Magnetic alloy preparation method based on four-arc pulling orientation crystal, magnetic alloy and application

Abstract

The invention discloses a magnetic alloy preparation method based on a four-arc pulling orientation crystal, a magnetic alloy and application, and belongs to the field of magnetic materials. The technical key points are as follows: a four-arc pulling oriented crystal method is adopted, and the method comprises the following steps: firstly, putting an obtained polycrystalline material into a rotatable water-cooled copper crucible, adjusting the positions of four arcs relative to a sample, and closing a cavity; then, a vacuum pump system is started, and the vacuum degree in the furnace is increased to 5 * 10 <-4 > Pa; thirdly, a certain amount of argon is introduced, and the air pressure of the cavity is maintained to be 5 * 10 < 2 > Pa; and then, removing oxygen in the cavity, turning on current switches of four electric arcs above the sample, slowly increasing the current to melt the raw material, and after the raw material is completely melted, immersing the lifting rod into the melted raw material to ensure that the raw material is in full contact with the melt, rotating and lifting the lifting rod, and gradually cooling and crystallizing the melt along with the lifting of the lifting rod to form an oriented crystal.

Description

Technical Field

[0001] This invention relates to the field of materials science, and more specifically, to a method for preparing magnetic alloys based on four-arc pulled orientation crystals, the magnetic alloys themselves, and their applications. Background Technology

[0002] Magnetostrictive materials are a class of intelligent functional materials with bidirectional energy conversion properties. They are capable of reversible mechanical deformation under an applied magnetic field or changing their magnetization state under mechanical stress, achieving efficient bidirectional conversion between electromagnetic and mechanical energy. Their physical essence stems from the spontaneous magnetization of ferromagnetic or ferrimagnetic materials below the Curie temperature, where the lattice within the magnetic domains deforms along the magnetization direction. When an external magnetic field is applied, the magnetic domains rearrange, macroscopically manifesting as elongation (positive magnetostriction) or shortening (negative magnetostriction) of the material. The core performance indicator, the magnetostriction coefficient λ (Δl / l), quantitatively characterizes the strain response intensity per unit field strength. They play a crucial role in aerospace, mechanical electronics, biomedicine, transportation, national defense, and everyday life.

[0003] With societal development, magnetostrictive materials have been extensively studied due to their unique properties. Traditional magnetostrictive materials such as Ni (λ≈-33ppm) and Fe-Al alloys (λ≈40ppm) are limited by their small magnetostriction coefficients, restricting them for a long time to basic applications such as low-frequency transducers. In the 1970s, rare-earth-iron compounds Terfenol-D (Tb 0.3 Dy 0.7 Fe 1.95 The discovery of [a specific material] marked the beginning of a technological revolution. Its magnetostriction coefficient λ is as high as 1500-2000 ppm, an improvement of 1-2 orders of magnitude compared to traditional magnetostrictive materials. Its electromechanical coupling coefficient reaches 0.72, and its energy density exceeds 14000 J / m³. 3This represents a significant breakthrough. This material, possessing both large strain and high response speed, has become synonymous with "super magnetostrictive material." However, its low resistivity limits its high-frequency applications, and its brittleness and high cost result in significant operational expenses. In 2000, a research team at the Ames Laboratory of Iowa State University first reported the excellent magnetostrictive properties of Fe-Ga alloys. When the atomic fraction of Ga atoms in Fe-Ga single crystals is in the range of 15%-25%, the magnetostrictive coefficient of Fe-Ga alloys can exceed 200 ppm; when the atomic fraction of Ga atoms is 19%, the maximum magnetostrictive coefficient of Fe-Ga alloys can reach 400 ppm, approaching the level of Terfenol-D, and the raw material cost is lower, reduced by 60% compared to Terfenol-D, attracting global attention. However, compared to oriented FeGa alloys, the room temperature magnetostrictive strain of polycrystalline cast alloys is relatively small (~50ppm). More complex processing methods such as directional rolling or directional solidification are required to obtain preferred orientation and thus improve the magnetostrictive strain, which also restricts the application of FeGa alloys in practical engineering fields.

[0004] In light of this, the research team proposed a magnetic alloy with large magnetostrictive strain at room temperature in CN118895560A. CN118895560A studied the magnetostriction of polycrystalline samples, but did not investigate oriented samples. A good orientation may lead to greater magnetostriction, so the research team, based on CN118895560A, studied the magnetostriction of oriented crystals. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a magnetic alloy with large magnetostrictive strain at room temperature, its preparation method, and its application.

[0006] The technical solution of this invention is:

[0007] A method for preparing a magnetic alloy based on a four-arc pulled orientation crystal includes the following steps:

[0008] S100, Ingredients: Weigh out Co, Cr, and Ga metal raw materials with a purity of 99.95% according to the ratio of Co:Cr:Ga = 2:1:1.

[0009] S200, fused polycrystalline: Place the weighed material into the crucible and use a mechanical pump to evacuate the vacuum level of the electric arc furnace cavity to 5×10⁻⁶. -4 Below Pa, argon gas is then introduced as a protective gas. The melting current is 100A. Each sample is melted 4 times to ensure uniform composition. The resulting polycrystalline sample is then polished to remove the oxide scale.

[0010] S300, Four-Arc Czochralski Method for Oriented Crystals: The obtained polycrystalline material is placed in a rotatable water-cooled copper crucible. The positions of the four arcs relative to the sample are adjusted, and the cavity is closed. The vacuum pump system is started, and the cavity is evacuated multiple times in cycles. The vacuum level inside the furnace is finally reduced to 5 × 10⁻⁶. -4 Pa, a certain amount of argon gas is introduced to maintain the cavity pressure at 5 × 10⁻⁶. 2 First, turn on the current switch of the tungsten needle above Ti to melt Ti for a period of time and remove the oxygen in the cavity (i.e., turn on the current switch of the tungsten needle above Ti to melt Ti and remove the oxygen in the cavity). Then, turn on the current switches of the four arcs above the sample and slowly increase the current to allow the raw material to melt. After ensuring complete melting, immerse the lifting rod into the melted raw material to ensure full contact with the melt. Set a good lifting speed and rotation speed for the lifting rod and slowly raise the lifting rod. As the lifting rod rises, the melt gradually cools and crystallizes to form oriented crystals.

[0011] Furthermore, the lifting rod rotates at 6 rpm, and its lifting rate is 20 mm / h.

[0012] A magnetic alloy is prepared by the aforementioned preparation method; it has the following chemical formula: Co2CrGa; the magnetic alloy is an oriented crystal.

[0013] Furthermore, the magnetic alloy exhibits a magnetostrictive strain of 183 ppm at a room temperature of 300 K and a critical magnetic field of 100 mT.

[0014] Furthermore, Co2CrGa belongs to the cubic crystal system, with space group Fm-3m and space group number 225.

[0015] Application of a magnetic alloy in magnetic actuation devices.

[0016] Application of a magnetic alloy in sonar systems or ultrasonic devices or precision positioning control or mechanical brakes.

[0017] The beneficial effects of this application are as follows:

[0018] First, the fundamental inventive concept of this invention lies in the fact that, in previous research (CN118895560A), the room-temperature magnetostrictive strain of Co2CrGa under an applied driving magnetic field (100mT) could only reach 60ppm. However, this invention achieves a breakthrough through both compositional and process innovations. Still using Co-Cr-Ga as the matrix, a four-arc Czochralski technique is employed to grow oriented crystals, avoiding the post-processing requirements for texturing traditional polycrystalline materials, thus achieving large magnetostriction (183ppm) at room temperature and low field (100mT).

[0019] Secondly, the reason why the magnetostrictive strain of the oriented crystal in this application differs significantly from that of the polycrystalline material in CN118895560A is as follows: The Co2CrGa proposed in CN118895560A is a polycrystalline material with random orientation. When an external magnetic field is applied, the random grains cause disordered local strain directions, which macroscopically cancel each other out, resulting in a relatively small average strain. However, for the oriented crystal proposed in this application, when an external magnetic field is applied, the local strain directions are highly consistent, macroscopically superimposed, resulting in a larger total strain. Attached Figure Description

[0020] The present invention will be further described in detail below with reference to the embodiments shown in the accompanying drawings, but this does not constitute any limitation on the present invention.

[0021] Figure 1 This is a diagram showing the preparation of the Co2CrGa sample obtained in Example 1 of this invention.

[0022] Figure 2 This is the XRD pattern of a Co2CrGa sample perpendicular to the growth direction obtained in Example 1 of this invention at a lifting rod rotation speed of 1 rpm and a lifting speed of 20 mm / h.

[0023] Figure 3 The results are the room temperature magnetization (MH) curves of a Co2CrGa sample perpendicular to the growth direction along different magnetic field directions, obtained in Example 1 of this invention, at a lifting rod rotation speed of 1 rpm and a lifting speed of 20 mm / h.

[0024] Figure 4 The results are the room temperature magnetostrictive strain-magnetic field curves of a Co2CrGa sample perpendicular to the growth direction obtained in Example 1 of this invention, at a lifting rod rotation speed of 1 rpm and a lifting speed of 20 mm / h, along different magnetic field directions.

[0025] Figure 5 The figure shows the in-plane magnetostrictive strain-magnetic field curve of the Co2CrGa sample perpendicular to the growth direction at room temperature, obtained in Example 1 of this invention, with a lifting rod rotation speed of 1.4 rpm and a lifting speed of 20 mm / h.

[0026] Figure 6 The magnetostrictive strain-magnetic field curves of a Co2CrGa sample perpendicular to the growth direction, obtained in Example 1 of this invention, are measured continuously at a lifting rod rotation speed of 1 rpm and a lifting speed of 3 mm / h.

[0027] Figure 7 These are the magnetostrictive test results of samples under different stretching rates and rotational speeds. Detailed Implementation

[0028] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the materials used in the following embodiments are conventional materials; and the experimental methods described are conventional methods.

[0029] The present invention will now be described in detail with reference to the accompanying drawings, providing a complete description of the technical solution of the present invention.

[0030] <Example 1>

[0031] The Co2CrGa in this application is prepared using the following steps:

[0032] S100, weigh out Co, Cr and Ga metal raw materials with a purity of 99.95% according to the ratio of Co:Cr:Ga = 2:1:1.

[0033] S200: Place the weighed material into the electric arc furnace crucible, and use a mechanical pump to evacuate the vacuum level of the electric arc furnace cavity to 5×10⁻⁶. - 4 Below Pa, argon gas was then introduced as a protective gas, the melting current was 100A, each sample was turned 3 times, and a total of 4 meltings were performed to ensure uniform composition.

[0034] S300: The obtained polycrystalline material is placed in a rotatable water-cooled copper crucible within a four-arc Czochralski single crystal pulling furnace. The positions of the four arcs relative to the sample are adjusted, the cavity is closed, and the vacuum pump system is activated to evacuate the furnace to a vacuum level of 5 × 10⁻⁶. -4 Pa, a certain amount of argon gas is introduced to maintain the cavity pressure at 5 × 10. 2 Pa, first turn on the current switch of the tungsten needle above Ti to melt Ti for a period of time and consume the remaining oxygen in the cavity. Then turn on the current switches of the four arcs and slowly increase the current to make the raw material just completely melt. After ensuring complete melting, immerse the lifting rod into the melted raw material to ensure full contact with the melt. Set the lifting rod and rotation speed appropriately and slowly raise the lifting rod. As the lifting rod rises, the melt gradually cools and crystallizes to form oriented crystals.

[0035] S400, schematic diagram of four-arc lifting sample (see below) Figure 1 The crystal structure of the alloy was determined using X-ray diffraction experiments. The results show that the Co2CrGa magnetic alloy ingot sample prepared in this invention has a cubic structure at room temperature, and its room temperature X-ray diffraction pattern is shown in the appendix. Figure 2 The magnetic and magnetostrictive properties of Co2CrGa magnetic alloys were measured. Figure 3 As shown, the room temperature magnetization-magnetic field curve of the Co2CrGa sample prepared in this invention is shown. Figure 4The figure shows the room temperature magnetostrictive strain-magnetic field curve of the Co2CrGa sample perpendicular to the growth direction, obtained in Example 1 of this invention at a lifting rod rotation speed of 1 rpm and a lifting speed of 20 mm / h. Figure 5 The image shows the magnetostrictive strain-magnetic field curve of the Co2CrGa sample at room temperature with an in-plane rotation angle perpendicular to the growth direction, obtained in Example 1 of this invention, at a lifting rod rotation speed of 1.4 rpm and a lifting speed of 20 mm / h. Figure 6 The magnetostrictive strain-magnetic field curve of the Co2CrGa sample obtained in Example 1 of this invention is measured continuously perpendicular to the growth direction at a lifting rod rotation speed of 1 rpm and a lifting speed of 3 mm / h. Figure 7 This is a summary of the magnetostriction of samples under different growth rates and rotation speeds.

[0036] The above-described embodiments are preferred embodiments of the present invention and are only used to facilitate the illustration of the present invention. They are not intended to limit the present invention in any way. Any person skilled in the art who makes local modifications or alterations to the technical content disclosed in the present invention without departing from the scope of the technical features of the present invention shall still fall within the scope of the technical features of the present invention.

Claims

1. A method for preparing a magnetic alloy based on a four-arc pulled orientation crystal, characterized in that, The steps include: S100, Ingredients: Weigh out Co, Cr, and Ga metal raw materials with a purity of 99.95% according to the ratio of Co:Cr:Ga = 2:1:

1. S200, fused polycrystalline; S300, a four-arc pulling orientation crystal method, which includes sub-steps S301 to S304; S301, the obtained polycrystalline material is placed in a rotatable water-cooled copper crucible, the positions of the four electric arcs relative to the sample are adjusted, and the cavity is closed; S302, Start the vacuum pump system to evacuate the furnace to a vacuum level of 5×10⁻⁶. -4 Pa; S303, a certain amount of argon gas is introduced to maintain the cavity pressure at 5×10. 2 Pa; S304, remove oxygen from the chamber, then turn on the current switches of the four arcs above the sample, slowly increase the current to allow the raw material to melt. After ensuring complete melting, immerse the lifting rod into the melted raw material to ensure full contact with the melt. Rotate the lifting rod to raise it. As the lifting rod rises, the melt gradually cools and crystallizes to form oriented crystals.

2. The method for preparing a magnetic alloy based on a four-arc pulled orientation crystal according to claim 1, characterized in that, The molten polycrystalline process in S200 includes: placing the weighed material into a crucible and using a mechanical pump to evacuate the electric arc furnace cavity to a vacuum level of 5 × 10⁻⁶. -4 Below Pa, argon gas is then introduced as a protective gas. The melting current is 100A, and each sample is melted 4 times to ensure uniform composition. The resulting polycrystalline sample needs to be polished to remove the oxide scale.

3. The method for preparing a magnetic alloy based on a four-arc pulled orientation crystal according to claim 1, characterized in that, The method for removing oxygen from the cavity in step S304 is as follows: turn on the current switch of the tungsten needle above Ti to melt Ti for a period of time and remove oxygen from the cavity.

4. The method for preparing a magnetic alloy based on a four-arc pulled orientation crystal according to claim 1, characterized in that, The lifting rod rotates at 6 rpm and its lifting rate is 20 mm / h.

5. The magnetic alloy prepared by the method for preparing magnetic alloys based on four-arc pulled oriented crystals as described in claim 4, characterized in that, The magnetic alloy is an oriented crystal with the chemical formula Co2CrGa.

6. The magnetic alloy as described in claim 5, characterized in that, The magnetic alloy exhibits a magnetostrictive strain of 183 ppm at room temperature (300 K) and a critical magnetic field of 100 mT.

7. The magnetic alloy as described in claim 6, characterized in that, Co2CrGa belongs to the cubic crystal system, with space group Fm-3m and space group number 225.

8. The application of the magnetic alloy according to claim 5 in magnetic actuation devices.

9. The application of the magnetic alloy according to claim 5 in sonar systems or ultrasonic devices or precision positioning control or mechanical brakes.

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