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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A deep neural network regressor for phase constitution estimation in the high entropy alloy system Al-Co-Cr-Fe-Mn-Nb-Ni

High Entropy Alloys (HEAs) are composed of more than one principal element and constitute a major paradigm in metals research. The HEA space is vast and an exhaustive exploration is improbable. Therefore, a thorough estimation of the phases present in the HEA is of paramount importance for alloy design. Machine Learning presents a feasible and non-expensive method for predicting possible new HEAs on-the-fly. A deep neural network (DNN) model for the elemental system of: Mn, Ni, Fe, Al, Cr, Nb, and Co is developed using a dataset generated by high-throughput computational thermodynamic calculations using Thermo-Calc. The features list used for the neural network is developed based on literature and freely available databases. A feature significance analysis matches the reported HEAs phase constitution trends on elemental properties and further expands it by providing so far-overlooked features. The final regressor has a coefficient of determination ( r 2 ) greater than 0.96 for identifying the most recurrent phases and the functionality is tested by running optimization tasks that simulate those required in alloy design. The DNN developed constitutes an example of an emulator that can be used in fast, real-time materials discovery/design tasks.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Entropy-driven melting point depression in fcc HEAs

High Entropy Alloys (HEAs) are an increasingly dominant alloy design paradigm. The premise of entropic stabilization of single-phase alloys has motivated much of the research on HEAs. Chemical complexity may indeed help stabilize single alloy phases relative to other lower-entropy competing solid phases. Paradoxically, this complexity may de-stabilize these alloys against the liquid phase, potentially limiting the application space of HEAs at elevated temperatures. In this work, we carry out a comprehensive investigation of the phase stability in the fcc CoCrFeMnNiV-Al HEA space using a state of the art CALPHAD database. By using modern visualization techniques and statistical analysis we examine the trade-off between chemical complexity and stability against the liquid state and identify a potentially difficult to overcome barrier for development of high temperature alloys, at least within the conventional fcc HEA space. Here, limited experimental data seem to be consistent with this analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Radiation‐Resistant Aluminum Alloy for Space Missions in the Extreme Environment of the Solar System

Future human exploration of the solar system demands advanced materials capable of withstanding extreme environments, particularly exposure to solar energetic particle radiation. Current material selection criteria for space applications prioritize a high strength-to-weight ratio, high corrosion resistance and manufacturability, favoring age-hardenable Al-based alloys. However, conventional precipitation-hardened Al alloys suffer from irradiation-assisted dissolution of strengthening phases at doses as low as 0.2 displacements-per-atom (dpa), undermining their performance. Furthermore, these alloys develop radiation-induced defects, such as dislocation loops and voids, even at low doses. This study presents a novel ultrafine-grained (UFG) Al-based alloy, designed using the crossover alloying concept and strengthened by T-phase precipitates, featuring a chemically-complex structure with 162 atoms in its unit cell composed of Mg 32 (Zn,Al) 49 . It is showed that T-phase precipitates have exceptional radiation tolerance up to 24 dpa. Owing to the nanoscale UFG structure, dislocation loops are suppressed, and voids are only observed beyond 75 dpa. Microtensile tests up to 20 dpa confirm the preservation of mechanical performance under irradiation. The results underline the potential of this alloy as a radiation-resistant, lightweight material for future space applications. Three key strategies enable this performance: (i) stabilization of a UFG microstructure, (ii) T-phase precipitation featuring a highly negative Gibbs free energy and chemically-complex giant unit cell, and (iii) precise process control to prevent grain growth during heat treatment and irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Additively-manufactured Al-0.3Zr-0.2Ce-0.2Cu alloy with high creep resistance and electrical conductivity

Here, a new, solute-lean Al-0.3Zr-0.2Ce-0.2Cu (wt.%) alloy is developed for additive manufacturing that overcomes the classical tradeoff between conductivity and creep resistance. The rapid-cooling-enabled supersaturation of Zr, and its uniform distribution in α-Al matrix, along with formation of submicron (Ce,Cu)-rich intermetallic particles on solidification lead to unusually high creep resistance at 200 °C. Near-zero secondary creep rates are achieved up to the alloy yield stress (YS) of 65 MPa at 200 °C in as-fabricated state. The Zr-solute-induced dislocation-climb suppression mechanism underlying this improvement also restricts dynamic recovery above YS, as noted from appreciable primary creep and its transitioning to near-zero secondary creep rates. A combination of relatively coarse, epitaxially-grown α-Al grains, low Zr concentration in α-Al, and the impurity-scavenging effect of Ce to purify α-Al matrix produces high electrical conductivity of ∼48 %IACS. Aging precipitation of L1 2 -Al 3 Zr nanoprecipitates doubles the YS (to ∼150 MPa) at room temperature and increases alloy conductivity to ∼58 %IACS, but loss of solid-solution Zr out of α-Al matrix leads to activation of dislocation climb, degrading the creep properties as compared to the supersaturated Al-Zr solid solution in the as-fabricated state. Compared to L1 2 -Al 3 Zr nanoprecipitates, submicron (Ce,Cu)-rich particles formed on solidification are more effective at impeding dislocation climb, producing a threshold stress for dislocation creep of ∼ 50 MPa at 200 °C. The new alloy design concepts, especially solute-induced dislocation-climb suppression for creep resistance, explored here may pave way for the design of new metallic alloys for thermal/electrical conductors and other high-temperature applications.

Additive Manufacturing↗
DOE OSTI2022

Engineering defect energy landscape of CoCrFeNi high-entropy alloys by the introduction of additional dopants

The concept of high-entropy alloys (HEAs) focusing on tuning the overall chemical complexity represents a novel alloy design strategy. In contrast, alloying of a metallic matrix with minor doping elements with limited and localized tunability has been a common practice to improve material performance. Combining the idea of globally engineering defect energy landscape in HEAs and the localized doping strategy in dilute alloys, in this work, we explore doping effects of minor elements in a HEA matrix to further enhance the overall and localized chemical tunability, aiming to improve its irradiation resistance. Specifically, we study the influence of minor Al, Cu, Ti, and Pd substitutional doping elements on defect energetics in a CoCrFeNi model HEA based on density-functional theory (DFT) calculations. The DFT results indicate that the formation and migration energies of vacancies can be strongly influenced when a dopant is introduced at the first nearest neighbor shells around a vacancy. On the other hand, interstitial energetics are only slightly affected. Among the four elements, Ti and Pd generally decrease vacancy formation energies and increase vacancy migration energies more significantly than Al and Cu. The doping effects become more pronounced when the concentration of the substitutional dopants increases. Based on the energy distributions obtained from DFT, we build a kinetic Monte Carlo (kMC) model to assess the impact of dopants on vacancy-mediated diffusivity in the doped HEAs. Our results suggest that Ti and Pd can lower the tracer diffusivity in the considered HEAs and act as trapping sites, whereas Cu may enhance the atomic transport. This work indicates that substitutional doping in HEAs is an effective strategy in metallurgy to further tune the defect and transport properties of complex alloys.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Computational design of high entropy alloy coating for hydrogen turbine applications

This project aims to develop novel high entropy alloy (HEA)-based coatings to protect critical components in hydrogen-fueled turbine power system. The HEA-coatings will demonstrate superior performance in hydrogen combustion environment to commercial NiCoCrAlY coating in current natural gas turbine system. The HEA coating facilitates the formation of a protective scale of alpha-alumina to slow down the inward diffusion of oxidizing species and the outward diffusion of metal elements, and possesses ultrahigh corrosion and spallation resistance to prolong the service lifetime of critical components in hydrogen turbine power system. Aimed to accelerate the discovery of novel HEA coating compositions, high throughput computational modeling including CALPHAD and density functional theory and machine learning are performed to predict phase stability, oxygen permeability, oxidation rate constant, coefficient of thermal expansion, and mechanical properties. Based on the modeling and machine learning prediction, experimental validation is performed. Preliminary results will be presented and approaches to minimize oxidation will be discussed.

alloy design↗
DOE OSTI2023

Development & Validation of Low-Cost, Highly-Durable, Spinel-Based Materials for SOFC Cathode-Side Contact (Final Report)

A cathode-side contact layer is required to provide and maintain stable electrical conduction paths between the interconnect and cathode in a solid oxide fuel cell (SOFC) stack assembly and thus minimize the ohmic resistance and stack power loss. Current cathode-interconnect contact materials are based on noble metals, electrically-conductive perovskites, their composite materials, etc. These materials are either too expensive or do not possess the overall balanced performance required for the cathode-side contact application. To achieve the DOE SOFC system cost and performance stability goals, a new generation of low-cost, high-performance contact materials needs to be developed. In this project, spinel-based materials thermally converted from the Fe-Ni and Co-Mn based alloy precursors were developed and validated for the cathode-side contact application. The precursor alloy compositions were optimized via a combination of composition screening in the (Ni,Fe) 3 O 4 and (Mn,Co) 3 O 4 spinel system, alloy design using physical metallurgy principles, and cost considerations. The alloy powders with the desired composition and particle size were manufactured via gas atomization. The optimal process parameters for thermal conversion of these alloy precursor layers to a spinel-based layer were identified, i.e., 900°C x 2h in air, which is close to the initial stack firing condition. The area-specific resistances (ASRs) of the interconnect/contact/cathode test assemblies with the developed contact layer were determined for various durations (up to 5000 h) under simulated cathodic operation conditions. Some of the alloy-derived spinel contacts exhibited the lowest ASR and ASR degradation rate. The in-stack performance of the most promising alloy-derived contact layer is currently being evaluated via stack testing. To reduce the stack cost, the Co-Mn based alloy powders were utilized as the precursor for synthesis of dense spinel-based interconnect coating. By optimizing both the initial powder size/distribution and the alloy powder composition, a dense (Mn,Co) 3 O 4 -based spinel coating was achieved. Furthermore, co-sintering of the coating/contact dual-layer structure under the initial stack firing condition was realized by utilizing the tailored Co-Mn alloy precursors. Cost analysis of the developed technology indicated a total stack cost reduction of around 10.6% with the implementation of co-sintering of the interconnect coating and the contact layer during initial stack firing. Since low-cost processes such as screen printing is utilized in the precursor application and no reduction heat treatment is needed for the coating formation, the developed technology can be readily implemented at the industrial partner’s manufacturing facilities with no additional capital investment needed.

08 HYDROGEN↗
DOE OSTI2025

Initial Design Curves for Alloy 709 for an Improved Creep-fatigue Design Method

Creep-fatigue (CF) interaction damage is the primary damage mode for high-temperature structural components subjected to cyclic loading. Over the past several decades, researchers within the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC), Section III, Division 5, have focused on developing elevated temperature code rules to ensure conservative structural designs that mitigate CF failure in high-temperature reactors. The existing CF evaluation methodologies in the Code are based on the creep and fatigue damage diagram approach, which is complex and often excessively conservative. The alternative CF evaluation approach proposed here is intended to significantly simplify the evaluation procedure while reducing conservatism in high-temperature component design analysis. This alternative CF evaluation method integrates the elastic–perfectly plastic (EPP) analysis approach with the simplified model test (SMT) CF design concept, leveraging the advantages of both methods. This report presents the preliminary analysis and the approach for developing CF design curves for Alloy 709, utilizing fatigue and CF data generated for the 100,000-hr Code Case to support its qualification to ASME Section III, Division 5 for Class A construction of high temperature reactors. This study is to support the incorporation of Alloy 709 in this alternative CF evaluation method. Recommendations for the remaining work needed to complete the effort are also provided.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Creep Property of Intermetallic Dispersive Steels for Nuclear Applications

To meet the materials performance demands of next-generation nuclear and high-temperature energy systems, a new class of intermetallic-dispersive steels (IDS) has been designed through integrated computational thermodynamics and alloy design strategies. The IDS alloys incorporate coherent L1₂ (γ′-Ni₃Al) nanoprecipitates within an Fe–Ni–Cr austenitic matrix, engineered to achieve both high temperature strength and thermodynamic stability while suppressing the formation of detrimental δ-Ni₃Nb and η-Ni₃Ti phases. Initial creep testing of Ti-IDS and TiTa-IDS alloys demonstrates rupture lives comparable to or exceeding those of Inconel 718 and ODS steels, despite being fabricated through conventional ingot metallurgy. Step-load creep tests identified a stress threshold near 300–350 MPa for the onset of tertiary creep, and in-situ neutron diffraction experiments on Ti-IDS revealed clear load partitioning between the matrix and γ′ precipitates: elastic strain is shared by both phases, while plastic strain localizes in the matrix. These results confirm that stable γ′–matrix interfaces play a dominant role in retarding dislocation motion and enhancing creep resistance. In FY26, the program will conduct repeat creep rupture testing of TiTa-IDS at 650 °C/400 MPa, initiate long-term rupture testing of TiNb-IDS, and perform TEM-based microstructural characterization to elucidate dislocation–precipitate interactions and microstructural stability. Collectively, these efforts will establish the mechanistic foundation for next-generation high-temperature structural materials based on the IDS concept.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2025

Rigorous computation of short-range order unifies its controversial effects in complex concentrated alloys

Direct experimental observations of chemical short-range order (SRO) in complex concentrated alloys (CCAs) have triggered high interest. However, the reported effects of SRO on yield stresses are controversial, and their atomic-scale mechanisms are elusive, which limits our ability to utilize SRO in alloy design. Here we tackle this challenge using an advanced computational approach that rigorously takes into account the critical lattice distortion in CCAs and further verify our theoretical predictions with experiments. We show that the CoCrNi model alloy has a narrow temperature window around 670 °C for SRO formation. This explains why the mechanical effect of SRO is observed in some experiments but not in others. Here, we propose an effective alloy-doping method to control SRO and reveal atomic-bonding types that dominate SRO formation for different alloys. The strategies and insights generally apply to a broad spectrum of alloys, laying the foundation for designing advanced alloys by manipulating their SRO.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Genomic materials design: CALculation of PHAse Dynamics

The CALPHAD system of fundamental phase-level databases, now known as the Materials Genome, has enabled a mature technology of computational materials design and qualification that has already met the acceleration goals of the national Materials Genome Initiative. Here, as first commercialized by QuesTek Innovations, the methodology combines efficient genomic-level parametric design of new material composition and process specifications with multidisciplinary simulation-based forecasting of manufacturing variation, integrating efficient uncertainty management. Recent projects demonstrated under the multi-institutional CHiMaD Design Center notably include novel alloys designed specifically for additive manufacturing. With the proven success of the CALPHAD-based Materials Genome technology, current university research emphasizes new methodologies for affordable accelerated expansion of more accurate CALPHAD databases. Rapid adoption of these new capabilities by US apex corporations has compressed the materials design and development cycle to under 2 years, enabling a new “materials concurrency” integrated into a new level of concurrent engineering supporting an unprecedented level of manufacturing innovation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Towards stacking fault energy engineering in FCC high entropy alloys

Stacking Fault Energy (SFE) is an intrinsic alloy property that governs much of the plastic deformation mechanisms observed in fcc alloys. While SFE has been recognized for many years as a key intrinsic mechanical property, its inference via experimental observations or prediction using, for example, computationally intensive first-principles methods is challenging. This difficulty precludes the explicit use of SFE as an alloy design parameter. In this work, we combine DFT calculations (with necessary configurational averaging), machine-learning (ML) and physics-based models to predict the SFE in the fcc CoCrFeMnNiV-Al high-entropy alloy space. The best-performing ML model is capable of accurately predicting the SFE of arbitrary compositions within this 7-element system. Finally, this efficient model along with a recently developed model to estimate intrinsic strength of fcc HEAs is used to explore the strength–SFE Pareto front, predicting new-candidate alloys with particularly interesting mechanical behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Lightweight High-Temperature Alloys Based on the AlFeSi System

Automotive applications need low-cost, lightweight, high-temperature alloys to enhance efficiencies in systems such as internal combustion engines. The aluminum-iron-silicon (Al-Fe-Si) system provides an opportunity to develop such a material, as it comprises three of the lowest cost elements abundant in nature. Specifically, the $τ_{11}$-Al 4 Fe 1.7 Si (historically called $τ_{10}$) ternary intermetallic phase is a lightweight and low-cost phase with promising mechanical properties at high temperatures. However, the $τ_{11}$-Al 4 Fe 1.7 Si phase has a narrow compositional range, which should be expanded to use this alloy at a commercial scale. To increase this compositional range, equilibrium phase boundaries were expanded using alloy design strategies.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Design and Characterization of Hierarchically-Strengthened, Cast Al-Ce-Ni-Mn-Sc-Zr Alloys for High-Temperature Applications

We characterize the microstructure and mechanical properties of cast Al-Ce-Ni-Mn-Sc-Zr alloys designed for structural use above 300 °C. We first report on the effect of Ni on the as-cast phase formation, where all alloys consist of fine Al11Ce3 and Ni-rich eutectic phases, but the identity of the Ni-rich phase varies with Ni content. Furthermore, these alloys contain four coarsening-resistant strengthening phases as determined from SEM and APT investigations: (i) Al11Ce3 and (ii) Ni-rich micron-scale platelets formed during eutectic solidification, (iii) L12-Al3(Sc,Zr) nanoprecipitates formed during secondary aging, and (iv) Mn solute in the α-Al matrix. The Al-Ce-Ni-Mn-Sc-Zr alloy possesses higher microhardness and creep resistance than compositionally simpler alloys containing fewer of the strengthening phases, indicating that these strengthening mechanisms synergize to provide increased ambient- and elevated-temperature strength.

Ekaputra, Clement↗
DOE OSTI2024

The radiation instability of thermally stable nanocrystalline platinum gold

Here, recent experimentally validated alloy design theories have demonstrated nanocrystalline binary alloys that are stable against thermally induced grain growth. An open question is whether such thermal stability also translates to stability under irradiation. In this study, we investigate the response to heavy ion irradiation of a nanocrystalline platinum gold alloy that is known to be thermally stable from previous studies. Heavy ion irradiation was conducted at both room temperature and elevated temperatures on films of nanocrystalline platinum and platinum gold. Using scanning/transmission electron microscopy equipped with energy-dispersive spectroscopy and automated crystallographic orientation mapping, we observe substantial grain growth in the irradiated area compared to the controlled area beyond the range of heavy ions, as well as compositional redistribution under these conditions, and discuss mechanisms underpinning this instability. These findings highlight that grain boundary stability against one external stimulus, such as heat, does not always translate into grain boundary stability under other stimuli, such as displacement damage.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Homogenization of Dendritic Structures and the High-Temperature Strength of the Refractory High-Entropy Alloy MoNbTaVW

MoNbTaVW, a pioneering refractory high-entropy alloy (RHEA), is renowned for its exceptional strength at elevated temperatures. Like most RHEAs, it solidifies into a dendritic microstructure with steep concentration gradients, necessitating heat treatment for equilibration. Steep concentration gradients typically complicate mechanical property analysis and modeling, key challenges for high-throughput alloy discovery. This study examines the effects of high-temperature homogenization (1800 °C for 8 hours) on the microstructure and mechanical properties of MoNbTaVW across temperatures up to 1200 °C. Postmortem microstructural analysis, coupled with chemical, crystallographic, and mechanical assessments, revealed that yield strength was surprisingly insensitive to homogenization, with less than a 3 pct difference between as-cast and heat-treated materials. Nanoindentation confirmed minimal nanohardness changes across the dendritic structure at room temperature. However, homogenization significantly enhanced high-temperature work hardening, producing higher peak compressive strength. Both as-cast and homogenized MoNbTaVW exhibited room-temperature strengths of 1400 MPa, exceeding previously reported values. These findings demonstrate that high-temperature treatment enables microstructural homogenization without compromising strength, a unique behavior among RHEAs. In conclusion, while not universally applicable, this insight highlights the importance of understanding microstructural development in experimental alloys and offers a pathway to design alloys that achieve homogeneous-like properties without heat treatment.

Rietema, C. J. [Lawrence Livermore National Labora↗