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In the absence of externally applied mechanical loading, it would seem counterintuitive that a solid particle sitting on the surface of another solid could not only sink into the latter, but also continue its rigid-body motion towards the interior, reaching a depth as distant as thousands of times the particle diameter. Here, we demonstrate such a case using in situ microscopic as well as bulk experiments, in which diamond nanoparticles ~100 nm in size move into iron up to millimeter depth, at a temperature about half of the melting point of iron. Each diamond nanoparticle is nudged as a whole, in a displacive motion towards the iron interior, due to a local stress induced by the accumulation of iron atoms diffusing around the particle via a short and easy interfacial channel. Our discovery underscores an unusual mass transport mode in solids, in addition to the familiar diffusion of individual atoms. It has long been believed that diffusion as individual atoms is the primary way for carbon to enter Fe crystals from outside. Here, the authors report an unusual mass transport way in solids, through which diamond nanoparticles can enter Fe spontaneously and translate inward for a long distance. [ABSTRACT FROM AUTHOR]

The mechanical reliability of metallic components is vital for the stable operation of electrical equipment, especially for those used in ultra-high voltage transmission and electromagnetic launching, where metallic materials inevitably suffer from high-density current and strong magnetic field. However, little has been known about the mechanical behavior of metals under the electric-magnetic coupling stimuli. Here, by performing quantitative electromechanical tests under the built-in magnetic field inside transmission electron microscope, we found that copper, one of most commonly used conductive metals, can be significantly softened by the coupled electrical-magnetic stimuli, manifested as notable yield strength drop by five-times and obvious creep deformation at room temperature. A plausible mechanism behind the unusual softening, local-Lorentz-force-assisted dislocations depinning, has been proposed. Our results shed new light on understanding the deformation-induced failure of metals served in electromagnetic environments, and also inspire a new mechanical processing way for reshaping metals at much lower loads and temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]

As a typical hard but brittle material, Si tends to fracture abruptly at a stress well below its theoretical strength, even if the tested volume goes down to submicron scale, at which materials are usually nearly free of flaws or extended defects. Here, via the thermal–oxidation–mediated healing of the surface that is the preferred site for cracks or dislocations initiation, the premature fracture can be effectively inhibited and the over 50% homogeneous plastic strain with the near‐theoretical strength (twice the value of the unhealed counterpart) are united in submicron‐sized Si particles. In situ transmission electron microscope observations and atomistic simulations elucidate the confinement effect from the passivated and smoothened thermal oxide, which retards the dislocation nucleation and transforms the dominant deformation mechanism from partial dislocation to the more mobile full dislocation. This work demonstrates an effective and feasible surface engineering pathway to optimize the mechanical properties of Si at small scales. [ABSTRACT FROM AUTHOR]