A β-solidifying γ-TiAl high-temperature titanium alloy and its preparation method

Abstract

The present invention belongs to the technical field of superalloys, and particularly relates to a β-solidifying γ-TiAl high-temperature titanium alloy. Further, it also relates to a preparation method of the β-solidifying γ-TiAl high-temperature titanium alloy. A β-solidifying γ-TiAl high-temperature titanium alloy provided by the present invention is composed of the following components by mass percentage: Al: 43% - 46%, Nb: 4% - 8%, Mn: 1% - 2%, Cr: 1% - 2%, B ≤ 1% and La ≤ 1%, and B and La are not 0; the balance is Ti and inevitable impurity elements. The solidification path of this alloy does not pass through the α-phase region, but only passes through the β-phase region, thus avoiding the peritectic reaction region, and can increase the diversity of the lamellar colony orientation during β-solidification, effectively refine the microstructure, eliminate the casting texture and avoid the problem of high and low density inclusions, obtaining a titanium alloy ingot with uniform composition and microstructure. This alloy can fully meet the usage requirements in the fields of aerospace, military industry, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of superalloys, and particularly relates to a β-solidifying γ-TiAl high-temperature titanium alloy. Further, it also relates to a preparation method of the β-solidifying γ-TiAl high-temperature titanium alloy. Background Art

[0002] Compared with traditional nickel-based alloys, the TiAl high-temperature titanium alloy has the advantages of low density, high specific strength, good high-temperature oxidation resistance, etc., making it a highly competitive material for heat-resistant structural parts in aerospace, aviation, and automotive engines.

[0003] With the continuous update and iteration in the fields of aerospace, military, etc., there are higher requirements for materials used in key parts such as aerospace engines. Therefore, it has become an inevitable trend to use TiAl high-temperature titanium alloys to replace traditional nickel-based alloy materials to achieve large-scale weight reduction of components and at the same time increase their working temperature. Summary of the Invention

[0004] The present invention is made based on the inventor's discovery and understanding of the following facts and problems:

[0005] At present, traditional TiAl high-temperature titanium alloys have defects such as poor room-temperature fracture toughness and plasticity. Therefore, based on traditional γ-TiAl high-temperature titanium alloys, designing a β-solidifying γ-TiAl high-temperature titanium alloy to coordinate the high-temperature plastic deformation of TiAl high-temperature titanium alloys, improve their low room-temperature plasticity, fracture toughness, and overcome the difficulties of thermomechanical processing at high temperatures has always been an important difficulty to be solved for TiAl high-temperature titanium alloys.

[0006] The embodiments of the present invention propose a β-solidifying γ-TiAl high-temperature titanium alloy. The solidification path of this alloy does not pass through the α-phase region, only through the β-phase region, thus avoiding the peritectic reaction zone. And when β-solidifying, it can increase the diversity of lamellar colony orientations, effectively refine the microstructure, eliminate the casting texture, and avoid the problem of high and low density inclusions, obtaining a titanium alloy ingot with uniform composition and microstructure.

[0007] A β-solidifying γ-TiAl high-temperature titanium alloy according to an embodiment of the present invention is composed of the following components by mass percentage: Al: 43% - 46%, Nb: 4% - 8%, Mn: 1% - 2%, Cr: 1% - 2%, B ≤ 1% and La ≤ 1%, and B and La are not 0; the balance is Ti and unavoidable impurity elements.

[0008] The advantages and technical effects brought by the β-solidified γ-TiAl high-temperature titanium alloy according to the embodiments of the present invention are as follows: 1. For the high-temperature titanium alloy according to the embodiments of the present invention, by adjusting the components and the content of each component in the alloy, the solidification path of the alloy does not pass through the α-phase region but only through the β-phase region, thus avoiding the peritectic reaction region, and increasing the diversity of the lamellar cluster orientation during β-solidification, effectively refining the microstructure, eliminating the casting texture and excluding the problems of high and low density inclusions, and obtaining a titanium alloy ingot with uniform composition and microstructure; 2. For the high-temperature titanium alloy according to the embodiments of the present invention, the added La element will combine with the oxygen element in the matrix to form La 2 O 3 , which not only absorbs the oxygen in the matrix to purify the matrix, but also forms heterogeneous nucleation sites during solidification, refines the grains, and the fine La-rich phase can play a role in solid solution strengthening.

[0009] In some embodiments, the mass percentage ratio of the Mn element to the Nb element is (0.8 - 1.0):4.

[0010] In some embodiments, the mass percentage ratio of the Mn element to the Cr element is (0.8 - 1.2):1.

[0011] In some embodiments, the mass percentage ratio of the B element to the La element is 1 - 2:2 - 1.

[0012] In some embodiments, the β-solidified γ-TiAl high-temperature titanium alloy is composed of the following components by mass percentage: Al: 43% - 46%, Nb: 4% - 8%, Mn: 1% - 2%, Cr: 1% - 2%, B: 0.3% - 1% and La: 0.5% - 1%; the balance is Ti and unavoidable impurity elements.

[0013] The embodiments of the present invention also provide a preparation method for a β-solidified γ-TiAl high-temperature titanium alloy, including the following steps:

[0014] (1) Mix the raw materials evenly according to the designed ratio and press them into electrode blocks. After vacuum welding the electrode blocks, melt them in a triple vacuum consumable arc furnace to obtain a high-temperature titanium alloy ingot;

[0015] (2) Perform homogenization annealing treatment and hot isostatic pressing treatment on the high-temperature titanium alloy ingot obtained in step (1) in sequence to obtain a β-solidified γ-TiAl high-temperature titanium alloy blank;

[0016] (3) Perform cogging forging and hot forging on the blank obtained in step (2) to obtain a β-solidified γ-TiAl high-temperature titanium alloy forging blank.

[0017] Advantages and technical effects brought by the preparation method of the β-solidified γ-TiAl high-temperature titanium alloy according to the embodiments of the present invention: 1. Compared with the traditional melting method of vacuum consumable arc furnace + skull furnace + vacuum consumable arc furnace, the method according to the embodiments of the present invention can effectively reduce the melting cost, and at the same time solve the matching problem between the ingot type and the crucible during the melting process. The prepared TiAl high-temperature titanium alloy has good comprehensive mechanical properties; 2. In the method according to the embodiments of the present invention, defects such as porosity and shrinkage cavity usually appear in the ingot after vacuum melting. Therefore, the obtained ingot needs to be processed to eliminate the defects therein, so that the as-cast alloy can obtain a uniform solidification structure and stable mechanical properties. By performing homogenization annealing treatment on the alloy, the segregation of Al element and β in the structure can be improved, and at the same time the stress concentration caused by rapid cooling after melting can be eliminated; 3. In the method according to the embodiments of the present invention, the prepared β-solidified γ-TiAl high-temperature titanium alloy still has good mechanical properties in an ultra-high temperature environment with a maximum temperature of 800 °C, which can fully meet the usage requirements of high-temperature titanium alloys in the fields of aerospace, military, etc.

[0018] In some embodiments, in the step (1), the raw materials are titanium metal, aluminum metal, aluminum-niobium alloy, aluminum-molybdenum alloy, aluminum-chromium alloy, aluminum-boron alloy, and lanthanum metal.

[0019] In some embodiments, in the step (2), the temperature of the homogenization annealing is 850-950 °C, and the annealing time is 18-24 h.

[0020] In some embodiments, in the step (2), the temperature of the hot isostatic pressing treatment is 1200-1300 °C, the pressure is 135-145 °C, and the treatment time is 4-5 h.

[0021] In some embodiments, in the step (3), the temperature of the cogging forging is 1350 °C - 1450 °C, and the temperature of the hot forging is 1150 °C - 1350 °C. Detailed Embodiments

[0022] The embodiments of the present invention will be described in detail below, which are intended to explain the present invention and should not be construed as a limitation to the present invention.

[0023] A β-solidified γ-TiAl high-temperature titanium alloy according to an embodiment of the present invention is composed of the following components by mass percentage: Al: 43% - 46%, Nb: 4% - 8%, Mn: 1% - 2%, Cr: 1% - 2%, B ≤ 1% and La ≤ 1%, B and La are not 0; the balance is Ti and unavoidable impurity elements.

[0024] In the β-solidifying γ-TiAl high-temperature titanium alloy according to the embodiments of the present invention, by adjusting the components and the contents of the components in the alloy, the solidification path of the alloy does not pass through the α-phase region but only through the β-phase region, thereby avoiding the peritectic reaction region, and the diversity of the lamellar cluster orientation can be increased during β solidification, effectively refining the microstructure, eliminating the casting texture and excluding the problems of high and low density inclusions, and obtaining a titanium alloy ingot with uniform composition and microstructure; the added La element combines with the oxygen element in the matrix to form La 2 O 3 , which not only absorbs the oxygen in the matrix to purify the matrix, but also forms heterogeneous nucleation sites during solidification, refines the grains, and the fine La-rich phase can play a role in solid solution strengthening.

[0025] In some embodiments, preferably, the mass percentage ratio of the Mn element to the Nb element is (0.8-1.0):4.

[0026] In the embodiments of the present invention, by controlling the mass percentages of the Mn element and the Nb element, not only can the formation of brittle intermetallic compounds by the Al element be inhibited, but also the c / a ratio of the lattice parameter of the α-phase can be reduced, which is beneficial to the slip of the α-phase, and the plasticity of the titanium alloy can be improved while ensuring the high-temperature performance, so that it has good processing performance.

[0027] In some embodiments, preferably, the mass percentage ratio of the Mn element to the Cr element is (0.8-1.2):1.

[0028] In the embodiments of the present invention, by controlling the mass percentages of the Mn element and the Cr element, the electron concentration of the alloy can be increased by controlling the ratio of Mn to Cr elements, strengthening the metallic bond, thereby improving the plasticity of the alloy.

[0029] In some embodiments, preferably, the mass percentage ratio of the B element to the La element is 1:2-2:1.

[0030] In the embodiments of the present invention, by adding the B element and controlling the addition ratio of the B element to the La element, the lamellar size in the solidified structure of the alloy gradually decreases, the segregation of the Al element can be significantly improved, the columnar crystal is transformed into an equiaxed crystal, α 2 and the γ-phase content increases, the β / β0-phase content decreases, significantly improving the room-temperature and high-temperature strength and elongation of the alloy, and improving the high-temperature fatigue performance, so that the β-solidifying γ-TiAl high-temperature titanium alloy has good forming performance and has the value of industrial production.

[0031] In some embodiments, preferably, the β-solidifying γ-TiAl high-temperature titanium alloy is composed of the following components by mass percentage: Al: 43% - 46%, Nb: 4% - 8%, Mn: 1% - 2%, Cr: 1% - 2%, B: 0.3% - 1% and La: 0.5% - 1%; the balance is Ti and inevitable impurity elements. Further preferably, the mass percentage of B is 0.5% - 1%; the mass percentage of La is 0.5% - 0.6%.

[0032] The embodiment of the present invention also provides a preparation method of a β-solidifying γ-TiAl high-temperature titanium alloy, comprising the following steps:

[0033] (1) Mix the raw materials evenly according to the designed ratio and press them into electrode blocks. After vacuum welding the electrode blocks, melt them in a triple vacuum consumable arc furnace to obtain a high-temperature titanium alloy ingot;

[0034] (2) Perform homogenization annealing treatment and hot isostatic pressing treatment on the high-temperature titanium alloy ingot obtained in the step (1) in sequence to obtain a β-solidifying γ-TiAl high-temperature titanium alloy blank;

[0035] (3) Perform cogging forging and hot forging on the blank obtained in the step (2) to obtain a β-solidifying γ-TiAl high-temperature titanium alloy forging blank.

[0036] The preparation method of the β-solidifying γ-TiAl high-temperature titanium alloy in the embodiment of the present invention, compared with the traditional melting method of vacuum consumable arc furnace + skull furnace + vacuum consumable arc furnace, can effectively reduce the melting cost, and at the same time solve the matching problem between the ingot type and the crucible during the melting process. The prepared TiAl high-temperature titanium alloy still has good comprehensive mechanical properties; after vacuum melting, the ingot usually has defects such as porosity and shrinkage cavity. Therefore, it is necessary to process the obtained ingot to eliminate the defects therein, so that the as-cast alloy can obtain a uniform solidification structure and stable mechanical properties. By performing homogenization annealing treatment on the alloy, the segregation of Al element and β in the structure can be improved, and at the same time the stress concentration caused by rapid cooling after melting can be eliminated; the prepared β-solidifying γ-TiAl high-temperature titanium alloy has good mechanical properties in an ultra-high temperature environment with a maximum temperature of 800°C, and can fully meet the usage requirements of high-temperature titanium alloys in the fields of aerospace, military, etc.

[0037] In some embodiments, preferably, in the step (1), the raw materials are metallic titanium, metallic aluminum, aluminum niobium alloy, aluminum molybdenum alloy, aluminum chromium alloy, aluminum boron alloy and metallic lanthanum. Further preferably, the metallic titanium is 0A grade military small titanium grains.

[0038] In some embodiments, preferably, in step (2), the temperature of the homogenization annealing is 850 - 950 °C, and the annealing time is 18 - 24 h. Further preferably, in step (2), the temperature of the hot isostatic pressing treatment is 1200 - 1300 °C, the pressure is 135 - 145 MPa, and the treatment time is 4 - 5 h.

[0039] In the implementation of the present invention, the treatment processes of homogenization annealing and hot isostatic pressing are further optimized, which can improve the Al element and β segregation in the structure, eliminate the stress concentration caused by rapid cooling after melting, and improve the treatment efficiency, making it more suitable for industrial production applications.

[0040] In some embodiments, preferably, in step (2), the β-solidifying γ-TiAl high-temperature titanium alloy blank is obtained by peeling the surface of the ingot, cutting off the riser end and the bottom.

[0041] In the embodiments of the present invention, by treating the surface of the alloy ingot, the surface contaminants on the ingot surface can be removed, ensuring that the ingot surface is flat and smooth, improving the cleanliness of the forging process, and further ensuring that the alloy has good comprehensive properties.

[0042] In some embodiments, preferably, in step (3), the temperature of the cogging forging is 1350 °C - 1450 °C, and the temperature of the high-temperature forging is 1150 °C - 1350 °C. Further preferably, in step (3), both the cogging forging and the high-temperature forging are one squat and one draw. Still further preferably, in step (3), both the cogging forging and the high-temperature forging are carried out on a hydraulic forging machine.

[0043] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0044] Example 1

[0045] (1) Mix A-grade military small-grain titanium, aluminum particles, aluminum-niobium alloy, aluminum-molybdenum alloy, aluminum-chromium alloy, aluminum-boron alloy, and lanthanum metal evenly according to the design ratio, and press them into electrode blocks, each weighing 12 Kg, with a total of 12 blocks. After vacuum welding the electrode blocks, store them in a drying oven, and then melt them using a three-time vacuum consumable melting furnace to obtain a high-temperature titanium alloy ingot;

[0046] (2) Perform homogenization annealing treatment on the obtained high-temperature titanium alloy ingot at 900 °C for 24 h; then perform hot isostatic pressing treatment on the ingot at a temperature of 1200 °C and a pressure of 135 MPa for 4 h. Subsequently, peel the surface of the ingot and cut off the riser end and the bottom to obtain a new type of β-solidifying γ-TiAl high-temperature titanium alloy blank;

[0047] (3) The obtained blank is subjected to cogging forging and hot forging on a hydraulic forging machine to obtain a forged blank of a new rare earth β-solidified γ-TiAl high-temperature titanium alloy. The temperature of cogging forging is 1400 °C, and the temperature of hot forging is 1300 °C.

[0048] The alloy composition prepared in Example 1 is shown in Table 1, and the performance is shown in Table 2.

[0049] The preparation methods of Examples 2 to 12 and Comparative Examples 1 to 2 are the same as that of Example 1. The difference lies in the alloy composition. The alloy compositions prepared in Examples 2 to 12 and Comparative Examples 1 to 2 are shown in Table 1, and the performance is shown in Table 2.

[0050] Table 1

[0051] Al(％) Nb(%) Mn(%) Cr(％) B(％) La(%) Ti(%) Example 1 43 4 1 1 0.3 0.5 remainder Example 2 46 8 2 2 0.3 0.5 remainder Example 3 43 4 1 1 1 1 remainder Example 4 46 8 2 2 1 1 remainder Example 5 43 4 1 1 1 0.5 remainder Example 6 46 8 2 2 1 0.5 remainder Example 7 43 4 1 1 0.5 0.6 remainder Example 8 46 8 2 2 0.5 0.6 remainder Example 9 46 6 2 2 0.5 0.6 remainder Example 10 43 4 1 2 0.5 0.6 remainder Example 11 43 4 1 1 0.3 1 remainder Example 12 43 4 1 1 1 0.3 remainder Comparative Example 1 43 4 1 1 0.5 0 remainder Comparative Example 2 43 4 1 1 0.5 1.5 remainder

[0052] Table 2

[0053]

[0054] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0055] Although the above embodiments have been shown and described, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made by those of ordinary skill in the art to the above embodiments are within the protection scope of the present invention.

Claims

1. A β-solidified γ-TiAl high-temperature titanium alloy, characterized in that, it consists of the following components by mass percentage as follows: Al: 43% - 46%, Nb: 4% - 8%, Mn: 1% - 2%, Cr: 1% - 2%, B ≤ 1% and La ≤ 1%, and B and La are not 0; the balance is Ti and unavoidable impurity elements; the mass percentage ratio of the B element to the La element is 1:2 - 2:

1.

2. The β-solidified γ-TiAl high-temperature titanium alloy according to claim 1, characterized in that, the mass percentage ratio of the Mn element to the Nb element is (0.8 - 1.0):

4.

3. The β-solidified γ-TiAl high-temperature titanium alloy according to claim 1, characterized in that, the mass percentage ratio of the Mn element to the Cr element is (0.8 - 1.2):

1.

4. The β-solidified γ-TiAl high-temperature titanium alloy according to claim 1, characterized in that, the β-solidified γ-TiAl high-temperature titanium alloy consists of the following components by mass percentage as follows: Al: 43% - 46%, Nb: 4% - 8%, Mn: 1% - 2%, Cr: 1% - 2%, B: 0.3% - 1% and La: 0.5% - 1%; the balance is Ti and unavoidable impurity elements.

5. A preparation method of the β-solidified γ-TiAl high-temperature titanium alloy according to any one of claims 1 - 4, characterized in that, it includes the following steps: (1) Mix the raw materials evenly according to the designed ratio and press them into electrode blocks. After vacuum welding the electrode blocks, use a triple vacuum consumable arc furnace to melt and obtain a high-temperature titanium alloy ingot; (2) Carry out homogenization annealing treatment and hot isostatic pressing treatment on the high-temperature titanium alloy ingot obtained in step (1) in sequence to obtain a β-solidified γ-TiAl high-temperature titanium alloy blank; (3) Carry out cogging forging and hot forging on the blank obtained in step (2) to obtain a β-solidified γ-TiAl high-temperature titanium alloy forging blank.

6. The preparation method of the β-solidified γ-TiAl high-temperature titanium alloy according to claim 5, characterized in that, in step (2), the temperature of the homogenization annealing is 850 - 950 °C, and the annealing time is 18 - 24 h.

7. The preparation method of the β-solidified γ-TiAl high-temperature titanium alloy according to claim 5 or 6, characterized in that, in step (2), the temperature of the hot isostatic pressing treatment is 1200 - 1300 °C, the pressure is 135 - 145 MPa, and the treatment time is 4 - 5 h.

8. The preparation method of the β-solidified γ-TiAl high-temperature titanium alloy according to claim 5, characterized in that, in step (3), the temperature of the cogging forging is 1350 °C - 1450 °C, and the temperature of the hot forging is 1150 °C - 1350 °C.

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