Exploring Grain Growth in Nanocrystalline Ni During Thermal Annealing: A Molecular Dynamics Study
Nanocrystalline materials have attracted significant research interest within the field of materials science, particularly nanocrystalline nickel. Thermal annealing, a fundamental topic of research, plays a critical role in determining the evolution of grain size in nanocrystalline metals. In this study, we investigate the isothermal grain growth behaviors of nanocrystalline nickel, focusing on the effect of annealing temperature. Molecular dynamics simulations using the Modified Embedded Atom Method (MEAM) potential developed by Lee et al.  were employed to provide detailed atomic-level information on the microscopic mechanisms involved in grain growth. Previous studies have demonstrated that annealing temperature has a significant impact on the grain growth of nanocrystalline metals. For instance, Simo ̃es et al.  observed significant grain growth in nanocrystalline copper thin films with increasing annealing time and temperature. Chojnowski et al.  found that annealing nanocrystalline chromium at temperatures above 400°C led to con- trolled grain growth. Chen et al.  reported a decrease in the frequency of annealing twins in highly rolled pure nickel as annealing temperatures increased.
In this study, atomistic simulations were conducted to investigate the grain growth mechanisms, grain boundary structure, and the effects of annealing temperature on microstructural properties during grain growth. The models were constructed using the Voronoi geometrical method to study the grain growth mechanism. Our findings reveal that during thermal annealing, nanocrystalline nickel exhibits stacking faults, twinning, changes in grain size, rotations, and translations, which facilitate crystalline growth and grain coalescence. Grain boundary migration, grain rotation mechanisms, and dislocations (or stacking faults) were identified as intermediate mechanisms in the grain growth process. These results provide insights into how annealing temperature controls the rate of grain growth and its impact on the appearance of different types of defects during the growth.
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