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The high cost of noble metal raw materials is a major limitation to the production of hydrogen from electrocatalytic water splitting. Nowadays, the poor activity and complex synthesis methods of non-noble electrocatalysts need to be urgently improved. Herein, we prepared the Fe-Si-B alloys with nanosheet structure on the surface by de-alloying process in KOH solution. Experimental results indicate that there are lots of B-doped Fe nanosheets on the surface due to the faster dissolution rate of Fe-Si phase in the alkaline solution. The small amounts of boron remaining and the oxidation of the Fe nanosheets could enhance the activity of the hydrogen evolution reaction (HER). The HER overpotential under 10 mA/cm2 is 214 mV. The coordination between elemental components and the de-alloying process not only increased the electrochemical surface area, but also enhanced electrocatalytic activity of iron atoms. This work provides a new idea for the design of Fe-based electrocatalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding how hydrogen affects the slip and twinning behaviors in metals is paramount for ensuring safe material use in a hydrogen environment and contributing to the development of hydrogen-resistant structural metals. Despite recent reports highlighting an increase in hydrogen-induced twinning in metals under applied deformations, the root case remains elusive. Here, we use molecular dynamics simulations to investigate how high hydrogen concentrations and shear direction affect edge-dislocation behavior in bcc iron. Our findings reveal that the pinning effect increases with hydrogen density along the dislocation line. This effect becomes more pronounced when shear is applied along the twinning direction. We demonstrate the nucleation of micro-twinning, characterized by a three atomic-layer thickness, originating from the dislocation under these conditions. The growth mechanism of this phenomenon aligns with Mahajan's model. Our findings identify the high shear stress as the primary driver for twinning, owing to the hydrogen's strong pinning effect. [Display omitted] [ABSTRACT FROM AUTHOR]

FeNiCoAlTaB shape-memory alloys are desirable alternatives to other smart metallic materials owing to their low base metal and processing costs. These alloys, however, require strong texture via thermomechanical treatments or directional solidification to obtain good functional properties. Here, we demonstrate the fabrication of FeNiCoAlTaB shape-memory wires by a rapid, continuous wire-casting process. These untextured wires exhibit 7% superelastic strains and 1.2 GPa tensile strength after training, and show good cyclability and low stress hysteresis at room temperature. These properties far surpass previous reports in untextured polycrystalline ferrous alloys, an improvement which we attribute to their unique oligocrystalline grain structure. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In situ irradiation in transmission electron microscope following pre-irradiation was performed on Fe-0.6Ni alloy to investigate the growth of dislocation loops under irradiation. The observations showed two types of loop growth behaviour. One type was almost linear growth with irradiation dose, possibly caused by loop absorbing freely migrating defects. The other was abrupt growth with rapid increase in diameter. It was found that nanometre-sized loop might migrate one-dimensionally, following which the large loop could absorb the small loop. This process can result in the abrupt growth of loop and broadening of loop size distribution. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Under high pressure of 4 GPa, cooling at 10 °C/s from 1050 °C to ambient temperature induces unprecedented hardening by a factor of 4 (600 HV) in a binary Fe-15 wt.%Cr alloy that is traditionally unable to be hardened via heat treatment. A martensite of body centered cubic structure was induced, having the common features of hierarchical packet-block-lath structure of lath martensite in ferrous alloys, but with substructure of high density of twinned variants (lath) of 31 nm in average thickness. This study allows good combination of hardening and high temperature oxidation resistance in binary Fe-Cr system without alloying extra elements. Image, graphical abstract [ABSTRACT FROM AUTHOR]

This article introduces a practical and straightforward strategy to take a paradigm shift in the high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) design concept from equiatomic alloys towards cost-effective ferrous medium-entropy alloys (FeMEAs). Upon deviating from the equiatomic composition in Fe-containing alloy system, we show that various FeMEAs can be developed by pseudo-binary methods. Further, we discuss an overview of the microstructural evolution and mechanical properties of recently-developed FeMEAs, which exhibit a broad spectrum of microstructures and mechanical properties. This viewpoint article highlights insights into the concept of FeMEAs, providing a potential direction for future development of HEAs and MEAs. [ABSTRACT FROM AUTHOR]

Although mechanical alloying can force immiscible elements into homogeneous solid solution due to its chemically "randomizing" nature, as microstructure design of powder-processed alloys advances, other alloy configurations are also sought. Here we study ball milling of Fe–Mg alloys and obtain a heterogeneous nanostructure, with grain boundaries decorated by solute even after reaching complete supersaturation and a steady-state grain size. Such nanocrystalline powders having grain boundary segregation in the as-milled state are particularly useful for thermal stability against grain growth. The high diffusivity of Mg is thought to shift the competition between ballistic mixing and equilibration, permitting such a structure to form. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The structural stability of CeFe 12 is investigated by using first-principles calculation. The formation energies of CeFe 12 relative to the Ce 2 Fe 17 + Fe phase and to the CeFe 2 + Fe phase are calculated with the assumptions of trivalency and tetravalency for Ce. We compare them with corresponding results for Nd, Sm, and Zr. Our results suggest that the tetravalent Ce is a promising stabilizer of the ThMn 12 structure. We also show that the stabilizing effect depends as much on the valency as on the size of R (rare-earth) element by investigating R Fe 12 where R is assumed to have a hypothetical valency. [ABSTRACT FROM AUTHOR]

The migration behaviors of minor-phase globules are comparatively studied inside (radius=) 200 μm and 400 μm droplets based on the model of Fe-58wt.%Sn alloy under reduced-gravity condition. It was found that the final relative positions of same-sized globules are not dependent on the droplet sizes, although the globule's migrating velocity and lifetime inside different-sized droplet alloys are different. This finding is contrary to the conventional understanding that the droplet size can exert great influence on the microstructures by controlling Marangoni motion, and moreover offers a new insight into how to design the desired structures in the droplet immiscible alloy. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Phase stress evolution of face-centered cubic (FCC) and deformation-induced body-centered cubic (BCC) phases was measured in recently developed ferrous medium-entropy alloy. This was done during tensile deformation at −137 °C using in situ neutron diffraction measurement for the quantitative interpretation of the role of martensitic transformation on the improved low-temperature tensile properties. The strain-hardening rate curve exhibits two-stage hardening behavior, and the phase stress and stress contribution from the BCC phase increases significantly while that from FCC phase decreases during plastic deformation. This is a direct demonstration that BCC phase contributes significantly to the increase in strength and strain hardening. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Room temperature strength of nine multi-principle element body-centered cubic alloys are predicted using atomistic potentials and a solution-hardening model. The complex solute dislocation interactions are estimated using Embedded Atom Method potentials. At least six of these alloys are known to form single-phase solid solutions on annealing. Assuming that strength is rate limited by screw motion by kink migration, the interaction energies are incorporated into Suzuki's model for kink-solute interactions and evaluated at room temperature. The method predicts room temperature yield strength across all the alloys with a standard error of 13%. Graphical abstract Fig: Room temperature yield strength of single phase BCC quaternary alloys, experimental data and Suzuki model predictions. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Liquids metal dealloying is a new technology to create porous materials. In this study, a commercial Incoloy 825 nickel superalloy is dealloyed for 1 h at 3 different temperatures to elaborate a fully porous FeCr-based metal with 3 different porous microstructures. The resulting porous metals showed unimodal pore distribution, hierarchical structure or, contain large ligaments inclusions. The passivation ability of the porous material was conformed irrespective of the microstructure. This letter proves the possibility of fabricating low cost high specific surface materials for electrochemical applications. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

A combined large-scale first principles approach with machine learning and materials informatics is proposed to quickly sweep the chemistry-composition space of advanced high strength steels (AHSS). AHSS are composed of iron and key alloying elements such as aluminum and manganese. A systematic exploration of the distribution of aluminum and manganese atoms in iron is used to investigate low stacking fault energies configurations using first principles calculations. To overcome the computational cost of exploring the composition space, this process is sped up using an automated machine learning tool: DeepHyper. Our results predict that it is energetically favorable for Al to stay away from a stacking fault, but Mn atoms do not affect the stacking fault energy and can stay in the vicinity of the fault. The distribution of Al and Mn atoms in systems containing stacking faults and the effects of their interactions on the equilibrium distribution are systematically analyzed. [ABSTRACT FROM AUTHOR]

We report the microstructures and mechanical properties of a novel Co-free Fe 46.0 Ni 28.6 Cr 18.5 Al 3.9 Ti 3.0 multicomponent alloy containing L1 2 particles with a high density and heterogeneous distribution. The sample annealed at 600 °C for 3 h exhibited various types of L1 2 particles such as continuous, discontinuous, and incoherent precipitates. The enhanced precipitation strengthening by the heterogeneous precipitation and activation of multiple strengthening mechanisms such as dislocation plasticity, multi-variant stacking faults, and deformation-induced 9R/D0 24 phases could lead to an exceptional combination of strength and ductility (ultimate tensile strength: 1465 MPa, yield strength: 1265 MPa, total elongation: 17%). [Display omitted] [ABSTRACT FROM AUTHOR]

Minor rare earth Tb addition greatly enhances the magnetostriction of Fe 83 Ga 17 alloy. However, the structural origin of the enhanced magnetostriction remains unclear, since it is quite difficult to detect Tb element directly. Here, high temperature annealing is designed to tune the Tb solubility for exploring its structure origin in the Tb doped Fe 83 Ga 17 ribbons. It is found during annealing a Tb-rich phase precipitates, leading to the decrease of the tetragonal distortion of the matrix, and the dramatic decrease of the magnetostriction accordingly. These results inversely consolidate that the enhanced magnetostriction is induced by solid soluted Tb element in Fe-Ga alloy. [ABSTRACT FROM AUTHOR]

We investigated the effects of hydrogen on the mechanical response and embrittlement behavior of Fe20Mn20Ni20Cr20Co and Fe30Mn10Cr10Co (at.%) alloys precharged with 100 MPa hydrogen gas. These alloys can be classified as stable and metastable austenite-based high entropy alloys (HEAs), respectively. We carried out tensile tests at initial strain rates of 10 −4 and 10 −2 s −1 at ambient temperature. Both HEAs revealed hydrogen embrittlement associated with localized plasticity-assisted intergranular crack initiation. It is important to note that hydrogen-assisted cracking of the metastable HEA occurred via localized plasticity for both the austenite and ε-martensite phases – an unusual observation for the latter. [ABSTRACT FROM AUTHOR]

Abstract A series of novel Co-free high-entropy alloys (HEAs) were developed by engineering nanoprecipitation in Fe-Ni-Cr-Mn-Al-Ti system, which exhibit a good combination of low cost, high strength and good ductility. The effects of Ti/Al ratio (from 0.6 to 1.7) on phase structures and mechanical properties were carefully investigated. Specifically, the alloy with a high Ti/Al ratio of 1.7 gives a high tensile strength of 1.25 GPa with a good ductility over 20 %, obviously outperforming other Co-free HEAs. The strain-hardening behaviors and deformation micro-mechanisms were analyzed by transmission electron microscope, which reveals the structural origins of their superior mechanical properties. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Here, in situ ion irradiation and rate theory calculations were employed to directly compare the radiation resistance of an oxide dispersion strengthened alloy with that of a conventional ferritic/martensitic alloy. Compared to the rapid buildup of dislocation loops, loop growth, and formation of network dislocations in the conventional ferritic/martensitic alloy, the superior radiation resistance of the oxide dispersion strengthened alloy is manifested by its stable dislocation structure under the same irradiation conditions. The results are consistent with rate theory calculations, which show that high-density nanoparticles can significantly reduce freely migrating defects and suppress the buildup of clustered defects. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Our first-principles investigation on the interaction of vacancies, interstitial H, and solute Cr atoms demonstrates although both Cr and Fe hydrides are unstable as stand-along materials, atomic layers of (Cr,Fe)H 2 are stable in H-supersaturated Fe-Cr alloy. They have coherent interfaces with the Fe matrix, but still can serve as sinks for self-interstitials, vacancies, and also He atoms, improving the irradiation resistance to void swelling. Manganese will enhance the stability of the thin-film, while C and W have strong destroying effect. This finding points to new possibilities of stabilizing an otherwise unstable compound by constraining it in an alloy. [ABSTRACT FROM AUTHOR]

0.2 at.%Nb doping to a Nd 12.83 Fe 76.7 Co 4.50 Ga 0.53 B 5.44 alloy suppress the surface crystallization in melt-spun ribbon, thereby suppressing the formation of non-oriented grains during the hot-deformation process to form bulk anisotropic magnet, which leads to the enhancement of remanence. High resolution transmission electron microscopy and three-dimension atom probe tomography revealed that the segregation of Nb at the grain boundaries hinders the grain growth during the hot-deformation process, thereby reducing the size and the aspect ratio of Nd 2 Fe 14 B grains and increasing coercivity. [ABSTRACT FROM AUTHOR]

In this work, on the basis of multiphase characterics of near Ga-27 at.% alloy, magnetic field annealing was applied in a directional solidification (DS) 〈001〉 oriented Fe 73 Ga 27 polycrystalline alloy, and the saturation magnetostriction of 370 ppm under low magnetic field has been achieved. Large numbers of multiphase nanoparticles are precipitated in this process; also the magnetic heterogeneities are used to enhance magnetostriction. Meanwhile, this method provides an approach for developing excellent magnetostrictive materials. [ABSTRACT FROM AUTHOR]

The concept of cell boundary (CB) engineering was proposed to explore the potential benefits of segregation engineering in obtaining superior mechanical properties in materials printed via laser powder bed fusion (LPBF). Mo-doped and Mo-free ferrous medium-entropy alloys (FeMEAs) were additively manufactured using LPBF. A high density of dislocation networks with Mo segregation along the CB was observed in the Mo-doped FeMEA. The Mo-doped FeMEA achieved significantly enhanced strength and ductility compared to the Mo-free counterpart. This strengthening effect was attributed to the higher contribution of back stress and improved strain hardening ability, facilitated by the Mo segregation and nano-precipitates at the CBs. This work presents a guideline for alloying design in additive manufacturing, aiming to produce high-quality products with excellent mechanical performance by utilizing the unique segregation engineering of LPBF-driven microstructures. [Display omitted] [ABSTRACT FROM AUTHOR]

Synchrotron X-ray microtomography and skeletonisation method were used to study the true 3D network structures and morphologies of the Fe-rich intermetallic phases in recycled Al-5.0%Cu-0.6%Mn alloys with 0.5% and 1.0% Fe. It was found that, the Fe-phases in the 1.0%Fe alloy have node lengths of 5–25 μm; while those in the 0.5%Fe alloy are of 3–17 μm. The Fe-phases in the 1.0%Fe alloy also developed sharper mean curvature with wider distribution than those in the 0.5%Fe alloy. Combining SEM studies of the deeply-etched samples, the true 3D structures of 4 different type Fe phases in both alloys are also revealed and demonstrated. [ABSTRACT FROM AUTHOR]

A novel principle of approaching an instable phase boundary (IPB) is developed for achieving large magnetostriction in Fe-Ga alloys. Unlike the usual approach by quenching at high temperature, the present Fe 81 Ga 19 alloy was quenched near the decomposition phase boundary (773 K) between A2 and (A2 + L1 2 ) after slow cooling to approach the equilibrium condition. The obtained magnetostriction is 120 ppm, 71.4% higher than that of the sample quenched at high temperature (1273 K). The enhanced magnetostriction is due to the lattice softening by quenching near IPB, which may add important insight into developing high-performance magnetostrictive materials. [ABSTRACT FROM AUTHOR]

The status of nanostructured ferritic alloys (NFAs) is summarized. The science underlying NFAs has emerged as a remarkably comprehensive and high quality body of research. The sequence of events and composition-processing paths needed to form and sustain the performance enabling nano-oxides are well established. The nano-oxides are predominantly Y 2 Ti 2 O 7 pyrochlore, and their role in providing outstanding mechanical properties and unique irradiation tolerance is described. Notably, however, producing defect-free NFA components remains a work in progress. The paper argues that the costs and supply of NFAs will be consistent with its selective application to advanced fission and fusion reactors. [ABSTRACT FROM AUTHOR]

The 2011 Fukushima Daiichi disaster raises the requirement of accident tolerant fuel (ATF) cladding. As promising candidates, the FeCrAl ternary alloy and SiC fiber reinforced SiC matrix (SiC/SiC) composites are discussed with details for recent development, as well as the issues of their in-core application and fabrication. Herein, the design of materials based on the Materials Genome Initiative (MGI) is introduced as the effective scheme in accelerating the development for ATF claddings. Correspondingly, the potential technical routes are provided and some examples of preliminary modelling studies as the preparation steps for MGI are presented. [ABSTRACT FROM AUTHOR]

Magnetometry was applied to investigate the formation of α / α ´ martensite in 13 ferrous alloys during immersion in boiling nitrogen and during re-heating to room temperature at controlled heating rates in the range 0.0083–0.83 K s − 1 . Data shows that in 3 of the alloys, those that form {5 5 7} γ martensite, no martensite develops during cooling. For all investigated alloys, irrespective of the type of martensite forming, thermally activated martensite develops during heating . The activation energy for thermally activated martensite formation is in the range 8–27 kJ mol − 1 and increases with the fraction of interstitial solutes in the alloy. [ABSTRACT FROM AUTHOR]

A nanopatterning method involving a ferromagnetic (FM)–paramagnetic (PM) phase transformation caused by ion irradiation has been developed. A (Fe 0.56 Mn 0.44 ) 50 Pt 50 film with the ordered L 1 0 structure and uniaxial magnetocrystalline anisotropy constant ( K u ) of 2.1 × 10 6 J m − 3 was fabricated. Mn ion irradiation produced a smooth FM dot array with dot diameters of 100 nm surrounded by the PM phase, which was obtained from the induced FM–PM phase transition caused by the structural transformation from the L 1 0 structure to the disordered A 1 structure and a slight increase in the Mn content. The magnetization reversal process was studied by investigating the angle dependence of the dot reversal field. [ABSTRACT FROM AUTHOR]

A hierarchical porous metal has been prepared by two-step liquid metal dealloying using an alloy precursor containing two soluble components and two metal baths. After the first dealloying step, one of the soluble components is dissolved and a coarse porous structure is formed. After a shorter dealloying step in another melt, the other soluble component is dissolved and a fine porous structure is formed within the previously formed coarse ligaments. The resultant porous metal presents a hierarchical morphology with a bimodal pore distribution, resulting in a higher porosity and surface-area-to-volume ratio than what can be formed by one-step dealloying methods. [ABSTRACT FROM AUTHOR]

The 2011 Fukushima Daiichi disaster raises the requirement of accident tolerant fuel (ATF) cladding. As promising candidates, the FeCrAl ternary alloy and SiC fiber reinforced SiC matrix (SiC/SiC) composites are discussed with details for recent development, as well as the issues of their in-core application and fabrication. Herein, the design of materials based on the Materials Genome Initiative (MGI) is introduced as the effective scheme in accelerating the development for ATF claddings. Correspondingly, the potential technical routes are provided and some examples of preliminary modelling studies as the preparation steps for MGI are presented. [ABSTRACT FROM AUTHOR]

Fe-33Mn-xC (x = 0, 0.3, 0.6, 0.8, and 1.1 mass%) fully austenitic steels showed ductility degradation owing to dynamic strain aging (DSA). The elongation increased with increasing carbon concentration at a strain rate of 10 − 2 s − 1 . However, in the steels with carbon contents of 0.6%, 0.8%, and 1.1%, the elongation decreased with increasing carbon concentration at a strain rate of 10 − 5 s − 1 where the DAS effect is distinct. Although all specimens showed ductile fracture with the formation of dimples, the work hardening-true stress relation of the Fe-33Mn-1.1C steel demonstrated fracture before satisfying Considère's criterion even at high strain rates. [ABSTRACT FROM AUTHOR]

Magnetometry was applied to quantify the fraction of austenite retained in Fe-C alloys subjected to various treatments. These treatments consisted of: (i) water quenching; (ii) water quenching followed by immersion in boiling nitrogen and again in water; (iii) as for (ii) but re-heating from 77 K at a rate of 0.0083 K s − 1 ; (iv) as for (iii) but (re-)heating at 0.167 K s − 1 interrupted by an isothermal step. Data was coupled with hardness measurements and demonstrates that the re-heating conditions from 77 K significantly influence the fraction of austenite retained at the end of the thermal cycle. [ABSTRACT FROM AUTHOR]

Glassy nanoparticles of a Fe 90 Sc 10 alloy have been studied using small- and wide-angle X-ray scattering. The results indicate that the surface shells have an electron density that is lower than the electron density in the cores of the glassy nanoparticles. The lower electron density seems to result primarily from a lower atomic packing density of the surface shells rather than from compositional variations due to surface segregation. During the consolidation of the glassy nanoparticles, the short-range order and the extra free volume content present in the shells may be transferred into the interfaces of the resulting bulk Fe 90 Sc 10 nanoglasses. [ABSTRACT FROM AUTHOR]

Tensile deformation behavior of the Fe-18Mn-1.5Al-0.6C twinning-induced plasticity steel has been investigated at room temperature, − 125 °C, and − 196 °C. The steel shows the largest ductility at − 125 °C and the smallest ductility at − 196 °C. While work hardening rate continuously decreases with strain at − 196 °C, the specimens tested at other temperatures show a stage where work hardening rate continuously increases with strain, which is more evident at − 125 °C. Stacking faults form most actively at − 125 °C and this contributes to a continuous increase in work hardening rate with strain and an increase in ductility at − 125 °C. [ABSTRACT FROM AUTHOR]

The influence of the chemical compositions of FePt films on the surface segregations of Pt was investigated by cross-sectional high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) of L1 0 -FePt granular films grown on single crystalline MgO substrates. Ab initio atomistic simulations revealed the surface segregation of Pt is detremental for the magentocrystalline anisotropy energy of the L1 0 -FePt grains. This detremental effect is pronounced for the grain size of less than 15 nm. We found that the Pt surface segregation can be suppressed by a trace addition of Ag to the FePt film. [ABSTRACT FROM AUTHOR]

A feasible strategy was developed to fabricate nanoporous iron-based metallic glasses (npFe-MGs) by selective dissolution of the electrochemically active α-Fe nanocrystalline phase from Fe-Nb-B composite alloys. The yielded npFe-MGs exhibited a ligament size of ~ 75 nm and a pore size of ~ 120 nm. Morphology of the npFe-MGs ( i.e. pore size and pore number) could be tailored by the selection of precursor alloys prepared by varying rapid solidification conditions. Such a selective phase-tailoring approach provides new insights to the preparation of metallic glasses with promising nanoporous structure to satisfy a variety of engineering requirements, e.g. catalysis, microwave absorption, capacitor, etc . [ABSTRACT FROM AUTHOR]

Single-phase equiatomic CoCrFeNi high entropy alloy (HEA) is a promising high-entropy base with high tensile ductility and fracture toughness. However, the equal molar fraction of these elements is not a sufficient and necessary condition to obtain a single solid solution with high entropies. Instead, our combination of both calculated phase diagram (CALPHAD) calculations and experimental verifications indicate that the single phase region in the Co-Cr-Fe-Ni HEA system can be extended from a point to a large single phase solid solution island. The significance of this study is that HEAs can be designed with a high design diversity. [ABSTRACT FROM AUTHOR]

The effect of carbon on the persistence of the slip in Fe–3 mass% Si was investigated. We applied micro-sized cantilever bending tests to obtain ψ–χ relationships that enable quantitative analysis of the persistence of the slip. It was demonstrated that the result from decarburized specimens using this method is consistent with those obtained in previous studies from bulk-sized tensile test specimens. This novel method eliminates the difficulty of preparing bulk-sized single-crystal specimens for investigating the persistence of the slip. The persistence of the slip weakened in aged specimens containing 0.016 mass% C and disappeared in quenched specimens with the same carbon content, where wavy slip bands were observed. The reason for these changes in the macroscopically apparent slip plane is explained by the assumption that the frequency of nucleating kink-pair in the competitive {110} planes is a function of the resolved shear stress. [Display omitted] [ABSTRACT FROM AUTHOR]

This work presents a unique low-cost Fe 62 Co 5 Ni 10 Cr 13 Si 7 Al 3 (at%) medium-entropy alloy (MEA) with ultra-high strength and ductility. A duplex partially recrystallized microstructure consisting of face-centered cubic (FCC) and body-centered cubic (BCC) phases was produced by cold-rolling and short-time annealing in the MEA. In the non-recrystallized area, there are high density dislocations, and the ultra-fine grained matrix has lots of nano-precipitates. This MEA has excellent yield strength (1237 MPa and 1640 MPa) and uniform elongation (12.7% and 29.1%) at 298 K and 77 K. Additionally, due to the high multi-stage strain hardening behavior, the ultimate tensile strength of ∼2109 MPa is obtained at 77K. The excellent cryogenic mechanical properties are mainly attributed to high density dislocations, ultra-fine grains, nano-precipitates, huge Lüders deformation, hetero-deformation-induced hardening, and deformation-induced martensitic transformation. [Display omitted] [ABSTRACT FROM AUTHOR]

Fe 3 B is a metastable high temperature phase and exists in orthorhombic and tetragonal structures. Here, we report on synthesis, structural and magnetic properties of tetragonal ( P 4 2 / n ) Fe 3 B stabilized by a very small substitution of Mo (1–3 at.%) for Fe. The (Fe 0.98 Mo 0.02 ) 3 B compound possesses a high Curie temperature of 780 K and high saturation magnetization of 175 A·m 2 /kg (1.60 T). Magnetocrystalline anisotropy field of around 0.8 T and anisotropy energy of 340 kJ/m 3 have been determined for magnetically-oriented fine particles of (Fe 0.98 Mo 0.02 ) 3 B. [ABSTRACT FROM AUTHOR]

Microstructures of FePt films deposited on MgO and MgAl 2 O 4 single crystalline substrates were studied using aberration corrected scanning transmission electron microscopy (STEM). The [100] and [010] variants of L1 0 -FePt were observed in-the-plane of the FePt grains deposited on the MgAl 2 O 4 substrate, which causes in-plane component in magnetization curves. The d-spacing of the (002) planes of L1 0 -FePt deposited on MgAl 2 O 4 is larger than that deposited on MgO. The reduction of lattice mismatch between FePt and the substrate results in the formation of out-of-plane tensile strain leading to increase in d 002 and the formation of the in-plane variants in the L1 0 -FePt grains. [ABSTRACT FROM AUTHOR]

During the interfacial reaction between novel Fe-Cr-B cast steel and molten aluminum the formation of a periodic layered structure was observed at the Cr-rich Fe 2 B/Al interface. The periodic layered structure was investigated by scanning electron microscopy and electron probe micro-analyzer. It was embedded in the Fe-Al intermetallics (reaction productions of the Fe substrate). Cr element had a key influence on the formation of PLS. A model describing the formation of periodic layered structure between novel Fe-Cr-B cast steel and molten aluminum is presented. [ABSTRACT FROM AUTHOR]

The size dependence of the mechanical behavior of a single crystalline equiatomic FeCrCoMnNi single phase high entropy alloy was studied using in situ SEM microcompression. Electron back-scattered diffraction was used in conjunction with high-resolution scanning electron microscopy to identify the dominant slip system activated for accommodating plastic flow. The scaling of the yield strength with the size of the micropillar is discussed in comparison with the size dependence observed in face-centered and body-centered cubic single crystalline metals. [ABSTRACT FROM AUTHOR]

An in situ silver decoration technique using a light microscope was developed. Hydrogen was introduced from the bottom surface of an annealed pure iron specimen, and its top surface was covered with a chemical solution containing silver ions. Samples were exposed for sufficient time for hydrogen permeation to occur from the back to the top surface. The resultant in situ silver decoration visualized that the hydrogen flux through low-angle grain boundaries is lower than that observed at high-angle grain boundaries. The in situ silver decoration technique can be used for kinetic analysis of solute hydrogen in ferritic iron and steels. [ABSTRACT FROM AUTHOR]

The densification mechanism of amorphous Fe 48 Cr 15 Mo 14 Y 2 C 15 B 6 alloy powder during isochronal spark plasma sintering was analyzed to determine the innate function of high heating rates. Densification ensued and concluded at gradually lower temperatures while attaining higher maximum rates with increasing heating rates in the first stage. The shrinkage behavior analyzed under the theoretical framework of viscous flow revealed a steady reduction in the activation energy leading to a resultant enhancement of densification rate in the initial stage. [ABSTRACT FROM AUTHOR]

The effect of heat treatments on superelasticity was investigated in a FeMnAlNi polycrystalline alloy using incremental tensile strain tests at room temperature. Large grains of more than several millimeters can be obtained by a cyclic heat treatment process and the average grain size can be controlled by the number of heat treatment cycles. Improved superelastic response is observed in samples with large relative grain sizes, exhibiting increased elongation to fracture, lower critical stress for transformation, and higher reversibility. [ABSTRACT FROM AUTHOR]

It is well-established that solute segregation to interfaces is driven by the reduction of their energy. Here we propose coherency strain energy reduction due to lattice misfit modification at an interphase boundary, as a distinct driving force for segregation. Our experiments with Fe-Au particles on a sapphire substrate, together with finite element method calculations demonstrated that the elastic energy contribution to the total driving force for Au segregation exceeds its interfacial energy counterpart for particles larger than ~ 10 nm in size. [ABSTRACT FROM AUTHOR]

The shape memory properties of a ferrous single crystalline alloy, FeNiCoAlNb, were investigated along the [100] orientation by superelasticity tests in both tension and compression. Aging was used to form nano-size precipitates to demonstrate and tailor their shape memory properties. After aging at 700 °C for 3 h, [001]-oriented FeNiCoAlNb shows high compression-tension asymmetry and shape recovery of about 4.5% in tension and 8.8% in compression. The superelastic behavior of [001]-oriented FeNiCoAlNb is weakly temperature dependent due to large transformation strain. FeNiCoAlNb has great potential for temperature independent and large scale actuator applications. [ABSTRACT FROM AUTHOR]

The present work reports a cuboidal B2-coherently-enhanced body-centered-cubic (BCC) alloy Al 0.7 CoCrFe 2 Ni with prominent tensile properties at both room (ultimate tensile strength σ b = 1223 MPa and elongation to fracture δ = 7.9%) and high temperatures. This multi-principal-element alloy is developed out of a cluster formula [Al–M 14 ]Al 1 issued from the cluster-plus-glue-atom model of a BCC structure. Here, the [Al–M 14 ] cluster is centered by Al, surrounded by fourteen average atoms M = Co 1/5 Cr 1/5 Fe 2/5 Ni 1/5 , and glued with one Al atom. Its excellent mechanical properties are attributed to a superalloy-like microstructure, characterized by cuboidal B2 nanoprecipitates coherently embedded in the BCC matrix. [ABSTRACT FROM AUTHOR]

A combined approach to calculate the thermodynamic properties of iron and alloy carbides including the thermal and magnetic contribution is derived. Special emphasis is placed on the role of Fe and Mo to the Gibbs free energy. Lower Mo concentration in the carbides corresponds to a higher thermal Gibbs free energy change. The higher Fe content and external magnetic field greatly increase the induced magnetization, reducing the magnetic Gibbs free energy substantially and therefore increase the formation temperature. The stability of M 2 C and M 3 C are mainly determined by the thermal factors, whereas magnetic field has a predominant contribution for M 6 C. [ABSTRACT FROM AUTHOR]