| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1600684 | Intermetallics | 2011 | 6 Pages |
In this paper, molecular dynamics simulations based on the second-moment approximation of tight-binding scheme have been performed to investigate the effect of cooling rate on solidification microstructures of liquid Ni. Two transitional structures characterized by one-dimensional (1D) and 2D periodicities respectively between the crystal and amorphous states have been found as the cooling rates range from 6 × 1012 K/s to 1 × 1013 K/s. As the cooling rates Q ≥ 1.5 × 1013 K/s, an amorphous structure can be obtained, whilst crystal structures are formed when Q ≤ 4 × 1012 K/s. Moreover, our results reveal that the intensity ratio (g21/g22) of the two subpeaks, which split from the second peak on the pair distribution function for the amorphous state, can act as a structural indicator to differentiate amorphous, translational structure and crystalline states. As such, one may determine the structure state of a material by estimating the value of g21/g22 from its pair distribution function.
Graphical abstractMolecular dynamics (MD) simulated instantaneous atomic images of the Ni system at 300 K resulted from different cooling rates. (a) Amorphous structure at Q3 = 1.5 × 1013 K/s. (b) 1D periodic structure at Q4 = 1 × 1013 K/s, the green arrow denotes the direction of the 1D periodic structure. (c) Detailed atomic configuration of the selected plane (blue atoms) in (b); (d) 2D periodic structure at Q6 = 6 × 1012 K/s, the green and blue arrows indicate the two directions of the 2D periodic structure. (e) 3D crystal structure at Q9 = 5 × 1011 K/s. All the insets in the top right corner of these figures display the corresponding fast Fourier transformation (FFT) patterns of the atomic configurations for different cooling rates.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Relationship between solidification microstructures and cooling rates of Ni has been established. ► Two transitional structures characterized by 1D and 2D periodicities respectively have been revealed. ► The fcc- and hcp-type close-packed planes constitute the 1D and 2D structures. ► Three different g21/g22 values correspond to the three structural states. ► The value of g21/g22 could act as a parameter to characterize the structural state.
