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Atomistic simulation of microvoid formation and its influence on crack nucleation in hexagonal titanium

He Yan Zhou Gang Liu Yan-Xia Wang Hao Xu Dong-Sheng Yang Rui

Atomistic simulation of microvoid formation and its influence on crack nucleation in hexagonal titanium

He Yan, Zhou Gang, Liu Yan-Xia, Wang Hao, Xu Dong-Sheng, Yang Rui
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  • Received Date:  20 July 2017
  • Accepted Date:  18 December 2017
  • Published Online:  05 March 2018

Atomistic simulation of microvoid formation and its influence on crack nucleation in hexagonal titanium

    Corresponding author: Wang Hao, haowang@imr.ac.cn
  • 1. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;
  • 2. University of Chinese Academy of Science, Beijing 100864, China;
  • 3. College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China;
  • 4. School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China;
  • 5. School of Physics, Liaoning University, Shenyang 110036, China
Fund Project:  Project supported by the State Key Development Program for Basic Research of China (Grant No. 2016YFB0701304), the National Natural Science Foundation of China (Grant Nos. 51671195, 11674233, 61603265), and the Technology Foundation of Shenyang Normal University, China (Grant No. L201521).

Abstract: During the plastic deformation of hexagonal metals, it is easy to generate the point defect clusters with complex shapes and configurations due to their anisotropic properties. The interactions among these clusters and between these clusters and moving dislocations significantly influence the physical and mechanical properties of hexagonal materials. However, none of these issues in particular concerning the evolutions of vacancy clusters, the formation of microvoids, and the crack nucleation and propagation, is comprehensively understood on an atomic scale. In the present work, we first employ the activation-relaxation technique, in combination with ab initio and interatomic potential calculations, to systematically investigate vacancy cluster configurations in titanium and the transformation between these clusters. The results indicate the stable and metastable configurations of vacancy clusters at various sizes and activation energies of their dissociation, combination and migration. It is found that the formation and migration energies decrease with the size of vacancy cluster increasing. Small vacancy clusters stabilize at configurations with special symmetry, while large clusters transform into microvoids or microcracks. High-throughput molecular dynamics simulations are subsequently employed to investigate the influences of these clusters on plastic deformation under tensile loading. The clusters are found to facilitate the crack nucleation by providing lower critical stress, which decreases with the size of the vacancy clusters increasing. Under tensile loading, cracks are first nucleated at small clusters and then grow up, while large clusters form microvoids and cracks directly grow up.

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