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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

The effect of ball-milling time and annealing temperature on fracture toughness of Ni-3 wt.% SiC using small punch testing

Highlights: • The fracture energy of Ni-SiC is strongly dependent on the grain size of Ni matrix • The ball-milling time governs the fracture behaviour of Ni-3 wt.% SiC • A higher proportion of big SiC particles at grain boundary is responsible for a lower fracture toughness - Abstract: A set of dispersion strengthened Ni-3 wt.% SiC samples have been prepared via a powder metallurgy route for an application in molten salt reactor (MSR) systems. A mixture of 97 wt.% Ni and 3 wt.% SiC powder was prepared by varying the ball-milling time (8, 24, 36 and 48 h). The ball-milling process was followed by powder consolidation using spark plasma sintering (SPS) and rapid cooling to room temperature. The samples were then annealed at different temperatures (300 °C, 700 °C and 850 °C). The fracture behaviour of the Ni-3 wt.% SiC samples was investigated using the Small Punch Test (SPT). A scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) and electron back-scatter diffraction (EBSD), as well as transmission electron microscopy (TEM) were employed to examine the microstructure of the tested Ni-3 wt.% SiC samples. The obtained results show that the SPT fracture energy is strongly dependent on the grain size of Ni matrix, which is affected by ball-milling times and annealing temperature. It has been further found that the segregation of large SiC particles at grain boundaries promotes intergranular fracture and thus significantly reduces the fracture energy. The results indicate that the distribution and size of SiC particles at grain boundary is mainly affected by the ball-milling time. Hence, the ball-milling time governs the fracture toughness of Ni-3 wt.% SiC samples.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Controlling the MC and M2C carbide precipitation in Ferrium® M54® steel to achieve optimum ultimate tensile strength/fracture toughness balance

Highlights: • Small and uniformly distributed undissolved Ti-rich MC carbides control the grain size during the austenitization • High austenitizing temperature (1060°C) allows the full dissolution of the coarse carbides (size > several of 100nm) • Intensive nanometer-sized carbides precipitate during tempering thanks to the high supersaturation of alloying elements • Coarse carbides dissolution and nanometer-size carbides precipitation is necessary to achieve high UTS/K{sub I}C balance - Abstract: Ferrium® M54® exhibits an excellent UTS/K{sub 1C} balance allowing its application in aeronautical structures. This steel belongs to the Co-Ni UHS steels family with M{sub 2}C nanometer-size carbide precipitation during tempering. These steels provide very high strength with a very good fracture toughness thanks to the M{sub 2}C fine precipitation during tempering, but also because coarse particles are dissolved during austenitizing without grain coarsening. The goal of this article is to identify the different carbide populations in M54®. A small addition of Ti in M54® forms a Ti-rich MC carbide precipitation that is stable at high temperature. Consequently, during austenitization at 1060 °C, all other types of coarse carbides are dissolved in the matrix without grain coarsening. As a very small part of the initial carbon content is needed to form MC carbides, efficient and intensive nanometric M{sub 2}C carbide precipitation takes place during tempering, leading to very high final strength. Due to this double precipitation of carbides in M54®, the steel achieves an outstanding UTS/K{sub 1C} balance.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Austenite and precipitation in secondary-hardening ultra-high-strength stainless steel

Highlights: • Austenite and precipitation in Ferrium S53 steel were analyzed. • Austenite decreased to less than 5% after cryogenic treatment and tempering. • M{sub 2}C carbide could segregate inside martensite lath or in the larger parallel microstructure. - Abstract: Ferrium S53 is a new secondary-hardening ultra-high-strength stainless steel, with more Cr than other Co-Ni ultra-high-strength steels. Austenite has a great effect on the fracture toughness of this metal, and the carbides that are precipitated are the main strengthening phase of Ferrium S53 steel; in this study, its microstructural changes during heat treatment were observed and analyzed by X-ray diffraction (XRD), Optical microscope (OM), SEM, and transmission electron microscopy (TEM). About 40.85% retained austenite in the quenched sample is decreased to less than 5% after cryogenic treatment and tempering. In the final sample, block austenite is retained austenite, and film austenite around 5 nm in width is reverted austenite. Inside the martensite lath, parallel twin-like structures are actually segregated M{sub 2}C precipitates, and most of them are smaller than 20 nm. These precipitates can be aggregated into a several-micron-long parallel zonal microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Superplasticity and machinability in a four-phase ceramic

Highlights: ► New fine grained ceramic composites of ZrO{sub 2}–Al{sub 2}O{sub 3}–Mg{sub 2}AlO{sub 4}–LaPO{sub 4} were synthesized. ► At high temperatures, deformation strain rates are comparable to superplastic TZP. ► These are machinable at room temperature using conventional tungsten drill bits. ► Magnetoplumbite can form under certain process conditions. -- Abstract: Fine grained four-phase ceramic materials were fabricated to have a combination of high temperature superplasticity and room temperature machinability. The composite ceramics were made of 25 vol.% 3Y-TZP/8YSZ–25 vol.% Al{sub 2}O{sub 3}–25 vol.% MgAl{sub 2}O{sub 4}–25 vol.% LaPO{sub 4}, using LaPO{sub 4} powders fabricated in-house. X-ray diffraction and scanning electron microscopy revealed that the grain size for the best mixed samples was in the range of 600 nm, tetragonal ZrO{sub 2} transformed into monoclinic, and reactions in the sintered samples produced a new phase, magnetoplumbite (LaMgAl{sub 11}O{sub 19}) with lath-like grains. The formation of magnetoplumbite was facilitated by the presence of yttria and by a liquid phase generated at elevated temperatures. These four-phase ceramics had a maximum hardness of 12 GPa and fracture toughness was no more than 3 MPa√m. Deformation rates at 1400 °C under 40 MPa stress were in the superplastic range of 10{sup −3} s{sup −1} for most compositions. These four-phase ceramics were machinable as demonstrated using conventional tungsten drill bits.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Effects of Transition Metals on the Grain Boundary Cohesion in Tungsten

We report on the effects of alloying transition metals on the interfacial cohesion of W {Sigma}27<110>{l_brace}525{r_brace} symmetrical tilt grain boundary (GB). Density-functional-theory calculations show that the effects are related to the sensitivity of the d-orbital's occupation with respect to the atomic environments at the GB. Systematic trends of cleavage energy as a function of the electronic valence of the impurities were observed across different interfacial positions. Segregation formation energies were calculated to study the stability of the substitutional sites. All of the energetically preferred sites also correspond to the positions at which the alloying elements increase the GB cleavage energy. For each element, the more stable the configuration, the higher the cleavage energy. This finding is crucial in designing polycrystalline W-alloys with improved fracture toughness. Considering the solubility limit, the results suggest that Ta, Nb, Re, Ru, and Os are potential additives against intergranular fracture.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Gold-titania interface toughening and thermal conductance enhancement using an organophosphonate nanolayer

We demonstrate that a mercaptan-terminated organophosphonate nanolayer at gold-titania interfaces can give rise to two- to three-fold enhancement in the interfacial fracture toughness and thermal conductance. Electron spectroscopy reveals that interfacial delamination occurs at the metal-molecule interface near the gold-sulfur bonds, consistent with density functional theory calculations of bond energies. Qualitative correlation between interfacial fracture toughness and bond energies suggest that organophosphonate nanolayers are resilient to humidity-induced degradation. These results, and the versatility of organophosphonates as surface functionalization agents for technologically relevant materials, unlock uncharted avenues for molecular engineering of interfaces in materials and devices for a variety of applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Atomic and electronic structure of Ni-Nb metallic glasses

Solid state {sup 93}Nb nuclear magnetic resonance spectroscopy has been employed to investigate the atomic and electronic structures in Ni-Nb based metallic glass (MG) model system. {sup 93}Nb nuclear magnetic resonance (NMR) isotropic metallic shift of Ni{sub 60}Nb{sub 35}Sn{sub 5} has been found to be ∼100 ppm lower than that of Ni{sub 60}Nb{sub 35}Zr{sub 5} MG, which is correlated with their intrinsic fracture toughness. The evolution of {sup 93}Nb NMR isotropic metallic shifts upon alloying is clearly an electronic origin, as revealed by both local hyperfine fields analysis and first-principle computations. This preliminary result indicates that, in addition to geometrical considerations, atomic form factors should be taken into a description of atomic structures for better understanding the mechanical behaviors of MGs.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Application technologies for effective utilization of advanced high strength steel sheets

Recently, application of high strength steel sheets for automobiles has increased in order to meet a demand of light weighting of automobiles to reduce a carbon footprint while satisfying collision safety. The formability of steel sheets generally decreases with the increase in strength. Fracture and wrinkles tend to occur easily during forming. The springback phenomenon is also one of the issues which we should cope with, because it makes it difficult to obtain the desired shape after forming. Advanced high strength steel sheets with high formability have been developed in order to overcome these issues, and at the same time application technologies have been developed for their effective utilization. These sheets are normally used for cold forming. As a different type of forming, hot forming technique has been developed in order to produce parts with ultra high strength. In this report, technologies developed at NSSMC in this field will be introduced.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Low beryllium content Zr-based bulk metallic glass composite with plasticity and work hardenability

A modified Zr-based bulk metallic glass matrix composite Zr{sub 47.67}Cu{sub 40}Ti{sub 3.66}Ni{sub 2.66}Be{sub 6} has been produced by increasing the contents of elements of Zr and Cu with higher Poisson ratio and reducing the contents of Ti, Ni, and Be elements with lower Poisson ratio based on famous metallic glass former Vitreloy 1. A compressive yielding strength of 1804 MPa, fracture strength of 1938 MPa and 3.5% plastic strain was obtained for obtained metallic glass composite. Also, work-hardening behavior was observed during compressive experiment which was ascribed to the interaction of the in situ precipitated CuZr phase and shear bands.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Insight on the inconsistencies of Barkhausen signal measurements for radiation damage on nuclear reactor steel

This paper focuses on the use of magnetic measurements, using Barkhausen signals to determine the irradiation effects, attempting to predict fracture toughness changes on nuclear reactor structural materials and correlating these measurements to mechanical testing and microstructure. For this study, two types of nuclear reactor materials were investigated: one sensitive to irradiation effects, the JRQ IAEA's reference material (A533B- -type); and one resistant material, 15KH2MFA WWER's reactor pressure vessel steel. The samples were carefully identified within the original heat block, i.e. forged or rolled plate. These calibrated samples were irradiated at different neutron fluences up to 10{sup 23} n/m{sup 2}. We show how microstructural anisotropy can mask the irradiation effects in the magnetic measurements. A correlation between irradiation effects and the magnetic measurements is explained based on this study.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Oxide driven strength evolution of silicon surfaces

Previous experiments have shown a link between oxidation and strength changes in single crystal silicon nanostructures but provided no clues as to the mechanisms leading to this relationship. Using atomic force microscope-based fracture strength experiments, molecular dynamics modeling, and measurement of oxide development with angle resolved x-ray spectroscopy we study the evolution of strength of silicon (111) surfaces as they oxidize and with fully developed oxide layers. We find that strength drops with partial oxidation but recovers when a fully developed oxide is formed and that surfaces intentionally oxidized from the start maintain their high initial strengths. MD simulations show that strength decreases with the height of atomic layer steps on the surface. These results are corroborated by a completely separate line of testing using micro-scale, polysilicon devices, and the slack chain method in which strength recovers over a long period of exposure to the atmosphere. Combining our results with insights from prior experiments we conclude that previously described strength decrease is a result of oxidation induced roughening of an initially flat silicon (1 1 1) surface and that this effect is transient, a result consistent with the observation that surfaces flatten upon full oxidation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Environmental Influence on Fracture and Delamination of Electrically Conductive Adhesives

This paper presents our continued work on developing a degradation model for electrically conductive adhesive (ECA) interconnects in photovoltaic modules. Here, we characterize the fracture mechanics properties of an epoxy based ECA, for both critical and subcritical loading conditions. Emphasis is put on the influence of different environmental conditions such as temperature and humidity. We found that high levels of humidity not only weaken the adhesive joint but also promote subcritical debonding at significantly lower driving forces than in dry environments.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2015

Novel hard, tough HfAlSiN multilayers, defined by alternating Si bond structure, deposited using modulated high-flux, low-energy ion irradiation of the growing film

Hf{sub 1−x−y}Al{sub x}Si{sub y}N (0 ≤ x ≤ 0.14, 0 ≤ y ≤ 0.12) single layer and multilayer films are grown on Si(001) at 250 °C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a single Hf{sub 0.6}Al{sub 0.2}Si{sub 0.2} target in mixed 5%-N{sub 2}/Ar atmospheres at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf{sub 1−x−y}Al{sub x}Si{sub y}N films are controlled by varying the energy E{sub i} of the ions incident at the film growth surface while maintaining the ion-to-metal flux ratio constant at eight. Switching E{sub i} between 10 and 40 eV allows the growth of Hf{sub 0.78}Al{sub 0.10}Si{sub 0.12}N/Hf{sub 0.78}Al{sub 0.14}Si{sub 0.08}N multilayers with similar layer compositions, but in which the Si bonding state changes from predominantly Si–Si/Si–Hf for films grown with E{sub i} = 10 eV, to primarily Si–N with E{sub i} = 40 eV. Multilayer hardness values, which vary inversely with bilayer period Λ, range from 20 GPa with Λ = 20 nm to 27 GPa with Λ = 2 nm, while fracture toughness increases directly with Λ. Multilayers with Λ = 10 nm combine relatively high hardness, H ∼ 24 GPa, with good fracture toughness.

36 MATERIALS SCIENCE↗
DOE OSTI2017

The Effect of Vanadium on Morphology and Chemical Composition of Carbides in High Alloyed Chromium–Molybdenum Steels

Despite of the permanent progress of technique and finding of the new, modern materials that successfully replace metals, steel continues to play an important role in the technical practice. The tendency is to discover the new alloys with better mechanical and technological characteristics, compared to conventional and standard types of steels. High-alloyed Cr–Mo steel, with a high content of Vanadium is the new type of wear resistant material, with high hardness and satisfactory impact and fracture toughness. During the solidification process Vanadium, as a strong carbide forming element, creates a network of M{sub 7}C{sub 3} type carbide grains around the metal matrix, while in the matrix, the finely dispersed V{sub 6}C{sub 5} type carbides are formed. In this paper, the chemical composition and morphology have been studied of carbides and the other phases present in the metal matrix in 1.4 wt % C, 12 wt % Cr, 1.0 wt % Mo steels with additions up to 3.0 wt % V. Experimental results indicate that Vanadium affects the solidification process in high Chromium steel. Vanadium is distributed between eutectic M{sub 7}C{sub 3} carbide and the matrix, but its content in carbides is considerably higher. Vanadium changed the microstructure parameters of phases present in the structure of alloys, including volume fraction, size and morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2011

OECD MCCI project Small-Scale Water Ingression and Crust Strength Tests (SSWICS) SSWICS-1 test data report : thermal hydraulic results. Rev. 0 September 20, 2002.

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core/concrete interaction (MCCI) when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. However, due to the integral nature of these tests, several questions regarding the crust freezing behavior could not be adequately resolved. These questions include: (1) To what extent does water ingression into the crust increase the melt quench rate above the conduction-limited rate and how is this affected by melt composition and system pressure and (2) What is the fracture strength of the corium crust when subjected to a thermal-mechanical load and how does it depend upon the melt composition? A series of separate-effects experiments are being conducted to address these issues. The first employs an apparatus designed to measure the quench rate of a pool of corium ({approx}{phi}30 cm; up to 20 cm deep). The main parameter to be varied in these quench tests is the melt composition since it is thought to have a critical influence on the crust cracking behavior which, in turn, alters quench rate. The issue of crust strength will be addressed with a second apparatus designed to mechanically load the crust produced by the quench tests. This apparatus will measure the fracture strength of the crust while under a thermal load created by a heating element beneath the crust. The two apparatuses used to measure the melt quench rate and crust strength are jointly referred to as SSWICS (Small-Scale Water Ingression and Crust Strength). This report describes results of the first water ingression test, designated SSWICS-1. The report includes a description of the test apparatus, the instrumentation used, plots of the recorded data, and some rudimentary data reduction to obtain an estimate of the heat flux from the corium to the overlying water pool.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2011

OECD MMCI Small-Scale Water Ingression and Crust Strength Tests (SSWICS) SSWICS-2 test data report : thermal hydraulic results, Rev. 0 September 20, 2002.

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core/concrete interaction (MCCI) when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. However, due to the integral nature of these tests, several questions regarding the crust freezing behavior could not be adequately resolved. These questions include: (1) To what extent does water ingression into the crust increase the melt quench rate above the conduction-limited rate and how is this affected by melt composition and system pressure and (2) What is the fracture strength of the corium crust when subjected to a thermal-mechanical load and how does it depend upon the melt composition? A series of separate-effects experiments are being conducted to address these issues. The first employs an apparatus designed to measure the quench rate of a pool of corium ({approx}{phi}30 cm; up to 20 cm deep). The main parameter to be varied in these quench tests is the melt composition since it is thought to have a critical influence on the crust cracking behavior which, in turn, alters quench rate. The issue of crust strength will be addressed with a second apparatus designed to mechanically load the crust produced by the quench tests. This apparatus will measure the fracture strength of the crust while under a thermal load created by a heating element beneath the crust. The two apparatuses used to measure the melt quench rate and crust strength are jointly referred to as SSWICS (Small-Scale Water Ingression and Crust Strength). This report describes results of the second water ingression test, designated SSWICS-2. The report includes a description of the test apparatus, the instrumentation used, plots of the recorded data, and some rudimentary data reduction to obtain an estimate of the heat flux from the corium to the overlying water pool.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2011

OECD MMCI Small-Scale Water Ingression and Crust Strength tests (SSWICS) SSWICS-1 final data report, Rev. 1 February 10, 2003.; Report, Rev. 1

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core/concrete interaction (MCCI) when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. However, due to the integral nature of these tests, several questions regarding the crust freezing behavior could not be adequately resolved. These questions include: (1) To what extent does water ingression into the crust increase the melt quench rate above the conduction-limited rate and how is this affected by melt composition and system pressure; and (2) What is the fracture strength of the corium crust when subjected to a thermal-mechanical load and how does it depend upon the melt composition? A series of separate-effects experiments are being conducted to address these issues. The first employs an apparatus designed to measure the quench rate of a pool of corium ({approx}{phi}30 cm; up to 20 cm deep). The main parameter to be varied in these quench tests is the melt composition since it is thought to have a critical influence on the crust cracking behavior which, in turn, alters quench rate. The issue of crust strength will be addressed with a second apparatus designed to mechanically load the crust produced by the quench tests. This apparatus will measure the fracture strength of the crust while under a thermal load created by a heating element beneath the crust. The two apparatuses used to measure the melt quench rate and crust strength are jointly referred to as SSWICS (Small-Scale Water Ingression and Crust Strength). This report describes results of the first water ingression test, designated SSWICS-1. The test investigated the quench behavior of a 15 cm deep, fully oxidized PWR corium melt containing 8 wt% limestone/common sand concrete decomposition products. The melt was quenched at nominally atmospheric pressure. The report includes a description of the test apparatus, the instrumentation used, plots of the recorded data, and data reduction to obtain an estimate of the corrected heat flux from the corium to the overlying water pool. A section of the report is devoted to calculations of the conduction-limited heat flux that accounts for heat losses to the crucible holding the corium. The remainder of the report describes post test examinations of the crust, which includes permeability and mechanical strength measurements, and chemical analysis.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗