A high-elasticity thermo-effect magnetic memory alloy and its preparation method

Abstract

This invention discloses a high-elasticity thermal effect magnetic memory alloy and its preparation method, belonging to the field of magnetic memory alloy preparation technology; a high-elasticity thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 A method for preparing magnetic memory alloys includes the following steps: uniformly mixing four metallic raw materials, Ni, Mn, Ga, and Ti, to obtain a mixture; sequentially subjecting the mixture to powder forging and isothermal aging treatment to obtain the high-elasticity thermal effect Mn alloy. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic memory alloy; wherein the isothermal aging treatment process is: holding at 500℃ for 10-30 minutes. That is, this invention prepares a high-strength Mn alloy using powder forging technology. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloys are then subjected to isothermal aging treatment to improve their elastothermal effect. This method solves the problems of low elastothermal effect, low Curie temperature, and large compositional deviation of existing magnetic shape memory alloys.

Description

Technical Field

[0001] This invention belongs to the field of magnetic memory alloy preparation technology, and particularly relates to a high elastic thermal effect magnetic memory alloy and its preparation method. Background Technology

[0002] Smart materials are an important field of materials research. Currently, the most studied materials include piezoelectric materials, magnetostrictive materials, and shape memory alloys. Piezoelectric ceramics, represented by PZT, and magnetostrictive materials, represented by Terfenol-D, can exhibit reversible strain under the action of an external electric / magnetic field, with a response frequency of up to 10 kHz. However, their maximum output strain is small (only about 0.2%) and their output stress is low (only a few MPa). Traditional shape memory alloys, represented by TiNi alloys, can exhibit a two-way shape memory effect through thermomechanical training, with a large output strain (4%) and high output stress (tens of MPa). However, their response frequency is low (a few Hz) due to the limitation of the temperature field. Neither of these can meet the urgent need for high-performance drive materials in smart mechanisms.

[0003] Magnetic shape memory alloys can output macroscopic strain under the action of an external magnetic field, exhibiting both large strain and fast response, making them an ideal intelligent driving material. Based on the mechanism of magnetically induced strain generation, magnetic shape memory alloys can be divided into two categories: one, represented by Ni₂MnGa, derives its magnetically induced strain from the rearrangement of martensitic twins driven by an external magnetic field, achieving a maximum magnetically induced strain of up to 10%, but the output stress is limited by the magnetocrystalline anisotropy, only reaching a few MPa; the other, represented by Ni-Mn-X (X = In, Sn, Sb) alloys, derives its magnetically induced strain from the magnetoinduced inverse martensitic transformation under the action of an external magnetic field. Its mechanism involves deforming the alloy in the martensitic state and placing it above the inverse martensitic transformation initiation temperature (A0). s At a slightly lower ambient temperature, a magnetic field is applied to the alloy, causing A s When the temperature drops, A s When the temperature drops below ambient temperature, a martensitic inverse phase transformation occurs without changing the ambient temperature, and the deformation is recovered. However, the Curie temperature and magnetically induced strain of Ni2MnGa and Ni-Mn-X alloys are currently relatively low, which limits their practical applications to some extent. Therefore, there is an urgent need to provide a magneto-controlled shape memory alloy with a high Curie temperature and large magnetically induced strain to achieve fast response, large output strain, and high output stress, meeting the requirements of high-performance drive materials for intelligent structures with multiple reciprocating motions.

[0004] Ferromagnetic shape memory alloys exhibit not only thermoelastic martensitic phase transformation characteristics but also magnetic field-induced martensitic phase transformation characteristics. However, improving the suppression of magnetic properties in the development and research of ferromagnetic shape memory alloys has been a focus of attention for many scholars. Recently, a non-L21 structure HeuslerMn alloy exhibiting both martensitic and magnetic phase transformations has been discovered. 53 Ni 25 Ga 22 Alloys. Compared to Ni2MnGa and Ni-Mn-X alloys, Mn 53 Ni 25 Ga 22 The alloy possesses a very high Curie temperature (588 K), 200 K higher than other shape memory alloys; its lattice distortion can reach 21.3%, approximately 2-2.5 times that of the Ni2MnGa alloy, suggesting the potential for achieving large output strain. However, unfortunately, Mn... 53 Ni 25 Ga 22 The alloy belongs to the intermetallic compound family and is highly brittle, which greatly limits its engineering applications; meanwhile, Mn 53 Ni 25 Ga 22 Because the alloy contains a high amount of volatile Mn, it is difficult to accurately obtain the alloy composition designed by researchers using conventional smelting methods. The composition and heat treatment process of the alloy have a direct impact on the martensitic transformation temperature and magnetic transformation temperature of the alloy, thus affecting the application range of the alloy.

[0005] To solve the existing Mn 53 Ni 25 Ga 22 To address the issues of high brittleness and low elasto-thermal effect in magnetic shape memory alloys, this invention first replaces Mn with a trace amount of Ti, and then synthesizes a Mn alloy with high elasto-thermal effect through powder forging and isothermal aging. 52.8 Ni 25 Ga 22 Ti 0.2 A new method for magnetic shape memory alloys. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a high-elasticity thermal effect magnetic memory alloy and its preparation method. A high-strength Mn alloy is prepared using powder forging technology. 52.8 Ni 25 Ga 22 Ti 0.2 A novel method for improving the elasto-thermal effect of magnetic memory alloys through isothermal aging treatment is proposed. This method solves the problems of low elasto-thermal effect, low Curie temperature, and large compositional deviation of existing magnetic memory alloys. The alloy prepared by this invention has a minimum fracture strength of ~1585MPa and a minimum Curie temperature of ~576K.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One of the technical solutions of this invention:

[0009] A high elastic thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 The preparation method of magnetic shape memory alloy includes the following steps:

[0010] A mixture of four metallic raw materials, Ni, Mn, Ga, and Ti, was prepared by uniformly mixing them.

[0011] The mixture was subjected to powder forging and isothermal aging treatment in sequence to obtain the high elasticity thermal effect Mn. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloy;

[0012] The isothermal aging process involves holding the temperature at 500℃ for 10-30 minutes, preferably 10 minutes.

[0013] Beneficial effects: Under the isothermal aging temperature and holding time specified in this invention, the grains can be coarsened slowly, avoiding the problem of deterioration of the mechanical properties of the prepared alloy.

[0014] Optionally, the four metal raw materials Ni, Mn, Ga and Ti are all pure metal powders with a purity of 95.95% and a powder diameter of 5-30 μm.

[0015] Optionally, based on atomic percentage, Ni∶Mn∶Ga∶Ti=25∶52.8∶22∶0.2.

[0016] Optionally, the powder forging process specifically includes:

[0017] The mixture was added to anhydrous ethanol and placed in a vacuum ball mill jar, where it was sequentially subjected to ball milling, pressing, sintering, forging, and homogenization heat treatment.

[0018] Furthermore, the ball-to-material ratio in the vacuum ball mill jar is 3:1.

[0019] Furthermore, the ball milling process includes:

[0020] First, ball mill at 200-500 rpm for 10-15 hours, then ball mill at 800-1000 rpm for 1-2 hours.

[0021] Furthermore, the conditions during the pressing process are: applying a pressure of 30MPa-60MPa, preferably 50MPa, during the pressing process.

[0022] Furthermore, the conditions during the sintering process are as follows:

[0023] Sinter at 800℃ for 20 minutes.

[0024] Furthermore, the conditions during the forging process are: a unidirectional forging force of 20-40 MPa, an initial forging temperature of 800°C, and a final forging temperature of 600°C; preferably, a unidirectional forging force of 30 MPa.

[0025] Furthermore, the conditions during the homogenization heat treatment process are: holding at 900°C for 12 hours.

[0026] Furthermore, the preparation method further includes ice-water quenching after the isothermal aging heat treatment.

[0027] The second technical solution of this invention:

[0028] A high elastic thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 The magnetic memory alloy is prepared by the above-described method.

[0029] Optionally, the high elasticity and thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 The elastothermal effect of magnetic shape memory alloys is 4.0-4.2K.

[0030] Compared with the prior art, the Mn prepared in Example 1 of this invention... 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloys have the following advantages and technical effects:

[0031] 1. The Mn prepared by this invention 52.8 Ni 25 Ga 22 Ti 0.2 The martensitic transformation temperature of magnetic shape memory alloys is approximately 205 K, which is similar to that of existing Mn alloys. 53 Ni 25 Ga 22 The alloys are almost identical;

[0032] 2. The Mn prepared by this invention 52.8 Ni 25 Ga 22 Ti 0.2The phase transition thermal hysteresis of magnetic shape memory alloys is approximately 100°C, which is higher than that of Mn alloys produced by conventional melting. 53 Ni 25 Ga 22 Phase transformation heat hysteresis temperature of the alloy (20℃);

[0033] 3. The Mn prepared by this invention 52.8 Ni 25 Ga 22 Ti 0.2 The elasto-thermal effect of the magnetic shape memory alloy is 4.2K, filling the gap in existing Mn alloys. 53 Ni 25 Ga 22 The gap in the study of the thermal effect of alloy bullets. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0035] Figure 1 Mn prepared by powder forging and isothermal aging in Examples 1-3 of this invention 52.8 Ni 25 Ga 22 Ti 0.2 DSC curves of the alloy after aging treatment at different times;

[0036] Figure 2 Mn prepared in Examples 1-3 and Comparative Examples 1-2 52.8 Ni 25 Ga 22 Ti 0.2 The room temperature microstructure morphology of the alloy;

[0037] Figure 3 Mn prepared in Examples 1-3 52.8 Ni 25 Ga 22 Ti 0.2 The stress-strain curves (a) and adiabatic temperature change curves (b) of the alloy after aging treatment for different times are shown in the superelastic test.

[0038] Figure 4 Mn prepared by powder forging and isothermal aging in Examples 1-3 52.8 Ni 25 Ga 22 Ti 0.2 The relationship between the microhardness of the alloy and the aging time after aging treatment for different times. Detailed Implementation

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0041] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0042] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0043] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0044] This invention discloses a high-elasticity thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 The preparation method of magnetic shape memory alloy includes the following steps:

[0045] Manganese powder, nickel powder, gallium powder and titanium powder with a purity of 95.95% and a powder diameter of 5-30μm are used as raw materials. 25 parts of Ni powder, 52.8 parts of Mn powder, 22 parts of Ga powder and 0.2 parts of Ti powder are mixed according to atomic percentage. Then an appropriate amount of anhydrous ethanol is added to the mixture. The metal powder mixed with anhydrous ethanol is placed in a vacuum ball milling jar. Ceramic balls are added at a ball-to-material ratio of 3:1. Then the vacuum ball milling jar is sealed in an argon-protected glove box.

[0046] Remove the ball mill jar and place it on a planetary ball mill. First, mix the material at 200-500 rpm for 10-15 hours, then mix it at 800-1000 rpm for 2-1 hours.

[0047] After high-energy ball milling, samples were taken in a glove box with a protected atmosphere to obtain uniformly mixed metal powder. This powder was then poured into a mold for pre-forming and sintered at 800℃ for 20 minutes. The sintered blank was then forged on a closed-die forging machine. Finally, the forged blank was placed in a vertical heat treatment furnace for high-temperature homogenization heat treatment to allow short-range diffusion of elements for homogenization, ultimately yielding high-performance Mn. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloy;

[0048] For high-performance Mn 52.8 Ni 25 Ga 22 Ti 0.2 The alloy undergoes aging treatment, the process of which involves heating the samples to 500℃ under vacuum conditions and holding for 10-30 minutes, followed by ice-water quenching, ultimately yielding Mn with high elastic-thermal effect. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloy.

[0049] This invention also discloses a high-elasticity thermal effect Mn prepared by the above preparation method. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloy.

[0050] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0051] All raw materials used in this invention were purchased from the market.

[0052] The technical solution of the present invention will be further illustrated by the following embodiments.

[0053] Example 1

[0054] A high elastic thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 The preparation method of magnetic shape memory alloy includes the following steps:

[0055] Manganese powder, nickel powder, gallium powder, and titanium powder with a purity of 95.95% and a powder diameter of 5-30μm were used as raw materials. 25 parts of Ni powder, 52.8 parts of Mn powder, 22 parts of Ga powder, and 0.2 parts of Ti powder were mixed according to atomic percentage. Then, an appropriate amount of anhydrous ethanol (mass ratio of anhydrous ethanol to mixed metal raw materials 1:9) was added. The metal powder mixed with anhydrous ethanol was placed in a vacuum ball mill jar, and ceramic balls were added at a ball-to-material ratio of 3:1. The vacuum ball mill jar was then sealed in an argon-protected glove box.

[0056] Remove the ball mill jar and place it on a planetary ball mill. First, mix the material at 350 rpm for 12 hours, then mix it at 900 rpm for 1.5 hours.

[0057] After high-energy ball milling, samples were taken in a glove box with a protected atmosphere to obtain uniformly mixed metal powder. This powder was then poured into a mold for pre-forming by pressing (pressure of 50 MPa). The powder was then sintered at 800℃ for 20 minutes. The sintered blank was then placed on a closed-die forging machine for forging (forging conditions: unidirectional forging force of 30 MPa, initial forging temperature of 800℃, and final forging temperature of 600℃). Finally, the forged blank was placed in a vertical heat treatment furnace for high-temperature homogenization heat treatment (temperature of 900℃, followed by holding at that temperature for 12 hours) to allow short-range diffusion of elements for homogenization. This yielded high-performance Mn. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloy;

[0058] For high-performance Mn 52.8 Ni 25 Ga 22 Ti 0.2 The alloy undergoes aging treatment, the process of which involves heating the sample to 500℃ under vacuum conditions inside a quartz tube, holding it at this temperature for 10 minutes, and then quenching it in ice water, ultimately yielding Mn with high elastic-thermal effect. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloy.

[0059] Example 2

[0060] The difference from Example 1 is that the aging time is 30 minutes, while the other conditions are the same as in Example 1.

[0061] Example 3

[0062] The difference from Example 1 is that the aging time is 60 minutes, while the other conditions are the same as in Example 1.

[0063] Comparative Example 1

[0064] The difference from Example 1 is that no aging process is performed, but all other conditions are the same as in Example 1.

[0065] The fracture strength of the alloy obtained in Comparative Example 1 without aging treatment is significantly lower than that of the alloy in Example 1 after aging treatment. The fracture strength of the alloy obtained in Comparative Example 1 without aging treatment is 925 MPa, while the fracture strength of the alloy in Example 1 after aging treatment is above 1500 MPa.

[0066] Comparative Example 2 (Normal Melting)

[0067] The difference from Example 1 is that Mn 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloys are prepared through normal smelting. The specific smelting process is as follows:

[0068] Samples were prepared using electrolytic nickel (99.99% purity), electrolytic manganese (99.95% purity), gallium (99.99% purity), and sponge titanium (99.99% purity) as raw materials in a non-consumable arc furnace under an argon protective atmosphere. Before melting, a mechanical pump and a molecular pump were used to evacuate the sample to a vacuum of 5 × 10⁻⁵. -3 Pa, then fill with high-purity argon gas to 2×10⁻⁶. -2 Pa, melting begins. To ensure the uniformity of the ingot's chemical composition, each sample is turned over and melted four times with magnetic stirring. The melted button ingots are then remelted to prepare button-shaped samples, which are then cooled and removed. The test materials are mechanically polished to remove surface impurities, cleaned with acetone, and then sealed under a vacuum of 10. -1 In a quartz tube of Pa, homogenization annealing is performed at 1173 K for 24 h, followed by quenching in water to obtain high degree of order.

[0069] The fracture strength of the alloy prepared in Comparative Example 2 was significantly lower than that of the alloy in Example 1. The fracture strength of the alloy prepared by normal melting was about 850 MPa, while the fracture strength of the alloy in Example 1 was above 1500 MPa.

[0070] Figure 1 Mn prepared by powder forging and isothermal aging in Examples 1-3 of this invention 52.8 Ni 25 Ga 22 Ti 0.2 DSC curves of the alloy after aging treatment at different times. Figure 1It can be seen that with the extension of aging time, the phase transformation temperature of the experimental alloy gradually decreases during the phase transformation process, and the latent heat of phase transformation also decreases. The reason for the gradual decrease in phase transformation temperature is mainly due to the gradual decrease in Mn content during aging, as shown in Table 1. After aging for 10 minutes, the experimental alloy showed only one latent heat peak during both heating and cooling, indicating a one-step martensitic phase transformation. After aging for 30 minutes and 60 minutes, the alloy showed one exothermic peak during heating, corresponding to the reverse transformation from tetragonal martensite to cubic parent phase; during cooling, a multi-step martensitic phase transformation occurred, resulting in multiple endothermic peaks. The energy dispersive spectroscopy (EDS) analysis results shown in Table 1 indicate that after aging at 500℃ for 10–60 minutes, the alloy matrix composition is close to the positive Mn2NiGa composition, and a pre-martensitic phase transformation may occur during cooling. Furthermore, the Mn content at different aging times at 500℃... 52.8 Ni 25 Ga 22 Ti 0.2 The phase transformation temperature of the alloy decreased rapidly with increasing aging time, and a significant phase transformation thermal hysteresis occurred during the transformation process. After 30 minutes of aging, the martensitic transformation completion temperature of the experimental alloy was below 150K. Mn prepared by powder forging followed by isothermal aging... 52.8 Ni 25 Ga 22 Ti 0.2 The alloy exhibits a relatively large phase transformation thermal hysteresis (the phase transformation hysteresis of normally smelted alloys is generally around 20°C, while the phase transformation hysteresis of the alloy prepared in Example 1 of this invention is approximately 100°C), but it is still about 80°C higher than that of alloys of the same composition prepared by normal smelting. This is mainly because, at an aging temperature of 500°C and a relatively short aging time, the precipitated small, elongated γ-phase has a pinning effect on the phase boundaries, which is the main reason for the increased phase transformation thermal hysteresis. As the aging time increases, the size of the precipitated phases increases, and the matrix becomes discontinuous due to the segmentation of the precipitated phases, increasing the phase transformation shear resistance and leading to an increased phase transformation thermal hysteresis. Furthermore, the change in lattice parameters during the phase transformation caused by aging precipitation is also an important factor affecting the phase transformation thermal hysteresis. The competitive effect of these factors results in a decrease in the phase transformation thermal hysteresis of the alloy.

[0071] Table 1

[0072]

[0073] Figure 2 Mn prepared in Examples 1-3 and Comparative Examples 1-2 52.8 Ni 25 Ga 22 Ti 0.2 The room temperature microstructure morphology of the alloy. (b)-(d) show the Mn alloy prepared by powder forging followed by isothermal aging. 52.8 Ni 25 Ga 22 Ti0.2 The room temperature microstructure of the alloy after aging treatment at different times. (a) Mn prepared in Comparative Example 1 without isothermal aging treatment. 52.8 Ni 25 Ga 22 Ti 0.2 Alloys, such as Figure 1 As can be seen in (a), the alloy contains a large number of tiny pores, resulting in poor mechanical properties and limiting its practical applications; when the alloy is aged at 500°C for 10 minutes (Example 1), the precipitation of the second phase is not obvious (e.g. Figure 1 As shown in (b), its microstructure cannot be observed under low-magnification SEM. When the aging time is extended to 30 minutes (Example 2), as... Figure 1 As shown in (c), fine strip-shaped precipitates can be clearly observed at both grain boundaries and within grains, with the precipitates being more abundant at grain boundaries than within grains. Extending the aging time to 60 minutes (Example 3) revealed obvious cracks at the alloy grain boundaries (e.g., Figure 1 (As shown in (d)), this may be caused by internal stress. Mn prepared through normal melting (Comparative Example 2) 52.8 Ni 25 Ga 22 Ti 0.2 The room temperature microstructure morphology of the alloy (e.g.) Figure 1 As shown in (e), numerous micrometer-sized pores were observed on the alloy surface, leading to a significant reduction in the alloy's mechanical properties. Therefore, for Mn... 52.8 Ni 25 Ga 22 Ti 0.2 The stress-strain curves and hardness of the alloy were observed by testing the effect of aging time.

[0074] Figure 3 Examples 1-3 show the stress-strain curves (a) and adiabatic temperature change curves (b) of the hyperelastic test after aging treatment for different times. Figure 3 As can be seen in (a), the strength of the alloy is about 200 MPa higher when the aging time is 10 minutes than when it is aged for 60 minutes. This is also due to the precipitated γ phase. At the beginning of aging, the precipitated phase is small and dispersed, which mainly plays a strengthening role in the alloy. However, as the aging time gradually increases, the precipitated phase gradually coarsens, resulting in a decrease in the strength of the alloy. Figure 3 Mn prepared by powder forging and isothermal aging (b) 52.8 Ni 25 Ga 22 Ti 0.2 The adiabatic temperature change curves of the alloy after aging treatment for different times. Above A... f(Austenitic phase transformation termination temperature) At a temperature of 10℃, with a yield of 2.8 × 10⁻⁶ -4 Loading speed and 2.8×10 -2 Direct measurement with a thermocouple under unloading rate conditions revealed that when the aging time was 10 minutes, the adiabatic temperature of the alloy became 4.2K; when the aging time was 30 minutes, the adiabatic temperature of the alloy became 4.0K; and when the aging time was 60 minutes, the adiabatic temperature of the alloy became 1.9K. This may be due to the precipitation of the γ phase, which does not participate in the martensitic phase transformation, during the aging process.

[0075] Figure 4 Mn prepared by powder forging and isothermal aging in Examples 1-3 52.8 Ni 25 Ga 22 Ti 0.2 The relationship curves between the microhardness of the alloy and the aging time after aging treatment for different times are shown in the figure. Figure 4 It can be seen that the alloy hardening curve does not show a clear hardening peak, and the microhardness of the alloy decreases monotonically with the extension of aging time. After aging at 500℃ for 10–60 minutes, the microhardness of the tested alloy decreases rapidly with the extension of aging time. Mn 52.8 Ni 25 Ga 22 Ti 0.2 The variation of the alloy's microhardness with aging time is closely related to the microstructural changes during the aging process. During high-temperature annealing and water quenching, a large number of thermal vacancies are formed in the alloy. These vacancies, along with the fine, dispersed precipitates formed during aging at lower temperatures, significantly strengthen the matrix, increasing the hardness of the alloy matrix. Analysis shows that at an aging temperature of 500℃, atomic diffusion capability remains constant. As the aging time increases, thermally formed vacancies are continuously removed, thus partially weakening the strengthening effect on the alloy matrix. Meanwhile, the precipitates grow slowly under diffusion control, with a negligible increase in quantity, and their volume fraction approaches equilibrium. The alloy enters the over-aging state very quickly. Therefore, the longer the aging time, the lower the microhardness. Furthermore, the precipitates are ductile phases relative to the matrix, reducing their strengthening effect on the second phase of the matrix, thus decreasing the hardness.

[0076] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A highly elastic thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 A method for preparing magnetic shape memory alloys, characterized in that, Includes the following steps: A mixture is obtained by uniformly mixing four metallic raw materials: Ni, Mn, Ga, and Ti. The mixture was subjected to powder forging and isothermal aging treatment in sequence to obtain the high elasticity thermal effect Mn. 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic shape memory alloy; The powder forging process includes the following steps: The mixture was added to anhydrous ethanol, placed in a vacuum ball mill jar, and then subjected to ball milling, pressing, sintering, forging and homogenization heat treatment in sequence. The conditions during the pressing process are: applying a pressure of 30MPa-60MPa during the pressing process; The conditions during the sintering process are: sintering at 800℃ for 20 minutes; The conditions during the forging process are as follows: the forging force applied in one direction is 20-40 MPa, the initial forging temperature is 800℃, and the final forging temperature is 600℃. The conditions during the homogenization heat treatment process are: holding at a heat treatment temperature of 900°C for 12 hours. The isothermal aging process involves holding the temperature at 500℃ for 10-30 minutes.

2. The high-elasticity thermal effect Mn according to claim 1 52.8 Ni 25 Ga 22 Ti 0.2 A method for preparing magnetic shape memory alloys, characterized in that, The four metal raw materials, Ni, Mn, Ga and Ti, are all pure metal powders with a purity of 95.95%; the powder diameter is 5-30 μm.

3. The high elasticity thermal effect Mn according to claim 1 52.8 Ni 25 Ga 22 Ti 0.2 A method for preparing magnetic shape memory alloys, characterized in that, The isothermal aging process is as follows: heat treatment at 500℃ for 10 minutes.

4. A high-elasticity thermal effect Mn according to claim 1 52.8 Ni 25 Ga 22 Ti 0.2 A method for preparing magnetic shape memory alloys, characterized in that, The ball-to-material ratio in the vacuum ball mill jar is 3:

1.

5. A high-elasticity thermal effect Mn according to claim 1 52.8 Ni 25 Ga 22 Ti 0.2 A method for preparing magnetic shape memory alloys, characterized in that, The ball milling process includes: First, ball mill at 200-500 rpm for 10-15 hours, then ball mill at 800-1000 rpm for 1-2 hours.

6. A high-elasticity thermal effect Mn according to claim 1 52.8 Ni 25 Ga 22 Ti 0.2 A method for preparing magnetic shape memory alloys, characterized in that, The preparation method further includes ice-water quenching after the isothermal aging heat treatment.

7. A highly elastic thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic memory alloy, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A high-elasticity thermal effect Mn according to claim 7 52.8 Ni 25 Ga 22 Ti 0.2 Magnetic memory alloy, characterized in that, The high elastic thermal effect Mn 52.8 Ni 25 Ga 22 Ti 0.2 The elastothermal effect of magnetic shape memory alloys is 4.0-4.2K.

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