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金属学报  2018, Vol. 54 Issue (1): 47-54    DOI: 10.11900/0412.1961.2017.00228
  本期目录 | 过刊浏览 |
王瑾, 余黎明, 黄远, 李会军, 刘永长()
天津大学材料科学与工程学院水利安全与仿真国家重点实验室 天津 300354
Effect of Crystal Orientation and He Density on Crack Propagation Behavior of bcc-Fe
Jin WANG, Liming YU, Yuan HUANG, Huijun LI, Yongchang LIU()
State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science & Engineering, Tianjin University, Tianjin 300354, China
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采用分子动力学模拟研究了300 K时不同He浓度下(001)[010]和(121)[111] 2种取向bcc-Fe裂纹模型的扩展行为。结果表明,当模型中不存在He时,裂纹取向不同,裂纹扩展机制不同:(001)[010]取向裂纹的扩展机制分为弹性变形、相变、裂纹尖端沿相变区解理断裂;(121)[111]取向裂纹的扩展机制分为弹性变形、堆垛孪晶、孪晶尖端应力集中诱发多空洞合并断裂。(121)[111]取向裂纹的屈服应力和应变大于(001)[010]取向裂纹,说明(121)[111]取向裂纹具有较强的抵制裂纹扩展的能力。He浓度对裂纹扩展行为的影响主要体现在2个方面:当He浓度较低(0.9%,原子分数)时,He的存在减缓了相变或者孪晶转变速率,降低了裂纹扩展速率;当He浓度较高(6.0%,原子分数)时,大量He团簇的存在促进了空洞形成,导致2种裂纹模型的断裂机制均变为He团簇诱发多空洞合并断裂,未出现相变或者孪晶。

关键词 bcc-Fe裂纹扩展He浓度分子动力学    

Radiation-induced damage, especially the effect of He, has always been one of the crucial issues in future fusion reactors. It is thus essential to further understand the formation of He bubbles and hardening characteristics for future development of fusion application materials, for instance bcc-Fe as a simple model. Behaviors of crack propagation have been investigated in two different orientated cracks (001)[010] and (121)[111] of bcc-Fe models under different densities of He at 300 K by molecular dynamics simulation. The results show that these behaviors are tailored by crack orientations on the condition of non-He atoms: (001)[010] orientated crack can be divided into elastic deformation, phase transformation and cleavage fracture of crack tip along phase transformation zone; however, (121)[111] orientated crack is elastic deformation, stacking twin and after that formation and coalescence of voids to rupture. Furthermore, the yield stress and strain of (121)[111] orientated crack are higher than (001)[010] orientated crack, therefore (121)[111] orientated crack has stronger ability to resist crack propagation. In addition, it is revealed that the influence of He density on the crack propagation exhibits two major aspects: when the density of He is lower (0.9%, atomic fraction), He can reduce the efficiency of phase or twin transformation and decrease the rate of crack propagation; when the density of He is higher (6.0%, atomic fraction), a large number of He clusters contribute to promote micro-voids nucleation, fracture mechanism for both crack models is the transformation of He clusters to voids, then voids coalescence, accelerating the occurrence of fracture. There is no twin or phase transformation in higher density of He.

Key wordsbcc-Fe    crack propagation    He density    molecular dynamics
收稿日期: 2017-06-14     
ZTFLH:  TG111.91  
作者简介: 作者简介 王 瑾,女,1989年生,博士


王瑾, 余黎明, 黄远, 李会军, 刘永长. 晶体取向和He浓度对bcc-Fe裂纹扩展行为的影响[J]. 金属学报, 2018, 54(1): 47-54.
Jin WANG, Liming YU, Yuan HUANG, Huijun LI, Yongchang LIU. Effect of Crystal Orientation and He Density on Crack Propagation Behavior of bcc-Fe. Acta Metall Sin, 2018, 54(1): 47-54.

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图1  含(001)[010]和(121)[111]取向裂纹的bcc-Fe模型局部断面视图
图2  2种不同取向裂纹的bcc-Fe模型应力-应变曲线
图3  (001)[010]取向裂纹模型随应变增加的构型演变图
Crack orientation Model x / nm y / nm z / nm Atomic fraction of He / % Number of atom
(001)[010] A1 2 42.8 42.8 0 314622
A2 2 42.8 42.8 0.9 317457
A3 2 42.8 42.8 6.0 333522
(121)[111] B1 2 44.5 41 0 315867
B2 2 44.5 41 0.9 318710
B3 2 44.5 41 6.0 334819
表1  含裂纹的bcc-Fe模型几何尺寸
图4  (121)[111]取向裂纹模型随应变增加的构型演变图
图5  不同He浓度下2种取向裂纹模型应力-应变曲线
图6  He浓度分别为0.9%和6.0%时(001)[010]取向裂纹模型随应变增加的构型演变图
图7  He浓度分别为0.9%和6.0%时(121)[111]取向裂纹模型随应变增加的构型演变图
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