Exploring the thermal stability of a bimodal nanoscale multilayered system

Riano, J. Sebastian; Hodge, Andrea M.

doi:10.1016/j.scriptamat.2019.02.043

Cited by 14 publications

(20 citation statements)

References 62 publications

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“…Hf-Ti, Mo-Au, Ta-Hf and W-Cr NMMs (2 µm total thickness), comprising alternating mixed and pure solute layers, were deposited on Si (100) substrates via DC magnetron sputtering following procedures described in previous manuscripts [ 17 , 18 , 19 , 20 ]. In these manuscripts, more detailed discussions of both the experimental approach and findings can be found.…”

Section: Methodsmentioning

confidence: 99%

“…For these scans, the enthalpy of the endothermic and exothermic transformations was measured over a baseline that was extracted using Origin Lab. In order to experimentally observe the microstructural changes correlating to these transformations, each multilayer system was annealed for 96 h at various temperatures up to 1000 °C inside a GSL1100X vertical tube furnace (MTI Corporation, Richmond, CA) under vacuum (5 × 10 −4 Pa) [ 17 , 18 , 19 , 20 ]. At the end of the heat-treatment, the samples were rapidly quenched in a low vapor pressure oil.…”

Section: Methodsmentioning

confidence: 99%

“…At the end of the heat-treatment, the samples were rapidly quenched in a low vapor pressure oil. The initial as-sputtered and final tailored microstructures (1000 °C) are the focus of this article in order to capture a more general understanding of the concluding microstructural transformations where details on intermediate microstructures can be found elsewhere [ 17 , 18 , 19 , 20 ]. Transmission electron microscopy (TEM) lamellas exposing the cross-section of the films were prepared via focus ion beam (FIB) lift-out techniques within a JEOL FIB-4500 microscope (JEOL, Tokyo, Japan), where the surface was protected from beam damage with a thin layer of C. The microstructure and local compositions of the films were studied via TEM imaging of the lamellas in a JEOL JEM-2100F TEM (JEOL, Tokyo, Japan) equipped with an Oxford X-MaxN 100 EDS detector.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, NMMs can leverage the favorable characteristics of nanostructured materials that can be credited to the high density of grain boundaries (GBs) and interfaces while expanding possible microstructural arrangements. As a result of these valuable attributes, NMMs have demonstrated capability as model systems for developing new equiaxed nanostructured materials [ 16 , 17 , 18 , 19 , 20 , 21 ]. Individual studies on different resulting microstructures are highly encouraging [ 22 , 23 , 24 ], but what remains in question is an overarching view of the mechanistic relationships between different initial multilayer structures and the final nanostructure achieved after thermally-driven microstructural transformations [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

“…The contributions of both interface properties and composition are generalized to identify global relationships between predictions of nanoscale microstructures and the final observed nanostructured microstructures. In this article, we present the microstructural synergies and differences within four distinct model systems (Hf-Ti [ 18 ], Ta-Hf [ 19 ], W-Cr [ 20 ], Mo-Au [ 17 ]) in their as-sputtered condition and after annealing at 1000 °C for 96 h. These model binary material systems were chosen because they are all predicted to exhibit nanocrystalline stability at high temperatures [ 30 , 31 ]. Furthermore, these systems are non-equiatomic to promote enhanced diffusion on the path toward multi-layered-to-equiaxed microstructural transformations.…”

Section: Introductionmentioning

confidence: 99%

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An Overview of Nano Multilayers as Model Systems for Developing Nanoscale Microstructures

2022

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The microstructural transformations of binary nanometallic multilayers (NMMs) to equiaxed nanostructured materials were explored by characterizing a variety of nanoscale multilayer films. Four material systems of multilayer films, Hf-Ti, Ta-Hf, W-Cr, and Mo-Au, were synthesized by magnetron sputtering, heat treated at 1000 °C, and subsequently characterized by transmission electron microscopy. Binary systems were selected based on thermodynamic models predicting stable nanograin formation with similar global compositions around 20–30 at.%. All NMMs maintained nanocrystalline grain sizes after evolution into an equiaxed structure, where the systems with highly mobile incoherent interfaces or higher energy interfaces showed a more significant increase in grain size. Furthermore, varying segregation behaviors were observed, including grain boundary (GB) segregation, precipitation, and intermetallic formation depending on the material system selected. The pathway to tailored microstructures was found to be governed by key mechanisms and factors as determined by a film’s initial characteristics, including global and local composition, interface energy, layer structure, and material selection. This work presents a global evaluation of NMM systems and demonstrates their utility as foundation materials to promote tailored nanomaterials.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Overview of Nano Multilayers as Model Systems for Developing Nanoscale Microstructures

2022

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Nanostructured Oxide‐Dispersion‐Strengthened CoCrFeMnNi High‐Entropy Alloys with High Thermal Stability

et al. 2021

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A nanostructured oxide‐dispersion‐strengthened (ODS) CoCrFeMnNi high‐entropy alloy (HEA) is synthesized by a powder metallurgy process. The thermal stability, including the grain size and crystal structure of the HEA matrix and oxide dispersions, is carefully investigated by X‐ray diffraction (XRD) and electron microscopy characterizations after annealing at 900 °C. The limited grain growth may be attributed to Zener pinning of yttria dispersions that impede the grain boundary mobility and diffusivity. The high hardness is caused by both the fine grain size and yttria dispersions, which are also retained after annealing at 900 °C. Herein, it is implied that the combination of ODS and HEA concepts may provide a new design strategy for the development of thermally stable nanostructured alloys for extreme environments.

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Unraveling Thermodynamic and Kinetic Contributions to the Stability of Doped Nanocrystalline Alloys using Nanometallic Multilayers

et al. 2022

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Targeted doping of grain boundaries is widely pursued as a pathway for combating thermal instabilities in nanocrystalline metals. However, certain dopants predicted to produce grain‐boundary‐segregated nanocrystalline configurations instead form small nanoprecipitates at elevated temperatures that act to kinetically inhibit grain growth. Here, thermodynamic modeling is implemented to select the Mo–Au system for exploring the interplay between thermodynamic and kinetic contributions to nanostructure stability. Using nanoscale multilayers and in situ transmission electron microscopy thermal aging, evolving segregation states and the corresponding phase transitions are mapped with temperature. The microstructure is shown to evolve through a transformation at lower homologous temperatures (<600 °C) where solute atoms cluster and segregate to the grain boundaries, consistent with predictions from thermodynamic models. An increase in temperature to 800 °C is accompanied by coarsening of the grain structure via grain boundary migration but with multiple pinning events uncovered between migrating segments of the grain boundary and local solute clustering. Direct comparison between the thermodynamic predictions and experimental observations of microstructure evolution thus demonstrates a transition from thermodynamically preferred to kinetically inhibited nanocrystalline stability and provides a general framework for decoupling contributions to complex stability transitions while simultaneously targeting a dominant thermal stability regime.

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Exploring the thermal stability of a bimodal nanoscale multilayered system

Cited by 14 publications

References 62 publications

An Overview of Nano Multilayers as Model Systems for Developing Nanoscale Microstructures

An Overview of Nano Multilayers as Model Systems for Developing Nanoscale Microstructures

Nanostructured Oxide‐Dispersion‐Strengthened CoCrFeMnNi High‐Entropy Alloys with High Thermal Stability

Unraveling Thermodynamic and Kinetic Contributions to the Stability of Doped Nanocrystalline Alloys using Nanometallic Multilayers

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