Fe Wt Research Articles

Specific of mechanical alloying of solid-liquid binary system Fe-Ga and effect of different process control agents

Mechanical alloying allows obtaining nonequilibrium structures in various systems, often possessing unique properties, including magnetic ones. Considering the unusual structural features of the magnetostrictive Fe-Ga alloy, this approach may be promising for this system. In this work, extensive experimental studies were carried out aimed at studying the features of mechanical alloying of Fe-Ga. The object of the study was the system Fe-20 wt% Ga in which disordered solid solution α-Fe(Ga) is formed. It was shown that high-intensity milling is an effective tool for mechanical alloying of solid-liquid binary system Fe-Ga, but a serious problem is a low powder recovery, less than 50 %. To solve this problem, various process control agents were tested. Their influence on powder recovery, process kinetics, particle size, carbon contamination, and magnetic properties was studied using a large set of techniques such as XRD, SEM, EDS, VSM, LIBS, and others. It has been shown that, based on a combination of factors, the optimal process control agent for this system is ethanol in an amount of 1 wt%

On the influence of austenite content in orientation selectivity and shear texture evolution during hot rolling of Fe-3 wt% Si grain-oriented electrical steel

A systematic investigation of the development of shear textures during hot rolling of Fe – 3 wt% Si steel has been carried out in the present work with a special focus on the influence of austenite in preferential orientation selectivity. This orientation selectivity was anticipated owing to the fact that texture evolution during thermomechanical processing is entirely an effect of crystallographic rotations and such rotations may experience constraining effects because of surrounding austenite. The influence of austenite on shear texture evolution was studied over a range of finish rolling temperatures (FRTs). The evolution of microstructure and microtexture within the surface-subsurface zone was studied adopting EBSD. Sharp Goss orientation was observed at lower FRT, while texture intensities of Brass and Copper were observed to be high at higher FRT. Additionally, it was inferred that in the surface-subsurface zone, next to the austenite, the ease of rotation about ND contributed to the higher observed frequency of the Brass orientation despite of its overall lesser fraction as compared to Copper orientation. The less observed frequency of Copper orientation near the austenite has been attributed to the resistance offered by the austenite to its adjacent ferrite grains while rotating about TD. This constraining effect of austenite has been shown to be consistent over the entire range of studied FRTs. Moreover, it has been shown that at higher rolling temperatures, the lower constraining effect by austenite paves the way for Goss orientation formation, which acts as the precursor to the formation of Brass at the FRT.

Application of Weak-Beam Dark-Field STEM for Dislocation Loop Analysis†.

Nanoscale dislocation loops formed by irradiation can significantly contribute to both irradiation hardening and embrittlement of materials when subjected to extreme nuclear reactor environments. This study explores the application of weak-beam dark-field (WBDF) scanning transmission electron microscopy (STEM) methods for quantitative irradiation-induced defect analysis in crystalline materials, with a specific focus on dislocation loop imaging and analysis. A high-purity Fe-5 wt% Cr model alloy was irradiated with 8 MeV Fe2+ ions at 450°C to a fluence of 8.8 × 1019 m-2, inducing dislocation loops for analysis. While transmission electron microscopy (TEM) has traditionally been the primary tool for dislocation imaging, recent advancements in STEM technology have reignited interest in using STEM for defect imaging. This study introduces and compares three WBDF STEM methods, demonstrating their effectiveness in suppressing background contrasts, isolating defect information for dislocation loop type classification, providing finer dislocation line images for small loop analysis, and presenting inside-outside contrast for identifying loop nature. Experimental findings indicate that WBDF STEM methods surpass traditional TEM approaches, yielding clearer and more detailed images of dislocation loops. The study concludes by discussing the potential applications of WBDF STEM techniques in defect analysis, emphasizing their adaptability across various material systems beyond nuclear materials.

Cobalt enrichment and metallogenic mechanism of the Galinge skarn iron deposit in the Eastern Kunlun metallogenic belt, western China

Skarn iron deposits, as representative examples of Co-rich magmatic-hydrothermal deposits, are attracting increasing attention due to rising cobalt demand worldwide. However, the specific Co enrichment mechanisms and metallogenic processes in skarn deposits remain elusive. This study presents high-precision in situ U–Pb geochronological data for garnet from skarns, major and trace element analyses of sulfarsenides and sulfides, and X-ray mapping in the Galinge deposit. The Galinge skarn iron deposit formed at 237.1 ± 0.3 Ma (garnet U–Pb dating), during which time the region was in the post-collisional stage. During this period, the crust was thickened, causing delamination of the lithospheric mantle, which further led to the upwelling of asthenospheric materials and partial melting of the lower crust. As the resultant mixed magma ascended, it reacted with carbonate strata to form skarn deposits. Cobalt shows two occurrence modes in the Galinge deposit: independent cobalt minerals such as skutterudite and cobaltite, and isomorphic substitution of Co with other metals in ore minerals (arsenopyrite, pyrrhotite, sphalerite, pyrite, magnetite, and chalcopyrite). Our results revealed that arsenopyrite is the most cobalt-enriched ore mineral in the Galinge deposit, with an average Co content of 34,077 ppm. Other minerals generally contain insignificant Co contents of less than 500 ppm, including sphalerite (471 ppm) > pyrite (194 ppm) > pyrrhotite (145 ppm) > alabandite (∼100 ppm) > magnetite (7 ppm) > chalcopyrite (2 ppm). In arsenopyrite, cobalt and nickel replace iron in accordance with the inverse correlation between the concentrations of cobalt and nickel (wt%) and that of iron. In pyrite and chalcopyrite, a portion of the isomorphic cobalt substitutes for Fe or Cu. The weak correlation between Co (ppm) and Cu or Fe (wt%) indicates that only isomorphic cobalt is carried out by substituting Fe or Cu. The negative correlation between Co + Fe and Zn or Mn suggests that cobalt and iron replace Zn or Mn in sphalerite and alabandite. No evidence of element substitution was observed in pyrrhotite. Our study highlights that during the early mineralization stage, cobalt in the magmatic-hydrothermal fluids migrated in the form of CoCl42-. Subsequently, under the influence of an increase in pH, CoCl42- reacts with H3AsO30 to form CoAs3 (skutterudite). With the continuous precipitation of arsenides and sulfarsenides, the As/S (reduced) ratio decreased, leading to the CoAs3 (skutterudite) changing to CoAsS (cobaltite).

Solidification and microstructure investigation on as-cast and annealed hypoeutectic Ti–Fe alloys

This work explored the solidification behavior, microstructure development, and resulting mechanical properties of hypoeutectic Ti–Fe alloys under both as-cast and annealed conditions. Ti-(27, 28, 29)Fe (wt%) alloys were synthesized through arc-melting, followed by annealing at 950 °C for 24 h and slow furnace cooling. The investigation procedures included thermodynamic calculations, differential scanning calorimetry, scanning electron microscopy, high-temperature laser-scanning confocal microscopy, X-ray diffraction, hardness measurements, and compression tests. The study demonstrated the efficacy of annealing treatments in reducing excess eutectic in the as-cast structure formed during solidification. Results from both thermodynamic calculation and experiment for the solidification process demonstrated reasonable agreement. The high β-stabilizing effect of Fe ensured the presence of the β phase at room temperature under both studied conditions. The solid-solution hardening of the β phase, coupled with the TiFe intermetallic, substantially contributed to the increased hardness and mechanical strength, although the increase in brittleness was noticeable in the as-cast state. Subsequent annealing enhanced plasticity but resulted in a reduction in strength, albeit maintaining yield strength at a considerable level, approximately 1450 MPa.

Determination of phase transformation kinetics under magnetic fields: Modeling based on magnetization and application in a Fe-1 wt.%Cu alloy

A phase transformation model based on magnetization is proposed in this paper, which accurately tracks the change in the phase transformation volume fraction with time/temperature f-T/t by analyzing phase transformation magnetization curves under a magnetic field. This allows for the determination of kinetic parameters related to the nucleation and growth processes such as the phase transformation rate df/dt-T/t and Avrami exponent n, enabling quantitative analysis of phase transformation kinetics under magnetic field effects. Additionally, the phase transformation magnetization under a magnetic field can be accurately fitted by combining the volume fraction calculation model with the Johnson–Mehl–Avrami equation, thus also obtaining the kinetics parameters. The aforementioned two models are applied to study the isothermal and isokinetic transformations of austenite (γ) to ferrite (α) in Fe-1 wt. %Cu alloys, demonstrating the effects of external conditions through variations in kinetic parameters.

Influence of electrochemical hydrogen charging on the mechanical, diffusional, and interfacial properties of an amorphous alumina coating on Fe-8 wt% Cr alloy

Amorphous alumina coatings, intended as hydrogen barriers, were successfully deposited on Fe-8 wt% Cr substrates by plasma ion-assisted deposition technique. The amorphous structure of the coatings was confirmed by transmission electron microscopy and X-ray diffraction. The interfacial and mechanical properties of the coating-substrate system were evaluated using an in-house custom-designed backside electrochemical hydrogen charging method. In this approach, the substrate side faces the electrolyte (hydrogen entry side) and the mechanical behavior was tested on the coating side (hydrogen exit side). A Kelvin-probe-based measurement was performed to determine the hydrogen diffusivity in these amorphous alumina coatings at room temperature using a similar backside charging approach. Chemical and microstructural characterizations, in combination with scratch and hardness testing, show that interfacial hydrogen accumulation is strongly responsible for drastic changes in the scratch morphology of the coating and its adhesion to the substrate. Scratch testing promises to be a quick and easy technique to fingerprint changes at the coating/substrate interface upon hydrogen exposure.Graphical abstract

Investigating the ductile to brittle transition phenomenon in binary Fe-Ni systems using molecular dynamics simulation

Ductile to brittle transition (DBT) phenomenon is commonly observed in BCC Fe-based systems, which significantly deteriorates their low temperature fracture toughness. Ni is known to be an effective alloying element to improve the low temperature toughness by reducing the ductile to brittle transition temperature (DBTT). The present article investigates the role of Ni in tailoring the DBT curve of BCC Fe by employing molecular dynamics (MD) simulation. Here, we performed mode-I loading of different pre-cracked systems (pure Fe, Fe-2 wt% Ni and Fe-4 wt% Ni alloys) over a temperature range of 1–800 K to construct their DBT curves. The DBT curves are subsequently correlated with the temperature sensitivity of fracture stress, which is estimated using the concept of critical strain energy release rate (GIC). The role of Ni in reducing the fracture stress sensitivity is responsible for decreasing the DBTT as well as the slope of the DBT region. The underlying mechanism is discussed in terms of the crack blunting effect of Ni which effectively increases the GIC and hence the fracture stress, particularly at the low temperature regimes. Besides, the significantly large strain rate imposed in MD simulation is mainly responsible for the higher DBTT values when compared with the experimental results. The present paper tackles this strain rate issue by using an appropriate strain rate sensitivity factor to rescale the simulated DBTT values down to the experimental ones, resulting in a good match between the simulated and experimental DBTT.

Effect of nitrogen atmosphere on the printability, microstructure, precipitation, and mechanical properties of laser powder bed fused Fe-xCr alloys

The role of the nitrogen atmosphere on the microstructure and tensile properties of laser powder bed fused (PBF-LB/M) Fe-xCr (x=0, 5, 10, 15, 24 wt%, mixed using elemental Fe and pre-alloyed Fe-46 wt% Cr powders) binary alloys was investigated and compared with those fabricated under an inert (argon) atmosphere. Microstructural characterization reveals the variations of grain morphology with the chemical composition and the distinct effects of nitrogen on grain refinement and texture. Additionally, PBF-LB/M performed under the nitrogen atmosphere leads to the formation of Cr and Fe nitrides in the alloy. Significant enhancements in strength were observed in Fe, Fe-5Cr, and Fe-10Cr fabricated under nitrogen atmosphere due possibly to the solid solution and precipitation strengthening caused by dissolved nitrogen and the nitrides, respectively. However, the Fe-15Cr and Fe-24Cr alloys processed under the nitrogen atmosphere are brittle and crack upon PBF-LB/M due to the residual stresses. The findings in this work enrich the understanding of the effects of fabrication atmospheres in additive manufacturing, insights of which can be extended to diverse categories of alloys.

S-scheme homojunction and activate site engineering over TiO2 for highly efficient photocatalytic nitrogen fixation

The presence of efficient catalytic active sites and an ample supply of electrons are the two indispensable factors for achieving photocatalytic nitrogen fixation. Herein, the Fe-doped TiO2 S-scheme anatase/rutile homojunction (F-T-A/R) was synthesized as a brilliant photocatalyst for photocatalytic nitrogen fixation from N2 to NH3 under ambient atmosphere. The optimized F-T-A/R photocatalyst (A/R = 98:2, Fe-2 wt%) exhibits an unprecedented NH3 generation rate of 358 μmol gcat-1h−1 in water solvent and under simulated solar light irradiation. Experimental and theoretical studies reveal that the constructed S-scheme homojunction in F-T-A/R is conducive to fluent charge separation and adequate supply of electrons on rutile with higher nitrogen fixing activity, while the tuned local electronic structure of oxygen vacancy with Fe doping is engineered to strengthen active sites, synergistically enhancing the photocatalytic nitrogen fixation.

Evaluation of fracture resistance behavior of Alloy 690 material upto 1000°C

Alloy 690 is a nickel-based alloy with a nominal composition of 30% Cr and 10% Fe (wt%). It is denoted as Ni-30Cr-10Fe. This alloy is currently being investigated by various researchers for its use in nuclear industry as a possible replacement of alloy 600 steam generator tubes because of its excellent resistance to inter-granular stress corrosion cracking in water reactor environment. Alloy 690 is mainly used in vitrification melters for immobilization of high level waste in nuclear recycle plant. The temperature of water reactor environment is considerably lower compared to that of vitrification application, where temperature can reach an order of 1000 to 1100˚C. The mechanical and fracture properties of alloy 690 at the elevated temperature is important from the point of view of design and safety analysis of vitrification melter components and it is not available in literature. For this purpose, single edged notched tensile specimens have been fabricated from alloy 690 plates of 10 mm thickness. The fracture specimens have been tested in the temperature range of 25˚C to 1000˚C, which is the operating range of vitrification melters. The crack initiation toughness was obtained using modified blunting line equation in order to account for material strain hardening effect at a given temperature. From the fracture test results, it was observed that the initiation toughness is lowest at 700˚C. To understand this behavior, scanning electron microscopy was carried out on the fracture surface of the tested specimens. The fracture surface of the specimen tested at 700˚C showed presence of brittle phases in the microstructure, which are responsible for lower value of fracture toughness at this condition. The results of this work shall be useful for design and analysis of vitrification melter components.

(Invited) Transition Metals in Ni/GDC for the Reversible Solid Oxide Cell Operation: Optimization of the Mo-Au-Ni Synergy and Further Enhancement Via Substitution of Mo with Fe

The study focused on the elucidation of the synergistic interaction of different wt.% loadings of Mo and Au in Ni/GDC, with the objective to find their optimum content for enhanced rSOC performance. In addition, the promoting effect of Fe in Ni/GDC was stabilized via co-deposition with Au and there is for the first-time comparison among the transition metal modifications of Mo-Au-Ni vs Fe-Au-Ni. A series of samples was prepared, where the content of Au varied between 1 and 3 wt.% and between 0.4 and 1 wt.% for Mo. Physicochemical characterization took place with XRF, BET, SEM, H2-TPR, TPH2O and in-situ H2O-XPS. The effect of the transition metals interaction on the performance of SoA Ni/GDC was investigated via electrochemical I-V and EIS measurements in rSOC operation, by applying different pH2O/pH2 mixtures in the temperature range of 900 – 800 oC. It was found that high Mo and/or Au wt.% content, results in larger Mo-Au-Ni particles and affects differently the bulk and surface interaction of the samples with H2O, as well as the Rohm and Rpol values of the fuel electrodes. The modified samples were less prone to bulk oxidation by H2O, while they exhibited higher surface oxidation of Ni and higher amount of Ce3+, compared to Ni/GDC. On the surface of the optimum 0.4wt.% Mo-1wt.%Au-Ni/GDC: (i) Ni was less oxidized, (ii) Au0 enrichment was more stable and (iii) Mo was more oxidized, overall affecting positively the Rpol versus the electrode with the higher loadings of 1 wt.% Mo-3 wt.% Au. The main degradation factor of the latter cell was ascribed to the increased Rohm . Finally, a new ternary 0.5 wt.% Fe-3 wt.% Au-Ni/GDC electrode is presented, which exhibited superior electrochemical rSOC performance and stability, compared to the optimum Mo-Au-Ni/GDC, highlighting the need for further research in the transition metals effect on SOCs.

Microstructural and micromechanical characterization of intergranular oxidation in Fe-15Cr alloy

Fe-Cr alloy has great potential as an interconnect material for SOFCs at temperatures up to 800 °C, with Cr providing excellent oxidation resistance through the formation of a protective chromium oxide layer. However, internal brittle oxides formed at grain boundaries (GBs) can lead to severe cracking and cause material failure. Here, we report the formation of internal GBs oxide in an Fe-15 wt%Cr alloy. We carried out microstructural and chemical characterization of the intergranular oxide and performed micromechanical testing and FEM simulation to study the fracture behavior at the GBs. Our findings provide insights for improving the oxidation resistance in the material design.

Correlation of microstructural and chemical bonding of FeNi-rGO nanocomposites

This study used the chemical reduction method to synthesize iron-nickel (FeNi)-reduced graphene oxide (rGO) nanocomposites. FeNi-rGO nanocomposites were characterized by Scanning Electron Microscope (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, UV-Vis spectroscopy and Energy dispersive spectroscopy (EDX) to investigate morphology, structural, chemical bonding, optical and compositional study respectively. SEM images revealed the connective network of grains first increased from 186 nm to 295 nm for Fe(1)-rGO to Fe(0.6)Ni(0.4)-rGO and then decreased from 250 nm to 217 nm for Fe(0.4)Ni(0.6)-rGO to Ni(1)-rGO with increased wt% of Ni and decreased wt% of Fe. The crystallite size estimated by the Debye Scherrer equation and WH-plotting also ranged from 12.32 nm to 27.40 nm and 18.70 nm to 27.32 nm respectively, with the increase in Fe wt%. However, the micro-strain of FeNi-rGO altered between 0.00276 and 0.00578. The metallic oxide chemical bond was found to be shifted to a higher frequency with the addition of Ni indicating an increase in the backing of oxygen or carbon with the metal network. The carbon defect parameter, ID/IG varied between 1.40 and 2.48. EDX data analysis showed the presence of C, O, Fe and Ni as primary elements. An increase in the bandgap of nanocomposites in response to UV–visible radiation was observed with the increase in wt% of Ni.

Unravelling the roles of TiN-nanoparticle inoculant in additively manufactured 316 stainless steel

As a potent grain refiner for steel casting, TiN is now widely used to refine γ-austenite in steel additive manufacturing (AM). However, the refining mechanism of TiN during AM remains unclear despite intensive research in recent years. This work aims to boost our understanding on the mechanism of TiN in refining the γ-austenite in AM-fabricated 316 stainless steel and its corresponding effect on the mechanical behaviour. Experimental results show that addition of 1 wt.% TiN nanoparticles led to complete columnar-to-equiaxed transition and significant refinement of the austenite grains to ∼2 µm in the 316 steel. Thermodynamic and kinetic simulations confirmed that, despite the rapid AM solidification, δ-ferrite is the primary solid phase during AM of the 316 steel and γ-austenite forms through subsequent peritectic reaction or direct transformation from the δ-ferrite. This implies that the TiN nanoparticles actually refined the δ-ferrite through promoting its heterogenous nucleation, which in turn refined the γ-austenite. This assumption is verified by the high grain refining efficiency of TiN nanoparticles in an AM-fabricated Fe-4 wt.%Si δ-ferrite alloy, in which δ-ferrite forms directly from the melt and is retained at room temperature. The grain refinement is attributed to the good atomic matching between δ-ferrite and TiN. Grain refinement in the 316 steel through 1 wt.% TiN inoculation not only eliminated the property anisotropy but also led to a high strain-hardening rate upon plastic deformation and thereby a superior strength-ductility synergy with yield strength of 561 MPa, tensile strength of 860 MPa and elongation of 48%.

Microstructure and strengthening of Al-6Ce-3Ni-0.7Fe (wt%) alloy manufactured by laser powder-bed fusion

An Al-6Ce-3Ni-0.7Fe (wt%) alloy was fabricated via laser powder-bed fusion and its microstructure, thermal stability, tensile properties, and creep properties are investigated for two rapid-solidification rates with different eutectic spacings. For both faster- and slower-cooled states, the as-fabricated alloy mostly shows elongated grains with very fine eutectic networks (∼40 nm lamellar width) comprising a high-volume fraction (∼18 %) of intermetallic phases. Faster-cooled samples, however, display a less continuous eutectic network with finer spacing (∼100 nm), leading to higher Orowan strengthening and therefore superior microhardness and yield stress up to ∼350 °C. Upon aging (300 – 450 °C), micron-size Al9(Ni,Fe)2 needle-like precipitates form within grains, and the Al11Ce3 eutectic network spheroidizes, while retaining a submicron width and spacing, resulting in 33–37 % drop in microhardness after 144 h aging at 400 °C. Limited tensile ductility (∼6 %) and creep ductility (∼1–2 %) are measured for both faster- and slower-cooled alloys due to an inhomogeneous microstructure, where cavitation preferentially initiates at melt-pool boundaries, precipitate-free zones, and/or denuded zones, eventually leading to local fracture. Denuded zones, induced by stress, form due to diffusional flow with stress-dependent orientations, and are identified as microstructurally weak regions leading to strain localization. The present alloy does not show a significant difference in 300 °C creep resistance between: (i) tensile and compressive loading, (ii) faster- and slower-cooled samples, and (iii) continuous and spheroidized eutectics. Creep resistance at 300 °C is comparable to that of a Ce-richer Al-10.5Ce-3.1Ni-1.2Mn (wt%) alloy, despite the formation of denuded zones and needle-like Al9(Ni,Fe)2 precipitates.

A novel Al-Si-Ni-Fe near-eutectic alloy for elevated temperature applications

A novel near-eutectic Al-15.0Si-4.1Ni-1.9Fe (wt%) alloy with a ternary eutectic reaction of Liquid→α-Al+Si+(Al,Si)5(Fe,Ni) was investigated. Eutectic Si and (Al,Si)5(Fe,Ni) phases exhibit short nanoscale fibrous morphologies with volume fractions of 14.3 ± 1.6% and 15.1 ± 1.9%, respectively. The (Al,Si)5(Fe,Ni) phase has a tetragonal Al2.7FeSi2.3-type crystal structure with excellent thermal stability, which contributes to high mechanical properties at room and elevated temperatures. First-principles density-functional theory (DFT) calculations reveal its chemical composition of tetragonal (Al4.75Si0.25)(Fe0.5Ni0.5) having Si solution at the Al sites with two Fe neighbours contributes to the lowest solution energy. The newly developed alloy has superior mechanical properties at room and elevated temperatures compared with other typical heat-resistant aluminium alloys, which has great potential for industrial applications.

Structural analysis of Cu-based FeCr reinforced composites prepared by mechanical alloying

Abstract Production and structural investigations of Cu-based FeCr reinforced composite were performed by using mechanical alloying, optical microscope, scanning electron microscope, X-ray diffraction and hardness test. The increment in FeCr addition caused the increment in the cold deformation rate. This situation resulted in breakage of the powder particles throughout mechanical alloying. Thus, the grain dimension of the FeCr powders decreased and the Fe wt.% in the CuCr powders advanced. The collision force between the Cu-Cr powder and the grinding ball weakened with the increase of FeCr concentration and resulted as higher reinforcement size. After mechanical milling, FeCr grains decreased in size more than copper grains due to the ductility of copper grains. The smaller crystals occurred after grinding, and increased the grain boundary zone for further spread of Cr into the Cu. Despite the high sintering process, the high sintering temperature improved the compactness of the alloys, but caused coarsening of the nanoparticles. The mechanical alloying time, reinforcement wt.% and sinter temperature were effective on the micro-hardness of the microstructure.

Enhancement of the intrinsic Ni/GDC activity under rSOC operation by means of Fe–Au doping: An electro-kinetic study

The investigation dealt with the effect of Fe and Au wt.% concentrations on the enhanced performance and stability of Ni/GDC under rSOC operation. Moreover, it focused on the comparison of the intrinsic electro-kinetics between the best performing Fe–Au-modified cell and Ni/GDC under SOE operation. The rSOC performance and stability of all cells was examined in the temperature range of 900–800 °C. The electro-kinetic measurements took place at 900 °C by varying the pH2O. All Fe–Au–Ni/GDC electrodes exhibited enhanced activity, compared to the SoA Ni/GDC, with variations in their stability after three rSOC cycles. Specifically, the fuel electrode with the lowest wt.% concentration in Fe and Au (0.5Fe–1Au–Ni/GDC) exhibited the highest activity and stability under rSOC operation. By increasing the wt.% loadings to 2 wt% Fe and 3 wt% Au, there was rapid degradation of the initially high performance, mainly due to increase of the ohmic resistance. SEM analysis showed higher macro-porosity on the reduced state of the modified electrodes, which in the case of the best performing 0.5Fe–1Au–Ni/GDC was the least affected after rSOC operation. Interestingly, the SOE performance of the examined Fe–Au-modified electrodes was not similarly inhibited by the decrease of temperature, compared to Ni/GDC. This was further clarified through electro-kinetic measurements, aiming to verify the effect from the Fe–Au doping on the intrinsic electrochemical activity of Ni/GDC for the H2O electrolysis reaction. Comparison between the SoA and the best performing 0.5Fe–1Au–Ni/GDC showed an enhancing effect on the intrinsic electro-kinetics of the modified electrode. Specifically, the dependence of the polarization resistance on the pH2O was found to be strongly positive, resulting in a higher apparent reaction order, compared to Ni/GDC.

The Effect of Termomechanical Treatment on the Low-Cyclic Fatigue Behavior in an Al–Cu–Mg–Ag Alloy

The mechanical behavior under monotonic and cyclic loadings has been studied in an Al–4.5Cu–0.56Mg–0.77Ag–0.42Mn–0.12Ti–0.05V–0.02Fe (wt %) alloy subjected to thermomechanical treatment (TMT), including a solution heat treatment, quenching in water, uniaxial tension with a plastic strain of 3%, andpeak aging at 190°C (state T83 according to the classification of the Aluminum Association). The T83-ed alloy demonstrates the lowest tensile strength properties in comparison with T6 state (traditional aging) and TMT,including rolling with a 40%-reduction (T840). Compared to T6 and T840 states, the lowest cyclic strength and cyclic strain hardening coefficients in the Ramberg-Osgood relationship was found to be in T83-ed alloy. To achieve long fatigue life, it is advisable to reduce to the minimum values the degree of intermediate plastic deformation required for straightening Al–Cu–Mg–Ag sheets after their buckling during high-temperature heating for quenching.