Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “solidification”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Measuring the melting curve of iron at super-Earth core conditions

The discovery of more than 4500 extrasolar planets has created a need for modeling their interior structure and dynamics. Given the prominence of iron in planetary interiors, we require accurate and precise physical properties at extreme pressure and temperature. A first-order property of iron is its melting point, which is still debated for the conditions of Earth’s interior. Here, we used high-energy lasers at the National Ignition Facility and in situ x-ray diffraction to determine the melting point of iron up to 1000 gigapascals, three times the pressure of Earth’s inner core. We used this melting curve to determine the length of dynamo action during core solidification to the hexagonal close-packed (hcp) structure. We find that terrestrial exoplanets with four to six times Earth’s mass have the longest dynamos, which provide important shielding against cosmic radiation.

58 GEOSCIENCES↗
DOE OSTI2013

Recrystallization and modification of the stainless-steel surface relief under photonic heat load in powerful plasma discharges

Targets made of ITER-grade 316L(N)-IG stainless steel and Russian-grade 12Cr18Ni10Ti stainless steel with a close composition were exposed at the QSPA-T plasma gun to plasma photonic radiation pulses simulating conditions of disruption mitigation in ITER. After a large number of pulses, modification of the stainless-steel surface was observed, such as the formation of a wavy structure, irregular roughness, and cracks on the target surface. X-ray and optic microscopic analyses of targets revealed changes in the orientation and dimensions of crystallites (grains) over a depth of up to 20 μm for 316L(N)-IG stainless steel after 200 pulses and up to 40 μm for 12Cr18Ni10Ti stainless steel after 50 pulses, which is significantly larger than the depth of the layer melted in one pulse (∼10 μm). In a series of 200 tests of ITER-grade 316L(N)-IG ITER stainless steel, a linear increase in the height of irregularity (roughness) with increasing number of pulses at a rate of up to ∼1 μm per pulse was observed. No alteration in the chemical composition of the stainless-steel surface in the series of tests was revealed. A model is developed that describes the formation of wavy irregularities on the melted metal surface with allowance for the nonlinear stage of instability of the melted layer with a vapor/plasma flow above it. A decisive factor in this case is the viscous flow of the melted metal from the troughs to tops of the wavy structure. The model predicts saturation of the growth of the wavy structure when its amplitude becomes comparable with its wavelength. Approaches to describing the observed stochastic relief and roughness of the stainless-steel surface formed in the series of tests are considered. The recurrence of the melting-solidification process in which mechanisms of the hill growth compete with the spreading of the material from the hills can result in the formation of a stochastic relief.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Laser-Induced Modification of the Surface of Ge{sub 2}Sb{sub 2}Te{sub 5} Thin Films: Phase Changes and Periodic-Structure Formation

Submicron periodic lattices are formed at the surface of phase-change-memory film materials based on the complex chalcogenide Ge{sub 2}Sb{sub 2}Te{sub 5} when exposed to nanosecond laser pulses. The geometric characteristics and structural properties of laser-induced lattices are studied by optical and atomic-force microscopies and Raman spectroscopy. It is shown that, at appropriately chosen parameters of exposure to laser radiation, it is possible to implement periodic modulation of the refractive index in the structures formed. Modulation is due to the postexposure solidification of grating ridges and valleys in different phase states, whose dielectric constants widely differ from each other. In the vicinity of the maxima of the wavy structure, the amorphous state is mainly formed, whereas in the region of minima, the Ge{sub 2}Sb{sub 2}Te{sub 5} structure corresponds mainly to the crystalline phase.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Tusas, Version 1.0

Tusas is a general / flexible software framework for solving coupled systems of onlinear partial differential equations. Tusas was originally developed for phase-field simulation of solidification. In order for Tusas to be effective, the PDEs must be compatible with structured or unstructured Lagrange (nodal) finite element discretizations and explicit (Euler) or implicit (Euler, Trapezoid, BDF2) temporal discretizations.

Newman, ChristopherK.↗
DOE OSTI2023

muMatScale

Code for modeling solidification microstructure based on the Cellular Automata method for binary/pseudo-binary alloys. This code is derived from the open-source software uMatIC developed at the Imperial College London https://www.imperial.ac.uk/engineering-alloys/research/software

Yuan, Lang [Univ. of South Carolina, Columbia, SC ↗
DOE OSTI2025

Establishing model credibility for process-microstructure-property relationships in additive manufacturing using exascale computing

Additive Manufacturing (AM) of alloys holds significant promise as a disruptive technology in various industries, yet its adoption is often hindered by challenges in achieving consistent part quality. These issues are primarily due to the complex process-microstructure-property (PSP) relationships inherent to AM. Computational models can greatly aid in understanding these relationships, but their widespread impact and adoption has been limited by a lack of validated, open-source, and computationally efficient PSP modeling frameworks and hardware limitations. Here, this study leverages the ExaAM software suite and data from the AMBench-2018 series of laser powder bed fusion (LPBF) benchmark experiments to perform a comprehensive model assessment, including verification, validation, sensitivity analysis, and uncertainty quantification. The RADICAL-EnTK workflow manager was used to perform an ensemble of heat transport, solidification, and mechanical response simulations on the exascale computer Frontier, considering uncertainties in critical model inputs such as laser spot size and nucleation parameters, and consisting of 125 explicit grain structure simulations and 7875 crystal plasticity simulations. For a selected location within the Inconel 625 AMBench-2018 test artifact, sensitivity analysis and uncertainty quantification were performed using the predicted distributions of grain structure and mechanical properties. Qualitative agreement was found between the predicted grain size and texture and the observed AMBench-2018 microstructure, the mean predicted yield stress was within 5% of the experimental measurement mean, and the mean predicted engineering stress at 5% strain was within 10% of the experimental measurement mean. The insights gained from development and validation of the ExaAM PSP modeling framework will help guide future directions for enhancing the credibility and reliability of PSP models in AM, thereby accelerating the adoption of AM technologies in various industries.

Additive manufacturing↗
DOE OSTI2016

Numerical investigation of electromagnetic pulse welded interfaces between dissimilar metals

The quality of an electromagnetic pulse weld is strongly affected by a variety of interacting physical phenomena including large plastic deformation, materials mixing, localised heating and rapid cooling, and possible localised melting and interfacial cracks and void. In the present study, a thermomechanically coupled dynamic model has been developed to quantitatively resolve the high speed impact joining interface characteristics as well as the process induced interface temperature evolution, defect formation and possible microstructural composition variations. Reasonably good agreement has been obtained between the predicted results and the experimental measurements in terms of interfacial morphology characteristics. The modelling framework is expected to provide further understanding of the hierarchical interfacial features of the non-equilibrium material joining process and the weld formation mechanisms.

Xu, W.↗
DOE OSTI2025

Time-temperature history and input files for ExaCA v2.0 scaling, performance, and demonstration simulations

The files in this data repository are used in various sections of the manuscript "ExaCA v2.0: A versatile, scalable, and performance portable cellular automata application for additive manufacturing solidification" by Rolchigo et al. (DOI: 10.1016/j.commatsci.2025.113734). The README file references dataset numbers as given in the manuscript's Table 2, as well as the manuscript's relevant subsections.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Thermal Effects on Microstructural Heterogeneity of Inconel 718 Materials Fabricated by Electron Beam Melting

Additive manufacturing (AM) technologies, also known as 3D printing, have demonstrated the potential to fabricate complex geometrical components, but the resulting microstructures and mechanical properties of these materials are not well understood due to unique and complex thermal cycles observed during processing. The electron beam melting (EBM) process is unique because the powder bed temperature can be elevated and maintained at temperatures over 1000 °C for the duration of the process. This results in three specific stages of microstructural phase evolution: (a) rapid cool down from the melting temperature to the process temperature, (b) extended hold at the process temperature, and (c) slow cool down to the room temperature. In this work, the mechanisms for reported microstructural differences in EBM are rationalized for Inconel 718 based on measured thermal cycles, preliminary thermal modeling, and computational thermodynamics models. The relationship between processing parameters, solidification microstructure, interdendritic segregation, and phase precipitation (δ, γ´, and γ´´) are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of thermal annealing on microstructure evolution and mechanical behavior of an additive manufactured AlSi10Mg part

The powder-bed laser additive manufacturing (AM) process is widely used in the fabrication of three-dimensional metallic parts with intricate structures, where kinetically controlled diffusion and microstructure ripening can be hindered by fast melting and rapid solidification. Therefore, the microstructure and physical properties of parts made by this process will be significantly different from their counterparts produced by conventional methods. This work investigates the microstructure evolution for an AM fabricated AlSi10Mg part from its nonequilibrium state toward equilibrium state. Special attention is placed on silicon dissolution, precipitate formation, collapsing of a divorced eutectic cellular structure, and microstructure ripening in the thermal annealing process. These events alter the size, morphology, length scale, and distribution of the beta silicon phase in the primary aluminum, and changes associated with elastic properties and microhardness are reported. In conclusion, the relationship between residual stress and silicon dissolution due to changes in lattice spacing is also investigated and discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2017

On single-phase status and segregation of an as-solidified septenary refractory high entropy alloy

Phase predictions and characterizations on as-solidified septenary refractory high-entropy alloy, CrMoNbReTaVW, are presented here. The simulated solidification process predicts a single body-centered-cubic (BCC) crystal structure with the tendency of compositional segregation. X-ray diffraction results confirm the “single-phase-like” BCC structure, while further experimental characterizations reveal the existence of multiple grains with significantly different compositions yet the same crystal structure and similar lattice parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Nondestructive evaluation of resistance spot-welded Al-steel joints

With increasing demand for better fuel economy for automobiles, multimaterial solutions are increasingly being utilized in the automotive industry for reducing weight in the vehicle body structure. This poses challenges in terms of joining dissimilar metals, especially those with vastly different properties such as aluminum to steel joining. General Motors has developed a new resistance spot-welding technique for dissimilar materials using a multi-ring domed (MRD) electrode and multiple solidification weld schedules to address this challenge. Originally developed for aluminum to aluminum resistance spot welding, this technology is being enabled as the mainstream aluminum joining solution to leverage existing infrastructure and workforce competency in resistance spot welding. With the recent expansion of MRD technology to aluminum to steel resistance spot welding, there is an ever-greater need to experimentally verify the quality of each aluminum to steel resistance spot-weld application with limited time and resources. Nondestructive evaluation (NDE) would allow the transfer of resistance spot-welding technology to dissimilar aluminum to steel joints. This article describes the current state of the art of aluminum to steel resistance spot welding and the challenges in developing a robust NDE process for this technology.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Technetium Getters to Improve Cast Stone Performance

The cementitious material known as Cast Stone has been selected as the preferred waste form for solidification of aqueous secondary liquid effluents from the Hanford Tank Waste Treatment and Immobilization Plant (WTP) process condensates and low-activity waste (LAW) melter off-gas caustic scrubber effluents. Cast Stone is also being evaluated as a supplemental immobilization technology to provide the necessary LAW treatment capacity to complete the Hanford tank waste cleanup mission in a timely and cost effective manner. Two radionuclides of particular concern in these waste streams are technetium-99 (99Tc) and iodine-129 (129I). These radioactive tank waste components contribute the most to the environmental impacts associated with the cleanup of the Hanford site. A recent environmental assessment of Cast Stone performance, which assumes a diffusion controlled release of contaminants from the waste form, calculates groundwater in excess of the allowable maximum permissible concentrations for both contaminants. There is, therefore, a need and an opportunity to improve the retention of both 99Tc and 129I in Cast Stone. One method to improve the performance of Cast Stone is through the addition of “getters” that selectively sequester Tc and I, therefore reducing their diffusion out of Cast Stone. In this paper, we present results of Tc and I removal from solution with various getters with batch sorption experiments conducted in deionized water (DIW) and a highly caustic 7.8 M Na Ave LAW simulant. In general, the data show that the selected getters are effective in DIW but their performance is comprised when experiments are performed with the 7.8 M Na Ave LAW simulant. Reasons for the mitigated performance in the LAW simulant may be due to competition with Cr present in the 7.8 M Na Ave LAW simulant and to a pH effect.

Cast Stone↗
DOE OSTI2021

Nanostructure and compositional segregation of soft magnetic FeNi-based nanocomposites with multiple nanocrystalline phases

Soft magnetic metal amorphous nanocomposite alloys are produced through rapid solidification and thermal annealing yielding nanocrystals embedded within an amorphous precursor. Similar free energies in Co-rich and FeNi-based alloy systems result in multiple nanocrystalline phases being formed during devitrification. Studies of multi-phase crystallization processes have been reported for Co-rich alloys but relatively few have investigated FeNi-based systems. A detailed characterization of compositional partitioning and microstructure of an optimally annealed FeNi-based MANC (Fe 70 Ni 30 ) 80 Nb 4 Si 2 B 14 alloy is presented through complementary high-resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). HRTEM demonstrates orientation relationships between FCC and BCC nanocrystals, suggesting heterogeneous nucleation of nanocrystals in the amorphous matrix or a cooperative mechanism of nucleation between BCC and FCC nanocrystallites. APT results show evidence for (i) the segregation of Fe and Ni between nanocrystals of different phases, (ii) B partitioning to the amorphous phase, and (iii) an Nb-enriched shell surrounding nanocrystals.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Development of high B s Fe–Ni-based metal amorphous nanocomposite by optimization of glass-forming ability

Thermocalc simulations identified compositions with good glass-forming ability (GFA) by locating minima in liquidus temperature, and solidification range in (Fe 70 Ni 30 ) x (B-Si-Nb) 100-x alloys with x = 82% and x = 85%, increased compared to previously developed x = 80% alloys. 3 compositions in the x = 82% system and 1 in the x = 85% system were successfully cast as amorphous magnetic ribbon. Magnetic properties of as-cast alloys showed improvements in Curie temperature and saturation induction, especially for the 85% alloy. Crystallization behavior in the 85% alloy was determined to occur as a 2-step process. Annealing studies showed (Fe 70 Ni 30 ) 82 Nb 2 Si 0 B 16 and (Fe 70 Ni 30 ) 82 Nb 3 Si 0 B 15 alloys to exhibit low coercivity and high B s with annealing. TEM results show significant crystallization in as-cast ribbon. The (Fe 70 Ni 30 ) 85 Nb 0.5 Si 0 B 14.5 alloy as-cast has small, uniformly distributed grains, allowing a useful nanocrystalline alloy to be produced as cast. Lastly, the parameter ΔT xg , the temperature range in which the material can be thermomechanically processed, was in the range of 12–23 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Modeling of non-equilibrium partitioning in direct metal deposited copper–iron concentrated alloys

The direct metal deposition (DMD) additive manufacturing process produces high cooling rates within a small melt pool and can lead to high amounts of solute trapping. These high cooling rates limit diffusion and lead to the formation of non-equilibrium phases. In this work, we utilize a numerical model to calculate the degree of solute trapping, defined as non-equilibrium partitioning. A theoretical case with overall composition fixed to 50Cu-50Fe at.%. was performed to observe the influence of increasing solidification rates. We then simulate DMD of equimolar Cu-Fe powder printed on mild steel substrate and the calculated non-equilibrium phase compositions were consistent with experimental observations reported earlier on this alloy composition. For a single deposited track, cooling rates are high enough to yield significant solute trapping. Here, the degree of solute trapping is highest near the free surface and has a gradient that correlates with the cooling rate gradient.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Integration of the Uncertainties of Anion and TOC Measurements into the Flammability Control Strategy for Sludge Batch 8 at the DWPF

The Savannah River National Laboratory (SRNL) has been working with the Savannah River Remediation (SRR) Defense Waste Processing Facility (DWPF) in the development and implementation of a flammability control strategy for DWPF’s melter operation during the processing of Sludge Batch 8 (SB8). SRNL’s support has been in response to technical task requests that have been made by SRR’s Waste Solidification Engineering (WSE) organization. The flammability control strategy relies on measurements that are performed on Slurry Mix Evaporator (SME) samples by the DWPF Laboratory. Measurements of nitrate, oxalate, formate, and total organic carbon (TOC) standards generated by the DWPF Laboratory are presented in this report, and an evaluation of the uncertainties of these measurements is provided. The impact of the uncertainties of these measurements on DWPF’s strategy for controlling melter flammability also is evaluated. The strategy includes monitoring each SME batch for its nitrate content and its TOC content relative to the nitrate content and relative to the antifoam additions made during the preparation of the SME batch. A linearized approach for monitoring the relationship between TOC and nitrate is developed, equations are provided that integrate the measurement uncertainties into the flammability control strategy, and sample calculations for these equations are shown to illustrate the impact of the uncertainties on the flammability control strategy.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Sludge Washing And Demonstration Of The DWPF Flowsheet In The SRNL Shielded Cells For Sludge Batch 8 Qualification

The current Waste Solidification Engineering (WSE) practice is to prepare sludge batches in Tank 51 by transferring sludge from other tanks to Tank 51. Tank 51 sludge is washed and transferred to Tank 40, the current Defense Waste Processing Facility (DWPF) feed tank. Prior to transfer of Tank 51 to Tank 40, the Savannah River National Laboratory (SRNL) typically simulates the Tank Farm and DWPF processes using a Tank 51 sample (referred to as the qualification sample). WSE requested the SRNL to perform characterization on a Sludge Batch 8 (SB8) sample and demonstrate the DWPF flowsheet in the SRNL shielded cells for SB8 as the final qualification process required prior to SB8 transfer from Tank 51 to Tank 40. A 3-L sample from Tank 51 (the SB8 qualification sample; Tank Farm sample HTF-51-12-80) was received by SRNL on September 20, 2012. The as-received sample was characterized prior to being washed. The washed material was further characterized and used as the material for the DWPF process simulation including a Sludge Receipt and Adjustment Tank (SRAT) cycle, a Slurry Mix Evaporator (SME) cycle, and glass fabrication and chemical durability measurements.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗