Magnetic Alloys Research Articles

Simultaneously enhancing strength and ductility of multiprincipal-element soft magnetic alloys

Herein, a boron-containing soft magnetic alloy (Al1.5Co4Fe2Cr)98.8B1.2 was fabricated. Compared to the boron-free alloy Al1.5Co4Fe2Cr, the boron-containing alloy exhibited an excellent combination of soft magnetic properties with tailored mechanical properties, with 1.6-fold increment in yield strength, 3.8-fold increment in plasticity, and minimal decrement in saturation magnetization.

Optimizing Tin Electroplating for MEMS Meissner-Effect Transition-Edge Sensors

Electroforming metal features into patterned polymer molds targeting MEMS microfabrication allows for the enhancement of electrical, mechanical, magnetic, and thermal properties1. Uniform and repeatable electroforming processes are important to achieve the final desired metal geometry to optimize performance. MEMS fabrication processes typically rely on average plating rates based on historical depositions to determine future plating rates and offer the user options to vary electroplating time, among other options, to meet the desired device height(s). Process repeatability is often difficult to achieve in these scenarios and can be challenging in R&D applications with limited throughput. Inherent changes from one sample to the next can occur in many forms including a change in active area of lithographically patterned photoresist molds, resistance of substrates/seed layers below electroplated layers, geometry of the layout, chemistry make-up, electroplating setup, and fast deposition rates can all affect plating rates from sample to sample. Some changes can be controlled through careful inspection and tracking, then accounted for. However, some changes cannot be observed, and deposition rates can change from sample to sample leading to ever-changing plating rates.These challenges were encountered during electroplating of tin disks coupled with planar superconducting coils of niobium targeting the microfabrication of Meissner-Effect Transition-Edge Sensor devices (ME-TES)2. We investigated two and three electrode setups using a modified Dow Chemical Solderon make-up chemistry targeting pure tin depositions as opposed to tin and silver alloy depositions. Those changes were coupled with chronopotentiometry, chronoamperometry, and pulse plating experiments to optimize tin electrodeposition. Once found, the optimum tin deposition process was built into a graphical user interface (GUI)3 that predicts electroplating rates and was then successfully applied to microfabricate ME-TES’s. This process methodology could benefit other metal MEMS-based electrodeposition processes such as nickel, copper, gold, magnetic alloys, etc. to optimize electroplating.(1) Buchheit, T. E.; Christenson, T. R.; Schmale, D. T.; Lavan, D. A. Understanding and tailoring the mechanical properties of LIGA fabricated materials. Materials Science of Microelectromechanical Systems (Mems) Devices 1999, 546, 121-126. DOI: Doi 10.1557/Proc-546-121.(2) Finnegan, P. Packaging & Solid-state Materials and Fabrication Processes. In Packaging & Solid-state Materials and Fabrication Processes, June 2023.(3) St. John, C. In-Situ Analysis of Chronopotentiometry Data to Predict Electrodeposition Rates. In 243rd ECS Meeting with SOFC-XVIII, Boston, MA, 2023.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525 SAND2022-10288A

Effect of Y2O3 on the Microstructures and Properties of Magnetic Field-Assisted Laser-Clad Co-Based Alloys

Effect of Y2O3 on the Microstructures and Properties of Magnetic Field-Assisted Laser-Clad Co-Based Alloys

Modeling the dynamic magneto-mechanical response of magnetic shape memory alloys based on Hamilton’s principle: The numerical algorithm

This paper is the second part of a variational modeling work on the dynamic magneto-mechanical response of magnetic shape memory alloys (MSMA). In the first part of this series work, the governing equations system for modeling the dynamic response of MSMA samples has been derived based on Hamilton’s principle, which contains the Maxwell’s equations, the magneto-mechanic equations, the evolution equations of internal variables and the twin interface motion criteria. In this paper, we aim to conduct comprehensive numerical simulations on the dynamic magneto-mechanical response of MSMA samples. To solve the governing system, the space–time finite element method is applied and a double-loop iterative numerical algorithm is proposed. By using this algorithm, the independent variables in the governing system and the motion of twin interfaces in the MSMA sample can be determined separately and iteratively. Besides that, a specific discretization of the sample is adopted to simplify the calculation of variant state distribution in the sample. To show the efficiency of the numerical algorithm, the magneto-mechanical response of a MSMA sample in stress-assisted dynamic field loading tests and field-assisted dynamic mechanical loading tests are studied. Based on the numerical results, some global response curves of the MSMA sample are plotted, which show good consistency with the experimental results. Furthermore, the current configuration of the sample and the distributions of some important physical fields in the sample can be simulated. The current work will be helpful for the design of novel actuators or energy harvesters with MSMA.

Two magnetic entropy peaks during one-step martensitic transformation in a Ni42Co8Mn37.5In12.5 alloy

Magnetic shape memory alloys with multiple entropy change (ΔSM ) peaks are promising to extend the working temperature window (ΔT eff) in active magnetic refrigeration. They usually have multi-step martensitic transformations, since the multiple variations of structure and magnetic states lead to the one-to-one corresponding ΔSM peaks. In this work, we report an interesting Ni42Co8Mn37.5In12.5 magnetocaloric alloy, which exhibits only one-step martensitic transformation but generates two considerable ΔSM peaks with the value of 7.2 J K−1 kg−1 and 9.9 J K−1 kg−1 under 6 T respectively. This phenomenon is attributed to the restriction internal stresses stemming from the lattice mismatch between martensite and austenite, the random local stresses produced by defects, the interfacial hindrances of wide phase boundaries, and the inhibition of dispersed precipitates, which divide the one-step transformation into two discrete stages. Such multiple ΔSM peaks are beneficial for expanding the working temperature window of magnetocaloric refrigerators.

Exploring the Magnetic Behavior of a Magnetic High-Entropy Alloy with Dual-Phase B20 Crystal Structure

Exploring the Magnetic Behavior of a Magnetic High-Entropy Alloy with Dual-Phase B20 Crystal Structure

Hybrid Solenoids Based on Magnetic Shape Memory Alloys

The mobility of today and tomorrow is characterized by technological change and new challenges in drive concepts such as electric or hydrogen vehicles. Abolishing conventional combustion engines creates even more need for switching or valve technology in mobility systems. For switching and controlling purposes, solenoids are used in large numbers and in a wide variety of applications, thus making a significant contribution to the overall success of the energy transition, and not only in the automotive sector. Despite their long existence, continued research is being carried out on solenoids involving new materials and actuator concepts. Great interest is focused on providing an adjustable force–displacement characteristic while simultaneously reducing the noise during switching. At IKFF, research is being conducted on hybrid electromagnets in the border area of switching and holding solenoids. This paper aims to present the major advantages of this hybrid drive concept based on an electromagnetic FEA simulation study of two drive concepts and specially developed and characterized prototypes with magnetic shape memory (MSM) alloys. The concepts differ in the spatial orientation of the MSM sticks to generate an active stroke of the plunger, which contributes to a beneficial force–displacement characteristic and lower power consumption while minimizing switching noise.

INVESTIGATION OF MAGNETIC HYSTERESIS PROPERTIES OF ISOTROPIC MAGNETICALLY HARD ALLOYS OF THE Fe-Cr-Co SYSTEM ALLOYED WITH TUNGSTEN

Hard magnetic alloys Fe-30Cr-20Co (wt.%) alloyed with tungsten in an amount of up to 3 wt.% were obtained by powder metallurgy. A study of magnetic properties showed that tungsten additions increase the values of the coercivity Hc and the maximum energy product (BH)max, but at the same time reduce the residual induction Br. This effect increases with increasing tungsten content in the material. The maximum values of Hc (55.8 kA/m) and (BH)max (17.2 kJ/m3) are observed in the alloy alloyed with 3 wt.% W. At the same time, the alloys studied in the work turned out to be sensitive to thermal conditions processing. According to X-ray phase analysis, after a full processing cycle, alloys contain a noticeable proportion of non-magnetic ɣ-phase, but the magnetic properties correspond to the level of cast analogues. During compression tests, all samples of tungsten alloyed alloys failed before reaching a deformation rate of 20%, while the unalloyed Fe-30Cr-20Co (wt.%) alloy deformed without failure under these conditions. Thus, tungsten additives reduce the ductility of the material.

Nanocomposite Didymium-Fe-B/Alnico magnetic alloys with core shell structure and improved magnetic properties

NdFeB-based permanent magnets have the highest maximum energy products, but their low Curie temperatures limit their applications. Alnico permanent magnets have relatively modest magnetic energy products, but have very high Curie and working temperatures. In this manuscript, we report new NdPrFeB/Alnico nanocomposite magnetic materials with enhanced Curie temperatures and maximum magnetic energy products. A special microstructure with the Alnico phase dispersed within the NdPrFeB phase results in excellent magnetic properties. The Curie temperature of the composite alloys is enhanced from 570 K to 643 K by adding 25% low-grade Alnico. The enhanced Curie temperature which results from the cobalt and nickel replacement for iron in the 2:14:1 phase, and the molecular field penetration improves the temperature stability of the magnets. The beneficial heterogeneous distribution of the constituent phases and elements was confirmed by transmission electron microscopy and electron diffraction spectroscopy analyses. The maximum energy product is enhanced from 110 kJ/m3 to 133 kJ/m3. Magnetostatic interaction and exchange interaction in the alloys were studied by means of Henkel plots and minor hysteresis loop measurements. Despite the high content of the Alnico phase with relatively large special dimensions, there were no kinks in the demagnetization curves either at 300 K or 400 K. Furthermore, no kink was noted at low and high applied fields in the demagnetization-magnetization process which shows the effective magnetic interactions. This work would elucidate the development of nanocomposite magnetic material with high energy product without the use of heavy rare earths and with the economical use of Nd and Pr.

In-Situ Study of Temperature- and Magnetic-Field-Induced Incomplete Martensitic Transformation in Fe-Mn-Ga

Significant interest in the stoichiometric and off-stoichiometric Fe2MnGa alloys is based on their complex phase transition behavior and potential application. In this study, temperature- and magnetic-field-induced phase transformations in the Fe41.5Mn28Ga30.5 magnetic shape memory alloy were investigated by in situ synchrotron high-energy X-ray diffraction and in situ neutron diffraction techniques. It was found that incomplete phase transformation and phase coexistence behavior are always observed while applying and removing fields in Fe41.5Mn28Ga30.5. Typically, even at 4 K and under 0 T, or increasing the magnetic field to 11 T at 250 K, it can be directly detected that the martensite and austenite are in competition, making the phase transition incomplete. TEM observations at 300 K and 150 K indicate that the anti-phase boundaries and B2 precipitates may lead to field-induced incomplete phase transformation behavior collectively. The present study may enrich the understanding of field-induced martensitic transformation in the Fe-Mn-Ga magnetic shape memory alloys.

Production of Magnetic Arsenic-Phosphorus Alloy Nanoribbons with Small Band Gaps and High Hole Conductivities.

Quasi-1D nanoribbons provide a unique route to diversifying the properties of their parent 2D nanomaterial, introducing lateral quantum confinement and an abundance of edge sites. Here, a new family of nanomaterials is opened with the creation of arsenic-phosphorus alloy nanoribbons (AsPNRs). By ionically etching the layered crystal black arsenic-phosphorus using lithium electride followed by dissolution in amidic solvents, solutions of AsPNRs are formed. The ribbons are typically few-layered, several micrometers long with widths tens of nanometers across, and both highly flexible and crystalline. The AsPNRs are highly electrically conducting above 130 K due to their small band gap (ca. 0.035 eV), paramagnetic in nature, and have high hole mobilities, as measured with the first generation of AsP devices, directly highlighting their properties and utility in electronic devices such as near-infrared detectors, quantum computing, and charge carrier layers in solar cells.

Effect of Preheating on the Mechanical Workability Improvement of High-Strength Electrical Steels during Tandem Cold Rolling

Cold-rolled silicon steel strip products are widely used as the main soft magnetic components in cores of electrical motors, generators, and transformers. In the case of rotating electrical machines, the so-called non-oriented electro-technical steels are normally applied. They are characterized by a similar behaviour to the induced magnetic field found in all sheet plane directions. The kind of soft magnetic alloys that defined herein not only possess an isotropy of electromagnetic properties, but also high mechanical strength; such alloys are called high-strength electro-technical (HSET) steels. These commercially produced HSET steels contain a high silicon content in the range of 3–4 wt.%. However, if the silicon content exceeds 3%, the machinability of Fe–Si alloys is dramatically reduced and they become much more brittle as a consequence. According to this, regular hot band brittle damage occurs during cold deformation at a high-speed tandem rolling mill. In accordance with these reasons, the production of thin high-strength silicon steel grades using the traditional methods of cold rolling deformation is extremely problematic and it is characterised by a high degree of steel sheet mechanical damage. In this scientific work, the effect of preheating hot-rolled strips on their mechanical workability improvement during tandem cold rolling was investigated. The results of this study indicate that the cold rolling of hot bands at elevated temperatures increases their resistance to brittle failure and mechanical plasticity. Moreover, the mathematical simulation clearly demonstrates that residual stress is distributed relatively homogeneously across the thickness of samples, which were cold rolled at 100 °C in contrast to the same ones deformed at room temperature.

3D printing of magnetostrictive property in 17/4 ph stainless steel

Additive manufacturing (AM) of metallic alloys significantly advances diverse areas of science/engineering with a prosperous future trend. Although this technology is also very attractive for smart materials development, the creation of a pre-programmed “4th dimension” property to appear in response to external stimuli represents an important challenge. Here we report on 3D printing of stainless steel based magnetic alloy and detail the ways to optimize the magnetisation and magnetostriction to be used for actuation and sensing. By controlling the printing parameters and sintering process, we are able to tune the magnetic and magnetoelastic properties of the 17/4 ph stainless steel, demonstrating material fabrication multi-function with a cost effective advantage. The stainless steel 17/4 ph samples in the as-printed (AP) and sintered steel (SS) stages are compared. In the developed SS sample, a remarkable increase of 18% in saturation magnetisation yet with 12.6 % lower coercivity was achieved. Moreover, the 54% higher magnetostriction was developed for the SS sample compared to the AP sample. Plus, the difference in anisotropy energy K1 was also lower for the SS sample. The structural and magnetic properties control are reported at each stage of the printing process, demonstrating development and optimization prospects of 3D printable metallic sensors and actuators.

First-principles-based statistical thermodynamic study of atomic interactions and phase stability in Ni-rich Ni-W alloys

Atomic interactions and phase stability in Ni-rich Ni-W alloys have been investigated by using first-principles methods and statistical thermodynamic simulations. First-principles methods have been employed to explore lattice expansion, enthalpies of formation, atomic interactions, and ordering energies of ordered as well as random structures in Ni-rich Ni-W alloys with consideration of the corresponding temperature-dependent magnetic states. It is found that atomic interactions in Ni-rich Ni-W alloys depend on alloy composition, atomic volume, and magnetic state. Nevertheless, the magnetic state of Ni greatly affects the formation enthalpies, which leads to a diverse phase separation behavior at finite temperature in Ni-rich Ni-W alloys. By using atomic interactions that reproduce the ordering energies obtained in the direct total energy calculations, our statistical thermodynamic simulations of chemical short-range order results show that fcc-based ordered D1a, D022, and Pt2Mo phases can be observed in Ni-20 at.% W, Ni-25 at.% W, and Ni-33 at.% W alloys, respectively. Moreover, the short-range order diffuse intensity and atomic stacking for aforementioned ordered phases have been analyzed, the order–disorder transition behaviors have been also investigated in detail for the Ni-rich Ni-W alloys up to 35 at.% W with comparison of current experimental results. Both magnetic state and alloy composition have the potential to induce the formation of distinct ordered phases, offering promising avenues for designing Ni-based alloys. The methodologies we used in this study can be applied to investigate the atomic interactions as well as phase stability in other alloy systems.

Magneto-structural transitions driven giant magnetocaloric effect in Ni42Mn43Cr4Sn11 Shape Memory Heusler Alloy near room temperature

In the current work, a Ni–Mn-X (X = Sn, In) type off-stoichiometric, polycrystalline magnetic shape memory alloy (MSMA) having nominal composition Ni42Mn43Cr4Sn11 (at. %) has been thoroughly investigated in terms of its crystal structure, microstructure, magnetic properties, and magnetocaloric effect (MCE). X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), differential scanning calorimetry (DSC), and magnetic and magneto-transport measurements are used to characterize it. By offering a significant value of parameters related to MCE at the first-order martensite transition (FOMT) and the second-order magnetic transition (SOMT), the “Cr” doping at the “Ni” site enables considerable magnetic refrigeration to occur close to room temperature (RT). The alloy crystallises into coexisting cubic L21 austenite and tetragonal L10 martensite phases, among which the first one prevails as the leading phase at room temperature (RT) without exhibiting any geometric frustration. Lattice strain is enumerated using the Williamson-Hall method. A huge working temperature spans of 29.65 K and 26.16 K; the maximum magnetic entropy changes of +8.70 J kg−1.K−1 and −5.04 J kg−1.K−1 and the maximum refrigerant capacities (RC) of 284.24 J. Kg−1 and 234.10 J. Kg−1 across FOMT and SOMT, respectively at an applied magnetic field of 6 T are found to be most suitable for real technological applications. This MSMA offers a comparatively low cost of the constituent elements (Ni, Mn, Cr, and Sn), as well as exhibits giant MCE and RC across both FOMT and SOMT, making it an excellent candidate for magnetic refrigeration near RT. It also opens up new avenues for future research on novel Heusler alloys of this type.

Neural Network Adaptive Control of Magnetic Shape Memory Alloy Actuator With Time Delay Based on Composite NARMAX Model

Magnetic shape memory alloy (MSMA) based actuator plays an important role in the field of micro and nano-fabrication due to its large stroke. However, the inherent hysteresis of MSMA seriously affects the application prospects of MSMA-based actuator in the field of precision positioning. In this study, a composite model is proposed for hysteresis in the MSMA-based actuator by coupling an improved fractional-order Bouc-Wen model to a nonlinear auto-regressive moving average with exogenous inputs (NARMAX) model. Based on the proposed model, a neural network adaptive control method is then used to control the MSMA-based actuator, and the controller design takes into account the effect of time delay on the system performance to improve the positioning accuracy of the MSMA-based actuator. First, we fuse the composite NARMAX model with the canonical form of the nonlinear system to describe the MSMA-based actuator. Then, a control strategy is developed to address the impact of the unknown time delay for controller design and achieve the satisfactory positioning accuracy of the MSMA-based actuator. By using Lyapunov theory, the tracking error is proven to be asymptotic convergence. Experimental studies are provided to validate the effectiveness of the proposed modeling and control schemes.

Fabrication and application prospects of Pr–Fe–B/Alnico nanocomposite alloys

The potentials of rare earth-based nanocomposite alloys have never been realized due to strict microstructural constraints. Owing to the easy demagnetization it is challenging to increase the soft magnetic phase content. To avoid the easy demagnetization, Pr–Fe–B/Alnico magnets were fabricated and reported in this manuscript. The content of the Alnico phase is increased from 0 to 25 wt%, while the content of Pr element is reduced to below the sub-stoichiometry of the 2:14:1 main phase. The maximum magnetic energy product, which is the figure-of-merit for permanent magnets, is increased from 122 kJ/m3 for the standard alloy to 146 kJ/m3 for the alloy with 15 wt% Alnico which shows a significant improvement considering the fact that the Curie point of the magnet is also increased by ∼66 K. The special microstructure contains distinctly and heterogeneously distributed 2:14:1 and Alnico phases. The dimensions of neither the 2:14:1 nor the Alnico phases meet the dimensional requirements of the nanocomposite magnets, but still the smooth demagnetization curves are noted for the alloys. The behavior of effective anisotropy, the performance of the magnets in applied magnetic field and the magnetic interactions among the various constituent grains were quantitatively studied by reversible susceptibility, irreversible susceptibility and recoil loop openness. This study may provide some guiding principles for the development of nanocomposite magnetic alloys with excellent magnetic properties by using much less RE elements.

Electronic structure, magnetism and martensitic transformation in all-d-metal Heusler alloys Mn2PtZ (Z = Sc, Ti, V)

The atomic ordering, electronic structure, magnetic properties and martensitic transformation of three new all-d-metal Heusler alloys Mn2PtZ (Z = Sc, Ti and V) have been investigated theoretically to discover new magnetic shape memory alloys (MSMAs). Depending on the different third transition metal element Z, Mn2PtSc and Mn2PtTi tend to form XA structure while Mn2PtV forms L21 structure. This difference is related to their DOS structures. Charge density difference calculations indicate enhanced d-d hybridization in these all-d-metal Heusler alloys. Mn2PtZ are all ferrimagnets with their Mn-Mn or Mn-V local spin moments antiparallel coupled. In these alloys, Mn2PtTi is a possible new MSMA with the energy difference ΔEM between the martensite and austenite as large as −262 meV/f.u., which indicates a high martensitic transformation temperature and is related to the Jahn-Teller effect in the electronic structure. A large volume effect of 2.9% cell shrinkage occurs during the martensitic transformation. All this makes Mn2PtTi a promising candidate for MSMAs with wide applications.

The magnetic field sensing performance of FeCo-based soft magnetic alloys with varying Fe/Co ratio

(FeCo)84CuB15 soft magnetic alloys with Fe/Co ratios (5:1, 3:1, and 1:1) were prepared using the planar flow casting method. The structural and magnetic properties together with magnetic field-sensing performance of the ribbons were investigated in detail. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the structural characterization. The magnetic parameters were determined by vibrating sample magnetometer and B-H loop tracer. The 2-D magnetic field variations on the surface of the ribbons were determined via a magnetic force microscope. The fluxgate sensors were prepared using the casted ribbons to test magnetic field sensing ability by measuring the second harmonic voltage induced in the pick-up coils by the lock-in amplifier. The working range and the noise of the sensors were also determined. The amorphous structure of the ribbons was confirmed by X-ray diffraction (XRD) patterns. The magnetic hysteresis measurements revealed the soft magnetic behaviour of the alloys having magnetization values as high as 1.3 T and coercivities around 1 Oe. As Fe/Co ratio increases, permeability values increase substantially. Meanwhile, the coercivities remained almost the same as close to 1 Oe. The alloys' magnetic field sensing feature decreased drastically as the Fe/Co ratio rose. Besides, noise parameters degraded. The linear response of the sensors to the external magnetic field (i.e., working range) enlarged with increasing Fe-content in the alloys.

Ultra-fine microstructure and exceptional low coercivity developed in a high-Bs Fe-Si-B-P alloy by co-alloying Ni, Mo, and Cu

Designing soft magnetic alloys with high saturation magnetic induction (Bs) is of great importance for improving the power density of electric and electronic devices. For high-Bs nanocrystalline alloys, the main problem is the grain coarsening effect induced by high Fe content (>80 at.%), which deteriorates the soft magnetic properties. In present work, we designed new Fe-based nanocrystalline alloys by microalloying a Fe-Si-B-P alloy. The co-alloying of Ni, Mo, and Cu effectively refines the microstructure of nanocrystalline alloys from 28.5 nm to 13.1 nm and increased the stability of soft magnetic properties. Even though there are 28-nm-large surface crystallites in the amorphous precursors, an exceptional low coercivity of 1–2 A/m with a high Bs of 1.81 T was developed after nanocrystallization. These excellent magnetic properties could be maintained within a wide annealing temperature window of 50 K and an annealing time window up to 600 s for high heating rate annealing.