NiTiHfTa high-temperature shape memory alloy and preparation process thereof

Abstract

The invention relates to the technical field of memory alloys, and particularly discloses a NiTiHfTa high-temperature shape memory alloy and a preparation process thereof. The invention relates to a NiTiHfTa high-temperature shape memory alloy, the chemical formula of the NiTiHfTa high-temperature shape memory alloy is (Ni < 5 > < 0.3 > Ti < 29.7 > Hf20) < 100-x > Tax, and x is greater than 1 and less than or equal to 10. The preparation process comprises the following steps: S1, preparing raw materials: respectively weighing Ni, Ti, Hf and Ta as raw materials according to the chemical formula of the memory alloy; and S2, alloy preparation, specifically, Ni, Ti, Hf and Ta raw materials are smelted, a cast ingot is obtained, and the memory alloy is obtained through homogenization treatment, hot rolling treatment and solution treatment. The memory alloy can be used in the fields of aerospace, automobile manufacturing, biomedicine and the like, and has the advantages of high processability and high shape memory.

Description

Technical Field

[0001] The present application relates to the technical field of shape memory alloys, and more specifically, to a NiTiHfTa high-temperature shape memory alloy and a preparation process thereof. Background Art

[0002] NiTi binary memory alloy is a unique functional material with good shape memory effect, superelasticity and biocompatibility. It is widely used in aerospace, automobile manufacturing and biomedicine. However, its martensitic phase transformation only occurs below 100°C, so there are many limitations in its application. In order to meet application requirements, researchers have developed NiTi (Pd, Pt, Au) and NiTi (Hf, Zr) alloys by alloying on the basis of NiTi binary alloy. Among them, NiTiHf alloy has attracted much attention due to its low cost and high phase transition temperature. However, the practical application of NiTiHf memory alloy is still limited by the following two important bottleneck issues.

[0003] First, the shape recovery property is not enough to meet the needs of engineering applications. The high critical stress of the reorientation of the martensitic variant of NiTiHf memory alloy makes its shape memory effect poor, and the Ni-poor NiTiHf alloy undergoes plastic deformation during the stress-induced martensitic phase transformation, which makes it unable to show superelastic effect. After aging, the Ni-rich NiTiHf alloy can precipitate the H phase coherent with the matrix to increase the critical slip stress of the alloy, so that it shows a certain superelasticity, but the recoverable deformation is still much lower than that of the binary NiTi memory alloy, so it is difficult to meet the needs of engineering applications.

[0004] Second, the processing performance is poor. Compared with the NiTi binary alloy, the addition of Hf in the NiTiHf alloy will cause serious lattice distortion, resulting in poor plasticity and difficulty in processing. 50.3 Ti 29.7 Hf 20 The alloy is cold rolled with a deformation of only 15%.

[0005] Therefore, how to make NiTiHf alloy obtain good processing performance and good shape recovery characteristics is a major difficulty in its engineering application. Summary of the invention

[0006] In order to make the memory alloy obtain good processing performance and good shape recovery characteristics, the present application provides a NiTiHfTa high temperature shape memory alloy and a preparation process thereof, adopting the following technical solutions:

[0007] In a first aspect, the present application provides a NiTiHfTa high temperature shape memory alloy, wherein the chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3Ti 29.7 Hf 20 ) 100-x Ta x , where 5<x≤10.

[0008] By adopting the above technical solution, the present application preferably adopts the addition of Ta as an alloying element in the NiTiHf alloy. Ta has a low solubility in the matrix, can form nano-scale and micron-scale strengthening phases, and can refine the grains, effectively improving the strength of the alloy; through thermal processing, the distribution of the strengthening phase in the matrix can also be adjusted, thereby improving the shape recovery effect of the alloy. The addition of the Ta element can also effectively improve the machinability of the memory alloy while maintaining the alloy phase transition temperature stable and not significantly reduced. Therefore, by adding the Ta element to the alloy substrate, the alloy can simultaneously obtain good processing performance and shape recovery characteristics.

[0009] The amount of Ta added to the alloy matrix is ​​optimized to be between 5 and 10, which can introduce appropriate strengthening phases into the alloy matrix, make the phase transition temperature of the alloy higher and more stable, obtain better shape memory effect, and improve the cold working ability of the alloy, which is beneficial to plastic processing.

[0010] Optionally, the chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 90 Ta 10 .

[0011] By adopting the above technical solution, the chemical formula of the memory alloy is further optimized, and the addition amount of the Ta alloy element is optimized. Under this addition amount, the memory alloy obtains better shape recovery characteristics and alloy phase transition temperature. Considering that the solubility of Ta in NiTiHf alloy is relatively low, this ratio is easy to adjust the alloy composition, and can obtain a better shape memory effect compared with the performance of existing alloys. For the memory alloy, it is necessary to ensure that the ratio of Ni and (Ti+Hf) is about 1:1, which can enable Ta and the alloy to obtain better solubility and promote the alloy to obtain excellent shape memory effect.

[0012] Optionally, the recoverable strain of the NiTiHfTa high temperature shape memory alloy can reach 3.2%.

[0013] In a second aspect, the present application provides a preparation process of a NiTiHfTa high temperature shape memory alloy, which adopts the following technical solution:

[0014] A preparation process of NiTiHfTa high temperature shape memory alloy comprises the following steps:

[0015] S1. Raw material preparation: according to the chemical formula of the memory alloy, Ni, Ti, Hf and Ta are weighed as raw materials respectively;

[0016] S2. Alloy preparation: Ni, Ti, Hf and Ta raw materials are melted to obtain ingots, and then the memory alloy is obtained through homogenization treatment, hot rolling treatment and solid solution treatment.

[0017] By adopting the above technical solution, the raw materials are sequentially subjected to smelting, homogenization treatment, hot rolling treatment and solution treatment, so as to obtain an alloy having both good processing performance and shape recovery characteristics.

[0018] Optionally, the temperature of the homogenization treatment is 900° C.-1050° C., and the time of the homogenization treatment is 1-6 hours.

[0019] By adopting the above technical solution, the temperature of the homogenization treatment is optimized. The appropriate temperature can make the strengthening phase evenly distributed in the alloy, so that the alloy obtains uniform strength and high-temperature recovery characteristics.

[0020] Optionally, the hot rolling treatment method is as follows: the ingot after homogenization treatment is placed at a temperature of 800° C.-850° C. for heat preservation treatment, and hot rolled with a rolling deformation of 0.5%-1% per pass to obtain an alloy plate.

[0021] By adopting the above technical solution, the rolling deformation is optimized, and the appropriate rolling deformation can form the desired shape during the rolling process, and is not prone to fracture, etc. Although the introduction of Ta improves the processing and deformation ability of the alloy, the alloy is still more prone to brittle fracture if the rolling deformation is too large.

[0022] Optionally, during the hot rolling process, the steel sheet needs to be returned to the furnace for 3-10 minutes of heat preservation after each rolling.

[0023] Optionally, the alloy plate has a thickness of 1-1.2 mm.

[0024] Optionally, the temperature of the solution treatment is 880-950° C., and the time of the solution treatment is 0.5-1 h.

[0025] By adopting the above technical solution, the alloy can obtain excellent toughness and deformation ability at a suitable solution temperature. If the solution temperature is too high, it is easy for the alloy to absorb oxygen at the grain boundary during rolling, which increases the brittleness of the alloy. If the solution temperature is too low, it is easy for the deformation resistance of the memory alloy to increase.

[0026] Optionally, the cooling method in the homogenization treatment and the solution treatment is water cooling.

[0027] By adopting the above technical solution, the water cooling method is relatively simple and has low cost.

[0028] In summary, this application has the following beneficial effects:

[0029] 1. Since the present application adopts the addition of Ta as an alloying element in the NiTiHf alloy, the solubility of Ta in the matrix is ​​low, and it can form nano-scale and micron-scale strengthening phases, and can refine the grains, effectively improving the strength of the alloy; through heat treatment, it can also adjust the distribution of the strengthening phase in the matrix, thereby improving the shape recovery effect of the alloy. The addition of the Ta element can also effectively improve the machinability of the memory alloy while maintaining the alloy phase transition temperature stable and not significantly reduced. Therefore, by adding the Ta element to the alloy substrate, the alloy can simultaneously obtain good processing performance and shape recovery characteristics.

[0030] 2. The memory alloy of the present application has good plastic processing ability, and the hot rolling deformation can reach more than 90%. In addition, the Hf content contained in it is reduced due to the addition of Ta, thereby reducing the production cost of the alloy.

[0031] 3. The phase transition temperature (Ms) of the memory alloy of the present application can reach 290° C., and has a shape recovery strain of up to 3.2%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The (Ni 50.3 Ti 29.7 Hf 20 ) 90 Ta 10 SEM schematic diagram of the;

[0033] Figure 2 The (Ni 50.3 Ti 29.7 Hf 20 ) 90 Ta 10 XRD schematic diagram of

[0034] Figure 3 The (Ni 50.3 Ti 29.7 Hf 20 ) 90 Ta 10 Schematic diagram of DSC. DETAILED DESCRIPTION

[0035] The present application is further described in detail below with reference to the embodiments.

[0036] Example

[0037] Example 1

[0038] On the one hand, the present application provides a NiTiHfTa high temperature shape memory alloy, the chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 100-x Ta x , 1<x≤10.

[0039] Specifically, x=10, the chemical formula of the memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 90 Ta 10 .

[0040] On the other hand, the present application provides a preparation process of NiTiHfTa high temperature shape memory alloy, comprising the following steps:

[0041] S1. Raw material preparation: According to the chemical formula of the memory alloy, Ni, Ti, Hf and Ta are weighed respectively and washed with ethanol as raw materials;

[0042] S2. Alloy preparation: Ni, Ti, Hf and Ta raw materials are placed in a vacuum induction melting furnace and repeatedly melted for 6-8 times to obtain an alloy ingot, which is then subjected to homogenization treatment, hot rolling treatment and solid solution treatment to obtain a memory alloy.

[0043] Among them, the smelting times are 8 times.

[0044] Homogenization treatment: The alloy ingot was homogenized at 900°C for 4 h and then cooled by water cooling.

[0045] Hot rolling treatment: the ingot after homogenization treatment is kept at 880°C for 50 minutes and then hot rolled. The rolling deformation is 0.5% per pass. Each rolling needs to be returned to the furnace for 3 to 10 minutes of heat preservation, and finally an alloy plate with a thickness of about 1.1 mm is obtained.

[0046] Solution treatment: The alloy plate was solution treated at 880°C for 0.5 h and then cooled with water.

[0047] Example 2

[0048] On the one hand, the present application provides a NiTiHfTa high temperature shape memory alloy, the chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 100-x Ta x , 1<x≤10.

[0049] Specifically, x=7, the chemical formula of the memory alloy is (Ni50.3 Ti 29.7 Hf 20 ) 93 Ta7.

[0050] On the other hand, the present application provides a preparation process of NiTiHfTa high temperature shape memory alloy, comprising the following steps:

[0051] S1. Raw material preparation: According to the chemical formula of the memory alloy, Ni, Ti, Hf and Ta are weighed respectively and washed with ethanol as raw materials;

[0052] S2. Alloy preparation: Ni, Ti, Hf and Ta raw materials are placed in a vacuum induction melting furnace and repeatedly melted for 6-8 times to obtain an alloy ingot, which is then subjected to homogenization treatment, hot rolling treatment and solid solution treatment to obtain a memory alloy.

[0053] Among them, the smelting times are 8 times.

[0054] Homogenization treatment: The alloy ingot was homogenized at 900°C for 4 h and then cooled by water cooling.

[0055] Hot rolling treatment: the ingot after homogenization treatment is kept at 880°C for 50 minutes and then hot rolled. The rolling deformation is 0.5% per pass. Each rolling needs to be returned to the furnace for 3 to 10 minutes of heat preservation, and finally an alloy plate with a thickness of about 1.1 mm is obtained.

[0056] Solution treatment: The alloy plate was solution treated at 880°C for 0.5 h and then cooled with water.

[0057] Example 3

[0058] On the one hand, the present application provides a NiTiHfTa high temperature shape memory alloy, the chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 100-x Ta x , 1<x≤10.

[0059] Specifically, x=7, the chemical formula of the memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 95 Ta5.

[0060] On the other hand, the present application provides a preparation process of NiTiHfTa high temperature shape memory alloy, comprising the following steps:

[0061] S1. Raw material preparation: According to the chemical formula of the memory alloy, Ni, Ti, Hf and Ta are weighed respectively and washed with ethanol as raw materials;

[0062] S2. Alloy preparation: Ni, Ti, Hf and Ta raw materials are placed in a vacuum induction melting furnace and repeatedly melted for 6-8 times to obtain an alloy ingot, which is then subjected to homogenization treatment, hot rolling treatment and solid solution treatment to obtain a memory alloy.

[0063] Among them, the smelting times are 8 times.

[0064] Homogenization treatment: The alloy ingot was homogenized at 900°C for 4 h and then cooled by water cooling.

[0065] Hot rolling treatment: the ingot after homogenization treatment is kept at 880°C for 50 minutes and then hot rolled. The rolling deformation is 0.5% per pass. Each rolling needs to be returned to the furnace for 3 to 10 minutes of heat preservation, and finally an alloy plate with a thickness of about 1.1 mm is obtained.

[0066] Solution treatment: The alloy plate was solution treated at 880°C for 0.5 h and then cooled with water.

[0067] Example 4

[0068] On the one hand, the present application provides a NiTiHfTa high temperature shape memory alloy, the chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 100-x Ta x , 1<x≤10.

[0069] Specifically, x=7, the chemical formula of the memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 97 Ta3.

[0070] On the other hand, the present application provides a preparation process of NiTiHfTa high temperature shape memory alloy, comprising the following steps:

[0071] S1. Raw material preparation: According to the chemical formula of the memory alloy, Ni, Ti, Hf and Ta are weighed respectively and washed with ethanol as raw materials;

[0072] S2. Alloy preparation: Ni, Ti, Hf and Ta raw materials are placed in a vacuum induction melting furnace and repeatedly melted for 6-8 times to obtain an alloy ingot, which is then subjected to homogenization treatment, hot rolling treatment and solid solution treatment to obtain a memory alloy.

[0073] Among them, the smelting times are 8 times.

[0074] Homogenization treatment: The alloy ingot was homogenized at 900°C for 4 h and then cooled by water cooling.

[0075] Hot rolling treatment: the ingot after homogenization treatment is kept at 880°C for 50 minutes and then hot rolled. The rolling deformation is 0.5% per pass. Each rolling needs to be returned to the furnace for 3 to 10 minutes of heat preservation, and finally an alloy plate with a thickness of about 1.1 mm is obtained.

[0076] Solution treatment: The alloy plate was solution treated at 880°C for 0.5 h and then cooled with water.

[0077] Comparative Example

[0078] Comparative Example 1

[0079] On the one hand, the present application provides a NiTiHfTa high temperature shape memory alloy, the chemical formula of the NiTiHfTa high temperature shape memory alloy is Ni 50.3 Ti 29.7 Hf 20 .

[0080] On the other hand, the present application provides a preparation process of NiTiHfTa high temperature shape memory alloy, comprising the following steps:

[0081] S1. Raw material preparation: According to the chemical formula of the memory alloy, Ni, Ti, and Hf are weighed respectively, and washed with ethanol as raw materials;

[0082] S2. Alloy preparation: Ni, Ti and Hf raw materials are placed in a vacuum induction melting furnace and repeatedly melted for 6-8 times to obtain alloy ingots, which are then subjected to homogenization treatment, hot rolling treatment and solid solution treatment to obtain a memory alloy.

[0083] Among them, the smelting times are 8 times.

[0084] Homogenization treatment: The alloy ingot was homogenized at 900°C for 4 h and then cooled by water cooling.

[0085] Hot rolling treatment: the ingot after homogenization treatment is kept at 880°C for 50 minutes and then hot rolled. The rolling deformation is 0.5% per pass. Each rolling needs to be returned to the furnace for 3 to 10 minutes of heat preservation, and finally an alloy plate with a thickness of about 1.1 mm is obtained.

[0086] Solution treatment: The alloy plate was solution treated at 880°C for 0.5 h and then cooled with water.

[0087] Organizational structure analysis and performance testing

[0088] (1) Microstructure observation: The surface morphology of the alloy was observed using a scanning electron microscope and an X-ray diffractometer.

[0089] (2) Phase transition temperature detection: The phase transition temperature of the alloy was measured using a scanning calorimeter.

[0090] (3) Recoverable strain test: At room temperature, the sample is first loaded to a specific prestrain value at a tensile rate of 0.2 mm / min, then unloaded, the free sample is heated to 50°C above Af, and kept warm for 10 min, and then its length is measured. The initial length of the sample is L0, the length after unloading after loading to a specific prestrain value is L1, and the length after heating is L2. The shape memory strain (ε SME ) is calculated as: SME =(L1-L2) / L0×100%, recoverable strain ε rec =ε SME +ε el (elastic strain).

[0091] (4) Hardness test: Use a digital microhardness tester to test the microhardness of the alloy.

[0092] Table 1 Performance test

[0093]

[0094] Combining the performance test comparison in Table 1, we can find that:

[0095] 1. By comparing Examples 1-3 with Comparative Examples 1-2, it can be found that the impact resistance and tensile strength of the cables prepared in Examples 1-3 are improved, which means that in the present application, a silica polyethylene glycol solution is used as a modifier to modify the aramid fiber, and the silica particles are loaded on the surface of the aramid fiber, thereby improving the strength of the aramid fiber and reducing the entanglement and agglomeration of the aramid fiber itself, so that the aramid fiber is evenly dispersed in the insulating layer, thereby obtaining uniform strength of the insulating layer.

[0096] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A NiTiHfTa high temperature shape memory alloy, characterized in that: The chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 100-x Ta x , where 5<x≤10.

2. The NiTiHfTa high temperature shape memory alloy according to claim 1, characterized in that: The chemical formula of the NiTiHfTa high temperature shape memory alloy is (Ni 50.3 Ti 29.7 Hf 20 ) 90 Ta 10 .

3. The NiTiHfTa high temperature shape memory alloy according to claim 1, characterized in that: The recoverable strain of the NiTiHfTa high temperature shape memory alloy can reach 3.2%.

4. A preparation process of NiTiHfTa high temperature shape memory alloy, characterized in that: The following steps are involved: S1. Raw material preparation: according to the chemical formula of the memory alloy, Ni, Ti, Hf and Ta are weighed as raw materials respectively; S2. Alloy preparation: Ni, Ti, Hf and Ta raw materials are melted to obtain ingots, and then the memory alloy is obtained through homogenization treatment, hot rolling treatment and solid solution treatment.

5. The process for preparing a NiTiHfTa high temperature shape memory alloy according to claim 4, characterized in that: The temperature of the homogenization treatment is 900° C.-1050° C., and the time of the homogenization treatment is 1-6 hours.

6. The process for preparing a NiTiHfTa high temperature shape memory alloy according to claim 4, characterized in that: The hot rolling treatment method is as follows: the ingot after homogenization treatment is placed at a temperature of 800°C-850°C for heat preservation treatment, and hot rolled, with a rolling deformation of 0.5%-1% per pass to obtain an alloy plate.

7. The process for preparing a NiTiHfTa high temperature shape memory alloy according to claim 6, characterized in that: During the hot rolling process, the steel needs to be returned to the furnace and kept warm for 3-10 minutes after each rolling.

8. The process for preparing a NiTiHfTa high temperature shape memory alloy according to claim 6, characterized in that: The thickness of the alloy plate is 1-1.2 mm.

9. The process for preparing a NiTiHfTa high temperature shape memory alloy according to claim 4, characterized in that: The temperature of the solution treatment is 880-950° C., and the time of the solution treatment is 0.5-1 h.

10. The process for preparing a NiTiHfTa high temperature shape memory alloy according to claim 4, characterized in that: The cooling method in the homogenization treatment and the solution treatment is water cooling.

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