Molecular dynamics simulations are carried out to investigate the deformation behaviors and mechanical properties of nanocrystalline Cu/Ni films under conditions of tensile strain at different strain rates. The results indicate that the Cu/Ni films have higher yield strength and higher strain rate sensitivity(m)at the higher strain rate. The nucleation of voids in Cu/Ni multilayers' interface is observed at a strain rate of 108s-1, whereas spallation in nanocrystalline Cu films is appeared at a strain rate of 1010s-1.For the higher strain rate loading conditions, the FCC, HCP, and OTHER atomic groups are changed significantly both in Cu and Ni films. However, striking structural changes are found only in the Cu films under conditions of tensile strain at lower strain rate. The simulation results show that increasing strain rates are benefit to the formation of HCP structure, while if the strain rates exceed a certain value, the increasing disorder atomic groups may impede the growth of HCP atomic groups.
ZHU X Y, PAN F, LIU X J, et al Microstructure and mechanical properties of nanoscale Cu/Ni multilayers[J]. Materials Science and Engineering A, 2010, 527 (4-5): 1243- 1248.
WANG T, LU Z X, YANG Z Y, et al Size effects on the mechanical properties of Cu/Ni multi-layer nano-wires: molecular dynamics simulation[J]. Chinese Journal of Computational Mechanics, 2011, 28 (Suppl): 147- 151.
3
CHELLALI M R, BALOGH Z, BOUCHIKHAOUI H Triple junction transport and the impact of grain boundary width in nanocrystalline Cu[J]. Nano Letter, 2012, 12 (7): 3448- 3454.
CHEN D, YAN Z J, YAN L Molecular dynamics simulation of strengthening mechanism of Cu/Ni multilayers[J]. Acta Materialia Sinica, 2008, 44 (12): 1461- 1464.
LIANG H, CHEN Y M, HU W J, et al Tensile property and fracture surface for MgAlZnY alloys at different strain rates[J]. Journal of Materials Engineering, 2012, (1): 66- 70.
6
LU L, LI S X, LU K An abnormal strain rate effect on tensile behavior in nanocrystalline copper[J]. Scripta Materialia, 2001, 45 (10): 1163- 1169.
7
SCHWAIGER R, MOSER B, CHOLLACOOP N, et al Some critical experiments on the strain-rate sensitivity of nanocrystalline nickel[J]. Acta Materialia, 2003, 51 (17): 5159- 5172.
8
VO N Q, AVERBACK R S, BELLON P, et al Yield strength in nanocrystalline Cu during high strain rate deformation[J]. Scripta Materialia, 2009, 61 (1): 76- 79.
9
DONGARE A M, RAJENDRAN A M, MATTINA B L Atomic scale simulations of ductile failure micromechanism in nanocrystalline Cu at high strain rates[J]. Physical Review B, 2009, 80 (10): 4108- 4118.
10
DERLET P M, SWYGENHOVEN H V Atomic positional disorder in fcc metal nanocrystalline grain boundaries[J]. Physical Review B, 2003, 67 (1): 4202- 4209.
11
PLIMPTON S J Fast parallel algorithms for short-range molecular dynamics[J]. Journal of Computational Physics, 1995, 117 (1): 1- 19.
12
MEHL M J, PAPACONSTANTOPOULOS D A Structural stability and lattice defects in copper: Ab initio, tight-binding, and embedded-atom calculations[J]. Physical Review B, 2001, 63 (22): 4106- 4121.
13
HOOVER W G Canonical dynamics: equilibrium phase-space distributions[J]. Physical Review A, 1985, 31 (3): 1695- 1697.
14
KELCHNER C L, PLIMPTON S J, HAMILTON J C Dislocation nucleation and defect structure during surface indentation[J]. Physical Review B, 1998, 58 (17): 11085- 11088.
15
WEI Y J, BOWER A F, GAO H J Enhanced strain-rate sensitivity in fcc nanocrystals due to grain-boundary diffusion and sliding[J]. Scripta Materialia, 2008, 56 (8): 1741- 1752.
16
KUMAR K S, SWYGENHOVEN H V, SURESH S Mechanical behavior of nanocrystalline metals and alloys[J]. Scripta Materialia, 2003, 51 (19): 5743- 5774.
17
WOLF D, YAMAKOV V, PHILLPOT S R, et al Deformation of nanocrystalline materials by molecular-dynamics simulation: relationship to experiments[J]. Acta Materialia, 2005, 53 (1): 1- 40.
18
JIA D, RAMESH K T, LU L, et al Compressive behavior of an electrodeposited nanostructured copper at quasistatic and high strain rates[J]. Scripta Materialia, 2001, 45 (5): 613- 620.
19
BRINGA E M, CARO A, WANG Y, et al Ultrahigh strength in nanocrystalline materials under shock loading[J]. Science, 2005, 309 (5742): 1838- 1841.
20
BRINGA E M, TRAIVIRATANA S, MEYERS M A Void initiation in fcc metals: Effect of loading orientation and nanocrystalline effects[J]. Acta Materialia, 2010, 58 (13): 4458- 4477.
21
BRANDL C, DERLET P M, SWYGENHOVEN H V Strain rates in molecular dynamics simulations of nanocrystalline metals[J]. Philosophical Magazine, 2009, 89 (34-36): 3465- 3475.
22
ASARO R J, SURESH S Mechanistic models for the activation volume and rate sensitivity in metals with nanocrystalline grains and nano-scale twins[J]. Acta Materialia, 2005, 53 (12): 3369- 3382.
23
CARREKER R P, HIBBARD W R Tensile deformation of high-purity copper as a function of temperature, strain rate, and grain size[J]. Acta Materialia, 1953, 1 (6): 654- 663.
24
JIANG Z G, LIU X, LI G G, et al Strain rate sensitivity of a nanocrystalline Cu synthesized by electric brush plating[J]. Appl Phys Lett, 2006, 88 (14): 3115- 3117.
25
WEI Q Strain rate effects in the ultrafine grain and nanocrystalline regimes-influence on some constitutive responses[J]. J Mater Sci, 2007, 42 (5): 1709- 1727.
26
TUCKER G J, TIWARI S, ZIMMERMAN J A, et al Investigating the deformation of nanocrystalline copper with microscale kinematic metrics and molecular dynamics[J]. J Mech Phys Solids, 2012, 60 (3): 471- 486.
27
TSUZUKI H, BRENICIO P S, RINO J P Accelerating dislocations to transonic and supersonic speeds in anisotropic metals[J]. Appl Phys Lett, 2008, 92 (19): 1909- 1911.
28
DONGARE A M, RAJENDRAN A M, LAMATTINA B, et al Atomic scale studies of spall behavior in nanocrystalline Cu[J]. J Appl Phys, 2010, 108 (11): 3518- 3527.
29
CHOI Y, PARK Y, HYUN S Mechanical properties of nanocrystalline copper under thermal load[J]. Physics Letters A, 2012, 376 (5): 758- 762.
30
MEYERS M A, MISHRA A, BENSON D J The deformation physics of nanocrystalline metals: experiments analysis and computations[J]. Nanostructured Materials, 2006, 58 (4): 41- 48.
2015, Vol. 43 
), 吴勇芝1,2, 黄鸿翔1,2
