NiTiNb Shape Memory Alloy and Its Preparation Method

Abstract

This invention discloses a NiTiNb shape memory alloy and its preparation method, relating to the field of shape memory materials. The NiTiNb shape memory alloy of this invention comprises Ni, Ti, and Nb; wherein the atomic percentage of Ni is 50.5%~51%, the atomic percentage of Ti is 48.2%~48.8%, and the atomic percentage of Nb is 0.2%~0.8%, with the sum of the atomic percentages of Ni, Ti, and Nb being 100%; and the NiTiNb shape memory alloy is a single-phase alloy, specifically a B2 phase alloy. The aforementioned NiTiNb shape memory alloy features a large phase transformation thermal hysteresis width, a B2 phase single-phase alloy microstructure, and a low Nb content, which on the one hand facilitates storage and transportation and reduces processing difficulty, and on the other hand helps improve phase transformation stability. Furthermore, the low Nb content helps reduce production costs.

Description

Technical Field

[0001] This invention relates to the field of shape memory materials technology, and more specifically, to a NiTiNb shape memory alloy and its preparation method. Background Technology

[0002] NiTi shape memory alloys possess reversible shape memory and superelastic properties, making them suitable for applications in aerospace, biomedicine, intelligent robotics, pipe fittings, and other fields. To facilitate storage and transportation while reducing processing difficulty, shape memory alloys need a wide phase transformation thermal hysteresis width. Furthermore, to adapt to low-temperature applications such as deep space exploration, they require good low-temperature driving performance. Current technologies often use Nb to lower the phase transformation temperature and increase the phase transformation thermal hysteresis width; however, NiTiNb alloys prepared using this method still suffer from the following problems: firstly, the phase transformation thermal hysteresis width remains relatively narrow; secondly, the alloy may contain... - The Nb phase or precipitate undergoes a two-step phase transformation, B2→R→B19', resulting in low phase transformation stability of the NiTiNb alloy; thirdly, the high cost of Nb leads to higher production costs. Summary of the Invention

[0003] The main objective of this invention is to provide a NiTiNb shape memory alloy and its preparation method, so as to solve the problems of narrow phase transformation thermal hysteresis width, low phase transformation stability and high production cost of NiTiNb alloy in the prior art.

[0004] To achieve the above objectives, according to one aspect of the present invention, a NiTiNb shape memory alloy is provided, comprising Ni, Ti, and Nb; wherein the atomic percentage of Ni is 50.5% to 51%, the atomic percentage of Ti is 48.2% to 48.8%, the atomic percentage of Nb is 0.2% to 0.8%, and the sum of the atomic percentages of Ni, Ti, and Nb is 100%; the NiTiNb shape memory alloy is a single-phase alloy, and the single-phase alloy is a B2 phase alloy.

[0005] Furthermore, the phase transformation thermal hysteresis width of NiTiNb shape memory alloy is greater than 60℃.

[0006] According to a second aspect of the present invention, a method for preparing a NiTiNb shape memory alloy is provided, comprising the following steps:

[0007] The NiTiNb alloy ingot is subjected to hot forging and hot rolling, or hot forging and hot drawing, in sequence to obtain the first profile;

[0008] The first profile is subjected to solution treatment to obtain the second profile;

[0009] The second profile was subjected to aging treatment to obtain a NiTiNb shape memory alloy;

[0010] The aging treatment temperature is 200℃~300℃, and the aging treatment time is 1h~20h.

[0011] Furthermore, after aging the second profile, the preparation method also includes: performing deformation treatment on the product obtained from the aging treatment to obtain NiTiNb shape memory alloy, wherein the deformation of the deformation treatment is 20%~30%.

[0012] Furthermore, the deformation treatment temperature is M. s +25℃~M s +40℃.

[0013] Furthermore, the heat treatment temperature is 750℃~850℃.

[0014] Furthermore, the heat treatment time is greater than or equal to 30 minutes.

[0015] Furthermore, the cooling method for the solution treatment is water cooling.

[0016] Furthermore, the aging process is cooled by water.

[0017] Furthermore, the heat preservation time for aging treatment is 10h~20h.

[0018] Furthermore, the hot forging temperature is 850℃~980℃.

[0019] Furthermore, the NiTiNb alloy ingot is subjected to hot forging and hot rolling in sequence to obtain the first profile, wherein the hot rolling temperature is 650℃~850℃.

[0020] Furthermore, the NiTiNb alloy ingot is subjected to hot forging and hot drawing in sequence to obtain the first profile, wherein the hot drawing temperature is 650℃~850℃.

[0021] Furthermore, the first profile is at least one of wire, sheet, and pipe, and / or the second profile is at least one of wire, sheet, and pipe.

[0022] Furthermore, by mixing elemental Ni, elemental Ti, and elemental Nb to obtain a mixture, the mixture is then smelted and cast sequentially to obtain a NiTiNb alloy ingot; the smelting is carried out in a vacuum environment with an absolute pressure below 0.1 Pa or in an inert gas atmosphere.

[0023] By applying the technical solution of this invention, and controlling the atomic percentages of Ni, Ti, and Nb, especially the Nb content which is only 0.2%~0.8%, firstly, it helps to increase the phase transformation thermal hysteresis width of NiTiNb shape memory alloys, reducing the difficulty of storage, transportation, and processing; secondly, it helps to avoid the formation of precipitated or inclusion phases, thereby improving phase transformation stability; and thirdly, it helps to significantly reduce the amount of Nb used, thus reducing production costs. Furthermore, the B2 phase single-phase alloy microstructure helps to improve phase transformation stability, increase maximum output strain, and increase strain recovery rate. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention.

[0025] Figure 1 The image shows the XRD pattern of the NiTiNb shape memory alloy prepared in Example 1 of this invention.

[0026] Figure 2 The image shows the XRD pattern of the NiTiNb shape memory alloy prepared in Example 12 of this invention.

[0027] Figure 3 The image shows the XRD pattern of the NiTiNb shape memory alloy prepared in Comparative Example 3 of this invention.

[0028] Figure 4 The image shows the XRD pattern of the NiTiNb shape memory alloy prepared in Comparative Example 4 of this invention.

[0029] Figure 5 The image shows the DSC curve of the NiTiNb shape memory alloy prepared in Example 1 of this invention.

[0030] Figure 6 The image shows the DSC curve of the NiTiNb shape memory alloy prepared in Example 4 of this invention.

[0031] Figure 7 The image shows the DSC curve of the NiTiNb shape memory alloy prepared in Comparative Example 1 of this invention.

[0032] Figure 8 The image shows the recovery force curve of the NiTiNb shape memory alloy prepared in Example 4 of this invention.

[0033] Figure 9 The image shows the recovery force curve of the NiTiNb shape memory alloy prepared in Example 5 of this invention.

[0034] Figure 10The strain-temperature curve of the NiTiNb shape memory alloy prepared in Example 1 of this invention is shown.

[0035] Figure 11 The strain-temperature curve of the NiTiNb shape memory alloy prepared in Example 10 of this invention is shown.

[0036] Figure 12 The strain-temperature curve of the NiTiNb shape memory alloy prepared in Example 12 of this invention is shown.

[0037] Figure 13 This is a Ni element distribution diagram of the NiTiNb shape memory alloy prepared in Example 1 of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] As described in the background section of this invention, existing technologies for NiTiNb alloys suffer from narrow phase transformation thermal hysteresis, low phase transformation stability, and high production costs. To address these issues, in a typical embodiment of this invention, a NiTiNb shape memory alloy is provided. This NiTiNb shape memory alloy comprises Ni, Ti, and Nb; wherein the atomic percentage of Ni is 50.5%~51%, the atomic percentage of Ti is 48.2%~48.8%, and the atomic percentage of Nb is 0.2%~0.8%, with the sum of the atomic percentages of Ni, Ti, and Nb being 100%; the NiTiNb shape memory alloy is a single-phase alloy, specifically a B2 phase alloy. The phase transformation type corresponding to the NiTiNb shape memory alloy is a one-step phase transformation from B2 to B19'.

[0040] Typically, but not limitingly, the atomic percentage of Nb is 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any two of these values; the atomic percentage of Ti is 48.2%, 48.3%, 48.4%, 48.5%, 48.6%, 48.7%, 48.8%, or any two of these values; and the atomic percentage of Ni is 50.5%, 50.6%, 50.7%, 50.8%, 50.9%, 51%, or any two of these values. Preferably, the atomic percentage of Ni is 50.5% to 51%, the atomic percentage of Ti is 48.2% to 48.5%, and the atomic percentage of Nb is 0.5% to 0.8%, with the sum of the atomic percentages of Ni, Ti, and Nb being 100%.

[0041] By controlling the atomic percentages of Ni, Ti, and Nb, especially with Nb content set at only 0.2% to 0.8%, several advantages are achieved: first, it increases the phase transformation thermal hysteresis width of the NiTiNb shape memory alloy, reducing the difficulty of its storage, transportation, and processing; second, it helps avoid the formation of precipitates or inclusions, thereby improving phase transformation stability; and third, it significantly reduces Nb usage, lowering production costs. The NiTiNb shape memory alloy provided in this application has a B2 phase single-phase alloy microstructure, which helps improve phase transformation stability and increase maximum output strain and strain recovery rate.

[0042] The phase transformation type of the above-mentioned NiTiNb shape memory alloy is a one-step phase transformation from B2 to B19', indicating that the phase transformation path of this shape memory alloy in the martensitic phase transformation is unique, which is beneficial to further improve the phase transformation stability.

[0043] In some embodiments, the phase transition thermal hysteresis width of the NiTiNb shape memory alloy is greater than 60°C. In M s +25℃~M s The product obtained by aging at +40℃ was subjected to deformation treatment with a deformation of 20%~30%. The resulting NiTiNb shape memory alloy exhibited a phase transformation thermal hysteresis width greater than 150℃, and A s Greater than 0℃.

[0044] In the embodiments described above, the phase transformation thermal hysteresis width of the NiTiNb shape memory alloy within the aforementioned range helps reduce storage and transportation difficulties, while also simplifying the construction process and reducing application costs. The NiTiNb shape memory alloy obtained through deformation treatment not only has a significantly increased phase transformation thermal hysteresis width, but also an austenite initiation temperature higher than the freezing point. This helps maintain the stable existence of the martensite phase during transportation and storage, thereby stabilizing the morphology of the NiTiNb shape memory alloy and reducing temperature control requirements during transportation and storage, thus lowering energy consumption.

[0045] It should be noted that, in this invention, the normal martensitic transformation temperature includes M. s M p and M f , of which M s The temperature representing the onset of the normal martensitic transformation, i.e., the temperature at which the parent phase or austenite phase begins to transform into the martensitic phase during the cooling process; M p The peak temperature representing the normal martensitic transformation, i.e., the temperature at which the rate of transformation from the parent phase or austenite phase to the martensitic phase reaches its maximum during the cooling process; M f The temperature representing the end of the normal martensitic transformation is the temperature at which all the parent phase or austenite phase transforms into martensite during the cooling process. The reverse martensitic transformation temperature includes A. s A p and A f , where A s Represents the starting temperature of the reverse martensitic transformation, that is, the temperature at which the martensitic phase begins to transform into the austenitic phase during the heating process; A p The peak temperature representing the reverse martensitic transformation, i.e., the temperature at which the rate of transformation from martensite to austenite reaches its maximum during heating; A f This represents the end temperature of the normal martensitic transformation, that is, the temperature at which the martensitic phase is completely transformed into the austenitic phase during the cooling process.

[0046] Phase change thermal hysteresis width T hys The calculation formula is: T hys =A p -M p .

[0047] For NiTiNb shape memory alloys that have not undergone deformation treatment, directly testing the A of NiTiNb shape memory alloys is recommended. p and M p The phase transition thermal hysteresis width can be calculated using the above formula.

[0048] For NiTiNb shape memory alloys that have undergone deformation treatment, it is necessary to test the M of the aging-treated product before deformation treatment. p Then, the product obtained from the aging treatment is subjected to deformation treatment to obtain NiTiNb shape memory alloy, and the A of the NiTiNb shape memory alloy is then tested. p Finally, the phase transition thermal hysteresis width is calculated using the above formula.

[0049] NiTiNb shape memory alloys undergo stress-induced martensitic transformation during deformation treatment. Therefore, the deformed NiTiNb alloy already has a martensitic structure. No temperature-induced martensitic transformation will occur during subsequent cooling; only the heating process will result in a temperature-induced reverse martensitic transformation. Therefore, the M measured before deformation treatment is directly used in this field. pA measured after temperature and deformation treatment p Temperature calculations were performed to determine the phase transformation thermal hysteresis width of the deformed NiTiNb shape memory alloy.

[0050] In another typical embodiment of the present invention, a method for preparing NiTiNb shape memory alloy is provided, comprising the following steps:

[0051] The NiTiNb alloy ingot is subjected to hot forging and hot rolling in sequence, or hot forging and hot drawing in sequence, to obtain the first profile; preferably, the NiTiNb alloy ingot is subjected to hot forging and hot drawing in sequence to obtain the first profile.

[0052] The first profile is subjected to solution treatment to obtain the second profile;

[0053] The second profile was subjected to aging treatment to obtain a NiTiNb shape memory alloy;

[0054] The aging treatment involves holding at a temperature of 200℃ to 300℃ for 1 hour to 20 hours. Typically, but not limitingly, the aging treatment temperature is within the range of 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, or any two of these values. Preferably, the aging treatment temperature is 250℃ to 300℃. Typically, but not limitingly, the aging treatment time is within the range of 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, or any two of these values. Preferably, the aging treatment time is 5 hours to 20 hours.

[0055] By limiting the holding temperature and time of the aging treatment within the aforementioned range, it is beneficial to form Ni nano-segregated regions through low-temperature aging. Furthermore, it helps to avoid the formation of precipitates or inclusions, resulting in a B2 phase single-phase alloy microstructure. Single-phase alloys help simplify the phase transformation path, improve phase transformation stability and strain recovery rate, and extend service life. It should be noted that obtaining a B2 phase single-phase alloy microstructure requires simultaneous control of the atomic percentages of Ni, Ti, and Nb, as well as the aging treatment conditions; satisfying only one of these conditions is insufficient to guarantee the formation of a B2 phase single-phase alloy microstructure. Furthermore, by controlling the atomic percentages of Ni, Ti, and Nb while introducing nano-segregated regions of Ni, the following effects can be achieved: First, the phase transformation thermal hysteresis width can be increased while significantly reducing the amount of Nb used, thereby reducing production costs and application difficulty; Second, the formation of Ni segregation helps to suppress dislocation generation during the phase transformation process, improves the reversibility of the phase transformation cycle, thereby improving the stability and fatigue durability of NiTiNb shape memory alloy during cyclic service and extending the service life of NiTiNb shape memory alloy; Third, it lowers the martensitic phase transformation temperature and enhances the driving force of NiTiNb shape memory alloy at low temperatures.

[0056] In some embodiments, after aging the second profile, the preparation method further includes: performing deformation treatment on the product obtained from the aging treatment to obtain a NiTiNb shape memory alloy, wherein the deformation amount of the deformation treatment is 20% to 30%. Typically, but not limitingly, the deformation amount of the deformation treatment is 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any two of these values. Preferably, the deformation amount of the deformation treatment is 26% to 30%. The deformation treatment includes stretching the two ends of the product obtained from the aging treatment to induce deformation. The methods for testing and calculating the deformation amount are as follows:

[0057] Deformation amount = (length of profile after deformation - length of profile before deformation) / length of profile before deformation × 100%.

[0058] Taking silk as an example, the deformation amount = (the length of the silk after deformation - the length of the silk before deformation) / the length of the silk before deformation × 100%.

[0059] In the above embodiments of this application, by subjecting the aging product to deformation treatment, a mechanoinduced martensitic phase transformation occurs during the deformation treatment process, which helps to increase the inverse martensitic phase transformation temperature. By limiting the deformation amount within the above range, it is helpful to adjust the internal structure of the alloy using appropriate plastic deformation, so as to generate more dislocations and microstrains inside the alloy. These structural changes help to further increase the phase transformation thermal hysteresis width and improve cycle stability.

[0060] In some embodiments, the deformation treatment temperature is M. s +25℃~M s +40℃. A typical, but not limiting, temperature for deformation treatment is M. s +25℃, M s +26℃, M s +27℃, M s +28℃, M s +29℃, M s +30℃, M s +31℃, M s +32℃, M s +33℃, M s +34℃, M s +35℃, M s +36℃, M s +37℃, M s +38℃, M s +39℃, M s +40℃ or any two of its values.

[0061] The product obtained by aging treatment is in a metastable state within the above temperature range. Applying stress to the product at this time can cause it to undergo moderate plastic deformation. In the above embodiments of this application, by performing deformation treatment within the above temperature range, it is helpful to increase the resistance to the transformation of martensite phase to austenite phase during heating, thereby increasing the reverse transformation temperature of martensite.

[0062] Simultaneously controlling the deformation treatment temperature and time within the above range helps to significantly increase the martensitic reverse transformation temperature of NiTiNb shape memory alloys, enabling A... s >0℃, and also helps to increase the phase transformation thermal hysteresis width of NiTiNb shape memory alloys to greater than 150℃.

[0063] In some embodiments, the heat treatment temperature is 750℃~850℃, preferably 750℃~800℃; the heat treatment time is greater than or equal to 30min, preferably 30min~90min, and more preferably 30min~60min; the cooling method for the solution treatment is water cooling.

[0064] In the above embodiments of this application, limiting the holding temperature and holding time of the solution treatment within the aforementioned range helps to promote the full dissolution of Nb into the NiTi matrix, resulting in a uniform single-phase structure. Limiting the cooling method of the solution treatment helps to rapidly cool the product obtained from the solution treatment, preserving its microstructure at high temperatures, and obtaining the second profile.

[0065] In some implementations, the aging process is cooled by water.

[0066] In the above embodiments of this application, by limiting the cooling method of the aging process, it is helpful to retain the Ni segregation structure and single-phase alloy structure of the product obtained by the aging process by controlling the cooling rate.

[0067] In some implementations, the aging treatment is carried out for 10 to 20 hours.

[0068] In the above embodiments of this application, further limiting the holding time of the aging treatment within the aforementioned range helps to slow down the diffusion of Ni atoms and form nano-segregated regions in the alloy matrix, thereby reducing the martensitic transformation temperature and increasing the thermal hysteresis width of the transformation. Simultaneously controlling the atomic percentages of Ni, Ti, and Nb and the aging treatment time helps to further improve the strain recovery rate while reducing the martensitic transformation temperature, thus enhancing the low-temperature driving performance of the NiTiNb shape memory alloy.

[0069] In some embodiments, the hot forging temperature is 850°C to 980°C. Preferably, the hot forging temperature is 850°C to 880°C.

[0070] In the above embodiments of this application, limiting the hot forging temperature within the above range helps to fully break down coarse grains and dendrites, thereby improving the density and uniformity of the billet.

[0071] In some embodiments, the NiTiNb alloy ingot is sequentially hot-forged and hot-rolled to obtain a first profile, wherein the hot-rolling temperature is 650°C to 850°C; the NiTiNb alloy ingot is sequentially hot-forged and hot-drawn to obtain the first profile, wherein the hot-drawing temperature is 650°C to 850°C. Preferably, the hot-drawing temperature is 650°C to 750°C.

[0072] In the embodiments described above in this application, limiting the temperature of hot rolling or hot drawing within the aforementioned range helps to further refine the grains and improve the uniformity of the billet's microstructure. Hot rolling or hot drawing also helps to process alloy ingots to a certain size at relatively high temperatures, obtaining profiles of the target dimensions.

[0073] In some embodiments, the first profile is at least one of wire, sheet, and pipe, and / or the second profile is at least one of wire, sheet, and pipe.

[0074] In the above embodiments of this application, limiting the profile type to the aforementioned range helps to improve the machinability of the profile and reduce the difficulty of application. The NiTiNb shape memory alloy of the above-mentioned profile type can be used to manufacture self-tightening clamps and sealing rings for low-temperature or normal-temperature pipelines, or for robot drives and other scenarios in extremely cold environments.

[0075] In some embodiments, elemental Ni, elemental Ti, and elemental Nb are mixed to obtain a mixture, which is then sequentially melted and cast to obtain a NiTiNb alloy ingot. Melting is carried out in a vacuum environment with an absolute pressure below 0.0001 kPa or in an inert gas atmosphere. The purity of elemental Ni, elemental Ti, and elemental Nb is greater than or equal to 99.99 wt.%; the inert gas is argon. A vacuum environment with an absolute pressure below 0.1 Pa refers to a vacuum level higher than 10 kPa. -1 Pa's environment.

[0076] In the embodiments described above in this application, melting and casting facilitate the uniform mixing of Ni, Ti, and Nb to prepare an alloy ingot, providing an alloy substrate for subsequent processing. Melting in a vacuum environment or an inert gas atmosphere helps improve the purity and density of the alloy ingot, while simultaneously controlling the percentage of alloying elements to remain stable during the melting process.

[0077] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0078] Some of the materials used in the examples and comparative examples are as follows:

[0079] Elemental Ni: purity 99.99%, purchased from PURE New Materials.

[0080] Elemental Ti: purity 99.99%, purchased from PURE New Materials.

[0081] Elemental Nb: purity 99.99%, purchased from PURE New Materials.

[0082] Example 1

[0083] This invention provides an embodiment of the NiTiNb shape memory alloy. The NiTiNb shape memory alloy in this embodiment comprises Ni, Ti, and Nb. The atomic percentages of the aforementioned elements and some parameters for preparing the NiTiNb shape memory alloy are shown in Table 1. Specifically, the atomic percentage of Ni is 51%, the atomic percentage of Ti is 48.5%, and the atomic percentage of Nb is 0.5%, denoted as Ni. 51 Ti 48.5 Nb 0.5 NiTiNb shape memory alloy is a single-phase alloy, specifically a B2 phase alloy. The preparation method of NiTiNb shape memory alloy includes the following steps:

[0084] S1, elemental Ni, elemental Ti, and elemental Nb are mixed to obtain a mixture, which is then melted and cast sequentially to obtain a NiTiNb alloy ingot. The NiTiNb alloy ingot is then hot-forged and hot-drawn sequentially to obtain a first profile; wherein, the melting is carried out in a vacuum environment with an absolute pressure below 0.1 Pa; the hot forging temperature is 850℃, and the hot drawing temperature is 750℃; the first profile is a wire.

[0085] S2, the first profile is subjected to solution treatment to obtain the second profile; the heat preservation temperature of the solution treatment is 750℃, the heat preservation time of the solution treatment is 30min; the cooling method of the solution treatment is water cooling; the second profile is a wire material;

[0086] S3, the second profile is subjected to aging treatment to obtain NiTiNb shape memory alloy; wherein, the holding temperature of the aging treatment is 250℃, the holding time of the aging treatment is 5h, and the cooling method of the aging treatment is water cooling.

[0087] Examples 2-3 and Comparative Examples 1-2

[0088] The NiTiNb shape memory alloy examples and comparative examples in this invention differ from Example 1 in that the element percentages are different, as shown in Table 1.

[0089] Comparative Example 3

[0090] The comparative example of the NiTiNb shape memory alloy in this invention differs from Example 1 in that the NiTiNb shape memory alloy is made of Ni 47 Ti 44 Nb9 multiphase alloy, and the preparation method includes the following steps:

[0091] S1, elemental Ni, elemental Ti, and elemental Nb are mixed to obtain a mixture, which is then melted and cast sequentially to obtain a NiTiNb alloy ingot. The NiTiNb alloy ingot is then hot-forged and hot-drawn sequentially to obtain a first profile. The melting is carried out in a vacuum environment with an absolute pressure below 0.1 Pa; the hot forging temperature is 850℃, and the hot drawing temperature is 750℃; the first profile is a wire.

[0092] S2, the first profile is subjected to solution treatment to obtain the second profile; wherein, the heat preservation temperature of the solution treatment is 850℃, the heat preservation time of the solution treatment is 1h; the cooling method of the solution treatment is water cooling; the second profile is a wire material.

[0093] S3, the second profile is subjected to deformation treatment to obtain NiTiNb shape memory alloy; the deformation amount of the deformation treatment is 16%, and the deformation treatment temperature is -90℃.

[0094] Example 4

[0095] The NiTiNb shape memory alloy embodiment of this invention differs from Embodiment 1 in that, in step S3, the second profile undergoes aging treatment, and then the product obtained from the aging treatment undergoes deformation treatment. The deformation amount of the deformation treatment is 26%, and the deformation treatment temperature is -90°C.

[0096] Examples 5-9

[0097] The difference between the NiTiNb shape memory alloy embodiment in this invention and embodiment 4 is that the deformation amount in S3 is different, as shown in Table 1.

[0098] Example 10

[0099] The difference between the NiTiNb shape memory alloy embodiment of this invention and Embodiment 1 is that the NiTiNb shape memory alloy comprises Ni, Ti, and Nb, wherein the atomic percentage of Ni is 50.8%, the atomic percentage of Ti is 48.7%, and the atomic percentage of Nb is 0.5%, denoted as Ni. 50.8 Ti 48.7 Nb 0.5 The preparation method of NiTiNb shape memory alloy includes the following steps:

[0100] S1, elemental Ni, elemental Ti and elemental Nb are mixed to obtain a mixture, which is then melted and cast sequentially to obtain a NiTiNb alloy ingot. The NiTiNb alloy ingot is then hot-forged and hot-rolled sequentially to obtain a first profile; wherein, the melting is carried out in an argon atmosphere; the hot forging temperature is 980℃, and the hot rolling temperature is 850℃; the first profile is a plate.

[0101] S2, the first profile is subjected to solution treatment to obtain the second profile; the heat preservation temperature of the solution treatment is 850℃, the heat preservation time of the solution treatment is 90min; the cooling method of the solution treatment is water cooling; the second profile is a sheet material;

[0102] S3, the second profile is subjected to aging treatment to obtain NiTiNb shape memory alloy; wherein, the holding temperature of the aging treatment is 200℃, the holding time of the aging treatment is 1h, and the cooling method of the aging treatment is water cooling.

[0103] Example 11

[0104] The difference between the NiTiNb shape memory alloy embodiment of this invention and Embodiment 1 is that the NiTiNb shape memory alloy comprises Ni, Ti, and Nb, wherein the atomic percentage of Ni is 50.5%, the atomic percentage of Ti is 48.7%, and the atomic percentage of Nb is 0.8%, denoted as Ni. 50.5 Ti 48.7 Nb0.8 The preparation method of NiTiNb shape memory alloy includes the following steps:

[0105] S1, elemental Ni, elemental Ti, and elemental Nb are mixed to obtain a mixture, which is then melted and cast sequentially to obtain a NiTiNb alloy ingot. The NiTiNb alloy ingot is then hot-forged and hot-drawn sequentially to obtain a first profile; wherein, the melting is carried out in an argon atmosphere; the hot forging temperature is 880℃, and the hot drawing temperature is 650℃; the first profile is a pipe.

[0106] S2, the first profile is subjected to solution treatment to obtain the second profile; the heat preservation temperature of the solution treatment is 800℃, the heat preservation time of the solution treatment is 60min; the cooling method of the solution treatment is water cooling; the second profile is a pipe.

[0107] S3, the second profile is subjected to aging treatment to obtain NiTiNb shape memory alloy; wherein, the holding temperature of the aging treatment is 300℃, the holding time of the aging treatment is 20h, and the cooling method of the aging treatment is water cooling.

[0108] Examples 12-14 and Comparative Example 4

[0109] The NiTiNb shape memory alloy examples and comparative examples in this invention differ from Example 1 in that the aging treatment time in S3 is different, as shown in Table 1.

[0110] Table 1

[0111]

[0112] Performance testing

[0113] The phase composition of the NiTiNb shape memory alloys prepared in Examples 1, 12 and Comparative Examples 3-4 was tested;

[0114] The Ni element distribution of the NiTiNb shape memory alloy prepared in Example 1 was tested;

[0115] The martensitic phase transformation temperature of the NiTiNb shape memory alloys prepared in Examples 1-14 and Comparative Examples 1-4 was tested, including M. s M p A s A p ;

[0116] The restoring force of the NiTiNb shape memory alloys prepared in Examples 4-9 and Comparative Example 3 was tested. The restoring force refers to the stress generated by the NiTiNb shape memory alloy during the heating process to restore its initial state while keeping the strain of the NiTiNb shape memory alloy constant.

[0117] The strain properties of the NiTiNb shape memory alloys prepared in Examples 1-3, Examples 10-14, Comparative Examples 1-2, and Comparative Example 4 were tested in a low-temperature environment, including maximum output strain and strain recovery rate. Maximum output strain refers to the maximum phase transformation strain that occurs in the NiTiNb shape memory alloy during cooling; strain recovery rate refers to the percentage of recoverable strain in the NiTiNb shape memory alloy.

[0118] The performance testing method is as follows:

[0119] (1) Phase composition: XRD test was conducted in accordance with the relevant test regulations of GB / T 30904-2014, and the instrument used was NANOPIX-WE transmission wide-angle X-ray diffractometer;

[0120] (2) Ni elemental distribution: Three-dimensional atom probe (APT) testing was performed using a LEAP 4000X HR three-dimensional atom probe instrument to characterize the compositional distribution of the sample. The measured data were reconstructed and analyzed using Camecaivas 3.6.12 software.

[0121] (3) Martensitic phase transformation temperature: The test temperature of DSC equipment is relatively narrow. Therefore, when the phase transformation temperature is higher than or equal to -160℃, DSC test is used to characterize the phase transformation characteristics. According to the relevant test regulations of GB / T 1425-2021, the mass of the test sample is 10 mg, the test temperature range is -165℃ to 0℃, the heating and cooling rate is 10℃ / min, and the instrument is a NETZSCH214 differential scanning calorimeter. When the phase transformation temperature is lower than -160℃, resistance test (ER) is used to characterize the phase transformation characteristics. The test temperature range is -190℃ to 100℃, the heating and cooling rate is 10℃ / min, and the instrument is an RTL550 resistance tester. The temperature at which the resistance begins to decrease is the martensitic phase transformation start temperature.

[0122] (4) Restoration force: The strain of the sample is kept constant, and the change of the recovery stress of the sample is tested in the temperature range of -90℃ to 75℃. The strain is obtained by deformation treatment. The heating and cooling rate is 10℃ / min. The instrument used is a KQL WDTⅡ-20 universal tensile testing machine.

[0123] (5) Strain performance: The sample is suspended on the ground and fixed at the end away from the ground. A constant stress is applied to the end close to the ground. The strain change of the sample is tested in the temperature range of 90℃ to -120℃. The stress on the sample is constant at 300MPa and the heating and cooling rate is 10℃ / min. The instrument used is a TA Q800 dynamic thermomechanical analyzer.

[0124] The performance test results are as follows:

[0125] The XRD patterns of the NiTiNb shape memory alloys prepared in Examples 1, 12, and Comparative Examples 3-4 are shown below. Figures 1-4 As shown, it can be seen that Figure 1 , Figure 2 , Figure 4 The XRD pattern showed only the diffraction peak of the B2 phase, indicating that the NiTiNb shape memory alloys prepared in Examples 1, 12 and 4 contained only the parent phase, and the parent phase was the B2 phase, making them single-phase alloys. Figure 3 In addition to the diffraction peaks of the B2 phase, the XRD pattern also showed diffraction peaks of elemental Nb, indicating that the NiTiNb shape memory alloy prepared in Comparative Example 3 is a two-phase alloy, consisting of a NiTi matrix phase and... The presence of the -Nb phase is mainly due to Nb segregation during smelting. The characteristics of the dual-phase alloy result in lower phase transformation stability of the NiTiNb shape memory alloy prepared in Comparative Example 3 compared to Examples 1, 12, and 4.

[0126] The DSC curves of Examples 1, 4 and Comparative Example 1 are shown below. Figures 5-7 As shown, the restoring force curves of Examples 4 and 5 are as follows. Figures 8-9 As shown, the strain-temperature curves for Examples 1, 10, and 12 are as follows: Figures 10-12 As shown in Tables 2 and 3, the martensitic transformation temperature, phase transformation hysteresis width, restoring force, maximum output strain, and strain recovery rate are all measured. In Comparative Example 2, the NiTiNb shape memory alloy had too much Nb, which suppressed the martensitic transformation, making it impossible to measure the transformation temperature, maximum output strain, and strain recovery rate; therefore, no relevant data were available. In Example 9, the peak position in the DSC curve was not obvious, making it impossible to obtain an accurate martensitic transformation temperature and thus determine the phase transformation hysteresis width. This was mainly because the excessive deformation resulted in a high dislocation content in the NiTiNb shape memory alloy, suppressing the martensitic transformation. The M... (The text abruptly ends here, likely due to an incomplete translation or a missing section.) p The temperature is outside the instrument's testing range, so the specific temperature cannot be measured.

[0127] The NiTiNb shape memory alloys prepared in Comparative Examples 1 and 4 both exhibited a two-step phase transformation: B2→R→B19'. That is, the martensitic phase transformation process was divided into B2... R phase transition and R B19' phase transition. B2 R phase transition and R The martensitic transformation temperatures of the B19' phase transformation are shown in Table 3. Furthermore, in the NiTiNb shape memory alloys prepared in Comparative Examples 1 and 4, the maximum output strain is the sum of the maximum transformation strains occurring during the B2→R and R→B19' phase transformations, and the strain recovery rate is the sum of the recoverable strain percentages of the R→B2 and B19'→R phase transformations, as shown in Table 2.

[0128] Table 2

[0129]

[0130] Table 3

[0131]

[0132] As shown in Tables 2 and 3, the NiTiNb shape memory alloys prepared in Comparative Examples 1 and 4 both exhibit a two-step phase transformation: B2→R→B19'. This indicates that Ni4Ti3 precipitates during the aging process, which leads to poor phase transformation stability of the NiTiNb shape memory alloy.

[0133] Comparative examples 1-3, 10-11, 1-2, and 4 show that controlling the element percentages and aging conditions of the shape memory alloy helps to prepare a NiTiNb shape memory alloy with a single-phase microstructure of B2 phase and a one-step phase transformation of B2→B19', thereby improving phase transformation stability. Furthermore, this invention utilizes a small amount of Nb to lower the martensitic positive phase transformation temperature and increase the phase transformation thermal hysteresis width, effectively reducing production costs.

[0134] Comparing Examples 1 and 4, it is evident that deformation treatment of the aging product helps to increase the inverse martensitic transformation temperature, thereby increasing the phase transformation thermal hysteresis width. Comparing Example 4 and Comparative Example 3, the phase transformation thermal hysteresis width of Example 4 increased by 26.2% compared to Comparative Example 3, the recovery force at 0°C increased by 31.3% compared to Comparative Example 3, and the recovery force at 75°C increased by 49.7% compared to Comparative Example 3. This indicates that simultaneously controlling the element percentage and deformation amount of the shape memory alloy helps to further increase the phase transformation thermal hysteresis width and improve the recovery force. Furthermore, according to Examples 4-9 and Comparative Example 3, controlling the deformation amount to 20%-30% helps to increase the phase transformation thermal hysteresis width to over 156°C.

[0135] Comparing Examples 1, 10-14 and Comparative Example 4, it can be seen that controlling the aging treatment time within a suitable range helps to reduce the normal martensite transformation temperature. In particular, when the aging treatment time is controlled within 10h to 20h, it helps to significantly reduce the normal martensite transformation temperature, thereby improving the low-temperature driving performance of NiTiNb shape memory alloy, specifically by simultaneously increasing the maximum output strain and strain recovery rate.

[0136] Ni element distribution diagram as follows Figure 13 As shown, in the NiTiNb shape memory alloy prepared in Example 1, the distribution of Ni in the crystal phase is uneven, and segregation occurs.

[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A NiTiNb shape memory alloy, characterized in that, The NiTiNb shape memory alloy comprises Ni, Ti, and Nb; wherein the atomic percentage of Ni is 50.5%~51%, the atomic percentage of Ti is 48.2%~48.8%, the atomic percentage of Nb is 0.2%~0.8%, and the sum of the atomic percentages of Ni, Ti, and Nb is 100%; the NiTiNb shape memory alloy is a single-phase alloy, and the single-phase alloy is a B2 phase alloy; the phase transformation type corresponding to the NiTiNb shape memory alloy is a one-step phase transformation from B2 to B19'; the phase transformation thermal hysteresis width of the NiTiNb shape memory alloy is greater than 60℃.

2. A method for preparing the NiTiNb shape memory alloy according to claim 1, characterized in that, Includes the following steps: The NiTiNb alloy ingot is subjected to hot forging and hot rolling in sequence, or hot forging and hot drawing in sequence, to obtain the first profile; The first profile is subjected to solution treatment to obtain the second profile; The second profile is subjected to aging treatment to obtain the NiTiNb shape memory alloy; The aging treatment is performed at a temperature of 200℃ to 300℃, and the aging treatment is performed for a duration of 1 hour to 20 hours.

3. The method for preparing NiTiNb shape memory alloy according to claim 2, characterized in that, After aging the second profile, the preparation method further includes: performing deformation treatment on the product obtained from the aging treatment to obtain the NiTiNb shape memory alloy, wherein the deformation of the deformation treatment is 20%~30%.

4. The method for preparing NiTiNb shape memory alloy according to claim 3, characterized in that, The temperature of the deformation treatment is M. s +25℃~M s +40℃.

5. The method for preparing NiTiNb shape memory alloy according to claim 2, characterized in that, At least one of the following conditions must be met: (1) The heat preservation temperature of the solution treatment is 750℃~850℃; (2) The heat preservation time of the solution treatment is greater than or equal to 30 min; (3) The cooling method for the solution treatment is water cooling; (4) The cooling method for the aging treatment is water cooling.

6. The method for preparing NiTiNb shape memory alloy according to claim 2 or 5, characterized in that, The heat preservation time for the aging treatment is 10h~20h.

7. The method for preparing NiTiNb shape memory alloy according to any one of claims 2 to 5, characterized in that, At least one of the following conditions must be met: (1) The hot forging temperature is 850℃~980℃; (2) The NiTiNb alloy ingot is subjected to hot forging and hot rolling in sequence to obtain a first profile, wherein the hot rolling temperature is 650℃~850℃; or, the NiTiNb alloy ingot is subjected to hot forging and hot drawing in sequence to obtain a first profile, wherein the hot drawing temperature is 650℃~850℃.

8. The method for preparing NiTiNb shape memory alloy according to any one of claims 2 to 5, characterized in that, The first profile is at least one of wire, sheet, and pipe.

9. The method for preparing NiTiNb shape memory alloy according to any one of claims 2 to 5, characterized in that, The second profile is at least one of wire, sheet, and pipe.

10. The method for preparing NiTiNb shape memory alloy according to any one of claims 2 to 5, characterized in that, The NiTiNb alloy ingot is obtained by mixing elemental Ni, elemental Ti, and elemental Nb, followed by melting and casting of the mixture in sequence. The melting is carried out in a vacuum environment with an absolute pressure of less than 0.1 Pa or in an inert gas atmosphere.

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