Multi-principal-element shape memory alloy with high cyclic stability and high-temperature linear superelasticity, its preparation method and application

Abstract

Multi-principal element shape memory alloy with high cyclic stability and high-temperature linear superelasticity, its preparation method and application. The present invention belongs to the field of shape memory alloys. The purpose of the present invention is to overcome the technical problems that existing shape memory alloys cannot take into account low processing costs, high shape memory effects, and high cyclic stability. The alloy of the present invention comprises the following components in atomic percentages: Ti: 25%, Zr: 25%, Ni: 40 - 45%, and the balance is Cu. The alloy of the present invention is formed by vacuum non-consumable arc melting. Compared with traditional Ni-Ti shape memory alloys, the alloy of the present invention exhibits unique linear superelasticity and excellent cyclic stability under high-temperature conditions, and in the high-temperature cyclic compression experiment, the yield strength reaches 757.5 MPa, the superelastic recoverable strain is 4.8%, and the deformation recoverable rate reaches 98.9%. It is expected to be used in aerospace engineering equipment and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of shape memory alloys, and particularly relates to a multi-principal element shape memory alloy with high cyclic stability and high-temperature linear superelasticity, and a preparation method and application thereof. Background Art

[0002] From aerospace to deep space and polar exploration, various high-performance engineering applications in extreme environments often require metal components to withstand large and reversible deformations at high temperatures; for example, the superelastic components used in Mars and lunar spacecraft usually work in the temperature range of -200°C to 125°C, and require as high strength and toughness as possible. At present, the shape memory effect and superelasticity related to martensitic transformation have attracted great attention to shape memory alloys in the above engineering fields.

[0003] At present, the commonly used Ni-Ti shape memory alloy has a relatively low phase transformation temperature and poor cyclic stability, which limits its application at high temperatures. Various new shape memory alloys developed through composition design optimization can improve this problem to a certain extent, but they all have their own insurmountable deficiencies. For example, Ni-Ti-based high-temperature shape memory alloys added with precious metal elements such as Pd, Pt, and Au have relatively high phase transformation temperatures (up to 1000°C at most) and excellent shape memory effects, but they are costly and difficult to process and form; in contrast, Cu-based and Ni-based high-temperature shape memory alloys are inexpensive, but have poor processing and forming capabilities and the shape memory effect needs to be improved. In recent years, (TiZrHf) 50 (NiCoCu) 50 The emergence of high-entropy shape memory alloys in the system is expected to successfully realize the engineering application of shape memory alloys in a wide temperature range. They do not contain precious metal elements and exhibit high yield strength, excellent superelasticity in a wide temperature range, and high damping and other characteristics, and are expected to be used in related fields such as precision instrument manufacturing and even deep space exploration. However, the high-entropy shape memory alloys reported at present all have the problem of large thermal / mechanical hysteresis. The wide phase transformation hysteresis will exacerbate the internal friction, seriously degenerate the function, and cannot be continuously recycled while causing waste of resources. However, aerospace engineering applications have put forward higher requirements for the superelasticity of shape memory alloys at high temperatures, so new shape memory alloys need to be developed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the technical problems that the existing shape memory alloys cannot take into account low processing costs, high shape memory effects, and high cyclic stability. The present invention provides a multi-principal element shape memory alloy with high cyclic stability and high-temperature linear superelasticity, and a preparation method and application thereof.

[0005] The purpose of the present invention is completed by the following technical solutions:

[0006] One of the objectives of the present invention is to provide a multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity. The multi-principal element shape memory alloy comprises the following components in atomic percentages: Ti: 25%, Zr: 25%, Ni: 40 - 45%, and the balance is Cu.

[0007] Preferably, the multi-principal element shape memory alloy comprises the following components in atomic percentages: Ti: 25%, Zr: 25%, Ni: 45%, Cu: 5%.

[0008] Preferably, the multi-principal element shape memory alloy comprises the following components in atomic percentages: Ti: 25%, Zr: 25%, Ni: 40%, Cu: 10%.

[0009] Another objective of the present invention is to provide a preparation method for a multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity. The preparation method is carried out according to the following steps:

[0010] It is melted by using a vacuum non-consumable arc melting furnace through multiple turnovers.

[0011] Preferably, before melting, first polish, and then ultrasonically clean each metal raw material with ethanol.

[0012] Preferably, before melting, put each metal raw material into a water-cooled copper crucible in ascending order of melting point.

[0013] Preferably, the melting is carried out in argon.

[0014] Preferably, the melting current is 400 - 500 A. After each metal raw material is melted into a liquid state, keep the arc melting for 3 - 4 min, then turn off the current. After the alloy cools down, turn it over and then carry out the next melting.

[0015] Preferably, repeat the turnover melting 4 times.

[0016] Another objective of the present invention is to provide an application of a multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity in the field of aerospace.

[0017] The remarkable effects of the present invention compared with the prior art:

[0018] The present invention provides a new multi-principal element shape memory alloy. Compared with the traditional Ni-Ti shape memory alloy, this alloy exhibits unique linear superelasticity and excellent cyclic stability under high-temperature conditions. And in the high-temperature cyclic compression experiment, the yield strength reaches 757.5 MPa, the recoverable strain of superelasticity is 4.8%, and the recoverable rate of deformation reaches 98.9%. This alloy is expected to be used in aerospace engineering equipment and has good application prospects. Description of the Drawings

[0019] Figure 1 For the Ni 45 Ti 25 Zr 25 X-ray diffraction pattern of the Cu5 shape memory alloy described in Example 1;

[0020] Figure 2 For the Ni 45 Ti 25 Zr 25 Microstructure diagram of the Cu5 shape memory alloy; where (a) - low magnification diagram, (b) - high magnification diagram;

[0021] Figure 3 For the Ni 45 Ti 25 Zr 25 Cyclic compression stress-strain curve of the Cu5 shape memory alloy at 180°C;

[0022] Figure 4 For the Ni 40 Ti 25 Zr 25 Cu 10 X-ray diffraction pattern of the shape memory alloy;

[0023] Figure 5 For the Ni 40 Ti 25 Zr 25 Cu 10 Microstructure diagram of the shape memory alloy; where (a) - low magnification diagram, (b) - high magnification diagram;

[0024] Figure 6 For the Ni 40 Ti 25 Zr 25 Cu 10 Cyclic compression stress-strain curve of the shape memory alloy at 180°C. Detailed implementation manners

[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used, unless otherwise specified, are all conventional materials, reagents, methods and instruments in the art, and those skilled in the art can obtain them through commercial channels.

[0027] As used in the following embodiments, the terms "comprising", "including", "having", "containing" or any other variation thereof are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or apparatus containing the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article or apparatus.

[0028] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, whether or not such ranges are separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoint values and all integers and fractions within the range. In the specification and claims of this application, range limitations may be combined and / or interchanged, and if not otherwise stated, these ranges include all sub-ranges subsumed therein.

[0029] The indefinite articles "a" and "an" before an element or component of the present invention do not limit the quantity requirement (i.e., the number of occurrences) of the element or component. Therefore, "a" or "an" should be interpreted to include one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0030] As used herein, "an embodiment" or "embodiments" of the present invention refers to specific features, structures, or characteristics that may be included in at least one implementation of the present invention. The phrase "in an embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0031] The endpoint values and any values within the ranges disclosed in the invention are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0032] Example 1

[0033] The preparation method of the multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity in this embodiment is carried out according to the following steps:

[0034] (1) Select Ni, Ti, Zr, and Cu with a purity greater than 99.9% as raw materials. Polish the surfaces of the above raw materials to remove the oxide scale, and then ultrasonically clean them with industrial ethanol for 10 min.

[0035] (2) Weigh accurately according to the atomic percentage of each element: 25 at.% Ti - 25 at.% Zr - 45 at.% Ni - 5 at.% Cu to complete the batching.

[0036] (3) Use a vacuum non-consumable arc furnace to melt button ingots to study the microstructure and properties of the alloy. Place the water-cooled copper crucible with the metal raw materials in order of increasing melting point. At the same time, place a piece of pure titanium in another crucible. After evacuating the furnace chamber, fill the furnace chamber with argon gas to half an atmosphere. Adjust the tungsten electrode above the pure titanium and then strike an arc. First, melt the pure titanium to eliminate the residual oxygen in the furnace chamber. Subsequently, adjust the tungsten electrode to the raw materials and start melting. The melting current is 450 A. After all the raw materials are melted, keep the arc melting for 3 min and then directly turn off the arc. After the alloy cools, turn it over and remelt it according to the above melting process. Repeat the turning and melting 4 times to obtain an alloy with uniform composition, that is, a multi-principal-element shape memory alloy with high cyclic stability and high-temperature linear superelasticity, denoted as Ni 45 Ti 25 Zr 25 Cu5.

[0037] Use wire cutting to cut a cuboid sample with dimensions of 6 mm × 6 mm × 5 mm from the middle part of the button ingot. Ultrasonically clean it with anhydrous ethanol, and polish it successively with 240#, 500#, 800#, 1000#, 1500#, and 2000# sandpapers to ensure that the test surface is smooth and parallel to the lower surface. Use an intelligent X-ray diffractometer of model Empyrean to scan and identify the sample at room temperature. The scanning angle is 20° - 80°, and the scanning speed is 5° / min. When testing, use the Kα ray of the Cu target as the diffraction source, the accelerating voltage is fixed at 40 KV, and the accelerating current is fixed at 40 mA. The XRD diffraction pattern of the shape memory alloy prepared in Example 1 is as shown in the appendix Figure 1 It can be seen that the alloy obtained in Example 1 is completely composed of the monoclinic B19' martensite phase.

[0038] A rectangular sample with a size of 6mm×6mm×5mm was cut from the middle of the button ingot by wire cutting, and then ultrasonically cleaned with anhydrous ethanol. It was polished with 240#, 500#, 800#, 1000#, 1500#, and 2000# sandpaper in turn, and then polished with a diamond polishing agent with a particle size of W3.5 until there were no scratches. The polished sample was corroded for 20s. The corrosive solution consisted of 8ml nitric acid, 2ml hydrofluoric acid, and 10ml water. The corroded sample was rinsed with water and anhydrous ethanol, and then the alcohol on the surface of the sample was dried with a hair dryer to complete the sample preparation. The results are as follows: Figure 2 As shown, it can be seen that the microstructure of the alloy after corrosion is composed of a pure black matrix phase and dispersed short rod-shaped second phase.

[0039] The size of the cutter in the middle of the button ingot is The cylindrical sample was gently ground off the wire cutting marks on the upper and lower surfaces of the sample and the oxide scale on the side with 180# sandpaper. After ultrasonic cleaning and drying, the sample was subjected to a cyclic compression test at 180°C with a fixed strain of 5% using an AGXplus 50kN electronic universal testing machine and a high-temperature furnace. The number of cycles was 10. The cyclic compression stress-strain curve of the shape memory alloy prepared in Example 1 at 180°C is shown in the figure below: Figure 3 As shown. It can be seen that the obtained alloy exhibited a deformation recovery rate of up to 83% in the first cycle training, and the recoverable strain was 4.15%. While maintaining linear superelasticity in the subsequent cycles, the yield strength continued to increase with the number of cycles, reaching 757.5MPa in the tenth cycle. After the tenth cycle, the deformation recovery rate reached 97.9%, and the recoverable strain reached 4.66%, which shows that the shape memory alloy prepared in Example 1 has unique linear superelasticity and excellent cyclic stability at high temperature.

[0040] Embodiment 2:

[0041] The preparation method of the multi-principal element shape memory alloy with both high cycle stability and high temperature linear superelasticity of this embodiment is carried out according to the following steps:

[0042] (1) Ni, Ti, Zr, and Cu with a purity greater than 99.9% are selected as raw materials, the surfaces of the raw materials are polished to remove oxide scale, and then industrial ethanol is used for ultrasonic cleaning for 10 minutes.

[0043] (2) Accurately weigh the atomic percentage of each element 25at.% Ti-25at.% Zr-40at.% Ni-10at.% Cu to complete the ingredient preparation.

[0044] (3) The microstructure and properties of the alloy were studied by melting button ingots using a vacuum non-consumable arc furnace. The metal raw materials were placed in a water-cooled copper crucible in ascending order of their melting points. At the same time, a piece of pure titanium was placed in another crucible. After evacuating the furnace chamber, argon gas was filled into the furnace chamber to half an atmosphere. The tungsten electrode was adjusted above the pure titanium and then the arc was initiated. First, pure titanium was melted to eliminate the residual oxygen in the furnace chamber. Subsequently, the tungsten electrode was adjusted to the raw materials to start melting. The melting current was 450 A. After all the raw materials were melted, the arc melting was maintained for 3 min, and then the arc was directly turned off. After the alloy cooled, it was flipped, and then remelted according to the above melting process. The flipping and remelting were repeated 4 times to obtain an alloy with uniform composition, namely a multi-principal element shape memory alloy with high cyclic stability and high-temperature linear superelasticity, denoted as Ni 40 Ti 25 Zr 25 Cu 10 .

[0045] A cuboid sample with dimensions of 6 mm × 6 mm × 5 mm was cut from the middle part of the button ingot using wire cutting. It was ultrasonically cleaned with anhydrous ethanol and polished successively with 240#, 500#, 800#, 1000#, 1500#, and 2000# sandpapers to ensure that the test surface was smooth and parallel to the lower surface. The sample was scanned and identified at room temperature using a smart X-ray diffractometer of model Empyrean. The scanning angle was 20° - 80°, and the scanning speed was 5° / min. When testing, the Kα ray of the Cu target was used as the diffraction source, the accelerating voltage was fixed at 40 KV, and the accelerating current was fixed at 40 mA. The XRD diffraction pattern of the shape memory alloy prepared in Example 2 is shown in the appendix Figure 4 As shown. It can be seen that the alloy obtained in Example 2 consists of a monoclinic B19' martensite phase and a B2 austenite phase, and at the same time, it can be observed that a small amount of (Ti,Zr)2(Ni,Cu) phase precipitates. However, the diffraction peak intensities of both the B19' phase and the (Ti,Zr)2(Ni,Cu) phase are very weak.

[0046] A cuboid sample with dimensions of 6 mm × 6 mm × 5 mm was cut from the middle part of the button ingot using wire cutting. It was ultrasonically cleaned with anhydrous ethanol and polished successively with 240#, 500#, 800#, 1000#, 1500#, and 2000# sandpapers. Then, it was polished with a diamond polishing agent with a particle size of W3.5 until there were no scratches. The polished sample was subjected to corrosion treatment for 20 s. The corrosion solution consisted of 8 ml of nitric acid, 2 ml of hydrofluoric acid, and 10 ml of water. After corrosion, the sample was rinsed with water and anhydrous ethanol, and then the alcohol on the surface of the sample was dried with an electric hair dryer to complete the sample preparation. The results are as Figure 5 shown. It can be seen that the microstructure of the corroded alloy consists of a pure black matrix phase and aggregated fishbone-shaped secondary phases.

[0047] The size of the cutter in the middle of the button ingot is The cylindrical sample was gently ground off the wire cutting marks on the upper and lower surfaces of the sample and the oxide scale on the side with 180# sandpaper. After ultrasonic cleaning and drying, the sample was subjected to a cyclic compression test at 180°C with a fixed strain of 5% using an AGXplus 50kN electronic universal testing machine and a high-temperature furnace. The number of cycles was 10. The cyclic compression stress-strain curve of the shape memory alloy prepared in Example 2 at 180°C is shown in the figure below: Figure 6 As shown. It can be seen that the deformation recovery rate of the alloy obtained in Example 2 is 82.8% and the recoverable strain is 4.14% during the first cycle training. While maintaining linear superelasticity during the subsequent cycles, the yield strength continues to increase with the number of cycles, reaching 637.1MPa at the tenth cycle. After the tenth cycle, the deformation recovery rate reaches 98.9% and the recoverable strain reaches 4.80%, which shows that the shape memory alloy prepared in Example 2 has unique linear superelasticity and excellent cyclic stability at high temperature.

[0048] The mechanism by which the shape memory alloy provided in the present invention has high-temperature linear superelasticity and excellent cyclic stability is mainly due to the significant solid solution strengthening effect caused by the severe lattice distortion effect of the alloy; in addition, at high temperatures, the hysteresis diffusion effect can effectively inhibit thermal softening phenomena such as atomic diffusion and precipitation phase formation, which is also one of the reasons why the shape memory alloy has high-temperature superelasticity.

[0049] From the above analysis, it can be seen that the Ni-Ti-Zr-Cu shape memory alloy of the present invention exhibits unique linear superelasticity and excellent cyclic stability under high temperature conditions, and in the high temperature cyclic compression test, the yield strength reaches 757.5MPa, the superelastic recoverable strain is 4.8%, and the deformation recoverable rate reaches 98.9%. The alloy is expected to be used in aerospace engineering equipment and has good application prospects.

[0050] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity, characterized in that, Comprising the following components in atomic percentages: Ti: 25%, Zr: 25%, Ni: 40%, Cu: 10%. The preparation method of the multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity is carried out according to the following steps: (1) Select Ni, Ti, Zr, and Cu with a purity greater than 99.9% as raw materials. Grind the surfaces of the above raw materials to remove the oxide scale, and then use industrial ethanol for ultrasonic oscillation cleaning for 10 min; (2) Weigh accurately according to the atomic percentages of each element: 25 at.% Ti - 25 at.% Zr - 40 at.% Ni - 10 at.% Cu to complete the batching; (3) Use a vacuum non-consumable arc furnace to melt button ingots to study the microstructure and properties of the alloy. Put the water-cooled copper crucible in order of increasing melting points of each metal raw material, and at the same time place a piece of pure titanium in another crucible. After evacuating the furnace chamber, fill the furnace chamber with argon to half an atmosphere; Adjust the tungsten electrode above the pure titanium and then strike an arc. First, melt the pure titanium to eliminate the residual oxygen in the furnace chamber, and then adjust the tungsten electrode to the raw materials to start melting. The melting current is 450 A. After all the raw materials are melted, keep the arc melting for 3 min and then directly turn off the arc; After the alloy cools, turn it over, and re-melt it according to the above melting process after turning it over. Repeat the turning and melting 4 times to obtain an alloy with uniform composition, that is, a multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity; Use wire cutting to cut a cylindrical sample with a diameter of 4 mm and a height of 6 mm in the middle of the button ingot. Gently grind off the wire cutting marks on the upper and lower surfaces and the oxide scale on the side of the sample with 180-mesh sandpaper. After ultrasonic cleaning and drying, use an electronic universal testing machine of model AGXplus 50 kN plus a high-temperature furnace to conduct a cyclic compression test with a fixed strain of 5% on the sample at 180 °C. The number of cycles is 10 times. During the cyclic process, while maintaining linear superelasticity, the yield strength increases continuously with the number of cycles and reaches 637.1 MPa at the tenth cycle. After the tenth cycle ends, the deformation recoverable rate reaches 98.9%, and the recoverable strain reaches 4.80%.

2. Application of the multi-principal element shape memory alloy with both high cyclic stability and high-temperature linear superelasticity described in claim 1 in the field of aerospace.

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