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The nanocrystalline metals are widely investigated due to their unique mechanical properties. Currently, the available studies about deformation mechanisms of metals mainly focus on face-centered cubic metals such as Ni, Cu and Au. However, the body-centered cubic metals are still very limited, despite their industrial importance. Here, we investigate the effects of grain size and temperature on the mechanical behavior of nano-polycrystal -Fe under uniaxial tensile loading by using molecular dynamics (MD) simulation. The models of nanocrystalline -Fe with the grain sizes of 3.95, 6.80, 9.70, 12.50, 15.50, 17.50, 20.70 and 26.00 nm are geometrically created in three dimensions by using Voronoi construction, and these models are relaxed to reach an equilibrium state. Then, each of them has a strain of 0.001 along the Z-direction in each step, keeping zero pressure in the X- and Y-directions until the strain increases up to 0.2. A 1.0 fs time step is used in all of the MD simulations. Based on the data output, the stress-strain curves at different grain sizes are obtained. The results indicate that the peak stresses of nano-polycrystal -Fe decrease with the decrease of grain size, exhibiting a breakdown in the Hall-Petch relation when the grain size is smaller than a critical size. The major deformation mechanism is found to change from dislocation slips and twinning-mediated plasticity in a model with a larger grain size to grain boundary sliding in a model with a smaller grain size. It should be noted that twinning is formed by the emission of 1/6111 partial dislocations along the {112} slip plane. The results show that crack formation during tension is a cause of reducing the flow stress of nano-polycrystal -Fe with a large grain size and that the Young's modulus of nano-polycrystal -Fe decreases with the grain size decreasing. The main reason for the crack nucleation is here that grain boundaries perpendicular to the loading direction bear higher stress and the twin band interacts with grain boundaries at a larger grain size, causing the stress to concentrate at the intersections of grain boundaries. The results also show the detwinning behavior and migration of deformed twins in nano-polycrystal -Fe. The detwinning behavior occurs via the migration of the intersection of grain boundary and twin, and this intersection is incoherent boundary. The migration of deformed twins proceeds by repeating initiation and glide of 1/6111 partial dislocations on adjacent {112} planes. In addition, we find that the nucleation and propagation of dislocation become easier at higher temperature than at lower temperature.
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Keywords:
- molecular dynamics /
- grain size /
- mechanical properties /
- deformed twins
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[2] Petch N J 1953 J. Iron Steel Inst. 174 25
[3] Bazarnik P, Huang Y, Lewandowska M, Langdon T G 2015 Mater. Sci. Eng. A 626 9
[4] Panin V E, Armstrong R W 2016 Phys. Mesomech. 19 35
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[12] Cao R G, Deng C 2015 Scripta Mater. 94 9
[13] Zhu Y X, Li Z H, Huang M S 2013 Scripta Mater. 68 663
[14] Li X F, Hu W Y, Xiao S F, Huang W Q 2008 Physica E 40 3030
[15] Wu D, Wang X L, Nieh T G 2014 J. Phys. D:Appl. Phys. 47 554
[16] Wang S, Hashimoto N, Ohnuki S 2013 Sci. Rep. 3 2760
[17] Ackland G J, Mendelev M I, Srolovitz D J, Han S, Barashev A V 2004 Phys-Condens. Mat. 16 S2629
[18] Terentyev D A, Malerba L, Hou M 2007 Phys. Rev. B:Condens. Matter 75 104108
[19] Ventelon L, Willaime F 2010 Philos. Mag. 90 1063
[20] Faken D, Jonsson H 1994 Compos. Mater. Sci. 2 279
[21] Stukowski A 2010 Modelling Simul. Mater. Sci. Eng. 18 015012
[22] Song H Y, Li Y L 2012 J Appl. Phys. 111 044322
[23] Zhou K, Liu B, Yao Y G, Zhong K 2014 Mater. Sci. Eng. A 615 92
[24] Jeon J B, Lee B J, Chang Y W 2011 Scripta Mater. 64 494
[25] Sainath G, Choudhary B K 2016 Comput. Mater. Sci. 111 406
[26] Chen M Q, Quek S S, Sha Z D, Chiu C H, Pei Q X, Zhang Y W 2015 Carbon 85 135
[27] Song Z, Artyukhov V I, Yakobson B I, Xu Z 2013 Nano Lett. 13 1829
[28] Zhang Y F, Millett P C, Tonks M, Biner S B 2012 Acta Mater. 60 6421
[29] Sainath G, Choudhary B K, JayakumarT 2015 Comput. Mater. Sci. 104 76
[30] Shi Z, Singh C V 2016 Scripta Mater. 113 214
[31] Wang J, Li N, Anderoglu O, Zhang X, Misra A, Huang J Y, Hirth J P 2010 Acta Mater. 58 2262
[32] Ovid'ko I A, Skiba N V, Sheinerman A G 2015 Rev. Adv. Mater. Sci. 43 38
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[1] Hall E O 1951 Proc. Phys. Soc. Sect. B 64 747
[2] Petch N J 1953 J. Iron Steel Inst. 174 25
[3] Bazarnik P, Huang Y, Lewandowska M, Langdon T G 2015 Mater. Sci. Eng. A 626 9
[4] Panin V E, Armstrong R W 2016 Phys. Mesomech. 19 35
[5] Wen P, Tao G, Ren B X, Pei Z 2015 Acta Phys. Sin. 64 126201 (in Chinese)[闻鹏, 陶刚, 任保详, 裴政2015 64 126201]
[6] Qin X F, Sun D L, Wang T, Zhao X, Xie L, Wu Q 2015 J. Alloys. Compd. 640 497
[7] Mauing K, Earthman J C, Mohamed F A 2012 Acta Mater. 60 5850
[8] He X, Bai Q S, Bai J X 2016 Acta Phys. Sin. 65 116101 (in Chinese)[何欣, 白清顺, 白锦轩2016 65 116101]
[9] Dolgusheva E B, Trubitsin V Y 2014 Comput. Mater. Sci. 84 23
[10] Lin C P, Liu X J, Rao Z H 2015 Acta Phys. Sin. 64 083601 (in Chinese)[林长鹏, 刘新健, 饶中浩2015 64 083601]
[11] Zhou K, Liu B, Yao Y J, Zhong K 2014 Mater. Sci. Eng. A 595 118
[12] Cao R G, Deng C 2015 Scripta Mater. 94 9
[13] Zhu Y X, Li Z H, Huang M S 2013 Scripta Mater. 68 663
[14] Li X F, Hu W Y, Xiao S F, Huang W Q 2008 Physica E 40 3030
[15] Wu D, Wang X L, Nieh T G 2014 J. Phys. D:Appl. Phys. 47 554
[16] Wang S, Hashimoto N, Ohnuki S 2013 Sci. Rep. 3 2760
[17] Ackland G J, Mendelev M I, Srolovitz D J, Han S, Barashev A V 2004 Phys-Condens. Mat. 16 S2629
[18] Terentyev D A, Malerba L, Hou M 2007 Phys. Rev. B:Condens. Matter 75 104108
[19] Ventelon L, Willaime F 2010 Philos. Mag. 90 1063
[20] Faken D, Jonsson H 1994 Compos. Mater. Sci. 2 279
[21] Stukowski A 2010 Modelling Simul. Mater. Sci. Eng. 18 015012
[22] Song H Y, Li Y L 2012 J Appl. Phys. 111 044322
[23] Zhou K, Liu B, Yao Y G, Zhong K 2014 Mater. Sci. Eng. A 615 92
[24] Jeon J B, Lee B J, Chang Y W 2011 Scripta Mater. 64 494
[25] Sainath G, Choudhary B K 2016 Comput. Mater. Sci. 111 406
[26] Chen M Q, Quek S S, Sha Z D, Chiu C H, Pei Q X, Zhang Y W 2015 Carbon 85 135
[27] Song Z, Artyukhov V I, Yakobson B I, Xu Z 2013 Nano Lett. 13 1829
[28] Zhang Y F, Millett P C, Tonks M, Biner S B 2012 Acta Mater. 60 6421
[29] Sainath G, Choudhary B K, JayakumarT 2015 Comput. Mater. Sci. 104 76
[30] Shi Z, Singh C V 2016 Scripta Mater. 113 214
[31] Wang J, Li N, Anderoglu O, Zhang X, Misra A, Huang J Y, Hirth J P 2010 Acta Mater. 58 2262
[32] Ovid'ko I A, Skiba N V, Sheinerman A G 2015 Rev. Adv. Mater. Sci. 43 38
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