A comparison of texture results obtained using precession electron diffraction and neutron diffraction methods at diminishing length scales in ordered bimetallic nanolamellar composites

Carpenter, John S.; Liu, X.-Y.; Darbal, Amith; Nuhfer, Noel T.; McCabe, Rodney J.; Vogel, Sven C.; Ledonne, Jon; Rollett, Anthony D.; Barmak, K.; Beyerlein, Irene J.; Mara, Nathan A.

doi:10.1016/j.scriptamat.2012.05.018

Cited by 51 publications

(21 citation statements)

References 35 publications

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“…To help understand the texture transition, we use electron backscatter diffraction (EBSD), which, in addition to texture, can locate orientations and phases within the microstructure (29)(30)(31)(32). With EBSD, we found that the transition is coincident with attainment of layers that are spanned by only one grain.…”

Section: Significancementioning

confidence: 99%

Emergence of stable interfaces under extreme plastic deformation

Beyerlein

Mayeur

Zheng³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

144

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Atomically ordered bimetal interfaces typically develop in nearequilibrium epitaxial growth (bottom-up processing) of nanolayered composite films and have been considered responsible for a number of intriguing material properties. Here, we discover that interfaces of such atomic level order can also emerge ubiquitously in large-scale layered nanocomposites fabricated by extreme strain (top down) processing. This is a counterintuitive result, which we propose occurs because extreme plastic straining creates new interfaces separated by single crystal layers of nanometer thickness. On this basis, with atomic-scale modeling and crystal plasticity theory, we prove that the preferred bimetal interface arising from extreme strains corresponds to a unique stable state, which can be predicted by two controlling stability conditions. As another testament to its stability, we provide experimental evidence showing that this interface maintains its integrity in further straining (strains > 12), elevated temperatures (> 0.45 T m of a constituent), and irradiation (light ion). These results open a new frontier in the fabrication of stable nanomaterials with severe plastic deformation techniques.texture | atomistic simulation | radiation resistance | thermal stability U nlike traditional materials, nanomaterials contain an unusually high density of interfaces that give rise to unprecedented properties such as ultrahigh strengths (1-5). Further, nanomaterials with nearly perfect, atomically ordered low-energy interfaces have been found to possess extraordinary thermal stability and radiation tolerance (1, 6-10). However, nanomaterials with disordered, high-energy interfaces are not stable in these same extreme conditions (11,12). The integrity of the interface is tied to how the nanomaterial was made. Near-equilibrium processes generate perfect interfaces prevailing across the material but only produce small amounts of material, such as epitaxial thin films (13,14). Ordinary large-scale metal-working (far from equilibrium) processes produce large amounts of nanostructured material suitable for technical application, but the interface types can vary within the same sample. For single-phase metals, the heavy straining can drive dislocations generated during deformation to organize into low-energy boundary structures (15, 16), some of which can be ordered (17) and others disordered (12,(18)(19)(20). Likewise, in heavily drawn two-phase composites, several kinds of bimetal interface structures have been reported, both ordered and disordered (21). Achieving uniformly ordered interfaces in bulk nanostructured metals presents a grand challenge in the design of materials that can be stable in the harsh environments demanded by the next generation of highly energy-efficient systems.Here we discover that a bulk metal-working technique that imposes extreme amounts of plastic strains can give rise to a preferred bimetal interface with perfect atomic order. Most remarkably, experimental evidence shows that this preferred interface occurs ubi...

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Section: Significancementioning

confidence: 99%

Emergence of stable interfaces under extreme plastic deformation

Beyerlein

Mayeur

Zheng³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

144

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“…These junctions formed via a reaction between intersecting interfacial dislocations under mechanical loading [28][29][30]. The interfaces in these cases were a stepped Kurdjumov-Sachs interface [30,34,35] or a twisted Nishiyama-Wasserman interface [36].…”

Section: Introductionmentioning

confidence: 99%

Glide dislocation nucleation from dislocation nodes at semi-coherent {1 1 1} Cu–Ni interfaces

et al. 2015

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a b s t r a c tUsing atomistic simulations and dislocation theory on a model system of semi-coherent {1 1 1} interfaces, it is shown that misfit dislocation nodes adopt multiple atomic arrangements corresponding to the creation and redistribution of excess volume at the nodes. Four distinctive node structures were identified: volume-smeared nodes with (i) spiral or (ii) straight dislocation patterns, and volume-condensed nodes with (iii) triangular or (iv) hexagonal dislocation patterns. Volume-smeared nodes contain interfacial dislocations lying in the Cu-Ni interface but volume-condensed nodes contain two sets of interfacial dislocations in the two adjacent interfaces and jogs across the atomic layer between the two adjacent interfaces. Under biaxial tension/compression applied parallel to the interface, it is shown that the nucleation of lattice dislocations is preferred at the nodes and is correlated with the reduction of excess volume at the nodes.

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“…Analyses using transmission electron microscopy can identify the parent grain orientation for a twin, but usually in a number of grains too small for sufficient statistics 9,24 . Even the recently developed technique of precession electron diffraction 25 , which can automatically map grain orientations at sufficient resolution, has not provided sufficient grain statistics for twinning correlations. Recently, we developed a novel, high spatial resolution EBSD technique through exploitation of a wedgemounting scheme (WM-EBSD) that can resolve orientations in nanoscale-size grains and collect this data over hundreds of square microns of material 26 .…”

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confidence: 99%

The critical role of grain orientation and applied stress in nanoscale twinning

McCabe¹,

Beyerlein

Carpenter³

et al. 2014

Nat Commun

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Numerous recent studies have focused on the effects of grain size on deformation twinning in nanocrystalline fcc metals. However, grain size alone cannot explain many observed twinning characteristics. Here we show that the propensity for twinning is dependent on the applied stress, grain orientation and stacking fault energy. The lone factor for twinning dependent on grain size is the stress necessary to nucleate partial dislocations from a boundary. We use bulk processing of controlled nanostructures coupled with unique orientation mapping at the nanoscale to show the profound effect of crystal orientation on deformation twinning. Our theoretical model reveals an orientation-dependent critical threshold stress for twinning, which is presented in the form of a generalized twinnability map. Our findings provide a newfound orientation-based explanation for the grain size effect: as grain size decreases the applied stress needed for further deformation increases, thereby allowing more orientations to reach the threshold stress for twinning.

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A comparison of texture results obtained using precession electron diffraction and neutron diffraction methods at diminishing length scales in ordered bimetallic nanolamellar composites

Cited by 51 publications

References 35 publications

Emergence of stable interfaces under extreme plastic deformation

Emergence of stable interfaces under extreme plastic deformation

Glide dislocation nucleation from dislocation nodes at semi-coherent {1 1 1} Cu–Ni interfaces

The critical role of grain orientation and applied stress in nanoscale twinning

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