A beta titanium alloy based on d-electron alloy design theory and a preparation method thereof

Abstract

The present application relates to the technical field of metal materials and its preparation, in particular to a kind of β titanium alloy and preparation method based on d-electron alloy design theory, β titanium alloy composition is designed by d-electron alloy design theory Ti2Al5Mo5CrxFeyNb, with the mass percentage of Ti2Al5Mo5CrxFeyNb is dosed, then vacuum melting is carried out, and ingot is obtained, wherein x is 1~3, y is 1~3;The ingot is subjected to homogenization treatment, then water cooling, and the sample before rolling is obtained;The sample before rolling is subjected to hot rolling, and the sample after hot rolling is obtained;The sample after hot rolling is subjected to solid solution treatment, and water cooling to room temperature, and the sample after solid solution treatment is obtained;The sample after solid solution treatment is subjected to aging treatment, and the β titanium alloy after aging treatment is obtained, the preparation technology of the present application is lower in cost, simple in process, convenient in operation, the prepared alloy has excellent mechanical properties, and is suitable for promotion and application.

Description

Technical Field

[0001] This invention relates to the field of metallic materials and their preparation technology, specifically to a β-titanium alloy based on d-electron alloy design theory and its preparation method. Background Technology

[0002] β-titanium alloys are an important category of titanium alloys. They possess rich microstructural features, and the unique combination of high specific strength and ductility gives them excellent overall performance. Furthermore, the various deformation modes and phase transformation types of β-titanium alloys significantly influence their overall properties. Metastable β-titanium alloys can undergo phase transformation / twinning during deformation, thereby increasing their strength, making them potentially attractive and a current research hotspot.

[0003] In recent years, researchers have attempted to control the β-phase stability of alloys through alloy design methods, hoping to introduce deformation strengthening and strength enhancement during material deformation by utilizing the twinning-induced plasticity (TWIP) / transformation-induced plasticity (TRIP) effect, thereby significantly improving the strength of the material. For multi-component β-titanium alloy systems, the interaction of multiple complex alloy components and the presence of a multi-phase microstructure make it difficult to determine the relationship between alloy properties, microstructure, and composition, further complicating development.

[0004] Currently, the commonly used alloy design methods for β-type titanium alloys mainly include the following three: the Mo equivalent method, the d-electron theory alloy design method, and the electron concentration method. However, it should be noted that the equivalent coefficients of each element in the MoE formula are calculated based on experimental results of binary alloys, and this method itself has a certain degree of error. While the electron concentration method can be widely used to guide the composition design of β-type titanium alloys, it mainly considers the influence of electronic factors on the alloy phase structure. For multi-component alloy systems, in addition to electron concentration, atomic size is also crucial. When the atomic size of the alloying elements differs significantly from that of titanium atoms, lattice distortion will occur. Therefore, using only a simple electron concentration parameter to characterize the precipitates and properties of the alloy has certain limitations and generally needs to be used in combination with other factors. Furthermore, existing d-electron theory alloy designs cannot simultaneously satisfy the characteristics of low cost and high performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a β-titanium alloy based on d-electron alloy design theory and its preparation method. This invention utilizes d-electron theory alloy design to control the β-phase stability of the alloy, aiming to introduce deformation strengthening during material deformation by leveraging twin-induced plasticity (TWIP) / transformation-induced plasticity (TRIP) effects to enhance strength. Simultaneously, appropriate heat treatment and deformation processing can also improve the microstructure and properties of the material, resulting in a novel β-titanium alloy with excellent comprehensive properties. With the continuous addition of β-phase stabilizing elements Fe and Nb, the strength of the samples continuously increases, and the strength is significantly improved after aging treatment. Furthermore, this preparation technology is low-cost, simple, and easy to operate, producing alloys with excellent mechanical properties, making it suitable for widespread application.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for preparing β-titanium alloy based on d-electron alloy design theory includes the following steps:

[0008] The composition of β-titanium alloy was designed using d-electron alloy design theory as Ti2Al5Mo5CrxFeyNb, where x and y represent the mass percentages of Fe and Nb, respectively, with x ranging from 1 to 3 and y ranging from 1 to 3.

[0009] The materials were batched according to the mass percentage of Ti2Al5Mo5CrxFeyNb, and then vacuum melted to obtain ingots, where x is 1 to 3 and y is 1 to 3.

[0010] The ingot is homogenized and then water-cooled to obtain a sample before rolling.

[0011] The sample before rolling is hot-rolled to obtain the hot-rolled sample.

[0012] The hot-rolled sample was subjected to solution treatment, and then cooled to room temperature with water to obtain the solution-treated sample.

[0013] The solution-treated sample was subjected to aging treatment to obtain an aged β-titanium alloy.

[0014] This invention utilizes d-electron theory alloy design to control the stability of the β-phase in titanium alloys, aiming to enhance strength through strain hardening by inducing twinning-induced plasticity / phase transformation-induced plasticity during material deformation. In terms of alloying element selection, this invention chooses lower-cost alloying elements (Bo and Md) to adjust their electronic properties, thereby controlling the stability of the titanium alloy and enabling phase transformation or twinning during deformation. This, in turn, improves the plasticity and tensile strength of the titanium alloy, resulting in a novel β-titanium alloy with excellent overall performance. From a process perspective, thermomechanical treatment technology can promote the refinement and uniform distribution of β-phase grains, optimizing the preparation process of β-titanium alloys, thereby improving the microstructure and mechanical properties of β-titanium alloys. This helps reduce the production cost of β-titanium alloys and improves their preparation efficiency and product quality.

[0015] In a preferred embodiment of the present invention, the homogenization treatment temperature is 900℃~1200℃, and the homogenization treatment time is 1h~3h.

[0016] In a preferred embodiment of the present invention, the hot rolling method is as follows: the sample before hot rolling is kept at 900℃~1100℃ for 10min~30min, and then hot rolling is performed, with a rolling amount of 0.3mm~0.6mm per pass, and after each rolling, it is kept at 900℃~1100℃ for 2min~5min.

[0017] In a preferred embodiment of the present invention, the solution treatment temperature is 800℃~900℃ and the solution treatment time is 10min~30min.

[0018] In a preferred embodiment of the present invention, the aging treatment temperature is 450℃~600℃, and the aging treatment time is 2h~8h.

[0019] In a preferred embodiment of the present invention, the smelting method is to place the raw materials into a water-cooled copper crucible vacuum non-consumable arc smelting furnace in order of increasing melting point for smelting.

[0020] In a preferred embodiment of the present invention, the raw materials used for smelting are all in block or granular form with a purity of ≥99.95%.

[0021] Another object of the present invention is to provide a β-titanium alloy prepared by any of the above-described preparation methods.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention designs a β-titanium alloy with a composition of Ti2Al5Mo5CrxFeyNb based on d-electronic alloy design theory, where x is 1-3 and y is 1-3. By selecting lower-cost Fe and Nb, the electronic properties of the alloy are adjusted to obtain a β-titanium alloy that simultaneously achieves low cost and high mechanical properties. The alloy is batched according to the mass percentage of Ti2Al5Mo5CrxFeyNb, then vacuum melted to obtain an ingot. The ingot is homogenized and then water-cooled to obtain a sample before rolling. The sample before rolling is hot-rolled to obtain a sample after hot rolling. The hot-rolled sample is solution-treated and then water-cooled to room temperature to obtain a sample after solution treatment. The solution-treated sample is then aged to obtain an aged β-titanium alloy. In terms of alloying element selection, this invention chooses lower-cost alloying elements to adjust their electronic properties (Bo and Md), thereby regulating the stability of the titanium alloy and enabling it to undergo phase transformation or twinning during deformation. This, in turn, improves the plasticity and tensile strength of the titanium alloy, resulting in a novel β-titanium alloy with excellent overall performance. From a process perspective, thermomechanical treatment technology can promote the refinement and uniform distribution of β-phase grains, optimize the preparation process of β-titanium alloys, and thus improve the microstructure and mechanical properties of β-titanium alloys. This helps to reduce the production cost of β-titanium alloys and improve their preparation efficiency and product quality.

[0024] 2. This invention utilizes the d-electron theory alloy design method to regulate the β-phase stability of the alloy, aiming to introduce deformation strengthening during material deformation by leveraging the twinning-induced plasticity / phase transformation-induced plasticity effect. Simultaneously, appropriate heat treatment and deformation processing methods can also be used to improve the microstructure and properties of the material, resulting in novel β-titanium alloys with excellent comprehensive performance. To obtain high-performance titanium alloys, it is necessary to ensure the homogeneity of composition during melting. Titanium alloys melted in a vacuum arc melting furnace can produce excellent ingots with homogeneous composition and fewer impurities. Homogenization treatment can accelerate element diffusion, eliminate compositional segregation during casting, and provide a better foundation for subsequent processing. Hot rolling can break up coarse grains in the casting state, significantly heal cracks, reduce or eliminate casting defects, thereby optimizing the microstructure and improving the alloy's machinability. Solution treatment at high temperatures after rolling is beneficial for homogenizing the microstructure and composition, and rapid cooling yields a homogeneous single-phase microstructure. Aging treatment can induce the precipitation or decomposition of second phases in the β-titanium alloy; these second phases provide effective strengthening, thereby increasing the strength of the titanium alloy. With the continuous addition of Fe and Nb elements, the strength of the alloy samples continuously increased, and the strength was significantly improved after aging treatment. Furthermore, this preparation technique is low-cost, simple, and easy to operate, producing alloys with excellent mechanical properties, making it suitable for widespread application.

[0025] 3. This invention uses the d-electron theory alloy design method to design a TiAlMoCr-based metastable β titanium alloy with TWIP / TRIP effect. Based on this, the stability of the β phase of the alloy is controlled by Fe and Nb, which are low-cost β-stabilizing elements, thereby controlling the plasticity and strength of the titanium alloy and obtaining a new β titanium alloy with good comprehensive performance. Attached Figure Description

[0026] Figure 1 Metallographic images of the Ti2Al5Mo5CrxFeyNb alloys prepared in Examples 1-2 and Comparative Examples 1-2 of this invention, (a) Ti2Al5Mo5Cr, (b)

[0027] Ti2Al5Mo5Cr1Nb, (c) Ti2Al5Mo5Cr1Fe1Nb, (d) Ti2Al5Mo5Cr1Fe3Nb.

[0028] Figure 2 The images show the microstructures of the Ti2Al5Mo5CrxFeyNb alloys prepared in Examples 1-2 and Comparative Examples 1-3 of this invention: (a) Ti2Al5Mo5Cr, (b) Ti2Al5Mo5Cr1Nb, (c) Ti2Al5Mo5Cr2Nb, (d) Ti2Al5Mo5Cr1Fe1Nb, and (e) Ti2Al5Mo5Cr1Fe3Nb.

[0029] Figure 3 The images show the microhardness of the Ti2Al5Mo5CrxFeyNb alloys prepared in the solid solution state in Examples 1-2 and Comparative Examples 1-3 of this invention. The contents of Fe and Nb increase sequentially from left to right.

[0030] Figure 4 The images show the microhardness of the Ti2Al5Mo5CrxFeyNb alloys prepared in the aged state according to Examples 1-2 and Comparative Examples 1-3 of this invention. The contents of Fe and Nb increase sequentially from left to right.

[0031] Figure 5 The stress-strain curves of Ti2Al5Mo5CrxFeyNb alloys prepared in Examples 1-2 and Comparative Examples 1-2 of this invention are shown in the room temperature tensile engineering diagrams.

[0032] Figure 6 The post-fracture surface metallographic structure of (a) Ti2Al5Mo5Cr and (b) Ti2Al5Mo5Cr1Fe3Nb alloy tensile specimens prepared in Comparative Example 1 and Example 2 of this invention.

[0033] Figure 7This is a transmission electron micrograph of the Ti2Al5Mo5Cr alloy prepared in Comparative Example 1 of this invention after tensile deformation. Detailed Implementation

[0034] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0036] The d-electron alloy design theory is not only a commonly used design method for β-type titanium alloys but also a current research focus, facilitating the understanding of alloy microstructure stability and strengthening mechanisms. D-electron transition elements with unpaired spins are the main strengthening elements in β-type titanium alloys. As the strength of the covalent bonds between their electrons gradually increases, the binding energy of transition elements in the metal or alloy gradually increases. This theory calculates new parameters Bo and Md from the electronic structure of the alloy. The Bo and Md values ​​of the alloy exhibit a simple linear relationship with component changes. Therefore, given the alloy composition, this invention only needs to calculate the Bo and Md values ​​to determine the alloy type, thus guiding the amount and selection of alloying elements, reducing experimental costs, and achieving more ideal experimental results. By selecting lower-cost Fe and Nb to adjust the electronic properties of the alloy, β-titanium alloys that simultaneously achieve low cost and high mechanical properties can be obtained. This not only provides a new approach for developing novel high-performance advanced metallic materials but also offers crucial alloy composition selection in areas where the performance of some traditional materials has reached its limits.

[0037] This invention modulates the stability of titanium alloys by selecting lower-cost alloying elements to adjust their electronic properties (Bo and Md), enabling them to undergo phase transformations or twinning during deformation. New parameters Bo and Md are calculated using the alloy's electronic structure. Bo measures the strength of interatomic covalent bonds, characterizing the overlap of electron clouds between atoms; a higher Bo value indicates stronger interatomic bonding. Md characterizes the combined effects of atomic size, electronegativity, and alloying factors. Based on d-electron alloy design theory, the following formula can be used...

[0038] Calculate using Equations 1 and 2:

[0039]

[0040] In the formula: i is an alloying element, X i denoted as the atomic percentage of alloying element i.

[0041] Equations 1 and 2 show that the Bo and Md values ​​of the alloy exhibit a linear relationship with the component changes. Therefore, given the alloy composition, the alloy type can be inferred by calculating the Bo and Md values. This helps the present invention select suitable alloying elements and determine their addition amounts, thereby achieving more ideal experimental results while reducing costs. Based on the alloy design objectives of the present invention, the Bo and Md values ​​of the designed composition are selected to be within the ranges of 2.783–2.787 and 2.348–2.368, respectively. Furthermore, considering cost, lower-cost Fe and Nb are ultimately selected to adjust its electronic properties (Bo and Md), and its microstructure and properties are studied.

[0042] Example 1

[0043] A method for preparing a Ti2Al5Mo5Cr1Fe1Nbβ titanium alloy includes the following steps:

[0044] (1) The raw materials were weighed using an electronic balance according to the mass percentage of Ti2Al5Mo5Cr1Fe1Nb. All raw materials used were in block or granular form with a purity ≥99.95%. The raw materials were placed in a water-cooled copper crucible vacuum non-consumable arc furnace according to their melting point from lowest to highest. The furnace was then evacuated to a vacuum level of 2×10⁻⁶. -3 Pa is used to charge a vacuum non-consumable arc furnace with argon gas of 99.999 wt.% purity for melting. Before melting the raw materials, sponge titanium is melted for two to three minutes with the current controlled at 630A. To ensure uniform composition, the titanium alloy ingot is turned over at least five times, finally obtaining a disc-shaped ingot.

[0045] (2) The above-mentioned circular ingot was radially cut into blocks with a length × width × height of 40mm × 30mm × 13.5mm using the electric spark wire cutting method. Then, the blocks were placed in a high-temperature resistant quartz glass tube with sponge titanium at the bottom and sealed with a hydrogen-oxygen sealing machine. During the process, a vacuum was circulated and argon gas was continuously introduced to reduce the air in the glass tube and prevent its oxidation. The as-cast test block was homogenized at 1100℃ for 2 hours and then water-cooled to obtain the sample before rolling.

[0046] (3) After grinding away the oxide layer and sharp edges on the sample surface before rolling with a grinding wheel, the sample was kept at 940℃ for 20 minutes, and then hot rolled along the length of the block. The amount rolled off each time was 0.5 mm, and after each rolling, it was kept at 940℃ for 3 minutes, finally obtaining a strip-shaped sample with a thickness of about 2.5 mm.

[0047] (4) The rolled sample was subjected to solution treatment at 870℃ for 20 minutes, and then cooled to room temperature with water to obtain the sample of the rolled alloy after solution treatment.

[0048] (5) The above-mentioned rolled alloy sample after solution treatment was cut into a block with a length × width × height of 7mm × 7mm × 2.5mm by electrical discharge wire cutting method, and then aged at 550℃ for 4h to obtain the aged sample.

[0049] Example 2

[0050] A method for preparing a Ti2Al5Mo5Cr1Fe3Nbβ titanium alloy includes the following steps:

[0051] (1) The raw materials were weighed using an electronic balance according to the mass percentage of Ti2Al5Mo5Cr1Fe3Nb. All raw materials used were in block or granular form with a purity ≥99.95%. The raw materials were placed in a water-cooled copper crucible vacuum non-consumable arc furnace according to their melting point from lowest to highest. The furnace was then evacuated to a vacuum level of 2×10⁻⁶. -3 Pa is used to charge a vacuum non-consumable arc furnace with argon gas of 99.999 wt.% purity for melting. Before melting the raw materials, sponge titanium is melted for two to three minutes with the current controlled at 630A. To ensure uniform composition, the titanium alloy ingot is turned over at least five times, finally obtaining a disc-shaped ingot.

[0052] (2) The above-mentioned circular ingot was radially cut into blocks with a length × width × height of 40mm × 30mm × 13.5mm using the electric spark wire cutting method. Then, the blocks were placed in a high-temperature resistant quartz glass tube with sponge titanium at the bottom and sealed with a hydrogen-oxygen sealing machine. During the process, a vacuum was circulated and argon gas was continuously introduced to reduce the air in the glass tube and prevent its oxidation. The as-cast test block was homogenized at 1100℃ for 2 hours and then water-cooled to obtain the sample before rolling.

[0053] (3) After grinding away the oxide layer and sharp edges on the sample surface before rolling with a grinding wheel, the sample was kept at 940℃ for 20 minutes, and then hot rolled along the length of the block. The amount rolled off each time was 0.5 mm, and after each rolling, it was kept at 940℃ for 3 minutes, finally obtaining a strip-shaped sample with a thickness of about 2.5 mm.

[0054] (4) The rolled sample was subjected to solution treatment at 870℃ for 20 minutes, and then cooled to room temperature with water to obtain the sample of the rolled alloy after solution treatment.

[0055] (5) The above-mentioned rolled alloy sample after solution treatment was cut into a block with a length × width × height of 7mm × 7mm × 2.5mm by electrical discharge wire cutting method, and then aged at 550℃ for 4h to obtain the aged sample.

[0056] Example 3

[0057] A method for preparing a Ti2Al5Mo5Cr1Fe3Nbβ titanium alloy includes the following steps:

[0058] (1) The raw materials were weighed using an electronic balance according to the mass percentage of Ti2Al5Mo5Cr1Fe3Nb. All raw materials used were in block or granular form with a purity ≥99.95%. The raw materials were placed in a water-cooled copper crucible vacuum non-consumable arc furnace according to their melting point from lowest to highest. The furnace was then evacuated to a vacuum level of 2×10⁻⁶. -3 Pa is used to charge a vacuum non-consumable arc furnace with argon gas of 99.999 wt.% purity for melting. Before melting the raw materials, sponge titanium is melted for two to three minutes with the current controlled at 600A. To ensure uniform composition, the titanium alloy ingot is turned over at least five times, finally obtaining a disc-shaped ingot.

[0059] (2) The above-mentioned circular ingot was radially cut into blocks with a length × width × height of 40mm × 30mm × 13.5mm using the electric spark wire cutting method. Then, the blocks were placed in a high-temperature resistant quartz glass tube with titanium sponge at the bottom and sealed with a hydrogen-oxygen sealing machine. During the process, a vacuum was circulated and argon gas was continuously introduced to reduce the air in the glass tube and prevent its oxidation. The as-cast blocks were homogenized at 900℃ for 1 hour and then water-cooled to obtain the sample before rolling.

[0060] (3) After grinding away the oxide layer and sharp edges on the surface of the sample before rolling with a grinding wheel, the sample was kept at 900℃ for 10 minutes, and then hot rolled along the length of the block. The amount rolled off each time was 0.3 mm, and after each rolling, it was kept at 900℃ for 2 minutes, and finally a strip-shaped sample with a thickness of about 2.5 mm was obtained.

[0061] (4) The rolled sample was subjected to solution treatment at 800℃ for 30 minutes, and then cooled to room temperature with water to obtain the sample of the rolled alloy after solution treatment.

[0062] (5) The above-mentioned rolled alloy sample after solution treatment was cut into a block with a length × width × height of 7mm × 7mm × 2.5mm by electrical discharge wire cutting method, and then aged at 450℃ for 8 hours to obtain the aged sample.

[0063] Example 4

[0064] A method for preparing a Ti2Al5Mo5Cr1Fe3Nbβ titanium alloy includes the following steps:

[0065] (1) The raw materials were weighed using an electronic balance according to the mass percentage of Ti2Al5Mo5Cr1Fe3Nb. All raw materials used were in block or granular form with a purity ≥99.95%. The raw materials were placed in a water-cooled copper crucible vacuum non-consumable arc furnace according to their melting point from lowest to highest. The furnace was then evacuated to a vacuum level of 2×10⁻⁶. -3 Argon gas with a purity of 99.999 wt.% is introduced into a vacuum non-consumable arc melting furnace for melting. Before melting the raw materials, sponge titanium is melted for two to three minutes with the current controlled at 650A. To ensure uniform composition, the titanium alloy ingot is turned over at least five times, finally obtaining a disc-shaped ingot.

[0066] (2) The above-mentioned circular ingot was cut radially into blocks with a length × width × height of 40mm × 30mm × 13.5mm using the electric spark wire cutting method. Then, the blocks were placed in a high-temperature resistant quartz glass tube with titanium sponge at the bottom and sealed with a hydrogen-oxygen sealing machine. During the process, a vacuum was circulated and argon gas was continuously introduced to reduce the air in the glass tube and prevent oxidation. The as-cast blocks were homogenized at 1200℃ for 3 hours and then water-cooled to obtain the sample before rolling.

[0067] (3) After grinding away the oxide layer and sharp edges on the sample surface before rolling with a grinding wheel, the sample was kept at 1100℃ for 30 minutes, and then hot rolled along the length of the block. The amount rolled off each time was 0.6 mm, and after each rolling, it was kept at 110℃ for 5 minutes, and finally a strip-shaped sample with a thickness of about 2.5 mm was obtained.

[0068] (4) The rolled sample was subjected to solution treatment at 900℃ for 10 min, and then cooled to room temperature with water to obtain the sample of the rolled alloy after solution treatment.

[0069] (5) The above-mentioned rolled alloy sample after solution treatment was cut into a block with a length × width × height of 7mm × 7mm × 2.5mm by electrical discharge wire cutting method, and then aged at 600℃ for 2h to obtain the aged sample.

[0070] Comparative Example 1

[0071] A method for preparing Ti2Al5Mo5Crβ titanium alloy includes the following steps:

[0072] (1) The raw materials were weighed using an electronic balance according to the mass percentage of Ti2Al5Mo5Cr. All raw materials used were in block or granular form with a purity ≥99.95%. The raw materials were placed in a water-cooled copper crucible vacuum non-consumable arc furnace according to their melting point from lowest to highest. The furnace was then evacuated to a vacuum level of 2×10⁻⁶. -3 Pa is used to charge a vacuum non-consumable arc furnace with argon gas of 99.999 wt.% purity for melting. Before melting the raw materials, sponge titanium is melted for two to three minutes with the current controlled at 630A. To ensure uniform composition, the titanium alloy ingot is turned over at least five times, finally obtaining a disc-shaped ingot.

[0073] (2) The above-mentioned circular ingot was radially cut into blocks with a length × width × height of 40mm × 30mm × 13.5mm using the electric spark wire cutting method. Then, the blocks were placed in a high-temperature resistant quartz glass tube with sponge titanium at the bottom and sealed with a hydrogen-oxygen sealing machine. During the process, a vacuum was circulated and argon gas was continuously introduced to reduce the air in the glass tube and prevent its oxidation. The as-cast test block was homogenized at 1100℃ for 2 hours and then water-cooled to obtain the sample before rolling.

[0074] (3) After grinding away the oxide layer and sharp edges on the sample surface before rolling with a grinding wheel, the sample was kept at 940℃ for 20 minutes, and then hot rolled along the length of the block. The amount rolled off each time was 0.5 mm, and after each rolling, it was kept at 940℃ for 3 minutes, finally obtaining a strip-shaped sample with a thickness of about 2.5 mm.

[0075] (4) The rolled sample was subjected to solution treatment at 870℃ for 20 minutes, and then cooled to room temperature with water to obtain the sample of the rolled alloy after solution treatment.

[0076] (5) The above-mentioned rolled alloy sample after solution treatment was cut into a block with a length × width × height of 7mm × 7mm × 2.5mm by electrical discharge wire cutting method, and then aged at 550℃ for 4h to obtain the aged sample.

[0077] Comparative Example 2

[0078] A method for preparing a Ti2Al5Mo5Cr1Nbβ titanium alloy includes the following steps:

[0079] (1) The raw materials were weighed using an electronic balance according to the mass percentage of Ti2Al5Mo5Cr1Nb. All raw materials used were in block or granular form with a purity ≥99.95%. The raw materials were placed in a water-cooled copper crucible vacuum non-consumable arc furnace according to their melting point from lowest to highest. The furnace was then evacuated to a vacuum level of 2×10⁻⁶.-3 Pa is used to charge a vacuum non-consumable arc furnace with argon gas of 99.999 wt.% purity for melting. Before melting the raw materials, sponge titanium is melted for two to three minutes with the current controlled at 630A. To ensure uniform composition, the titanium alloy ingot is turned over at least five times, finally obtaining a disc-shaped ingot.

[0080] (2) The above-mentioned circular ingot was radially cut into blocks with a length × width × height of 40mm × 30mm × 13.5mm using the electric spark wire cutting method. Then, the blocks were placed in a high-temperature resistant quartz glass tube with sponge titanium at the bottom and sealed with a hydrogen-oxygen sealing machine. During the process, a vacuum was circulated and argon gas was continuously introduced to reduce the air in the glass tube and prevent its oxidation. The as-cast test block was homogenized at 1100℃ for 2 hours and then water-cooled to obtain the sample before rolling.

[0081] (3) After grinding away the oxide layer and sharp edges on the sample surface before rolling with a grinding wheel, the sample was kept at 940℃ for 20 minutes, and then hot rolled along the length of the block. The amount rolled off each time was 0.5 mm, and after each rolling, it was kept at 940℃ for 3 minutes, finally obtaining a strip-shaped sample with a thickness of about 2.5 mm.

[0082] (4) The rolled sample was subjected to solution treatment at 870℃ for 20 minutes, and then cooled to room temperature with water to obtain the sample of the rolled alloy after solution treatment.

[0083] (5) The above-mentioned rolled alloy sample after solution treatment was cut into a block with a length × width × height of 7mm × 7mm × 2.5mm by electrical discharge wire cutting method, and then aged at 550℃ for 4h to obtain the aged sample.

[0084] Comparative Example 3

[0085] A method for preparing Ti2Al5Mo5Cr2Nbβ titanium alloy includes the following steps:

[0086] (1) The raw materials were weighed using an electronic balance according to the mass percentage of Ti2Al5Mo5Cr2Nb. All raw materials used were in block or granular form with a purity ≥99.95%. The raw materials were placed in a water-cooled copper crucible vacuum non-consumable arc furnace according to their melting point from lowest to highest. The furnace was then evacuated to a vacuum level of 2×10⁻⁶. -3 Pa is used to charge a vacuum non-consumable arc furnace with argon gas of 99.999 wt.% purity for melting. Before melting the raw materials, sponge titanium is melted for two to three minutes with the current controlled at 630A. To ensure uniform composition, the titanium alloy ingot is turned over at least five times, finally obtaining a disc-shaped ingot.

[0087] (2) The above-mentioned circular ingot was radially cut into blocks with a length × width × height of 40mm × 30mm × 13.5mm using the electric spark wire cutting method. Then, the blocks were placed in a high-temperature resistant quartz glass tube with sponge titanium at the bottom and sealed with a hydrogen-oxygen sealing machine. During the process, a vacuum was circulated and argon gas was continuously introduced to reduce the air in the glass tube and prevent its oxidation. The as-cast test block was homogenized at 1100℃ for 2 hours and then water-cooled to obtain the sample before rolling.

[0088] (3) After grinding away the oxide layer and sharp edges on the sample surface before rolling with a grinding wheel, the sample was kept at 940℃ for 20 minutes, and then hot rolled along the length of the block. The amount rolled off each time was 0.5 mm, and after each rolling, it was kept at 940℃ for 3 minutes, finally obtaining a strip-shaped sample with a thickness of about 2.5 mm.

[0089] (4) The rolled sample was subjected to solution treatment at 870℃ for 20 minutes, and then cooled to room temperature with water to obtain the sample of the rolled alloy after solution treatment.

[0090] (5) The above-mentioned rolled alloy sample after solution treatment was cut into a block with a length × width × height of 7mm × 7mm × 2.5mm by electrical discharge wire cutting method, and then aged at 550℃ for 4h to obtain the aged sample.

[0091] The above-mentioned rolled alloy sample after solution treatment was cut into 16.4mm×43mm hook-type tensile specimens by electrical discharge wire cutting method; grinding, polishing and cleaning: first, it was polished smooth with 80~2000# SiC sandpaper, then it was electrolytically polished, and finally it was cleaned with anhydrous ethanol in an ultrasonic cleaner for 10 minutes, and then it was taken out and dried for later use.

[0092] Results Analysis

[0093] Figure 1 These are metallographic images of the Ti2Al5Mo5CrxFeyNb alloys prepared in Examples 1-2 and Comparative Examples 1-2 of this invention. (a) to (d) show the Fe and Nb contents increasing sequentially from... Figure 1 It can be seen that the alloy is composed of coarse β-phase grains with relatively uniform grain size, indicating that the alloy obtained a single β-phase grain structure after solution treatment.

[0094] Figure 2The images show the microstructure of the Ti2Al5Mo5CrxFeyNb alloys prepared in Examples 1-2 and Comparative Examples 1-3 of this invention, with (a) to (e) showing an increasing Fe and Nb content. It can be seen that at an aging temperature of 550℃, needle-like α phases precipitated at the grain boundaries and within the Ti2Al5Mo5Cr alloy. The α phases precipitated at the grain boundaries are significantly larger than those precipitated within the grains, which may be related to the ease with which solute atoms diffuse towards the grain boundaries, and the grain boundary α phases exhibit a continuous distribution. The Ti2Al5Mo5Cr1Nb alloy also shows a large number of needle-like α phases precipitated at both grain boundaries and within the grains, with some grain boundary α phases precipitating continuously. Comparison shows that at the same aging time, the size of the precipitated α phases in different alloys increases with the increase of β-phase stabilizing elements, especially with the increase of Fe content, resulting in the greatest change in the precipitated α phase size. As can be clearly seen from the figure, the alloy without added Fe has little effect on the precipitation of the α phase, which is needle-shaped. However, the alloy with added Fe shows a clear trend in the size of the α phase.

[0095] Figure 3 The images show the microhardness of the Ti2Al5Mo5CrxFeyNb alloys prepared in the solid solution state in Examples 1-2 and Comparative Examples 1-3 of this invention. From left to right, the contents of Fe and Nb increase sequentially. It can be seen that adding 1% Nb to the Ti2Al5Mo5Cr-based alloy slightly improves the hardness of the material. Further adding 1% Fe significantly increases the hardness. The results indicate that adding the β-stabilizing elements Fe and Nb to the Ti2Al5Mo5Cr matrix can significantly improve the hardness of the material, and the hardness-enhancing effect of Fe on the Ti2Al5Mo5Cr alloy is significantly stronger than that of Nb. Figure 4 The images show the microhardness of the Ti2Al5Mo5CrxFeyNb alloys prepared in the aged state according to Examples 1-2 and Comparative Examples 1-3 of this invention. From left to right, the contents of Fe and Nb increase sequentially. After aging treatment, a second phase is generated, which significantly improves the hardness of the alloy.

[0096] Figure 5 The room temperature tensile stress-strain curves of Ti2Al5Mo5CrxFeyNb alloys prepared in Examples 1-2 and Comparative Examples 1-2 of this invention are shown. As can be seen from the figures, with the addition of β-phase stabilizing elements, the strength of the alloy is significantly improved, while the plasticity is somewhat lost.

[0097] Figure 6The post-fracture surface metallographic structures of (a) Ti2Al5Mo5Cr and (b) Ti2Al5Mo5Cr1Fe3Nb alloy tensile specimens prepared in Comparative Example 1 and Example 2 of this invention are shown. The linear characteristics of the Ti2Al5Mo5Cr sample are not as clear as those of the Ti2Al5Mo5Cr1Fe3Nb sample, which may indicate that a phase transformation occurred in the Ti2Al5Mo5Cr sample in addition to slip. Subsequent observation using TEM yielded the following results. Figure 7 As shown, the transmission electron microscopy (TEM) microstructure of the Ti2Al5Mo5Cr alloy after tensile deformation is mainly composed of martensite generated by phase transformation, with a small amount of twins present. Most of the slip lines in the Ti2Al5Mo5Cr1Fe3Nb sample are relatively clear, and the morphology indicates relatively coarse linear features after tensile fracture, which may be due to deformation twins. Figure 6 (b) In some areas, a good orientation relationship can be observed between the slip traces in the grains and the slip traces in the adjacent grains; this grain boundary is a special grain boundary. Therefore, in general, with the continuous addition of Fe and Nb elements, the plasticity of the alloy sample continuously decreases while the strength continuously increases. The Ti2Al5Mo5Cr alloy has the best plasticity, while the Ti2Al5Mo5Cr1Fe3Nb alloy has the highest strength.

[0098] In summary, this invention utilizes d-electron theory alloy design to control the stability of the β-phase in the alloy, aiming to enhance its strength by inducing strain hardening during material deformation through twinning-induced plasticity / phase transformation-induced plasticity effects. Regarding alloy element selection, this invention chooses lower-cost alloying elements (Bo and Md) to adjust their electronic properties, thereby controlling the stability of the titanium alloy and enabling phase transformation or twinning during deformation. This, in turn, improves the plasticity and tensile strength of the titanium alloy, resulting in a novel β-titanium alloy with excellent overall performance. From a process perspective, thermomechanical treatment technology can promote the refinement and uniform distribution of β-phase grains, optimizing the preparation process of the β-titanium alloy, thereby improving its microstructure and mechanical properties. This helps reduce the production cost of β-titanium alloys and improves their preparation efficiency and product quality.

[0099] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0100] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing β-titanium alloys based on d-electron alloy design theory, characterized in that, Includes the following steps: The composition of β-titanium alloy was designed as Ti2Al5Mo5CrxFeyNb based on d-electron alloy design theory, where x and y represent the mass percentages of Fe and Nb, respectively, with x ranging from 1 to 3 and y ranging from 1 to 3. The raw materials were prepared according to the mass percentage of Ti2Al5Mo5CrxFeyNb, and then vacuum melted to obtain ingots. The ingot is homogenized and then water-cooled to obtain a sample before rolling. The sample before rolling is then hot-rolled to obtain a sample after hot rolling. The hot-rolled sample was subjected to solution treatment, and then water-cooled to room temperature to obtain a solution-treated sample. The solution-treated sample was then subjected to aging treatment to obtain an aged β-titanium alloy.

2. The method for preparing β-titanium alloy based on d-electron alloy design theory according to claim 1, characterized in that, The homogenization treatment temperature is 900℃~1200℃, and the homogenization treatment time is 1h~3h.

3. The method for preparing β-titanium alloy based on d-electron alloy design theory according to claim 1, characterized in that, The hot rolling method is as follows: the sample before hot rolling is kept at 900℃~1100℃ for 10min~30min, and then hot rolling is carried out. The amount rolled off each time is 0.3mm~0.6mm, and after each rolling, it is kept at 900℃~1100℃ for 2min~5min.

4. The method for preparing β-titanium alloy based on d-electron alloy design theory according to claim 1, characterized in that, The solution treatment temperature is 800℃~900℃, and the solution treatment time is 10min~30min.

5. The method for preparing β-titanium alloy based on d-electron alloy design theory according to claim 1, characterized in that, The aging treatment temperature is 450℃~600℃, and the aging treatment time is 2h~8h.

6. The method for preparing β-titanium alloy based on d-electron alloy design theory according to claim 1, characterized in that, The smelting method involves placing the raw materials into a water-cooled copper crucible vacuum non-consumable arc smelting furnace in order of increasing melting point.

7. The method for preparing β-titanium alloy based on d-electron alloy design theory according to claim 1, characterized in that, The raw materials used for smelting are all in block or granular form with a purity of ≥99.95%.

8. A β-titanium alloy based on d-electron alloy design theory prepared by the preparation method according to any one of claims 1-7.

9. The β-titanium alloy based on d-electron alloy design theory according to claim 8, characterized in that, The β-titanium alloy has a Bo value of 2.783–2.787 and a Md value of 2.348–2.368.

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