Preparation method of shape memory alloy plate with high-temperature hyperelasticity

Abstract

The invention discloses a preparation method of a shape memory alloy plate with high-temperature hyperelasticity, and belongs to the technical field of shape memory alloys. The shape memory alloy is nickel-titanium-tantalum alloy, and the preparation method mainly comprises the steps of hot rolling, sheath cold rolling, severe plastic deformation and recrystallization annealing, so that the microstructure is refined, and the grain size is regulated and controlled. The nickel-titanium-tantalum shape memory alloy plate prepared by the method has good superelasticity when the temperature is higher than 100 DEG C, the recoverable strain is greater than 5%, and meanwhile, the nickel-titanium-tantalum shape memory alloy plate has relatively high cycling stability. Compared with nickel-titanium-hafnium high-temperature shape memory alloy, only 5.7% of Ta is added into the shape memory alloy plate, the cost of raw materials is remarkably reduced, and the shape memory alloy plate is a superelastic material which can be applied to the high-temperature environment of 100-180 DEG C.

Description

Technical Field

[0001] The invention relates to a method for preparing a shape memory alloy plate with high-temperature superelasticity, belonging to the technical field of shape memory alloys. Background Art

[0002] Nickel-titanium shape memory alloy is the most successful shape memory alloy in commercial applications. Due to its excellent superelasticity, it performs well in situations that require high elasticity and repeatable deformation, and has become an important material that is increasingly widely used in engineering and biomedical fields. For example, in the medical field, it can be made into self-expanding vascular stents for the treatment of coronary heart disease, atherosclerosis and other diseases. However, the martensitic phase transition temperature of nickel-titanium shape memory alloy is lower than 100°C, which causes its superelasticity to be significantly weakened or even completely disappear in the high temperature range above 100°C. Therefore, the development of shape memory alloys with high-temperature superelasticity (i.e., superelastic temperature above 100°C) has important practical application value.

[0003] There are currently two main methods to achieve high temperature superelasticity in shape memory alloys. One is to increase the dislocation slip critical stress of binary nickel-titanium alloys and inhibit plastic deformation at high temperatures to achieve high temperature superelasticity, such as conventional cold working (such as cold rolling) of nickel-titanium alloys, followed by appropriate post-processing heat treatment. Reference 1 “High temperature superelasticity realized in equiatomic Ti-Ni conventional shape memory alloy by severe cold rolling, Materials&Design 193 (2020) 108875” reports the cold-rolled Ni 50 Ti 50 The alloy sheet has high temperature superelasticity at 210°C, but its recoverable strain is small (only 3%) and its plasticity is poor. So far, there are only a few reports on the high temperature superelasticity of binary nickel-titanium shape memory alloys.

[0004] Another method to obtain high-temperature superelasticity is to develop a multi-component nickel-titanium-based alloy with a high phase transition temperature, such as NiTiHf high-temperature shape memory alloy. Reference 2 "A method for improving the superelasticity of NiTiHf high-temperature shape memory alloy, patent application number 202410583982.5" uses a preparation process combining hot rolling and electric pulse treatment to obtain Ni 50.3 Ti 29.7 Hf 20The alloy sheet has high temperature superelasticity above 200°C, but the recoverable strain is only 3.65%. Document 3 "A preparation method of high superelastic NiTiHf high temperature shape memory alloy, patent application number 202110344508.3" prepared Ni by jacket hot rolling + aging method 50.3 Ti 29.7 Hf 20 The alloy plate has a superelasticity of 5.18% at 215°C. Although the above nickel-titanium-hafnium alloy has high-temperature superelasticity, the Hf content in the alloy is as high as 20% (atomic percentage). Due to the high price of Hf, the cost of raw materials is high. In addition, the alloy ingots need to be homogenized at above 1000°C for 48 to 72 hours, which is time-consuming and energy-consuming. Summary of the invention

[0005] The present invention aims at the disadvantage that the superelastic temperature of the existing NiTi shape memory alloy is low, and provides a simple and easy preparation method. The nickel-titanium-tantalum shape memory alloy sheet prepared by the method has good superelasticity at a high temperature above 100°C. The preparation method of a shape memory alloy sheet with high-temperature superelasticity provided by the present invention successfully prepares a nickel-titanium-tantalum alloy sheet through the steps of hot rolling, jacket cold rolling large plastic deformation and recrystallization annealing, and shows good superelasticity in the temperature range of 100 to 180°C, and has high cyclic stability, making it a high-temperature superelastic material.

[0006] The present invention provides a method for preparing a shape memory alloy plate having high temperature superelasticity, comprising the following steps:

[0007] Step 1: Take the composition as Ni 48.2 Ti 41.1 Ta 5.7 (atomic percentage) of a nickel-titanium-tantalum alloy ingot, subjected to a homogenization heat treatment at 900° C., water-cooled, and then hot-rolled to obtain a nickel-titanium-tantalum alloy plate;

[0008] Step 2: Solution treat the nickel-titanium-tantalum alloy plate at 900°C for 0.5 to 1 h, and then water cool it;

[0009] Step 3: Cut the nickel-titanium-tantalum alloy plate into a nickel-titanium-tantalum alloy rectangular plate with a length of x mm and a width of y mm; put the cut nickel-titanium-tantalum alloy rectangular plate into a 304 stainless steel plate with a hollowed-out middle, form a gap fit on both sides, place a 304 stainless steel plate on the upper and lower sides respectively, and combine them into a sheath structure by welding;

[0010] Step 4: annealing the sheath structure at 570° C. for 0.5 to 1 h, then air-cooling, and cold-rolling at room temperature; after the cold rolling, cutting the stainless steel sheet to obtain a nickel-titanium-tantalum alloy sheet;

[0011] Step 5: Anneal the nickel-titanium-tantalum alloy sheet at 350-500° C. and then water-cool it to obtain a high-temperature superelastic shape memory alloy sheet.

[0012] Furthermore, in step 1, the homogenization heat treatment time is 6 to 7 hours; and the thickness of the nickel-titanium-tantalum alloy plate is 1.7 to 2.0 mm.

[0013] Furthermore, in step 3, the length of the hollowed-out stainless steel plate is x+10mm, the width is y+10mm, and the thickness is 1.7-2.0mm; the length of the hollowed-out portion is x+0.1mm, and the width is y+0.1mm; the hollowed-out portion runs through the entire stainless steel plate, and the cut nickel-titanium-tantalum alloy rectangular plate is placed in the hollowed-out portion; the stainless steel plates placed on the upper and lower surfaces are x+10mm long, y+10mm wide, and 0.7-1.2mm thick.

[0014] Furthermore, in step 3, during welding, the welding position is the joint of the stainless steel plate along the length direction.

[0015] Furthermore, in step 4, during the cold rolling, the rolling direction is the length direction of the sheath structure.

[0016] Furthermore, in step 4, during the cold rolling, the rolling deformation amount of each pass is 2% to 3%, and the total deformation amount is 50% to 55%.

[0017] Furthermore, in step 4, during the cold rolling, the jacket structure is allowed to air-cool to room temperature after each rolling pass before the next rolling pass.

[0018] Furthermore, in step 5, the annealing time is 1 hour.

[0019] The invention provides a shape memory alloy plate with high temperature superelasticity. The superelastic recoverable strain of the nickel-titanium-tantalum shape memory alloy plate is above 5% within the temperature range of 100 to 180°C.

[0020] The beneficial effects of the present invention are:

[0021] 1. The nickel-titanium-tantalum alloy involved in the present invention comprises Ni 48.2 Ti 41.1 Ta 5.7(atomic percentage), through a preparation method including hot rolling, jacket cold rolling large plastic deformation and recrystallization annealing, a nickel-titanium-tantalum shape memory alloy sheet with a thickness of 0.8 to 1.0 mm is obtained, which has good superelasticity at a temperature above 100°C, and the maximum recoverable strain can reach 5.8%, while having high cyclic stability. Compared with the binary nickel-titanium alloy sheet with high-temperature superelasticity in the prior art, the recoverable strain of the nickel-titanium-tantalum alloy sheet prepared by the present invention is increased by more than 2%, and is also improved compared with the nickel-titanium-hafnium high-temperature shape memory alloy. The nickel-titanium-tantalum alloy sheet prepared by the present invention is a superelastic material that can be used in high-temperature environments.

[0022] 2. Compared with other nickel-titanium-hafnium high-temperature shape memory alloy plates in the prior art, the shape memory alloy plate with high-temperature superelasticity provided by the present invention only adds 5.7% Ta, and the cost of raw materials is significantly reduced; the homogenization treatment temperature of the alloy ingot is reduced to 900°C, and the insulation time is shortened to 6 to 7 hours.

[0023] 3. The sheath structure involved in the preparation method provided by the present invention is simple in design and easy to implement. The 304 stainless steel used for the sheath is inexpensive, the homogenization treatment temperature of the alloy ingot is low, and the insulation time is short. It has the advantages of low cost, low energy consumption, simple operation, and suitability for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic flow chart of the preparation method of the present invention;

[0025] Figure 2 Ni prepared by the method of the present invention 48.2 Ti 41.1 Ta 5.7 Superelastic curve of alloy plate at 110℃;

[0026] Figure 3 Conventional hot-rolled Ni 48.2 Ti 41.1 Ta 5.7 The alloy plate is at a temperature higher than the martensitic reverse transformation temperature (A f ) when the hyperelastic curve. DETAILED DESCRIPTION

[0027] The accompanying drawings provided herein are used to further illustrate the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In addition, a comparative example ( Figure 3 ) is used to compare with the embodiments to illustrate the advantages of the present invention.

[0028] like Figure 1 As shown, the present invention discloses a method for preparing a shape memory alloy sheet with high temperature superelasticity, comprising the following steps:

[0029] (1) The actual composition of Ni is prepared by conventional smelting method 48.2 Ti 41.1 Ta 5.7 (atomic percentage) of nickel-titanium-tantalum alloy ingots, homogenized at 900°C (6 hours of heat preservation, water cooling);

[0030] (2) hot rolling the nickel-titanium-tantalum alloy ingot obtained in step (1) to obtain a nickel-titanium-tantalum alloy plate with a final thickness of 1.7 to 2.0 mm;

[0031] (3) subjecting the nickel-titanium-tantalum alloy plate obtained in step (2) to a solution treatment at 900° C. for 0.5 to 1 h, and then water cooling;

[0032] (4) cutting the nickel-titanium-tantalum alloy plate obtained in step (3) into a rectangular plate of a certain size;

[0033] (5) placing the nickel-titanium-tantalum alloy rectangular plate obtained in step (4) into a hollowed-out 304 stainless steel plate to form a clearance fit, the clearance being 0.1 mm; placing a 304 stainless steel plate on each of the upper and lower surfaces thereof, and welding them together to form a sheath structure, wherein the welding position is the joint of the stainless steel plates along the length direction; the hollowed-out 304 stainless steel plate has the same thickness as the nickel-titanium-tantalum alloy plate after hot rolling in step (2); the thickness of the 304 stainless steel plates placed on the upper and lower surfaces is 0.7 to 1.2 mm;

[0034] (6) annealing the sheath structure obtained in step (5) at 570° C. for 0.5 to 1 hour, and then air cooling;

[0035] (7) cold rolling the sheath structure obtained in step (6) at room temperature; the rolling direction is the length direction of the sheath structure; the rolling deformation amount (calculated as the thickness change amount) of each pass is 2% to 3%, and the total deformation amount is 50% to 55%; after each rolling pass, the sheath structure is air-cooled to room temperature before the next rolling pass is performed;

[0036] (8) after the cold rolling, the 304 stainless steel sheet is cut to obtain a nickel-titanium-tantalum alloy sheet with a final thickness of 0.8 to 1.0 mm;

[0037] (9) The nickel-titanium-tantalum alloy sheet obtained in step (8) is annealed at 350-500° C. for 1 h, and then water-cooled to obtain a high-temperature superelastic shape memory alloy sheet.

[0038] The present invention is described in more detail with reference to the following examples.

[0039] Example 1

[0040] A Ni with high temperature superelasticity 48.2 Ti 41.1 Ta5.7 The preparation method of the shape memory alloy sheet comprises the following specific steps:

[0041] (1) According to Ni 48.2 Ti 41.1 Ta 5.7 The atomic percentage of pure nickel (Ni), pure titanium (Ti) and pure tantalum (Ta) was weighed and then button-shaped ingots were obtained by vacuum arc melting, and then subjected to homogenization heat treatment at 900°C (keeping temperature for 6 hours, water cooling);

[0042] (2) hot rolling the nickel-titanium-tantalum alloy ingot obtained in step (1) to obtain a Ni-Ti-Tantalum alloy with a final thickness of 1.7 mm. 48.2 Ti 41.1 Ta 5.7 Alloy plate;

[0043] (3) Ni obtained in step (2) 48.2 Ti 41.1 Ta 5.7 The alloy plates were solution treated at 900 °C for 0.5 h and then water cooled;

[0044] (4) Ni obtained in step (3) 48.2 Ti 41.1 Ta 5.7 The alloy plate is cut into a rectangular plate with a length of 40 mm and a width of 15 mm;

[0045] (5) placing the nickel-titanium-tantalum alloy rectangular plate obtained in step (4) into a hollowed-out 304 stainless steel plate (the inner hollowed-out structure has a length of 40 mm + 0.1 mm and a width of 15 mm + 0.1 mm, and the outer contour has a length of 50 mm, a width of 25 mm, and a thickness of 1.7 mm), placing a 304 stainless steel plate (length of 50 mm, width of 25 mm, and thickness of 1 mm) on each of the upper and lower surfaces, and welding the stainless steel plates at the joints along the length direction to form a sheath structure;

[0046] (6) annealing the sheath structure obtained in step (5) at 570° C. for 1 hour, and then air cooling;

[0047] (7) cold rolling the sheath structure obtained in step (6) at room temperature, with the rolling direction being the length direction of the sheath structure, and the rolling deformation (calculated as the thickness change) of each pass being 3%. After each rolling pass, the alloy is allowed to fully cool to room temperature before the next rolling pass is performed, and the total rolling deformation is 53%;

[0048] (8) After the cold rolling, the 304 stainless steel sheet was cut to obtain a Ni 48.2 Ti 41.1 Ta 5.7 Alloy plates;

[0049] (9) Ni obtained in step (8) 48.2 Ti 41.1 Ta 5.7 The alloy sheets were annealed at 400 °C for 1 hour and then water-cooled.

[0050] The Ni 48.2 Ti 41.1 Ta 5.7 A dog-bone tensile specimen with a size of 10 mm × 1 mm × 0.85 mm was cut from the shape memory alloy sheet, and the cutting marks on the surface were removed with sandpaper. The specimen was subjected to a superelastic test on an Instron 3365 electronic universal material testing machine equipped with a temperature control box. The test temperature was 110 ° C and the strain rate was 0.2 mm / min. The obtained superelastic curve is shown in Figure 2 As shown. Under 6% pre-strain, Ni 48.2 Ti 41.1 Ta 5.7 The superelastic recoverable strain (ε) of the shape memory alloy is about 5.8%.

[0051] To further illustrate the advantages of the present invention, Comparative Example 1 is provided below for superelasticity comparison.

[0052] Comparative Example 1

[0053] Conventional hot rolled Ni 48.2 Ti 41.1 Ta 5.7 Shape memory alloy sheet: The alloy composition of this comparative example is completely consistent with that of Example 1. The specific steps of the preparation method are 3 steps in total, which are consistent with steps (1), (2) and (3) in Example 1.

[0054] Specific preparation method:

[0055] (1) According to Ni 48.2 Ti 41.1 Ta 5.7 The atomic percentage of pure nickel (Ni), pure titanium (Ti) and pure tantalum (Ta) was weighed and then button-shaped ingots were obtained by vacuum arc melting, and then subjected to homogenization heat treatment at 900°C (keeping temperature for 6 hours, water cooling);

[0056] (2) hot rolling the nickel-titanium-tantalum alloy ingot obtained in step (1) to obtain a Ni-Ti-Tantalum alloy with a final thickness of 1.7 mm. 48.2 Ti 41.1 Ta 5.7 Alloy plate;

[0057] (3) Ni obtained in step (2) 48.2 Ti 41.1 Ta 5.7 The alloy plates were solution treated at 900 °C for 0.5 h and then water cooled;

[0058] The Ni 48.2 Ti 41.1 Ta 5.7 The shape memory alloy sheet is tested according to the test method in Example 1 at a temperature higher than the reverse martensitic transformation temperature (A f ) when a hyperelastic test is performed, and the obtained hyperelastic curve is as follows Figure 3 As shown in Figure 2, under a pre-strain of 6%, the superelastic recoverable strain (ε) of the alloy is about 1.6%.

[0059] By comparing Example 1 with Comparative Example 1, it can be seen that the high-temperature superelasticity of the nickel-titanium-tantalum shape memory alloy sheet prepared by the method provided by the present invention is significantly higher than that of conventional hot rolling.

[0060] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a shape memory alloy sheet with high temperature superelasticity, characterized in that: The following steps are involved: Step 1: Take the composition as Ni 48.2 Ti 41.1 Ta 5.7 The nickel-titanium-tantalum alloy ingot is subjected to homogenization heat treatment at 900°C, water-cooled, and then hot-rolled to obtain a nickel-titanium-tantalum alloy plate; Step 2: Solution treat the nickel-titanium-tantalum alloy plate at 900°C for 0.5 to 1 h, and then water cool it; Step 3: Cut the nickel-titanium-tantalum alloy plate into a nickel-titanium-tantalum alloy rectangular plate with a length of x mm and a width of y mm; put the cut nickel-titanium-tantalum alloy rectangular plate into a 304 stainless steel plate with a hollowed-out middle, form a gap fit on both sides, place a 304 stainless steel plate on the upper and lower sides respectively, and combine them into a sheath structure by welding; Step 4: annealing the sheath structure at 570° C. for 0.5 to 1 h, then air-cooling, and cold-rolling at room temperature; after the cold rolling, cutting the stainless steel sheet to obtain a nickel-titanium-tantalum alloy sheet; Step 5: Anneal the nickel-titanium-tantalum alloy sheet at 350-500° C. and then water-cool it to obtain a high-temperature superelastic shape memory alloy sheet.

2. The method for preparing a shape memory alloy sheet with high temperature superelasticity according to claim 1, characterized in that: In step 1, the homogenization heat treatment time is 6 to 7 hours; the thickness of the nickel-titanium-tantalum alloy plate is 1.7 to 2.0 mm.

3. The method for preparing a shape memory alloy sheet with high temperature superelasticity according to claim 1, characterized in that: In step 3, the length of the hollowed-out stainless steel plate is x+10mm, the width is y+10mm, and the thickness is 1.7-2.0mm; the length of the hollowed-out portion is x+0.1mm, and the width is y+0.1mm; the length of the stainless steel plates placed on the upper and lower surfaces is x+10mm, the width is y+10mm, and the thickness is 0.7-1.2mm.

4. The method for preparing a shape memory alloy sheet with high temperature superelasticity according to claim 1, characterized in that: In step 3, during welding, the welding part is the joint of the stainless steel plate along the length direction.

5. The method for preparing a shape memory alloy sheet with high temperature superelasticity according to claim 1, characterized in that: In step 4, during the cold rolling, the rolling direction is the length direction of the sheath structure.

6. The method for preparing a shape memory alloy sheet with high temperature superelasticity according to claim 1, characterized in that: In step 4, during the cold rolling, the rolling deformation amount of each pass is 2% to 3%, and the total deformation amount is 50% to 55%.

7. The method for preparing a shape memory alloy sheet with high temperature superelasticity according to claim 1, characterized in that: In step 4, during the cold rolling, the jacket structure is allowed to air-cool to room temperature after each rolling pass before the next rolling pass.

8. The method for preparing a shape memory alloy sheet with high temperature superelasticity according to claim 1, characterized in that: In step 5, the annealing time of the nickel-titanium-tantalum alloy sheet is 1 hour.

9. A shape memory alloy sheet prepared by the method according to any one of claims 1 to 8, characterized in that: The shape memory alloy plate has a superelastic recoverable strain of more than 5% within a temperature range of 100 to 180°C.

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