A deep-temperature copper-aluminum-manganese shape memory alloy, its preparation method and application

Abstract

This invention relates to a deep-temperature copper-aluminum-manganese shape memory alloy, its preparation method, and its applications. The method uses Cu, Al, and Mn as main raw materials, supplemented with one or more trace alloying elements Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni, and Cr. These are mixed according to chemical dosage ratios, placed in a crucible within a vacuum induction furnace, evacuated, melted, and then subjected to cyclic annealing in a heat treatment furnace. The cooled product is then forged and stress-relief annealed to obtain the alloy. The alloy prepared by this method has a wide compositional range and broad preparation conditions. By adjusting the alloy composition and subsequent heat treatment, cold and hot working processes, different grain sizes and shape memory properties can be obtained. The alloy has a polycrystalline microstructure, a phase transformation temperature as low as approximately 100K, and a deformation rate as high as 20%. It has advantages such as convenient preparation, simple process, and stable performance, and is widely applicable to applications such as low-temperature automatic control structures and low-temperature throttling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of functional metals and shape memory alloy materials, and particularly relates to a deep low temperature copper-aluminum-manganese shape memory alloy, a preparation method and application. BACKGROUND

[0002] The copper-aluminum-manganese shape memory alloy is an intelligent functional material integrating sensing and driving functions, and has many advantages such as excellent shape memory effect, super-elasticity, corrosion resistance, economy and practicality, temperature sensitivity and the like. At present, it has been widely applied to many fields such as mechanical manufacturing, medical devices, electronic communication, temperature sensors, aerospace, civil construction and daily life. The shape memory effect temperature of ordinary copper-based shape memory alloy is generally in the range of 173K-473K [Castillo C L D, et al., Scipta Mater, 1987.]. However, in some deep low temperature application fields such as moon exploration, infrared detection, low temperature sensing and the like, the phase transition point temperature needs to be lower. Theoretically, the increase of aluminum and manganese elements can significantly reduce the shape memory effect temperature (such as the martensite phase transition starting temperature, Ms point) of the alloy. However, in actual production and application, the Ms point of the copper-aluminum-manganese alloy is very sensitive to the composition of aluminum and manganese. The change of 1% of aluminum or manganese can cause the change of tens of degrees of temperature, and the copper-aluminum-manganese alloy has problems such as great brittleness, poor processability, easy occurrence of intergranular brittle fracture, low cycle life and the like, which seriously restricts its applicable range, especially the application in low temperature field. Existing researches show that the root of the great brittleness of the polycrystalline copper-aluminum-manganese shape memory alloy lies in: 1) the elastic anisotropy factor of the alloy is too large; 2) the martensite phase transition strain in the alloy has strong orientation dependence. The ordinary polycrystal with random grain orientation is not coordinated in the process of phase transition and deformation between grains, and large stress concentration is easily generated at the grain boundary, thereby causing the grain boundary cracking. For this reason, Omori et al. [Omori T., et al., Science, 2013.] proposed that the copper-aluminum-manganese single crystal alloy is prepared by the process of continuous tensile treatment + heat treatment (i.e. tensile heat cycle treatment) to induce abnormal grain growth. However, the tensile heat cycle treatment process is complex, difficult to prepare and high in cost. Moreover, the single crystal copper-aluminum-manganese alloy has too low deformation amount due to the blocked martensite coordinated deformation. Therefore, it is of great significance to develop a deep low temperature polycrystalline copper-aluminum-manganese shape memory alloy with phase transition point temperature <173K and large and stable deformation amount for broadening the application of copper-based shape memory alloy, especially the practical application in low temperature field. SUMMARY

[0003] In order to overcome the above problems existing in the prior art, the present application provides a deep low temperature copper-aluminum-manganese shape memory alloy, a preparation method and application, which are used to solve the above problems existing in the prior art.

[0004] A preparation method of a deep cryogenic copper-aluminum-manganese shape memory alloy, comprising the following steps:

[0005] S1. Selecting Cu, Al and Mn as main raw materials, supplemented by one or more of trace alloying elements Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni, Cr, mixing and then placing in a vacuum induction furnace crucible, vacuumizing and smelting to obtain an ingot;

[0006] S2. Placing the ingot into a heat treatment furnace for cyclic annealing treatment to obtain an annealed product;

[0007] S3. Forging the annealed product to refine the grains, heating to 720-740 DEG C for a period of time, and then opening the forging, and the final forging temperature is not lower than 680 DEG C;

[0008] S4. Placing the product after forging into a heat treatment furnace for stress relief annealing to obtain a deep cryogenic copper-aluminum-manganese shape memory alloy.

[0009] According to the aspect and any possible implementation manner as described above, an implementation manner is further provided, and the S2 specifically comprises: firstly, increasing the temperature of the treatment furnace from room temperature to 400-650 DEG C in the alpha + beta two-phase region, and maintaining for a first time period; secondly, increasing the temperature to 700-800 DEG C in the beta single-phase region, and maintaining for a second time period; thirdly, decreasing the temperature to 400-650 DEG C in the alpha + beta two-phase region, and maintaining for a third time period; fourthly, increasing the temperature to 700-800 DEG C in the beta single-phase region, and maintaining for a fourth time period, and cooling to obtain a cooled product, i.e., the annealed product.

[0010] According to the aspect and any possible implementation manner as described above, an implementation manner is further provided, and the aspect further comprises S5. Processing the deep cryogenic copper-aluminum-manganese shape memory alloy material obtained in S4 into a sample, and measuring the metallographic structure, phase transition point and deformation amount.

[0011] According to the aspect and any possible implementation manner as described above, an implementation manner is further provided, and the first time period, the second time period and the fourth time period are all 20-120 min; and the third time period is 30-180 min.

[0012] The application further provides a deep cryogenic copper-aluminum-manganese shape memory alloy, which is obtained by using the preparation method.

[0013] According to the aspect and any possible implementation manner as described above, an implementation manner is further provided, and the deep cryogenic copper-aluminum-manganese shape memory alloy has a component expression of Cu a Al b Mn c M dM is one or more combinations of Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni, and Cr, with a mass percentage of 60%≤a≤86%, 7%≤b≤20%, 7%≤c≤20%, 0%≤d≤5%, and a+b+c+d=100%.

[0014] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the deep cryogenic copper-aluminum-manganese shape memory alloy is polycrystalline and has a grain size ≤500um.

[0015] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the martensitic phase transformation temperature of the deep cryogenic copper-aluminum-manganese shape memory alloy is 77K to 150K.

[0016] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the low-temperature deformation of the deep cryogenic copper-aluminum-manganese shape memory alloy is up to 20%.

[0017] This invention also provides an application of deep-temperature copper-aluminum-manganese shape memory alloy in a low-temperature throttling refrigerator.

[0018] Beneficial effects of the present invention

[0019] The present invention discloses a method for preparing a deep-low temperature copper-aluminum-manganese shape memory alloy. The method involves selecting Cu, Al, and Mn as main raw materials, supplemented with one or more trace alloying elements Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni, and Cr. After mixing, the mixture is placed in a crucible within a vacuum induction furnace, evacuated, melted, and then subjected to cyclic annealing in a heat treatment furnace. The cooled product is then forged and stress-relief annealed to obtain the deep-low temperature copper-aluminum-manganese shape memory alloy. This invention has the following advantages:

[0020] (1) The deep low temperature copper-aluminum-manganese shape memory alloy provided by the present invention has a large composition range and a wide range of preparation conditions. For example, aluminum and manganese can be controlled within a large range. The preparation method is simpler and more economical than the "stretching + thermal cycling treatment" method, and the temperature range in the method is also wider.

[0021] (2) The method of the present invention controls and obtains different grain sizes and memory deformation properties by adjusting the alloy composition and subsequent heat treatment, cold and hot working and other technical means.

[0022] (3) The deep low temperature copper-aluminum-manganese shape memory alloy prepared by the present invention has a polycrystalline microstructure and has the advantages of convenient preparation, simple process and stable performance.

[0023] (4) The copper-aluminum-manganese alloy prepared by the present invention has excellent low-temperature shape memory effect and a phase transformation temperature of 100K to 120K, which makes up for the shortcomings of low-temperature application of copper-based alloys.

[0024] (5) The copper-aluminum-manganese alloy prepared by the present invention has both low-temperature shape memory effect and low-temperature superelasticity, and can be widely used in low-temperature automatic control structures and low-temperature throttling applications. Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of the present invention;

[0026] Figure 2 The microstructure and composition analysis diagram of the low-temperature copper-aluminum-manganese alloy in this embodiment of the invention are shown.

[0027] Figure 3 This is the low-temperature deformation curve of the deep-temperature copper-aluminum-manganese alloy sample in an embodiment of the present invention. Detailed Implementation

[0028] To better understand the technical solution of this invention, the content of this invention includes, but is not limited to, the specific embodiments described below. Similar technologies and methods should be considered within the scope of protection of this invention. To make the technical problems to be solved, the technical solutions, and advantages of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments.

[0029] It should be understood that the embodiments described in this invention are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0030] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0031] like Figure 1 As shown, a method for preparing a deep-low temperature copper-aluminum-manganese shape memory alloy according to the present invention includes the following steps:

[0032] S1. Select Cu, Al and Mn as the main raw materials, supplemented with one or more trace alloying elements Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni and Cr, according to the chemical dosage ratio, place them in a crucible in a vacuum induction furnace, evacuate the vacuum, melt and obtain an ingot.

[0033] S2. The ingot is placed in a heat treatment furnace for cyclic annealing. First, the furnace temperature is raised from room temperature to 400-650°C in the α+β two-phase region and held for a first time period. Then, the temperature is raised to 700-800°C in the β single-phase region and held for a second time period. Then, the temperature is lowered to 400-650°C in the α+β two-phase region and held for a third time period. Then, the temperature is raised to 700-800°C in the β single-phase region and held for a fourth time period. The cooled product is obtained.

[0034] S3. Forge the cooled product to refine the grains, heat it to 720-740℃ and hold it for a period of time before forging, and finally forge it at a temperature not lower than 680℃.

[0035] S4. The product obtained after forging is placed in a heat treatment furnace for stress-relief annealing to obtain a deep low temperature copper-aluminum-manganese shape memory alloy.

[0036] Specifically, the preparation process of the present invention is as follows:

[0037] The aforementioned low-temperature copper-aluminum-manganese shape memory alloy is prepared using the following steps:

[0038] (1). Select Cu, Al and Mn as the main raw materials, supplemented with one or more trace alloying elements such as Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni, Cr, etc., according to the chemical dosage ratio, place them in a crucible of a vacuum induction furnace, evacuate the vacuum, melt and obtain an ingot. In this step, the composition range of Al and Mn is relatively wide, and there is a relatively wide range of proportions to choose from.

[0039] (2) The ingot is placed in a heat treatment furnace for cyclic annealing. First, the temperature is raised from room temperature to the (α+β) two-phase region of about 400-650℃ and held for 20-120 min. Then, the temperature is raised to the β single-phase region of about 700-800℃ at a rate of 1-20℃ / min and held for 20-120 min. Then, the temperature is lowered to the (α+β) two-phase region of about 400-650℃ at a rate of 1-20℃ / min and held for 30-180 min. Then, the temperature is raised to the β single-phase region of about 700-800℃ at a rate of 1-20℃ / min and held for 20-120 min. Finally, the ingot is cooled. The β phase is a disordered BCC structure, i.e., body-centered cubic, while the α phase is a primary solid solution of Cu with an FCC structure, i.e., face-centered cubic. This step directly adopts cyclic annealing, making the method simpler and more economical, and the overall temperature range is also relatively wide. By adjusting the ratio of the α and β phases, the martensitic phase transformation can be facilitated.

[0040] (3) The annealed ingot, i.e. the cooled ingot, is forged on a forging machine to refine the grains. The parameters are: 680℃ for 2 hours, then heated to 720-740℃ for 20 minutes before forging, and the final forging temperature is not lower than 680℃.

[0041] (4) The forged material is placed in a heat treatment furnace for stress relief annealing at 300-500℃ for 0.5-1h to obtain a deep low temperature copper-aluminum-manganese shape memory alloy material.

[0042] (5) The above-mentioned cryogenic copper-aluminum-manganese shape memory alloy was processed into samples, and its metallographic properties, phase transformation points, and deformation were measured. The measurements showed that the cryogenic copper-aluminum-manganese shape memory alloy of this invention has a low-temperature martensitic phase transformation temperature of 77–150 K, a deformation as high as 20%, and a polycrystalline grain size of less than 500 μm. Through the above preparation method, a shape memory alloy with cryogenic characteristics and high deformation (low brittleness) was prepared. This invention, through the control of composition and process, refines the grain size and solves the problems of high brittleness, poor processing performance, easy intergranular fracture, and low cycle life inherent in copper-aluminum-manganese alloys.

[0043] Preferably, the deep-low temperature copper-aluminum-manganese shape memory alloy prepared by the method of the present invention is a polycrystalline material with a grain size ≤500um, a martensitic phase transformation temperature (Ms point) between 77K and 150K, a maximum low-temperature deformation of up to 20%, and its low-temperature deformation is relatively stable after multiple high and low temperature cycles, with a maximum deformation deviation of less than 10%. For example, after 150 high and low temperature cycles, the deformation of the alloy does not change much, that is, the deformation is relatively stable.

[0044] Example 1

[0045] A deep-temperature copper-aluminum-manganese alloy has the following composition: Cu, 66.3 wt.%; Al, 27.3 wt.%; Mn, 6.4 wt.%. The alloy's microstructure is as follows: Figure 2 As shown in Table 1, the phase transition temperature is approximately 100K. Other properties are also shown in Table 1, indicating that this alloy is suitable for cryogenic applications, especially for cryogenic intelligent throttling refrigerators.

[0046] Table 1

[0047]

[0048] The performance parameters in Table 1 are explained as follows:

[0049] Ms point is the temperature at which the martensitic phase transformation of shape memory alloys begins, and it is also the low-temperature phase transformation point of the alloy.

[0050] Shape memory performance, as demonstrated by a copper-aluminum-manganese shape memory alloy used in cryogenic throttling devices.

[0051] The low-temperature deformation rate of the gold sample is used as an indicator. When the temperature is below the Ms point, the alloy sample shrinks. When the temperature rises back to room temperature, the sample automatically stretches back to its original position. The magnitude of the sample deformation rate represents the low-temperature shape memory performance of the alloy.

[0052] The grain size is the size of the grains observed by metallography, and the alloy components are the various elements that make up the alloy. Different serial numbers represent different compositions of copper-aluminum-manganese shape memory alloys. Among them, the alloys in serial numbers 5-7 do not include Fe. The grain size, Ms point and shape memory function (i.e. sample deformation rate) of the alloys are all excellent.

[0053] Example 2

[0054] A deep-temperature copper-aluminum-manganese alloy has the following composition: Cu, 78 wt.%; Al, 12 wt.%; Mn, 9.8 wt.%; Be, 0.2 wt.%. The phase transformation temperature is approximately 108 K, and the grain size is ≤300 μm. Other properties are shown in Table 1. Compared with the reference example, the low-temperature deformation rate is significantly improved. The low-temperature deformation is stable after multiple high and low temperature cycles, indicating that the alloy is suitable for low-temperature applications, especially for low-temperature intelligent throttling refrigerators.

[0055] Example 3

[0056] A cryogenic copper-aluminum-manganese alloy has the following composition: Cu, 78 wt.%; Al, 12 wt.%; Mn, 9.8 wt.%; Be, 0.3 wt.%; Fe, 0.2 wt.%, with a grain size ≤500 μm. Other properties are shown in Table 1. Figure 3 As shown, the shrinkage is significantly increased, reaching up to 20%, indicating that this alloy is suitable for low-temperature applications, especially for low-temperature intelligent throttling refrigerators. Figure 3 The horizontal axis represents time, and the vertical axis represents shrinkage rate. Three samples are used for comparison in the figure.

[0057] This invention also provides a low-temperature copper-aluminum-manganese shape memory alloy, which is obtained by the aforementioned preparation method, wherein the composition expression of the low-temperature copper-aluminum-manganese shape memory alloy is Cu a Al b Mn c M d M is one or more combinations of Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni, and Cr, with a mass percentage of 60%≤a≤86%, 7%≤b≤20%, 7%≤c≤20%, 0%≤d≤5%, and a+b+c+d=100%.

[0058] Preferably, when a = 80.8, b = 11, c = 9, d = 0.2, and M = Be, the composition expression of the copper-aluminum-manganese shape memory alloy is Cu. 80.8 Al 11 Mn9Be 0.2 .

[0059] Preferably, the deep-low temperature copper-aluminum-manganese shape memory alloy is polycrystalline with a grain size ≤500µm. The martensitic phase transformation has a strong orientation dependence, and the grain size is appropriate, avoiding the problem of low strain and high brittleness caused by single orientation due to excessively large grains.

[0060] Preferably, the martensitic phase transformation temperature of the deep low temperature copper-aluminum-manganese shape memory alloy is 77K to 150K, and more preferably 100K to 120K.

[0061] Preferably, the cryogenic copper-aluminum-manganese shape memory alloy has a maximum cryogenic deformation of 20%, which means it has a high deformation capacity and can be opened and closed more effectively in cryogenic refrigeration applications, thus improving refrigeration and throttling effects.

[0062] This invention also provides an application of a deep-temperature copper-aluminum-manganese shape memory alloy in a cryogenic throttling refrigerator. Cryogenic throttling refrigerators require a low-temperature sensing smart switch with a temperature range of approximately 110K. Therefore, the alloy prepared according to the method of this invention has a suitable low-temperature phase transition point range. Furthermore, the alloy prepared by the method of this invention exhibits a deformation of up to 20%. Therefore, using the alloy of this invention as the smart switch in a cryogenic throttling refrigerator results in a high degree of opening and closing and relatively stable operation. Thus, the alloy of this invention is particularly suitable for cryogenic throttling, especially for use in smart throttling switches.

[0063] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for preparing a cryogenic copper-aluminum-manganese shape memory alloy, characterized in that, S1. selecting Cu, Al and Mn as main raw materials, and optionally adding one or more of trace alloying elements Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni and Cr, mixing and placing in a vacuum induction furnace crucible, vacuumizing and smelting to obtain an ingot; S2. placing the ingot in a heat treatment furnace for cyclic annealing treatment, specifically: first increasing from room temperature to 400-650 ℃ in the (α+β) two-phase region, holding for 20-120 min, then increasing at a rate of 1-20 ℃ / min to 700-800 ℃ in the β single-phase region, holding for 20-120 min, then decreasing at a rate of 1-20 ℃ / min to 400-650 ℃ in the (α+β) two-phase region, holding for 30-180 min, then increasing at a rate of 1-20 ℃ / min to 700-800 ℃ in the β single-phase region, holding for 20-120 min, and cooling to obtain a cooled product, i.e. an annealed product, wherein the β phase is disordered BCC structure, i.e. body-centered cubic, and the α phase is primary solid solution of FCC structure Cu, i.e. face-centered cubic; S3. performing forging on the annealed product to refine the grains, heating to 720-740 ℃, holding for a period of time, and then forging, and the final forging temperature is not lower than 680 ℃; S4. placing the product after forging in a heat treatment furnace for stress relief annealing to obtain a cryogenic copper-aluminum-manganese shape memory alloy. Further comprising S5. processing the cryogenic copper-aluminum-manganese shape memory alloy material obtained in S4 into a sample, and measuring the metallographic structure, phase transition point and deformation amount. The alloy is obtained by the method of any one of claims 1-2. The cryogenic copper-aluminum-manganese shape memory alloy is polycrystalline and the grain size is ≤500 μm. The martensitic phase transition temperature of the cryogenic copper-aluminum-manganese shape memory alloy is 77K-150K.

2. The method of claim 1, wherein the cryogenic Cu-Al-Mn shape memory alloy is prepared by the steps of: preparing a Cu-Al-Mn alloy by melting and casting; and heat-treating the Cu-Al-Mn alloy at a temperature of 400 to 600°C for 1 to 10 hours. The maximum low-temperature deformation amount of the cryogenic copper-aluminum-manganese shape memory alloy is 20%.

3. A cryogenic copper-aluminum-manganese shape memory alloy characterized by, 8. Use of the cryogenic copper-aluminum-manganese shape memory alloy of any one of claims 3-7 in a low-temperature throttling refrigerator.

4. The cryogenic Cu-Al-Mn shape memory alloy according to claim 3, characterized in that The cryogenic copper-aluminum-manganese shape memory alloy composition expression is Cu a Al b Mn c M d , wherein M is one or more combinations of Be, Fe, C, Ti, Zr, V, Ta, Nb, W, Mo, Ni, Cr, mass percentage is 60%≤a≤86%, 7%≤b≤20%, 7%≤c≤20%, 0%≤d≤5%, and a+b+c+d=100%.

5. The cryogenic Cu-Al-Mn shape memory alloy according to claim 3, characterized in that, ​ 6. The cryogenic Cu-Al-Mn shape memory alloy of claim 3, wherein ​ 7. The cryogenic Cu-Al-Mn shape memory alloy of claim 3, wherein ​ ​

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