Method for refining size of beta-type gamma-TiAl alloy lamellar cluster

Abstract

The invention discloses a method for refining the size of a beta-type gamma-TiAl alloy lamellar cluster, which comprises the following steps: primary heat treatment: heating a blank to 1050-1180 DEG C, preserving heat for 1-3 hours, and separating out an interface beta 0 phase in a blank lamellar layer; forging: placing the blank subjected to the primary heat treatment in a die, and starting forging; secondary heat treatment is conducted, specifically, the forged blank is subjected to high-temperature short-time treatment, and an alloy lamellar group is prepared; and the size of the alloy lamellar cluster is 80-110 [mu] m. Compared with the prior art, the prepared alloy lamellar cluster is small in size and high in production efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of metal material preparation, and in particular to a method for refining the size of β-type γ-TiAl alloy lamellae. Background Art

[0002] TiAl alloy has the advantages of low density, high specific strength, high specific rigidity and excellent high-temperature creep resistance, and has broad application prospects in the fields of aviation, aerospace, weapons, etc. According to the solidification path classification, TiAl alloys are divided into α-peritectic solidification and β-solidification alloys. Among them, the β-type γ-TiAl alloy adds a large amount of β-type stabilizing elements (Nb, Mo, etc.), and the service temperature and strength of the alloy are improved. At the same time, the introduction of a large number of blocky grain boundary β0 phases makes the β-type γ-TiAl alloy easy to crack and reduces the room temperature performance. This type of alloy faces problems such as composition segregation, narrow hot working window, difficulty in eliminating residual lamellar layers, and uneven organization. Studies have shown that fine full-lamellar organization has the best comprehensive performance and is more suitable for high-temperature service conditions.

[0003] At present, the commonly used processes for grain refinement include heat treatment, alloying and hot working.

[0004] Heat treatment to refine lamellar clusters is a common method for refining lamellar clusters. For example, the Chinese invention patent "A TiAl alloy grain refinement method" with the authorization announcement number CN103498065B proposes a method of cyclic heat treatment in the solid-liquid two-phase zone, which is to remelt the coarse columnar crystals and melt the dendrites, which can serve as new nucleation pointers for nucleation and growth, so that the grains are refined. The Chinese invention application "A Ti or TiAl alloy casting and its solidification structure refinement method" with the application publication number CN116083742A proposes to break the dendrites by melting and casting into a horizontal mechanical vibrating mold, thereby achieving grain refinement. However, the performance and batch stability of cast TiAl alloys are lower than those of deformed TiAl alloys, and cannot meet the needs of high-strength parts. In addition, due to size limitations, cyclic heat treatment is time-consuming and expensive.

[0005] Alloying and hot working are effective methods for refining lamellar clusters. PJMaziasz et al. published "Effects of B and W alloying additions on the formation and stability of lamellar structures in two-phaseγ-TiAl" in Intermetallics magazine. By adding β-stabilizing elements such as Nb and W to TiAl alloys, the alloy is solidified in a β-solidified manner and the lamellar clusters and lamellar spacing are refined by hindering the grain boundaries and phase boundaries during the phase transformation. Patent (CN 117802433) proposes a preparation method and application of TiAl alloy rods. By extruding twice or more times, adjusting the extrusion ratio and temperature, the grain size of the rod is fully refined. However, this method is limited by the size of the equipment and is mainly based on round or square rods.

[0006] In summary, for β-type γ-TiAl alloys with coarse lamellar structures, it is impossible to effectively break up the entire lamellar structure through heat treatment. The traditional hot working process has high temperature and the residual lamellar clusters cannot be effectively broken up, which leads to uneven structure and limited grain refinement. Therefore, it is necessary to propose an improvement on the existing refinement method of β-type γ-TiAl alloys. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for refining the size of β-type γ-TiAl alloy lamellae with small alloy lamellae size and high production efficiency in view of the above technical status.

[0008] The technical solution adopted by the present invention to solve the above technical problems is: a method for refining the size of β-type γ-TiAl alloy lamellae, characterized in that it comprises the following steps:

[0009] S1 primary heat treatment: heating the blank to 1050-1180°C and keeping the temperature for 1-3 hours, so that an interfacial β0 phase is precipitated in the blank layer;

[0010] S2 forging: Place the blank after primary heat treatment in the die and start forging;

[0011] S3 secondary heat treatment: subjecting the forged billet to high temperature and short time treatment; the size of the alloy lamellar clusters is 80 to 110 μm.

[0012] Preferably, the blank in step S1 is titanium-aluminum alloy.

[0013] In order to reduce thermal deformation, preferably, the material preparation before the heat treatment is also included: the titanium aluminum alloy billet is polished and cleaned, and then packaged in a steel sleeve or a pure titanium sleeve. Due to the intrinsic brittleness of titanium aluminum alloy and the narrow thermal processing window, during the high-temperature thermal deformation process without a sleeve (>1000℃), the alloy temperature drops significantly due to the temperature drop of thermal radiation and the heat conduction of the contact mold, and the deformation resistance increases accordingly, resulting in a greater tendency for the alloy to crack. The method of adding a sleeve can alleviate the temperature drop and ensure that the alloy is thermally deformed within the thermal processing window.

[0014] Preferably, the step S2 further comprises: preheating the forging die, wherein the preheating temperature is 200-300°C.

[0015] Preferably, the step S2 is: preheating the forging die, the preheating temperature is 200-300°C; using a manipulator to grab the blank and place it in the die to start forging, the forging rate is 0.1-5s -1 The cumulative forging deformation is 60-80%, and it is air-cooled to room temperature after forging.

[0016] In order to release stress and reduce the risk of cracking, preferably, the step S2 is forged for 2 to 5 times, and each forging pass is kept warm for 20 to 40 minutes. The organizational state after forging in step S2 is an unstable state, that is, the characteristics of the lamellar group being broken and the lamellar bending after forging make the alloy in an unstable state with high distortion energy and large internal stress. The deformation pass is set based on the overall deformation amount: if the deformation pass is increased too much and the deformation amount of a single pass is small, the lamellar group may not be effectively broken, resulting in a decrease in the effect of grain refinement and uneven organization. Due to the narrow forging process window, the temperature drop in each forging pass causes the alloy to deviate from the forging temperature, and the deformation resistance will also increase, resulting in an increased risk of cracking. Therefore, without destroying the forging organization, the alloy organization characteristics can be more accurately controlled by heating to near the set forging temperature through short-term insulation, and stress can be released.

[0017] Preferably, step S3 is: heating to 1300-1330°C, keeping the temperature for 10-30 minutes, and then air cooling to room temperature; then heating to 800-900°C, and keeping the temperature for 4-8 hours. The temperature of the secondary heat treatment can obtain full-lamellar structure characteristics suitable for high-temperature service.

[0018] Preferably, the temperature rise in step S3 is carried out along with the furnace, and the heating rate is 5-10° C. / min.

[0019] Compared with the prior art, the advantages of the present invention are as follows: the present invention utilizes a primary heat treatment to heat to 1050-1180°C and keep the temperature for 1-3 hours, at which temperature β0 phase particles are gradually dispersed and precipitated inside the α2 lamellae, so that the lamellae of the billet obtain an interface β0 phase, and the interface β0 phase is utilized to coordinate the lamellae deformation during the thermal deformation process, so as to obtain a better broken original lamellae structure, so that the forged structure has higher distortion energy and anisotropy; then, the subsequent secondary heat treatment is utilized to input additional heat energy, and the combined effect of distortion energy and heat energy enables the alloy to fully and sufficiently recrystallize, and provides more nucleation points for the anisotropy of the structure, so as to achieve a refinement effect, and the alloy lamellae cluster size is 80-110 μm, and the heat treatment steps are simple and the production efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of the present invention;

[0021] Figure 2 This is a microstructure photograph of the TiAl alloy billet of Example 1;

[0022] Figure 3 This is a microstructure photo of the TiAl alloy after forging in Example 2;

[0023] Figure 4 The microstructure photo of the TiAl alloy after the secondary heat treatment of Example 2;

[0024] Figure 5 The microstructure photo of the TiAl alloy after forging in Comparative Example 1;

[0025] Figure 6 This is a microstructure photograph of the TiAl alloy after secondary heat treatment in comparative example 1. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings.

[0027] Example 1

[0028] The method for refining the size of β-type γ-TiAl alloy lamellae comprises the following steps:

[0029] S1 primary heat treatment: The Ti-43.9Al-4Nb-1Mo alloy billet (referred to as TiAl alloy or TNM alloy, i.e. titanium aluminum alloy) is ground and then ultrasonically cleaned; then, it is packaged in a steel sheath or a pure titanium sheath, and then the packaged billet is placed in a heat treatment furnace and heated to 1050°C at 5-10°C / min and kept warm for 3h, so that a large amount of interfacial β0 phase can be precipitated in the sheet.

[0030] S2 high temperature forging: preheat the forging die to maintain at 200-300℃, use a manipulator to grab the blank and place it in the die to start forging, the forging rate is 0.1s -1 ; A total of 5 forging passes were carried out, with 30 minutes of insulation between each pass; the cumulative forging deformation was 60-80%, and finally air-cooled to room temperature.

[0031] S3 secondary heat treatment: the forged billet is subjected to high temperature and short-time treatment, the temperature is raised to 1300℃ with the furnace at a heating rate of 5-10℃ / min, kept at this temperature for 10-30min, and air-cooled to room temperature after being taken out of the furnace; the temperature is raised to 800℃ with the furnace at a heating rate of 5-10℃ / min, kept at this temperature for 8 hours, and a fine and uniform structure of the lamellar cluster can be obtained, and the size of the alloy lamellar cluster is 80-110μm.

[0032] Example 2

[0033] The method for refining the size of β-type γ-TiAl alloy lamellae comprises the following steps:

[0034] S1 primary heat treatment: The Ti-43.9Al-4Nb-1Mo alloy billet is polished and ultrasonically cleaned; then, it is packaged in a steel sleeve or a pure titanium sleeve, and then the packaged billet is placed in a heat treatment furnace and heated to 1150°C at 5-10°C / min and kept warm for 2h, so that a large amount of interfacial β0 phase can be precipitated in the sheet.

[0035] S2, high temperature forging: preheat the forging die to maintain at 200-300℃, use a manipulator to grab the blank and place it in the die to start forging, the forging rate is 1s -1 ; Forging was performed for 3 times, with 30 minutes of heat preservation between each pass; the cumulative forging deformation was 60-80%, and finally air-cooled to room temperature. The microstructure of the TiAl alloy after forging is shown in the figure below. Figure 3 shown.

[0036] S3 secondary heat treatment: The forged billet is subjected to high temperature and short-time treatment, and the temperature is raised to 1320℃ with the furnace at a heating rate of 5-10℃ / min, kept at this temperature for 15 minutes, taken out of the furnace, and air-cooled to room temperature; the temperature is raised to 850℃ with the furnace at a heating rate of 5-10℃ / min, and kept at this temperature for 6 hours, and a fine and uniform structure of lamellar clusters can be obtained. The microstructure photos of TiAl alloy after secondary heat treatment are shown in Figure 2. Figure 4 As shown, the size of the alloy flakes is 80 to 110 μm.

[0037] Example 3

[0038] The method for refining the size of β-type γ-TiAl alloy lamellae comprises the following steps:

[0039] S1 primary heat treatment: The Ti-43.9Al-4Nb-1Mo alloy billet is polished and ultrasonically cleaned; then, it is packaged in a steel sleeve or a pure titanium sleeve, and then the packaged billet is placed in a heat treatment furnace and heated to 1180°C at 5-10°C / min and kept warm for 1h, so that a large amount of interfacial β0 phase can be precipitated in the sheet layer.

[0040] S2 High temperature forging: Preheat the forging die to maintain at 200-300℃, use a manipulator to grab the blank and place it in the die to start forging, the forging rate is 5s -1 ; Carry out two forging passes, and keep warm for 30 minutes between each forging pass; the cumulative forging deformation is 60-80%, and finally air-cooled to room temperature.

[0041] S3 secondary heat treatment: the forged billet is subjected to high temperature and short-time treatment, the temperature is raised to 1330℃ with the furnace at a heating rate of 5-10℃ / min, kept at this temperature for 10 minutes, taken out of the furnace, and air-cooled to room temperature; the temperature is raised to 900℃ with the furnace at a heating rate of 5-10℃ / min, kept at this temperature for 4 hours, and a fine and uniform structure of the lamellar cluster can be obtained, and the size of the alloy lamellar cluster is 80-110μm.

[0042] Comparative Example 1

[0043] The difference between this comparative example and Example 1 is that the temperature of the furnace heating in step S1 for the primary heat treatment is 1250°C. The microstructure of the TiAl alloy after forging in this comparative example is shown in Figure 5 The microstructure of TiAl alloy after secondary heat treatment is shown in Figure 6 ,Depend on Figure 6 and Figure 4 It can be seen that the size of the alloy flake clusters in the comparative example is significantly larger than that of the alloy flake clusters in Example 2.

Claims

1. A method for refining the size of β-type γ-TiAl alloy lamellae, characterized in that: The following steps are involved: S1. Primary heat treatment: heating the blank to 1050-1180°C and keeping the temperature for 1-3 hours to precipitate an interfacial β0 phase in the blank layer; S2 forging: Place the blank after primary heat treatment in the die and start forging; S3 secondary heat treatment: the forged billet is subjected to high temperature and short time treatment to obtain alloy lamellar clusters; the size of the alloy lamellar clusters is 80 to 110 μm.

2. The thinning method according to claim 1, characterized in that: The blank in step S1 is titanium-aluminum alloy.

3. The thinning method according to claim 2, characterized in that: It also includes the material preparation before the primary heat treatment: the titanium-aluminum alloy is ground and cleaned and then packaged in a steel sleeve or a pure titanium sleeve.

4. The thinning method according to claim 1, characterized in that: The step S2 also includes: preheating the forging die, wherein the preheating temperature is 200-300°C.

5. The thinning method according to claim 4, characterized in that: The step S2 is: preheating the forging die, the preheating temperature is 200-300° C.; using a manipulator to grab the blank and place it in the die to start forging, the forging rate is 0.1-5s -1 The cumulative forging deformation is 60-80%, and it is air-cooled to room temperature after forging.

6. The thinning method according to claim 5, characterized in that: The step S2 is performed by forging for 2 to 5 times, and heat preservation is performed for 20 to 40 minutes between each forging time.

7. The thinning method according to claim 1, characterized in that: The step S3 is: heating to 1300-1330° C., keeping the temperature for 10-30 minutes, and then air cooling to room temperature; and then heating to 800-900° C., and keeping the temperature for 4-8 hours.

8. The thinning method according to claim 7, characterized in that: The temperature in step S3 is increased along with the furnace, and the heating rate is 5-10° C. / min.

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