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Thermal, Mechanical and Radiation Stability of Nanostructured Metals

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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 24923

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Dr. Khalid Hattar

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Guest Editor

Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, NM 87185, USA
Interests: in situ transmission electron microscopy (TEM); ion beam modification (IBM); extreme environments; in situ scanning electron microscopy (SEM); nanostructure stability
Special Issues, Collections and Topics in MDPI journals

Dr. Fadi F Abdeljawad

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Guest Editor

Department of Mechanical Engineering, Department of Materials Science and Engineering, Clemson University, Clemson, SC, USA
Interests: theoretical and computational materials science; interface thermodynamics; machine learning; additive manufacturing; microstructural evolution

Special Issue Information

Dear Colleagues,

Nanostructured metals ranging from nanocrystalline and nanolayer to nanoporous and nanocomposite structures exhibit unique combinations of properties and functionalities that are not typically found in their counterparts. These include mechanical strength, hardness, wear, transport, catalytic activity, and radiation tolerance, to name a few. However, very few of these metals, alloys, or metal matrix composites have found industrial applications, due largely to the poor stability of nanostructures. Nanostructured metals are at highly non-equilibrium states, due to the high density of interfaces and associated interfacial contribution to the free energy of these materials systems. This in turn constitutes a large driving force for several coarsening and homogenization processes. The ability to mitigate such coarsening phenomena and retain the nanocrystalinity under continuous service conditions and for extended time scales is arguably one of the main obstacles to the large scale commercialization of these systems. In recent years, studies have suggested several metallurgical routes to increase the stability of these systems. Understanding the stability of nanostructured metals is a rapidly emerging field that has the potential to greatly advance the integration of nanomaterials into applications with long term or extreme environments.

The format of welcomed articles includes full papers, communications, and reviews. Potential topics include, but are not limited to:

Thermodynamic and kinetic stability of metals
Solute and multiphase stability
Nanostructured systems including: Nanocrystalline, Nanolayers, Nanoporous, Nanoscale precipitants
Modeling via molecular dynamics, Monte Carlo, or mesoscale approaches
Production via thin film growth, additively manufacturing, and bulk processing
Extreme environments

Dr. Khalid Hattar
Dr. Fadi F Abdeljawad
Guest Editors

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

nanostructured metals
structural stability
thermal annealing
mechanical stability
radiation stability
grain boundary and interface mobility

Published Papers (11 papers)

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Research

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11 pages, 3015 KiB

Open AccessArticle

Compositional Effects of Additively Manufactured Refractory High-Entropy Alloys under High-Energy Helium Irradiation

by Eric Lang, Kory Burns, Yongqiang Wang, Paul G. Kotula, Andrew B. Kustas, Sal Rodriguez, Assel Aitkaliyeva and Khalid Hattar

Nanomaterials 2022, 12(12), 2014; https://doi.org/10.3390/nano12122014 - 10 Jun 2022

Cited by 5 | Viewed by 2347

Abstract

High-Entropy Alloys (HEAs) are proposed as materials for a variety of extreme environments, including both fission and fusion radiation applications. To withstand these harsh environments, materials processing must be tailored to their given application, now achieved through additive manufacturing processes. However, radiation application opportunities remain limited due to an incomplete understanding of the effects of irradiation on HEA performance. In this letter, we investigate the response of additively manufactured refractory high-entropy alloys (RHEAs) to helium (He) ion bombardment. Through analytical microscopy studies, we show the interplay between the alloy composition and the He bubble size and density to demonstrate how increasing the compositional complexity can limit the He bubble effects, but care must be taken in selecting the appropriate constituent elements. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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21 pages, 11223 KiB

Open AccessArticle

Phase Transitions of Cu and Fe at Multiscales in an Additively Manufactured Cu–Fe Alloy under High-Pressure

by Arya Chatterjee, Dmitry Popov, Nenad Velisavljevic and Amit Misra

Nanomaterials 2022, 12(9), 1514; https://doi.org/10.3390/nano12091514 - 29 Apr 2022

Cited by 5 | Viewed by 1762

Abstract

A state of the art, custom-built direct-metal deposition (DMD)-based additive manufacturing (AM) system at the University of Michigan was used to manufacture 50Cu–50Fe alloy with tailored properties for use in high strain/deformation environments. Subsequently, we performed preliminary high-pressure compression experiments to investigate the structural stability and deformation of this material. Our work shows that the alpha (BCC) phase of Fe is stable up to ~16 GPa before reversibly transforming to HCP, which is at least a few GPa higher than pure bulk Fe material. Furthermore, we observed evidence of a transition of Cu nano-precipitates in Fe from the well-known FCC structure to a metastable BCC phase, which has only been predicted via density functional calculations. Finally, the metastable FCC Fe nano-precipitates within the Cu grains show a modulated nano-twinned structure induced by high-pressure deformation. The results from this work demonstrate the opportunity in AM application for tailored functional materials and extreme stress/deformation applications. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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13 pages, 9073 KiB

Open AccessArticle

Compositionally-Driven Formation Mechanism of Hierarchical Morphologies in Co-Deposited Immiscible Alloy Thin Films

by Max Powers, James A. Stewart, Rémi Dingreville, Benjamin K. Derby and Amit Misra

Nanomaterials 2021, 11(10), 2635; https://doi.org/10.3390/nano11102635 - 08 Oct 2021

Cited by 8 | Viewed by 1549

Abstract

Co-deposited, immiscible alloy systems form hierarchical microstructures under specific deposition conditions that accentuate the difference in constituent element mobility. The mechanism leading to the formation of these unique hierarchical morphologies during the deposition process is difficult to identify, since the characterization of these microstructures is typically carried out post-deposition. We employ phase-field modeling to study the evolution of microstructures during deposition combined with microscopy characterization of experimentally deposited thin films to reveal the origin of the formation mechanism of hierarchical morphologies in co-deposited, immiscible alloy thin films. Our results trace this back to the significant influence of a local compositional driving force that occurs near the surface of the growing thin film. We show that local variations in the concentration of the vapor phase near the surface, resulting in nuclei (i.e., a cluster of atoms) on the film’s surface with an inhomogeneous composition, can trigger the simultaneous evolution of multiple concentration modulations across multiple length scales, leading to hierarchical morphologies. We show that locally, the concentration must be above a certain threshold value in order to generate distinct hierarchical morphologies in a single domain. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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26 pages, 83076 KiB

Open AccessArticle

Nano-Structured Materials under Irradiation: Oxide Dispersion-Strengthened Steels

by Joël Ribis, Isabelle Mouton, Cédric Baumier, Aurélie Gentils, Marie Loyer-Prost, Laurence Lunéville and David Siméone

Nanomaterials 2021, 11(10), 2590; https://doi.org/10.3390/nano11102590 - 01 Oct 2021

Cited by 6 | Viewed by 2026

Abstract

Oxide dispersion-strengthened materials are reinforced by a (Y, Ti, O) nano-oxide dispersion and thus can be considered as nanostructured materials. In this alloy, most of the nanoprecipitates are (Y, Ti, O) nano-oxides exhibiting a Y₂Ti₂O₇ pyrochlore-like structure. However, the lattice structure of the smallest oxides is difficult to determine, but it is likely to be close to the atomic structure of the host matrix. Designed to serve in extreme environments—i.e., a nuclear power plant—the challenge for ODS steels is to preserve the nano-oxide dispersion under irradiation in order to maintain the excellent creep properties of the alloy in the reactor. Under irradiation, the nano-oxides exhibit different behaviour as a function of the temperature. At low temperature, the nano-oxides tend to dissolve owing to the frequent ballistic ejection of the solute atoms. At medium temperature, the thermal diffusion balances the ballistic dissolution, and the nano-oxides display an apparent stability. At high temperature, the nano-oxides start to coarsen, resulting in an increase in their size and a decrease in their number density. If the small nano-oxides coarsen through a radiation-enhanced Ostwald ripening mechanism, some large oxides disappear to the benefit of the small ones through a radiation-induced inverse Ostwald ripening. In conclusion, it is suggested that, under irradiation, the nano-oxide dispersion prevails over dislocations, grain boundaries and free surfaces to remove the point defects created by irradiation. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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7 pages, 3931 KiB

Open AccessCommunication

Limitations of Thermal Stability Analysis via In-Situ TEM/Heating Experiments

by Osman El-Atwani, Hyosim Kim, Cayla Harvey, Mert Efe and Stuart A. Maloy

Nanomaterials 2021, 11(10), 2541; https://doi.org/10.3390/nano11102541 - 28 Sep 2021

Viewed by 1650

Abstract

This work highlights some limitations of thermal stability analysis via in-situ transmission electron microscopy (TEM)-annealing experiments on ultrafine and nanocrystalline materials. We provide two examples, one on nanocrystalline pure copper and one on nanocrystalline HT-9 steel, where in-situ TEM-annealing experiments are compared to bulk material annealing experiments. The in-situ TEM and bulk annealing experiments demonstrated different results on pure copper but similar output in the HT-9 steel. The work entails discussion of the results based on literature theoretical concepts, and expound on the inevitability of comparing in-situ TEM annealing experimental results to bulk annealing when used for material thermal stability assessment. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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15 pages, 7178 KiB

Open AccessArticle

Stable, Ductile and Strong Ultrafine HT-9 Steels via Large Strain Machining

by Osman El-Atwani, Hyosim Kim, Jonathan G. Gigax, Cayla Harvey, Berk Aytuna, Mert Efe and Stuart A. Maloy

Nanomaterials 2021, 11(10), 2538; https://doi.org/10.3390/nano11102538 - 28 Sep 2021

Cited by 3 | Viewed by 1669

Abstract

Beyond the current commercial materials, refining the grain size is among the proposed strategies to manufacture resilient materials for industrial applications demanding high resistance to severe environments. Here, large strain machining (LSM) was used to manufacture nanostructured HT-9 steel with enhanced thermal stability, mechanical properties, and ductility. Nanocrystalline HT-9 steels with different aspect rations are achieved. In-situ transmission electron microscopy annealing experiments demonstrated that the nanocrystalline grains have excellent thermal stability up to 700 °C with no additional elemental segregation on the grain boundaries other than the initial carbides, attributing the thermal stability of the LSM materials to the low dislocation densities and strains in the final microstructure. Nano-indentation and micro-tensile testing performed on the LSM material pre- and post-annealing demonstrated the possibility of tuning the material’s strength and ductility. The results expound on the possibility of manufacturing controlled nanocrystalline materials via a scalable and cost-effective method, albeit with additional fundamental understanding of the resultant morphology dependence on the LSM conditions. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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11 pages, 2424 KiB

Open AccessArticle

Evidence for a High Temperature Whisker Growth Mechanism Active in Tungsten during In Situ Nanopillar Compression

by Gowtham Sriram Jawaharram, Christopher M. Barr, Khalid Hattar and Shen J. Dillon

Nanomaterials 2021, 11(9), 2429; https://doi.org/10.3390/nano11092429 - 18 Sep 2021

Cited by 2 | Viewed by 2654

Abstract

A series of nanopillar compression tests were performed on tungsten as a function of temperature using in situ transmission electron microscopy with localized laser heating. Surface oxidation was observed to form on the pillars and grow in thickness with increasing temperature. Deformation between 850 °C and 1120 °C is facilitated by long-range diffusional transport from the tungsten pillar onto adjacent regions of the Y₂O₃-stabilized ZrO₂ indenter. The constraint imposed by the surface oxidation is hypothesized to underly this mechanism for localized plasticity, which is generally the so-called whisker growth mechanism. The results are discussed in context of the tungsten fuzz growth mechanism in He plasma-facing environments. The two processes exhibit similar morphological features and the conditions under which fuzz evolves appear to satisfy the conditions necessary to induce whisker growth. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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16 pages, 3829 KiB

Open AccessArticle

Atomistic Assessment of Solute-Solute Interactions during Grain Boundary Segregation

by Thomas P. Matson and Christopher A. Schuh

Nanomaterials 2021, 11(9), 2360; https://doi.org/10.3390/nano11092360 - 11 Sep 2021

Cited by 8 | Viewed by 2519

Abstract

Grain boundary solute segregation is becoming increasingly common as a means of stabilizing nanocrystalline alloys. Thermodynamic models for grain boundary segregation have recently revealed the need for spectral information, i.e., the full distribution of environments available at the grain boundary during segregation, in order to capture the essential physics of the problem for complex systems like nanocrystalline materials. However, there has been only one proposed method of extending spectral segregation models beyond the dilute limit, and it is based on simple, fitted parameters that are not atomistically informed. In this work, we present a physically motived atomistic method to measure the full distribution of solute-solute interaction energies at the grain boundaries in a polycrystalline environment. We then cast the results into a simple thermodynamic model, analyze the Al(Mg) system as a case study, and demonstrate strong agreement with physically rigorous hybrid Monte Carlo/molecular statics simulations. This approach provides a means of rapidly measuring key interactions for non-dilute grain boundary segregation for any system with an interatomic potential. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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22 pages, 48871 KiB

Open AccessArticle

The Role of Grain Boundary Diffusion in the Solute Drag Effect

by R. K. Koju and Y. Mishin

Nanomaterials 2021, 11(9), 2348; https://doi.org/10.3390/nano11092348 - 10 Sep 2021

Cited by 8 | Viewed by 2912

Abstract

Molecular dynamics (MD) simulations are applied to study solute drag by curvature-driven grain boundaries (GBs) in Cu–Ag solid solution. Although lattice diffusion is frozen on the MD timescale, the GB significantly accelerates the solute diffusion and alters the state of short-range order in lattice regions swept by its motion. The accelerated diffusion produces a nonuniform redistribution of the solute atoms in the form of GB clusters enhancing the solute drag by the Zener pinning mechanism. This finding points to an important role of lateral GB diffusion in the solute drag effect. A 1.5 at.%Ag alloying reduces the GB free energy by 10–20% while reducing the GB mobility coefficients by more than an order of magnitude. Given the greater impact of alloying on the GB mobility than on the capillary driving force, kinetic stabilization of nanomaterials against grain growth is likely to be more effective than thermodynamic stabilization aiming to reduce the GB free energy. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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15 pages, 1636 KiB

Open AccessEditor’s ChoiceArticle

Bayesian Data Assimilation of Temperature Dependence of Solid–Liquid Interfacial Properties of Nickel

by Yuhi Nagatsuma, Munekazu Ohno, Tomohiro Takaki and Yasushi Shibuta

Nanomaterials 2021, 11(9), 2308; https://doi.org/10.3390/nano11092308 - 06 Sep 2021

Cited by 11 | Viewed by 2994

Abstract

Temperature dependence of solid–liquid interfacial properties during crystal growth in nickel was investigated by ensemble Kalman filter (EnKF)-based data assimilation, in which the phase-field simulation was combined with atomic configurations of molecular dynamics (MD) simulation. Negative temperature dependence was found in the solid–liquid interfacial energy, the kinetic coefficient, and their anisotropy parameters from simultaneous estimation of four parameters. On the other hand, it is difficult to obtain a concrete value for the anisotropy parameter of solid–liquid interfacial energy since this factor is less influential for the MD simulation of crystal growth at high undercooling temperatures. The present study is significant in shedding light on the high potential of Bayesian data assimilation as a novel methodology of parameter estimation of practical materials an out of equilibrium condition. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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Review

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16 pages, 2094 KiB

Open AccessReview

Thermal and Radiation Stability in Nanocrystalline Cu

by Marie Thomas, Heather Salvador, Trevor Clark, Eric Lang, Khalid Hattar and Suveen Mathaudhu

Nanomaterials 2023, 13(7), 1211; https://doi.org/10.3390/nano13071211 - 29 Mar 2023

Cited by 1 | Viewed by 1200

Abstract

Nanocrystalline metals have presented intriguing possibilities for use in radiation environments due to their high grain boundary volume, serving as enhanced irradiation-induced defect sinks. Their promise has been lessened due to the propensity for nanocrystalline metals to suffer deleterious grain growth from combinations of irradiation and/or elevated homologous temperature. While approaches for stabilizing such materials against grain growth are the subject of current research, there is still a lack of central knowledge on the irradiation–grain boundary interactions in pure metals despite many studies on the same. Due to the breadth of available reports, we have critically reviewed studies on irradiation and thermal stability in pure, nanocrystalline copper (Cu) as a model FCC material, and on a few dilute Cu-based alloys. Our study has shown that, viewed collectively, there are large differences in interpretation of irradiation–grain boundary interactions, primarily due to a wide range of irradiation environments and variability in materials processing. We discuss the sources of these differences and analyses herein. Then, with the goal of gaining a more overarching mechanistic understanding of grain size stability in pure materials under irradiation, we provide several key recommendations for making meaningful evaluations across materials with different processing and under variable irradiation conditions. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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