Two-stage solid solution and aging heat treatment method for improving tensile strength of SiCf / Ti2AlNb composite material

Abstract

The invention relates to a two-stage solid solution and aging heat treatment method for improving the tensile strength of a SiCf / Ti2AlNb composite material, and belongs to the field of heat treatment of the SiCf / Ti2AlNb composite material. For the SiCf / Ti2AlNb composite material subjected to hot isostatic pressing molding in a Ti2AlNb three-phase region, the method of two-stage solid solution heat treatment and third-stage stable aging heat treatment is adopted, an obtained Ti2AlNb matrix structure has the characteristic of three-phase coexistence of a grain boundary alpha2 phase, an equiaxial B2 phase and a needle-shaped O phase, and the room high-temperature tensile strength is improved. According to the method, by adopting the two-stage solid solution and aging heat treatment process, microscopic structure optimization, regulation and control of the Ti2AlNb matrix in the composite material are achieved, the tensile strength of a traditional SiCf / Ti2AlNb composite material is improved, and an important technical approach is provided for design and application of SiCf / Ti2AlNb composite material structural parts.

Description

Technical Field

[0001] The present invention relates to a method for improving SiC f / Ti2AlNb composite materials tensile strength double-stage solid solution + aging heat treatment method, belongs to SiC f / Ti2AlNb composite material heat treatment field. Technical Background

[0002] High-speed aircraft high-temperature structural components are in urgent need of lightweight and high-strength materials. The development of traditional metals is approaching the material limit, and the selection of materials for key aerospace components is gradually leaning towards composite materials. SiC fiber reinforced titanium matrix composites (SiC f Compared with titanium alloy, SiC has high specific strength, high specific modulus and excellent high temperature performance, and is a key material for further improving the performance of aircraft. f / Ti2AlNb composite materials have high operating temperature and good stability and can be prepared into various types of structural parts. f The mechanical properties of SiC / Ti2AlNb composites have become the main focus of component design and application. f One of the factors affecting the mechanical properties of SiC / Ti2AlNb composites is the microstructure of the Ti2AlNb matrix. Ti2AlNb alloys are usually composed of three phases: O phase with an ordered cubic structure, α2 phase with a close-packed hexagonal structure, and B2 / β phase with a body-centered cubic structure. f / Ti2AlNb composites have a significant impact on the mechanical properties.

[0003] SiC f The microstructure and phase composition of the magnetron sputtered Ti2AlNb matrix in the SiC / Ti2AlNb composite material are quite different from those of the traditional Ti2AlNb alloy forgings. The conventional heat treatment system of Ti2AlNb alloy is used to improve the SiC f The tensile properties of SiC / Ti2AlNb composites are limited. f The room temperature tensile properties of SiC / Ti2AlNb composites have not been significantly improved, so it is necessary to develop a suitable f / Ti2AlNb composites matrix microstructure control method to improve the high temperature tensile properties of the composites.

[0004] Patent publication number CN115889777A proposes a SiC f / Ti2AlNb heterogeneous core material reinforced TC17 composite material and preparation method, continuous SiC fiber reinforced Ti2AlNb based composite material is selected as heterogeneous core material, TC17 alloy is selected as sheath, through heterogeneous core material SiC f / Ti2AlNb composite reinforced TC17 alloy. Hot isostatic pressing process is used to achieve SiC f / Ti2AlNb heterogeneous core material and TC17 sheath are well combined. The heat treatment system is mainly to achieve a good combination of heterogeneous core material and sheath, and is not specifically for SiC f / Ti2AlNb composite material itself is optimized to improve its own tensile strength.

[0005] Patent publication number CN106637013A proposes a heat treatment method for improving the high-temperature strength of a Ti2AlNb-based alloy. The method utilizes pretreatment, solution treatment, quenching, and aging treatments. The treatment targets alloy plates. Due to the lack of fiber reinforcement, the unique properties of the composite material after incorporation with SiC fibers are not considered. Using a single solution treatment method, the phase composition cannot be controlled. The solution treatment temperature is 1150°C, the holding time is 1 to 1.5 hours, and the quenching medium is water. Water quenching can lead to internal stress cracks in the composite material.

[0006] The patent with publication number CN119392138A proposes a heat treatment method to improve the high-temperature strength and plasticity of Ti2AlNb alloy. By gradually cooling the Ti2AlNb alloy and forging it, combined with solid solution and aging heat treatment, it mainly solves the problem of poor strength and plasticity matching of Ti2AlNb alloy under high temperature conditions. It focuses on improving the high-temperature strength and plasticity of the alloy, and cannot accurately control the phase composition (such as α2, B2 and O phases) of the composite material sputtering matrix. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for improving SiC f / Ti2AlNb composite tensile strength double-stage solid solution + aging heat treatment method, for SiC f The microstructure characteristics of the sputtered matrix of the SiC / Ti2AlNb composite material are studied by optimizing the heat treatment system of the Ti2AlNb matrix and regulating the proportion of the three phases in the Ti2AlNb matrix. f / Ti2AlNb composite materials have obvious effect on room temperature tensile strength.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method to improve SiC fA two-stage solid solution + aging heat treatment method for the tensile strength of Ti2AlNb / Ti2AlNb composites uses a two-stage solid solution and a third-stage aging heat treatment to complete the Ti2AlNb matrix microstructure control, including the following steps:

[0010] Step 1: First stage B2 phase single phase region solution heat treatment

[0011] SiC f / Ti2AlNb composites were solution heat treated at 1050℃~1100℃ for 1h~2h and then air-cooled to room temperature;

[0012] Step 2: Second stage α2+B2+O three-phase solution heat treatment

[0013] The SiC obtained in step 1 f / Ti2AlNb composite materials were solution heat treated at 950℃~1000℃, kept at this temperature for 1h~2h, and then cooled to room temperature in air;

[0014] Step 3: The third stage of β / B2+O two-phase region stabilization aging heat treatment

[0015] The SiC obtained in step 2 f The / Ti2AlNb composite material is subjected to aging heat treatment at 720°C to 770°C with a holding time of 12h to 36h and then air-cooled to room temperature.

[0016] The improvement of SiC f Double-stage solid solution + aging heat treatment method for tensile strength of SiC / Ti2AlNb composites f / Ti2AlNb composite materials were prepared by magnetron sputtering pioneer wire method combined with three-phase zone hot isostatic pressing process.

[0017] The improvement of SiC f / Ti2AlNb composite tensile strength double-stage solid solution + aging heat treatment method, hot isostatically pressed SiC f In the Ti2AlNb / Ti2AlNb composite material, the Ti2AlNb matrix structure is an equiaxed α2+B2+O phase, and the volume proportions of α2, B2 and O phases are 35-45%, 30-50% and 10-25% respectively.

[0018] The improvement of SiC f / Ti2AlNb composite tensile strength double-stage solid solution + aging heat treatment method, SiC after heat treatment fIn the Ti2AlNb / Ti2AlNb composite material, the Ti2AlNb matrix structure is composed of three phases: α2, B2 and O, as well as Ti3AlC precipitated from high-temperature solid solution. The volume proportions of α2, B2, O and Ti3AlC are 15-25%, 30-45%, 25-37% and 3-8%, respectively.

[0019] The improvement of SiC f Double-stage solid solution + aging heat treatment method for tensile strength of SiC / Ti2AlNb composites f In the / Ti2AlNb composite material, the thickness of the carbon coating on the SiC fiber surface is above 0.5μm, and the volume fraction of SiC fiber accounts for f / Ti2AlNb composite material accounts for 35% to 65% of the total volume fraction.

[0020] The design concept of the present invention is:

[0021] The present invention mainly focuses on the SiC formed by hot isostatic pressing in Ti2AlNb three-phase region. f / Ti2AlNb composite materials adopt a two-stage solid solution heat treatment and a third-stage stabilization aging heat treatment method. First, solid solution heat treatment is carried out in the B2 phase single-phase region (1050℃~1100℃ for 1h~2h air cooling to dissolve the initial O phase and α2 phase, form a uniform B2 single-phase structure, and provide a basis for subsequent regulation). Then, solid solution heat treatment is carried out in the α2+B2+O three-phase region (950℃~1000℃ for 1h~2h air cooling to precipitate equiaxed α2 phase at the B2 grain boundary and form needle-shaped O phase in the crystal to improve the grain boundary strength). Finally, By carrying out stabilization aging heat treatment in the β / B2+O two-phase region (holding time at 720℃~770℃ and air cooling for 24h to promote the full precipitation and uniform distribution of the O phase, while inhibiting the transformation of the B2 phase to the α2 phase and enhancing the high-temperature stability), the Ti2AlNb matrix structure is obtained, which has the matrix structure characteristics of the coexistence and synergistic strengthening of the grain boundary α2 phase, the equiaxed B2 phase and the acicular O phase. In addition, precise control of the α2 phase, B2 phase and O phase in the Ti2AlNb matrix structure is achieved, so that it reaches a proportion and morphology that is more conducive to improving the tensile strength.

[0022] The present invention fully considers SiC f The difference in the organizational structure and phase composition between the sputtered matrix of the Ti2AlNb composite material and the traditional Ti2AlNb alloy forging can effectively control the microstructure according to the characteristics of the composite material. The present invention realizes the optimization and control of the microstructure of the Ti2AlNb matrix in the composite material by adopting a double-stage solid solution + aging heat treatment process, which improves the traditional SiC f / Ti2AlNb composite materials have a tensile strength of f It provides an important technical approach for the design and application of / Ti2AlNb composite structural parts.

[0023] The advantages and beneficial effects of the present invention are:

[0024] 1. The present invention proposes a method to improve the SiC f The double-stage solid solution + aging heat treatment method for the tensile strength of SiC / Ti2AlNb composite materials is different from the single-stage solid solution of alloy forgings. It adopts a two-stage temperature gradient design for the high α2 phase characteristics of the sputtered matrix, and a third stage stabilization aging heat treatment. The aging temperature takes into account both O phase refinement and prevention of fiber damage, avoiding the intensification of fiber-matrix interface reaction at high temperature. f / Ti2AlNb composite sputtering matrix is difficult to optimize, suitable for the manufacture of aerospace high-temperature components.

[0025] 2. The present invention realizes SiC f The matrix phase composition of the SiC / Ti2AlNb composite material is precisely controlled, and the grain boundary α2 phase, needle-like O phase and Ti3AlC particles are synergistically strengthened to improve the f / Ti2AlNb composites at room temperature tensile strength, f / Ti2AlNb composite material has important value in the design and application of structural parts. f Compared with the SiC / Ti2AlNb composite materials, the heat treated f The room temperature tensile strength of the / Ti2AlNb composite material is increased by 100MPa to 150MPa, and the tensile strength at 750℃ is increased by 60MPa to 130MPa.

[0026] 3. The heat treatment method proposed in the present invention can be used to complete the experiment using a conventional heat treatment furnace, and is feasible and extensive in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The SiC before heat treatment (hot isostatic pressing) in the embodiment f Microstructure of the matrix of the Ti2AlNb / Ti2AlNb composite material. In the figure, 11-B2 phase, 12-α2 phase, and 13-O phase.

[0028] Figure 2 The SiC after heat treatment (heat treatment state) in the embodiment f Microstructure of the matrix of the / Ti2AlNb composite material. In the figure, 21-B2 phase, 22-α2 phase, 23-O phase, 24-Ti3AlC.

[0029] Figure 3 The SiC after heat treatment (heat treatment state) in the embodiment f / Ti2AlNb composite matrix electron backscattered diffraction (EBSD) pattern. DETAILED DESCRIPTION

[0030] In the specific implementation process, SiC was prepared by combining magnetron sputtering technology with hot isostatic pressing process. f / Ti2AlNb composite tensile specimen blank. f / Ti2AlNb composites were characterized for microstructure, including the phase composition of Ti2AlNb matrix, the thickness of carbon coating on SiC fiber surface and the thickness of SiC f Fiber volume fraction in SiC / Ti2AlNb composites. f / Ti2AlNb composites were subjected to three-stage solution aging heat treatment to f / Ti2AlNb composite tensile specimen blanks were processed into specimen structures, and tensile strength tests were carried out at room temperature and 750℃.

[0031] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] In this embodiment, a method for improving SiC f A two-stage solid solution + aging heat treatment method for improving the tensile strength of a Ti2AlNb composite material comprises the following steps:

[0034] (1) Preparation of SiC by magnetron sputtering precursor wire method combined with three-phase hot isostatic pressing process f / Ti2AlNb composite material sample blank;

[0035] First, SiC fibers are prepared by chemical vapor deposition (CVD) to form single-filament SiC fibers. A pyrolytic carbon layer is deposited on the SiC fiber surface to inhibit high-temperature interfacial reactions. A Ti2AlNb alloy is then sputtered onto the SiC fibers using magnetron sputtering to form precursor fibers. The Ti2AlNb alloy consists of 22% Al, 24% Nb, 0.5% Mo, and the balance Ti, calculated by atomic percentage. The fibers are then hot isostatically pressed in a three-phase zone, and the pressure inside the hot isostatic pressing equipment is evacuated to below 2×10 -2 MPa, heated to 960℃ at a heating rate of 5℃ / min, kept at 130MPa for 4h, and cooled to room temperature with the furnace to obtain continuous SiC fiber reinforced Ti2AlNb(SiC f / Ti2AlNb) composite materials, the volume fraction of SiC fiber accounts for f / Ti2AlNb composite material accounts for 50% of the total volume fraction.

[0036] (2) Characterization of hot isostatically pressed SiC using scanning electron microscopy f Ti2AlNb matrix structure in Ti2AlNb / Ti2AlNb composite materials. The Ti2AlNb matrix is composed of equiaxed α2+B2+O. The matrix microstructure is as follows: Figure 1 As shown, the volume proportions of the α2, B2 and O phases in the matrix are approximately 40.7%, 48.9% and 10.4%, respectively, among which the O phase content is the least.

[0037] (3) Characterization of hot isostatically pressed SiC using scanning electron microscopy f In the SiC / Ti2AlNb composite fiber, the thickness of the carbon coating on the surface of the SiC fiber is 1.2 μm, which meets the requirements of the method of the present invention.

[0038] (4) Carry out the first stage B2 phase single phase region solid solution heat treatment. f / Ti2AlNb composites were solution heat treated at 1070℃ for 1h and then air-cooled to room temperature.

[0039] (5) Carry out the second stage of α2+B2+O three-phase region solid solution heat treatment. f / Ti2AlNb composites were solution heat treated at 970℃ for 1h and then air-cooled to room temperature.

[0040] (6) Perform the third stage of β / B2+O two-phase region stabilization aging heat treatment. f / Ti2AlNb composites were subjected to aging heat treatment at 750℃ for 24h and then air-cooled to room temperature.

[0041] (7) Characterization of heat-treated SiC using scanning electron microscopy f Ti2AlNb matrix structure in Ti2AlNb / Ti2AlNb composite materials. The Ti2AlNb matrix is composed of equiaxed α2+B2+O. The matrix microstructure is as follows: Figure 2 As shown in Figure 2, the matrix is composed of three phases: α2, B2, and O, as well as Ti3AlC solid solution precipitated at high temperature. Figure 3 As shown in the EBSD image, the volume proportions of α2, B2, O, and Ti3AlC are approximately 20.1%, 34.3%, 32.4%, and 5.3%, respectively (totaling 92.1%). Since the sample resolution of EBSD experimental images is usually less than 100%, after normalization (measured value / 92.1%), the volume proportions of α2, B2, O, and Ti3AlC are approximately 21.8%, 37.2%, 35.2%, and 5.8%, respectively.

[0042] (8) Hot isostatic pressing and heat treated SiCf / Ti2AlNb composite materials were subjected to tensile tests at room temperature and 750℃, 3 specimens were tested under each condition, and the average tensile strength is listed in Table 1. f Compared with the SiC / Ti2AlNb composite material, the double-stage solid solution + aging f The room temperature tensile strength of / Ti2AlNb composite materials increased by 135MPa and the 750℃ tensile strength increased by 100MPa.

[0043] Table 1 SiC f High temperature performance of / Ti2AlNb composites

[0044]

[0045] The implementation results show that the present invention proposes a method to improve SiC f / Ti2AlNb composite materials tensile strength double-stage solid solution + aging heat treatment method, using this method to control the SiC f / Ti2AlNb composite microstructure, improved SiC f / Ti2AlNb composite materials have high room temperature tensile strength (room temperature tensile strength can reach more than 1650MPa, 750℃ high temperature tensile strength can reach more than 1350MPa), f The design and application of / Ti2AlNb composite structural parts are of great significance.

Claims

1. A method to improve SiC f / Ti2AlNb composite material tensile strength double-stage solid solution + aging heat treatment method, characterized in that, The Ti2AlNb matrix microstructure is controlled by a two-stage solid solution treatment and a third-stage aging heat treatment, including the following steps: Step 1: First stage B2 phase single phase region solution heat treatment SiC f / Ti2AlNb composites were solution heat treated at 1050℃~1100℃ for 1h~2h and then air-cooled to room temperature; Step 2: Second stage α2+B2+O three-phase solution heat treatment The SiC obtained in step 1 f / Ti2AlNb composite materials were solution heat treated at 950℃~1000℃, kept at this temperature for 1h~2h, and then cooled to room temperature in air; Step 3: The third stage of β / B2+O two-phase region stabilization aging heat treatment The SiC obtained in step 2 f The / Ti2AlNb composite material is subjected to aging heat treatment at 720°C to 770°C with a holding time of 12h to 36h and then air-cooled to room temperature.

2. The method for improving SiC according to claim 1 f / Ti2AlNb composite material tensile strength double-stage solid solution + aging heat treatment method, characterized in that, SiC f / Ti2AlNb composite materials were prepared by magnetron sputtering pioneer wire method combined with three-phase zone hot isostatic pressing process.

3. The method for improving SiC according to claim 2 f / Ti2AlNb composite material tensile strength double-stage solid solution + aging heat treatment method, characterized in that, Hot isostatically pressed SiC f In the Ti2AlNb / Ti2AlNb composite material, the Ti2AlNb matrix structure is an equiaxed α2+B2+O phase, and the volume proportions of α2, B2 and O phases are 35-45%, 30-50% and 10-25% respectively.

4. The method for improving SiC according to claim 3 f / Ti2AlNb composite material tensile strength double-stage solid solution + aging heat treatment method, characterized in that, SiC after heat treatment f In the Ti2AlNb / Ti2AlNb composite material, the Ti2AlNb matrix structure is composed of three phases: α2, B2 and O, as well as Ti3AlC precipitated from high-temperature solid solution. The volume proportions of α2, B2, O and Ti3AlC are 15-25%, 30-45%, 25-37% and 3-8%, respectively.

5. The method for improving SiC according to claim 2 f / Ti2AlNb composite material tensile strength double-stage solid solution + aging heat treatment method, characterized in that, SiC f In the / Ti2AlNb composite material, the thickness of the carbon coating on the SiC fiber surface is above 0.5μm, and the volume fraction of SiC fiber accounts for f / Ti2AlNb composite material accounts for 35% to 65% of the total volume fraction.

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