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金属学报  2024, Vol. 60 Issue (6): 848-856    DOI: 10.11900/0412.1961.2022.00606
  研究论文 本期目录 | 过刊浏览 |
α-Fe单晶拉伸变形热-动力学的分子动力学模拟
柏智文1, 丁志刚1, 周爱龙1, 侯怀宇1(), 刘伟1, 刘峰2,3()
1 南京理工大学 材料科学与工程学院 南京 210094
2 西北工业大学 凝固技术国家重点实验室 西安 710072
3 西北工业大学 分析与测试中心 西安 710072
Molecular Dynamics Simulation of Thermo-Kinetics of Tensile Deformation of α-Fe Single Crystal
BAI Zhiwen1, DING Zhigang1, ZHOU Ailong1, HOU Huaiyu1(), LIU Wei1, LIU Feng2,3()
1 Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
2 State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi 'an 710072, China
3 Analytical & Testing Center, Northwestern Polytechnical University, Xi 'an 710072, China
引用本文:

柏智文, 丁志刚, 周爱龙, 侯怀宇, 刘伟, 刘峰. α-Fe单晶拉伸变形热-动力学的分子动力学模拟[J]. 金属学报, 2024, 60(6): 848-856.
Zhiwen BAI, Zhigang DING, Ailong ZHOU, Huaiyu HOU, Wei LIU, Feng LIU. Molecular Dynamics Simulation of Thermo-Kinetics of Tensile Deformation of α-Fe Single Crystal[J]. Acta Metall Sin, 2024, 60(6): 848-856.

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摘要: 

材料的微观结构和变形机制决定了其强度和塑性。特别是位错的成核和运动在晶体材料的塑性变形过程中起着至关重要的作用。本工作采用分子动力学模拟方法,研究了α-Fe沿着[010]、[111]、[1ˉ10][11ˉ2]晶向单向拉伸条件下的变形热-动力学行为,分析了相应的位错产生和演变。结果表明,沿不同晶向拉伸时材料表现出不同的屈服强度,由高到低依次为[111]、[1ˉ10][11ˉ2]、[010]。沿不同的晶向拉伸时,位错密度变化趋势、位错类型及位错萌生时间均有不同,位错萌生时间越早,材料屈服强度越低。温度升高一般会使得单晶Fe在拉伸过程中位错萌生的时间提前,同时伴随弹性模量和强度的降低。对位错演化的热-动力学和广义稳定性分析表明,拉伸过程的热力学驱动力与动力学能垒的变化趋势相反,则广义稳定性数值与晶向及温度相关。

关键词 α-Fe分子动力学位错热-动力学广义稳定性    
Abstract

The microstructure and deformation mechanisms determine the strength and plasticity of structural materials. Specifically, the nucleation and movement of dislocations play a crucial role in the plastic deformation processing of crystalline materials. Just like the phase transformation, the plastic deformation and evolution of dislocations can be described as a kinetic behavior resulting from a thermodynamic driving force. In recent years, this research group has introduced the concept of thermo-dynamic correlation,which reflects the correlation between thermodynamics and kinetics as a trade-off relationship between thermodynamic driving forces (ΔG) and kinetic energy barriers (Q). It was found that an increase in ΔG is always accompanied by a decrease in Q in the processes of phase transformations and plastic deformations, and vice versa. Based on the so-called synergy rule of thermodynamics and kinetics, a new idea for the design and optimization of mechanical properties of materials has been proposed, that is the generalized stability criteria for phase transformation and deformation. The ΔG and Q are correlated by the concept of generalized stability, and it was suggested by many cases of metallic materials design that high driving forces and high generalized stability correspond to high strength and high ductility. To understand the thermo-dynamic correlation in the material deformation process and apply the generalized stability criteria for materials design, it is essential to comprehend the law of dislocation movement and evolution, and quantitatively describe the relationship between the driving force and the energy barrier of dislocation movement. The molecular dynamics (MD) simulation method has become an important means of studying the deformation mechanism of materials, dispite some limitations such as high deformation rate and small size of the description object. In this work, the thermo-kinetic behaviors of α-Fe deformation along [010], [111], [1ˉ10], and [11ˉ2] crystal directions under uniaxial tension were studied by using MD simulation. The dislocation generation and evolution of α-Fe during the tensile process were analyzed. The results indicate that the yield strength of the material varies along the grain direction, with the order from high to low being [111], [110], [11ˉ2], and [010]. When stretching along different crystal directions, the trend of dislocation density, dislocation type, and dislocation initiation time differs. The earlier the dislocation initiation time, the lower the yield strength. Generally, the dislocation initiation time of single crystal iron advances with an increase in temperature and a decrease in elastic modulus and strength. The results of thermo-kinetic and generalized stability analysis of dislocation evolution show that the thermo-kinetic driving force is opposite to the kinetic energy barrier, and the generalized stability value depends on crystal orientation and temperature.

Key wordsα-Fe    molecular dynamics    dislocation    thermo-kinetics    generalized stability
收稿日期: 2022-11-30     
ZTFLH:  TG141  
基金资助:国家自然科学基金重点项目(52130110)
通讯作者: 侯怀宇,hyhou@njust.edu.cn,主要从事计算材料学的研究;
刘 峰,liufeng@nwpu.edu.cn,主要从事相变热动力学及高强度合金制备等研究;
Corresponding author: HOU Huaiyu, associate professor, Tel: 13813008713, E-mail: hyhou@njust.edu.cn;
LIU Feng, professor, Tel: (029)88460374, E-mail: liufeng@nwpu.edu.cn
作者简介: 柏智文,女,1997年生,硕士
Crystal orientationModel size / nmAtomic number
XYZLXLYLZ
[100][010][001]19.98759.96119.9872058000
[11ˉ2][111][1ˉ10]19.58359.84119.7861992144
[111][1ˉ10][11ˉ2]19.78259.76319.5831989120
[1ˉ10][11ˉ2][111]19.78659.44919.7821999200
表1  单晶α-Fe拉伸模拟模型的尺寸
图1  α-Fe在10 K温度下沿不同晶向拉伸过程的应力-应变曲线和势能变化曲线
图2  10 K下不同晶向α-Fe屈服时的局域原子结构分布
图3  10 K下α-Fe沿不同晶向的位错密度曲线
图4  α-Fe沿[010]晶向在不同温度下的应力-应变曲线及不同晶向在不同温度下的屈服应力
图5  α-Fe在不同温度下沿[010]和[111]晶向拉伸时的位错密度曲线
图6  α-Fe在10 K下沿不同晶向变形中的驱动力、动力学能垒和广义稳定性
图7  α-Fe沿[010]晶向在不同温度下塑性变形时的驱动力、能垒及广义稳定性曲线
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