Grain growth in a bulk nanocrystalline Co alloy during tensile plastic deformation

Fan, G. J.; Fu, Lin; Qiao, Dongchun; Choo, Hahn; Liaw, Peter K.; Browning, Nigel D.

doi:10.1016/j.scriptamat.2006.02.041

Cited by 62 publications

(39 citation statements)

References 31 publications

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“…Away from the strain localization, grains remain equiaxed and a similar size as the starting structure. Mechanically-induced grain growth has been observed in a number of nanocrystalline metals such as Al, 10,41 Ni, 42,43 and Cu, 9 as well as alloys such as Ni-Fe, 44,45 Ni-W, 46,47 and Co-P. 48 This grain growth can be caused by a combination of grain boundary migration and coalescence due to grain rotation, and has been shown to be driven by high shear stress. 49 While small areas of high shear strain are observed at ε = 5.0%, a path of high strain that spans the sample becomes clear at approximately ε = 5.4%, after a major stress drop in the stress-strain curve presents in Fig.…”

Section: A Atomic-level Observations Of Localization Processesmentioning

confidence: 99%

Strain localization in a nanocrystalline metal: Atomic mechanisms and the effect of testing conditions

Rupert¹

2013

Journal of Applied Physics

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Abstract:Molecular dynamics simulations are used to investigate strain localization in a model nanocrystalline metal. The atomic mechanisms of such catastrophic failure are first studied for two grain sizes of interest. Detailed analysis shows that the formation of a strain path across the sample width is crucial, and can be achieved entirely through grain boundary deformation or through a combination of grain boundary sliding and grain boundary dislocation emission.Pronounced mechanically-induced grain growth is also found within the strain localization region. The effects of testing conditions on strain localization are also highlighted, to understand the conditions that promote shear banding and compare these observations to metallic glass behavior. We observed that, while strain localization occurs at low temperatures and slow strain rates, a shift to more uniform plastic flow is observed when either strain rate or temperature is increased. We also explore how external sample dimensions influence strain localization, but find no size effect for the grain sizes and samples sizes studied here.2

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Section: A Atomic-level Observations Of Localization Processesmentioning

confidence: 99%

Strain localization in a nanocrystalline metal: Atomic mechanisms and the effect of testing conditions

Rupert¹

2013

Journal of Applied Physics

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“…Stress induced grain growth has been observed over a range of the grain size spanning 4 to 100 nm in fcc metals by MD simulations or experimental studies. [2][3][4][5][6][7][8][9][10]14,15 For example, Shan et al…”

Section: Resultsmentioning

confidence: 99%

“…[2][3][4][5][6][7][8][9][10] However, for NC hcp pure metals, it seems to be an exception. Because negligibly insignificant grain growth was observed in an NC Co metal deformed by cold rolling (24% reduction in the 2 Tensile engineering stress s-strain e curves for NC Ni and Ni-75%Co alloy: normalised strain hardening rate H versus engineering strain e is shown in inset, where H is defined as H5(ds/de/s) e ; short arrows indicate locations of maximum uniform strain thickness).…”

Section: Resultsmentioning

confidence: 99%

Study on nanocrystalline dual phase Ni–Co alloy with high strength and excellent ductility

Xu¹,

Dai²,

Wu³

et al. 2011

Materials Science and Technology

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In the present study, the room temperature mechanical properties of nanocrystalline Ni and Ni-75 wt-%Co alloy, prepared by pulse electrodeposition, were contrasted. Both higher strength and higher ductility were obtained for the Ni-75%Co alloy with a dual phase structure and an average grain size of 7?2 nm. By means of TEM observations of grain structures before and after tensile deformation for Ni and Ni-75%Co samples, a link between the ductility and the variation of stress induced grain growth during tensile deformation was established. Observations of TEM showed stress induced grain growth during tensile deformation, subjected to very high stresses and large strains, is very insignificant for the Ni-75%Co alloy in sharp contrast to the significant stress induced grain growth occurring in Ni. It was proposed that suppression of stress induced grain growth during tensile deformation can delay and even prohibit formation of shear banding plastic instability and thus enhances uniform strain leading to an enhanced ductility.

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“…Thus, this mechanism will only be relevant for nanograined copper. Moreover, SCM is believed to be the main cause of the grain coarsening observed to take place at low temperatures in nanograined polycrystals under stress: grain growth under nanoindentations, near loaded crack tips or during further plastic deformation processing or fatigue of nanomaterials [24][25][26][27][28][29][30][31][32][33][34][35]. Numerical MD simulations support such observations [36][37][38][39][40].…”

Section: Introductionmentioning

confidence: 83%

Plastic deformation by conservative shear-coupled migration of tilt boundaries with intergranular nano-cracks or precipitates

Luque

Aldazábal

Martı́nez-Esnaola

et al. 2010

Philosophical Magazine

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. Plastic deformation by conservative shear-coupled migration of tilt boundaries with intergranular nanocracks or precipitates. Philosophical Magazine, Taylor & Francis, 2010, 90 (27-28) We present molecular dynamics (MD) simulations of the shear-coupled migration (SCM) behaviour of symmetrical tilt boundaries perturbed by the presence of nano-cracks or nano-precipitates lying on the boundary plane. The simulations have been performed for copper bicrystals at room temperature (300 K). The tilt boundary gets pinned by the crack tip or by the precipitates; shear-coupled migration occurs only ahead of the pinning points. Bulging of the tilt boundary reduces the shear stress on the boundary surface near the pinning points. In the case of cracks the local deviation of the boundary from the crack plane close to the crack tip hinders mode II crack propagation; in fact, some crack healing is observed in some cases. The applied stress grows until depinning of the boundary takes place by SCM bulging or by the combined action of SCM with another deformation mechanism (emission of dislocations from the pinning point vicinity, grain boundary sliding).

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Grain growth in a bulk nanocrystalline Co alloy during tensile plastic deformation

Cited by 62 publications

References 31 publications

Strain localization in a nanocrystalline metal: Atomic mechanisms and the effect of testing conditions

Strain localization in a nanocrystalline metal: Atomic mechanisms and the effect of testing conditions

Study on nanocrystalline dual phase Ni–Co alloy with high strength and excellent ductility

Plastic deformation by conservative shear-coupled migration of tilt boundaries with intergranular nano-cracks or precipitates

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