Abstract
In this study, molecular dynamics (MD) simulations coupled with multi-scale shock technique (MSST) are used to predict the Hugoniot curve PH, Grüneisen coefficient γ and melting temperature Tm of single crystal (SC) and nanocrystalline (NC) aluminum (Al) with grain sizes of 6 and 60 nm at dynamic high pressure. The linear relation between the shock wave velocity and particle velocity is reproduced, and the results indicate that there is nearly no difference for the Hugoniot of SC and NC Al, which could be explained by the fact that the grain size effect on PH can be negligible at high pressure. Some empirical models are used to predict γ and Tm, which exhibit an opposite behavior. In addition, it is found that the melting pressure and temperature are 107.5 GPa, 3063 K for SC Al, while they are 109.5 GPa, 3082 K for NC Al, which have a reasonable agreement with the published work.
Highlights
In high-pressure physics, knowledge of the shock Hugoniot, Gruneisen coefficient (γ) and melting temperature (T m) is essential to investigate the equation of state (EOS) of metallic materials.[1,2,3]
The results showed that the method presented by the former was better at high pressure compared with two other ones
Zou et al.[29] studied T m of Al under a wide range of pressure based on the Lindemann’s law and the Debye model, and the results showed a good agreement with experimental data.[25]
Summary
In high-pressure physics, knowledge of the shock Hugoniot, Gruneisen coefficient (γ) and melting temperature (T m) is essential to investigate the equation of state (EOS) of metallic materials.[1,2,3] The Hugoniot relation has been an increasing concern, because it could be used to characterize the Gruneisen EOS and shock-induced melting of metals. Vocadlo et al.[28] determined the melting curve of Al up to 150 GPa using ab initio MD, which exhibited an agreement with shock data.[25] Zou et al.[29] studied T m of Al under a wide range of pressure based on the Lindemann’s law and the Debye model, and the results showed a good agreement with experimental data.[25] Nie et al.[21] studied T m of Al on the basis of γ presented by Burakovsky et al.[19] and Jacobs et al.,[20] respectively, and concluded that these two equations of T m were almost the same melting curve. The detail investigation path of the present paper is firstly utilize MSST to obtain a linear equation between the shock wave velocity (us) and the particle velocity (up) for single crystal (SC) and nanocrystalline (NC) Al. The Hugoniot curve is determined based on the Hugoniot relation. Γ and T m are calculated to obtain the melting characteristic of Al at high pressure
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