Titanium alloy nucleation particles, titanium alloy refiner and preparation method thereof, titanium alloy

Abstract

The application belongs to the technical field of titanium alloy processing, and provides a titanium alloy nucleation particle, a titanium alloy refiner, a preparation method of the titanium alloy refiner, and a titanium alloy. By adding a small amount of the titanium alloy refiner into the titanium alloy, the Bf-TiB particles can be endogenously generated as the nucleation particles of the beta-Ti grains and alpha-Ti, so as to promote the nucleation and refinement of the beta-Ti grains and alpha-Ti structure. The nucleation particles have a remarkable effect on the structure homogenization of the cast dual-phase titanium alloy, eliminate the grain boundary Widmanataten structure and intracrystalline basketweave structure, and obtain complete alpha lamellar colony structure. Meanwhile, the nucleation particles are in a state of dispersion distribution, avoiding the enrichment problem at the grain boundary of the existing nucleation particles. In addition, the refinement process of the titanium alloy is simple, the amount of the refiner is small, and the refinement process is easy to control. The titanium alloy has important practical application value for controlling the structure and performance of the alloy.

Description

Technical Field

[0001] This application belongs to the field of titanium alloy processing technology, and particularly relates to a titanium alloy nucleating particle, a titanium alloy refining agent and its preparation method, and a titanium alloy. Background Technology

[0002] Titanium and titanium alloys possess characteristics such as low density, high specific strength, and excellent high-temperature performance, making them widely used in high-performance and high-temperature structural components in key fields. my country has abundant titanium reserves, and as a novel structural material with excellent performance, my country has successively developed high-temperature titanium alloys, high-strength titanium alloys, low-temperature titanium alloys, and corrosion-resistant titanium alloys for different usage conditions and application areas. Cast titanium alloys contain coarse Widmanstätten structures distributed along grain boundaries, interwoven basketweave structures within the grains, and α-lamellae bundle structures. The mechanical properties differ depending on the morphology of the as-cast microstructure, and the inhomogeneity of the as-cast microstructure is the main reason for the poor mechanical properties of cast titanium alloys. The as-cast microstructure of titanium alloys has a significant impact on subsequent alloy forming processes, product quality, and mechanical properties; therefore, improving the as-cast microstructure of titanium alloys is a crucial way to control material quality and performance.

[0003] Grain refinement is a key method for improving the uniformity of the microstructure of titanium alloys while simultaneously enhancing their strength and ductility. Adding nucleating agents to the molten titanium alloy can produce uniform and fine grains; this method is simple to implement and highly effective, making it a commonly used microstructure refinement technique. Reported titanium alloy grain refiners include B, C, SiC, TiB2, TiC, Fe, Cu, Y2O3, and La2O3. Among these refiners, SiC, TiB2, and TiC particles dissolve in the molten titanium, releasing B or C elements, which promote nucleation by increasing the alloy composition and thus undercooling. Botanicals (B) are the most efficient element for refining the grains of titanium alloys, but they also cause a large number of TiB (space group Pnma) particles to precipitate at grain boundaries, significantly reducing the plasticity of the titanium alloy while increasing its strength. Adding alloying elements such as Fe and Cu, which have a certain solid solubility in titanium alloys, can improve compositional supercooling and promote grain refinement, but this also increases the alloy's strength while decreasing its plasticity. While Y2O3 and La2O3 can exist stably in molten titanium alloys, the two-dimensional lattice mismatch between Y2O3 and La2O3 particles and β-Ti alloys is poor, and they tend to accumulate and grow at grain boundaries, seriously harming the alloy's plasticity. Therefore, they are not very effective at refining β-Ti grains and cannot provide effective nucleation sites for α-Ti nucleation, nor can they improve the uniformity of the α-Ti microstructure.

[0004] Therefore, it is necessary to develop a titanium alloy nucleating agent that has significant grain refinement and microstructure homogenization effects while avoiding excessive particle accumulation. Summary of the Invention

[0005] The purpose of this application is to provide a titanium alloy nucleation particle, aiming to develop a titanium alloy nucleation particle with obvious grain refinement and microstructure homogenization effects while avoiding excessive particle enrichment.

[0006] This application embodiment is implemented as follows: a titanium alloy nucleating particle, wherein the titanium alloy nucleating agent comprises Bf-TiB particles; the crystal structure of the Bf-TiB particles is orthorhombic, the space group is Cmcm, and the lattice parameters are as follows.

[0007] Another objective of this application is to provide a titanium alloy refining agent, wherein the titanium alloy refining agent is an intermediate alloy containing submicron or nano-sized boride particles; adding the titanium alloy refining agent to the titanium alloy can generate Bf-TiB particles as described above.

[0008] Another objective of this application is a method for preparing the above-mentioned titanium alloy refining agent, comprising:

[0009] The diluent, boron source powder, and metal powder are mixed evenly and then pressed into a compact; the metal powder can form a boride with a space group of Cmcm with boron.

[0010] The pressed blank is sintered under vacuum or inert atmosphere at a temperature of 750℃~1000℃ to obtain a titanium alloy refining agent.

[0011] Another objective of this application is a method for refining titanium alloys, comprising:

[0012] Titanium alloy raw materials are melted to obtain titanium alloy liquid;

[0013] Add the titanium alloy refining agent as described above to the titanium alloy liquid and mix evenly to obtain a metal liquid; the mass of the boride particles in the titanium alloy refining agent is not greater than 1% of the total mass of the metal liquid;

[0014] The molten metal is cast to obtain a refined titanium alloy.

[0015] Another objective of this application is to provide a titanium alloy, which is obtained by refining the titanium alloy using the aforementioned refining method.

[0016] This application provides a titanium alloy refining agent. By adding a small amount of this refining agent to a titanium alloy, Bf-TiB particles can be generated as nucleation particles for β-Ti and α-Ti grains, thereby promoting the nucleation and refinement of β-Ti and α-Ti structures. Furthermore, this nucleating agent has a significant effect on homogenizing the microstructure of cast dual-phase titanium alloys, eliminating Widmanstätten structure at grain boundaries and basketweave structure within grains, resulting in a completely α-layered bundled structure. Simultaneously, the nucleation particles are in a dispersed distribution state, avoiding the problem of enrichment at grain boundaries present in existing nucleation particles. In addition, the refining process for titanium alloys is simple, requires a small amount of refining agent, and is easy to control, making it of significant practical application value for controlling the microstructure and properties of titanium alloys and other alloys. Attached Figure Description

[0017] Figure 1 The unrefined as-cast metallographic image of the TC4 alloy provided in Comparative Example 1 of this application;

[0018] Figure 2 The XRD pattern of the titanium alloy refining agent provided in Example 1 of this application;

[0019] Figure 3 This is a SEM image of the titanium alloy refining agent provided in Example 1 of this application;

[0020] Figure 4 Transmission electron microscope image and corresponding electron diffraction pattern of Bf-TiB particles provided in Example 1 of this application;

[0021] Figure 5 Metallographic image of TC4 alloy provided in Example 1 of this application;

[0022] Figure 6 This is a SEM image of the TC4 alloy provided in Example 2 of this application;

[0023] Figure 7 The XRD pattern of the titanium alloy refining agent provided in Example 3 of this application;

[0024] Figure 8 Metallographic image of TC4 alloy provided in Example 3 of this application;

[0025] Figure 9 The image shows a SEM image of the TC4 alloy provided in Comparative Example 3 of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] This application provides a titanium alloy nucleating particle that exhibits significant grain refinement and microstructure homogenization while avoiding excessive particle accumulation. It comprises Bf-TiB particles with an orthorhombic crystal system, space group Cmcm, and lattice parameters of [missing information].

[0028] This application provides a titanium alloy refining agent. By adding the titanium alloy refining agent to a titanium alloy, the aforementioned Bf-TiB particles can be generated internally. This titanium alloy refining agent can be an intermediate alloy containing submicron or nano-sized boride particles. Specifically, by adding an intermediate alloy containing submicron or nano-sized (average particle size below 0.6 micrometers) boride particles to a molten titanium alloy, the generated Bf-TiB particles promote the nucleation and refinement of β-Ti grains and α-Ti microstructure. It is worth noting that when the boride particle size reaches the micrometer level, TiB with space group Pnma is generated instead of Bf-TiB with space group Cmcm. The generated TiB particles or whiskers aggregate at grain boundaries, reducing the plasticity and toughness of the titanium alloy.

[0029] This application also provides a method for preparing the above-mentioned titanium alloy refining agent, comprising:

[0030] The diluent, boron source powder, and metal powder are mixed evenly and then pressed into a compact; the metal powder can form a boride with a space group of Cmcm with boron.

[0031] The pressed blank is sintered under vacuum or inert atmosphere at a temperature of 750℃~1000℃ to obtain a titanium alloy refining agent.

[0032] In the embodiments of this application, the diluent can be aluminum powder or iron powder, etc., and its main function is to act as a diluent for the reaction to slow down the reaction and refine the generated boride particles.

[0033] In the embodiments of this application, the source of boron can be not only elemental boron powder, but also other compound powders or metal powders containing element B, such as boron carbide powder, ferroboron powder, etc.

[0034] In the embodiments of this application, the metal powder is a group VB or group VIB metal powder, which may be a metal powder or alloy powder containing one or more of the elements niobium, vanadium, tantalum, chromium and molybdenum.

[0035] The boron source powder has a particle size of less than 1 μm; the group VB or group VIB metal powder has a particle size of less than 10 μm. Smaller raw material particle sizes facilitate reaction and sintering, allowing for a reduction in sintering temperature and time, but this increases powder cost. The diluent used has a particle size of 13–48 μm, but its effect on the system is negligible.

[0036] In this embodiment, the molar ratio of boron to Group VB or Group VIB metal is 2.5-1.0, and the diluent accounts for 50-90% of the total mass of the mixture. The chemical composition of Bf-TiB is fixed. Taking aluminum powder as the diluent and niobium powder as the metal powder as an example, the Nb and B molar ratio in the Al-Nb-B powder mixture is within a certain range. When the molar ratio is around 0.5, NbB2 can be generated, while a molar ratio greater than 0.5 will generate some Al3Nb; a molar ratio less than 0.5 will generate some AlB2 and NbB. These two compounds have little impact on the refining effect, only changing the actual content of NbB2. The higher the actual content of NbB2, the better the refining effect of the titanium alloy. However, there is an upper limit to the content when adding it to the titanium alloy; otherwise, a second phase will be generated, leading to a decrease in plasticity. Furthermore, aluminum powder, as a diluent for the reaction, can slow down the reaction and refine the generated NbB2 particles. When the aluminum content is low, micron-sized NbB2 particles will be generated. The refining effect of these large particles is not as good as that of nano-sized particles.

[0037] Alternatively, the compact can be made by wrapping it in aluminum foil; the compact can be sintered by placing it in a graphite crucible; the protective atmosphere can be an atmosphere of gases such as nitrogen, argon, or helium.

[0038] Preferably, the step of uniformly mixing the diluent, boron source powder, and metal powder before pressing specifically includes:

[0039] After mixing the diluent, boron source powder, and metal powder, a reactant powder is obtained.

[0040] The reactant powder and zirconia grinding balls (6-20 mm in diameter) are placed in a mixing tank for ball milling. The ball-to-powder ratio is set to 6:1-20:1, the ball milling speed is 50-100 r / min, and the ball milling time is 2-4 hours to obtain a mixed powder.

[0041] The mixed powder is taken out, wrapped in aluminum foil, placed in a cylindrical steel mold, and pressed into a cylindrical blank on a hydraulic testing machine.

[0042] This application also provides an application of the above-mentioned titanium alloy refining agent in refining the alloy structure. By mechanically pulverizing the titanium alloy refining agent and adding it to the molten titanium alloy, it reacts with the titanium alloy to generate Bf-TiB solid solution particles in situ, which are used to refine the titanium alloy grains and / or homogenize the structure and / or strengthen and toughen it, thus obtaining a titanium alloy with refined Bf-TiB nucleation particles.

[0043] This application also provides a method for refining titanium alloys, including:

[0044] Titanium alloy raw materials are melted to obtain titanium alloy liquid;

[0045] The titanium alloy refining agent described above is added to the titanium alloy liquid and mixed evenly to obtain a metal liquid;

[0046] The molten metal is cast to obtain a refined titanium alloy.

[0047] The amount of boride particles added to the titanium alloy refining agent is less than 1% by mass. The refining effect is greater with higher addition amounts, but exceeding 1% will result in a second phase at the grain boundaries, leading to a decrease in plasticity. Preferably, the mass of the boride particles in the titanium alloy refining agent is no more than 0.5% of the total mass of the molten metal.

[0048] This application also provides a titanium alloy refined by the above-described titanium alloy refining method.

[0049] Preferably, the average grain size of the cast titanium alloy after casting through a graphite mold is 188–593 μm, and the average size of the α-Ti layered bundle structure is 20–40 μm.

[0050] The technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the titanium alloy nucleating particles and titanium alloy refining agents. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0051] Additionally, it should be noted that the values ​​given in the following embodiments are as accurate as possible. However, those skilled in the art will understand that due to unavoidable measurement errors and experimental issues, each number should be understood as an approximation rather than an absolutely accurate value.

[0052] Comparative Example 1

[0053] This comparative example provides an unrefined initial titanium alloy, the preparation method of which includes the following steps:

[0054] S1. Place the pre-weighed titanium alloy (TC4) in a water-cooled copper crucible and put it into a vacuum induction melting furnace, and heat it to 1973K. The composition of the titanium alloy is: Ti 95wt.%, Al 6wt.%, V 4wt.%.

[0055] S2. After the titanium alloy is completely melted, keep it at that temperature for 10 minutes to obtain the alloy liquid.

[0056] S3. The heat-insulated alloy liquid is poured into a graphite mold, and after solidification and cooling, a blank titanium alloy sample is obtained.

[0057] S4. The as-cast grain structure of the blank titanium alloy (i.e., the unrefined titanium alloy) is as follows: Figure 1 As shown, its average grain size is 1380 μm.

[0058] Example 1

[0059] This embodiment prepares a highly efficient titanium alloy refining agent, which can be used to refine the microstructure of titanium alloys, but is not limited thereto. Specifically, the titanium alloy refining agent contains NbB2 particles, wherein the molar ratio of Nb to B is 1:2, and the mass fraction of boride particles is 15 wt.%. The preparation method of the titanium alloy refining agent includes the following steps:

[0060] S1. Preparation of powder for reaction compact: Weigh 85g of aluminum powder with a particle size of 13μm, 12.16g of niobium powder with a particle size of 5μm, and 2.84g of boron powder with a particle size of 100nm, and set aside.

[0061] S2. Mix the weighed aluminum powder, niobium powder, and boron powder to obtain reactant powder. Then, place the prepared reactant powder and zirconia grinding balls (5-22 mm in diameter) into a mixing tank for ball milling. Set the ball-to-powder ratio to 6:1, the ball milling speed to 60 r / min, and the ball milling time to 8 hours to obtain a mixture. Then, take out the mixture, wrap it in aluminum foil, place it in a cylindrical steel mold, and press it into a cylindrical blank with a diameter of 30 mm on a hydraulic testing machine.

[0062] S3. Wrap the compact with graphite paper and place it in the graphite mold used for in-situ sintering reaction; turn on the power of the hot pressing sintering furnace, evacuate to below 10 Pa, set the heating rate to 30 K / min, and continue heating until the furnace temperature reaches 1123 K. Hold at this temperature for 20 min, then remove the sample and air-cool it to room temperature to obtain a titanium alloy refiner containing NbB2 particles; the characterization results of the submicron NbB2 particles are as follows. Figure 2 and Figure 3 As shown. Among them, Figure 2 The image shows the XRD pattern of the titanium alloy refining agent. Figure 3 This is a SEM image of the titanium alloy refining agent NbB2.

[0063] In addition, this embodiment also provides a method for refining titanium alloys, which involves using the titanium alloy refining agent prepared in Example 1 to refine the initial titanium alloy described in Comparative Example 1, specifically including the following steps:

[0064] S4. Place the pre-weighed titanium alloy in a water-cooled copper crucible and put it into a vacuum induction melting furnace, and heat it to 1973K. The composition of the titanium alloy is: Ti 90wt.%, Al 6wt.%, V 4wt.%.

[0065] S5. After the titanium alloy is completely melted, keep it at that temperature for 10 minutes to obtain the alloy liquid.

[0066] S6. Add the titanium alloy refining agent prepared in Example 1 to the above-mentioned molten metal and perform induction stirring for 3 minutes to obtain the molten metal, wherein the amount of NbB2 particles added is 0.1 wt.%.

[0067] S7. The molten metal obtained above is poured into a graphite mold and solidified to obtain the titanium alloy refined by the Bf-TiB particle nucleating agent. Transmission electron microscopy (TEM) images and corresponding electron diffraction patterns of the Bf-TiB particles are shown below. Figure 4 As shown.

[0068] The average grain size of the obtained titanium alloy was refined to 566 μm, a reduction of nearly 2.5 times, and no TiB whiskers appeared at the grain boundaries. Experimental results are as follows... Figure 5 As shown.

[0069] Example 2

[0070] This embodiment prepares a highly efficient titanium alloy refining agent, which can be used to refine the microstructure of titanium alloys, but is not limited thereto. Specifically, the titanium alloy refining agent contains NbB2 particles, wherein the molar ratio of Nb to B is 1:2, and the mass fraction of boride particles is 10 wt.%. The preparation method of the titanium alloy refining agent includes the following steps:

[0071] S1. Preparation of powder for reaction compact: Weigh 85g of aluminum powder with a particle size of 13μm, 12.16g of niobium powder with a particle size of 5μm, and 2.84g of boron powder with a particle size of 100nm, and set aside.

[0072] S2. Mix the weighed aluminum powder, niobium powder, and boron powder to obtain reactant powder. Then, place the prepared reactant powder and zirconia grinding balls (5-22 mm in diameter) into a mixing tank for ball milling. Set the ball-to-powder ratio to 6:1, the ball milling speed to 60 r / min, and the ball milling time to 8 hours to obtain a mixture. Then, take out the mixture, wrap it in aluminum foil, place it in a cylindrical steel mold, and press it into a cylindrical blank with a diameter of 30 mm on a hydraulic testing machine.

[0073] S3. Wrap the compact with graphite paper and place it in the graphite mold used for in-situ sintering reaction; turn on the power of the hot pressing sintering furnace, evacuate to below 10 Pa, set the heating rate to 30 K / min, and continue until the temperature inside the furnace reaches 1123 K. Hold the temperature for 20 minutes, then take out the sample and air cool it to room temperature to obtain a titanium alloy refiner containing submicron NbB2 particles.

[0074] In addition, this embodiment also provides a method for refining titanium alloys, which involves using the titanium alloy refining agent prepared in Example 2 to refine the initial titanium alloy described in Comparative Example 1, specifically including the following steps:

[0075] S4. Place the pre-weighed titanium alloy in a water-cooled copper crucible and put it into a vacuum induction melting furnace, and heat it to 1973K. The composition of the titanium alloy is: Ti 90wt.%, Al 6wt.%, V 4wt.%.

[0076] S5. After the titanium alloy is completely melted, keep it at that temperature for 10 minutes to obtain the alloy liquid.

[0077] S6. Add the titanium alloy refining agent prepared in Example 2 to the above-mentioned molten metal and perform induction stirring for 3 minutes to obtain the molten metal, wherein the amount of NbB2 particles added is 1.0 wt.%.

[0078] S7. The molten metal obtained above is poured into a graphite mold and solidified to obtain a titanium alloy refined by Bf-TiB particle nucleating agent.

[0079] The resulting titanium alloy had an average grain size refined to 280 μm, with Bf-TiB particles uniformly distributed within the grains, such as... Figure 6 As shown, no large number of TiB whiskers appeared at the β grain boundaries.

[0080] Example 3

[0081] This embodiment prepares a highly efficient titanium alloy refining agent, which can be used to refine the microstructure of titanium alloys, but is not limited thereto. Specifically, the titanium alloy refining agent contains VB2 particles, wherein the molar ratio of V to B is 1:2, and the mass fraction of boride particles is 30 wt.%. The preparation method of the titanium alloy refining agent includes the following steps:

[0082] S1. Preparation of powder for reaction compact: Weigh 70g of aluminum powder with a particle size of 13μm, 20.8g of vanadium powder with a particle size of 5μm, and 9.2g of boron powder with a particle size of 500nm, and set aside.

[0083] S2. Mix the weighed aluminum powder, vanadium powder, and boron powder to obtain reactant powder; then, place the prepared reactant powder and zirconia grinding balls (5-22 mm in diameter) into a mixing tank for ball milling, setting the ball-to-powder ratio to 6:1, the ball milling speed to 60 r / min, and the ball milling time to 8 hours to obtain a mixture; then take out the mixture, wrap it in aluminum foil, place it in a cylindrical steel mold, and press it into a cylindrical blank with a diameter of 30 mm on a hydraulic testing machine.

[0084] S3. Wrap the compact with graphite paper and place it in the graphite mold used for in-situ sintering reaction; turn on the power of the hot pressing sintering furnace, evacuate to below 10 Pa, set the heating rate to 30 K / min, and continue heating until the furnace temperature reaches 1123 K. Hold at this temperature for 20 minutes, then remove the sample and air-cool it to room temperature. This yields a titanium alloy refining agent containing submicron VB2 particles, as shown in the XRD pattern. Figure 7 As shown.

[0085] In addition, this embodiment also provides a method for refining titanium alloys, which involves using the titanium alloy refining agent prepared in Example 3 to refine the initial titanium alloy described in Comparative Example 1, specifically including the following steps:

[0086] S4. Place the pre-weighed titanium alloy in a water-cooled copper crucible and put it into a vacuum induction melting furnace, and heat it to 1973K. The composition of the titanium alloy is: Ti 90wt.%, Al 6wt.%, V 4wt.%.

[0087] S5. After the titanium alloy is completely melted, keep it at that temperature for 10 minutes to obtain the alloy liquid.

[0088] S6. Add the titanium alloy refining agent prepared in Example 3 to the above-mentioned molten metal and perform induction stirring for 3 minutes to obtain the molten metal, wherein the amount of VB2 particles added is 0.2 wt.%.

[0089] S7. The molten metal obtained above is poured into a graphite mold and solidified to obtain a titanium alloy refined by Bf-TiB particle nucleating agent.

[0090] The average grain size of the obtained titanium alloy was refined to 430 μm, such as Figure 8 As shown, no large number of TiB whiskers appeared at the β grain boundaries.

[0091] Example 4

[0092] This embodiment prepares a highly efficient titanium alloy refining agent, which can be used to refine the microstructure of titanium alloys, but is not limited thereto. Specifically, the titanium alloy refining agent contains TaB2 particles, wherein the molar ratio of Ta to B is 1:2, and the mass fraction of boride particles is 30 wt.%. The preparation method of the titanium alloy refining agent includes the following steps:

[0093] S1. Preparation of powder for reaction compact: Weigh 70g of aluminum powder with a particle size of 13μm, 20.8g of tantalum powder with a particle size of 5μm, and 9.2g of boron powder with a particle size of 500nm, and set aside.

[0094] S2. Mix the weighed aluminum powder, tantalum powder, and boron powder to obtain reactant powder; then, place the prepared reactant powder and zirconia grinding balls (5-22 mm in diameter) into a mixing tank for ball milling, setting the ball-to-powder ratio to 6:1, the ball milling speed to 60 r / min, and the ball milling time to 8 hours to obtain a mixture; then take out the mixture, wrap it in aluminum foil, place it in a cylindrical steel mold, and press it into a cylindrical blank with a diameter of 30 mm on a hydraulic testing machine.

[0095] S3. Wrap the compact with graphite paper and place it in the graphite mold used for in-situ sintering reaction; turn on the power of the hot pressing sintering furnace, evacuate to below 10 Pa, set the heating rate to 30 K / min, and continue heating until the temperature inside the furnace reaches 1023 K. Hold the temperature for 20 minutes, then take out the sample and air cool it to room temperature to obtain a titanium alloy refiner containing submicron TaB2 particles.

[0096] In addition, this embodiment also provides a method for refining titanium alloys, which involves using the titanium alloy refining agent prepared in Example 3 to refine the initial titanium alloy described in Comparative Example 1, specifically including the following steps:

[0097] S4. Place the pre-weighed titanium alloy in a water-cooled copper crucible and put it into a vacuum induction melting furnace, and heat it to 1873K. The composition of the titanium alloy is: Ti 90wt.%, Al 6wt.%, V 4wt.%.

[0098] S5. After the titanium alloy is completely melted, keep it at that temperature for 10 minutes to obtain the alloy liquid.

[0099] S6. Add the titanium alloy refining agent prepared in Example 4 to the above-mentioned molten metal and perform induction stirring for 3 minutes to obtain the molten metal, wherein the amount of TaB2 particles added is 0.2 wt.%.

[0100] S7. The molten metal obtained above is poured into a graphite mold and solidified to obtain a titanium alloy refined by Bf-TiB particle nucleation.

[0101] The average grain size of the obtained titanium alloy was refined to 480 μm, and no large number of TiB whiskers appeared at the β grain boundaries.

[0102] Comparative Example 2

[0103] The titanium alloy refining agent contains NbB2 particles, wherein the molar ratio of Nb / B is 1:2, and the mass fraction of NbB2 particles is 50 wt.%. The preparation method of the nucleating agent preform includes the following steps:

[0104] S1. Preparation of powder for reaction compact: Weigh 50g of aluminum powder with a particle size of 13μm, 40.4g of niobium powder with a particle size of 30μm, and 9.6g of boron powder with a particle size of 10μm, and set aside.

[0105] S2. Mix the weighed aluminum powder, niobium powder, and boron powder to obtain reactant powder. Then, place the prepared reactant powder and zirconia grinding balls (5-22 mm in diameter) into a mixing tank for ball milling. Set the ball-to-powder ratio to 6:1, the ball milling speed to 60 r / min, and the ball milling time to 8 hours to obtain a mixture. Then, take out the mixture, wrap it in aluminum foil, place it in a cylindrical steel mold, and press it into a cylindrical blank with a diameter of 30 mm on a hydraulic testing machine.

[0106] S3. Wrap the compact with graphite paper and place it in the graphite mold used for in-situ sintering reaction; turn on the power of the hot pressing sintering furnace, evacuate to below 10 Pa, set the heating rate to 30 K / min, when the furnace temperature is 1123 K, hold for 20 min, then air cool to room temperature, take out the sample, and you can obtain the titanium alloy refiner containing NbB2.

[0107] In this comparative example, the NbB2 particles had an average particle size of 3 micrometers and contained Al3Nb. The main reason for this is that the excessively large particle size led to incomplete reaction, resulting in the formation of micrometer-sized NbB2 precursors.

[0108] Comparative Example 3

[0109] This titanium alloy refining agent contains NbB2 particles, wherein the molar ratio of Nb / B is 1:2, and the mass fraction of NbB2 particles is 60 wt.%. The preparation method of this titanium alloy refining agent includes the following steps:

[0110] S1. Preparation of powder for reaction compact: Weigh 40g of aluminum powder with a particle size of 13μm, 48.5g of niobium powder with a particle size of 5μm, and 11.5g of boron powder with a particle size of 500nm, and set aside.

[0111] S2. Mix the weighed aluminum powder, niobium powder, and boron powder to obtain reactant powder. Then, place the prepared reactant powder and zirconia grinding balls (5-22 mm in diameter) into a mixing tank for ball milling. Set the ball-to-powder ratio to 6:1, the ball milling speed to 60 r / min, and the ball milling time to 8 hours to obtain a mixture. Then, take out the mixture, wrap it in aluminum foil, place it in a cylindrical steel mold, and press it into a cylindrical blank with a diameter of 30 mm on a hydraulic testing machine.

[0112] S3. Wrap the compact with graphite paper and place it in the graphite mold used for in-situ sintering reaction; turn on the power of the hot pressing sintering furnace, evacuate to below 10 Pa, set the heating rate to 30 K / min, when the furnace temperature is 1123 K, hold for 20 min, then air cool to room temperature, take out the sample, and you can obtain a titanium alloy refiner containing NbB2; the average particle size of NbB2 particles is 2.2 micrometers.

[0113] S4. Place the pre-weighed titanium alloy in a water-cooled copper crucible and put it into a vacuum induction melting furnace, and heat it to 1973K. The composition of the titanium alloy is: Ti 90wt.%, Al 6wt.%, V 4wt.%.

[0114] S5. After the titanium alloy is completely melted, keep it at that temperature for 10 minutes to obtain the alloy liquid.

[0115] S6. Add the titanium alloy refining agent prepared above to the above molten metal and perform induction stirring for 3 minutes to obtain molten metal, wherein the actual amount of NbB2 particles added is 0.5 wt.%.

[0116] S7. The molten metal obtained above is poured into a graphite mold and solidified to obtain a cast titanium alloy.

[0117] The average β grain size of the obtained titanium alloy was reduced to 560 μm, and a large number of micron-sized plate-like or needle-like TiB particles existed at the β grain boundaries, such as... Figure 9 As shown, its space group is Pnma. The main reason is that the reactant ratio is not suitable. The reaction produces micron-sized NbB2 particles, which decompose after the addition of Ti melt to form TiB whiskers with a Pnma structure.

[0118] Comparative Example 4

[0119] This titanium alloy refining agent contains NbB2 particles, wherein the molar ratio of Nb / B is 1:2, and the mass fraction of NbB2 particles is 15 wt.%. The preparation method of this titanium alloy refining agent includes the following steps:

[0120] S1. Preparation of powders for reaction compacts: Weigh out the appropriate mass proportions of aluminum powder, 5μm niobium powder, and 0.5μm boron powder according to the component ratio, and set aside.

[0121] S2. Mix the weighed aluminum powder, niobium powder, and boron powder to obtain reactant powder. Then, place the prepared reactant powder and zirconia grinding balls (5-22 mm in diameter) into a mixing tank for ball milling. Set the ball-to-powder ratio to 6:1, the ball milling speed to 60 r / min, and the ball milling time to 8 hours to obtain a mixture. Then, take out the mixture, wrap it in aluminum foil, place it in a cylindrical steel mold, and press it into a cylindrical blank with a diameter of 30 mm on a hydraulic testing machine.

[0122] S3. Wrap the compact with graphite paper and place it in the graphite mold used for in-situ sintering reaction; turn on the power of the hot pressing sintering furnace, evacuate to below 10 Pa, set the heating rate to 30 K / min, when the furnace temperature is 1223 K, hold for 20 min, then air cool to room temperature, take out the sample, and you can get the nucleating agent precursor containing NbB2; the average particle size of NbB2 particles is 0.3 micrometers.

[0123] S4. Place the pre-weighed titanium alloy in a water-cooled copper crucible and put it into a vacuum induction melting furnace, and heat it to 1973K. The composition of the titanium alloy is: Ti 90wt.%, Al 6wt.%, V 4wt.%.

[0124] S5. After the titanium alloy is completely melted, keep it at that temperature for 10 minutes to obtain the alloy liquid.

[0125] S6. Add the titanium alloy refining agent prepared above to the above molten metal and perform induction stirring for 3 minutes to obtain molten metal, wherein the actual amount of NbB2 particles added is 1.5 wt.%.

[0126] S7. The molten metal obtained above is poured into a graphite mold and solidified to obtain a cast titanium alloy.

[0127] The average β grain size of the titanium alloy decreased to approximately 200 μm, with a large number of micron-sized plate-like or needle-like TiB particles at the β grain boundaries, with space group Pnma. This is mainly due to the excessive addition of submicron NbB2 particles, which generate TiB whiskers at the grain boundaries.

[0128] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0129] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A titanium alloy refining agent, characterized in that, The titanium alloy refining agent is an intermediate alloy containing submicron or nano-sized boride particles; adding the titanium alloy refining agent to the titanium alloy can generate endogenous Bf-TiB particles; the crystal structure of the Bf-TiB particles is orthorhombic, with space group Cmcm and lattice parameters a=3.23±0.05 Å, b=8.48±0.05 Å, c=3.03±0.05 Å; the metallic element in the boride particles is one or more of V, Nb, Ta, Cr, and Mo.

2. A method for preparing the titanium alloy refining agent according to claim 1, characterized in that, include: The diluent, boron source powder, and metal powder are mixed evenly and then pressed into a compact; the metal powder can form a boride with a space group of Cmcm with boron. The pressed blank is sintered under vacuum or inert atmosphere at a temperature of 750℃~1000℃ to obtain a titanium alloy refining agent.

3. The method for preparing the titanium alloy refining agent as described in claim 2, characterized in that, The diluent accounts for 50-90% of the total mass of the mixture, and the molar ratio of boron to metal powder is 1.0-2.

5.

4. The method for preparing the titanium alloy refining agent as described in claim 2, characterized in that, The metal powder is one or more of niobium powder, vanadium powder, tantalum powder, chromium powder, and molybdenum powder, or an alloy powder.

5. The method for preparing the titanium alloy refining agent as described in claim 2, characterized in that, The boron source powder has a particle size of less than 1 μm; the metal powder has a particle size of less than 10 μm.

6. A method for refining titanium alloys, characterized in that, include: Titanium alloy raw materials are melted to obtain titanium alloy liquid; The titanium alloy refining agent as described in claim 1 is added to the titanium alloy molten metal and mixed uniformly to obtain a molten metal; the mass of the boride particles in the added titanium alloy refining agent is not greater than 1% of the total mass of the molten metal. The molten metal is cast to obtain a refined titanium alloy. The refined titanium alloy eliminates the Widmanstätten structure at grain boundaries and the basketweave structure within the grains, forming a uniform α-Ti layered cluster structure, with Bf-TiB nucleation particles dispersed and no grain boundary TiB whiskers generated.

7. A titanium alloy, characterized in that, The titanium alloy is obtained by refining the titanium alloy according to claim 6.

8. The titanium alloy according to claim 7, characterized in that, The titanium alloy has an average grain size of 188~593μm and an average size of 20~40μm for the α-Ti layered bundle structure.

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