High-temperature-oxidation-resistant low-silver-content AgCuGa noble metal dual-phase alloy material

Abstract

The invention discloses a high-temperature-oxidation-resistant low-silver-content AgCuGa noble metal dual-phase alloy material, and belongs to the technical field of silver-copper brazing filler metal alloy preparation. The key point of the silver content AgCuGa noble metal dual-phase alloy material is 60% lt; cu + Ga is smaller than or equal to 65%, and the Ga / Cu ratio is larger than or equal to 0.224. In cooperation with the preparation method, the material is mainly composed of an Ag-rich phase and a Cu-rich phase, Ga is mainly in the Cu-rich phase, the Ag-rich phase only contains a very small amount of Ga element, Ga atoms of the Ga element in the Cu-rich phase are rapidly and autonomously distributed at a high temperature, a Ga2O3-rich continuous compact nano oxide layer is formed on the surface, the oxide film effectively inhibits O atom internal diffusion, the volume ratio of the metal Ga to the Ga2O3 is remarkably reduced, and the material is suitable for large-scale production. And a complete and compact high-protective oxidation film is formed, excellent oxidation resistance is achieved in 700 DEG C air, and the shear strength of a brazed joint is superior to that of Ag-28Cu alloy vacuum brazing under the protection of low-flow inert gas.

Description

Technical Field

[0001] The invention belongs to the technical field of silver-copper solder alloy preparation, and particularly relates to a low-silver-content AgCuGa noble metal duplex alloy material that is resistant to high-temperature oxidation. Background Art

[0002] Due to the addition of various metals or non-metals, the structure of vacuum electronic devices has become more and more complicated, which makes it difficult for traditional welding methods to cope with the connection problem between complex and changeable materials; silver-copper solder alloy has been widely used in industrial production due to its advantages such as suitable melting point, high brazing strength, good corrosion resistance and excellent electrical conductivity; Ag-28Cu alloy is one of the earliest Ag-Cu solder alloys, which has the advantages of moderate brazing temperature and good brazing joint performance. It is the most preferred vacuum solder alloy for brazing and sealing vacuum electronic devices such as vacuum switch tubes, microwave devices and transmitting tubes. However, Ag-28Cu alloy has high cost due to its high Ag content; in order to reduce the Ag content and cost, there are methods in the prior art to increase the Cu content in Ag-Cu binary alloy or add Cu to it. Attempts have been made to incorporate low-melting-point elements; although low-melting-point elements can lower the solidus and liquidus temperatures of solder alloys, the addition of these elements will also affect their microstructure and other properties. Moreover, the solid solubility of low-melting-point elements in Ag and Cu is low, and brittle phases will be generated when the solder alloy is prepared by the smelting method; Ga has the characteristics of a low melting point (29.76°C) and a high boiling point (2403°C), making it a very promising candidate for low-melting-point elements. Adding Ga can improve the flowability of certain lead-free solders and lower the melting point of Ag-Cu-Ga alloys; in addition, Ag-Cu-Ga alloys not only have good processing properties in the preparation of alloy sheets, but also have higher shear strength after vacuum brazing than Ag-28Cu alloys under the same brazing time and temperature.

[0003] At present, there is little research on the high-temperature oxidation resistance of Ag-Cu-Ga alloys, and the focus is mainly on using Ga to improve brazing strength. For example, Liu Xu et al. (Structure and Properties of AgCuGa Brazing Alloys, 2020) studied the structure and properties of AgCuGa brazing alloys with Ga content of 5wt.%, 10wt.%, and 20wt.%, and only found that when the Ga content was 5wt.%, the melting point of Ag-55Cu-5Ga alloy (the cast structure of the alloy was mainly composed of Cu-rich phase, Ag-rich phase and Ag-Cu-Ga eutectic phase) was Moderate, the solid-liquid temperature difference is small, although it improves the brazing joint strength to a certain extent, and is considered to be expected to replace Ag-28Cu alloy, but the Cu+Ga content does not exceed 60%; Zhang Dechuan ("Study on Preparation and Brazing Performance of Ag-Cu-Ga Alloys" 2021) prepared Ag-28Cu-5Ga, Ag-34Cu-5Ga, Ag-39Cu-5Ga, Ag-49Cu-5Ga, Ag-55Cu by adding 5wt.% Ga on the basis of Ag-28Cu alloy. -5Ga five alloys, the results showed that: at the same brazing temperature and brazing time, the brazing strength of Ag-28Cu and the five alloys to Kovar alloy were 217MPa, 366MPa, 390MPa, 445MPa, 299MPa, and 200MPa respectively; Ag-39Cu-5Ga (Cu+Ga=44%, Ga / Cu=0.113) had the highest brazing strength. Compared with the Ga and Cu ratio in Ag-39Cu-5Ga, further increasing the Ga / Cu or Cu+Ga All of these will lead to a decrease in brazing strength, that is, the increase in shear strength of the brazed joint is not linearly related to the change of Cu+Ga and Ga / Cu. Under the same brazing conditions, the brazing strength of Ag-55Cu-5Ga alloy is lower than that of Ag-28Cu alloy, which is inconsistent with the view of Liu Xu et al. that Ag-55Cu-5Ga is expected to replace Ag-28Cu alloy. During the research process of the present invention, it was found that Ag-49Cu-5Ga has poor oxidation resistance in air at 700℃ and the shear strength of the brazed joint is also not ideal. According to the Ag-49Cu- x Ga ( x=(5, 7, 10), a series of AgCuGa alloys with different compositions were prepared. It was only found that at 810 °C, as the Ga content increased, the spreading area on the surfaces of oxygen-free copper and oxygen-free nickel sheets increased, the wetting angle decreased, and the spreading coefficient increased. Among them, Ag-49Cu-10Ga (Cu + Ga = 59%, Ga / Cu = 0.204) had the best wettability on oxygen-free copper and nickel sheets. Although the shear strength of the joints of these alloys was higher than that of the Ag-28Cu alloy when brazing oxygen-free copper and oxygen-free nickel, they did not show good high-temperature oxidation resistance. Therefore, the relationship between the Cu and Ga ratios and their high-temperature oxidation resistance could not be obtained from the previous research on Ag-Cu-Ga alloys. Li Hui et al. (''Influence of Trace Ga Element on the Oxidation Resistance of Low-Silver Lead-Free Brazing Alloys'' in 2012) studied the influence of trace Ga element on the oxidation resistance of Sn-0.3Ag-0.7Cu. Although Sn-0.3Ag-0.7Cu-0.02Ga was a low-silver copper-containing lead-free brazing alloy and the addition of trace Ga improved its oxidation resistance, the Sn-based alloy system did not belong to the Ag-Cu-Ga alloy system, and Ga / Cu = 0.0285 in it. The effective temperature range for the oxidation resistance improvement of Sn-0.3Ag-0.7Cu-remained below 320 °C, which was not an improvement in high-temperature oxidation resistance. Therefore, the relationship between the Cu and Ga ratios and the high-temperature oxidation resistance of Ag-Cu-Ga alloys could not be found from the research of Li Hui et al. either.

[0004] Ag-Cu-Ga alloys are usually brazed at high temperatures of 730 - 810 °C. The oxidation resistance at 700 °C provides support for exploring low-temperature brazing materials, and the revealed mechanism can provide guidance for composition optimization and improvement of brazing performance. If the Ag-Cu-Ga alloy has excellent oxidation resistance in air at 700 °C, simplified protection measures such as low-flow inert gas can be used instead of high-vacuum brazing during brazing. Therefore, the development of Ag-Cu-Ga alloys with excellent oxidation resistance in air at 700 °C is very beneficial to the development of silver-copper brazing technology. Summary of the Invention

[0005] Aiming at the above problems, the purpose of the present invention is to provide a low-silver-content AgCuGa noble metal two-phase alloy material with high-temperature oxidation resistance. This alloy material has excellent oxidation resistance in air at 700 °C and can further reduce the silver content.

[0006] The technical purpose of the present invention is achieved as follows. The composition of the low-silver-content AgCuGa noble metal two-phase alloy material with high-temperature oxidation resistance is: 60% < Cu + Ga ≤ 65% and the Ga / Cu ratio ≥ 0.224, C ≤ 0.05, O ≤ 0.002, P ≤ 0.002, Pb ≤ 0.001, Zn ≤ 0.001, Cd ≤ 0.001, and the rest are components Ag and inevitable impurities. Its preparation method is realized according to the following steps: 1) According to the component content of the low-silver-content AgCuGa noble metal two-phase alloy material, put the required pure Ag and pure Cu into the induction crucible of the vacuum induction furnace for smelting; 2) After completely melting the pure Ag and pure Cu with a power of 40 - 45 kW, immediately adjust the power of the vacuum induction furnace to 0 kW, cut off the power and condense for 30 - 35 minutes to make the surface of the alloy in the induction crucible form a film and cool down. Then open the furnace and put pure Ga on the surface of the alloy with a formed film in the induction crucible. After pumping vacuum, raise the power to 20 - 30 kW at a rate of 10 kW / min, keep it for 3 - 4 minutes, then directly increase it to 45 kW, keep it for 2 - 3 minutes, then reduce the power to 25 kW and keep it for 0.5 - 1 minute, and then reduce the power to 8 - 10 kW for casting to obtain the low-silver-content AgCuGa noble metal two-phase alloy material.

[0007] In order to improve the high-temperature oxidation resistance of the AgCuGa alloy in air at 700 °C, the core components of the AgCuGa noble metal two-phase alloy material in the present invention are controlled to be 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224. Through the preparation method of the present invention, the obtained alloy material is mainly composed of Ag-rich phase and Cu-rich phase, and Ga is mainly in the Cu-rich phase, and only a very small amount of Ga is contained in the Ag-rich phase; precisely through the control of Cu + Ga and Ga / Cu, Ga in the Cu-rich phase can rapidly perform the autonomous distribution of Ga atoms at high temperature and form a continuous and dense nano-oxide layer rich in Ga2O3 on the surface of the alloy. This oxide film extremely effectively inhibits the inward diffusion of O atoms. Coupled with the significant reduction of the volume ratio of metallic Ga to its oxidation product Ga2O3, a complete and dense highly protective oxide film is formed; compared with the prior art, the technical effects of the present invention are as follows: 1. Conduct an isothermal oxidation test on the AgCuGa noble metal two-phase alloy material described in the present invention in air at 700 °C. The alloy hardly gains weight within 30 minutes, and the oxide film does not turn black, having excellent high-temperature oxidation resistance. When brazing, simplified protection measures such as low-flow inert gas are used instead of high-vacuum brazing, and the antioxidant performance is better. It can be used as a low-temperature brazing material and has extremely high promotion value; 2. Under the protection of low-flow inert gas for brazing, the shear strength of the brazed joint of the AgCuGa noble metal two-phase alloy material described in the present invention is better than that of the Ag-28Cu alloy by vacuum brazing; 3. By controlling Cu + Ga and Ga / Cu, the Ag content in the AgCuGa noble metal two-phase alloy material described in the present invention is further reduced to below 40%, even close to or reaching 35%. Specific embodiments

[0008] The following further illustrates the present invention with reference to embodiments, but does not limit the present invention in any way. Any transformation or replacement based on the teachings of the present invention belongs to the protection scope of the present invention.

[0009] The composition of the high-temperature oxidation-resistant low-silver-content AgCuGa noble metal duplex alloy material described in this invention is as follows: 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224, C ≤ 0.05, O ≤ 0.002, P ≤ 0.002, Pb ≤ 0.001, Zn ≤ 0.001, Cd ≤ 0.001, and the rest are component Ag and inevitable impurities; its preparation method is realized according to the following steps: 1) According to the component content of the low-silver-content AgCuGa noble metal duplex alloy material, put the required pure Ag and pure Cu into the induction crucible of a vacuum induction furnace for melting; 2) After completely melting the pure Ag and pure Cu with a power of 40 - 45 kW, immediately adjust the power of the vacuum induction furnace to 0 kW, cut off the power and condense for 30 - 35 minutes to form a film on the surface of the alloy in the induction crucible and cool down, then open the furnace and put pure Ga on the surface of the alloy with a film in the induction crucible, evacuate the air, and increase the power to 20 - 30 kW at a rate of 10 kW / min, keep it for 3 - 4 minutes and then directly increase it to 45 kW, keep it for 2 - 3 minutes and then reduce the power to 25 kW and keep it for 0.5 - 1 minute, reduce the power to 8 - 10 kW for casting and molding, thus obtaining the low-silver-content AgCuGa noble metal duplex alloy material.

[0010] Furthermore, in step 1), the surface oxides of the required pure Ag and pure Cu are removed with sandpaper and the surfaces are cleaned with acetone, and then the surfaces are dried in a vacuum oven at 400 °C.

[0011] Furthermore, in step 1), when calculating the batching of pure Ag, the yield is calculated according to 98.5%.

[0012] Furthermore, in step 2), when calculating the batching of pure Ga, the yield is calculated according to 94%; the batching method of the pure Ga is as follows: a. If the room temperature is lower than 29.7 °C, put the solid pure Ga into a clean beaker, then place the beaker in a constant temperature water bath at > 40 °C for heating. After the solid pure Ga becomes liquid metal, quickly weigh and batch it. After batching, it will re-solidify into a solid state when placed at room temperature, and be prepared for melting; b. If the room temperature is higher than 29.8 °C, directly weigh and batch the liquid metal pure Ga. After batching, put the liquid metal pure Ga into a clean beaker, and then place the beaker in ice water for solidification, and be prepared for melting.

[0013] Furthermore, in step 2), the pure Ag and pure Cu are completely melted with a power of 43 kW.

[0014] Further, after vacuum pumping in step 2), the power is increased to 25 kW at a rate of 10 kW / min.

[0015] Further, the power is reduced to 9 kW in step 2) for casting.

[0016] Example 1 Preparation of a low-silver-content AgCuGa noble metal two-phase alloy material 1. Alloy composition design: C ≤ 0.05, O ≤ 0.002, P ≤ 0.002, Pb ≤ 0.001, Zn ≤ 0.001, Cd ≤ 0.001, Cu = 51.0%, Ga = 11.5%, Cu + Ga = 62.5% and Ga / Cu = 0.225 (satisfying 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224), and the rest are components Ag and unavoidable impurities.

[0017] 2. Batching calculation: Batching calculation is carried out according to the component content of the target low-silver-content two-phase noble metal alloy material; when calculating the pure Ag in batching, the yield is calculated according to 98.5%; when calculating the pure Ga in batching, the yield is calculated according to 94%; therefore, it can be calculated that the required pure Cu is 255. g, pure Ag is 190.4 g, and pure Ga is 61.2 g.

[0018] 3. Batching method: The room temperature is 20 °C, which is lower than 29.7 °C. Place the solid pure Ga in a clean beaker, and then place the beaker in a constant temperature water bath at >40 °C for heating. After the solid pure Ga becomes liquid metal, quickly carry out weighing batching (61.2 g). After batching, it will re-solidify into a solid state when placed at room temperature and is ready for melting; the surface oxides of the prepared pure Ag and pure Cu need to be removed with sandpaper and the surface needs to be cleaned with acetone, and then dried at 400 °C in a vacuum box.

[0019] 4. Alloy melting: Place the required pure Ag and pure Cu in a vacuum induction furnace for melting. After all the pure Ag and pure Cu are melted clear at a power of 40 kW, immediately adjust the power of the vacuum induction furnace to 0 kW, cut off the power and condense for 32 minutes to form a film on the surface of the alloy in the induction furnace and cool down. Then open the furnace and place the pure Ga on the surface of the film in the induction crucible. After vacuum pumping, slowly increase the power to 20 kW. After 3 minutes, directly increase it to 45 kW, keep it for 2 minutes and then reduce it to 25 kW and keep it for 0.5 minutes. Then reduce the power to 8 kW for casting to obtain a low-silver-content AgCuGa noble metal two-phase alloy material.

[0020] 5. Composition testing: The comparison between the designed composition and the measured composition of the alloy material is shown in Table 1, and in the obtained alloy, Cu + Ga = 62.2% and Ga / Cu = 0.224: Table 1 Designed and measured compositions of the alloy material in Example 1 (wt.%) In this embodiment, the total weight of the nickel-based superalloy designed is 0.5 kg.

[0021] 6. High-temperature oxidation resistance test: An isothermal oxidation experiment was carried out on the obtained alloy in an atmospheric environment (air) at 700 °C. The results showed that the alloy hardly gained weight within 30 minutes. The Ga atoms on the alloy surface were self-distributed to form a continuous and dense nano-scale thick oxide film. The oxide film did not turn black, showing excellent antioxidant properties.

[0022] 7. Brazing test: Brazing oxygen-free copper-nickel-plated stainless steel. In an atmospheric environment, the brazing temperature was raised from room temperature to 700 °C at a rate of 10 °C / min. First, low-flow Ar gas was introduced for protection at a gas flow rate of 5 L / min. Then, the oxygen-free copper-nickel-plated stainless steel sample to be brazed was placed. After stabilizing at 700 °C for 10 min, the temperature was continued to be raised to 790 °C at a rate of 5 °C / min for brazing, and the brazing time was 10 min. The results showed that the original metallic color of the filler metal could be seen at the brazed joint, and no black oxide film was found. After measurement, the shear strength of the brazed joint was about 223 MPa.

[0023] Example 2 Preparation of a low-silver-content AgCuGa noble metal two-phase alloy material 1. Alloy composition design: C≤0.05, O≤0.002, P≤0.002, Pb≤0.001, Zn≤0.001, Cd≤0.001, Cu = 52.0%, Ga = 12.0%, Cu + Ga = 64.0% and Ga / Cu = 0.231 (meeting 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224), and the rest are components Ag and unavoidable impurities.

[0024] 2. Batching calculation: Batching calculation was carried out according to the component content of the target low-silver-content two-phase noble metal alloy material. When calculating the pure Ag in the batching, the recovery rate was calculated according to 98.5%. When calculating the pure Ga in the batching, the recovery rate was calculated according to 94%. Therefore, the required pure Cu was calculated to be 260.0 g, pure Ag was 182.7 g, and pure Ga was 63.8 g.

[0025] 3. Batching method: The room temperature was 23 °C, which was lower than 29.7 °C. The solid pure Ga was placed in a clean beaker, and then the beaker was placed in a constant temperature water bath at >40 °C for heating. After the solid pure Ga became liquid metal, it was quickly weighed and batched (63.8 g). After batching, it would re-solidify into a solid state when placed at room temperature and was ready for melting. The surface oxides of the prepared pure Ag and pure Cu needed to be removed with sandpaper and the surfaces were cleaned with acetone, and then the surfaces were dried in a vacuum box at 400 °C.

[0026] 4. Alloy Melting: Place the required pure Ag and pure Cu in a vacuum induction furnace for melting. After completely melting the pure Ag and pure Cu using a power of 43 kW, immediately adjust the power of the vacuum induction furnace to 0 kW, cut off the power and condense for 30 minutes to form a film on the surface of the alloy in the induction furnace and lower the temperature. Then, open the furnace and place pure Ga on the surface of the film in the induction crucible. After evacuating, slowly increase the power to 25 kW, directly increase to 45 kW after 4 minutes, maintain for 2 minutes and then lower to 25 kW and maintain for 1 minute, and lower the power to 10 kW for casting to obtain a low silver content AgCuGa noble metal duplex alloy material.

[0027] 5. Through composition testing, the comparison between the designed composition and the measured composition of this alloy material is shown in Table 2. In the alloy, Cu + Ga = 63.7% and Ga / Cu = 0.227: Table 2 Designed Composition and Measured Composition (wt.%) of the Alloy Material in Example 2 In this example, the total weight of the designed nickel-based superalloy is 0.5 kg.

[0028] 6. High Temperature Oxidation Resistance Test: Conduct an isothermal oxidation experiment on the obtained alloy in a 700 °C atmospheric environment (air). It is found that within 30 minutes, the alloy hardly gains weight, and the Ga atoms on the alloy surface self-distribute to form a continuous and dense oxide film with a nanoscale thickness. The oxide film does not turn black, showing excellent oxidation resistance.

[0029] 7. Brazing Test: The brazing test conditions are the same as those in Example 1, only replacing the alloy material obtained in Example 1 with the alloy material obtained in Example 2; it is found that the original metal color of the filler metal can be seen at the brazed joint, and no black oxide film is found; after measurement, the shear strength of the brazed joint is about 208 MPa.

[0030] Example 3 Preparation of a Low Silver Content AgCuGa Noble Metal Duplex Alloy Material 1. Alloy Composition Design: C ≤ 0.05, O ≤ 0.002, P ≤ 0.002, Pb ≤ 0.001, Zn ≤ 0.001, Cd ≤ 0.001, Cu = 53.0%, Ga = 12.0%, Cu + Ga = 65.0% and Ga / Cu = 0.226 (meeting 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224), and the rest are component Ag and unavoidable impurities.

[0031] 2. Batching Calculation: Conduct batching calculations according to the component content of the target low silver content duplex noble metal alloy material; when calculating the pure Ag during batching, the yield is calculated according to

[0032] 3. Batching method: When the room temperature is 25°C (lower than 29.7°C), place the solid pure Ga in a clean beaker, then heat the beaker in a constant temperature water bath at >40°C. After the solid pure Ga becomes liquid metal, quickly weigh the batch (63.8g). After the batch is placed at room temperature, it will solidify into a solid state and be ready for smelting. Use sandpaper to remove the surface oxides of the prepared pure Ag and pure Cu, clean the surface with acetone, and then dry the surface in a 400°C vacuum oven.

[0033] 4. Alloy smelting: Place the required pure Ag and pure Cu in a vacuum induction furnace for smelting. After completely melting the pure Ag and pure Cu using a power of 45kW, immediately adjust the power of the vacuum induction furnace to 0kW, shut down the power and condense for 35 minutes to allow the alloy surface in the induction furnace to form a film and cool down. Then, open the furnace and place pure Ga on the film-forming surface of the induction crucible. After vacuuming, slowly increase the power to 30kW, increase it to 45kW after 3 minutes, maintain it for 3 minutes, then reduce it to 25kW and maintain it for 0.5 minutes. Reduce the power to 9kW for casting to obtain a low-silver content AgCuGa noble metal duplex alloy material.

[0034] 5. After composition testing, the design composition and the measured composition of the alloy material are compared in Table 3. In the alloy, Cu+Ga=64.7% and Ga / Cu=0.225: Table 3 Designed and measured compositions of alloy materials in Example 3 (wt.%) In this embodiment, the total weight of the nickel-based high-temperature alloy is designed to be 0.5 kg.

[0035] 6. High-temperature oxidation resistance test: The obtained alloy was subjected to an isothermal oxidation test in an atmospheric environment (air) at 700°C. The results showed that the alloy hardly gained weight within 30 minutes, and Ga atoms on the alloy surface autonomously distributed to form a continuous and dense nanometer-thick oxide film. The oxide film did not turn black, demonstrating excellent oxidation resistance.

[0036] 7. Brazing Test: The brazing test conditions were the same as those in Example 1, except that the alloy material obtained in Example 3 was used instead of the alloy material obtained in Example 1. The results showed that the original metallic color of the brazing filler metal was visible at the brazing joint, and no black oxide film was found. The shear strength of the brazing joint was measured to be 197 MPa.

[0037] It is not difficult to find from Examples 1, 2, and 3 that the AgCuGa noble metal two-phase alloy material described in the present invention exhibits excellent oxidation resistance in air at 700 °C, and its oxidation resistance is even better during brazing under low-flow inert gas protection; it is found that when vacuum brazing oxygen-free copper-nickel-plated stainless steel with an Ag-28Cu alloy, the shear strength of the brazed joint is about 180 MPa; in the prior art, vacuum brazing is selected for the Ag-28Cu alloy precisely to avoid high-temperature oxidation of the filler metal, and also because of avoiding high-temperature oxidation, the shear strength of the brazed joint is about 180 MPa; if the Ag-28Cu alloy is brazed under low-flow inert gas protection, due to the lower oxygen control level than vacuum brazing and the inevitable high-temperature oxidation, the shear strength of the brazed joint will inevitably drop sharply due to the high-temperature oxidation of the filler metal; relatively speaking, the shear strength of the AgCuGa noble metal two-phase alloy material described in the present invention during brazing under low-flow inert gas protection is significantly better than that of the Ag-28Cu alloy by vacuum brazing. If both are brazed under low-flow inert gas protection, the difference in the shear strength of the brazed joint will be even greater.

[0038] Comparative Example 1 AgCuGa noble metal two-phase alloy material with low silver content 1. Alloy composition design: C ≤ 0.05, O ≤ 0.002, P ≤ 0.002, Pb ≤ 0.001, Zn ≤ 0.001, Cd ≤ 0.001, Cu = 49.0%, Ga = 5.0%, Cu + Ga = 54.0% and Ga / Cu = 0.102 (not meeting 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224), and the rest are component Ag and unavoidable impurities.

[0039] 2. Batching calculation: Batching calculation is carried out according to the component content of the target low-silver-content two-phase noble metal alloy material; when calculating the batching of pure Ag, the yield of 98.5% is not calculated; when calculating the batching of pure Ga, the yield of 94% is not calculated; therefore, the required pure Cu is 245.0 g, pure Ag is 230 g, and pure Ga is 25 g can be calculated.

[0040] 3. Batching method: The room temperature is 23 °C, lower than 29.7 °C. Place solid pure Ga in a clean beaker, and then place the beaker in a constant temperature water bath at > 40 °C. After the solid pure Ga becomes liquid metal, quickly weigh and batch (25 g). After batching, it will re-solidify into a solid state when placed at room temperature and is ready for melting; the surface oxides of the prepared pure Ag and pure Cu need to be removed with sandpaper and the surface is cleaned with acetone, and then dried in a vacuum box at 400 °C.

[0041] 4. Alloy melting: Put the required pure Ag and pure Cu in a vacuum induction furnace for melting. After melting all the pure Ag and pure Cu with a power of 42 kW, immediately adjust the power of the vacuum induction furnace to 0 kW, cut off the power and condense for 30 minutes to make the surface of the alloy in the induction furnace form a film and cool down. Then open the furnace and put pure Ga on the surface of the film in the induction crucible. After evacuating, slowly increase the power to 20 kW, and directly increase it to 45 kW after 4 minutes. Keep it for 3 minutes and then reduce it to 25 kW and keep it for 1 minute. Reduce the power to 10 kW for casting to obtain a low-silver-content AgCuGa noble metal duplex alloy material.

[0042] 5. Through composition testing, the comparison between the designed composition and the measured composition of this alloy material is shown in Table 4. In the alloy, Cu + Ga = 53.3% and Ga / Cu = 0.092: Table 4 Designed and measured compositions (wt.%) of the alloy material in Comparative Example 1 In this embodiment, the total weight of the designed nickel-based superalloy is 0.5 kg.

[0043] 6. High-temperature oxidation resistance test: Conduct an isothermal oxidation experiment on the obtained alloy in a 700 °C atmospheric environment (air). It is found that within 30 minutes, the alloy significantly increases in weight, the oxide film on the alloy surface turns black, and the oxide film peels off in most areas, showing poor oxidation resistance.

[0044] 7. Brazing test: The brazing test conditions are the same as those in Example 1, only replacing the alloy material obtained in Example 1 with the alloy material obtained in Comparative Example 1; it is found that although there is low-flow Ar gas protection, during the 10-minute stabilization of the brazing temperature at 700 °C, the filler metal at the brazed joint has gradually shown obvious blackening, and there is a small amount of black oxide product peeling off; after measurement, the shear strength of the brazed joint is only 59 MPa.

[0045] Comparative Example 2 Low-silver-content AgCuGa noble metal duplex alloy material 1. Alloy composition design: C ≤ 0.05, O ≤ 0.002, P ≤ 0.002, Pb ≤ 0.001, Zn ≤ 0.001, Cd ≤ 0.001, Cu = 50.0%, Ga = 7.0%, Cu + Ga = 57.0% and Ga / Cu = 0.14 (not satisfying 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224), and the rest are component Ag and unavoidable impurities.

[0046] 2. Ingredient Calculation: The ingredient calculation is based on the target low-silver content dual-phase precious metal alloy material composition. The pure Ag ingredient calculation was not based on a 98.5% yield; the pure Ga ingredient calculation was not based on a 94% yield. Therefore, the required pure Cu is calculated to be 250.0g, pure Ag is 215g, and pure Ga is 35g.

[0047] 3. Batching method: When the room temperature is 22°C (lower than 29.7°C), place solid pure Ga in a clean beaker, then heat the beaker in a constant temperature water bath at >40°C. After the solid pure Ga turns into liquid metal, quickly weigh and batch the ingredients (35g). After the ingredients are prepared, they will solidify again at room temperature and are ready for smelting. Use sandpaper to remove the surface oxides of the prepared pure Ag and pure Cu, clean the surface with acetone, and then dry the surface in a 400°C vacuum oven.

[0048] 4. Alloy smelting: Place the required pure Ag and pure Cu in a vacuum induction furnace for smelting. After completely melting the pure Ag and pure Cu using a power of 40kW, immediately adjust the power of the vacuum induction furnace to 0kW, shut down the power and condense for 31 minutes to allow the alloy surface in the induction furnace to form a film and cool down. Then, open the furnace and place pure Ga on the film-forming surface of the induction crucible. After vacuuming, slowly increase the power to 23kW, increase it to 45kW after 4 minutes, maintain it for 2 minutes, then reduce it to 25kW and maintain it for 0.5 minutes. Reduce the power to 8kW for casting to obtain a low-silver content AgCuGa noble metal duplex alloy material.

[0049] 5. After composition testing, the design composition and the measured composition of the alloy material are compared in Table 5. The alloy contains Cu+Ga=57.0% and Ga / Cu=0.14: Table 5 Designed and measured compositions of alloy materials in Comparative Example 2 (wt.%) In this embodiment, the total weight of the nickel-based high-temperature alloy is designed to be 0.5 kg.

[0050] 6. High-temperature oxidation resistance test: The obtained alloy was subjected to an isothermal oxidation test in an atmospheric environment (air) at 700°C. The results showed that the alloy gained significant weight within 30 minutes, the oxide film on the alloy surface turned black, and the oxide film fell off in most areas, indicating poor oxidation resistance.

[0051] 7. Brazing test: The brazing test conditions were the same as those in Example 1, except that the alloy material obtained in Comparative Example 2 was used to replace the alloy material obtained in Example 1. It was found that although there was low-flow Ar gas protection, during the 10-minute stabilization of the brazing temperature at 700 °C, the filler metal at the brazed joint had already shown obvious yellow-brown color. During the subsequent heating and brazing process, the high-temperature oxidation of the filler metal continued to intensify, the surface color of the sample deepened and gradually turned black. Although no oxidation products fell off, after measurement, the shear strength of the brazed joint was only 83 MPa.

[0052] From Comparative Examples 1 and 2, it is不难发现 that since Cu + G, Ga / Cu does not meet 60% < Cu + Ga ≤ 65% and Ga / Cu ratio ≥ 0.224, although low-flow inert gas protection is adopted, obvious high-temperature oxidation has occurred during the 10-minute stabilization of the obtained alloy at 700 °C, thus affecting the metallurgical bonding process of the brazing interface and greatly reducing the shear strength of the brazed joint.

[0053] Combining Examples 1, 2, 3 and Comparative Examples 1, 2, it can be determined that the low-silver-content AgCuGa noble metal two-phase alloy material described in the present invention controls 60%

Claims

1. A low-silver content AgCuGa noble metal dual-phase alloy material resistant to high-temperature oxidation, characterized in that: The composition of the low-silver-content AgCuGa noble metal biphasic alloy material is as follows: 60% < Cu + Ga ≤ 65% and the Ga / Cu ratio ≥ 0.224, C ≤ 0.05, O ≤ 0.002, P ≤ 0.002, Pb ≤ 0.001, Zn ≤ 0.001, Cd ≤ 0.001, and the rest are the components Ag and inevitable impurities; its preparation method is realized according to the following steps: 1) According to the component content of the low-silver-content AgCuGa noble metal biphasic alloy material, put the required pure Ag and pure Cu into the induction crucible of a vacuum induction furnace for melting; 2) After completely melting the pure Ag and pure Cu with a power of 40 - 45 kW, immediately adjust the power of the vacuum induction furnace to 0 kW, cut off the power and condense for 30 - 35 minutes to make the alloy surface in the induction crucible form a film and cool down. Then open the furnace and put pure Ga on the surface of the alloy with a formed film in the induction crucible. After evacuating the air, increase the power to 20 - 30 kW at a rate of 10 kW / min, keep it for 3 - 4 minutes and then directly increase it to 45 kW, keep it for 2 - 3 minutes and then reduce the power to 25 kW and keep it for 0.5 - 1 minute, and then reduce the power to 8 - 10 kW for casting to obtain the low-silver-content AgCuGa noble metal biphasic alloy material.

2. The AgCuGa noble metal dual-phase alloy material with low silver content and high temperature oxidation resistance according to claim 1, characterized in that: In step 1), remove the oxides on the surface of the required pure Ag and pure Cu with sandpaper and clean the surface with acetone, and then dry the surface in a vacuum oven at 400 °C.

3. The AgCuGa noble metal dual-phase alloy material with low silver content and high temperature oxidation resistance according to claim 1, characterized in that: In step 1), when calculating the batching of pure Ag, the recovery rate is calculated according to 98.5%.

4. The AgCuGa noble metal dual-phase alloy material with low silver content and high temperature oxidation resistance according to claim 1, characterized in that: In step 2), when calculating the batching of pure Ga, the recovery rate is calculated according to 94%; the batching method of the pure Ga is as follows: a. If the room temperature is lower than 29.7 °C, put the solid pure Ga in a clean beaker, and then put the beaker in a constant temperature water bath at > 40 °C for heating. After the solid pure Ga becomes liquid metal, quickly weigh and batch it. After batching, it will re-solidify into a solid at room temperature and be prepared for melting; b. If the room temperature is higher than 29.8 °C, directly weigh and batch the liquid metal pure Ga. After batching, put the liquid metal pure Ga in a clean beaker, and then place the beaker in ice water for solidification and be prepared for melting.

5. The AgCuGa noble metal dual-phase alloy material with low silver content and high temperature oxidation resistance according to claim 1, characterized in that: In step 2), completely melt the pure Ag and pure Cu with a power of 43 kW.

6. The AgCuGa noble metal dual-phase alloy material with low silver content and high temperature oxidation resistance according to claim 1, characterized in that: In step 2), after evacuating the air, increase the power to 25 kW at a rate of 10 kW / min.

7. The AgCuGa noble metal dual-phase alloy material with low silver content and high temperature oxidation resistance according to claim 1, characterized in that: In step 2), reduce the power to 9 kW for casting.

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