A porosity-controllable additive manufacturing method of a nickel-manganese-tin-cobalt alloy and application of a resultant product

Abstract

A kind of porosity controllable additive manufacturing method of nickel-manganese-tin-cobalt alloy and application of the obtained product.The present application belongs to the field of solid refrigeration.The present application aims at the intrinsic brittleness of nickel-manganese-tin-based alloy,which is difficult to be processed into complex-shaped parts by traditional casting and numerical control processing,limiting its application.Meanwhile,aiming at the problem that the existing additive manufacturing method is easy to produce residual stress and element segregation,which affects the structural integrity and magnetic heat performance of the alloy.The present application uses water-based binder to carry out layer-by-layer spray forming of alloy powder,then adds deoxidizer and manganese powder,and carries out high-temperature sintering under vacuum condition to obtain nickel-manganese-tin-cobalt alloy with controllable porosity.The method of the present application effectively avoids the oxidation of the sample,so that the sample maintains good magnetic-structural characteristics,and obtains nickel-manganese-tin-based alloy with specific porosity,phase transition temperature interval near room temperature,and magnetic heat performance comparable to that prepared by traditional method,which shows broad application prospects in the field of magnetic refrigeration and other fields.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solid refrigeration, and particularly relates to a porosity-controllable additive manufacturing method of a nickel-manganese-tin-cobalt alloy and application of a product obtained by the method. BACKGROUND

[0002] With climate warming and energy crisis, people pay more and more attention to efficient, clean and sustainable energy technology. According to statistics, people's demand for refrigeration consumes more than 20% of the global electricity. Although the traditional gas compression refrigeration technology has been developed for more than 200 years, it still has problems such as low efficiency, difficulty in miniaturization, noise pollution and easy to cause greenhouse effect. In recent years, magnetic refrigeration technology based on magnetic heat effect is considered as a promising technology that can replace traditional gas compression refrigeration. Although the research on magnetic refrigeration technology has been more than half a century, its development still stays at the level of prototype machine. In addition to the problems such as complex structure, the selection and manufacturing of materials are also one of the bottleneck problems limiting its practical application.

[0003] The nickel-manganese-tin-based alloy system does not contain rare earth elements and toxic elements, is low in cost and environmentally friendly, and can undergo a large thermal effect of martensitic phase transition near room temperature, which is one of the potential choices of magnetic refrigeration working medium. It is found that appropriate doping of cobalt element (5-6 at.%) in the nickel-manganese-tin alloy system can enhance its ferromagnetic properties while not producing large thermal hysteresis, and thus is an effective method to improve its magnetic heat performance. However, the nickel-manganese-tin-based alloy has intrinsic brittleness and is difficult to be processed into complex configurations to meet the actual needs. SUMMARY

[0004] The present application is aimed at the intrinsic brittleness of the nickel-manganese-tin-based alloy, and the traditional casting and numerical control processing methods are difficult to process it into complex-shaped parts. At the same time, aiming at the problems that the existing additive manufacturing methods are easy to produce residual stress and element segregation, affecting the structural integrity and magnetic heat performance, the present application provides an additive manufacturing method of a nickel-manganese-tin-cobalt alloy, which uses a binder jetting assisted sintering method to produce a porous structure of the nickel-manganese-tin-cobalt alloy with controllable porosity, which is helpful for the heat transfer of the refrigeration working medium. In addition, the method of the present application has wide application range and can be carried out at room temperature and atmospheric conditions, while effectively avoiding the problems such as oxidation, residual stress and element segregation existing in the existing forming methods.

[0005] The technical scheme of the present application is as follows:

[0006] One of the purposes of the present application is to provide a porosity-controllable additive manufacturing method of a nickel-manganese-tin-cobalt alloy, which is carried out according to the following steps:

[0007] S1: After drying the alloy powder prepared by gas atomization, the powder is loaded into the powder bin of a 3D printer, and then a water-based binder is used for layer-by-layer jetting forming. After solidification, a green body is obtained;

[0008] S2: Put the green body into a quartz tube, then add deoxidizing agent and manganese powder, while avoiding the contact between the green body and the deoxidizing agent and manganese powder;

[0009] S3: Seal the quartz tube after vacuumizing, then perform high-temperature sintering, remove the quartz tube after cooling, and obtain the nickel-manganese-tin-cobalt alloy with controllable porosity.

[0010] Preferably, the alloy powder composition in S1 satisfies the atomic stoichiometric ratio of Ni 41 Mn 43 Sn 10 Co6.

[0011] Preferably, the gas atomization process in S1 is as follows: weigh the alloy powder composition, high-frequency induction smelting, and then gas atomization of the alloy liquid under 3-4 MPa.

[0012] More preferably, the smelting temperature is 1500-1700℃, and the smelting time is 40-60 min.

[0013] More preferably, the atomizing gas is 99.999% high-purity argon, and the tapping temperature is 70-90℃.

[0014] Preferably, the particle size of the alloy powder in S1 is ≤16μm.

[0015] Preferably, the drying temperature in S1 is 70-90℃, and the smelting time is 4-8h.

[0016] Preferably, the water-based binder in S1 is ethylene glycol monomethyl ether.

[0017] Preferably, the spray forming parameters in S1 are as follows: powder bed temperature is 40-50℃, powder filling rate is 50-60%, single layer thickness is 70-80μm, recoating speed is 130-150mm / s, binder saturation is 60-80%, droplet volume is 20-40pL, and drying time is 10-15s.

[0018] Preferably, the solidification in S1 is performed in a vacuum drying oven, with a temperature of 180-200℃ and a time of 8-12h.

[0019] Preferably, the deoxidizing agent in S2 is high-purity titanium sheet cleaned with ethanol solution.

[0020] Preferably, the manganese powder in S2 is equal in volume to the green body, and the particle size is 300 mesh.

[0021] Preferably, the specific process of vacuumizing in S3 is as follows: ① first vacuumize to 10 -1 Pa or below; ② backfill 0.5-1bar argon, continue vacuumizing, and repeat 2-3 times; ③ add liquid nitrogen in the vacuum pump, vacuumize to 10-4 Pa, backfill 0.1-0.2 bar argon.

[0022] Preferably, the high-temperature sintering temperature in S3 is 900-1000℃, and the time is 8-24h.

[0023] The second object of the present application is to provide a nickel-manganese-tin-cobalt alloy printed by the additive manufacturing method, which has a magnetic entropy change of 23.3 J·kg -1 ·K -1 and a refrigeration capacity value of 379.8 J·kg -1 .

[0024] Further limited, the nickel-manganese-tin-cobalt alloy structure is in the form of honeycomb coal, and the honeycomb channel diameter is 0.5-1.0mm.

[0025] The third object of the present application is to provide an application of the nickel-manganese-tin-cobalt alloy as a magnetic heat material in the field of refrigeration.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] The present application provides a new additive manufacturing method for nickel-manganese-tin-cobalt alloy parts, which uses a binder jetting assisted sintering method to produce a porous structure nickel-manganese-tin-cobalt alloy with controllable porosity. At the same time, the pre-sintering process of titanium and manganese powder is combined to make the organic matter fully react in the high-temperature sintering process, thereby realizing the removal of organic matter and effectively avoiding sample oxidation, so that the sample maintains good magnetic-structural properties. A nickel-manganese-tin-based alloy with specific porosity, a phase transition temperature interval near room temperature, and magnetic heat performance comparable to traditional preparation methods is obtained, which has broad application prospects in the field of magnetic refrigeration and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the characteristic graph of the alloy powder obtained in Example 1 of the present application; wherein (a) is the powder morphology, and (b) is the particle size distribution graph;

[0029] Figure 2 is the morphology graph of the nickel-manganese-tin-cobalt alloy obtained in Example 1 of the present application; wherein (a) is a macroscopic photograph, and (b) is a secondary electron morphology graph of the sample surface;

[0030] Figure 3 is the backscattered electron diffraction graph of the sample cross section under different sintering times; wherein (a) is Comparative Example 1, (b) is Example 1, (c) is Example 2, and (d) is Example 3;

[0031] Figure 4 is the room temperature X-ray diffraction spectrum of the sample under different sintering times;

[0032] Figure 5 Magnetization-temperature curves of the samples obtained in Example 2 under a magnetic field of 5T for different sintering times;

[0033] Figure 6 Magnetization-magnetic field strength curves and magnetic entropy change-temperature curves of the samples obtained in Example 2; wherein (a) is the magnetization-magnetic field strength curve, and (b) is the magnetic entropy change-temperature curve. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0035] The experimental methods used in the following examples are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0036] The terms "comprising", "including", "containing", "having" or any other similar forms are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or device that comprises a list of elements is not necessarily limited to those elements, but can include other elements not explicitly listed or inherent to such composition, step, method, article, or device.

[0037] When an equivalent, concentration, or other value or parameter is expressed in a range, a preferred range, or a series of upper preferred values and lower preferred values, it should be understood that all ranges formed by any pair of an upper limit or preferred value and a lower limit or preferred value, regardless of whether the range is explicitly disclosed, are specifically disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range. In the specification and claims of the present application, range definitions can be combined and / or interchanged, unless otherwise stated, and these ranges include all sub-ranges contained therein.

[0038] The indefinite articles "a" and "an" preceding an element or component of the application are not intended to be construed to mean only one of an element or component. Therefore "one" or "a" should be interpreted as "one or at least one" and the singular form "a" or "an" includes the plural unless the number is obviously meant to be singular only. Thus, for example, reference to "a compound" can mean one or more compounds.

[0039] Example 1

[0040] (1) Preparation of alloy powder:

[0041] First, 99.98% high-purity nickel sheet, 99.93% high-purity manganese sheet, 99.90% high-purity tin block, and 99.95% high-purity cobalt block were cleaned with aqua regia (a mixture of concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 3:1), 10% mass fraction of dilute nitric acid solution, 10% mass fraction of sodium hydroxide solution, and 30% mass fraction of nitric acid solution for 5 minutes, respectively, until the surface of the raw materials showed a metallic luster. Subsequently, they were placed in distilled water and ultrasonically cleaned for 5 minutes, repeated for more than 3 times, and then cleaned with anhydrous ethanol for 2 minutes and dried with a hair dryer for standby.

[0042] Then, 15.25 kg of nickel sheet, 15.05 kg of manganese sheet, 7.52 kg of tin block, and 2.24 kg of cobalt block were weighed according to the atomic stoichiometric ratio of Ni 41 Mn 43 Sn 10 Co6, and on this basis, in order to offset the loss of elements during atomization, 5% of the total mass of the metal materials was additionally added as high-purity manganese sheet.

[0043] Next: The raw materials were placed in a ceramic crucible and melted by high-frequency induction method, and vacuum melting was carried out at 1600°C for 40 minutes to obtain an alloy liquid.

[0044] Subsequently: The alloy liquid was atomized by gas atomization using 99.999% high-purity argon gas, the atomization pressure was 3.5 MPa, and the tapping temperature was 80°C. After atomization, alloy powder of different particle sizes was obtained, which was sieved using sieves of different mesh sizes to obtain alloy powder with a particle size of ≤16 μm, which was sealed in a nylon bag.

[0045] The morphology and particle size distribution of the obtained alloy powder are shown in Figure 1 , wherein, Figure 1 (a) is the morphology of the powder, from which it can be seen that the size of the powder is randomly distributed and has good sphericity. Particle size analysis of the powder showed the particle size distribution as shown in Figure 1 (b). It can be measured that the d 10 = 4.6 μm, d 50 = 8.7 μm, and d 90 = 15.6 μm.

[0046] (2) Binder jetting:

[0047] Firstly, in order to ensure the flowability of the powder, the alloy powder prepared in step (1) is placed in a vacuum drying oven at 80°C for 4 hours before printing, and then loaded into the ExOne metal 3D printer.

[0048] Then, water-based binder ethylene glycol monomethyl ether (Exone manufacturer's brand: BS004) is used for layer-by-layer spray forming, the powder bed temperature is 45°C, the powder is first laid, the powder filling rate is 55%, the single layer thickness is 75μm, the binder is sprayed after rolling the alloy powder bed, the rolling speed is 140mm / s, the binder saturation is 70%, the droplet volume is 30pL, the drying time is 12s, after printing, the whole powder bed is transferred to a vacuum drying oven, and the sample is solidified at 200°C for 10 hours, and then cooled in the oven. The green body is obtained. Then the green body is placed in the substrate, the surface floating powder is carefully removed with a brush, and the powder is sprayed with an air gun. At this time, the green body has low bonding strength, so careful operation is required to avoid damage to the structure.

[0049] (3) Sintering:

[0050] Firstly, the green body obtained in step (2) is placed in a quartz tube, then high-purity titanium sheets cleaned with alcohol for 15 minutes are added as oxygen scavengers, and manganese powder with a particle size of 300 mesh is added in an amount equal to the volume of the green body. In order to maintain the characteristics of the sample, the sample should not be in contact with the manganese powder and titanium sheets before sintering.

[0051] Subsequently, the open end of the quartz tube is connected to a vacuum pump, and vacuum is applied for 15 minutes to achieve a vacuum degree of 10 -1 Pa in the quartz tube, then 1 bar of 99.999% high-purity argon gas is backfilled, and the gas is washed twice. Finally, the vacuum pipeline is cooled with liquid nitrogen, and vacuum is applied for 5 minutes to reduce the vacuum degree in the quartz tube to 10 -4 Pa, and then 0.1 bar of 99.999% high-purity argon gas is backfilled. The open end of the quartz tube is softened using an oxyacetylene flame and sealed.

[0052] Finally, the vacuum-sealed quartz tube is placed in a high-temperature furnace at room temperature, and the temperature is raised to 950°C at a rate of 10°C / min, and held for 8 hours (i.e. the sintering time is 8 hours). After that, the sample is taken out of the high-temperature furnace and placed on the ground, and cooled to room temperature in air. Then, the quartz tube is knocked and the sample is taken out.

[0053] The macroscopic photograph and the secondary electron morphology of the surface of the obtained sample are shown in Figure 2 , and Figure 2(a) is a macroscopic photograph of the sample, showing that its forming features are quite fine. Meanwhile, from... Figure 2 As can be seen in (b), the sample has a large number of pore structures. The sources of pores are: the structural design itself, the overlap between different passes, the overlap between layers, and the pores between powders.

[0054] Example 2: The difference between this example and Example 1 is that the heat preservation time is 16 hours. Other steps and parameters are the same as in Example 1.

[0055] Example 3: The difference between this example and Example 1 is that the heat preservation time is 24 hours. Other steps and parameters are the same as in Example 1.

[0056] Comparative Example 1: The difference between this example and Example 1 is that the heat preservation time is 2 hours. Other steps and parameters are the same as in Example 1.

[0057] Example of effect 1:

[0058] Backscattered electron diffraction images of the cross-sections of samples from Examples 1-3 and Comparative Example 1 at different sintering times are shown below. Figure 3 As shown, from Figure 3 (a) It can be seen that a second phase was formed inside the sample with a shorter sintering time (2h); from Figure 3 (b) It can be seen that with the extension of sintering time (8h), the second phase inside the sample disappears; from Figure 3 (d) It can be seen that as the sintering time is further increased to 24h, the pores inside the sample decrease and gradually close.

[0059] Example 2:

[0060] The X-ray diffraction patterns of samples from Examples 1-3 and Comparative Example 1 at different sintering times at room temperature are shown below. Figure 4 As shown in the figure, a martensitic structure appears in the sample as the sintering time increases, indicating that the sample exhibits phase transformation characteristics, and the phase transformation temperature is near room temperature. While samples with shorter sintering times show characteristics of a second phase, their average structure remains the L21 structure.

[0061] Example of effect 3:

[0062] The magnetization intensity versus temperature curves of samples from Examples 1-3 and Comparative Example 1 under different sintering times under a constant magnetic field of 5T are shown below. Figure 5It can be seen from the figure that when the sintering time is short (2h), the magnetization of the sample is low, and the phase transition temperature interval and phase transition hysteresis are large; when the sintering time is 8h, the first-order phase transition characteristics of the sample are restored, the magnetization of the sample is high, the phase transition interval is narrow, and the phase transition hysteresis is small. The magnetic properties of the samples with sintering time of 16h and 24h have no obvious difference with the sample with sintering time of 8h, which shows that the process of the application is stable, the adaptive interval is wide, and the repeatability is strong.

[0063] Effect example 4:

[0064] The magnetization-magnetic field strength curve and the magnetic entropy change-temperature curve calculated based on Maxwell equation of the sample of example 2 are shown in the figure. Figure 6 It can be obtained that the magnetic entropy change of the sample reaches 23.3J·kg -1 ·K -1 under the change of 5T magnetic field, the refrigeration capacity value is 379.8J·kg -1 , the effective refrigeration capacity value after subtracting the average hysteresis is 165.8J·kg -1 , and the phase transition temperature interval is 18.4K. This result reaches the performance of the alloy prepared by the traditional method, and is expected to promote the application of the nickel-manganese-tin alloy system.

[0065] The above is only the preferred specific implementation of the application, these specific implementations are different implementation manners based on the overall concept of the application, and the protection scope of the application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method of controlled porosity additive manufacturing of a nickel-manganese-tin-cobalt alloy, characterized in that, The following steps are taken: S1: After drying the alloy powder prepared by gas atomization, it is loaded into the powder bin of the 3D printer, and then layer-by-layer spray forming is carried out using a water-based binder. After curing, a green body is obtained; S2: The green body is placed in a quartz tube, and then deoxidizing agent and manganese powder are added while avoiding contact between the green body and the deoxidizing agent and manganese powder; S3: After the quartz tube is vacuumed and sealed, high-temperature sintering is carried out. After cooling, the quartz tube is removed, and a nickel-manganese-tin-cobalt alloy with controllable porosity is obtained; In S1, the alloy powder composition satisfies Ni 41 Mn 43 Sn 10 The atomic stoichiometric ratio of Co6 is ≤16 μm. In S1, the water-based binder is ethylene glycol monomethyl ether, and in S3, the high-temperature sintering temperature is 900-1000℃, and the time is 8-24h.

2. The method of claim 1, wherein, In S1, the spray forming parameters are: powder bed temperature 40-50℃, powder filling rate 50-60%, single layer thickness 70-80μm, recoating speed 130-150mm / s, binder saturation 60-80%, droplet volume 20-40pL, and drying time 10-15s.

3. The method of claim 1, wherein, In S1, the curing is carried out in a vacuum drying oven at a temperature of 180-200℃ for 8-12h.

4. The method of claim 1, wherein, In S2, the manganese powder is equal in volume to the green body, and the particle size is 300 mesh.

5. The method of any one of claims 1-4, wherein the printed nickel-manganese-tin-cobalt alloy is characterized by, It reaches 23.3 J·kg –1 ·K –1 under 5T magnetic field change, and the refrigeration capacity value reaches 379.8 J·kg –1 .

6. The nickel-manganese-tin-cobalt alloy according to claim 5, characterized in that The nickel-manganese-tin-cobalt alloy structure is in the form of honeycomb coal, and the diameter of the honeycomb channel is 0.5-1.0mm.

7. The application of the nickel-manganese-tin-cobalt alloy printed by the method of any one of claims 1-4 as a magnetocaloric material in the field of refrigeration.

Images