Preparation method and application of large-size aluminum flat target material

Abstract

The application belongs to the technical field of target materials, and particularly relates to a preparation method and application of a large-size aluminum plane target material; the preparation method of the large-size aluminum plane target material is as follows: after high-purity aluminum ingots are preheated by stepwise temperature rising, multi-direction upsetting and drawing is performed in the length, width and height directions, and the cumulative deformation is not less than 50%; then, room temperature cold rolling is performed, and rolling is performed to 1200*1130*12mm; finally, annealing is performed at 150-250 DEG C, and air cooling is performed to room temperature, so that the large-size aluminum plane target material is obtained; the large-size aluminum plane target material prepared has uniform and small microstructure, small grains on the sputtering surface and the cross section, small size difference, and excellent microstructure consistency; no microstructure defects exist in the inside; when the large-size aluminum plane target material is applied as a magnetron sputtering target material, high-quality large-size liquid crystal panels can be prepared through uniform deposition rate, and the large-size aluminum plane target material is a high-performance large-size aluminum plane target material, and can solve the technical problem of low performance of the large-size aluminum plane target material prepared by the existing process.

Description

Technical Field

[0001] This application belongs to the field of target technology, and in particular relates to a method for preparing and applying a large-size aluminum planar target. Background Technology

[0002] Magnetron sputtering is one of the core processes for preparing high-performance functional thin films. Its basic principle is as follows: In a vacuum environment, argon gas is ionized by a high-voltage electric field to generate argon ions. The argon ions are accelerated under the synergistic effect of the magnetic field and the electric field to form a high-energy ion beam, which then bombards the surface of the target material placed on the cathode, causing the target atoms or molecules to be sputtered out and deposited on the substrate surface to form a thin film.

[0003] As flat panel displays continue to evolve towards higher image quality and larger sizes, the requirements for uniformity of film deposition in panels are becoming increasingly stringent. To ensure a uniform deposition rate over a large area of ​​coating, aluminum targets for magnetron sputtering must possess core characteristics such as uniform composition distribution, consistent microstructure, and small grain size. Compared to traditional pure aluminum materials, high-purity aluminum has become an irreplaceable key material in the aluminum wiring process of display panels due to its low resistivity, high conductivity, and excellent anti-electromigration properties.

[0004] However, aluminum itself has low hardness. When the target size increases significantly, it is prone to deformation under heat and stress during sputtering, which affects the coating quality and the lifespan of the target. Therefore, achieving uniformity control, grain refinement and elimination of internal defects in large-size high-purity aluminum planar targets is the main challenge currently faced by the manufacturing technology. At present, the manufacturing of such targets mostly adopts the rolling process. However, conventional hot rolling process is limited by factors such as uneven temperature field distribution and uncontrollable recrystallization behavior. It is difficult to achieve both uniformity of structure and positional accuracy in large-size targets, resulting in lower performance. There is an urgent need to develop new manufacturing processes for large-size high-purity aluminum planar targets. Summary of the Invention

[0005] In view of this, this application provides a method for preparing large-size aluminum planar targets and its application, which solves the technical problem of low performance of large-size aluminum planar targets prepared by existing processes.

[0006] The first aspect of this application provides a method for preparing a large-size aluminum planar target, comprising the following steps:

[0007] The preheating process involves preheating the high-purity aluminum ingots using a stepped heating method to obtain preheated high-purity aluminum ingots.

[0008] Forging steps: The surface temperature of the preheated high-purity aluminum ingot is controlled to be no less than 200℃. The ingot is then upsetting and drawing in the length, width and height directions in sequence, followed by stress-relief annealing to obtain the forged high-purity aluminum ingot.

[0009] The rolling process involves cooling the forged high-purity aluminum ingot to room temperature and then cold rolling it to obtain a large-sized aluminum flat surface.

[0010] The heat treatment steps are as follows: The rolled large-size aluminum flat surface is subjected to annealing heat treatment to obtain a large-size aluminum flat surface target.

[0011] Preferably, in the preheating step, the high-purity aluminum ingot has a purity ≥5N and is cylindrical.

[0012] Preferably, in the preheating step, the stepped heating preheating process includes: a first step of heating to 150~300℃ for 120~180min, and a second step of heating to 250~350℃ for 60~90min.

[0013] Preferably, in the forging step, the upsetting and drawing process includes: for the length, width, or height direction, upsetting is performed through multiple deformation processes to ensure that the compression deformation is not less than 50%, and drawing is performed through multiple deformation processes to ensure that the elongation deformation is not less than 50%;

[0014] Preferably, in the forging step, the upsetting process involves 2 to 4 passes of deformation processing, with a single pass deformation amount of 15% to 25%.

[0015] The stretching process involves 2 to 4 passes of deformation processing, with a single pass deformation amount of 15% to 25%.

[0016] Preferably, in the forging step, the stress-relief annealing temperature is 125~175℃ and the time is 10~20min.

[0017] Preferably, in the forging step, the process of upsetting and drawing in the length, width, and height directions and stress-relieving annealing is repeated 2 to 4 times.

[0018] Preferably, in the rolling step, the cooling to room temperature process includes: cooling the forged high-purity aluminum ingot to room temperature using a flowing water body at room temperature.

[0019] Preferably, in the rolling step, the cold rolling process includes: performing multiple cold rolling processes to widen and multiple cold rolling processes to lengthen, to obtain a large-size aluminum flat surface with a length, width and height of 1200*1130*12mm.

[0020] Preferably, in the rolling step, the single-pass deformation amount of the cold rolling widening is 20%~25%, the single-pass deformation amount of the last cold rolling elongation is not less than 30%, and the single-pass deformation amount of the remaining cold rolling elongation is 20%~25%.

[0021] Preferably, in the heat treatment step, the annealing heat treatment temperature is 150~250℃ and the time is 15~60min.

[0022] Preferably, the high-purity aluminum ingot is selected from high-purity aluminum ingots that have undergone grinding pretreatment;

[0023] The large-size aluminum planar target material is selected from large-size aluminum planar targets that have undergone leveling treatment.

[0024] The second aspect of this application provides the application of the large-size aluminum planar target prepared by the preparation method described in the first aspect in the preparation of flat panel displays.

[0025] Preferably, the flat panel display is selected from one of the following: liquid crystal display, organic light-emitting diode display, plasma display, quantum dot light-emitting diode display, and micro light-emitting diode display.

[0026] Compared with the prior art, the method for preparing a large-size aluminum planar target provided in this application has at least the following beneficial effects:

[0027] 1. The large-size aluminum planar target prepared in this application has a uniform and fine microstructure, with a grain size of only 120~155μm on the sputtering surface and 126.3~176.2μm on the cross section. The difference between the grain size on the sputtering surface and the cross section does not exceed 6.3μm, which shows excellent microstructure consistency.

[0028] 2. The large-size aluminum planar target material prepared by the preparation method provided in this application has no internal defects. Through three-dimensional upsetting with a cumulative deformation of more than 50%, the porosity, looseness and microcracks inside the ingot are fully welded together. Combined with cold rolling and low-temperature recovery annealing at 150℃ to eliminate internal stress, a fully dense and defect-free microstructure is finally obtained.

[0029] 3. The large-size aluminum planar target prepared in this application has a size of 1200×1130×12mm, which meets the size requirements of sputtering targets for large-size OLED liquid crystal panels and can prepare high-quality liquid crystal panels through uniform deposition rate. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic flowchart illustrating the preparation method of the large-size aluminum planar target provided in Embodiment 1 of this application. Detailed Implementation

[0032] This application provides a method for preparing large-size aluminum planar targets and its application, which solves the technical problem of low performance of large-size aluminum planar targets prepared by existing processes.

[0033] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] Example 1

[0035] This embodiment provides a method for preparing a large-size aluminum planar target, the process flow diagram of which is shown below. Figure 1 As shown, it includes the steps of preheating, forging, rolling, and heat treatment.

[0036] The preheating step includes:

[0037] High-purity aluminum ingots are used. The ingots are made by vacuum melting process and are cylindrical with a purity of ≥5N. Then, the surface of the high-purity aluminum ingots is pre-treated by grinding to remove surface oxides and defects, prevent the introduction of impurities and defects, and improve the target material forming rate and flatness.

[0038] The high-purity aluminum ingot, after being polished and pretreated, is placed in a box-type resistance heating furnace for step-by-step preheating, with the furnace temperature monitored by thermocouples. First, the furnace temperature is raised to 200°C and held for 150 minutes. Then, the temperature is raised to 250°C and held for another 90 minutes to obtain the preheated high-purity aluminum ingot. Compared with direct heating, this step uses step-by-step preheating, which saves energy by reducing waiting time and ensures a more uniform temperature distribution in the high-purity aluminum ingot, which is beneficial for subsequent forging.

[0039] The forging steps include:

[0040] The temperature of the preheated high-purity aluminum ingot is controlled to be no less than 200℃. A three-way upsetting process is adopted, in which the preheated high-purity aluminum ingot is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation amount of the upsetting ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a compression deformation of 50%. The deformation amount of the elongation ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a stretch deformation of 50%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃ for 15 minutes to remove the stress. Force annealing completes the first upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, deformation uniformity is achieved, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0041] The temperature of the high-purity aluminum ingot after the first upsetting forging is controlled to be no less than 200℃. A three-axis upsetting process is adopted, in which the high-purity aluminum ingot after the first upsetting forging is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation amount of the upsetting ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a compression deformation amount of 50%. The deformation amount of the elongation ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve an elongation deformation amount of 50%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃. Stress-relief annealing for 15 minutes is performed to complete the second upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, deformation uniformity is achieved, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is performed by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0042] The high-purity aluminum ingot, after its second upsetting and forging, is kept at a temperature no lower than 200°C. A three-axis upsetting process is employed, where the high-purity aluminum ingot, after its second upsetting and forging, is sequentially upset in its length, width, and height directions. During the upsetting process, the single-pass deformation for upsetting is 15%~25%, repeated three times to achieve a compression deformation of 50%. Similarly, the single-pass deformation for elongation is 15%~25%, repeated three times to achieve a stretch deformation of 50%. Finally, the ingot is forged back to its original dimensions and then placed in a warm-induction furnace, heated to 150°C for 1 minute. After 5 minutes of stress-relief annealing, the third upsetting and drawing forging is completed. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, the deformation uniformity is ensured, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0043] The rolling process includes:

[0044] The high-purity aluminum ingot, which has undergone three upsetting and forging processes, is rapidly cooled to room temperature with flowing water to prevent static recrystallization. Then, it is directly cold rolled. The cold rolling process involves three passes of cold rolling to widen the ingot, with a single pass deformation of 20% to 25%. After widening to the target size, the ingot is reversed and lengthened, and then three passes of cold rolling are performed to lengthen it. The first two passes have a single pass deformation of 20% to 25%, and the last pass has a single pass deformation of 30%, ensuring that the grains are fully broken and refined, resulting in a large-sized aluminum flat surface with a length, width, and height of approximately 1200*1130*12mm.

[0045] The heat treatment steps include:

[0046] The large-size aluminum flat surface obtained by cold rolling is annealed at 150℃ for 15 minutes, and then air-cooled to room temperature to improve the internal structure of the rolled aluminum plate, ensure the uniformity of the internal structure of the target material, and eliminate intergranular defects and internal stress. Finally, a leveling post-treatment is performed to obtain the large-size aluminum flat target material.

[0047] Example 2

[0048] To investigate the effect of stepped heating preheating on the performance of large-size aluminum planar targets, this embodiment provides a method for preparing large-size aluminum planar targets, including a preheating step, a forging step, a rolling step, and a heat treatment step.

[0049] The preheating step includes:

[0050] High-purity aluminum ingots are used. The ingots are made by vacuum melting process and are cylindrical with a purity of ≥5N. Then, the surface of the high-purity aluminum ingots is pre-treated by grinding to remove surface oxides and defects, prevent the introduction of impurities and defects, and improve the target material forming rate and flatness.

[0051] The high-purity aluminum ingot, after being polished and pretreated, is placed in a box-type resistance heating furnace for step-by-step preheating, with the furnace temperature monitored by thermocouples. First, the furnace temperature is raised to 300°C and held for 150 minutes. Then, the temperature is raised to 350°C and held for another 90 minutes to obtain the preheated high-purity aluminum ingot. Compared with direct heating, this step uses step-by-step preheating, which saves energy by reducing waiting time and ensures a more uniform temperature distribution in the high-purity aluminum ingot, which is beneficial for subsequent forging.

[0052] The forging steps include:

[0053] The temperature of the preheated high-purity aluminum ingot is controlled to be no less than 200℃. A three-way upsetting process is adopted, in which the preheated high-purity aluminum ingot is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation amount of the upsetting ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a compression deformation of 50%. The deformation amount of the elongation ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a stretch deformation of 50%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃ for 15 minutes to remove the stress. Force annealing completes the first upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, deformation uniformity is achieved, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0054] The temperature of the high-purity aluminum ingot after the first upsetting forging is controlled to be no less than 200℃. A three-axis upsetting process is adopted, in which the high-purity aluminum ingot after the first upsetting forging is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation amount of the upsetting ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a compression deformation amount of 50%. The deformation amount of the elongation ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve an elongation deformation amount of 50%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃. Stress-relief annealing for 15 minutes is performed to complete the second upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, deformation uniformity is achieved, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is performed by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0055] The high-purity aluminum ingot, after its second upsetting and forging, is kept at a temperature no lower than 200°C. A three-axis upsetting process is employed, where the high-purity aluminum ingot, after its second upsetting and forging, is sequentially upset in its length, width, and height directions. During the upsetting process, the single-pass deformation for upsetting is 15%~25%, repeated three times to achieve a compression deformation of 50%. Similarly, the single-pass deformation for elongation is 15%~25%, repeated three times to achieve a stretch deformation of 50%. Finally, the ingot is forged back to its original dimensions and then placed in a warm-induction furnace, heated to 150°C for 1 minute. After 5 minutes of stress-relief annealing, the third upsetting and drawing forging is completed. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, the deformation uniformity is ensured, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0056] The rolling process includes:

[0057] The high-purity aluminum ingot, which has undergone three upsetting and forging processes, is rapidly cooled to room temperature with flowing water to prevent static recrystallization. Then, it is directly cold rolled. The cold rolling process involves three passes of cold rolling to widen the ingot, with a single pass deformation of 20% to 25%. After widening to the target size, the ingot is reversed and lengthened, and then three passes of cold rolling are performed to lengthen it. The first two passes have a single pass deformation of 20% to 25%, and the last pass has a single pass deformation of 30%, ensuring that the grains are fully broken and refined, resulting in a large-sized aluminum flat surface with a length, width, and height of approximately 1200*1130*12mm.

[0058] The heat treatment steps include:

[0059] The large-size aluminum flat surface obtained by cold rolling is annealed at 150℃ for 15 minutes, and then air-cooled to room temperature to improve the internal structure of the rolled aluminum plate, ensure the uniformity of the internal structure of the target material, and eliminate intergranular defects and internal stress. Finally, a leveling post-treatment is performed to obtain the large-size aluminum flat target material.

[0060] Example 3

[0061] To investigate the effect of annealing heat treatment on the properties of large-size aluminum planar targets, this embodiment provides a method for preparing large-size aluminum planar targets, including a preheating step, a forging step, a rolling step, and a heat treatment step.

[0062] The preheating step includes:

[0063] High-purity aluminum ingots are used. The ingots are made by vacuum melting process and are cylindrical with a purity of ≥5N. Then, the surface of the high-purity aluminum ingots is pre-treated by grinding to remove surface oxides and defects, prevent the introduction of impurities and defects, and improve the target material forming rate and flatness.

[0064] The high-purity aluminum ingot, after being polished and pretreated, is placed in a box-type resistance heating furnace for step-by-step preheating, with the furnace temperature monitored by thermocouples. First, the furnace temperature is raised to 200°C and held for 150 minutes. Then, the temperature is raised to 250°C and held for another 90 minutes to obtain the preheated high-purity aluminum ingot. Compared with direct heating, this step uses step-by-step preheating, which saves energy by reducing waiting time and ensures a more uniform temperature distribution in the high-purity aluminum ingot, which is beneficial for subsequent forging.

[0065] The forging steps include:

[0066] The temperature of the preheated high-purity aluminum ingot is controlled to be no less than 200℃. A three-way upsetting process is adopted, in which the preheated high-purity aluminum ingot is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation amount of the upsetting ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a compression deformation of 50%. The deformation amount of the elongation ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a stretch deformation of 50%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃ for 15 minutes to remove the stress. Force annealing completes the first upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, deformation uniformity is achieved, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0067] The temperature of the high-purity aluminum ingot after the first upsetting forging is controlled to be no less than 200℃. A three-axis upsetting process is adopted, in which the high-purity aluminum ingot after the first upsetting forging is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation amount of the upsetting ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a compression deformation amount of 50%. The deformation amount of the elongation ingot in a single pass is 15%~25%, and it is carried out in 3 passes to achieve an elongation deformation amount of 50%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃. Stress-relief annealing for 15 minutes is performed to complete the second upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, deformation uniformity is achieved, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is performed by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0068] The high-purity aluminum ingot, after its second upsetting and forging, is kept at a temperature no lower than 200°C. A three-axis upsetting process is employed, where the high-purity aluminum ingot, after its second upsetting and forging, is sequentially upset in its length, width, and height directions. During the upsetting process, the single-pass deformation for upsetting is 15%~25%, repeated three times to achieve a compression deformation of 50%. Similarly, the single-pass deformation for elongation is 15%~25%, repeated three times to achieve a stretch deformation of 50%. Finally, the ingot is forged back to its original dimensions and then placed in a warm-induction furnace, heated to 150°C for 1 minute. After 5 minutes of stress-relief annealing, the third upsetting and drawing forging is completed. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, the deformation uniformity is ensured, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0069] The rolling process includes:

[0070] The high-purity aluminum ingot, which has undergone three upsetting and forging processes, is rapidly cooled to room temperature with flowing water to prevent static recrystallization. Then, it is directly cold rolled. The cold rolling process involves three passes of cold rolling to widen the ingot, with a single pass deformation of 20% to 25%. After widening to the target size, the ingot is reversed and lengthened, and then three passes of cold rolling are performed to lengthen it. The first two passes have a single pass deformation of 20% to 25%, and the last pass has a single pass deformation of 30%, ensuring that the grains are fully broken and refined, resulting in a large-sized aluminum flat surface with a length, width, and height of approximately 1200*1130*12mm.

[0071] The heat treatment steps include:

[0072] The large-size aluminum flat surface obtained by cold rolling is annealed at 250℃ for 60 minutes, and then air-cooled to room temperature to improve the internal structure of the rolled aluminum plate, ensure the uniformity of the internal structure of the target material, and eliminate intergranular defects and internal stress. Finally, a leveling post-treatment is performed to obtain the large-size aluminum flat target material.

[0073] Comparative Example 1

[0074] To investigate the effect of room temperature cold rolling on the properties of large-size aluminum planar targets, this comparative example provides a method for preparing large-size aluminum planar targets, including a preheating step, a forging step, a rolling step, and a heat treatment step.

[0075] The preheating step includes:

[0076] High-purity aluminum ingots are used. The ingots are made by vacuum melting process and are cylindrical with a purity of ≥5N. Then, the surface of the high-purity aluminum ingots is pre-treated by grinding to remove surface oxides and defects, prevent the introduction of impurities and defects, and improve the target material forming rate and flatness.

[0077] The high-purity aluminum ingots that have undergone grinding and pretreatment are placed in a box-type resistance heating furnace for step-by-step preheating and the furnace temperature is monitored by thermocouples. First, the furnace temperature is preheated to 200°C and held for 150 minutes. Then, the temperature is further increased to 250°C and held for another 90 minutes to obtain the preheated high-purity aluminum ingots.

[0078] The forging steps include:

[0079] The temperature of the preheated high-purity aluminum ingot is controlled to be no less than 200℃. A three-way upsetting process is adopted, in which the preheated high-purity aluminum ingot is upset in the length, width and height directions in sequence. During the upsetting process, the deformation amount of the upsetting in a single pass is 15%~25%, and it is carried out in 3 passes to make the compression deformation amount 50%. The deformation amount of the elongation in a single pass is 15%~25%, and it is carried out in 3 passes to make the elongation deformation amount 50%. Finally, it is forged back to the original size and then placed in a warm infeed furnace for stress relief annealing at 150℃ for 15 minutes to complete the first upsetting forging.

[0080] The temperature of the high-purity aluminum ingot after the first upsetting and forging is controlled to be no less than 200℃. A three-way upsetting and forging process is adopted, in which the high-purity aluminum ingot after the first upsetting and forging is upset in the length, width and height directions in sequence. During the upsetting and forging process, the deformation amount of the upsetting in a single pass is 15%~25%, and it is carried out in 3 passes to make the compression deformation amount 50%. The deformation amount of the elongation in a single pass is 15%~25%, and it is carried out in 3 passes to make the elongation deformation amount 50%. Finally, it is forged back to the original size, and then placed in a warm induction furnace and heated at 150℃ for 15 minutes for stress relief annealing to complete the second upsetting and forging.

[0081] The high-purity aluminum ingot, after the second upsetting and forging, is kept at a temperature no lower than 200°C. A three-way upsetting and forging process is adopted, in which the high-purity aluminum ingot after the second upsetting and forging is upset in three directions: length, width, and height. During the upsetting and forging process, the deformation amount of the upsetting in a single pass is 15%~25%, and it is carried out in 3 passes to achieve a compression deformation amount of 50%. The deformation amount of the elongation in a single pass is 15%~25%, and it is carried out in 3 passes to achieve an elongation deformation amount of 50%. Finally, it is forged back to its original size and then placed in a warm induction furnace for stress relief annealing at 150°C for 15 minutes to complete the third upsetting and forging.

[0082] The rolling process includes:

[0083] The high-purity aluminum ingot, which has undergone three upsetting and forging processes, is rapidly cooled to room temperature by flowing water to prevent static recrystallization. Then, it is heated to 300°C for hot rolling. The hot rolling process involves three passes to widen the ingot, with a single pass deformation of 20% to 25%. After widening to the target size, the ingot is reversed and lengthened by three passes of hot rolling. The first two passes have a single pass deformation of 20% to 25%, and the last pass has a single pass deformation of 30%.

[0084] The heat treatment steps include:

[0085] The large-size aluminum flat surface obtained by hot rolling is annealed at 150℃ for 15 minutes, then air-cooled to room temperature after being removed from the furnace, and then leveled to obtain the large-size aluminum flat surface target material.

[0086] Comparative Example 2

[0087] To investigate the effect of three-dimensional upsetting process on the performance of large-size aluminum planar targets, this comparative example provides a method for preparing large-size aluminum planar targets, including a preheating step, a forging step, a rolling step, and a heat treatment step.

[0088] The preheating step includes:

[0089] High-purity aluminum ingots are used. The ingots are made by vacuum melting process and are cylindrical with a purity of ≥5N. Then, the surface of the high-purity aluminum ingots is pre-treated by grinding to remove surface oxides and defects, prevent the introduction of impurities and defects, and improve the target material forming rate and flatness.

[0090] The high-purity aluminum ingots that have undergone grinding and pretreatment are placed in a box-type resistance heating furnace for step-by-step preheating and the furnace temperature is monitored by thermocouples. First, the furnace temperature is preheated to 200°C and held for 150 minutes. Then, the temperature is further increased to 250°C and held for another 90 minutes to obtain the preheated high-purity aluminum ingots.

[0091] The forging steps include:

[0092] The temperature of the preheated high-purity aluminum ingot is controlled to be no less than 200℃. A three-axis upsetting process is adopted, in which the preheated high-purity aluminum ingot is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation per pass of the upsetting is 5%~10%, and it is carried out in 3 passes to achieve a compression deformation of 20%. The deformation per pass of the elongation is 5%~10%, and it is carried out in 3 passes to achieve an elongation deformation of 20%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃ for 15 minutes to relieve stress. Annealing completes the first upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, the deformation uniformity is ensured, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0093] The temperature of the high-purity aluminum ingot after the first upsetting forging is controlled to be no less than 200℃. A three-directional upsetting process is adopted, in which the high-purity aluminum ingot after the first upsetting forging is upset sequentially in the length, width, and height directions. During the upsetting process, the deformation amount of the upsetting ingot in a single pass is 5%~10%, and it is carried out in 3 passes to achieve a compression deformation amount of 20%. The deformation amount of the elongation ingot in a single pass is 5%~10%, and it is carried out in 3 passes to achieve an elongation deformation amount of 20%. Finally, it is forged back to its original size and then placed in a warm-infeed furnace and heated at 150℃ for 1 minute. After 5 minutes of stress-relief annealing, the second upsetting and drawing forging is completed. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, the deformation uniformity is ensured, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0094] The high-purity aluminum ingot, after its second upsetting and forging, is kept at a temperature no lower than 200℃. A three-axis upsetting process is employed, where the high-purity aluminum ingot, after its second upsetting and forging, is sequentially upset in its length, width, and height directions. During the upsetting process, the single-pass deformation for upsetting is 5%~10%, repeated three times to achieve a compression deformation of 20%. Similarly, the single-pass deformation for elongation is 5%~10%, repeated three times to achieve a stretch deformation of 20%. Finally, the ingot is forged back to its original dimensions and then placed in a warm-infeed furnace, heated at 150℃ for 15 minutes. The stress-relief annealing process is completed after the third upsetting and drawing forging. By performing three upsetting and three drawing operations in the length, width, and height directions of the high-purity aluminum ingot, the deformation uniformity is ensured, and defects such as porosity, looseness, and microcracks inside the ingot are eliminated. At the same time, the temperature of the high-purity aluminum ingot is controlled to be no lower than 200℃ to avoid deformation hardening and cooling hardening that could cause cracks during the upsetting and drawing process. During the upsetting and drawing process, if the surface temperature of the high-purity aluminum ingot is lower than 200℃, it needs to be returned to the furnace for reheating. The reheating is carried out by heating in the furnace at 250℃ for 45 minutes, and then the ingot is taken out of the furnace and upsetting and drawing continues.

[0095] The rolling process includes:

[0096] The high-purity aluminum ingot, which has undergone three upsetting and forging processes, is rapidly cooled to room temperature with flowing water to prevent static recrystallization. Then, it is directly cold rolled. The cold rolling process involves three passes of cold rolling to widen the ingot, with a single pass deformation of 20% to 25%. After widening to the target size, the ingot is reversed and lengthened, and then three passes of cold rolling are performed to lengthen it. The first two passes have a single pass deformation of 20% to 25%, and the last pass has a single pass deformation of 30%, ensuring that the grains are fully broken and refined, resulting in a large-sized aluminum flat surface with a length, width, and height of approximately 1200*1130*12mm.

[0097] The heat treatment steps include:

[0098] The large-size aluminum flat surface obtained by cold rolling is annealed at 150℃ for 15 minutes, and then air-cooled to room temperature to improve the internal structure of the rolled aluminum plate, ensure the uniformity of the internal structure of the target material, and eliminate intergranular defects and internal stress. Finally, a leveling post-treatment is performed to obtain the large-size aluminum flat target material.

[0099] Experimental Example 1

[0100] This experimental example characterizes the structure of the large-size aluminum planar targets provided in Examples 1-3 and Comparative Examples 1-2. The structural characterization process includes: first, cutting samples of appropriate size from the large-size aluminum planar targets; then, removing surface scratches by coarse grinding (sandpaper) and fine grinding (metallographic sandpaper); and finally, obtaining a smooth mirror surface through polishing. The microstructure was revealed using chemical etching agents or electrolysis, and the samples were observed using an optical microscope or an electron microscope. Images were taken and the microstructure characteristics were recorded. Grain size and defect size were measured. The test results are shown in Table 1.

[0101] Table 1: Characterization results of large-size aluminum planar target structures provided in Examples 1-3 and Comparative Examples 1-2

[0102]

[0103] As can be seen from Table 1, the preparation methods provided in Examples 1-3 of this application produce large-size aluminum planar targets with a length, width, and height of approximately 1200*1130*12mm. The targets have a uniform and defect-free microstructure, a sputtering grain size of 120~155μm, and a cross-sectional grain size of 126.3~176.2μm. They are high-performance large-size aluminum planar targets that meet the requirements for magnetron sputtering targets for display panels such as OLED liquid crystal display panels.

[0104] As can be seen from Table 1, compared with the large-size aluminum planar target provided in the examples, the large-size aluminum planar target prepared by the preparation method provided in Comparative Example 1 has generally poor microstructure uniformity, and the grains on the sputtering surface and cross-section are coarse with large size differences. This indicates that it is difficult to control the microstructure uniformity of large-size aluminum planar targets using hot rolling process, and the grains are prone to coarseness. This may be because when hot rolling at 300℃, high-purity aluminum has entered the recrystallization temperature range. However, due to the large size of the aluminum planar, the heat dissipation rate of the edge and the middle of the aluminum planar is different during rolling, and the recrystallization process of each region is not synchronized. The grains in the region that crystallizes first will continue to grow, while the grains in the region that crystallizes later are still in the stage of deformation energy storage accumulation. Ultimately, this results in generally poor microstructure uniformity and coarse grains in the target. This makes it difficult to obtain a uniform deposition rate when the large-size aluminum planar target provided in Comparative Example 1 is used as a magnetron sputtering target, and the performance of the prepared OLED liquid crystal display panels and other display panels is poor.

[0105] Furthermore, as shown in Table 1, compared with the large-size aluminum planar target provided in the examples, the large-size aluminum planar target prepared by the method provided in Comparative Example 2 has generally poor microstructure uniformity, with coarse grains and large size differences on the sputtering surface and cross-section. This indicates that the upsetting and drawing process with low deformation is insufficient to fully break down the as-cast coarse columnar crystals and dendrites inside the high-purity aluminum ingot. When the deformation is low, plastic flow is mainly concentrated near the grain boundaries of the high-purity aluminum ingot and in local soft orientation regions, while the coarse grains in the core basically retain their original appearance, forming a situation of "surface deformation, core undisturbed". The non-uniform structure and coarse structure are inherited by the subsequent cold rolling process. At the same time, the compressive stress provided by the 20% upsetting deformation is insufficient to effectively weld the porosity, looseness and microcracks inside the ingot. These defects become stress concentration sources during cold rolling and subsequent use. The recrystallization nucleation driving force is weak during subsequent annealing at 150°C, the number of crystal nuclei is small and the grains are coarse. This makes it difficult to obtain a uniform deposition rate when the large-size aluminum planar target provided in Comparative Example 2 is used as a magnetron sputtering target, and the performance of the prepared OLED liquid crystal display panel and other display panels is poor.

[0106] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a large-size aluminum planar target, characterized in that, Includes the following steps: High-purity aluminum ingots are preheated by step heating to obtain preheated high-purity aluminum ingots. The surface temperature of the preheated high-purity aluminum ingot is controlled to be no less than 200℃. It is then upsetting and drawing in the length, width and height directions in sequence, followed by stress-relieving annealing to obtain the forged high-purity aluminum ingot. The forged high-purity aluminum ingot is cooled to room temperature and then cold-rolled to obtain a large-size aluminum flat surface. Large-size aluminum flat surfaces are annealed and heat-treated to obtain large-size aluminum flat surface targets.

2. The method for preparing a large-size aluminum planar target according to claim 1, characterized in that, The high-purity aluminum ingot has a purity of ≥5N and is cylindrical.

3. The method for preparing a large-size aluminum planar target according to claim 1, characterized in that, The stepped heating preheating process includes: first, heating to 150~300℃ for 120~180 minutes, and second, heating to 250~350℃ for 60~90 minutes.

4. The method for preparing a large-size aluminum planar target according to claim 1, characterized in that, The upsetting and drawing process includes: for the length, width or height direction, upsetting is carried out through multiple deformation processes to ensure that the compression deformation is not less than 50%, and drawing is carried out through multiple deformation processes to ensure that the elongation deformation is not less than 50%.

5. The method for preparing a large-size aluminum planar target according to claim 4, characterized in that, The upsetting process involves 2 to 4 passes of deformation processing, with a single pass deformation amount of 15% to 25%. The stretching process involves 2 to 4 passes of deformation processing, with a single pass deformation amount of 15% to 25%.

6. The method for preparing a large-size aluminum planar target according to claim 1, characterized in that, The cold rolling process includes: performing multiple cold rolling processes to widen the surface and multiple cold rolling processes to lengthen it, resulting in a large-size aluminum flat surface with dimensions of 1200*1130*12mm.

7. The method for preparing a large-size aluminum planar target according to claim 1, characterized in that, The single-pass deformation amount of the cold rolling process is 20%~25%, the single-pass deformation amount of the last cold rolling process extension is not less than 30%, and the single-pass deformation amount of the remaining cold rolling process extension is 20%~25%.

8. The method for preparing a large-size aluminum planar target according to claim 1, characterized in that, The annealing heat treatment is performed at a temperature of 150~250℃ for a time of 15~60min.

9. The application of the large-size aluminum planar target material prepared by the preparation method according to any one of claims 1-8 in the preparation of flat panel displays.

10. The application according to claim 9, characterized in that, The flat panel display is selected from one of the following: liquid crystal display, organic light-emitting diode display, plasma display, quantum dot light-emitting diode display, and micro light-emitting diode display.

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