A compact MnCoSi-based giant magnetostrictive material

Abstract

The application discloses a dense MnCoSi-based giant magnetostrictive material, which is composed of MnCo 1‑x Pt x Si, belongs to the field of magnetostrictive material preparation, and comprises the following steps: designing a MnCo 1‑x Pt x Si material system by partially replacing Co in the MnCoSi material with the element Pt, and then preparing a dense alloy ingot by arc melting under the protection of an argon atmosphere. The application adjusts the martensitic transformation temperature of the MnCoSi material by changing the content of the doped Pt, so that the martensitic transformation is eliminated, the dense MnCoSi-based material without macroscopic cracks is obtained, and the material maintains a large room-temperature reversible magnetostrictive effect, which is helpful to promote the practical application of the giant magnetostrictive material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of giant magnetostrictive material preparation and relates to a dense MnCoSi-based giant magnetostrictive material. BACKGROUND

[0002] High-energy-density giant magnetostrictive materials can realize rapid and efficient conversion between mechanical energy and electromagnetic energy, and have direct application value in the fields of underwater acoustic transducers, ultrasonic transducers and sensors of low-frequency sonar detection systems. There are two typical giant magnetostrictive materials, Terfenol-D and Fe-Ga, but both of them are difficult to have large magnetostrictive effect and good mechanical properties.

[0003] As a large class of magnetic functional materials, magnetic phase transition alloys can produce giant magnetostrictive effect due to the large change of lattice constant in the process of magnetic field-induced phase transition, such as the magnetostriction value of 2500 ppm of textured Ni-Mn-based polycrystal under a magnetic field of 5 T. This provides a new idea for the development of giant magnetostrictive materials. In recent years, domestic and foreign researches have shown that the orthorhombic MnCoSi magnetic phase transition alloy belonging to the Pnma space group has strong magneto-elastic coupling, and the non-collinear magnetic structure can be induced to transform into a collinear ferromagnetic structure under an external magnetic field, and has a special triple point. The magnetostriction effect is significant in the process of metamagnetic phase transition. Based on the sensitivity of metamagnetic phase transition, researchers have flexibly regulated the phase transition order of MnCoSi metamagnetic phase transition alloy through alloying and stress engineering, greatly reduced the critical magnetic field and eliminated the magnetic hysteresis loss, and obtained reversible giant magnetostrictive effect at room temperature and low field. However, the MnCoSi alloy undergoes a martensitic structure phase transition at a high temperature of about 1100 K, and the volume of the alloy expands dramatically and changes obviously in the process of phase transition, which induces the partial rupture of the rigid and directional covalent bond in the alloy, and the macroscopic MnCoSi ingot is full of centimeter-level cracks, and even breaks and is not complete, which directly leads to the poor mechanical properties of the MnCoSi-based alloy and cannot be processed into a shape. Therefore, in view of the application, we urgently need to obtain a dense MnCoSi-based alloy ingot to improve the mechanical properties of the alloy. SUMMARY

[0004] The application aims at the problems of a large number of centimeter-level cracks and poor mechanical properties of the MnCoSi-based material, and proposes a dense MnCoSi-based giant magnetostrictive material by using the method of Pt element doping.

[0005] The technical scheme of the application is as follows: a dense MnCoSi-based giant magnetostrictive material, in which Pt atoms partially replace Co atoms in the MnCoSi material, and the material is expressed as MnCo 1-x Pt x Si in terms of atomic percentage.

[0006] Better, x ≥0.25, x Preferably 0.25~0.3, x 0.3 is more preferred. As the Pt content increases, the structural phase transition that induces material fragmentation can be suppressed, thereby improving the material density and mechanical properties. However, if the Pt content is too high, the magnetism will disappear and there will be no giant magnetostrictive effect. If the Pt content is too low, the sample will expand and spontaneously fragment due to martensitic phase transformation.

[0007] The method for preparing the dense MnCoSi-based giant magnetostrictive material comprises: preparing MnCo by arc melting under argon atmosphere protection. 1-x Pt x The Si alloy ingot was vacuum-sealed in a quartz tube, annealed at 800°C for 60 hours, and then slowly cooled to room temperature over 72 hours.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] 1) The present invention uses Pt to replace the Co position in the MnCoSi material. As the Pt content increases, the martensitic phase transition temperature in the high temperature zone of the material gradually increases, while the melting point gradually decreases. x When the temperature of the structural phase transition of the material is nominally higher than the melting point, there is only a single liquid-solid phase transition in the material, and the martensitic phase transition is completely suppressed. This fundamentally solves the problem of spontaneous expansion and fragmentation of the sample caused by the martensitic phase transition. The proposed MnCo 0.7 Pt 0.3 The Si material is relatively complete and dense, without macroscopic centimeter-level cracks, and the mechanical properties and machining properties of the material are enhanced. The present invention has important significance for the practical application of MnCoSi-based giant magnetostrictive materials.

[0010] 2) When doped with Pt, the magnetostrictive phase transition and giant magnetostrictive effect of the MnCoSi-based material are always maintained without hysteresis, and the corresponding magnetostrictive phase transition critical field exhibits an abnormal non-monotonic change that first increases and then decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 For the positive MnCoSi material and the MnCo prepared by the present invention 0.75 Pt 0.25 Si、MnCo 0.7 Pt 0.3 Comparison of room temperature X-ray diffraction (XRD) patterns of Si.

[0012] Figure 2 For the positive MnCoSi material and the MnCo prepared by the present invention 0.7 Pt 0.3Actual photos of Si and MnCo 0.7 Pt 0.3 Backscattered scanning electron microscopy image of Si.

[0013] Figure 3 MnCo prepared by the present invention 0.7 Pt 0.3 Compressive stress-strain curve of Si.

[0014] Figure 4 It is the positive separation of MnCoSi and the preparation of MnCo by the present invention. 0.7 Pt 0.3 Differential scanning calorimetry curve of Si.

[0015] Figure 5 MnCo prepared by the present invention 0.7 Pt 0.3 Isothermal magnetization curve of Si.

[0016] Figure 6 MnCo prepared by the present invention 0.7 Pt 0.3 Magnetostriction curve of Si under changing magnetic field.

[0017] Figure 7 MnCo prepared by the present invention 0.75 Pt 0.25 Backscattered scanning electron microscopy image of Si. DETAILED DESCRIPTION

[0018] The present invention adopts arc melting under argon atmosphere protection to prepare MnCo 1-x Pt x The Si alloy ingot is vacuum-sealed in a quartz tube, annealed at 800°C for 60 hours, and then slowly cooled to room temperature over 72 hours to obtain a dense MnCoSi-based giant magnetostrictive material.

[0019] It should be noted that the present invention is not limited to the arc melting alloy preparation method. MnCo prepared by induction melting, powder metallurgy and other methods 1-x Pt x The Si material remains dense without macroscopic centimeter-scale cracks and exhibits good machinability.

[0020] The present invention will be described in further detail below with reference to the examples, but the embodiments of the present invention are not limited thereto. Example 1

[0021] MnCo was prepared according to the above method 0.7 Pt 0.3 Si material. Characterization and performance testing are carried out below.

[0022] Figure 1 MnCoSi and Pt-doped MnCo 0.75 Pt 0.25 Si, MnCo 0.7 Pt 0.3 X-ray diffraction pattern (XRD) of Si material at room temperature. It can be seen that the Pt doping does not introduce impurity phase consistent with the diffraction peaks of the normal MnCoSi, and MnCo 0.7 Pt 0.3 Si still maintains a single orthorhombic TiNiSi type structure.

[0023] Figure 2 MnCoSi and MnCo 0.7 Pt 0.3 Macroscopic morphology and microscopic scanning electron microscopy (SEM) images of Si. It can be seen in the figure that the surface of the normal MnCoSi ingot is full of centimeter-level cracks, while the MnCo 0.7 Pt 0.3 The surface of the MnCo 0.7 Pt 0.3 Si material has no obvious defects.

[0024] Figure 3 MnCo 0.7 Pt 0.3 Stress-strain curve of the standard sample of Si, it can be seen in the figure that the compressive strength of the material reaches 85 MPa, which is much higher than the compressive strength of the normal MnCoSi material (~5 MPa).

[0025] Figure 4 MnCoSi and MnCo 0.7 Pt 0.3 High-temperature differential scanning calorimetry curve of Si. It can be seen that the normal MnCoSi has two pairs of endothermic / exothermic peaks during the heating and cooling processes, and has obvious thermal hysteresis, which corresponds to the martensitic phase transition between the hexagonal-orthorhombic and the liquid-solid phase transition, while the MnCo 0.7 Pt 0.3 Si only has one pair of endothermic / exothermic peaks, which corresponds to the liquid-solid phase transition. Therefore, the introduction of Pt suppresses the martensitic phase transition, eliminates the root cause of spontaneous fragmentation of the material, and improves the density and mechanical properties of the ingot.

[0026] Figure 5 MnCo 0.7 Pt 0.3 Isothermal magnetization curves of Si at temperatures of 280, 300 and 320 K. The near S-shaped curve indicates that the material has a metamagnetic phase transition near room temperature, and the metamagnetic phase transition has no magnetic hysteresis and is reversible, which ensures the reversible magnetostrictive effect of the material.

[0027] Figure 6 MnCo is tested using the strain gauge method 0.7 Pt 0.3 The magnetostriction curve of Si polycrystalline material changes with magnetic field. The figure shows that the critical magnetic field for the material's magnetostrictive effect is about 1.6 T, and the saturation magnetostriction value is about 400 ppm, which is greater than the saturation magnetostriction value of Fe-Ga single crystal.

[0028] Figure 7 MnCo 0.75 Pt 0.25 SEM image of Si material. It can be seen in the figure that MnCo 0.75 Pt 0.25 The Si material is uniform and flat, without defects such as a large number of cracks and holes. Example 2

[0029] MnCo was prepared by the same smelting method as in Example 1. 0.75 Pt 0.25 Si material.

[0030] Depend on Figure 1 It can be seen that MnCo 0.75 Pt 0.25 Si material has a single orthorhombic TiNiSi type structure; Figure 7 The SEM photos also show that the material has good density and no obvious cracks; the compressive strength measured by a universal testing machine reached 80MPa; by measuring the isothermal magnetization curve near room temperature, it was found that the material has a reversible magnetic phase transition with a critical field of 2.1 T; the magnetostriction value measured by the strain gauge method is up to 500 ppm. Example 3

[0031] A positive-fraction MnCoSi material was prepared by the same smelting method as in Example 1 for comparison.

[0032] Depend on Figure 1 It can be seen that the positively divided MnCoSi material has a single orthorhombic TiNiSi type structure; Figure 2 The macroscopic morphology photos show that the positive-fraction MnCoSi material is covered with macroscopic cracks and has poor density; the compressive strength of the positive-fraction material measured by a universal testing machine is only 5 MPa; by measuring the isothermal magnetization curve near room temperature, it is found that the material's magnetic phase transition has magnetic hysteresis, and the critical field is as high as 2.7 T; the saturation magnetostriction value measured by the strain gauge is as high as 1300 ppm.

[0033] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A dense MnCoSi-based giant magnetostrictive material, characterized in that: The Co atoms in the MnCoSi material are partially replaced by Pt atoms. In terms of atomic percentage, the expression of the material is MnCo 1-x Pt x Si, x ≥0.25, the alloy ingot of the material has a complete and dense appearance without centimeter-level macro cracks.

2. The material according to claim 1, wherein x It is 0.25~0.

3.

3. The material according to claim 1, wherein x is 0.

3.

4. The material according to claim 3, wherein x When the polycrystalline magnetostriction value of the material is 0.3, it is 400ppm.

5. The material according to any one of claims 1 to 4, characterized in that The material has a magnetostrictive phase transition and a giant magnetostrictive effect at room temperature.

6. The material according to any one of claims 1 to 4, characterized in that The room temperature magnetostriction of this material is reversible and hysteresis-free.

7. A method for preparing a dense MnCoSi-based giant magnetostrictive material according to any one of claims 1 to 6, characterized in that: include: MnCo was prepared by arc melting under argon protection. 1-x Pt x The Si alloy ingot was vacuum-sealed in a quartz tube, annealed at 800°C for 60 hours, and then slowly cooled to room temperature over 72 hours.

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