Fine grain heterogeneous titanium alloy material with composite strengthening effect and preparation method

Abstract

The invention discloses a fine grain heterogeneous titanium alloy material with a composite strengthening effect and a preparation method, and belongs to the field of high-toughness titanium-based composites.The preparation method comprises the steps that a prepared raw material added with large-particle LaB6 is smelted into a cast ingot through vacuum induction smelting; the cast ingot is subjected to hot rolling after being homogenized, and a target titanium alloy plate is obtained; according to the obtained titanium-based alloy, under the condition that plasticity is not sacrificed, the longitudinal tensile yield strength is improved to 870 MPa, the tensile strength is improved to 1050 MPa, and the ductility can reach 24%; the transverse tensile yield strength is equivalent to the tensile strength. According to the method, smelting and thermal machining are cooperatively controlled, LaB6 particles of 1-5 mm are directly introduced into the titanium-based alloy in a smelting mode to serve as a reinforcing phase raw material, so that TiB whiskers and La2O3 particles are generated in situ in the smelting process of LaB6 to refine crystal grains, a heterogeneous structure is formed through thermal machining, the good plasticity of the titanium alloy is kept, and meanwhile the strength of the titanium alloy is improved. And the yield strength and the tensile strength are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of high-strength and high-toughness titanium-based composite materials, and in particular to a fine-grained heterogeneous titanium alloy material with composite strengthening effect and its preparation method. Background Technology

[0002] Titanium and titanium alloys have become key structural materials for high-end equipment in aerospace, marine engineering and biomedicine due to their high specific strength, excellent corrosion resistance and good biocompatibility.

[0003] Currently, using lanthanum hexaboride as a reinforcing phase precursor has become a research hotspot. After decomposition in titanium melt, LaB6 can generate TiB whiskers and La2O3 particles in situ, achieving a synergistic effect of grain boundary pinning and particle reinforcement. Existing technologies, such as Chinese invention patent publication number CN120330522A, disclose a method for preparing nano-lanthanum hexaboride-reinforced titanium-based composite materials. This technology involves ball milling LaB6 and titanium powder, followed by hot pressing sintering and hot rolling processes to prepare the composite material.

[0004] The existing methods have significant limitations: Currently, powder metallurgy routes, such as hot pressing and sintering, typically require long-term ball milling and other pretreatment processes to achieve uniform and refined raw materials in the preparation of composite materials, in order to avoid the segregation and floating of reinforcing phase (such as lanthanum hexaboride, LaB6) particles. This process not only significantly increases the complexity of the process and production costs, but also restricts its applicability in the large-scale production of large structural components. In contrast, traditional metallurgical routes, represented by melting combined with thermomechanical processing (such as hot rolling and forging), are more suitable for the industrial production of large titanium alloy structural components due to their inherent cost advantages and forming capabilities. However, for lanthanum hexaboride-reinforced titanium-based composite systems, how to achieve uniform distribution of the reinforcing phase while precisely controlling the matrix microstructure (such as obtaining fine grains or heterogeneous structures) through the synergistic control of melting and thermomechanical processing, thereby achieving a synergistic improvement in the strength and toughness of the material, has not yet been disclosed as a complete, efficient, and industrially feasible process solution. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a fine-grained heterogeneous titanium alloy material with composite strengthening effect and its preparation method. By synergistically controlling the melting parameters and subsequent thermomechanical processing, large-size (1-5mm) LaB6 particles are directly introduced into the titanium-based alloy Ti80 as a reinforcing phase material by melting, replacing the fine powder with strict particle size distribution accuracy requirements in the traditional process. During the melting process, LaB6 generates TiB short rod-shaped whiskers and La2O3 oxygen-rich particles in situ, forming a composite strengthening effect. While maintaining the good plasticity of the titanium alloy, its yield strength and tensile strength are significantly improved.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A fine-grained heterogeneous titanium alloy material with composite strengthening effect has the following chemical composition by mass percentage: Al: 6wt%, Nb: 3wt%, Zr: 2wt%, Mo: 1wt%, LaB6: 0.5wt%-2wt%, with the balance being Ti and unavoidable impurities. Mechanical property tests show that the yield strength of this fine-grained heterogeneous titanium alloy material with composite strengthening effect is 870MPa-1150MPa, the tensile strength is 1025MPa-1250MPa, and the elongation is 8.3%-24%.

[0007] A method for preparing a fine-grained heterogeneous titanium alloy material with a composite strengthening effect includes the following steps: Step 1: Prepare an alloy raw material consisting of Ti-6Al-3Nb-2Zr-1Mo-xLaB6; the added LaB6 particles have a size of 1mm-5mm and a purity ≥99.9%. Step 2: Place the raw materials prepared in Step 1 into the vacuum melting furnace chamber, place zirconium blocks in the chamber, maintain vacuum, and pass an electric arc to melt the raw material particles into ingot blocks. Turn the ingot blocks over and add magnetic stirring to mix the raw materials evenly. Turn the ingot blocks over multiple times until there are no particle protrusions on the melting surface of the ingot blocks, so as to promote the in-situ reaction of lanthanum hexaboride to generate TiB whiskers and La2O3 particles as dual reinforcing phases. After rapid cooling, a fine-grained ingot containing a large number of non-equilibrium metastable phases and nano phases is obtained. Step 3: Place the fine-grained ingot obtained in Step 2 into a tube furnace for composition homogenization treatment; Step 4: The fine-grained ingot after the composition homogenization treatment in Step 3 is first rolled in the single-phase region to obtain the first plate. Then, the first plate is rolled and deformed in the two-phase region and water-cooled. Fine-grained structure and heterogeneous structure are constructed simultaneously in the matrix to obtain a fine-grained heterogeneous titanium alloy material with composite strengthening effect.

[0008] A further improvement to the technical solution of the present invention is that, in step 2, the vacuum in the vacuum melting furnace chamber is maintained at 10... -3 Pa; the arc current is 2A; the magnetic stirring current is 5A; the number of times to flip is 5-8.

[0009] A further improvement of the technical solution of the present invention is that: in step 3, the composition homogenization treatment involves placing the button alloy ingot into a tube furnace and heating it to 1050℃-1150℃ at a heating rate of 10℃ / min; holding it at that temperature for 1.5h-2.5h; and then water cooling to obtain a fine-grained ingot with uniformly diffused composition.

[0010] A further improvement of the technical solution of the present invention is that: in step 4, when the ingot is initially rolled in the single-phase region, the rolling temperature is 100℃-150℃ above the phase transformation point of the Ti-6Al-3Nb-2Zr-1Mo-xLaB6 alloy material, and the rolling temperature is controlled at 1040℃-1060℃.

[0011] A further improvement of the technical solution of the present invention is that: in step 4, when the ingot is initially rolled in the single-phase region, the button ingot is first placed in a muffle furnace and kept warm for 25-35 minutes, the number of rolling cycles is 15-20, and the rolling deformation is 45%-50% of the thickness before deformation.

[0012] A further improvement of the technical solution of the present invention is that: in step 4, when the first plate is rolled in the two-phase region, the rolling temperature is 50℃-100℃ below the phase transformation point of the Ti-6Al-3Nb-2Zr-1Mo-xLaB6 alloy material, and the rolling temperature is controlled at 940℃-960℃.

[0013] A further improvement of the technical solution of the present invention is that: in step 4, when rolling the first plate in the two-phase region, the first plate is first placed in a muffle furnace and kept warm for 25-35 minutes, the rolling is performed 8-10 times, and the rolling deformation is 65%-70% of the thickness of the first plate.

[0014] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: 1. This invention, through synergistic coupling control of melting parameters and thermomechanical processing, directly introduces large-sized (1-5mm) lanthanum hexaboride (LaB6) particles as a reinforcing phase into the titanium-based alloy Ti80 via melting, replacing the fine powder with stringent particle size and distribution precision requirements in traditional processes (hot pressing and sintering). This method not only significantly reduces the difficulty and cost of raw material pretreatment but also effectively avoids the segregation and floating problems easily caused by powder, thus achieving a more uniform distribution of the reinforcing phase in the composite material. Through this process, LaB6 generates TiB short rod-shaped whiskers and La2O3 oxygen-rich particles in situ during melting, forming a composite strengthening effect that significantly improves the yield strength and tensile strength of the titanium alloy while maintaining its good plasticity.

[0015] 2. In this invention, the lanthanum hexaboride particles added generate fine TiB whiskers and nano-La2O3 particles in situ by controlling the melting parameters. The TiB whiskers promote heterogeneous nucleation, effectively refining the matrix grains; simultaneously, the La2O3 particles exert a significant pinning effect on grain boundaries. The combination of whiskers and nanoparticles significantly refines the titanium alloy grains, providing a grain-refining strengthening mechanism. This greatly improves the overall performance of the material, and the optimal range of LaB6 addition composition has been determined through optimization.

[0016] 3. This invention provides a complete process solution from melting to forming, applicable to titanium-based composite materials using lanthanum hexaboride as raw material. The core of this process lies in obtaining TiB whiskers and La2O3 particles through a controlled in-situ reaction, and then using subsequent thermomechanical processing in synergy to stably achieve the fine graining and heterogeneous microstructure of the titanium alloy, thereby ensuring efficient and reliable improvement of material properties through a multi-level strengthening mechanism.

[0017] 4. The preparation method provided by this invention has strong process compatibility, does not require complex or expensive special equipment, has a clear technology transfer path and short process, and has excellent potential for large-scale industrial production and cost-effectiveness. It can be widely used in high-end industrial manufacturing fields such as aerospace structural parts and engine blades.

[0018] 5. The fine-grained heterogeneous titanium alloy material with composite strengthening effect prepared by this invention has comprehensive performance that reaches or even surpasses the level of traditional high-precision powder processing, and the process is simpler and the production efficiency is higher, making it suitable for large-scale industrial production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 The image shows the metallographic microstructure of the fine-grained heterogeneous titanium alloy material with composite strengthening effect prepared in Example 2 of this invention. Among them, (a) and (b) are metallographic images of titanium alloy containing 0.5wt%LaB6 at a 50µm scale, and (c) and (d) are metallographic images of titanium alloy containing 0.5wt%LaB6 at a 20µm scale. Figure 2 The image shows the metallographic microstructure of the fine-grained heterogeneous titanium alloy material with composite strengthening effect prepared in Example 3 of this invention. Among them, (a) and (b) are metallographic images of titanium alloy containing 1wt%LaB6 at a scale of 50µm, and (c) and (d) are metallographic images of titanium alloy containing 1wt%LaB6 at a scale of 20µm. Figure 3 The image shows the metallographic microstructure of the fine-grained heterogeneous titanium alloy material with composite strengthening effect prepared in Example 4 of this invention. Among them, (a) and (b) are metallographic images of titanium alloy materials containing 2wt% LaB6 at a scale of 50µm, and (c) and (d) are metallographic images of titanium alloy materials containing 2wt% LaB6 at a scale of 20µm. Figure 4 The image shows the metallographic microstructure of the fine-grained heterogeneous titanium alloy material with composite strengthening effect prepared in Comparative Example 1 of this invention. Among them, (a) and (b) are metallographic images of titanium alloy materials without LaB6 at a scale of 50µm, and (c) and (d) are metallographic images of titanium alloy materials without LaB6 at a scale of 20µm. Figure 5 Comparison of longitudinal tensile curves of Ti-6Al-3Nb-2Zr-1Mo prepared in Comparative Example 1, Ti-6Al-3Nb-2Zr-1Mo-0.5LaB6 prepared in Example 2, Ti-6Al-3Nb-2Zr-1Mo-1LaB6 prepared in Example 3, and Ti-6Al-3Nb-2Zr-1Mo-2LaB6 prepared in Example 4 in this invention; Figure 6 The image shows a comparison of the transverse tensile curves of Ti-6Al-3Nb-2Zr-1Mo prepared in Comparative Example 1, Ti-6Al-3Nb-2Zr-1Mo-0.5LaB6 prepared in Example 2, Ti-6Al-3Nb-2Zr-1Mo-1LaB6 prepared in Example 3, and Ti-6Al-3Nb-2Zr-1Mo-2LaB6 prepared in Example 4. Detailed Implementation

[0020] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: In the following examples, the weight of the melted button ingots is 80g. The titanium-based alloy consists of titanium (Ti), aluminum (Al), niobium (Nb), zirconium (Zr), and molybdenum (Mo) particles with a purity ≥99.99%. The lanthanum hexaboride particles have a size of 1mm-5mm and a purity ≥99.9%. Example

[0022] A method for preparing a fine-grained heterogeneous titanium alloy material with a composite strengthening effect, wherein the mass ratio of the composition is Ti-6Al-3Nb-2Zr-1Mo-0.1LaB6, the preparation method includes the following steps: Step 1: Preparation of the titanium-based alloy matrix and LaB6 particles: The Ti, Al, Nb, Zr, and Mo particles used were ultrasonically cleaned in anhydrous ethanol for 20 minutes, followed by acid washing. After cleaning and drying, the following proportions were prepared: Al: 4.8006 g, Nb: 2.4002 g, Zr: 1.6001 g, Mo: 0.8002 g, LaB6: 0.0800 g, and the remainder was Ti: 70.3189 g. The raw materials were obtained after the proportions were prepared.

[0023] Step 2, Melting: Place the raw materials into the vacuum melting furnace chamber, and simultaneously place Zr blocks inside the chamber to prevent the influence of oxygen during the melting process. Maintain a vacuum of 10°C. -3 A 2A electric arc is applied to melt the raw material particles into an ingot. The ingot is then turned over and a magnetic stirrer (5A) is used to mix the raw materials evenly. This process is repeated 5-8 times until there are no protruding particles on the molten surface. After cooling, a silver-white button-shaped ingot is obtained. The dimensions of the silver-white button-shaped ingot are: diameter 45.89mm and thickness 13.45mm.

[0024] Step 3, homogenization of composition: The ingot block obtained in step 2 is placed into a tube furnace. After the tube furnace is cleaned, the temperature is increased to 1100℃ at a rate of 10℃ / min. The temperature is held for 2 hours to allow the components to fully diffuse. Water cooling is then performed to obtain a button ingot with homogeneous composition.

[0025] Step 4, Hot rolling: The muffle furnace is heated at a rate of 10℃ / min and kept at 1050℃. The button ingot is placed in the muffle furnace and held for 30 minutes. Then, it is rolled at a rate of 0.4mm each time by the hot rolling mill. After each rolling, it is held at 1050℃ for 1 minute. After the plate thickness is rolled to 7mm, it is water cooled.

[0026] The muffle furnace is kept at 950℃. The plate after the first rolling step is placed into the muffle furnace and held for 30 minutes. Then, it is rolled at a rate of 0.4 mm per roll in the hot rolling mill. After each roll, it is held at 950℃ for 1 minute. The plate is then water-cooled after the thickness is rolled to 2 mm.

[0027] The titanium alloy material containing 0.1 wt% LaB6 prepared by the above steps was wire-cut, ground and polished, and then tested for its mechanical properties using a universal testing machine. Its yield strength was 800 MPa, tensile strength was 950 MPa, and elongation was 24%. Example

[0028] A method for preparing a fine-grained heterogeneous titanium alloy material with a composite strengthening effect, wherein the mass ratio of the composition is Ti-6Al-3Nb-2Zr-1Mo-0.5LaB6, the preparation method includes the following steps: Step 1: Preparation of the titanium-based alloy matrix and LaB6 particles: The Ti, Al, Nb, Zr, and Mo particles used were ultrasonically cleaned in anhydrous ethanol for 20 minutes, followed by acid washing. After cleaning and drying, the following proportions were prepared: Al: 4.8004 g, Nb: 2.4005 g, Zr: 1.6004 g, Mo: 0.8002 g, LaB6: 0.4001 g, and the remainder being Ti: 69.1984 g. The raw materials were obtained after the proportions were prepared.

[0029] Step 2, Melting: Place the raw materials into the vacuum melting furnace chamber, and simultaneously place zirconium blocks inside the chamber to prevent the influence of oxygen during the melting process. Evacuate to 10... -3 A 2A electric arc is applied to melt the raw material particles into an ingot. The ingot is then turned over and a magnetic stirrer (5A) is used to mix the raw materials evenly. This process is repeated 5-8 times until there are no protruding particles on the molten surface. After cooling, a silver-white button-shaped ingot is obtained. The dimensions of the silver-white button-shaped ingot are: diameter 46.77mm and thickness 13.44mm.

[0030] Step 3, homogenization of composition: The ingot block obtained in step 2 is placed into a tube furnace. After three gas washings in the tube furnace, the temperature is increased to 1100℃ at a rate of 10℃ / min. The temperature is held for 2 hours to allow the components to fully diffuse. Water cooling is then performed to obtain a button ingot with homogeneous composition.

[0031] Step 4, Hot rolling: The muffle furnace is heated at a rate of 10℃ / min and kept at 1050℃. The button ingot is placed in the muffle furnace and held for 30 minutes. Then, it is rolled at a rate of 0.4mm each time by the hot rolling mill. After each rolling, it is held at 1050℃ for 1 minute. After the plate thickness is rolled to 7mm, it is water cooled.

[0032] The muffle furnace is kept at 950℃. The plate after the first rolling step is placed in the muffle furnace and kept at 30 minutes. Then, it is rolled at a rate of 0.4 mm per roll in the hot rolling mill. After each roll, it is kept at 950℃ for 1 minute. The plate is rolled to a thickness of 2 mm and then water-cooled.

[0033] The microstructure of the titanium alloy material containing 0.5wt% LaB6 prepared by the above steps after wire cutting, polishing, and etching is as follows: Figure 1 As shown, Figure 1 Images (a) and (b) are metallographic images of a titanium alloy containing 0.5 wt% LaB6 at a 50 µm scale, and images (c) and (d) are metallographic images of a titanium alloy containing 0.5 wt% LaB6 at a 20 µm scale. Figure 1It is evident that titanium alloys containing 0.5 wt% LaB6 exhibit finer and more uniform grains compared to titanium alloys without added LaB6. Equiaxed and lath-like α phases are evenly distributed, forming an heterogeneous microstructure of varying sizes. The mechanical properties of the prepared tensile samples were determined using a universal testing machine. The longitudinal tensile yield strength was 870 MPa, the tensile strength was 1025 MPa, and the elongation was 24%. The transverse tensile yield strength and tensile strength were comparable to those in the longitudinal tensile test. Example

[0034] A method for preparing a fine-grained heterogeneous titanium alloy material with a composite strengthening effect, wherein the mass ratio of the composition is Ti-6Al-3Nb-2Zr-1Mo-1LaB6, the preparation method includes the following steps: Step 1: Preparation of the titanium-based alloy matrix and LaB6 particles: The Ti, Al, Nb, Zr, and Mo particles used were ultrasonically cleaned in anhydrous ethanol for 20 minutes, followed by acid washing. After cleaning and drying, the following proportions were prepared: Al: 4.8003g, Nb: 2.4002g, Zr: 1.6002g, Mo: 0.8001g, LaB6: 0.8001g, and the remainder was Ti: 67.9991g. The raw materials were obtained after the proportions were prepared.

[0035] Step 2, Melting: Place the raw materials into the vacuum melting furnace chamber, and simultaneously place zirconium blocks inside the chamber to prevent the influence of oxygen during the melting process. Maintain the vacuum at 10°C. -3 A 2A electric arc is applied to melt the raw material particles into an ingot. The ingot is then turned over and a magnetic stirrer (5A) is used to mix the raw materials evenly. This process is repeated 5-8 times until there are no protruding particles on the molten surface. After cooling, a silver-white button-shaped ingot is obtained. The dimensions of the silver-white button-shaped ingot are: diameter 45.68mm and thickness 13.89mm.

[0036] Step 3, homogenization of composition: The ingot block obtained in step 2 is placed into a tube furnace. After the tube furnace is cleaned, the temperature is increased to 1100℃ at a rate of 10℃ / min. The temperature is held for 2 hours to allow the components to fully diffuse. Water cooling is then performed to obtain a button ingot with homogeneous composition.

[0037] Step 4, Hot rolling: The muffle furnace is heated at a rate of 10℃ / min and kept at 1050℃. The button ingot is placed in the muffle furnace and held for 30 minutes. Then, it is rolled at a rate of 0.4mm each time by the hot rolling mill. After each rolling, it is held at 1050℃ for 1 minute. After the plate thickness is rolled to 7mm, it is water cooled.

[0038] The muffle furnace is kept at 950℃. The plate after the first rolling step is placed in the muffle furnace and kept at 30 minutes. Then, it is rolled at a rate of 0.4 mm per roll in the hot rolling mill. After each roll, it is kept at 950℃ for 1 minute. The plate is rolled to a thickness of 2 mm and then water-cooled.

[0039] The microstructure of the titanium alloy material containing 1wt% LaB6 prepared by the above steps after wire cutting, polishing, and etching is as follows: Figure 2 As shown, Figure 2 Metallographic images (a) and (b) are of titanium alloy containing 1 wt% LaB6 at a 50 µm scale, while (c) and (d) are of titanium alloy containing 1 wt% LaB6 at a 20 µm scale. Figure 2 It is evident that titanium alloys containing 1 wt% LaB6 exhibit some large lath-like α phases, but the distribution of equiaxed α phases and lath-like α phases remains relatively uniform. The mechanical properties of the prepared tensile samples were determined using a universal testing machine. The longitudinal tensile yield strength was 920 MPa, the tensile strength was 1125 MPa, and the elongation was 8.3%. The transverse tensile strength and yield strength were comparable to those in the longitudinal tensile test. Example

[0040] A method for preparing a fine-grained heterogeneous titanium alloy material with a composite strengthening effect, wherein the mass ratio of the composition is Ti-6Al-3Nb-2Zr-1Mo-2LaB6, the preparation method includes the following steps: Step 1: Preparation of the titanium-based alloy matrix and LaB6 particles: The Ti, Al, Nb, Zr, and Mo particles used were ultrasonically cleaned in anhydrous ethanol for 20 minutes, followed by acid washing. After cleaning and drying, the following proportions were prepared: Al: 4.8002g, Nb: 2.4001g, Zr: 1.6000g, Mo: 0.8001g, LaB6: 1.6001g, and the remainder was Ti: 68.7995g. The raw materials were obtained after the proportions were prepared.

[0041] Step 2, Melting: Place the raw materials into the vacuum melting furnace chamber, and simultaneously place zirconium blocks inside the chamber to prevent the influence of oxygen during the melting process. Maintain the vacuum at 10°C. -3 A 2A electric arc is applied to melt the raw material particles into an ingot. The ingot is then turned over and a magnetic stirrer (5A) is used to mix the raw materials evenly. This process is repeated 5-8 times until there are no protruding particles on the molten surface. After cooling, a silver-white button-shaped ingot is obtained. The dimensions of the silver-white button-shaped ingot are: diameter 46.34mm and thickness 13.61mm.

[0042] Step 3, homogenization of composition: The ingot block obtained in step 2 is placed into a tube furnace. After the tube furnace is cleaned, the temperature is increased to 1100℃ at a rate of 10℃ / min. The temperature is held for 2 hours to allow the components to fully diffuse. Water cooling is then performed to obtain a button ingot with homogeneous composition.

[0043] Step 4, Hot rolling: The muffle furnace is heated at a rate of 10℃ / min and kept at 1050℃. The button ingot is placed in the muffle furnace and held for 30 minutes. Then, it is rolled at a rate of 0.4mm each time by the hot rolling mill. After each rolling, it is held at 1050℃ for 1 minute. After the plate thickness is rolled to 7mm, it is water cooled.

[0044] The muffle furnace is kept at 950℃. The plate after the first rolling step is placed in the muffle furnace and kept at 30 minutes. Then, it is rolled at a rate of 0.4 mm per roll in the hot rolling mill. After each roll, it is kept at 950℃ for 1 minute. The plate is rolled to a thickness of 2 mm and then water-cooled.

[0045] The microstructure of the titanium alloy sheet containing 2wt% LaB6 prepared by the above steps after wire cutting, polishing, and etching is as follows: Figure 3 As shown, Figure 3 In the image, (a) and (b) are metallographic images of titanium alloy containing 2wt% LaB6 at a 50µm scale, and (c) and (d) are metallographic images of titanium alloy containing 2wt% LaB6 at a 20µm scale. Figure 3 It is evident that in titanium alloys containing 2wt% LaB6, the α-phase size further increases, and the grain size also becomes larger, but the microstructure remains relatively uniform. The mechanical properties of the prepared tensile samples were determined using a universal testing machine. The longitudinal tensile strength of Ti-2LaB6 was 1150 MPa, the tensile strength was 1250 MPa, and the elongation was 8.3%. The transverse tensile strength and yield strength were comparable to those in the longitudinal tensile test. Example

[0046] A method for preparing a fine-grained heterogeneous titanium alloy material with a composite strengthening effect, wherein the mass ratio of the composition is Ti-6Al-3Nb-2Zr-1Mo-5LaB6, the preparation method includes the following steps: Step 1: Preparation of the titanium-based alloy matrix and lanthanum hexaboride particles: The Ti, Al, Nb, Zr, and Mo particles used were ultrasonically cleaned in anhydrous ethanol for 20 minutes, followed by acid washing. After cleaning and drying, the following proportions were prepared: Al: 4.8002 g, Nb: 2.4001 g, Zr: 1.6000 g, Mo: 0.8001 g, LaB6: 4.0001 g, and the remainder was Ti: 66.3986 g. The raw materials were obtained after the proportions were prepared.

[0047] Step 2, Melting: Place the raw materials into the vacuum melting furnace chamber, and simultaneously place zirconium blocks inside the chamber to prevent the influence of oxygen during the melting process. Maintain the vacuum at 10°C. -3A 2A electric arc is applied to melt the raw material particles into an ingot. The ingot is then turned over and a magnetic stirrer (5A) is used to mix the raw materials evenly. This process is repeated 5-8 times until there are no protruding particles on the molten surface. After cooling, a silver-white button-shaped ingot is obtained. The dimensions of the silver-white button-shaped ingot are: diameter 45.18mm and thickness 15.62mm.

[0048] Step 3, homogenization of composition: The ingot block obtained in step 2 is placed into a tube furnace. After the tube furnace is cleaned, the temperature is increased to 1100℃ at a rate of 10℃ / min. The temperature is held for 2 hours to allow the components to fully diffuse. Water cooling is then performed to obtain a button ingot with homogeneous composition.

[0049] Step 4, Hot rolling: The muffle furnace is heated at a rate of 10℃ / min and kept at 1050℃. The button ingot is placed in the muffle furnace and held for 30 minutes. Then, it is rolled at a rate of 0.4mm each time by the hot rolling mill. After each rolling, it is held at 1050℃ for 1 minute. After the plate thickness is rolled to 7mm, it is water cooled.

[0050] The muffle furnace is kept at 950℃. The plate after the first rolling step is placed in the muffle furnace and kept at 30 minutes. Then, it is rolled at a rate of 0.4 mm per roll in the hot rolling mill. After each roll, it is kept at 950℃ for 1 minute. The plate is rolled to a thickness of 2 mm and then water-cooled.

[0051] The titanium alloy sheet containing 5wt% LaB6 prepared by the above steps was wire-cut, polished, and then tested for mechanical properties in a universal testing machine. Its longitudinal tensile yield strength was 1050 MPa, tensile strength was 1200 MPa, and elongation was 3.1%. Its transverse tensile yield strength and tensile strength were comparable to those in the longitudinal tensile test.

[0052] In summary, the five LaB6-containing titanium-based alloys were prepared using the same process parameters. Under these conditions, the mechanical properties of titanium alloys with different LaB6 contents were tested. The titanium alloy with 0.1 wt% LaB6 content did not show a significant improvement in mechanical properties compared to the titanium alloy without LaB6. The titanium-based alloy with 5 wt% LaB6 content suffered from a severe mismatch between strength and ductility, rendering it unusable. A comparison of the mechanical properties of titanium alloys with preferred LaB6 contents of 0.5 wt% (Example 2), 1 wt% (Example 3), and 2 wt% (Example 4) with those without LaB6 (Comparative Example 1) is provided. Figure 5 , Figure 6 As shown, Figure 5 This is a longitudinal stretch curve. Figure 6 This is a graph showing the horizontal stretching. (From...) Figure 5 and Figure 6It can be seen that the lanthanum hexaboride-reinforced titanium-based alloy material prepared by this invention can increase the longitudinal tensile yield strength to 870 MPa and the tensile strength to 1050 MPa without sacrificing plasticity, and the elongation can reach 24%. The transverse tensile yield strength is comparable to the tensile strength, and the yield strength is increased by 100 MPa and the tensile strength is increased by 115 MPa compared with the titanium-based alloy without the addition of lanthanum hexaboride particles.

[0053] Comparative Example 1 A titanium-based alloy, Ti-6Al-3Nb-2Zr-1Mo, which does not contain lanthanum hexaboride particles, is prepared as follows: S1. Preparation of titanium-based alloy matrix raw materials: The Ti, Al, Nb, Zr, and Mo particles used were ultrasonically cleaned in anhydrous ethanol for 20 min, followed by acid washing. After cleaning and drying, the following proportions were prepared: Al: 4.8002 g, Nb: 2.4004 g, Zr: 1.6001 g, Mo: 0.8000 g, with the remainder being Ti: 70.3993 g. The Ti80 raw material was obtained after the proportions were prepared.

[0054] S2. Melting: Place the raw materials into the vacuum melting furnace chamber, and simultaneously place zirconium blocks inside the chamber to prevent the influence of oxygen during the melting process. Evacuate to 10... -3 Pa, an electric arc (2A) is passed through to melt the raw material particles into an ingot block. The ingot block is turned over and a magnetic stirrer (5A) is added to mix the raw material evenly. The ingot block is turned over 5-8 times until there are no particle protrusions on the molten surface. After cooling, a Ti80 silver-white button-shaped ingot block is obtained.

[0055] S3. Composition homogenization: The ingot block obtained in step S2 is placed in a tube furnace. After the tube furnace is cleaned, the temperature is increased to 1100℃ at a rate of 10℃ / min. The temperature is held for 2 hours to allow the components to fully diffuse. The ingot is then water-cooled to obtain a Ti80 button ingot with uniform composition.

[0056] S4. Hot rolling: The muffle furnace is heated to 1050℃ at a heating rate of 10℃ / min. The button ingot is placed in the muffle furnace and held for 30 minutes. Then, it is rolled at a rate of 0.4mm each time by the hot rolling mill. After each rolling, it is held at 1050℃ for 1 minute. After the plate thickness is rolled to 7mm, it is water cooled.

[0057] The muffle furnace is kept at 950℃. The plate after the first rolling step is placed in the muffle furnace and kept at 30 minutes. Then, it is rolled at a rate of 0.4 mm per roll in the hot rolling mill. After each roll, it is kept at 950℃ for 1 minute. The plate is rolled to a thickness of 2 mm and then water-cooled.

[0058] The microstructure of the LaB6-free titanium alloy material prepared through the above steps, after wire cutting, polishing, and etching, is as follows: Figure 4 As shown, Figure 4In the image, (a) and (b) are metallographic images of LaB6-free titanium alloys at a 50µm scale, and (c) and (d) are metallographic images of LaB6-free titanium alloys at a 20µm scale. Figure 4 It is evident that the LaB6-free titanium alloy material exhibits fine grains and a uniform microstructure. The LaB6-free titanium alloy material prepared through the above steps was wire-cut, ground, and polished before its mechanical properties were tested using a universal testing machine. The results showed a yield strength of 778 MPa, a tensile strength of 910 MPa, and an elongation of 25%.

[0059] In summary, this invention incorporates the rare earth element lanthanum hexaboride into a titanium-based alloy, obtaining a titanium alloy material with fine-grained heterogeneous strengthening through a complete and synergistic smelting and thermomechanical processing technology. Lanthanum hexaboride in-situ generates TiB and La2O3 in the matrix. TiB typically precipitates in the form of fine needle-like or rod-like morphologies. It exhibits good coherence with the titanium matrix and can serve as a heterogeneous nucleation site, effectively promoting the nucleation of the α-Ti phase during solidification, thereby significantly refining the grain size. The high-hardness, high-strength TiB fibers also act as a second-phase strengthening agent, improving the alloy's strength, stiffness, and wear resistance. Fine La2O3 particles can pin grain boundaries, inhibiting grain growth at high temperatures, thus achieving grain refinement. Furthermore, La can react with impurity elements (such as S and P) in the alloy, purifying the melt.

[0060] This invention selects melting as the means of adding LaB6 to titanium-based alloys, fundamentally solving the problems of macroscopic uniformity and large-scale production. In vacuum induction melting, electromagnetic induction generates a strong magnetic stirring effect; in vacuum consumable arc melting, the heating of the arc and the dripping of molten metal droplets also cause the molten pool to flow. This strong convection effectively breaks up the agglomeration of LaB6 particles and forces them to be transported to various parts of the melt, thereby greatly improving the macroscopic distribution uniformity of the reinforcing phase. A small current is specifically designed to be used during the melting process to better promote the in-situ decomposition of LaB6 without causing it to agglomerate. It is suitable for preparing large-size, near-net-shape billets.

[0061] This invention, through innovative process design, successfully solves the three major pain points in the preparation of LaB6 reinforced titanium matrix composites: difficulty in achieving uniformity, poor plasticity, and difficulty in large-scale production. It yields a novel high-performance titanium matrix composite material with uniform structure, both strength and toughness, excellent performance, and ease of industrial production, which has great engineering application value and market prospects.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fine-grained heterogeneous titanium alloy material with a composite strengthening effect, characterized in that, Its chemical composition by mass percentage is: Al: 6wt%, Nb: 3wt%, Zr: 2wt%, Mo: 1wt%, LaB6: 0.5wt%-2wt%, with the balance being Ti and unavoidable impurities. The fine-grained heterogeneous titanium alloy material with composite strengthening effect has a yield strength of 870MPa-1150MPa, a tensile strength of 1025MPa-1250MPa, and an elongation of 8.3%-24% after mechanical property testing.

2. A method for preparing a fine-grained heterogeneous titanium alloy material with composite strengthening effect as described in claim 1, characterized in that, Includes the following steps: Step 1: Prepare an alloy raw material consisting of Ti-6Al-3Nb-2Zr-1Mo-xLaB6; the added LaB6 particles have a size of 1mm-5mm and a purity ≥99.9%. Step 2: Place the raw materials prepared in Step 1 into the vacuum melting furnace chamber, place zirconium blocks in the chamber, maintain vacuum, and pass an electric arc to melt the raw material particles into ingot blocks. Turn the ingot blocks over and add magnetic stirring to mix the raw materials evenly. Turn the ingot blocks over multiple times until there are no particle protrusions on the melting surface of the ingot blocks, so as to promote the in-situ reaction of lanthanum hexaboride to generate TiB whiskers and La2O3 particles as dual reinforcing phases. After rapid cooling, a fine-grained ingot containing a large number of non-equilibrium metastable phases and nano phases is obtained. Step 3: Place the fine-grained ingot obtained in Step 2 into a tube furnace for composition homogenization treatment; Step 4: The fine-grained ingot after the composition homogenization treatment in Step 3 is first rolled in the single-phase region to obtain the first plate. Then, the first plate is rolled and deformed in the two-phase region and water-cooled. Fine-grained structure and heterogeneous structure are constructed simultaneously in the matrix to obtain a fine-grained heterogeneous titanium alloy material with composite strengthening effect.

3. The preparation method according to claim 2, characterized in that, In step 2, the vacuum inside the vacuum melting furnace chamber is maintained at 10. -3 Pa; the arc current is 2A; the magnetic stirring current is 5A; the number of times to flip is 5-8.

4. The preparation method according to claim 2, characterized in that, In step 3, the composition homogenization treatment involves placing the button alloy ingot into a tube furnace and heating it to 1050℃-1150℃ at a heating rate of 10℃ / min; holding it at that temperature for 1.5h-2.5h; and then water cooling to obtain a fine-grained ingot with uniformly diffused composition.

5. The preparation method according to claim 2, characterized in that, In step 4, when the ingot is initially rolled in the single-phase region, the rolling temperature is 100℃-150℃ above the phase transformation point of the Ti-6Al-3Nb-2Zr-1Mo-xLaB6 alloy material, and the rolling temperature is controlled at 1040℃-1060℃.

6. The preparation method according to claim 2, characterized in that, In step 4, when the ingot is initially rolled in the single-phase region, the button ingot is first placed in a muffle furnace and held for 25-35 minutes. The rolling is performed 15-20 times, and the rolling deformation is 45%-50% of the thickness before deformation.

7. The preparation method according to claim 2, characterized in that, In step 4, when the first plate is rolled in the two-phase region, the rolling temperature is 50℃-100℃ below the phase transformation point of the Ti-6Al-3Nb-2Zr-1Mo-xLaB6 alloy material, and the rolling temperature is controlled at 940℃-960℃.

8. The preparation method according to claim 2, characterized in that, In step 4, when rolling the first plate in the two-phase region, the first plate is first placed in a muffle furnace and held for 25-35 minutes, and the rolling is performed 8-10 times. The rolling deformation is 65%-70% of the thickness of the first plate.

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