In this study, the deformation mechanisms operating with stress in bulk nanocrystalline (NC) titanium–nickel with an average grain size below a critical size of 10–20 nm have been investigated. We demonstrate a sequential variation of the deformation mechanism from grain boundary (GB) sliding and grain rotation to grain growth and dislocation activity with the increase of the deformation stress. These deformation mechanisms are different from the previous understanding that below a critical grain size of 10–20 nm, GB sliding and grain rotation govern plastic deformation of NC materials.
MeyersM. A., MishraA. and BensonD. J.: ‘Mechanical properties of nanocrystalline materials’, Prog. Mater. Sci., 2006, 51, 427–556. doi: 10.1016/j.pmatsci.2005.08.003
2.
SchiøtzJ., Di TollaF. D. and JacobsenK. W.: ‘Softening of nanocrystalline metals at very small grain sizes’, Nature, 1998, 391, 561–563. doi: 10.1038/35328
3.
SchiotzJ. and JacobsenK. W.: ‘A maximum in the strength of nanocrystalline copper’, Science, 2003, 301, 1357–1359. doi: 10.1126/science.1086636
4.
YamakovV., WolfD., PhillpotS. R., MukherjeeA. K. and GleiterH.: ‘Crossover in Hall–Petch behaviour in nanocrystalline materials by molecular-dynamics simulation’, Phil. Mag. Lett., 2003, 83, 385–393. doi: 10.1080/09500830031000120891
5.
ShanZ. W., StachE. A., WiezorekJ. M. K., KnappJ. A., FollstaedtD. M. and MaoS. X.: ‘Grain boundary-mediated plasticity in nanocrystalline nickel’, Science, 2004, 305, 654–657. doi: 10.1126/science.1098741
6.
ZhuX. Q., FengQ., LiuD. Z., NieA. M., LiuJ. B., ZhangX. B. and GengL. M.: ‘In situ high resolution transmission electron microscopy investigation of deformation mechanism in sub-10-nm Au crystals’, Mater. Sci. Technol., 2014, 30, 774–781. doi: 10.1179/1743284713Y.0000000408
7.
YuanF. P. and WuX. L.: ‘Size effects of primary/secondary twins on the atomistic deformation mechanisms in hierarchically nanotwinned metals’, J. Appl. Phys., 2013, 113, 203516.
8.
ZhuR. T., ZhangX. X., LiY. F. and ZhouJ. Q.: ‘Impact behavior and constitutive model of nanocrystalline Ni under high strain rate loading’, Mater. Design, 2013, 49, 426–432. doi: 10.1016/j.matdes.2013.01.060
9.
WangL. H., HanX. D., LiuP., YueY. H., ZhangZ. and MaE.: ‘In situ observation of dislocation behavior in nanometer grains’, Phys. Rev. Lett., 2010, 105, 135501.
10.
ShanZ. W., WiezorekJ. M. K., StachE. A., FollstaedtD. M., KnappJ. A. and MaoS. X.: ‘Dislocation dynamics in nanocrystalline nickel’, Phys. Rev. Lett., 2007, 98, 095502. doi: 10.1103/PhysRevLett.98.095502
11.
WangL. H., LiuP., GuanP. F., YangM. J., SunJ. L., ChengY. Q., HirataA., ZhangZ., MaE. and ChenM. W.: ‘In situ atomic-scale observation of continuous and reversible lattice deformation beyond the elastic limit’. Nat. Commun., 2013, 4, 2413.
12.
StolyarovV. V.: ‘Deformability and nanostructuring of TiNi shape-memory alloys during electroplastic rolling’, Mater. Sci. Eng. A, 2009, 503, 18–20. doi: 10.1016/j.msea.2008.01.094
13.
ZhangH. T., LiX. H. and ZhangX. Y.: ‘Grain-size-dependent martensitic transformation in bulk nanocrystalline TiNi under tensile deformation’, J. Alloys Compd, 2012, 544, 19–23. doi: 10.1016/j.jallcom.2012.08.014
WilliamsonG. K. and HallW. H.: ‘X-ray line broadening from filed aluminium and wolfram’, Acta Metall., 1953, 1, 22–31. doi: 10.1016/0001-6160(53)90006-6
16.
MasumuraR. A., HazzledineP. M. and PandeC. S.: ‘Yield stress of fine grained materials’, Acta Mater., 1998, 46, 4527–4534. doi: 10.1016/S1359-6454(98)00150-5
17.
PandeC. S. and CooperK. P.: ‘Nanomechanics of Hall–Petch relationship in nanocrystalline materials’, Prog. Mater. Sci., 2009, 54, 689–706. doi: 10.1016/j.pmatsci.2009.03.008
18.
InaekyanK., BrailovskiV., ProkoshkinS., KorotitskiyA. and ChernavinaA.: ‘Microhardness of binary near-equiatomic Ti–Ni alloys after severe cold rolling and post-deformation annealing’, ESOMAT 2009, 2009, 05011.
19.
ShanZ. W., StachE. A., WiezorekJ. M. K., KnappJ. A., FollstaedtD. M. and MaoS. X.: ‘Response to comment on “Grain boundary-mediated plasticity in nanocrystalline nickel”’, Science, 2005, 308, 356. doi: 10.1126/science.1107389
20.
ShanZ. W., KnappJ. A., FollstaedtD. M., StachE. A., WiezorekJ. M. K. and MaoS. X.: ‘Inter- and intra-agglomerate fracture in nanocrystalline nickel’, Phys. Rev. Lett., 2008, 100, 105502. doi: 10.1103/PhysRevLett.100.105502
21.
FangT. H., LiW. L., TaoN. R. and LuK.: ‘Revealing extraordinary intrinsic tensile plasticity in gradient nano-grained copper’, Science, 2011, 331, 1587–1590. doi: 10.1126/science.1200177
22.
LiJ. C. M.: ‘Mechanical grain growth in nanocrystalline copper’, Phys. Rev. Lett., 2006, 96, 215506.
23.
KochC. C.: ‘Optimization of strength and ductility in nanocrystalline and ultrafine grained metals’, Scripta Mater., 2003, 49, 657–662. doi: 10.1016/S1359-6462(03)00394-4
24.
WangY. M., ChenM. W., ZhouF. Z. and MaE.: ‘High tensile ductility in a nanostructured metal’, Nature, 2002, 419, 912–915. doi: 10.1038/nature01133