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Using molecular dynamics simulation, a CuZr metallic glass was subjected to cyclic indentation to investigate cyclic hardening. Structural changes occurring after each indentation cycle were analyzed by examining the radial changes of the structural motifs in the vicinity of the indenter surface. The analysis revealed initial local structural modifications that corresponded to a more relaxed glass state, followed by a slow restoration of the initially destroyed structures. These findings provide new insights into the microstructural causes of cyclic hardening in metallic glasses. 

Abstract Nanograined metals have the merit of high strength, but usually suffer from low work hardening capacity and poor thermal stability, causing premature failure and limiting their practical utilities. Here we report a “nanodispersion-in-nanograins” strategy to simultaneously strengthen and stabilize nanocrystalline metals such as copper and nickel. Our strategy relies on a uniform dispersion of extremely fine sized carbon nanoparticles (2.6 ± 1.2 nm) inside nanograins. The intragranular dispersion of nanoparticles not only elevates the strength of already-strong nanograins by 35%, but also activates multiple hardening mechanisms via dislocation-nanoparticle interactions, leading to improved work hardening and large tensile ductility. In addition, these finely dispersed nanoparticles result in substantially enhanced thermal stability and electrical conductivity in metal nanocomposites. Our results demonstrate the concurrent improvement of several mutually exclusive properties in metals including strength-ductility, strength-thermal stability, and strength-electrical conductivity, and thus represent a promising route to engineering high-performance nanostructured materials.