High-elasticity modulus magnetic memory alloy prepared based on liquid die forging method and preparation method thereof

Abstract

The application discloses a high-elasticity-modulus magnetic memory alloy prepared based on a liquid die forging method and a preparation method thereof, and belongs to the technical field of magnetic memory alloy preparation. 51‑x Ni 25 Ga 24 Gd x , wherein x=0.4-0.6. The preparation method of the high-elasticity-modulus magnetic memory alloy prepared based on the liquid die forging method comprises the following steps: taking nickel powder, manganese powder, gallium powder and gadolinium powder according to atomic percentage, ball-milling and mixing, and then sequentially performing liquid die forging and pressure forming to obtain the high-elasticity-modulus magnetic memory alloy. The application adopts trace rare earth element Gd element to replace Mn element, and adopts a liquid die forging technology to prepare a high-performance magnetic memory alloy. The magnetic memory alloy has the characteristics of high elastic modulus and small brittleness, and solves the problems of large brittleness and low elastic modulus of the existing Mn2NiGa magnetic memory alloy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of magnetic memory alloy, and more particularly relates to a high-elastic-modulus magnetic memory alloy prepared based on a liquid die forging method and a preparation method thereof. BACKGROUND

[0002] Magnetic drive shape memory alloys have the advantages of high corresponding frequency and large output strain, and have received high attention in recent years. As of now, magnetic drive shape memory alloys have been found in many alloys, mainly including: Ni-Mn-Ga, Ni-Fe-Ga, Fe-Pd, Fe-Pt, Ni-Mn-Al, Ni-Mn-X (X = In, Sn, Sb), Co-Ni-Ga (Al), Mn-Ni-Ga alloys, etc. According to the mechanism of magnetic-induced strain generation, magnetic shape memory alloys can be divided into two categories: one is represented by Ni2MnGa, and the other is represented by Ni-Mn-X (X = In, Sn, Sb). Unfortunately, the Curie temperature of the Ni2MnGa and Ni-Mn-X (X = In, Sn, Sb) alloys is relatively low, and the magnetic-induced strain is relatively small, which limits their practical application to a certain extent. Therefore, it is necessary to develop magnetic control shape memory alloys with high Curie temperature and large magnetic-induced strain to realize fast response, large output strain and high output stress, and meet the requirements of intelligent structures for high-performance driving materials for multiple reciprocating movements. In particular, Ni2MnGa alloys belong to intermetallic compounds and have the defect of intrinsic brittleness, which greatly limits the practical range of the alloys.

[0003] Recently, a Heusler Mn2NiGa alloy with martensitic phase transformation and magnetic transformation and non-L21 structure has been found. Compared with Ni2MnGa and Ni-Mn-X alloys, the Mn2NiGa alloy has a very high Curie temperature (588K), which is 200K higher than that of other memory alloys; the lattice distortion can reach 21.3%, which is about 2-2.5 times that of the Ni2MnGa alloy, and a larger output strain can be expected. Unfortunately, the Mn2NiGa alloy contains a relatively high content of Mn element which is easy to evaporate, so it is difficult to obtain accurate alloy composition by using conventional methods. At the same time, the composition and heat treatment process of the alloy have a direct impact on the martensitic phase transformation temperature and the magnetic transformation temperature of the alloy. In the existing Mn2NiGa alloy, a γ phase which does not participate in the martensitic phase transformation is precipitated, and the γ phase is a soft phase which can cause a significant decrease in the mechanical properties of the alloy. Therefore, it is of great significance to develop a magnetic memory alloy with small brittleness and high elastic modulus. SUMMARY

[0004] The application aims to provide a high-elastic-modulus magnetic memory alloy prepared based on a liquid die forging method and a preparation method thereof, so as to solve the problems existing in the prior art and realize the preparation of a magnetic memory alloy with small brittleness and high elastic modulus.

[0005] To achieve the above object, the present application provides the following solutions.

[0006] One of the technical solutions of the present application provides a high-elasticity modulus magnetic memory alloy prepared based on a liquid die forging method, and the chemical formula of the high-elasticity modulus magnetic memory alloy is Mn 51-x Ni 25 Ga 24 Gd x , wherein x = 0.4-0.6.

[0007] Preferably, the chemical formula of the high-elasticity modulus magnetic memory alloy is Mn 51-x Ni 25 Ga 24 Gd x , wherein x = 0.5.

[0008] The second technical solution of the present application provides a preparation method of the high-elasticity modulus magnetic memory alloy prepared based on the liquid die forging method, and the preparation method comprises the following steps.

[0009] According to atomic percentage, nickel powder, manganese powder, gallium powder and gadolinium powder are ball-mixed, and then liquid die forging and pressure forming are sequentially performed to obtain the high-elasticity modulus magnetic memory alloy.

[0010] Preferably, the purity of the nickel powder, the manganese powder, the gallium powder and the gadolinium powder is independently ≥ 99.95%, and the particle size is independently 10-100 μm.

[0011] Preferably, the ball-to-material ratio of the ball-mixing is 3:1; the ball-mixing comprises: first mixing at 300-400 r / min for 2-5 h, and then mixing at 800-1000 r / min for 2-4 h.

[0012] Preferably, the liquid die forging comprises: placing the mixed material obtained by the ball-mixing in a mold preheated at 700-750 ℃, and starting to press when the temperature of the mixed material obtained by the ball-mixing reaches 700-800 ℃.

[0013] Further, the parameters of the pressing are as follows: the specific pressure of the liquid forging is 60-80 MPa, and the pressure holding time is 20-30 s.

[0014] Preferably, the pressure forming comprises unidirectional pressure forming and multidirectional pressure forming.

[0015] Further, the unidirectional pressure forming comprises: performing pressure forming on the sample obtained by the liquid die forging in one direction; and the parameters of the unidirectional pressure forming are as follows: the pressure is 4-50 MPa, and the pressure holding time is 10-15 min.

[0016] Further, the multi-directional press forming includes: press forming the liquid-state die-cast sample in three different directions respectively; and the parameters of the multi-directional press forming are: the pressure is independently 4-50 MPa, and the pressure holding time is independently 10-15 min.

[0017] The application uses trace rare earth element Gd element to replace Mn element, and uses liquid-state die forging technology to prepare a high-performance magnetic memory alloy (chemical formula is Mn 51-x Ni 25 Ga 24 Gd x Wherein, x=0.4-0.6), the magnetic memory alloy has the characteristics of high elastic modulus and small brittleness, and solves the problems of large brittleness and low elastic modulus of the existing Mn2NiGa magnetic memory alloy.

[0018] Liquid-state die forging is a new technology combining casting and forging, which has the advantages of simple casting process, low production cost, complex shape of products, fine and uniform grain structure, good mechanical properties and high forming precision, and has the following advantages: (1) In the forming process, the liquid metal crystallizes and solidifies under the action of isostatic pressure from beginning to end, and the solidified metal layer is deformed plastically under pressure, and has a hot deformation structure, fine grain and uniform structure, and the pressure makes the outer side of the workpiece close to the inner wall of the die, so that the shape and size of the workpiece are accurate. (2) Because the plastic deformation of the solidified layer consumes part of the energy, the isostatic pressure of the liquid metal is not constant, but decreases with the thickening of the solidified layer. (3) Under the action of pressure, the solid-liquid zone is forced to compensate, so as to eliminate internal shrinkage and porosity of the workpiece and improve the mechanical properties of the workpiece. (4) Compared with ordinary hot die forging, the fluidity of the liquid metal is much greater than that of the solid metal, and the filling performance of the die cavity is better, and a complex shaped workpiece can be formed by one set of die. (5) The density and mechanical properties are basically the same as those of the die forging.

[0019] The application uses trace rare earth element Gd element to replace Mn element, and uses liquid-state die forging technology to prepare a high-performance magnetic memory alloy (chemical formula is Mn

[0020] The elastic modulus of the alloy material is directly related to the number of holes contained therein, and when the alloy material prepared contains fewer holes, the density thereof is higher, and the elastic modulus is increased. The liquid die forging technology can reduce the holes in the prepared alloy material, thereby effectively improving the elastic modulus of the magnetic memory alloy.

[0021] The liquid die forging process generates some defects such as pores due to liquid and solid shrinkage, and the present application further reduces the defects formed in the alloy during solidification after the liquid die forging, increases the density of the alloy, and improves the mechanical properties of the alloy.

[0022] The present application can greatly improve the mechanical properties of the alloy and refine the grains to a certain extent, and obviously reduce the brittleness of the alloy by means of the combined forming mode of liquid die forging and pressure forming.

[0023] The present application can avoid the volatilization of the Mn element by means of the combined forming mode of liquid die forging and pressure forming to prepare the magnetic memory alloy.

[0024] In addition, the magnetic memory alloy (chemical formula: Mn 51-x Ni 25 Ga 24 Gd x wherein x = 0.4-0.6) prepared by the present application can refine the grains, avoid brittle fracture of the coarse grains in the pressing process, and improve the mechanical properties of the alloy.

[0025] The present application has the following technical effects:

[0026] 1. The martensite phase transition temperature of the magnetic memory alloy (chemical formula: Mn 51-x Ni 25 Ga 24 Gd x wherein x = 0.4-0.6) prepared by the present application changes little compared with the conventional Mn2NiGa, which indicates that the magnetic memory alloy prepared by the present application maintains the same high martensite phase transition temperature as the existing magnetic memory alloy.

[0027] 2. The elastic modulus of the magnetic memory alloy (chemical formula: Mn 51-x Ni 25 Ga 24 Gd x wherein x = 0.4-0.6) prepared by the present application is 26 GPa, which is increased by 100% compared with the existing Mn2NiGa alloy.

[0028] 3. The magnetic memory alloy (chemical formula: Mn 51-x Ni25 Ga 24 Gd x The grain size of the magnetic memory alloy (chemical formula: Mn2NiGa (x), wherein x = 0.4-0.6) prepared by the application is 25 microns, which is reduced by 50-75% compared with the grain size of the existing Mn2NiGa alloy.

[0029] 4、 The magnetic memory alloy (chemical formula: Mn2NiGa (x), wherein x = 0.4-0.6) prepared by the application has small brittleness. 51-x Ni 25 Ga 24 Gd x The fracture strain of the alloy can reach 26% when x = 0.5.

[0030] 5、 The magnetic memory alloy (chemical formula: Mn2NiGa (x), wherein x = 0.4-0.6) prepared by the application has the same microstructure as the existing Mn2NiGa alloy. 51-x Ni 25 Ga 24 Gd x The fracture strain of the alloy can reach 26% when x = 0.5. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 DSC curves of the magnetic memory alloys prepared in Example 1 and Comparative Examples 1-2;

[0032] Figure 2 Elastic modulus of the magnetic memory alloys prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4;

[0033] Figure 3 Particle size distribution diagrams of the magnetic memory alloys prepared in Example 1 and Comparative Examples 1-3, wherein a is Example 1, b is Comparative Example 1, c is Comparative Example 2 and d is Comparative Example 3;

[0034] Figure 4 Influence of the addition amount of Gd element on the micro-morphology of the magnetic memory alloy, wherein a is Comparative Example 1, b is Comparative Example 2 and c is Example 1;

[0035] Figure 5 X-ray diffraction analysis spectrum of the magnetic memory alloys prepared in Example 1 and Comparative Examples 1-2;

[0036] Figure 6 Structure diagram of the mold used for preparing the magnetic memory alloy, wherein a is a mold assembly diagram, b is an inner sleeve assembly diagram, c is a lower punch, d is an upper punch, e is an outer sleeve and f is a lower gasket ring;

[0037] Figure 7 Physical diagrams of the samples prepared in Example 1 and Example 2;

[0038] Figure 8Stress-strain curve of the magnetic memory alloy prepared for Examples 3-4 and Comparative Example 3;

[0039] Figure 9 Differential scanning calorimetry (DSC) curve of the magnetic memory alloy prepared for Examples 1-3 and Comparative Example 2. DETAILED DESCRIPTION

[0040] The following detailed description of various exemplary embodiments of the application should not be considered to place limitations on the present application unless specifically recited therein.

[0041] It should be understood that the terms used herein are for the purpose of describing particular embodiments and are not intended to limit the present application. In addition, for numerical ranges recited in the present application, it is contemplated that each intervening value, to the upper and lower limits of the ranges is also specifically disclosed. Each smaller range that falls within the integer ranges is also specifically disclosed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0042] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the content of the present specification will control.

[0043] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0044] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0045] The nickel powder, manganese powder, gallium powder and gadolinium powder used in the following examples and comparative examples of the present application were purchased from Beijing Xingrongyuan Technology Co., Ltd.

[0046] The equipment used in the following examples and comparative examples of the present application was as follows: JC-QM series vertical semi-circular planetary ball mill (JC-QM-16) purchased from Qingdao Juchuang Times Environmental Protection Technology Co., Ltd., and WDW-50 type universal testing machine purchased from Jinan Xinghuo Testing Machine Co., Ltd.

[0047] The mold used in the following examples and comparative examples of the present application comprises an outer sleeve, a lower punch, an upper punch, a lower gasket and an inner sleeve (as shown in Figure 5 The mold is made of 5CrMnMo, and the assembly steps are as follows: the outer sleeve is a cylindrical body with a length of 115 mm, an inner diameter of 50 mm and an outer diameter of 90 mm, the inner sleeve is composed of two inner sleeves 1 and two inner sleeves 2, the shape surrounded by the inner sleeve is a rectangle with a length of 15 mm and a width of 25 mm, the outer circle is formed in a circular shape with a gap with the outer sleeve, the lower gasket is placed at the bottom of the mold to fix the inner sleeve, the upper punch is first placed into the square hole from the lower part, then the molten liquid alloy is added into the square hole, and then the lower punch is placed.

[0048] The purity of the nickel powder, manganese powder, gallium powder and gadolinium powder used in the following examples and comparative examples of the present application is 99.95%, and the particle size is 10-100 μm.

[0049] The standard followed in the test of the elastic modulus and brittleness of the magnetic memory alloy in the following examples and comparative examples of the present application is ISO 6892-1.

[0050] Example 1

[0051] The present example provides a preparation method of a magnetic memory alloy with a chemical formula of Mn 50.5 Ni 25 Ga 24 Gd 0.5 , and the specific steps are as follows:

[0052] According to the atomic percentage, the nickel powder, manganese powder, gallium powder and gadolinium powder are ball-milled and mixed, then alcohol is added, the mixed metal powder mixed with alcohol is placed into a vacuum ball mill jar, ceramic balls are added at a ball-to-material ratio of 3:1, then the vacuum ball mill jar is sealed in a glove box under argon protection, the vacuum ball mill jar is taken out and placed on a planetary ball mill, the mixture is mixed at a speed of 300 r / min for 5 h, and then mixed at a speed of 900 r / min for 3 h. After ball milling, the sample is taken in the glove box with argon protection, and the uniformly mixed metal powder is obtained. The mold is preheated at 750℃ for 1 min. The uniformly mixed metal powder is melted to obtain a molten liquid raw material, the molten liquid raw material is poured into a mold with an inner wall wrapped with 0.5 mm thick graphite paper, and the mold is assembled and the molten liquid raw material is poured according to the above method. Liquid die forging is carried out, and the process parameters of liquid die forging are as follows: the liquid forging specific pressure is 70 MPa, the pressure is started at 800℃, and the holding time is 25 s. After liquid die forging, the alloy sample and the mold are placed together on a universal testing machine under a pressure of 30 MPa, and the holding time is 12 min. After cooling, a rectangular sample with a diameter of 15×15×25 mm is obtained, and the chemical formula of the magnetic memory alloy is Mn 50.5 Ni 25 Ga24 Gd 0.5 magnetic memory alloy.

[0053] Example 2

[0054] The difference from Example 1 is that the pressing in one direction in Example 1 is increased to pressing in three directions, specifically, the obtained 15x15x25mm cuboid sample is pressed in two other three-dimensional directions in addition to the pressing direction described in Example 1, and the pressing pressure and pressure holding time in the other two three-dimensional directions are the same as in Example 1. The rest is the same as in Example 1.

[0055] Example 3

[0056] This embodiment provides a preparation method of a magnetic memory alloy with a chemical formula of Mn 50.6 Ni 25 Ga 24 Gd 0.4 , and the specific steps are as follows:

[0057] According to atomic percentage, nickel powder, manganese powder, gallium powder and gadolinium powder are ball-milled and mixed, then alcohol is added, the mixed metal powder mixed with alcohol is placed in a vacuum ball mill jar, ceramic balls are added according to a ball-to-material ratio of 3:1, then the vacuum ball mill jar is sealed in an argon-protected glove box, the vacuum ball mill jar is taken out and placed on a planetary ball mill, the mixture is mixed at a speed of 300r / min for 5h, and then mixed at a speed of 900r / min for 3h. After ball milling, the sample is taken in the argon-protected glove box, and a uniformly mixed metal powder is obtained. The mold is preheated at 750℃ for 1min. The uniformly mixed metal powder is melted to obtain a molten liquid raw material, the molten liquid raw material is poured into a mold with an inner wall wrapped with 0.5mm thick graphite paper, and the mold is assembled and the molten liquid raw material is poured according to the above method. Liquid die forging is carried out, and the process parameters of liquid die forging are as follows: the liquid forging specific pressure is 70MPa, the pressure is started at 800℃, and the pressure holding time is 25s. After liquid die forging, the alloy sample and the mold are placed together on a universal testing machine under a pressure of 30MPa, and the pressure is held for 12min. After one direction of pressing, a cuboid sample with a diameter of 15x15x25mm is obtained, and a magnetic memory alloy with a chemical formula of Mn 50.6 Ni 25 Ga 24 Gd 0.4 is obtained after cooling.

[0058] Example 4

[0059] This embodiment provides a preparation method of a magnetic memory alloy with a chemical formula of Mn 50.4 Ni 25 Ga 24 Gd 0.6 , and the specific steps are as follows:

[0060] According to atomic percentage, take nickel powder, manganese powder, gallium powder and gadolinium powder to carry out ball milling mixing, then add alcohol thereto, put the mixed metal powder mixed with alcohol into a vacuum ball milling jar, add ceramic balls in a ball-to-material ratio of 3:1, then seal the vacuum ball milling jar in a glove box under argon protection, take out the vacuum ball milling jar and place it on a planetary ball mill, first mix at a speed of 300 r / min for 5 h, then mix at a speed of 900 r / min for 3 h. After ball milling, sample in the glove box under argon protection, to obtain uniformly mixed metal powder. Preheat the mold at 750°C for 1 min. Melt the uniformly mixed metal powder to obtain molten liquid raw material, pour the molten liquid raw material into a mold with an inner wall wrapped with 0.5 mm thick graphite paper, assemble the mold and pour the molten liquid raw material according to the above method. Perform liquid die forging, and the process parameters of liquid die forging are as follows: the liquid forging specific pressure is 70 MPa, the pressurization starts at 800°C, and the pressure holding time is 25 s. After liquid die forging, place the alloy sample and the mold together on a universal testing machine under a pressure of 30 MPa, and hold the pressure for 12 min, to obtain a cuboid sample with a diameter of 15x15x25 mm after pressing in one direction, and the chemical formula of the magnetic memory alloy is Mn 50.4 Ni 25 Ga 24 Gd 0.6 .

[0061] Comparative Example 1

[0062] The present comparative example provides a preparation method of a magnetic memory alloy with a chemical formula of Mn 51 Ni 25 Ga 24 . The specific steps are as follows:

[0063] According to the atomic percentage, take the nickel powder, manganese powder and gallium powder to mix by ball milling, then add alcohol to the mixture, put the mixed metal powder mixed with alcohol into a vacuum ball mill jar, add ceramic balls with a ball-to-material ratio of 3:1, then seal the vacuum ball mill jar in a glove box under argon protection, take out the vacuum ball mill jar and place it on a planetary ball mill, first mix at a speed of 300 r / min for 5 h, then mix at a speed of 900 r / min for 3 h. After ball milling, sample in the glove box with argon protection, and the uniformly mixed metal powder is obtained. Preheat the mold at 750°C for 1 min. Melt the uniformly mixed metal powder to obtain a molten liquid raw material, pour the molten liquid raw material into a mold with an inner wall wrapped with 0.5 mm thick graphite paper, assemble the mold and pour the molten liquid raw material according to the above method. Perform liquid die forging, and the process parameters of liquid die forging are as follows: the liquid forging specific pressure is 70 MPa, the pressure is started at 800°C, and the holding time is 25 s. After liquid die forging, the alloy sample and the mold are placed together on a universal testing machine under a pressure of 30 MPa, and the pressure is held for 12 min. After cooling, a rectangular sample with a diameter of 15×15×25 mm is obtained, and the chemical formula of the magnetic memory alloy is Mn 51 Ni 25 Ga 24 .

[0064] Comparative Example 2

[0065] The present comparative example provides a preparation method of a magnetic memory alloy with a chemical formula of Mn 50.9 Ni 25 Ga 24 Gd 0.1 .

[0066] According to atomic percentage, take nickel powder, manganese powder, gallium powder and gadolinium powder to carry out ball milling mixing, then add alcohol thereto, put the mixed metal powder mixed with alcohol into a vacuum ball milling jar, add ceramic balls in a ball-to-material ratio of 3:1, then seal the vacuum ball milling jar in a glove box under argon protection, take out the vacuum ball milling jar and place it on a planetary ball mill, first mix at a speed of 300 r / min for 5 h, then mix at a speed of 900 r / min for 3 h. After ball milling, sample in the glove box under argon protection, to obtain uniformly mixed metal powder. Preheat the mold at 750°C for 1 min. Melt the uniformly mixed metal powder to obtain molten liquid raw material, pour the molten liquid raw material into the mold with the inner wall wrapped with 0.5 mm thick graphite paper, assemble the mold and pour the molten liquid raw material according to the above method. Perform liquid die forging, and the process parameters of liquid die forging are as follows: the liquid forging specific pressure is 70 MPa, the pressurization starts at 800°C, and the pressure holding time is 25 s. After liquid die forging, place the alloy sample and the mold together on a universal testing machine under a pressure of 30 MPa, and hold the pressure for 12 min, to obtain a cuboid sample with a diameter of 15x15x25 mm after pressing in one direction, and the chemical formula of the magnetic memory alloy is Mn 50.9 Ni 25 Ga 24 Gd 0.1 .

[0067] Comparative Example 3

[0068] A Mn-Ni-Ga-Gd alloy was prepared by a conventional melting method, and the melting process and parameters were as follows: pure electrolytic nickel with a purity of 99.99%, 99.95% electrolytic manganese, 99.99% gallium and 99.99% rare earth Gd were used as raw materials, and a non-consumable arc furnace was used to prepare the sample under the protection of argon atmosphere. Before melting, a mechanical pump and a molecular pump were used to vacuumize to 5x10 -3 Pa, then high-purity argon was filled to 2x10 -2 Pa, and the melting started. In order to ensure the uniformity of the chemical composition of the ingot, each sample was flipped and melted four times and was subjected to magnetic stirring, then the melted button ingot was re-melted to prepare a button-shaped sample, and the sample was taken out after cooling. The sample was mechanically polished to remove surface impurities, washed with acetone, and then sealed in a quartz tube with a vacuum degree of 10 -1 Pa, and was subjected to homogenization annealing treatment at 1173 K for 5 h, and was quenched into water to obtain high order degree.

[0069] The mechanical properties of the alloy obtained in the present comparative example were detected. The test results showed that the fracture strength was 900 MPa, and the fracture strain was 12.8%.

[0070] Comparative Example 4

[0071] A Mn 50.5Ni 25 Ga 24 Gd 0.5 magnetic memory alloy, the specific steps are:

[0072] According to atomic percentage, take nickel powder, manganese powder, gallium powder and gadolinium powder to carry out ball milling mixing, then add alcohol to it, put the mixed metal powder mixed with alcohol into a vacuum ball mill jar, add ceramic balls at a ball-to-material ratio of 3:1, then seal the vacuum ball mill jar in a glove box under argon protection, take out the vacuum ball mill jar and place it on a planetary ball mill, first mix at a speed of 300 r / min for 5 h, and then mix at a speed of 900 r / min for 3 h. The mold is preheated at 750 DEG C for 1 min. After ball milling, pour the uniformly mixed metal powder into the mold of the sintering furnace, and carry out discharge plasma sintering on SPS1050 produced by Japan Zyo Carbon Co., Ltd. The process parameters of sintering are: the maximum pulse current is 5000 A, the maximum sintering temperature is 2000 DEG C, the maximum axial pressure is 100 kN, the vacuum degree is 6 Pa, and the pressure maintaining time is 10 min. After cooling, the chemical formula of the obtained magnetic memory alloy is Mn 50.5 Ni 25 Ga 24 Gd 0.5 .

[0073] The martensitic phase transition temperature of the magnetic memory alloy obtained in Example 1 and Comparative Examples 1-2 is tested, and the obtained results are shown in Figure 1 .

[0074] It can be known from Figure 1 that the Mn 51-x Ni 25 Ga 24 Gd x (x=0, 0.1 or 0.5) alloy has only one endothermic and exothermic peak in the heating and cooling processes, indicating that the thermal induced martensitic forward and reverse phase transitions of all the alloys are one-step phase transitions, that is, the Mn 51-x Ni 25 Ga 24 Gd x (x=0, 0.1 or 0.5) alloy prepared by the liquid die forging method has the same typical one-step thermal elastic martensitic phase transition as the as-cast Mn2NiGa alloy, and has a high martensitic phase transition temperature. It is proved that the Mn 51- x Ni 25 Ga 24 Gd x (x=0.5) alloy has high high-temperature stability and magnetocaloric effect.

[0075] The room temperature mechanical properties of the magnetic memory alloys obtained in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4 are tested, and the obtained results are shown inFigure 2 shown.

[0076] Depend on Figure 2 It can be seen that the Mn prepared in Comparative Examples 1 and 2 51-x Ni 25 Ga 24 Gd x The elastic modulus of the alloys (x = 0 or 0.1) is basically the same, but the Mn 51-x Ni 25 Ga 24 Gd x The elastic modulus of the alloy prepared with (x = 0.5) reached 26 GPa, significantly superior to the alloys described in Comparative Examples 1 and 2. Furthermore, the elastic modulus of the alloy prepared in Example 1 was significantly superior to that of the alloy described in Comparative Example 4. This is due to the reduction of voids in the alloy material during the liquid die forging process. As is well known, the elastic modulus of a material is very sensitive to voids. When the prepared alloy contains fewer voids, its density is higher, and thus its elastic modulus increases.

[0077] The relative density and grain size of the magnetic memory alloys obtained in Example 1 and Comparative Examples 1 to 3 were tested. The results are as follows: Figure 3 shown.

[0078] Figure 3 Graphs showing particle size distributions of magnetic memory alloys prepared in Example 1 and Comparative Examples 1 to 3, wherein a represents Example 1, b represents Comparative Example 1, c represents Comparative Example 2, and d represents Comparative Example 3.

[0079] Depend on Figure 3 It can be seen that the majority of the grain sizes in Example 1 are between 0 and 30 μm, the grain size is finer, and the mechanical properties of the alloy are better; the density of the alloy is 96.5%. The majority of the grain sizes in Comparative Example 1 are between 10 and 60 μm, and the grain size distribution is relatively wide, resulting in a low density of the alloy, which is 88.5%. The majority of the grain sizes in Comparative Example 2 are between 20 and 50 μm, and the grain size distribution is significantly more concentrated than that in Comparative Example 1, and the density of the alloy is 90.6%. The majority of the grain sizes in Comparative Example 3 are between 70 and 100 μm, the grains are relatively coarse, and the density of the alloy is 80.4%.

[0080] Figure 4 The figure shows the effect of the addition amount of Gd element on the micromorphology of magnetic memory alloy, wherein a is comparative example 1, b is comparative example 2, and c is embodiment 1.

[0081] Depend on Figure 3 and Figure 4It can be seen that as the amount of Gd element added increases, the grain size of the alloy material decreases significantly, and as the amount of Gd element added increases, a white second phase appears on the surface of the alloy material, especially at the grain boundaries. At the same time, it is found that the density of the alloy material increases with the increase in the amount of Gd element added. This is because the addition of the rare earth element Gd increases the specific surface area of ​​the alloy material, increases the surface activity and lattice activity, and is beneficial to the preparation process. Therefore, within the limited range of the amount of Gd element added, the increase in the amount of Gd element added makes the density of the alloy material higher. Specifically, the grain diameter of the alloy material obtained in Example 1 is the smallest, and the grain diameter is concentrated at no more than 30μm, while the grain diameter of the alloy materials obtained in Comparative Example 1 and Comparative Example 2 increases slightly, but is significantly smaller than the existing Mn2NiGa magnetic memory alloy prepared by a smelting furnace.

[0082] Figure 5 The X-ray diffraction analysis patterns of the magnetic memory alloys prepared in Example 1 and Comparative Examples 1-2 are shown.

[0083] Depend on Figure 5 It can be seen that the microstructures of the alloy materials prepared in Example 1 and Comparative Examples 1-2 are consistent with the microstructure of the Mn2NiGa magnetic memory alloy prepared in the existing melting furnace, except that the diffraction intensity at individual positions is slightly different (this is caused by noise).

[0084] Figure 7 This is a physical picture of the samples prepared in Example 1 and Example 2.

[0085] Depend on Figure 7 It can be seen that the samples prepared in Example 1 and Example 2 are found to be rectangular in shape, have no defects in appearance, and have good appearance quality.

[0086] Figure 8 The stress-strain curves of the magnetic memory alloys prepared in Example 1, Example 3, Example 4 and Comparative Example 3 are shown in FIG. Figure 8 In the figures, x=0.5 represents Example 1, x=0.4 represents Example 3, x=0.6 represents Example 4, and normal smelting represents Comparative Example 3.

[0087] Depend on Figure 8 It can be seen that the magnetic memory alloy prepared by the present invention (chemical formula is Mn 51-x Ni 25 Ga 24 Gd x , among which, the brittleness of x=0.4~0.6) is small, and when x=0.5, the fracture strain of the alloy can reach 26%.

[0088] Figure 9 The differential scanning calorimetry (DSC) curves of the magnetic memory alloys prepared in Examples 1 to 3 and Comparative Example 2 are shown.

[0089] It can be seen that the preparation method of the magnetic memory alloy has a great influence on the phase transition temperature of the alloy itself. Figure 9

[0090] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be mutually referred to.

[0091] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.​

Claims

1. A high modulus magnetic memory alloy prepared by a liquid die casting method, characterized in that, The high modulus magnetic memory alloy has a chemical formula of Mn 51-x Ni 25 Ga 24 Gd x wherein x=0.4~0.

6.

2. The high elastic modulus magnetic memory alloy prepared based on the liquid die forging method according to claim 1, characterized in that, The high modulus magnetic memory alloy has a chemical formula of Mn 51-x Ni 25 Ga 24 Gd x wherein x = 0.

5.

3. The method for producing a high elastic modulus magnetic memory alloy based on the liquid die casting method as claimed in claim 1 or 2, characterized in that, The method comprises the following steps: According to the atomic percentage, the nickel powder, the manganese powder, the gallium powder and the gadolinium powder are ball-mixed, then sequentially subjected to liquid-state mold calcination and pressure forming to obtain the high-elasticity modulus magnetic memory alloy.

4. The production method according to claim 3, characterized by, The purity of the nickel powder, the manganese powder, the gallium powder and the gadolinium powder is independently greater than or equal to 99.95%, and the particle size is independently 10-100 μm.

5. The preparation method according to claim 3, characterized in that The ball-to-material ratio of the ball-mixing is 3:1; the ball-mixing comprises: first mixing at 300-400 r / min for 2-5 h, and then mixing at 800-1000 r / min for 2-4 h.

6. The preparation method according to claim 3, characterized in that The pressure forming comprises unidirectional pressure forming and multidirectional pressure forming.

7. The production method according to claim 6, characterized by, The unidirectional pressure forming comprises: pressure forming the sample obtained by the liquid-state mold calcination in one direction; the parameters of the unidirectional pressure forming are: the pressure is 4-50 MPa, and the pressure maintaining time is 10-15 min.

8. The preparation method according to claim 6, characterized in that The multidirectional pressure forming comprises: pressure forming the sample obtained by the liquid-state mold calcination in three different directions respectively; the parameters of the multidirectional pressure forming are: the pressure is independently 4-50 MPa, and the pressure maintaining time is independently 10-15 min.

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