Suppressed ballistic transport of dislocations at strain rates up to 109 s–1 in a stable nanocrystalline alloy
Qi Tang, Jianxiong Li, B.C. Hornbuckle, Anit K. Giri, Kristopher A. Darling, Mostafa Hassani
Abstract
Dislocations are crucial to plastic deformation in crystals. At extreme strain rates, their motion shifts from thermally activated glide to ballistic transport, causing significant drag due to interactions with phonons, which can lead to embrittlement and failure in metals. The concept of dislons, quantized dislocations, has emerged to better understand these types of interactions. Similar to quantum treatment of dislocation-electron interactions, confining dislocations to nanometer scales, especially in nanocrystalline metals, could also yield unique mechanical behaviors different from bulk materials. Here, we present evidence showing that in Cu-3Ta, a thermo-mechanically stable nanocrystalline alloy, the phonon drag effect is entirely suppressed even at ultra-high strain rates (109 s−1). This is due to the stable confinement of dislocations within several-nanometer range, limiting their velocity and interaction with phonons. Our study indicates that in confined environments, the dislocation-phonon drag effect is minimal, potentially improving material performance under extreme conditions. Ballistic transport of dislocations and the resulting phonon drag are known to occur in crystalline metals under high strain rates, causing embrittlement. Here, we leverage dislocation confinement at the nanometer scale to entirely suppress the phonon drag regime, even at strain rates as high as 109 s−1.