Disruption of Thermally-Stable Nanoscale Grain Structures by Strain Localization

Nanocrystalline metals with average grain sizes of only a few nanometers have recently been observed to fail through the formation of shear bands. Here, we investigate this phenomenon in nanocrystalline Ni which has had its grain structure stabilized by doping with W, with a specific focus on understanding how strain localization drives evolution of the nanoscale grain structure. Shear banding was initiated with both microcompression and nanoindentation experiments, followed by site-specific transmission electron microscopy to characterize the microstructure. Grain growth and texture formation were observed inside the shear bands, which had a wide variety of thicknesses. These evolved regions have well-defined edges, which rules out local temperature rise as a possible formation mechanism. No structural evolution was found in areas away from the shear bands, even in locations where significant plastic deformation had occurred, showing that plastic strain alone is not enough to cause evolution. Rather, intense strain localization is needed to induce mechanically-driven grain growth in a thermally-stable nanocrystalline alloy.Comment: 6 figure

Demonstrating a long-coherence dual-rail erasure qubit using tunable transmons

Quantum error correction with erasure qubits promises significant advantages over standard error correction due to favorable thresholds for erasure errors. To realize this advantage in practice requires a qubit for which nearly all errors are such erasure errors, and the ability to check for erasure errors without dephasing the qubit. We experimentally demonstrate that a "dual-rail qubit" consisting of a pair of resonantly-coupled transmons can form a highly coherent erasure qubit, where the erasure error rate is given by the transmon $T_1$ but for which residual dephasing is strongly suppressed, leading to millisecond-scale coherence within the qubit subspace. We show that single-qubit gates are limited primarily by erasure errors, with erasure probability $p_\text{erasure} = 2.19(2)\times 10^{-3}$ per gate while the residual errors are $\sim 40$ times lower. We further demonstrate mid-circuit detection of erasure errors while introducing $< 0.1\%$ dephasing error per check. Finally, we show that the suppression of transmon noise allows this dual-rail qubit to preserve high coherence over a broad tunable operating range, offering an improved capacity to avoid frequency collisions. This work establishes transmon-based dual-rail qubits as an attractive building block for hardware-efficient quantum error correction.Comment: 8+12 pages, 16 figure

Product recall strategy in the supply chain: utility and culture

Purpose: Product recalls have the potential to damage firm and consumer quality reputation. While globalization has brought about various economic benefits, expanding supply chain networks have also made it more difficult for downstream organizations to manage product recall strategy. This study aims to examine the role of culture on a manufacturer\u27s initiation of a recall and the severity of the remedy chosen for the product recall. Design/methodology/approach: Utilizing the culture-specific argument, this study uses an exploratory approach to assess how cultural variables impact recall strategy utilizing a large-scale data analysis with a cross-sectional time-series panel of 898 firms. Findings: The results provide support for the expected utility hypothesis that the more severe the consequence, the more likely a manufacturer will decide to recall the product. Moreover, the more likely the manufacturer will provide greater returns to the consumer. However, these relationships are impacted to differing degrees by the manufacturer\u27s cultural origin. Originality/value: These results provide evidence to researchers about how culture impacts the expected utility hypothesis in the decision theory. The study examines how deeply embedded cultural variables impact the relationship between the foreseeable consequence of the product recall and the recall facilitator and remedy

Grain boundary structure and interfacial complexions for the creation of tough, stable nanostructured metals

Nanocrystalline metals have been the focus of current literature due to their interesting mechanical properties. This is a result of having nanometer sized grains and high volume fraction of grain boundaries. While these materials have high strength, the large number of boundaries is also responsible for the limited ductility and thermal instability often observed for nanocrystalline systems. Despite the current efforts in the literature, these challenges still prevent widespread use of nanocrystalline metals in real engineering applications. In this thesis, we study these problems by focusing on tailoring the grain boundary structure and chemistry and propose a methodology that can be used to mitigate those challenges. First, we study the plastic flow and failure as a function of grain boundary volume fraction (i.e., grain size) using microcompression in a nanocrystalline Ni-W. Since grain boundary physics are extremely important here, we also study how the relaxation of nonequilibrium grain boundaries affects failure. We show that nanocrystalline metals with larger grain boundary volume fractions and relaxed boundary structures are stronger, but also more likely to fail prematurely through catastrophic shear banding. We also show that shear banding can create a dynamic microstructure leading to grain coarsening. A major take-away from this work is that disordered grain boundaries can actually be beneficial. Therefore, in the next study we introduce amorphous complexions, highly disordered grain boundaries, through grain boundary doping as an all-in-one solution to design against failure and thermal instability. We use nanocrystalline Cu with the addition of Zr as our model system to explore complexion engineering in these materials. High resolution transmission electron microscopy in conjunction with energy dispersive x-ray spectroscopy demonstrates segregation of Zr to the boundaries of Cu-Zr alloys created with mechanical alloying. This provided evidence for the formation of amorphous grain boundaries complexions under certain conditions. Microcompression and in-situ bending experiments are then used to quantify the effect of doping on mechanical behavior. Finally, our results show that strength, strain-to-failure, failure mode, and thermal stability can be controlled with boundary doping. The proposed methodology described here is rather general and can be applied to other material systems to make bulk nanocrystalline metals with improved mechanical properties

Product recall strategy in the supply chain: utility and culture

Product recalls have the potential to damage firm and consumer quality reputation. While globalization has brought about various economic benefits, expanding supply chain networks have also made it more difficult for downstream organizations to manage product recall strategy. This study aims to examine the role of culture on a manufacturer\u27s initiation of a recall and the severity of the remedy chosen for the product recall