Atomistic Simulations under Extreme Conditions

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Computation and Simulation on Metals".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 8385

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Guest Editor
College of Materials Science and Engineering, Hunan University, Changsha 410082, China
Interests: analytic embedded atom potentials and Atomistic computer simulation (MD and MC); lattice defects; nanostructured metals and alloys; surface segregation, adsorption, and catalysis; light elements in metals and alloys; thermal barrier coatings
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Dear Colleagues,

Materials under extreme conditions have been revolutionized in the past few years due to technological breakthroughs, e.g., diamond anvil cell and shock wave compression. The response of materials to the broad range of such conditions provides insight into new phenomena, exposes failure modes that limit technological possibility, and presents novel routes for making new materials. Therefore, understanding the behavior of materials under extreme conditions is essential to increase their service lifetime and develop new materials with improved properties.

However, it is still challenging to observe the microstructure evolution under extreme conditions from an experimental viewpoint. The atomistic simulation method, i.e., molecular dynamics simulation, is an effective tool to study the effect of specific nanostructural features on the overall mechanical behavior of the material. The force of each atom at any time is obtained through the interaction potential function between atoms, and classical Newtonian mechanics are used to calculate the speed and coordinates. Thus, the evolution of the microstructure, potential deformation mechanisms, and other related properties under extreme conditions can be studied.

This Special Issue aims to publish papers that advance the field of atomistic simulation methods to discover new materials and investigate existing metal materials under extreme conditions. Papers that report on the development of new methods or the enhancement of existing approaches are of interest.

Prof. Dr. Wangyu Hu
Guest Editor

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Keywords

  • molecular dynamics
  • extreme conditions
  • interatomic potentials
  • mechanical properties

Published Papers (4 papers)

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Research

11 pages, 5885 KiB  
Article
Deformation Mechanism of Solidified Ti3Al Alloys with Penta Twins under Shear Loading
by Xiaotian Guo, Han Xie, Zihao Meng and Tinghong Gao
Metals 2022, 12(8), 1356; https://doi.org/10.3390/met12081356 - 15 Aug 2022
Cited by 2 | Viewed by 1275
Abstract
Owing to the excellent mechanical properties of the Ti3Al alloy, the study of its microstructure has attracted the extensive attention of researchers. In this study, a Ti3Al alloy was grown based on molecular dynamics using a decahedral precursor. Face [...] Read more.
Owing to the excellent mechanical properties of the Ti3Al alloy, the study of its microstructure has attracted the extensive attention of researchers. In this study, a Ti3Al alloy was grown based on molecular dynamics using a decahedral precursor. Face centered cubic nanocrystals with tetrahedral shapes were formed and connected by twin boundaries (TBs) to form penta twins. To understand the shear response of the Ti3Al alloy with multiple and penta twins, a shear load perpendicular to the Z-axis was applied to the quenched sample. The TBs slipped as Shockley dislocations commenced and propagated under shear loading, causing the detwinning of the penta twins and the failure of the system, indicating that the plastic deformation had been due to Shockley dislocations. The slip mechanism of multi-twinned structures in the Ti3Al alloy is discussed in detail. This study would serve as a useful guide for the design and development of advanced alloy materials. Full article
(This article belongs to the Special Issue Atomistic Simulations under Extreme Conditions)
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13 pages, 10043 KiB  
Article
The Microstructural Evolution of Nickel Single Crystal under Cyclic Deformation and Hyper-Gravity Conditions: A Molecular Dynamics Study
by Xiaojuan Deng, Yudi Xiao, Yiwu Ma, Bowen Huang and Wangyu Hu
Metals 2022, 12(7), 1128; https://doi.org/10.3390/met12071128 - 1 Jul 2022
Cited by 4 | Viewed by 1655
Abstract
Turbine blades are subjected to cyclic deformation and intensive hyper-gravity force during high-speed rotation. Therefore, understanding the dynamic mechanical behavior is important to improve the performance of the blade. In this work, [001](010), [110](−110), and [11−2](111) pre-existing crack models of nickel single crystals [...] Read more.
Turbine blades are subjected to cyclic deformation and intensive hyper-gravity force during high-speed rotation. Therefore, understanding the dynamic mechanical behavior is important to improve the performance of the blade. In this work, [001](010), [110](−110), and [11−2](111) pre-existing crack models of nickel single crystals under increasing cyclic tensile deformations were studied by using molecular dynamics simulations. In addition, a novel hyper-gravity loading method is proposed to simulate the rotation of the blade. Four hyper-gravity intensities, i.e., 1 × 1012 g, 3 × 1012 g, 6 × 1012 g, and 8 × 1012 g, and different temperatures were applied during the cyclic deformation. The fatigue life decreased rapidly with the elevated hyper-gravity strength, although the plastic mechanism is consistent with the zero-gravity condition. The stress intensity factor for the first dislocation nucleation indicates that the critical stress strongly depends on the temperatures and hyper-gravity intensities. Moreover, the crack length in relation to hyper-gravity intensity is discussed and shows anisotropy along the direction of hyper-gravity. A temperature-induced brittle-to-ductile transition is observed in the [001](010) crack model. The present work enhances our understanding of the fatigue mechanism under hyper-gravity conditions from an atomistic viewpoint. Full article
(This article belongs to the Special Issue Atomistic Simulations under Extreme Conditions)
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16 pages, 8136 KiB  
Article
Solidification of Undercooled Liquid under Supergravity Field by Phase-Field Crystal Approach
by Nengwen Hu, Yongfeng Huang, Kun Wang, Wangyu Hu, Jun Chen and Huiqiu Deng
Metals 2022, 12(2), 232; https://doi.org/10.3390/met12020232 - 26 Jan 2022
Cited by 4 | Viewed by 2535
Abstract
Solidification under a supergravity field is an effective method to control the solidified microstructure, which can be used to prepare materials with excellent comprehensive properties. In order to explore the influence of supergravity on the solidification behavior, a phase-field crystal model for the [...] Read more.
Solidification under a supergravity field is an effective method to control the solidified microstructure, which can be used to prepare materials with excellent comprehensive properties. In order to explore the influence of supergravity on the solidification behavior, a phase-field crystal model for the solidification under supergravity fields is developed and utilized to study the supergravity-controlled solidification behaviors. The results show that the grains in the solidification structures are refined in a supergravity field. The grain size in a zero-gravity field is uniformly distributed in the sample, but gradually decreases along the direction of the supergravity, showing a graded microstructure. The simulations show real-time images of the nucleation and growth of grains during solidification. In a supergravity field, solidification occurs preferentially in the liquid subject to greater gravity and advances in the opposite direction of supergravity with the time evolution. In addition, the driving force of crystallization in liquid is calculated to explain the effect of the supergravity field on the solidification structure from a thermodynamic point of view. Our findings are expected to provide a new approach and insight for understanding the solidification behaviors under supergravity. Full article
(This article belongs to the Special Issue Atomistic Simulations under Extreme Conditions)
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13 pages, 7898 KiB  
Article
Effect of Vacancies on Dynamic Response and Spallation in Single-Crystal Magnesium by Molecular Dynamic Simulation
by Chenying Jiang, Zhiyong Jian, Shifang Xiao, Xiaofan Li, Kun Wang, Huiqiu Deng and Wangyu Hu
Metals 2022, 12(2), 215; https://doi.org/10.3390/met12020215 - 24 Jan 2022
Cited by 2 | Viewed by 2109
Abstract
The effect of vacancies on dynamic response and spallation in single-crystal magnesium (Mg) is investigated by nonequilibrium molecular dynamics simulations. The initial vacancy concentration (Cv) ranges from 0% to 2.0%, and the shock loading is applied along [0001] and [10–10] [...] Read more.
The effect of vacancies on dynamic response and spallation in single-crystal magnesium (Mg) is investigated by nonequilibrium molecular dynamics simulations. The initial vacancy concentration (Cv) ranges from 0% to 2.0%, and the shock loading is applied along [0001] and [10–10] directions. The simulation results show that the effects of vacancy defects are strongly dependent on the shock directions. For shock along the [0001] direction, vacancy defects have a negligible effect on compression-induced plasticity, but play a role in increasing spall damage. In contrast, for shock along the [10–10] orientation, vacancy defects not only provide the nucleation sites for compression-induced plasticity, which mainly involves crystallographic reorientation, phase transition, and stacking faults, but also significantly reduce spall damage. The degree of spall damage is probably determined by a competitive mechanism between energy absorption and stress attenuation induced by plastic deformation. Void evolution during spallation is mainly based on the emission mechanism of dislocations. The {11–22} <11–23> pyramidal dislocation facilitates the nucleation of void in the [0001] shock, as well as the {1–100} <11–20> prismatic dislocation in the [10–10] shock. We also investigated the variation of spall strength between perfect and defective Mg at different shock velocities. The relevant results can provide a reference for future investigations on spall damage. Full article
(This article belongs to the Special Issue Atomistic Simulations under Extreme Conditions)
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