Diffusion-Mediated Superelongation in Metal Nanorods

We report in situ electron microscopy observation of the superelongation deformation of low-melting-point metal nanorods. Specifically, metal nanorods with diameters as small as 143 nm can undergo uniform stretching by an extraordinary 786% at $\ensuremath{\sim}0.87{T}_{\mathrm{m}}$ without necking. Moreover, the corresponding fracture stress exhibits a pronounced size effect. By combining experimental observations with molecular dynamic simulations, a crystal-core--liquid-shell structure is revealed, based on which a constitutive model that incorporates diffusion creep mechanism and surface tension effect is developed to rationalize the findings. This study not only establishes a pioneering reference for comprehending the diffusion-dominated constitutive response of nanoscale materials but also has substantial implications for strategic design and processing of metals in high-temperature applications.