A CoHf planar target and its preparation method

Abstract

This application belongs to the field of target preparation technology and discloses a method for preparing a CoHf planar target. The method involves first heating and melting cobalt and hafnium metals in an overlapping and alternating manner in a vacuum crucible, followed by furnace cooling to obtain a CoHf alloy ingot. The CoHf alloy ingot is then melted and poured into a mold. After pouring, it is cooled to room temperature in the furnace to obtain a CoHf target blank. The mold is placed on an auxiliary tool and is in a swinging state during the pouring process. Subsequently, the CoHf target blank is placed in a carbon tube furnace for annealing, followed by cutting and polishing to obtain a CoHf planar target. This application effectively reduces the residual stress of the CoHf planar target and improves the relative density of the CoHf planar target to a certain extent through the above method. In addition, this application also discloses a CoHf planar target.

Description

Technical Field

[0001] This application relates to the field of target preparation technology, and in particular to a CoHf planar target and its preparation method. Background Technology

[0002] Magnetic thin films with tunable microwave magnetic properties have wide applications in tunable microwave signal processing devices, including tunable inductors, tunable resonators, phase shifters, and tunable filters. Therefore, fabricating magnetic thin films with easily adjustable ferromagnetic resonance (FMR) frequencies and permeability is of great significance. Studies have shown that FMR frequencies and permeability are closely related to the magnetic anisotropy and saturation magnetization of the thin film, and these can be adjusted by changing the magnetic anisotropy. Rotational anisotropy has been used to adjust the high-frequency characteristics of ferrite-doped CoFe thin films or thin films with rotatable stripe domain structures; however, these methods have drawbacks such as difficulty in large-scale adjustment of rotatable anisotropy and the fact that alternating bias only adjusts the anisotropy of ultrathin films. In practical production applications, the key to fabricating high-performance magnetic thin films lies in how to adjust the anisotropy of thin films in multilayer structures by changing the interlayer thickness and interlayer interactions. Related research found that by depositing CoHf thin films of different thicknesses on Hf chips, the resonant frequency of the films can be tuned from 2.1 GHz to 3.4 GHz, theoretically solving the difficulties in the practical application of ultrathin films.

[0003] The above research results indicate to some extent that CoHf sputtering targets have potential in microwave applications, but there are currently no reports on relevant target preparation methods in the industry. There are generally two methods for preparing targets. One is through powder metallurgy, where alloy powder is hot-pressed into shape. This process is costly and has a relatively long production cycle when preparing small batches of small-sized targets. During production, the alloy powder is prone to oxidation, making it difficult to ensure that the oxygen content of the finished target is <500 ppm. Casting, on the other hand, has lower preparation costs and allows for better control of the alloy's oxygen content, making it a more reasonable approach for preparing CoHf targets. In actual production, CoHf alloys are extremely fragile after casting, and due to their high hardness and brittleness, they are prone to cracking during machining. Therefore, eliminating residual stress in the target blank is crucial in actual production.

[0004] Chinese patent application 201110337933.6 discloses a production process for a large high-purity molybdenum planar target for a flat panel display, including: molybdenum powder analysis, powder selection, powder preparation; mold loading; pressing; sintering; rolling; annealing; milling width; wire cutting end face and chamfering; grinding.

[0005] The planar high-purity molybdenum target produced by this method has the following advantages: the length of the molybdenum target can reach over 2700 mm; the Mo content is ≥99.95%; the relative density is ≥99%; the grain structure is uniform; its flatness is less than 0.05; the surface roughness is Ra0.2; the surface is free of defects such as cracks, peeling, folds, indentations, pits, and metallic or non-metallic indentations; the length of internal cracks in the target is no greater than 0.04 mm, and there are no bubbles or large crystals.

[0006] As can be seen from the above schemes, the way these schemes reduce target cracking is more through the specific control of the above process parameters, rather than by vibrating the mold during the casting process.

[0007] Chinese patent application 201610532488.1 discloses a casting method for low-stress bed castings using vibration solidification. The method involves first creating a sand mold for the bed casting, then melting and pouring the molten metal, followed by three-dimensional vibration solidification. Using wavelet spectrum analysis, a low-frequency three-dimensional resonance field of 10-200Hz is applied after the molten metal has just filled the mold cavity. A high-frequency three-dimensional resonance field of 200-2000Hz is then implemented within ±50℃ of the Fe-C eutectic point as the molten metal cools. The sand mold is then left to stand, and the riser and gating system are removed. The flash is then cleaned. The low-frequency three-dimensional resonance field promotes the molten metal to fill the mold cavity, overcoming casting defects such as porosity, inclusions, segregation, and shrinkage cavities commonly found in traditional casting processes. The high-frequency three-dimensional resonance increases the supercooling of the molten metal, promoting solidification nucleation, increasing the number of nuclei, and facilitating the refinement of the crystal structure. This process is simple, low-cost, easy to operate, pollution-free, and widely applicable. It can significantly improve the quality of castings and reduce their residual stress.

[0008] Although the above methods demonstrate that vibration can reduce residual stress in castings, it should be noted that although both the target material and the casting are produced by casting, the control of vibration during the casting process differs due to the differences in their materials.

[0009] The problem this solution aims to solve is: how to provide a method for preparing CoHf planar targets that can reduce residual stress in the target material. Summary of the Invention

[0010] The purpose of this application is to provide a method for preparing CoHf planar targets that reduces residual stress in the target material, thereby reducing the cracking rate of the target material.

[0011] To achieve the above objectives, this application discloses a method for preparing a CoHf planar target, comprising the following steps:

[0012] Step 1: Cobalt and hafnium metals are arranged in an overlapping and alternating pattern in a vacuum crucible, heated and melted, and then cooled in the furnace to obtain CoHf alloy ingots;

[0013] Step 2: Melt the CoHf alloy ingot obtained in Step 1 and pour it into the mold. After pouring, cool it to room temperature in the furnace and remove it from the furnace to obtain the CoHf target billet. The mold is placed on the auxiliary fixture and is in a swinging state during the pouring process.

[0014] Step 3: Place the CoHf target blank obtained in Step 2 into a carbon tube furnace for annealing, then cut and polish it to obtain a CoHf planar target.

[0015] Preferably, the auxiliary tooling includes a placement platform for placing the mold, the placement platform being an arched plate-shaped placement platform, the mold being placed on the placement platform and the two sides of the mold forming mutually symmetrical receiving spaces with the placement platform;

[0016] The accommodating space is provided with an L-shaped elastic gasket. During the casting process, the L-shaped elastic gasket drives the mold to swing up and down alternately around the axis of symmetry of the mutually symmetrical accommodating spaces.

[0017] The L-shaped elastic gasket is an L-shaped elastic gasket made of carbon spring steel with a carbon content of 0.62% to 0.90%.

[0018] The L-shaped elastic gasket has a long side length of 90–110 mm, a short side length of 10–20 mm, and a thickness of 0.4–0.5 mm.

[0019] The mold is a cylindrical mold with a diameter of 180-200 mm, a thickness of 15-20 mm, and a height of 90-120 mm.

[0020] In step 2, the flow rate of the molten CoHf alloy ingot during casting is 100-170 ml / s or ml / s, and the casting time is 3-5 s.

[0021] Preferably, the number of L-shaped elastic pads is the same as the number of accommodating spaces, or the number of L-shaped elastic pads is a multiple of the number of accommodating spaces.

[0022] Preferably, there are four L-shaped elastic pads, which are set at the four corners of the mold to drive the mold to swing up and down alternately around the axis of symmetry of the symmetrical accommodating space during the casting process.

[0023] Preferably, there are two L-shaped elastic pads, which are arranged correspondingly to the two sides of the mold, so as to drive the mold to swing up and down alternately around the axis of symmetry of the mutually symmetrical accommodating space during the casting process.

[0024] Preferably, in step 1, the molar ratio of cobalt to hafnium is 70-80:20-30.

[0025] Preferably, step 2 specifically involves: placing the CoHf alloy ingot obtained in step 1 in a crucible, heating it to 1300–1650 °C for 4–6 min, and holding it at that temperature for 5–7 min after the CoHf alloy ingot has melted. Then, pouring the molten CoHf alloy into a mold placed on an auxiliary tool.

[0026] Preferably, step 3 specifically involves: placing the CoHf target blank obtained in step 2 into a carbon tube furnace, heating it to 760±10 ℃ at a heating rate of 30~50 ℃ / h at 1×10-3~4×10-3 Pa, annealing it for 5~7 h, and then cooling it to room temperature at a cooling rate of 30~50 ℃ / h after annealing to obtain a CoHf planar target.

[0027] In addition, this application also discloses a CoHf planar target, which is prepared by the above-described method for preparing a CoHf planar target.

[0028] Preferably, the density of the CoHf planar target is 10.612–10.816 g / cm³. 3 .

[0029] The beneficial effects of this application are as follows: This application discloses a method for preparing a CoHf planar target. In the process of casting the target material, the mold placed on the auxiliary tooling is made to swing by the impact force brought by the pouring of the molten metal during the casting process. This reduces the bubbles inside the molten metal to a certain extent and disperses the stress to various parts of the target blank, thereby reducing the residual stress of the CoHf planar target. At the same time, combined with the annealing treatment of the target blank, the residual stress inside the target material is fully released. Attached Figure Description

[0030] Figure 1 These are schematic diagrams of the auxiliary fixtures used in Examples 1-3;

[0031] Figure 2 The CoHf planar target prepared in Example 1;

[0032] Figure 3 The CoHf planar target prepared in Comparative Example 1;

[0033] Figure 4 The CoHf planar target prepared in Comparative Example 2 is shown. Detailed Implementation

[0034] The present application will be clearly and completely described below with reference to its embodiments. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0035] Before demonstrating the embodiments, it is necessary to explain the auxiliary fixtures used in the embodiments:

[0036] The auxiliary fixtures used in the following embodiments 1-3 include a placement platform 1 for placing the mold 2. The placement platform 1 is an arched plate-shaped placement platform 1. The mold 2 is placed on the placement platform 1 and the two sides of the mold 2 form mutually symmetrical receiving spaces with the placement platform 1.

[0037] The accommodating space is provided with an L-shaped elastic pad 3. During the casting process, the L-shaped elastic pad 3 drives the mold 2 to swing up and down alternately around the axis of symmetry of the mutually symmetrical accommodating spaces.

[0038] The L-shaped elastic gasket 3 is an L-shaped elastic gasket 3 made of carbon spring steel with a carbon content of 0.8%;

[0039] The L-shaped elastic gasket 3 has a long side length of 90mm, a short side length of 10mm, and a thickness of 0.4mm.

[0040] The mold 2 is a cylindrical mold 2 with a diameter of 180mm, a thickness of 15mm, and a height of 90mm.

[0041] The number of L-shaped elastic pads 3 is 4, and they are set corresponding to the 4 corners of the mold 2. It should be noted that, since the mold 2 is a cylindrical mold 2 in actual use, the above-mentioned "4 corners of the mold 2" are actually the 4 corners of the circumscribed square of the circle on the bottom interface of the cylindrical mold 2. Of course, when the mold 2 is a cuboid mold 2, the "4 corners of the mold 2" are the 4 corners of the bottom surface of the rectangular mold 2. At the same time, due to the above-mentioned arrangement, the force on the mold 2 is more uniform, so as to drive the mold 2 to swing up and down alternately around the axis of symmetry of the mutually symmetrical accommodating space during the casting process.

[0042] Example 1

[0043] Step 1: Weigh cobalt and hafnium in a molar ratio of 76:24, then arrange the cobalt and hafnium in an overlapping and alternating pattern in a vacuum crucible, heat and melt them, and then cool them in the furnace to obtain CoHf alloy ingots;

[0044] Step 2: Place the CoHf alloy ingot obtained in Step 1 in a crucible and heat it to 1300℃ for 4 minutes. After the CoHf alloy ingot melts, keep it at that temperature for 5 minutes. Then pour the CoHf alloy melt into a mold placed on an auxiliary tool. During the pouring process, the flow rate of the CoHf alloy melt is 100 ml / s and the pouring time is 5 seconds.

[0045] Step 3: Place the CoHf target blank obtained in Step 2 into a carbon tube furnace, and heat it at a 1×10⁻⁶ temperature. -3 Pa was heated to 750℃ at a heating rate of 30℃ / h and annealed for 5 h. After annealing, it was cooled to room temperature at a cooling rate of 30℃ / h to obtain a CoHf planar target.

[0046] Example 2

[0047] Step 1: Weigh cobalt and hafnium in a molar ratio of 76:24, then arrange the cobalt and hafnium in an overlapping and alternating pattern in a vacuum crucible, heat and melt them, and then cool them in the furnace to obtain CoHf alloy ingots;

[0048] Step 2: Place the CoHf alloy ingot obtained in Step 1 in a crucible and heat it to 1650 ℃ for 6 minutes. After the CoHf alloy ingot melts, hold it at that temperature for 7 minutes. Then pour the CoHf alloy melt into a mold placed on an auxiliary tool. During the pouring process, the flow rate of the CoHf alloy melt is 100 ml / s and the pouring time is 5 seconds.

[0049] Step 3: Place the CoHf target blank obtained in Step 2 into a carbon tube furnace, and heat it at a temperature of 4×10⁻⁶. -3 Pa was heated to 770 °C at a heating rate of 50 °C / h and annealed for 7 h. After annealing, it was cooled to room temperature at a cooling rate of 50 °C / h to obtain a CoHf planar target.

[0050] Example 3

[0051] Step 1: Weigh cobalt and hafnium in a molar ratio of 76:24, then arrange the cobalt and hafnium in an overlapping and alternating pattern in a vacuum crucible, heat and melt them, and then cool them in the furnace to obtain CoHf alloy ingots;

[0052] Step 2: Place the CoHf alloy ingot obtained in Step 1 in a crucible and heat it to 1500 ℃ for 5 minutes. After the CoHf alloy ingot melts, hold it at that temperature for 6 minutes. Then pour the CoHf alloy melt into a mold placed on an auxiliary tool. During the pouring process, the flow rate of the CoHf alloy melt is 100 ml / s and the pouring time is 5 seconds.

[0053] Step 3: Place the CoHf target blank obtained in Step 2 into a carbon tube furnace, and heat it at a temperature of 2×10⁻⁶. -3 Pa was heated to 760℃ at a heating rate of 40℃ / h and annealed for 6h. After annealing, it was cooled to room temperature at a cooling rate of 40℃ / h to obtain a CoHf planar target.

[0054] Example 4

[0055] It is basically the same as Example 1, except that the molar ratio of cobalt and hafnium is 70:30.

[0056] Example 5

[0057] It is basically the same as Example 1, except that the molar ratio of cobalt and hafnium is 80:20.

[0058] Example 6

[0059] It is basically the same as Example 1, except that the long side of the L-shaped elastic gasket is 110mm, the short side is 20mm, and the thickness is 0.5mm. Example

[0060] It is basically the same as Example 1, except that the long side of the L-shaped elastic gasket is 100mm, the short side is 15mm, and the thickness is 0.45mm.

[0061] Example 8

[0062] The process is basically the same as in Example 1, except that in step 2, the flow rate of the molten CoHf alloy is 170 ml / s and the pouring time is 3 seconds.

[0063] Example 9

[0064] The process is basically the same as in Example 1, except that in step 2, the flow rate of the molten CoHf alloy is 125 ml / s and the pouring time is 4 s.

[0065] Example 10

[0066] It is basically the same as Example 1, except that the mold is a cylindrical mold with a diameter of 200mm, a thickness of 20mm, and a height of 120mm.

[0067] Example 11

[0068] It is basically the same as Example 1, except that the mold is a cylindrical mold with a diameter of 190mm, a thickness of 18mm, and a height of 110mm.

[0069] Comparative Example 1

[0070] It is basically the same as Example 1, except that in step 2, the mold is in a stationary state.

[0071] Comparative Example 2

[0072] The process is basically the same as in Example 1, except that in step 2, the mold moves continuously in the vertical direction, meaning the mold as a whole vibrates up and down rather than swings.

[0073] Comparative Example 3

[0074] The process is basically the same as in Example 1, except that in step 2, the mold moves horizontally continuously, meaning the mold as a whole vibrates horizontally rather than oscillates.

[0075] Performance testing:

[0076] Weigh the target material, measure its mass and volume, and calculate its density.

[0077] The cracking of the target material is observed with the naked eye and recorded with a camera;

[0078] The relative densities of the target materials prepared in the examples and comparative examples are shown in Table 1:

[0079] Table 1

[0080] Group <![CDATA[Density (g / cm 3 ).]]> Group <![CDATA[Density (g / cm 3 )]]> Example 1 10.713 Example 8 10.725 Example 2 10.721 Example 9 10.795 Example 3 10.803 Example 10 10.714 Example 4 10.658 Example 11 10.754 Example 5 10.634 Comparative Example 1 9.876 Example 6 10.714 Comparative Example 2 10.139 Example 7 10.789 Comparative Example 3 10.094

[0081] Results analysis:

[0082] 1. Through Example 1 and Comparative Example 1 in combination Figure 1-2 It is evident that when the mold is in a static state during the casting process, the density of the mold decreases significantly and cracks appear.

[0083] 2. Through Example 1 and Comparative Examples 2-3, combined with Figure 1 , Figure 3 It is evident that when the vibration state of the mold is altered during the casting process, although the density of the mold is increased to some extent as shown in Table 1, cracking still occurs in the actual production process.

[0084] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a CoHf planar target, characterized in that, Includes the following steps: Step 1: Cobalt and hafnium metals are arranged in an overlapping and alternating pattern in a vacuum crucible, heated and melted, and then cooled in the furnace to obtain CoHf alloy ingots; Step 2: Melt the CoHf alloy ingot obtained in Step 1 and pour it into the mold. After pouring, cool it to room temperature in the furnace and remove it from the furnace to obtain the CoHf target billet. The mold is placed on the auxiliary fixture and is in a swinging state during the pouring process. Step 3: Place the CoHf target blank obtained in Step 2 into a carbon tube furnace for annealing, then cut and polish it to obtain a CoHf planar target; The auxiliary fixture includes a placement platform for placing the mold. The placement platform is an arched plate-shaped platform. The mold is placed on the placement platform and the two sides of the mold form mutually symmetrical receiving spaces with the placement platform. The accommodating space is provided with an L-shaped elastic gasket. During the casting process, the L-shaped elastic gasket drives the mold to swing up and down alternately around the axis of symmetry of the mutually symmetrical accommodating spaces. The L-shaped elastic gasket is an L-shaped elastic gasket made of carbon spring steel with a carbon content of 0.62% to 0.90%. The L-shaped elastic gasket has a long side length of 90–110 mm, a short side length of 10–20 mm, and a thickness of 0.4–0.5 mm. The mold is a cylindrical mold with a diameter of 180-200 mm, a thickness of 15-20 mm, and a height of 90-120 mm. In step 2, the flow rate of the molten CoHf alloy ingot during casting is 100-170 ml / s, and the casting time is 3-5 s.

2. The method for preparing a CoHf planar target according to claim 1, characterized in that, The number of L-shaped elastic gaskets is the same as the number of accommodating spaces, or the number of L-shaped elastic gaskets is a multiple of the number of accommodating spaces.

3. The method for preparing a CoHf planar target according to claim 1, characterized in that, The number of L-shaped elastic pads is four, and they are set at the four corners of the mold to drive the mold to swing up and down alternately around the axis of symmetry of the mutually symmetrical accommodating space during the casting process.

4. The method for preparing a CoHf planar target according to claim 1, characterized in that, There are two L-shaped elastic pads, which are set on both sides of the mold to drive the mold to swing up and down alternately around the axis of symmetry of the symmetrical accommodating space during the casting process.

5. The method for preparing a CoHf planar target according to claim 1, characterized in that, In step 1, the molar ratio of cobalt to hafnium is 70-80:20-30.

6. The method for preparing a CoHf planar target according to claim 1, characterized in that, Step 2 specifically involves placing the CoHf alloy ingot obtained in step 1 into a crucible, heating it to 1300–1650 °C for 4–6 min, and holding it at that temperature for 5–7 min after the CoHf alloy ingot has melted. Then, the CoHf alloy melt is poured into a mold placed on an auxiliary tool.

7. The method for preparing a CoHf planar target according to claim 1, characterized in that, Step 3 specifically involves placing the CoHf target blank obtained in step 2 into a carbon tube furnace and heating it at a temperature of 1×10⁻⁶. -3 ~ 4×10 -3 Pa was heated to 760±10 ℃ at a heating rate of 30-50 ℃ / h, annealed for 5-7 h, and then cooled to room temperature at a cooling rate of 30-50 ℃ / h to obtain a CoHf planar target.

8. A CoHf planar target, characterized in that, The CoHf planar target was prepared by any of the methods described in claims 1-7.

9. The CoHf planar target according to claim 8, characterized in that, The density of the CoHf planar target is 10.612–10.816 g / cm³. 3 .

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