Method for processing an object with at least one magnetocalorically active phase

Abstract

Method for processing an object (1; 10; 20) comprising a magnetocalorically active phase (2; 12), comprising: Providing an object (1; 10; 20) with at least one magnetocalorically active phase (2; 12) having a magnetic phase transition temperature T c exhibits and Removing at least part of the object (1; 10; 20) while the object (1; 10; 20) is at a temperature above the magnetic phase transition temperature T c remains, wherein the object (10; 20) is heated during the removal of part of the object (10; 20) by applying a heated machining fluid to prevent, that the magnetocalorically active phase (2; 12) undergoes a phase change.

Description

[0001] The application relates to an object having at least one magnetocalorically active phase and to methods for processing an object having at least one magnetocalorically active phase.

[0002] The magnetocaloric effect describes the adiabatic conversion of a magnetically induced entropy change into heat generation or heat absorption. Applying a magnetic field to a magnetocalorically active material can induce an entropy change that results in heat generation or heat absorption. This effect can be harnessed for cooling and / or heating.

[0003] Magnetic heat exchangers, as disclosed in US 6 676 772 B2, typically comprise a pump recirculation system, a heat exchange medium such as a cooling liquid, a chamber packed with particles of a magnetically cooling material exhibiting the magnetocaloric effect, and a means for applying a magnetic field to the chamber.

[0004] Magnetic heat exchangers are, in principle, more energy-efficient than gas compression / expansion cycle systems. They are also considered environmentally friendly because they do not use chemicals such as chlorofluorocarbons (CFCs), which are believed to contribute to ozone depletion.

[0005] Recently, materials have been developed such as La(Fe la Si a ) 13 , Gd5 (Si, Ge)4, Mn (As, Sb) and MnFe (P, As), which have a Curie temperature T cat or near room temperature. The Curie temperature affects the operating temperature of the material in a magnetic heat exchange system. Consequently, these materials are suitable candidates for use in applications such as building climate control, domestic and industrial refrigerators and freezers, and automotive air conditioning systems.

[0006] The document WO 2008 / 099234 A1 discloses an article for a magnetic heat exchanger made of (La 1-a M a ) (Fe1- b - c T b Y c ) 13 - d X e ,where 0 ≤ a ≤ 0.9, 0 ≤ b ≤ 0.2, 0.05 ≤ c ≤ 0.2, -1 ≤ d ≤ +1, 0 ≤ e ≤ 3,M is one or more of the elements Ce, Pr and Nd, T is one or more of the elements Co, Ni, Mn, Cr, Y is one or more of the elements Si, Al, As, Ga, Ge, Sn and Sb, X is one or more of the elements H, B, C, N, Li, Be.

[0007] The document US 2005 / 0172643 A1 discloses a heterostructure with a magnetocaloric effect, which has a core layer made of a magnetostructural material with a giant magnetocaloric effect and a coating made of a constricting material.

[0008] The document US 2007 / 0220901 A1 discloses a magnetic cooling material made of magnetic material particles having a magnetocaloric effect and an oxidation-resistant film formed on the surfaces of the magnetic material particles.

[0009] Consequently, magnetic heat exchange systems are being developed to practically realize the advantages offered by the newly developed magnetocalorically active materials. However, further improvements are desirable to enable more extensive application of magnetic heat exchange technology.

[0010] An object of the present application is to provide a method for producing an article comprising at least one magnetocalorically active phase for use in magnetic heat exchangers in a cost-effective and reliable manner.

[0011] A method for processing an object having at least one magnetocalorically active phase having a magnetic phase transition temperature T c is provided, in which at least a portion of the article is removed while the article is kept at a temperature above the magnetic phase transition temperature T c remains.

[0012] In the method, the object is heated during the removal of the part of the object by applying a heated machining fluid to prevent the magnetocalorically active phase from undergoing a phase change.

[0013] This method of processing an article having at least one magnetocalorically active phase can further be used to process an intermediate product, for example to separate the article into two or more smaller articles and / or to provide the desired manufacturing tolerances of the external dimensions in a cost-effective and reliable manner.

[0014] In particular, in the case of machining intermediate products having larger dimensions, for example blocks having dimensions of at least 10 mm or several tens of millimeters, the inventors have observed that undesirable cracks form in the article during machining, which limits the number of smaller articles with the desired dimensions that could be produced from a larger intermediate product.

[0015] The inventors have further observed that these undesirable cracks can be largely avoided when performing the machining if the temperature of the article is kept at a temperature above or below the magnetic phase transition temperature T c remains.

[0016] The method used to produce the article having at least one magnetocalorically active phase can be selected as desired. Powder metallurgy processes have the advantage that ingots with large dimensions can be produced cost-effectively. Powder metallurgy processes such as milling, pressing, and sintering of pretreated powders to form a reaction-sintered article, or milling of powders containing at least a portion of a magnetocalorically active phase followed by pressing and sintering to form a sintered article can be used.

[0017] The article having at least one magnetocalorically active phase can also be produced by other methods such as molding, rapid solidification of a melt, spinning, and so on and then working using the method of the present invention.

[0018] A magnetocalorically active material is defined as one that undergoes a change in entropy when exposed to a magnetic field. The entropy change can, for example, result from a change from ferromagnetic to paramagnetic behavior. The magnetocalorically active material can exhibit an inflection point only in part of a temperature range, where the sign of the second derivative of the magnetization with respect to the applied magnetic field changes from positive to negative.

[0019] A magnetocalorically passive material is defined here as a material that shows no significant change in entropy when exposed to a magnetic field.

[0020] A magnetic phase transition temperature is defined as a transition from one magnetic state to another. Some magnetocalorically active phases exhibit a transition from antiferromagnetic to ferromagnetic, which is associated with a change in entropy. Some magnetocalorically active phases exhibit a transition from ferromagnetic to paramagnetic, which is associated with a change in entropy. For these materials, the magnetic transition temperature can also be referred to as the Curie temperature.

[0021] To maintain the temperature of the object at a temperature above the magnetic phase transition temperature during processing, the object is heated during the removal of the part of the object.

[0022] Heating of the object is carried out by applying a heated processing fluid, such as water, organic solvent or oil.

[0023] In one embodiment, after formation of the magnetocalorically active phase, the article is heated at a temperature above its magnetic phase transition temperature T c held until the processing of the article is completed. This embodiment can be achieved by storing the article at temperatures above the magnetic phase transition temperature T c after the formation of the magnetocalorically active phase by heat treatment.

[0024] The article can be transported from the furnace in which it was manufactured, while the furnace is at a temperature above the magnetic phase transition temperature of the article, to a reheating furnace maintained at a temperature above the magnetic phase transition temperature, in a sufficiently short time so that the temperature of the article does not fall below the magnetic phase transition temperature. Similarly, the article is transported from the reheating furnace to the processing station, while the temperature of the object is kept above the magnetic phase transition temperature.

[0025] The object is heated while a part of the object is removed to prevent the magnetocalorically active phase from undergoing a phase change, or the object is cooled while a part of the object is removed to prevent the magnetocalorically active phase from undergoing a phase change.

[0026] The phase change can be a change in entropy, a change from ferromagnetic to paramagnetic behavior, or a change in volume or a change in the linear thermal expansion coefficient.

[0027] Without being bound by theory, a phase change that occurs in a temperature range around the magnetic phase transition temperature can result in the formation of cracks within the article if, during processing, the temperature of the article changes in such a way that the article undergoes a phase change.

[0028] Performing machining of the object by removing one or more parts while maintaining the object at a temperature where the phase change does not occur prevents the phase change occurring in the object during machining and eliminates any stress associated with the phase change occurring in the object during machining. Therefore, the object can be machined reliably, the manufacturing rate can be increased, and production costs can be reduced.

[0029] The part of the object can be removed by a number of methods. For example, the part of the object can be removed by machining and / or mechanical grinding, mechanical polishing or chemical-mechanical polishing and / or by electrical spark cutting or wire erosion cutting.

[0030] A combination of these processes can also be applied to a single object. For example, the object can be separated into two or more separate parts by removing a portion of the object using wire EDM, and then the surfaces can be subjected to mechanical grinding, which removes another portion to achieve a desired surface finish.

[0031] Part of the article may also be removed to form a channel in the surface of the article, for example, a channel for directing the flow of the heat exchange medium during operation of the article in a magnetic heat exchanger. Part of the article may also be removed to provide at least one through-hole. A through-hole may also be used to direct the flow of the heat exchange medium and thus increase the effective surface area of ​​the article to improve the thermal transfer between the article and the heat exchange medium.

[0032] In another embodiment, the object has a magnetocalorically active phase that exhibits a transition in length or volume at a temperature dependent upon the transition. In this embodiment, at least a portion is removed at a temperature above or below the transition. The transition can occur in a temperature range that is greater than the temperature range in which a measurable entropy change occurs.

[0033] The transition can be made by (L 10% - L 90% ) x 100 / L > 0.35, where L is the length of the object at temperatures below the transition, L 10% the length of the object at 10% of the maximum change in length and L 90% at 90% of the maximum length change. This range characterizes the fastest possible change in length per unit temperature T.

[0034] In one embodiment, the magnetocalorically active phase exhibits a negative linear thermal expansion coefficient with increasing temperatures. This behavior can be observed for a magnetocalorically active phase containing a NaZn 13 -like structure, for example a (La 1-a M a ) (Fe 1-b- c T b Y c ) 13-d X e -based phase, where 0 ≤ a ≤ 0.9, 0 ≤ b ≤ 0.2, 0.05 ≤ c ≤ 0.2, -1 ≤ d ≤ +1, 0 ≤ e ≤ 3, M is one or more of the elements Ce, Pr and Nd, T is one or more of the elements Co, Ni, Mn and Cr, Y is one or more of the elements Si, Al, As, Ga, Ge, Sn, Sb and X is one or more of the elements H, B, C, N, Li and Be.

[0035] In a further embodiment, the magnetocalorically active phase of the article consists essentially of or consists of (La 1-a M a ) (Fe1- b - c T bY c ) 13 - d X e -based phase.

[0036] In further embodiments, the article comprises at least two or a plurality of magnetocalorically active phases, each having a different magnetic phase transition temperature T c A portion of the object is removed while the object is kept at a temperature above the highest magnetic phase transition temperature T c the majority of magnetocalorically active phases or below the lowest magnetic phase transition temperature T c the majority of the magnetocalorically active phases remain.

[0037] The two or more magnetocalorically active phases may be randomly distributed throughout the article. Alternatively, the article may have a layered structure, with each layer consisting of a magnetocalorically active phase that has a magnetic phase transition temperature different from the magnetic phase transition temperature of the other layers.

[0038] In particular, the article may have a layered structure with a plurality of magnetocalorically active phases having magnetic phase transition temperatures such that the magnetic phase transition temperature increases in one direction of the article and therefore decreases in the opposite direction. Such an arrangement enables the operating temperature of the magnetic heat exchanger in which the article is used to be increased.

[0039] When two or more magnetocalorically active phases are each associated with a phase change such as a change in length or volume, the part of the object is removed while the object is kept at a temperature above the temperature range at which the phase change or phase changes occur.

[0040] The use also provides an article having at least one magnetocalorically active phase having a magnetic phase transition temperature T C and which is processed by one of the methods according to one of the embodiments described above.

[0041] An article has at least one magnetocalorically active phase having a magnetic phase transition temperature T cAt least one surface of the article has a machined surface quality. A machined surface quality is characterized by the machining process used to produce the surface.

[0042] Structurally, the machined surface may have a roughness typical of the machining process. For example, a ground surface may be characterized by a surface roughness typical of manufacturing by grinding the material, and a wire EDM cut surface may have a plurality of generally parallel grooves extending along the length of the surface.

[0043] In one embodiment, at least one surface of the article has a length greater than 15 mm.

[0044] The use also provides for the use of the article produced by a method according to one of the previously described embodiments for a magnetic heat exchange.

[0045] Embodiments will now be explained with reference to the drawings.

[0046] Fig. 1 shows a method of processing an article having a magnetocalorically active phase by mechanical grinding and polishing according to a first embodiment.

[0047] Fig. Figure 2 shows a method of machining an article having a magnetocalorically active phase by wire erosion cutting, according to a second embodiment, and

[0048] Fig. 3 shows a method of machining an object having a plurality of magnetocalorically active phases by wire discharge cutting according to a third embodiment.

[0049] Fig. Figure 1 shows a method of processing an object 1 having a magnetocalorically active phase 2. The magnetocalorically active phase 2 is a La (Fe1- a -3Co a Si b ) 13 -based phase and has a magnetic phase transition temperature T c of 44°C. For this phase, the magnetic phase transition temperature can also be described as a Curie temperature when the phase undergoes a transition from ferromagnetic to paramagnetic.

[0050] In this embodiment, the article is manufactured using powder metallurgy techniques. Specifically, a powder mixture with a suitable overall composition is compressed and reactively sintered to form article 1. However, the processing method according to the present application can also be used for articles having one or more magnetocalorically active phases and produced by other methods such as molding or sintering a pretreated powder, the powder consisting essentially of magnetocalorically active phases itself.

[0051] In the first embodiment, the object 1 is processed by mechanical grinding, which is shown schematically in Fig. 1 is represented by the arrows 3. In particular, Fig. 1 illustrates the mechanical grinding of an outer surface 4 of the object 1. The position of the outer surface 4 of the object 1 in an as-manufactured state is shown by the dashed line 4', and the position of the outer surface 4 after machining is shown by a solid line. The surface 4 has the contour and roughness typical of a ground surface.

[0052] Processing the object 1 by grinding the outer surface of the surfaces can be performed to improve the surface finish and / or to improve the dimensional tolerances of the object 1. Polishing can also be used to produce a finer surface finish.

[0053] It was observed that article 1 may contain cracks when removed from the furnace after reaction sintering. It was observed that crack formation is greater in larger articles, for example, articles with dimensions greater than 5 mm. It was observed that if the cooling rate is reduced in the range of the Curie temperature, crack formation in article 1 is avoided.

[0054] After sintering, the object was cooled from approximately 1050°C to 60°C within one hour, which is slightly above the Curie temperature of the magnetocalorically active phase of 44°C. Object 1 was then slowly cooled from 60°C to 30°C.

[0055] Without being bound by theory, it is assumed that crack formation during cooling of article 1 to room temperature after reactive sintering is related to the negative thermal expansion coefficient of the magnetocalorically active phase of article 1 as it passes through the Curie temperature of 44°C. By reducing the cooling rate while the magnetocalorically active phase passes through its Curie temperature, cracks can be avoided due to the reduction of stress within article 1.

[0056] According to an embodiment which is not part of the claimed invention, the processing of the object 1 in this embodiment is carried out by mechanical grinding and polishing such that the temperature T of the object during the processing process is below the Curie temperature T c the magnetocalorically active phase, namely T, < T c remains.

[0057] The measures required to keep the temperature of the object 1 below the Curie temperature T c during processing can be chosen, among other parameters, on the basis of the T c of the magnetocalorically active phase, the heat generated by mechanical grinding and polishing and the property of the object 1 itself to dissipate heat from the surface being ground.

[0058] A cooling agent such as a cooling liquid can be used at least on the surface 4 being machined in order to control the temperature of the object 1 so that it remains below the Curie temperature T c The cooling of the object 1 is shown schematically in Fig. 1 shown by the arrow 5. The object 1 can also be completely immersed in a liquid which is at a temperature below the Curie temperature T c held, be immersed.

[0059] However, the method of the first embodiment is not limited to machining by mechanical grinding or polishing. Other methods may also be used to remove one or more parts of the object 1, for example, chemical mechanical polishing, electrical discharge cutting, and wire cutting while the temperature T a of the object under the T c remains.

[0060] Furthermore, the article can be separated into two or more separate parts, one or more through-holes can be formed extending from one side of the article to the other, or a channel can be formed into a surface of the article. The through-hole and channel can be adapted to carry the cooling fluid when the article is operated in a magnetic heat exchanger.

[0061] Whenever any machining process is used, the cooling of the object is selected so that the object's temperature remains below the Curie temperature of the magnetocaloric phase 2 and does not rise above it. The required cooling and the means used to provide it may vary depending on the machining method chosen, as the heat generation and material removal rate may vary for different machining processes, as well as depending on the machining conditions used.

[0062] Fig. Figure 2 shows a method of processing an article 10 according to a second embodiment of the claimed invention, wherein the article has a magnetocalorically active phase 12. As in the first embodiment, the method by which the article 10 is manufactured is unimportant.

[0063] The method of the second embodiment is described in Fig. 2 using the wire discharge cutting technique, shown schematically by arrows 13, to machine the article 10. However, the method of the second embodiment is not limited to wire discharge cutting or other methods mentioned above and also used.

[0064] To avoid cracking during cooling of the article 10 after reactive sintering, the article 10 can be slowly cooled to below T c In this embodiment, the article 10 is cooled at temperatures above T c processed, and the object 10 is heated to temperature T c heated again before the object 10 is processed.

[0065] The cooling rate for the storage temperature as well as the heating rate to reach the working temperature are chosen to be slow enough to avoid cracking when the object 10 reaches the Curie temperature T c passes through.

[0066] The cooling and heating rates required to prevent cracking also depend on the size of the object. The cooling and heating rates should be progressively reduced for increasingly larger objects.

[0067] In the method of the second embodiment, the temperature T a of the object 10 at a temperature above the Curie temperature T c the magnetocalorically active phase 12 is maintained throughout the entire processing process, namely T a > T c. When a wire EDM cutting technique is used, the temperature of the object 10 can be raised to temperatures above the Curie temperature by heating the liquid in which the object 10 is immersed during the wire cutting process. The heating is shown schematically in Fig. 2 shown by arrow 11.

[0068] Depending on the thermal capacity of the liquid, it may be possible to heat the part to a temperature above the Curie temperature before wire EDM cutting and allow the thermal capacity of the bath to provide the necessary temperature without additional heating from an external source during machining.

[0069] Wire EDM may be used to separate the article 10 to form one or more separate parts as discs 15 or 16 in this embodiment, as well as to form one or more channels 17 in one or more of the surfaces 18 of the article 10.

[0070] The side surfaces 19 of the discs 15, 16, as well as the sides forming the channel 17, have a wire EDM surface finish. These surfaces have a multitude of grooves extending in directions parallel to the direction in which the wire cuts through the material.

[0071] The channel 17 may have dimensions and be arranged in the surface 18 such that it directs the flow of a heat exchange fluid during the operation of a magnetic heat exchanger for which the article 10 or parts of the article 10 provide the operating means.

[0072] Fig. Figure 3 shows a method for processing an article 20 having a plurality of magnetocalorically active phases 22, 23 and 24. The article 20 has a layered structure, with each layer 25, 26 and 27 having a magnetocalorically active phase having a different T c In this embodiment, the first layer 25 comprises a magnetocalorically active phase 22 with a T c of 3°C, the second layer 26 is positioned on the first layer 25 and comprises a magnetocaloric phase 23 having a T c of 15°C, and the third layer 27 is arranged on the second layer 26 and comprises a magnetocaloric phase 24 with a T c of 29°C.

[0073] In the method according to the third embodiment, parts of the object 20 are removed while the temperature T aof the article remains above the highest Curie temperature of the magnetocalorically active phases present in the article 20. Furthermore, in the third embodiment, the article 20, after its manufacture and before processing is carried out, is kept at a temperature above the highest Curie temperature of the plurality of magnetocalorically active phases in this embodiment with T c of 29°C of the third layer 27. The object 20 is only allowed to cool below the highest Curie temperature, 29°C in this embodiment, after all processing has been completed.

[0074] This can be achieved by removing the article 20 thus produced from the furnace in which it is heated at a temperature above the highest T c sintered, is removed and transported to another heating furnace while the temperature is above the highest Curie temperature T cIn a further embodiment, the article 20 is held in the furnace in which it was produced at a holding temperature above the highest Curie temperature T c leave.

[0075] In the embodiment, the Fig. 3, the article 20 is separated into a plurality of discs 28, 29 by wire erosion cutting, which is shown schematically by the arrows 30. The production of a third disc 31 is also shown in Fig. 3 before the separation is completed.

[0076] If the article is further processed, for example by providing a protective layer, this further processing can be carried out at temperatures either above or below the Curie temperature. When using the method of the third embodiment, the protective layer can also be applied at temperatures above the Curie temperature without exposing it to the temperature T aof the article 20, namely the discs 28, 29 and 31 and so on, to fall below the highest Curie temperature of the majority of the magnetocalorically active phases.

[0077] The procedures used in the Fig. 1 and Fig. 2, and their alternatives can also be performed on an article having a plurality of magnetocalorically active phases. The majority of magnetocalorically active phases can be arranged in a layered structure within the article, but can also have other arrangements within the article, for example, a random arrangement within the article.

[0078] The article may also comprise magnetocalorically passive phases. The magnetocalorically passive phases may be provided in the form of a coating on the grains of the magnetocalorically active phase, which acts, for example, as a protective and / or corrosion-resistant layer.

[0079] A combination of different machining processes can be used to produce a final product from the manufactured article. For example, the manufactured article can be ground on its outer surfaces to produce external dimensions with a tighter manufacturing tolerance. Channels can then be formed into the surface to provide cooling channels, and the article can then be separated into a plurality of final products. However, the different machining processes are carried out while the temperature of the article is above or below the magnetic phase transition temperature T c or if the object has a plurality of magnetocaloric phases of different T c at temperatures above or below the highest T c or the lowest T c .

[0080] Without being bound by theory, it is believed that by maintaining the article at temperatures either below or above the magnetic phase transition temperature during processing, a phase change that occurs at temperatures in the range of the magnetic phase transition temperature will not occur during processing, and stresses associated with the phase change are avoided. By avoiding stress during processing due to a phase change, cracks and spalling of the article during processing can be prevented.

[0081] Additionally, and without being bound by theory, it is believed that by maintaining the article at temperatures either above or below the magnetic phase transition temperature during processing, a change in the volume of the magnetocalorically active phase that occurs at temperatures in the range of the magnetic phase transition temperature is avoided. Without being bound by theory, it is believed that cracking and spalling of the article during processing is prevented by preventing the change in the length of the lattice parameters by preventing a change in volume during processing.

[0082] The magnetocaloric phase may also undergo a phase change during a temperature range above or below the magnetic phase transition temperature, or exhibit a temperature-dependent change in the length of the volume at temperatures close to the magnetic phase transition temperature. The portion of the object exhibiting such a magnetocalorically active phase may be removed at temperatures either above or below the temperature range at which the phase change occurs.

[0083] Magnetocalorically active phases, such as a La(Fe1- a - b Si a CO b ) 13 have been shown to exhibit a negative volume change at temperatures above the Curie temperature. Objects containing these phases have been successfully processed using the methods described here.

[0084] It was observed that a large block containing a magnetocaloric phase of La (Fe1- a - b Si a CO b ) 13 could be singulated to form a plurality of discs having a thickness of 0.6 mm by performing wire EDM at a temperature above the ingot's Curie temperature. In contrast, discs of this thickness could not be produced without cracks when wire EDM was performed under normal conditions where the cooling medium was maintained at 20°C.

[0085] A specific example and comparison will now be described. Example

[0086] A sintered block containing a magnetocalorically active phase with a silicon content of 3.5 wt%, a cobalt content of 4.9 wt%, a lanthanum content of 16.7 wt%, the balance iron, and a Curie temperature of 29°C was fabricated using a powder sintering technique. The block was machined by wire EDM. The cooling liquid was heated to 50°C, which is above the block's Curie temperature of 29°C, and wire EDM cutting was performed at this temperature. A plurality of slices with a thickness of 0.6 mm (millimeters) were produced. No cracks were observed in the individual slices. Comparison example

[0087] For comparison, the same block was subjected to wire EDM machining while the cooling fluid temperature in the wire EDM machine was set at 20°C, which is slightly lower than the Curie temperature of 29°C. It was observed that a cylindrical contraction region formed around the cutting wire and cracks extending in directions perpendicular to the cutting wire.

[0088] It is assumed that within the cylindrical region the local temperature of the material has risen above its Curie temperature, while outside this region the temperature has fallen below T c Due to the large negative thermal expansion coefficient of approximately -0.4% of the magnetocalorically active phase when T c, strong stresses are generated in the vicinity of the erosion wire, leading to the observed cracks. Homogeneous, crack-free slices with a thickness of 0.6 mm could not be produced.

Claims

[1] Method for processing an object (1; 10; 20) comprising a magnetocalorically active phase (2; 12), comprising: Providing an article (1; 10; 20) with at least one magnetocalorically active phase (2; 12) having a magnetic phase transition temperature T c and Removing at least a part of the object (1; 10; 20) while the object (1; 10; 20) is at a temperature above the magnetic phase transition temperature T c remains, wherein the object (10; 20) is heated during the removal of the part of the object (10; 20) by applying a heated processing fluid to prevent that the magnetocalorically active phase (2; 12) undergoes a phase change. [2] Method according to claim 1, characterized bythat after the formation of the magnetocalorically active phase (2; 12) the object (1; 10) is at a temperature above its magnetic phase transition temperature T c is held until the processing of the object (1; 10) is completed. [3] Method according to claim 1 or claim 2, characterized by that a part of the object (1; 10; 20) is removed by machining. [4] Method according to one of claims 1 to 3, characterized by that a part of the object (1; 10; 20) is removed by mechanical grinding, mechanical polishing or chemomechanical polishing. [5] Method according to one of claims 1 to 4, characterized by that a part of the object (1; 10; 20) is removed by electrical spark cutting or wire erosion cutting. [6] Method according to one of claims 1 to 5, characterized bythat the object (10) is separated into two separate parts (15, 16) by removing a part of the object (10). [7] Method according to one of claims 1 to 6, characterized by that at least one channel (17) is formed in a surface of the object (10) or at least one through-hole in the object (10) by removing a part. [8] Method according to one of claims 1 to 7, characterized by that the magnetocalorically active phase (2) showing a temperature-dependent transition in length or volume and at least a part of it is removed at a temperature above the transition. [9] Method according to claim 8, characterized by that the transition through (L 10% - L 90% ) x 100 / L < 0.

2. [10] Method according to one of claims 1 to 8, characterized bythat the magnetocalorically active phase (2) has a negative linear thermal expansion coefficient at increasing temperatures. [11] Method according to one of claims 1 to 10, characterized by that the magnetocalorically active phase (2) is a NaZn 13 -like structure. [12] Method according to one of claims 1 to 11, characterized by that the magnetocalorically active phase (2) consists essentially of a (La 1-a M a ) (Fe1- b - c T b Y c ) 13-d X e -based phase, 0 ≤ a ≤ 0.9, 0 ≤ b ≤ 0.2, 0.05 ≤ c ≤ 0.2, -1 ≤ d ≤ +1, 0 ≤ e ≤ 3, M is one or more of the elements Ce, Pr and Nd, T is one or more of the elements Co, Ni, Mn and Cr, Y is one or more of the elements Si, Al, As, Ga, Ge, Sn, Sb and X is one or more of the elements H, B, C, N, Li and Be. [13] Method according to claim 12, characterized bythat the magnetocalorically active phase (2) consists of a (La 1-a M a ) (Fe1- b - c T b Y c ) 13 - d X e -based phase. [14] Method according to one of claims 1 to 13, characterized by that the article (20) has a plurality of magnetocalorically active phases (22, 23, 24), each having a different magnetic phase transition temperature T c wherein a part of the article (20) is removed while the article (20) is at a temperature above the highest magnetic phase transition temperature T c the multitude of magnetocalorically active phases (22, 23, 24) remains.

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