High-entropy alloys exhibit exceptional mechanical properties at cryogenic temperatures, due to the activation of twinning in addition to dislocation slip. The coexistence of multiple deformation pathways raises an important question regarding how individual deformation mechanisms compete or synergize during plastic deformation. Using in situ neutron diffraction, we demonstrate the interaction of a rich variety of deformation mechanisms in high-entropy alloys at 15 K, which began with dislocation slip, followed by stacking faults and twinning, before transitioning to inhomogeneous deformation by serrations. Quantitative analysis showed that the cooperation of these different deformation mechanisms led to extreme work hardening. The low stacking fault energy plus the stable face-centered cubic structure at ultralow temperatures, enabled by the high-entropy alloying, played a pivotal role bridging dislocation slip and serration. Insights from the in situ experiments point to the role of entropy in the design of structural materials with superior properties.

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In this Brief Report, we investigate the generation of bright quadripartite entanglement of continuous variables in an experimentally realizable system involving second-order harmonic generation with competing nondegenerate optical parametric downconversion. By using the well-known van Loock-Furusawa criterion for continuous variable correlations, we find that the genuine quadripartite entanglement can be generated in the system over a wide range of controllable parameters. Besides this, it is shown that the bipartite entanglement between any two field modes can be achievable. In addition, the dependence of the quantum correlations on the pump parameter is also discussed.

Phase transformation is an effective means to increase the ductility of a material. However, even for a commonly observed face-centered-cubic to hexagonal-close-packed (fcc-tohcp) phase transformation, the underlying mechanisms are far from being settled. In fact, different transformation pathways have been proposed, especially with regard to nucleation of the hcp phase at the nanoscale. In CrCoNi, a so-called medium-entropy alloy, an fccto-hcp phase transformation has long been anticipated. Here, we report an in situ loading study with neutron diffraction, which revealed a bulk fcc-to-hcp phase transformation in CrCoNi at 15 K under tensile loading. By correlating deformation characteristics of the fcc phase with the development of the hcp phase, it is shown that the nucleation of the hcp phase was triggered by intrinsic stacking faults. The confirmation of a bulk phase transformation adds to the myriads of deformation mechanisms available in CrCoNi, which together underpin the unusually large ductility at low temperatures.

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Whether for insects or for aircrafts, landing is one of the indispensable links in the verification of airworthiness safety. The mechanisms by which insects achieve a fast and stable landing remain unclear. An intriguing example is provided by honeybees (Apis mellifera ligustica), which use the swinging motion of their abdomen to dissipate residual flying energy and to achieve a smooth, stable, and quick landing. By using a high-speed camera, we observed that touchdown is initiated by honeybees extending their front legs or antennae and then landing softly on a wall. After touchdown, they swing the rest of their bodies until all flying energy is dissipated. We suggested a simplified model with mass-spring dampers for the body of the honeybee and revealed the mechanism of flying energy transfer and dissipation in detail. Results demonstrate that body translation and abdomen swinging help honeybees dissipate residual flying energy and orchestrate smooth landings. The initial kinetic energy of flying is transformed into the kinetic energy of the abdomen's rotary movement. Then, the kinetic energy of rotary movement is converted into thermal energy during the swinging cycle. This strategy provides more insight into the mechanism of insect flying, which further inspires better design on aerial vehicle with better landing performance.