Preparation method of molybdenum-niobium alloy plate

Abstract

The invention belongs to the technical field of powder metallurgy, and particularly relates to a preparation method of a molybdenum-niobium alloy plate. The preparation method comprises the following steps: mixing molybdenum powder and niobium powder to obtain mixed powder; the mixed powder is placed in a sheath, then cold pressing, cold pressing pressure relief, first preheating, hot pressing, hot pressing pressure relief and first heat preservation heat treatment are sequentially conducted, and finally a molybdenum-niobium plate blank is obtained after the sheath is removed; the molybdenum-niobium plate blank is sequentially subjected to second preheating, hot rolling and second heat preservation heat treatment, and a molybdenum-niobium rolled plate is obtained; and the molybdenum-niobium rolled plate is subjected to sintering and solid solution treatment under the vacuum condition, and the molybdenum-niobium alloy plate is obtained. Grain growth is avoided, and meanwhile, the problems of low density and molybdenum and niobium two-phase separation are further solved by combining hot rolling and subsequent sintering solid solution treatment. According to the method, the molybdenum-niobium alloy plate with complete solid solution of molybdenum and niobium, fine crystal grains, high compactness and excellent comprehensive performance can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, and specifically relates to a method for preparing molybdenum-niobium alloy plates. Background Technology

[0002] Molybdenum-niobium alloy targets are widely used in the field of sputtering coating for flat panel displays, and the preparation process of the molybdenum-niobium alloy plates used in them is crucial. Currently, there are two main processes for preparing molybdenum-niobium alloy plates. One is the sintering method, which involves mixing molybdenum and niobium powders, forming them through cold isostatic pressing, and then vacuum sintering them into plates. This method requires less equipment investment but results in lower density and coarser grains, leading to poorer film quality. The other is the hot isostatic pressing method, which involves mixing molybdenum and niobium powders, forming them through cold isostatic pressing, and then densifying them through hot isostatic pressing. Subsequently, depending on the needs, it can be directly processed into plates or hot-rolled before being processed into plates. This method requires more equipment investment, and the resulting molybdenum and niobium phases cannot be completely dissolved, easily causing inhomogeneity in the grain structure of the molybdenum-niobium target, affecting the subsequent sputtering effect.

[0003] In summary, the current preparation of molybdenum-niobium alloy plates suffers from problems such as low density, separation of molybdenum and niobium phases, and uneven grain distribution. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing molybdenum-niobium alloy plates. The preparation method provided by this invention can avoid grain growth, achieve densification of molybdenum-niobium alloy plates, and achieve complete solid solution of molybdenum and niobium, with uniform distribution of the two phases. This solves the problems of low density and separation of molybdenum and niobium phases in molybdenum-niobium alloy plates, and obtains molybdenum-niobium alloy plates with excellent comprehensive performance.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing molybdenum-niobium alloy plates, comprising the following steps: (1) Molybdenum powder and niobium powder are mixed to obtain a mixed powder, wherein the mixing time is ≥3h; (2) The mixed powder is placed in a sleeve, and then cold pressing, cold pressing depressurization, first preheating, hot pressing, hot pressing depressurization and first heat preservation treatment are performed in sequence. Finally, the sleeve is removed to obtain a molybdenum-niobium slab. The temperature of the first preheating is ≥1100℃, the pressure of the hot pressing is ≥600MPa, the holding time of the hot pressing is ≥60s, and the temperature of the first heat preservation treatment is ≥1100℃. (3) The molybdenum-niobium slab is subjected to a second preheating, hot rolling and a second heat treatment in sequence to obtain a molybdenum-niobium rolled plate, wherein the temperature of the second preheating is ≥1250℃; (4) The molybdenum-niobium rolled sheet is subjected to sintering and solution treatment under vacuum conditions to obtain the molybdenum-niobium alloy sheet.

[0006] Preferably, in step (1), the mixing is carried out in a three-dimensional mixer, which is equipped with a flying knife. The flying knife is turned on for 1 to 3 hours during the mixing process, and the flying knife speed is ≥2800 rpm.

[0007] Preferably, in step (2), the pressure of the cold pressing is 200~400MPa and the holding time is 15~60s; the cold pressing is carried out at room temperature and the cold pressing is carried out in a forging press using a mold.

[0008] Preferably, in step (2), the temperature of the first preheating is 1100~1350℃.

[0009] Preferably, in step (2), the hot pressing pressure is 600~800MPa, the hot pressing holding time is 60~120s, and the hot pressing is carried out in a forging press using a mold.

[0010] Preferably, in step (2), the temperature of the first heat treatment is 1100~1350℃ and the heat treatment time is 10~30min.

[0011] Preferably, in step (3), the temperature of the second preheating is 1250~1400℃ and the time is 30~60min.

[0012] Preferably, in step (3), the hot rolling is a multi-pass hot rolling process; the total deformation of the hot rolling is ≥60%.

[0013] Preferably, in step (3), the temperature of the second heat treatment is 1250~1400℃ and the heat treatment time is 10~30min.

[0014] Preferably, in step (4), the temperature of the sintering and solution treatment is 1400~1800℃ and the holding time is 10~60min.

[0015] This invention provides a method for preparing molybdenum-niobium alloy sheet, comprising the following steps: (1) mixing molybdenum powder and niobium powder to obtain a mixed powder, wherein the mixing time is ≥3h; (2) placing the mixed powder in a sleeve, and then sequentially performing cold pressing, cold pressing depressurization, first preheating, hot pressing, hot pressing depressurization and first heat treatment, and finally removing the sleeve to obtain a molybdenum-niobium slab, wherein the temperature of the first preheating is ≥1100℃, the pressure of the hot pressing is ≥600MPa, the holding time of the hot pressing is ≥60s, and the temperature of the first heat treatment is ≥1100℃; (3) sequentially performing a second preheating, hot rolling and a second heat treatment on the molybdenum-niobium slab to obtain a rolled molybdenum-niobium sheet, wherein the temperature of the second preheating is ≥1250℃; (4) performing a sintering and solution treatment on the rolled molybdenum-niobium sheet under vacuum conditions to obtain the molybdenum-niobium alloy sheet. This invention first optimizes the mixing time of molybdenum and niobium powder to ensure thorough and uniform mixing of the two raw material powders. Then, it employs a mechanical pressing method (i.e., cold pressing, cold pressing depressurization, first preheating, hot pressing, hot pressing depressurization, and first heat treatment), simultaneously optimizing the first preheating temperature, hot pressing pressure, and holding time. This allows the molybdenum-niobium alloy sheet to achieve densification at a lower temperature, preventing grain growth. Furthermore, combining hot rolling with subsequent sintering and solution treatment under vacuum conditions further solves the problems of insufficient density and separation of the molybdenum and niobium phases. Compared to existing mainstream methods such as vacuum sintering and hot isostatic pressing, this invention can obtain molybdenum-niobium alloy sheets with excellent comprehensive properties, characterized by complete solid solution of molybdenum and niobium, fine grains, and high density. Attached Figure Description

[0016] Figure 1 The image shows the metallographic structure of the molybdenum-niobium alloy plate prepared in Example 1 of this invention. Figure 2 The image shows the metallographic structure of the molybdenum-niobium alloy plate prepared in Comparative Example 1 of this invention. Figure 3 The image shows the metallographic structure of the molybdenum-niobium alloy plate prepared in Comparative Example 2 of this invention. Detailed Implementation

[0017] This invention provides a method for preparing molybdenum-niobium alloy plates, comprising the following steps: (1) Molybdenum powder and niobium powder are mixed to obtain a mixed powder, wherein the mixing time is ≥3h; (2) The mixed powder is placed in a sleeve, and then cold pressing, cold pressing depressurization, first preheating, hot pressing, hot pressing depressurization and first heat preservation treatment are performed in sequence. Finally, the sleeve is removed to obtain a molybdenum-niobium slab. The temperature of the first preheating is ≥1100℃, the pressure of the hot pressing is ≥600MPa, the holding time of the hot pressing is ≥60s, and the temperature of the first heat preservation treatment is ≥1100℃. (3) The molybdenum-niobium slab is subjected to a second preheating, hot rolling and a second heat treatment in sequence to obtain a molybdenum-niobium rolled plate, wherein the temperature of the second preheating is ≥1250℃; (4) The molybdenum-niobium rolled sheet is subjected to sintering and solution treatment under vacuum conditions to obtain the molybdenum-niobium alloy sheet.

[0018] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0019] This invention involves mixing molybdenum powder and niobium powder to obtain a mixed powder, wherein the mixing time is ≥3 hours. In this invention, the molybdenum powder is preferably low-oxygen molybdenum powder, and the oxygen content of the molybdenum powder is preferably ≤0.05 wt.%. The mesh size of the molybdenum powder is -325 mesh. The niobium powder is preferably low-oxygen niobium powder, and the oxygen content of the niobium powder is preferably ≤0.1%. The mesh size of the niobium powder is -325 mesh. In this invention, the mass ratio of the molybdenum powder and niobium powder is determined according to the content of molybdenum and niobium elements in the molybdenum-niobium alloy plate.

[0020] In this invention, the mixing is preferably carried out in a three-dimensional mixer. The three-dimensional mixer is preferably equipped with a flying knife. The flying knife is preferably activated for 1-3 hours during the mixing process. The flying knife rotation speed is preferably ≥2800 rpm. The mixing time is preferably 3-6 hours, and in the embodiments, it can be 3 hours, 4 hours, 5 hours, or 6 hours. In this invention, because the flying knife rotates at a relatively high speed, both the motor and the flying knife easily generate a lot of heat; therefore, the flying knife adopts an intermittent working mode, and the flying knife is activated intermittently. The cumulative activation time of the flying knife is preferably 1-3 hours.

[0021] This invention uses a three-dimensional mixer for mixing. By controlling the mixing parameters, it is possible to obtain a uniformly distributed molybdenum-niobium mixture.

[0022] After obtaining the mixed powder, the present invention places the mixed powder in a sleeve, and then performs cold pressing, cold pressing depressurization, first preheating, hot pressing, hot pressing depressurization and first heat treatment in sequence. Finally, after removing the sleeve, a molybdenum-niobium slab is obtained. The temperature of the first preheating is ≥1100℃, the pressure of the hot pressing is ≥600MPa, the holding time of the hot pressing is ≥60s, and the temperature of the first heat treatment is ≥1100℃.

[0023] In this invention, the cold pressing is performed at room temperature. The cold pressing is preferably performed using a die in a forging press. The pressure of the cold pressing is preferably 200-400 MPa, and in the embodiments, it can be 200 MPa, 300 MPa, or 400 MPa. The holding time of the cold pressing is preferably 15-60 s, and in the embodiments, it can be 15 s, 20 s, 30 s, 40 s, 50 s, or 60 s. After the cold pressing is completed, the pressure is released slowly, and the pressure release rate is preferably 10-30 MPa / s, and in the embodiments, it can be 20 MPa / s. By controlling the pressure and holding time of the cold pressing, this invention can achieve densification and molding of mixed powder raw materials at room temperature; at the same time, by controlling the pressure release rate of the cold pressing, this invention can regulate the stress state, densification uniformity, and microstructure evolution of the material during the pressure unloading process, avoiding defects such as cracking, delamination, and excessive springback in the sheet material, ultimately ensuring the dimensional accuracy, mechanical properties, and adaptability of the product for subsequent processing.

[0024] In this invention, after the cold pressing and depressurization are completed, the gaps in the cold-pressed casing are preferably welded, followed by the first preheating treatment. The first preheating is performed in a heating furnace. The preferred temperature for the first preheating is 1100~1350℃, and in embodiments it can be 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, or 1350℃. In this invention, after the first preheating reaches the temperature, the intermediate alloy material is quickly removed for the hot pressing.

[0025] In this invention, the hot pressing is preferably performed using a die in a forging press. The initial temperature of the hot pressing is preferably 1100~1350℃, and in the embodiments it can be 1100℃, 1150℃, 1200℃, 1250℃, 1300℃ or 1350℃. The pressure of the hot pressing is preferably 600~800MPa, and in the embodiments it can be 600MPa, 700MPa or 800MPa. The holding time of the hot pressing is preferably 60~120s, and in the embodiments it can be 60s, 70s, 80s, 90s, 100s, 110s or 120s. After the hot pressing is completed, the hot pressing is depressurized slowly, and the depressurization rate is preferably 5~15MPa / s, and in the embodiments it can be 10MPa / s. This invention achieves grain densification under high-temperature conditions by controlling the temperature, pressure, and holding time of hot pressing, while preventing grain growth. The invention also controls the rate of pressure release during hot pressing, which helps to achieve densification and interfacial bonding of the billet. The pressure release rate defined by this invention is adapted to the plasticity, diffusion characteristics, and phase transformation laws of materials under high-temperature hot pressing conditions, avoiding unique defects at high temperatures (such as thermal cracking, abnormal grain growth, and interfacial debonding), and ensuring the density, microstructure uniformity, and mechanical properties of the sheet material.

[0026] In this invention, the first heat treatment is performed in a heating furnace. The temperature of the first heat treatment is preferably 1100~1350℃, and in the embodiments it can be 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, or 1350℃. The holding time of the first heat treatment is preferably 10~30 minutes, and in the embodiments it can be 10 minutes, 20 minutes, or 30 minutes.

[0027] In this invention, after the first heat treatment is completed, the product is preferably air-cooled to room temperature to obtain a molybdenum-niobium slab.

[0028] After obtaining the molybdenum-niobium slab, the present invention sequentially performs a second preheating, hot rolling and a second heat treatment to obtain a molybdenum-niobium rolled plate, wherein the temperature of the second preheating is ≥1250℃.

[0029] In this invention, the second preheating treatment is performed in a heating furnace. The preferred temperature for the second preheating is 1250~1400℃, and in embodiments, it can be 1250℃, 1300℃, 1350℃, or 1400℃. The preferred time for the second preheating treatment is 30~60 minutes, and in embodiments, it can be 30 minutes, 40 minutes, 50 minutes, or 60 minutes. Since hot rolling requires the slab to be kept at a high temperature, this invention achieves uniform temperature distribution in the slab requiring hot pressing by controlling the holding time of the second preheating treatment.

[0030] In this invention, the hot rolling is performed on a hot rolling mill. The hot rolling is preferably a multi-pass, single-heat hot rolling process. The total deformation of the hot rolling is preferably ≥60%.

[0031] In this invention, the second heat treatment is performed in a heating furnace. The preferred temperature for the second heat treatment is 1250~1400℃, and in the embodiments, it can be 1250℃, 1300℃, 1350℃, or 1400℃. The holding time for the second heat treatment is 10~30 minutes, and in the embodiments, it can be 10 minutes, 20 minutes, or 30 minutes.

[0032] In this invention, after the second heat treatment is completed, the furnace is preferably cooled to room temperature to obtain a molybdenum-niobium rolled sheet.

[0033] After obtaining the molybdenum-niobium rolled sheet, the present invention performs sintering and solution treatment on the molybdenum-niobium rolled sheet under vacuum conditions to obtain the molybdenum-niobium alloy sheet.

[0034] In this invention, the sintering and solution treatment is preferably carried out in a vacuum furnace. The temperature of the sintering and solution treatment is preferably 1400~1800℃, and in the embodiments it can be 1400℃, 1500℃, 1600℃, 1700℃ or 1800℃. The holding time of the sintering and solution treatment is preferably 10~60min, and in the embodiments it can be 10min, 20min, 30min, 40min, 50min or 60min.

[0035] In this invention, after the sintering and solution treatment is completed, the furnace is preferably cooled to room temperature to obtain the molybdenum-niobium alloy plate.

[0036] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 This embodiment provides a method for preparing molybdenum-niobium alloy plates, specifically including the following steps: Step 1: Mixing. Molybdenum powder and niobium powder are placed in a three-dimensional mixer equipped with a fly knife and mixed for 6 hours. The fly knife speed is 2800 rpm and the fly knife is on for 2 hours.

[0038] Step 2: Hot pressing. The mixed powder is loaded into a sleeve and pressed at room temperature using a mold and forging press. The pressing pressure is 400 MPa, and the holding time is 60 s. Then, the pressure is slowly released at a rate of 20 MPa / s. The gaps of the cold-pressed sleeve are welded, and the mixture is placed in a heating furnace and preheated to 1350℃. It is then quickly removed and pressed again using a mold and forging press at a pressure of 800 MPa and a holding time of 120 s. After that, the pressure is slowly released at a rate of 10 MPa / s. The mixture is then placed back into the heating furnace and held for 30 min. Finally, it is air-cooled to room temperature, and the surface sleeve is removed to obtain a molybdenum-niobium slab.

[0039] Step 3: Rolling. The molybdenum-niobium slab is placed in a heating furnace for preheating at 1400℃ for 60 minutes. After being removed, it is hot rolled in a single pass on a hot rolling mill with a total deformation of 60%. Finally, it is placed back into the heating furnace and held at that temperature for 30 minutes, and then cooled to room temperature in the furnace to obtain the rolled molybdenum-niobium sheet.

[0040] Step 4: Sintering. The molybdenum-niobium rolled sheet is placed in a vacuum furnace for sintering and solution treatment at a temperature of 1800℃ for 10 minutes. Then it is cooled to room temperature in the furnace to obtain the molybdenum-niobium alloy sheet.

[0041] Comparative Example 1 This comparative example provides a method for preparing molybdenum-niobium alloy sheet using hot isostatic pressing-rolling, specifically including the following steps: The process involves mixing molybdenum and niobium powders, followed by cold isostatic pressing at 200 MPa and hot isostatic pressing at 1350℃ to densify them, and then processing them directly into sheets as needed.

[0042] Comparative Example 2 This comparative example provides a method for preparing molybdenum-niobium alloy plates, which employs a vacuum sintering process at 1950℃ for 4 hours, specifically including the following steps: Molybdenum and niobium powders are mixed, shaped, vacuum sintered (1950℃×4h), and then processed into plates.

[0043] Test case Figure 1 The image shows the metallographic structure of the molybdenum-niobium alloy plate prepared in Example 1 of this invention. Figure 2 The image shows the metallographic structure of the molybdenum-niobium alloy plate prepared in Comparative Example 1 of this invention. Figure 3 The image shows the metallographic structure of the molybdenum-niobium alloy sheet prepared in Comparative Example 2 of this invention. Table 1 shows the performance results of the molybdenum-niobium alloy sheets prepared in Example 1 and Comparative Examples 1-2.

[0044] Table 1. Performance results of the molybdenum-niobium alloy plates prepared in Examples 1 and Comparative Examples 1-2

[0045] From Table 1, Figures 1-3 The results show that this invention employs a novel three-dimensional mixing process to ensure a uniformly distributed molybdenum-niobium mixture; mechanical hot pressing enables densification of the molybdenum-niobium alloy sheet at a lower temperature, preventing grain growth and facilitating subsequent hot rolling; finally, the combination of hot rolling and subsequent high-temperature treatment solves the problems of insufficient density and separation of the molybdenum and niobium phases. This invention produces a molybdenum-niobium alloy sheet with excellent comprehensive performance. Compared with existing mainstream methods such as vacuum sintering and hot isostatic pressing, this invention can obtain a molybdenum-niobium alloy sheet with complete solid solution of molybdenum and niobium, fine grains, and high density.

[0046] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a molybdenum-niobium alloy plate, characterized in that, Includes the following steps: (1) Molybdenum powder and niobium powder are mixed to obtain a mixed powder, wherein the mixing time is ≥3h; (2) The mixed powder is placed in a sleeve, and then cold pressing, cold pressing depressurization, first preheating, hot pressing, hot pressing depressurization and first heat preservation treatment are performed in sequence. Finally, the sleeve is removed to obtain a molybdenum-niobium slab. The temperature of the first preheating is ≥1100℃, the pressure of the hot pressing is ≥600MPa, the holding time of the hot pressing is ≥60s, and the temperature of the first heat preservation treatment is ≥1100℃. (3) The molybdenum-niobium slab is subjected to a second preheating, hot rolling and a second heat treatment in sequence to obtain a molybdenum-niobium rolled plate, wherein the temperature of the second preheating is ≥1250℃; (4) The molybdenum-niobium rolled sheet is subjected to sintering and solution treatment under vacuum conditions to obtain the molybdenum-niobium alloy sheet.

2. The preparation method according to claim 1, characterized in that, In step (1), the mixing is carried out in a three-dimensional mixer, which is equipped with a flying knife. The flying knife is turned on for 1 to 3 hours during the mixing process, and the flying knife speed is ≥2800 rpm.

3. The preparation method according to claim 1, characterized in that, In step (2), the pressure of the cold pressing is 200~400MPa and the holding time is 15~60s; the cold pressing is carried out at room temperature and the cold pressing is carried out in a forging press using a mold.

4. The preparation method according to claim 1, characterized in that, In step (2), the temperature of the first preheating is 1100~1350℃.

5. The preparation method according to claim 1 or 4, characterized in that, In step (2), the hot pressing pressure is 600~800MPa, the hot pressing holding time is 60~120s, and the hot pressing is carried out in a forging press using a mold.

6. The preparation method according to claim 1, characterized in that, In step (2), the temperature of the first heat treatment is 1100~1350℃ and the heat treatment time is 10~30min.

7. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the second preheating is 1250~1400℃ and the time is 30~60min.

8. The preparation method according to claim 1 or 7, characterized in that, In step (3), the hot rolling is a multi-pass hot rolling process; the total deformation of the hot rolling is ≥60%.

9. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the second heat treatment is 1250~1400℃ and the heat treatment time is 10~30min.

10. The preparation method according to claim 1, characterized in that, In step (4), the temperature of the sintering and solution treatment is 1400~1800℃, and the holding time is 10~60min.

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