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The demand for advanced Al-based alloys with tailored structural and magnetic properties has intensified for applications requiring a high thermal stability and performance under challenging conditions. This study investigated the phase evolution, magnetic properties, thermal stability, and microstructural changes in the Al-based alloys Al82Fe16Nb2 and Al82Fe14Nb2Mn2, synthesized via mechanical alloying (MA), using stearic acid as a process control agent. The X-ray diffraction results indicated that Al82Fe16Nb2 achieved a β-phase solid solution with 13–14 nm crystallite sizes after 5 h of milling, reaching an amorphous state after 10 h. In contrast, Al82Fe14Nb2Mn2 formed a partially amorphous structure within 10 h, with enhanced stability with additional milling. Magnetic measurements indicated that both alloys possessed soft magnetic behavior under shorter milling times (1–5 h) and transitioned to hard magnetic behavior as amorphization progressed. This phenomenon was associated with a decrease in saturation magnetization (Ms) and an increase in coercivity (Hc) due to structural disorder and residual stresses. Thermal stability analyses on 10 h milled samples conducted via differential scanning calorimetry showed exothermic peaks between 300 and 800 °C, corresponding to phase transformations upon heating. Post-annealing analyses at 550 °C demonstrated the presence of phases including Al, β-phase solid solutions, Al₁3Fe₄, and residual amorphous regions. At 600 °C, the Al3Nb phase emerged as the β-phase, and the amorphous content decreased, while annealing at 700 °C fully decomposed the amorphous phases into stable crystalline forms. Microstructural analyses demonstrated a consistent reduction in and homogenization of particle sizes, with particles decreasing to 1–3 μm in diameter after 10 h. Altogether, these findings highlight MA's effectiveness in tuning the microstructure and magnetic properties of Al–Fe–Nb (Mn) alloys, making these materials suitable for applications requiring a high thermal stability and tailored magnetic responses. [ABSTRACT FROM AUTHOR]

To promote energy savings, high efficiency and miniaturization of power electronic devices, Fe–Si–B–P–Cu nanocrystalline soft magnetic materials with high saturation magnetization (Bs) parallel to that of the 6.5 wt% Si steel and low coercivity (Hc) are desired. In this work, 30 μm-thick Fe84Si3B10P2Cu1 and Fe84.5Si3B9.5P2Cu1 (at.%) amorphous/nanocrystalline precursor ribbons were melt-spun, which has high Fe contents comparable to that of the 6.5 wt% Si steel. These ribbons consist of an amorphous matrix and pre-existing α-Fe of approximately 28–30 nm in size possessed relatively low and similar-value activation energy of nucleation and growth in the range of 224–249 kJ/mol. Which could induce strong crystallization competition and effectively suppress coarsening of the pre-existing α-Fe. The Fe84Si3B10P2Cu1 nanocrystalline alloy obtained by rapid-annealing (∼100 °C/s) the amorphous/nanocrystalline precursor at 480 °C for 30 s (Fe84-480) exhibited a fine and uniform nanostructure containing α-Fe with small average grain size of approximately 23.1 nm and high volume fraction. The Fe84-480 alloy possessed a high Bs of approximately 1.88 T, a low Hc of 8.6 A/m, and good bendability revealed by relatively large bending fracture strain of ∼1.65%, making it a promising soft magnetic material for power electronic devices.

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For decades, materials scientists have relied on the process-structure–property paradigm to guide investigations into material behaviors. Traditional studies often examine a limited number of process-structure–property variables, striving to elucidate mechanisms governing material response. However, this approach is time consuming and can limit exploration, as well as the discovery of process-structure–property relations in novel materials. In this paper, we combined combinatorial sputter deposition and multi-modal high-throughput materials characterization with feedforward neural networks to establish high-dimensional process-structure–property relations in Pt-Au alloys, yielding nanocrystalline alloys with high hardness and low resistivity relevant to electrical contact switch applications. We mapped three indicators of process conditions (composition and two atomic deposition characteristics) onto four indicators of material structure (X-ray diffraction, film thickness, density, and surface roughness) and two indicators of material properties (hardness and resistivity), resulting in 784 unique combinations evaluated over a 13-dimensional space. The neural networks predicted Pt-Au alloys with 18–24 at.% Au, when deposited at specific conditions, to have a nanoindentation hardness up to 7.2 GPa. This high hardness value, comparable to some steels, represents a 3-fold improvement in hardness over “hard gold”, a commonly used electrical contact alloy, while maintaining requisite electrical conductivity. The neural network models provide an avenue to identify expected process windows capable of maximizing material performance.

The present study examines the high-temperature (500–800 °C) oxidation behavior of Fe-10Cr-(3,5) Al alloys and studies the effect of nanocrystalline structure and Al content on their resistance to oxidation. The nanocrystalline (NC) alloy powder was synthesized via planetary ball milling. The prepared NC alloy powder was consolidated using spark plasma sintering to form NC alloys. Subsequently, an annealing of the NC alloys was performed to transform them into microcrystalline (MC) alloys. It was observed that the NC alloys exhibit superior resistance to oxidation compared to their MC counterparts at high temperatures. The superior resistance to oxidation of the NC alloys is attributed to their considerably finer grain size, which enhances the diffusion of those elements to the metal–oxide interface that forms the protective oxide layer. Conversely, the coarser grain size in MC alloys limits the diffusion of the oxide-forming components. Furthermore, the Fe-10Cr-5Al alloy showed greater resistance to oxidation than the Fe-10Cr-3Al alloy. [ABSTRACT FROM AUTHOR]

Crucial limitations on the permissible energy dissipation are one main factor hindering the use of soft magnetic cores at high frequencies. However, applications find limited support in present-day empirical magnetic loss models, which can hardly afford seamless high-frequency extrapolation of the predicting tools available at low frequencies. This is the case, for example, of very thin soft magnetic plates and ribbons, where the rise of eddy currents and their shielding effects at high frequencies must be attuned to the rate-dependent magnetic constitutive equation of the material. We provide in this work a comprehensive broadband (DC-1 GHz) magnetic characterization and the associated physical modeling of the energy loss and permeability properties of different types of amorphous and nanocrystalline ribbons, $6~\mu $ m to $25~\mu $ m thick, endowed with transverse induced anisotropy (7 – 251 J/m3) and well-defined transverse domain structure. The achieved condition of quasi-linear response and excellent broadband soft magnetic properties is shown to conform to an analytical treatment of the dynamics of the magnetization process, which is mostly accomplished by moment rotations and increasingly so under increasing frequencies. By virtue of their spatially homogeneous character, rotations provide a loss contribution matching the classical loss framework. Its broadband calculation by Maxwell’s diffusion equation is carried out by introducing a rate-dependent magnetic constitutive equation of the material, worked out in terms of complex susceptibility using the Landau-Lifshitz equation. The separation between domain wall (low frequencies) and rotational (high frequencies, including spin damping and eddy currents) loss contributions is eventually obtained across a many-decade-wide frequency range.

The induced magnetic anisotropy, domain structure and magnetic properties of nanocrystallized Fe72.9Si15.8B6.9Nb3.2Cu1Co0.2 materials by continuous stress-annealing at 803–903 K under 0–75 MPa were systematically investigated. It was found that the tensile stress applied during annealing is beneficial to reduce the coercivity and core loss by refining the grain size of α-Fe phase. The remanence and permeability for the annealed samples at 853–903 K are negatively correlated with the induced anisotropy, which increases with the applied tensile stress. The stress-annealed samples yield magnetic easy plane perpendicular to the stress axis with an induced anisotropy constant greater than 1200 J/m3. The nanocrystalline cores with a low AC coercivity of 6.0 A/m and low core loss of 16.1 W/kg in combination with a high DC bias capability was successfully fabricated by stress-annealing the amorphous precursor at 878 K under 40 MPa. The current nanocrystalline material has potential for the application as anti-DC transformers in the electronic field. [ABSTRACT FROM AUTHOR]

Nanocrystalline (NC) materials are prone to grain-coarsening at low temperatures—requiring extra solute-element addition for stability. While this approach is established mainly in simple-binary-alloys, it is adjudged “complex” for multicomponent-alloys due to complex-interactions among constituent-elements. We report for the first time that nanograins in multicomponent-high entropy alloy (HEA) stabilize themselves without requiring additional solute if constituent-HEA-elements with highest mixing enthalpy and melting point preferentially segregate to grain boundaries (GBs); a process we term self-stabilization effect in HEAs. Using in-situ X-ray diffraction, scanning/transmission electron microscopy, and atom-probe-tomography (APT), we show that Cr and Fe in NC-AlCoCrFe-HEA (9 nm grain-size) segregate at GBs by site-competition to stabilize it at 0.5Tm (Tm–melting temperature). At 0.6Tm, GB-desegregation is established to be precursor to phase decomposition, and it competes with nanograin stability; this culminates in the onset of grain coarsening at this temperature. Compared with the literature (e.g., NC-AlCoCrFeNi), NC-AlCoCrFe HEA shows exceptional nanograin-stability at high homologous-temperatures; this suggests possible breakdown of the cocktail and sluggish-effects in HEAs, since more elements do not necessarily improve nanograin stability. To the authors’ knowledge, this is the finest stable-NC-HEA produced—it paves a new way of engineering NC-HEAs without coarsening in scalable solid-state processes that require substantially-high temperatures.

Magnetometry and atomic force microscopy (AFM) were used to study the magnetic and structural properties of the R–Fe–B-type (R = Y, Nd, Gd, Ho) alloys. The alloys were synthesized by means of induction melting. The nanocrystalline state of the R–Fe–B-type alloys was reached, mainly, by melt spinning (MS). A multistage treatment of R–Fe–B-type alloys, which included severe plastic deformation of melt-quenched ribbons and subsequent heat treatment, was also used. The surface morphology of samples was studied in detail to interpret the observed magnetic hysteresis loops of the samples. It was found that the type of rare earth ion and treatment methods had the most important influence on the microstructure and magnetic properties. Magnetic and structural properties of the R-Fe-B-type (R = Y, Nd, Gd, Ho) alloys were studied. Samples were synthesized by means of induction melting with subsequent melt spinning. A multistage treatment including severe plastic deformation and heat treatment was also performed. The surface morphology of samples was studied in details to interpret the observed magnetic properties. The type of R ion and treatment methods had the most important influence on the microstructure and magnetic properties. [ABSTRACT FROM AUTHOR]

The present study investigated the surface morphology, phase composition, mechanical properties, and corrosion resistance of Ni-W alloy coatings prepared under current densities of 1–5 A/dm², after undergoing heat treatment at 400 °C, 600 °C, and 900 °C. The grain size of the as-plated Ni-W alloy coating was below 10 nm. After heat treatment at different temperatures, the grain size increased, reaching a maximum value of around 30 nm at 900 °C. Heat treatment crystallized and altered the structure of the coating. Different heat treatment temperatures yielded different precipitates, including Ni4W, Ni6W6C, and WC. The highest coating hardness (820–940 Hv) was achieved at 400 °C, while the best corrosion resistance was achieved at 600 °C. The precipitation hardening phase can be obtained by proper heat treatment temperature, yielding the desired properties of the composite coating. [ABSTRACT FROM AUTHOR]

A theoretical two-dimensional (2D) model is proposed that describes the effect of grain boundary (GB) segregations on the fracture toughness of nanocrystalline or ultrafine-grained alloys. It is shown that GB segregations can lead to crack curvature, providing both crack surface roughness and crack deflection near the crack tip. Within the model, the growth of cracks along GBs under the action of a tensile load is considered. The effects of brittle GB segregations on the crack surface roughness and crack deflection near the crack tip are analyzed, and the associated increase in the fracture toughness of the material is calculated. It is shown that toughening can be achieved if segregations are very brittle and occupy a moderate proportion of GBs. In particular, a sufficiently large (up to 50%) fraction of GBs containing very brittle segregations can increase the fracture toughness by 30–35%. The results of the model can be applied to thin nanocrystalline or ultrafine-grained films. [ABSTRACT FROM AUTHOR]

The article presents both molecular dynamics calculations of binary Fe–Ni alloys and experimental studies of Ti and Co alloyed nanocrystalline alloys with a B2–Ti(Fe, Co) matrix structure as well as bcc-(Nb, Ti) and B2– eutectic phases Ti(Fe, Co). The structures of membrane alloys based on Fe–Ni (arrangement of atoms in coordination polyhedra and interatomic distances between atoms), as well as the kinetics of hydrogen - diffusion and permeability have been studied. It is shown that in the membranes of alloyed alloys with the substitution of Ni for cobalt Fe35-XCoXTi35Nb30, with an excess of Fe than for cobalt, mechanical brittleness is manifested in the B2–TiFe phase, and the plasticity of the B2 phase also decreases. At the same time, the resistance to an increase in hydrogen absorption is also weakened, up to mechanical destruction of membranes, so that in high-entropy alloys Fe0,2Ni0,2Cr0,2Co0,2Mn0,2, Fe0,2Co0,2Cr0,2 Ti0,2Al0,2 Fe and Co in equal parts. Other intermetallic alloys are also promising, having more complex compositions with high or moderate entropy, for example, Zr0,2Ti0,2Nb0,2V0,2Co0,2 and Zr0,2Ti0,2Ta0,2V0,2Co0,2, in addition to hydrogen evolution, also have storage properties. Within the framework of molecular dynamics, the effect of strain hardening of membrane HEA alloys is experimentally presented - the mechanism of synergy with multiple deformation. As a result of such hardening, a partial transformation of the austenitic phase into a martensite phase occurs with the formation of twinning in their fcc/hcp grains and the formation of a two-phase matrix structure.

Nanocrystalline alloys are known for their high density of grain boundaries (GBs), which results in low thermal stability and a tendency for coarsening. In this work, we investigated Fe–Cu alloys to explore the effects of Cu concentration on the thermal stability of nanocrystalline samples. Using hybrid molecular dynamics (MD) and Monte Carlo (MC) simulations, annealing treatments of nanocrystalline samples with varied Cu concentrations were conducted. The simulation results revealed that Cu atoms tended to accumulate at GBs. Subsequently, the model with Cu segregation was subjected to mechanical creep loading at various temperatures. Through the analysis of atomic structure evolution during creep deformation, it was found that Cu segregation efficiently stabilizes GBs and restricts their movement. The present findings highlight that the thermal stability of nanocrystalline Fe–Cu alloys can be effectively improved by introducing suitable Cu segregation at GBs. [ABSTRACT FROM AUTHOR]

The effect of V addition on the hardness and corrosion of aluminum alloy 2024 (AA2024) produced by high‐energy ball milling has been investigated. High‐energy ball milled alloys exhibited enhanced solid solubility of alloying elements and ultrafine grains. The addition of V improved the corrosion resistance of the AA2024 alloy, which was attributed to the deposition of V on the cathodic particles and therefore decrease in their ability to sustain large cathodic currents. [ABSTRACT FROM AUTHOR]

Magnetic small-angle neutron scattering is employed to investigate the magnetic interactions in (Fe0.7Ni0.3)86B14 alloy, a HiB-NANOPERM-type soft magnetic nanocrystalline material, which exhibits an ultrafine microstructure with an average grain size below 10 nm. The neutron data reveal a significant spin-misalignment scattering which is mainly related to the jump of the longitudinal magnetization at internal particle–matrix interfaces. The field dependence of the neutron data can be well described by micromagnetic small-angle neutron scattering theory. In particular, the theory explains the `clover-leaf-type' angular anisotropy observed in the purely magnetic neutron scattering cross section. The presented neutron data analysis also provides access to the magnetic interaction parameters, such as the exchange-stiffness constant, which plays a crucial role towards the optimization of the magnetic softness of Fe-based nanocrystalline materials.

A theoretical two-dimensional (2D) model is proposed that describes the effect of grain boundary (GB) segregations on the fracture toughness of nanocrystalline or ultrafine-grained alloys. It is shown that GB segregations can lead to crack curvature, providing both crack surface roughness and crack deflection near the crack tip. Within the model, the growth of cracks along GBs under the action of a tensile load is considered. The effects of brittle GB segregations on the crack surface roughness and crack deflection near the crack tip are analyzed, and the associated increase in the fracture toughness of the material is calculated. It is shown that toughening can be achieved if segregations are very brittle and occupy a moderate proportion of GBs. In particular, a sufficiently large (up to 50%) fraction of GBs containing very brittle segregations can increase the fracture toughness by 30–35%. The results of the model can be applied to thin nanocrystalline or ultrafine-grained films.

The effect of annealing up to 538 °C (1000 °F) on the hardness and ductility of two electrodeposited bulk nanocrystalline cobalt-phosphorus alloys (L-nCoP, 0.14 at%P and H-nCoP, 2.17 at%P) was investigated. Through a combination of electron microscopy and X-ray/synchrotron diffraction characterization, hardness and bend ductility measurements as well as density functional theory calculations, it is shown that hardness is controlled by four additive contributions. At 0.14 at%P, grain size strengthening and likely grain boundary relaxation are the dominant strengthening mechanisms. In the 2.17 at%P alloy, the contributions from solute strengthening and cobalt phosphide precursors and precipitates are much more significant and typical age strengthening behavior is observed with a peak hardness temperature of 371 °C (700 °F). The bend ductility at 0.14 at%P was in the 12–17 % range up to 482 °C (900 °F). In contrast, the ductility at 2.17 at%P decreased rapidly with increasing annealing temperatures approaching values less than 1 % at 427 °C (800 °F) due to excessive cobalt phosphide precursor and precipitate formation. The dominant deformation mechanism in both alloys was found to be basal dislocation slip. [ABSTRACT FROM AUTHOR]

Nanocrystalline alloys are promising structural materials yet lack thermal stability in many cases. Recent work shows that interface structure has an outsize effect on the thermal behavior of nanostructured alloys. This work focuses on the role of controlled heterophase interface structure in the thermal evolution of model Cu/Nb nanolaminates. We introduce 3D interfaces containing nanoscale heterogeneities in all spatial dimensions between Cu and Nb, forming 3D Cu/Nb. TEM, nanoindentation, and DSC are used in tandem to establish thermal stability and to identify shifts in microstructure as a function of static annealing temperature. 3D interfaces are shown to survive annealing to 300 °C for 1 hr., while 3D Cu/Nb microstructure evolves to form low-density and voided regions correlating to the onset of layer pinch-off between 500 and 600 °C annealing temperatures. A diffusivity- and vacancy energetics-based mechanism is developed to explain void formation driven by 3D interface degradation at elevated temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

We report a machine learning (ML) and Python assisted strategy to accelerate the design and verification of Fe–based amorphous and nanocrystalline alloy with desired properties. Linear Regression (LR), Support Vector Regression (SVR), Decision Tree Regression (DTR), Artificial Neural Network (ANN) and Random Forest Regression (RFR) are employed to build prediction models of soft magnetic properties, such as saturation magnetic flux density (Bs), coercivity force (Hc), magnetization (Ms), Curie temperature (Tc), maximum permeability (µmax) and effective permeability (µe). It is found that ANN has the excellent fitting ability with largest coefficient of determination (R2) to predict the soft magnetic properties of new designed alloys. Then, Python screening is used to find the alloy compositions with best soft magnetic properties of Fe–B–P–C–Nb system. Finally, Fe83B9P3C4Nb1 alloy with good soft magnetic properties has been designed and prepared to verify. It is indicated that the soft magnetic properties of Fe83B9P3C4Nb1 amorphous and nanocrystalline alloy predicted by ML are in agreement with the experimental measured results. These findings indicate that ML and Python assisted approach can accelerate the design of Fe–based alloys with desired properties accurately.

• Gd-substituted nanocrystalline Nd-Fe-B alloys show a notable increase in thermal stability. • Gd substitution increases the Curie temperature (T c) of the RE 2 Fe 14 B phase. • Temperature coefficients α and β for Nd-Fe-B alloys are enhanced by Gd substitution. • Gd exhibits a heightened propensity for incorporation into the RE 2 Fe 14 B grains. Thermal demagnetization of Nd-Fe-B permanent magnets at elevated temperature presents a noteworthy challenge. Current research endeavors are concentrated on enhancing the thermal stability of Nd-Fe-B magnets. This study investigates the use of the cost-effective element Gd as a substitute for Nd in nanocrystalline melt-spun [(Nd 0.8 Pr 0.2) 1-x Gd x ] 14.3 Fe 76.9 B 5.9 M 2.9 (M = Co, Cu, Al and Ga) (wt.%; x = 0–0.6) alloys. Although Gd substitution is not conducive to the magnetic properties of the alloys at room temperature, the Gd-substituted alloys exhibit excellent high-temperature performance. The Curie temperature (T c) of the RE 2 Fe 14 B phase increases from 582 K to 643 K, with increasing Gd substitution from 0 to 0.6. The α and β coefficients for Gd-free (x = 0) alloy are −0.120 %/K and −0.468 %/K, respectively. By Gd substitution, they respectively increase to −0.068 %/K and −0.295 %/K for x = 0.6 alloy, which are superior to that of reported nanocrystalline Nd-Fe-B alloys and commercially sintered Nd-Fe-B magnets. Microstructural analysis revealed that Gd substitution promotes grain refinement. Furthermore, it was observed that Gd is uniformly distributed across both the grain boundary and main grains. Overall, this study offers a cost-effective and straightforward approach for enhancing the thermal stability of Nd-Fe-B magnets. [ABSTRACT FROM AUTHOR]

Grain boundary (GB) solute segregation has been used as a strategy to tailor the properties and processing pathways of a wide range of metallic alloys. GB solute drag results when segregated alloying elements exert a resistive force on migrating GBs hindering their motion. While GB segregation has been the subject of active research, a detailed understanding of solute drag and the migration kinetics of doped boundaries is still lacking, especially in technologically-relevant alloys. Through theoretical analysis, mesoscale modeling, and machine learning studies, we investigate GB segregation and solute drag and establish design maps relating drag effects to relevant alloy and GB properties, i.e., the complete alloy design space. We find that solute drag is dominant in immiscible alloys with far-from-dilute compositions in agreement with experimental observations of GB segregation in metallic alloys. Our analysis reveals that solute–solute interactions within the GB and the degree of segregation asymmetry greatly influence solute drag values. In broad terms, our work provides future avenues to employ GB segregation to control boundary dynamics during materials processing or under service conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (HEAs) possess many useful properties such as high strength and high-temperature stability. So far, most studies on refractory HEAs have been limited to a few well-known compositions and on their coarse-grain bulk forms. Here we fabricate nanocrystalline (TiZrHf)x(NbTa)1−x HEA thin films with a large range of compositions (x = 0.07–0.90) by the direct current (DC) magnetron co-sputtering technique and measure their mechanical properties using the nanoindentation method. All the as-deposited HEA thin films show a solid-solution body-centered cubic (bcc) structure. As the compositional ratio (x) increases, the elastic modulus decreases from 153 to 123 GPa, following the trend of the rule of mixture. As x increases, the hardness first decreases from 6.5 GPa (x = 0.07) to the lowest value (4.6 GPa, x = 0.48) and then increases to the highest value (7.1 GPa, x = 0.90), showing a concave trend. The change in hardness might be attributed to the combinational influence caused by the atomic size and modulus effects, as well as the texture effect. The authors also propose a few open questions for future studies on this and related HEA systems. [ABSTRACT FROM AUTHOR]

Grain growth is prevalent in nanocrystalline (NC) materials at low homologous temperatures. Solute element addition is used to offset excess energy that drives coarsening at grain boundaries (GBs), albeit mostly for simple binary alloys. This thermodynamic approach is considered complicated in multi-component alloy systems due to complex pairwise interactions among alloying elements. Guided by empirical and GB-segregation enthalpy considerations for binary-alloy systems, a novel alloy design strategy, the "pseudo-binary thermodynamic" approach, for stabilizing NC-high entropy alloys (HEAs) and other multi-component-alloy variants is proposed. Using Al 25 Co 25 Cr 25 Fe 25 as a model-HEA to validate this approach, Zr, Sc, and Hf, are identified as the preferred solutes that would segregate to HEA-GBs to stabilize it against growth. Using Zr, NC-Al 25 Co 25 Cr 25 Fe 25 HEAs with minor additions of Zr are synthesized, followed by annealing up to 1123 K. Using advanced characterization techniques- in situ X-ray diffraction (XRD), scanning/transmission electron microscopy (S/TEM), and atom probe tomography, nanograin stability due to coupling self-stabilization and solute-GB segregation effects is reported in HEAs up to substantially high temperatures. The self-stabilization effect originates from the preferential GB-segregation of constituent HEA-elements that stabilizes NC-Al 25 Co 25 Cr 25 Fe 25 up to 0.5T m (T m -melting temperature). Meanwhile, solute-GB segregation originates from Zr segregation to NC-Al 25 Co 25 Cr 25 Fe 25 GBs; this results in further stabilization of the phase and grain-size (≈14 nm) up to ≈0.58 and ≈0.64T m , respectively., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

The effects of minor alloying addition of Cu on the glass-forming ability and crystallization process of Fe71.7−xB16.7Si8.3Zr3.3Cux and Fe72.5−xB16.7Si8.3Hf2.5Cux (x = 0, 0.3, 0.7, 1.0 and 1.3; at%) alloys were investigated. It was found that the critical glass formation size of rod samples gradually decreased from 2.5 to 1 mm with increasing Cu content in these alloys. Single α-Fe phase nanocrystalline alloys were obtained after isothermal annealing the Fe–B–Si–Zr/Hf–Cu glassy alloys containing 0.7–1.0 at% Cu. The Fe71B16.7Si8.3Zr3.3Cu0.7 alloy exhibited good soft magnetic properties with a high saturation magnetization (~ 1.22 T) and a low coercive force (~ 0.6 A/m) after annealing at 853 K for 10 min due to the precipitation of α-Fe nanoparticles of 8 nm size in the glassy matrix. The structural evolution on annealing and the variation tendencies against Cu content of the glass transition temperature, thermal stability and glass-forming ability of the Fe–B–Si–Zr/Hf–Cu amorphous alloys were discussed using a dual-cluster local structure model. [ABSTRACT FROM AUTHOR]

The mechanocatalytic formation of carbonaceous films at the interface between sliding metallic contacts is simultaneously advantageous for reducing friction and adhesion in several tribological applications and detrimental for electrical contacts as they can induce device failure by increasing the contact resistance. Yet, remarkably little is still known about the chemistry, structural and mechanical properties, and tunability of these interfacial layers. In this study, we performed contact pressure-dependent tribological experiments in dry nitrogen containing trace organics on four, nanocrystalline Pt–Au alloys ([Au] from 0 at.% to 10 at.%) – a promising class of alloys for ultralow wear and electrical contact applications. The ex-situ , multi-technique characterization results did not only provide insights into the chemical nature and mechanical behavior of the mechanocatalytic, carbon-rich films formed on Pt–Au surfaces, but also revealed the interplay between catalytic and mechanochemical tribofilm formation controlled by the composition-dependent electronic structure of the Pt–Au substrate and the applied contact pressure. The results of this work provide guidelines for tailoring nanocrystalline alloys to control their mechanocatalytic activity on the basis of variations of the alloy mechanical properties and element's electronic structure with the alloy stoichiometry. [Display omitted] [ABSTRACT FROM AUTHOR]

Impact of rapid annealing on the soft magnetic properties of the Fe80Nb3Cu1Si6B10 alloy has been investigated. Parent as-quenched ribbons were prepared by planar flow casting method. Rapid thermal treatments (7-30s) has been conducted at 500°C using the preheated Cu blocks to ensure elevated heating rate of more than 100 K/s. Reference samples were isothermally annealed in the vacuum furnace for 1 h at the same temperature. X-Ray diffraction unveiled formation of nanocrystalline structure of bcc α-Fe(Si) grains, embedded in the residual amorphous matrix in all processed samples, irrespective of the annealing technique. Evolution of coercivity and saturation magnetization values, obtained from the measured hysteresis loops, showed improved magnetic softness of the rapidly annealed samples, compared to the as-quenched and conventionally processed ones. Significant embrittlement of the samples after nanocrystallization has been observed regardless of annealing time and thermal treatment technique used.

This paper presents the results of research on the structure of bulk rapidly-cooled alloys. The investigated alloys, with the general formula: Fe45+xCo25−xNb9Cu1B20, were produced using the injectioncasting method. The materials were produced in the form of two sets of rods with diameters of either 0.5 mm or 1 mm. Structural studies confirmed that the alloys have a nanocrystalline structure. The following crystalline phases were identified within the volume of the alloys: α-Fe, Fe23B6 and Co23B6, with the last two phases mixed with each other. Additionally, in the alloy samples with a diameter of 1 mm, an unidentified crystalline phase was formed during the solidification process. The magnetic properties of the alloys were determined on the basis of measurements associated with their primary magnetisation curves and static magnetic hysteresis loops. It was found that the addition of Fe, at the expense of Co, reduces the value of the coercive field. Moreover, the 1 mm diameter alloy samples were found to exhibit inferior soft magnetic properties, compared to the 0.5 mm diameter samples. The higher value of the coercivity field, determined for the Fe45Co25Nb9Cu1B20 alloy, is believed to be associated with the presence of residual ordering with hard magnetic properties. For the investigated alloy samples, the process of magnetisation in strong magnetic fields is associated with the suppression of thermally-excited spin-waves. [ABSTRACT FROM AUTHOR]

Nanocrystalline Sm0.5Y0.5Co5 alloys were prepared by mechanical milling, and their magnetic properties were investigated using a physical property measurement system (PPMS) to observe the presence of magnetic interactions and determine the dipolar interaction field. Isothermal remanent magnetization curves (mr) and the normalized direct current demagnetization (md) were measured. The dipolar interaction field the for nanocrystalline Sm0.5Y0.5Co5 alloys was determined, and was representative of the magnetic interactions.

Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this approach in addressing the significant materials challenges imposed by the fusion environment. Here, we employ a ternary alloy design approach for stabilizing W against recrystallization and grain growth while simultaneously enhancing its manufacturability through powder metallurgical processing. Mechanical alloying and grain refinement in W-10 at.% Ti-(10,20) at.% Cr alloys are accomplished through high-energy ball milling with transitions in the microstructure mapped as a function of milling time. We demonstrate the multi-modal nature of the resulting nanocrystalline grain structure and its stability up to 1300 °C with the coarser grain size population correlated to transitions in crystallographic texture that result from the preferred slip systems in BCC W. Field-assisted sintering is employed to consolidate the alloy powders into bulk samples, which, due to the deliberately designed compositional features, are shown to retain ultrafine grain structures despite the presence of minor carbides formed during sintering due to carbon impurities in the ball-milled powders.

There have been considered the characteristics and structure forming of amorphous and nanocrystalline binary and ternary alloys based on Pd, as well as high-entropy Zr − Cu (Ni, Ti) compositions based on binary Ni − Ti, Ni − V and ternary Zr − Cu − Ti systems, which are difficult to manufacture, however, can significantly improve the economic efficiency of the processes of separation, purification of hydrogen and its safe storage. The analysis of the formation specificities of stable functional structures of membrane amorphous and nanocrystalline alloys in depending on their ability to hydride formation was also carried out.

Development of ultra-high strength and corrosion-resistant aluminum (Al) alloys is demonstrated by a combination of suitable alloying elements and processing technology able to cause extended solid solubility and nanocrystalline structure. Binary Al-transition metal (M: Cr, Ni, Mo, Si, Ti, Mn, V, Nb) alloys, produced by high-energy ball milling and subsequent cold compaction, have exhibited significantly high hardness and corrosion resistance compared to any commercial Al alloy. The cyclic potentiodynamic polarization tests revealed a significant improvement in pitting and repassivation potentials. X-ray diffraction analysis revealed the grain refinement

Magnetic properties and high-frequency impedance of nanocrystalline Fe73.5Si16.5B6Nb3Cu1 ribbons are studied in a high-temperature range of 300 to 723 K. The exchange-coupled state of nanocrystallites was found to be destructed at a temperature of about 530 K, which is substantially lower than the Curie temperature of the amorphous phase that is close to 635 K. It was found that, at an ac frequency of above 5 MHz, the marked magnetoimpedance effect (more than 50% for the magneoimpedance ratio in the case of complete impedance) is observed over the whole temperature range under study. This similar behavior can be essential in designing special-purpose magnetic field sensors intended for high-temperature applications. [ABSTRACT FROM AUTHOR]

The composition Au 49 Ag 5.5 Pd 2.3 Cu 26.9 Si 16.3 (at.%) is of interest as the basis for the development of gold-based bulk metallic glasses for application in jewellery. In-situ heating in transmission electron microscopy (TEM) and differential scanning calorimetry (DSC, both conventional and fast) are used to obtain a comprehensive characterization of the decomposition on heating a melt-spun glass of this composition. Linking TEM with DSC over a range of heating rates 0.083‒2000 K s‒1, allows the sample temperature in the TEM heating stage to be calibrated. On heating up to melting, the glass decomposes in up to four stages: (1) complete transformation to single-phase nanocrystalline (Au,Cu) 7 Si; (2) grain growth of this phase; (3) precipitation of (Pd,Ag)Si, reducing the supersaturation of silicon in the (Au,Cu) 7 Si matrix; (4) with the precipitate phase remaining stable, decomposition of the matrix to a mixture of (Au,Ag) 8 Cu 2 , AuCu and Cu 3 Au phases. At all stages, grain diameters remain sub-micrometre; some of the stable nanocrystalline microstructures may themselves be of interest for applications. The characterization of the decomposition can assist in the optimization of the glass composition to improve tarnish-resistance, while retaining adequate glass-forming ability, formability in thermoplastic processing, and resistance to crystallization. For materials in general, the close correlation of in-situ TEM and DSC results should find wide use in characterizing complex transformation sequences. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The present work reports the effect of Ta on densification and microstructure evolution during non-isothermal and spark plasma sintering of nanocrystalline W. Nanocrystalline W-5wt.%Ta alloy powder was synthesised using mechanical alloying. The nanocrystalline powder was characterised thoroughly using X-ray diffraction line profile analysis. Furthermore, the shrinkage behaviour of nanocrystalline powder was investigated during non-isothermal sintering using dilatometry. Subsequently, the alloy powder was consolidated using spark plasma sintering up to 1600°C. The role of Ta on stabilising the microstructure during spark plasma sintering of nanocrystalline W was investigated in detail using electron backscatter diffraction. The average grain size of spark plasma sintered W-5wt.%Ta alloy was observed as 1.73 ± 1 µm. [ABSTRACT FROM AUTHOR]

Interfacial solute segregation behavior of P in nanocrystalline (NC) Ni alloys is investigated at the atomic scale using cross-correlative PED-APT measurements and atomistic simulations. Inhomogeneous P-segregation in grain boundaries (GBs) of NC Ni is observed from both experimental measurements and simulation calculations. Interfacial excess (IE) of the solute within GBs is further studied as function of GB misorientation. Significant scatter is detected in the IE of boundaries with similar misorientation angles and even within special boundaries with identical Σ values. From atomistic simulations, a general trend of increasing IE with initial GB energy and volume is observed but with poor correlation, indicating that the segregation behavior cannot be captured with a single average measure of the entire GB character. Rather the results suggest that the extent of interfacial solute segregation correlates better with fraction of high energy atomic sites in the boundary. By comparing IE values with thermodynamic model predictions, it is shown that the interfacial segregation behavior is strongly influenced by the energy distribution of atomic sites in the GBs. However, in order to predict the extent of solute segregation, the evolution of the atomic energy landscape in the GB with continuous solute segregation must be considered. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Metallic glass ribbons of composition Fe83(Sn/P)5B12 with or without 2% phosphorus substitution were irradiated with a 5 MeV electron beam, and 4 MGy dose. We examined the effect of irradiation on magnetic properties in amorphous sample, and its result in nanocrystallized sample. Both irradiated and non-irradiated samples were annealed at 400 °C for 1/2 h in vacuum to obtain the nanocrystalline phase. The P-containing ribbon is better in terms of magnetic softness but the saturation induction is reduced by 2.5%. Both the materials show merely minute effects of the irradiation after nanocrystallization. [ABSTRACT FROM AUTHOR]

Magnetization curves were measured using the methods of isothermal remanent magnetization (IRM) and direct current demagnetization (DCD) for nanocrystalline Sm0.5Y0.5Co5 alloys. The study of magnetic properties for nanocrystalline Sm0.5Y0.5Co5 alloys was performed with the Physical Property Measurement System (PPMS). The alloys exhibited a high remanent coercivity of 2.1 MA/m. The ratio of magnetic susceptibilities for nanocrystalline Sm0.5Y0.5Co5 alloys was χd/χr = 4.6, indicating the presence of magnetic interactions in the alloys. Nanocrystalline Sm0.5Y0.5Co5 alloys with magnetic interactions were studied by measuring ΔM curves against the magnetic field, and the alloys showed dipolar and exchange interactions. [ABSTRACT FROM AUTHOR]

Nanocrystalline alloys can be stabilized through selective grain boundary segregation of specific solute element additions. Increasing attention is being paid to ternary and higher order systems, where complex interactions govern segregation. To efficiently study the large composition spaces of such systems, we apply a high-throughput combinatorial technique revealing nanocrystalline stability through composition-grain-size maps. We compare two systems with distinct binary and ternary alloy interactions: In Pt–AuAg both binaries are expected to be stable, whereas in Pt–AuPd the Pt–Pd binary is unstable and Au-induced co-segregation of Pd was previously reported. For ternary Pt–AuAg we find excellent thermal stability throughout. The Pt–AuPd system, by contrast, divides into an unstable regime, where Pd solute dominates and precipitates, and a stable regime, where Au solute dominates and retains Pd in the grain boundary. Overall, by combining current theory and the introduced combinatorial approach, stable multicomponent nanocrystalline composition spaces can be rapidly determined. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A supersaturated solid solution nanostructure of an immiscible Co Cu system is among the promising nanocrystalline (NC) alloys offering enhanced thermal and mechanical stability. In this paper, experiments were conducted to study the phase transformation and tailoring microstructure from a homogeneous/single-phase to a heterogeneous/dual-phase solid solution layered Co Cu nanostructure via pulsed electrochemical deposition (PED). The increasing concentration of sodium dodecyl sulfate (SDS) in electrolyte played a crucial role in stabilizing a homogeneous solid solution Co Cu nanostructure. On the other hand, the opposite approach led to the formation of heterogeneous solid solution Co Cu alloys in the form of multilayered nanostructure consisting of the primary and secondary solid solution Co Cu differing in 10–15 at.% Cu. The separation of primary and secondary phase is more prominent with the extended pulsed periods. The mechanical properties of selected single- and dual-phase alloys were investigated through micro-pillar compression, revealing that a combination of a high yield strength and an elevated strain hardening can be achieved in NC materials through a combined solid solution strengthening and hardening through nano-twin (NT). [Display omitted] • Pulsed deposition of homogeneous and heterogeneous solid solution Co Cu nanostructure • SDS plays the vital roles to stabilize homogeneous nanostructure. • Heterogeneous nanostructure was more pronounced with extended pulse period. • The deposits show the highest yield strength among nanostructure Cu, Co, and Co Cu alloys. [ABSTRACT FROM AUTHOR]

• Effects of B, C, Si and P additions on Fe 86 B 14 prepared by ultra-rapid annealing (URA) were investigated. • The effectiveness of URA was affected by metalloid additives and the soft magnetic properties after URA were degraded. • Addition of 1 at% Cu was found to be effective in enhancing the effectiveness of URA. • Multiple compositions were identified to exhibit low coercivity (H c < 3 A/m) where high glass-formability is expected. The effects of metalloid additives (ML = B, C, Si and P) on the structural and magnetic properties were investigated for nanocrystalline Fe 86- x B 14 ML x alloys prepared by ultra-rapid annealing (URA) of melt-spun ribbons. It was found that the effectiveness of URA was affected by these elements and the soft magnetic properties after URA were degraded. Contrarily, addition of 1 at% Cu was found to be effective in enhancing the effectiveness of URA and coercivity (H c) after URA was reduced significantly by Cu addition. These effects of additives on the soft magnetic properties after URA were well understood by considering the activation energy of crystallization. [ABSTRACT FROM AUTHOR]

• Sm 1 Fe 9.5 Co 1 Mo 1.5 showed a 23% energy product enhancement over specimen without cobalt. • Achieved a nearly single 1:12 phase in cast ingots and annealed hot-compacted samples. • Sm 1 Fe 9.5 Co 1 Mo 1.5 's relatively high anisotropy and increased coercivity indicate strong magnet potential. Bulk magnets with the composition of Sm 1 Fe 10.5−x Co x Mo 1.5 (where x = 0, 1, and 2) with the tetragonal ThMn 12 structure were prepared and their intrinsic magnetic properties were studied. The cast samples were then subjected to high-energy-ball-milling (HEBM), followed by hot-compaction at 650 °C. The compacted samples were annealed at temperatures ranging from 700 °C to 1000 °C to obtain high coercivity. The effects of Co on the magnetic properties, including the Curie temperature T C , saturation magnetization M S , anisotropy field H A , and energy product (BH) max were investigated. It is observed that Co substitution increases the Curie temperature, the saturation magnetization, and the remanence, but decreases the anisotropy field and the coercivity. Among the investigated samples, the isotropic Sm 1 Fe 9.5 Co 1 Mo 1.5 showed the highest energy product (21.5 kJ/m3) after annealing at 750 °C for 48 h, marking a 23 % enhancement relative to our specimen without cobalt substitution. [ABSTRACT FROM AUTHOR]

The development of Fe-based nanocrystalline alloys with high saturation magnetization (Bs), excellent magnetic softness and good manufacturability is highly desirable. Here, the effect of substituting 1 at% P for B and Si on the thermal stability, microstructure and magnetic properties of Fe76Cu0.8Nb2.2B9Si12 alloy has been studied in detail. It was found that replacing B with P effectively reduces the coercivity (Hc) of the alloy without deteriorating the Bs and permeability (μ). However, replacing Si with P has little effect on the Hc and Bs, yet significantly reduces the μ. The variation in the magnetic properties can be well understood from the evolution of the microstructure and magnetic anisotropy induced by P microalloying. The Fe76Cu0.8Nb2.2B8Si12P1 alloy with a good processing window, a high Bs of 1.41 T, a great μ of 29,000 at 1 kHz and a low Hc of 0.6 A/m is suitable for high-power electronic devices.