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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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Keywords:
- atomistic simulation /
- mechanical behavior /
- vacancy cluster /
- crack
[1] Bache M R 2003 Int. J. Fatigue 25 1079
[2] Dunne F P E, Rugg D, Walker A 2007 Int. J. Plast. 23 1061
[3] Sinha V, Mills M J, Williams J C 2004 Metall. Mater. Trans. A 35 3141
[4] Pilchak A L, Williams R E A, Williams J C 2010 Metall. Mater. Trans. A 41 106
[5] Veyssière P, Wang H, Xu D S, Chiu Y L 2008 IOP Conf. Series: Mater. Sci. Eng. 3 012018
[6] Xu D S, Wang H, Yang R, Veyssière P 2008 IOP Conf. Series: Mater. Sci. Eng. 3 012024
[7] Wang H, Xu D S, Yang R, Veyssière P 2008 Acta Mater. 56 4608
[8] Wang H, Xu D S, Yang R, Veyssière P 2009 Acta Mater. 57 3725
[9] Wang H, Xu D S, Yang R, Veyssière P 2011 Acta Mater. 59 1
[10] Wang H, Xu D S, Yang R, Veyssière P 2011 Acta Mater. 59 10
[11] Wang H, Xu D S, Yang R, Veyssière P 2011 Acta Mater. 59 19
[12] Wang H, Rodney D, Xu D S, Yang R, Veyssière P 2011 Phys. Rev. B 84 220103
[13] Wang H, Rodney D, Xu D S, Yang R, Veyssière P 2012 Philos. Mag. 93 186
[14] Wang H, Xu D S, Veyssière P, Yang R 2013 Acta Mater. 61 3499
[15] Wang H, Xu D S, Yang R 2014 Model. Simul. Mater. Sci. Eng. 22 085004
[16] Sinha V, Mills M J, Williams J C 2006 Metall. Mater. Trans. A 37 2015
[17] Sparkman D M, Millwater H R, Ghosh S 2013 Fatigue Fract. Eng. Mater. Struct. 36 994
[18] Dunne F P E 2014 Curr. Opin. Solid State Mater. Sci. 18 170
[19] Zope R R, Mishin Y 2003 Phys. Rev. B 68 024102
[20] Parrinello M, Rahman A 1981 J. Appl. Phys. 52 7182
[21] Nose S 1984 J. Chem. Phys. 81 511
[22] Martínez E, Uberuaga B P 2015 Sci. Rep. 5 9084
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[1] Bache M R 2003 Int. J. Fatigue 25 1079
[2] Dunne F P E, Rugg D, Walker A 2007 Int. J. Plast. 23 1061
[3] Sinha V, Mills M J, Williams J C 2004 Metall. Mater. Trans. A 35 3141
[4] Pilchak A L, Williams R E A, Williams J C 2010 Metall. Mater. Trans. A 41 106
[5] Veyssière P, Wang H, Xu D S, Chiu Y L 2008 IOP Conf. Series: Mater. Sci. Eng. 3 012018
[6] Xu D S, Wang H, Yang R, Veyssière P 2008 IOP Conf. Series: Mater. Sci. Eng. 3 012024
[7] Wang H, Xu D S, Yang R, Veyssière P 2008 Acta Mater. 56 4608
[8] Wang H, Xu D S, Yang R, Veyssière P 2009 Acta Mater. 57 3725
[9] Wang H, Xu D S, Yang R, Veyssière P 2011 Acta Mater. 59 1
[10] Wang H, Xu D S, Yang R, Veyssière P 2011 Acta Mater. 59 10
[11] Wang H, Xu D S, Yang R, Veyssière P 2011 Acta Mater. 59 19
[12] Wang H, Rodney D, Xu D S, Yang R, Veyssière P 2011 Phys. Rev. B 84 220103
[13] Wang H, Rodney D, Xu D S, Yang R, Veyssière P 2012 Philos. Mag. 93 186
[14] Wang H, Xu D S, Veyssière P, Yang R 2013 Acta Mater. 61 3499
[15] Wang H, Xu D S, Yang R 2014 Model. Simul. Mater. Sci. Eng. 22 085004
[16] Sinha V, Mills M J, Williams J C 2006 Metall. Mater. Trans. A 37 2015
[17] Sparkman D M, Millwater H R, Ghosh S 2013 Fatigue Fract. Eng. Mater. Struct. 36 994
[18] Dunne F P E 2014 Curr. Opin. Solid State Mater. Sci. 18 170
[19] Zope R R, Mishin Y 2003 Phys. Rev. B 68 024102
[20] Parrinello M, Rahman A 1981 J. Appl. Phys. 52 7182
[21] Nose S 1984 J. Chem. Phys. 81 511
[22] Martínez E, Uberuaga B P 2015 Sci. Rep. 5 9084
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