title: Thermomechanical Behavior of Molded Metallic Glass Nanowires.
abstract: Metallic glasses are disordered materials that offer the unique ability to perform thermoplastic forming operations at low thermal budget while preserving excellent mechanical properties such as high strength, large elastic strain limits, and wear resistance owing to the metallic nature of bonding and lack of internal defects. Interest in molding micro- and nanoscale metallic glass objects is driven by the promise of robust and high performance micro- and nanoelectromechanical systems and miniature energy conversion devices. Yet accurate and efficient processing of these materials hinges on a robust understanding of their thermomechanical behavior. Here, we combine large-scale thermoplastic tensile deformation of collections of Pt-based amorphous nanowires with quantitative thermomechanical studies of individual nanowires in creep-like conditions to demonstrate that superplastic-like flow persists to small length scales. Systematic studies as a function of temperature, strain-rate, and applied stress reveal the transition from Newtonian to non-Newtonian flow to be ubiquitous across the investigated length scales. However, we provide evidence that nanoscale specimens sustain greater free volume generation at elevated temperatures resulting in a flow transition at higher strain-rates than their bulk counterparts. Our results provide guidance for the design of thermoplastic processing methods and methods for verifying the flow response at the nanoscale.
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Magagnosc
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409, USA.
authors.forename: Golden
authors.initials: G
authors.lastname: Kumar
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Jan
authors.initials: J
authors.lastname: Schroers
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.|Department of Materials, University of California, Santa Barbara, California 93106, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Gianola