CN114109752B - Shape memory alloy driving element - Google Patents
Shape memory alloy driving element Download PDFInfo
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- CN114109752B CN114109752B CN202111313598.6A CN202111313598A CN114109752B CN 114109752 B CN114109752 B CN 114109752B CN 202111313598 A CN202111313598 A CN 202111313598A CN 114109752 B CN114109752 B CN 114109752B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/006—Resulting in heat recoverable alloys with a memory effect
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
- C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
Abstract
The invention provides a shape memory alloy driving element, which is made of a shape memory alloy material and comprises a driving execution section and a constraint section, wherein the shape memory alloy in the driving execution section has a crystal structure, and the shape memory alloy in the constraint section has an amorphous/crystalline complex phase structure. The invention further provides a processing technology of the shape memory alloy driving element. The shape memory alloy driving element provided by the invention has a double microstructure, can be used for intelligent execution devices such as a thermostatic valve and a high-temperature alarm, realizes millimeter-level to micrometer-level accurate control, and provides key element materials for microelectronic devices, minimally invasive surgical instruments and micro/nano-level medical robots.
Description
Technical Field
The invention belongs to the field of alloy materials, relates to a shape memory alloy driving element, and in particular relates to a shape memory alloy driving element and a processing technology thereof.
Background
Along with the continuous promotion of miniaturized demands of sensing and executing devices in the fields of aerospace, precision machinery, consumer electronics, medical appliances, robots and the like, a series of intelligent materials with integrated mechanics and functions are developed for miniature executing elements. Among them, the shape memory alloy integrates displacement & temperature sensing and large strain driving functions, and the shape memory alloy torsion spring and the linear motion actuator are now effective alternatives to the electric motor in terms of electric and braking, because they have inherent potential to realize mass and volume savings which cannot be realized by the conventional actuators.
The intelligent shape memory alloy executing device is to realize continuous and reciprocating multi-cycle operation, and the structure of the intelligent shape memory alloy executing device comprises a shape memory alloy executing element and a constraint unit. The shape memory alloy actuator is usually in the form of a spring or wire having a shape memory effect and a set operating temperature T 0 When the temperature is higher than T 0 When the shape memory alloy element undergoes martensite reverse phase transformation, and stress/strain is output; and when the temperature is reduced to T 0 In the following, the martensitic phase transformation of the material of the shape memory alloy element occurs, and the martensitic phase is again in a soft state, and a restraining force is required to restore the shape memory alloy element to a pre-operation state and position. Existing actuators typically use springs or reeds to provide the restraining force.
However, in the design process of the intelligent execution device of the shape memory alloy, the design and selection of the spring or the reed often have trouble, and there are several problems: 1) The volume of the intelligent execution device system cannot be further reduced, and the maximum advantage of the intelligent execution device of the shape memory alloy is weakened; 2) The corresponding form of the mechanics of the spring has fundamental defects, particularly in a low strain mode, the stress and displacement are not linear; when the strain quantity exceeds a certain value, the spring is easy to fatigue, the mechanical behavior of the spring is correspondingly attenuated and cannot be matched with the millions-level cycle life of the shape memory alloy element, and the action precision of the actuator is affected; 3) The structural design of the reed is very complex, and the cost is high; 4) The connection of shape memory alloy elements to springs or reeds, i.e. heterogeneous elements, has a great bottleneck, especially in the field of micro-actuators.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a shape memory alloy driving element having a dual microstructure and having the function of a thermally driven intelligent actuator.
To achieve the above and other related objects, a first aspect of the present invention provides a shape memory alloy driving element made of a shape memory alloy (shape memory alloys, SMA) material, comprising a driving execution section, the shape memory alloy within the driving execution section having a crystalline structure, and a constraint section, the shape memory alloy within the constraint section having an amorphous/crystalline complex phase structure.
Preferably, the shape memory alloy material is one of a titanium nickel base shape memory alloy or a titanium nickel copper base shape memory alloy.
More preferably, the titanium content in the titanium-nickel-based shape memory alloy is 48.5-51.5%.
More preferably, the titanium content in the titanium-nickel-copper-based shape memory alloy is 48.5-51.5%, and the copper content is less than or equal to 8%.
Preferably, the driving execution section and the constraint section are sequentially arranged along the linear direction, and the ratio of the length of the driving execution section to the length of the constraint section is 1:2-1:5.
Preferably, the elastic modulus of the crystal structure is 75-90 GPa.
Preferably, the effective strain of the crystal structure is 7-9%. More preferably, the effective strain of the crystal structure is 8%.
Preferably, the elastic modulus of the amorphous/crystalline complex phase structure is 40-65 GPa.
Preferably, the effective strain of the amorphous/crystalline complex phase structure is 4-5%. More preferably, the amorphous/crystalline complex phase structure has an effective strain of 4%.
A second aspect of the present invention provides a process for manufacturing a shape memory alloy driving element, comprising the steps of:
1) Continuously cold drawing the shape memory alloy wire to obtain a shape memory alloy fiber, wherein in the multiple cold drawing processes, the first annealing treatment is carried out between two adjacent processes to enable the shape memory alloy fiber to form an amorphous/crystalline complex phase structure;
2) And dividing the shape memory alloy fiber into a driving execution section and a constraint section, performing gradient heat treatment, performing secondary annealing treatment on the driving execution section to form a crystal structure, and performing water cooling treatment on the constraint section to maintain an amorphous/crystal complex phase structure to obtain the shape memory alloy driving element.
Preferably, in step 1), the continuous cold drawing reduces the diameter of the wire by cold drawing to make it a fiber, before the continuous cold drawing.
Preferably, in the step 1), the diameter of the shape memory alloy fiber is less than or equal to 2mm.
Preferably, in step 1), the number of processing times of the single cold drawing process is 3 to 6.
Preferably, in the step 1), in the continuous cold drawing, the reduction ratio of the cold drawing step at the end is 7 to 12%, and the reduction ratio of the cold drawing step at the other steps except the end is 4 to 9%.
More preferably, the cold drawing process is not followed by a first annealing treatment.
Preferably, in step 1), the first annealing treatment is an annealing treatment under a protective atmosphere. The protective atmosphere is argon.
Preferably, in step 1), the temperature of the first annealing treatment is 350-550 ℃.
Preferably, in step 1), the time of the first annealing treatment is 20-50s. More preferably, the time of the first annealing treatment is 30 to 40 seconds.
Preferably, in step 1), the strength of the amorphous/crystalline complex phase structure is not less than 1800MPa.
Preferably, in step 1), the strain amount of the amorphous/crystalline complex phase structure is not less than 4%.
Preferably, in the step 2), the temperature of the second annealing treatment is 450-750 ℃, and the time of the second annealing treatment is 30 minutes to 12 hours.
Preferably, in step 2), the second annealing treatment is an annealing treatment under a protective atmosphere. The protective atmosphere is argon.
Preferably, in the step 2), the water cooling treatment temperature is less than or equal to 120 ℃.
A third aspect of the present invention provides use of the shape memory alloy driving element described above in the manufacture of an intelligent actuator.
Preferably, the intelligent executing device is a thermostatic valve or a high-temperature alarm.
Preferably, in the intelligent executing device, the length of the shape memory alloy driving element is more than or equal to 2cm.
Preferably, in the intelligent executing device, the pre-strain amount of the shape memory alloy driving element is 2-6% of the whole length of the shape memory alloy driving element.
Preferably, in the intelligent executing device, the stroke of the driving executing section of the shape memory alloy driving element is 0.5-3% of the whole length of the driving executing section.
Preferably, in the intelligent executing device, the positioning displacement precision of the driving executing section of the shape memory alloy driving element is more than or equal to 90%.
Preferably, in the intelligent executing device, the power-on amount of the shape memory alloy driving element is 1-3Hz pulse power, the power-on time is 0.07-0.10s, and the current value is 50-300mA.
As described above, the shape memory alloy driving element provided by the invention has the following beneficial effects:
(1) The invention provides a shape memory alloy driving element, which is used as a shape memory alloy fiber to obtain a complex phase structure through precision cold processing and a dual microstructure through gradient heat treatment, wherein a driving execution section is of a traditional polycrystal structure, has a shape memory effect and bears a temperature sensing execution function; the constraint section is an amorphous/nanocrystalline complex phase structure, has high strength and linear elasticity, and is used for bearing the constraint recovery function and the strain sensing and feedback functions.
(2) The shape memory alloy driving element provided by the invention can be used for monitoring displacement change by setting the working temperature of the driving execution section and restricting the section to have single resistance-strain correlation, namely displacement-resistance single linear relation.
(3) The shape memory alloy driving element provided by the invention can be used for thermally driving intelligent executing devices such as a thermostatic valve and a high-temperature alarm, realizes millimeter-level to micrometer-level accurate control, and provides key element materials for microelectronic devices, minimally invasive surgical instruments and micro/nano-level medical robots.
Drawings
FIG. 1 is a photograph showing the structure of an amorphous/crystalline complex phase structure obtained by cold drawing in the present invention.
FIG. 2 is a schematic diagram showing the gradient heat treatment mode of the shape memory alloy driving element in the present invention.
FIG. 3 is a diagram showing the driving effect of the driving element of the shape memory alloy according to the present invention.
Fig. 4 is a graph showing the effect of drawing the shape memory alloy wire to reduce the diameter of the wire in the present invention.
FIG. 5 is a schematic diagram showing the unit work output of the shape memory alloy driving element according to the present invention.
Detailed Description
The invention is further illustrated below in connection with specific examples, which are to be understood as being illustrative of the invention and not limiting the scope of the invention.
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
A first aspect of the present invention provides a shape memory alloy driving element made of a shape memory alloy material, comprising a driving execution section and a constraint section, the shape memory alloy in the driving execution section having a crystalline structure, the shape memory alloy in the constraint section having an amorphous/crystalline complex phase structure.
In a preferred embodiment, the shape memory alloy material is one of a titanium nickel based shape memory alloy or a titanium nickel copper based shape memory alloy. The shape memory alloy has a thermal driving function.
Further, the titanium content in the titanium-nickel-based shape memory alloy is 48.5-51.5%.
Further, the titanium content in the titanium-nickel-copper-based shape memory alloy is 48.5-51.5%, and the copper content is less than or equal to 8%.
In a preferred embodiment, as shown in fig. 3, the driving execution section and the constraint section are sequentially arranged along a straight line direction, and the ratio of the length of the driving execution section to the length of the constraint section is 1:2-1:5.
In a preferred embodiment, the crystal structure is a complete crystal structure with a grain size between 0.1 and 30 microns. The crystal structure has a shape memory effect and bears a temperature sensing execution function.
In a preferred embodiment, the elastic modulus of the crystal structure is 75-90 GPa.
In a preferred embodiment, the effective strain of the crystal structure is 7-9%, preferably 8%.
In a preferred embodiment, as shown in fig. 1, the amorphous/crystalline complex phase structure refers to two configurations of a microstructure including an amorphous matrix and a crystal structure of dispersed grains, wherein the grain size is 50 nm or less, and the grains are nanocrystalline. The amorphous/crystalline complex phase structure has high strength and linear elasticity, and is used for restraining and restoring functions and strain sensing and feedback functions. In addition, the amorphous/crystalline complex phase structure has a single linear relationship of displacement-resistance, and can be used for monitoring displacement variation.
In a preferred embodiment, the amorphous/crystalline complex phase structure has an elastic modulus of 40-65 GPa.
In a preferred embodiment, the effective strain of the amorphous/crystalline complex phase structure is 4-5%, preferably 4%.
As shown in fig. 2, a second aspect of the present invention provides a process for manufacturing a shape memory alloy driving element, comprising the steps of:
1) Continuously cold drawing the shape memory alloy wire to obtain a shape memory alloy fiber, wherein in the multiple cold drawing processes, the first annealing treatment is carried out between two adjacent processes to enable the shape memory alloy fiber to form an amorphous/crystalline complex phase structure;
2) And dividing the shape memory alloy fiber into a driving execution section and a constraint section, performing gradient heat treatment, performing secondary annealing treatment on the driving execution section to form a crystal structure, and performing water cooling treatment on the constraint section to maintain an amorphous/crystal complex phase structure to obtain the shape memory alloy driving element.
In a preferred embodiment, in step 1), the continuous cold drawing reduces the diameter of the wire by cold drawing to make it into a fiber, before the continuous cold drawing. The cold drawing is as shown in fig. 4, the shape memory alloy wire is passed through a special die, one pass to gradually reduce the diameter of the wire.
In a preferred embodiment, in step 1), the diameter of the shape memory alloy fiber is 2mm or less.
In a preferred embodiment, in step 1), the number of processes of the cold drawing process in a single pass is 3 to 6.
In a preferred embodiment, in step 1), the number of the continuous cold drawing steps is adjusted according to the requirement.
In a preferred embodiment, in step 1), the continuous cold drawing has a reduction ratio of 7 to 12% in the cold drawing process in the last pass and 4 to 9% in the cold drawing process in the other passes except the last pass. The continuous cold drawing ensures the forming rate and ensures that the plastic deformation rate is not lower than a threshold value. The reduction ratio refers to the deformation amount of cold drawing deformation of the wire, and is used for explaining the reduction of the wire area at the outlet end compared with the wire area at the inlet, if the reduction ratio is too small, the efficiency is low, and if the reduction ratio is too high, the wire breakage phenomenon is easy to occur.
Further, the cold drawing process is not followed by a first annealing treatment.
In a preferred embodiment, in step 1), the first annealing treatment is an annealing treatment under a protective atmosphere. The protective atmosphere is argon.
In a preferred embodiment, in step 1), the temperature of the first annealing treatment is 350 to 550 ℃. The first annealing treatment ensures the texture and grain size of the fiber.
In a preferred embodiment, in step 1), the time of the first annealing treatment is 20 to 50s, preferably 30 to 40s.
In a preferred embodiment, in step 1), the strength of the amorphous/crystalline complex phase structure is not less than 1800MPa.
In a preferred embodiment, in step 1), the strain content of the amorphous/crystalline complex phase structure is not less than 4%. Amorphous/crystalline complex phase structures have linear elastic characteristics.
In a preferred embodiment, in step 2), as shown in fig. 2, the ratio of the length of the driving execution section to the constraint section is 1:2 to 1:5.
In a preferred embodiment, in step 2), the temperature of the second annealing treatment is 450 to 750 ℃ and the time of the second annealing treatment is 30 minutes to 12 hours, as shown in fig. 2. The heating time of the second annealing treatment is reduced along with the temperature rise, and the time is matched with the temperature.
In a preferred embodiment, in step 2), as shown in fig. 2, the second annealing treatment is an annealing treatment under a protective atmosphere. The protective atmosphere is argon.
In a preferred embodiment, in step 2), the water-cooling treatment temperature is 120 ℃ or less, as shown in fig. 2. The confinement section requires maintenance of low temperature to maintain the amorphous/crystalline complex phase structure.
In a preferred embodiment, in step 2), as shown in FIG. 2, the water-cooling treatment is performed by placing the shape memory alloy material of the restraint section into a low-temperature liquid so that the temperature is kept at 120 ℃ or less without a surge. In particular, the water cooling treatment may be performed in a cold water bath.
A third aspect of the present invention provides use of the shape memory alloy driving element described above in the manufacture of an intelligent actuator. As shown in fig. 3, the intelligent executing device is a temperature control deforming device with intelligent sensing and executing functions in the fields of aerospace, precision machinery, consumer electronics, medical equipment, robots and the like, and in particular, the intelligent executing device is a thermostatic valve or a high-temperature alarm.
In a preferred embodiment, in the intelligent execution device, the length of the shape memory alloy driving element is equal to or more than 2cm. The length of the shape memory alloy driving element is set according to the stroke requirement of the intelligent executing device.
In a preferred embodiment, the pre-strain amount of the shape memory alloy driving element in the smart actuator is 2-6% of its overall length.
In a preferred embodiment, in the smart actuator, the stroke of the actuating section of the shape memory alloy actuating element is 0.5-3% of its overall length.
In a preferred embodiment, in the intelligent executing device, the positioning displacement precision of the driving executing section of the shape memory alloy driving element is more than or equal to 90%. The length of the driving execution section can be regulated and controlled to reach the micron level; the drive stroke of the drive execution segment may be as low as nanometer.
In a preferred embodiment, in the intelligent executing device, the power-on amount of the shape memory alloy driving element is 1-3Hz pulse power, the power-on time is 0.07-0.10s, and the current value is 50-300mA.
Example 1
Ni is selected 50.2 Ti 49.8 The shape memory alloy wire is subjected to continuous cold drawing, the diameter of the wire is reduced, the wire is made into fiber, and the diameter of the fiber is 1mm. And in the multiple cold drawing processes, the first annealing treatment is carried out between two adjacent processes. The other cold drawing processes except the last cold drawing process were performed at a reduction ratio of 7%, the single cold drawing was performed by passing through 3 dies, the first annealing treatment was performed by heating under an argon atmosphere as a protective atmosphere, the temperature of the first annealing treatment was 450 ℃ for 30 seconds, and the wire was drawn to a fiber with a diameter of 0.2 mm. After the final cold drawing process is performed at a reduction ratio of 9%, the first annealing treatment is not performed, and only the obtained shape memory alloy fiber is straightened to obtain amorphous/crystallineComplex phase structure. The strength of the amorphous/crystalline complex phase structure is more than or equal to 1800MPa, and the strain capacity is more than or equal to 4%.
Then, the shape memory alloy fiber is divided into a driving execution section and a restraint section, and gradient heat treatment is carried out. The driving execution section is annealed for the second time under the protection atmosphere of argon, the annealing temperature is 600 ℃, the time is 1 hour, the driving execution section is crystallized, the crystal grains grow up, the crystal structure is presented, the shape memory effect is achieved, and the phase transition temperature from martensite to parent phase is measured to be 62 ℃. Placing the restraint section in a cold water bath to ensure that the temperature is less than or equal to 120 ℃ and keeping an amorphous/crystalline complex phase structure. Thus obtaining the required shape memory alloy driving element sample # 1. Wherein the elastic modulus of the crystal structure is 80GPa and the effective strain is 8%. The elastic modulus of the amorphous/crystalline complex phase structure was 50GPa and the effective strain was 4%.
And cutting out a sample 1# of the shape memory alloy driving element, and setting according to the length ratio of the driving execution section to the constraint section of 1:3. And the amount of the pre-strain was set to 5% of the overall length. And connecting and fixing the shape memory alloy driving element sample 1# with a power supply, wherein the length of the driving execution section is 3cm, the length of the constraint section is 9cm, and the length of the pre-strain amount is 0.6cm (5% of the whole length). The two ends are loaded with power supplies, in particular 1Hz pulse power, the power-on time is 0.1s, the current value is 300mA, the circuit is interrupted in the rest time, and the material dissipates heat and lowers the temperature. And observing the joint part of the driving execution section and the constraint section, generating reciprocating motion, circulating for 100 times, wherein the total stroke of the execution process reaches 0.12cm (which is 1% of the whole length), and the displacement precision reaches 91.8%. The details are shown in Table 1.
Example 2
Ni is selected 50.2 Ti 49.8 The shape memory alloy wire is subjected to continuous cold drawing, the diameter of the wire is reduced, the wire is made into fiber, and the diameter of the fiber is 1mm. And in the multiple cold drawing processes, the first annealing treatment is carried out between two adjacent processes. The other cold drawing processes except the last cold drawing process are processed at a reduction ratio of 6%, the single cold drawing is processed by 3 dies, the first annealing treatment is heated under the protection of argon gas, and the first annealing is performedThe temperature was 400℃and the time was 40 seconds, and the filaments were drawn to fibers having a diameter of 0.03 mm. After the final cold drawing process is processed at a reduction ratio of 7%, the first annealing treatment is not performed, and only the obtained shape memory alloy fiber is straightened, so that an amorphous/crystalline complex phase structure is obtained. The strength of the amorphous/crystalline complex phase structure is more than or equal to 1800MPa, and the strain capacity is more than or equal to 4%.
Then, the shape memory alloy fiber is divided into a driving execution section and a restraint section, and gradient heat treatment is carried out. The driving execution section is annealed for the second time under the protection atmosphere of argon, the annealing temperature is 560 ℃, the time is 40 minutes, the crystallization of the driving execution section is realized, the crystal grains grow up, the crystal structure is presented, the shape memory effect is realized, and the phase transition temperature from martensite to parent phase is measured to be 60 ℃. Placing the restraint section in a cold water bath to ensure that the temperature is less than or equal to 120 ℃ and keeping an amorphous/crystalline complex phase structure. Thus obtaining the required shape memory alloy driving element sample # 2. Wherein the elastic modulus of the crystal structure is 85GPa and the effective strain is 9%. The elastic modulus of the amorphous/crystalline complex phase structure was 60GPa and the effective strain was 5%.
And cutting out a shape memory alloy driving element sample No. 2, and setting according to the length ratio of the driving execution section to the constraint section of 1:4. And the amount of the pre-strain was set to 5% of the overall length. And after the shape memory alloy driving element sample No. 2 is connected and fixed with a power supply, the length of the driving execution section is 5mm, the length of the constraint section is 20mm, and the length of the pre-strain amount is 1.25mm (5% of the whole length). The two ends are loaded with power supplies, in particular 3Hz pulse power, the power-on time is 0.08s, the current value is 70mA, the circuit is interrupted in the rest time, and the material dissipates heat and lowers the temperature. The joint part of the driving execution section and the constraint section is observed, the reciprocating motion is generated by 100 times, the total stroke of the execution process reaches 0.23mm (0.92% of the whole length), and the displacement precision reaches 98.4%. The details are shown in Table 1.
Example 3
Ni is selected 45 Ti 50 Cu 5 The shape memory alloy wire is subjected to continuous cold drawing, the diameter of the wire is reduced, the wire is made into a fiber, and the diameter of the fiber is 1.5mm. Then in the multi-channel cold drawing process,and carrying out primary annealing treatment between two adjacent working procedures. The other cold drawing processes except the last cold drawing process were performed at a reduction ratio of 6%, the single cold drawing was performed by passing through 3 dies, the first annealing treatment was performed by heating under an argon atmosphere as a protective atmosphere, the temperature of the first annealing treatment was 550 ℃ for 30 seconds, and the wire was drawn to a fiber having a diameter of 0.1 mm. After the final cold drawing process is processed at the reduction ratio of 8%, the first annealing treatment is not performed, and only the obtained shape memory alloy fiber is straightened, so that the amorphous/crystalline complex phase structure is obtained. The strength of the amorphous/crystalline complex phase structure is more than or equal to 1800MPa, and the strain capacity is more than or equal to 4%.
Then, the shape memory alloy fiber is divided into a driving execution section and a restraint section, and gradient heat treatment is carried out. The driving execution section is annealed for the second time in the presence of argon as protective atmosphere, the annealing temperature is 600 ℃ and the time is 30 minutes, so that the crystallization of the driving execution section, the growth of crystal grains and the crystal structure are realized, the shape memory effect is realized, and the phase transition temperature from martensite to parent phase is 71 ℃. Placing the restraint section in a cold water bath to ensure that the temperature is less than or equal to 120 ℃ and keeping an amorphous/crystalline complex phase structure. Thus obtaining the required shape memory alloy driving element sample 3#. Wherein the elastic modulus of the crystal structure is 75GPa and the effective strain is 7%. The elastic modulus of the amorphous/crystalline complex phase structure was 40GPa and the effective strain was 4%.
And cutting out a sample 3# of the shape memory alloy driving element, and setting according to the length ratio of the driving execution section to the constraint section of 1:3.5. And its pre-strain amount was set to 4% of the overall length. And connecting and fixing the shape memory alloy driving element sample 3# with a power supply, wherein the length of the driving execution section is 2cm, the length of the constraint section is 7cm, and the length of the pre-strain amount is 0.18cm (which is 2% of the whole length). The two ends are loaded with power supplies, specifically 1Hz pulse power, the power-on time is 0.1s, the current value is 120mA, the circuit is interrupted in the rest time, and the material dissipates heat and lowers the temperature. The joint part of the driving execution section and the constraint section is observed to generate reciprocating motion, the cycle is 100 times, the total stroke of the execution process reaches 0.07cm (0.78% of the whole length), and the displacement precision reaches 95.9%. The details are shown in Table 1.
Example 4
Ni is selected 45 Ti 50 Cu 5 The shape memory alloy wire is subjected to continuous cold drawing, the diameter of the wire is reduced, the wire is made into a fiber, and the diameter of the fiber is 1.5mm. And in the multiple cold drawing processes, the first annealing treatment is carried out between two adjacent processes. The other cold drawing processes except the last cold drawing process were performed at a reduction ratio of 6%, the single cold drawing was performed by passing through 3 dies, the first annealing treatment was performed by heating under an argon atmosphere as a protective atmosphere, the temperature of the first annealing treatment was 550 ℃ for 30 seconds, and the wire was drawn to a fiber having a diameter of 0.02 mm. After the final cold drawing process is processed at a reduction ratio of 10%, the first annealing treatment is not performed, and only the obtained shape memory alloy fiber is straightened, so that an amorphous/crystalline complex phase structure is obtained. The strength of the amorphous/crystalline complex phase structure is more than or equal to 1800MPa, and the strain capacity is more than or equal to 4%.
Then, the shape memory alloy fiber is divided into a driving execution section and a restraint section, and gradient heat treatment is carried out. The driving execution section is annealed for the second time under the protection atmosphere of argon, the annealing temperature is 450 ℃, the time is 60 minutes, the crystallization of the driving execution section is realized, the crystal grains grow up, the crystal structure is presented, the shape memory effect is realized, and the phase transition temperature from martensite to parent phase is measured to be 70 ℃. Placing the restraint section in a cold water bath to ensure that the temperature is less than or equal to 120 ℃ and keeping an amorphous/crystalline complex phase structure. Thus obtaining the required shape memory alloy driving element sample # 4. Wherein the elastic modulus of the crystal structure is 90GPa and the effective strain is 9%. The elastic modulus of the amorphous/crystalline complex phase structure was 65GPa and the effective strain was 5%.
And cutting out a sample 4# of the shape memory alloy driving element, and setting according to the length ratio of the driving execution section to the constraint section of 1:2. And its pre-strain amount was set to 6% of the overall length. And after the shape memory alloy driving element sample 4# is connected and fixed with a power supply, the length of the driving execution section is 0.4mm, the length of the constraint section is 0.8mm, and the length of the pre-strain amount is 0.07mm (5.83% of the whole length). The two ends are loaded with power supplies, in particular 3Hz pulse power, the power-on time is 0.07s, the current value is 50mA, the circuit is interrupted in the rest time, and the material dissipates heat and lowers the temperature. The joint part of the driving execution section and the constraint section is observed, the reciprocating motion is generated by 100 times, the total stroke of the execution process reaches 0.02mm (1.67% of the whole length), and the displacement precision reaches 99.0%. The details are shown in Table 1.
As can be seen from table 1, the present invention is based on the discovery that the shape memory alloy fiber material with amorphous/crystalline complex phase structure obtained by cold drawing deformation control is used as the matrix of the driving element, and the research shows that the shape memory alloy driving element of the present invention has higher unit output work compared with the conventional shape memory alloy phase change driving element, as shown in fig. 5. The material has the characteristics of linear elasticity of amorphous alloy and ultra-large shape memory recoverable strain in the strain process, has lower modulus and shows a 'spring type' mechanical property, and is very suitable for application scenes of large elastic strain; meanwhile, the resistance-strain of the material is in a single linear relation, and the material has a specific displacement monitoring function. After crystallization by heat treatment, the material has typical heat execution/driving properties. The invention obtains the double microstructure fiber material through a unique creative process, and realizes the integration of driving and restraint. The embodiment proves that the device has flexible design, can realize the displacement driving execution function from millimeter to micron, has the displacement control precision reaching more than 90 percent, and has the response frequency increased and the precision correspondingly increased as the driving element is smaller in size. The driving element of the invention does not need to add an extra displacement monitoring element, greatly reduces the volume and the cost compared with the traditional device, integrates displacement sensing and driving, and truly realizes the material, namely the device.
TABLE 1
While the invention has been described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and additions may be made without departing from the scope of the invention. Equivalent embodiments of the present invention will be apparent to those skilled in the art having the benefit of the teachings disclosed herein, when considered in the light of the foregoing disclosure, and without departing from the spirit and scope of the invention; meanwhile, any equivalent changes, modifications and evolution of the above embodiments according to the essential technology of the present invention still fall within the scope of the technical solution of the present invention.
Claims (10)
1. A driving element made of a shape memory alloy material, comprising a driving execution section and a constraint section, the shape memory alloy in the driving execution section having a crystalline structure, the shape memory alloy in the constraint section having an amorphous/crystalline complex phase structure.
2. A driving element according to claim 1, wherein the shape memory alloy material is one of a titanium nickel base shape memory alloy or a titanium nickel copper base shape memory alloy.
3. A driving element according to claim 1, wherein the driving execution section and the constraint section are arranged in sequence in a straight line direction, and the ratio of the lengths of the driving execution section and the constraint section is 1:2-1:5.
4. A driving element according to claim 1, characterized in that the elastic modulus of the crystal structure is 75-90 GPa, the effective strain of the crystal structure is 7-9%; the elastic modulus of the amorphous/crystalline complex phase structure is 40-65 GPa, and the effective strain of the amorphous/crystalline complex phase structure is 4-5%.
5. A process for manufacturing a drive element according to any one of claims 1-4, comprising the steps of:
1) Continuously cold drawing the shape memory alloy wire to obtain a shape memory alloy fiber, wherein in the multiple cold drawing processes, the first annealing treatment is carried out between two adjacent processes to enable the shape memory alloy fiber to form an amorphous/crystalline complex phase structure;
2) And dividing the shape memory alloy fiber into a driving execution section and a constraint section, performing gradient heat treatment, performing secondary annealing treatment on the driving execution section to form a crystal structure, and performing water cooling treatment on the constraint section to maintain an amorphous/crystal complex phase structure to obtain the shape memory alloy driving element.
6. A process for manufacturing a driving element according to claim 5, wherein in step 1), the reduction ratio of the cold drawing process in the last pass is 7 to 12% and the reduction ratio of the cold drawing process in the other passes except the last pass is 4 to 9%.
7. A process for manufacturing a driving element according to claim 5, wherein in step 1) or 2), the first annealing treatment and/or the second annealing treatment is an annealing treatment under a protective atmosphere, and the protective atmosphere is argon.
8. A process for manufacturing a driving element according to claim 5, wherein in step 1), the temperature of the first annealing treatment is 350-550 ℃, and the time of the first annealing treatment is 20-50s.
9. A process for manufacturing a driving element according to claim 5, wherein in step 2), the temperature of the second annealing treatment is 450 to 750 ℃, and the time of the second annealing treatment is 30 minutes to 12 hours.
10. Use of a driving element according to any of claims 1-4 for the manufacture of a smart actuator.
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