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Interface Engineered Amorphous Alloys for Thermoplastic Forming of Bulk Metallic Glasses

The object of this research is to understand the mechanisms underpinning strain delocalization  in interface engineered amorphous alloys containing intergranular regions of excess free volume. Molecular dynamics simulations of shear localization are employed collectively with advanced characterization and nanomechanical testing of these materials to elucidate the role of interfacial structure and amorphous grain size in the mechanics of strain delocalization. Innovations in additive spray manufacturing are being developed to enable transformational microstructures that effectively delocalize the accumulation of plastic strain via distributed microplasticity. A chief societal impact of this research is the ability to produce ductile amorphous alloy sheets via additive spray manufacturing that can be used to revolutionize the sheet metal industry as well as produce bulk metallic glass components through net-shape thermoplastic forming.

  Nanocrystalline Tungsten Alloys  

Enabling Stable Nanocrystalline Tungsten Alloys as Plasma-facing Materials for Fusion Reactors

Plasma-facing materials (PFMs) in future fusion devices will be exposed to demanding operating conditions involving high heat fluxes, aggressive particle and neutron fluxes, and high stresses.  Although tungsten has emerged as a promising candidate, there are a number of outstanding issues yet to be resolved, including high temperature stability, mechanical performance, and radiation tolerance.  The aim of this research is to address these limitations in tandem by precisely tailoring the volume fraction, chemistry, and structural state of grain boundaries in tungsten.  These novel materials, known as solute-stabilized nanostructured tungsten alloys, will be designed and screened through thermodynamic modeling coupled with in situ electron microscopy experiments.  Select alloys will then be scaled via powder metallurgy processes to synthesize bulk materials for mapping structure-property-performance correlations.  The insights established through this research will markedly enhance the state of tungsten alloys for fusion applications and in turn, provide opportunities to validate their performance under relevant PFM conditions. 


Tailoring the Stability & Deformation of Nanocrystalline Alloys through Hierarchical Engineering

Crystalline-amorphous nanolaminates represent a unique class of hierarchically structured materials where deformation is governed by a confluence of mechanisms deriving from defect interactions with both phase and grain boundaries. Using molecular dynamics simulations, we explore the influence of microstructural length scales on the underlying deformation mechanisms.  Illustrative deformation mechanism maps capturing contributions from the dominant mechanisms are constructed to provide new insights into mechanistic transitions as a function of phase and interfacial volume fraction.  Guided by the insights from atomistic simulations, nanocrystalline modulated alloy nanolaminates are synthesized via electrodeposition and used to correlate measured mechanical properties with the deformation mechanisms predicted through simulations.


Elucidating the Process of Shear Delocalization in Metallic Glass Matrix Composites

This research combines experiments and computational modeling to study the unique behavior of metallic glass matrix composites, which represents are a new class of structural materials where the mechanics uncovered will illuminate new microstructural design methodologies that have the potential to transform the classical application space of structural metals.  We leverage nanoindentation techniques to explore the role of crystalline inclusions in shear band nucleation and propagation as a function of the governing microstructural length scales in these unique materials. 


Grain Boundary Engineering in Solute Stabilized Nanocrystalline Alloys

Stable nanocrystalline metals employing solute enriched grain boundary phases are being realized in a myriad of alloy systems and driving extraordinary advances in the design, processing, and technological applications of bulk nanocrystalline materials.  However, augmenting the chemical and structural state of grain boundaries to achieve adequate thermal stability also has marked impacts on the mechanical behavior. The objective of this research is to understand the effects of grain boundary doping on mechanical behavior focusing on two specific phenomena – stabilization against stress-assisted grain growth and grain boundary segregation strengthening. We combine molecular dynamics simulations with with in situ experiments to probe the mechanisms responsible for these processes and understand their manifestation in the measured mechanical response. Alloy systems of particular interest include iron based alloys for next-generation fission reactors and aluminum alloys for specific strength materials with applications in the automotive and aerospace industries. 

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