A high magnetic heat effect bulk rare earth-based high-entropy amorphous alloy and a preparation method thereof

Abstract

This invention discloses a bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect and its preparation method. The rare-earth-based high-entropy amorphous alloy material has the molecular formula (RE1,RE2,RE3,...,RE...). n ) a Co b Al c In the formula, a, b, and c represent the atomic percentages of the corresponding elements, with 15 ≤ b ≤ 20, 25 ≤ c ≤ 30, a + b + c = 100, and 3 ≤ n ≤ 6; where RE is an element among Gd, Tb, Dy, Ho, Er, and Tm. This invention, based on the GdTbDyCoAl high-entropy amorphous alloy, partially or completely replaces Gd, Tb, and Dy elements with RE elements to obtain a high-entropy amorphous alloy possessing both high magnetocaloric effect and amorphous formation capability. This alloy exhibits stable magnetocaloric properties, a wide magnetic change temperature range, and does not contain easily volatile or easily oxidized elements. The high-entropy amorphous alloy preparation process of this patent is simple, requiring no other special treatment to form a completely amorphous structure, achieving a critical size of over 5 mm, and possessing excellent magnetocaloric properties. This high-entropy amorphous alloy material has promising application prospects in the field of low-temperature magnetic refrigeration technology.

Description

Technical Field

[0001] The present invention relates to the technology of rare-earth-based high-entropy amorphous alloy low-temperature magnetic refrigeration materials, and particularly to bulk rare-earth-based high-entropy amorphous alloys with both high magnetocaloric effect and amorphous formation ability and a preparation method thereof. Background Art

[0002] The energy utilization rate is becoming an increasingly concerned topic nowadays. According to statistics, less than 40% of the energy in the United States is effectively utilized, and the rest is consumed in the form of heat dissipation, etc. In energy use, a series of refrigerations such as air conditioners and refrigerators account for a considerable part of the consumption. At present, the mainstream refrigeration technology in the market is gas compression refrigeration. However, this refrigeration method has low efficiency, and the use of some refrigerants may cause damage to the environment. With the increasingly severe global environment and the gradual increase of environmental protection requirements in various countries, it is urgent to develop an efficient and green refrigeration method. Compared with traditional gas compression refrigeration, magnetic refrigeration has significant advantages such as high efficiency and environmental friendliness. Magnetic refrigeration utilizes the magnetocaloric effect of materials to regulate the change of magnetic entropy of materials in a magnetic field to change the temperature of materials, and realizes the transfer of heat in the magnetic refrigeration cycle. How to design magnetic refrigeration materials with excellent magnetothermal properties has become a new goal.

[0003] People have made many explorations on new magnetic refrigeration materials and prepared a series of magnetic refrigeration materials with large magnetic entropy change, including La-Fe-Si, Gd-Si-Ge, Ni-Mn-Ga and other series of alloys. These alloys show very large magnetic entropy change near the Curie temperature. However, the magnetic phase transition temperature range of these materials is narrow and the refrigeration capacity is poor. Chinese Patent CN112430757A discloses a magnetic refrigeration material with giant magnetocaloric effect, Mn 1-x R x CoGe, wherein, R is a rare-earth element, preferably La and Y; 0 < x ≤ 0.1, and its maximum magnetic entropy change can be higher than 15.61 J·kg -1 ·K -1However, for compound refrigerants like MnFePAs, challenges include the high vapor pressures and toxicity of As and P; in many systems, the thermal effects of structural entropy change and magnetic entropy change are opposite, canceling out the effective thermal effect; and most current materials have narrow operating temperature ranges, preventing them from operating over a wider temperature range and achieving large magnetic entropy changes. Compared to the crystalline materials mentioned above, high-entropy amorphous materials, while not exhibiting large magnetic entropy changes, possess a wide magnetic transition range due to their short-range ordered and long-range disordered atomic structure. Their high entropy characteristics also result in high entropy stability and low magnetic and thermal hysteresis, leading to high magnetic refrigeration efficiency. Furthermore, as magnetic refrigerants, high-entropy amorphous alloys exhibit increased resistance and reduced eddy current losses due to electron scattering caused by their disordered structure. The complex magnetic entropy change process increases the full width at half maximum (FWHM) of the magnetic entropy, and the multi-stage crystallization process improves thermal stability, thereby increasing efficiency. Chinese patent CN105296893A discloses an A... 20 B 20 C 20 T 20 Al 20 A high magnetic entropy change alloy, wherein A, B, and C are all different from each other and are selected from one of the rare earth elements Gd, Tb, Dy, Ho, Er, and Tm, respectively, and T is selected from one of Co, Ni, and Fe. This alloy system, by substituting transition elements, achieved a maximum magnetic entropy change of 12.23 J·kg⁻¹. -1 ·K -1 The magnetic entropy change value. However, the critical size of this alloy is only 1 mm, and its relative magnetic cooling capacity is only 325 J / kg. -1 This greatly limits the application of this alloy. Chinese patent CN109295400A discloses a Gd 10 Tb 10 Dy 10 Ho 10 Er 10 R 10 Ni 10 Co 10 T 10 Al 10 A deca-element high magnetic entropy change high-entropy alloy, wherein R is selected from one rare earth element from La, Ce, Pr, Nd, Sm, Tm, Yb, and Y; and T is selected from one element from Fe, Cu, and Ag. This alloy system exhibits a high magnetic entropy change value, reaching a maximum of 10.64 J·kg⁻¹. -1 ·K -1 However, this alloy has poor forming ability, only able to form strips, and its relative magnetic cooling capacity is only 532 J·kg. -1 This greatly limits the application of this alloy. Chinese patent CN110616386A discloses a Gd a Co bAl c Y d M e A rare-earth-based high-entropy amorphous alloy, where a, b, c, d, and e represent the atomic percentages of the corresponding elements, with 24.8 ≤ a ≤ 25.4, 24.8 ≤ b ≤ 25.4, 24.8 ≤ c ≤ 25.4, 5 ≤ d ≤ 15, 10 ≤ e ≤ 20, and a + b + c + d + e = 100. M is one of Dy, Er, or Ho. This alloy system exhibits a high magnetic entropy change, reaching a maximum of 7.35 J·kg⁻¹. -1 ·K -1 The relative magnetic refrigeration capacity can reach up to 488 J·kg -1 However, the alloy has poor forming ability, with a critical size of only 1 mm, which greatly limits its application.

[0004] To improve refrigeration efficiency and meet the refrigeration needs of today's home appliances, medical equipment, and aerospace industries, designing a rare-earth-based high-entropy amorphous alloy with both good magnetocaloric properties and forming ability has become a new goal. Summary of the Invention

[0005] Objective of the invention: In view of the technical problems existing in the prior art, the objective of the present invention is to provide a bulk rare earth-based high-entropy amorphous alloy with both high magnetocaloric effect and amorphous formation capability; another objective of the present invention is to provide a method for preparing a bulk rare earth-based high-entropy amorphous alloy with high magnetocaloric effect.

[0006] Technical solution: This invention provides a bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect, its molecular formula being (RE1, RE2, RE3, ..., RE...). n ) a Co b Al c In the formula, a, b, and c represent the atomic percentages of the corresponding elements, and 15≤b≤20, 25≤c≤30, a+b+c=100, 3≤n≤6; where RE is an element among Gd, Tb, Dy, Ho, Er, and Tm.

[0007] Preferably, the RE element has an atomic percentage content.

[0008] Preferably, RE consists of 3 to 6 elements selected from Gd, Tb, Dy, Ho, Er, and Tm.

[0009] Further preferred values ​​are 54≤a≤58, 16≤b≤18, and 26≤c≤28.

[0010] The rare earth-based high-entropy amorphous alloy has a completely amorphous phase structure.

[0011] Furthermore, the Curie temperature of the rare-earth-based high-entropy amorphous alloy is 25-33 K, and the maximum magnetic entropy change is 8.02-8.81 J·kg. -1 ·K -1 The relative magnetic refrigeration capacity reaches 491-599 J·kg -1 .

[0012] Furthermore, the configurational entropy of the rare earth-based high-entropy amorphous alloy is 1.50-1.974R, where R is a gas constant.

[0013] This invention also discloses a method for preparing the above-mentioned bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect, comprising the following steps:

[0014] (1) Prepare raw materials according to the atomic percentages in the molecular formula of the alloy system elements RE (RE = Gd, Tb, Dy, Ho, Er, Tm), Co, and Al;

[0015] (2) The raw materials prepared in step (1) are loaded into an electric arc melting furnace and melted under an inert atmosphere. After cooling, a master alloy ingot with uniform composition is obtained.

[0016] (3) The master alloy ingot obtained in step (2) is broken into small pieces and then cleaned using ultrasound. Amorphous ribbons are prepared using the single-roller spinning method: the fragments are placed in an open quartz tube, the distance between the quartz tube and the copper mold is adjusted, the cavity is closed, and a vacuum of less than or equal to 5 × 10⁻⁶ is drawn. -3 The pressure difference is then reduced to approximately 0.03 MPa by argon gas, followed by induction heating to melt the bulk material. The melted material is then immediately sprayed onto a high-speed rotating copper mold to obtain an amorphous alloy strip. During the strip preparation process, the glass tube opening size, copper roller speed, spray pressure difference, and cooling time are strictly controlled to ensure consistent strip preparation conditions.

[0017] (4) Remove the surface oxide layer from the master alloy ingot obtained in step (2). Prepare amorphous rods using copper mold suction casting: Place the ingot on a copper mold, close the cavity, and evacuate to a vacuum of 5 × 10⁻⁵. -3 Pa, then argon gas is filled to make the cavity pressure about -0.05 MPa, and electric arc heating melts the block. The pressure difference between the inside and outside of the cavity is used to draw the molten alloy liquid into the copper mold. After the sample in the copper mold has completely cooled, it is taken out and the copper mold is opened to obtain the amorphous alloy rod.

[0018] In step (1), the purity of the RE, Co, and Al elements is not less than 99 wt.%.

[0019] Step (2) specifically involves placing the master element alloy prepared in step (1) into a high-vacuum electric arc melting furnace, and first drawing a high vacuum of not less than 5×10. -3Pa, then fill the cavity with an appropriate amount of argon gas as a protective gas. Use electric arc melting, and repeat the melting process at least 5 times. After cooling for 10 minutes, remove the sample, wipe it with alcohol, weigh the master alloy (with an error not exceeding 0.02g), and finally bag it and clean the electric arc furnace.

[0020] Preferably, in step (3), the diameter of the copper mold is 5 mm, resulting in an amorphous alloy rod with a diameter of 5 mm. The rare earth-based high-entropy amorphous alloy provided by this invention is a rare earth-based high-entropy amorphous alloy composed of RE, Co, and Al elements. Among them, RE elements can ensure that the alloy has a large magnetic entropy change value; Co elements can improve the resistivity of the alloy and reduce alloy loss; Al elements can reduce the oxygen content in the alloy, which is beneficial to the formation of amorphous alloy.

[0021] The amorphous structure of the rare earth-based high-entropy amorphous alloy of the present invention was determined by X-ray diffraction (XRD). The XRD pattern showed only broad diffuse diffraction peaks, indicating that the high-entropy amorphous alloy of the present invention is a completely amorphous structure.

[0022] The thermal properties of the rare-earth-based high-entropy amorphous alloy of the present invention were measured using differential scanning calorimetry (DSC). The amorphous alloy material of the present invention was heated to crystallize at a heating rate of 20 Kelvin / min, and the glass transition temperature (Tg) was recorded. g ), initial crystallization temperature (T) x The width ΔT of the supercooled liquid phase region was obtained. x (ΔT x =T x -T g The thermal stability of the rare earth-based high-entropy amorphous alloy of the present invention was evaluated by the width of the supercooled liquid phase region and the crystallization behavior.

[0023] Magnetocaloric properties, including Curie temperature (T), were tested using a magnetic measurement system (MPMS). c ), magnetic entropy change (-|ΔS) M |), and by integrating Maxwell's relation, the magnetic entropy change curve of the amorphous alloy was obtained, and the magnetic refrigeration capacity of the rare earth-based high-entropy amorphous alloy was further calculated.

[0024] Beneficial effects: Compared with the prior art, the rare earth-based high-entropy amorphous alloy of the present invention has the following advantages: (1) The amorphous alloy size is more than 5 mm; (2) By adjusting the contents of Gd, Tb, Dy, Ho and Er, the magnetic properties of the rare earth-based amorphous alloy are improved, especially the configuration entropy value is increased, which has a broadening effect on the half-width of the magnetic entropy change of the alloy, reduces the Curie temperature of the alloy, and improves the low-temperature magnetic refrigeration capacity to a certain extent; (3) The thermal stability of the rare earth-based amorphous alloy is improved, especially the glass transition temperature and the initial crystallization temperature are increased, and the width of the supercooled liquid phase region can reach 60-70K, which plays an important role in the stable application of the alloy; (4) This series of rare earth-based high-entropy amorphous alloy magnetic refrigeration materials not only have a large half-width, but also have a large maximum magnetic entropy change value, which determines that the alloy has a large magnetic refrigeration capacity, which can reach 491-599 J·kg. -1 (5) Due to the disordered long-range structure of amorphous materials, there is basically no hysteresis phenomenon when an external magnetic field is applied; due to its poor conductivity, it can also effectively hinder the generation of eddy currents in changing magnetic fields, making its cooling efficiency high; (6) This rare earth-based high-entropy amorphous alloy is easy to prepare and does not require additional heat treatment steps.

[0025] Therefore, the rare earth-based high-entropy amorphous alloy material of the present invention has the advantages of large amorphous forming ability and high magnetocaloric effect, and has good application prospects, such as being applicable to the fields of refrigerators, air conditioners and other technologies. Attached Figure Description

[0026] Figure 1 These are the XRD patterns of the ribbon-like rare earth-based high-entropy amorphous alloys in Comparative Examples and Examples 1-3;

[0027] Figure 2 These are the XRD patterns of the bulk rare-earth-based high-entropy amorphous alloys in Examples 1-3;

[0028] Figure 3 These are the DSC curves of the striped rare earth-based high-entropy amorphous alloys in Comparative Examples and Examples 1-3;

[0029] Figure 4 These are the magnetization curves of the strip-shaped rare earth-based high-entropy amorphous alloys in Comparative Examples and Examples 1-3;

[0030] Figure 5 This is the isothermal magnetization curve of the rare earth-based high-entropy amorphous alloy in Example 3;

[0031] Figure 6 This is the Arrot curve of the rare earth-based high-entropy amorphous alloy in Example 3;

[0032] Figure 7 These are the magnetic entropy change curves of the rare earth-based high-entropy amorphous alloys in Comparative Examples and Examples 1-3;

[0033] Figure 8 The relative cooling capacity of the rare earth-based high-entropy amorphous alloys in Comparative Examples and Examples 1-3 is shown. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0035] Example 1:

[0036] In this embodiment, the molecular formula of the rare earth-based high-entropy amorphous alloy material is (Gd 1 / 3 Tb 1 / 3 Ho 1 / 3 ) 54 Co 18 Al 28 .

[0037] The preparation method of this rare earth-based high-entropy amorphous alloy material is as follows:

[0038] (1) Gadolinium, terbium, holmium, cobalt, and aluminum raw materials with a purity greater than 99% are selected according to the molecular formula (Gd 1 / 3 Tb 1 / 3 Ho 1 / 3 ) 54 Co 18 Al 28 Weigh and dispense ingredients according to the atomic percentages shown.

[0039] (2) Place the prepared master element alloy from step (1) into a high-vacuum electric arc melting furnace, and first evacuate the furnace to a high vacuum of not less than 5×10. -3 Pa, then fill the cavity with an appropriate amount of argon gas as a protective gas. Use electric arc melting, and repeat the melting process at least 5 times. After cooling for 30 minutes, remove the sample, wipe it with alcohol, weigh the master alloy (with an error not exceeding 0.02g), and finally bag it and clean the electric arc furnace.

[0040] (3) The master alloy ingot obtained in step (2) is broken into small pieces and then cleaned using ultrasound. Amorphous ribbons are prepared using the single-roller spinning method: the fragments are placed in an open quartz tube, the distance between the quartz tube and the copper mold is adjusted, the cavity is closed, and a vacuum of less than or equal to 5 × 10⁻⁶ is drawn. -3 Pa, then argon gas is introduced to make the internal and external pressure difference about 0.03 MPa, and induction heating is used to melt the block, which is then immediately sprayed onto a high-speed rotating copper mold to obtain an amorphous alloy strip.

[0041] (4) Remove the surface oxide layer from the master alloy ingot obtained in step (2). Prepare amorphous rods using copper mold suction casting: Place the ingot on a copper mold, close the cavity, and evacuate to a vacuum of 5 × 10⁻⁵. -3Pa, then argon gas is filled to make the cavity pressure about -0.05MPa, and electric arc heating melts the block. The molten alloy liquid is drawn into a copper mold with a diameter of 5mm by the pressure difference inside and outside the cavity, and an amorphous alloy rod with a diameter of 5mm is obtained.

[0042] The XRD pattern of the strip-shaped amorphous alloy obtained in step (3) was tested using a D8 Advance polycrystalline X-ray diffractometer. The results are as follows: Figure 1 As shown, the strips of this alloy have an amorphous structure.

[0043] The DSC curve of the amorphous alloy obtained in step (3) was measured using a NETZSCH DSC 404F3 differential scanning calorimeter. The heating rate was set to 20 Kelvin / min. The results are as follows: Figure 2 As shown, the glass transition temperature T of this amorphous alloy g The initial crystallization temperature is 618.10 K, and the initial crystallization temperature is T. x The temperature is 683.70 K, and the width of the supercooled liquid phase region is ΔT. x It is 65.60K.

[0044] The Curie temperature T of the alloy was measured using a magnetic measurement system (MPMS). c And isothermal magnetization curves, to obtain as follows Figure 3 The magnetization curves with and without the field shown are obtained by integrating Maxwell's relation. Figure 6 The magnetic entropy change curve of the amorphous alloy shown is obtained from (Gd) 1 / 3 Tb 1 / 3 Ho 1 / 3 ) 54 Co 18 Al 28 alloy T c At 47 K, the maximum magnetic entropy change is 8.81 J·kg. -1 ·K -1 The half-peak width is 67.97 K, and the relative magnetic cooling capacity (RCP) is 598.82 J·kg. -1 .

[0045] Example 2:

[0046] In this embodiment, the molecular formula of the rare earth-based high-entropy amorphous alloy material is (Gd 1 / 4 Tb 1 / 4 Dy 1 / 4 Ho 1 / 4 ) 58 Co 16 Al 26 .

[0047] The preparation method of this rare earth-based high-entropy amorphous alloy material is as follows:

[0048] (1) Gadolinium, terbium, dysprosium, holmium, cobalt, and aluminum raw materials with a purity greater than 99% are mixed according to the molecular formula (Gd 1 / 4 Tb 1 / 4 Dy 1 / 4 Ho 1 / 4 ) 58 Co 16 Al 26 Weigh and dispense ingredients according to the atomic percentages shown.

[0049] (2) Place the prepared master element alloy from step (1) into a high-vacuum electric arc melting furnace, and first evacuate the furnace to a high vacuum of not less than 5×10. -3 Pa, then fill the cavity with an appropriate amount of argon gas as a protective gas. Use electric arc melting, and repeat the melting process at least 5 times. After cooling for 30 minutes, remove the sample, wipe it with alcohol, weigh the master alloy (with an error not exceeding 0.02g), and finally bag it and clean the electric arc furnace.

[0050] (3) The master alloy ingot obtained in step (2) is broken into small pieces and then cleaned using ultrasound. Amorphous ribbons are prepared using the single-roller spinning method: the fragments are placed in an open quartz tube, the distance between the quartz tube and the copper mold is adjusted, the cavity is closed, and a vacuum of less than or equal to 5 × 10⁻⁶ is drawn. -3 Pa, then argon gas is introduced to make the internal and external pressure difference about 0.03 MPa, and induction heating is used to melt the block, which is then immediately sprayed onto a high-speed rotating copper mold to obtain an amorphous alloy strip.

[0051] (4) Remove the surface oxide layer from the master alloy ingot obtained in step (2). Prepare amorphous rods using copper mold suction casting: Place the ingot on a copper mold, close the cavity, and evacuate to a vacuum of 5 × 10⁻⁵. -3 Pa, then argon gas is filled to make the cavity pressure about -0.05MPa, and electric arc heating melts the block. The molten alloy liquid is drawn into a copper mold with a diameter of 5mm by the pressure difference inside and outside the cavity, and an amorphous alloy rod with a diameter of 5mm is obtained.

[0052] The XRD pattern of the strip-shaped amorphous alloy obtained in step (3) was tested using a D8 Advance polycrystalline X-ray diffractometer. The results are as follows: Figure 1 As shown, the strips of this alloy have an amorphous structure.

[0053] The DSC curve of the amorphous alloy obtained in step (3) was measured using a NETZSCH DSC 404F3 differential scanning calorimeter. The heating rate was set to 20 Kelvin / min. The results are as follows: Figure 2 As shown, this amorphous alloy exhibits two-stage crystallization, and the glass transition temperature T of the amorphous alloy was also measured. g The initial crystallization temperature is 630.64 K, and the initial crystallization temperature is T. x1 The temperature is 698.69 K, and the width of the supercooled liquid phase region is ΔT. x It is 68.05K.

[0054] The Curie temperature T of the alloy was measured using a magnetic measurement system (MPMS). c And isothermal magnetization curves, to obtain as follows Figure 3 The magnetization curve shown is obtained by integrating Maxwell's relation. Figure 6 The magnetic entropy change curve of the amorphous alloy shown is obtained from (Gd) 1 / 4 Tb 1 / 4 Dy 1 / 4 Ho 1 / 4 ) 58 Co 16 Al 26 alloy T c At 42K, the maximum magnetic entropy change is 8.58 J·kg. -1 ·K -1 The half-peak width is 63.67 K, and the relative magnetic cooling capacity (RCP) is 546.12 J·kg. -1 .

[0055] Example 3:

[0056] In this embodiment, the molecular formula of the rare earth-based high-entropy amorphous alloy material is (Gd 1 / 5 Tb 1 / 5 Dy 1 / 5 Ho 1 / 5 Er 1 / 5 ) 55 Co 17 Al 28

[0057] The preparation method of this rare earth-based high-entropy amorphous alloy material is as follows:

[0058] (1) Gadolinium, terbium, dysprosium, holmium, erbium, cobalt, and aluminum raw materials with a purity greater than 99% are selected according to the molecular formula (Gd 1 / 5 Tb 1 / 5 Dy 1 / 5Ho 1 / 5 Er 1 / 5 ) 55 Co 17 Al 28 Weigh and dispense ingredients according to the atomic percentages shown.

[0059] (2) Place the prepared master element alloy from step (1) into a high-vacuum electric arc melting furnace, and first evacuate the furnace to a high vacuum of not less than 5×10. -3 Pa, then fill the cavity with an appropriate amount of argon gas as a protective gas. Use electric arc melting, and repeat the melting process at least 5 times. After cooling for 30 minutes, remove the sample, wipe it with alcohol, weigh the master alloy (with an error not exceeding 0.02g), and finally bag it and clean the electric arc furnace.

[0060] (3) The master alloy ingot obtained in step (2) is broken into small pieces and then cleaned using ultrasound. Amorphous ribbons are prepared using the single-roller spinning method: the fragments are placed in an open quartz tube, the distance between the quartz tube and the copper mold is adjusted, the cavity is closed, and a vacuum of less than or equal to 5 × 10⁻⁶ is drawn. -3 Pa, then argon gas is introduced to make the internal and external pressure difference about 0.03 MPa, and induction heating is used to melt the block, which is then immediately sprayed onto a high-speed rotating copper mold to obtain an amorphous alloy strip.

[0061] (4) Remove the surface oxide layer from the master alloy ingot obtained in step (2). Prepare amorphous rods using copper mold suction casting: Place the ingot on a copper mold, close the cavity, and evacuate to a vacuum of 5 × 10⁻⁵. -3 Pa, then argon gas is filled to make the cavity pressure about -0.05MPa, and electric arc heating melts the block. The molten alloy liquid is drawn into a copper mold with a diameter of 5mm by the pressure difference inside and outside the cavity, and an amorphous alloy rod with a diameter of 5mm is obtained.

[0062] The XRD pattern of the strip-shaped amorphous alloy obtained in step (3) was tested using a D8 Advance polycrystalline X-ray diffractometer. The results are as follows: Figure 1 As shown, the strips of this alloy have an amorphous structure.

[0063] The DSC curve of the amorphous alloy obtained in step (3) was measured using a NETZSCH DSC 404F3 differential scanning calorimeter. The heating rate was set to 20 Kelvin / min. The results are as follows: Figure 2 As shown, this amorphous alloy exhibits two-stage crystallization, and the glass transition temperature T of the amorphous alloy was also measured. g The initial crystallization temperature is 636.56 K, and the initial crystallization temperature is T. x1 The temperature is 704.70 K, and the width of the supercooled liquid phase region is ΔT. x It is 68.14K.

[0064] The Curie temperature T of the alloy was measured using a magnetic measurement system (MPMS). c And isothermal magnetization curves, to obtain as follows Figure 3 The magnetization curve shown is obtained by integrating Maxwell's relation. Figure 6 The magnetic entropy change curve of the amorphous alloy shown is obtained from (Gd) 1 / 5 Tb 1 / 5 Dy 1 / 5 Ho 1 / 5 Er 1 / 5 ) 55 Co 17 Al 28 alloy T c At 33 K, the maximum magnetic entropy change is 8.02 J·kg. -1 ·K -1The half-peak width is 61.21 K, and the relative magnetic cooling capacity (RCP) is 491.05 J·kg. -1 .

[0065] Comparative example

[0066] In this embodiment, the molecular formula of the rare earth-based high-entropy amorphous alloy material is (Gd 1 / 3 Tb 1 / 3 Dy 1 / 3 ) 55 Co 17.5 Al 27.5 .

[0067] The preparation method of this rare earth-based high-entropy amorphous alloy material is as follows:

[0068] (1) Gadolinium, terbium, dysprosium, cobalt, and aluminum raw materials with a purity greater than 99% are selected according to the molecular formula (Gd 1 / 3 Tb 1 / 3 Dy 1 / 3 ) 55 Co 17.5 Al 27.5 Weigh and dispense ingredients according to the atomic percentages shown.

[0069] (2) Place the prepared master element alloy from step (1) into a high-vacuum electric arc melting furnace, and first evacuate the furnace to a high vacuum of not less than 5×10. -3 Pa, then fill the cavity with an appropriate amount of argon gas as a protective gas. Use electric arc melting, and repeat the melting process at least 5 times. After cooling for 30 minutes, remove the sample, wipe it with alcohol, weigh the master alloy (with an error not exceeding 0.02g), and finally bag it and clean the electric arc furnace.

[0070] (3) The master alloy ingot obtained in step (2) is broken into small pieces and then cleaned using ultrasound. Amorphous ribbons are prepared using the single-roller spinning method: the fragments are placed in an open quartz tube, the distance between the quartz tube and the copper mold is adjusted, the cavity is closed, and a vacuum of less than or equal to 5 × 10⁻⁶ is drawn. -3 Pa, then argon gas is introduced to make the internal and external pressure difference about 0.03 MPa, and induction heating is used to melt the block, which is then immediately sprayed onto a high-speed rotating copper mold to obtain an amorphous alloy strip.

[0071] The XRD pattern of the strip-shaped amorphous alloy obtained in step (3) was tested using a D8 Advance polycrystalline X-ray diffractometer. The results are as follows: Figure 1 As shown, the strips of this alloy have an amorphous structure.

[0072] The DSC curve of the amorphous alloy obtained in step (3) was measured using a NETZSCH DSC 404F3 differential scanning calorimeter. The heating rate was set to 20 Kelvin / min. The results are as follows: Figure 2 As shown, the glass transition temperature T of this amorphous alloyg The initial crystallization temperature is 617.37 K, and the initial crystallization temperature is T. x The temperature is 685.90 K, and the width of the supercooled liquid phase region is ΔT. x It is 68.53K.

[0073] The Curie temperature T of the alloy was measured using a magnetic measurement system (MPMS). c And isothermal magnetization curves, to obtain as follows Figure 3 The magnetization curves with and without the field shown are obtained by integrating Maxwell's relation. Figure 6 The magnetic entropy change curve of the amorphous alloy shown is obtained from (Gd) 1 / 3 Tb 1 / 3 Dy 1 / 3 ) 55 Co 17.5 Al 27.5 alloy T c The maximum magnetic entropy change is 8.04 J·kg at 57 K. -1 ·K -1 The half-peak width is 66.01 K, and the relative magnetic cooling capacity (RCP) is 530.70 J·kg. -1 .

Claims

1. A bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect, characterized in that, Its molecular formula is selected from: (Gd 1 / 3Tb 1 / 3 Ho 1 / 3 ) 54 Co 18 Al 28 、(Gd 1 / 4 Tb 1 / 4 Dy 1 / 4 Ho 1 / 4 ) 58 Co 16 Al 26 、(Gd 1 / 5 Tb 1 / 5 Dy 1 / 5 Ho 1 / 5 Er 1 / 5 ) 55 Co 17 Al 28 The rare-earth-based high-entropy amorphous alloy has a completely amorphous phase structure; its Curie temperature is 25-33 K, and its maximum magnetic entropy change is 8.02-8.81 J·kg. -1 ·K -1 The relative magnetic refrigeration capacity reaches 491-599 J·kg -1 The configurational entropy of the rare earth-based high-entropy amorphous alloy is 1.50-1.974 R, where R is the gas constant.

2. A method for preparing a bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect as described in claim 1, characterized in that, Includes the following steps: (1) Prepare raw materials by mixing Gd, Tb, Dy, Ho, Er, Co, and Al elements according to the atomic percentages in the molecular formula; (2) Melt the raw materials prepared in step (1) under an inert atmosphere and cool them to obtain a master alloy ingot with uniform composition. (3) After breaking the master alloy ingot obtained in step (2) into small pieces, it is cleaned by ultrasonication; amorphous strips are prepared by single-roller spinning method; or, the surface oxide layer of the master alloy ingot obtained in step (2) is removed, and amorphous rods are prepared by copper mold suction casting method.

3. The method for preparing bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect according to claim 2, characterized in that, In step (1), the purity of the Gd, Tb, Dy, Ho, Er, Co, and Al elements is not less than 99 wt.%.

4. The method for preparing bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect according to claim 2, characterized in that, Step (2) specifically involves placing the master element alloy prepared in step (1) into a high-vacuum electric arc melting furnace, and first drawing a high vacuum of not less than 5×10. -3 Pa, then fill the cavity with an appropriate amount of argon gas as a protective gas; use electric arc melting, and melt repeatedly at least several times before cooling.

5. The method for preparing bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect according to claim 2, characterized in that, In step (3), the amorphous ribbon is prepared by single-roller spinning method as follows: the fragments are placed into an open quartz tube, the distance between the quartz tube and the copper mold is adjusted, the cavity is closed and a vacuum of less than or equal to 5 × 10⁻⁶ is drawn. -3 Pa, then argon gas is introduced to make the internal and external pressure difference 0.03 MPa, and induction heating is used to melt the block, which is then immediately sprayed onto a high-speed rotating copper mold to obtain an amorphous alloy strip.

6. The method for preparing bulk rare-earth-based high-entropy amorphous alloy with high magnetocaloric effect according to claim 2, characterized in that, In step (3), the preparation of amorphous rods using the copper mold suction casting method specifically involves: placing the ingot on a copper mold, closing the cavity, and drawing a vacuum of less than or equal to 5 × 10⁻⁶. -3 Pa, then argon gas is introduced to make the cavity pressure -0.05 MPa, and electric arc heating is used to melt the block. The molten alloy liquid is drawn into the copper mold by the pressure difference between the inside and outside of the cavity. After the sample in the copper mold has completely cooled, it is taken out and the copper mold is opened to obtain the amorphous alloy rod.

Images