High-plasticity fatigue-resistant dual-state fine-grain titanium alloy, preparation method and application thereof

Abstract

The application discloses a high-plasticity fatigue-resistant dual-state fine-grain titanium alloy and a preparation method and application thereof. The alloy comprises Al, V, Mo, Zr, Hf, Ir and Sm, and the balance is Ti. The dual-state fine-grain titanium alloy of the application is recorded as alloy UM0607, the addition of transition elements Ir and Sm inhibits the diffusion of elements such as Al, Ta and V, and the primary alpha phase of the alloy is refined, the fine equiaxed alpha phase effectively prevents crack initiation and propagation, and the alloy thus has good plasticity and fatigue resistance; as a strong beta phase stabilizing element, a large amount of Ir and Sm is dissolved in the beta phase, and the volume fraction of the beta phase of the alloy is increased. The elongation of the examples of the application all reaches 16.0% or more, the fatigue crack propagation instability cycle number is greater than 120,000 times, and the alloy is an excellent material for preparing spectacle frames and connecting structural members.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new materials, and particularly relates to a high-plasticity fatigue-resistant dual-state fine-grain titanium alloy and a preparation method and application thereof. BACKGROUND

[0002] With the development of economy, glasses frames made of titanium have entered the life of the public. The density of metal titanium is small, about 4.51 g / cm3, higher than that of aluminum and lower than that of steel, copper and nickel. Titanium has high strength, small density, high hardness, high melting point and strong corrosion resistance. Therefore, the titanium alloy glasses frame has the characteristics of super lightness in metal materials, good hardness, non-deformation, corrosion resistance, non-rust, non-skin allergy and durability. Pure titanium TA1 is an alpha titanium alloy, which has the advantages of light weight, corrosion resistance and good biological safety, but the elasticity and strength are slightly poor. Therefore, on the one hand, the thickness of the glasses frame is reduced to reduce the weight, and on the other hand, the service performance is reduced due to the small thickness of the material, which still puzzles the application of the titanium alloy glasses frame.

[0003] The service performance requirements of titanium alloy eyeglass frames mainly include the ability to resist fracture and deformation, which are reflected in the toughness and fatigue performance of titanium alloy materials. Titanium alloy materials are generally composed of close-packed hexagonal (alpha phase), body-centered cubic (beta phase) and face-centered cubic (gamma phase), and the microstructure has a significant impact on mechanical properties and fatigue performance. Ti-Al-V-Mo-Zr alloy usually contains lamellar, martensitic, fully equiaxed and bimodal microstructures, among which equiaxed and lamellar alpha phases have higher strength and ductility. The dual-phase titanium alloy Ti-6Al-4V has a lamellar structure, and its mechanical properties and fatigue performance are significantly improved due to the lamellar structure. The dual-phase (α + β) titanium alloy is widely used in engineering practice due to its special microstructure and good comprehensive performance. The microstructure of the dual-phase titanium alloy has high diversity, and the differences in the microstructure make the properties of the titanium alloy change richly and uncertainly. The different microstructure characteristics have a complex influence on the fatigue performance. The dual-phase titanium alloy with α phase as the base phase is composed of primary α phase, lamellar secondary α phase and β phase. It is generally believed that the primary α phase has high fatigue crack initiation resistance, and the lamellar structure has strong fatigue crack propagation resistance. The dual-phase titanium alloy with primary α phase and a certain proportion of lamellar structure has better fatigue performance. There are two common methods to obtain the dual-phase structure: one method is to obtain it by heating deformation at a higher temperature in the (α+β) two-phase region; the other method is to heat treat the equiaxed structure in the high temperature (α+β) two-phase region. It is found that it is difficult to accurately control the experimental parameters to obtain the ideal structure when the dual-phase titanium alloy structure is regulated by heat treatment process. For the structure with a high proportion of primary α, the influence of element partition effect is the dominant factor of the change of structure and performance. The addition of Mo and Zr as stabilizers in the titanium alloy can refine the α lath, reduce the phase transition temperature and improve the heat treatment strengthening effect. Zr can reduce the martensitic transformation temperature, and adding Zr is an effective method to reduce the martensitic transformation temperature without greatly reducing the lattice deformation strain and obtaining the solid solution strengthening effect. Replacing part of Al in Ti-Al-V alloy with Zr can reduce the precipitation of Al3Ti, thereby improving the ductility of the titanium alloy without sacrificing the strength. Therefore, optimizing the chemical composition of the titanium alloy and controlling the influence of the composition on the structure are feasible paths to obtain the ideal dual-phase fine-grained structure. SUMMARY

[0004] The present application aims to overcome at least one of the deficiencies of the prior art and provide a high-plasticity fatigue-resistant dual-phase fine-grained titanium alloy, a preparation method and application thereof.

[0005] The technical scheme adopted by the present application is as follows:

[0006] In a first aspect, the present application provides:

[0007] A high-plasticity fatigue-resistant dual-state fine-grain titanium alloy has a mass composition of: Al 5.2-6.8%, V 3.5-4.5%, Mo 0.3-1.0%, Zr 0.3-1.2%, Hf 0.05-0.3%, transition elements Ir and rare earth Sm, a total of 0.1-0.5%, inevitable impurities, and the balance of Ti.

[0008] In some examples of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy, the content of Ir is 0.05-0.25%.

[0009] In some examples of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy, the content of Sm is 0.05-0.25%.

[0010] In some examples of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy, the content of Ir is 0.05-0.25% and the content of Sm is 0.05-0.25%.

[0011] In some examples of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy, the mass ratio of Ir to Sm is 1:(1-2.5).

[0012] In some examples of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy, the content of Ir is 0.05-0.25%, the content of Sm is 0.05-0.25%, and the mass ratio of Ir to Sm is 1:(1-2.5).

[0013] In some examples of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy, there are granular alpha phases with a size of 7-35 microns and lamellar secondary alpha phases with a lamellar thickness of 4-8 microns.

[0014] In some examples of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy, the content of inevitable impurities is not more than 0.1%.

[0015] The second aspect of the present application provides:

[0016] A structural member comprising the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy according to the first aspect of the present application.

[0017] In some examples of the structural member, the structural member is a spectacle frame or a spectacle connecting structural member.

[0018] The third aspect of the present application provides:

[0019] A method for preparing the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy according to the first aspect of the present application, comprising the following steps:

[0020] Alloy smelting: smelting raw materials into one body to obtain an alloy ingot;

[0021] Blank forging: the alloy ingot is forged at 880-950 DEG C to obtain a forged blank;

[0022] Solution and aging treatment: the forged blank is subjected to graded solution and aging treatment to obtain the high-plasticity fatigue-resistant dual-phase titanium alloy.

[0023] In some examples of the preparation method, the specific passes of forging are: Φ10.0 mm→Φ9.4 mm→Φ8.6 mm→Φ7.4 mm→Φ6.2 mm→Φ5.5 mm→Φ4.5 mm.

[0024] In some examples of the preparation method, the operation of each stage of the graded solution and aging treatment is: (960-990 DEG C) / 40 min+(900-930 DEG C) / 90 min+(500-600 DEG C) / 4-10 h.

[0025] In some examples of the preparation method, the specific passes of forging are: Φ10.0 mm→Φ9.4 mm→Φ8.6 mm→Φ7.4 mm→Φ6.2 mm→Φ5.5 mm→Φ4.5 mm, and the operation of each stage of the graded solution and aging treatment is: (960-990 DEG C) / 40 min+(900-930 DEG C) / 90 min+(500-600 DEG C) / 4-10 h.

[0026] In some examples of the preparation method, the method of smelting is vacuum consumable smelting.

[0027] The present application has the following beneficial effects:

[0028] The dual-phase fine-grained titanium alloy of some examples of the present application, denoted as alloy UM0607, has an elongation greater than 16%, a fatigue crack propagation instability cycle number greater than 120,000 times, has the advantages of high plasticity and fatigue resistance, can fully meet the bending forming in the manufacturing process of the spectacle frame and the fatigue environment in use, and is beneficial to prolonging the service life of the spectacle frame.

[0029] The dual-state fine-grain titanium alloy UM0607 of some examples of the present application can improve the nucleation rate and diffusion activation energy of the crystal nucleus, reduce the surface tension and growth rate of the crystal nucleus, hinder the growth of the secondary phase crystal nucleus, and refine the secondary lamellar alpha phase. The doping of the rare earth element Ir in the titanium alloy can generate a second phase through reaction, and the second phase particles with high melting point can act as the nucleation points of the primary alpha matrix, promote a large number of nucleation in the alloy solidification process, and thus refine the primary alpha phase of the alloy. At the same time, the second phase particles hinder the growth of the beta-Ti grains during the heat treatment process, have a refining effect on the microstructure of the dual-state titanium alloy, and thus make the dual-state titanium alloy have a finer grain structure. The dual-state fine-grain structure can effectively improve the strength of the titanium alloy, the fine equiaxed primary alpha phase can reduce the initiation of the fatigue crack, and the fine lamellar secondary alpha phase can effectively reduce the propagation rate of the fatigue crack, thus improving the fatigue failure resistance of the alloy. In addition, when the dual-phase titanium alloy is subjected to plastic deformation, the rare earth element can reduce the interlayer spacing of the alpha and beta phases, thus improving the microstructure of the material and improving the plasticity and fatigue resistance of the alloy. At the same time, the rare earth element Sm can affect the recrystallization process of the deformed titanium alloy, hinder the nucleation and growth of the recrystallized grains. The oxygenophilic rare earth element Sm eliminates the adverse effects of the brittle elements and improves the plasticity of the alloy. Therefore, the addition of the rare earth element significantly refines the microstructure of the titanium alloy, the generated appropriate amount of dispersed particles hinder the sliding of dislocations, grain boundaries and phase boundaries, and thus improve the strength and fatigue crack initiation resistance of the alloy.

[0030] The dual-state fine-grain titanium alloy UM0607 of some examples of the present application adds the transition elements Ir and Sm to inhibit the diffusion of elements such as Al, Ta, and V, refine the primary alpha phase of the alloy, and effectively prevent the initiation and propagation of cracks, thus making the alloy have good plasticity and fatigue resistance. As a strong beta phase stabilizing element, a large amount of Ir and Sm is dissolved in the beta phase, and the volume fraction of the beta phase of the alloy is increased. The elongation of the examples of the present application all reaches 16.0% or more, and the fatigue crack propagation instability cycle number is greater than 120,000 times, which is an excellent material for preparing spectacle frames and connecting structure parts. The oxidation reaction of the titanium alloy under high temperature conditions is usually accompanied by strong destruction, which makes the mechanical properties of the titanium alloy worse and shortens the service life. The addition of a small amount of Sm can slow down the oxidation rate and improve the oxidation resistance. The main reason is that the rare earth element can effectively protect the titanium alloy matrix by promoting the generation of Al2O3 oxidation film, and if the rare earth oxide is added in the form of rare earth oxide, the density of the material can be obviously improved, the thickness of the oxidation layer can be reduced, and thus the oxidation resistance of the alloy can be optimized. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The microstructure diagram of the high-plasticity fatigue-resistant dual-state fine-grain titanium alloy obtained in Example 1 of the present application.

[0032] Figure 2 This is a microstructure diagram of the high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy obtained in Example 3 of the present invention.

[0033] Figure 3 This is a microstructure diagram of the high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy obtained in Example 5 of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be further illustrated below with examples and experimental data.

[0035] The alloy composition of each embodiment and comparative example of the present invention is shown in Table 1, wherein the amount of unavoidable impurities does not exceed 0.1%, and the balance is Ti.

[0036] Table 1. Alloy composition (mass percentage) of different embodiments and comparative examples

[0037]

[0038] For ease of comparison, the preparation methods for each example are as follows:

[0039] S1) Weigh out sponge Ti, pure metal and rare earth according to the composition of the alloy, mix them evenly, and press them into electrodes in a mold;

[0040] S2) The pressed electrodes are welded together with high-melting-point metals and subjected to three vacuum consumable melting processes. The melting current is 8-18 kA, the melting voltage is 30-35 V, and the vacuum degree of each melting process is independently 0.6-3 Pa, to obtain an alloy ingot.

[0041] S3) The gold ingot is forged in multiple passes at a temperature of 880℃-950℃. The specific passes are: Φ10.0 mm→Φ9.4 mm→Φ8.6 mm→Φ7.4 mm→Φ6.2 mm→Φ5.5 mm→Φ4.5 mm, to obtain the forging billet.

[0042] S4) Solution and aging treatment: The alloy after multiple forging processes is subjected to staged solution and aging treatment to obtain the high-plasticity fatigue-resistant dual-state titanium alloy; the operation of each stage of the staged solution and aging treatment is as follows: (960-990℃) / 40min+(900-930℃) / 90min+(500-600℃) / 4-10h.

[0043] Comparison of the properties of alloys from different embodiments

[0044] The performance of the alloys of the examples and the comparative examples was tested, wherein the fatigue performance was detected by using an MTS fatigue testing machine; the testing method of the strength and the elongation was determined according to GB / T 228.1-2010 "Metallic Materials Tensile Testing Part 1: Room Temperature Testing Method". The performance testing results of the examples and the comparative examples are shown in Table 2.

[0045] Table 2, performance testing results of the examples and the comparative examples

[0046]

[0047] As can be seen from Table 2, compared with the comparative examples, the elongation of the examples 1-5 is significantly better, and the fatigue resistance is significantly better.

[0048] Figure 1 It is a microstructure diagram of the high-plasticity and fatigue-resistant dual-state fine-grained titanium alloy obtained in the example 1 of the present application. It can be seen that the titanium alloy for eyeglass frames prepared by the scheme of the present application has typical dual-state organizational characteristics, the dual-state organizational structure of the primary alpha phase with a size of 7-35 μm and the lamellar secondary alpha and flaky secondary beta phase with a lamellar thickness of 4-8 μm, thereby improving the plasticity and fatigue resistance of the alloy.

[0049] Figure 2 It is a microstructure diagram of the high-plasticity and fatigue-resistant dual-state fine-grained titanium alloy obtained in the example 3 of the present application. It can be seen that the dual-state fine-grained titanium alloy for eyeglass frames prepared by the scheme of the present application further refines the primary alpha phase and the flaky secondary beta phase in the dual-state organization by adjusting the content and proportion of the rare earth elements, the microstructure of the alloy is more fine and uniform, and the plasticity and fatigue resistance of the alloy are also improved.

[0050] Figure 3 It is a microstructure diagram of the high-plasticity and fatigue-resistant dual-state fine-grained titanium alloy obtained in the example 5 of the present application. It can be seen that the dual-state fine-grained titanium alloy for eyeglass frames prepared by the scheme of the present application finds that different addition proportions have an influence on the dual-state organization of the alloy during the adjustment of the content of the rare earth elements.

[0051] The above is a further detailed description of the present application, which cannot be regarded as a limitation on the specific implementation of the present application. For ordinary skilled persons in the technical field to which the present application belongs, simple deduction or replacement without departing from the concept of the present application is within the protection scope of the present application.

Claims

1. A high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy, characterized in that, It has a granular α phase with a size of 7–35 μm and a lamellar secondary α phase with a thickness of 4–8 μm. Its mass composition is: Al 5.2–6.8%, V 3.5–4.5%, Mo 0.3–1.0%, Zr 0.3–1.2%, Hf 0.05–0.3%, transition element Ir and rare earth Sm totaling 0.1–0.5%, with an Ir to Sm mass ratio of 1:(1–2.5). Unavoidable impurities are present, and the balance is Ti. Its preparation method includes the following steps: Ingredients: Weigh the raw materials according to the composition of the high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy; Alloy smelting: melting raw materials into a single alloy to obtain an alloy ingot; Forging of billet: The alloy ingot is forged at 880-950°C to obtain a forged billet; Solution treatment and aging treatment: The forged billet is subjected to graded solution treatment and aging treatment. The operation of each stage of the graded solution treatment and aging treatment is: (960~990℃) / 40min+(900~930℃) / 90min+(500~600℃) / 4~10h, to obtain the high plasticity fatigue-resistant dual-state titanium alloy.

2. The high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy according to claim 1, characterized in that, The content of Ir is 0.05-0.25%.

3. The high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy according to claim 1, characterized in that, The content of Sm is 0.05-0.25%.

4. The high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy according to any one of claims 1 to 3, characterized in that, The smelting method is vacuum consumable melting.

5. The high-plasticity, fatigue-resistant, dual-phase fine-grained titanium alloy according to any one of claims 1 to 3, characterized in that, The specific forging steps are: Φ10.0 mm→Φ9.4 mm→Φ8.6 mm→Φ7.4 mm→Φ6.2 mm→Φ5.5 mm→Φ4.5 mm.

6. A structural component comprising the high-plasticity, fatigue-resistant, dual-state fine-grained titanium alloy as described in any one of claims 1 to 5.

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