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金属学报  2019, Vol. 55 Issue (11): 1477-1486    DOI: 10.11900/0412.1961.2019.00025
  研究论文 本期目录 | 过刊浏览 |
位错密度梯度结构Cu单晶微柱压缩的三维离散位错动力学模拟
熊健1,魏德安1,陆宋江1,阚前华1,康国政1,张旭1,2()
1. 西南交通大学力学与工程学院应用力学与结构安全四川省重点实验室 成都 610031
2. 西安交通大学机械结构强度与振动国家重点实验室 西安 710049
A Three-Dimensional Discrete Dislocation Dynamics Simulation on Micropillar Compression of Single Crystal Copper with Dislocation Density Gradient
XIONG Jian1,WEI Dean1,LU Songjiang1,KAN Qianhua1,KANG Guozheng1,ZHANG Xu1,2()
1. Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province, School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, China
2. State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China
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摘要: 

采用离散位错动力学模拟了位错密度梯度结构Cu单晶微柱的压缩过程,分析了加载方向垂直于位错密度梯度方向和平行于位错密度梯度方向对微柱压缩各向异性响应的影响。压缩应力-应变响应结果表明:加载方向平行于位错密度梯度方向时,弹-塑性转变的临界应力更高,但应变较大时的塑性流动应力不受加载方向的影响。进一步分析塑性应变和位错密度的空间分布和时间演化表明:当加载方向垂直于位错密度梯度方向时,位错密度最低区的位错源首先激活,随后位错密度更高区的位错源激活,整个变形过程伴随多个滑移带产生,整体模型的变形更加均匀;当加载方向平行于位错密度梯度方向时,位错源的开动首先在模型的中间层发生,然后向两端扩展,整个模型的塑性变形主要集中在一个滑移带。

关键词 微柱压缩离散位错动力学位错密度梯度塑性变形加载方向    
Abstract

In recent years, many gradient materials have been studied. The metal materials with gradient microstructure mainly include: grain size distribution gradient, twin density gradient, dislocation density gradient, solute or precipitate density gradient, or combinations thereof. There are many studies of gradient nanograined material, but few studies of the dislocation density gradient. In fact, the dislocation density gradient structure is ubiquitous. The Taylor relation is only applicable to reveal the relationship between dislocation density and plastic flow stress, without the description of its dependence on dislocation density gradient. Discrete dislocation dynamics (DDD) has its advantage in describing plastic deformation in terms of dislocation motion and dislocation interactions. In this work, Three-dimensional discrete dislocation dynamics (3D-DDD) simulation was performed to investigate the compression behavior of single crystal copper micropillar with dislocation density gradient structure. The effects of loading direction perpendicular and parallel to the direction of dislocation density gradient on the anisotropic responses of micropillar compression were analyzed. The compressional stress-strain response shows that, when the loading direction is parallel to the gradient direction, the critical stress of elastic-plastic transition is higher. However, the plastic flow stress is not affected by the loading direction when the strain is relative larger. Further analysis of spatial-temporal evolution of plastic strain and dislocation density indicate that: when the loading direction is perpendicular to the dislocation density gradient direction, the dislocation sources are firstly activated in the region with the lowest dislocation density, then the dislocations in the region with higher dislocation density are activated subsequently; and the whole deformation process is accompanied with multiple slip bands, then the deformation of the whole model is relatively more uniform. When the loading direction is parallel to the dislocation density gradient direction, the dislocation sources start to activate in the middle layer of the model, then expand to the two adjacent ends; and the plastic deformation of the whole model mainly concentrates in only one slip band.

Key wordsmicropillar compression    discrete dislocation dynamics    dislocation density gradient    plastic deformation    loading direction
收稿日期: 2019-01-28     
ZTFLH:  TG146.1  
基金资助:国家自然科学基金项目Nos(11672251);国家自然科学基金项目Nos(11872321);机械结构强度与振动国家重点实验室开放课题项目No(SV2018-KF-10)
通讯作者: 张旭     E-mail: xzhang@swjtu.edu.cn
Corresponding author: Xu ZHANG     E-mail: xzhang@swjtu.edu.cn
作者简介: 熊健,男,1994年生,硕士生

引用本文:

熊健,魏德安,陆宋江,阚前华,康国政,张旭. 位错密度梯度结构Cu单晶微柱压缩的三维离散位错动力学模拟[J]. 金属学报, 2019, 55(11): 1477-1486.
Jian XIONG, Dean WEI, Songjiang LU, Qianhua KAN, Guozheng KANG, Xu ZHANG. A Three-Dimensional Discrete Dislocation Dynamics Simulation on Micropillar Compression of Single Crystal Copper with Dislocation Density Gradient. Acta Metall Sin, 2019, 55(11): 1477-1486.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2019.00025      或      https://www.ams.org.cn/CN/Y2019/V55/I11/1477

图1  离散位错动力学模拟中位错的离散化处理

Layer

Number of source

Dislocation density

1012 m-2

Dislocation spacing

nm

Bottom layer10038.0162
Middle layer20076.5114
Top layer300114.093
表1  模型各层的位错源数量、初始位错密度与位错间距
ParameterValueUnit
Burgers vector (b)0.256nm
Mean dislocation density (ρ)76.51012 m-2
Mean dislocation source length (lFRS)400nm
Poisson's ratio (ν)0.324-
Shear modulus (μ)54.6GPa
Drag coefficient (B)1×10-4Pa·s
表2  Cu单晶微柱离散位错动力学模拟的材料参数
图2  位错密度梯度结构模型在不同加载方向下的初始位错构型
图3  位错密度梯度结构Cu单晶微柱在不同加载方向下的等效应力-应变曲线以及位错密度演化曲线
Slip systemX direction [11ˉ0]Z direction [1ˉ1ˉ2]
(111)[1ˉ10]00
(111)[1ˉ01]00
(111)[01ˉ1]00
(1ˉ11)[110]00.272
(1ˉ11)[101]0.4080.136
(1ˉ11)[01ˉ1]0.4080.408
(11ˉ1)[110]00.272
(11ˉ1)[011]0.4080.136
(11ˉ1)[1ˉ01]0.4080.408
(111ˉ)[1ˉ10]00
(111ˉ)[011]00.272
(111ˉ)[101]00.272
表3  不同加载方向下Cu单晶微柱各个滑移系的Schmid因子
图4  不同加载方向下的主滑移系
图5  位错密度梯度结构模型沿X轴加载时不同应变时的位错微结构
图6  位错密度梯度结构模型沿着X轴方向加载时在不同应变时表面的塑性应变分布
图7  位错密度梯度结构模型沿X轴加载时,位错密度不同的各层塑性应变及位错密度随应变的变化
图8  位错密度梯度结构模型沿Z轴加载时不同应变时的位错微结构
图9  位错密度梯度结构模型沿着Z轴方向加载时在不同应变时表面的塑性应变分布
图10  位错密度梯度结构模型沿Z轴加载时,位错密度不同的各层塑性应变及位错密度随应变的变化
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