A heat treatment method of a Ti2AlNb alloy plate

Abstract

The application relates to the technical field of alloy materials, in particular to a heat treatment method of a Ti2AlNb alloy plate. The heat treatment method of the Ti2AlNb alloy plate comprises the following steps: heat treating the Ti2AlNb alloy plate, wherein the heat treatment comprises first heat treatment, second heat treatment and third heat treatment; the holding temperature T1 of the first heat treatment is 960-1030 DEG C, and the holding time is 1-4 h; the holding temperature T2 of the second heat treatment is 880-950 DEG C, and the holding time is 1-8 h; the holding temperature T3 of the third heat treatment is 760-840 DEG C, and the holding time is 2-48 h. According to the heat treatment method, the strain in the deformation process is uniformly distributed through the uniform distribution of the O-phase laths on the B2 / β phase, stress concentration can be avoided, a good match between the strength and the toughness can be obtained, the precision requirement of the furnace temperature is reduced, the process is simple, and the stability is high.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, and more specifically, to a heat treatment method for Ti2AlNb alloy plates. Background Technology

[0002] Ti2AlNb alloy is a lightweight, heat-resistant structural material that can be used for extended periods at temperatures ranging from 600℃ to 750℃ or for short-term applications at even higher temperatures. As an intermetallic compound alloy, Ti2AlNb alloy possesses excellent high-temperature specific strength and specific modulus due to its long-range ordered crystal structure and strong bonding between metal atoms, while also exhibiting good creep resistance. These superior properties make it a promising candidate for aerospace structural materials, significantly contributing to improving the thrust-to-weight ratio, fuel efficiency, and high-temperature performance of aircraft.

[0003] Ti2AlNb alloys typically consist of two or three phases: O, B2 / β, and α2. The phase composition and content of the alloy can vary significantly due to changes in hot working processes, composition, and heat treatment regimes. The phase equilibrium in Ti2AlNb alloys is a multi-phase equilibrium, and its phase equilibrium process is highly complex. The phase transformation process is also very sensitive to thermal response, and microstructural parameters such as phase composition and content significantly affect the alloy's mechanical properties. To obtain superior overall performance, deformed Ti2AlNb alloys are generally subjected to a dual heat treatment regime of solution treatment and aging. After this treatment, Ti2AlNb alloys exhibit a significant inverse relationship between strength and toughness. To achieve a better balance between strength and toughness, process parameters such as the temperature and cooling rate of the solution heat treatment must be strictly controlled. Improper control can lead to significant performance fluctuations, severely restricting its engineering applications in aerospace structural components.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] One objective of this invention is to provide a heat treatment method for Ti2AlNb alloy plates, addressing the technical problem that existing heat treatment methods for Ti2AlNb alloy plates struggle to achieve a good balance between strength and toughness, resulting in unsatisfactory overall performance. The heat treatment method for Ti2AlNb alloy plates of this invention achieves uniform strain distribution during deformation through the uniform distribution of multi-scale O-phase laths on the B2 / β phase, avoiding stress concentration, achieving a good balance between strength and toughness, reducing the precision requirements for furnace temperature, simplifying the process, and demonstrating high stability.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0007] A heat treatment method for Ti2AlNb alloy plates includes the following steps:

[0008] Ti2AlNb alloy sheet is heat-treated, including a first heat treatment, a second heat treatment, and a third heat treatment, to obtain a heat-treated Ti2AlNb sheet. The holding temperature T1 of the first heat treatment is 960–1030℃, and the holding time is 1–4 h. The holding temperature T2 of the second heat treatment is 880–950℃, and the holding time is 1–8 h. The holding temperature T3 of the third heat treatment is 760–840℃, and the holding time is 2–48 h.

[0009] In some embodiments, the holding temperature T1 of the first heat treatment is 970-1000℃, and the holding time is 1-3h; the holding temperature T2 of the second heat treatment is 900-945℃, and the holding time is 1-5h; the holding temperature T3 of the third heat treatment is 770-810℃, and the holding time is 8-30h.

[0010] In some embodiments, the holding temperature T1 of the first heat treatment is 975-990℃ and the holding time is 1.5-2.5h; the holding temperature T2 of the second heat treatment is 900-945℃ and the holding time is 1.5-4h; and the holding temperature T3 of the third heat treatment is 770-810℃ and the holding time is 15-26h.

[0011] In some embodiments, the temperature difference between the holding temperature T1 of the first heat treatment and the holding temperature T2 of the second heat treatment satisfies: 20℃≤T1-T2≤150℃; the temperature difference between the holding temperature T2 of the second heat treatment and the holding temperature T3 of the third heat treatment satisfies: 40℃≤T2-T3≤190℃;

[0012] In some embodiments, the method further includes performing a first cooling treatment on the Ti2AlNb alloy plate after the first heat treatment.

[0013] In some embodiments, the Ti2AlNb alloy sheet after the second heat treatment is subjected to a second cooling treatment.

[0014] In some embodiments, the Ti2AlNb alloy sheet after the third heat treatment is subjected to a third cooling treatment.

[0015] In some embodiments, the first cooling process, the second cooling process, and the third cooling process each independently include at least one of furnace temperature-controlled cooling, air cooling, and liquid quenching.

[0016] In some embodiments, the preparation method of the Ti2AlNb alloy plate specifically includes the following steps: subjecting the Ti2AlNb alloy forged slab to a first rolling, a first annealing, a second rolling, a cladding rolling, and post-treatment; the temperature of the first rolling is higher than the temperature of the second rolling.

[0017] In some embodiments, the thickness of the Ti2AlNb alloy plate is 0.8–4 mm.

[0018] In some embodiments, the temperature of the first rolling is 990–1100°C.

[0019] In some embodiments, the thickness of the sheet obtained after the first rolling is 20 to 30 mm.

[0020] In some embodiments, the annealing temperature is 980–1060°C, and the annealing time is 1–4 hours.

[0021] In some embodiments, the temperature of the second rolling is 850–960°C, and the rolling time is 10–180 min.

[0022] In some embodiments, the thickness of the sheet obtained after the second rolling is 4 to 10 mm.

[0023] In some embodiments, the temperature of the cladding rolling is 850–960°C, and the cladding rolling time is 60–180 min.

[0024] In some embodiments, the post-processing includes a second annealing, leveling, sanding, and pickling, wherein the temperature of the second annealing and the leveling are each independently 800-900°C, and the time of the second annealing and the leveling are each independently 10-120 min.

[0025] In some embodiments, the microstructure of the heat-treated plate includes a plurality of O-phase laths, the length of the O-phase laths in the long axis direction is 0.3 to 10 μm, and the length in the short axis direction is 0.05 to 4 μm; the volume fraction of the O-phase laths is 45% to 80%.

[0026] In some embodiments, the heat-treated sheet has a tensile strength of 950–1200 MPa, a yield strength of 800–1050 MPa, and an elongation of 6%–15% under a test condition of 23°C.

[0027] In some embodiments, the heat-treated sheet has a tensile strength of 750–950 MPa, a yield strength of 600–850 MPa, an elongation of 10%–30% under a test condition of 650°C, and a durability of 80–200 h at 360 MPa.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The heat treatment method for Ti2AlNb alloy plates of this invention employs a combination of suitable first, second, and third heat treatment conditions to obtain a Ti2AlNb alloy microstructure with multi-scale O-phase laths. The first heat treatment is a solution treatment, which dissolves the O phase in the original microstructure, resulting in an α2+B2 two-phase microstructure, providing a better matrix structure for subsequent aging treatment to precipitate the O phase. The second and third heat treatments are both aging treatments. The second heat treatment, under suitable conditions, is held at a higher temperature range in the O+B2 two-phase region, precipitating coarse O-phase laths. The third heat treatment, under suitable conditions, is held at a lower temperature range in the O+B2 two-phase region, precipitating fine O-phase laths. This invention achieves uniform strain distribution during deformation through the uniform distribution of multi-scale O-phase laths on the B2 / β phase, avoiding stress concentration and resulting in a good balance between strength and toughness. Meanwhile, the above heat treatment process reduces the precision requirements of furnace temperature, and the process is simple to implement, highly stable, and suitable for the preparation of Ti2AlNb alloys with good strength and toughness matching. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a microstructure diagram of the Ti2AlNb heat-treated plate material in Example 1 of the present invention;

[0032] Figure 2 This is a rolled microstructure image of the Ti2AlNb alloy sheet in Example 1 of the present invention;

[0033] Figure 3 This is a microstructure image of the Ti2AlNb alloy plate after annealing and leveling in Example 1 of the present invention;

[0034] Figure 4 This is a microstructure diagram of the Ti2AlNb heat-treated plate material in Comparative Example 1 of the present invention. Detailed Implementation

[0035] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0036] According to one aspect of the present invention, the present invention relates to a heat treatment method for Ti2AlNb alloy sheet, comprising the following steps:

[0037] Ti2AlNb alloy sheet is heat-treated, the heat treatment including a first heat treatment, a second heat treatment and a third heat treatment, to obtain a heat-treated sheet; the holding temperature T1 of the first heat treatment is 960-1030℃, and the holding time of the first heat treatment is 1-4h; the holding temperature T2 of the second heat treatment is 880-950℃, and the holding time of the second heat treatment is 1-8h; the holding temperature T3 of the third heat treatment is 760-840℃, and the holding time of the third heat treatment is 2-48h.

[0038] This invention addresses Ti2AlNb alloy sheets with good superplasticity that are finally rolled in the O+B2 two-phase region. To improve the comprehensive mechanical properties of Ti2AlNb alloy sheets with good superplasticity, a heat treatment method is provided. This invention employs a combination of suitable first, second, and third heat treatment conditions to obtain a Ti2AlNb alloy microstructure with multi-scale O-phase laths. The first heat treatment is a solution treatment, which dissolves the O phase in the original microstructure, obtaining an α2+B2 two-phase microstructure. This provides a better matrix structure for subsequent aging treatment to precipitate the O phase. In some embodiments, the holding temperature T1 of the first heat treatment is 960–1030℃, including but not limited to 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, or any value within a range of two. In some embodiments, the holding time of the first heat treatment is 1 to 4 hours, including but not limited to 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any value between two of these. Both the second and third heat treatments are aging treatments. Through the second heat treatment under suitable conditions, holding at a higher temperature range in the O+B2 two-phase region can precipitate coarse O-phase laths. In some embodiments, the holding temperature T2 of the second heat treatment is 880 to 950°C, including but not limited to 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, or any value between two of these. The holding time of the second heat treatment is 1 to 8 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or any value between two of these. Through the third heat treatment under suitable conditions, holding at a lower temperature range in the O+B2 two-phase region can precipitate fine... In some embodiments, the holding temperature T3 of the third heat treatment for small O-phase laths is 760–840°C, including but not limited to 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, or 840°C, or any value between two of these. The holding time of the third heat treatment is 2–48 hours, including but not limited to 2 hours, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, or 48 hours, or any value between two of these. This invention achieves uniform strain distribution during deformation through the uniform distribution of multi-scale O-phase laths on the B2 / β phase, avoiding stress concentration and thus achieving a good match between strength and toughness. Simultaneously, the above heat treatment process reduces the precision requirements of furnace temperature, is simple to implement, and has high stability, making it suitable for the preparation of Ti2AlNb alloys with a good match between strength and toughness.

[0039] In some embodiments, the microstructure of the heat-treated plate includes a plurality of O-phase laths, wherein the length of the O-phase laths in the long axis direction is 0.3 to 10 μm (e.g., 0.3 μm, 0.5 μm, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, etc.), and the length in the short axis direction is 0.05 to 4 μm (e.g., 0.05 μm, 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, etc.); and the volume fraction of the O-phase laths is 45% to 80% (e.g., 45%, 50%, 55%, 60%, 65%, 68%, 70%, 72%, 75%, or 80%, etc.).

[0040] In some embodiments, the holding temperature T1 of the first heat treatment is 970-1000℃, and the holding time is 1-3h; the holding temperature T2 of the second heat treatment is 900-945℃, and the holding time is 1-5h; the holding temperature T3 of the third heat treatment is 770-810℃, and the holding time is 8-30h.

[0041] In some embodiments, the holding temperature T1 of the first heat treatment is 975-990℃ and the holding time is 1.5-2.5h; the holding temperature T2 of the second heat treatment is 900-945℃ and the holding time is 1.5-4h; and the holding temperature T3 of the third heat treatment is 770-810℃ and the holding time is 15-26h.

[0042] In some embodiments, the temperature difference between the holding temperature T1 of the first heat treatment and the holding temperature T2 of the second heat treatment satisfies: 20℃≤T1-T2≤150℃, where T1-T2 can be, for example, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, or any range between the two. In some embodiments, the temperature difference between the holding temperature T2 of the second heat treatment and the holding temperature T3 of the third heat treatment satisfies the following condition: 400℃ ≤ T2 - T3 ≤ 190℃. T2 - T3 can be, for example, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 105℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, or any range between the two. The temperature difference between the holding temperature T1 of the first heat treatment and the holding temperature T2 of the second heat treatment, and the temperature difference between the holding temperature T2 of the second heat treatment and the holding temperature T3 of the third heat treatment, respectively satisfying the above ranges, is more conducive to ensuring the uniform precipitation of multi-scale O phase in the Ti2AlNb alloy, and to achieving uniform strain distribution during deformation, avoiding stress concentration, thereby obtaining a Ti2AlNb alloy with a good match between strength and toughness.

[0043] In some embodiments, the process further includes: performing a first cooling treatment on the Ti2AlNb alloy sheet after the first heat treatment. In some embodiments, performing a second cooling treatment on the Ti2AlNb alloy sheet after the second heat treatment. In some embodiments, performing a third cooling treatment on the Ti2AlNb alloy sheet after the third heat treatment. The first cooling treatment, the second cooling treatment, and the third cooling treatment each independently include at least one of furnace-controlled cooling, air cooling, and liquid quenching. Liquid quenching includes oil quenching or quenching with an aqueous solution of PAG (polyethylene glycol) of a certain concentration.

[0044] In some embodiments, the preparation method of the Ti2AlNb alloy sheet specifically includes the following steps: subjecting the Ti2AlNb alloy forged slab to a first rolling, a first annealing, a second rolling, a cladding rolling, and post-treatment; the temperature of the first rolling is higher than the temperature of the second rolling. In some embodiments, the temperature of the first rolling is 990–1100℃, for example, 990℃, 1000℃, 1050℃, 1100℃, etc. The thickness of the sheet obtained after the first rolling is 20–30 mm, for example, 20 mm, 22 mm, 25 mm, 28 mm, or 30 mm, etc. The annealing temperature is 980–1060℃, for example, 980℃, 990℃, 1000℃, 1020℃, 1040℃, 1060℃, etc., and the annealing time is 1–4 hours, for example, 1 hour, 2 hours, 3 hours, or 4 hours, etc. The second rolling temperature is 850–960℃, for example, 850℃, 870℃, 880℃, 900℃, 910℃, 920℃, 930℃, 950℃, 960℃, etc., and the second rolling time is 10–180 min, for example, 10 min, 20 min, 50 min, 100 min, 120 min, or 180 min, etc. The thickness of the sheet obtained after the second rolling is 4–10 mm, for example, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm, etc. The cladding rolling temperature is 850–960℃, for example, 850℃, 880℃, 900℃, 920℃, 950℃, 960℃, etc., and the cladding rolling time is 60–180 min, for example, 60 min, 70 min, 90 min, 100 min, 110 min, 120 min, 150 min, or 180 min, etc. The post-processing includes a second annealing, leveling, sanding, and pickling. The temperatures for the second annealing and leveling are each independently 800–900°C, such as 800°C, 820°C, 850°C, 880°C, or 900°C. The times for the second annealing and leveling are each independently 10–120 min, such as 10 min, 20 min, 50 min, 70 min, 100 min, or 120 min. In the preparation method of Ti2AlNb alloy plates, the final rolling in the O+B2 two-phase region is to refine the grains, obtain an equiaxed structure, and improve superplasticity.

[0045] In some embodiments, the preparation method of Ti2AlNb alloy sheet specifically includes: (a) high-temperature initial rolling of the billet: The Ti2AlNb alloy forged slab is first initially rolled near the β phase transformation point at a temperature range of 990–1100°C. The holding time is determined according to the slab thickness, and the holding coefficient is calculated as 0.3–0.8 min / mm. Depending on the slab thickness, one or more rolling passes can be performed to roll the forged slab into a sheet with a thickness of 20–30 mm. (b) high-temperature annealing of the slab: The initially rolled sheet is subjected to high-temperature annealing treatment at a temperature of 980–1060°C for a holding time of 1–4 h. After holding, it is cooled by air cooling or oil quenching. (c) Low-temperature rolling of sheet metal: The high-temperature annealed sheet metal is rolled in the O+B2 two-phase region. The holding temperature before rolling is 850-960℃, and the holding time is determined according to the sheet thickness. The holding coefficient is calculated at 0.3-0.8 min / mm, and the specific holding time is 10-180 min. The sheet metal is rolled to a thickness of 4-10 mm. Multiple rolling cycles or online reheating can be performed as needed. (d) Sheet metal cladding rolling and subsequent treatment: The low-temperature rolled sheet metal is ground, cut, and pickled before being clad. The cladding rolling temperature is 850-960℃, and the holding time is 60-180 min. After rolling, the cladding is removed to obtain the rolled sheet metal. The rolled sheet metal is then annealed and leveled. The annealing and leveling temperatures are 800-900℃, and the holding times are 10-120 min, respectively. The leveled sheet metal is then sanded and pickled to obtain Ti2AlNb alloy sheet metal with a thickness of 0.8-4 mm.

[0046] In some embodiments, the heat-treated sheet has a tensile strength of 950–1200 MPa (e.g., 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, etc.) under a test condition of 23°C, a yield strength of 800–1050 MPa (e.g., 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, etc.), and an elongation of 6%–15% (e.g., 6%, 9%, 12%, 13%, or 15%, etc.). In some embodiments, the heat-treated sheet exhibits a tensile strength of 750–950 MPa (e.g., 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, etc.) under a test condition of 650°C, a yield strength of 600–850 MPa (e.g., 600 MPa, 650 MPa, 750 MPa, 800 MPa, 850 MPa, etc.), an elongation of 10%–30% (e.g., 10%, 15%, 20%, 25%, 30%, etc.), and a creep rupture at 360 MPa of 80–200 h (e.g., 80 h, 100 h, 120 h, 160 h, or 200 h, etc.). The Ti2AlNb heat-treated sheet obtained by the heat treatment method of the present invention possesses suitable strength and toughness, and excellent comprehensive mechanical properties.

[0047] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0048] Example 1

[0049] A heat treatment method for Ti2AlNb alloy plates includes the following steps:

[0050] (1) Preparation of Ti2AlNb alloy plate:

[0051] a) High-temperature initial rolling of slab: The Ti2AlNb alloy forged slab is first rolled near the β phase transformation point at an initial rolling temperature of 1050℃. The heat preservation coefficient is calculated as 0.5min / mm. The forged slab is rolled into a plate with a thickness of 25mm.

[0052] b) High-temperature annealing of slabs: The initially rolled slabs are subjected to high-temperature annealing treatment at 1030℃ for 2.5 hours. After holding, they are cooled by air cooling or oil quenching.

[0053] c) Low-temperature rolling of sheet metal: The high-temperature annealed sheet metal is rolled in the O+B2 two-phase region. The holding temperature before rolling is 960℃, the holding coefficient is calculated as 0.5min / mm, and the specific holding time is 100min. The sheet metal is rolled into a thickness of 6mm. Multiple rolling processes or online reheating can be performed as needed.

[0054] d) Sheet cladding rolling and subsequent processing: Low-temperature rolled sheets are ground, cut, and pickled before being clad. The cladding rolling temperature is 960℃, and the holding time is 110 min. After rolling, the sheets are unpacked to obtain the rolled sheet. The microstructure of the rolled sheet is shown in [reference needed]. Figure 2 The rolled sheet was annealed and leveled at 850℃ and 850℃ respectively, with a holding time of 60 min. The leveled sheet was then sanded and pickled to obtain a 2 mm thick Ti2AlNb alloy sheet. The microstructure of the annealed and leveled sheet is shown in the figure. Figure 3 .

[0055] (2) The Ti2AlNb alloy plate obtained in step (1) is subjected to heat treatment, which includes a first heat treatment, a second heat treatment and a third heat treatment.

[0056] First heat treatment: Tensile specimens were cut from a 2mm thick Ti2AlNb alloy plate. Six tensile specimens with dimensions of 2mm thickness × width × length = 160mm × 26mm and three creep specimens with dimensions of 2mm thickness × width × length = 121mm × 25mm were cut. After sealing with a quartz tube, the first heat treatment was carried out at a temperature of 980℃ for 2 hours. After the first heat treatment, air cooling was performed.

[0057] Second heat treatment: Take the quartz tube that has undergone the first heat treatment and perform a second heat treatment. The temperature of the second heat treatment is 940℃ and the time is 2 hours. After the second heat treatment, air cooling is used.

[0058] Third heat treatment: Take the quartz tube that has undergone the second heat treatment and perform the third heat treatment. The temperature of the third heat treatment is 780℃ and the time is 24 hours. After the third heat treatment, air cooling is used.

[0059] The microstructure of the Ti2AlNb heat-treated plate after the third heat treatment is shown in the figure. Figure 1 The dimensions of the laths along the long axis range from 0.3 μm to 10 μm, and the dimensions along the short axis range from 0.05 μm to 4 μm. The volume fraction of the precipitated laths is 70%.

[0060] Example 2

[0061] A heat treatment method for Ti2AlNb alloy plates differs from that in Example 1 in that:

[0062] The temperature of the first heat treatment is 970℃, and the time of the first heat treatment is 3 hours.

[0063] The second heat treatment temperature is 900℃, and the second heat treatment time is 5 hours.

[0064] The temperature of the third heat treatment is 770℃, and the time of the third heat treatment is 30h.

[0065] The microstructure of the Ti2AlNb alloy plate after the third heat treatment shows that the size of the laths in the long axis direction is 0.3μm to 8μm, the size in the short axis direction is 0.03μm to 3μm, and the volume fraction of the precipitated laths is 73%.

[0066] Example 3

[0067] A heat treatment method for Ti2AlNb alloy plates differs from that in Example 1 in that:

[0068] The temperature of the first heat treatment is 1000℃, and the time of the first heat treatment is 1.5h.

[0069] The second heat treatment temperature is 945℃, and the second heat treatment time is 1.5h.

[0070] The temperature of the third heat treatment is 810℃, and the time of the third heat treatment is 8 hours.

[0071] The microstructure of the Ti2AlNb alloy plate after the third heat treatment shows that the size of the laths in the long axis direction is 0.3μm to 9μm, the size in the short axis direction is 0.08μm to 4.3μm, and the volume fraction of the precipitated laths is 68%.

[0072] Example 4

[0073] A heat treatment method for Ti2AlNb alloy plates differs from that in Example 1 in that:

[0074] The temperature of the first heat treatment is 960℃, and the time of the first heat treatment is 4 hours.

[0075] The second heat treatment temperature is 880℃, and the second heat treatment time is 8 hours.

[0076] The temperature of the third heat treatment is 760℃, and the time of the third heat treatment is 48h.

[0077] The microstructure of the Ti2AlNb alloy plate after the third heat treatment shows that the size of the laths in the long axis direction is 0.2μm to 6μm, the size in the short axis direction is 0.01μm to 3μm, and the volume fraction of the precipitated laths is 76%.

[0078] Example 5

[0079] A heat treatment method for Ti2AlNb alloy plates differs from that in Example 1 in that:

[0080] The temperature of the first heat treatment is 1030℃, and the time of the first heat treatment is 1 hour.

[0081] The second heat treatment temperature is 950℃, and the second heat treatment time is 1 hour.

[0082] The temperature of the third heat treatment is 840℃, and the time of the third heat treatment is 2 hours.

[0083] The microstructure of the Ti2AlNb alloy plate after the third heat treatment shows that the size of the laths in the long axis direction is 0.3μm to 10μm, the size in the short axis direction is 0.06μm to 4.6μm, and the volume fraction of the precipitated laths is 63%.

[0084] Comparative Example 1

[0085] A heat treatment method for Ti2AlNb alloy plates differs from that in Example 1 in that:

[0086] In step (2), the obtained Ti2AlNb alloy plate is subjected to heat treatment, which includes a first heat treatment and a second heat treatment. The temperature of the first heat treatment is 960℃ and the time is 2h. After the first heat treatment, it is air-cooled. The temperature of the second heat treatment is 800℃ and the time is 24h. After the second heat treatment, it is air-cooled.

[0087] The microstructure of the Ti2AlNb alloy plate obtained in this comparative example is shown in the figure below. Figure 4 As shown.

[0088] Comparative Example 2

[0089] A heat treatment method for Ti2AlNb alloy plates differs from that in Example 1 in that:

[0090] The temperature of the first heat treatment is 1050℃, and the time of the first heat treatment is 0.5h.

[0091] The second heat treatment temperature is 850℃, and the second heat treatment time is 10h.

[0092] The temperature of the third heat treatment is 700℃, and the time of the third heat treatment is 50h.

[0093] Experimental Example

[0094] The Ti2AlNb alloy sheet from Example 1 that was not heat-treated was subjected to superplasticity tests (tensile strength and elongation), and the test results are shown in Table 1.

[0095] The Ti2AlNb alloy plates of each embodiment and comparative example were subjected to room temperature tensile property tests, 650℃ tensile property tests, and 650℃ / 350MPa creep rupture property tests, as follows:

[0096] Samples were processed and room temperature tensile properties were tested in accordance with the requirements of national standard GB / T 228.1.

[0097] Samples were processed and tensile properties were tested at 650℃ according to the requirements of national standard GB / T 228.2.

[0098] The durability test specimens were processed and tested at 650℃ / 350MPa in accordance with the requirements of the national standard GB / T 2039.

[0099] The performance test results of the heat-treated Ti2AlNb alloy sheet are shown in Table 2.

[0100] Table 1. Superplasticity test results of Ti2AlNb alloy sheets without heat treatment

[0101]

[0102] As shown in Table 1, the Ti2AlNb alloy sheet without heat treatment in Example 1 of the present invention has good superplasticity.

[0103] Table 2 Test Results

[0104]

[0105]

[0106] As shown in Table 2, the heat treatment method for Ti2AlNb alloy plates of the present invention, employing appropriate first, second, and third heat treatment conditions in combination, can obtain a Ti2AlNb alloy microstructure with multi-scale O-phase laths. The appropriate first heat treatment dissolves the O phase in the original microstructure, yielding an α2+B2 two-phase microstructure. The appropriate second heat treatment precipitates coarse O-phase laths, and the appropriate third heat treatment precipitates fine O-phase laths. The uniform distribution of multi-scale O-phase laths on the B2 / β phases in this invention ensures uniform strain distribution during deformation, avoiding stress concentration and achieving a good balance between strength and toughness. The above heat treatment process reduces the precision requirements of furnace temperature, is simple to implement, and has high stability. The Ti2AlNb heat-treated plates obtained by the heat treatment method of this invention exhibit excellent comprehensive properties.

[0107] The Ti2AlNb heat-treated sheet obtained by the dual heat treatment method in Comparative Example 1 exhibits poor strength and toughness matching, and extremely poor creep resistance at high temperatures. The heat treatment method for the Ti2AlNb alloy sheet in Comparative Example 2, where the heat treatment conditions are not within the scope of protection of this invention, results in Ti2AlNb heat-treated sheets with poor creep resistance.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat treatment method for Ti2AlNb alloy plates, characterized in that, Includes the following steps: The Ti2AlNb alloy sheet is heat-treated, and the heat treatment includes a first heat treatment, a second heat treatment and a third heat treatment to obtain a heat-treated Ti2AlNb sheet. The holding temperature T1 of the first heat treatment is 970~1000℃, and the holding time is 1~3h; The holding temperature T2 for the second heat treatment is 930~945℃, and the holding time is 1~5h; The holding temperature T3 of the third heat treatment is 770~790℃, and the holding time is 8~30h; The temperature difference between the holding temperature T2 of the second heat treatment and the holding temperature T3 of the third heat treatment satisfies: 40℃≤T2-T3≤160℃; The first heat treatment is a solution treatment, which is used to dissolve the O phase in the original tissue to obtain an α2+B2 two-phase tissue; the second heat treatment is an aging treatment, which is used to precipitate coarse O phase laths; and the third heat treatment is used to precipitate fine O phase laths. The Ti2AlNb alloy plate after the first heat treatment is subjected to a first cooling treatment, which is air cooling. The Ti2AlNb alloy plate after the second heat treatment is subjected to a second cooling treatment, which is air cooling. The Ti2AlNb alloy plate after the third heat treatment is subjected to a third cooling treatment, which is air cooling. The preparation method of the Ti2AlNb alloy plate specifically includes the following steps: subjecting the Ti2AlNb alloy forged slab to a first rolling, a first annealing, a second rolling, a cladding rolling, and post-treatment; the temperature of the first rolling is higher than the temperature of the second rolling; the post-treatment includes a second annealing, leveling, sanding, and pickling; the temperature of the first rolling is 990~1100℃; the thickness of the plate obtained after the first rolling is 20~30mm; the temperature of the second annealing and the leveling are each independently 800~900℃, and the time of the second annealing and the leveling are each independently 10~120min; The microstructure of the heat-treated Ti2AlNb plate includes several O-phase laths, the length of which is 0.3~10μm along the major axis and 0.05~4μm along the minor axis; the volume fraction of the O-phase laths is 45%~80%. The temperature of the first annealing is 980~1060℃, and the time of the first annealing is 1~4h; The second rolling temperature is 850~960℃, and the second rolling time is 10~180min; The thickness of the sheet obtained after the second rolling process is 4~10mm; The temperature of the cladding rolling is 850~960℃, and the cladding rolling time is 60~180min.

2. The heat treatment method for Ti2AlNb alloy plate according to claim 1, characterized in that, The thickness of the Ti2AlNb alloy plate is 0.8~4mm.

3. The heat treatment method for Ti2AlNb alloy plate according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The tensile strength of the Ti2AlNb heat-treated plate under the test condition of 23℃ is 950~1200MPa, the yield strength is 800~1050MPa, and the elongation is 6%~15%; (2) The Ti2AlNb heat-treated plate has a tensile strength of 750~950MPa, a yield strength of 600~850MPa, an elongation of 10%~30% and a durability of 80~200h at 360MPa under the test conditions of 650℃.

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