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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Enhancing Mechanical Properties of Carbon–Silicon Steel through Two–Stage Quenching and Partitioning with Bainitic Transformation: Ultimate Tensile Strength of 1875 MPa and Total Elongation of 8.03%

To achieve the desired microstructural properties, the ongoing development and innovation in new structural steels require novel thermal processing. This study aims to improve the mechanical properties of a commercial spring carbon–silicon steel by tailoring its microstructure through a process involving quenching and partitioning (Q&P) followed by bainitic transformation. A two–stage Q&P process is proposed to generate a nanoscale dispersion of stable retained austenite and carbides within the tempered martensite and bainite microstructure. The resulting tensile properties demonstrate a yield strength of 1280 MPa, an ultimate tensile strength of 1875 MPa, and a total elongation of 8.03%. These values surpass those of conventional spring 9254 steel, highlighting the effectiveness of the thermal treatment design. Microstructure analysis reveals the presence of tempered martensite, bainite sheaves, nanoscale carbides, and aggregates of retained austenite. Moreover, the resulting body–centered cubic matrix exhibits minimal lattice tetragonality of ≈1.0051, coupled with stable retained austenite featuring a carbon concentration of ≈3.42 ± 0.5 wt%, resulting in outstanding strength–ductility properties. In conclusion, these findings indicate that the proposed two–stage Q&P process, followed by bainitic transformation, significantly enhances the mechanical properties of carbon–silicon steels, making it a promising candidate for high–performance spring applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Adhesion Capabilities of Permanent Foaming Fixatives

DOE-EM have identified an operational requirement for a fixative that can immobilize and/or encapsulate residual contamination in 3D void volumes (pipes, gloveboxes, waste containers, etc.) during D and D activities. Failure to safely and effectively immobilize residual contamination can: Put workers at risk; Contaminate the public and environment; Drive up costs. Commercial-off-the-shelf (COTS) polyurethane (PU) foams is one possible solution and is currently being investigated by Savannah River National Lab (SRNL). Adhesion testing will dictate how well PU foams will adhere and immobilize residual contamination onto a substrate. Results can provide a performance criteria for Section 5 of ASTM E3191: Standard Specification for Permanent Foaming Fixatives Used to Mitigate Spread of Radioactive Contamination. Initial mechanical testing showed intumescent rigid PU foams were best in class (tensile, compression, TGA/DSC) Application of intumescent rigid PU foam in pipe scenario with 'contamination' showed excellent adhesion capabilities as long as foam had contact with pipe. The foam, however, was not able to penetrate 'contamination' but created pockets where the contamination interacted with the substrate. Pretreatment options of pipe were considered to produce better immobilization capabilities. Pretreatment options included COTS products like baking spray, rubber cement, and soap. Foam was still able to immobilize on a global sense, but not a local sense. Essentially acted as a mechanical plug. A tensile tester (MTS Criterion Series 43) was utilized to evaluate the tensile adhesion strength of 6 COTS PU foams. ASTM D1623: Tensile and Tensile Adhesion Properties of Rigid Cellular Plastics. Procedures: PU foams were cured between two smooth 2'' x 2'' 304 stainless steel coupons with hinges glued on plates for gripping support. Parameters Used: Pull rate of 0.1 in/min. Calculations: Tensile adhesion strength, elongation, and ImageJ analysis of how PU foam is left on substrate. Outcome: The PU foam with the best adhesion capabilities would be downselected for further evaluation to be used as a permanent foaming fixative. The rigid PU foams had the best adhesion capabilities with the R1 foam having a max load of 236 N. One of the I-R2 samples reached almost 450 N and another sample reached 2500 N before slipping. The other intumescent foam, I-F4, had the most coverage on the stainless steel coupon's surface from the ImageJ results (61.43% surface coverage). The intumescent foam, I-R2, will be the foam of choice for future testing due its fire retardant and adhesion capabilities. Future directions: Conduct the following experiment in a pipe scenario with the down-selected PU foam. Procedures: PU foam will be cured between in a 304 stainless steel pipe (ID: 4'', OD: 4.5'', Height: 4''). Parameters Used: Compression testing results will be referenced to determine if foam's adhesion strength would be greater its compression strength as its being compressed. Calculations: Compression strength, shear stress, total time elapsed. Conduct further adhesion testing with the down-selected PU foam (I-R2) to be treated as a permanent foaming fixative (PFF). Determine the minimum contact the PFF should have with the substrate for adequate results. Evaluate if PFF's adhesion capabilities is time dependent (3.1.5 of ASTM E3911). Subject PFF to seismic stressors addressed in Safety Basis of Interim Operation documents (SBIO) to further evaluate adhesion capabilities.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Mechanical Behavior Assessment of Ti-6Al-4V ELI Alloy Produced by Laser Powder Bed Fusion

The present work correlates the quasi-static, tensile mechanical properties of additively manufactured Ti-6Al-4V extra low interstitial (ELI, Grade 23) alloy to the phase constituents, microstructure, and fracture surface characteristics that changed with post-heat treatment of stress relief (670 °C for 5 h) and hot isostatic pressing (HIP with 100 MPa at 920 °C for 2 h under an Ar atmosphere). Ti-6Al-4V ELI alloy tensile specimens in both the horizontal (i.e., X and Y) and vertical (Z) directions were produced by the laser powder bed fusion (LPBF) technique. Higher yield strength (1141 MPa), higher tensile strength (1190 MPa), but lower elongation at fracture (6.9%), along with mechanical anisotropy were observed for as-stress-relieved (ASR) samples. However, after HIP, consistent and isotropic mechanical behaviors were observed with a slight reduction in yield strength (928 MPa) and tensile strength (1003 MPa), but with a significant improvement in elongation at fracture (16.1%). Phase constituents of acicular α' phase in ASR and lamellar α + β phases in HIP samples were observed and quantified to corroborate the reduction in strength and increase in ductility. The anisotropic variation in elongation at fracture observed for the ASR samples, particularly built in the build (Z) direction, was related to the presence of “keyhole” porosity.

42 ENGINEERING↗
DOE OSTI2023

Well-Tunable, 3D-printable, and Fast Autonomous Self-Healing Elastomers

Self-healing elastomers provide extended longevity of functional materials, due to their unique adaptability and durability. However, a major scientific challenge remains in developing materials with a rapid healing process combined with decent mechanical properties, that can be prepared by a relatively simple synthesis approach. Herein, we report a versatile design approach on self-healing elastomers by incorporating two different hydrogen bonding containing monomers, i.e., 2-[[(butylamino)carbonyl]oxy]ethyl acrylate (BCOE) and 2-ureido-4[1H]pyrimidinone (UPy) functionalized ethyl methacrylate. Poly(BCOE-r-UPy)s are synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization, and controlling the ratio of two monomers enables well-tunable mechanical properties with tensile strength ranging from 0.04 to 6.3 MPa and tensile strain up to 3,000 %. The characteristic dissociation energy is calculated from a temperature dependence of terminal relaxation followed by subtracting the segmental relaxation. The rapid autonomous self-healing is achieved when the molar composition of Poly(BCOE-r-UPy) is tailored to BCOE/UPy = 99/1. The self-healing process is monitored in situ by a helium-ion microscope, and its macroscopic study using tensile tests indicates that Poly(BCOE-r-UPy1) with 1 % molar ratio of UPy recovers 70 % of its original toughness at ambient temperature within 10 mins. 3D printing of Poly(BCOE-r-UPy) affords a self-healable 3D structure, demonstrating the adaptability of Poly(BCOE-r-UPy) for on-demand fabrication. The simplicity of synthesis, well-tunable mechanical properties, unique self-healability, and 3D printing capability of Poly(BCOE-r-UPy)s indicate their potential for a range of applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Relating phase transitions to pore size distributions and mechanical mortar properties in CSA-OPC-C$ based systems – The potential impact of delayed straetlingite formation

The scope of this research is to investigate the performance evolution of five ternary CSA-OPC-Cs systems. Time resolved thermodynamic modeling was employed to gain insight into changes in the volume fractions of the hydrating pastes and link these changes to trends in the pore size distributions of the mortars. Pore solution analyses were performed to investigate which hydrates have the potential to exert high crystallization pressures. In three out of five blends the resulting tensile stress exceeded the tensile strength of the materials, resulting in the occurrence of coarse pores, which could be linked to the measured compressive strengths. Two damaging crystallization processes were identified in the investigated blends. One is the continuous precipitation of ettringite at high supersaturation in a system with high anhydrite addition. The other is the delayed crystallization of straetlingite at high supersaturation and crystallization pressure in the confined environment of mature pastes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Estimation of constituent properties of concrete materials with an artificial neural network based method

Multi-scale models are developed for heterogeneous concrete materials to estimate their macroscopic mechanical properties in terms of micro-structural data. One crucial challenge of those models is the identification of local properties of constituent phases. In this paper, we present an efficient method based on Artificial Neural Networks (ANN). Typical concrete materials are taken as example. A macroscopic analytical strength criterion is established from three steps of nonlinear homogenization procedure. The macroscopic strength of materials is determined as a function of the frictional coefficient and cohesion of solid cement particles at nanometer scale, intra-particle pores, inter-particle pores and aggregates (inclusions). The objective is to identify the nanoscopic frictional coefficient and cohesion of cement particle from measured macroscopic values of uniaxial compression and tensile strengths. For this purpose, a numerical method based on the ANN is developed. With the analytical macroscopic strength criterion, sensitivity studies are first realized to identify the most important micro-structural parameters influencing the macroscopic strength of concrete. A simplified analytical macroscopic strength criterion is then proposed. A large dataset is further constructed through the inversion of the analytical strength criterion by using the aggregates volume fraction, porosity, macroscopic uniaxial tensile and compressive strengths as input variables and the frictional coefficient and cohesion of cement particles as output unknowns. An ANN model containing four hidden layers and 100 neurons in each layer is constructed and trained by using this dataset. Various types of validation of the ANN model are performed. It is found that the proposed ANN based model can effectively predict the frictional coefficient and cohesion of porous cement paste at the microscopic scale with a very good accuracy.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Alloy 709 Materials Procurement

Qualifying a new material for design and construction of elevated temperature nuclear components under Section III Division 5 of the BPVC requires measurement of a variety of properties, including tensile, creep, fatigue and creep-fatigue behavior in the relevant temperature range, and from the relevant product form, from a commercial scale heat. For the ART program the desired product form is hot rolled plate. This procurement is for a unique composition of stainless steel for which a commercial scale heat represents melting about 50,000 pounds of the alloy, resulting in about 45,000 pounds of usable plate. The Alloy 709 plate from this purchase will be provided to INL, Argonne National Laboratory and Oak Ridge National Laboratory for characterization of the relevant properties to support Code qualification.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Tailoring High Hardness and Rigidity in Biodegradable Thermoplastic Polyurethanes

In response to escalating environmental concerns, there is a pressing demand for materials capable of delivering both sustainability and robust mechanical properties, thereby substituting nonrenewable counterparts in various applications. This study presents a comprehensive investigation into the synthesis and characterization of biobased aliphatic thermoplastic polyurethanes (TPUs) that exhibit impressive mechanical properties, including tensile strength in the range of 48–41 MPa and flexural modulus up to 2.2 GPa. These biodegradable TPUs displayed high shore A and D hardness between 95 and 98 and 51–42, respectively, and thus can be categorized as “extra hard” plastics according to the durometer scale for PUs. Herein, we have prepared a series of four 100% biobased polyester polyols from biobased diacid and chain-extender as precursors with molecular weights varying from 500 to 1400 g/mol. The corresponding TPUs that were prepared by using an aliphatic diisocyanate were evaluated for their thermal stability, microphase separation, mechanical properties, and biodegradation. By leveraging renewable feedstocks, these TPUs offer a sustainable alternative to petroleum-derived materials, with their mechanical performance meeting conventional benchmarks. Furthermore, postcomposting analysis revealed significant surface degradation, affirming their biodegradability and environmental compatibility.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Microstructure and properties of additively manufactured Al–Ce–Mg alloys

Additive manufacturing of aluminum alloys is largely dominated by a near-eutectic Al-Si compositions, which are highly weldable, but have mechanical properties that are not competitive with conventional wrought Al alloys. In addition, there is a need for new Al alloys with improved high temperature properties and thermal stability for applications in the automotive and aerospace fields. In this work, we considered laser powder bed fusion additive manufacturing of two alloys in the Al–Ce–Mg system, designed as near-eutectic (Al–11Ce–7Mg) and hyper-eutectic (Al–15Ce–9Mg) compositions with respect to the binary L → Al + Al 11 Ce eutectic reaction. The addition of magnesium is used to promote solid solution strengthening. A custom laser scan pattern was used to reduce the formation of keyhole porosity, which was caused by excessive vaporization due to the high vapor pressure of magnesium. The microstructure and tensile mechanical properties of the alloys were characterized in the as-fabricated condition and following hot isostatic pressing. The two alloys exhibit significant variations in solidification structure morphology. These variations in non-equilibrium solidification structure were rationalized using a combination of thermodynamic and thermal modeling. Both alloys showed higher yield strength than AM Al-10Si-Mg for temperatures up to 350 °C and better strength retention at elevated temperatures than additively manufactured Scalmaloy.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Revealing Deformation Mechanisms in Polymer-Grafted Thermoplastic Elastomers via In Situ Small-Angle X-ray Scattering

The tunable properties of thermoplastic elastomers (TPEs), through polymer chemistry manipulations, enable these technologically critical materials to be employed in a broad range of applications. The need to “dial-in” the mechanical properties and responses of TPEs generally requires the design and synthesis of new macromolecules. In these designs, TPEs with nonlinear macromolecular architectures outperform the mechanical properties of their linear copolymer counterparts, but the differences in the deformation mechanism providing enhanced performance are unknown. Here, in situ small-angle X-ray scattering (SAXS) measurements during uniaxial extension reveal distinct deformation mechanisms between a commercially available linear poly(styrene)–poly(butadiene)–poly(styrene) (SBS) triblock copolymer and the grafted SBS version containing grafted poly(styrene) (PS) chains from the poly(butadiene) (PBD) midblock. The neat SBS (φ SBS = 100%) sample deforms congruently with the macroscopic dimensions, with the domain spacing between spheres increasing and decreasing along and transverse to the stretch direction, respectively. At high extensions, end segment pullout from the PS-rich domains is detected, which is indicated by a disordering of SBS. Conversely, the PS-grafted SBS that is 30 vol % SBS and 70% styrene (φ SBS = 30%) exhibits a lamellar morphology, and in situ SAXS measurements reveal an unexpected deformation mechanism. During deformation, there are two simultaneous processes: significant lamellar domain rearrangement to preferentially orient the lamellae planes parallel to the stretch direction and crazing. The samples whiten at high strains as expected for crazing, which corresponds with the emergence of features in the 2D SAXS pattern during stretching consistent with fibril-like structures that bridge the voids in crazes. The significant domain rearrangement in the grafted copolymers is attributed to the new junctions formed across multiple PS domains by the grafting of a single chain. In conclusion, the in situ SAXS measurements provide insights into the enhanced mechanical properties of grafted copolymers that arise through improved physical cross-linking that leads to nanostructure domain reorientation for self-reinforcement and craze formation where fibrils help to strengthen the polymer.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Microstructure evolution, enhanced aging kinetics, and mechanical properties of AA7075 alloy after friction extrusion

In the present study we utilized Friction Extrusion (FE) a solid phase processing technique to produce fully consolidated dense 5 mm rods of AA7075 alloy. The combination of large shear stresses and temperatures at the tool-billet interface during the FE process resulted in the formation of dynamically recrystallized ~2.0 μm equiaxed grains and fine uniformly distributed stable η (MgZn 2 ) precipitates ~25–100 nm in size. Formation of such a microstructure resulted in lower solutionizing temperature and times (flash annealing) as compared to the conventionally extruded counterparts. Here we demonstrate for the first time that the solutionizing times for the T6 heat treatment of AA7075 can be reduced by three times using this FE process. In addition to being an energy efficient process, FE also serves to improve the performance of AA7075 alloys by retaining their strength while enhancing the ductility of the material. The tensile data for samples that were flash annealed and artificially aged after FE processing showed exceptional increase in ultimate tensile strength by over 19% and yield strength by over 59%, compared with an as-FE-processed sample.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Ultra-grain refinement creates FCC pure cobalt with high strength and high ductility

Although pure cobalt is generally known to have a hexagonal close-packed (HCP) structure at room temperature, we show that its high-temperature face-centered cubic (FCC) phase can be strongly stabilized through grain refinement, resulting in FCC pure cobalt at room temperature. Ultrafine-grained (UFG) FCC cobalt exhibits a hierarchical microstructure consisting of dense stacking fault (SF) networks in the dominant FCC grains and numerous SFs and thin FCC layers within a few HCP plates. This unique microstructure leads to a high tensile strength exceeding 1 GPa, together with a tensile elongation of over 35%, thereby surpassing the well-known strength–ductility trade-off of pure metals. In-situ synchrotron X-ray diffraction revealed that the UFG FCC cobalt exhibited a markedly enhanced deformation-induced FCC→HCP martensitic transformation, which provided sustained strain hardening through the transformation-induced plasticity (TRIP) effect. Furthermore, ultra-grain refinement dramatically suppressed premature void and crack formation, causing a transition in the fracture mode from brittle to ductile. These findings advance the fundamental understanding of the phase stability and TRIP-assisted deformation in elemental cobalt and offer new guidelines for the microstructure-driven design of high-performance cobalt-based structural alloys.

Metastability↗
DOE OSTI2023

3D Printed eutectic aluminum alloy has facility for site-specific properties

Additive manufacturing (AM) has the ability to print structures with site-specific properties. Existing AM approaches for site-specific properties are, however, based on complex processing-microstructure relationships in conventional alloys that were not designed for this purpose. Here, in this work, we report a straightforward approach for achieving site-specific properties that takes advantage of eutectic solidification characteristics. We demonstrate that the yield strength of a eutectic Al-Cu-Ce-Zr alloy can be tuned by varying the laser scan speed in concert with hatch spacing in laser powder bed fusion AM. A faster speed increases solidification rate resulting in finer eutectic spacing and higher strength. The hatch spacing is reduced at faster speeds to ensure overlap between melt pools which become smaller with increasing scan speed. The yield strength and its anisotropy relative to build direction are further tunable with a heat treatment. The scan speed-eutectic spacing-strength relationship is successfully applied to print a complex pattern of site-specific hardness in the alloy. The generalized principle of using AM for a eutectic alloy to create site-specific properties and anisotropy in properties is demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Strain hardening magnesium-silicate-hydrate composites (SHMSHC) reinforced with short and randomly oriented polyvinyl alcohol microfibers

Magnesium-silicate-hydrate (M-S-H) cement has emerged as an alternative binder with potentially lower energy requirements and emissions. Due to the intrinsically low pH values of its matrix, however, normal steel reinforcement is not appropriate for M-S-H system. To toughen the matrix and to overcome the brittle nature of the material, a new strain hardening magnesium-silicate-hydrate composite (SHMSHC) is developed for the first time by incorporating 2 vol% short and randomly oriented polyvinyl alcohol (PVA) microfibers. The resulting SHMSHC exhibits significant strain hardening with a tensile strain capacity of more than 3%, a compressive strength beyond 50 MPa and a tensile strength of around 3 MPa. Remarkably, saturated multiple cracking with a tight crack width less than 10 μm invisible to the human naked eyes was observed. The newly developed SHMSHC addresses the fundamental challenge of M-S-H binder and is expected to widen possible application areas of M-S-H system.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Use of microbial carbonation process to enable self‑carbonation of reactive MgO cement mixes

The low hydration and carbonation of reactive MgO cement (RMC) under ambient conditions causes prolonged setting and low compressive strengths (~4 MPa). This study proposed a unique technique which led to the enhancement of the hydration and carbonation processes via the synergistic combination of microbial carbonation process (MCP) with a hydration agent (HA) that enabled the self‑carbonation of RMC-based mixes without using of any special curing environments. Through hydrolysing urea (CO(NH{sub 2}){sub 2}) using ureolytic bacteria, CO{sub 3}{sup 2−} ions were produced to facilitate the carbonation of dissolved Mg{sup 2+} ions to form hydrated magnesium hydroxy carbonates (HMHCs). The self‑carbonation of RMC enabled by the MCP resulted in formation of brucite with a poor crystallinity and its rapid conversion into HMHCs, which improved the setting time and compressive strength of RMC-based samples. The simultaneous use of MCP with 2 M urea and HA revealed HMHCs with improved morphologies, resulting in the highest compressive strength (~15 MPa).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Cryo-quenched Fe–Ni–Cr alloy decorative steel single crystals II: Alloy phases, structure, hardness, tensile, tribological, magnetic and electronic properties

We have previously reported (Boatner et al., J. Alloys Compd. 691 (2017) 666–671) on the discovery, formation, processing, and application of a new decorative ternary steel alloy and on its use in a wide range of practical applications including: custom and commercial knives, art objects, jewelry, electronics, and furniture. This decorative property results when polished single crystals of the 70 wt%Fe-15 wt%Ni-15 wt% Cr austenitic alloy are cryo-quenched into the martensitic phase resulting in the formation of a three-dimensional raised pattern of mixed austenitic/martensitic laths. These laths propagate across large dimensions of the material due to the absence of grain boundaries in the single crystal. The macroscopic optically reflective 3-D decorative pattern reproduces the structural symmetry inherent in the single-crystal orientation. This pattern results solely from the metallurgical phase properties of the ternary alloy and is completely distinct from the properties of Damascus steels or more modern so-called pattern-welded steels. Here we use X-ray diffraction, nanoindentation, hardness measurements/scratch testing, tribological measurements, and alloy resistivity and magnetization methods to obtain a more fundamental and comprehensive study of the effects of the austenitic/martensitic phase transition on the structural and physical properties of the 70 wt%Fe-15 wt%Ni-15 wt% Cr alloy. These results reveal new insight into irreversible phenomena that are associated with the inhibited phase transition on heating of the two-phase, mixed austenitic/martensitic structure that is formed subsequent to cryo-quenching the alloy crystal to 77 K.

36 MATERIALS SCIENCE↗