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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...

Please cite this article as: Luscher, D.J., Mayeur, J.R., Mourad, H.M., Hunter, A., Kenamond, M.A., Coupling continuum dislocation transport with crystal plasticity for application to shock loading conditions AbstractWe have developed a multi-physics modeling approach that couples continuum dislocation transport, nonlinear thermoelasticity, crystal plasticity, and consistent internal stress and deformation fields to simulate the single-crystal response of materials under extreme dynamic conditions. Dislocation transport is modeled by enforcing dislocation conservation at a slip-system level through the solution of advection-diffusion equations. Nonlinear thermoelasticity provides a thermodynamically consistent equation of state to relate stress (including pressure), temperature, energy densities, and dissipation. Crystal plasticity is coupled to dislocation transport via Orowan's expression where the constitutive description makes use of recent advances in dislocation velocity theories applicable under extreme loading conditions. The configuration of geometrically necessary dislocation density gives rise to an internal stress field that can either inhibit or accentuate the flow of dislocations. An internal strain field associated with the internal stress field contributes to the kinematic decomposition of the overall deformation. The paper describes each theoretical component of the framework, key aspects of the constitutive theory, and some details of a one-dimensional implementation. Results from single-crystal copper plate impact simulations are discussed in order to highlight the role of dislocation transport and pile-up in shock loading regimes. The main conclusions of the paper reinforce the utility of the modeling approach to shock problems.

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