Heat treatment method of Ti2AlNb alloy plate

Abstract

The invention relates to the technical field of alloy materials, in particular to a heat treatment method of a Ti2AlNb alloy plate. A heat treatment method for a Ti2AlNb alloy plate comprises the steps that the Ti2AlNb alloy plate is subjected to heat treatment, and the heat treatment comprises first heat treatment, second heat treatment and third heat treatment; the heat preservation temperature T1 of the first heat treatment is 960-1030 DEG C, and the heat preservation time is 1-4 hours; the heat preservation temperature T2 of the second heat treatment is 880-950 DEG C, and the heat preservation time is 1-8 hours; the heat preservation temperature T3 of the third heat treatment is 760-840 DEG C, and the heat preservation time is 2-48 hours. According to the heat treatment method, the multi-scale O-phase laths are uniformly distributed on the B2 / beta phase, so that the strain in the deformation process is uniformly distributed, the stress concentration can be avoided, the strength and the toughness can be well matched, the requirement on the precision of the furnace temperature is reduced, the process is simple, and the stability is high.

Description

Technical Field

[0001] The invention relates to the technical field of alloy materials, and in particular to a heat treatment method for a Ti2AlNb alloy plate. Background Art

[0002] Ti2AlNb alloy is a lightweight, heat-resistant structural material that can be used for a long time at 600℃~750℃ or for a short time at a higher temperature. Ti2AlNb alloy is an intermetallic compound alloy. Due to its long-range order in the crystal structure and the strong bonding force between metal atoms, it has the advantages of excellent high-temperature specific strength and specific modulus, and has good creep resistance. The above excellent properties make it show great application potential in aerospace structural materials, which is of great significance for improving the thrust-to-weight ratio of aircraft, improving fuel efficiency and high-temperature service performance.

[0003] Ti2AlNb alloys are usually composed of two or three phases of O phase, B2 / β phase and α2 phase. The phase composition and content of the alloy will change significantly due to changes in hot working process, composition and heat treatment system. The phase equilibrium in Ti2AlNb alloy belongs to multi-phase equilibrium. Its phase equilibrium process is very complex and the phase transformation process is very sensitive to thermal response. In addition, the microstructural parameters such as phase composition and content in the alloy will significantly affect the mechanical properties of the alloy. In order to obtain better comprehensive performance, the deformed Ti2AlNb alloy is generally subjected to a double heat treatment system of solid solution and aging. The strength and toughness of the Ti2AlNb alloy treated by the above system have an obvious inverted relationship. In order to obtain a better match between strength and toughness, the process parameters such as the temperature and cooling rate of the solid solution heat treatment need to be strictly controlled. Improper control will lead to large fluctuations in performance, which seriously restricts its engineering application in aerospace structural parts.

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

[0005] One object of the present invention is to provide a heat treatment method for a Ti2AlNb alloy plate to solve the technical problem that the heat treatment method for a Ti2AlNb alloy plate in the prior art is difficult to achieve a good match between strength and toughness, and the comprehensive performance of the Ti2AlNb alloy plate is not ideal. The heat treatment method for a Ti2AlNb alloy plate of the present invention can distribute the strain evenly during the deformation process by uniformly distributing multi-scale O-phase laths on the B2 / β phase, thereby avoiding stress concentration, achieving a good match between strength and toughness, reducing the accuracy requirements for furnace temperature, and making the process simple to implement and having high stability.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0007] A heat treatment method for a Ti2AlNb alloy plate comprises the following steps:

[0008] The Ti2AlNb alloy plate is subjected to heat treatment, and the heat treatment includes a first heat treatment, a second heat treatment and a third heat treatment to obtain a Ti2AlNb heat-treated plate; the insulation temperature T1 of the first heat treatment is 960-1030°C, and the insulation time is 1-4h; the insulation temperature T2 of the second heat treatment is 880-950°C, and the insulation time is 1-8h; the insulation temperature T3 of the third heat treatment is 760-840°C, and the insulation time is 2-48h.

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

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

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

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

[0013] In some implementations, a second cooling treatment is performed on the Ti2AlNb alloy sheet after the second heat treatment.

[0014] In some implementations, a third cooling treatment is performed on the Ti2AlNb alloy sheet after the third heat treatment.

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

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

[0017] In some implementations, the Ti2AlNb alloy plate has a thickness of 0.8 to 4 mm.

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

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

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

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

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

[0023] In some implementations, the coating and rolling temperature is 850-960° C., and the coating and rolling time is 60-180 min.

[0024] In some embodiments, the post-treatment includes second annealing, leveling, sanding and pickling, the temperature of the second annealing and the leveling are independently 800-900° C., and the time of the second annealing and the leveling are 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 0.3-10 μm, and the length in the short axis direction is 0.05-4 μm; the volume fraction of the O-phase laths is 45%-80%.

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

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

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The heat treatment method of the Ti2AlNb alloy plate of the present invention adopts appropriate first heat treatment, second heat treatment and third heat treatment conditions to cooperate with each other, and a Ti2AlNb alloy microstructure with multi-scale O-phase laths can be obtained; wherein, the first heat treatment is solid solution, and the O phase in the original structure can be dissolved by the appropriate first heat treatment to obtain an α2+B2 two-phase structure, which provides a better matrix structure for the subsequent precipitation of the O phase by aging treatment; the second heat treatment and the third heat treatment are both aging treatments, and the second heat treatment under appropriate conditions is carried out by heat preservation in a higher temperature range of the O+B2 two-phase region to precipitate coarse O-phase laths, and the third heat treatment under appropriate conditions is carried out by heat preservation in a lower temperature range of the O+B2 two-phase region to precipitate fine O-phase laths; the present invention uniformly distributes the strain in the deformation process by uniformly distributing the multi-scale O-phase laths on the B2 / β phase, avoids stress concentration, and can obtain a good match between strength and toughness. At the same time, the heat treatment process has lower requirements on the accuracy of furnace temperature, and the process is simple to implement and has high stability, which is suitable for the preparation of Ti2AlNb alloys with well-matched strength and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

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

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

[0034] Figure 4 This is the microstructure diagram of the Ti2AlNb heat-treated plate in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

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

[0037] The Ti2AlNb alloy plate is subjected to heat treatment, and the heat treatment includes a first heat treatment, a second heat treatment and a third heat treatment to obtain a heat-treated plate; the insulation temperature T1 of the first heat treatment is 960-1030°C, and the insulation time of the first heat treatment is 1-4h; the insulation temperature T2 of the second heat treatment is 880-950°C, and the insulation time of the second heat treatment is 1-8h; the insulation temperature T3 of the third heat treatment is 760-840°C, and the insulation time of the third heat treatment is 2-48h.

[0038] The present invention provides a heat treatment method for a Ti2AlNb alloy plate having good superplasticity after final rolling in the O+B2 two-phase region to improve the comprehensive mechanical properties of the Ti2AlNb alloy plate having good superplasticity. The present invention adopts appropriate first heat treatment, second heat treatment and third heat treatment conditions to cooperate with each other to obtain a Ti2AlNb alloy microstructure with multi-scale O-phase laths; wherein, the first heat treatment is solid solution, and the O phase in the original structure can be dissolved by the appropriate first heat treatment to obtain an α2+B2 two-phase structure, which provides a better matrix structure for the subsequent precipitation of the O phase through aging treatment. In some embodiments, the holding temperature T1 of the first heat treatment is 960-1030°C, including but not limited to 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, etc., or any range value between the two. In some embodiments, the holding time of the first heat treatment is 1 to 4 hours, including but not limited to 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, etc., or any range between the two. The second heat treatment and the third heat treatment are both aging treatments. Through the second heat treatment under suitable conditions, the heat preservation is carried out in the higher temperature range of the O+B2 two-phase region, and coarse O-phase laths can be precipitated. 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, etc., or any range between the two. The holding time of the second heat treatment is 1 to 8h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc., or any range between the two; through the third heat treatment under suitable conditions, the heat preservation is carried out in the lower temperature range of the O+B2 two-phase region, and fine O-phase laths can be precipitated. Small O-phase lath, in some embodiments, the holding temperature T3 of the third heat treatment 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 range between the two; the holding time of the third heat treatment is 2-48h, including but not limited to 2h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h or 48h, or any range between the two; the present invention distributes the strain uniformly during the deformation process through the uniform distribution of multi-scale O-phase laths on the B2 / β phase, avoiding stress concentration, so that a good match between strength and toughness can be obtained. At the same time, the above heat treatment process has a lower requirement on the accuracy of the furnace temperature, and the process is simple to implement and has high stability, which is suitable for the preparation of Ti2AlNb alloys with good matching of strength and toughness.

[0039] 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 (for example, 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 (for example, 0.05 μm, 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, etc.); the volume fraction of the O-phase laths is 45% to 80% (for example, 45%, 50%, 55%, 60%, 65%, 68%, 70%, 72%, 75% or 80%, etc.).

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

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

[0042] In some embodiments, the temperature difference between the insulation temperature T1 of the first heat treatment and the insulation temperature T2 of the second heat treatment satisfies: 20℃≤T1-T2≤150℃, and T1-T2 can be, for example, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc., or any range value 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: 400°C≤T2-T3≤190°C, and T2-T3 can be, for example, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 105°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, etc., or any range value 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 meet the above range, which is more conducive to ensuring the uniform precipitation of multi-scale O phase in the Ti2AlNb alloy, and is conducive to achieving uniform distribution of strain during deformation, avoiding stress concentration, and thus obtaining a Ti2AlNb alloy with good matching of strength and toughness.

[0043] In some embodiments, the Ti2AlNb alloy sheet after the first heat treatment is subjected to a first cooling treatment. In some embodiments, the Ti2AlNb alloy sheet after the second heat treatment is subjected to a second cooling treatment. In some embodiments, the Ti2AlNb alloy sheet after the third heat treatment is subjected to a third cooling treatment. The first cooling treatment, the second cooling treatment, and the third cooling treatment each independently include at least one of furnace temperature control cooling, air cooling, and liquid quenching. Liquid quenching includes oil quenching or quenching with a PAG (polyalkylene glycol) aqueous solution having a certain concentration.

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

[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 firstly initial rolled near the β phase transformation point, the initial rolling temperature range is 990-1100°C, the holding time is determined according to the thickness of the slab, the insulation coefficient is calculated as 0.3-0.8min / mm, and one or more fire rolling can be performed according to the thickness of the slab, and the forged slab is rolled into a plate with a thickness of 20-30mm. (b) high temperature annealing of the slab: the initially rolled plate is subjected to high temperature annealing treatment, the annealing system is 980-1060°C, the insulation time is 1-4h, and after insulation, it is cooled by air cooling or oil quenching. (c) Low-temperature rolling of plates: The high-temperature annealed plates are rolled in the O+B2 two-phase region. The insulation temperature before rolling is 850-960℃. The insulation time is determined according to the thickness of the plate. The insulation coefficient is calculated as 0.3-0.8min / mm. The specific insulation time is 10-180min. The plates are rolled into plates with a thickness of 4-10mm. Multiple fire rolling or online reheating can be performed as needed. (d) Plate cladding rolling and subsequent treatment: The low-temperature rolled plates are assembled after grinding, cutting and pickling. The cladding rolling temperature is 850-960℃ and the insulation time is 60-180min. After rolling, the rolled plates are unpacked to obtain the rolled plates; the rolled plates are annealed and leveled. The annealing and leveling temperatures are 800-900℃ and the insulation time is 10min-120min respectively. The leveled plates are sanded and pickled to obtain Ti2AlNb alloy plates with a thickness of 0.8-4mm.

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

[0047] The following is further explained in conjunction with specific embodiments and comparative examples.

[0048] Example 1

[0049] A Ti2AlNb alloy plate heat treatment method comprises the following steps:

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

[0051] a) High temperature initial rolling of slab: The Ti2AlNb alloy forged slab is firstly initial rolled near the β phase transformation point, the initial rolling temperature is 1050°C, the insulation coefficient is calculated as 0.5min / mm, and the forged slab is rolled into a plate with a thickness of 25mm.

[0052] b) High temperature annealing of slab: The initially rolled plate is subjected to high temperature annealing treatment at 1030°C for 2.5 hours. After the annealing treatment, the plate is cooled by air cooling or oil quenching.

[0053] c) Low-temperature rolling of plates: The high-temperature annealed plates are rolled in the O+B2 two-phase region. The insulation temperature before rolling is 960°C, the insulation coefficient is calculated as 0.5min / mm, the specific insulation time is 100min, and the plates are rolled into a thickness of 6mm. Multiple-fire rolling or online reheating can be carried out as needed.

[0054] d) Plate cladding rolling and subsequent treatment: The low-temperature rolled plates are ground, cut, pickled and then packaged. The cladding rolling temperature is 960°C and the holding time is 110 min. After rolling, the plates are unpacked to obtain the rolled plates. The microstructure of the rolled plates is shown in Fig. Figure 2 The rolled sheet was annealed and leveled at 850℃ and 850℃ respectively, and the holding time was 60min. The leveled sheet was sanded and pickled to obtain a Ti2AlNb alloy sheet with a thickness of 2mm. The microstructure of the annealed and leveled sheet is shown in Fig. Figure 3 .

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

[0056] First heat treatment: tensile specimens were cut from 2mm Ti2AlNb alloy plates. Six tensile specimens with dimensions of thickness × width × length = 2mm × 160mm × 26mm and three endurance specimens with dimensions of thickness × width × length = 2mm × 121mm × 25mm were taken. The first heat treatment was carried out after sealing the quartz tube. The temperature of the first heat treatment was 980°C and the time of the first heat treatment was 2h. Air cooling was used after the first heat treatment.

[0057] Second heat treatment: take the quartz tube that has undergone the first heat treatment for the second heat treatment, the second heat treatment temperature is 940°C, the second heat treatment time is 2h, and air cooling is used after the second heat treatment.

[0058] Third heat treatment: take the quartz tube that has undergone the second heat treatment for the third heat treatment, the temperature of the third heat treatment is 780°C, the time of the third heat treatment is 24h, and air cooling is used after the third heat treatment.

[0059] The microstructure of the Ti2AlNb heat-treated plate after the third heat treatment is completed. Figure 1 The size of the lath in the long axis direction is 0.3μm to 10μm, the size in the short axis direction is 0.05μm to 4μm, and the volume fraction of the precipitated lath is 70%.

[0060] Example 2

[0061] A heat treatment method for a Ti2AlNb alloy plate, which differs from Example 1 in that:

[0062] The temperature of the first heat treatment is 970° C., and the time of the first heat treatment is 3 h.

[0063] The second heat treatment temperature is 900° C., and the second heat treatment time is 5 h.

[0064] The temperature of the third heat treatment is 770° C., and the time of the third heat treatment is 30 hours.

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

[0066] Example 3

[0067] A heat treatment method for a Ti2AlNb alloy plate, which differs from Example 1 in that:

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

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

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

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

[0072] Example 4

[0073] A heat treatment method for a Ti2AlNb alloy plate, which differs from Example 1 in that:

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

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

[0076] The temperature of the third heat treatment is 760° C., and the time of the third heat treatment is 48 hours.

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

[0078] Example 5

[0079] A heat treatment method for a Ti2AlNb alloy plate, which differs from Example 1 in that:

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

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

[0082] The temperature of the third heat treatment is 840° C., and the time of the third heat treatment is 2 h.

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

[0084] Comparative Example 1

[0085] A heat treatment method for a Ti2AlNb alloy plate, which differs from Example 1 in that:

[0086] In step (2), the obtained Ti2AlNb alloy plate is subjected to heat treatment, and the heat treatment includes a first heat treatment and a second heat treatment, wherein the temperature of the first heat treatment is 960°C, the time is 2 hours, and air cooling is adopted after the first heat treatment. The temperature of the second heat treatment is 800°C, the time is 24 hours, and air cooling is adopted after the second heat treatment.

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

[0088] Comparative Example 2

[0089] A heat treatment method for a Ti2AlNb alloy plate, which differs from Example 1 in that:

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

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

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

[0093] Experimental example

[0094] The Ti2AlNb alloy sheet that was not heat treated in Example 1 was subjected to superplastic properties test (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 test, 650°C tensile property test and 650°C / 350MPa endurance property test, as follows:

[0096] The specimens were processed and tested for room temperature tensile properties according to the national standard GB / T 228.1.

[0097] The specimens were processed and the 650℃ tensile properties were tested according to the national standard GB / T 228.2.

[0098] According to the requirements of national standard GB / T 2039, the endurance test specimens are processed and the endurance performance at 650℃ / 350MPa is tested.

[0099] The performance test results of the Ti2AlNb alloy plate after heat treatment are shown in Table 2.

[0100] Table 1 Superplastic properties test results of Ti2AlNb alloy plates without heat treatment

[0101]

[0102] It can be seen from Table 1 that the Ti2AlNb alloy sheet material that has not been heat treated in Example 1 of the present invention has good superplasticity.

[0103] Table 2 Test results

[0104]

[0105]

[0106] As can be seen from Table 2, the heat treatment method of the Ti2AlNb alloy plate of the present invention adopts the appropriate first heat treatment, second heat treatment and third heat treatment conditions to cooperate with each other, and a Ti2AlNb alloy microstructure with multi-scale O-phase laths can be obtained. The O phase in the original structure can be dissolved by the appropriate first heat treatment to obtain an α2+B2 two-phase structure; the coarse O-phase laths can be precipitated by the second heat treatment under appropriate conditions, and the fine O-phase laths can be precipitated by the third heat treatment under appropriate conditions; the present invention uniformly distributes the strain during the deformation process through the uniform distribution of multi-scale O-phase laths on the B2 / β phase, avoids stress concentration, and can obtain a good match between strength and toughness; the above heat treatment process has a lower requirement for the accuracy of the furnace temperature, and the process is simple to implement and has high stability. The Ti2AlNb heat-treated plate obtained by the heat treatment method of the present invention has excellent comprehensive performance.

[0107] The strength and toughness of the Ti2AlNb heat-treated plate obtained by the double heat treatment method of comparative example 1 are poorly matched, and the durability at high temperature is extremely poor. The heat treatment conditions of the Ti2AlNb alloy plate heat treatment method of comparative example 2 are not within the protection scope of the present invention, and the durability of the obtained Ti2AlNb heat-treated plate is poor.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat treatment method for a Ti2AlNb alloy sheet, characterized in that: The following steps are involved: The Ti2AlNb alloy plate is subjected to heat treatment, wherein the heat treatment includes a first heat treatment, a second heat treatment and a third heat treatment to obtain a Ti2AlNb heat-treated plate; The holding temperature T1 of the first heat treatment is 960-1030°C, and the holding time is 1-4h; The second heat treatment has a holding temperature T2 of 880 to 950°C and a holding time of 1 to 8 hours; The insulation temperature T3 of the third heat treatment is 760-840° C., and the insulation time is 2-48 hours.

2. The heat treatment method of the Ti2AlNb alloy sheet according to claim 1, characterized in that: The first heat treatment has a holding temperature T1 of 970 to 1000°C and a holding time of 1 to 3 hours; The second heat treatment has a holding temperature T2 of 900 to 945°C and a holding time of 1 to 5 hours; The insulation temperature T3 of the third heat treatment is 770-810° C., and the insulation time is 8-30 hours.

3. The heat treatment method of the Ti2AlNb alloy sheet according to claim 1, characterized in that: The holding temperature T1 of the first heat treatment is 975-990°C, and the holding time is 1.5-2.5h; The holding temperature T2 of the second heat treatment is 900-945°C, and the holding time is 1.5-4h; The insulation temperature T3 of the third heat treatment is 770-810° C., and the insulation time is 15-26 hours.

4. The heat treatment method of the Ti2AlNb alloy sheet according to claim 1, characterized in that: The temperature difference between the insulation temperature T1 of the first heat treatment and the insulation temperature T2 of the second heat treatment satisfies: 20°C≤T1-T2≤150°C; The temperature difference between the insulation temperature T2 of the second heat treatment and the insulation temperature T3 of the third heat treatment satisfies: 40°C≤T2-T3≤190°C.

5. The heat treatment method of the Ti2AlNb alloy sheet according to claim 1, characterized in that: The present invention also includes: performing a first cooling treatment on the Ti2AlNb alloy plate after the first heat treatment; and / or, performing a second cooling treatment on the Ti2AlNb alloy plate after the second heat treatment; And / or, performing a third cooling treatment on the Ti2AlNb alloy sheet after the third heat treatment.

6. The heat treatment method of the Ti2AlNb alloy sheet according to claim 5, characterized in that: The first cooling treatment, the second cooling treatment and the third cooling treatment each independently include at least one of temperature-controlled cooling in a furnace, air cooling and liquid quenching.

7. The heat treatment method of the Ti2AlNb alloy sheet according to claim 1, characterized in that: The preparation method of the Ti2AlNb alloy plate specifically comprises the following steps: The Ti2AlNb alloy forged slab is subjected to first rolling, first annealing, second rolling, cladding rolling and post-treatment; the temperature of the first rolling is greater than the temperature of the second rolling; And / or, the thickness of the Ti2AlNb alloy plate is 0.8-4 mm.

8. The heat treatment method of the Ti2AlNb alloy sheet according to claim 7, characterized in that: Contains at least one of the following features (1) to (7): (1) The temperature of the first rolling is 990-1100° C.; (2) The thickness of the plate obtained after the first rolling is 20 to 30 mm; (3) The annealing temperature is 980-1060° C. and the annealing time is 1-4 hours; (4) The temperature of the second rolling is 850-960° C., and the time of the second rolling is 10-180 min; (5) The thickness of the plate obtained after the second rolling is 4 to 10 mm; (6) The coating rolling temperature is 850-960° C., and the coating rolling time is 60-180 min; (7) The post-treatment includes a second annealing, leveling, sanding and pickling. The temperature of the second annealing and the leveling is independently 800 to 900° C., and the time of the second annealing and the leveling is independently 10 to 120 minutes.

9. The heat treatment method of the Ti2AlNb alloy sheet according to claim 1, characterized in that: The microstructure of the Ti2AlNb heat-treated plate includes a plurality of O-phase laths, the length of the O-phase laths in the long axis direction is 0.3-10 μm, and the length in the short axis direction is 0.05-4 μm; the volume fraction of the O-phase laths is 45%-80%.

10. The heat treatment method of the Ti2AlNb alloy sheet according to claim 1, characterized in that: Contains 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°C is 950-1200 MPa, the yield strength is 800-1050 MPa, and the elongation is 6%-15%; (2) The tensile strength of the Ti2AlNb heat-treated plate under the test condition of 650°C is 750-950 MPa, the yield strength is 600-850 MPa, the elongation is 10%-30%, and the durability at 360 MPa is 80-200 h.

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