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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Interlayer fusion bonding of semi-crystalline polymer composites in extrusion deposition additive manufacturing

This work focuses on the evolution of interlayer fracture toughness properties of fiber-reinforced, semi-crystalline polymers in the extrusion deposition additive manufacturing (EDAM) process. Further, this work bridges the gap between the additive process conditions (time-temperature history) and the effective layer-to-layer fracture properties developed within a printed component. This is the first step to predict delamination that can occur during printing, during cooling to room temperature after printing, and during service performance of an additively manufactured geometry. A phenomenological model is developed for fusion bonding of semi-crystalline polymer matrix composites by coupling the interdiffusion of polymer chains with the evolution of polymer crystallinity. While the interdiffusion is captured by reptation theory of polymer dynamics, the evolution of crystallinity is modeled by phenomenological crystallization kinetics and crystal melting dynamics. Further, a methodology is developed to determine the critical strain energy release rate, G IC of the interlayer interface and experiments are conducted utilizing the double cantilever beam fracture test geometry. In conclusion, predictions of GIC as a function of thermal history are compared with experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Defects and anomalies in powder bed fusion metal additive manufacturing

Metal additive manufacturing is a disruptive technology that is revolutionizing the manufacturing industry. Despite its unrivaled capability for directly fabricating metal parts with complex geometries, the wide realization of the technology is currently limited by microstructural defects and anomalies, which could significantly degrade the structural integrity and service performance of the product. Accurate detection, characterization, and prediction of these defects and anomalies have an important and immediate impact in manufacturing fully-dense and defect-free builds. As such, this review seeks to elucidate common defects/anomalies and their formation mechanisms in powder bed fusion additive manufacturing processes. They could arise from raw materials, processing conditions, and post-processing. While defects/anomalies in laser welding have been studied extensively, their formation and evolution remain unclear. Additionally, the existence of powder in powder bed fusion techniques may generate new types of defects, e.g., porosity transferring from powder to builds. Practical strategies to mitigate defects are also addressed through fundamental understanding of their formation. Such explorations enable the validation and calibration of models and ease the process qualification without costly trial-and-error experimentation.

42 ENGINEERING↗
DOE OSTI2024

Multifunctional nitrile additives for inducing pseudo-concentration gel-polymer electrolyte: Enabling stable high-voltage lithium metal batteries

High-voltage lithium metal batteries (LMBs) are promising for next-generation high-energy storage systems. Unfortunately, their implementation has been severely plagued by the interfacial instability between the high-voltage cathodes/lithium metal (LM) anodes and electrolytes. To tackle these challenges, a novel nitrile additive, 1,4-dicyanobenzene (DCB) (Synonyms: terephthalonitrile), is added to the in situ polymerized pentaerythritol tetraacrylate-based gel polymer electrolyte (GPE). The DCB additive, as demonstrated both theoretically and experimentally, plays a crucial role in altering the Li+ coordinated solvation structure within the GPE. This alteration leads to the formation of a pseudo-concentrated electrolyte with a tightly packed Li+ cluster, expanding the electrochemical stability window of the electrolyte. Moreover, the DCB-included GPE significantly improves its compatibility with both LM anode and high-voltage cathode, attributed to the modified solvation structure and the generated LiF-rich electrolyte/electrode interphases. Accordingly, the GPE enables stable cyclic performance of LMBs based on a 4.9 V LiNi 0.5 Mn 1.5 O 4 cathode at a low relative negative/positive ratio of 4, achieving a high reversible capacity of 123.8 mAh g -1 with a capacity retention of 87.7% over 500 cycles at 0.5 C. This work provides new insights into enhancing the cyclability of high-voltage LMBs via the synergistic effect of additives and GPE.

25 ENERGY STORAGE↗
DOE OSTI2025

Convective heat transfer enhancement through additively built multiscale micro-tetrahedron features

Use of Additive Manufacturing (AM) to improve the heat transfer characteristics of tip shrouds in high-pressure turbines is being considered by industries. Existing designs of these components integrate micro-cooling channels to reduce the bulk temperature for improved life. In this research, closely packed micro tetrahedron features in addition to AM roughness has been considered. Further, this multiscale surface characteristics increased surface area per unit volume available for heat exchange. Micro-tet features were designed, manufactured, characterized, and evaluated systematically while increasing their height. An enormous increase in the overall wetted surface area by 200 % was measured. The convective heat transfer enhancement was ~3.72 times EDM rough coupon, and friction factor enhancement was ~5.5 times EDM rough coupon. Furthermore, the proposed design offers 2.5 times enhanced heat transfer for a given 2 W pumping power compared to our EDM rough coupon. Heat transfer enhancement was observed to not vary strongly with increased Reynolds number. Such complex designs are only possible through additive manufacturing for increased heat transfer with little pressure penalty. Finally, increasing the micro-tet height for increased surface area and improved heat exchange beyond an upper limit might not be a significant benefit as it gets compensated by increasing skin friction.

42 ENGINEERING↗
DOE OSTI2020

Fatigue behavior and modeling for additive manufactured 304L stainless steel: The effect of surface roughness

The fatigue strength of additively manufactured metallic parts in their as-built surface condition is mainly dominated by the surface roughness. Post-processing is often inevitable to reduce surface roughness effects even though post-processing diminishes the main advantage of additive manufacturing, which is net-shaped direct-to-service production. This work investigates the underlying mechanisms responsible for fatigue failure of additively manufactured 304L stainless steel parts in as-built and machined/polished surface conditions. Both strain- and force-controlled, fully reversed fatigue tests were conducted to gain a comprehensive understanding of surface roughness effects on fatigue behavior. The sensitivity to surface roughness is shown to be dependent on the control mode, with stress-based fatigue tests showing greater sensitivity than strain-based fatigue tests. Moreover, the fatigue life estimation for as-built specimens was performed based on surface roughness parameters as well as the fatigue properties of the specimens in machined/polished surface condition of the material without using any fatigue data of specimens in as-built surface condition. Accordingly, the effect of surface roughness on the fatigue behavior could be estimated reasonably well in both strain-life and stress-life approaches.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Gradient process parameter optimization in additive friction stir deposition of aluminum alloys

As one of the most novel additive manufacturing methods, currently selection and optimization of processing parameters in additive friction stir deposition (AFSD) have mainly relied on experiments and subsequent characterization of microstructural and mechanical properties. Such approaches are both time- and resource-consuming. Therefore, an ultrasound elastography enhanced gradient process parameter optimization method was applied in the present work to obtain a window of optimized processing parameters for AFSD processing of aluminum alloy by varying both rotational and linear deposition speeds. Further, the quality of AFSD processed layer was investigated for physical nature of surface, dynamic elastic modulus, and microstructural aspects in cross-sections of the deposited layer. The efficiency in exploring process parameters was significantly enhanced by implementing a high-throughput screening experimental design based on application of gradient process parameters and continuous ultrasound elastographs. In addition, the applied ultrasonic elastography technique assisted in evaluating the homogeneity in microstructure and mechanical properties of AFSD sample over the entire gradients of the process parameters. The techniques adopted in current work can be further extended to identify suitable parameters for AFSD fabrication of components with desired mechanical properties such as hardness, fatigue, etc.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Microstructure and high temperature properties of tungsten processed via electron beam melting additive manufacturing

There is considerable interest in the adoption of additive manufacturing for processing refractory metals. The layer-wise fabrication approach enables opportunities for producing complex geometries which cannot be otherwise be achieved via powder metallurgy. However, the processing science is still in its nascent stages and structure–property relations are relatively unexplored. Fundamental research is needed to further develop the technology and enable the fabrication of refractory metals for high temperature applications. Here we focus on the processing of pure tungsten using electron beam melting additive manufacturing. Experimentally we develop a suitable processing window for achieving high density crack free material. Microstructural analysis reveals that the microstructure generally consists of a columnar structure with a (111) build direction fiber preference, although, fiber switching was observed. Process induced deformation is believed to drive the formation of subgrains whose boundaries exhibit a high dislocation density. Additionally, high temperature tensile testing reveals that the material exhibits excellent properties closer to that of annealed tungsten. Significant mechanical anisotropy was observed to be present which is likely driven by strong crystallographic texture.

36 MATERIALS SCIENCE↗
DOE OSTI2021

In situ synchrotron X-ray imaging and mechanical properties characterization of additively manufactured high-entropy alloy composites

Laser beam directed energy deposition has become an increasingly popular advanced manufacturing technique for materials discovery as a result of the in situ alloying capability. In this study, we leverage an additive manufacturing enabled high throughput materials discovery approach to explore the composition space of a graded W x (CoCrFeMnNi) 100–x sample spanning 0 ≤ x ≤ 21 at%. In addition to microstructural and mechanical characterization, synchrotron high speed x-ray computer aided tomography was conducted on a W 20 (CoCrFeMnNi) 80 composition to visualize melting dynamics, powder-laser interactions, and remelting effects of previously consolidated material. Results reveal the formation of the Fe 7 W 6 intermetallic phase at W concentrations> 6 at%, despite the high configurational entropy. Unincorporated W particles also occurred at W concentrations> 10 at% accompanied by a dissolution band of Fe 7 W 6 at the W/matrix interface and hardness values greater than 400 HV. In this work, the primary strengthening mechanism is attributed to the reinforcement of the Fe 7 W 6 and W phases as a metal matrix composite. The in situ high speed x-ray imaging during remelting showed that an additional laser pass did not promote further mixing of the Fe 7 W 6 or W phases suggesting that, despite the dissolution of the W into the Fe 7 W 6 phase being thermodynamically favored, it is kinetically limited by the thickness/diffusivity of the intermetallic phase, and the rapid solidification of the laser-based process.

36 MATERIALS SCIENCE↗
DOE OSTI2021

On the existence of orthorhombic martensite in a near-α titanium base alloy used for additive manufacturing

Additive manufacturing is a state-of-the-art production technology to produce tailor-made and highly complex parts. Among various other alloys, Ti base alloys are frequently used in this manufacturing technique due to their well-balanced properties and their wide range of applications. Allotropic phases and the occurrence of athermal phase transformations are the main reasons why these alloys hold a great development potential and are the basis of extensive use. High cooling rates during manufacturing lead to martensitic phases and the formation of nanometer-sized microstructures resulting in extraordinary strength. Simultaneously, such high cooling rates cause a high amount of lattice defects and the occurrence of residual stresses, which finally may result in delamination effects and cracks. Usually, a common approach to reduce residual stresses during additive manufacturing is to decrease thermal gradients by increasing the heat input or preheating the building platform. Instead of applying the typical approaches to lower thermal gradients, this study deals with the origin of the ‘softer’ orthorhombic martensite by accelerating the solidification process. The implementation of the orthorhombic phase in bulk components was inspired by a new phase transformation herein reported for the first time in the powder material, which also validates the possible occurrence of two martensitic phases in the same alloy. Various sophisticated characterization techniques like high energy and high-temperature X-ray diffraction, high-resolution transmission electron microscopy as well as atom probe tomography were applied to characterize this softer orthorhombic martensitic phase in detail aiming to highlight the opportunities accompanied by this new approach for additive manufacturing of titanium alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Phase stability in cast and additively manufactured Al-rich Al-Cu-Ce alloys

Additively manufactured (AM) eutectic Al alloy systems have been studied extensively for advantageous thermal stability and mechanical properties due to their refined microstructures. Al-Cu-Ce alloys are one subset of these AM eutectic alloys. Here we studied phase stability in AM Al-Cu-Ce alloys and compared it to that of conventionally cast ones. A new phase, Al 8 Cu 3 Ce, was identified in the microstructures of both AM and cast Al-Cu-Ce alloys. This Al 8 Cu 3 Ce phase was not previously included on experimental or thermodynamically calculated phase diagrams of the Al-Cu-Ce system. Therefore, we performed additional thermodynamic modeling of the system. These models were experimentally validated with cast and subsequently heat-treated Al-Cu-Ce alloys. We found that despite the refined microstructure of the AM alloys, the phases formed were consistent with the cast alloys, suggesting that AM processing did not significantly alter the formation and stability of phases from that in the conventional alloys. In conclusion, this work has resolved inconsistent previous descriptions of the Al-Cu-Ce ternary phase diagram in the Al-rich region and resulted in the addition of the Al 8 Cu 3 Ce as an equilibrium phase above 500 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Heterogeneous phase transformation pathways in additively manufactured Al-Ce-Mn alloys

Heat treatment of additively manufactured Al-Ce based multicomponent alloys leads to complex microstructure evolution. In this research, the ability to extend the phase transformation theories involving nucleation of a product phase from a heterogeneous multi-phase microstructure typical to that of additively manufactured samples is explored. The Al-10Ce-8Mn (wt%) was used as a model alloy system. Under additive manufacturing conditions different solidification microstructures were obtained due to spatial and temporal variations of thermal gradients (G) and liquid-solid interface velocities (R) within a given melt pool. Near the melt pool boundary (high G and low R, referred as MPB region), initially, Al 20 Mn 2 Ce forms from the liquid followed by a eutectic of FCC Al and Al 11 Ce 3 . In the melt pool interiors (low G and high R referred as ES region) a eutectic structure between FCC Al and Al 20 Mn 2 Ce is observed. During subsequent heat treatments, the MPB and ES regions transform into different sets of microstructures. In the MPB region, a fine globular microstructure containing FCC Al, Al 11 Ce 3 , Al 6 Mn, and Al 12 Mn results from the decomposition of Al 20 Mn 2 Ce. In the ES region a faceted Al 51 Mn 7 Ce 4 plate phase results from the decomposition of Al 20 Mn 2 Ce. The formation of the Al 51 Mn 7 Ce 4 phase within the eutectic microstructure at the boundaries of FCC Al and Al 20 Mn 2 Ce has not been reported in the literature. Further, these two distinct phase transformation pathways are rationalized based on the role of driving force on the nucleation of (Al 6 Mn) and/or metastable intermetallic (Al 51 Mn 7 Ce 4 ) phases at the interface of aluminum (FCC) and the non-equilibrium intermetallic (Al 20 Mn 2 Ce) phases.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Multi-material additive manufacturing of aluminum 6061-T6 alloy with stainless steel 304: Suppression of intermetallic compounds and interface growth mechanism

Fabricating integrated aluminum-steel structures is difficult because of metallurgical incompatibilities that promote intermetallic compound (IMC) formation at their interfaces. This work introduces a practical route for additively manufacturing 6061-T6 aluminum alloy (AA6061-T6) directly onto 304 stainless steel (SS304) using a high shear strain rate-assisted interfacial bonding mechanism. Through the friction extrusion deposition-based additive manufacturing method, both single- and multi-layer deposits of AA6061-T6 were successfully fabricated on SS304, yielding a robust hybrid multi-material structure. Comprehensive analyses of deposition quality, interface porosity, and bonding performance showed that the interface achieved a tensile strength exceeding 154 MPa under quasi-static loading. Microstructural observations revealed that the deposited aluminum layers experienced severe plastic deformation, resulting in pronounced grain refinement. Importantly, the interfacial zone was found to be free of brittle IMCs, instead containing a thin amorphous layer that evolved through a non-linear reaction-zone growth law. This solid-state additive strategy establishes a promising pathway for lightweight structural systems, nuclear energy component cladding, and multifunctional engineering components, redefining how dissimilar metals can be integrated for advanced applications.

Aluminum alloy↗
DOE OSTI2022

Evolution of carbide precipitates in Haynes® 282 superalloy processed by wire arc additive manufacturing

Precipitation hardening regulated with heat treatments is a critical technique for tuning the mechanical properties of Ni-based superalloys fabricated with additive manufacturing, where mechanical deformation is no longer viable for microstructural refinement. As one of the key precipitates, carbides prevail in the additively manufactured alloys, whose precipitation kinetics remain largely vague. This work studies the influence of heat treatments on the evolution of MC- and M 23 C 6 -type carbides within a Haynes® 282 superalloy prepared by wire arc additive manufacturing (WAAM). SEM-EDS analysis was performed to identify the evolution pathways of the carbides, and TEM and XRD characterizations were carried out to track the crystallographic features. The MC-type carbides are originally present in the as-printed alloy, which distribute uniformly across the whole material and remain largely unchanged in size during the heat treatments. By contrast, the incipiently non-existent M 23 C 6 -type carbides precipitate during an aging treatment at 1010 °C, which majorly extend along the grain boundaries as kinetically feasible sites. Further experimental and computational analysis confirms the enhancing effect of the M 23 C 6 -type carbides on the Vickers hardness. For the first time, this work revealed the evolution pathways of carbides within a Haynes® 282 superalloy prepared by WAAM, providing critical information for tunning the microstructure and mechanical properties. Finally, the carbide evolution kinetics established in this work can be potentially extended to other alloys prepared with WAAM, providing critical information to prevent mechanical failures associated with carbide coarsening.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Performance of discontinuity-free components produced by additive turning computer aided manufacturing strategy

Computer aided manufacturing (CAM) techniques for directed energy deposition (DED) affect the material properties of the manufactured component based on the scan strategy used. In this study, we investigate the material characteristics of turning-style toolpath strategies to generate axisymmetric components with additive manufacturing (AM), referred to in this research as additive turning. This novel approach leverages existing CAM technology for turning, where the component rotates around a stationary cutting tool, to generate toolpath trajectories for DED with varying wall-thicknesses and controlled deposition angles. This strategy allows for entire components to be deposited in one continuous deposition, resulting in reduced cycle-time and improved material usage efficiency compared to conventional AM strategies where the beam is switched off at the end of every layer. Results from this study show that the use of additive turning can produce over 99 % dense components with less variation and anisotropy in texture and hardness, as well as a lower variation in elongation to failure when compared to conventional strategies. This research highlights that various CAM strategies could be deployed for AM to improve process efficiency or enable localized control over part performance.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Direct measurement of the effective properties of an additively manufactured titanium octet truss unit cell using high energy X-ray diffraction

Additively manufactured lattice structures offer a high specific strength-to-density ratio in comparison to conventional, fully dense parts. The small feature size and intricate geometry of lattice structures make it challenging to directly characterize their mechanical properties. This study presents direct measurement of the elastic mechanical properties of an additively manufactured titanium alloy octet truss unit cell. Strut stress and strain were measured using high-energy X-ray diffraction during quasi-static compressive loading. The crystallographic stress-strain relationship was converted into the stress-strain relationship of the octet truss lattice unit cell using the known symmetry of the struts. The sample studied herein was best fit by an orthorhombic linear elastic stress-strain relationship. In conclusion, this technique shows promise for studying additively manufactured lattice structures at length scales not previously reported.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Solid additive engineering enables high-efficiency and eco-friendly all-polymer solar cells

Currently, morphology optimization of all-polymer solar cells (all-PSCs) strongly depends on the use of solvent additives, which are usually highly toxic and harmful to the environment and human health. Here, we report a green and volatile solid additive, 2-methoxynaphthalene (2-MN). It was found that the incorporation of 2-MN into a PM6:PY-DT blend can effectively manipulate the aggregations of PM6 and PY-DT during film depositing and thermal annealing processes and results in highly ordered molecular packing and favorable phase-separated morphology. Consequently, a record-high efficiency of 17.32% is achieved for the PM6:PY-DT device. Moreover, 2-MN-processed all-PSCs were fabricated by using non-halogenated solvent. High efficiencies of 17.03% and 16.67% are obtained for all-PSCs fabricated under nitrogen atmosphere and ambient conditions, respectively. Finally, our work shows that the utilization of 2-MN as a green and solid additive is a simple and feasible strategy to optimize the morphology and sheds new light on eco-friendly fabrication and application of all-PSCs.

14 SOLAR ENERGY↗
DOE OSTI2021

A critical review and commentary on recent progress of additive manufacturing and its impact on membrane technology

Membrane separations has been increasingly recognized as a key technology platform for improving the energy efficiency of many separations processes. Likewise, additive manufacturing (AM), or 3-dimensional (3D) printing as it is often called, is a rapidly emergent technology platform for manufacturing in many industrial sectors. It has become increasingly common to marry these two platforms to take advantage of the additive nature of 3D printing with the increasing need for membrane technology that is adaptable to separations needs. Conventional membrane manufacturing approaches, such as casting, typically result in thick membranes that limit productivity and potentially waste material in a non-performing support layer. Interfacial polymerization (IP) offered a new vision for thin-film composite desalination membranes, yet it was limited to certain chemistries while exhibiting other drawbacks. Additive manufacturing offers certain benefits over these techniques to membranes, including the ability to expand the library of materials that can be processed while also offering a degree of customization that is impossible in conventional manufacturing. This review article evaluates an increasing body of literature on using printing to make membranes and considers the limitations and opportunities for printing to enhance existing membrane technology and expand the reach of membranes into other industries. Furthermore, we also provide a perspective from leading experts in membrane technology to see where there are opportunities to use printing in different membrane science disciplines.

36 MATERIALS SCIENCE↗