A lightweight ultra-high-strength cast beta titanium alloy material and a preparation method thereof

Abstract

The application provides a light-weight super-high-strength cast beta titanium alloy material and a preparation method thereof, and belongs to the technical field of titanium alloy materials. Light-weight elements Al, Zr and V are added as alloy elements, the alloy composition is Ti 50%~71%, Al 7%~12.5%, V 11%~15% and Zr 11%~16% in terms of atomic ratio, and a uniform single-phase beta titanium alloy is prepared. Through the interaction between the alloy elements, the solid solubility in the titanium matrix is improved, the beta phase region is expanded, the target beta titanium alloy does not have brittle phases such as phase separation and intermetallic compounds, the solid solution strengthening effect is maximized, and the chemical ordering is promoted, so that the strength of the alloy is enhanced and the plasticity is improved. In addition, the application does not need complex thermal mechanical processing regulation and control such as forging, rolling or solid solution aging, and the high-strength and high-toughness matching of yield strength >=1000MPa and elongation after fracture >=12% can be realized in the as-cast state.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy materials technology, and in particular to a lightweight, ultra-high strength cast β-titanium alloy material and its preparation method. Background Technology

[0002] Titanium alloys, due to their high specific strength, excellent corrosion resistance, and biocompatibility, have irreplaceable application value in aerospace, marine engineering, biomedicine, and high-end consumer electronics. However, the extremely poor machinability and high forming difficulty of titanium alloys have long restricted their large-scale industrial application. The low thermal conductivity of titanium alloys causes heat to be highly concentrated in the cutting edge area during machining, exacerbating tool adhesion and wear; their high chemical reactivity also makes them prone to diffusion and chemical reactions with tool materials, resulting in a significant reduction in tool life and high unit machining costs. At the same time, the complex phase transformation behavior of titanium alloys causes them to exhibit strong thermo-mechanical coupling nonlinear dynamic characteristics of high temperature, high strain, and high strain rate during hot deformation, which places extremely high demands on the precise control of forming process parameters. Existing titanium alloy components usually require precise control of multiple forging, rolling, hot extrusion, and other thermomechanical processing steps to obtain ideal microstructure and mechanical properties, which not only results in a narrow process window and high difficulty in quality control, but also significantly prolongs the production cycle and increases manufacturing costs.

[0003] Currently, the research and development of high-performance titanium alloys mainly revolves around two major systems: α+β dual-phase alloys and metastable β alloys. A balance between strength and plasticity is sought through the synergistic control of heat treatment and hot deformation processes. However, the performance of these alloys is highly dependent on precise hot working process windows, requiring strict constraints on deformation temperature, strain rate, and subsequent solution treatment and aging parameters. Any deviation can lead to microstructure coarsening or the precipitation of harmful phases, significantly reducing overall mechanical properties. Meanwhile, cast titanium alloys often suffer from insufficient strength and toughness due to coarse grains and compositional segregation. The tensile strength of existing cast high-strength titanium alloys typically only reaches the 1000 MPa level, and even then, hot isostatic pressing or complex heat treatment is still required to achieve this level, highlighting the significant complexity of the process.

[0004] For cast β titanium alloys, how to obtain a uniform and stable β single-phase solid solution structure through composition optimization design, give full play to the solid solution strengthening effect, and achieve a synergistic match between ultra-high strength and good toughness directly in the as-cast state without the need for complex thermomechanical processing such as forging, rolling and solid solution aging, while taking into account the requirements for lightweight materials, has become a major technical challenge that urgently needs to be overcome in the field of titanium alloy materials. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a lightweight, ultra-high strength cast β-titanium alloy material and its preparation method, in order to solve the technical problems of insufficient mechanical properties of existing cast titanium alloys and the need to rely on complex thermomechanical processing such as forging, rolling or solution aging to obtain a high strength-toughness match. This invention enables the direct acquisition of β-single-phase titanium alloys with a yield strength ≥1000MPa and elongation after fracture ≥12% under casting conditions, meeting the requirements of near-net-shape integrated forming of large-size complex structural components in aerospace, deep-sea engineering and biomedical fields.

[0006] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a lightweight, ultra-high strength cast β-titanium alloy material, composed of Ti, Al, V, and Zr, with the atomic ratios being Ti 50%~71%, Al 7%~12.5%, V 11%~15%, and Zr 11%~16%; the alloy material is a β single-phase solid solution.

[0007] Preferably, the atomic ratio is 61%~71% Ti, 7%~11% Al, 11%~14% V, and 11%~16% Zr.

[0008] Preferably, the atomic ratio is 50%~61% Ti, 10%~12.5% ​​Al, 12.5%~15% V, and 12.5%~15% Zr.

[0009] On the other hand, the present invention also provides a method for preparing the above-mentioned lightweight ultra-high strength cast β-titanium alloy material, comprising the following steps: S1. Select Ti, Al, V and Zr single metal blocks with a purity of 99.99% as raw materials, weigh each raw material according to the preset atomic ratio, and obtain the weighed raw materials; S2. The weighed raw materials are thoroughly mixed, washed with alcohol, and dried to obtain clean and dry raw materials to be smelted; S3. The raw material to be melted is subjected to vacuum arc melting. After uniform melting, it is vacuum copper mold casting and cooled to form a titanium alloy ingot. S4. The titanium alloy ingot is cut and polished sequentially to obtain the lightweight ultra-high strength cast β titanium alloy material.

[0010] Preferably, in step S3, a gas washing operation is performed before the vacuum arc melting, and the number of gas washing operations is 2 to 5.

[0011] Preferably, the gas washing process involves a cycle of vacuuming, filling with argon gas, and then vacuuming again.

[0012] Preferably, in step S3, the vacuum arc melting is repeated at least 6 times.

[0013] Preferably, in step S3, the vacuum degree of the vacuum arc melting is not higher than 5 × 10⁻⁶. -4 Pa.

[0014] Compared with the prior art, the present invention discloses at least the following technical effects: (1) This invention effectively improves the solid solubility of alloying elements in titanium matrix and expands the β phase region through the synergistic effect of Ti, Al, V and Zr lightweight alloying elements, and prepares a β single-phase solid solution with uniform structure, no phase separation and no brittle phases such as intermetallic compounds. With the help of solid solution strengthening and Zr-Al short-range ordered chemical ordering effect, a high strength and high toughness matching of yield strength ≥1000MPa, elongation after fracture ≥12% and average hardness ≥330HV1 can be directly achieved in the as-cast state, thereby simultaneously improving the strength, toughness and structural stability of the alloy, and meeting the requirements of high-end application fields for material performance.

[0015] (2) The β titanium alloy prepared by the present invention can obtain excellent performance through conventional casting processes such as vacuum arc melting and vacuum copper mold casting. It does not require thermomechanical processing such as forging, rolling, hot extrusion and precision heat treatment such as solution aging. It completely gets rid of the limitations of complex process windows, greatly simplifies the production process, shortens the component manufacturing cycle, and reduces processing costs and hot processing scrap rate. It is suitable for the integrated near-net-shape forming requirements of large-size and complex-shaped titanium alloy components.

[0016] (3) The present invention adopts a lightweight element alloying design, which significantly improves the specific strength of the material while ensuring the ultra-high strength and toughness of the alloy. It has good weldability and multi-form adaptability, and can meet various preparation processes such as plastic forming, powder metallurgy, and additive manufacturing. It can be widely used in many fields such as aerospace, deep-sea engineering, biomedicine, and high-end manufacturing, and has outstanding economic effects and broad industrial application prospects. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for preparing a lightweight, ultra-high strength cast β-titanium alloy material according to the present invention; Figure 2 This is a SEM image of the β-titanium alloy material provided in Embodiment 1 of the present invention; Figure 3 The XRD pattern of the β-titanium alloy material provided in Embodiment 1 of the present invention; Figure 4The stress-strain curve of the β-titanium alloy material provided in Embodiment 1 of the present invention; Figure 5 This is a SEM image of the tensile fracture surface of the β-titanium alloy material provided in Embodiment 1 of the present invention. Detailed Implementation

[0019] 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, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown, this invention provides a method for preparing a lightweight, ultra-high strength cast β-titanium alloy material, comprising the following steps: S1. Select Ti, Al, V and Zr single metal blocks with a purity of 99.99% as raw materials, weigh each raw material according to the preset atomic ratio, and obtain the weighed raw materials.

[0022] S2. The weighed raw materials are thoroughly mixed, cleaned with alcohol, and dried to obtain clean and dry raw materials to be smelted.

[0023] S3. The raw material to be melted is subjected to vacuum arc melting. After uniform melting, it is vacuum copper mold casting and cooled to form a titanium alloy ingot.

[0024] S4. The titanium alloy ingot is cut and polished sequentially to obtain the lightweight ultra-high strength cast β titanium alloy material.

[0025] The aforementioned lightweight, ultra-high strength cast β-titanium alloy material is composed of Ti, Al, V, and Zr, with the following atomic ratios: Ti 50%~71%, Al 7%~12.5%, V 11%~15%, and Zr 11%~16%. More specifically, it includes, with the following atomic ratios: Ti 61%~71%, Al 7%~11%, V 11%~14%, and Zr 11%~16%. Additionally, it also includes, with the following atomic ratios: Ti 50%~61%, Al 10%~12.5%, V 12.5%~15%, and Zr 12.5%~15%.

[0026] Specifically, this invention combines three types of lightweight alloying elements—Al, V, and Zr—with a titanium matrix. Based on the lattice regulation effect of each element and the synergistic coupling mechanism between components, it achieves the construction of a full β-single-phase matrix at the microstructure level. Under the premise of avoiding the precipitation of brittle intermetallic compounds, it fully releases the solid solution strengthening potential, ultimately enabling the cast alloy to simultaneously achieve lightweight, ultra-high strength, and excellent plasticity.

[0027] Al, V, and Zr are all low-density, lightweight components. After being dissolved into the titanium lattice, they do not significantly increase the material's weight. They strengthen the matrix through lattice distortion while continuously optimizing the overall specific strength of the alloy. Al atoms incorporated into the titanium matrix enhance the interatomic bonding forces within the lattice, broadening the upper limit of solid solution accommodation for other alloying elements in the β-Ti lattice. This strengthens the matrix while preserving sufficient space for plastic deformation, preventing material embrittlement. V is a isomorphous β-stabilizing element with an atomic radius and lattice configuration highly compatible with the β-titanium matrix. It can achieve a wide and unlimited solid solution range in the β phase, continuously broadening the composition range of the stable β phase and suppressing the formation of brittle martensite induced by phase transformation during cooling. Zr can lower the critical transformation temperature of the β phase to low-temperature phase transformation and the martensite precipitation initiation temperature, thermodynamically suppressing the formation of the α'' metastable brittle phase, further expanding the composition range of the stable β phase, and improving the thermodynamic stability of the matrix β phase.

[0028] Meanwhile, the coexisting Al and Zr atoms within the matrix can coordinate and arrange themselves to form a Zr-Al short-range ordered microstructure within the alloy. This ordered structure effectively hinders dislocation slip movement during tensile deformation under external forces, enhancing the material's work hardening ability and further increasing the alloy's yield strength. Furthermore, these three elements each perform their respective functions and cooperate with each other, fully leveraging the synergistic effects of multiple solid solution processes. This ensures that the solidified alloy maintains a complete and homogeneous β-phase solid solution structure, free from component segregation, phase separation, and various harmful intermetallic brittle phases.

[0029] The above content will be further described below through specific implementation methods.

[0030] Example 1 Step 1: Using Ti, Al, V, and Zr single-metal blocks with a purity of 99.99% as raw materials, design the atomic ratio of β-titanium alloy as Ti 60 Al 10 V 15 Zr 15 Accurately weigh each metal raw material according to the atomic ratio, clean them separately with alcohol, and then dry them for later use.

[0031] Step 2: The process involves vacuum arc melting, followed by argon gas purging three times and evacuation to a vacuum level of 5 × 10⁻⁶. -4After backfilling with argon gas, Zr in the oxygen-absorbing station is melted first, followed by the melting of other alloy components. Electromagnetic stirring is activated during the melting process, and the melting is repeated six times to ensure thorough and uniform mixing of the elements. After melting, vacuum copper mold casting is performed, followed by rapid cooling to obtain a titanium alloy ingot.

[0032] The microstructure and phase structure of the obtained titanium alloy were characterized by microscopy. Figure 2 As shown, scanning electron microscopy (SEM) reveals that the alloy material has a uniform and defect-free microstructure; Figure 3 As shown, X-ray diffraction (XRD) results indicate a β-single-phase supersaturated solid solution with no intermetallic compounds. The stress-strain curve obtained from room temperature tensile testing is shown below. Figure 4 As shown, the yield strength is 1025 MPa, the ultimate tensile strength is 1032 MPa, and the elongation is 13.5%. Figure 5 As shown, the tensile fracture morphology of the titanium alloy material exhibits numerous dimples, indicating that the fracture mode is ductile fracture.

[0033] Example 2 Step 1: Using Ti, Al, V, and Zr single-metal blocks with a purity of 99.99% as raw materials, design the atomic ratio of β-titanium alloy as Ti 61 Al9V 14 Zr 16 Weigh each metal raw material according to the atomic ratio, clean it with alcohol, and then dry it for later use.

[0034] Step 2: The same vacuum arc melting process as in Example 1 is used for preparation, including: gas washing 3 times, and vacuuming to 5×10⁻⁶. -4 Pa first melts Zr, then melts other components, repeats the melting process 6 times under electromagnetic stirring, and finally casts the product.

[0035] The obtained titanium alloy was characterized by microstructure and phase structure. The results showed that the microstructure was uniform and defect-free, and XRD analysis revealed it to be a β-single-phase supersaturated solid solution with no intermetallic compounds. The mechanical property test results are shown in Table 1.

[0036] Example 3 Step 1: Using Ti, Al, V, and Zr single-metal blocks with a purity of 99.99% as raw materials, design the atomic ratio of β-titanium alloy as Ti 65 Al 11 V 11 Zr 13 Weigh each metal raw material according to the atomic ratio, clean it with alcohol, and then dry it for later use.

[0037] Step 2: The same vacuum arc melting process as in Example 1 is used for preparation.

[0038] The obtained titanium alloy was characterized by microstructure and phase structure. The results showed that the microstructure was uniform and defect-free, and XRD analysis revealed it to be a β-single-phase supersaturated solid solution with no intermetallic compounds. The mechanical property test results are shown in Table 1.

[0039] Comparative Example 1 Step 1: Using Ti, Al, V, and Zr single-metal blocks with a purity of 99.99% as raw materials, design the atomic ratio of the titanium alloy as Ti 53 Al 12 V 18 Zr 17 Weigh each metal raw material according to the atomic ratio, clean it with alcohol, and then dry it for later use.

[0040] Step 2: Melting and casting are carried out using the same vacuum arc melting process as in Example 1.

[0041] The obtained titanium alloy was characterized by microstructure and phase structure. The results showed that the microstructure was uniform and defect-free, and XRD analysis revealed it to be a β-single-phase supersaturated solid solution with no intermetallic compounds. The mechanical property test results are shown in Table 1.

[0042] Comparative Example 2 Step 1: Using Ti, Al, V, and Zr single-metal blocks with a purity of 99.99% as raw materials, design the atomic ratio of the titanium alloy as Ti 86 Al4V5Zr5. Weigh each metal raw material according to the atomic ratio, clean it with alcohol, and then dry it for later use.

[0043] Step 2: Melting and casting are carried out using the same vacuum arc melting process as in Example 1.

[0044] The obtained titanium alloy was characterized by its microstructure and phase structure. The results showed that the microstructure was uniform and defect-free, and XRD analysis revealed it to be an α+β dual-phase supersaturated solid solution with no intermetallic compounds. The mechanical property test results are shown in Table 1.

[0045] Comparative Example 3 Step 1: Using Ti, Al, V, and Zr single-metal blocks with a purity of 99.99% as raw materials, design the atomic ratio of the titanium alloy as Ti 91 Al3V2Zr3. Weigh out each metal raw material according to the atomic ratio, clean with alcohol, and dry for later use.

[0046] Step 2: Melting and casting are carried out using the same vacuum arc melting process as in Example 1.

[0047] The obtained titanium alloy was characterized by its microstructure and phase structure. The results showed that the microstructure was uniform and defect-free, and XRD analysis revealed it to be an α+β dual-phase supersaturated solid solution with no intermetallic compounds. The mechanical property test results are shown in Table 1.

[0048] The mechanical properties of the alloys obtained in Examples 1-3 and Comparative Examples 1-3 were tested. Vickers hardness was determined using a microhardness tester with a loading force of 1000g and a holding time of 10s. Room temperature tensile tests were performed on a universal testing machine to obtain yield strength, ultimate tensile strength, and elongation after fracture. Density was measured using the Archimedes displacement method. The test results are summarized in Table 1.

[0049] Table 1 Performance test results of different embodiments and comparative examples

[0050] As can be seen from the data in Table 1, the yield strength of Examples 1-3 of the present invention all exceed 1000 MPa, the elongation is all greater than 12%, the average hardness is not less than 334 HV1, and the density is 4.79~4.92 g / cm³. 3 This achieves a synergistic balance of high strength, good plasticity, and lightweight. Comparative Example 1, while exhibiting higher strength (yield strength 1054 MPa), has an elongation of only 1.1%, classifying it as a brittle material that fails to meet the basic plasticity requirements of structural components. This is due to its excessively high V and Zr content. Comparative Examples 2 and 3, due to insufficient alloying, have an α+β dual-phase microstructure, resulting in yield strengths far below 1000 MPa. Although they possess good plasticity, their strength is insufficient.

[0051] Therefore, by adopting the above-mentioned lightweight ultra-high strength cast β titanium alloy material and its preparation method, the technical problems of insufficient mechanical properties of existing cast titanium alloys and the need to rely on complex thermomechanical processing such as forging, rolling or solution aging to obtain high strength and toughness matching are solved. It is possible to directly obtain β single-phase titanium alloy with yield strength ≥1000MPa and elongation after fracture ≥12% under casting conditions, which meets the requirements of large-size complex structural components for near-net-shape forming in aerospace, deep-sea engineering and biomedical fields.

[0052] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0053] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A lightweight, ultra-high strength cast β-titanium alloy material, characterized in that, Composed of Ti, Al, V, and Zr, with atomic ratios of Ti 50%~71%, Al 7%~12.5%, V 11%~15%, and Zr 11%~16%; the alloy material is a β single-phase solid solution.

2. The lightweight, ultra-high strength cast β-titanium alloy material according to claim 1, characterized in that, The atomic ratios are: Ti 61%~71%, Al 7%~11%, V 11%~14%, Zr 11%~16%.

3. The lightweight ultra-high strength cast β-titanium alloy material according to claim 1, characterized in that, The atomic ratio is 50%~61% Ti, 10%~12.5% ​​Al, 12.5%~15% V, and 12.5%~15% Zr.

4. A method for preparing lightweight, ultra-high strength cast β-titanium alloy material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Select Ti, Al, V and Zr single metal blocks with a purity of 99.99% as raw materials, weigh each raw material according to the preset atomic ratio, and obtain the weighed raw materials; S2. The weighed raw materials are thoroughly mixed, washed with alcohol, and dried to obtain clean and dry raw materials to be smelted; S3. The raw material to be melted is subjected to vacuum arc melting. After uniform melting, it is vacuum copper mold casting and cooled to form a titanium alloy ingot. S4. The titanium alloy ingot is cut and polished sequentially to obtain the lightweight ultra-high strength cast β titanium alloy material.

5. The method according to claim 4, characterized in that, In step S3, a gas washing operation is performed before the vacuum arc melting, and the number of gas washing operations is 2 to 5.

6. The method according to claim 5, characterized in that, The gas washing process involves a cycle of vacuuming, filling with argon gas, and then vacuuming again.

7. The method according to claim 4, characterized in that, In step S3, the vacuum arc melting is repeated at least 6 times.

8. The method according to claim 4, characterized in that, In step S3, the vacuum degree of the vacuum arc melting is not higher than 5 × 10⁻⁶. -4 Pa.

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