Strengthening Nanotwinned Metals beyond the Hall-Petch Limit

Technical Report · Thu Nov 14 04:00:00 EST 2019

DOI:https://doi.org/10.2172/1574142· OSTI ID:1574142

Sansoz, Frederic ^[1]

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1. Univ. of Vermont, Burlington, VT (United States); The University of Vermont

A research partnership program was conducted to study the roles of trace element segregation as a fundamentally new mechanism of grain-boundary and twin-boundary strengthening in nanocrystalline-nanotwinned face-centered-cubic silver metals. The goals were to create new metals that break the decades-old theoretical Hall-Petch strength limit, and to study a new class of super-strong conducting materials. This program combined synergistic experimental and computational studies at the atomic scale, using a wide range of resources and scientific expertise at the University of Vermont, Ames Laboratory and Lawrence Livermore National Laboratory. This research led to a discovery that annealing of nanotwinned silver with trace concentrations of Cu solute atoms (<1.0 wt.%) results in grain sizes and twin spacings well below those previously obtained for silver. These new materials, termed as nanocrystalline-nanotwinned silver, showed a record hardness 42% higher than the Hall-Petch limit in pure nanotwinned silver or stronger metals like copper, with excellent retention of electrical conductivity and microstructure stability at elevated temperature. This research used large-scale hybrid Monte-Carlo/molecular-dynamics atomistic simulations and ab-initio calculations to predict new impurity-segregation behaviors and fundamentally new plastic deformation mechanisms in nanocrystalline-nanotwinned silver metals. A new interatomic potential for atomistic simulation of segregation of Ni impurity in Ag grain-boundaries and plasticity of Ag-Ni alloys was developed.

• Research Organization: Univ. of Vermont, Burlington, VT (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: SC0016270
• OSTI ID: 1574142
• Report Number(s): DOE-UVM--0016270; 8026563837
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE