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Aircraft-mounted gas turbine engines may need to employ a variety of inlet ducts to perform various missions. An inertial particle separator (IPS) is a type of inlet duct that can remove harmful du...

Although clean energy generation utilizing the Oxygen Reduction Reaction (ORR) can be considered a promising strategy, this approach remains challenging by the dependence on high loadings of noble metals, mainly Platinum (Pt). Therefore, efforts have been directed to develop new and efficient electrocatalysts that could decrease the Pt content (e.g., by nanotechnology tools or alloying) or replace them completely in these systems. The present investigation shows that high catalytic activity can be reached towards the ORR by employing 1.8 ± 0.7 nm Ir nanoparticles (NPs) deposited onto MnO

Providing materials with smart functionalities such as self-healing properties is primarily a domain for organic materials, although their applicability is restricted to mild environments and loads due to poor thermal and mechanical properties. This work seeks to achieve the active functionalities obtained in organic materials but in ceramics, which are much more heat resistant and robust. Ceramic coatings were produced by Plasma Electrolytic Oxidation (PEO), which is an environmentally friendly technique that offers an alternative to potentially carcinogenic treatments used widely in the automotive and aircraft industries to protect light alloys against corrosion. The active functionalisation was achieved by incorporating corrosion inhibitors encapsulated into halloysite nanotubes (HNTs) into the PEO coatings. This allowed a controlled release of active agents when detecting environmental pH changes associated with the corrosion initiation of the metal substrate. Three corrosion inhibitors – vanadate, molybdate salts and 8–hydroxyquinoline (8–HQ) – were assessed within the PEO–HNT system and demonstrated considerable improvements in the corrosion resistance by decreasing the kinetics of both anodic and cathodic reactions. For immersion times up to 72 h, the vanadate offered a consistently higher corrosion resistance which was followed by molybdate, whereas the positive effect of 8–HQ was time-limited. The improvement in corrosion resistance was associated with the combined enhancement of the barrier and active protection properties of ceramic coatings. All coatings containing corrosion inhibitors were capable of providing self-healing to small scratches whereas only vanadate could partially restore more severe damages.

Natural particles, such as sand and dust, often have irregular, angular shapes without porosity. Such sedimentary particles can have a significantly different drag coefficients than spherical particles, and a robust drag coefficient model is needed to accurately predict their trajectory in multiphase flows. Such a model requires quantitative characterization of their shape. Herein it is shown that the Corey Shape Factor is a suitable parameter to characterize particle drag coefficient for a wide variety of particles with Reynolds numbers up to 2 × 105. This is accomplished by investigating the shape effects for both the Stokes drag regime and for the Newton drag regime to provide a comprehensive and validated drag model for irregular angular particles as a function of Corey Shape Factor. In addition, the shape of ISO 12103 Arizona Road Dust is measured (for the first time) to allow use of the corresponding drag model.

The presence of hydrogen sulfide (H2S) in typical oilfield environments promotes hydrogen absorption and subsequent failure of high-strength steels by sulfide stress cracking (SSC). Plasma nitriding is as a potential method to increase the resistance of the 17-4 PH to SSC, although further investigation is required to evaluate the corrosion resistance of the modified layer when it is exposed to H2S-containing environments. The aim of this study was therefore to evaluate the corrosion resistance of the 17-4 PH in typical oilfield environment. Samples were plasma nitrided at low (420°C) and high (500°C) temperatures and immersed in produced water with mixed H2S and CO2. The electrochemical data and scanning electron microscopy (SEM) micrographs showed that there were no detrimental effects on the corrosion resistance when plasma nitriding was performed at low temperature (420°C), whereas the integrity of the modified layer was compromised when an elevated temperature (500°C) was applied. The enhanced resistance to localized corrosion of the nitride case obtained after the low-temperature surface modification was attributed to the formation of a compound layer of mixed M4N/M2-3N, the inner section being more corrosion resistant than the outer part, as revealed by SEM micrographs.

An inertial particle separator (IPS) is a particulate removal device typically installed at the inlet of a gas turbine to mitigate effects of sand ingestion on the engine. This system can minimize particulate ingestion during helicopter landings in austere brownout conditions so as to increase engine life. Typically, IPS systems have lower engine power losses than alternative engine inlet filtration technologies. The present study investigates the effect of IPS particle removal and power losses as a function of scavenge leg geometry. Performance was evaluated based on particle separation efficiency, particle image velocimetry, and surface flow visualization, as well as power loss and mass flow rate variations. Of the various scavenge geometries considered, it was found that flow constriction with a hub-side ramp most improved separation efficiency, while also stabilizing mass flow rates and generally reducing power loss. This is attributed to a reduction in the level of flow separation by the addition of a favorable pressure gradient and geometry changes downstream of the attached flow region.

DDR5 Differential DIMM (DDIMM) is being defined in JEDEC and uses OMI as a host interface with the data transfer rate per data differential pair being specified at 25.6Gb/s minimum at present and at 51.2Gb/s maximum in the future. This is a significant data rate increase for DRAM modules over conventional single-ended data transferring DIMMs. For example, the DDR5 LRDIMM data transfer rate per pin is 3.2Gbps. This study utilizes the DDIMM early engineering samples with DDR4 to evaluate the OMI channel running at 25.6Gb/s.Validating the DDIMM PCB wiring for the high-speed differential memory bus requires accurate high-speed link simulations. These simulations require accurate models representing differential wiring in the DDIMM PCB stack up. The models must be built using not only representative physical dimensions but also accurate frequency dependent material properties obtained through PCB characterization. The simulation results of the initial study in 2018-19 concluded that the typical Copper Clad Laminate (CCL) and prepreg material used in the industry standard R/LR DIMM leads to signal integrity degradation relative to a better reference material at 25.6Gb/s OMI bus data rate[l]. This paper is based on 2019-20 DDIMM test results and the full channel time domain eye diagram analysis with BER at 10˄-15 assuming an improved DDIMM PCB stack up with hybrid structure to satisfy signal integrity while minimize the material cost premium.DDIMM will be paired with the Storage Networking Industry Association (SNIA) SFF-TA-1002 high speed connector which differs significantly from the JEDEC RDIMM connector for improved electrical signaling characteristics. The connector to PCB interface design has been studied as it is of utmost importance for achieving good signal integrity[l]. The DDIMM test samples for this study include the high speed connector to PCB interface attributes such as Plated Through Hole (PTH) in ground contact pad, ground plane void under OMI signal pad and tie bar removal.The challenges of DDIMM PCB mechanical interaction with SFF-TA-1002 connector have been highlighted in the initial study[l]. This study uses early engineer samples to evaluate the insertion/extraction performance. Future work will use test vehicle of PCB/connector pairs to characterize the high speed electrical performance and evaluate the contact reliability.In summary, this paper presented the full channel simulation result assuming an improved DDIMM PCB material/stack-up at 25.6Gbps for comparison with the performance that baselined in the initial work with the industry standard PCB material. Physical characterization of the engineering samples has been conducted to baseline the DDIMM PCB to connector contact interface. Electrical test is performed with early engineering samples in IBM high speed system to verify the simulation result.

Hypersonic vehicles operate at extreme environments at narrow margins of safety. High-speed flight in the atmosphere when volcanic ash and other meteorological particles are present can cause damag...

Carbon deposition on 20Cr25Ni steel at 700 °C has been investigated in CO2-based gases containing 0.7 vol%, 1.0 vol% and 1.4 vol% CO, each with ∼1000vpm C2H4, at 700 °C. Filamentary carbon deposits were formed at the two lowest CO contents but not at 1.4 vol% CO. TEM analyses have shown that the different CO levels change the propensity for deposition by altering the ratio of Ni:Fe in the nanometre sized catalytic particles produced during oxidation.

Austenitic stainless steel is used as fuel cladding in advanced gas-cooled nuclear reactors (AGR). At elevated temperatures, when the steel is exposed to CO2 based environments filamentary carbon deposits form on the surface of the steel. This filamentary carbon deposition is known to be catalysed by metallic nickel-rich particles. Adding trace amount of carbonyl sulphide (COS) into the gas mixtures suppresses the carbon deposition. In this current work, it has been shown that at 600 °C, the formation of filamentary carbon was suppressed by the addition of 215 ppb COS to a depositing gas mixture (containing approximately 1000 vppm C2H4/1% CO/bal. CO2) which was known to provide the environment suitable for carbon deposition. Samples exposed to the gas mixtures with and without 215 ppb COS were characterised using electron microscopy techniques to understand the formation mechanism of the nickel-rich particles and the inhibition mechanism due to the addition of COS. Electron diffraction study shows that the nickel-rich particles in the oxide layers assume the same crystallography as that of the austenitic metal underneath, regardless of the COS addition. The current observations also show that the metal-oxide interfaces was nickel-rich and a simple model has been proposed to explain the formation of nickel-rich particles within the subsurface oxide. Furthermore, it was found that when COS was added the surface of the nickel-rich particles in the oxide layer was found to be sulphur-rich by energy dispersive spectroscopy (EDS) on a scanning transmission electron microscope (STEM). It is believed that the surface sulphur adsorption onto the nickel-rich particles, rather than bulk sulphide formation, resulted in the inhibition of carbon deformation on the steel.

A computer program, Activity, was developed to predict the activity and gamma lines of materials irradiated with an ion beam. It uses the TENDL (Koning and Rochman, 2012) [1] proton reaction cross section database, the Stopping and Range of Ions in Matter (SRIM) (Biersack et al., 2010) code, a Nuclear Data Services (NDS) radioactive decay database (Sonzogni, 2006) [2] and an ENDF gamma decay database (Herman and Chadwick, 2006) [3]. An extended version of Bateman’s equation is used to calculate the activity at time t, and this equation is solved analytically, with the option to also solve by numeric inverse Laplace Transform as a failsafe. The program outputs the expected activity and gamma lines of the activated material. Program summary Program title: Activity Catalogue identifier: AFBS_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AFBS_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU GPL v3 No. of lines in distributed program, including test data, etc.: 688828 No. of bytes in distributed program, including test data, etc.: 71056048 Distribution format: tar.gz Programming language: Fortran. Computer: PCs or HPCs. Operating system: Linux (tested on Debian). Has the code been vectorized or parallelized?: OpenMPI RAM: 250MB per process + 200MB overhead Classification: 2.2, 17.8. Nature of problem: To calculate the predicted activity of an ion irradiated target. The expected range of ion energies is between 1MeV and 200MeV; this is the range of the available ion cross section data. Solution method: The program loads cross section data from the TENDL database and trajectory data from a SRIM [1] simulation exyz data file. It uses this data to calculate the production/loss rate of each isotope in the simulated target. Radioactive decay equations are used to calculate the amounts and activity of each radioactive isotope at the set time. Running time: Typically the Activity program runs each input from seconds to no more than several minutes. References: [1] SRIM — The stopping and range of ions in matter (2010). Ziegler, James F., Ziegler, M.D. and Biersack, J.P. 2010, Nuclear Instruments and Methods in Physics Research Section B, Vol. 268, pp. 1818–1823.

The DIAMOND beamline I13L is dedicated to multi-scale and multi-modal imaging in real and reciprocal space. The beamline consists of two independently operating experimental stations, located at a distance of more than 200 m from the source. The Imaging Branch performs micro-tomography with in-line phase contrast in the 6-30 keV energy range. In addition, a grating interferometry setup and a full-field microscope for nano-tomography are currently implemented. Other techniques providing high-resolution three-dimensional information, in particular coherent X-ray diffraction, are hosted on the Coherence Branch. All imaging methods are tested to operate with large energy bandwidths and therefore shorter exposure times. To this end, two options are currently used: the so-called 'pink-beam' mode using a reflecting mirror and X-ray filters and monochromatic mode using a multilayer monochromator. The operation mode enables science for in-situ and operando studies across a wide range of scientific areas.

DDR5 Differential DIMM (DDIMM) is being defined in JEDEC and will be introduced to the market in 2020. DDR5 DDIMM uses OMI (OpenCAPI Memory Interface) as the host interface. On the DDIMM printed circuit board (PCB), the minimum data transfer rate per data differential pair over the OMI bus is 25.6Gbps. This is a significant data rate increase for DRAM modules over conventional single-ended data transferring DIMMs. For example, the DDR5 LRDIMM data transfer rate per pin is 3.2Gbps. Careful attention must be paid to the bill of materials of the DDIMM to control its cost towards general market acceptance of this new DIMM technology. As a result, it is desired to use standard loss FR-4 material to build the DDIMM PCB. Validating the DDIMM PCB wiring for the high-speed differential memory bus requires accurate high-speed link simulations. These simulations require accurate models representing differential wiring in the DDIMM PCB stack-up. The models must be built using not only representative physical dimensions but also accurate frequency dependent material properties obtained through PCB characterization. The Short Pulse Propagation (SPP) method will be used to extract PCB frequency dependent material properties. PCB suppliers usually have different Copper Clad Laminate (CCL) and prepreg material set selections largely due to the supplier relations. The test coupons of this study will be built using CCL and prepreg materials from two suppliers. System level differential memory bus simulation based on SPP characterization will be performed and the simulation results from different material/stack-up designs will be benchmarked. DDR5 DDIMM will be paired with the Storage Networking Industry Association (SNIA) SFF-TA-1002 high speed connector which differs significantly from the JEDEC RDIMM connector for improved electrical signaling characteristics. In this work, the SNIA high-speed connector to PCB interface design will be studied as it is of utmost importance for achieving good signal integrity. In addition to high speed signal integrity, the DDIMM PCB mechanical interaction with the SFF-TA-1002 connector is studied and it will be highlighted in this paper. The PCB mechanical outline design proposal is made to mitigate module/connector mechanical interference. To understand the PCB yield impact, DIMM PCB suppliers' process capabilities for critical feature/dimensions will be studied as well.

FEMME, a multi-scale Finite Element Microstructure MEshfree fracture model has been applied to simulate the effect of microstructure on the development of discontinuous cracking and damage coalescence during the Hertzian indentation of a SiC-SiC fibre composite. This was studied experimentally by digital volume correlation analysis of high-resolution synchrotron X-ray computed tomographs, which quantified the damage via measurement of the 3D displacement fields within the material. The experimental data are compared with the model simulations, and demonstrate the applicability of the modelling strategy to simulate damage development in a heterogeneous quasi-brittle material. The paper shows the influence of the microstructure in the material.The interaction between the fibres and the pores is reproduced successfully.In the material, the inhomogeneous strain and displacement fields are reproduced.

Grain boundaries (GB) in an austenitic stainless steel were analysed using electron microscopy techniques and the results show that there exists a threshold misorientation angle below which GBs are likely to be immune to sensitisation. No direct correlation was found between the extent of corrosion attack and the associated misorientation angles of random high angle GBs (HAGBs). GB attacks were observed when the chromium concentration at GB was below 14.3 wt% and substantial attack occurred when the chromium concentration was

For the first time in two decades, the U.S. Supreme Court is scheduled in the 2014–2015 term to review the thorny planning and legal subject of local government regulation of outdoor signs and billboards and the core First Amendment requirement that regulations of speech be ”content neutral“. In basic terms, the content‐neutrality doctrine prohibits the government from regulating a speaker's content or message–including messages on outdoor signs. In Reed v. Town of Gilbert, the Court will be asked to decide whether Gilbert, Arizona's sign code, which distinguishes among several categories of signs, including religious, political, and ideological signs, meets the content neutrality requirement. In so doing, the Court may provide direction on how far local governments can go in regulating speech based on message, and the Court can resolve a longstanding division among the federal appellate courts over the meaning of content neutrality

This paper presents high resolution X-ray tomographic observations of intergranular stress corrosion crack nucleation and growth. In-situ experiments have been performed on beam line ID19 at the European Synchrotron Radiation Facility (ESRF). High-resolution tomography provides non-destructive, three-dimensional information of the shape and depth of damage. To the authors? knowledge, these are the first such observations of stress corrosion, and demonstrate the potential for high resolution, synchrotron, X-ray tomography as a tool for observing pitting, intergranular corrosion and intergranular cracking.The application of high-resolution synchrotron X-ray tomography to two in-situ experiments is described. Localised corrosion and intergranular cracking in sensitised 5083 aluminium alloy has been studied. These results show the progressive development, transition, and coalescence of two forms of damage within the bulk of the sample. In-situ observations of intergranular cracks in sensitised 302 stainless steel have also been obtained. These provide evidence for crack bridging ligaments, caused by the high resistance of special grain boundaries. Further applications of high resolution X-ray tomography are described, such as in-situ studies of pitting and the transition from pitting to cracking in aluminium alloys and stainless steels, including the effects of near-surface residual stress.

Oxidation of Super 304H and shot-peened Super 304H austenitic stainless steel was conducted over a temperature range of 600 – 700°C in steam at atmospheric pressure and compared with oxidation in laboratory air. It was observed that the mass gain was higher in steam compared with air. It should be noted that the shot-peening treatment improved the oxidation resistance in both air and steam considerably. Furthermore, spallation was only observed on the pickled Super 304H specimens and only in steam after exposures at 650°C and 700°C. The protective films found at the base of the duplex oxide grown on pickled Super 304H in air and steam were found to differ in that after exposure to air, a chromium rich film was present whereas after exposure to steam, a less protective Cr–Mn spinel was present. The oxidation kinetics were assumed to be parabolic for purposes of comparison and parabolic rate constants, Kp, were calculated for oxide growth under the different oxidation conditions. The Kp value for th...

The effect of an Excimer laser treatment on the corrosion resistance of friction stir welds in AA2024-T351 has been studied by means of electrochemical techniques and immersion tests. The results show a decrease in anodic and cathodic reactivity in the weld region after the laser treatment, achieved due to the formation of a 3–5 μm thick corrosion resistant layer. Immersion tests in 0·1M NaCl confirm that the presence of the treatment decreases the severity of corrosion attack. However they also show that, if the laser layer is damaged by a scratch, corrosion occurs preferentially in the scratch area. Delamination of the laser treated layer can also occur as a consequence of corrosion propagation during the exposure of laser treated samples.

The corrosion protection afforded by laser surface melting (LSM) AA7449-T7951 friction stir welds was investigated. LSM produced melting of the constituent particles and formation of a homogeneous 3–5 μm thick layer. Electrochemical tests showed a reduction in cathodic reactivity after LSM. The breakdown potentials, however, did not change significantly, indicating an anodically reactive surface. In situ and ex situ observation after immersion in 0.1 M NaCl showed that LSM reduced the depth attack in the weld region (particularly the HAZ), affording sacrificial protection to the substrate. Delamination of the treatment can occur during corrosion propagation.

SCC in turbine disc steels exposed to simulated steam-condensate tends to nucleate preferentially from corrosion pit precursors. The evolution of these cracks is not straightforward and not well understood. In this work, unique three-dimensional X-ray microtomographic images have confirmed that cracks develop predominantly at the shoulder of the pit, near the pit/surface interface, for specimens stressed to 50–90% σ0.2. In support of this observation, FEA of model pits indicate that strain is a maximum on the pit wall just below the pit mouth. Implications of these observations for the pit-to-crack transition and predictive-modelling of crack nucleation and growth are discussed.

Corrosion behaviour of the banded structure known as ‘onion ring’ in the nugget of friction stir weld AA2024-T351 was investigated to find the relation to microstructure. A micro-electrochemical cell with a 50 μm diameter glass pipette tip was used for electrochemical measurements. It was found that onion rings consisted of two bands: ‘dark’ bands that contain fewer constituent particles but show extensive precipitation of S phase and ‘light’ bands that contain fewer S phase precipitates but greater numbers of constituent particles. Electrochemical results showed that the light band has more noble (less active) open circuit potential compared to the dark band. Microstructurally, this is due to the lower number of S precipitates and therefore the possibility of higher Cu solid solution within the band compared to that of the dark band.

Cryogenic cooling with CO2 was applied during friction stir welding of AA2024-T351 in order to reduce the temperature increase during welding, and thus improve the corrosion resistance of the weld. The effect of cryogenic cooling on corrosion susceptibility was investigated with gel visualisation, immersion tests and local electrochemical measurements. The most susceptible area for both uncooled and cooled welds was in the heat-affected zone (HAZ) region, which showed intergranular attack. Cryogenic cooling had no detectable influence on the degree of anodic reactivity in the weld region. However, it did decrease the width of the reactive HAZ.

The evolution of stress corrosion cracks from pits is important in many industrial applications but continues to be a challenge in both measurement and prediction. Life prediction in these circumstances has to account for pit growth kinetics, the conditions for the transition from pits to cracks, and the growth rate of cracks in the short and long crack domain. An example of importance is the performance of steam turbine rotors in power generation. Although stress corrosion failures are comparatively rare, the consequences can be severe and occasionally catastrophic. Consequently, considerable effort is being focused on evaluating the effect of operational variables on pitting and crack growth and in developing an improved basis for structural integrity assessment. A preliminary mathematical model based on deterministic equations with statistically variable input parameters was developed for simulating the evolution of the pit depth distribution at different exposure times, and the transformation to stress corrosion cracks was based on the Kondo criteria. The model predicted some features of the damage well but recent novel measurements of the evolution of stress corrosion cracks from pits combined with finite element analysis of the strain distribution suggest that the transition from a pit to a crack is more complex than can be accounted for by the Kondo approach.

Susceptibility to localized corrosion of AlMgSi (AA6016 and AA6111) alloys in certain aggressive environments is high. In this study, synchrotron X-ray microtomography was used to monitor non-destructively corrosion processes within bulk materials. In the selected aggressive solutions, surface–deformed layers showed high localized corrosion susceptibility, but are more stable than the bulk of the alloy during corrosion propagation. In addition, exfoliation-like attack was observed as a transition from intergranular attack. This directed corrosion is not related to grain or crystallographic structure. Finally, intermetallic particles dissolution inside the materials after contact with aggressive solution of the intergranular corrosion path was evidenced.

The effect of welding parameters (rotation speed and travel speed) on the corrosion behaviour of friction stir welds in the high strength aluminium alloy AA2024–T351 was investigated. It was found that rotation speed plays a major role in controlling the location of corrosion attack. Localised intergranular attack was observed in the nugget region for low rotation speed welds, whereas for higher rotation speed welds, attack occurred predominantly in the heat-affected zone. The increase in anodic reactivity in the weld zone was due to the sensitisation of the grain boundaries leading to intergranular attack. Enhancement of cathodic reactivity was also found in the nugget as a result of the precipitation of S-phase. The results were compared with samples of AA2024–T351 that had been heat treated to simulate the thermal cycle associated with welding, and with samples that had been exposed to high temperatures for extended periods to cause significant over-ageing.

A modified version of the Cu-depletion electrochemical framework was used to explain the metallurgical factor causal to intergranular stress corrosion cracking (IGSCC) susceptibility in two Al–Cu–Mg–Ag alloys (i.e., Al–5.0%Cu–0.8%Mg–0.5%Ag and Al–5.4%Cu–0.5%Mg–0.5%Ag). This framework was also used to explain the specific cases of IGSCC susceptibility in the under-aged condition and increased IGSCC resistance with over-aging. Susceptibility in the under-aged and T8 (peak-aged) conditions is consistent with the grain boundary Cu-depletion mechanism and high concentrations of Cu in solid solution in grain interiors. Improvement in resistance to IGSCC of the over-aged T8+ condition (i.e., T8 temper followed by an additional thermal exposure of 5000 h at 107.2 °C) can be explained by elimination of the differential Cu concentration adjacent to the grain boundary compared to that of the grain interior. The resultant leveling of Cu concentration leads to the suppression of a preferential dissolution path at the grain boundaries associated with IGSCC.

The corrosion susceptibility of friction stir welds in AA2024-T351 was found to vary with the weld processing parameters. Corrosion attack was investigated with in situ X-ray tomography, which showed how the penetration of corrosion into the interior of the structure varied with weld microstructure. The susceptibility to corrosion was related to the degree of overageing by comparing the corrosion behaviour to samples of the base alloy that had been aged at different temperatures. A systematic increase first in the anodic reactivity and then the cathodic reactivity of the overaged structures with temperature can be used to predict the location of the region of the weld with the highest susceptibility to corrosion. Similar investigations were made for a dissimilar weld between AA2024 and AA7010. Laser surface melting produces a thin homogeneous melted and rapidly solidified layer over the weld surface leading to a substantial improvement in corrosion resistance.

AA5182 (Al-4.5 wt% Mg) can become susceptible to intergranular corrosion (IGC) with time at moderately elevated service temperatures owing to precipitation of Mg-rich β-phase at grain boundaries, which can lead to stress corrosion cracking (SCC). The IGC and SCC susceptibility of AA5182 was found to depend strongly on sensitisation heat treatments. AFM and TEM studies demonstrated that the degree of precipitation and thus susceptibility to attack for a boundary can be related to its crystallographic misorientation. Low angle boundaries (

The corrosion behaviour of a dissimilar metal friction stir weld between AA2024–T351 and AA7010–T7651 was investigated. Gel visualisation and immersion tests were used to examine the effect of galvanic coupling between the two components. A microelectrochemical cell with a 400 μm diameter glass tip was used to measure the anodic and cathodic reactivities at different positions in the weld region as well as in the base alloys. It was found that the net anodic attack was in the 7010 alloy with the highest susceptibility in the nugget region. The nugget region of 2024 was protected by its high net cathodic reactivity owing to the precipitation of S phase particles.

The early stages of stress-assisted corrosion and stress corrosion crack (SCC) initiation from machine-notched aluminum alloy (AA) 2096 (UNS A92096) specimens, lacking prefatigue cracks, were investigated. Double-notched tensile specimens of an extremely SCC-susceptible underaged (i.e., 4-h artificially aging at 160°C) temper of AA2096 were exposed in an alternate immersion (A/I) 0.6 sodium chloride (NaCl) environment. Focused ion beam (FIB) sectioning/secondary electron imaging methods were used to study and document the earliest stages of pit, intersubgranular corrosion, corrosion fissure, and SCC development starting from LT surfaces. SCC in machine-notched AA2096 involved several stages: trenching of the alloy matrix along bands of constituent particles, constituent particle-induced pit or trench coalescence, elongated corrosion fissure growth initially by general dissolution on the length scale of subgrains and the transition to intersubgranular attack, followed by the initiation/transition ...

Alternative aluminum alloys are under consideration for drop-in replacement and refurbishment of corrosion and stress corrosion cracking prone AA7075-T6 (UNS A97075) components on aging military aircraft. An assessment of new materials for refurbishment and replacement of older generation, aging components is necessary for a viable life extension program. A quantitative database of stress corrosion cracking (SCC) properties of old generation materials compared to currently available materials is needed as a guideline/justification for part replacement. This effort evaluates AA7150-T7751 (UNS A97150) and AA7040-T7651 (UNS A97040), both which meet mechanical property requirements and are thought to be superior to AA7075-T6 in terms of corrosion performance. Specifically, stress corrosion crack growth rates for these plate alloys were documented and found to be similar in various bulk aqueous chloride environments and to represent a significant improvement over measured rates for AA7075-T651.

The susceptibility of aluminum alloy 7075 (AA7075 [UNS A97075]) to intergranular stress corrosion cracking (SCC) in the peak strength T6 temper is alleviated through the use of the T73, or over-aged temper, which provides improved SCC resistance with a 10% to 15% strength loss compared to the T6 temper. Previous research has indicated that retrogression and re-aging (RRA) heat treatments reduce the trade-off between T6 strength and T73 SCC resistance. The short-term heat treatment they used, however, limited the applicability of RRA to thin sections of material. The primary goals of this research effort were to determine if lower retrogression temperatures could be used in the RRA process to extend the applicability of this heat treatment to thick section aircraft components and to quantify any observed improvements. Alternate immersion (AI) and double-cantilever beam (DCB) tests were conducted in a 0.6-M sodium chloride (NaCl) solution to evaluate the SCC resistance of various tempers. Improveme...

Superoxide anion and nitric oxide can react to form the highly oxidizing species peroxynitrite. The objective of this research was to determine if peroxynitrite can promote the discoloration of myoglobin under conditions expected in muscle foods. Reagent peroxynitrite (25-100 microM) caused rapid and extensive formation of metmyoglobin from oxymyoglobin with the majority of metmyoglobin formation occurring during the first 5-10 min of incubation. Carbon dioxide caused a small decrease in the ability of peroxynitrite to oxidize oxymyoglobin, and peroxynitrite-promoted conversion of oxymyoglobin to metmyoglobin increased with decreasing pH (5.5-7.0). Differential scanning calorimetry suggested that peroxynitrite caused minimal changes in myoglobin structure. These results indicate that peroxynitrite can promote the conversion of oxymyoglobin to metmyoglobin under the conditions expected in muscle foods.

The need to populate the fusion materials engineering data base has long been recognized, the IFMIF facility being the present proposed neutron source for this purpose. Re-evaluation of the regulatory approach for the EU proposed DEMO device shows that the specification of the neutron source can be reduced with respect to IFMIF, allowing lower risk technology solutions to be considered. The justification for this approach is presented and a description of a proposed facility, FAFNIR, is presented with more detailed discussion of the accelerator and target designs., Comment: 7 pages, 4 figures. arXiv admin note: text overlap with arXiv:1407.5660. text overlap with arXiv:1407.5660