A deformed high-Nb-TiAl alloy with a fine, near-γ microstructure and its preparation method

Abstract

This invention provides a fine-grained, near-γ-like microstructure of a deformable high-Nb-TiAl alloy and its preparation method, relating to the technical field of deformation preparation of TiAl intermetallic compounds. The alloy composition is Al 43-48 at%, Nb 5-10 at%, B 0-0.5 at%, W 0-0.5 at%, Y 0-0.3 at%, with the balance being Ti and unavoidable impurities. The preparation method employs a process of vacuum arc remelting + vacuum solidification melting + vacuum arc remelting + casting + stress-relief annealing + surface oxide removal + anti-oxidation treatment + cladding + (α+γ) two-phase region high-specific-heat extrusion deformation. Compared to other traditional methods, this invention's method yields a fine-grained, near-γ-like microstructure with an average grain size controlled at 2-30 μm. This microstructure exhibits excellent room-temperature and high-temperature mechanical properties, particularly excellent room-temperature strength and ductility, showing broad application prospects in aerospace and vehicle engine fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of deformation preparation of TiAl intermetallic compounds, and particularly relates to a deformed high-Nb-TiAl alloy with a fine similar near-gamma structure and a preparation method. BACKGROUND

[0002] High-Nb-TiAl intermetallic compounds have been widely concerned in the fields of aviation, aerospace and automobile in recent years due to their low density, high specific strength, high specific modulus, good high-temperature creep resistance, fatigue resistance, oxidation resistance and combustion resistance. In particular, the density of high-Nb-TiAl alloy is half of that of nickel-based high-temperature alloy, and the alloy can maintain good high-temperature stability in the high-temperature range of 800-850 DEG C. Compared with traditional TiAl alloys, the service temperature of the high-Nb-TiAl alloy can be relatively increased by 60-100 DEG C, and the alloy has great application potential and market prospect.

[0003] Among the four typical microstructures of high-Nb-TiAl alloys, it is generally believed that the near / full lamellar structure has good mechanical properties, but the plasticity is low and the hot workability is poor, which seriously limits the further application of the alloy in industrial production. Therefore, it is of great significance to develop high-Nb-TiAl alloys with good room temperature strength-plasticity trade-off characteristics and high high-temperature strength in engineering application.

[0004] The near-gamma structure (NG) is composed of equiaxed gamma grains and fine alpha2 grains distributed at the gamma grain boundaries, and the volume fraction of the gamma phase is generally higher than 90%, and the average grain size is usually between 30-50 mu m. It is generally believed that the TiAl alloy with the near-gamma structure has good microstructure stability, but its room temperature plasticity is poor and the strength is low. It is of great scientific research significance and important industrial application value to improve the near-gamma structure by using some technical means and to improve the strength and plasticity of the structure.

[0005] In the traditional hot deformation process, hot extrusion deformation can significantly improve the mechanical properties of TiAl alloy. In the literature "Improvement of microstructure, mechanical properties and hot work ability of a TiAl-Nb-Mo alloy through hot extrusion", it is reported that compared with the as-cast alloy, hot extrusion deformation can break the coarse as-cast structure, and a duplex (DP) structure is obtained after hot extrusion. The DP structure is composed of lamellar groups and equiaxed γ, and the two forms are about 50% each. The DP structure has good room temperature mechanical properties, and the room temperature plasticity can reach 1-2%, but the high temperature service performance is generally not high. The extrusion ratio reported in the literature is usually 5-12, and there is a certain unevenness in the edge and core structure of the rod under this deformation condition.

[0006] Chinese patent CN116024457A discloses a high-strength TiAl alloy with tensile strength greater than 750 MPa and its additive manufacturing method. The composition of the TiAl alloy is fixed, and electron beam selective melting additive manufacturing is used. The subsequent hot isostatic pressing obviously limits the shape and performance of the prepared material, and the tensile strength and elongation are low; the elongation at 800°C is low.

[0007] Chinese patent CN114150181A discloses a low-cost easily deformable lightweight high-strength TiAl alloy and its preparation method. The alloy composition is Ti-(40-45)Al-(3-8)Mn, which needs to be melted twice to obtain an ingot, and then prepared by high temperature forging and air cooling; the room temperature tensile strength and elongation are low, and the elongation at 700°C is low.

[0008] Chinese patent CN108559872A discloses a TiAl alloy and its preparation method. The alloy composition is complex, and the preparation process needs complicated procedures such as extrusion deformation and isothermal forging. The uniform annealing, solid solution heat treatment and aging heat treatment used in heat treatment increase the production cost, the room temperature tensile strength and elongation are low, and the room temperature processing performance is poor; the yield strength ratio at 800°C is low, and the material has poor deformation resistance, which is not conducive to the use of the material in high temperature environment at 800°C.

[0009] Chinese patent CN115522152A discloses a method for simultaneously improving the high-temperature strength and plasticity of TiAl alloy. By changing the aging temperature and holding time of the solid solution aging heat treatment process, part of the lamellar structure in the TNM alloy is successfully transformed into pearlite structure, forming a three-phase three-state structure with a pearlite content of not more than 50%, which is defined as T-T50 structure. The T-T50 structure can obtain a yield strength of about 150 MPa higher than that of the full lamellar structure or a tensile strength at least equivalent to that of the full lamellar structure at 750℃, while the plasticity is increased by 2-3 times. Obviously, the tensile strength and yield strength at 750℃ are relatively high, while the elongation is relatively low, and the strength-plasticity product is relatively low.

[0010] Based on this, the present application obtains an improved quasi-near-gamma (QNG) structure through a hot extrusion deformation process with a large extrusion ratio (≥22). The structure is more uniform, and is named quasi-near-gamma (QNG) structure. The average grain size of the QNG structure is 2-30 μm, and the QNG structure has a weak wire texture and a phase content distribution of γ: 70-80%; α2: 10-20%; B2: 2-10%. The QNG structure can simultaneously achieve the technical purposes of high strength and high plasticity of high-Nb TiAl alloy at room temperature, and high yield strength ratio and high strength-plasticity product at 800℃. SUMMARY

[0011] The technical problems to be solved by the present application are that the current near-gamma (NG) Nb-TiAl alloy has large average grain size, high volume fraction of γ phase, poor room temperature plasticity, low strength, low high-temperature yield strength ratio, and low strength-plasticity product. In addition, the hot extrusion deformation in the traditional hot deformation process can improve the room temperature performance of the Nb-TiAl alloy, but cannot improve the high-temperature performance. The possible process steps have technical defects such as high cost, low efficiency, insignificant improvement effect, or inability to improve both room temperature and high-temperature performance.

[0012] To solve the above technical problems, the technical solutions of the present application are as follows:

[0013] A deformed high-Nb TiAl alloy with a fine quasi-near-gamma structure, the chemical composition and atomic percentage of the deformed high-Nb TiAl alloy are as follows: Al 43-48 at%, Nb 5-10 at%, W 0-0.5 at%, B 0-0.5 at%, Y 0-0.3 at%, and the balance being Ti and unavoidable impurities; wherein: the atomic percentage of W, B and Y cannot be 0, and the total atomic percentage of W+B+Y is between 0.3-1.0 at%.

[0014] Preferably, the deformed high-Nb TiAl alloy has a multi-phase structure containing a γ-TiAl phase with an ordered L12 structure, a D019 19The α2-Ti3Al phase of the structure, the β-Ti phase of the B2 structure; the three-phase proportion is respectively: 70-80% of the γ-TiAl phase, 10-20% of the α2-Ti3Al phase, and 2-10% of the β-Ti phase.

[0015] Preferably, the average grain size of the deformed high-Nb-TiAl alloy is controlled to be 2-30 μm, and has a weak texture, the average size of the γ-TiAl phase is controlled to be 5-30 μm, the average size of the α2-Ti3Al phase is controlled to be 5-15 μm, and the average size of the β-Ti phase is controlled to be 2-20 μm.

[0016] Preferably, the deformed high-Nb-TiAl alloy is subjected to room / high temperature tensile property test, and it is found that: at room temperature, the density is 4.0-4.2 g / cm 3 , the tensile strength is 950-1100 MPa, the yield strength is 800-910 MPa, the ductility is 3.00-5.00%, and the strength-plasticity product is 2.85-5.0 GPa%; when stretched at 800°C, the tensile strength is 550-650 MPa, the yield strength is 450-550 MPa, the ductility is 22.96-56.36%, and the strength-plasticity product is 15.5-33.5 GPa%.

[0017] A preparation method of the deformed high-Nb-TiAl alloy based on the fine similar near-γ structure, the preparation method of the deformed high-Nb-TiAl alloy comprising the following steps:

[0018] S1: selecting and proportioning the raw materials according to the composition of the deformed high-Nb-TiAl alloy based on the fine similar near-γ structure to obtain smelting raw materials;

[0019] S2: sequentially subjecting the smelting raw materials of S1 to three times of smelting of vacuum consumable arc smelting, vacuum skull smelting, and vacuum consumable arc smelting, and then casting to obtain an alloy ingot;

[0020] S3: subjecting the alloy ingot of S2 to stress relief annealing treatment to obtain a stress relief ingot;

[0021] S4: subjecting the surface of the stress relief ingot of S3 to machining treatment for removing surface oxide scale, and then polishing and smoothing and rounding the corners to obtain an extrusion billet;

[0022] S5: subjecting the extrusion billet of S4 to oxidation prevention treatment to obtain a surface oxidation-prevention extrusion billet;

[0023] S6: subjecting the surface oxidation-prevention extrusion billet of S5 to extrusion billet cladding treatment to obtain a cladded extrusion billet;

[0024] S7: The extruded billet wrapped in the S6 casing is subjected to pre-extrusion heating and heat preservation treatment, followed by extrusion hot deformation and cooling to room temperature. After removing the casing, a deformed high Nb-TiAl alloy with a fine near-γ microstructure is obtained.

[0025] Preferably, the alloy ingot size of S2 is φ(250-350)×(500-600)mm.

[0026] Preferably, the S2 alloy ingot has a density of 4.0-4.2 g / cm³ at room temperature. 3 Its tensile strength is 550-650 MPa, yield strength is 500-600 MPa, ductility is 0.2-0.6%, and strength-ductility product is 0.11-0.39 GPa%. When stretched at 800℃, its tensile strength is 450-550 MPa, yield strength is 400-450 MPa, ductility is 3-6%, and strength-ductility product is 1.35-3.3 GPa.

[0027] Preferably, the stress-relief annealing treatment in S3 is carried out at a temperature of 700-900℃ for 12-36 hours.

[0028] Preferably, the stress-relief ingot of S3 has a density of 4.0-4.2 g / cm³ at room temperature. 3 Its tensile strength is 500-600 MPa, yield strength is 450-550 MPa, ductility is 0.4-0.8%, and strength-ductility product is 0.2-0.48 GPa%. When stretched at 800℃, its tensile strength is 450-550 MPa, yield strength is 400-450 MPa, ductility is 3-6%, and strength-ductility product is 1.35-3.3 GPa.

[0029] Preferably, the machining process for removing surface oxide scale in S4 includes turning, rough turning, finish turning and rough grinding, and the surface roughness is Ra = 3.2-6.3 μm after smoothing.

[0030] Preferably, the extruded blank size of S4 is φ(200-300)×(500-550)mm.

[0031] Preferably, the anti-oxidation treatment in S5 includes surface coating preparation, anti-oxidation heat treatment, surface anti-oxidation powder adhesion, and surface chemical anti-oxidation treatment.

[0032] Preferably, the anti-oxidation treatment in S5 is prepared by surface coating, which can be achieved by spraying the blank with an anti-oxidation coating with a thickness of 1-3 mm using a spraying equipment.

[0033] Preferably, in step S5, an anti-oxidation coating is sprayed onto the billet using a spraying device. After spraying, the billet is dried in a furnace, and then three sprayings are performed to check for any omissions or defects, ensuring that there are no exposed parts of the alloy. Furthermore, the anti-oxidation coating has a uniform thickness and is tightly bonded to the surface of the alloy, preventing it from peeling off during subsequent processes and use.

[0034] Preferably, the extruded billet encapsulation process in S6 adopts a double-layer encapsulation structure. The outer encapsulation is made of 304L stainless steel, with one end open and the other end closed. The height-to-diameter ratio of the encapsulation is controlled at 2:1-4:1, and the thickness is 5-15mm. The inner layer is a molybdenum sheet with a thickness of 0.1-1mm.

[0035] Preferably, in S6, the extruded blank is encased in a sleeve, and the outer sleeve has dimensions of φ(270-325)×(550-650)mm (i.e., inner diameter d is (255-305)mm and height h is (510-610)mm), and an air vent of φ(3-10)mm is drilled at the center of the outer sleeve cover.

[0036] Preferably, in the heating stage of S7, the furnace temperature is controlled at a heating rate of 8-12℃ / s below 1000℃ and 5-8℃ / s above 1000℃; when the furnace temperature reaches 1275-1280℃, the holding time is 240-360min; after the holding time, the billet is coated with a layer of glass powder with a thickness of 1-2mm; the extrusion cylinder and press head are preheated to 300-400℃; at the same time, to prevent heat loss of the billet, the billet transfer time is no more than 60s.

[0037] Preferably, the extrusion parameters of the extruded billet in S7 are: extrusion rate of 20-70 mm / s, extrusion temperature selected in the (α+γ) two-phase region of the alloy, and extrusion ratio ≥22.

[0038] Preferably, the cooling method for the S7 medium-pressure billet is sand cooling.

[0039] The above technical solution has at least the following advantages compared with the existing technology:

[0040] The present invention proposes a deformable high Nb-TiAl alloy with a fine, near-γ microstructure and its preparation method, which can solve the problem of the strength-plasticity contradiction in high Nb-TiAl alloys in the prior art, so that the strength and plasticity of the alloy can be significantly improved at both room temperature and high temperature.

[0041] This invention achieves a fine, near-γ-like microstructure through a traditional hot extrusion deformation process, exhibiting high repeatability, low cost, and high efficiency. This microstructure possesses excellent room / high-temperature properties, making it of paramount importance for the engineering applications of high-Nb-TiAl alloys.

[0042] The deformable high-Nb-TiAl alloy prepared by this invention breaks the dilemma of the strength-plasticity trade-off at room temperature. Its tensile strength can reach (1092±20) MPa, its yield strength can reach (900±11) MPa, its yield strength ratio is not less than 0.81, and its room temperature plasticity can reach 3.2-5.0%, which is significantly better than the performance of TiAl alloys reported so far. At the same time, when stretched at 800℃, its plasticity can reach 56.36%, and its strength-plasticity product can reach 33.48 GPa%, which provides a better raw material for the next step of medium and high temperature (above 1000℃) or even below 1000℃ die forging.

[0043] Furthermore, the deformed high-Nb-TiAl alloy of the present invention can obtain different types of microstructures through different heat treatment methods, with a large space for microstructure adjustment, which can better match various working conditions and provide a new way to broaden industrial applications. This method can be applied to other types of TiAl-based alloys. The method is simple and can realize large-scale industrial applications in engineering.

[0044] In summary, compared with other traditional methods, the method of this invention creatively obtains a multiphase structure that is beneficial to improving room temperature and high temperature performance by adjusting the composition content and high extrusion specific heat. This allows the room temperature plasticity, strength, and high temperature yield strength ratio and strength-ductility product of the deformed high Nb-TiAl alloy to be synergistically improved. The process is simple and conducive to large-scale industrial production and widespread use. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0046] Figure 1 The following are macroscopic images of industrial-grade large ingots used in Examples 1-6 of the present invention, wherein: (a) a photograph of the as-cast state obtained after three melting and annealing treatments, and (b) a macroscopic image of the extrusion state after an extrusion ratio ≥22;

[0047] Figure 2 The diagram shows the QNG microstructure and properties of a deformed Ti45Al8Nb0.2W0.1B0.05Y alloy with a fine, near-γ microstructure, according to Example 1 of this invention. (a) The QNG microstructure is obtained when the extrusion ratio is 33:1. (b) The corresponding tensile properties are shown, where RT is room temperature tensile strength, 800℃ is 800℃ tensile strength, UTS is tensile strength, YS is yield strength, and δ is ductility.

[0048] Figure 3The diagram shows the QNG microstructure and properties of a deformed Ti45Al8Nb0.2W0.1B0.05Y alloy with a fine, near-γ microstructure, according to Example 2 of this invention. (a) The QNG microstructure is obtained when the extrusion ratio is 25:1. (b) The corresponding tensile properties are shown, where RT is room temperature tensile strength, 800℃ is 800℃ tensile strength, UTS is tensile strength, YS is yield strength, and δ is ductility.

[0049] Figure 4 The diagram shows the QNG microstructure and properties of a deformed Ti45Al8Nb0.2W0.3B0.1Y alloy with a fine, near-γ microstructure, according to Example 3 of this invention. (a) The QNG microstructure is obtained when the extrusion ratio is 22:1. (b) The corresponding tensile properties are shown, where RT is room temperature tensile strength, 800℃ is 800℃ tensile strength, UTS is tensile strength, YS is yield strength, and δ is ductility.

[0050] Figure 5 The diagram shows the QNG microstructure and properties of a deformed Ti45Al8Nb0.3W0.2B0.05Y alloy with a fine, near-γ microstructure, according to Example 4 of this invention. (a) The QNG microstructure is obtained when the extrusion ratio is 22:1. (b) The corresponding tensile properties are shown, where RT is room temperature tensile strength, 800℃ is 800℃ tensile strength, UTS is tensile strength, YS is yield strength, and δ is ductility.

[0051] Figure 6 The diagram shows the QNG microstructure and properties of a deformed Ti44Al8.5Nb0.4W0.25B0.1Y alloy with a fine, near-γ microstructure, according to Example 5 of this invention. (a) The QNG microstructure is obtained when the extrusion ratio is 30:1. (b) The corresponding tensile properties, where RT is room temperature tensile strength, 800℃ is 800℃ tensile strength, UTS is tensile strength, YS is yield strength, and δ is ductility.

[0052] Figure 7 The diagram shows the QNG microstructure and properties of a deformed Ti46Al8Nb0.2W0.2B0.02Y alloy with a fine, near-γ microstructure, according to Example 6 of this invention. (a) The QNG microstructure is obtained when the extrusion ratio is 30:1. (b) The corresponding tensile properties are shown, where RT is room temperature tensile strength, 800℃ is 800℃ tensile strength, UTS is tensile strength, YS is yield strength, and δ is ductility. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] Example 1

[0055] A wrought high Nb-TiAl alloy with a fine, near-γ microstructure, wherein the chemical composition and atomic percentage of the wrought high Nb-TiAl alloy are as follows: Al 45at%, Nb 8at%, W 0.2at%, B 0.1at%, Y 0.05at%, with the balance being Ti and unavoidable impurities; wherein the total atomic percentage of W+B+Y is 0.35at%.

[0056] The preparation method of the deformed high Nb-TiAl alloy includes the following steps:

[0057] S1: Select and weigh raw materials according to the composition of the deformed high Nb-TiAl alloy with fine, near-γ microstructure to obtain smelting raw materials;

[0058] S2: The raw materials for S1 were successively melted three times: vacuum arc melting, vacuum solidification melting, and vacuum arc melting, before being cast into an alloy ingot with a diameter of φ270×550mm. The density of the alloy ingot at room temperature was 4.11g / cm³. 3 The tensile strength is 624 MPa, the yield strength is 590 MPa, the ductility is 0.33%, and the strength-ductility product is 0.21 GPa%. When stretched at 800℃, its tensile strength is 550 MPa, the yield strength is 450 MPa, the ductility is 5.5%, and the strength-ductility product is 3.03 GPa%.

[0059] S3: The alloy ingot of S2 is subjected to stress-relief annealing at 900℃ for 24 hours, followed by furnace cooling to obtain the stress-relief ingot. Figure 1 As shown in (a), the density of the stress-relief ingot at room temperature is 4.11 g / cm³. 3 The tensile strength is 605 MPa, the yield strength is 575 MPa, the ductility is 0.6%, and the strength-ductility product is 0.36 GPa%. When stretched at 800℃, its tensile strength is 540 MPa, the yield strength is 435 MPa, the ductility is 5.9%, and the strength-ductility product is 3.19 GPa%.

[0060] S4: The surface of the stress-relief ingot of S3 is machined to remove the surface oxide scale, then polished smooth to Ra=3.2μm, and the corners are rounded to obtain an extruded billet of φ240×500mm;

[0061] S5: The extruded billet of S4 is subjected to anti-oxidation treatment. The anti-oxidation treatment is a surface coating preparation. The anti-oxidation coating is sprayed onto the billet using a spraying equipment. After spraying, it is placed in the furnace to dry. Then, after checking for omissions and filling defects, it is sprayed three times to obtain an extruded billet with surface anti-oxidation. The coating thickness is 2mm. The coating is uniform and has a strong bond with the alloy.

[0062] S6: The surface anti-oxidation extruded billet of S5 is subjected to extruded billet encapsulation treatment to obtain an encapsulated extruded billet; wherein: the extruded billet encapsulation treatment adopts a double-layer encapsulation structure, the outer encapsulation is made of stainless steel 304L material, one end is open and the other end is closed, the dimensions of the outer encapsulation are φ270×550mm (i.e. the inner diameter d is 245mm and the height h is 510mm), and a φ5mm vent hole is drilled at the center of the top cover of the outer encapsulation, with a thickness of 10mm; the inner layer is a molybdenum sheet with a thickness of 0.5mm;

[0063] S7: The extruded billet wrapped in the S6 casing undergoes pre-extrusion heating and heat preservation treatment. During the heating stage, the furnace temperature is controlled at a heating rate of 8℃ / s below 1000℃ and 5℃ / s above 1000℃. When the furnace temperature reaches 1280℃, the heat preservation time is 300min. After the heat preservation is completed, the billet is coated with a layer of glass powder with a thickness of 1mm.

[0064] Afterwards, the material is hot-deformed by extrusion and sand-cooled to room temperature. The extrusion cylinder and indenter are preheated to 350°C, the extrusion rate is 50 mm / s, the extrusion temperature is selected in the (α+γ) two-phase region of the alloy, and the extrusion ratio is 33:1. Simultaneously, to prevent heat loss from the billet, the billet transfer time is 45 s. After removing the cladding, a fine, near-γ microstructure of deformed high-Nb-TiAl alloy is obtained, such as... Figure 1 As shown in (b);

[0065] The deformed high-Nb-TiAl alloy described in this embodiment has a multiphase structure, containing an ordered L12 structured γ-TiAl phase and D0 at room temperature. 19 The structure consists of an α2-Ti3Al phase and a B2-structured β-Ti phase; the proportions of the three phases are: 77% γ-TiAl phase, 15.4% α2-Ti3Al phase, and 6.6% β-Ti phase.

[0066] like Figure 2As shown in (a), the average grain size of the deformed high Nb-TiAl alloy described in this embodiment is controlled at 8.36 μm and has a weak filamentous texture. The average size of the γ-TiAl phase is controlled at 9.1 μm, the average size of the α2-Ti3Al phase is controlled at 5.8 μm, and the average size of the β-Ti phase is controlled at 2.9 μm.

[0067] The deformed high-Nb-TiAl alloy described in this embodiment underwent room / high-temperature tensile property testing, which revealed that its density was 4.11 g / cm³ at room temperature. 3 The tensile strength is (990±20) MPa, the yield strength is (850±10) MPa, the yield ratio is not less than 0.856, the ductility is 4.8-5.02%, and the maximum strength-ductility product is 5.07 GPa%. When stretched at 800℃, its tensile strength is (569±25) MPa, the yield strength is (476±15) MPa, the yield ratio is not less than 0.836, the ductility is 56.36%, and the strength-ductility product is 33.48 GPa%. Figure 2 As shown in (b).

[0068] Example 2

[0069] A wrought high Nb-TiAl alloy with a fine, near-γ microstructure, wherein the chemical composition and atomic percentage of the wrought high Nb-TiAl alloy are as follows: Al 45at%, Nb 8at%, W 0.2at%, B 0.1at%, Y 0.05at%, with the balance being Ti and unavoidable impurities; wherein the total atomic percentage of W+B+Y is 0.35at%.

[0070] The preparation method of the deformed high Nb-TiAl alloy includes the following steps:

[0071] S1: Select and weigh raw materials according to the composition of the deformed high Nb-TiAl alloy with fine, near-γ microstructure to obtain smelting raw materials;

[0072] S2: The raw materials for S1 were successively melted three times: vacuum arc melting, vacuum solidification melting, and vacuum arc melting, before being cast into an alloy ingot with a diameter of φ270×550mm. The density of the alloy ingot at room temperature was 4.12g / cm³. 3 The tensile strength is 620 MPa, the yield strength is 585 MPa, the ductility is 0.3%, and the strength-ductility product is 0.19 GPa%. When stretched at 800℃, its tensile strength is 535 MPa, the yield strength is 440 MPa, the ductility is 5.5%, and the strength-ductility product is 2.9 GPa%.

[0073] S3: The alloy ingot of S2 is subjected to stress-relief annealing at 900℃ for 24 hours, followed by furnace cooling to obtain the stress-relief ingot. Figure 1 As shown in (a), the density of the stress-relief ingot at room temperature is 4.12 g / cm³. 3 The tensile strength is 610 MPa, the yield strength is 570 MPa, the ductility is 0.5%, and the strength-ductility product is 0.35 GPa%. When stretched at 800℃, its tensile strength is 530 MPa, the yield strength is 438 MPa, the ductility is 5.7%, and the strength-ductility product is 3.1 GPa%.

[0074] S4: The surface of the stress-relief ingot of S3 is machined to remove the surface oxide scale, then polished smooth to Ra=3.2μm, and the corners are rounded to obtain an extruded billet of φ240×500mm;

[0075] S5: The extruded billet of S4 is subjected to anti-oxidation treatment. The anti-oxidation treatment is a surface coating preparation. The anti-oxidation coating is sprayed onto the billet using a spraying equipment. After spraying, it is placed in the furnace to dry. Then, after checking for omissions and filling defects, it is sprayed three times to obtain an extruded billet with surface anti-oxidation. The coating thickness is 2mm. The coating is uniform and has a strong bond with the alloy.

[0076] S6: The surface anti-oxidation extruded billet of S5 is subjected to extruded billet encapsulation treatment to obtain an encapsulated extruded billet; wherein: the extruded billet encapsulation treatment adopts a double-layer encapsulation structure, the outer encapsulation is made of stainless steel 304L material, one end is open and the other end is closed, the dimensions of the outer encapsulation are φ270×550mm (i.e. the inner diameter d is 245mm and the height h is 510mm), and a φ5mm vent hole is drilled at the center of the top cover of the outer encapsulation, with a thickness of 10mm; the inner layer is a molybdenum sheet with a thickness of 0.5mm;

[0077] S7: The extruded billet wrapped in the S6 casing undergoes pre-extrusion heating and heat preservation treatment. During the heating stage, the furnace temperature is controlled at a heating rate of 8℃ / s below 1000℃ and 5℃ / s above 1000℃. When the furnace temperature reaches 1280℃, the heat preservation time is 300min. After the heat preservation is completed, the billet is coated with a layer of glass powder with a thickness of 1mm.

[0078] Afterwards, the material is hot-deformed by extrusion and sand-cooled to room temperature. The extrusion cylinder and indenter are preheated to 350°C, the extrusion rate is 50 mm / s, the extrusion temperature is selected in the (α+γ) two-phase region of the alloy, and the extrusion ratio is 25:1. Simultaneously, to prevent heat loss from the billet, the billet transfer time is 45 s. After removing the cladding, a fine, near-γ microstructure of deformed high-Nb-TiAl alloy is obtained, such as... Figure 1 As shown in (b);

[0079] The deformed high-Nb-TiAl alloy described in this embodiment has a multiphase structure, containing an ordered L12 structured γ-TiAl phase and D0 at room temperature. 19 The structure consists of an α2-Ti3Al phase and a B2-structured β-Ti phase; the proportions of the three phases are: 76.3% γ-TiAl phase, 16.1% α2-Ti3Al phase, and 5.9% β-Ti phase.

[0080] like Figure 3 As shown in (a), the average grain size of the deformed high Nb-TiAl alloy described in this embodiment is controlled at 11.54 μm and has a weak filamentous texture. The average size of the γ-TiAl phase is controlled at 14.5 μm, the average size of the α2-Ti3Al phase is controlled at 7.3 μm, and the average size of the β-Ti phase is controlled at 5.7 μm.

[0081] The deformed high-Nb-TiAl alloy described in this embodiment underwent room / high-temperature tensile property testing, which revealed that its density was 4.12 g / cm³ at room temperature. 3 The tensile strength is (985±23) MPa, the yield strength is (855±10) MPa, the yield ratio is not less than 0.868, the ductility is 3.6%, and the maximum strength-ductility product is 3.63 GPa%. When stretched at 800℃, its tensile strength is (560±25) MPa, the yield strength is (470±16) MPa, the yield ratio is not less than 0.838, the ductility is 30.12%, and the strength-ductility product is 17.62 GPa%. Figure 3 As shown in (b).

[0082] Example 3

[0083] A wrought high Nb-TiAl alloy with a fine, near-γ microstructure, wherein the chemical composition and atomic percentage of the wrought high Nb-TiAl alloy are as follows: Al 45at%, Nb 8at%, W 0.2at%, B 0.3at%, Y 0.1at, with the balance being Ti and unavoidable impurities; wherein the total atomic percentage of W+B+Y is 0.6at%.

[0084] The preparation method of the deformed high Nb-TiAl alloy includes the following steps:

[0085] S1: Select and weigh raw materials according to the composition of the deformed high Nb-TiAl alloy with fine, near-γ microstructure to obtain smelting raw materials;

[0086] S2: The raw materials for S1 were successively melted three times: vacuum arc melting, vacuum solidification melting, and vacuum arc melting, before being cast into an alloy ingot with a diameter of φ270×550mm. The density of the alloy ingot at room temperature was 4.12g / cm³. 3The tensile strength is 635 MPa, the yield strength is 590 MPa, the ductility is 0.25%, and the strength-ductility product is 0.16 GPa%. When stretched at 800℃, its tensile strength is 540 MPa, the yield strength is 450 MPa, the ductility is 3.5%, and the strength-ductility product is 1.9 GPa%.

[0087] S3: The alloy ingot of S2 is subjected to stress-relief annealing at 850℃ for 36 hours, followed by furnace cooling to obtain the stress-relief ingot. Figure 1 As shown in (a), the density of the stress-relief ingot at room temperature is 4.12 g / cm³. 3 The tensile strength is 620 MPa, the yield strength is 570 MPa, the ductility is 0.45%, and the strength-ductility product is 0.28 GPa%. When stretched at 800℃, its tensile strength is 530 MPa, the yield strength is 438 MPa, the ductility is 5.7%, and the strength-ductility product is 3.1 GPa%.

[0088] S4: The surface of the stress-relief ingot of S3 is machined to remove the surface oxide scale, then polished smooth to Ra=3.2μm, and the corners are rounded to obtain an extruded billet of φ240×500mm;

[0089] S5: The extruded billet of S4 is subjected to anti-oxidation treatment. The anti-oxidation treatment is a surface coating preparation. The anti-oxidation coating is sprayed onto the billet using a spraying equipment. After spraying, it is placed in the furnace to dry. Then, after checking for omissions and filling defects, it is sprayed three times to obtain an extruded billet with surface anti-oxidation. The coating thickness is 2mm. The coating is uniform and has a strong bond with the alloy.

[0090] S6: The surface anti-oxidation extruded billet of S5 is subjected to extruded billet encapsulation treatment to obtain an extruded billet encapsulated in an encapsulated manner; wherein: the extruded billet encapsulation treatment adopts a double-layer encapsulation structure, the outer encapsulation is made of stainless steel 304L material, one end is open and the other end is closed, the dimensions of the outer encapsulation are φ270×550mm (i.e., the inner diameter d is 245mm and the height h is 510mm), and a φ7mm vent hole is drilled at the center of the top cover of the outer encapsulation, with a thickness of 10mm; the inner layer is a molybdenum sheet with a thickness of 0.5mm;

[0091] S7: The extruded billet wrapped in the S6 casing undergoes pre-extrusion heating and heat preservation treatment. During the heating stage, the furnace temperature is controlled at a heating rate of 8℃ / s below 1000℃ and 5℃ / s above 1000℃. When the furnace temperature reaches 1280℃, the heat preservation time is 300min. After the heat preservation is completed, the billet is coated with a layer of glass powder with a thickness of 1.5mm.

[0092] Afterwards, the material was hot-deformed by extrusion and sand-cooled to room temperature. The extrusion cylinder and indenter were preheated to 350°C, the extrusion rate was 50 mm / s, the extrusion temperature was selected in the (α+γ) two-phase region of the alloy, and the extrusion ratio was 22:1. At the same time, to prevent heat loss of the billet, the billet transfer time was 45 s. After removing the cladding, a deformed high Nb-TiAl alloy with a fine microstructure similar to that of near-γ was obtained.

[0093] The deformed high-Nb-TiAl alloy described in this embodiment has a multiphase structure, containing an ordered L12 structured γ-TiAl phase and D at room temperature. 019 The structure consists of an α2-Ti3Al phase and a B2-structured β-Ti phase; the proportions of the three phases are: 77.5% γ-TiAl phase, 15.8% α2-Ti3Al phase, and 5.9% β-Ti phase.

[0094] like Figure 4 As shown in (a), the average grain size of the deformed high Nb-TiAl alloy described in this embodiment is controlled at 14.97 μm and has a weak filamentous texture. The average size of the γ-TiAl phase is controlled at 20.5 μm, the average size of the α2-Ti3Al phase is controlled at 8.6 μm, and the average size of the β-Ti phase is controlled at 11.5 μm.

[0095] The deformed high-Nb-TiAl alloy described in this embodiment underwent room / high-temperature tensile property testing, which revealed that its density was 4.12 g / cm³ at room temperature. 3 The tensile strength is (950±20) MPa, the yield strength is (865±11) MPa, the yield ratio is not less than 0.91, the ductility is 3.36%, and the maximum strength-ductility product is 3.19 GPa%. When stretched at 800℃, its tensile strength is (558±18) MPa, the yield strength is (482±11) MPa, the yield ratio is not less than 0.86, the ductility is 27.12%, and the strength-ductility product is 15.13 GPa%. Figure 4 As shown in (b).

[0096] Example 4

[0097] A wrought high Nb-TiAl alloy with a fine, near-γ microstructure, wherein the chemical composition and atomic percentage of the wrought high Nb-TiAl alloy are as follows: Al 45at%, Nb 8at%, W 0.3at%, B 0.2at%, Y 0.05at%, with the balance being Ti and unavoidable impurities; wherein the total atomic percentage of W+B+Y is 0.55at%.

[0098] The preparation method of the deformed high Nb-TiAl alloy includes the following steps:

[0099] S1: Select and weigh raw materials according to the composition of the deformed high Nb-TiAl alloy with fine, near-γ microstructure to obtain smelting raw materials;

[0100] S2: The raw materials for S1 were successively melted three times: vacuum arc melting, vacuum solidification melting, and vacuum arc melting, before being cast into an alloy ingot with a diameter of φ260×560mm. The density of the alloy ingot at room temperature was 4.14g / cm³. 3 The tensile strength is 630 MPa, the yield strength is 590 MPa, the ductility is 0.33%, and the strength-ductility product is 0.21 GPa%. When stretched at 800℃, its tensile strength is 540 MPa, the yield strength is 442 MPa, the ductility is 5.7%, and the strength-ductility product is 3.08 GPa%.

[0101] S3: The alloy ingot of S2 is subjected to stress-relief annealing at 900℃ for 24 hours, followed by furnace cooling to obtain the stress-relief ingot. Figure 1 As shown in (a), the density of the stress-relief ingot at room temperature is 4.14 g / cm³. 3 The tensile strength is 623 MPa, the yield strength is 565 MPa, the ductility is 0.52%, and the strength-ductility product is 0.32 GPa%. When stretched at 800℃, its tensile strength is 525 MPa, the yield strength is 438 MPa, the ductility is 6.0%, and the strength-ductility product is 3.15 GPa%.

[0102] S4: The surface of the stress-relief ingot of S3 is machined to remove the surface oxide scale, then polished smooth to Ra=6.3μm, and the corners are rounded to obtain an extruded billet of φ240×520mm;

[0103] S5: The extruded billet of S4 is subjected to anti-oxidation treatment. The anti-oxidation treatment is a surface coating preparation. The anti-oxidation coating is sprayed onto the billet using a spraying equipment. After spraying, it is placed in the furnace to dry. Then, after checking for omissions and filling defects, it is sprayed three times to obtain an extruded billet with surface anti-oxidation. The coating thickness is 2mm. The coating is uniform and has a strong bond with the alloy.

[0104] S6: The surface anti-oxidation extruded billet of S5 is subjected to extruded billet encapsulation treatment to obtain an encapsulated extruded billet; wherein: the extruded billet encapsulation treatment adopts a double-layer encapsulation structure, the outer encapsulation is made of stainless steel 304L material, one end is open and the other end is closed, the dimensions of the outer encapsulation are φ270×570mm (i.e. the inner diameter d is 245mm and the height h is 530mm), and a φ5mm vent hole is drilled at the center of the top cover of the outer encapsulation, with a thickness of 10mm; the inner layer is a molybdenum sheet with a thickness of 0.5mm;

[0105] S7: The extruded billet wrapped in the S6 casing undergoes pre-extrusion heating and heat preservation treatment. During the heating stage, the furnace temperature is controlled at a heating rate of 8℃ / s below 1000℃ and 5℃ / s above 1000℃. When the furnace temperature reaches 1280℃, the heat preservation time is 300min. After the heat preservation is completed, the billet is coated with a layer of glass powder with a thickness of 1.5mm.

[0106] Afterwards, the material is hot-deformed by extrusion and sand-cooled to room temperature. The extrusion cylinder and indenter are preheated to 350°C, the extrusion rate is 50 mm / s, the extrusion temperature is selected in the (α+γ) two-phase region of the alloy, and the extrusion ratio is 22:1. Simultaneously, to prevent heat loss from the billet, the billet transfer time is 45 s. After removing the cladding, a fine, near-γ microstructure of deformed high-Nb-TiAl alloy is obtained, such as... Figure 1 As shown in (b);

[0107] The deformed high-Nb-TiAl alloy described in this embodiment has a multiphase structure, containing an ordered L12 structured γ-TiAl phase and D0 at room temperature. 19 The structure consists of an α2-Ti3Al phase and a B2-structured β-Ti phase; the proportions of the three phases are: 79.0% γ-TiAl phase, 14.5% α2-Ti3Al phase, and 5.3% β-Ti phase.

[0108] In this embodiment, the average grain size of the deformed high-Nb-TiAl alloy is controlled at 18.36 μm, and it exhibits a weak fibrous texture. The average size of the γ-TiAl phase is controlled at 27.1 μm, the average size of the α2-Ti3Al phase is controlled at 10.3 μm, and the average size of the β-Ti phase is controlled at 14.6 μm. Figure 5 As shown in (a).

[0109] The deformed high-Nb-TiAl alloy described in this embodiment underwent room / high-temperature tensile property testing, which revealed that its density was 4.14 g / cm³ at room temperature. 3 The tensile strength is (947±22) MPa, the yield strength is (854±13) MPa, the yield ratio is not less than 0.9, the ductility is 3.2%, and the maximum strength-ductility product is 3.03 GPa%. When stretched at 800℃, its tensile strength is (680±17) MPa, the yield strength is (570±13) MPa, the yield ratio is not less than 0.83, the ductility is 22.96%, and the strength-ductility product is 15.61 GPa%. Figure 5 As shown in (b).

[0110] Example 5

[0111] A wrought high Nb-TiAl alloy with a fine, near-γ microstructure, wherein the chemical composition and atomic percentage of the wrought high Nb-TiAl alloy are as follows: Al 44at%, Nb 8.5at%, W 0.4at%, B 0.25at%, Y 0.1at, with the balance being Ti and unavoidable impurities; wherein the total atomic percentage of W+B+Y is 0.75at%.

[0112] The preparation method of the deformed high Nb-TiAl alloy includes the following steps:

[0113] S1: Select and weigh raw materials according to the composition of the deformed high Nb-TiAl alloy with fine, near-γ microstructure to obtain smelting raw materials;

[0114] S2: The raw materials for S1 were successively melted three times: vacuum arc melting, vacuum solidification melting, and vacuum arc melting, before being cast into an alloy ingot with a diameter of φ320×530mm. The density of the alloy ingot at room temperature was 4.17g / cm³. 3 The tensile strength is 648 MPa, the yield strength is 589 MPa, the ductility is 0.28%, and the strength-ductility product is 0.18 GPa%. When stretched at 800℃, its tensile strength is 605 MPa, the yield strength is 545 MPa, the ductility is 3.3%, and the strength-ductility product is 2.0 GPa%.

[0115] S3: The alloy ingot of S2 was subjected to stress-relief annealing at 850℃ for 36 hours, followed by furnace cooling to obtain a stress-relief ingot; the density of the stress-relief ingot at room temperature was 4.17 g / cm³. 3 The tensile strength is 640 MPa, the yield strength is 578 MPa, the ductility is 0.30%, and the strength-ductility product is 0.19 GPa%. When stretched at 800℃, its tensile strength is 612 MPa, the yield strength is 550 MPa, the ductility is 3.7%, and the strength-ductility product is 2.26 GPa%.

[0116] S4: The surface of the stress-relief ingot of S3 is machined to remove the surface oxide scale, then polished smooth to Ra=6.0μm, and the corners are rounded to obtain an extruded billet of φ296×500mm;

[0117] S5: The extruded billet of S4 is subjected to anti-oxidation treatment. The anti-oxidation treatment is a surface coating preparation. The anti-oxidation coating is sprayed onto the billet using a spraying equipment. After spraying, it is placed in the furnace to dry. Then, after checking for omissions and filling defects, it is sprayed three times to obtain an extruded billet with surface anti-oxidation. The coating thickness is 3mm. The coating is uniform and has a strong bond with the alloy.

[0118] S6: The surface anti-oxidation extrusion blank of S5 is subjected to extrusion blank encapsulation treatment to obtain an extrusion blank encapsulated in an encapsulated manner; wherein: the extrusion blank encapsulation treatment adopts a double-layer encapsulation structure, the outer encapsulation is made of stainless steel 304L material, one end is open and the other end is closed, the size of the outer encapsulation is φ320×560mm (i.e. the inner diameter d is 300mm and the height h is 510mm), and a φ10mm vent hole is drilled at the center of the top cover of the outer encapsulation, with a thickness of 10mm, and the inner layer is a molybdenum sheet with a thickness of 0.5mm;

[0119] S7: The extruded billet wrapped in the S6 casing undergoes pre-extrusion heating and heat preservation treatment. During the heating stage, the furnace temperature is controlled at a heating rate of 10℃ / s below 1000℃ and 6℃ / s above 1000℃. When the furnace temperature reaches 1275℃, the heat preservation time is 360min. After the heat preservation is completed, the billet is coated with a layer of glass powder with a thickness of 2mm.

[0120] Afterwards, the material is hot-deformed by extrusion and sand-cooled to room temperature. The extrusion cylinder and indenter are preheated to 400°C, the extrusion rate is 30 mm / s, the extrusion temperature is selected in the (α+γ) two-phase region of the alloy, and the extrusion ratio is 30:1. At the same time, in order to prevent heat loss of the billet, the billet transfer time is not greater than 60 s. After removing the cladding, a fine, near-γ microstructure of deformed high Nb-TiAl alloy is obtained.

[0121] The deformed high-Nb-TiAl alloy described in this embodiment has a multiphase structure, containing an ordered L12 structured γ-TiAl phase and D0 at room temperature. 19 The structure consists of an α2-Ti3Al phase and a B2-structured β-Ti phase; the proportions of the three phases are: 79.5% γ-TiAl phase, 16.3% α2-Ti3Al phase, and 3.9% β-Ti phase.

[0122] like Figure 6 As shown in (a), the average grain size of the deformed high Nb-TiAl alloy described in this embodiment is controlled at 9.5 μm and has a weak filamentous texture. The average size of the γ-TiAl phase is controlled at 13.25 μm, the average size of the α2-Ti3Al phase is controlled at 7.1 μm, and the average size of the β-Ti phase is controlled at 4.7 μm.

[0123] The deformed high-Nb-TiAl alloy described in this embodiment underwent room / high-temperature tensile property testing, which revealed that its density was 4.17 g / cm³ at room temperature. 3The tensile strength is (1078±19) MPa, the yield strength is (900±11) MPa, the yield ratio is not less than 0.83, the ductility is 3.32%, and the strength-ductility product is 3.57 GPa%. When stretched at 800℃, its tensile strength is (554±23) MPa, the yield strength is (478±15) MPa, the yield ratio is not less than 0.86, the ductility is 51.22%, and the strength-ductility product is 28.3 GPa%. Figure 6 As shown in (b).

[0124] Example 6

[0125] A wrought high Nb-TiAl alloy with a fine, near-γ microstructure, wherein the chemical composition and atomic percentage of the wrought high Nb-TiAl alloy are as follows: Al 46at%, Nb 8at%, W 0.2at%, B 0.2at%, Y 0.02at%, with the balance being Ti and unavoidable impurities; wherein the total atomic percentage of W+B+Y is 0.42at%.

[0126] The preparation method of the deformed high Nb-TiAl alloy includes the following steps:

[0127] S1: Select and weigh raw materials according to the composition of the deformed high Nb-TiAl alloy with fine, near-γ microstructure to obtain smelting raw materials;

[0128] S2: The raw materials for S1 were successively melted three times: vacuum arc melting, vacuum solidification melting, and vacuum arc melting, before being cast into an alloy ingot with a diameter of φ320×550mm. The density of the alloy ingot at room temperature was 4.13g / cm³. 3 The tensile strength is 640 MPa, the yield strength is 580 MPa, the ductility is 0.3%, and the strength-ductility product is 0.19 GPa%. When stretched at 800℃, the tensile strength is 610 MPa, the yield strength is 540 MPa, the ductility is 3.8%, and the strength-ductility product is 2.3 GPa%.

[0129] S3: The alloy ingot of S2 was subjected to stress-relief annealing at 800℃ for 36 hours, followed by furnace cooling to obtain a stress-relief ingot; the density of the stress-relief ingot at room temperature was 4.13 g / cm³. 3 The tensile strength is 630 MPa, the yield strength is 565 MPa, the ductility is 0.42%, and the strength-ductility product is 0.26 GPa%. When stretched at 800℃, its tensile strength is 610 MPa, the yield strength is 524 MPa, the ductility is 4.2%, and the strength-ductility product is 2.56 GPa%.

[0130] S4: The surface of the stress-relief ingot of S3 is machined to remove the surface oxide scale, then polished smooth to Ra=5.5μm, and the corners are rounded to obtain an extruded billet of φ296×510mm;

[0131] S5: The extruded billet of S4 is subjected to anti-oxidation treatment. The anti-oxidation treatment is a surface coating preparation. The anti-oxidation coating is sprayed onto the billet using a spraying equipment. After spraying, it is placed in the furnace to dry. Then, after checking for omissions and filling defects, three sprayings are performed to obtain an extruded billet with surface anti-oxidation. The coating thickness is 2.5mm, and the coating is uniform and has strong adhesion to the alloy.

[0132] S6: The surface anti-oxidation extrusion blank of S5 is subjected to extrusion blank encapsulation treatment to obtain an extrusion blank encapsulated in an encapsulated manner; wherein: the extrusion blank encapsulation treatment adopts a double-layer encapsulation structure, the outer encapsulation is made of stainless steel 304L material, one end is open and the other end is closed, the size of the outer encapsulation is φ320×570mm (i.e. the inner diameter d is 300mm and the height h is 520mm), and a φ10mm vent hole is drilled at the center of the top cover of the outer encapsulation, with a thickness of 10mm, and the inner layer is a molybdenum sheet with a thickness of 0.5mm;

[0133] S7: The extruded billet wrapped in the S6 casing undergoes pre-extrusion heating and heat preservation treatment. During the heating stage, the furnace temperature is controlled at a heating rate of 10℃ / s below 1000℃ and 6℃ / s above 1000℃. When the furnace temperature reaches 1275℃, the heat preservation time is 360min. After the heat preservation is completed, the billet is coated with a layer of glass powder with a thickness of 2mm.

[0134] Afterwards, the material is hot-deformed by extrusion and sand-cooled to room temperature. The extrusion cylinder and indenter are preheated to 400°C, the extrusion rate is 30 mm / s, the extrusion temperature is selected in the (α+γ) two-phase region of the alloy, and the extrusion ratio is 30:1. At the same time, in order to prevent heat loss of the billet, the billet transfer time is not greater than 60 s. After removing the cladding, a fine, near-γ microstructure of deformed high Nb-TiAl alloy is obtained.

[0135] The deformed high-Nb-TiAl alloy described in this embodiment has a multiphase structure, containing an ordered L12 structured γ-TiAl phase and D0 at room temperature. 19 The structure consists of an α2-Ti3Al phase and a B2-structured β-Ti phase; the proportions of the three phases are: 77.8% γ-TiAl phase, 15.6% α2-Ti3Al phase, and 5.6% β-Ti phase.

[0136] like Figure 7As shown in (a), the average grain size of the deformed high Nb-TiAl alloy described in this embodiment is controlled at 10.21 μm and has a weak filamentous texture. The average size of the γ-TiAl phase is controlled at 14.3 μm, the average size of the α2-Ti3Al phase is controlled at 6.8 μm, and the average size of the β-Ti phase is controlled at 5.1 μm.

[0137] The deformed high-Nb-TiAl alloy described in this embodiment underwent room / high-temperature tensile property testing, which revealed that its density was 4.13 g / cm³ at room temperature. 3 The tensile strength is (1092±20) MPa, the yield strength is (886±14) MPa, the yield ratio is not less than 0.81, the ductility is 3.04%, and the strength-ductility product is 3.3 GPa%. When stretched at 800℃, its tensile strength is (560±21) MPa, the yield strength is (472±14) MPa, the ductility is 48.92%, and the strength-ductility product is 27.4 GPa%. Figure 7 As shown in (b).

[0138] The present invention proposes a deformable high Nb-TiAl alloy with a fine, near-γ microstructure and its preparation method, which can solve the problem of the strength-plasticity contradiction in high Nb-TiAl alloys in the prior art, so that the strength and plasticity of the alloy can be significantly improved at both room temperature and high temperature.

[0139] This invention achieves a fine, near-γ-like microstructure through a traditional hot extrusion deformation process, exhibiting high repeatability, low cost, and high efficiency. This microstructure possesses excellent room / high-temperature properties, making it of paramount importance for the engineering applications of high-Nb-TiAl alloys.

[0140] The deformable high-Nb-TiAl alloy prepared by this invention breaks the dilemma of the strength-plasticity trade-off at room temperature. Its tensile strength can reach (1092±20) MPa, its yield strength can reach (900±11) MPa, its yield strength ratio is not less than 0.81, and its room temperature plasticity can reach 3.2-5.0%, which is significantly better than the performance of TiAl alloys reported so far. At the same time, when stretched at 800℃, its plasticity can reach 56.36%, and its strength-plasticity product can reach 33.48 GPa%, which provides a better raw material for the next step of medium and high temperature (above 1000℃) or even below 1000℃ die forging.

[0141] Furthermore, the deformed high-Nb-TiAl alloy of the present invention can obtain different types of microstructures through different heat treatment methods, with a large space for microstructure adjustment, which can better match various working conditions and provide a new way to broaden industrial applications. This method can be applied to other types of TiAl-based alloys. The method is simple and can realize large-scale industrial applications in engineering.

[0142] In summary, compared with other traditional methods, the method of this invention creatively obtains a multiphase structure that is beneficial to improving room temperature and high temperature performance by adjusting the composition content and high extrusion specific heat. This allows the room temperature plasticity, strength, and high temperature yield strength ratio and strength-ductility product of the deformed high Nb-TiAl alloy to be synergistically improved. The process is simple and conducive to large-scale industrial production and widespread use.

[0143] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A deformed high-Nb-TiAl alloy of a fine similar near-gamma structure, characterized in that, The chemical composition and atomic percentage of the deformed high-Nb-TiAl alloy are as follows: Al 43-48 at%, Nb 5-10 at%, W 0-0.5 at%, B 0-0.5 at%, Y 0-0.3 at%, and the balance of Ti and inevitable impurities; wherein the atomic percentage of W, B and Y cannot be 0, and the total atomic percentage of W+B+Y is between 0.3-1.0 at%. The preparation method adopts the process of vacuum self-consumption arc melting + vacuum condensate melting + vacuum self-consumption arc melting + casting + stress relief annealing + removal of surface oxide skin + anti-oxidation treatment + cladding + large extrusion ratio hot extrusion deformation in the (α+γ) two-phase region. The extrusion parameters of the extrusion blank are as follows: the extrusion rate is 20-70 mm / s, the extrusion temperature is selected in the (α+γ) two-phase region of the alloy, and the extrusion ratio is greater than or equal to 22. The average grain size of the deformed high-Nb-TiAl alloy is controlled to be 2-30 μm, and the alloy has weak wire texture; the average size of the γ-TiAl phase is controlled to be 5-30 μm, the average size of the α2-Ti3Al phase is controlled to be 5-15 μm, and the average size of the β-Ti phase is controlled to be 2-20 μm. The deformed high-Nb-TiAl alloy has a multi-phase structure, containing an ordered L12 structure γ-TiAl phase, a D0 19 structure α2-Ti3Al phase, and a B2 structure β-Ti phase at room temperature; the three-phase proportions are respectively: 70-80% of the γ-TiAl phase, 10-20% of the α2-Ti3Al phase, and 2-10% of the β-Ti phase. The deformed high-Nb-TiAl alloy is subjected to room / high temperature tensile property test, and it is found that at room temperature, the density of the alloy is 4.0-4.2 g / cm 3 , the tensile strength is 950-1100 MPa, the yield strength is 800-910 MPa, the ductility is 3.00-5.00%, and the product of strength and plasticity is 2.85-5.0 GPa%; at 800 DEG C, the tensile strength is 550-650 MPa, the yield strength is 450-550 MPa, the ductility is 22.96-56.36%, and the product of strength and plasticity is 15.5-33.5 GPa%.

2. A method for producing a wrought high-Nb-TiAl alloy based on the fine similar near-gamma texture according to claim 1, characterized by, The preparation method of the deformed high-Nb-TiAl alloy comprises the following steps: S1: selecting and proportioning the raw materials according to the composition of the deformed high-Nb-TiAl alloy with fine similar near-γ structure to obtain smelting raw materials; S2: sequentially subjecting the smelting raw materials of S1 to three times of smelting of vacuum self-consumption arc melting, vacuum condensate melting and vacuum self-consumption arc melting, and then casting to obtain an alloy ingot; S3: subjecting the alloy ingot of S2 to stress relief annealing treatment to obtain a stress relief ingot; S4: subjecting the surface of the stress relief ingot of S3 to machining treatment for removing the surface oxide skin, and then polishing and rounding the corners to obtain an extrusion blank; S5: subjecting the extrusion blank of S4 to anti-oxidation treatment to obtain a surface anti-oxidation extrusion blank; S6: subjecting the surface anti-oxidation extrusion blank of S5 to extrusion blank cladding treatment to obtain a cladded extrusion blank; S7: subjecting the cladded extrusion blank of S6 to temperature rising and holding treatment before extrusion, and then extruding hot deformation and cooling to room temperature, and removing the cladding to obtain the deformed high-Nb-TiAl alloy with fine similar near-γ structure.

3. The method for preparing the deformed high-Nb-TiAl alloy with a fine, near-γ microstructure according to claim 2, characterized in that, The temperature of the stress relief annealing treatment in S3 is 700-900 °C, and the time is 12-36 h.

4. The method for preparing the deformed high-Nb-TiAl alloy with a fine, near-γ microstructure according to claim 2, characterized in that, The machining treatment for removing the surface oxide skin in S4 comprises turning, rough turning, finish turning and rough grinding, and the polishing is Ra=3.2-6.3 μm.

5. The method for preparing the deformed high-Nb-TiAl alloy with a fine, near-γ microstructure according to claim 2, characterized in that, The anti-oxidation treatment in S5 comprises surface coating preparation, anti-oxidation heat treatment, surface anti-oxidation powder adhesion and surface chemical anti-oxidation treatment.

6. The method of claim 2, wherein the deformed high-Nb TiAl alloy having a fine similar near γ structure is prepared by the steps of: preparing a TiAl alloy containing 5-20 wt% of Nb; and heat-treating the TiAl alloy at a temperature of 900-1100°C for 1-10 hours. The extrusion blank cladding treatment in S6 adopts a double-layer cladding structure, the outer cladding adopts stainless steel 304L material, one end is open and the other end is closed, the cladding height-diameter ratio is controlled to be 2:1-4:1, the thickness is 5-15 mm, and the inner layer is molybdenum sheet with a thickness of 0.1-1 mm.

7. The method for preparing the deformed high-Nb-TiAl alloy with a fine, near-γ microstructure according to claim 2, characterized in that, In S7, the temperature control in the heating stage, the heating rate is 8-12℃ / s below 1000℃, and the heating rate is 5-8℃ / s above 1000℃; when the furnace temperature is heated to 1275-1280℃, the holding time is 240-360min; after the holding is finished, the blank is wrapped with a layer of glass powder with a thickness of 1-2mm; the extrusion cylinder and the pressure head are preheated to 300-400℃; at the same time, the heat loss of the blank is prevented, and the blank transfer time is not more than 60s.

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