Laser Additive Manufacturing of Magnetic Materials

Journal of Magnetism and Magnetic Materials, 2001

We report here a large (300}400 K) increase of the decoupling temperature (¹?K ) with increasing crystalline fraction in Nanoperm-type alloys. This is in contrast to the Finemet-type alloys where ¹?K varies some tens of K only around the original as-cast amorphous ¹ when the amorphous precursor is annealed around the "rst crystallization peak. H and M /M , versus ¹ measurements have been used to monitor the exchange decoupling of the nanosized particles, because these parameters are more sensitive to decoupling than M and , which show no characteristic change at the decoupling. This enhancement of ¹?K has been tentatively attributed to the increasing boron content of the residual amorphous matrix whereas the zirconium atoms agglomerate in the grain boundary region.

Journal of Magnetism and Magnetic Materials, 1995

A ferromagnetic solid solution with a nomina] atomic composition FeroCUr~ and a body-cen~ structure has been obtained by high-energy ball milling. The decomposition of the system is monitored by X-ray diffraction (XRD), measurements and M~ssbauer spectroscopy. According to XRDo for heating lcmpe.~tures below 723 K there is only a bcc ph.".~e in the material, while fvr heating temperatures above 723 K a new phase, with a fcc structure, appears, suggesting lha~ the solid solution has decomposc'd into bce-Fe and fcc-Cu. However, the magnetic behavior observed during the decomposition process indicates that this evolution is more complex than the simple deeomposition into the equilibrmm phases. This behavior can be summarized in two points: (1) a decrease in the ma~-tization at 5 K, and (2) dra~Ii¢ cha~'cs in the coercive field with the thermal treatment, soft magnetic behavior for the matc~"ial in the as-milled sta~e, ~a~g~ netism for low heating temperatures and a hardening of the mat~al ~ to above 723 K, for which the va|~es of the coercive field at room temperature are several times higher than those for the as-milled sampte. The Mtissbat~r st~ctrosc~y performed at room temperature shows thai for the heat-u~ated samples ~i~ Fe atoms are in two differem phases: a ferromagnetic phase, which evolves to bcc-Fe, and a paramag,~et~: phase.

IEEE Transactions on Magnetics, 1978

Journal of Alloys and Compounds, 2021

While BCC FeeCo alloys form an important class of soft magnetic alloys, they are often challenging to process in near net shape, due to the formation of the hard embrittling ordered B2 phase. Additive manufacturing (AM) technologies, such as laser engineered net shaping (LENS), permit processing these alloys in complex near-net shapes while controlling the extent of B2 ordering. The as-deposited samples, consist of elongated BCC grains, and exhibited reasonable values of saturation magnetization (M s) but rather high coercivity (H c). After annealing (950 C/30 min), the Hc values further increased due to the formation of fine recrystallized BCC grains, although these grains were relatively free of residual stresses. A second annealing step (500 C/50 h) resulted in the M s increasing by 25% and H c reducing by 63%. Detailed Transmission Electron Microscopy (TEM) analysis revealed substantially larger ordered B2 domains, separated by anti-phase domain (APD) boundaries in the two-step annealed condition, as compared to the single-step annealed (950 C/30 min) condition which consisted on nanometer scale weakly ordered B2 domains homogeneously distributed within a disordered BCC matrix. Therefore, the magnetic properties of the LENS processed alloys are significantly affected by the extent of B2 ordering, which can be engineered via appropriate post-processing heat treatments.

Journal of Alloys and Compounds, 2020

Accelerated development of soft magnetic materials is vital for addressing the challenges associated with improving the performance of electrical machines, transformer cores, electric vehicles etc. A combina- torial assessment of the structural, magnetic and mechanical properties of Co100-xFex (x 1⁄4 30 to 70) and Ni100-xFex (x 1⁄4 30 to 70) alloys has been carried out on samples fabricated via laser additive manufacturing (AM). Co100-xFex showed a bcc structure in the composition range studied while Ni100-xFex exhibited either single phase fcc or a mixture of fcc and bcc phases, depending on the composition. The saturation magnetization (Ms) for both Co100-xFex and Ni100-xFex compositionally graded alloys increases monotonically with increasing Fe content while the coercivity (Hc) variation is not monotonic. The Ms value of 199.3 emu/g for Co70Fe30 increases to 248 emu/g for Co30Fe70 alloys. Ni70Fe30 exhibits a Ms of 119.8 emu/g which increases to 168.7 emu/g for Ni30Fe70. The peak hardness is 260 VHN for the Co100- xFex series and 160VHN for the Ni100-xFex series. Such AM processed graded magnetic materials can be used for accelerated experiments to discover novel materials.

Journal of Magnetism and Magnetic Materials, 2000

The magnetic and the structural properties have been investigated for Fe Nb M Si B (M"Cu, Mn, Pt) alloys in their as-received and heat-treated state. Di!erential scanning calorimeter and scanning electrical resistivity were used to study crystallization behaviour and to examine the in#uence of the nucleation elements Cu, Mn and Pt on the structural and magnetic properties of Fe-based nanocrystalline materials. The temperature coe$cient of resistivity above Curie temperature was found to be very low (0.2;10\ K\) in the Cu containing alloy as compared to the alloys which contained Mn or Pt. A broad exothermic DSC peak for the formation of Fe Si nanoparticles was absent when Cu was replaced by Mn or Pt. Instead, a sharp exothermic peak for the formation of Fe (SiB) phase was observed with an onset at 875 K. The magnetic properties of the three alloys measured after stress relaxed annealing were similar. However, after "rst-stage crystallization, the soft magnetic properties were further enhanced only in Cu containing alloys due to the formation of Fe Si nanoparticles. Such nanoparticles together with di!erent intermetallic phases like FeMn or FePt were formed in Mn or Pt containing alloys. Moreover, the NbFeSi phase was also formed in the latter alloys after higher temperature annealing which reduced not only the amount of the Fe Si phase but also the grain re"ning e!ect due to the lesser amount of Nb available at the grain boundary. When Cu was replaced by Mn or Pt, the formation of di!erent intermetallics reduced the volume fraction of Fe Si nanoparticles and the lesser amount of grain re"ning Nb made the materials magnetically inferior after annealing above 775 K.

IEEE Transactions on Magnetics, 2004

Journal of Optoelectronics and Advanced Materials

The time evolution of the physical properties of hard and soft magnetic materials is shortly reviewed. Then, we analyse the magnetic properties of Nd5Fe67Cr8Nb2B18 nanocomposites, Nd-Fe-Co-Al-B hard magnetic phases and magnets as well as of Nd2Fe14-xMxC0.8B0.2 (M=Ni, Cu and Al) alloys. Some data on soft magnetic materials are also given. Finally, the magnetocaloric properties of ternary Gd-Co-B compounds are reported. Hard and soft magnetic materials, Magnetocaloric effect a) based on lecture given at MATEHN International Conference

2012

Following this Introduction, the remaining sections of this report contain a description of the progress with DOE funding during the final period of this program; a description of the status of the personnel who worked on this project (Section II); lists of the publications, invited talks, seminars and colloquia crediting DOE sponsorship (Section III); and a summary of current and pending federal support (Section IV). The References are at the end. Our DOE-funded research efforts were directed toward studies of magnetism at surfaces and interfaces in high-quality, well-characterized materials prepared by Molecular Beam Epitaxy (MBE) and sputtering. We have an exceptionally well-equipped laboratory for these studies, with: Thin film preparation equipment: three heavily-instrumented MBE machines, two computercontrolled, multi-target sputtering machines, a large rf sputtering machine, and an electron beam gun evaporator. Characterization equipment: various x-ray diffraction instruments including an 18 kW rotating anode x-ray source with Bragg-Brentano ș-2ș, low-angle, wide film Debye-Scherrer (Read), Laue, and Seemann-Bohlin; Scanning Tunneling and Atomic Force Microscopy (STM and AFM); Auger, X-ray Photoelectron Spectroscopy (XPS) Ion Scattering Spectrometry (ISS), and Secondary Ion Mass Spectrometry (SIMS); Reflected High and Low Energy Electron Spectroscopy (RHEED and LEED); and Scanning and Transmission Electron Microscopy (SEM and TEM); Equipment to study magnetic properties of surfaces and ultra-thin magnetic films and interfaces in multi-layers and superlattices: in situ (to 2.2 kOe at 10-10 torr) and ex situ (to 15 kOe)

Fe 91-x Mo 8 Cu 1 B x (x = 12, 15, 17, 20) amorphous and nanocrystalline alloys were studied to examine the influence of B content on their microstructure and magnetic behaviour. Changes in the magnetic properties provoked by microstructural evolution upon thermal treatments of as-cast samples were also analyzed. Nanocrystallization kinetics can be described by an isokinetic approach except for the 20 at.% B content alloy. The Curie temperature of the amorphous as-cast samples increases with the alloy's B content. Mö ssbauer results suggest the presence of Mo atoms in the nanocrystals. Crystalline volume fraction and mean grain size of the nanocrystals at the end of the nanocrystallization process are higher for the lowest B content alloy. The 20 at.% B content alloy develops a boride phase just after the early stages of the nanocrystallization process, which provokes a magnetic hardening in this alloy. The softest magnetic behaviour of the studied compositions corresponds to nanocrystallized 17 at.% B content alloy.