关键词: molecular dynamics simulation, rapid solidification, crystal structure, dislocation interaction

Abstract: Dislocations and other atomic-level defects play a crucial role in determining the macroscopic properties of crystalline materials, but it is extremely difficult to observe the evolution of dislocations due to the limitations of the most advanced experimental techniques. Therefore, in this work, the rapid solidification processes of Ni₄₇Co₅₃ alloy at five cooling rates are studied by molecular dynamics simulation, and the evolutions of their microstructures and dislocations are investigated as well. The results show that face-centered cubic (FCC) structures are formed at the low cooling rate, and the crystalline and amorphous mixture appear at the critical cooling rate, and the amorphous are generated at the high cooling rate. The crystallization temperature and crystallinity decrease with cooling rate increasing. Dislocations are few at the cooling rates of 1×10¹¹ K/s, 5×10¹² K/s, and 1×10¹³ K/s, and they are most abundant at the cooling rates of 5×10¹¹ K/s and 1×10¹² K/s, in which their dislocation line lengths are both almost identical. There appear a large number of dislocation reactions at both cooling rates, in which the interconversion between perfect and partial dislocations is primary. The dislocation reactions are more intense at the cooling rate of 5×10¹¹ K/s, and the slip of some dislocations leads to the interconversion between FCC structure and hexagonal close packed (HCP) structure, which causes the twin boundaries (TBs) to disappear. The FCC and HCP are in the same atomic layer, and dislocations are formed at the junction due to the existence of TBs at the cooling rate of 1×10¹² K/s. The present research is important in understanding the dislocation mechanism and its influence on crystal structure at atomic scales.

Key words: molecular dynamics simulation, rapid solidification, crystal structure, dislocation interaction