besides the counter-intuitive increase in D-p (D of the first peak), H-p increases monotonically; W-p, D-v, and H-v decrease monotonically; only W-v first decreases and then increases. They all change critically when phase transition happens. After the nucleation, orientation-disordered HCP- regions, as the grain boundaries or defects of FCC crystals, rapidly transform into FCC structures, and then the surviving HCP-regions regularize into few parallel layers or orientation-disordered HCP- regions. If parallel layers result in dislocation pinning, structural evolution terminates; otherwise, it continues. These findings will have a positive impact on the development of the solidification and nucleation theory.

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