Multiphase Heterogeneous Nanolayers Enable Concurrent Strengthening and Ductility in Nanocrystalline Metal Films.

Abstract

Ag is attractive for thin-film applications requiring high thermal and electrical conductivity, yet increasing strength and strain resistance without compromising the physical performance in pure Ag remains difficult. Here, experiments and atomistic simulations reveal a nanoscale strengthening mechanism in which ultrathin semicrystalline Ni-rich nanolayers are intercalated between thicker nanocrystalline Ag films, forming a stable multilayered structure composed of pure nanocrystalline Ag and multiphase Ni-Ag nanoalloy. This architecture yields a hardness of 2.6 GPa, a tensile strength of 677 MPa, and 6.6% plastic elongation, all surpassing previous Ag thin-film records while preserving high electrical conductivity. Chemical and structural heterogeneities confined within the intercalated nanolayers promote multiphase interface-mediated plasticity, which markedly enhances strain hardening and tensile ductility relative to conventional crystalline Ag-Ni nanolaminates at similar Ag thickness. This nanoscale strengthening mechanism provides a general strategy for designing nanocrystalline metallic films with exceptional mechanical and physical properties.