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高应变率压缩下纳米孔洞对金属铝塑性变形的影响研究
引用本文:第伍旻杰,胡晓棉. 高应变率压缩下纳米孔洞对金属铝塑性变形的影响研究[J]. 物理学报, 2015, 64(17): 170201-170201. DOI: 10.7498/aps.64.170201
作者姓名:第伍旻杰  胡晓棉
作者单位:1. 中国工程物理研究院研究生部, 北京 100088;2. 北京应用物理与计算数学研究所, 计算物理国家重点实验室, 北京 100088
摘    要:本文利用分子动力学模拟方法研究了含纳米孔洞金属铝在[110]晶向高应变率单轴压缩下弹塑性变形的微观过程. 对比单孔洞和完整单晶的模型, 讨论了多孔金属的应力应变关系及其位错发展规律. 研究结果表明, 对于多孔模型的位错积累过程, 位错密度随应变的增加可大致分为两个线性阶段. 由同一个孔洞生成的位错在相互靠近过程中, 其滑移速度越来越小; 随着位错继续滑移, 源自不同孔洞的位错之间开始交叉相互作用导致应变硬化. 达到流变峰应力之后又由于位错密度增殖速率升高发生软化. 当应变增加到11.8%时, 所有孔洞几乎完全坍缩, 并观察到在此过程中有棱位错生成.

关 键 词:分子动力学  纳米孔洞  纳米多孔  位错
收稿时间:2015-02-24

Plastic deformation in nanoporous aluminum subjected to high-rate uniaxial compression
Diwu Min-Jie,Hu Xiao-Mian. Plastic deformation in nanoporous aluminum subjected to high-rate uniaxial compression[J]. Acta Physica Sinica, 2015, 64(17): 170201-170201. DOI: 10.7498/aps.64.170201
Authors:Diwu Min-Jie  Hu Xiao-Mian
Affiliation:1. Graduate School, China Academy of Engineering Physics, Beijing 100088, China;2. National Lab of Computational Physics, Beijing Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Abstract:The mechanical behavior of nanoporous monocrystal aluminum subjected to uniaxial compressive loading at a rate of 2×109 s- 1 along [110] crystallographic orientation is studied using molecular dynamics simulations. Subjected to such a loading, nanovoids act as the effective sources of dislocation nucleation and emission, four of the twelve {111}<110> slip systems may be activated. With the same strain of 3.8%, dislocation nucleation will occur in both the sample of multiple voids and that with a single void. The configuration of multiple voids decreases the required stress for the onset of dislocation nucleation and emission in comparison with the sample with an isolated void of the same size. Because of the emission of trial partials, the accumulation of dislocation density can be changed into a piecewise linear process by the dislocation density propagation rate dρd/dε: in the initial stage of plastic deformation we obtain dρd/dε≈1.07×1018 m-2, but this changes to dρd/dε≈5.36×1018 m-2 at higher deformation. The velocity of dislocation is calculated to be subsonic and is a variable value during the plastic deformation. Dislocation loop pairs emit from the same void, glide and approach to each other, leading to the reduction of dislocation velocity. Then one loop of each pair continues to glide to intersect mutually and finally interact with the loops emitted from other voids, causing a strain hardening to reach the peak flow stress of 4.3 GPa. There is a post-yield softening corresponding to the onset of rapid dislocation density proliferation at higher dislocation densities. With the temperature evolution of the sample with multiple voids during plastic deformation, the density of mobile dislocations is calculated to be one magnitude lower than the total dislocation density. There is a decrease of mobile dislocation densities at large strains, showing that the mobile dislocation are diminished by the formation of dislocation forest and junctions. At the onset of their nucleation, the dislocations are all Shockley partials, however, when dislocation intersection happens, the majority are still Shockley partials, while the rest consists of Frank partials, perfect fcc dislocations and other dislocation ingredients. Voids collapse at the strain of 11.8%. No twins are found in the present simulation due to the high stacking-fault energy of aluminum. Prismatic dislocation loop emission is observed in this simulation.
Keywords:molecular dynamics  nanovoid  nanoporous  dislocation
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