Cu-Al-Mn shape memory alloy and preparation method and application thereof

Abstract

The invention provides a Cu-Al-Mn shape memory alloy and a preparation method and application thereof.The method comprises the following steps that alloy raw materials are smelted, and a Cu-Al-Mn alloy ingot casting blank is obtained; the Cu-Al-Mn alloy cast ingot blank is subjected to homogenization treatment and then sequentially subjected to hot forging, hot rolling, hot drawing and cold drawing, and a Cu-Al-Mn alloy profile is obtained; and the Cu-Al-Mn alloy profile is sequentially subjected to circulating heating and cooling solution treatment and aging treatment, and the Cu-Al-Mn shape memory alloy is obtained. The performance of the Cu-Al-Mn shape memory alloy prepared through the method can reach 90% of that of common commercial Ni-Ti-based shape memory alloy, and the production cost can be as low as 1 / 10 of the selling price of domestic commercial Ni-Ti-based shape memory alloy at present.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, and in particular to a Cu-Al-Mn shape memory alloy, its preparation method, and its applications. Background Technology

[0002] Shape memory alloys (SMAs) possess outstanding advantages such as lightweight, high strength, corrosion resistance, and fatigue resistance, while also exhibiting two other properties: superelasticity and shape memory effect. Superelasticity refers to the ability to undergo significant elastic deformation under external force and return to its original shape after the force is removed. The shape memory effect refers to the ability of an alloy, after being shaped at a low temperature, to automatically return to its original shape when heated to a certain temperature. In civil engineering, the superelastic properties of SMAs are commonly used to provide structures with post-vibration self-resetting and self-repair capabilities, thereby effectively reducing the degree of damage to building structures and the difficulty and cost of repair.

[0003] Currently, research on vibration reduction and toughening technologies for engineering structures based on hyperelastic SMA materials is relatively mature both domestically and internationally. However, the promotion of related products and structural systems remains challenging, primarily because the commonly used SMA material is nickel-titanium SMA alloy, which is relatively expensive. The production cost of copper-aluminum-manganese SMA alloys can be as low as 1 / 10 that of nickel-titanium SMA alloys, while achieving 90% of their performance, meeting the needs of most engineering applications. However, domestic research on copper-aluminum-manganese SMA is still limited, and related products face significant technological barriers and import monopolies.

[0004] Therefore, how to prepare a low-cost Cu-Al-Mn shape memory alloy with superelastic self-resetting capability to solve the problem of high cost of existing nickel-titanium-based shape memory alloys is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a Cu-Al-Mn shape memory alloy, its preparation method, and its application. The method provided by this invention can obtain a Cu-Al-Mn shape memory alloy with low cost and excellent superelastic self-resetting ability.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing Cu-Al-Mn shape memory alloy, comprising the following steps: The alloy raw materials are smelted to obtain Cu-Al-Mn alloy ingot billets; the composition of the Cu-Al-Mn alloy ingot billets, by atomic percentage, includes: Cu 70.1~72.1%; Al 16.1~18.0%; the remainder is Mn; The Cu-Al-Mn alloy ingot billet is homogenized to obtain Cu-Al-Mn alloy forging billet. The Cu-Al-Mn alloy forging billet is sequentially subjected to hot forging, hot rolling, hot drawing and cold drawing to obtain Cu-Al-Mn alloy profiles; The Cu-Al-Mn alloy profile is subjected to cyclic heating and cooling solution treatment and aging treatment in sequence to obtain Cu-Al-Mn shape memory alloy; the upper plateau temperature of the cyclic heating and cooling solution treatment is 800~950℃, and the lower plateau temperature of the cyclic heating and cooling solution treatment is 400~600℃.

[0007] Preferably, the vacuum degree of the homogenization process is ≤1×10⁻⁶. -2 Pa; the homogenization treatment temperature is 700~850℃; the homogenization treatment holding time is 6~12h.

[0008] Preferably, the hot forging temperature is 800~850℃; the hot forging ratio is 3~5.

[0009] Preferably, the hot rolling temperature is 800~850℃.

[0010] Preferably, the hot drawing temperature is 700~800℃; the total deformation of the hot drawing is 10~20%.

[0011] Preferably, when the deformation of the cold drawing pass reaches 20-30%, intermediate annealing is performed, and the temperature of the intermediate annealing is 600-750℃; the holding time of the intermediate annealing is 0.5h-1.5h.

[0012] Preferably, the cyclic heating and cooling solution treatment method is to perform a cyclic heating and cooling solution treatment, which includes: heating the Cu-Al-Mn alloy profile to an upper plateau temperature at a first heating rate, and holding it at the upper plateau temperature for a first time; then cooling it to a lower plateau temperature at a first cooling rate, and holding it at the lower plateau temperature for a second time; then heating it to the upper plateau temperature at a second heating rate, and holding it at the upper plateau temperature for a third time, and then cooling it to room temperature.

[0013] Preferably, the aging treatment temperature is 200~400℃; the aging treatment time is 20min~60min.

[0014] The present invention also provides Cu-Al-Mn shape memory alloy prepared by the preparation method described in the above technical solution.

[0015] This invention also provides the application of the Cu-Al-Mn shape memory alloy described in the above technical solution in...

[0016] This invention provides a method for preparing Cu-Al-Mn shape memory alloy, comprising the following steps: melting alloy raw materials to obtain Cu-Al-Mn alloy ingot billets; the composition of the Cu-Al-Mn alloy ingot billets, by atomic percentage, includes: Cu 70.1~72.1%; Al 16.1~18.0%; the remainder being Mn; homogenizing the Cu-Al-Mn alloy ingot billets to obtain Cu-Al-Mn alloy forging billets; sequentially hot-forging, hot-rolling, hot-drawing, and cold-drawing the Cu-Al-Mn alloy forging billets to obtain Cu-Al-Mn alloy profiles; sequentially subjecting the Cu-Al-Mn alloy profiles to cyclic heating and cooling solution treatment and aging treatment to obtain Cu-Al-Mn shape memory alloy; the upper plateau temperature of the cyclic heating and cooling solution treatment is 800~950℃, and the lower plateau temperature of the cyclic heating and cooling solution treatment is 400~600℃. This invention, through homogenization treatment, can eliminate or reduce chemical composition segregation and microstructure inhomogeneity generated during casting, thus laying the foundation for subsequent processing and ultimately achieving excellent shape memory properties. This invention enables the production of forged billets or bars through hot forging; rapid grain refinement and shaping through hot rolling; and the extraction of billets through die holes via hot drawing, achieving small-sized products while maintaining good plasticity. Cold drawing further refines the substructure, improves strength, and forms texture, allowing the martensitic variants of the alloy to exhibit preferred orientation during phase transformation, thereby enabling the alloy to exhibit better shape memory effects and superelasticity in specific directions. Through cyclic heating and cooling solution treatment, this invention can eliminate unstable and irreversible martensitic variants early on, leaving mainly reversible thermoelastic martensite, which makes the phase transformation path more stable during subsequent use and improves the cyclic stability of the shape memory effect. Finally, through aging treatment, this invention can improve strength and stability by controlling nanoscale precipitates. The results of the examples show that the Cu-Al-Mn shape memory alloy prepared by the method provided by the present invention can achieve about 90% of the performance of commonly used commercial Ni-Ti-based shape memory alloys, which is sufficient to meet the needs of most engineering applications; at the same time, its mass production cost can be as low as 1 / 10 of the current domestic commercial Ni-Ti-based shape memory alloy price. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the heating and cooling solution treatment in Embodiment 1 of the present invention; Figure 2 Tensile specimen images of Cu-Al-Mn shape memory alloy rods prepared in Examples 1-2 and Comparative Examples 1-2 of this invention; Figure 3Hysteresis curves of axial cyclic tensile stress-strain relationship of Cu-Al-Mn shape memory alloy rods prepared in Examples 1-2 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0018] This invention provides a method for preparing Cu-Al-Mn shape memory alloy, comprising the following steps: The alloy raw materials are smelted to obtain Cu-Al-Mn alloy ingot billets; the composition of the Cu-Al-Mn alloy ingot billets, by atomic percentage, includes: Cu 70.1~72.1%; Al 16.1~18.0%; the remainder is Mn; The Cu-Al-Mn alloy ingot billet is homogenized to obtain Cu-Al-Mn alloy forging billet. The Cu-Al-Mn alloy forging billet is sequentially subjected to hot forging, hot rolling, hot drawing and cold drawing to obtain Cu-Al-Mn alloy profiles; The Cu-Al-Mn alloy profile is subjected to cyclic heating and cooling solution treatment and aging treatment in sequence to obtain Cu-Al-Mn shape memory alloy; the upper plateau temperature of the cyclic heating and cooling solution treatment is 800~950℃, and the lower plateau temperature of the cyclic heating and cooling solution treatment is 400~600℃.

[0019] This invention involves melting alloy raw materials to obtain Cu-Al-Mn alloy ingot blanks.

[0020] In this invention, the composition of the Cu-Al-Mn alloy ingot billet, by atomic percentage, includes: Cu 70.1~72.1%; Al 16.1~18.0%; the remainder being Mn.

[0021] The Cu-Al-Mn alloy ingot blank provided by this invention comprises 70.1% to 72.1% Cu by atomic percentage. As one embodiment of this invention, the atomic percentage of Cu can be 70.1%, 70.2%, 70.3%, 70.4%, 70.5%, 71.2%, 71.3%, 71.4%, 71.5%, 71.6%, 71.7%, 71.8%, 71.9%, 72.0%, or 72.1%.

[0022] The Cu-Al-Mn alloy ingot blank provided by this invention comprises Al 16.1% to 18.0% by atomic percentage. As one embodiment of this invention, the atomic percentage of Al can be 16.1%, 16.2%, 16.3%, 16.4%, 16.5%, 16.6%, 16.7%, 17.1%, 17.2%, 17.3%, 17.4%, 17.5%, 17.6%, 17.7%, 17.8%, or 18.0%.

[0023] The composition of the Cu-Al-Mn alloy ingot blank provided by the present invention includes the balance Mn by atomic percentage.

[0024] In this invention, the alloy raw materials preferably include Cu, Al, and Mn. The preferred purity of the alloy raw materials is: Cu ≥ 99.95 wt%; Al ≥ 99.80 wt%; Mn ≥ 99.9 wt%. This invention uses high-purity alloy raw materials, which can reduce impurities in Cu-Al-Mn shape memory alloys.

[0025] In this invention, the melting is preferably vacuum melting, and the vacuum degree of the vacuum melting is preferably 0.45 × 10⁻⁶. -3 ~0.55×10 -3 Pa, more preferably 0.5 × 10 Pa -3 Pa. In this invention, the protective gas for vacuum melting is preferably argon. In this invention, the temperature for vacuum melting is preferably 1300~1450℃, more preferably 1350~1400℃. In this invention, the time for vacuum melting is preferably 20~50min, more preferably 30~40min. In an embodiment of this invention, the melting can be carried out in a medium-frequency vacuum induction furnace.

[0026] In this invention, the melt obtained from the smelting is preferably cooled to room temperature to obtain a Cu-Al-Mn alloy ingot billet. This invention does not impose any particular limitation on the cooling rate; any conventional cooling method may be used.

[0027] After obtaining the Cu-Al-Mn alloy ingot blank, the present invention performs homogenization treatment on the Cu-Al-Mn alloy ingot blank to obtain Cu-Al-Mn alloy forging blank.

[0028] In this invention, the vacuum degree of the homogenization process is preferably ≤1×10⁻⁶. -2 Pa. In this invention, the homogenization process is preferably carried out in a vacuum furnace. By controlling the vacuum level within the above-mentioned range, this invention can reduce the impurity content.

[0029] In this invention, the homogenization treatment temperature is preferably 700~850℃; the homogenization treatment holding time is preferably 6~12h. As one embodiment of this invention, the homogenization treatment temperature can be 700℃, 750℃, 800℃, or 850℃; the homogenization treatment holding time can be 6h, 7h, 8h, 9h, 10h, 11h, or 12h. This invention, through homogenization treatment, can eliminate or reduce chemical composition segregation and microstructure inhomogeneity generated during the casting process, thereby laying the foundation for subsequent processing and ultimately obtaining excellent shape memory properties.

[0030] After obtaining the Cu-Al-Mn alloy forging billet, the present invention sequentially performs hot forging, hot rolling, hot drawing and cold drawing on the Cu-Al-Mn alloy forging billet to obtain Cu-Al-Mn alloy profiles.

[0031] In this invention, the hot forging temperature is preferably 800~850℃; the forging ratio of hot forging is preferably 3~5. As one embodiment of this invention, the hot forging temperature can be 800℃, 810℃, 820℃, 830℃, 840℃ or 850℃.

[0032] In this invention, the hot rolling temperature is preferably 800~850℃. As one embodiment of this invention, the hot rolling temperature can be 800℃, 810℃, 820℃, 830℃, 840℃, or 850℃. This invention does not have a particular limitation on the hot rolling time, as long as the diameter of the alloy bar billet reaches the desired range.

[0033] In this invention, the diameter of the alloy bar billet obtained by hot forging and hot rolling is preferably 15~20mm.

[0034] In this invention, the preferred hot drawing temperature is 700-800℃. As one embodiment of this invention, the hot drawing temperature can be 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, or 800℃. This invention, through hot drawing, enables the deformation of the alloy billet to reach the desired range.

[0035] In this invention, the total deformation of the hot drawing is preferably 10-20%. As one embodiment of this invention, the total deformation of the hot drawing can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%. This invention does not specifically limit the number of hot drawing passes; it is sufficient to control the total deformation of the hot drawing within the above range.

[0036] This invention enables the cold drawing of Cu-Al-Mn alloy profiles to achieve the required diameter range. In an embodiment of this invention, the diameter of the Cu-Al-Mn alloy profile can be 8 mm.

[0037] In this invention, when the deformation amount in the cold drawing pass reaches 20-30%, more preferably 25-30%, intermediate annealing is performed. The temperature of the intermediate annealing is preferably 600-750℃, and the holding time of the intermediate annealing is preferably 0.5h-1.5h. As one embodiment of this invention, the temperature of the intermediate annealing can be 600℃, 650℃, 700℃, or 750℃. This invention, through intermediate annealing, can eliminate internal stress and obtain a uniform microstructure, providing a good foundation for subsequent heat treatment. In this invention, the deformation amount in each pass refers to the diameter reduction rate of each cold drawing.

[0038] After obtaining the Cu-Al-Mn alloy profile, the present invention subjectes the Cu-Al-Mn alloy profile to cyclic heating and cooling solution treatment and aging treatment in sequence to obtain Cu-Al-Mn shape memory alloy.

[0039] In this invention, the upper plateau temperature of the cyclic heating and cooling solution treatment is 800~950℃, and the lower plateau temperature is 400~600℃. As one embodiment of this invention, the upper plateau temperature of the cyclic heating and cooling solution treatment can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, or 950℃; the lower plateau temperature of the cyclic heating and cooling solution treatment can be 400℃, 420℃, 450℃, 480℃, 500℃, 520℃, 550℃, 580℃, or 600℃. The present invention performs cyclic heating and cooling solution treatment at the above-mentioned temperature, which can eliminate unstable and irreversible martensitic variants in the early stage, leaving mainly reversible thermoelastic martensite. This makes the phase transformation path more stable in subsequent use and improves the cyclic stability of the shape memory effect.

[0040] In this invention, the method of cyclic heating and cooling solution treatment is preferably performed in cycles according to the heating and cooling solution treatment method. The method of heating and cooling solution treatment preferably includes: heating the temperature of the Cu-Al-Mn alloy profile to an upper plateau temperature at a first heating rate, and holding it at the upper plateau temperature for a first time; then cooling it to a lower plateau temperature at a first cooling rate, and holding it at the lower plateau temperature for a second time; then heating it to the upper plateau temperature at a second heating rate, holding it at the upper plateau temperature for a third time, and then cooling it to room temperature.

[0041] In this invention, the first heating rate is preferably 10~20℃ / min. As one embodiment of this invention, the first heating rate can be 10℃ / min, 15℃ / min, or 20℃ / min.

[0042] In this invention, the temperature of the upper platform is 800~950℃.

[0043] In this invention, the first heat preservation time is preferably 15-30 minutes, more preferably 20-30 minutes.

[0044] In this invention, the first cooling rate is preferably 5~15℃ / min. As one embodiment of this invention, the first cooling rate can be 5℃ / min, 10℃ / min, or 15℃ / min.

[0045] In this invention, the temperature of the lower platform is 400~600℃.

[0046] In this invention, the second heat preservation time is preferably 15-30 min, more preferably 20-30 min.

[0047] In this invention, the second heating rate is preferably 10~20℃ / min. As one embodiment of this invention, the second heating rate can be 10℃ / min, 15℃ / min, or 20℃ / min.

[0048] In this invention, the second heat preservation time is preferably 15-30 min, more preferably 20-30 min.

[0049] In this invention, the cooling is preferably water quenching or oil quenching.

[0050] In this invention, the number of cycles is preferably 3 to 5. This invention enhances its superelastic self-resetting ability and heat treatment efficiency by employing cyclic heating and cooling aging treatment.

[0051] In this invention, the aging treatment temperature is preferably 200~400℃; the aging treatment time is 20min~60min. As one embodiment of this invention, the aging treatment temperature can be 200℃, 220℃, 250℃, 280℃, 300℃, 320℃, 350℃, 380℃, or 400℃; the aging treatment time can be 20min, 30min, 40min, 50min, or 60min. This invention, through aging treatment, can control nanoscale precipitates, thereby improving the strength and stability of Cu-Al-Mn shape memory alloys.

[0052] The present invention preferably involves water quenching the alloy after solution treatment to obtain a Cu-Al-Mn shape memory alloy.

[0053] The method provided by this invention controls the composition of each element and sequentially performs homogenization treatment, hot forging, hot rolling, hot drawing, cold drawing, cyclic heating and cooling solution treatment, and aging treatment on the obtained Cu-Al-Mn alloy ingot billet, which can obtain Cu-Al-Mn shape memory alloy with excellent strength, stiffness and superelastic self-resetting ability.

[0054] The present invention also provides Cu-Al-Mn shape memory alloy prepared by the preparation method described in the above technical solution.

[0055] This invention also provides the application of the Cu-Al-Mn shape memory alloy described above in marine concrete structures and island / town infrastructure construction.

[0056] This invention does not impose any special limitations on the application of the Cu-Al-Mn shape memory alloy in marine concrete structures and island / town infrastructure construction; conventional application methods for Cu-Al-Mn shape memory alloys can be used.

[0057] The Cu-Al-Mn shape memory alloy prepared by this invention has excellent properties of strength, stiffness and superelastic self-resetting ability, and can therefore be used in the above-mentioned fields to reduce construction costs.

[0058] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0059] Example 1 A method for preparing Cu-Al-Mn shape memory alloy, comprising the following steps: (1) Using 15 kg of Cu 70.8 Al 17.6 Mn 11.6 Based on the total weight of the alloy, according to the ratio of Cu content 70.8at%, Al content 17.6at%, and Mn content 11.6at%, copper with a purity of 99.95wt.%, aluminum with a purity of 99.80wt.%, and manganese with a purity of 99.9wt.% were weighed and mixed evenly to obtain the alloy raw material. The alloy raw material is placed in a medium-frequency vacuum induction furnace, and a vacuum is drawn to a vacuum degree of 0.5 × 10⁻⁶. -3Pa, argon gas was introduced for protection; the melting temperature was raised to 1380℃, refined for 20 minutes, and after cooling, approximately 15 kg of Cu-Al-Mn alloy ingot blank (Cu 70.8 Al1 7.6 Mn 11.6 Alloy forging billet).

[0060] (2) Place the Cu-Al-Mn alloy ingot blank into a vacuum furnace and evacuate it to a vacuum degree of 0.2 × 10⁻⁶. - 2 Pa, then homogenized by holding at 800℃ for 12 hours, followed by furnace cooling. After furnace removal, the surface oxide scale, defects, and risers are removed by machining to obtain Cu-Al-Mn alloy forging billet (Cu 70.8 Al1 7.6 Mn 11.6 Alloy forging billet).

[0061] (3) The Cu-Al-Mn alloy forging billet is heated to 800℃ and held for 5 hours. At this temperature, it is first hot-forged and then hot-rolled into an alloy bar billet with a diameter of 15mm. The alloy bar billet with a diameter of 15mm is then hot-drawn at a temperature of 700℃, with the deformation per pass controlled at 10~20%, until it is drawn to a diameter of 12mm. Then it is cold-drawn. During the cold drawing, an intermediate annealing treatment at 650℃ is required when the total deformation reaches 20~30%. Finally, it is processed into a Cu-Al-Mn alloy profile with a diameter of 8mm (Cu 70.8 Al 17. 6Mn 11.6 Shape memory alloy rods and profiles); (4) The Cu-Al-Mn alloy profile is subjected to cyclic heating and cooling solution treatment at an upper plateau temperature of 900℃ and a lower plateau temperature of 500℃, with the number of cycles being 3. A schematic diagram of the heating and cooling solution treatment is shown below. Figure 1 As shown, the specific method is as follows: The Cu-Al-Mn alloy profile is heated to 900℃ at a heating rate of 10℃ / min at room temperature and held for 20 min; then cooled to 500℃ at a cooling rate of 6℃ / min and held for 15 min; finally, heated to 900℃ at a heating rate of 10℃ / min and held for 30 min, and then water-quenched to room temperature; subsequently, it is aged at 250℃ for 30 min to obtain the Cu-Al-Mn shape memory alloy (Cu...). 70.8 Al 17.6 Mn 11.6 Shape memory alloy rod, designated as sample number 3).

[0062] Example 2 A method for preparing Cu-Al-Mn shape memory alloy, comprising the following steps: (1) to (3) are the same as in Example 1; (4) The Cu-Al-Mn alloy profile is subjected to cyclic heating and cooling solution treatment with an upper plateau temperature of 900℃ and a lower plateau temperature of 500℃. The number of cycles is 5. The heating and cooling solution treatment method is as follows: the Cu-Al-Mn alloy profile is heated to 900℃ at room temperature at a heating rate of 10℃ / min and held for 20min, then cooled to 500℃ at a cooling rate of 6℃ / min and held for 15min, then heated to 900℃ at a heating rate of 10℃ / min and held for 30min, and then water quenched to room temperature; then aged at 250℃ for 30min to obtain Cu-Al-Mn shape memory alloy (Cu 70.8 Al 17.6 Mn 11.6 Shape memory alloy rod, designated as sample number 4).

[0063] Comparative Example 1 A method for preparing Cu-Al-Mn shape memory alloy, comprising the following steps: (1) to (3) are the same as in Example 1; (4) The Cu-Al-Mn alloy profile was solution-treated at 900℃ for 20 hours and then quenched in water to room temperature; subsequently, it was aged at 250℃ for 30 minutes to obtain Cu-Al-Mn shape memory alloy (Cu 70.8 Al 17.6 Mn 11.6 Shape memory alloy rod, designated as sample number 1.

[0064] Comparative Example 2 A method for preparing Cu-Al-Mn shape memory alloy, comprising the following steps: (1) to (3) are the same as in Example 1; (4) The Cu-Al-Mn alloy profile was solution-treated at 900℃ for 40 h and then quenched in water to room temperature; subsequently, it was aged at 250℃ for 30 min to obtain Cu-Al-Mn shape memory alloy (Cu 70.8 Al 17.6 Mn 11.6 Shape memory alloy rod, designated as sample number 2).

[0065] Comparative Example 3 The commercially available Ni-Ti based shape memory alloy sample, designated as sample number 5, was sourced from Xi'an Siwei Intelligent Materials Co., Ltd.

[0066] Test case (1) The Cu-Al-Mn shape memory alloy rods No. 1, 2, 3, and 4 prepared in Examples 1-2 and Comparative Examples 1-2 were machined into the following shapes on a lathe according to the national standard "Metallic Materials - Tensile Testing - Part 1: Test at Room Temperature" (GB / T 228.1-2010). Figure 2 The tensile specimens shown were then subjected to axial cyclic tensile mechanical property tests to investigate the effects of different solution heat treatment methods on the heat treatment efficiency and superelastic self-resetting ability of Cu-Al-Mn shape memory alloys. Figure 2 In the image, (a) shows the tensile testing apparatus; and (b) shows the morphology of the tensile specimen.

[0067] Figure 3 The figures shown are the hysteresis curves of the axial cyclic tensile stress-strain relationship of Cu-Al-Mn shape memory alloy rods prepared in Examples 1-2 and Comparative Examples 1-2. Figure 3 As can be seen, compared with sample 1, sample 2 showed a decrease in peak intensity and a reduction in residual strain after unloading; this indicates that increasing the duration of the traditional isothermal solution treatment can enhance the superelastic self-resetting ability of Cu-Al-Mn shape memory alloy to some extent. However, the effect is not very significant; as the solution treatment time increased from 20h to 40h, the residual strain corresponding to a 6% tensile amplitude decreased from approximately 2.38% to 1.85%.

[0068] from Figure 3 It can also be seen that, compared with sample 2, sample 3 showed a slight decrease in peak intensity and a significant reduction in residual strain after unloading (from approximately 1.85% to 0.62%). This indicates that, compared with traditional isothermal solution treatment, the cyclic heating and cooling solution treatment method proposed in this invention can more effectively improve the hyperelastic self-resetting ability of Cu-Al-Mn shape memory alloys. Meanwhile, the total solution treatment time for sample 3 was only approximately 9.1 hours, a reduction of 77.3% compared to sample 2, meaning that the cyclic solution treatment method can also greatly improve the solution treatment efficiency of Cu-Al-Mn shape memory alloys.

[0069] from Figure 3 It can also be seen that, compared with sample 3, the peak strength of sample 4 decreased again, and the residual strain after unloading decreased again (from approximately 0.62% to 0.43%). This indicates that the superelastic self-resetting ability of the Cu-Al-Mn shape memory alloy is further enhanced with the increase of the number of heating and cooling cycles. However, at this point, the strength of the Cu-Al-Mn alloy is relatively low, and the improvement in self-resetting ability is not significant. When selecting the number of heating and cooling cycles, the strength, stiffness, and superelastic self-resetting ability of the Cu-Al-Mn shape memory alloy should be comprehensively considered.

[0070] (2) The Cu-Al-Mn shape memory alloy rods prepared in Examples 1-2 and Comparative Examples 1-2 and the commercial Ni-Ti-based shape memory alloy sample provided in Comparative Example 3 were tested respectively. The solution treatment time, residual strain corresponding to 6% tensile strain amplitude and mass production cost (or domestic selling price) are shown in Table 1.

[0071] Table 1 Comparison of solution treatment time and self-resetting ability of samples

[0072] As shown in Table 1, the superelastic self-resetting capability of the Cu-Al-Mn shape memory alloy prepared by this invention can approach or even exceed that of domestically commercialized Ni-Ti-based shape memory alloys, and its strength can reach 76-89% of that of commercially available Ni-Ti-based shape memory alloys, which is sufficient to meet the needs of most engineering applications. Furthermore, the mass production cost of the Cu-Al-Mn shape memory alloy prepared by this invention is only 9.4-10.4% of the selling price of domestically commercialized Ni-Ti-based shape memory alloys, significantly reducing costs.

[0073] The results above demonstrate that the Cu-Al-Mn shape memory alloy prepared by the method provided in this invention achieves approximately 90% of the performance of commonly used commercial Ni-Ti-based shape memory alloys, which is sufficient to meet the needs of most engineering applications. Its mass production cost can be as low as 1 / 10 of the current domestic price of commercial Ni-Ti-based shape memory alloys, making it highly suitable for industrial fields such as marine concrete structures and island / reef / urban infrastructure construction, where SMA biocompatibility is not required, the requirements for hyperelasticity are relatively low, and the demand for large quantities necessitates a significant reduction in material costs.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a Cu-Al-Mn shape memory alloy, characterized in that, Includes the following steps: The alloy raw materials are smelted to obtain Cu-Al-Mn alloy ingot billets; The Cu-Al-Mn alloy ingot blank comprises, by atomic percentage: Cu 70.1~72.1%; Al 16.1~18.0%; the remainder being Mn; The Cu-Al-Mn alloy ingot billet is homogenized to obtain Cu-Al-Mn alloy forging billet. The Cu-Al-Mn alloy forging billet is sequentially subjected to hot forging, hot rolling, hot drawing and cold drawing to obtain Cu-Al-Mn alloy profiles; The Cu-Al-Mn alloy profile was subjected to cyclic heating and cooling solution treatment and aging treatment in sequence to obtain Cu-Al-Mn shape memory alloy. The upper platform temperature of the cyclic heating and cooling solution treatment is 800~950℃, and the lower platform temperature of the cyclic heating and cooling solution treatment is 400~600℃.

2. The preparation method according to claim 1, characterized in that, The vacuum degree of the homogenization process is ≤1×10⁻⁶. - 2 Pa; the homogenization treatment temperature is 700~850℃; the homogenization treatment holding time is 6~12h.

3. The preparation method according to claim 1, characterized in that, The hot forging temperature is 800~850℃; the hot forging ratio is 3~5.

4. The preparation method according to claim 1, characterized in that, The hot rolling temperature is 800~850℃.

5. The preparation method according to claim 1, characterized in that, The hot drawing temperature is 700~800℃; the total deformation of the hot drawing is 10~20%.

6. The preparation method according to claim 1, characterized in that, When the deformation of the cold drawing pass reaches 20%~30%, intermediate annealing is performed. The temperature of the intermediate annealing is 600~750℃, and the holding time of the intermediate annealing is 0.5h~1.5h.

7. The preparation method according to claim 1, characterized in that, The method of cyclic heating and cooling solution treatment is to perform cyclic heating and cooling solution treatment. The method of cyclic heating and cooling solution treatment includes: heating the Cu-Al-Mn alloy profile to the upper plateau temperature at a first heating rate, and holding it at the upper plateau temperature for a first time; then cooling it to the lower plateau temperature at a first cooling rate, and holding it at the lower plateau temperature for a second time; then heating it to the upper plateau temperature at a second heating rate, and holding it at the upper plateau temperature for a third time, and then cooling it to room temperature.

8. The preparation method according to claim 1, characterized in that, The aging treatment temperature is 200~400℃; the aging treatment time is 20min~60min.

9. The Cu-Al-Mn shape memory alloy prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the Cu-Al-Mn shape memory alloy of claim 9 in marine concrete structures and island / town infrastructure construction.

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