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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 OSTI2016

Texture development during rolling of α+β dual-phase ZrNb alloys - 2016-0070

The texture evolution during high-temperature rolling (800 deg. C) of two model zirconium-niobium alloys was studied using electron backscatter diffraction. The aim was to decouple the relative importance of deformation and phase transformation on the final texture in an effort to elucidate the origin of the strong α-transverse basal texture commonly found in the hot-rolled product. The analysis uses a reconstruction software based on the Burgers relation to reconstruct the high-temperature β orientations, with the indexed α as input. In the low niobium content alloy, the texture evolution of the {11 2-bar 0}<10 1-bar 0> component was consistent with deformation in both α and β phases, along with a variant selection mechanism that occurred during the β → α phase transformation. Variant selection was observed to depend on the orientation of the deformed prior β grains. In the high niobium content alloy, a lower α volume fraction during hot rolling gave rise to different β textures and promoted the formation of a Goss component. This contributed to the {11 2-bar 0} <10 1-bar 0> component upon cooling, with variant selection enhanced by anisotropic grain breakup. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2018

Distinct Recrystallization Pathways in a Cold-Rolled Al-2%Mg Alloy Evidenced by In-Situ Neutron Diffraction

The time-of-flight neutron diffraction data collected in-situ on Oak Ridge National Laboratory’s (ORNL, Oak Ridge, TN, USA) VULCAN and Los Alamos National Laboratory’s (LANL, Los Alamos, NM, USA) High-Pressure-Preferred-Orientation (HIPPO) diffractometers have been analyzed complementarily to show the texture evolution during annealing of a cold-rolled Al-2%Mg alloy. The texture analysis aimed to identify the components present in the initial rolling (or deformation) texture and in the thermally-activated recrystallization texture, respectively. Using a quasi-Monte-Carlo (QMC) approach, a new method has been developed to simulate the weighted texture components, and to obtain inverse pole figures for both rolling and normal directions. As such, distinct recrystallization pathways during annealing in isochronal conditions, can be revealed in terms of the evolution of the texture components and their respective volume fractions. Moreover, the recrystallization kinetics associated with the cube and random texture components are analyzed quantitatively using a similar approach developed for differential scanning calorimetry (DSC).

36 MATERIALS SCIENCE↗
DOE OSTI2014

Rolling Element Bearing Stiffness Matrix Determination (Presentation)

Current theoretical bearing models differ in their stiffness estimates because of different model assumptions. In this study, a finite element/contact mechanics model is developed for rolling element bearings with the focus of obtaining accurate bearing stiffness for a wide range of bearing types and parameters. A combined surface integral and finite element method is used to solve for the contact mechanics between the rolling elements and races. This model captures the time-dependent characteristics of the bearing contact due to the orbital motion of the rolling elements. A numerical method is developed to determine the full bearing stiffness matrix corresponding to two radial, one axial, and two angular coordinates; the rotation about the shaft axis is free by design. This proposed stiffness determination method is validated against experiments in the literature and compared to existing analytical models and widely used advanced computational methods. The fully-populated stiffness matrix demonstrates the coupling between bearing radial, axial, and tilting bearing deflections.

17 WIND ENERGY↗
DOE OSTI2012

On the effect of deep-rolling and laser-peening on the stress-controlled low- and high-cycle fatigue behavior of Ti-6Al-4V at elevated temperatures up to 550?C

The effect of surface treatment on the stress/life fatigue behavior of a titanium Ti-6Al-4V turbine fan blade alloy is investigated in the regime of 102 to 106 cycles to failure under fully reversed stress-controlled isothermal push-pull loading between 25? and 550?C at a frequency of 5 Hz. Specifically, the fatigue behavior was examined in specimens in the deep-rolled and laser-shock peened surface conditions, and compared to results on samples in the untreated (machined and stress annealed) condition. Although the fatigue resistance of the Ti-6Al-4V alloy declined with increasing test temperature regardless of surface condition, deep-rolling and laser-shock peening surface treatments were found to extend the fatigue lives by factors of more than 30 and 5-10, respectively, in the high-cycle and low-cycle fatigue regimes at temperatures as high as 550?C. At these temperatures, compressive residual stresses are essentially relaxed; however, it is the presence of near-surface work hardened layers, with a nanocystalline structure in the case of deep-rolling and dense dislocation tangles in the case of laser-shock peening, which remain fairly stable even after cycling at 450?-550?C, that provide the basis for the beneficial role of mechanical surface treatments on the fatigue strength of Ti-6Al-4V at elevated temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Baryogenesis from ultra-slow-roll inflation

The ultra-slow-roll (USR) inflation represents a class of single-field models with sharp deceleration of the rolling dynamics on small scales, leading to a significantly enhanced power spectrum of the curvature perturbations and primordial black hole (PBH) formation. Such a sharp transition of the inflationary background can trigger the coherent motion of scalar condensates with effective potentials governed by the rolling rate of the inflation field. We show that a scalar condensate carrying (a combination of) baryon or lepton number can achieve successful baryogenesis through the Affleck-Dine mechanism from unconventional initial conditions excited by the USR transition. Viable parameter space for creating the correct baryon asymmetry of the Universe naturally incorporates the specific limit for PBHs to contribute significantly to dark matter, shedding light on the cosmic coincidence problem between the baryon and dark matter densities today.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

An Integrated Simulation of Multiple-Pass U-10Mo Alloy Hot Rolling and Static Recrystallization

To achieve a desired microstructure and minimize the thickness variation in rolled foils, researchers must understand the effects of foil fabrication process variables on microstructure evolution. We developed an integrated simulation of deformation and recrystallization that employs the finite element method (FEM) and the kinetic Monte Carlo (KMC) Potts model, respectively, to investigate microstructure evolution during multiple-pass hot rolling and heat treatment in polycrystalline U-10Mo fuel. Scanning electron microscopy and electron backscatter diffraction images of microstructures were directly used as input in FEM calculation of deformation, and the calculated strains were used to determine the driving force of nucleation and growth of recrystallized grains in the Potts model. Grain structures predicted by the Potts model were used to update the grain structure and material properties for FEM. Simulation alternated between FEM and the Potts model to simulate grain structure evolution during multiple rolling and heat treatments. The initial model parameters were determined by benchmarking the recrystallization kinetics against experimental data. Then, the model was applied to predict the grain structure evolution. Results showed that our model can capture the coupling between deformation and recrystallization and can quantitatively reproduce the observed U-10Mo recrystallization and grain growth kinetics. The simulation results demonstrated that the developed model can predict U-10Mo grain structures as a function of initial microstructure and foil fabrication parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2018

High- and Low-Temperature Deformation Behavior of Different Orientation Hot-Rolled Annealed Zircaloy-4

In this paper, the hot-rolled annealed Zircaloy-4 samples with different orientation were subjected to uniaxial compression with a strain rate of 0.001 s{sup −1} to obtain the stress-strain curves of different initial orientation samples at different temperatures. Electron backscatter diffraction (EBSD) technique and transmission electron microscope (TEM) technique were used to analyze the microstructures and textures of compressed samples. The mechanical properties and microstructural evolution of rolling directions (RD), transverse directions (TD) and normal directions (ND) were investigated under the conditions of – 150 °C low temperature, room temperature and 200 °C high temperature (simulated lunar temperature environment). The results show that the strength of Zircaloy-4 decreases with the increase in deformation temperature, and the strength in three orientations is ND > TD > RD. The deformation mechanism of hot-rolled annealed Zircaloy-4 with different orientation is different. In RD, {101̄0}〈a〉 prismatic slip has the highest Schmid factor (SF), so it is most easy to activate the slip, followed by TD orientation, and ND orientation is the most difficult to activate. The deformed grains abide slip→twinning→slip rule, and the different orientation Zircaloy-4 deformation mechanisms mainly are the twinning coordinated with the slip.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Evolution of Second-Phase Particles in 6111 Aluminum Alloy Processed by Hot and Cold Rolling

The evolution of coarse Al{sub 9.9}Fe{sub 2.65}Ni{sub 1.45} phase, spherical Al{sub 12}(Mn,Fe){sub 3}Si phase and rod-like Q phase in a 6111 aluminum alloy during hot and cold rolling deformation processes was systematically investigated in this work. The results showed that the coarse Al{sub 9.9}Fe{sub 2.65}Ni{sub 1.45} particles are mainly distributed at the grain boundaries, accompanied by the co-formation of Al{sub 12}(Fe,Mn){sub 3}Si phase and Mg{sub 2}Si phase, while the spherical Al{sub 12}(Mn,Fe){sub 3}Si particles are mainly distributed in the grain interiors. Hot rolling has little effects on the size and distribution of both phases, but cold deformation can severely decrease the size of the particles by breaking the particles into small pieces. In addition, the temperature of 450 °C is not high enough for the dissolution of Q phase in the Al matrix, but the Q particles can be broken into small pieces due to the stress concentration during both hot and cold rolling deformation. In addition, the influences of phase evolution, dislocations and recrystallization on the mechanical properties evolution were also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Texture Analysis for Enhancement of R-value in Asymmetrically Rolled Al Alloy Sheet

When Al alloy sheet is reduced in thickness by 84% with asymmetric rolling and heat treatment, this sheet simultaneously develops a {001}〈110〉 texture, which decreases the R-value, and a 〈111〉//normal direction (ND) texture, which enhances the R-value. To control the intensities of these {001}〈110〉 and 〈111〉//ND texture components, an 84% heavy asymmetrically rolled and heat-treated AA1050 Al alloy sheet was 20% light asymmetrically rolled and heat-treated at 500 °C for 1 h. This process increased the amount of 〈111〉//ND texture component and reduced the amount of the {001}〈110〉 texture component, resulting in an R-bar -value of 1.3. This was 2.13 times higher than the R-bar -value of 0.61 obtained for the initial specimen that had {001}〈100〉 component.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Through-Thickness Strain Gradient in a Hot-Rolled Al-Mg Alloy Obtained by Nanoindentation and Glancing Angle X-Ray Diffraction

Combined nanoindentation and glancing angle X-ray diffraction (GAXD) methods were used to study the mechanical properties of near-surface microstructures (NSMs) of a hot-rolled 5xxx aluminum alloy. Nanoindentations with a sharp indenter were carried out with penetration depth ranging from 250 nm to 4500 nm at the near-surface regions as well as the bulk of the hot-rolled alloy. The primary indentation parameter presented here was the hardness, given that plastic strain obtained from GAXD experiment could be correlated with the hardness value. Analysis of nanoindentation hardness results proved that NSMs of this alloy on average were harder than the bulk due to the presence of different surface features discussed here. The GAXD experiments were performed between a minimum incident angle 0.025°, equivalent to 765 nm penetration depth, and a maximum angle 1°, equivalent to 3000 nm penetration depth. The strain-induced broadening in the diffraction peaks was calculated by the Williamson–Hall technique. Both indentation hardness and glancing angle diffraction results confirmed strain gradient as a function of depth in the NSMs of the alloy. Both techniques also showed that the thickness of the subsurface layer (i.e., several micrometers below the surface) of hot-rolled sample was approximately 2.44 μm at the tested areas. Additionally, reported results provided evidence for the ability to use glancing angle X-ray diffraction as a nondestructive tool for the measurement of subsurface layers' thickness as well as microstrain (non-uniform or plastic strain) as a function of depth.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A Benders based rolling horizon algorithm for a dynamic facility location problem

This study presents a well-known capacitated dynamic facility location problem (DFLP) that satisfies the customer demand at a minimum cost by determining the time period for opening, closing, or retaining an existing facility in a given location. To solve this challenging NP-hard problem, this paper develops a unique hybrid solution algorithm that combines a rolling horizon algorithm with an accelerated Benders decomposition algorithm. Extensive computational experiments are performed on benchmark test instances to evaluate the hybrid algorithm’s efficiency and robustness in solving the DFLP problem. Computational results indicate that the hybrid Benders based rolling horizon algorithm consistently offers high quality feasible solutions in a much shorter computational time period than the standalone rolling horizon and accelerated Benders decomposition algorithms in the experimental range.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2013

Chemical banding revealed by chemical etching in a cold-rolled metastable stainless steel

The current work describes the metallographic characterization of the initial microstructure of a cold rolled precipitation hardening semi-austenitic stainless steel (12Cr–9Ni–4Mo–2Cu–1Ti, in wt.%). The use of the Lichtenegger and Blöch (L–B) color etching solution has been shown to reveal not only the phases present in the microstructure, but also the existence of chemical banding along the rolling direction. The L–B reagent has been found to color the microstructure in bands depending on what alloying elements have segregated to each band. Two-dimensional electron probe microanalysis (EPMA) maps have shown that Ni, Cu and Ti segregate together in the bands, while Cr has an opposite behavior. Mo has a mixed segregation behavior although much weaker than the other elements and more prompt to segregate like Ni does. A direct comparison of light optical micrographs with the EPMA maps of the same area of the microstructure has enable to establish a direct relationship between the alloying element band concentration and the resulting etching color contrast obtained with the L–B reagent. Thermodynamic calculations predict that solidification in this steel takes place with ferrite as the primary phase. Equilibrium partitioning coefficient calculations seem to support the observed segregation patterns. - Highlights: • A cold rolled metastable stainless steel has been characterized thoroughly. • EPMA shows that Ni, Cu and Ti segregate together; Cr in an opposite way. • L–B color etching is sensitive to the segregation of these chemical elements. • This chemical banding has been reduced by applying a homogenization heat treatment. • Partitioning coefficient calculations agree with the observed segregation patterns.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Cold rolling texture evolution of TiB2 particle reinforced Al-based composites by Neutron Diffraction and EBSD analysis

Highlights: • Texture development of in-situ TiB{sub 2} particle reinforced Al matrix composites after cold rolling were characterized. • The sum of rolling texture volume fractions has been significantly reduced by the weak texture in particle deformation zone. • Recrystallization nuclei with the Cube and Rotated-Cube orientations were observed in the particle deformation zones. • Small TiB{sub 2} particles within Al grains kept the parallel relationship with surrounding matrix during the deformation. - Abstract: Texture development of particle-reinforced metal matrix materials (P-MMCs) has not been understood well, especially the effects of second-phase particles during the deformation. In this work, we have investigated the texture evolution of TiB{sub 2}/Al composites during cold rolling by Neutron Diffraction and EBSD analysis. Two forms of TiB{sub 2} particles influenced the texture evolution in different ways. The particle-clusters aggregated along grain boundaries led to a reduction of texture volume fraction; recrystallization nuclei with weak texture appeared around these particle-clusters. Small non-shearable TiB{sub 2} particles dispersed inside Al matrix contributed to strong Copper texture component at high strains; the individual particles rotated together with Al matrix during the deformation. These revealed effects of particles on the texture development in TiB{sub 2}/Al composites provide a reference for the texture control of P-MMCs.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Effects of Cold Rolling on Microstructure and Mechanical Properties of Fe-30Mn-3Si-4Al-0.093C TWIP Steel

The effects of cold rolling on microstructure evolution and the associated mechanical properties of Fe-30Mn-3Si-4Al-0.093C twinning-induced plasticity (TWIP) steel are examined in this work with reduction rates of 10%, 20%, 30%, 40%, 50%, 60%, and 70%. Through texture analysis and transmission electron microscopy (TEM) observations, it is suggested that slip, mechanical twinning, the interaction between dislocation/twin boundaries (TB), and shear band have influenced the observed mechanical behavior and development of texture. Special components of weak initial textures are preferential for mechanical twinning, resulting in an increase in strain hardening rate. By mechanical twinning, the {111}<112> orientation is rotated into a position at the vicinity of the {110}<001> Goss orientation, and the {552}<115> (Cu-twin) texture is transformed to the {110}<001> orientation. The evolution of texture is closely related to the onset of shear banding resulting from deformation twinning. The sample with 10% cold reduction exhibits a favorable combination of yield strength and ductility, indicating a considerable capacity for energy absorption. With increasing rolling reductions, the deformation of the samples becomes inhomogeneous due to the high anisotropy of the microstructure. The localized shear bands resulting from the excessive cold rolling are detrimental to the ductility of the present TWIP steel.

Shen, Yongfeng↗
DOE OSTI2020

Comparison of semi-doped PANI/DBSA complex achieved by thermal doping and roll-mill process: A new perspective for application

Conductive polymers have garnered extensive attention over the last few decades owing to their vast applications and relative ease of production. One such polymer is PANI; with versatile thermo-mechanical, chemical, and electrical properties, has been researched for varied applications in the field of electronics, electrodes and corrosion protection. In this study, we focus on an alternative route to process semi-doped PANI/DBSA complexes with special focus on material properties for improved processability. This study investigates the influence of two different material preparation techniques: roll-milling and thermal-doping, on the formability and processability of such polymer-complex systems. Results confirm similar doping levels achieved in both processes and shear-thinning behavior was only observed for roll-milled samples. These results underline the formability of roll-milled PANI/DBSA with thermosetting resins. It essentially explains the production route and offers a perspective for commercial manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Elastic Properties of Rolled Uranium -- 10 wt.% Molybdenum Nuclear Fuel Foils

In situ neutron diffraction data was collected during elastic loading of rolled foils of uranium-10 wt.% molybdenum bonded to a thin layer of zirconium. Lattice parameters were ascertained from the diffraction patterns to determine the elastic strain and, subsequently, the elastic moduli and Poisson’s ratio in the rolling and transverse directions. The foil was found to be elastically isotropic in the rolling plane with an effective modulus of 86 + / - 3 GPa and a Poisson’s ratio 0.39 + / - 0.04.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2021

Inline Rolling Shear Alignment: Deposition and Long-Range Order of Block Polymer Templates in a Fast, Single-Step Process

We report the first demonstration of a rapid, single-step technique to align block polymer, thin-film nanostructures that is amenable to continuous speeds ≥10 mm/s. This method, termed Inline Rolling Shear Alignment (IRSA), uses an elastomeric roller coupled with an electric hysteresis brake to shear films before the casting solvent fully evaporates, and it can enable high throughput, large-area manufacturing of patterns such as nanowire templates. IRSA is adaptable to various polymer systems including diblock and triblock polymers, and a post-shear annealing step can yield high-quality nanostructures with orientation parameters >0.99 and defect densities as low as 5 defect-pairs/μm 2 . To demonstrate the effectiveness of IRSA, platinum nanowires were produced from this rapid deposition and alignment approach using poly(styrene-b-2-vinylpyridine), followed by open-air, atmospheric-pressure plasma etching. Furthermore, this integrated concept, with 50x faster operation than existing processes, could be leveraged for cost-effective manufacturing of macroscopically aligned nanostructures in roll-to-roll systems.

36 MATERIALS SCIENCE↗