CN112899596A - Method for improving refrigeration performance by regulating stress-strain response of nickel-titanium alloy - Google Patents
Method for improving refrigeration performance by regulating stress-strain response of nickel-titanium alloy Download PDFInfo
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- CN112899596A CN112899596A CN202110258414.4A CN202110258414A CN112899596A CN 112899596 A CN112899596 A CN 112899596A CN 202110258414 A CN202110258414 A CN 202110258414A CN 112899596 A CN112899596 A CN 112899596A
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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
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
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- C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
- C09K5/08—Materials not undergoing a change of physical state when used
- C09K5/14—Solid materials, e.g. powdery or granular
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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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Abstract
The invention provides a method for regulating stress-strain response of nickel-titanium alloy to improve refrigeration performance, which is characterized by comprising the following steps of: step 1, preparing a nanocrystalline nickel titanium matrix with average grain size of about 5-50 nm by adopting a slow cold rolling process; step 2, grinding and polishing the nickel titanium prepared in the step 1 to a mirror surface; and 3, performing surface thermal processing on the nickel-titanium obtained in the step 2 by using continuous laser beams, and designing nickel-titanium blocks with different coarse-fine crystal ratios by controlling 3 parameters of laser power (50-200W), laser scanning speed (100-3000 mm/s) and laser scanning line spacing (5-500 mu m). The invention utilizes the laser processing technology to accurately design the grain size distribution in the strong plastic transformation nickel titanium, and realizes the stress-strain response regulation and control and the refrigeration performance optimization. In addition, the preparation method is simple in process, mature in theory and low in cost, can quickly set processing parameters according to actual requirements and carry out mass production of components, and has a very wide application prospect.
Description
Technical Field
The invention belongs to the field of microstructure design and thermodynamic performance regulation of metal materials, and particularly relates to a method for preparing a gradient grain structure superelasticity nickel-titanium shape memory alloy with different coarse and fine grain ratios.
Background
Nitinol is currently the most widely used shape memory alloy. However, different fields require different mechanical properties, for example, considerable energy absorption and ductility as an anti-seismic damping device, and high strength and cycling stability and low phase transition dissipation as cardiovascular stents and spectacle frames. In addition, the current solid-state refrigeration field taking nickel-titanium alloy as a core component requires that the material not only has large latent heat of a coarse crystal structure, but also has low energy dissipation of an ultrafine nano crystal structure. Aiming at the application of nickel-titanium alloy in solid refrigeration, a method is urgently needed, the coarse-grain and fine-grain ratio can be accurately regulated and controlled according to actual requirements, so that the regulation and control of stress-strain response and phase change behavior are achieved, and the optimization of refrigeration performance is realized.
Disclosure of Invention
Aiming at the existing application requirements, the technical scheme adopted by the invention for solving the problems in the prior art is as follows:
a method for regulating stress-strain response of nickel-titanium alloy to improve refrigeration performance is characterized by comprising the following steps:
step 1, preparing a nanocrystalline superelasticity nickel-titanium shape memory alloy sheet substrate with the average grain size of 5-50 nm by adopting a strong plastic deformation (hereinafter referred to as strong plastic deformation) process of multi-pass slow cold rolling;
and 3, performing surface thermal processing on the nickel-titanium alloy obtained in the step 2 by using continuous laser beams, and designing nickel-titanium alloy blocks with different coarse-fine crystal ratios by controlling 3 parameters of laser power (50-200W), laser scanning speed (100-3000 mm/s) and laser scanning line spacing (5-500 mu m).
The ultra-fine nanocrystalline nickel-titanium alloy substrate in step 1 may be other types of memory alloys, such as shape memory alloys like nickel-titanium alloy, copper-nickel alloy, copper-aluminum alloy, copper-zinc alloy, iron-based alloy cobalt alloy, and the like.
In the step 1, the entry speed of the rolled piece is controlled to be below 10mm/s in the forced plastic deformation cold rolling process, the pressing vector of the roller is not more than 0.5mm each time, and the cold water cooling roller and the nickel-titanium plate can be discontinuously used in the cold rolling process.
The raw material in the step 1 is a commercial superelasticity nickel-titanium alloy plate with the grain size larger than 100nm, in order to enable the plate to deform uniformly and generate less microcracks in the process of the cold rolling of the superplastic deformation, the stainless steel plate is wrapped by the nickel-titanium outer layer, the average grain size of the matrix is reduced to be below 50nm through unidirectional multi-pass rolling, and the deformation of the plate is preferably 20-60%.
In the step 2, the rolled nickel-titanium plate is manually ground, the abrasive paper is changed from thick to thin, and after no visible scratch is formed, the nickel-titanium plate is placed in polishing liquid for vibration polishing until no visible scratch is formed under a light mirror.
In the step 3, the laser can form a decreasing temperature field on the surface of the rolled sheet along the thickness direction, the input energy is further controlled by controlling 3 parameters of laser power, laser scanning speed and scanning line spacing, and the parameters can be adjusted according to the geometric dimension and the initial microstructure of the machined component in practical application, so that a sample which meets the requirements and contains ideal coarse and fine crystal distribution is prepared.
And 3, the operation in the step 3 needs to be carried out in a closed cabin, firstly, a sample needing to be processed is fixed on a substrate in the cabin, the closed cabin is vacuumized, then argon is introduced, and laser surface processing is carried out after the oxygen content is reduced to be below 200 ppm.
The invention has the following advantages:
the invention utilizes the laser processing technology to accurately design the grain size distribution in the nickel-titanium matrix with strong plastic deformation, and realizes the stress-strain response regulation and control and the refrigeration performance optimization of the nickel-titanium shape memory alloy. In addition, the preparation method is simple in process, accurate in operation, mature in theory, low in cost, capable of quickly setting processing parameters according to actual requirements and carrying out mass production on components, and has a very wide application prospect.
Drawings
FIG. 1 is a schematic view of the processing technique and microstructure distribution of the material according to the present invention;
FIG. 2 is a stress-strain response evolution diagram of a nickel-titanium alloy with different coarse-fine grain ratio (volume ratio) gradient grain structure prepared by the method of the present invention;
FIG. 3 is a graph showing the evolution of solid state refrigeration performance of nickel-titanium alloys with different grain structure having different ratios of coarse to fine (volume ratio) prepared by the method of the present invention.
Detailed Description
Referring to fig. 1, a method for improving the refrigerating performance by regulating the stress-strain response of a nickel-titanium alloy is shown, wherein a commercial superelastic nickel-titanium alloy plate with an initial thickness of 1.5mm and an average grain size of 1500nm is processed according to the following steps:
A. preparing a nanocrystalline super-elastic nickel-titanium shape memory alloy matrix with the average grain size of about 10nm by adopting a multi-pass slow forced plastic deformation cold rolling process;
B. polishing the prepared nanocrystalline nickel-titanium alloy to a mirror surface;
C. the polished 3 groups of nickel titanium samples were subjected to surface heat treatment with a laser power of 100W, a scanning speed of 1000mm/s and scanning pitches of 10 μm, 20 μm and 30 μm, respectively.
In step A, the ultra-fine nano-crystalline nickel-titanium alloy substrate may be other types of memory alloys, such as nickel-titanium alloy, copper-nickel alloy, copper-aluminum alloy, copper-zinc alloy, iron-based alloy, cobalt alloy, and other shape memory alloys. The inlet speed of a rolled piece is controlled to be below 10mm/s in the cold rolling process, the pressing vector of the roller is not more than 0.5mm each time, and the cold water cooling roller and the nickel-titanium plate can be discontinuously used in the rolling process. The raw material is a commercial superelasticity nickel-titanium alloy plate with the grain size larger than 100nm, and in order to enable the plate to deform uniformly and generate less microcracks in the cold rolling process, the stainless steel plate is wrapped by the nickel-titanium outer layer. The average grain size of the matrix is reduced to below 50nm through unidirectional multi-pass rolling, and the deformation of the plate is preferably between 20 and 60 percent.
And step B, manually grinding the rolled nickel-titanium plate, wherein the abrasive paper is from coarse to fine, and after no visible scratch is formed, placing the nickel-titanium plate in polishing solution for vibration polishing until no visible scratch is formed under a light mirror.
In the step C, the laser forms a decreasing temperature field on the surface of the processed sample along the depth direction. The laser power, the laser scanning speed and the scanning line interval can be controlled by 3 parameters so as to control the input energy. In practical application, the geometrical size and the initial microstructure of the component can be machined according to requirements, so that a sample which meets the requirements and contains ideal coarse and fine crystal distribution can be prepared. The ratio of coarse and fine grains of the nickel-titanium with the gradient grain structure prepared by 3 parameters in the embodiment is 18 percent, 40 percent and 60 percent respectively, and the grain size decreases gradually along the plate thickness direction.
The results of the tests based on this example show that the gradient grain structure obtained after treatment according to the method of the present invention can achieve regulation of stress-strain response. Specifically, as the ratio of coarse grains in the material increases, the stress-strain curve gradually changes from near linear elasticity (possessing a narrow hysteresis loop) to pseudo-elastic transition (possessing a distinct hysteresis loop) possessing a distinct phase transition plateau, as shown in fig. 2. As can be seen from FIG. 3, the method can also regulate and control the solid-state refrigeration performance of the nickel-titanium alloy, and the result shows that the refrigeration temperature drop delta T is reduced along with the increase of the proportion of coarse crystals in the materialadMonotonically increasing. Notably, the energy efficiency ratio COP of material refrigerationmatShows non-monotonic change with the coarse and fine crystal ratio, and reaches the local maximum value when the coarse and fine crystal ratio is 18%.
The scope of the present invention is not limited to the above examples, and it is apparent that those skilled in the art can make various modifications and variations to the present invention without departing from the scope and spirit of the invention. It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Claims (7)
1. A method for regulating stress-strain response of nickel-titanium alloy to improve refrigeration performance is characterized by comprising the following steps:
step 1, preparing a nanocrystalline superelasticity nickel-titanium shape memory alloy matrix with the average grain size of 5-50 nm by adopting a multi-pass slow cold rolling process;
step 2, polishing and polishing the nanocrystalline nickel-titanium alloy prepared in the step 1 to a mirror surface;
and 3, carrying out surface hot processing on the nickel-titanium alloy obtained in the step 2 by using continuous laser beams, and designing nickel-titanium alloy blocks with different coarse-fine crystal ratios by controlling 3 parameters of laser power (50-200W), laser scanning speed (100-3000 mm/s) and laser scanning line spacing (5-500 mu m).
2. The method of modulating the stress-strain response of nitinol to improve refrigeration performance of claim 1, wherein: the ultra-fine nanocrystalline nickel-titanium alloy substrate in step 1 may be other types of memory alloys, such as shape memory alloys like nickel-titanium alloy, copper-nickel alloy, copper-aluminum alloy, copper-zinc alloy, iron-based alloy cobalt alloy, and the like.
3. The method of modulating the stress-strain response of nitinol to improve refrigeration performance of claim 1, wherein: in the step 1, the inlet speed of the rolled piece is controlled to be below 10mm/s in the cold rolling process, the pressing vector of the roller is not more than 0.5mm each time, and the cold water cooling roller and the nickel-titanium plate can be discontinuously used in the cold rolling process.
4. The method of modulating the stress-strain response of nitinol to improve refrigeration performance of claim 1, wherein: the raw material in the step 1 is a commercial superelasticity nickel-titanium alloy plate with the grain size larger than 100nm, in order to enable the plate to deform uniformly and generate less microcracks in the cold rolling process, the nickel-titanium outer layer wraps a stainless steel plate, the average grain size of the matrix is reduced to be below 50nm through unidirectional multi-pass rolling, and the deformation of the plate is preferably 20-60%.
5. The method of modulating the stress-strain response of nitinol to improve refrigeration performance of claim 1, wherein: in the step 2, the rolled nickel-titanium plate is manually ground, the abrasive paper is changed from thick to thin, and after no visible scratch is formed, the nickel-titanium plate is placed in polishing liquid for vibration polishing until no visible scratch is formed under a light mirror.
6. The method of modulating the stress-strain response of nitinol to improve refrigeration performance of claim 1, wherein: in the step 3, the laser can form a decreasing temperature field on the surface of the processed sample along the plate thickness direction, the input energy is further controlled by controlling 3 parameters of the laser power, the laser scanning speed and the scanning line spacing, and the parameters can be adjusted according to the geometric dimension and the initial microstructure of the processed component in practical application, so that the sample which meets the requirements and contains ideal coarse and fine crystal distribution is prepared.
7. The method of modulating the stress-strain response of nitinol to improve refrigeration performance of claim 1, wherein: and 3, the operation in the step 3 needs to be carried out in a closed cabin, firstly, a sample needing to be processed is fixed on a substrate in the cabin, the closed cabin is vacuumized, then argon is introduced, and laser surface processing is carried out after the oxygen content is reduced to be below 200 ppm.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008156706A (en) * | 2006-12-25 | 2008-07-10 | Nissan Motor Co Ltd | Method for producing shape memory member |
| CN105821180A (en) * | 2016-04-07 | 2016-08-03 | 浙江工贸职业技术学院 | Method for constructing coarse grain-fine grain gradient structure on surface of metal material and gradient structure |
| CN109518103A (en) * | 2018-12-28 | 2019-03-26 | 武汉大学 | A method of Nitinol refrigeration efficiency is improved than, service life and temperature stability |
| CN110582587A (en) * | 2017-04-28 | 2019-12-17 | 美敦力公司 | shape memory article and method of performance control |
| CN111468553A (en) * | 2020-04-08 | 2020-07-31 | 重庆理工大学 | Nickel-titanium shape memory alloy plate with gradient grain structure |
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2021
- 2021-03-09 CN CN202110258414.4A patent/CN112899596A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008156706A (en) * | 2006-12-25 | 2008-07-10 | Nissan Motor Co Ltd | Method for producing shape memory member |
| CN105821180A (en) * | 2016-04-07 | 2016-08-03 | 浙江工贸职业技术学院 | Method for constructing coarse grain-fine grain gradient structure on surface of metal material and gradient structure |
| CN110582587A (en) * | 2017-04-28 | 2019-12-17 | 美敦力公司 | shape memory article and method of performance control |
| CN109518103A (en) * | 2018-12-28 | 2019-03-26 | 武汉大学 | A method of Nitinol refrigeration efficiency is improved than, service life and temperature stability |
| CN111468553A (en) * | 2020-04-08 | 2020-07-31 | 重庆理工大学 | Nickel-titanium shape memory alloy plate with gradient grain structure |
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