Fe-ni nanocomposite alloy

Abstract

To provide an FE-NI nanocomposite alloy that reduces a loss caused by a change in magnetic field, by increasing resistivity.SOLUTION: Crystalline particles 110, which contain an iron (Fe)-nickel (Ni) compound, are separated from each other within an amorphous matrix 120. A nanocomposite 100 is constituted between the crystalline particles and the amorphous matrix so that one or more barriers 130 can inhibit the growth of the crystalline particles. The amorphous matrix contains the crystalline particles with increased resistivity. A loss caused by a change in magnetic field applied to the crystalline particles is reduced in comparison with a state of the absence of the amorphous matrix.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (Priority Claim) This application claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 16 / 434,869, filed Jun. 7, 2019, the entire contents of each of which are incorporated herein by reference.

[0002] (Government Rights) This invention was made with U.S. Government support under Contract No. DMR0804020 awarded by the National Science Foundation. This invention was made with U.S. Government support under Contract No. W911NF-14-1-0184 awarded by the Army Research Laboratory. The U.S. Government has certain rights in this invention.

[0003] (background) The present disclosure relates generally to nanocomposite alloys. More specifically, the present disclosure relates to Fe—Ni nanocomposite alloys.

[0004] Ferromagnetic materials have a Curie temperature T C A magnetically saturated material is one in which electron spin dipole moments order in the absence of a magnetic field over a volume called a magnetic domain below a temperature called . In an applied magnetic field of sufficient strength, a magnetically saturated material has a single magnetic domain encompassing the sample volume. At zero magnetic field, it is energetically advantageous to have multiple magnetic domains to minimize the demagnetizing field. When an external magnetic field is applied, there are two ways that magnetic domains can align with the magnetic field: (1) domain growth or (2) domain rotation. In domain growth, magnetic domains already aligned with the magnetic field expand at the expense of their neighbors by domain wall motion. Domain rotation occurs when, instead of domain wall motion, individual atomic moments rotate to align with the applied magnetic field.

[0005] Magnetic materials are broadly divided into two groups: soft magnets and hard / permanent magnets. The two groups are distinguished by their coercive force, with soft magnets having much lower values ​​and permanent magnets being difficult to demagnetize. Other important magnetic properties are saturation magnetization and permeability. Saturation magnetization is the magnitude of the magnetization of a single magnetic domain, while permeability relates the strength of the external magnetic field to the magnitude of the induced internal magnetic field. Developing the right balance of these properties for various applications drives magnetic materials research.

[0006] Michael Faraday first demonstrated the law of induction (or electromagnetic induction) using an iron core. As the power industry developed and adopted AC current, iron cores were found to have too many losses due to their low resistivity, leading to high losses due to standard eddy currents. For this reason, silicon steel was researched beginning in the 1880s and dominated the market by the 1930s. Silicon steel remains the industry standard for high-voltage AC power transformers. More specialized applications required higher induction, which found use in military applications and reduced cost, leading to the development of iron-cobalt alloys. Iron-cobalt alloys have the highest induction of any transition metal alloy. This can be understood in relation to the Slater-Pauling curve. Other applications, such as sensors and motors, require higher permeability than silicon steel. For these applications, an iron-nickel alloy, permalloy, was developed. Summary of the Invention

[0007] (overview) The nanocomposite comprises crystalline particles in an amorphous matrix, wherein the crystalline particles comprise iron (Fe)-nickel (Ni) compounds and are separated from one another by the amorphous matrix; and one or more barriers between the crystalline particles and the amorphous matrix, wherein the barriers are configured to inhibit the growth of the crystalline particles during their formation, the one or more barriers being between the crystalline particles and the amorphous matrix; wherein the amorphous matrix comprises an increased resistivity compared to the resistivity of the crystalline particles; and wherein the amorphous matrix is ​​configured to reduce loss of the crystalline particles caused by a change in a magnetic field applied to the crystalline particles compared to loss of the crystalline particles that would occur without the amorphous matrix.

[0008] Furthermore, this paper has shown that Fe has good glass-forming ability (GFA) by models based on Thermocalc simulations and experimental validation. 70 Ni 30 ) 80 (B-Si-Nb) 20A series of compositions in the system are described. In particular, the range of B=14-18%, Si=0-7%, and Nb=0-6% has excellent GFA and is the preferred embodiment of this application. Furthermore, some of these alloys have a large ΔTxg = (Tx - Tg), where Tx corresponds to the primary crystallization temperature and Tg corresponds to the glass transition temperature of the amorphous phase, which will enable processing by various thermomechanical means at high temperatures, including stamping, rolling, and die forming. Examples of embodiments of advanced manufacturing processes uniquely compatible with these alloys include: (1) hot rolling above the Tg of the amorphous precursor to thin the ribbon prior to nanocrystallization; (2) hot stamping the ribbon above the Tg of the amorphous precursor to form a laminate of the desired geometry; (3) induction rolling, which uses eddy currents in the ribbon to create a heat source via RF excitation of rollers; and (4) hot rolling simultaneously with nanocrystallization of alloy compositions in which the grain boundary amorphous phase is engineered to maintain a low Tg as the crystallization process progresses. xg is observed, and even after nanocrystallization, these alloys can be thermomechanically processed.

[0009] In some implementations, the crystalline particles comprise a metastable, face-centered cubic Fe—Ni group. In some implementations, the Fe—Ni group comprises γ-FeNi nanocrystals.

[0010] In some implementations, the barrier comprises niobium (Nb), wherein the amorphous matrix comprises boron (B) and silicon (Si), which together configure to enable glass-forming capabilities of the amorphous matrix. In some implementations, the nanocomposite material comprises a copper (Cu) nucleating agent configured to increase nucleation of crystalline particles during a molding process compared to nucleation of crystalline particles during a molding process without the copper nucleating agent, wherein the crystalline particles are reduced by 10% or more as a result of the increased nucleation.

[0011] In some implementations, the crystalline particles comprise an average diameter of 5 to 20 nm.

[0012] In some implementations, the nanocomposite forms a ribbon 15-30 μm thick, and in some implementations, the nanocomposite includes magnetic anisotropy that is longitudinal along the ribbon.

[0013] In some implementations, the nanocomposite material contains 50 atomic % or less of one or more metals, including boron (B), carbon (C), phosphorus (P), silicon (Si), chromium (Cr), tantalum (Ta), niobium (Nb), vanadium (V), copper (Cu), aluminum (Al), molybdenum (Mo), manganese (Mn), tungsten (W), and zirconium (Zr). The nanocomposite contains 30 atomic % or less of cobalt (Co). In some implementations, the nanocomposite contains about 30 atomic % of Ni. In some implementations, the resistivity of the crystalline particles is about 100 μΩ·cm, and the resistivity of the amorphous matrix is ​​about 150 μΩ·cm. In some implementations, the amorphous matrix is ​​annealed to enable a superplastic response of the nanocomposite. In some implementations, the crystalline particles within the amorphous matrix and diffusion barrier comprise a strain-annealed structure tuned to a relative permeability of greater than 10,000. The changing magnetic field applied to the crystalline particles occurs at a frequency between 400 Hz and 5 kHz. In some implementations, the losses include eddy current losses.

[0014] In some embodiments, a rotor comprises one or more layers, each comprising: γ-FeNi nanocrystals in an amorphous matrix, wherein the γ-FeNi nanocrystals have an average resistivity less than 100 μΩ·cm and the amorphous matrix has a resistivity equal to or greater than 100 μΩ·cm; and one or more boron diffusion barriers between each of the one or more γ-FeNi nanocrystals and the amorphous matrix, each of the one or more diffusion barriers configured to inhibit diffusional growth of the γ-FeNi nanocrystals during formation of the γ-FeNi nanocrystals; wherein the γ-FeNi nanocrystals are about 70 atomic % Ni; wherein the γ-FeNi nanocrystals have an average diameter between 5 nm and 30 nm; and wherein each of the one or more composite layers has a thickness less than about 25 μm.

[0015] In some implementations, each composite layer is a strain-annealed composite comprising a relative permeability greater than 10000. In some implementations, each composite layer further comprises copper.

[0016] In some implementations, an electric motor includes a rotor and a stator configured to drive the rotor, the stator including multiple laminations less than 30 μm thick, each lamination including crystalline particles within an amorphous matrix, each lamination including an iron (Fe)-nickel (Ni) compound and separated from one another by the amorphous matrix; and one or more barriers between the crystalline particles and the amorphous matrix, the barriers configured to inhibit growth of the crystalline particles during their formation, a barrier of the one or more barriers being between the crystalline particles and the amorphous matrix; wherein the rotor is configured to operate at a frequency greater than 400 Hz.

[0017] In some implementations, the method involves fabricating amorphous precursors of nanocomposites through heat treatment with or without applied stress, resulting in unique metastable multiphase microstructures.

[0018] The applied stress during annealing induces anisotropy that depends on the chemistry. The anisotropy induced in Fe-rich alloys is along the ribbon axis, increasing permeability. The anisotropy induced in Ni-rich alloys is transverse to the ribbon axis, decreasing permeability. Further alloying additions can increase resistivity by approximately 40% without significantly affecting magnetic properties. The addition of Cu alters the crystallization rate, refining the metallographic structure and producing smaller grains. The use of different glass formers alters the formability and affects the mechanical properties of the nanocomposite. Applications for these alloys include high-switching frequency electric motors, such as axial motors with rare-earth-free permanent magnets, and motor designs using only soft magnetic materials, such as switched reluctance motors.

[0019] In some implementations, the nanocomposite is a material ranging from 20% to 80% Ni. The metallography can be controlled by melt spinning and by various post-processing methods, such as strain annealing, to tailor properties to meet various application demands.

[0020] The nanocomposites described below include several advantages. Certain alloy compositions described below have attractive superplastic responses to enable more practical stamping of useful shapes. In iron-rich compositions, strain annealing can induce anisotropy along the ribbon direction, thereby increasing magnetic permeability along the ribbon direction. The crystallization product is metastable γ-FeNi in Fe-rich compositions, in addition to α-FeNi in Fe-rich compositions. The nanocomposites described below improve the efficiency of motors operating at high rotational speeds.

[0021] The nanocomposites described below are useful for high-frequency applications. For example, laminated silicon steel is traditionally used in motors. However, laminated silicon steel is inefficient at high frequencies due to conventional anomalous eddy current losses. Using higher frequencies is attractive due to the potential for higher power output (motor power is the product of torque and rotational frequency). The nanocomposites described below reduce losses during high-frequency switching of the magnetic field. This allows for higher frequencies to be applied to motor stators containing nanocomposites without sacrificing power efficiency or requiring larger motors. Higher frequencies would allow for a reduction in the size and mass of inductive components. Cost savings can be realized through reduced motor size. Many motor designs use permanent magnets to generate or induce magnetic flux. Because motor size can be reduced at high frequencies, devices using rare-earth permanent magnets can use significantly less rare-earth material. This is attractive due to concerns about the cost and availability of rare-earth metals.

[0022] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0023] [Figure 1]FIG. 1 shows a diagram of crystallites (or crystallites) surrounded by a diffusion barrier in an amorphous matrix. [Figure 2] 2A-2B show examples of Fe-Ni alloys. [Figure 3] Figure 3 shows a comparison of the motors. [Figure 4] FIG. 4 displays a graph of the losses during a magnetic switching cycle. [Figure 5] FIG. 5 is a diagram of the TO diagram configuration of a binary alloy. [Figure 6] FIG. 6 shows various amorphous alloy matrices. [Figure 7] FIG. 7 shows the Fe—Ni binary phase diagram. [Figure 8] FIG. 8 shows the saturation magnetization as a function of composition for the as-cast alloys. [Figure 9] FIG. 9 is an X-ray diffraction diagram. [Figure 10] FIG. 10 shows the Tg, primary, and secondary crystallization temperatures as a function of composition. [Figure 11] FIG. 11 shows the MH data for Fe70Ni30 after casting and strain annealing. [Figure 12] FIG. 12 shows a graph showing the HTXRD of each of the Fe-rich Fe—Ni alloys. [Figure 13] Figures 13A-13B are examples of motors. [Figure 14] 14A-14B show the simulation results of glass forming ability (GFA) for various material compositions. [Figure 15] FIG. 15 illustrates an example of a hot rolling mill system for processing one or more alloy compositions. [Figure 16] FIG. 16 shows an example of a roll bonding scheme for applying heat to an alloy composition. [Figure 17] FIG. 17 shows a graph containing the change in glass transition temperature Tg with respect to the change in annealing temperature.

[0024] (Detailed explanation) FIG. 1 illustrates a nanocomposite material 100 including one or more crystalline particles 110, an amorphous matrix 120, and a diffusion barrier 130. The crystalline particles 110 are formed by a crystallization process, described in more detail below. Generally, each crystalline particle 110 (also known as a crystallite) includes small or microscopic "crystals" formed during cooling of a metallic material, such as an Fe-Ni alloy. The crystalline particles 110 generally include a regular or near-regular lattice of atoms, as seen in FIG. 1. Grain boundaries are interfaces where crystalline particles contact other materials, such as an amorphous matrix. Generally, the crystalline particles 110 do not contact each other but are located within (e.g., embedded in) an amorphous matrix that includes a relatively high-resistivity material between the relatively low-resistivity crystalline particles. The crystalline particles 110 have an average diameter of 5 to 30 nm and are formed of an Fe-Ni alloy. In some implementations, the nanocomposite includes a material ranging from 20% to 80% Ni. The crystalline particles 110 may have an average size of 5 to 20 nm embedded in an amorphous matrix 120. In some implementations, the crystalline particles 110 include an Fe-Ni alloy. The properties of the crystalline particles 110 (e.g., magnetic or resistive properties) can be adjusted by adding additional materials. As described in more detail below, other metals, such as cobalt or copper, are included in the crystalline particles 110. In some implementations, crystalline particles 110 formed from different alloys, such as different Fe-Ni alloys, are used to adjust the resistivity, permeability, or other properties of the nanocomposite. In some implementations, the crystalline particles 110 are each formed from the same material or alloy as the nanocomposite 100. In some implementations, the crystalline particles 110 vary in composition throughout the nanocomposite 100.

[0025] Generally, the amorphous matrix 120 includes a metal or metalloid that forms a non-crystalline solid, such as a solid lacking the long-range order characteristic of a crystal. The amorphous matrix 120 has a relatively high resistivity compared to the crystalline particles 110. The crystalline particles 110 are located within the amorphous matrix 120 and are generally separated from one another by the amorphous matrix. The resistivity, relative permeability, and other properties of the amorphous matrix 120 can be adjusted by adjusting the composition of the amorphous matrix. In some implementations, the amorphous matrix 120 includes one or more of the metalloids or early transition metals described in connection with FIG. 6. Generally, the average spacing between the crystalline particles 110 provided by the amorphous matrix 120 is smaller than the average diameter of the crystalline particles (e.g., <10-15 nm).

[0026] Generally, the diffusion barrier 130 is a metal or metalloid configured to inhibit the growth of the crystalline grains 110 during annealing or other forming processes. The inclusion of the diffusion barrier 130 material can tailor the size of the crystalline grains 110 and therefore the resistivity, relative permeability, etc. of the nanocomposite 100. In some implementations, the diffusion barrier 130 prevents the crystalline grains 110 from colliding with each other.

[0027] Crystallization is a phase transformation controlled by nucleation and growth kinetics. The function of glass formers is to control the crystallization rate. From Johnson-Mehl-Avrami-Kolmogorov (JMAK) kinetics, the transformed volume fraction (X) can be expressed as a function of temperature (T) and time (t) in a TTT diagram. The JMAK equation is:

[0028]

number

[0029] where ti is the incubation period, n varies from 1 to 4, and k is the rate constant, which can be expressed as:

[0030]

number

[0031] From the determination of X at various temperatures, k and Q can be calculated. JMAK kinetics is based on three assumptions that do not apply to nanocomposite systems: 1) growth stops when precipitates collide with each other; 2) 100% of the volume is converted; and 3) nucleation is uniform.

[0032] However, in the case of nanocrystallization, early transition metal atoms are expelled from the crystalline phase and form a diffusion barrier around the crystal, retarding further growth. This invalidates assumptions 1 and 2, and soft impingement corrections must be employed. There are several feasible methods for determining X: T of the amorphous phase C is the T of the crystallite C If the T is lower than , the magnetization data will confirm the crystallization. The magnetization of the sample will initially be solely from the amorphous phase. C As the temperature approaches , the magnetization will decrease. When primary crystallization occurs, the magnetization will increase. During cooling, the remaining amorphous phase will again contribute to the total magnetization. By comparing the magnetization of the initial amorphous phase, the crystalline, and the residual amorphous, the volume fraction of crystallites can be determined.

[0033] Another method for determining the crystallite volume fraction is to use XRD. By fitting a Gaussian curve to the peaks present in the diffraction pattern, the peak areas can be determined. By comparing the amorphous peak area to the crystalline peak area, the relative proportions can be determined. This is particularly feasible using synchrotron radiation, as the data can have high time resolution.

[0034] While primary crystallization from amorphous materials is beneficial from a device perspective, secondary crystallization is detrimental to magnetic properties. In secondary crystallization, metalloids and glass-forming elements form crystalline intermetallic phases with transition metals. Due to their detrimental effect on rapid grain growth, it is important to determine the rate of secondary crystallization so that it can be prevented during device use. In some implementations, the crystalline grains 110 in Figure 1 contain metastable face-centered cubic Fe-Ni groups, as shown in Figures 2A-2B. Figure 2A shows an alloy 200 containing disordered γ-FeNi (Ni in white, Fe in gray). Figure 2B shows an alloy 210 containing L12 FeNi3.

[0035] Phase diagram:

[0036] The binary Fe-Ni phase diagram is shown in Figure 8a-b. The phase boundary is where the Gibbs free energies of the two phases are equal. However, due to the alloy's glass-forming properties, the system is not in equilibrium. Thus, when the system crystallizes from the amorphous structure after casting, as was also the case for the nearly equiatomic FeCo system, it is not possible to be certain whether the resulting crystallites are FeNi3 or γ-FeNi without XRD or TEM evidence of superlattice reflections.

[0037] In addition to the equilibrium phase, Figure 8B shows the T of the γ-FeNi and α-Fe phases as a function of composition. C In conventional motor applications, high T C Therefore, the region where Ni is close to 70% is important. Furthermore, when Ni3Fe is crystallized instead of the γ phase, T C Even on the Fe-rich side of the figure, T C can be high enough for motor applications.

[0038] Fe-Ni nanocomposite materials allow for a wide range of compositions. Metastable γ-FeNi nanocrystals can be used rather than α-Fe nanocrystals, and even Fe-rich compositions can be used. In Ni-rich Fe-Ni nanocomposites, crystallization leads to the ordered L12 structure with γ-FeNi or Ni3Fe (Figure 1).

[0039] Some Fe-Ni alloys have attractive properties for applications. For example, 50-50 Fe-Ni alloys have the highest saturation magnetization. For Ni-rich alloys, 78% Ni Permalloy is important because it has zero magnetostriction coefficient and high permeability of about 100,000. Since not all properties can be optimized at once, the composition is usually selected with the specific device application in mind. Recently, Fe-rich Fe-Ni alloys have been developed with T near room temperature. C Because of this, they have been investigated for use in magnetocaloric cooling applications.

[0040] Nanocomposite 100 includes Fe-Ni-based metallic amorphous nanocomposite (MANC) materials for motors with compositions ranging from 20% to 80% Ni. Interestingly, there is evidence of asperomagnetism in certain iron-rich alloys. Varying the composition of the glass formers also affects castability and mechanical properties. Of the early transition elements, Nb can typically be cast in air, while Hf and Zr cannot. Varying the metalloid mixture can also improve formability and allow for tuning of the magnetostriction coefficient.

[0041] The principle of electric motor operation can be explained with reference to equation (1), which relates Faraday's law of induction to the voltage response of an ideal core driven by AC current.

[0042]

number

[0043] Here, ω = 2πf, where f is frequency. Holding all other variables constant, increasing f reduces A at constant voltage. This means that increasing frequency reduces device size. However, increasing frequency also increases losses. Therefore, if a smaller device is desired, materials must be designed that have lower losses at high frequencies. A motor is measured by its power density, or the amount of power output per unit volume of the motor. Figure 3 shows three rotors designed with comparable power outputs. The top two are made of Si-steel, while the bottom rotor is made of HITPERM alloy. As can be seen, using HITPERM alloy and greater magnetization allows for a smaller rotor design, resulting in higher power density. Preliminary designs in COMSOL Multiphysics suggest that switching from Si-steel operating at 60 Hz to Fe-Ni MANC operating at 1 kHz could reduce the motor size by nearly 50%. Figure 3 shows a comparison of a Si-steel rotor (top) to a HITPERM alloy (bottom) with the same power output.

[0044] The nanocomposites described herein include materials for improving the efficiency of motors operating at high rotational speeds by using Fe-Ni nanocomposites, which are more economical than their Co-Fe counterparts for motor applications. Metallographic microstructures are controlled by various post-processing methods, such as melt-spinning and strain annealing, as described in further detail below. This process allows various alloy properties (such as permeability, induced anisotropy, and grain size) to be tailored to meet the demands of various motor applications. For example, in Fe-rich compositions, strain annealing induces anisotropy in the ribbon direction. Furthermore, certain alloy compositions described below have attractive superplastic responses that enable more practical stamping of shapes useful for motor laminations.

[0045] loss:

[0046] Figure 4 shows a graph 400 representing three loss sources as a function of frequency. AC losses in magnetic materials can be divided into those resulting from (1) magnetic hysteresis, (2) conventional eddy currents, and (3) anomalous eddy currents. Each of these losses has a different frequency dependency. Hysteresis loss is related to the area within the hysteresis loop of the material, which is the energy / volume lost in one magnetic cycle. Since it is a constant amount per cycle, the total power loss is linear with time. The coercivity (H) of the material C ) decreases, the hysteresis loss can decrease. This is one reason why using nanocomposite materials is beneficial. When the crystallite size decreases below a certain amount, H C is significantly reduced, thereby reducing losses.

[0047] Traditional eddy current losses are related to the fact that AC currents generate alternating magnetic fields that induce eddy currents in materials. These currents generate I, which heats up the material. 2 R causes power loss. Conventional eddy current losses are described by Equation 2:

[0048]

number

[0049] With coefficient b given by Eq.

[0050]

number

[0051] where t is thickness and ρ is resistivity. Therefore, to minimize conventional eddy currents, thin cross sections and high resistivity are desired. Thin cross sections are obtained by melt spinning the alloy. Relevant variables are wheel speed, casting temperature, discharge pressure, and nozzle-wheel gap distance. Standard silicon steel used in motors has a laminate thickness approaching 0.6 mm. Using a 25 μm thick ribbon reduces eddy current losses by about two orders of magnitude. Nanocomposite 100 makes it possible to fabricate ribbons of about 15-30 μm. Hysteresis losses and eddy current losses are often expressed by the Steinmetz equation:

[0052]

number

[0053] P is the power loss, and k, α, and β are empirical fits to the data.

[0054] To model the resistivity of nanocomposites, it is useful to consider three phases: a crystalline phase, an amorphous phase, and a shell phase composed primarily of glass-former and growth-inhibitor atoms. The advantage of the amorphous structure is that it has a higher resistivity than a chemically identical crystalline phase, thereby increasing the resistivity of the nanocomposite and thereby reducing conventional eddy current losses. Of the three, the crystalline phase has the lowest resistivity, while the shell has the highest glass-former concentration, resulting in the highest resistivity. For example, the resistivity of an amorphous ribbon nanocomposite after casting is approximately 150 μΩ·cm. The resistivity of the crystallites is approximately 100 μΩ·cm. Without a shell, the path to lowest resistance would be to maximize the distance traveled within the crystallite relative to the amorphous matrix. However, a highly resistive shell complicates this. Previous modeling has shown that a small crystal grain size (e.g., <10–15 nm), a high glass-former concentration within the shell, and a thick shell around the crystallites are each desirable to maximize resistivity.

[0055] A third source of loss is anomalous eddy currents. Anomalous loss is due to domain wall motion when the magnetization of the material is switched. Domain wall motion is reduced if magnetic anisotropy is induced so that the magnetic domains align transversely to the ribbon direction in the absence of a magnetic field.

[0056] Phase relations in the Fe-Ni pseudobinary system:

[0057] Glass Formation:

[0058] Before addressing the Fe-Ni pseudobinary system, we investigate the kinetics of glass-forming ability and nanocrystallization. The glass-forming ability (GFA) of a material describes the inhibition of nucleation and growth of stable crystalline phases. This involves preventing elements in the liquid from partitioning into the crystalline phase. The GFA of a material is determined by its glass-forming temperature (T rg ) and is expressed as:

[0059]

number

[0060] where T g is the glass transition temperature, and T L is the liquidus temperature. T g Below T, the structure freezes. g Above this temperature, the material becomes viscous and flowable. To facilitate glass formation, T g should be maximized, and T L should be minimized. The thermodynamics of glass formation is shown in Figure 5, T0 diagrams 500, 510. The T0 curve describes all points where the free energy of the liquid and solid phases is equal. For compositions between the T0 curves, the liquid can only lower the free energy by diffusion into the α and β phases. Outside the T0 curve, the liquid can form solid crystals without diffusion. Within the T0 curve, the melt reaches the T g If it is quenched fast enough below this temperature, diffusion does not occur and the atomic structure of the liquid freezes.

[0061] Suzuki created the first amorphous alloy matrix that can be used to develop nanocrystalline alloys. The matrix is ​​a graphical representation of Inoue's rule for forming a magnetic glass. The glass should contain three components with significantly different atomic radii and a negative heat of mixing.

[0062] Various alloy combinations can be seen in matrix 600 in Figure 6. In Figure 6, FM is a ferromagnetic late transition metal element, EM is an early transition metal, and ML is a metalloid. Nb is a common EM used as a diffusion growth inhibitor because it allows for casting in air, which is important for industrial scale. The diffusion barrier limits primary crystallization, so the resulting crystallites are small. Boron is a preferred metalloid because it has virtually zero solubility in the FM crystals formed during primary crystallization, and T C is increased in the amorphous matrix by the resulting B enrichment. Silicon is required along with boron to ensure glass-forming ability. The use of other transition metals and metalloids in different amounts is expected to change the glass formability and mechanical properties of the resulting alloy. Nanocomposites can contain up to 50 atomic % of one or more metals, including boron (B), carbon (C), phosphorus (P), silicon (Si), chromium (Cr), tantalum (Ta), niobium (Nb), vanadium (V), copper (Cu), aluminum (Al), molybdenum (Mo), manganese (Mn), tungsten (W), and zirconium (Zr). In some implementations, the nanocomposite contains up to 30 atomic % of cobalt (Co).

[0063] Examples of manufacturing and laboratory tools:

[0064] The nanocomposite material is (Fe x Ni 1-x ) 80 Nb4Si2B 14The general chemical formula is , where x may vary over a wide range. All materials are arc-melted multiple times from pure elements in a controlled atmosphere to achieve chemical homogeneity. The ingots are then melt-spun in a controlled atmosphere. Casting conditions such as wheel speed, discharge temperature, discharge pressure, and nozzle-wheel distance are all controlled to produce amorphous ribbons. Amorphousness is first checked by a simple bend test. Typically, if the sample is not amorphous, it will be very brittle and break when bent. If it passes the bend test, X-ray diffraction (XRD) may be performed to confirm that the casting is amorphous.

[0065] Once an amorphous ribbon is produced, differential scanning calorimetry (DSC) measurements are used to determine the primary and secondary crystallization temperatures, and possibly the glass transition temperature. DSC measures the heat supplied to a sample and a reference. The reference and sample are maintained at the same temperature. During the transition, the amount of heat required to maintain the same temperature increases or decreases depending on whether the transition is endothermic or exothermic. By measuring the change in the rate of heat supply, the transformation temperature can be estimated.

[0066] By determining the transformation temperature, the activation energy of crystallization can be calculated. The amorphous phase is metastable, and a certain amount of energy is required to nucleate the crystalline phase. This gives the activation energy Q in equation (6). The most convenient way to determine the activation energy of crystallization is to use Kissinger kinetics. The Kissinger equation can be expressed as:

[0067]

number

[0068] where α is the heating rate, T x is the crystallization temperature, and Q Kis the activation energy (not to be confused with the activation energy derived using the Kissinger equation and JMAK kinetics). Then Q K is 1 / T x Q is the slope of the line plotting the left-hand side of equation (7) against Q. One energy barrier contributing to Q is the energy required to nucleate a critical nucleus size. Below the critical size, the formed crystals will be unstable, and the free energy will decrease if the crystal dissolves in the liquid due to the solid-liquid interfacial energy. Once nuclei larger than the critical size are formed, they will grow during crystallization. During primary crystallization, growth is a temperature-dependent diffusion process, which contributes another factor to Q. Primary crystallization is thought to be controlled by volume diffusion, which grows parabolically with time, at least until soft impingement occurs. During primary crystallization, the amorphous matrix becomes enriched with the glass-forming elements. Other factors contributing to Q are the reduction in volume free energy from crystallization and misfit strain energy.

[0069] Because the magnetic properties of the material are important, a vibrating sample magnetometer (VSM) is used to determine the M-H loop and M-T curve at the relevant magnetic field and temperature, respectively. The operation of the VSM is explained by applying Faraday's induction law. A magnetic field is applied to the sample to magnetize it. The sample is connected to a drive head that vibrates the sample at 60 Hz. This generates a spatially and temporally varying magnetic field, which induces a current in a series of pickup coils that is proportional to the induced magnetization of the sample.

[0070] The magnetization data can also be used to estimate the volume fraction of crystallized ribbons by utilizing Brillouin function fitting, which simplifies the spin-only dipole moment to the following form:

[0071]

number

[0072] where M is the magnetization and T is the temperature. The Brillouin function can be used to extrapolate the magnetization curve to 0 K. If we know the specific magnetization of the crystalline phase, we can determine the fraction of the sample that is crystalline. The amorphous phase usually begins at the temperature of primary crystallization, T x1 Lower than T C Therefore, the T of the amorphous phase of the ribbon after casting C The magnetization becomes zero at T x1 When the magnetization reaches , the magnetization increases as a function of the transformed volume fraction. After crystallization, the sample is cooled and the amorphous phase again contributes to the magnetization. By fitting a Brillouin function to the crystalline phase, the magnetization resulting from the presence of crystallites can be determined. By comparing this value with the specific magnetization value of the crystallites, the mass percentage of the crystalline phase can be calculated. This technique has been demonstrated in recent publications.

[0073] As mentioned earlier, XRD is used to ensure the amorphous nature of the ribbon after casting, but also to check the phase transformations that occur during annealing. X-ray diffraction instruments fundamentally rely on Bragg's law:

[0074]

number

[0075] As shown in diagram 900 of Figure 9, where n is an integer, λ is the X-ray wavelength, d is the atomic lattice spacing, and θ is the angle between the X-ray and the atomic plane. Traditional XRD instruments use a single λ and vary the θ value. Advanced Photon Source offers energy dispersive XRD using a range of wavelengths and with a fixed θ value.

[0076] The XRD crystallite size after crystallization can also be estimated using Scherrer analysis. The diffraction peaks are first fitted to a Gaussian curve. For a Gaussian distribution, the width of the peak is related to the integral width as follows:

[0077]

number

[0078] where β is the integral width and w is the width. Instrumental broadening is then removed from the peak integral width by quadratic subtraction. The resulting integral width can be attributed to the crystal size. The calculated integral width β s is used to estimate crystal size using the Scherrer equation:

[0079]

number

[0080] where d is the average grain size and K is a shape factor, typically between 0.9 and 1. Generally, the material after casting is expected to have a predominantly broad amorphous halo. Material that has undergone primary crystallization should have a greatly reduced amorphous halo, but the crystalline peaks will still be broad due to the smaller crystallite size.

[0081] Materials can also be strain-annealed, which has multiple effects. From DSC, the primary and secondary crystallization temperatures are determined. The cast ribbon is then strain-annealed between the two temperatures. The ribbon is annealed in a tube furnace under atmospheric conditions. This creates a nanocomposite and improves the magnetic inductance of the metal foil. Additionally, the permeability of the ribbon can be adjusted by varying the stress applied during annealing. After strain-annealing, XRD data is collected to confirm crystallization, and magnetic data is collected to confirm the effects of strain-annealing. Strain-annealing is also used to demonstrate superplasticity in the amorphous phase. Superplasticity can be simply defined as the ability of a material to undergo large plastic deformation in tension without fracture. T g Above T, metallic glasses become viscous supercooled liquids capable of viscous flow.g The viscosity between melting and crystallization can vary by seven orders of magnitude. These supercooled liquids can experience large plastic strains under applied stress. Processing is similar to that of thermoplastics, and formability is temperature dependent. The main difference is that amorphous glasses are metastable, so the superplastic forming region of this system is likely limited by the secondary crystallization temperature. Elongation measurements are made by marking the ribbon with a hot marker before strain annealing and measuring how far the mark moves after the sample is annealed. Example results show that (Fe 60 Ni 40 ) 80 Nb4Si2B 14 The sample shows almost 100% elongation.

[0082] Test Results:

[0083] DSC:

[0084] Glass transition temperature (T g ), primary crystallization temperature (T x1 ) and secondary crystallization temperature (T x2 DSC curves were collected for a wide range of Fe-Ni compositions where T g is important. g Above this temperature, it is possible to stamp these shapes for use as motor stators. Furthermore, T is used to determine the maximum temperature a material can tolerate before irreparable damage to its properties occurs. x1 and T x2 It is important to know the temperature range between . These results can be seen in graph 1000 of FIG.

[0085] Superplastic formability distinguishes certain metallic glasses from other metals by allowing them to be shaped and processed similarly to thermoplastics. When stamped, many layers can be stacked to build a component. Figure 13A shows an example of an electric motor 1300 from above, showing a stator 1310 and rotor 1320 containing a nanocomposite (e.g., nanocomposite 100 of Figure 1). Figure 13B shows an example of an electric motor 1330 from a side perspective. The stator 1310 is constructed from a stack 1340 of nanocomposite layers 1340a-n. As noted above, the layers 1340a-n each have a thickness of less than 30 μm to reduce losses during high-frequency operation. The stack 1340 of nanocomposite layers is a cheaper manufacturing method than laser cutting, which would otherwise have to be used.

[0086] VSM:

[0087] In Figure 8, diagram 800, we show how the saturation induction of Fe-Ni alloys depends on the Ni content. As expected from the Slater-Pauling curve, higher Fe contents increase induction. The data in Figure 8, diagram 800, are for as-cast samples. Towards the Ni-rich end, M S The M of the material after primary crystallization begins to drop below the value required for the application. S is expected to be higher than that of the amorphous phase.

[0088] Furthermore, as can be seen in diagram 1000 of FIG. 10, an exemplary (Fe 70 Ni 30 ) 80 Nb4Si2B 14MT curves were collected for the alloy. While one would normally expect the magnetization to increase as the temperature is decreased, it can be seen that the magnetization eventually begins to decrease with temperature. This can be explained as a spin-glass phenomenon. When the temperature is cooled below the ferromagnetic-asperomagnetic (or non-blocking magnetic) transition, the spins are frozen in such that they cant with respect to each other, but all cant angles are within a hemisphere. Upon heating, the asperomagnetic phase becomes metastable, and the magnetization approaches the cooling curve as the temperature approaches room temperature. The canted spins reduce the magnetization available for motor applications. Due to the temperature dependence, this is of greater concern for cryomotor applications.

[0089] Diagram 1100 in FIG. 11 shows (Fe 70 Ni 30 ) 80 Nb4Si2B 14 The MH curves for a sample of this alloy were cast and strain-annealed at 200 MPa and 470°C. The permeability of the strain-annealed sample is almost an order of magnitude higher than that of the as-cast case. We demonstrate an increase in permeability from 4000 to 16000. The Ni-rich ribbons are expected to have the opposite effect, as the signs of the magnetostriction coefficients are opposite. MH data were collected for several other Fe-rich alloys that were cast and strain-annealed. All of the other alloys show an increase in permeability upon strain annealing.

[0090] XRD:

[0091] High temperature XRD (HTXRD) shows the as-cast (Fe 65 Ni 35 ) 80 Nb4Si2B 14The alloy was analyzed. Peaks were fitted using a crystal model in CrystalDiffract. Peaks from the corundum background are marked orange, FCC peaks are marked green, and BCC peaks are marked blue. The presence of Cu Kα1 and Kα2 radiation doubles the corundum peak. As can be seen, the ribbons start out primarily amorphous, but there is a prominent broad FCC {002} peak. By 500°C, primary crystallization occurs, revealing both FCC and BCC peaks. Previous studies predict that further heating beyond the α-to-γ transition temperature of Fe will convert α-Fe to γ-Fe, which will not revert upon cooling. The phase fractions of crystallites and amorphous matrix can also be determined by fitting Gaussian or pseudo-Voigt curves to the peaks. The ratio of the peak areas provides the phase fraction. (Fe 75 Ni 25 ) 80 Nb4Si2B 14 The values ​​for the base alloy are shown in graph 1210 of FIG.

[0092] Virtual Bound States (VBS) and Resistivity:

[0093] VBS theory states that d electrons of dilute transition elements (TEs) move up the Fermi energy of a parent alloy composed of late transition metals (TLs) and are added to empty spin states. Each TE atom will contribute an empty TL 3d state. The TE atoms create perturbation energy wells that scatter conduction electrons, thereby increasing resistivity.

[0094] (Fe 70 Ni 30 ) 80 Nb4Si2B 14 We added vanadium to the base alloy at the expense of (FeNi) and measured the resistivity over a range of V content from 0.5% to 5%. We found that adding V can increase the resistivity by approximately 40% without significantly degrading the magnetic properties.

[0095] Cu addition:

[0096] DSC can provide the activation energy for crystallization and the Avrami index. 70 Ni 30 ) 80 Nb4Si2B 14 The Avrami exponent of the alloy is 2.5, which corresponds to continuous nucleation and three-dimensional crystal growth. 70 Ni 30 ) 79 Nb4Si2B 14 The Avrami index of Cu1 alloy is 1.5, which corresponds to instantaneous nucleation and three-dimensional growth, which would provide a finer crystal structure and further reduce losses.

[0097] Figures 14A-14B show simulation results for the glass-forming ability (GFA) of various material compositions. As previously mentioned, metal-amorphous nanocomposites (MANCs) are soft magnetic materials consisting of nanocrystalline particles surrounded by an amorphous matrix. They combine a higher saturation induction than amorphous metal ribbons (AMRs) with lower coercivity and higher electrical resistivity than crystalline materials, reducing hysteresis and eddy current losses. MANCs are fabricated by planar flow casting in the form of amorphous ribbons and then annealed to induce crystallization. Due to the amorphous precursor to the nanocrystalline state, glass-forming ability (GFA) is important for alloy development. Typically, in AMR and MANC alloys, magnetic induction is sacrificed for glass-forming ability (and resistivity) compared to crystalline materials (e.g., Si steels), because the addition of glass-forming elements reduces these properties. Optimizing the GFA allows for a reduction in the glass-former content, resulting in better performance. The advancement of MANC alloys in which the amorphous phase has higher GFA values ​​impacts the formability of such materials in applications such as hot stamping motor laminations (e.g., in the case of the motor described in connection with Figures 13A-13B).

[0098] The GFA is defined by the minimum cooling rate (Rc) required to form an amorphous material. Because Rc is difficult to measure experimentally, several parameters have been developed to rank the GFA of amorphous materials. Glass-forming alloys are designed according to three empirical guidelines. First, the material generally contains at least three atomic species. Second, the material contains a difference in atomic size of 12% or more. Third, there is a negative enthalpy of mixing of the elements in the liquid phase. The first two rules also result from the "confusion principle," which states that additional alloy complexity and atomic size differences slow the rate of crystallization and increase the likelihood of amorphous phase formation. In addition to the slow rate, multiple atomic species also reduce the free energy advantage of forming a crystalline phase. To form alloys with four or more components, the equilibrium structure can have a very large unit cell. The long-range order of these phases minimizes the free energy reduction from crystallization (compared to the liquid). The third rule is based on the need to prevent elements from breaking apart in liquids.

[0099] Models based on atomic size differences have been proposed to explain and predict GFA by maximizing the liquid density and resulting amorphous phase. As the amorphous phase density increases, the driving force for crystallization decreases. Generally, alloys with the smallest volume change upon solidification and therefore higher density in the liquid state have the largest GFA. Higher liquid density increases viscosity and reduces the free volume of the supercooled liquid, both of which reduce the diffusion rate and slow the rate of crystallization. While such models predict the required concentrations of alloying elements based on atomic size for binary and ternary alloys, they become overly complicated for higher-order systems. Another model, the maximum possible amorphization range (MPAR), correlates the GFA of an alloy system to the composition range between the maximum solid solubility of the eutectic. Again, this model is impractical beyond ternary alloys.

[0100] Kinetic predictions of GFA are also possible. Highly viscous alloys tend to have improved GFA because high viscosity reduces the diffusion rate and slows the nucleation and growth of crystalline phases. The effect of additional alloying elements on GFA strongly depends on the viscosity of the elements in the liquid state. However, viscosity is difficult to measure and cannot be easily used to predict GFA.

[0101] As mentioned above, theories based on the three empirical rules, as well as kinetics, are unable to predict GFA or serve as nothing more than relative guidelines for alloy development. Furthermore, due to the large variations in metallic glass structure, there are exceptions to all proposed rules, meaning that many potential alloys remain unidentified. The ability to sample a large compositional space and identify superior glass formers would be highly advantageous for alloy development.

[0102] Furthermore, compositions near or at the eutectic have good GFAs. In eutectic alloys, the liquid phase is stable down to lower temperatures, at which point viscosity increases, diffusion slows, and amorphous structures form more easily. Furthermore, because the material crystallizes into two phases at equilibrium, the alloying elements must partition between the phases, slowing the crystallization rate.

[0103] Based on the idea of ​​improving the GFA by identifying the eutectic composition, thermodynamic calculations can be used to identify the minimum liquidus temperature for a range of compositions.

[0104] Soft magnetic alloys have several important differences from other amorphous alloys. Most amorphous alloys are bulk metallic glasses (BMGs) that contain very high percentages of alloying elements (>40%), allowing them to remain amorphous at low cooling rates. In contrast, magnetic alloys typically contain less than 30% alloying elements, with the goal of reducing this as much as possible. Reducing the alloying additions increases the saturation magnetization and decreases the coercivity due to the increased content of magnetic elements. Soft magnetic alloys therefore fall into the category of marginal glass formers, or alloys that require rapid solidification techniques for fabrication. This is generally not a significant issue, as the thin materials produced by rapid solidification are ideal for reducing eddy current losses. However, the alloy must have a sufficient glass former area (GFA) to remain amorphous at the cooling rates achievable by rapid solidification.

[0105] Applying the method described above, (Fe 70 Ni 30 ) 80 (B-Si-Nb) 20 Compositions with good GFA were rapidly identified in a soft magnetic alloy system. This system is studied using a combination of thermodynamic modeling and experimental validation, as described below. Thermocalc simulations were used to identify regions with minimum liquidus temperatures and freezing ranges by varying Nb, Si, and B over a full range of levels up to 20%. Furthermore, because one goal of increasing the GFA of soft magnetic alloys is to increase the proportion of magnetic elements, the simulations were repeated for alloys with lower concentrations of glass formers.

[0106] Furthermore, it is advantageous for power magnetic applications that ribbons can be processed into laminates by hot stamping, with the ribbon thickness, material structure, and anisotropy being controlled by the rolling process. Hot forming of amorphous materials can be performed by blow molding. Alternatively, forming can be performed by forcing through a die at elevated temperatures. Compatibility with such processes can be determined by analyzing the temperature range between the glass transition temperature and the crystallization temperature, and preferred alloy systems should be designed to allow for a suitable processing temperature window.x significantly lower than T g The value of T is displayed. g Below this, the material cannot deform, but g Above this temperature, the material may exhibit viscous flow. x Above this temperature, crystallization will prevent further deformation, but for some compositions, during or after the crystallization stage, the T of the grain boundary amorphous precursor may be below the processing temperature of interest. g Therefore, the effect of the concentration of the three glass formers on these temperatures is measured.

[0107] Model-based composition selection

[0108] The results of Thermocalc simulations for liquidus temperature and freezing range are shown in Figures 14A and 14B, as shown in graphs 1400 and 1410, respectively. Graph 1400 shows the liquidus temperature for various compositions. Graph 1410 shows the freezing range for various compositions. The GRA ranking is represented by the shaded dots. As shown in graph 1400, the minimum values ​​for both the liquidus and freezing range are identified for 0-7% Si, 14-18% B, and 0-6% Nb, which are found to have the highest GFA and are considered exemplary embodiments. The GFA is a function of the parameter T rg =(T g / T l ) and the temperature range ΔT xg =(T x -T g ) was measured. As mentioned above, ΔT xg Alloys with large positive T have a wide temperature range in which they can be thermomechanically formed, but rg The GFA tends to be low, making it promising for hot forming applications. Nevertheless, the combination of good GFA and large ΔT xg Several exemplary alloys have been identified in this composition range that have both T rg , GFA ranking, and ΔT xg are shown in Table 1 below.

[0109] [Table 1]

[0110] Large ΔT xg Advanced manufacturing processes utilizing alloys

[0111] ΔT xg A unique advantage of alloys with a large positive value of α is their compatibility with advanced manufacturing processes, including stamping, forming, rolling, and related processes, which can be used to modify laminate geometry, ribbon thickness, material anisotropy, and structure in ways that would otherwise be impossible with existing prior art MANC alloy systems. Several exemplary embodiments are described below of advanced manufacturing processes enabled by this unique alloy property, along with potential applications and end-use component performance benefits.

[0112] Hot Stamping Process

[0113] Laminate stamping is an established process for crystalline soft magnetic alloys used in transformer and motor applications. However, its application to amorphous alloys on a production scale is severely limited by the very hard mechanical properties of the rapidly solidifying ribbons, which tend to cause high wear of the stamping dies. T below the crystallization temperature g The value of ΔT xg Amorphous alloys have high T g It offers the possibility of a high temperature stamping process that is higher but below the crystallization temperature. The stamped laminate can then be subjected to a post-stamping annealing treatment to optimize the metallography and magnetic properties.

[0114] Hot rolling process:

[0115] Rolling is a standard process in the optimization of large-scale soft magnetic crystalline alloys, but its application to amorphous alloys has also been limited by the mechanical properties of amorphous soft ferromagnetic materials. A particularly attractive aspect of the application of rolling processes to amorphous and MANC alloy systems for soft magnetic applications is the potential to significantly reduce eddy current losses by reducing ribbon thickness without adversely affecting the overall ribbon quality and continuity. Thickness reduction through rapid solidification treatment adjustments is limited to approximately 10-15 microns due to the formation of pinholes and other ribbon defects during the casting process as the ribbon thickness decreases, thereby limiting frequency performance to an upper limit of approximately 100 kHz. Rolling processes to further reduce the thickness of cast ribbons offer the potential to further reduce eddy current losses and increase the maximum operating frequency of this class of rapidly solidified alloys.

[0116] In addition to thickness reduction, rolling may enable the exploitation of new anisotropy mechanisms, including crystallographic texture, slip-induced anisotropy, etc. ΔT xg The alloy with high T g and T x The ribbons are well suited for hot rolling applications at temperatures between 0.1 and 0.25, where viscous flow is activated without crystallization, ensuring successful thickness reduction without ribbon breakage or defects. Subsequent heat treatments can be applied to the ribbons to optimize their magnetic properties. In some cases, the grain boundary amorphous phase is present at a sufficiently low T g To retain this, engineered MANC alloys are compatible with hot rolling processes without the need for two- or multi-step process schemes to reduce thickness prior to partial devitrification to optimize magnetic properties. In some cases, hot rolling in combination with or following a crystallization process may enable unique induced anisotropy mechanisms by controlling the shape, crystallographic texture, bond orientation configuration, and defect structure of the embedded nanocrystals.

[0117] FIG. 15 shows a schematic diagram of a hot rolling mill system 1500 in which driven heated nip rollers pull material off a dancer and rewind it onto a slip clutch rewinder. Air pressure is supplied to adjustable-height heated nip rollers 1518 to contact and feed the strip 1506 through the roll assembly. The system 1500 includes a feed spool 1502 and a rewind spool 1504. Ribbon material 1506 is fed through the system 1500. The ribbon material 1506 is fed onto a dancer arm 1510, which is moved by a motor control 1512. The ribbon material 1506 travels through guide rollers 1508a to an adjustable-height heated nip roller 1518. The heated nip roller presses the ribbon material 1506 onto an idle roller 1514 and across a drive roller 1516. The ribbon material 1506 is immediately annealed and then directed onto the unwind spool 1504 through guide rollers 1508b and 1508c.

[0118] Induction rolling process / roll bonding process:

[0119] In some implementations, it may be desirable to avoid direct heating of rolls, which require large thermal mass, and specially designed rolls that retain mechanical properties, resulting in oxidation during long-term operation of the hot rolling process. Another processing approach involves direct induction heating of the material being processed by applying an RF electromagnetic potential across the rolls, which induces highly localized eddy current losses and associated heating within the strip material. In this way, combined with the application of mechanical stresses due to the presence of the rolls, very fast heating rates can be achieved within the ribbon. This alternative processing scheme eliminates the need to provide continuous thermal excitation to the rolls or maintain a constant, high operating temperature, thereby reducing wear, oxidation, and mechanical property degradation, making the process scalable and manufacturable.

[0120] Localized induction annealing also offers advantages in terms of further optimizing the heat treatment, which may be advantageous, predetermined optimized metallurgies achieved with other MANC compositions that have large associated saturation inductions through rapid thermal annealing procedures. In addition to hot rolling of rapidly solidifying metal strip materials, more advanced processes are also contemplated, including roll bonding with other metals to optimize mechanical, electrical, and / or magnetic properties. For example, roll bonding with thin Al foil or other oxidizable metals to create an optimized MANC metallurgy, followed by an oxidation step during thermal annealing, may increase stack resistance, reduce associated eddy current losses, and increase the maximum operating temperature for performance.

[0121] 16, an example of a roll bonding system 1600 is shown. Rollers 1602a and 1602b can be directly heated thermally, or an applied RF potential can be applied to the rollers to inductively heat the base material 1606 and cladding material 1604 through eddy currents.

[0122] Hot forming and blow molding process:

[0123] Because an ideal metal structure exhibits large grains with minimal defects to avoid domain wall pinning and associated magnetic losses, the formation of conventional soft magnetic crystalline alloys presents significant challenges due to the degradation of magnetic properties resulting from mechanical forming. The formation of amorphous alloys above their glass transition temperature is an advantage that has been exploited in many structural material applications, such as bulk metallic glasses. However, the forming process requires high temperatures above the T g This has not been previously utilized in soft magnetic amorphous alloys because of the crystallization at temperatures above which viscous flow improves formability. The newly developed MANC alloys mentioned above have a high ΔT xg This provides an opportunity for the forming and blow molding of soft magnetic alloys with a subsequent crystallization process whereby the metallographic structure and magnetic properties can be successfully optimized to the desired final shape.

[0124] Forming after nanocrystallization

[0125] Since MANC materials have a residual amorphous phase, the above process can be applied to materials that are already nanocrystalline. This requires a large ΔT in the residual amorphous phase, as the crystalline particles are too small to deform significantly. xg During the nanocrystallization process, glass-forming elements are released from the crystals into the residual amorphous matrix, changing its composition. Therefore, a large ΔT is required, even if it is large in the amorphous precursor. xg As shown in graph 1700 of FIG. 17, the existence of a large ΔT xg To confirm this, (Fe 70 Ni 30 ) 80 B 15 Si0Nb5 and (Fe 70 Ni 30 ) 80 B 12 The Si3Nb5 samples were crystallized to various degrees and T g Graph 1700 shows the T g This indicates that the change in glass transition temperature due to crystallization is relatively small. g In the partially crystallized sample, T g No significant changes were observed in T x This means that the ΔT of the crystallized sample is unchanged. xg is confirmed to be large.

[0126] Fe-Ni nanocomposite materials are a relatively unexplored alloy system, more affordable than Fe-Co alloys, yet promising excellent soft magnetic properties. Nanocomposite alloys can be used in motor applications where maximum saturation magnetization is desired. A sufficiently high Curie temperature and secondary crystallization temperature are also important. Nanocomposite alloys are deformable above their glass transition temperature, allowing them to be easily formed into motor rotors or stators. These alloys have higher efficiency at high frequencies than silicon steels commonly used in motors.

[0127] Other embodiments are within the scope and spirit of the specification, claims, and disclosure. Furthermore, due to the nature of software, the functionality described above may be implemented using software, hardware, firmware, hardwiring, or any combination thereof. The features implementing the functionality may also be physically located in various locations, including being distributed such that portions of the functionality are implemented in different physical locations. The use of the term "a" throughout this specification and application is not used in an exclusive manner and is therefore not meant to exclude the plural meaning of "a" or the meaning of "one or more." Furthermore, to the extent that priority is claimed to a provisional patent application, it should be understood that the provisional patent application is not exclusive and includes examples of how the technology described herein may be implemented.

[0128] It will thus be seen that the above objects have been efficiently attained in the light of what has become apparent from the foregoing description, and that certain changes may be made in carrying out the above methods and in the above structures. Without departing from the spirit and scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

[0129] Although several exemplary implementations of nanocomposites have been described, those skilled in the art will appreciate that various modifications can be made without departing from the spirit and scope of the described embodiments.

Claims

1. crystalline particles in an amorphous matrix, wherein the crystalline particles comprise iron (Fe)-nickel (Ni) compounds and are separated from one another by the amorphous matrix; and one or more barriers between the crystalline particles and the amorphous matrix, wherein the barriers are configured to inhibit growth of the crystalline particles during their formation, and one barrier of the one or more barriers is between the crystalline particles and the amorphous matrix; the amorphous matrix comprises an increased resistivity compared to the resistivity of the crystalline particles; A nanocomposite, wherein the amorphous matrix is ​​configured to reduce loss of the crystalline particles caused by a change in a magnetic field applied to the crystalline particles compared to loss of the crystalline particles that would occur in the absence of the amorphous matrix.

2. 10. The nanocomposite of claim 1, wherein the crystalline particles comprise metastable, face-centered cubic Fe-Ni groups.

3. The nanocomposite of claim 2 , wherein the Fe—Ni matrix comprises γ-FeNi nanocrystals.

4. 10. The nanocomposite of claim 1, wherein the barrier comprises niobium (Nb) and the amorphous matrix comprises boron (B) and silicon (Si) configured together to enable glass-forming capabilities of the amorphous matrix.

5. 10. The nanocomposite of claim 1, further comprising a copper (Cu) nucleating agent configured to increase nucleation of the crystalline particles during a molding process compared to nucleation of the crystalline particles during a molding process without the copper nucleating agent, wherein the increased nucleation results in a reduction of the crystalline particles by 10% or more.

6. 10. The nanocomposite of claim 1, wherein the crystalline particles comprise an average diameter of 5 to 20 nm.

7. 10. The nanocomposite of claim 1, which forms ribbons having a thickness of 15 to 30 μm.

8. The nanocomposite of claim 7 comprising a magnetic anisotropy that is longitudinal along the ribbon.

9. 10. The nanocomposite of claim 1, further comprising up to 50 atomic % of one or more metals comprising boron (B), carbon (C), phosphorus (P), silicon (Si), chromium (Cr), tantalum (Ta), niobium (Nb), vanadium (V), copper (Cu), aluminum (Al), molybdenum (Mo), manganese (Mn), tungsten (W), and zirconium (Zr).

10. 10. The nanocomposite of claim 1 comprising up to 30 atomic percent cobalt (Co).

11. 10. The nanocomposite of claim 1 comprising about 30 atomic % Ni.

12. 10. The nanocomposite of claim 1, wherein the crystalline particles have a resistivity of about 100 μΩ cm and the amorphous matrix has a resistivity of about 150 μΩ cm.

13. 10. The nanocomposite of claim 1, wherein the amorphous matrix is ​​annealed to enable a superplastic response of the nanocomposite.

14. 10. The nanocomposite of claim 1, wherein the crystalline particles in the amorphous matrix and diffusion barrier comprise a strain-annealed structure tuned to a relative magnetic permeability greater than 10,000.

15. 10. The nanocomposite of claim 1, wherein the variation in magnetic field applied to the crystalline particles occurs at a frequency between 400 Hz and 5 kHz.

16. The nanocomposite of claim 1 , wherein the losses include eddy current losses.

17. one or more composite layers, wherein each layer of the composite layers comprises γ-FeNi nanocrystals in an amorphous matrix, the γ-FeNi nanocrystals having an average resistivity less than 100 μΩ cm, and the amorphous matrix having a resistivity greater than 100 μΩ cm; and one or more boron diffusion barriers each between one or more of the γ-FeNi nanocrystals and the amorphous matrix, each of the one or more diffusion barriers configured to inhibit diffusion growth of the γ-FeNi nanocrystals during formation of the γ-FeNi nanocrystals; The γ-FeNi nanocrystals have a Ni content of about 70 atomic %; The average diameter of the γ-FeNi nanocrystals is 5 nm to 30 nm; The rotor lamination, wherein the one or more composite layers are each less than about 25 μm thick.

18. The rotor lamination of claim 17 , wherein the composite layers are strain-annealed composites each comprising a relative permeability greater than 10,000.

19. The rotor lamination of claim 17 , wherein each of the composite layers further comprises copper.

20. 1. An electric motor including a rotor and a stator configured to drive the rotor, The stator comprises multiple laminations less than 30 μm thick, each lamination comprising: crystalline particles in an amorphous matrix, wherein the crystalline particles comprise iron (Fe)-nickel (Ni) compounds and are separated from one another by the amorphous matrix; and one or more barriers between the crystalline particles and the amorphous matrix, wherein the barriers are configured to inhibit growth of the crystalline particles during their formation, and one barrier of the one or more barriers is between the crystalline particles and the amorphous matrix; The electric motor, wherein the rotor is configured to operate at a frequency greater than 400 Hz.

Images