Shaping method for amorphous TiNi-based shape memory alloy loaded with direct current annealing

Abstract

The invention discloses a shaping method for amorphous TiNi-based shape memory alloy loaded direct current annealing. The shaping method specifically comprises the following steps: carrying out annealing treatment on a TiNi-based shape memory alloy wire; and the annealed TiNi-based shape memory alloy wire is subjected to drawing deformation and put into a model, loads are added to the TiNi-based shape memory alloy wire, direct current annealing treatment is carried out, and the shaped amorphous TiNi-based shape memory alloy can be obtained. According to the method, the amorphous TiNi shape memory alloy is loaded and subjected to millisecond-level rapid direct current annealing for shaping treatment, so that the TiNi shape memory alloys with different shapes are obtained, the shaping temperature of the amorphous TiNi shape memory alloy is obviously lower than that of the conventional TiNi shape memory alloy, and the TiNi shape memory alloy obtained through the shaping method has the advantages that the shape of the amorphous TiNi shape memory alloy is uniform and uniform. The grain size can be reduced to 15 nm, and the mechanical property of the TiNi shape memory alloy product is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material forming, and particularly relates to a shaping method for annealing an amorphous TiNi-based shape memory alloy under a direct current load. Background Art

[0002] TiNi-based shape memory alloys exhibit a shape memory effect due to reversible martensitic transformation, and thus have been widely used in fields such as aviation and medicine. To meet the application requirements, TiNi-based shape memory alloys need to be made into specific shapes, such as spring shapes, stent shapes, fastening rings, and orthodontic wires. Therefore, before application, the TiNi-based shape memory alloy needs to be shaped. The shaping treatment used in the prior art is based on the principle of recovery and recrystallization of the TiNi-based shape memory alloy after cold deformation. First, a small amount of cold deformation is performed on the TiNi-based shape memory alloy (taking alloy wire as an example, the cross-sectional area shrinkage rate of the wire after cold deformation is 15%-40%) to obtain a TiNi-based shape memory alloy with a certain dislocation density. Then, the cold-deformed TiNi shape memory alloy is placed in a preset mold, and a specific-shaped TiNi shape memory alloy product is obtained through annealing treatment (annealing temperature is 500-700°C). However, because the recovery and recrystallization temperature of the TiNi-based shape memory alloy is relatively high (annealing temperature is 500-700°C), the grain size of the TiNi-based shape memory alloy obtained by the previous shaping treatment using the principle of recovery and recrystallization of the TiNi-based shape memory alloy is relatively large (greater than 100 nanometers). Therefore, it is difficult for the obtained TiNi-based shape memory alloy to exhibit a high superelastic stress to meet the requirements of alloy lightweight and miniaturization in fields such as aviation and medicine. Summary of the Invention

[0003] The object of the present invention is to provide a shaping method for annealing an amorphous TiNi-based shape memory alloy under a direct current load, which solves the problem that the existing shaping method results in a low superelastic stress of the TiNi shape memory alloy.

[0004] The technical solution adopted by the present invention is a shaping method for annealing an amorphous TiNi-based shape memory alloy under a direct current load, which is specifically implemented according to the following steps: Step 1, annealing the TiNi-based shape memory alloy wire; Step 2, performing drawing deformation on the annealed TiNi-based shape memory alloy wire; Step 3, placing the drawn-deformed TiNi-based shape memory alloy wire in a mold, applying a load to the TiNi-based shape memory alloy wire, and performing direct current annealing treatment to obtain a shaped amorphous TiNi-based shape memory alloy.

[0005] The characteristics of the present invention also lie in that In Step 1, the annealing temperature is 800°C - 1200°C, and the annealing time is 2 min - 20 min.

[0006] In Step 1, the TiNi-based shape memory alloy wire is specifically any one of a TiNi binary shape memory alloy wire, a TiNi-based ternary shape memory alloy wire, and a TiNi-based quaternary shape memory alloy wire.

[0007] In Step 2, the drawing temperature is 0°C - 100°C, and the cross-sectional area shrinkage rate of the TiNi-based shape memory alloy wire after drawing deformation is between 70% and 90%.

[0008] In Step 3, the load is 30 N - 100 N; the current for direct current annealing treatment is 6 A - 12 A, and the annealing time is 15 ms - 80 ms.

[0009] In Step 3, the grain size of the shaped TiNi-based shape memory alloy is 15 nanometers - 30 nanometers.

[0010] The beneficial effects of the present invention are as follows: The method of the present invention first uses an amorphous TiNi shape memory alloy for loading and performs shaping treatment by rapid direct current annealing in milliseconds to obtain TiNi shape memory alloys with different shapes. The shaping temperature is significantly lower than that of conventional TiNi shape memory alloys. Moreover, for the TiNi shape memory alloy obtained by the shaping method of the present invention, the grain size can be reduced to 15 nm, significantly improving the mechanical properties of the TiNi shape memory alloy product. In addition, the preparation process of the present invention is simple, has good repeatability, and is easy to operate, and is expected to provide new ideas for the research and development of high-performance nano-sized TiNi shape memory alloy products. Description of the Drawings

[0011] Figure 1 is a transmission electron microscope photograph of the NiTi shape memory alloy wire provided in Example 1 of the present invention after cold drawing deformation; Figure 2 is a transmission electron microscope photograph of the cold-drawn NiTi shape memory alloy wire provided in Example 1 of the present invention after direct current annealing; Figure 3 is a statistical chart of the average grain size of the cold-drawn NiTi shape memory alloy wire provided in Example 1 of the present invention after annealing; Figure 4 is a photograph of different-shaped wires obtained by subjecting the amorphous NiTi shape memory alloy wire provided in Example 1 of the present invention to load direct current annealing shaping treatment; Figure 5It is the stress-strain curve diagram of the TiNi shape memory alloy wire (1#) obtained by the load direct current annealing treatment provided in Embodiment 1 of the present invention, the TiNi shape memory alloy wire (2#) obtained without applying a load, and the TiNi shape memory alloy wire (3#) obtained by the conventional recovery and recrystallization sizing method; Figure 6 It is the stress-strain curve diagram of the TiNi shape memory alloy wire obtained after sizing at 15 ms (1#), 25 ms (2#), 30 ms (3#), and 40 ms (4#) in the load direct current annealing treatment provided in Embodiment 1 of the present invention. Specific implementation manners

[0012] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation manners.

[0013] The sizing method of the amorphous TiNi-based shape memory alloy of the present invention by load direct current annealing is specifically implemented according to the following steps: Step 1, annealing the TiNi-based shape memory alloy wire with a diameter of 1 mm; The annealing temperature is 800 °C - 1200 °C, and the annealing time is 2 min - 20 min; The TiNi-based shape memory alloy wire is specifically any one of a TiNi binary shape memory alloy wire, a TiNi-based ternary shape memory alloy wire, and a TiNi-based quaternary shape memory alloy wire; The TiNi-based ternary shape memory alloy wire is specifically any one of a TiNiFe shape memory alloy wire, a TiNiNb shape memory alloy wire, a TiNiCu shape memory alloy wire, a TiNiZr shape memory alloy wire, and a TiNiCr shape memory alloy wire; The TiNi-based quaternary shape memory alloy wire is specifically a TiNiNbCu shape memory alloy wire or a TiNiNbFe shape memory alloy wire; Step 2, subjecting the annealed TiNi-based shape memory alloy wire to drawing deformation, the drawing temperature is 0 °C - 100 °C, and the cross-sectional area shrinkage rate of the TiNi-based shape memory alloy wire after drawing deformation is between 70% - 90%; Specifically, the whole wire is drawn from a diameter of 1 mm to 0.5 mm without any heat treatment during the deformation process; Among them, during the process of drawing the wire from a diameter of 1 mm to 0.7 mm, the diameter change of the wire after each drawing pass is 0.02 mm (i.e., 1 mm - 0.98 mm - 0.96 mm... 0.70 mm). Since the alloy wire has accumulated a certain amount of plastic deformation and work hardening when it reaches 0.70 mm, in order to prevent fracture during the subsequent drawing deformation process, during the process of drawing the alloy wire from a diameter of 0.70 mm to a diameter of 0.50 mm, the diameter change of the wire after each drawing pass is 0.01 mm (i.e., 0.70 mm - 0.69 mm - 0.68 mm... 0.5 mm); Step 3: Place the drawn and deformed TiNi-based shape memory alloy wire into a mold, apply an additional load to the TiNi-based shape memory alloy wire, and perform direct current annealing treatment to obtain the shaped amorphous TiNi-based shape memory alloy; The load is 30 N - 100 N; the current for the direct current annealing treatment is 6 A - 12 A, and the annealing time is 15 ms - 80 ms; The grain size of the shaped TiNi-based shape memory alloy is 15 nanometers - 30 nanometers; The present invention is the first to use an amorphous TiNi shape memory alloy for load direct current annealing treatment for shaping to obtain TiNi shape memory alloy wires of different shapes, which is significantly different from the conventional TiNi shape memory alloys that are shaped based on recovery and recrystallization to obtain TiNi shape memory alloys of different shapes. Among them, the shaping temperature in the present invention is significantly lower than that of the conventional TiNi shape memory alloys for shaping, and the grain size of the TiNi shape memory alloy obtained by the shaping method proposed in the present invention can be reduced to 15 nm, which is significantly smaller than that of the conventional TiNi shape memory alloys shaped based on recovery and recrystallization to obtain TiNi shape memory alloys of different shapes. Moreover, the present invention applies an additional load treatment to the alloy wire before direct current annealing, which helps the grain orientation and distribution after the crystallization of the alloy amorphous phase, thereby significantly improving the mechanical properties of the TiNi shape memory alloy product. The preparation process of the present invention is simple, has good repeatability, and is easy to operate. The obtained TiNi shape memory alloy wire products of different shapes can be used in cardiovascular stents, esophageal stents, and orthodontic wires in the medical field, as well as memory alloy springs and fastening rings in the aviation field.

[0014] Example 1 The shaping method of the amorphous TiNi shape memory alloy with load direct current annealing of the present invention includes the following steps: Heat-treat a TiNi shape memory alloy wire with a diameter of 1 mm in a muffle furnace, the annealing temperature is 1000 °C, and the annealing time is 5 minutes; The TiNi shape memory alloy wire after annealing treatment is drawn and deformed at 25°C. The diameter of the wire before drawing is 1 mm, and the diameter of the wire after drawing is 0.5 mm. No heat treatment is performed during the drawing process, and the deformation amount after drawing is 75% (the cross-sectional area shrinkage rate of the wire). The drawn amorphous TiNi shape memory alloy wire is obtained. The transmission electron microscope photograph of its microstructure is as shown in Figure 1 shown, and it can be seen from Figure 1 that the TiNi shape memory alloy wire is composed of amorphous after drawing deformation, which indicates that the TiNi alloy wire is composed of amorphous before the load direct current annealing treatment and shaping of the alloy wire in the present invention.

[0015] The drawn and deformed TiNi shape memory alloy wire is subjected to millisecond-level direct current annealing treatment in a mold. An additional load (100 N) is applied to the wire before the electric annealing, the current is 8 A, and the annealing time is 15 ms; the transmission electron microscope photograph of the microstructure of the TiNi shape memory alloy wire obtained after the annealing treatment is as shown in Figure 2 shown, indicating that the TiNi shape memory alloy wire obtained after the annealing treatment is composed of nanocrystals. The statistical distribution diagram of its average grain size is as shown in Figure 3 shown, indicating that its average grain size is 15 nanometers.

[0016] After the above shaping treatment, TiNi shape memory alloy wires of different shapes are obtained, as shown in Figure 4 shown, indicating that the shaping method of the amorphous TiNi shape memory alloy provided by the present invention can effectively obtain TiNi shape memory alloys of different shapes.

[0017] Example 2 Furthermore, by comparing the mechanical properties (the drawing deformation amount is 20% of the cross-sectional shrinkage rate of the wire, and the shaping temperature is 500°C) of the TiNi shape memory alloy wire (1#) obtained by shaping the amorphous TiNi memory alloy by load direct current annealing treatment in Example 1, the TiNi shape memory alloy wire (2#) obtained by shaping the amorphous TiNi memory alloy without applying a load treatment, and the TiNi shape memory alloy wire (3#) obtained by the conventional recovery and recrystallization shaping method, the results are as shown in Figure 5 shown, and it can be seen that the superelastic properties of the alloy obtained by the present invention are significantly better than those of the alloy wire without applying a load electric annealing treatment and the TiNi shape memory alloy obtained by the conventional recovery and recrystallization shaping method reported in the past.

[0018] Example 3 Furthermore, compare the superelastic properties of the TiNi shape memory alloy wires with different annealing times in the shaping of the amorphous TiNi memory alloy by load direct current annealing treatment in Example 1. The results are as shown in Figure 6As shown, the wire samples of 1#, 2#, 3# and 4# are TiNi shape memory alloy wires obtained by setting after 15 ms, 25 ms, 30 ms and 40 ms respectively in the load direct current annealing treatment. It can be seen that as the direct current annealing time increases, the superelastic stress of the alloy after setting gradually decreases, and the residual strain gradually increases. That is, the method involved in the present invention can conveniently regulate the superelastic properties of TiNi shape memory alloy wires, and promote the application of alloy wires in different fields and different environments.

[0019] Example 4 The setting method of the amorphous TiNi-based shape memory alloy of the present invention by loading direct current annealing is specifically implemented according to the following steps: Step 1, anneal the TiNi-based shape memory alloy wire with a diameter of 1 mm; The annealing temperature is 800 °C, and the annealing time is 2 min; The TiNi-based shape memory alloy wire is specifically a TiNiFe shape memory alloy wire; Step 2, perform drawing deformation on the annealed TiNi-based shape memory alloy wire. The drawing temperature is 10 °C, and the cross-sectional area shrinkage rate of the TiNi-based shape memory alloy wire after drawing deformation is 70%; Step 3, put the drawn-deformed TiNi-based shape memory alloy wire into a mold, apply a load to the TiNi-based shape memory alloy wire, and then perform direct current annealing treatment to obtain the set amorphous TiNi-based shape memory alloy; The load is 30 N; the current of the direct current annealing treatment is 6 A, and the annealing time is 15 ms.

[0020] Example 5 The setting method of the amorphous TiNi-based shape memory alloy of the present invention by loading direct current annealing is specifically implemented according to the following steps: Step 1, anneal the TiNi-based shape memory alloy wire with a diameter of 1 mm; The annealing temperature is 1200 °C, and the annealing time is 15 min; The TiNi-based shape memory alloy wire is specifically a TiNi binary shape memory alloy wire; Step 2, perform drawing deformation on the annealed TiNi-based shape memory alloy wire. The drawing temperature is 10 °C, and the cross-sectional area shrinkage rate of the TiNi-based shape memory alloy wire after drawing deformation is 80%; Step 3, put the drawn-deformed TiNi-based shape memory alloy wire into a mold, apply a load to the TiNi-based shape memory alloy wire, and then perform direct current annealing treatment to obtain the set amorphous TiNi-based shape memory alloy; The load is 80 N; the current for direct current annealing treatment is 10 A, and the annealing time is 20 ms.

[0021] Example 6 For the shaping method of the amorphous TiNi shape memory alloy loaded with direct current annealing of the present invention, the selection of shaping the amorphous TiNi shape memory alloy is due to the process of amorphous to crystal transformation occurring during annealing, resulting in atomic rearrangement to shape the amorphous TiNi shape memory alloy. At the same time, in order to obtain the amorphous TiNi shape memory alloy, large plastic deformation is required, so the cold drawing deformation amount is selected to be 70-90% (the cross-sectional area shrinkage rate of the wire). In order to make the grain size of the shaped TiNi shape memory alloy less than 40 nanometers and improve the shaping efficiency of the TiNi shape memory alloy wire, direct current annealing treatment is selected. In order to promote the grain orientation and distribution after the alloy is annealed by electricity, an additional load is applied to the wire and then the electric annealing treatment is carried out.

Claims

1. A setting method for direct current annealing of an amorphous TiNi-based shape memory alloy, characterized in that, The implementation is specifically carried out according to the following steps: Step 1: Anneal the TiNi-based shape memory alloy wire; Step 2: Perform drawing deformation on the annealed TiNi-based shape memory alloy wire; Step 3: Place the drawn-deformed TiNi-based shape memory alloy wire into a mold, apply a load to the TiNi-based shape memory alloy wire, and perform direct current annealing treatment to obtain the shaped amorphous TiNi-based shape memory alloy.

2. The shaping method of annealing a non-crystalline TiNi-based shape memory alloy under direct current as claimed in claim 1, wherein In the said Step 1, the annealing temperature is 800°C - 1200°C, and the annealing time is 2 min - 20 min.

3. The setting method of the amorphous TiNi-based shape memory alloy loaded with direct current annealing according to claim 1, characterized in that, In the said Step 1, the TiNi-based shape memory alloy wire is specifically any one of TiNi binary shape memory alloy wire, TiNi-based ternary shape memory alloy wire, and TiNi-based quaternary shape memory alloy wire.

4. The setting method of the amorphous TiNi-based shape memory alloy loaded with direct current annealing according to claim 3, characterized in that, The TiNi-based ternary shape memory alloy wire is specifically any one of TiNiFe shape memory alloy wire, TiNiNb shape memory alloy wire, TiNiCu shape memory alloy wire, TiNiZr shape memory alloy wire, and TiNiCr shape memory alloy wire.

5. The shaping method of the amorphous TiNi-based shape memory alloy loaded with direct current annealing according to claim 3, characterized in that, The TiNi-based quaternary shape memory alloy wire is specifically TiNiNbCu shape memory alloy wire or TiNiNbFe shape memory alloy wire.

6. The setting method of the amorphous TiNi-based shape memory alloy loaded with direct current annealing according to claim 1, characterized in that, In the said Step 2, the drawing temperature is 0°C - 100°C, and the cross-sectional area shrinkage rate of the drawn-deformed TiNi-based shape memory alloy wire is between 70% - 90%.

7. The setting method of the amorphous TiNi-based shape memory alloy loaded with direct current annealing according to claim 6, characterized in that, In the said Step 3, the load is 30 N - 100 N; the current for the direct current annealing treatment is 6 A - 12 A, and the annealing time is 15 ms - 80 ms.

8. The setting method of the amorphous TiNi-based shape memory alloy loaded with direct current annealing according to claim 7, characterized in that, In the said Step 3, the grain size of the shaped TiNi-based shape memory alloy is 15 nanometers - 30 nanometers.

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