NiFeMo Alloy Research Articles

Interdiffusivity matrices and atomic mobilities in fcc Ni–Fe–Mo alloys: Experiment and modeling

Accurate diffusivities in fcc Ni–Fe–Mo alloys are of significant importance in designing high-quality magnetic alloys. In this work, totally twelve fcc single-phase diffusion couples are assembled to determine the diffusivities of fcc Ni–Fe–Mo alloys at 1373, 1423 and 1437 K. The diffusivity matrices at the intersection compositions of diffusion paths are determined by the Matano-Kirkaldy method. In addition, the diffusivity matrices along the whole composition profiles of individual diffusion couple and the atomic mobilities of fcc Ni–Fe–Mo alloys are evaluated by the numerical inverse approach incorporated in CALTPP program. The reliability of the obtained atomic mobilities is verified by comparing the predicted diffusion behaviors with the experimental ones. Furthermore, applying the presently obtained atomic mobilities in combination with thermodynamic descriptions, the three-dimensional maps of interdiffusivites, activation energy and frequency-factor planes of fcc Ni–Fe–Mo alloys are constructed to display the composition- and temperature-dependent diffusion properties. The presently obtained diffusivities and atomic mobilities of the Ni–Fe–Mo fcc phase are expected to contribute to high-efficiency Ni–Fe–Mo magnetic alloy design.

Microstructural evolution and magnetic influence mechanism of Cr in-situ alloying SLM-formed NiFeMo alloys

NiFeMo is prevalently employed in the field of aerospace and electronic devices owing to its excellent soft magnetic properties. Besides, the incorporation of elements through in-situ alloying presents a novel strategy for performance modulation in Selective Laser Melting (SLM), presenting a novel pathway toward the advancement of soft magnetic materials. In this study, (NiFeMo)100-xCrx alloys (x=0 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%) were prepared utilizing Cr in-situ alloying SLM. The magnetic properties as well as microstructural characterization were conducted by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), high-resolution transmission electron microscopy (HRTEM) (Tecnai-G2-F30), and direct current B-H hysteresis curve testing equipment (MATS-2010S). The results indicate that the microstructure of the SLM-formed NiFeMo alloy through in-situ chromium alloying is predominantly characterized by columnar grains growing along the build direction. With an increase in the in-situ alloying ratio of chromium, the lattice parameters of the FCC phase structure of the NiFeMo alloy decrease from 3.582 Å to 3.503 Å, the average grain size monotonically decreases, and the maximum texture strength monotonically weakens. Furthermore, during the in-situ alloying SLM process, chromium is dissolved into the FCC γ-(Ni, Fe) of the NiFeMo alloy, forming dispersed, chromium-rich precipitates of larger sizes. This leads to a reduction in the intrinsic magnetic properties of the NiFeMo alloy, affecting the exchange coupling interaction between magnetic atoms and the motion of magnetic domains. Compared to the NiFeMo alloy, the saturation magnetization of the (NiFeMo)97.5Cr2.5 alloy is reduced to 0.4685 T, and the coercive force is increased to 37.7 A/m. However, when the chromium content is 1 wt%, the initial magnetic permeability of the (NiFeMo)99Cr1 alloy is 2.337 mH/m, which is an enhancement of 1.9422 mH/m compared to the NiFeMo alloy.

Effect of Mo in-situ alloying on microstructure and magnetic properties of (NiFeMo)100−xMox alloy

This study aimed to modulate the magnetic properties of selective laser melting NiFeMo alloy. This was achieved via the controlled addition of Mo elemental in-situ alloying content to change the tissue morphology and crystal structure of SLM-formed (NiFeMo)100−xMox alloy (x = 0 wt%, 0.25 wt%, 0.5 wt%, 0.75 wt%, 1.0 wt%, 1.25 wt%, 1.5 wt%, 2.0 wt%). The results of scanning electron microscopy (SEM), X-ray diffraction, electron backscatter diffraction (EBSD), DC B-H hysteresis tester, and transmission electron microscopy (Titan-G2) indicate that all samples are predominantly face-centered-cubic (FCC) γ- (Ni, Fe) solid solutions and typical soft-magnetic hysteresis line features. However, the lattice parameter a of γ- (Ni, Fe) decreased and then increased with increasing Mo content. When the added Mo content is 0–1.25 wt%, the Mo particles inside the (NiFeMo)100−xMox alloy become nucleation sites, creating a diffusive metallurgical behavior with the Ni and Fe elements, and preventing the growth of columnar crystals, leading to the reduction of LAGBs density and the enhancement of the {111} texture orientation in the easy magnetization direction, increasing Bs and the decrease of Hc of the NiFeMo alloy. At the Mo content of 1.25 wt%, the soft magnetic properties were optimal, with Bs and Hc being 0.704 T and 17.31 A/m, respectively. Conversely, when the added Mo content was 1.5–2.0 wt%, the solubility of Mo elements in the γ- (Ni, Fe) solid solution was limited, which resulted in the occurrence of metallurgical defects within the organization such as unfused Mo particles, unfused areas, and porosity. Moreover, when the added Mo content increased to 2.0 wt%, the {111} lattice spacing in the easy magnetization direction increased by 0.2261 nm compared to the NiFeMo alloy, and the average lattice distortion Δε increased to 0.16%, causing a decrease in the soft magnetic performance of the (NiFeMo)98Mo2 alloy, with Bs reducing to 0.6666 T and Hc increasing to 23.44 A/m.

Temperature influence on NiFeMo nanoparticles magnetic properties and their viability in biomedical applications.

NiFeMo alloy nanoparticles were synthesized by co-precipitation in the presence of organic additives. Nanoparticles thermal evolution shows that there is a significant increase in the average size (from 28 to 60 nm), consolidating a crystalline structure of the same type as the Ni3 Fe phase but with lattice parameter a=0.362 nm. Measurements of magnetic properties follow this morphological and structural evolution increasing saturation magnetization (Ms) by 578% and reducing remanence magnetization (Mr) by 29%. Cell viability assays on as-synthesized revealed that nanoparticles (NPs) are not cytotoxic up to a concentration of 0.4μg/mL for both non-tumorigenic (fibroblasts and macrophages) and tumor cells (melanoma).

Tunable d-band center of a NiFeMo alloy with enlarged lattice strain enhancing the intrinsic catalytic activity for overall water-splitting.

Developing efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) under alkaline conditions is prospective for reducing energy consumption during water electrolysis. In this work, we successfully synthesized nanocluster structure composites composed of NiFeMo alloys with controllable lattice strain by the electrodeposition method at room temperature. The unique structure of NiFeMo/SSM (stainless steel mesh) facilitates the exposure of abundant active sites and promotes mass transfer and gas exportation. The NiFeMo/SSM electrode exhibits a low overpotential of 86 mV at 10 mA cm-2 for the HER and 318 mV at 50 mA cm-2 for the OER, and the assembled device reveals a low voltage of 1.764 V at 50 mA cm-2. Moreover, both the experimental results and theoretical calculations reveal that the dual doping of Mo and Fe can induce the tunable lattice strain of nickel, which in turn changes the d-band center and electronic interaction of the catalytically active site, and finally enhances the HER and OER catalytic activity. This work may provide more options for the design and preparation of bifunctional catalysts based on non-noble metals.

NiFeMo Alloy Inverse-Opals on Ni Foam As Outstanding Catalysts for Alkaline Electrolytic Water Splitting

Hydrogen, a clean energy carrier with a high gravimetric energy density, is currently most economically produced with steam reforming of natural gases, in which fossil fuels are used as the raw material and CO2 is generated as a side product, both not environmentally sustainable. Renewable energy driven electrocatalytic water splitting is considered the most promising route for future hydrogen production. Its production cost, dominated by the electric energy consumption, however places it in a disadvantageous position, and highly efficient, cost-effective, and durable electrocatalysts, aiming to reduce the necessary working potential for cost competiveness, are critically important for the prevailing of the technology. The present work developed, based on the essential concept of improving quantity and quality of active sites of the catalyst, NiFeMo alloy inverse-opals on nickel foam as an extraordinary catalyst for alkaline electrolytic water splitting, achieving ultralow overpotentials of 33 and 249 mV for the hydrogen evolution reaction (HER) and 198 and 293 mV for the oxygen evolution reaction (OER) at current densities of 10 and 500 mA cm-2, respectively. Ultralow cell voltages of only 1.47 and 1.75 V are enough to deliver current densities of 10 and 500 mA cm-2, respectively, for overall water splitting, outperforming the benchmark couple, Pt/C and IrO2, and state-of-the-art electrolytic water splitting cells. The stability of the product is also outstanding, remaining stable after operations at an ultrahigh current density of 500 mA cm-2 for 50 hours. The success of the product catalyst is attributed to the much increased active site number with the construction of inverse-opals on nickel foam and the much enhanced intrinsic activities of the active sites through synergistic effects between the three constituent elements.

Magnetic shielding promotion via the control of magnetic anisotropy and thermal Post processing in laser powder bed fusion processed NiFeMo-based soft magnet

The aim of this study is to promote the magnetic shielding characteristics of laser powder bed fusion (LPBF) processed NiFeMo alloy. This was achieved via controlling the crystallographic texture of the builds to increase the grain population along the easy axis of magnetisation, as well as the use of post-process hydrogen heat treatment (HT) and hot isostatic pressing (HIP) processes. The as-fabricated microstructure typically demonstrates weak magnetic properties due to the alignment of the crystallographic orientation/spin order along the [100] hard axis of magnetisation, which is parallel to the build direction since it is also the preferred growth direction during solidification in cubic materials. Tilting the build orientation to align the easy magnetisation axes [110] and [111] along the build principal directions results in an improvement in the magnetic shielding characteristics normal and transverse to the build principal directions. Furthermore, the HT/HIP processes further promoted the soft ferromagnetic characteristics, with the best magnetic shielding properties being registered for the [111] tilted sample following both HIP and HT, demonstrating 60–100 folds improvement compared with the as-fabricated condition. The improved ferromagnetism following HIP + HT was due to several combined effects, including stress relief, consolidation of gas pores, recrystallisation, and grain growth. The post-processing sequence (HT + HIP vs. HIP + HT) appeared to affect the resulting magnetic characteristics. Finally, the tensile properties for the builds were characterised to ensure that both functional and mechanical behaviours would achieve the required performance.

NiFeMo alloy inverse-opals on Ni foam as outstanding bifunctional catalysts for electrolytic water splitting of ultra-low cell voltages at high current densities

NiFeMo alloy inverse-opals were created on nickel foam as an extraordinary bifunctional catalyst for alkaline electrolytic water splitting, achieving ultralow overpotentials of 33 and 249 mV for the hydrogen evolution reaction and 198 and 293 mV for the oxygen evolution reaction at current densities of 10 and 500 mA cm−2, respectively. Ultralow cell voltages of only 1.47 and 1.75 V are enough to deliver current densities of 10 and 500 mA cm−2, respectively, for overall water splitting, outperforming the benchmark couple, Pt/C and IrO2. The stability of the product is also outstanding, remaining stable after operations at an ultrahigh current density of 500 mA cm−2 for 50 h. The success of the product catalyst is attributed to the much increased active site number with the construction of inverse-opals on nickel foam and the much enhanced intrinsic activities of the active sites through synergistic effects between the three constituent elements.

Trimetallic NiFeMo for Overall Electrochemical Water Splitting with a Low Cell Voltage

We report the development of an efficient and earth-abundant catalyst for electrochemical overall water splitting. Trimetallic NiFeMo alloy is synthesized by hydrothermal deposition from inorganic precursors and subsequent low-temperature thermal annealing. A complete cell made of NiFeMo electrodes on nickel foam exhibits a low voltage of 1.45 V at 10 mA/cm2 as a result of low overpotentials for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). High-resolution transmission electron microscopy reveals that nanometer-sized single-crystal domains of Ni, Fe, and Mo are intimately integrated at the atomic level, which enables a synergistic effect of metallic Ni, Fe, and Mo for efficient HER, while self-formed Ni–Fe–Mo (oxy)hydroxides on the surface of the NiFeMo anode become active sites for OER. Such a multimetallic alloy and its (oxy)hydroxides represent a typical HER/OER catalyst couple, and our method provides a new route to develop efficient low-cost metallic alloys for overall w...

Bonding and high-temperature reliability of NiFeMo alloy/n-type PbTe joints for thermoelectric module applications

PbTe is an extremely important thermoelectric (TE) material, due to its high TE conversion efficiency. Consequently, our effort focuses on developing PbTe-based TE modules, which requires developing novel approaches for bonding metallic contacts to PbTe. In this study, Fe, Mo, and NiFeMo alloy foils were directly bonded to n-type PbTe using a rapid hot press at 600, 700, or 800 °C under a pressure of 40 MPa and for various holding times. We find that in the case of Fe and Mo, it is difficult to form a metallurgically bonded high strength joint with PbTe. However, we find that NiFeMo alloy does effectively bond to PbTe at 700 °C, but not at 600 °C. Significant liquid Pb, which might be due to the reaction of PbTe with Ni, is found that penetrates along the NiFeMo grain boundaries near NiFeMo/PbTe joints during bonding at 700 °C where the extent of liquid Pb penetration can be controlled with the time of bonding. Furthermore, the Seebeck coefficient of bulk PbTe with NiFeMo contacts is similar to that without NiFeMo contacts. Finally, the accelerated thermal aging of NiFeMo/PbTe elements at 600 °C for 240 h shows that the failure mechanism of NiFeMo/PbTe joints under operating conditions is the continued formation and penetration of eutectic liquid NiFeMo–PbTe and liquid Pb along the NiFeMo grain boundaries.

The analysis of the material flow kinematics during Ni–Fe–Mo alloy forging

The paper presents an analysis of material flow kinematics in the forging process of Ni–Fe–Mo alloy, with regard to eliminating casting defects. The as-delivered alloy was examined (microstructural analysis, X-ray phase analysis) in order to determine its comprehensive characteristics. An elongated section was chosen for forging, which allowed us to examine areas of various degrees of forging in the volume under investigation. This also allowed us to observe complex thermo-mechanical conditions during the forging process and after its completion. As a part of this study, numerical simulations of the forging process of this material under varying thermo-mechanical conditions were performed. The simulations were conducted using QForm3D software. The results of the numerical modeling were used to determine the most favorable parameters for the forging process under industrial conditions. The applicability of the assumed thermo-mechanical parameters was verified by analyzing the microstructure and mechanical properties of the final forgings.

Room temperature ferromagnetism down to 10 nanometer Ni–Fe–Mo alloy films

Magnetic behavior of a few pulsed laser deposited soft ferromagnetic thin films of Ni–Fe–Mo alloys of different thickness on sapphire single crystals is interpreted on the basis of their structural characteristics. Highly textured thin films have high void density due to island-like growth. X-ray reflectivity (XRR) of the thin films indicate that instead of a uniform density there are effectively three layers with density gradient across the thickness, which is further supported by atomic force microscopy and cross-sectional scanning electron microscopy. Rutherford backscattering spectroscopy and energy dispersive spectrum measurements reveal that the composition in the films is not too far from that of the bulk target with a trend of enhanced Fe yield in the films. The structural disorder strongly affected the magnetic property of the films resulting in much higher values of the Curie temperature TC and coercive field HC than those of the bulk targets. Bifurcations of low-field zero-field-cooled and field-cooled magnetization reflect the disorder-induced anisotropy in the thin films. The spin wave stiffness constants D are higher than their bulk counterparts which are supportive of the enhanced Fe yield in the films. The saturation magnetization, M calculated from measurements in field transverse to the films strongly supports the thickness found from XRR. Finally, even the 10nm thin films have sizable M and HC and TC >300K, making them good candidates for magnetic applications. Overall, the magnetic behavior and the structural characteristics have reasonably complemented each other.

AC magnetic properties of the bulk Fe–Ni and Fe–Ni–Mo soft magnetic alloys prepared by warm compaction

Soft magnetic properties of bulk crystalline samples were investigated. Rapidly quenched ribbons of Ni 81Fe 19 alloy and ball milled swarfs of ingot of Ni 79Fe 16Mo 5 alloy were warm consolidated at a pressure of 800 MPa to get bulk compacts. The frequency dependence of the peak permeability and total core losses in the range 0.2–1000 kHz and DC coercivity were studied. The core losses of the samples versus the maximum induction value B max at 20 kHz were investigated. The magnetic properties of the Ni–Fe and Ni–Fe–Mo alloys show dependence to its initial, master powder and annealing conditions. The results show that further annealing improves soft magnetic properties. The absolute values of losses and coercivity of Ni–Fe and Ni–Fe–Mo compacts are comparable to that of the material prepared by convention way in the form of thin sheet. Also, found that soft magnetic properties are better with Ni–Fe–Mo alloy as compared to Ni–Fe alloy.

Soft Magnetic Properties in Bulk Permalloy Alloys Fabricated by a Warm Consolidation

Soft magnetic properties of bulk NiFe and NiFeMo alloys consolidated by hot compaction were studied. During annealing the compacts residual stresses diminish by relaxation and soft magnetic properties improve. The lowest coercivity of bulk NiFe and NiFeMo alloys are 11.0 and 11.2 A/m, respectively, while the total losses are 1.81 and 1.42 W/g at f = 10 kHz and Bmax = 0:2 T.

Studies on electrodeposition of corrosion resistant Ni–Fe–Mo alloy

A study to optimize the process parameters for electrodeposition of a Ni–Fe–Mo alloy is reported. A 22full factorial design was successfully employed for the experimental design analysis of the results. The optimum experimental conditions for producing the corrosion resistant alloy were 120 mA/cm2 current density, 20 rpm cathode rotation, 9.0 pH at 30 °C. The alloy was deposited at 61% current efficiency, with an average composition of 62 wt% Ni, 17wt% Fe, 21wt% Mo and traces of boron, and with Ecorr −0.506 V, Rp 8.883 × 103 Ohm cm2 and Icorr 6.468 × 10−7 A/cm2. The deposit obtained under these conditions had an amorphous character, good adherence, high corrosion resistance and a nodular morphology. Electrochemical corrosion tests verified that the electrodeposited Ni–Fe–Mo alloy had better corrosion resistance than the Fe–Mo alloy.

The influence of mechanical milling on structure and soft magnetic properties of NiFe and NiFeMo alloys

Ni–Fe-based alloys (permalloys) are commonly used as soft magnetic materials, exhibiting high permeability, low coercivity, low magnetostriction and high-saturation magnetization. In particular, Ni–Fe–Mo alloys have high relative permeability and low eddy current losses. We have investigated the structure and magnetic properties of powders prepared by mechanical milling of NiFe (81 wt% of Ni) microcrystalline ribbon and NiFeMo (79 wt% of Ni, 16 wt% of Fe) swarfs in a high-energy planetary ball mill. The coercivity of NiFe rapidly increases up to 1600 A/m for 35 h and the coercivity of NiFeMo increases gradually up 1800 A/m for all time of milling (500 h). The XRD analysis revealed that there is major phase FeNi 3 (with Curie temperature of 550 °C) as well as minor phases NiO and Fe 3O 4 for milled NiFe alloy. The milled NiFeMo alloy consists of FeNi 3 phase and other phase, whose Curie temperature was detected by thermomagnetic analysis to be about 650 °C.

An ab-initio theoretical investigation of the soft-magnetic properties of permalloys

We study Ni 80 Fe 20 -based permalloys with the relativistic spin-polarized Korringa–Kohn–Rostoker electronic structure method. Treating the compositional disorder with the coherent potential approximation, we investigate how the magnetocrystalline anisotropy, K, and magnetostriction, λ , of Ni-rich Ni–Fe alloys vary with the addition of small amounts of non-magnetic transition metals, Cu and Mo. From our calculations we follow the trends in K and λ and find the compositions of Ni–Fe–Cu and Ni–Fe–Mo where both are near zero. These high permeability compositions of Ni–Fe–Cu and Ni–Fe–Mo match well with those discovered experimentally. We monitor the connection of the magnetic anisotropy with the number of minority spin electrons N ↓ . By raising N ↓ via artificially increasing the band-filling of Ni 80 Fe 20 , we are able to reproduce the key features that underpin the magnetic softening we find in the ternary alloys. The effect of band-filling on the dependence of magnetocrystalline anisotropy on atomic short-range order in Ni 80 Fe 20 is also studied. Our calculations, based on a static concentration wave theory, indicate that the susceptibility of the high permeability of the Ni–Fe–Cu and Ni–Fe–Mo alloys to their annealing conditions is also strongly dependent on the alloys’ compositions. An ideal soft magnet appears from these calculations.

Synthesis and characterization of high-energy ball milled Ni–15%Fe–5%Mo

Nickel-based alloys are commonly used as soft magnetic materials, exhibiting high permeability, low coercivity and high saturation magnetization. In particular, Ni–Fe–Mo alloys have very high relative permeability and low eddy current losses. In this work, nanocrystalline Ni–15%Fe–5%Mo alloy has been synthesized by high-energy ball milling. X-ray powder diffraction (XRPD) has been employed to follow the structural evolution during the ball milling process. The Williamson–Hall method was used to calculate grain size and residual strain from the XRPD data. The grain size was found to be about 8nm and the residual stain was about 0.6% after 100h of milling. The coercivity of the milled powder was found to be affected by grain size and residual strain. The morphology of the powders was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

A NiFeMo Electroplating Bath for Micromachined Structures

A number of micromachined magnetic sensors and actuators require materials with desirable magnetic properties such as high permeability and thicknesses in the range of several micrometers. Materials with appropriate magnetic properties have been reporte d for magnetic storage applications, but often in thickness ranges insufficient for micromachined sensors and actuators. We report the results of an electroplating bath for the deposition of a high permeability, low coercivity material, a NiFeMo alloy. Using this bath, the NiFeMo alloy may be electrodeposited up to 5 μm in thickness. The residual stress of the electroplated NiFeMo material remains larger than that for NiFe (Permalloy) electrodeposits.

Processing of sintered stainless steel parts: P. Beiss, (Sintermetallwerk Krebsöge, Radervormwald, Germany)

Ni–Fe-based alloys (permalloys) are commonly used as soft magnetic materials, exhibiting high permeability, low coercivity, low magnetostriction and high-saturation magnetization. In particular, Ni–Fe–Mo alloys have high relative permeability and low eddy current losses. We have investigated the structure and magnetic properties of powders prepared by mechanical milling of NiFe (81 wt% of Ni) microcrystalline ribbon and NiFeMo (79 wt% of Ni, 16 wt% of Fe) swarfs in a high-energy planetary ball mill. The coercivity of NiFe rapidly increases up to 1600 A/m for 35 h and the coercivity of NiFeMo increases gradually up 1800 A/m for all time of milling (500 h). The XRD analysis revealed that there is major phase FeNi3 (with Curie temperature of 550 °C) as well as minor phases NiO and Fe3O4 for milled NiFe alloy. The milled NiFeMo alloy consists of FeNi3 phase and other phase, whose Curie temperature was detected by thermomagnetic analysis to be about 650 °C.