A seven-element medium-entropy alloy brazing filler metal, its preparation method and brazing method

Abstract

This invention relates to the field of brazing technology, and proposes a Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy brazing filler metal and its application method for brazing pure titanium and titanium alloys. The invention provides a Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy brazing filler metal, characterized in that the weight percentage of the filler metal components is: Ti: 10.0~16.0; Nb: 1.0~8.0; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance. The invention has the following technical advantages: the melting point of the filler metal varies between 780℃ and 810℃ depending on the composition; the filler metal is easily prepared into amorphous ribbons; and when brazing pure titanium-pure titanium and pure titanium-titanium alloys at a brazing temperature of 845℃~865℃, the joint exhibits both good strength and ductility.

Description

Technical Field

[0001] This invention belongs to the field of brazing technology, and particularly relates to a seven-element medium-entropy alloy brazing filler metal, its preparation method, and its brazing method. Background Technology

[0002] Titanium and its alloys have high specific strength and good corrosion resistance, making them one of the main structural materials for modern aircraft and engines. They can reduce the weight of aircraft or engines and improve structural efficiency. For brazing of titanium alloys, Ti-based (Ti content greater than 40% by weight) or TiZr-based (Ti content greater than 35% by weight and Zr content greater than 20% by weight) brazing filler metals are usually selected as brazing materials to obtain better joint microstructure and corresponding higher joint strength and better corrosion resistance.

[0003] However, the phase transition temperature T of pure titanium β The required brazing temperature is 882℃, and brazing connections should be performed at temperatures below 882℃. Furthermore, to ensure that the pure titanium base material being brazed does not undergo a phase transformation during the brazing process, a safer brazing temperature should be below 872℃. Therefore, considering that brazing is generally performed at a temperature 30℃-50℃ higher than the melting temperature of the brazing filler metal, the ideal brazing filler metal for joining pure titanium materials should ideally have a melting temperature below 822℃. In addition, and very importantly, for brazing connections of pure titanium and titanium alloys, whether in aircraft ductwork or thin-walled complex structures for aerospace and marine heat exchangers, brazed joints require a good match of strength and plasticity to ensure the safety and service life of the welded structure.

[0004] However, currently, Ti-based or TiZr-based brazing filler metals have high liquidus temperatures. For example, the typical Ti-15Cu-15Ni alloy (by weight) has a high liquidus temperature and is only suitable for brazing the β-phase transformation temperature T. β Titanium alloys with a liquidus temperature above 960℃, such as the Ti-13Zr-21Cu-9Ni alloy (by weight), still have a high liquidus temperature, limiting brazing connections to 920℃-940℃. While some brazing fillers can achieve brazing connections of pure titanium and titanium alloys at temperatures around 880℃, the brazed joint strength rarely exceeds 500MPa, and the joints still exhibit significant brittleness.

[0005] Generally, after solving the basic weldability of a certain base material, further reducing the melting temperature of the filler metal to further lower the required brazing temperature, while also increasing the joint strength and reducing the brittleness of the brazed joint, is a highly challenging technical challenge. Currently, there is a lack of filler metal materials that can braze pure titanium or pure titanium and titanium alloys at temperatures below 872℃, and that produce brazed joints with both high strength and ductility. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy brazing filler metal. The brazing filler metal provided by the present invention has a liquidus temperature between 780℃ and 810℃, and can be used for brazing pure titanium or pure titanium and titanium alloy at temperatures below 872℃. Moreover, the brazed joint obtained has both good strength and plasticity.

[0007] This invention provides a Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy solder, wherein the weight percentage of the solder components is as follows:

[0008] Ti: 10.0~16.0; Nb: 1.0~8.0; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance.

[0009] Preferably, the weight percentage of the solder components is:

[0010] Ti: 10.0~16.0; Nb: 1.0~5.4; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance.

[0011] Preferably, the liquidus temperature of the brazing filler metal is 780℃~810℃;

[0012] The solder is one or more of the following medium-entropy alloy solders: amorphous foil strip, powder, or alloy block.

[0013] This invention provides a method for preparing a seven-element medium-entropy alloy solder, comprising:

[0014] A) Prepare alloy ingots by smelting metal raw materials;

[0015] B) Prepare medium-entropy alloy brazing filler metal from alloy ingots; the shape of the medium-entropy alloy brazing filler metal includes one of amorphous foil strip, powder or alloy block.

[0016] Preferably, step B) specifically includes one or more of the following steps:

[0017] i) The alloy ingot is prepared into alloy powder brazing filler metal by argon atomization powder preparation method or plasma rotating electrode atomization method;

[0018] ii) The alloy ingot is processed into amorphous alloy foil brazing filler metal using a single-roller rapid quenching method;

[0019] iii) Mechanically crush the alloy ingot to obtain a brazing alloy block.

[0020] This invention provides the application of the Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy brazing filler metal described in any one of the above-mentioned claims in brazing pure titanium and / or titanium alloys.

[0021] This invention provides a brazing method for pure titanium / or titanium alloys, comprising the following steps:

[0022] a) Material preparation: Prepare the base material of pure titanium and / or titanium alloy to be welded, and after pretreatment, obtain the pretreated base material;

[0023] b) Add solder to the surface of the pretreated base material to be welded to obtain the assembled component; the solder is the solder described in the above technical solution or the solder prepared by the preparation method described in the above technical solution;

[0024] c) Brazing the assembled components yields the final product.

[0025] Preferred,

[0026] The pretreatment step a) specifically involves removing oxides, oils, or surface contaminants from the surface of the base material;

[0027] Step b) further includes controlling the brazing gap between the substrates to be brazed to be 0.01~0.08mm using tooling fixtures.

[0028] Preferably, the brazing temperature in step c) is specifically:

[0029] When the substrate contains pure titanium, the brazing temperature T b Temperature range: 845℃~865℃;

[0030] When the base material is entirely titanium alloy, the brazing temperature T b Not higher than the phase transformation temperature of the corresponding titanium alloy.

[0031] Preferably, the brazing method in step c) is vacuum brazing or induction heating brazing;

[0032] The specific vacuum brazing parameters are: the vacuum level inside the furnace is not less than 1×10⁻⁶. -3 Pa, heating at a rate of 20~40℃ / min to 500℃; continuing to heat at a rate of 20-25℃ / min to 800℃; then continuing to heat at a rate of 15~25℃ / min to T b Hold the temperature for 10 to 25 minutes; then cool down at a rate of 15 to 25°C / min until the furnace reaches room temperature.

[0033] The specific parameters for induction heating brazing are as follows: under inert gas conditions, the vacuum level inside the furnace is not less than 1×10⁻⁶. -3 Pa, heated to T at a heating rate of 50℃ / min to 100℃ / min. b Keep warm for 1 to 10 minutes, then stop induction heating and allow to cool naturally to room temperature.

[0034] Compared with the prior art, the present invention provides a Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy brazing filler metal, characterized in that the weight percentage of the brazing filler metal composition is: Ti: 10.0~16.0; Nb: 1.0~8.0; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance. The present invention has the following technical advantages: the melting point of the brazing filler metal varies between 780℃ and 810℃ depending on the composition; the brazing filler metal is easily prepared into amorphous ribbons; and it can be used to braze pure titanium-pure titanium and pure titanium-titanium alloys at brazing temperatures of 845℃~865℃, resulting in joints with both good strength and ductility.

[0035] The advantages and beneficial effects of the brazing filler metal of this invention are as follows:

[0036] (1) Characteristics and advantages of the alloy element composition of the solder: The design principle of multi-element medium-entropy alloy is adopted. The alloy is composed of 5 or more elements. The comprehensive strengthening and toughening effect is achieved through significant saturated solid solution strengthening effect, strong lattice distortion caused by atomic size difference, and multiple strengthening and toughening mechanisms (including fine grain strengthening, dislocation strengthening, precipitation strengthening, etc.). The invention patent of this application designs a total of 7 constituent elements. Among them, Zr, Ti, Nb and Hf are the most representative elements of typical TiZrHfNb(Mo, Ta) system high-entropy alloy. These elements can be infinitely miscible with each other and have no tendency to form brittle intermetallic compounds. Therefore, the TiZrHfNb quaternary system high-entropy alloy has good room temperature plasticity. For example, its room temperature elongation can reach 14.9%. Meanwhile, Ni, Cu, and Co are added to the solder alloy as melting point reducing elements. Through the principles of ternary low-melting-point eutectics such as Cu-Ni-Ti, Cu-Ni-Zr, and Ti-Ni-Nb, as well as binary low-melting-point eutectics such as Co-Ti and Co-Zr, they collectively lower the melting point of the solder alloy. (See appendix) Figure 1 -Appendix Figure 5 Furthermore, thermodynamic calculations show that the mixing entropy ΔS of the seven-element solder alloy of this invention is... mix (J.K.) -1 mol -1 The value is between 10.20 and 11.89, satisfying the thermodynamic condition ΔS for high-entropy alloys. mixThe value falls within the range of 1.0R-1.5R, indicating that it belongs to the medium-entropy alloy brazing filler metal. Therefore, it can play a good role in strengthening and toughening in brazed joints of pure titanium and pure titanium combined with titanium alloy.

[0037] (2) The brazing alloy of this invention is designed with full consideration of the requirement that it must have good amorphous foil forming ability. Especially for the brazing connection of heat exchangers with complex multi-layer thin-walled structures composed of pure titanium fins and titanium alloy partitions, the use of complete and continuous amorphous alloy foil for pre-welding filling and assembly between layers can ensure convenient and efficient assembly, as well as stable and controllable brazing quality. Among the seven constituent elements of the brazing alloy of this invention, one category is Zr, Ti, Nb, and Hf, and the other category is Ni, Cu, and Co. Each category contains similar elements, but the two categories of elements overlap and are considered dissimilar elements, as shown in the appendix. Figure 6 By combining appropriate amounts of each component to achieve a combined melting point reduction, this design approach fully utilizes the design principles of amorphous alloys, such as the "eutectic point criterion, atomic size differences, and coexistence of similar and dissimilar elements." Therefore, the solder of this invention, while ensuring a sufficiently low melting temperature, exhibits significantly better amorphous foil formation capability than the Zr-Ti-Ni system and ZrTiNiNb(Hf) solder. Using a single-roll rapid quenching method, amorphous solder foil with a width of 30-60 mm and a thickness of 25-55 μm can be stably obtained. Solder foils from different batches all exhibit amorphous characteristics (see attached figure). Figure 7 Meanwhile, because the solder of this invention has a strong ability to form amorphous foil strips, the yield of solder foil strips is increased to more than twice that of solders such as Zr-Ti-Ni system solders and Zr-Ti-Ni-Nb(Hf).

[0038] (3) The melting temperature of the brazing alloy is effectively reduced, which can meet the requirement that the brazing temperature of pure titanium materials is below 872℃. In the Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element brazing alloy applied for, Hf and Nb are refractory metals with melting points as high as 2222℃ and 2468℃, respectively. However, their contents are controlled at a low level when designing the brazing alloy, namely: Nb: 1.0~8.0; Hf: 0.2~5.0 (weight percentage). At the same time, as mentioned above, the brazing alloy of this application uses Ni, Cu and Co to reduce melting point. The melting point reduction effect is much better than that of Cu, Ni, Co alone or any two of them. The actual liquidus temperature of the brazing alloy is between 780℃ and 810℃. Therefore, brazing can be carried out in the range of 845-865℃, which avoids damage to the properties of the base material caused by excessive brazing temperature and is conducive to saving energy in the brazing process. This combined melting point reduction method, with balanced content of three elements (Ni: 5.0–9.0; Cu: 4.0–9.0; Co: 1.0–6.5 by weight), ensures that the amount of each melting point reduction element does not exceed 9.0 by weight. This effectively avoids the tendency of strong brittle intermetallic compounds to form in the brazed joint due to excessive addition of a single element when melting point reduction is relied upon. In particular, the small amount of Co plays a melting point reduction role. At the same time, no Co-Ti or Co-Zr intermetallic compounds were found in the brazed joint, but rather existed in the form of a solid solution in the (Zr, Ti, Nb, Hf) solid solution. Co itself does not cause joint brittleness but plays an important role in strengthening the brazed joint. Therefore, the total content of Ni+Cu elements, which are prone to causing intermetallic compound formation, added to the brazing alloy of this invention for melting point reduction is controlled between 9.0 and 18.0 by weight.

[0039] (4) The microstructure of pure titanium-pure titanium and pure titanium-titanium alloy brazed joints under brazing conditions of 865℃-15min using the brazing filler metal of the present invention is shown in the attached figure. Figure 8 As shown, no bright white intermetallic compounds such as (Ti, Zr) and (Ni, Cu) were observed in the joint microstructure. Therefore, using the brazing filler metal of this application, the brazed joint obtained under suitable brazing process conditions exhibits both good strength and ductility.

[0040] (5) The brazing filler metal of the present invention achieves a comprehensive effect of high strength and good plasticity for brazed joints of pure titanium and pure titanium and titanium alloy combination under the conditions of brazing temperature of 845℃-865℃ and appropriate brazing time: the average tensile strength of the brazed joint at room temperature is 530MPa-570MPa, which reaches more than 91% of the pure titanium material being welded, and the average elongation of the joint is 10%-22%. It fundamentally eliminates the brittle characteristics of the brazed joint corresponding to the traditional brazing filler metal, realizes the strong plasticity matching of the joint, and can ensure the safety and service life of the welded structure.

[0041] (6) As mentioned above, the content of high-melting-point elements Hf and Nb in the brazing filler metal of the present invention is controlled at a low level, and the addition of the three melting-reducing elements Ni, Cu, and Co is relatively balanced. These factors are conducive to obtaining a uniformly composed ingot through smelting. Furthermore, a uniformly composed, non-segregated amorphous alloy foil brazing filler metal can be easily obtained from the uniformly composed ingot through a single-roller rapid quenching method. On the other hand, the uniformly composed ingot was verified by two methods: argon atomization powder preparation and plasma rotating electrode atomization. There was no local arcing or sparking during the powder preparation process. The powder preparation process is safe and stable, and a uniformly composed powdered brazing filler metal can be obtained.

[0042] (7) The brazing alloy has the characteristics of high alloying. During the brazing process, Cu, Ni and Co elements diffuse into the pure titanium and titanium alloy matrix to be welded, and Ti elements diffuse into the brazing seam. Therefore, the brazed joint is a TiZrNb(Hf) based super solid solution. The content of Cu, Ni and Co elements is relatively low. Therefore, the brazed joint not only has good strength and toughness, but also the high alloying characteristics of the brazed joint ensure its good corrosion resistance. Attached Figure Description

[0043] Figure 1 The Cu-Ni-Ti ternary phase diagram;

[0044] Figure 2 The Cu-Ni-Zr ternary phase diagram;

[0045] Figure 3 The Ti-Ni-Nb ternary phase diagram;

[0046] Figure 4 Co-Ti binary phase diagram;

[0047] Figure 5 The Co-Zr binary phase diagram;

[0048] Figure 6 This is a schematic diagram showing the positions of the constituent elements of the solder of this invention in the periodic table;

[0049] Figure 7XRD patterns of different batches of amorphous foil ribbons;

[0050] Figure 8 Microstructure of pure titanium-pure titanium and pure titanium-titanium alloy brazed joints under brazing conditions of 865℃-15min. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort, including but not limited to minor adjustments or changes to the chemical composition of the brazing filler metal, minor adjustments or simple changes to the brazing process, preparation of brazing filler metal foils with wider or thinner widths due to different brazing filler metal quenching equipment, preparation of other forms of brazing filler metal using the brazing filler metal chemical composition representing the spirit of the present invention, changing the grade of the pure titanium material or titanium alloy material being welded, etc., all fall within the scope of protection of the present invention.

[0052] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The invention is by no means limited to any of the specific arrangements and methods set forth below, but covers any improvements, substitutions, and modifications to the structures, methods, and devices without departing from the spirit of the invention.

[0053] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0054] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items.

[0055] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0056] This invention provides a Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy solder, wherein the weight percentage of the solder components is as follows:

[0057] Ti: 10.0~16.0; Nb: 1.0~8.0; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance.

[0058] According to the present invention, the preferred weight percentage of the brazing filler metal composition is:

[0059] Ti: 10.0~16.0; Nb: 1.0~5.4; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance.

[0060] The liquidus temperature of the brazing filler metal described in this invention is 780℃~810℃.

[0061] The brazing filler metal of this invention uses a combination of Ni, Cu, and Co elements to reduce melting point. The melting point reduction effect is much better than that of Cu, Ni, Co alone or any two of them combined. The actual liquidus temperature of the brazing filler metal is between 780℃ and 810℃, so brazing can be performed in the range of 845-865℃. This avoids damage to the properties of the base material caused by excessively high brazing temperature and also helps to save energy in the brazing process.

[0062] In some embodiments, the titanium-containing material may include, but is not limited to: a ribbed panel structure made of pure titanium material and / or titanium alloy material; a thin-walled structure made of pure titanium material and / or titanium alloy material; a sandwich structure made of pure titanium material and / or titanium alloy material; and any structure of titanium alloy-titanium alloy. The brazing filler metal is one or more of the following shapes of medium-entropy alloy brazing filler metal: amorphous foil strip, powder, alloy block, etc.

[0063] This invention patent application incorporates seven constituent elements. Zr, Ti, Nb, and Hf are the four most representative elements of the typical TiZrHfNb(Mo, Ta) system high-entropy alloy. These elements are infinitely miscible with each other and have no tendency to form brittle intermetallic compounds. Therefore, the TiZrHfNb quaternary high-entropy alloy exhibits good room-temperature plasticity, such as a room-temperature elongation of up to 14.9%. Simultaneously, Ni, Cu, and Co are added to the solder alloy as melting point reducing elements. Through the principles of ternary low-melting-point eutectics such as Cu-Ni-Ti, Cu-Ni-Zr, and Ti-Ni-Nb, as well as binary low-melting-point eutectics such as Co-Ti and Co-Zr, they collectively lower the melting point of the solder alloy. (See appendix) Figure 1 -Appendix Figure 5Furthermore, thermodynamic calculations show that the mixing entropy ΔS of the seven-element solder alloy of this invention is... mix (J.K.) -1 mol -1 The value is between 10.20 and 11.89, satisfying the thermodynamic condition ΔS for high-entropy alloys. mix The value falls within the range of 1.0R-1.5R, indicating that it belongs to the medium-entropy alloy brazing filler metal. Therefore, it can play a good role in strengthening and toughening in brazed joints of pure titanium and pure titanium combined with titanium alloy.

[0064] This invention provides a method for preparing a seven-element medium-entropy alloy solder, comprising:

[0065] A) Prepare alloy ingots by smelting metal raw materials;

[0066] B) Prepare medium-entropy alloy brazing filler metal from alloy ingots; the shape of the medium-entropy alloy brazing filler metal includes one of amorphous foil strip, powder or alloy block.

[0067] The present invention first prepares alloy ingots by melting metal raw materials.

[0068] Use high-purity Zr, Ti, Ni, Cu, Co, Nb, and Hf elements with a purity of 99.5%-99.9%, and weigh them according to the weight ratio; or use high-purity Zr containing 1%-2.5% Hf element, add Hf element to the raw materials required for solder by adding high-purity Zr containing a certain amount of Hf element, and add pure Hf separately according to the insufficient Hf content in the required composition, while keeping the purity of other elements unchanged.

[0069] This invention preferably employs an electric arc melting method under inert gas protection to melt raw materials into alloy ingots. Recommended parameters for electric arc melting are: vacuuming the melting chamber to 5 × 10⁻⁶. -1 After pressing MPa, purge with argon to standard atmospheric pressure, use an arc ignition current of 60A, a stable melting current of 180A, and a melting time of 15~20s. To ensure uniform alloy composition, it is recommended to melt 2~4 times.

[0070] Medium-entropy alloy brazing filler metal was prepared from alloy ingots.

[0071] In some embodiments of the present invention, one or more of the following steps are specifically included:

[0072] i) The alloy ingot is prepared into alloy powder brazing filler metal by argon atomization powder preparation method or plasma rotating electrode atomization method;

[0073] The specific parameters for argon atomization powder production described in this invention include: for Cu, Co, and Hf ZrTi-based seven-component solders, a crucible-free atomization powder production method using a large-angle conical induction coil is proposed, in which the master alloy rod is clamped and suspended in a special conical induction coil. The melting chamber and atomization chamber are pre-evacuated, and then high-purity argon gas is introduced for protection until the vacuum level is not less than 2.0 × 10⁻⁶. -2 Pa; Place the bar stock in an inert gas environment of argon or helium, clamp the bar stock with a fixture and place it in a conical induction coil; The conical induction coil has a height of 400-600mm, a lower diameter of 55-60mm, and a cone angle of 35-75°; The power supply for providing current to the induction coil has a power of 20-25KW and a frequency of 4000Hz; The bar stock feed speed is 2.5-6.5mm / s; The atomization chamber pressure is 3.0-5.5MPa.

[0074] The parameters of the plasma rotating electrode atomization method of the present invention specifically include: during the preparation process of the rotating electrode atomization method, the working pressure of the inert gas in the atomization chamber is 0.115~0.135MPa, the rotation speed is 40000~55000r / min, the current is 710~820A, and the feed speed is 1.5~2mm / s.

[0075] ii) The alloy ingot is processed into amorphous alloy foil brazing filler metal using a single-roller rapid quenching method. Specific parameters of the single-roller rapid quenching method of this invention include: in an inert gas environment of argon or helium, the ingot is placed in a quartz crucible, and the quartz tube crucible is placed in a ring-shaped induction coil; the induction coil height is 300-600 mm, and the lower end opening width is 30-50 mm; the ingot feed speed is 0.2-0.5 m / s; the single-roller rotation speed is 1300-1800 r / min; and the injection pressure is 50-70 kPa.

[0076] iii) Mechanically crush the alloy ingot to obtain a brazing alloy block;

[0077] This invention provides the application of the Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy brazing filler metal described in any one of the above-mentioned claims in brazing pure titanium and / or titanium alloys.

[0078] The Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy brazing filler metal of the present invention can be used not only for brazing between pure titanium, between pure titanium and titanium alloys, but also for brazing between titanium alloys, and can achieve good results.

[0079] This invention provides a brazing method for pure titanium / or titanium alloys, comprising the following steps:

[0080] a) Material preparation: Prepare the base material of pure titanium and / or titanium alloy to be welded, and after pretreatment, obtain the pretreated base material;

[0081] b) Add brazing filler metal to the surface of the pretreated base material to be welded to obtain the assembled component;

[0082] c) The assembled components are brazed to obtain the final product. The brazing filler metal is the brazing filler metal described in the above technical solution or the brazing filler metal prepared by the preparation method described in the above technical solution.

[0083] The pure titanium / or titanium alloy mentioned above in this invention includes pure titanium-pure titanium, pure titanium-titanium alloy, and titanium alloy-titanium alloy.

[0084] The brazing method for pure titanium / or titanium alloys provided by this invention first includes material preparation.

[0085] The base material of pure titanium and / or titanium alloy to be welded is prepared and pretreated to obtain pretreated base material; the pretreatment specifically involves removing oxides, oils or surface contaminants from the surface of the base material; the present invention does not limit the specific removal method, but any method known to those skilled in the art is acceptable.

[0086] A solder is added to the surface of the pretreated base material to be welded to obtain an assembled component; the solder is one or more solders prepared by the preparation method described in the above technical solution.

[0087] Preferably, the brazing gap between the substrates to be brazed is controlled to be 0.01~0.08mm by using tooling fixtures.

[0088] This invention does not limit how the above-mentioned tooling fixture controls the brazing gap; any method known to those skilled in the art is acceptable.

[0089] The assembled components are then brazed to obtain the final product.

[0090] The assembled components are placed in a vacuum brazing furnace, with a vacuum level of not less than 1×10⁻⁶. -3 Pa.

[0091] The brazing temperature is selected based on the phase transformation temperature of the base material.

[0092] In some embodiments of the present invention, the brazing temperature is specifically as follows:

[0093] When the substrate contains pure titanium, the brazing temperature T b Temperature range: 845℃~865℃;

[0094] When the matrix is ​​entirely titanium alloy, then T b The phase transformation temperature shall not exceed that of the corresponding titanium alloy. The phase transformation temperature of this invention is the transition temperature between the α and β phases of the titanium alloy.

[0095] The brazing method described in this invention is vacuum brazing or induction heating brazing;

[0096] In some embodiments of the present invention, the vacuum degree inside the furnace is not less than 1×10⁻⁶. -3 Pa, heating at a rate of 20~40℃ / min to 500℃; continuing to heat at a rate of 20-25℃ / min to 800℃; then continuing to heat at a rate of 15~25℃ / min to T b Hold the temperature for 10 to 25 minutes; then cool down at a rate of 15 to 25°C / min until the furnace reaches room temperature.

[0097] In some embodiments of the present invention, the induction heating brazing parameters are specifically as follows: under inert gas conditions, the vacuum degree inside the furnace is not less than 1×10⁻⁶. -3 Pa, heated to T at a heating rate of 50℃ / min to 100℃ / min. b Keep warm for 1 to 10 minutes, then stop induction heating and allow to cool naturally to room temperature.

[0098] Using the brazing filler metal of this application, brazed joints obtained under suitable brazing process conditions exhibit both good strength and ductility. For brazed joints of pure titanium and pure titanium combined with titanium alloys, the brazing filler metal of this invention achieves a comprehensive effect of high strength and good ductility under brazing temperatures of 845-865℃ and suitable brazing times: the average tensile strength of the brazed joint at room temperature is 530MPa-570MPa, reaching more than 91% of the pure titanium material being welded, while the average elongation of the joint is 10%-22%. This fundamentally eliminates the brittle characteristics of brazed joints corresponding to traditional brazing filler metals, achieving a strong-ductile match in the joint, and ensuring the safety and service life of the welded structure.

[0099] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0100] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a brazing filler metal, its preparation method, and its brazing method.

[0101] The preparation of the solder in all embodiments of the present invention is as follows:

[0102] 1. Selection of raw materials:

[0103] High-purity Zr, Ti, Ni, Cu, Co, Nb, and Hf elements with a purity of 99.5%-99.9% were used and weighed according to the weight ratio in Table 1; alternatively, high-purity Zr containing 1%-2.5% Hf was used, with Hf added to the raw materials required for the brazing filler metal using high-purity Zr containing a certain amount of Hf. Any remaining Hf content was then added separately from pure Hf, while the purity of other elements remained unchanged. Extensive experiments revealed that the selection of brazing process parameters significantly impacts the accuracy of the results. All parameters in this invention are optimized data obtained based on experiments. Specific data are shown in Table 1.

[0104] 2. Preparation of solder:

[0105] Under inert gas protection, the raw materials are melted into alloy ingots using an electric arc melting method. To ensure uniform alloy composition, it is recommended to melt 2-4 times. The brazing filler metal is prepared using one or more of the following methods: the alloy ingot is prepared into alloy powder brazing filler metal using argon atomization powdering or plasma rotating electrode atomization; the alloy ingot is prepared into amorphous alloy foil brazing filler metal using a single-roll rapid quenching method; and the alloy ingot is mechanically crushed to obtain brazing filler metal alloy blocks.

[0106] 3. Brazing:

[0107] (1) Material preparation: Prepare the base material of pure titanium or titanium alloy to be welded, and remove oxides, oil or surface deposits from the surface of the base material.

[0108] (2) Assembly: Apply one or two types of brazing filler metal to the surface of the base material to be welded; place the assembled component into a vacuum brazing furnace, with a vacuum degree of not less than 1×10⁻⁶. -3 Pa.

[0109] (3) Brazing process: The brazing gap between the interfaces to be joined is controlled within the range of 0~0.1mm using tooling fixtures. The brazing temperature is selected based on the phase transformation temperature of the base material. When the base material contains pure titanium, the brazing temperature T is... b The temperature range is 845℃ to 865℃; when the matrix is ​​entirely titanium alloy, then T b The temperature should not exceed the phase transformation temperature of the corresponding titanium alloy. If vacuum brazing is used, the temperature should be increased at a rate of 20-40℃ / min to 500℃; then increased at a rate of 20-25℃ / min to 800℃; and finally increased again at a rate of 15-20℃ / min to T. b Hold at that temperature for 10-25 minutes; then cool down at a rate of 15-25℃ / min until room temperature is reached. If induction brazing is used, heat to T at a rate of 50℃ / min to 100℃ / min. bKeep warm for 1 to 10 minutes, then stop induction heating and allow to cool naturally to room temperature.

[0110] Table 1 Examples of solder composition

[0111]

[0112] Examples 1-9:

[0113] Regarding the Zr-Ti-Ni-Cu-Co-Nb-Hf brazing filler metal and its application method, the liquidus temperature of the filler metal is between 785-808℃. (1) Preparation of the filler metal; (2) The base material is a combination of TA2-TA18 and TA2-TA2 materials, where TA2 is industrial pure titanium; the nominal composition of TA18 is: Ti-3Al-2.5V (weight percentage). Cut the amorphous alloy foil strip into the required shape and fix it to one side of the TA2-TA18 material combination by resistance spot welding, with a brazing gap of 0.01-0.08mm. (3) Place the assembled components into a vacuum brazing furnace, with a vacuum degree of 4.5×10 -3 Pa, select brazing temperature T b The temperature is 845-865℃, and the holding time is 18-25 minutes. The obtained TA2-TA18 joint has a room temperature tensile strength of up to 550MPa-570 MPa and an elongation of 14%-22%; at the same time, the TA2-TA2 joint has a room temperature tensile strength of up to 530MPa and an elongation of 17%-25%.

[0114] Table 2 Tensile strength of joints obtained in Examples 1-9

[0115]

[0116] Examples 10-20:

[0117] Regarding the Zr-Ti-Ni-Cu-Co-Nb-Hf brazing filler metal and its application method, the liquidus temperature of the filler metal is between 780-805℃. (1) Preparation of the filler metal; (2) The base material is a combination of TA2-TC4 and TA2-TA18 materials, where TA2 is industrial pure titanium; the nominal composition of TC4 is: Ti-6Al-4V (weight percentage). Cut the amorphous alloy foil strip into the required shape and fix it to one side of the TA2-TC4 and TA2-TA18 material combination by resistance spot welding, with a brazing gap of 0.03-0.06mm. (3) Place the assembled component into a vacuum brazing furnace, with a vacuum degree of 5.8×10 -3 Pa, select brazing temperature T bWith a temperature range of 845-865℃ and a holding time of 15 minutes, the room temperature tensile strength of the TA2-TC4 joint reached 545MPa, and the elongation reached 8%-14%; meanwhile, the room temperature tensile strength of the TA2-TA18 joint reached 560MPa, and the elongation reached 9%-15%.

[0118] Table 3 Tensile strength of joints obtained in Examples 10-20

[0119]

[0120] Examples 21-30:

[0121] Regarding the Zr-Ti-Ni-Cu-Co-Nb-Hf brazing filler metal and its application method, the liquidus temperature of the filler metal is between 783-792℃. (1) Preparation of the filler metal; (2) The base material is a combination of TA2-TA2, TA2-TA18, and TA2-TC4 materials, where TA2 is industrial pure titanium. Cut the rapidly cooled foil strip into the required shape and fix it to one side of the TA2-TA2, TA2-TA18, and TA2-TC4 material combination by resistance spot welding, with a brazing gap of 0.03-0.05mm. (3) Place the assembled component into a vacuum brazing furnace, with a vacuum degree of 6.5×10 -3 For brazing at 845-860℃ for 15-20 minutes, the TA2-TA18 joint achieved a room temperature tensile strength of 560 MPa and an elongation of 12%-20%. Simultaneously, the TA2-TA2 joint achieved a room temperature tensile strength of 545 MPa and an elongation of 14%-22%. The TA2-TC4 joint achieved a room temperature tensile strength of 570 MPa and an elongation of 10%-13%. For brazing at 860-865℃ for 10 minutes, the TA2-TA18 and TA2-TC4 joints achieved room temperature shear strengths exceeding 420 MPa. For brazing at 845-860℃ for 10 minutes, the TA2-TA2, TA2-TA18, and TA2-TC4 joints all achieved room temperature shear strengths exceeding 320 MPa.

[0122] Table 4 Tensile strength of joints obtained in Examples 21-30

[0123]

[0124] While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be readily understood by those skilled in the art that various changes may be made to suit particular circumstances, materials, compositions, substances, methods, or processes to the objectives, spirit, and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy solder, characterized in that, The weight percentage of the solder components is: Ti: 10.0~16.0; Nb: 1.0~8.0; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance; The liquidus temperature of the brazing filler metal is 780℃~810℃; Ni, Cu, and Co are added to the solder alloy as melting point reducing elements. They work together to reduce the melting point of the solder alloy through the principles of Cu-Ni-Ti, Cu-Ni-Zr, Ti-Ni-Nb ternary low-melting eutectic and Co-Ti, Co-Zr binary low-melting eutectic. The mixed entropy ΔS of the seven-element medium-entropy alloy solder mix J.K. -1 mol -1 The value is between 10.20 and 11.

89.

2. The Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy solder according to claim 1, characterized in that, The weight percentage of the solder components is: Ti: 10.0~16.0; Nb: 1.0~5.4; Hf: 0.2~5.0; Ni: 5.0~9.0; Cu: 4.0~9.0; Co: 1.0~6.5; Zr: balance.

3. The Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy solder according to claim 1, characterized in that, The solder is one or more of the following medium-entropy alloy solders: amorphous foil strip, powder, or alloy block.

4. A method for preparing a Zr-Ti-Nb-Hf-Ni-Cu-Co seven-element medium-entropy alloy solder according to any one of claims 1 to 3, characterized in that, include: A) Prepare alloy ingots by smelting metal raw materials; B) Prepare medium-entropy alloy brazing filler metal from alloy ingots; The medium-entropy alloy brazing filler metal is in one of the following forms: amorphous foil strip, powder, or alloy block.

5. The preparation method according to claim 4, characterized in that, Step B) specifically includes one of the following steps: i) The alloy ingot is prepared into alloy powder brazing filler metal by argon atomization powder preparation method or plasma rotating electrode atomization method; ii) The alloy ingot is processed into amorphous alloy foil brazing filler metal using a single-roller rapid quenching method; iii) Mechanically crush the alloy ingot to obtain a brazing alloy block.

6. The application of the Zr-Ti-Nb-Hf-Ni-Cu-Co heptagonal medium-entropy alloy brazing filler metal according to any one of claims 1 to 3 in brazing pure titanium and / or titanium alloys.

7. A brazing method for pure titanium and / or titanium alloys, characterized in that, Includes the following steps: a) Material preparation: Prepare the base material of pure titanium and / or titanium alloy to be welded, and after pretreatment, obtain the pretreated base material; b) Add brazing filler metal to the surface of the pretreated base material to be welded to obtain the assembled component; the brazing filler metal is the brazing filler metal according to any one of claims 1 to 3 or the brazing filler metal prepared by the preparation method according to any one of claims 4 to 5; c) Brazing the assembled components yields the final product.

8. The brazing method according to claim 7, characterized in that, The pretreatment in step a) specifically involves removing oxides and oil from the surface of the base material; Step b) further includes controlling the brazing gap between the substrates to be brazed to be 0.01~0.08mm using tooling fixtures.

9. The brazing method according to claim 7, characterized in that, The brazing temperature in step c) is specifically: When the substrate contains pure titanium, the brazing temperature T b Temperature range: 845℃~865℃; When the base material is entirely titanium alloy, the brazing temperature T b Not higher than the phase transformation temperature of the corresponding titanium alloy.

10. The brazing method according to claim 9, characterized in that, Step c) The brazing method is vacuum brazing or induction heating brazing; The specific vacuum brazing parameters are: the vacuum level inside the furnace is not less than 1×10⁻⁶. -3 Pa, heating at a rate of 20~40℃ / min to 500℃; continuing to heat at a rate of 20-25℃ / min to 800℃; then continuing to heat at a rate of 15~25℃ / min to T b Hold the temperature for 10 to 25 minutes; then cool down at a rate of 15 to 25°C / min until the furnace reaches room temperature. The specific parameters for induction heating brazing are as follows: under inert gas conditions, the vacuum level inside the furnace is not less than 1×10⁻⁶. -3 Pa, Heat to T at a heating rate of 50℃ / min to 100℃ / min b Keep warm for 1 to 10 minutes, then stop induction heating and allow to cool naturally to room temperature.

Images