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

Area of Science:

• Materials Science
• Nanotechnology
• Mechanical Engineering

Background:

• Pure silver (Ag) films offer excellent thermal and electrical conductivity but lack sufficient strength and strain resistance for many applications.
• Improving mechanical properties of Ag thin films without sacrificing conductivity has been a persistent challenge in materials science.

Purpose of the Study:

• To investigate a novel nanoscale strengthening mechanism for silver thin films.
• To develop a multilayered Ag-Ni structure that enhances mechanical properties while preserving electrical conductivity.

Main Methods:

• Fabrication of multilayered Ag-Ni thin films using ultrathin semicrystalline Ni-rich nanolayers intercalated between nanocrystalline Ag films.
• Characterization through experiments and atomistic simulations to reveal nanoscale strengthening mechanisms.
• Evaluation of mechanical properties (hardness, tensile strength, plastic elongation) and electrical conductivity.

Main Results:

• Achieved a hardness of 2.6 GPa, tensile strength of 677 MPa, and 6.6% plastic elongation, setting new records for Ag thin films.
• The multilayered structure, composed of pure nanocrystalline Ag and multiphase Ni-Ag nanoalloy, maintained high electrical conductivity.
• Interface-mediated plasticity within the Ni-Ag nanolayers significantly enhanced strain hardening and ductility compared to conventional nanolaminates.

Conclusions:

• A novel nanoscale strengthening mechanism involving multiphase interface-mediated plasticity was identified in Ag-Ni multilayered films.
• This architecture provides a general strategy for designing nanocrystalline metallic films with superior mechanical and physical properties.
• The developed Ag-Ni thin films show promise for applications requiring both high conductivity and enhanced mechanical performance.