A multi-component high-strength low-elastic modulus dual-phase metastable beta titanium alloy and a preparation method thereof

Abstract

The application discloses a multi-component high-strength low-elastic modulus dual-phase metastable beta titanium alloy and a preparation method thereof. The titanium alloy takes titanium as a main element, and comprises five beta phase stabilizing elements of vanadium, molybdenum, niobium, chromium and iron, an alpha phase stabilizing element of aluminum and a neutral element of zirconium. The Mo equivalent and electron concentration design method is adopted, so that the Mo equivalent is 7.9, and the e / a electron concentration is 4.07, so that the martensite phase change is more easily induced at room temperature, the elastic modulus of the alloy is reduced, and plasticity is provided. Meanwhile, the deformation twinning is also induced, the work hardening capacity is improved, the increased martensite phase interface and twinning interface hinder the movement of dislocations, and thus the alloy strength is improved. The dual-phase metastable beta titanium alloy quenched after dual-phase zone solid solution treatment has a tensile strength of more than 1 GPa, a yield strength of more than 770 MPa, even reaching 850 MPa, and a plastic elongation of more than 11%, and at the same time, the elastic modulus is lower than 55 GPa.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy materials technology, specifically to a multi-component biphase metastable β titanium alloy and its preparation method. Background Technology

[0002] Titanium and titanium alloys possess excellent mechanical and physical properties, including high specific strength, low elastic modulus, high fatigue resistance, high toughness, excellent corrosion resistance, good formability, and excellent biocompatibility. They are widely used in aerospace, energy, petrochemical, and biomedical fields. The strength of traditional titanium alloys ranges from 400 to 1500 MPa, depending on the alloy grade, while their elastic modulus ranges from 50 to 120 GPa. The high strength and low elastic modulus of titanium alloys endow them with excellent elastic deformation capabilities, making them widely used in the aerospace field as structurally functional integrated materials.

[0003] Currently, α+β and β-type titanium alloys used in springs and fasteners generally employ an α+β two-phase microstructure to achieve high strength, but also have a relatively high elastic modulus (90–120 GPa), resulting in lower elastic properties. This makes it difficult to meet the requirements of advanced aircraft for high-strength, high-elasticity materials. Furthermore, to obtain medical titanium alloys with an elastic modulus close to that of human bone, more than 20 β-type medical titanium alloys with lower elastic modulus have been developed in various alloy systems. These new materials have reduced their elastic modulus by approximately 40%, reaching 60–65 GPa, but this is still significantly higher than that of human bone (10–30 GPa). They do not completely solve the problem of stress matching and transmission between implanted devices and bone tissue, cannot eliminate degenerative changes such as bone resorption, and are unable to prevent implant failure due to loosening. However, the elastic modulus of metallic materials typically increases with increasing strength. Therefore, developing high-strength titanium alloys with lower elastic modulus is a critical and challenging problem that urgently needs to be solved. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a multi-component high-strength, low-elastic-modulus biphase metastable β-titanium alloy and its preparation method. This titanium alloy improves its strength and reduces its elastic modulus by designing its composition and content.

[0005] This invention is achieved through the following technical solution:

[0006] A multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy, comprising, by mass percentage, 4-5% Al, 4-5% Mo, 3% V, 1-2% Cr, 1-2% Zr, 1% Fe, and 2% Nb, with the balance being Ti and unavoidable impurity elements.

[0007] Preferably, in the α+β dual-phase solid solution state, the tensile yield strength of the dual-phase metastable β titanium alloy is 850 MPa, the tensile strength is greater than 1 GPa, the tensile elastic modulus is less than 55 GPa, and the plastic elongation is 11.9%.

[0008] Preferably, the microstructure of the dual-phase metastable β-titanium alloy includes β-phase grains and 10% by volume of spherical primary α-phase.

[0009] Preferably, the size of the spherical primary α phase is about 1 μm, and the size of the β grains is about 3 μm.

[0010] A method for preparing a multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy includes the following steps:

[0011] Titanium alloy ingots were solution quenched below their phase transformation temperature to obtain a biphase metastable β-titanium alloy.

[0012] Preferably, the phase transition point temperature is 830±5℃.

[0013] Preferably, the smelting method for the titanium alloy ingot is as follows:

[0014] The raw materials are mixed evenly according to the mass percentage, and the evenly mixed raw materials are subjected to multiple vacuum melting processes to obtain alloy ingots.

[0015] Preferably, a non-consumable vacuum electric arc furnace is used for smelting, and the number of smelting cycles is not less than 5.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] This invention provides a multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy. Titanium is the main element, containing seven other alloying elements. A certain amount of Fe is added to strengthen the α-phase, increasing the critical shear stress for dislocation slip within the α-phase, thereby improving the overall strength of the alloy. Furthermore, while Nb has the weakest stabilizing effect on the β-phase, it significantly reduces the elastic modulus. A Mo equivalent and electron concentration design method is used, resulting in a Mo equivalent of 7.9 and an e / a electron concentration of 4.07. This facilitates the induction of martensitic phase transformation at room temperature, reducing the alloy's elastic modulus and providing plasticity. It also induces deformation twinning, improving work hardening ability. The increased martensitic and twin interfaces hinder dislocation movement, thus increasing the alloy's strength. In the β-phase dual-phase solid solution state, this metastable β-titanium alloy exhibits a tensile yield strength of 850 MPa, a tensile strength exceeding 1 GPa, a tensile elastic modulus below 55 GPa, and a plastic elongation of 11.9%. In its single-phase solid solution state, this alloy exhibits a tensile yield strength of 690 MPa, a tensile strength of 950 MPa, a tensile modulus of elasticity of 58 GPa, and a plastic elongation of 15.7%. In the medical field, this alloy can effectively reduce or avoid stress shielding of bone tissue, thereby reducing the size and weight of medical devices. It also meets the requirements of advanced aircraft for high-strength, high-elasticity springs and fasteners.

[0018] The metastable β-titanium alloy of this invention contains eight alloying elements, including titanium. After heat treatment and quenching below the phase transformation point, a primary α-phase precipitates, and solid-solution atoms redistribute between the α and β phases. Typically, α-stabilizing elements such as Al preferentially dissolve into the α-phase, leaving a small amount in the β-phase to achieve thermodynamic equilibrium. Simultaneously, Al promotes the precipitation of the secondary α-phase and prevents the formation of the ω-phase. Too low a content results in insignificant solid-solution strengthening and may lead to a lower phase transformation point, hindering hot deformation processes. Conversely, too high a content leads to an ordered trend, detrimental to the material's fracture toughness. β-stabilizing elements, including Mo, V, Cr, Zr, Fe, and Nb, mostly remain in the β-phase, with only a small amount dissolving into the α-phase. Because Mo diffuses slowly in titanium alloys, it inhibits the coarsening of the α phase and refines the β subgrains. V strengthens the α phase through solid solution treatment and reduces its c / a ratio, which is beneficial for α phase slip, resulting in lower rheological resistance and better plasticity in the titanium alloy. Cr primarily strengthens through solid solution treatment, improving the material's plasticity, toughness, and hardenability. Certain amounts of Zr and Fe strengthen the α phase, increasing the critical shear stress for dislocation slip within the α phase, thereby improving the overall strength of the alloy. Furthermore, Nb has the weakest β phase stabilizing effect but significantly reduces the elastic modulus. Therefore, this invention controls the solution treatment temperature of the metastable β titanium alloy to adjust the volume ratio of the α / β phases, changing the distribution of each stabilizing element in both phases. This allows for simultaneous solid solution strengthening and deformation mechanism adjustment, ensuring both low modulus and high strength in the metastable β titanium alloy. Attached Figure Description

[0019] Figure 1 Microstructure of the biphase metastable β-titanium alloy prepared in Example 1 of this invention;

[0020] Figure 2 The tensile property curves of the metastable β-titanium alloy of this invention are compared after single-phase solid solution and two-phase solid solution treatment. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. These descriptions are intended to explain the invention and not to limit it.

[0022] A multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy, comprising, by mass percentage, 4-5% Al, 4-5% Mo, 3% V, 1-2% Cr, 1-2% Zr, 1% Fe, and 2% Nb, with the balance being Ti and unavoidable impurity elements.

[0023] This multi-component, high-strength, low-modulus, dual-phase metastable β-titanium alloy uses titanium as the main element and contains seven other alloying elements, including five β-phase stabilizing elements (vanadium, molybdenum, niobium, chromium, and iron), the α-phase stabilizing element aluminum, and the neutral element zirconium. Through careful design of its composition and content, a Mo equivalent of 7.9 and an e / a electron concentration of 4.07 are achieved, making it easier to induce martensitic phase transformation at room temperature, reducing the alloy's elastic modulus and providing plasticity. It also induces deformation twins, improving work hardening ability. The increased martensitic phase interface and twin interface hinder dislocation movement, thereby increasing the alloy's strength. In the α+β dual-phase solid solution state, its tensile yield strength reaches 850 MPa, its tensile strength exceeds 1 GPa, while its tensile elastic modulus is below 55 GPa, and its plastic elongation is 11.9%.

[0024] The preparation method of the above-mentioned multi-component high-strength, low-elastic-modulus dual-phase metastable β-titanium alloy includes the following processes:

[0025] Step 1: Mix all ingredients evenly according to their mass percentages;

[0026] Step 2: The uniformly mixed raw materials are subjected to multiple vacuum melting processes to obtain alloy ingots;

[0027] The melting process is carried out using a non-consumable vacuum electric arc furnace, and the melting is performed no less than 5 times.

[0028] Step 3: The ingot obtained in Step 2 is hot-rolled to obtain a metastable β titanium alloy plate, and then solution-quenched in the α+β dual-phase region to obtain a dual-phase metastable β titanium alloy.

[0029] The phase transformation temperature of this alloy is 830±5℃.

[0030] In the preparation method of this invention, the alloy ingot obtained by melting is heat-treated and quenched below the phase transformation point, which precipitates the primary α phase. Solid solution atoms also undergo redistribution between the α and β phases. Typically, α-stabilizing elements such as Al preferentially dissolve into the α phase, leaving a small amount in the β phase to achieve thermodynamic equilibrium. β-stabilizing elements, including Mo, V, Cr, Zr, Fe, and Nb, mostly remain in the β phase, with only a small amount dissolving into the α phase. Therefore, this invention controls the solution treatment temperature of the metastable β titanium alloy to adjust the volume ratio of the α / β phases, changing the distribution of each stabilizing element in the α / β phases, thereby altering the stability of the martensitic phase. This adjusts the triggering stress of the martensitic phase transformation and the volume fraction of induced deformation twins, ensuring the low modulus and high strength of the metastable β titanium alloy.

[0031] Example 1

[0032] A multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy, the composition of which, by weight percentage, includes 4% Al, 4% Mo, 3% V, 2% Cr, 2% Zr, 1% Fe and 2% Nb, with the balance being Ti and unavoidable impurity elements.

[0033] The raw materials are mixed evenly according to the above mass percentages. The mixed raw materials are melted in a non-consumable vacuum arc furnace five times to obtain an alloy ingot. The alloy ingot is then hot-rolled to obtain a metastable β titanium alloy plate. The metastable β titanium alloy plate is then solution treated in the α+β dual-phase region at 800℃ and then quenched to obtain a multi-component high-strength, low-elastic-modulus dual-phase metastable β titanium alloy.

[0034] The microstructure of the prepared metastable β-titanium alloy is as follows: Figure 1 As shown, the microstructure of this titanium alloy contains approximately 10% by volume of spherical primary α phase with a size of about 1 μm, and β grains with a size of about 3 μm. The room temperature tensile properties of this dual-phase metastable β titanium alloy were tested according to the requirements of GB / T228.1-2010 standard, and its tensile property curves are shown below. Figure 2 The tensile strength R of the alloy was measured. m Yield strength R 0.2 Elongation A t The elastic modulus E is shown in Table 1.

[0035] Example 2

[0036] A multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy, comprising, by weight percentage, 5% Al, 5% Mo, 3% V, 1% Cr, 1% Zr, 1% Fe, and 2% Nb, with the balance being Ti and unavoidable impurity elements, and a phase transformation temperature T of approximately 830±5℃.

[0037] The raw materials are mixed evenly according to the above mass percentages. The mixed raw materials are melted in a non-consumable vacuum arc furnace five times to obtain an alloy ingot. The alloy ingot is then hot-rolled to obtain a metastable β-titanium alloy plate. The metastable β-titanium alloy plate is then solution-treated at a phase transformation temperature below 820±5℃ for 30 minutes and then quenched to obtain a biphase metastable β-titanium alloy.

[0038] The dual-phase metastable β-titanium alloy was subjected to room temperature tensile property testing according to the requirements of GB / T228.1-2010 standard. The tensile strength R of the alloy was measured. m Yield strength R 0.2 Elongation A t The elastic modulus E is shown in Table 1.

[0039] Example 3

[0040] A multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy, the composition of which, by weight percentage, includes 4.5% Al, 4.5% Mo, 3% V, 1.5% Cr, 1.5% Zr, 1% Fe and 2% Nb, with the balance being Ti and unavoidable impurity elements.

[0041] The raw materials are mixed evenly according to the above mass percentages. The mixed raw materials are melted in a non-consumable vacuum arc furnace five times to obtain an alloy ingot. The alloy ingot is then hot-rolled to obtain a metastable β-titanium alloy plate. The metastable β-titanium alloy plate is then solution-treated at a phase transformation temperature below 810±5℃ for 30 minutes and then quenched to obtain a biphase metastable β-titanium alloy.

[0042] Comparative Example 1

[0043] A multi-component, high-strength, low-elastic-modulus, single-phase metastable β-titanium alloy, the composition of which, by weight percentage, includes 4% Al, 4% Mo, 3% V, 2% Cr, 2% Zr, 1% Fe and 2% Nb, with the balance being Ti and unavoidable impurity elements.

[0044] The alloy cost of this comparative example is the same as that of Example 1. The difference lies in the heat treatment process. In this comparative example, after solution treatment at 850°C, the alloy is quenched to obtain a single-phase metastable β-titanium alloy.

[0045] The dual-phase metastable β-titanium alloy was subjected to room temperature tensile property testing according to the requirements of GB / T228.1-2010 standard. Its tensile property curves are shown below. Figure 2 The tensile strength R of the alloy was measured. m Yield strength R 0.2 Elongation A t The elastic modulus E is shown in Table 1.

[0046] Comparative Example 2

[0047] A multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy, the composition of which, by weight percentage,

[0048] It contains 4.6% Al, 4.7% Mo, 7.1% V, 1.5% Cr, 1.3% Zr, with the balance being Ti and unavoidable impurity elements. The phase transition temperature T is approximately 800±5℃.

[0049] The heat treatment process of this comparative example is the same as that of Example 1, except that the alloy cost is different. This comparative example does not add Fe or Nb elements and is a few-component titanium alloy.

[0050] In the preparation of this comparative example, a dual-phase metastable β-titanium alloy was obtained by solution treatment at 780℃ followed by quenching. Room temperature tensile properties were tested according to the requirements of GB / T228.1-2010 standard, and the tensile strength R of the alloy was measured. m Yield strength R 0.2 Elongation A t The elastic modulus E is shown in Table 1.

[0051] Table 1. Performance test results of metastable β-titanium alloys in the examples and comparative examples. As shown in Table 1, the dual-phase metastable β-titanium alloys of Examples 1 and 2 of the present invention, after solution treatment in the dual-phase region and subsequent quenching, exhibit tensile strengths exceeding 1 GPa, yield strengths exceeding 770 MPa (even reaching 850 MPa), and plastic elongation exceeding 11%. Simultaneously, their elastic moduli are all below 55 GPa. Comparative Example 1 is a multi-component single-phase metastable β-titanium alloy with a tensile yield strength of 690 MPa, a tensile strength of 950 MPa, a tensile elastic modulus of 58 GPa, and a plastic elongation of 15.7%. Comparative Example 2 is a dual-phase metastable β-titanium alloy without Fe and Nb elements, with a tensile yield strength of 823 MPa, a tensile strength of 923 MPa, a tensile elastic modulus of 59 GPa, and a plastic elongation of 25.5%.

[0052] Compared to the single-phase metastable β-titanium alloy of Comparative Example 1, the biphase metastable β-titanium alloys of Examples 1 and 2 show significantly improved tensile strength and yield strength, and a significantly lower elastic modulus, with only a slight decrease in plastic elongation. Compared to the few-principal-element biphase metastable β-titanium alloy without Fe and Nb elements in Comparative Example 2, the biphase metastable β-titanium alloys of Examples 1 and 2, despite having lower plastic elongation, show significantly improved tensile strength and yield strength, and a significantly lower elastic modulus. This demonstrates that the multi-component high-strength, low-elastic-modulus biphase metastable β-titanium alloy of the present invention can effectively reduce or avoid stress shielding of bone tissue in the medical field, reduce the size and weight of medical devices, and also meet the requirements of advanced aircraft for high-strength, high-elasticity springs and fastener materials.

[0053] The aforementioned multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy uses titanium as the main element and contains seven other alloying elements, including five β-phase stabilizing elements (vanadium, molybdenum, niobium, chromium, and iron), the α-phase stabilizing element aluminum, and the neutral element zirconium. A Mo equivalent and electron concentration design method is employed, resulting in a Mo equivalent of 7.9 and an e / a electron concentration of 4.07. This facilitates the induction of martensitic phase transformation at room temperature, reducing the alloy's elastic modulus and providing plasticity. Simultaneously, it induces deformation twinning, enhancing work hardening ability. The increased martensitic phase interfaces and twin interfaces hinder dislocation movement, thereby improving alloy strength. The dual-phase metastable β-titanium alloy, after solution treatment in the dual-phase region and subsequent quenching, exhibits a tensile strength exceeding 1 GPa, a yield strength exceeding 770 MPa (even reaching 850 MPa), and a plastic elongation exceeding 11%. Simultaneously, the elastic modulus is below 55 GPa.

[0054] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A multi-component, high-strength, low-elastic-modulus, dual-phase metastable β-titanium alloy, characterized in that, By mass percentage, it includes 4% Al, 4% Mo, 3% V, 2% Cr, 2% Zr, 1% Fe and 2% Nb, with the balance being Ti and unavoidable impurity elements. The microstructure of the dual-phase metastable β titanium alloy includes β phase grains and 10% volume fraction of spherical primary α phase, wherein the size of the spherical primary α phase is 1 micrometer and the size of the β grains is 3 micrometers. The method for preparing the multi-component high-strength, low-elastic-modulus biphase metastable β-titanium alloy. The process includes the following: A dual-phase metastable β-titanium alloy was obtained by solution quenching a titanium alloy ingot below its phase transformation temperature, wherein the phase transformation temperature was 830°C. 5℃; In the α+β dual-phase solid solution state, the tensile yield strength of the dual-phase metastable β titanium alloy is 850 MPa, the tensile strength is greater than 1 GPa, the tensile elastic modulus is 53 GPa, and the plastic elongation is 11.9%.

2. The multi-component high-strength, low-elastic-modulus dual-phase metastable β-titanium alloy according to claim 1, characterized in that, The smelting method for the titanium alloy ingot is as follows: The raw materials are mixed evenly according to the mass percentage, and the evenly mixed raw materials are subjected to multiple vacuum melting processes to obtain alloy ingots.

3. The multi-component high-strength, low-elastic-modulus biphase metastable β-titanium alloy according to claim 2, characterized in that, The melting process is carried out using a non-consumable vacuum electric arc furnace, and the melting is performed no less than 5 times.

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