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The results of a study aimed at investigating the presence of silver in the strengthening phases of age-hardenable AlCuMgSi alloys are presented. HR STEM observations were performed on Al-4Cu-0.55Mg-0.5Si--0.15Zr-0.1Ti-0.5Ag (wt%) alloy samples aged or crept at 200 °C to monitor the evolution of secondary phases over long times. Results showed that in the peak aged condition silver mostly segregated at the surface of some strengthening precipitates types. This occurred specifically at the particle/matrix interface of θ' phase while particles, matching the wide compositional range of the quaternary Q' phase were free from Ag. A third population of strengthening particles having the shape of a core-shell rod was also observed. They were characterized by a Mg- and Si-rich core and a Cu- and Ag-rich shell. The exposure at 200 °C for up to 570 h, caused an evident coarsening of Q' and θ' plate-like particles, and the Ag surface enrichment of the latter went progressively lost. On the contrary, silver concentrated inhomogeneously on the surface of the core-shell particles for which a relatively low coarsening rate was observed. [ABSTRACT FROM AUTHOR]

For the application in heavy wall pressure vessels such as hydrocracking reactors in the petrochemical industry, creep-resistant 2.25Cr–1Mo-0.25V steel is usually joined via submerged-arc welding. To ensure a long service lifetime at elevated temperatures and high pressures, the steel plates and weldments must maintain a beneficial combination of toughness and creep strength for several years. One approach to adjust the weldments' mechanical properties is to perform a post-weld heat treatment (PWHT). This study is dedicated to the impact of the PWHT-temperature and -time on the complex interplay of microstructure, precipitates and mechanical properties of 2.25Cr–1Mo-0.25V weld metal. The mechanical testing showed that a higher PWHT-temperature increases the weld metal's impact toughness and ductility while simultaneously decreasing its strength and creep resistance. The high-resolution investigation with transmission electron microscopy and high-energy X-ray diffraction demonstrated that this is linked to accelerated recovery processes and severe coarsening of fine MX carbonitrides. At lower PHWT-temperatures, the absolute increase of the MX phase fraction during PWHT and the MX coarsening is less pronounced, allowing the MX carbonitrides to effectively contribute to precipitation hardening by maintaining their fine size. Besides MX carbonitrides, the weld metal consists of Cr-rich M 7 C 3 and M 23 C 6 as well as a substantial amount of Mo- and V-rich M 2 C carbides. The precipitate transformation sequence during PWHT was found to be M 3 C→M 3 C + MX + M 7 C 3 →M 3 C + MX + M 7 C 3 +M 23 C 6 +M 2 C→MX + M 7 C 3 +M 23 C 6 +M 2 C, whereas prolonged annealing times at higher PWHT-temperatures again lead to the dissolution of M 7 C 3 in favor of MX. [Display omitted] • Besides M 7 C 3 , M 23 C 6 and MX, heat-treated 2.25Cr–1Mo-0.25V weld metal also possesses a substantial amount of M 2 C carbides. • The heat treatment temperature is decisive for the MX and M 2 C fraction, as well as the MX/M 2 C-ratio. • The carbide transformation sequence in 2.25Cr–1Mo-0.25V weld metal at 690–720 °C is M 3 C.→ M 3 C + MX + M 7 C 3 → M 3 C + MX + M 7 C 3 +M 23 C 6 +M 2 C → MX + M 7 C 3 +M 23 C 6 +M 2 C. • Prolonged PWHT at 705 and 720 °C causes dissolution of M 7 C 3, which is related to an increase of the MX fraction. [ABSTRACT FROM AUTHOR]

After casting and solidification, Al-cast cylinder heads undergo a sequence of heat treatments to achieve the required strength. The phases responsible for the strengthening appear after solution heat treatment, quenching and artificial ageing. Although the state-of-the-art describes the occurrence of phases in this alloy for some treatment conditions, we missed modelled solutions to predict phases and their characteristics after any heat treatment. This work focuses on developing and validating a complete modelling routine to obtain the precipitates along any heat treatment history of an AlSi7Cu0.5Mg alloy. Firstly, we simulated the solidification process of the casting using the Scheil-approach. Secondly, we calculated the phases formed during cooling, solution heat treatment and ageing using the classical nucleation theory with the MatCalc© software based on the CALPHAD method. Finally, we validated the model with heat flow obtained by calorimetry and microstructures obtained by electron microscopy. After validation, the model can simulate the strengthening phases and explain the hardness ageing curves. On the other hand, the model to date could not reproduce the occurrence of the Ti 17 Al 5 Si 14 phase formed at low temperatures. This Ti-rich phase serves as nucleation sites for a fraction of the Q′ phases and decreases the β phases' precipitation kinetics. [Display omitted] • Ti caused the precipitation of τ1-Ti1 7 Al 5 Si 14. The τ1 phase decreases the precipitation kinetics of the β-familiy phases. • The hardening phases formed at low ageing temperatures are from the β family and at high temperatures from the Q family. • We experimentally validated a thermodynamic-based calculation of the phases formed and transformed during heating. • The validated model can predict the phases formed during ageing. [ABSTRACT FROM AUTHOR]

This paper computes the uncertainties associated with the power system state variables obtained with the help of phasor measurement units (PMUs). An integer-quadratic- programming-based method is used to determine the minimum number and the optimal locations of the PMUs to ensure complete topological observability of the system. Three approaches are used to estimate the uncertainties in the state variables: the use of the classical uncertainty propagation theory, the Monte Carlo method, and the random fuzzy variables (RFVs). The methods are applied on a test system, and the results are presented. The choice of method depends on the application; suggestions are offered based on the conclusions of the work in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Relative rate coefficients (in cm3 molecule−1 s−1) for the gas-phase reactions of OH radicals and Cl atoms with diethyl sulfide (DES) and ethyl methyl sulfide (EMS) have been determined at 298K and atmospheric pressure using long path in situ FTIR analysis: The rate coefficients did not show any dependence on the oxygen partial pressure and are compared with previous determinations. Reactivity trends and atmospheric implications are discussed. [Copyright &y& Elsevier]

Effects of Eu (up to 500 ppm) and P (up to 40 ppm) on solidification and precipitation of Al-7Si-0.3Mg based alloys refined by solute Ta (0.12 wt%) and stochiometric Al-2.2Ti-1B grain refiner were investigated using optical microscopy, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) as well as density functional theory (DFT) calculations. It was found that (i) solute Ta can refine α-Al grains and is unaffected by the addition of Eu and/or P. (ii) 200 ppm Eu is eligible enough to modify eutectic Si although its modification effect can be enhanced with higher Eu additions (up to 500 ppm). (iii) A high P concentration (40 ppm) counteracts the modification effect in the alloy modified with 200 ppm Eu and therefore unmodified structure is obtained. (iv) Even with the addition of Eu and P, the activation energy of stable β-Mg 2 Si is calculated to be very low (60–70 kJ/mol), indicating a short time for the precipitation of β-precipitates. Furthermore, one possible nucleation sequence in Al-Si-Mg based alloys modified with Eu or Sr has been proposed based on the lattice mismatch calculation and thermodynamic stability. Finally, DFT calculations suggest that Eu is energetically favourable for TPRE growth mechanism. The present investigation provides new insights into controlling solidification microstructure (mainly for the grain refinement of α-Al and eutectic grains) and precipitation microstructure (mainly for β-MgSi precipitate) of Al-7Si-0.3Mg based alloys via the addition of Ta and TiB 2 as a refiner of α-Al and the addition of Eu and P as a modifier of eutectic Si. • Solute Ta can refine α-Al grains and is unaffected by the addition of Eu and/or P. • 200 ppm Eu is eligible enough to modify eutectic Si. • A high P concentration (40 ppm) counteracts the modification effect in the alloy modified with 200 ppm Eu. • The activation energy of stable β-Mg 2 Si is calculated to be very low. • Eu is energetically favourable for TPRE growth mechanism. [ABSTRACT FROM AUTHOR]

The electric power systems together with the entire energy sector are rapidly evolving towards a low-carbon, secure, and competitive economy facing revolutionary transformations from technical structure to economic value chain. Pathways to achieve sustainability led to the development of new technologies, accommodation of larger shares of unpredictable and stochastic electricity transfer from sources to end-users without loss of reliability, new business models and services, data management, and so on. The new technologies and incentives for local energy communities along with large development of microgrids are main forces driving the evolution of the low voltage energy sector changing the context and paradigm of rigid contractual binding between utilities and end-user customers (now progressing to flexible prosumers with generation and storage capabilities). The flexibility and operation of a prosumer can be enhanced by a non-intrusive time-frequency analysis of distorted power quality waveforms for both generation and demand at the point of common connection. Therefore, it becomes of importance to discriminate among successive quasi-steady-state operation of a given local system using only the aggregated waveforms information available in the PCC. This paper focuses on the Hilbert–Huang method with modifications such as empirical mode decomposition improved with masking signals based on the Fast Fourier Transform, Hilbert spectral analysis, and a post-processing method for separating components and their amplitudes and frequencies within distorted power signals for a low-voltage prosumer operation. The method is used for a time-frequency-magnitude representation with promising localization capabilities enabling efficient operation for prosumers. [ABSTRACT FROM AUTHOR]

The extremely high surface-to-volume ratio of nanoporous platinum (np-Pt) produced by dealloying was applied for tuning electrical resistance by surface charging. In the as-dealloyed state, a characteristic sign-inversion of the charging-induced resistance variation occurs, which can be associated with the electronic structure of PtO. After electrochemical reduction, the relative resistance variations of np-Pt of up to 58% could be generated by electrochemically induced adsorption and desorption, which was 1 order of magnitude larger compared with that of cluster-assembled nanocrystalline Pt. Although the maximum resistance variation was also higher than that of dealloyed nanoporous gold (np-Au), the resistance variation related to the imposed charge was reduced owing to the higher bulk resistance of Pt compared with that of Au. The sign-inversion behavior of the resistance could be recovered by re-oxidation. [ABSTRACT FROM AUTHOR]

The present work explores the processability of an advanced aluminum alloy, namely AlCu-TiB 2 , by selective laser melting (SLM), and the correlation between microstructure and mechanical properties of as built specimens. The principal process parameters of the laser emission in pulsed wave (PW) mode, namely laser power and exposure time, were varied to achieve full density parts starting from prealloyed powders. Detailed analysis of defects in the highest relative density conditions was performed thzrough X-ray computed tomography. It was found that the highest relative density, up to 99.5%, was achieved at a laser energy density of 82 J/mm3. Microstructure of as-built specimens was analyzed through scanning electron microscopy, coupled with EDX and EBSD analyses, and transmission electron microscopy. The as-built microstructure was considerably uniform, and characterized by fine equiaxed grains, decorated with micrometric and nanometric second phases and an even distribution of reinforcing TiB 2 particles; no epitaxial grain growth was observed. Finally, tensile behaviour of the as-built specimens indicates a yield and ultimate tensile stress of 325 MPa and 395 MPa, respectively, combined with an elongation of 13%. The low work hardening rate and jerky flow characterizing plastic deformation are analyzed and discussed. [Display omitted] • The selective laser melting processability of an AlCu alloy with in-situ TiB 2 nanoparticles was explored and analysed. • Multi-scale microstructural analysis revealed fine equiaxed grains and several micrometric and nanometric secondary phases. • Mechanical behaviour was characterized by low strain hardening and evident jerky flow. [ABSTRACT FROM AUTHOR]

Exploration of microbial-meteorite redox interactions highlights the possibility of bioprocessing of extraterrestrial metal resources and reveals specific microbial fingerprints left on extraterrestrial material. In the present study, we provide our observations on a microbial-meteorite nanoscale interface of the metal respiring thermoacidophile Metallosphaera sedula. M. sedula colonizes the stony meteorite Northwest Africa 1172 (NWA 1172; an H5 ordinary chondrite) and releases free soluble metals, with Ni ions as the most solubilized. We show the redox route of Ni ions, originating from the metallic Ni° of the meteorite grains and leading to released soluble Ni2+. Nanoscale resolution ultrastructural studies of meteorite grown M. sedula coupled to electron energy loss spectroscopy (EELS) points to the redox processing of Fe-bearing meteorite material. Our investigations validate the ability of M. sedula to perform the biotransformation of meteorite minerals, unravel microbial fingerprints left on meteorite material, and provide the next step towards an understanding of meteorite biogeochemistry. Our findings will serve in defining mineralogical and morphological criteria for the identification of metal-containing microfossils. [ABSTRACT FROM AUTHOR]

Solid State Transformers (SST) may become, in the near future, key technological enablers for decentralized energy supply systems. They have the potential to unleash new technologies and operation strategies of microgrids and prosumers to move faster towards a low carbon-based economy. This work proposes a paradigm change in the hierarchically and distributed operated power systems where SSTs are used to asynchronously connect the many small low voltage (LV) distribution networks, such as clusters of prosumers or LV microgrids, to the bulk power system. The need for asynchronously coupled microgrids requires a design that allows the LV system to operate independently from the bulk grid and to rely on its own control systems. The purpose of this new approach is to achieve immune and resilient by design configurations that allow maximizing the integration of Local Renewable Energy Resources (L-RES). The paper analyses from the stability point of view, through simplified numerical simulations, the way in which SST-interconnected microgrids can become immune to disturbances that occur in the bulk power system and how sudden changes in the microgrid can damp out at the Point of Common Coupling (PCC), thus achieving better reliability and predictability in both systems and enabling strong and healthy distributed energy storage systems (DESSs). Moreover, it is shown that in a fully inverter-based microgrid there is no need for mechanical or synthetic inertia to stabilize the microgrid during power unbalances. This happens because the electrostatic energy stored in the capacitors connected behind the SST inverter can be used for a brief time interval, until automation is activated to address the power unbalance for a longer term. [ABSTRACT FROM AUTHOR]

Provides a listing of the editors, board members, and current staff for this issue of the publication. [ABSTRACT FROM PUBLISHER]

Provides a listing of current staff, committee members and society officers. [ABSTRACT FROM AUTHOR]

Provides a listing of current staff, committee members and society officers. [ABSTRACT FROM PUBLISHER]