Effect of the loading mode on the evolution of the deformation mechanisms in randomly textured magnesium polycrystals − comparison of experimental and modeling results, International Journal of Plasticity (2015),

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The dislocation density and the average twin boundary frequency is determined quantitatively in as-deposited and cold-rolled nanotwinned Cu thin films by high-resolution X-ray line profile analysis. After cold-rolling the dislocation density increases considerably, whereas the twin boundary frequency decreases only slightly. The physical parameters of the substructure provided by the quantitative X-ray analysis are in agreement with earlier transmission electron microscopy observations. The flow stress of the as-deposited and the cold-rolled films is directly correlated with the average thickness of twin lamellae and the dislocation density by taking into account the Hall-Petch and Taylor type strengthening mechanisms.

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Hyperfine interaction (HF) is of key importance for the functionality of solid-state quantum information processing, as it affects qubit coherence and enables nuclear-spin quantum memories. In this work, we complete the theory of the basic HF mechanisms (Fermi contact, dipolar, orbital) in carbon nanotube quantum dots by providing a theoretical description of the orbital HF. We find that orbital HF induces an interaction between the nuclear spins of the nanotube lattice and the valley degree of freedom of the electrons confined in the quantum dot. We show that the resulting nuclear-spin-electron-valley interaction (i) is approximately of Ising type; (ii) is essentially local, in the sense that a radius-and dot-length-independent atomic interaction strength can be defined; and (iii) has an atomic interaction strength that is comparable to the combined strength of the Fermi contact and dipolar interactions. We argue that orbital HF provides a new decoherence mechanism for single-electron valley qubits and spin-valley qubits in a range of multivalley materials. We explicitly evaluate the corresponding inhomogeneous dephasing time T * 2 for a nanotube-based valley qubit.

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In situ neutron‐diffraction experiments at the spallation neutron source, simultaneously illuminating the diffraction of the matrix and the strengthening nano precipitates, allow the determination of their plastic deformation. An irreversible neutron‐diffraction‐profile evolution of the nano precipitates is observed. However, there is no conclusive trend of the nano‐precipitate peak‐width evolution subjected to the greater stress levels. Hence, in the present work, molecular‐dynamics simulations are applied to reveal the deformation mechanisms of the nano precipitate and its interaction with the surrounding matrix. The microstructure size, dislocation content, and structural parameters of the nano precipitates, quantified by X‐ray, transmission electron microscopy, and small‐angle neutron scattering, are used as the simulation input and reference. The simulation results show that there are two competing deformation mechanisms, which lead to the fluctuation of the nano‐precipitate‐diffraction widths, occurring during the higher plastic deformation stages.