Refrigeration material, preparation method, and cooler

Abstract

Provided are a refrigeration material, a preparation method, and a cooler. The refrigeration material is NixTi100-x, x ranging from 50.6 to 58.0. The refrigeration material NixTi100-x comprises: austenitic (B2 phase) coarse grains and nano precipitates. A NiTi alloy rich in Ni (a Ni atomic percentage of 50.6% to 58.0%) containing the nano precipitates is used for refrigeration, wherein oversaturated Ni can effectively reduce the phase transition temperature and widen the lower limit of a superelastic temperature range, and the nano precipitates can strengthen the austenitic coarse grains (increasing the high-temperature yield strength) and increase the upper limit of the superelastic temperature range of the material, so that the alloy material can exhibit superelasticity at least in a temperature range from 203 K to 503 K (a total temperature span of 300 K). Due to large latent heat generated by the phase transition of the coarse grains of formula (I), a temperature change from 5 K to 33.6 K can be generated during adiabatic compression deformation, wherein temperature spans corresponding to adiabatic temperature drops of ≥10 K and ≥20 K can reach 200 K and 110 K, respectively. By using the NiTi refrigeration material having a wide temperature range, refrigeration and heating devices such as a refrigerator, an air conditioner, and a heat pump can be manufactured.

Description

A refrigeration material, preparation method and refrigerator Technical Field

[0001] This application belongs to the field of materials technology, and in particular relates to a refrigeration material, a preparation method thereof, and a refrigerator. Background Technology

[0002] Today, air conditioners, refrigerators, freezers, and high-temperature heat pumps have become ubiquitous necessities in our daily lives and industrial production. While providing us with convenience, these devices not only consume vast amounts of energy but also have a serious environmental impact due to their vapor compression refrigeration method. According to statistics from relevant departments, in 2019 alone, refrigeration consumed approximately 20% of the world's electricity and accounted for 7.8% of global greenhouse gas emissions; these figures are projected to double by 2050. This undoubtedly exacerbates the energy crisis and the risk of global warming, forcing us to find a new, green, and efficient refrigeration technology as soon as possible.

[0003] Among all possible alternatives, elasto-thermal (also known as elasto-calorie) refrigeration technology based on the latent heat of stress-induced martensitic phase transformation in shape memory alloys is a green, efficient, sustainable, and easy-to-operate emerging solid-state cooling / heating method that holds promise for alleviating the energy crisis and environmental problems facing humanity. Using this technology, based on NiTi shape memory alloys, various refrigeration prototypes have been developed. By increasing the loading frequency and heat transfer efficiency, and employing series active regeneration methods, the most advanced elasto-thermal refrigeration prototype has achieved a cooling power of 260W and a cooling temperature range (the difference between heat output and cold output) of 50.6K (277.1K to 327.7K). While these figures are encouraging, they are still less than the cooling capacity (kilowatt level) and temperature range (at least covering the temperature range of 233K to 453K) achievable by traditional vapor compression cycles. In terms of temperature range alone, current refrigeration prototypes can only be used for air conditioning (289K to 303K), and cannot be used to manufacture refrigerators / freezers (233K to 258K) or high-temperature heat pumps (313K to 453K). The main reason for this limitation is that currently commercially available NiTi shape memory alloys have a smaller adiabatic temperature change (4K to 15K – at room temperature) and a narrower operating temperature range (only 60K to 70K), concentrated near room temperature, compared to traditional vapor compression refrigerants. Due to these material characteristics, current prototypes can only achieve a slightly wider cooling / heating temperature range using multi-stage refrigeration or active regeneration methods, which significantly restricts the application range of elasto-thermal refrigeration. Therefore, to meet the needs of elasto-thermal refrigeration, it is urgent to develop a new NiTi refrigerant with a wide temperature range and large elasto-thermal (large adiabatic temperature change) properties. Summary of the Invention

[0004] This application provides a refrigeration material, wherein the refrigeration material is Ni.x Ti 100-x x is 50.6-58.0 (i.e., Ni atomic weight percentage is 50.6%-58.0%), wherein the refrigeration material Ni x Ti 100-x This includes an austenitic (B2) phase and nano-precipitated phases. The nano-precipitated phases and supersaturated Ni are used to broaden the upper and lower limits of its superelastic temperature range, respectively, achieving wide-temperature-range superelasticity. Within its superelastic temperature range, stress-induced... Phase change can release (during loading) and absorb (during unloading) latent heat, thereby achieving heating and cooling.

[0005] Preferably, x is 51.0-53.0, meaning the atomic weight of Ni in the refrigerant is 51.0%-53.0%, and the volume fraction of austenite (B2 phase) at room temperature is 88%-70%, with an average particle size of 10-500 μm, preferably 100-300 μm. More preferably, x is 51.3-51.5, because the austenite content is sufficiently high and the grains are coarse at the micron level, when an external force is applied to cause a phase transformation of the austenite, the refrigerant can generate a large latent heat.

[0006] Specifically, the nanoprecipitated phase can be Ti3Ni4, TiNi3, or Ti2Ni3, with a volume fraction of 10%-30%. The average particle size of the nanoprecipitated phase is 1-50 nm, and the average spacing is 3-20 nm. Preferably, the nanoprecipitated phase is lenticular Ti3Ni4, with a volume fraction of 13%-14%, an average major axis of 2-18 nm, an average minor axis of 2-9 nm, and an average spacing of 6-10 nm, and is coherent with the austenitic matrix. The ultrafine nanoprecipitated phase is uniformly dispersed in the austenitic matrix, which can effectively strengthen the matrix, increase its critical plastic flow stress, and effectively hinder dislocation movement during cyclic phase transformation, thereby improving its resistance to functional degradation.

[0007] Because the matrix is ​​rich in Ni, it is prone to the formation of antisite defects, which leads to the temperature-induced martensitic phase transformation of the NiTi refrigerant mentioned above. Phase transitions are significantly suppressed in temperature ranges above 213 K (and even lower). At these temperatures, the material primarily undergoes dispersion. Phase transition. Because the temperature-induced B2→B19′ phase transition is significantly suppressed, the material still contains the B2 and R phases at temperatures as low as 213 K, and stress-induced phase transition can occur. Phase change, so it can still cool and heat at temperatures as low as 213K.

[0008] Due to the reinforcing effect of the nano-precipitates, the high-temperature yield strength of the matrix is ​​significantly increased, enabling the material to undergo stress-induced martensitic phase transformation without plastic slip at very high temperatures. This ensures that the material can still be used for cooling and heating at very high temperatures (up to 503K).

[0009] A method for preparing a refrigeration material, comprising:

[0010] Ni and Ti were mixed and smelted into an alloy according to a molar ratio of (50.6-58):(49.4-42);

[0011] The alloy was homogenized at 1173-1323K for 12-48 hours and then water-quenched.

[0012] The water-quenched alloy was subjected to aging treatment at a temperature of 573-973K for 5-300 minutes to obtain the refrigerant Ni. x Ti 100-x .

[0013] The alloy can be prepared using any of the following methods: electric arc melting, electron beam melting, induction melting, or suspension melting (including suction casting). Ni and Ti can be made from raw materials such as powder, granules, sheets, plates, or ingots. The alloy can also be made into materials in the above forms (powder, granules, wire, sheets, plates, ingots, bars, and tubes, etc.), without limitation. Specifically, the melting method can be high-temperature heating melting or electric melting.

[0014] Furthermore, after melting into gold and before homogenization, the prepared alloy is subjected to hot isostatic pressing at a temperature of 1323-1473K and a hydrostatic pressure of 100-300MPa for 1-10 hours, and then cooled in the furnace.

[0015] Preferably, the hot isostatic pressing (HIP) temperature is 1373-1423 K, the time is 3-8 h, and the hydrostatic pressure is 150-300 MPa. By subjecting the alloy to HIP, the porosity generated during alloy preparation can be reduced, which helps improve the fatigue resistance of the refrigerant during phase transition in the refrigeration cycle and extends its service life.

[0016] Preferably, the homogenization treatment is carried out at a temperature of 1223-1273 K for 14-24 hours. Homogenization and solution treatment of the alloy within this temperature range not only allows the components to diffuse rapidly within the material to achieve homogenization, but also dissolves undesirable precipitates formed during the initial melting and cooling process. Subsequently, rapid annealing with water quenching is used to further prevent the precipitation of nanophases. After the above homogenization treatment, a clean NiTi alloy with no nanophase precipitates and uniform composition is obtained, facilitating the formation of the desired nanophase precipitates during subsequent aging treatment.

[0017] Furthermore, the preferred aging treatment temperature is 623-873 K, and the time is 5-50 min. Aging treatment within this preferred temperature range yields Ti3Ni4 nanoprecipitates with a major axis of 2-18 nm, a minor axis of 2-9 nm, and a spacing of 6-10 nm, as well as an austenitic phase with a particle size of 100-300 μm. At this point, the volume fraction of the Ti3Ni4 nanoprecipitates is 13%-14%, uniformly dispersed in the austenitic matrix, which can significantly strengthen the matrix and improve its functional stability.

[0018] The wide-temperature-range elastic-thermal refrigeration material can be applied to refrigeration and heating equipment such as refrigerators, freezers, air conditioners, and heat pumps, and is not limited to these applications.

[0019] This application utilizes NiTi alloys rich in Ni (Ni atomic weight 50.6%-58.0%) for cooling. The supersaturated Ni effectively lowers the phase transformation temperature and widens the lower limit of the superelastic temperature range, while the nano-precipitated phase strengthens the coarse austenite grains (increasing its high-temperature yield strength) and raises the upper limit of the material's superelastic temperature range. This allows the alloy to exhibit superelasticity at least within a temperature range of 203K to 503K (a total temperature span of 300K). Thanks to the coarse grains… The large latent heat generated by the phase change can produce a temperature change of 5K to 33.6K during adiabatic compression deformation (the magnitude of which depends on the ambient temperature); among which, the temperature ranges with adiabatic temperature drop values ​​of ≥10K and ≥20K can reach 200K and 110K respectively, thereby realizing wide-temperature-range cooling and heating. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 is a schematic diagram of the morphology of the refrigeration material prepared in Example 1 of this application;

[0022] Figure 2 is a microstructure test diagram of the refrigeration material prepared in Example 1 of this application;

[0023] Figure 3 is a DSC (heat flow) curve of the refrigeration material prepared in Example 1 of this application;

[0024] Figure 4 shows the in-situ temperature-varying XRD (X-ray diffraction) pattern of the refrigeration material prepared in Example 1 of this application;

[0025] Figure 5 is a temperature-dependent compressive stress-strain curve of the refrigeration material prepared in Example 1 of this application;

[0026] Figure 6 shows the temperature and stress-dependent adiabatic temperature drop of the refrigeration material prepared in Example 1 of this application;

[0027] Figure 7 shows the cyclic compressive stress-strain curves of the refrigeration material prepared in Example 1 of this application at different temperatures and the temperature oscillation diagram generated synchronously. Detailed Implementation

[0028] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0029] Example 1

[0030] (1) Ni and Ti particles with a purity of 99.99% (size: The materials were mixed in a molar ratio of 51.5:48.5 and placed in a vacuum arc melting furnace, where they were melted into an alloy under an argon atmosphere. To ensure that the gas in the material was fully released, a low current of 150A was used for the initial melting, followed by melting with a maximum current of 240A. To ensure the uniformity of the alloy composition, the entire melting process involved five remelting steps.

[0031] (2) The alloy was subjected to hot isostatic pressing at 1323K for 5 hours with a hydrostatic pressure of 150MPa and then cooled in the furnace.

[0032] (3) The cooled alloy was subjected to homogenization treatment at 1173K for 10 hours and then water quenched.

[0033] (4) Cut the homogenized ingot into small square columns with dimensions of 2.5mm×2.5mm×5mm, place them in a heat treatment furnace, heat them from 723K to 773K at a rate of 5K / min for aging treatment for 200min, and then immediately quench them in water to obtain a high-Ni NiTi refrigerant that can be used for wide-temperature-range elasto-thermal refrigeration / pumping heat.

[0034] The names and models of the equipment used in the preparation process, as well as the testing instruments used on the refrigeration materials, are as follows:

[0035] EBSD, Electron Backscattering Diffraction, Model: MIRA3LMH;

[0036] TEM, transmission electron microscope, model: JEM2010;

[0037] HRTEM, high-resolution transmission electron microscope, model: JEM2010;

[0038] DSC, Differential Scanning Calorimeter, Model: Netzsch DSC-214;

[0039] XRD, X-ray diffractometer, model: Rigaku Smartlab;

[0040] High and low temperature static compression testing machine, model: Instron 5969;

[0041] Low-temperature MTS fatigue testing machine, model: Landmark 370.10.

[0042] Figure 1 shows the NiTi refrigerant alloy ingot prepared in Example 1, and its microstructure is shown in Figure 2. In Figure 2, (a), (b), and (c) are EBSD, TEM, and HRTEM images, respectively. As shown in Figure 2, the microstructure of this refrigerant consists of micron-sized coarse-grained austenite (B2 phase, see Figure 2(a), (1-i), and (1-ii)) and ultra-dense, ultra-fine nano-precipitates (particles in Figure 2(b)). The average grain size of the B2 phase is 281 μm (see Figure 2(a) and (d)), the average long axis of the precipitates is 8.7 nm, the average short axis is 4.7 nm, and the average spacing is 8.2 nm (see Figure 2(c)).

[0043] The refrigerant prepared in Example 1 was subjected to DSC and XRD tests, as shown in Figures 3 and 4, which characterized the temperature-induced martensitic phase transformation behavior of the refrigerant. Figures 3 and 4 show that the refrigerant only undergoes a partially diffuse temperature-induced phase transformation above 213 K. Phase transition; its Phase transitions were significantly suppressed.

[0044] The refrigerant in Example 1 was subjected to high and low temperature compression tests and adiabatic temperature drop characterization using an Instron 5969 high and low temperature static compression tester and thermocouples. The results are shown in Figures 5 and 6. Figure 5 shows that the refrigerant exhibits superelasticity in the temperature range of 213K to 503K (a temperature span of nearly 300K) without exceeding its yield strength. Figure 6 shows that the refrigerant can produce a temperature drop of -5K to -33.6K in the range of 203K to 503K; the adiabatic temperature drop amplitudes ≥10K and ≥20K can reach 200K and 110K, respectively.

[0045] The functional stability of the refrigerant prepared in Example 1 was tested using a low-temperature MTS fatigue testing machine. Cyclic compressive stress-strain tests were performed on it at different temperatures, and the synchronous temperature oscillations were recorded using thermocouples (N is the number of cycles, and the loading frequency is 10 Hz). The results are shown in Figure 7. As can be seen from Figure 7, after tens of thousands of cycles, the residual strain of the refrigerant is negligible, and the adiabatic temperature change remains almost unchanged, demonstrating excellent cyclic stability.

[0046] The above content is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions and improvements made within the scope and principles of this application are included within the scope of protection of this application.

Claims

1. A refrigeration material, characterized in that, The cooling material is Ni x Ti 100-x x is 50.6-58.0, wherein the cooling material Ni x Ti 100-x Includes: austenitic phase and nanoprecipitated phase.

2. The refrigeration material according to claim 1, characterized in that, x is 51.0-53.

0.

3. The refrigeration material according to claim 1, characterized in that, The volume fraction of the nano-precipitated phase is 10%-30%, and the nano-precipitated phase is Ti3Ni4, TiNi3, or Ti2Ni3.

4. The refrigeration material according to claim 1, characterized in that, The average particle size of the austenitic phase is 10-500 μm.

5. The refrigeration material according to claim 1 or 3, characterized in that, The average particle size of the nanoprecipitated phase is 1-50 nm, and the spacing is 3-20 nm.

6. A method for preparing a refrigeration material as described in any one of claims 1 to 5, characterized in that, include: Ni and Ti were mixed and smelted into an alloy according to a molar ratio of (50.6-58.0):(49.4-42.0); The alloy was homogenized at 1173-1323K for 12-48 hours and then water-quenched. The water-quenched alloy was subjected to aging treatment at a temperature of 573-973K for 5-300 minutes to obtain the refrigerant Ni. x Ti 100-x .

7. The preparation method according to claim 6, characterized in that, After being smelted into an alloy, it also includes: The prepared alloy was subjected to hot isostatic pressing at a temperature of 1323-1473K and a hydrostatic pressure of 100-300MPa for 1-10 hours, and then cooled in the furnace.

8. The preparation method according to claim 6, characterized in that, The aging treatment temperature is 623-873K and the time is 5-200min.

9. The preparation method according to claim 6, characterized in that, The molar ratio of Ni to Ti is (51.0-53.0):(49.0-47.0).

10. A wide-temperature-range elastic-thermal cooler, characterized in that, include: The refrigeration material as described in claims 1 to 5; Alternatively, a refrigeration material prepared by the preparation method described in claims 6 to 9.

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