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1.
Laboratory procedures were established to produce advanced aluminum 2XXX+ Zr alloy powder metallurgy sheet in the T8X temper. The sheet was tested for tensile and Kahn Tear properties in the longitudinal and long transverse directions. The results from the laboratory-produced sheet were compared to the results of a pilot-scale NASA contractual study which used the same alloy powders, leading to the conclusion that laboratory-scale sheet properties are good to excellent predictors of the pilot-scale tensile properties and tear notch toughness values. Tear resistance toughness at pilot scale was not satisfactorily predicted by the laboratory results.  相似文献   

2.
A computational approach, which targets on the prediction of SiC recession caused by SiO2 scale volatility under combustion environments, was developed in this study. In this approach, thermodynamic calculation was integrated with a gaseous-diffusion model to calculate the fluxes of volatile species, such as SiO(g), Si(OH)4(g), SiO(OH)2(g), and SiO(OH)(g), produced by the reaction of SiO2 scale with the combustion air. The resulted weight loss of SiC was then calculated under a variety of combustion environments. The benefit of using environmental barrier coating (EBC) in the protection of SiC from recession was demonstrated by the calculation. It is shown that the weight loss of SiC-based ceramics could be significantly reduced when EBCs, such as mullite (Al6Si2O13 or written as 3Al2O3·2SiO2) or SrAS2 (SrO·Al2O3·2SiO2), are used. The effects of combustion conditions, such as temperature and total pressure, on the volatility of SiO2 scale were also discussed.  相似文献   

3.
Tracer diffusivities provide the most fundamental information on diffusion in materials, and are the foundation of robust diffusion databases that enable the use of the Onsager phenomenological formalism with no major assumptions. Compared to traditional radiotracer techniques that utilize radioactive isotopes, the secondary ion mass spectrometry (SIMS)-based thin-film technique for tracer diffusion is based on the use of enriched stable isotopes that can be accurately profiled using SIMS. An overview of the thin-film method for tracer diffusion studies using stable isotopes is provided. Experimental procedures and techniques for the measurement of tracer diffusion coefficients are presented for pure magnesium, which presents some unique challenges due to the ease of oxidation. The development of a modified Shewmon-Rhines diffusion capsule for annealing Mg and an ultra-high vacuum system for sputter deposition of Mg isotopes are discussed. Optimized conditions for accurate SIMS depth profiling in polycrystalline Mg are provided. An automated procedure for correction of heat-up and cool-down times during tracer diffusion annealing is discussed. The non-linear fitting of a SIMS depth profile data using the thin-film Gaussian solution to obtain the tracer diffusivity along with the background tracer concentration and tracer film thickness is demonstrated. An Arrhenius fit of the Mg self-diffusion data obtained using the low-temperature SIMS measurements from this study and the high-temperature radiotracer measurements of Shewmon and Rhines (Trans. AIME 250:1021-1025, 1954) was found to be a good representation of both types of diffusion data over a broad range of temperatures between 250 and 627 °C (523 and 900 K).  相似文献   

4.
A new process called structural reaction injection molding (SRIM) has been developed to combine the high strength and modulus properties of fiber reinforced composites with the advantages of the reaction injection molding process. Along with the process, a new reactive resin has been developed expressly for the structural RIM process. With the new resin and SRIM process conventional design methods can be used, but the designer must also consider several facets of the structural RIM process.  相似文献   

5.
“Excuse me,” said a graduate student that I’ve not seen before, “I’d like to get some time on the Auger.” “Fine” I reply, “If you are going to need a lot of time, Nancy will train you so that you can use the machine yourself. If it’s only a small project, she’ll work with you. In either case, see Nancy to get a session scheduled.” Shaking off the last remnants of sleep, I realize that I’ve forgotten the most important question, “Oh, just a minute …. Why? … I mean, what do you want to find out?” And so begins a discussion which leads to the recommendation that, instead of Auger spectroscopy, the student use a combination of SIMS and STEM. We schedule time appropriately.  相似文献   

6.
Electroless Ni-Co-P coating and Ni-Co-P-SiO2 nanocomposites were successfully applied on AZ91D magnesium alloy via environmentally friendly cerium-lanthanum-permanganate treatment and their properties were compared with traditionally binary Ni-P coating. The prepared coatings were analyzed using scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy. Moreover, the corrosion behavior of the coatings in 3.5 wt.% NaCl was evaluated by two electrochemical methods. It is found that the Ni-Co-P coating possesses more uniform and compact structure and better corrosion protection characteristics in comparison with the Ni-P coating. The plating rate of Ni-Co-P bath is relatively lower than the Ni-P bath, but it significantly increases after addition of SiO2 nanoparticles more probably due to adsorption of silica nanoparticles on alloy surface. The corrosion resistance of Ni-Co-P-SiO2 composite coatings was superior with respect to Ni-P and Ni-Co-P coatings due to formation of thick and compact coating with tortuous grain boundaries.  相似文献   

7.
The method of heat generation, heat transfer characteristics, and ingot structure are very different in the VAR and ESR processes, which result in different tendencies and mechanisms for macrosegregation formation in forged IN-718. Freckles are niobium rich and can be generated in both ESR and VAR, with higher incidence in ESR than VAR. White spots are niobium lean and can only be found in VAR-processed materials. Freckles are indige-nous in nature, and result from the flow of solute-rich interdendritic liquid in the mushy zone during solidification. The most plausible cause for white spots is exogenous material, which remains unmelted, falling into the molten pool. The best way to minimize the formation of freckles is to improve the ingot heat transfer rate, a more difficult task in ESR than in VAR.  相似文献   

8.
The following Is the third installment of an eight-part series which examines some of the programs featured at the Computer Software for Metallurgical Calculations Conference, which todk place late in 1985 at the University of Missouri-Rolla.  相似文献   

9.
The electrochemical, spectroscopic and microscopic analyses of cytochrome c and its immobilization on bare glassy carbon (GC) and platinum (Pt) electrodes were performed. Cytochrome c interaction was examined by studying cyanide and arsenic as model compounds for these types of behavior. Subtractively normalized interfacial Fourier transform infrared (SNIFTIR) spectroscopy, fluorescence and electrochemical methods, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) were used to characterize the protein in the immobilized state and to confirm that the protein was not denatured upon binding to the pre-treated bare GC and Pt electrodes. The spherical morphology of the immobilized protein, which is typical of native cytochrome c, was observed using AFM. The protein binding was monitored as a decrease in peak currents (by CV) for the immobilized protein. Under analysis was also a decrease in emission intensities by fluorescence in solution, by the FTIR and SNIFTIR spectroscopies. Fluorescence and AFM proved the existence of the binding process between the protein and the analytes. This behavior was confirmed by the FTIR and SNIFTIR spectroscopies, which gave evidence that the binding event took place at the amino acids side chain of the protein.  相似文献   

10.
Various commercially available unidirectional (UD) non-crimp-fabrics (NCFs) are currently used for manufacturing carbon fiber reinforced plastic (CFRP) parts. These UD NCFs can differ significantly in their forming behavior. For optimizing and ensuring the manufacturability of the forming process of CFRP parts manufactured from UD NCFs these differences have to be taken into account. This motivates developing an efficient and universally applicable modular modeling approach for describing the in-plane forming behavior of various UD NCFs. The first component of this modular approach is a hyperelastic material model that accurately predicts the fiber orientation of UD NCFs during forming. This material model is implemented via a user-defined material subroutine in the commercial finite element package LS-DYNA. The second component is a simple truss structure that allows modeling the various stitch patterns of the different UD NCFs. This modular model can be calibrated via simple tensile tests. To demonstrate the versatility of this approach, the in-plane forming behavior of three different UD NCFs is validated by comparing experimental data and simulation results of the common picture frame test.  相似文献   

11.
NASA Lewis Research Center is presently involved in developing structurally reliable metal and ceramic matrix composites for application in advanced gas turbine engines. This paper examines the general property requirements for the high performance fibers of these composites. Also presented are examples of how these fiber property guidelines are influencing current fiber improvement and evaluation studies, with specific emphasis on commercially available boron and SiC fibers.  相似文献   

12.
An increase in the utilization efficiency of CaO, one of the major fluxing agents used in various steelmaking processes, is required to reduce the amount of discharged slag and energy consumption of the process. The authors have intensively focused on the development of innovative dephosphorization process by using so called “multi-phase flux” composed of solid and liquid phases. This article summarizes the research on the above topic done by the authors, in which the formation mechanisms of P2O5-containing phase during CaO or 2CaO·SiO2 dissolution into molten slag, the phase relationship between solid and liquid phases at equilibrium, and thermodynamic properties of P2O5-containing phase have been clarified. The reactions between solid CaO or 2CaO·SiO2 and molten CaO-FeO x -SiO2-P2O5 slag were observed by dipping solid specimen in the synthesized slag at 1573 K or 1673 K. The formation of the CaO-FeO layer and dual-phase layer of solid 2CaO·SiO2 and FeO x -rich liquid phase was observed around the interface from the solid CaO side toward the bulk slag phase side. Condensation of P2O5 into 2CaO·SiO2 phase as 2CaO·SiO2-3CaO·P2O5 solid solution was observed in both cases of CaO and 2CaO·SiO2 as solid specimens. Measurement of the phase relationship for the CaO-FeO x -SiO2-P2O5 system confirmed the condensation of P2O5 in solid phase at low oxygen partial pressure. The thermodynamics of 2CaO·SiO2-3CaO·P2O5 solid solution are to be clarified to quantitatively simulate the dephosphorization process, and the current results are also introduced. Based on the above results, the reduction of CaO consumption, the discharged slag curtailment, and energy-saving effects have been discussed.  相似文献   

13.
This work reports an efficient reactor, i.e., oxygen-rich side blow furnace (OSBF), for high-lead slag reduction. An OSBF with a cross-sectional area of 8.4 m2 was applied in an industrial-scale test and the results were compared with those from a traditional high-lead slag reduction reactor, i.e., blast furnace (BF), with which an additional electric heating fore well (EHFW) was connected for slag cleaning. By using the OSBF, Pb and Cu recoveries were raised by 1.07% and 7.99% compared with those from the traditional BF+EHFW, respectively. The optimal slag type for recovering metal values in the OSBF was also analyzed. Within the range of Fe/SiO2 = 1.56–1.87 and CaO/SiO2 = 0.8–1.05, lower Pb and Cu contents of the slag can be achieved with Fe/SiO2 = 1.65–1.75 and CaO/SiO2 = 1.0.  相似文献   

14.
Several advances in materials technology have resulted from the operation of the Savannah River nuclear materials production facility in Aiken, South Carolina. Among the research contributions of the Savannah River Site (SRS) to materials science and engineering are a greater understanding of stress-corrosion cracking and hydrogen embrittlement, and the development of technologies utilizing nuclear sources for heat and radiation. These advances arose from the technologies developed at SRS for the production, separation and packaging of nuclear materials.  相似文献   

15.
The family of plate steels represented by ASTM Specification A7101 is finding increasing applications. These low carbon, Cu-Ni-Cr-Mo-Cb, copper precipitation hardened steels have been identified by a number of designations over the years. During early development in the late 1960’s and first commercial production in 1970, the steels were known as IN-787 (trademark of International Nickel Company).2 ASTM specifications were subsequently developed for structural (A710) and pressure vessel (A736) applications over ten years ago. More recent interest and application of this family of steels by the U.S. Navy has lead to development of a military specification MIL-S-24645 (SH),3 also initially known as “HSLA-80.” Significant tonnage is being produced for the U.S. Navy as a replacement for HY80 (MIL-S-16216) in cruiser deck, bulkhead and hull applications.4 In these applications, the enhanced weldability and requirement of no preheat at this high strength and toughness level has been the main motivation for its use. Over the past 15 years, A710 type steels have also been used in a variety of applications, including off-shore platforms, pressure vessels, arctic linepipe valves and off-highway mining truck frames.  相似文献   

16.
In the present work iron oxide nanoparticles have been synthesized by alkaline solvo thermal method using anhydrous ferric chloride, sodium hydroxide, polyethylene glycol and cetyl trimethyl ammonium bromide and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray Spectroscopy (EDX) and Thermal Gravimetric Analysis (TGA). XRD indicated that the product is a mixture of different phases of iron oxide viz. gamma-Fe2O3 (maghemite, tetragonal), Fe2O3 (maghemite, cubic), Fe3O4 (magnetite, cubic) and ?-Fe2O3(epsilon iron oxide). FESEM studies indicated that size of the particles is observed in the range of about 19.8 nm to 48 nm. EDX spectral analysis reveals the presence of carbon, oxygen, iron in the synthesized nanoparticles. The FTIR spectra indicated absorption bands due to O-H stretching, C-O bending, N-H stretching and bending, C-H stretching and Fe-O stretching vibrations. TGA curve represented weight loss of around 3.0446 % in the sample at temperature of about 180°C due to the elimination of the water molecules absorbed by the nanoparticles from the atmosphere.  相似文献   

17.
Mechanical properties, microstructure, exfoliation corrosion (EXCO), and intergranular corrosion (IGC) behaviors of the spray-formed 7075 aluminum alloy after T6, T73, retrogression (R), and re-aging (RRA) treatment, respectively, were studied by using tensile tester, transmission electron microscope, and scanning electron microscope. The results show that the T6 process can increase the ultimate tensile strength (UTS) up to 760 MPa, while it decreases the elongation, the EXCO, and the IGC resistance of the alloy. The T73 process can improve elongation, the EXCO, and the IGC resistance of the alloy. The corrosion resistance of the alloy can also be improved by R and RRA processes with retrogression times increase. The tiny precipitated phases distributed homogeneously in the matrix can increase the UTS. The close-connected discrete grain boundary phases (GBP) and the narrow precipitate free zones (PFZ) will lower the elongation, the EXCO, and the IGC resistance of the alloy. Contrarily, the discrete GBP and wide PFZ can improve the elongation, the EXCO, and the IGC resistance of the alloy. The EXCO and the IGC behaviors for the spray-formed 7075 alloy after different aging treatments have been established according to the standards of ASTM G34-2001 (2007) and ASTM G110-1992 (2009).  相似文献   

18.
Nanocrystalline thin films of ZnO have been fabricated using the pulsed laser deposition method. The influence of the ion/atom ratio on the structural, morphological, and electrical parameters of these films is considered. It is established that, in the case of ion action on thin films, their crystalline structure and electrophysical properties are significantly changed. It is demonstrated that modes of ion-assisted deposition can help to control the average grain size in the range from 75.4 ± 2.0 nm to 79.1 ± 2.0 nm, the roughness in the range from 2.14 ± 1.11 nm to 7.30 ± 1.25 nm, and the resistivity and mobility in the range from (22.6 ± 2) × 10?4 Ohm cm to (33.6 ± 2) × 10?4 Ohm cm and from 28.21 ± 4.60 cm2/V s to 71.92 ± 2.50 cm2/V s, respectively.  相似文献   

19.
This research aims to study the effect of accelerated weathering conditions on the photodegradation characteristics for fibrillar silicate clay-filled Polypropylene (PP) nanocomposites in the presence of metallocene linear low density polyethylene (m-LLDPE). Silane-treated attapulgite (ATP) clay along with ethylene octene elastomer-grafted maleic anhydride (POE-g-MAH) was used to compatibilize both blend and nanocomposite system. The result showed that developed PP/m-LLDPE nanocomposites displayed good UV resistance with little change in retained stress-at-break and elongation-at-break values. Balanced loss of toughness values noted maintaining higher fracture toughness values for nanocomposites containing 5 phr ATP clay. Infrared analysis was used to detect progress of degradation followed by change in carbonyl index revealed predominated chain scission in late irradiation, while crosslinking was dominant for initial irradiation period. An increase in crystallinity during UV exposure (chemi-crystallization) was detected with exposure time for all compositions and virtually independent of initial structure of the polymer. The highest value of crystallization observed for PP and the lowest one for nanocomposites containing 5 phr of ATP clay revealed good oxidation stability. Surface morphology revealed induced degradation throughout cross-section of PP, while severity of the surface degradation was significantly reduced for developed nanocomposites.  相似文献   

20.
In this study, the AlN/Cu bonding was explored using the brazing technique. During AlN/Cu brazing, the temperature was set at 800, 850, and 900 °C for 10, 20, 30, and 60 min, respectively. We studied the bonding mechanism, microstructure formation, and the mechanical characteristics of the bond. The reaction layer developed at the interface of AlN/Cu is observed to be TiN. The activation energy of TiN is about 149.91 kJ/mol. The reaction layer thickness is linearly dependent on the temperature and duration at 800 and 850 °C for 60 min and 900 °C for 30 min. However, the growth of the reactive layers decreases gradually at 900 °C when the duration changed from 30 to 60 min. The strength of the specimens with thickness ranging between 1 and 1.5 μm is 40-51 MPa.  相似文献   

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