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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Microstructure, Thermal, and Mechanical Properties Relationships in U and UZr Alloys (Final Report)

Uranium-zirconium (U-Zr) alloys are candidate fuel systems for transmutation based reactors that can be used to burn long-lived minor actinides and fission products in fast spectrum reactors. Metallic fuels have also been gaining more recent attention for applications as accident tolerant fuels, as well as for use in small modular reactors. This research focused on a “science-based” approach to capture the connections between U and U-Zr alloys’ three-dimensional (3-D) microstructure, thermal properties, and mechanical properties through closely coordinated experiments and modeling efforts from the unirradiated to the irradiated fuels. Advanced characterization and modeling techniques were used to understand irradiation-induced microstructural evolution and its direct impact on the thermal and mechanical properties of U and U-Zr fuel. Closely coordinated experiments and modeling were performed to provide crucial data that does not currently exist. Overall, this research spanned multiple length and time scales within the models and experiments. The scope of the research encompassed the understanding of the irradiation effects in U and various U-Zr alloys with particular attention paid to three task areas: (1) microstructural evolution, (2) in-situ/ex-situ thermal and mechanical properties, and (3) multiscale modeling connections to microstructure, thermal, and mechanical properties. This research resulted in (1) the 3-D characterization of neutron irradiated U-Zr fuel in multiple phase regions to better understand fission gas swelling and constituent redistribution, (2) development of a microstructural model linking thermal and mechanical properties via in situ Raman and nanoindentation, (3) and mesoscale phase field modeling was coupled with the AEH method in the MOOSE framework was used to calculate the effective thermal conductivities of U-Zr fuels consisting of α-U and δ-UZr 2 heterogeneous microstructures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Evolution of microstructure, strain and physical properties in oxide nanocomposite films

Using LSMO:ZnO nanocomposite films as a model system, we have researched the effect of film thickness on the physical properties of nanocomposites. It shows that strain, microstructure, as well as magnetoresistance strongly rely on film thickness. The magnetotransport properties have been fitted by a modified parallel connection channel model, which is in agreement with the microstructure evolution as a function of film thickness in nanocomposite films on sapphire substrates. The strain analysis indicates that the variation of physical properties in nanocomposite films on LAO is dominated by strain effect. These results confirm the critical role of film thickness on microstructures, strain states, and functionalities. Furthermore, it shows that one can use film thickness as a key parameter to design nanocomposites with optimum functionalities.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure Characteristic and Mechanical Properties of High-Strength Mg-Nd-Zn-Zr Alloy Seamless Tube Produced by Integrated Extrusion

Large size seamless tubes of Mg-3.0Nd-0.4Zn-0.4Zr alloy (NZ30K, in weight percent) were prepared by integrating backward extrusion with forward extrusion. Microstructure, mechanical properties, aging behavior and texture of the tubes were investigated. The microstructure of as-extruded tube is characterized by the blend of considerably elongated grains and fine equiaxed grains. The maximum values of yield strength and ultimate tensile strength, i.e., 191 and 245 MPa, were obtained in the as-extruded tubes, and these values were increased to 212 and 267 MPa in the peak-aged tubes (T5), implying an increasing ratio of 9 and 11%, respectively. The peak value of the Vickers’ micro-hardness of the NZ30K tubes extruded at 673, 723 and 753 K are 66, 64 and 60 (kilogram-force per square millimeter), respectively. The texture of NZ30K tube is weak, the primary mechanism behind which is suggested to be the particle-induced nucleation responsible for the promotion of recrystallization.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure evolution and mechanical properties of the compressively deformed AgInCd alloy during annealing treatment

Highlights: • The microstructure of AgInCd alloy during annealing treatment is investigated. • Nanoscale deformation twins are formed in the deformed AgInCd alloy. • Deformation twins are transformed into stacking faults by detwinning mechanism. • Annealing twins show higher thermal stability than deformation twins. - Abstract: The microstructure evolution and mechanical properties of the compressively deformed AgInCd alloy during annealing treatment have been investigated in the present study. In the deformed AgInCd alloy, many deformation markings are formed and these deformation markings are mainly composed of nanoscale deformation twins. The AgInCd alloy exhibits a significant work hardening capability because of the formation of deformation twins. The recrystallization temperature of the deformed AgInCd alloy is between 300 °C and 350 °C. In the AgInCd alloy annealed at 300 °C, the deformation twins are eliminated and a large number of dark strips consisting of stacking faults are presented in the un-recrystallized regions, indicating that the deformation twins are transformed into stacking faults by the detwinning mechanism. The annealing twins show higher thermal stability than the deformation twins. The strength and microhardness of the deformed AgInCd alloy gradually decrease with the increase of annealing temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Three-Dimensional Additively Manufactured Microstructures and Their Mechanical Properties

Metal additive manufacturing (AM) allows for the freeform creation of complex parts. However, AM microstructures are highly sensitive to the process parameters used. Resulting microstructures vary significantly from typical metal alloys in grain morphology distributions, defect populations and crystallographic texture. AM microstructures are often anisotropic and possess three-dimensional features. These microstructural features determine the mechanical properties of AM parts. Here, we reproduce three “canonical” AM microstructures from the literature and investigate their mechanical responses. Stochastic volume elements are generated with a kinetic Monte Carlo process simulation. A crystal plasticity-finite element model is then used to simulate plastic deformation of the AM microstructures and a reference equiaxed microstructure. Results demonstrate that AM microstructures possess significant variability in strength and plastic anisotropy compared with conventional equiaxed microstructures.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Comparison of the Microstructure and Flux Pinning Properties of Polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-d} Containing Zn{sub 0.95}Mn{sub 0.05}O or Al{sub 2}O{sub 3} Nanoparticles

Here we compare the microstructure and flux pinning properties of polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-d} (Y-123 or YBCO) containing either Al{sub 2}O{sub 3} or Zn{sub 0.95}Mn{sub 0.05}O nanoparticles. Samples were prepared using a standard solid-state reaction process, and nanoparticles were added up to a concentration of 0.1 wt%. The crystal structure, microstructure, electrical and magnetic properties were analyzed using X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM), and electrical resistivity and DC magnetization measurements, respectively. TEM observations showed that the addition of Zn{sub 0.95}Mn{sub 0.05}O resulted in a high density of fine twins and a variety of interacting microstructures, while Al{sub 2}O{sub 3} addition resulted in a high density of Al-rich nanoscale inhomogeneities embedded in the Y-123 matrix. Flux pinning forces were determined, and predominant pinning mechanisms in the prepared samples were proposed. We evaluated the superconducting properties of YBCO considering the effects of adding insulating or magnetic nanoparticles.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Numerical simulation of temperature field, microstructure evolution and mechanical properties of HSS during hot stamping

The hot stamping of boron steels is widely used to produce ultra high strength automobile components without any spring back. The ultra high strength of final products is attributed to the fully martensitic microstructure that is obtained through the simultaneous forming and quenching of the hot blanks after austenization. In the present study, a mathematical model incorporating both heat transfer and the transformation of austenite is presented. A FORTRAN program based on finite element technique has been developed which permits the temperature distribution and microstructure evolution of high strength steel during hot stamping process. Two empirical diffusion-dependent transformation models under isothermal conditions were employed respectively, and the prediction capability on mechanical properties of the models were compared with the hot stamping experiment of an automobile B-pillar part.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Microstructural, mechanical and optical properties research of a carbon ion-irradiated Y 2 SiO 5 crystal

Ion irradiation has been a popular method to modify properties of different kinds of materials. Ion-irradiated crystals have been studied for years, but the effects on microstructure and optical properties during irradiation process are still controversial. In this study, we used 6 MeV C ions with a fluence of 1 × 10 15 ion/cm 2 irradiated Y 2 SiO 5 (YSO) crystal at room temperature, and discussed the influence of C ion irradiation on the microstructure, mechanical and optical properties of YSO crystal by Rutherford backscattering/channeling analyzes (RBS/C), X-ray diffraction patterns (XRD), Raman, nano-indentation test, transmission and absorption spectroscopy, the prism coupling and the end-facet coupling experiments. We also used the secondary ion mass spectrometry (SIMS) to analyze the elements distribution along sputtering depth. Finally, 6 MeV C ions with a fluence of 1 × 10 15 ion/cm 2 irradiated caused the deformation of YSO structure and also influenced the spectral properties and lattice vibrations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Influence of the Composition on the Solidification Path, Microstructure Evolution and Mechanical Properties of Al-Cu-Mg Alloys

The influence of the initial composition on the solidification path, microstructure evolution, thermophysical properties and mechanical properties of Al-Cu-Mg alloys was investigated. The solidification paths of the investigated alloys were determined by analyzing the solidification structure, and then the experimentally determined paths were compared with those from the calculated results. Three of the investigated alloys experienced typical ternary eutectic solidification, and the other four alloys experienced quasiperitectic reactions. Due to differences in the initial compositions, different eutectic morphologies were formed during the solidification process. The binary eutectic phases, (α-Al + Al{sub 2}Cu) and (α-Al + Al{sub 6}CuMg{sub 4}), and the (α-Al + Al{sub 6}CuMg{sub 4} + Al{sub 8}Mg{sub 5}) ternary eutectic phase tended to exhibit divorced growth, and the (α-Al + Al{sub 2}CuMg), (α-Al + Al{sub 6}CuMg{sub 4}) and (α-Al + Al{sub 2}Cu + Al{sub 2}CuMg) eutectic phases tended to exhibit coupled growth. The results indicated that the initial composition, solidification path, microstructure and morphology could greatly affect the melting enthalpy, microhardness and compressive strength of the investigated Al-Cu-Mg alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The microstructure effects on irradiation response of ferritic – martensitic steels

Microstructural optimization to achieve greater mechanical strength has been one of the focuses in ferritic–martensitic steels development. However, these optimized microstructures’ effects on the radiation response are not well known. In this work, two ferritic–martensitic steels (9Cr-NbMo and 9Cr-Ta) underwent neutron irradiation in the High Flux Isotope Reactor, and their room-temperature post-irradiation tensile properties and microstructure evolutions were investigated and compared. These two steels exhibit similar pre-irradiation tensile behavior, and their yield strengths are higher than that of other ferritic–martensitic steels by about 200–250 MPa. Microstructural characterization on pre-irradiated materials reveals a smaller grain size in 9Cr-Ta (2.8 ± 0.3 μm in 9Cr-Ta versus 4.3 ± 0.5 μm in 9Cr-NbMo) but higher dislocation density and precipitate density in 9Cr-NbMo. As is common for ferritic–martensitic steels at low irradiation temperatures (less than about 0.45T m ), irradiation-induced hardening at 400 °C was observed for both alloys. Irradiation at 490 °C causes the two alloys to exhibit different tensile behavior: 9Cr-Ta softens by 208 MPa in yield stress, whereas 9Cr-NbMo maintains strength. Additionally, microstructural characterizations were performed, including precipitate growth, dislocation, and defect formation. Using the barrier hardening model for microstructure–property correlation, the softening in irradiated 9Cr-Ta is primarily attributed to the significant dislocation recovery, while the strength lost from the slight dislocation recovery in 9Cr-NbMo was compensated by the additional strength from the irradiation-induced cavities. The microstructure effect (primarily precipitate, dislocation and boundary) on the radiation response is discussed herein.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Investigation on Microstructural Evolutions and Mechanical Properties of P92 Steel During Thermal Processing

The evolution of the microstructure of P92 steel during heat processing has a significant effect on the final performance of steel products and is thus an area of critical interest. Accordingly, the grain growth behavior of austenite and δ-ferrite changes in P92 steel is comprehensively investigated in this study through thermodynamic calculations and physical simulation. The results show that the A{sub C1}, A{sub C3} and γ–δ transformation temperatures of P92 steel are 841 °C, 878 °C and 1095 °C, respectively, which are comparable to the measured values of 850 °C, 879 °C and 1175 °C, respectively. When the temperature exceeds the A{sub C1} temperature, the austenite grain size increases with increasing temperature and longer holding times, and the growth rate of austenite grains increases with higher temperatures but decreases with holding time at a certain temperature. A model that shows the austenite grain growth kinetics is established: D{sup n} − D{sub 0}{sup n} = 2.03 × 10{sup 16}exp(− 498,770/RT)t, in which the time exponent n decreases from 4.52 to 2.11 with an increase in temperature from 1000 °C to 1200 °C due to the reduced pinning effect resultant of the dissolution of precipitates, M{sub 23}C{sub 6}, VX and NbX at 887 °C, 1073 °C and 1200 °C, respectively. The formation of δ-ferrite at 1200 °C when held for 600 s and 1300 °C when held for 60 ~ 600 s causes a smaller austenite grain size. The relationship between the evolution of the microstructure of P92 steel and the mechanical properties is also studied. The results show that the prior austenite grain size has an inverse relationship with impact energy and ultimate tensile strength at 620 °C, while the presence of soft δ-ferrite leads to a reduction in the microhardness, impact energy and ultimate tensile strength at 620 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure, Texture, and Mechanical Properties of Ni-W Alloy After Accumulative Roll Bonding

In this study, the microstructure, texture, and mechanical properties evolution of Ni-14W (wt.%) alloy processed up to four cycles of accumulative roll-bonding (ARB) were investigated using electron backscatter diffraction, microhardness measurements, and tensile tests. The initial equiaxed grains, with an average size of 10 μm, underwent a strong refinement after ARB processing. The elongated ultrafine grains were parallel to the rolling direction, with a grain thickness of 0.2 µm. The texture after ARB processing was characterized by the typical rolling components (Copper, S and Brass), which showed a tendency toward stabilization after four cycles. The microhardness increased substantially (+ 86%) and seemed to saturate after three cycles. The tensile tests demonstrated that Ni-14W samples subjected to ARB processing exhibited high strength (> 1200 MPa after three ARB cycles) and very poor ductility.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Microstructure, mechanical and electrical properties of nanocrystalline W-Mo thin films

The effect of sputtering pressure on the surface/interface microstructure, crystal phase, mechanical properties and electrical characteristics of nanocrystalline W-Mo films is reported. The W-Mo films (≈300 nm) with variable microstructure were deposited under variable argon (Ar) sputtering pressure (P Ar ), which is varied in the range of 3-19 mTorr. X-ray diffraction analyses indicate that the W-Mo films crystallize in thermodynamically stable α-phase of W. However, the crystal-quality degradation occurs for W-Mo films deposited at higher P Ar due to difference in the adatom mobilities. The average grain size (d) of the W-Mo films was in the range of 11-24 nm; grain size decreases with increasing P Ar . The effect of P Ar and associated microstructure are significant on the mechanical characteristics; the hardness (H) and modulus of elasticity (E r ) of W-Mo films deposited at lower P Ar were higher but decreases continuously with increasing P Ar . The W-Mo films deposited under optimum sputtering pressure exhibit superior mechanical characteristics: H=40 GPa, E r =275 GPa, H/E r =0.8, and H 3 /E r 2 =0.145 GPa, which are higher compared to pure, α-phase W-films. The W-Mo films deposited at P Ar =3-9 mTorr exhibit high resistivity≈350-400 μΩ-cm, which decreases to 150-200 μΩ-cm for films deposited at higher P Ar . Based on the results, structure-mechanical-electrical property correlation in W-Mo films is established.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Microstructural Evolution and Mechanical Properties of Cold-deformed Al-5Cu Alloy Samples After Isothermal Heat Treatments

Abstract.In this paper, the microscopic morphology of a semi solid Al5Cu alloy by strain induced melt activated (SIMA) process were investigated, and the effects of predeformation, microstructural evolution, aging response and hardness changes were determined. The microstructural observation shows that while the grain boundaries started to appear after 620 deg. C, globular grains surrounded wet boundaries needed for SSP were obtained at 650 deg. C. The grain sizes exhibited ununiformity from the outer surface to the center of the sample because of ununiform predeformation. Although isothermal heat treatments reduced hardness, age hardening gave back the hardness loss.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure, Texture, and Mechanical Properties of AM60 Magnesium Alloy Processed by Extrusion and Multidirectional Forging

In the present paper, multidirectional forging (MDF), as a severe plastic deformation process, was carried out on an extruded AM60 magnesium alloy. The microstructure, texture, and mechanical properties of the MDFed samples were examined. Microstructural findings indicated that the grain size of the alloy decreased from 10.2 to 3.7 µm after six MDF passes, carried out at a constant temperature of 220 °C. Textural studies revealed that after six MDF passes, the fiber texture of the extruded material was transformed to another texture, in which the basal planes tend to rotate toward 45{sup o} to the transverse direction. Shear punch testing (SPT) was employed to assess the shear yield stress (SYS) and ultimate shear strength (USS) at room temperature. Both SYS and USS were enhanced after two MDF passes, but decreased in the next pressing stages, despite developing finer grains at higher levels of imposed strain. The observed drop in strength is ascribed to texture softening that counterbalances the grain refinement strengthening effects. The variation in average microhardness values after different passes of MDF showed the trend that was in concurrence with the rise and fall of the SPT results. Finally, the changes in mechanical properties were discussed, based on the microstructural and textural findings.

36 MATERIALS SCIENCE↗
DOE OSTI2018

An efficient algorithm for generating diverse microstructure sets and delineating properties closures

Properties closures delineate the theoretical objective space for materials design problems, allowing designers to make informed trade-offs between competing constraints and target properties. In this paper, we present a new algorithm called hierarchical simplex sampling (HSS) that approximates properties closures more efficiently and faithfully than traditional optimization based approaches. By construction, HSS generates samples of microstructure statistics that span the corresponding microstructure hull. As a result, we also find that HSS can be coupled with synthetic polycrystal generation software to generate diverse sets of microstructures for subsequent mesoscale simulations. Finally, by more broadly sampling the space of possible microstructures, it is anticipated that such diverse microstructure sets will expand our understanding of the influence of microstructure on macroscale effective properties and inform the construction of higher-fidelity mesoscale structure-property models.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Linking Initial Microstructure to ORR Related Property Degradation in SOFC Cathode: A Phase Field Simulation

Microstructure evolution driven by thermal coarsening is an important factor for the loss of oxygen reduction reaction rates in SOFC cathode. In this work, the effect of an initial microstructure on the microstructure evolution in SOFC cathode is investigated using a recently developed phase field model. Specifically, we tune the phase fraction, the average grain size, the standard deviation of the grain size and the grain shape in the initial microstructure, and explore their effect on the evolution of the grain size, the density of triple phase boundary, the specific surface area and the effective conductivity in LSM-YSZ cathodes. It is found that the degradation rate of TPB density and SSA of LSM is lower with less LSM phase fraction (with constant porosity assumed) and greater average grain size, while the degradation rate of effective conductivity can also be tuned by adjusting the standard deviation of grain size distribution and grain aspect ratio. The implication of this study on the designing of an optimal initial microstructure of SOFC cathodes is discussed.

25 ENERGY STORAGE↗
DOE OSTI2014

Characterization of microstructure, texture and magnetic properties in twin-roll casting high silicon non-oriented electrical steel

An Fe-6.5 wt.% Si-0.3 wt.% Al as-cast sheet was produced by twin-roll strip casting process, then treated with hot rolling, warm rolling and annealing. A detailed study of the microstructure and texture evolution at different processing stages was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. The initial as-cast strip showed strong columnar grains and pronounced < 001 >//ND texture. The hot rolled and warm rolled sheets were characterized by large amounts of shear bands distributed through the thickness together with strong < 110 >//RD texture and weak < 111 >//ND texture. After annealing, detrimental < 111 >//ND texture almost disappeared while beneficial (001)<210 >, (001)<010 >, (115)<5 − 10 1 > and (410) < 001 > recrystallization textures were formed, thus the magnetic induction of the annealed sheet was significantly improved. The recrystallization texture in the present study could be explained by preferred nucleation and grain growth mechanism. - Highlights: • A high silicon as-cast strip with columnar structure was produced. • A thin warm rolled sheet without large edge cracks was obtained. • Microstructure and texture evolution at each stage were investigated. • Beneficial (001)<210 >, (001)<010 >, (410)<001 > recrystallization textures were formed. • The magnetic induction of annealed sheet was significantly improved.

36 MATERIALS SCIENCE↗