Composite brazing filler metal for low-temperature low-corrosion brazing of titanium alloy and brazing method

Abstract

The invention relates to the technical field of welding, and provides a composite brazing filler metal for low-temperature low-corrosion brazing of a titanium alloy and a welding method.The composite brazing filler metal / welding flux is formed by mixing nanoscale Ti powder and Zr-Cu-Ni alloy powder according to a certain proportion, and when used, the composite brazing filler metal / welding flux is pre-arranged between to-be-welded base metal through a volatile binder; the whole workpiece to be welded is subjected to good brazing and / or instantaneous liquid phase diffusion bonding in a vacuum furnace through a specific heat preservation process. According to the method, melting of brazing filler metal / welding flux can be achieved at the temperature of 830 DEG C or below through the quaternary eutectic reaction between the Zr-Cu-Ni alloy and Ti; by means of the surface effect and the volume effect of the nano powder, the melting efficiency and the melting sufficiency of the alloy powder at the low temperature are promoted, and a well-combined welding joint is obtained; ti powder and Zr-Cu-Ni alloy powder preferentially react with Cu / Ni elements in the brazing / instantaneous liquid phase diffusion welding process, and corrosion of titanium alloy base metal can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a composite filler metal for low-temperature and low-dissolution brazing of titanium alloy and a welding method. BACKGROUND

[0002] With the development of China's aviation technology and national defense strength, modern advanced fighter aircraft, missiles and other equipment have higher and higher requirements for flight speed / altitude, range, maneuverability, stealth, service life and safety reliability, and the performance of the fuselage / misile body structure material is also put forward higher requirements. The metal honeycomb wallboard structure is a kind of bionic composite lightweight structure developed for this reason, which has the advantages of light weight, high specific strength, high specific stiffness, good impact resistance, good heat insulation performance, good noise reduction performance, and can reduce the infrared characteristics, and is concerned by the aviation industry. In recent years, titanium alloy honeycomb wallboard structure and other metal honeycomb structures have been applied to some aircraft cabin doors, hatch covers and other components, and their outstanding performance advantages have been verified. Relevant reports show that the manufacturing of titanium alloy honeycomb wallboard structure has become one of the key technologies of the current latest generation of fighter aircraft, and there is an increasingly strong demand in the manufacturing of next-generation fighter aircraft and hypersonic aircraft and other weapon equipment.

[0003] The metal honeycomb wallboard structure imitates the honeycomb structure of bees, and is usually integrally welded by upper and lower thin panels and intermediate honeycomb core. Since the metal honeycomb core is thin-walled, has poor rigidity and complex profile structure, the welding of the honeycomb core and the thin panel of the skin is generally realized by brazing. Although brazing is one of the most operational metal honeycomb wallboard structure manufacturing methods, the traditional brazing method and brazing material still have great difficulty in welding titanium alloy and other metal honeycomb wallboard structures, and the key technical problems can be summarized as follows: ① The brazing temperature is high, which has a great influence on the performance of the titanium alloy base material. The liquidus temperature of the traditional high-temperature brazing filler metal for titanium alloy suitable for the welding of the honeycomb wallboard structure of the aircraft (titanium-based filler metal, titanium-zirconium-based filler metal) is usually high, and in order to obtain good wettability of the filler metal to the base material and ensure the bonding rate of a large number of connecting interfaces between the honeycomb core and the inner skin, the brazing temperature needs to be higher than the phase transition temperature of the titanium alloy. During the brazing process, the titanium alloy base material will undergo allotropy transformation, resulting in a serious decline in the performance of the titanium alloy base material; ② The filler metal alloy has a large dissolution to the base material (wallboard), which seriously reduces the performance of the brazed joint, especially the shear performance. Since the melting point of titanium is high, Cu, Ni and other elements are often added to the filler metal alloy (titanium-based filler metal, titanium-zirconium-based filler metal) to reduce the melting point of the filler metal. These elements will quickly diffuse into the titanium alloy base material during brazing, resulting in alloying and a decrease in the melting point of the surface of the base material, and then forming a dissolution defect, which seriously affects the mechanical properties of the brazed joint, especially the shear performance.

[0004] The key problems of the above titanium alloy brazing limit the application of titanium alloy honeycomb panel structure in more fuselage components, hinder the performance improvement of modern fighter and other equipment to some extent, and even affect the development and research of new generation fighter and advanced supersonic aircraft and other equipment. Therefore, it is urgent to develop high-reliability brazing method and material suitable for titanium alloy thin-walled honeycomb panel structure welding.

[0005] Currently, the brazing filler metal system that can be used for titanium alloy brazing mainly includes three types: Ag-based, Al-based and Ti / Zr-based. Ag-based filler metal generally has a suitable melting point, good wettability to titanium alloy base material, and relatively high plasticity of brazed joint. However, Ag-based filler metal is very sensitive to Cl ions, has poor corrosion resistance, and poor high-temperature mechanical properties of brazed joint, which greatly limits the application of Ag-based filler metal in the manufacture of aerospace titanium alloy honeycomb panel structure. Al-based filler metal has low melting point, and the brazing temperature is far below the titanium alloy allotropic transformation temperature, which can better avoid the performance damage of titanium alloy base material during brazing. However, the brazed joint of titanium alloy using Al-based filler metal will form a large amount of TiAl intermetallic compound, resulting in high brittleness and low fatigue strength of the joint, as well as poor high-temperature mechanical properties, which is not suitable for the manufacture of aerospace titanium alloy honeycomb panel structure. Ti / Zr-based filler metal generally has a high melting point, and the high-temperature performance, corrosion resistance and heat resistance of the brazed joint are much higher than those of the above two types of filler metal, which can meet the requirements of aerospace titanium alloy honeycomb panel structure, and is the most promising filler metal for high-quality brazing of aerospace titanium alloy honeycomb panel structure.

[0006] According to the types of added alloying elements, Ti / Zr-based filler metal can be further divided into Ti-Cu-Ni system, Ti-Zr-Ni system, Ti-Zr-Cu system, Ti-Zr-Be system and Ti-Zr-Cu-Ni system. Ti-Cu-Ni, Ti-Zr-Cu and Ti-Zr-Ni system filler metal has a high melting point, and the brazing temperature generally needs to reach 970-1000℃, which is higher than the phase transition temperature of titanium alloy (TC4 titanium alloy 980-1010℃, TC1 titanium alloy 920-930℃). After brazing, the base material undergoes phase transition and grain coarsening, resulting in a significant decrease in the mechanical properties of titanium alloy base material and an increase in brittleness. At the same time, brazing at high temperature also causes serious dissolution of titanium alloy base material, which seriously threatens the overall performance and reliability of the brazed component, and is difficult to meet the requirements of titanium alloy honeycomb panel thin-walled structure.

[0007] Ti-Zr-Cu-Ni filler metals add Cu and Ni elements to reduce the melting point. Zr element, which is in the same subgroup as Ti and is mutually soluble, can further reduce the melting point and improve the wettability of the filler metal. Compared with Ti-Cu-Ni filler metal, the Ti-Zr-Cu-Ni filler metal has a lower melting point, and the brazed joint has more stable corrosion resistance and high-temperature performance. In addition, there is no protection requirement for toxic elements, and the brazing operability is better. However, the existing Ti-Zr-Cu-Ni filler metal has a lower melting point than the phase transition temperature of titanium alloy. In order to ensure the wetting and spreading properties and the welding rate of the complex interface during the brazing of the honeycomb structure, the brazing temperature is often higher than the phase transition temperature of the titanium alloy. This leads to the phase transition of the titanium alloy base material during brazing, the grain coarsening, and the performance degradation after brazing. At the same time, the Cu and Ni elements quickly diffuse into the titanium alloy base material during high-temperature brazing, resulting in a decrease in the melting point of the base material surface and the formation of corrosion defects, which seriously affect the mechanical properties of the brazed component. To solve the above problems, the existing research reports mainly include three categories: 1) increasing the content of Cu and Ni elements to further reduce the melting point, reduce the performance damage of the base material, and improve the overall joint performance; 2) reducing the content of Cu and Ni elements, adding Co, Fe, Al, Sn, and other elements to reduce the melting point, reduce corrosion and compounds, and improve the joint performance; 3) adding rare earth elements to improve the joint performance. Increasing the content of Cu and Ni elements can significantly reduce the melting point of the Ti-Zr-Cu-Ni filler metal. However, the brazing seam width of these filler metals is significantly increased compared to the original gap, indicating that the titanium alloy base material has been significantly corroded. At the same time, a large amount of compounds is formed in the brazing seam due to the reaction between high-content Cu and Ni elements and Ti, resulting in high brittleness of the brazed joint, which must be improved through heat treatment. For the brazing of aerospace titanium alloy honeycomb structures, simply reducing the melting point of the Ti-Zr-Cu-Ni filler metal by increasing the content of Cu and Ni elements is obviously difficult to obtain a joint that meets the use requirements. Adding Co, Fe, Al, Sn, and other elements to the Ti-Zr-Cu-Ni filler metal to replace part of the Cu and Ni elements can to some extent avoid the corrosion of the base material and a large amount of intermetallic compounds. However, the melting point reduction effect of Co, Fe, Al, and other elements is limited, the brazing temperature of this kind of filler metal is still above the phase transition temperature of TC1 titanium alloy, the performance of the base material is still prone to damage, and Co, Fe, Al, and other elements also react with Ti to form brittle intermetallic compounds, so the joint strength is difficult to further improve. Adding a small amount of rare earth elements to the Ti / Zr-based filler metal can significantly improve the mechanical properties of the joint. Although the joint performance is greatly improved, the rare earth elements cannot reduce the melting point of the filler metal, and the brazing temperature of the joint with the best mechanical properties is as high as 990-1080℃.For the brazing of titanium alloy honeycomb thin-walled structure, such a high brazing temperature will cause the titanium alloy base material grain to be severely coarsened, the mechanical properties of the whole component will be greatly reduced, and the performance advantages of the honeycomb structure are difficult to fully play. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a composite filler for low-temperature and low-dissolution brazing of titanium alloy and a welding method, which opens up a new way to solve the problems of base material damage and dissolution in the metallurgical connection of titanium and titanium alloy and even other titanium-based metal materials.

[0009] The present application adopts the following technical solutions: On the one hand, the present application provides a composite filler for low-temperature and low-dissolution brazing of titanium alloy, which comprises a mixture of Ti powder and Zr-Cu-Ni alloy powder in a certain proportion, wherein the Ti powder and the Zr-Cu-Ni alloy powder are both nanoscale powders; and the mass ratio of the Ti powder to the Zr-Cu-Ni alloy powder is 1: (1.5-2.3).

[0010] According to any possible implementation manner described above, further provided is an implementation manner, wherein the composition of the Zr-Cu-Ni alloy powder is Zr: 46%-57%, Cu: 22%-27%, and Ni: 21%-27% by mass ratio.

[0011] According to any possible implementation manner described above, further provided is an implementation manner, wherein the average particle size of the Ti powder and the Zr-Cu-Ni alloy powder is less than 1000 nm.

[0012] According to any possible implementation manner described above, further provided is an implementation manner, wherein the average particle size of the Ti powder and the Zr-Cu-Ni alloy powder is 50-500 nm.

[0013] According to any possible implementation manner described above, further provided is an implementation manner, wherein the melting point of the composite filler is less than 830℃.

[0014] On the other hand, the present application further provides a low-temperature and low-dissolution brazing method for titanium alloy, which uses the composite filler described above, and the method comprises the following steps: S1. Weighing Ti powder and Zr-Cu-Ni alloy powder according to a set mass percentage and mixing them uniformly; S2. Adding an acidic organic binder to the mixture obtained in step S1 and stirring until a uniform paste state is achieved to obtain a composite filler; S3. Polishing, cleaning and blowing dry the surface of the workpiece to be welded; S4. Uniformly coating a layer of the composite filler prepared in step S2 on the surface of the part to be welded; S5. Place the workpiece to be welded in a vacuum heating furnace, heat to the set temperature to promote the complete volatilization of the organic binder, then raise the temperature to 825℃-835℃ and hold. S6. The welded workpiece is cooled as a whole in the furnace.

[0015] In addition to any of the possible implementations described above, another implementation is provided in which, in step S2, the acidic organic binder is turpentine oil containing acetate.

[0016] In addition to any of the possible implementations described above, another implementation is provided in which, in step S5, the workpiece to be welded is placed in a vacuum heating furnace, heated to 200-250°C and held for 3-5 minutes to promote the complete volatilization of the organic binder, and then heated to 825°C-835°C and held for 10-30 minutes.

[0017] In addition to any of the possible implementations described above, another implementation is provided in which the heating rate in step S5 is higher than 100°C / min.

[0018] In addition to any of the possible implementations described above, a further implementation is provided in which the tensile strength of the welded workpiece is greater than 500 MPa.

[0019] The beneficial effects of this invention are as follows: 1. By utilizing the quaternary eutectic reaction between Zr-Cu-Ni alloy and Ti, the melting of brazing filler metal / solder can be achieved at a relatively low temperature (below 830℃).

[0020] 2. Furthermore, by utilizing the surface and volume effects of nanoparticles, the composite brazing filler / solder can be melted below the eutectic temperature, improving the melting efficiency and fluidity of alloy powders at lower temperatures, thereby obtaining well-bonded titanium alloy welded joints at lower temperatures (below 830℃).

[0021] 3. Acidic organic binders not only facilitate the pre-positioning / coating of composite brazing filler metals / solders, but also effectively break down the dense oxide film on the surface of nanopowders and activate the surface of nanopowders during the welding process, further improving the welding quality of titanium alloys.

[0022] 4、Ti powder and Zr-Cu-Ni alloy powder can preferentially react with Cu / Ni elements during brazing / instantaneous liquid phase diffusion welding process, which can reduce the dissolution of titanium alloy base material. The reaction between Ti and Cu / Ni elements in Zr-Cu-Ni alloy mainly occurs at the interface (surface) between the liquid alloy and Ti powder and Ti base material, and element diffusion needs to pass through the interface. The specific surface area of the powder is large, which means that the reaction area of Ti powder with Cu / Ni elements is much larger than that of Ti base material, so the reaction of base material Ti with Cu / Ni elements can be greatly inhibited; at the same time, lower brazing temperature can also inhibit the reaction rate. Under the action of the above two aspects, the base material dissolution can be controlled at a low level.

[0023] 5、The welding method described in the application adopts a heating rate higher than 100℃ / min, which can effectively avoid the oxidation of the surface of the nano-powder for a long time, and reduce the defect rate of the titanium alloy welded joint. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The figure shows the differential scanning calorimetry (DSC) results of the composite filler prepared by mixing nano-sized Ti powder and Zr-Cu-Ni alloy powder (100nm pure Ti powder and 500nm Zr-Cu-Ni alloy powder with a weight ratio of 1:1.7) in Example 1 of the application.

[0025] Figure 2 The figure shows the SEM microstructure (eutectic structure) of the composite filler prepared by mixing nano-sized Ti powder and Zr-Cu-Ni alloy powder (100nm pure Ti powder and 500nm Zr-Cu-Ni alloy powder with a weight ratio of 1:2.3) in Example 2 of the application.

[0026] Figure 3 The figure shows the SEM micrograph of the TC4 titanium alloy joint vacuum brazed by the composite filler with a mass ratio of nano-sized Ti powder and Zr-Cu-Ni alloy powder of 1:1.7 and the welding method provided by the application; (a) overall joint micrograph; (b) local enlarged view of joint micrograph; (c) enlarged view of eutectic structure micrograph of joint.

[0027] Figure 4 The figure shows the shear strength of the TC4 titanium alloy joint brazed by the composite filler prepared by mixing nano-sized Ti powder and Zr-Cu-Ni alloy powder (100nm pure Ti powder and 500nm Zr-Cu-Ni alloy powder with a weight ratio of 1:2.3) in the embodiment of the application.

[0028] Figure 5It is shown that the vacuum brazing TC4 titanium alloy joint morphology SEM diagram of the composite filler metal with the mass ratio of nanoscale Ti powder and Zr-Cu-Ni alloy powder 1:2.3 and the welding method provided by the application, (a) joint morphology overall diagram, (b) joint morphology local enlarged view.

[0029] Figure 6 It is shown that the flowchart of the titanium alloy low-temperature low-erosion brazing method of the embodiment of the application. DETAILED DESCRIPTION

[0030] The specific embodiments of the application will be described in detail below with reference to specific drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered in isolation, and they can be combined with each other to achieve better technical effects.

[0031] The composite filler metal for titanium alloy low-temperature low-erosion brazing of the embodiment of the application comprises a mixed powder of Ti powder and Zr-Cu-Ni alloy powder in a certain proportion, and the Ti powder and the Zr-Cu-Ni alloy powder are both nanoscale powders; the mass ratio of the Ti powder and the Zr-Cu-Ni alloy powder is 1:(1.5-2.3).

[0032] It should be noted that the Ti elemental powder must be mixed with the Zr-Cu-Ni alloy powder, not the traditional Ti-Zr-Cu-Ni alloy powder. The Ti elemental powder and the Zr-Cu-Ni alloy powder can only undergo a quaternary eutectic reaction during welding, and the quaternary eutectic reaction and the surface effect of nanoscale powder must be utilized to obtain a composite filler metal / welding material with a melting point lower than 830℃, so as to realize brazing / instantaneous liquid phase diffusion welding at a temperature lower than 830℃.

[0033] The reason why the titanium powder and the Zr-Cu-Ni alloy powder are mixed to become the composite filler metal in the application is mainly to consider the efficiency of element diffusion and eutectic reaction at a lower temperature. If the titanium (melting point 1668℃), zirconium (melting point 1852℃), copper (melting point 1083℃), and nickel (melting point 1453℃) four kinds of elemental powder are directly mixed, since the melting points of the four kinds of elemental powder are all higher than 1000℃, brazing at a temperature below 830℃ can only realize eutectic reaction through element diffusion in the solid state, and the reaction efficiency is extremely low. The Zr-Cu-Ni alloy powder (eutectic point temperature lower than 900℃) itself has a lower melting point, and in the nanoscale, the powder surface energy is high, and the melting point is further reduced. The powder surface micro-liquid phase can be formed at a brazing temperature below 830℃, and then react with the Ti powder to form a eutectic liquid phase, accelerate the reaction, and thus ensure the brazing efficiency and the bonding quality of the brazing interface.

[0034] In one embodiment, the Zr-Cu-Ni alloy powder has a composition of Zr: 46-57%, Cu: 22-27%, and Ni: 21-27% by mass.

[0035] In one embodiment, the Ti powder and the Zr-Cu-Ni alloy powder have an average particle size of less than 1000 nm.

[0036] In one embodiment, the Ti powder and the Zr-Cu-Ni alloy powder have an average particle size of 50-500 nm.

[0037] In one embodiment, the composite brazing filler / welding filler has a melting point of less than 830°C.

[0038] The composite brazing filler / welding filler of the present application can be used for brazing / welding of titanium and titanium alloys.

[0039] As shown in Figure 6 FIG. 1, the present application provides a low-temperature and low-erosion brazing method for titanium alloys, which uses the composite brazing filler described above, and the method comprises the following steps: S1, weighing Ti powder and Zr-Cu-Ni alloy powder according to a set mass percentage, and mixing them uniformly; S2, adding an acidic organic binder to the mixture obtained in step S1, and stirring until a uniform paste is obtained, to obtain a composite brazing filler; S3, polishing, cleaning and drying the surface of the workpiece to be welded; S4, uniformly coating the surface of the part to be welded with the composite brazing filler prepared in step S2; S5, placing the workpiece to be welded as a whole in a vacuum heating furnace, heating to a set temperature, promoting complete volatilization of the organic binder, and then heating to 825-835°C and holding; S6, cooling the workpiece as a whole in the furnace.

[0040] In one embodiment, in step S2, the acidic organic binder is an acidic turpentine oil containing acetic acid.

[0041] The acidic organic binder is used for mixing before welding and coating on the part to be welded of the workpiece, and the functions of the acidic organic binder include bonding the powder for convenient coating in various positions, breaking the dense oxide film on the surface of the nano-powder, and activating the surface of the nano-powder.

[0042] In one embodiment, in step S5, the workpiece to be welded is placed as a whole in a vacuum heating furnace, heated to a temperature in the range of 200-250°C and held for 3-5 min, to promote complete volatilization of the organic binder, and then heated to 825-835°C and held for 10-30 min.

[0043] In one embodiment, the heating rate in step S5 is higher than 100°C / min.

[0044] In one embodiment, the tensile strength of the welded workpiece is greater than 500 MPa.

[0045] Embodiment 1 This embodiment is a composite filler / welding material and a brazing method for low-temperature / low-erosion brazing / transient liquid phase diffusion welding of titanium alloys. The welding method comprises: Step 1, 100 nm particle size pure Ti powder and 500 nm particle size Zr-Cu-Ni alloy powder are weighed in a weight ratio of 1:1.7, respectively; Step 2, the mixed powder of step 1 is mixed into a uniform paste-like solder using acetic acid and turpentine organic binder, and the weight ratio of the mixed powder and the organic binder is 1:0.1; Step 3, after polishing and cleaning the surface of the TC4 titanium alloy base material, uniformly coat the prepared paste-like solder on the TC4 titanium alloy base material to be welded, and the coating thickness is 0.1-0.5 mm; Step 4, place the assembled workpiece into a vacuum brazing furnace, heat at 200°C for 5 min to promote complete volatilization of the acidic organic binder; heat at a rate of 120°C / min to 830°C, and hold for 10 min, then cool down with the furnace; Step 5, when the furnace temperature drops to 100°C, open the furnace door and take out the workpiece, and the welding is completed.

[0046] Figure 1 The differential scanning calorimetry (DSC) results of the composite filler prepared by mixing the nano-sized Ti powder and the Zr-Cu-Ni alloy powder (100 nm pure Ti powder and 500 nm Zr-Cu-Ni alloy powder in a weight ratio of 1:1.7) in Example 1 are shown. The results show that the melting point of the composite filler is 817°C.

[0047] The results show that the solder melts fully and the interface is well bonded, as shown in Figure 3 The base material has a low erosion degree, and the average tensile strength of the joint can reach more than 500 MPa.

[0048] Embodiment 2 This embodiment is a composite filler / welding material and a brazing method for low-temperature / low-erosion brazing / transient liquid phase diffusion welding of titanium alloys, comprising: Step 1, 100 nm particle size pure Ti powder and 500 nm particle size Zr-Cu-Ni alloy powder are weighed in a weight ratio of 1:2.3, respectively; Step 2, the mixed powder of step 1 is mixed into a uniform paste-like solder using acetic acid and turpentine organic binder, and the weight ratio of the mixed powder and the organic binder is 1:0.1; Step 3, after polishing and cleaning the surface of the TC4 titanium alloy base material, evenly coating a layer of mixed paste solder on the TC4 titanium alloy base material to be welded part, the coating thickness is 0.1-0.5mm; Step 4, the assembled workpiece is put into the vacuum brazing furnace, and the acid organic binder is promoted to volatilize completely at 200℃ for 5min; the temperature is raised to 830℃ at a heating rate of 120℃ / min, and the temperature is kept for 10min, and then the furnace is cooled; Step 5, when the furnace temperature drops to 100℃, open the door, take out the workpiece, and complete the welding.

[0049] Figure 2 The microstructure (eutectic structure) SEM diagram of the composite solder prepared by mixing the nanoscale Ti powder and the Zr-Cu-Ni alloy powder (100nm pure Ti powder and 500nm Zr-Cu-Ni alloy powder in a weight ratio of 1:2.3) in Example 2 is shown.

[0050] The results show that the solder is fully melted, the interface is well combined, and the base material is less eroded, as shown in Figure 5 The average tensile strength of the joint can reach more than 500 MPa, as shown in Figure 4 .

[0051] The application utilizes the quaternary eutectic reaction between Zr-Cu-Ni alloy and Ti, and can realize the melting of the solder at a lower temperature (below 830℃); at the same time, with the surface effect and volume effect of the nano-powder, the melting efficiency and fullness of the alloy powder at a lower temperature are promoted, so as to obtain a well combined welded joint; in addition, the Ti powder and the Zr-Cu-Ni alloy powder preferentially react with Cu / Ni elements in the brazing / instantaneous liquid phase diffusion welding process, which can reduce the erosion of the titanium alloy base material. Under the above effects, the application can realize the low-temperature / low-erosion connection of titanium and titanium alloy.

[0052] Although several embodiments of the present application have been given in the present text, those skilled in the art should understand that the embodiments in the present text can be changed without departing from the spirit of the present application. The above embodiments are only exemplary, and the embodiments in the present text should not be used as a limitation of the scope of the present application.

Claims

1. A composite filler material for low temperature low solubility brazing of titanium alloys, characterized in that, The composite filler material comprises a mixed powder of Ti powder and Zr-Cu-Ni alloy powder, both of which are nanoscale powders; the mass ratio of the Ti powder and the Zr-Cu-Ni alloy powder is 1:(1.5-2.3).

2. The composite filler for low corrosion brazing of titanium alloys at low temperature according to claim 1, wherein The Zr-Cu-Ni alloy powder comprises Zr: 46-57%, Cu: 22-27%, and Ni: 21-27% by mass.

3. The composite filler for low corrosion brazing of titanium alloys at low temperature according to claim 1, wherein The average particle size of the Ti powder and the Zr-Cu-Ni alloy powder is less than 1000 nm.

4. The composite filler for low corrosion brazing of titanium alloys at low temperature according to claim 3, wherein The average particle size of the Ti powder and the Zr-Cu-Ni alloy powder is 50-500 nm.

5. The composite filler for low corrosion brazing of titanium alloys at low temperature according to claim 1, wherein The melting point of the composite filler material is less than 830℃.

6. A low temperature, low dissolution brazing method for titanium alloys, characterized by, The brazing method uses the composite filler material according to any one of claims 1-5, and the method comprises: S1. Weighing the Ti powder and the Zr-Cu-Ni alloy powder according to a set mass percentage and mixing them uniformly; S2. Adding an acidic organic binder to the mixture obtained in step S1 and stirring until a uniform paste is formed to obtain the composite filler material; S3. Polishing, cleaning, and drying the surface of the workpiece to be welded; S4. Uniformly coating the surface of the part to be welded with the composite filler material prepared in step S2; S5. Placing the workpiece to be welded in a vacuum heating furnace, heating to a set temperature, promoting the complete volatilization of the organic binder, and then heating to 825-835℃ and holding; S6. Cooling the workpiece to be welded in the furnace.

7. The method of brazing titanium alloys at cryogenic temperatures with low dissolution according to claim 6, characterized in that, In step S2, the acidic organic binder is an acidic turpentine oil containing acetic acid.

8. The method of brazing titanium alloys at cryogenic temperatures with low dissolution according to claim 6, characterized in that, In step S5, the workpiece to be welded is placed in a vacuum heating furnace, heated to a temperature in the range of 200-250℃ and held for 3-5 min to promote the complete volatilization of the organic binder, and then heated to 825-835℃ and held for 10-30 min.

9. The method of brazing titanium alloys at cryogenic temperatures with low dissolution according to claim 6, characterized in that, In step S5, the heating rate is higher than 100℃ / min.

10. The method of brazing titanium alloys at cryogenic low-solubility temperatures of claim 6, wherein, The tensile strength of the welded workpiece is greater than 500 MPa.

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