A thermomechanical method of controlling precipitate size of silicides in silicon-containing titanium-based composites

Abstract

A kind of thermomechanical method for regulating precipitated size of silicide in silicon-containing titanium-based composite material, it relates to the field of titanium-based composite material, the method of the present application is to place sintered discontinuous reinforced silicon-containing titanium-based composite material after cutting and polishing in thermomechanical machine, so that the material is uniformly distributed along the temperature distribution in the deformation direction;Thermomechanical treatment is carried out under the condition that the temperature is 600-800 DEG C and the pressure is 100-300 MPa, stop thermomechanical treatment after reaching the specified deformation, unload and air cooling, that is, complete.The present application realizes the accurate regulation of the precipitated size of silicide in titanium-based composite material by adjusting the two parameters of temperature and stress in thermomechanical treatment process simultaneously, and widens the custom interval of the precipitated size of silicide.The present application is applied to the field of in-situ autogenous titanium-based composite material organization design and regulation technology.

Description

Technical Field

[0001] This invention belongs to the field of in-situ self-generated titanium-based composite material microstructure design and control technology, specifically involving a method for precisely controlling the size of silicide precipitation in titanium-based composite materials by adjusting temperature and stress parameters in thermomechanical processing. Background Technology

[0002] Discontinuously reinforced titanium matrix composites exhibit higher heat resistance, strength, creep resistance, and oxidation resistance compared to traditional titanium alloys, making them indispensable key materials in the aerospace field. The design of discontinuously reinforced titanium matrix composites began in the 1990s. Through continuous composition optimization, high-temperature resistant titanium matrix composites have gradually formed, using near-α-type high-temperature titanium alloys based on the Ti-Al-Sn-Zr-Mo-Si system as the matrix and whisker-like TiBw or granular TiCp as the reinforcing phase. In recent years, inspired by the multi-level and multi-scale structures of natural biomaterials, the design of discontinuously reinforced titanium matrix composites has focused on controlling the distribution of the reinforcing phase, gradually developing network, fibrous, layered, and pellet-like discontinuously reinforced titanium matrix composites, with their comprehensive mechanical properties continuously breaking existing records.

[0003] Si, as one of the most effective alloying elements for improving the high-temperature resistance of titanium matrix composites, is widely added to discontinuously reinforced titanium matrix composites, including mesh, layered, and fibrous structures. Due to the low solubility of Si in near-α type titanium alloys, it often exists as silicides at the phase interfaces. The interfacial distribution of silicides can pin the α / β phase interface, thereby significantly improving the high-temperature strength and creep resistance of discontinuously reinforced titanium matrix composites. However, due to the strong pinning effect of silicides at the interface, stress concentration at the interface is often exacerbated during room temperature deformation, thus worsening the room temperature plasticity of discontinuously reinforced titanium matrix composites. This effect becomes increasingly pronounced with increasing silicide size.

[0004] Rational control of the distribution, size, and morphology of silicides is beneficial for achieving a synergistic improvement in the room-temperature strength, plasticity, and high-temperature resistance of discontinuously reinforced titanium matrix composites. Currently, most silicide control techniques rely on heat treatment, using single-phase solution treatment and two-phase aging to regulate silicide size and thus improve the room-temperature plasticity of discontinuously reinforced titanium matrix composites. However, the controllable variable of traditional heat treatment techniques is relatively singular (temperature), which limits the customizable range of silicide size to some extent. Furthermore, traditional heat treatment techniques essentially utilize the phase transformation of titanium alloys, resulting in precipitation sites at the α / β phase interface regardless of the silicide's size. This fails to fundamentally address the stress concentration caused by the silicide interface distribution characteristics, hindering further improvement in the comprehensive mechanical properties of discontinuously reinforced titanium matrix composites.

[0005] In summary, there is an urgent need for a new method that can refine the silicide precipitation size and precisely control the precipitation size to solve the above problems. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides a thermomechanical method for controlling the precipitation size of silicides in titanium-based composite materials.

[0007] The present invention discloses a thermomechanical method for controlling the precipitation size of silicides in silicon-titanium-based composite materials, which is carried out according to the following steps:

[0008] (1) Cut the sintered discontinuous reinforced silicon-titanium matrix composite material and polish the front and side surfaces of the cut material.

[0009] (2) Place the polished material in a thermomechanical machine to make the temperature distribution of the material uniform along the deformation direction;

[0010] (3) Perform thermomechanical treatment at a temperature of 600-800℃ and a pressure of 100-300MPa. Stop the thermomechanical treatment after the specified deformation is reached, unload the parts and air cool them down to complete the process.

[0011] Furthermore, the thermomechanical treatment temperature is 650–750°C, and the pressure is 150–250 MPa.

[0012] Furthermore, the temperature and pressure combinations are: temperature 650℃ + pressure 150MPa, temperature 650℃ + pressure 200MPa, temperature 650℃ + pressure 250MPa, temperature 700℃ + pressure 150MPa, temperature 700℃ + pressure 200MPa, and temperature 750℃ + pressure 150MPa.

[0013] Furthermore, the sintered discontinuous reinforced titanium matrix composite material is obtained by mixing raw materials, performing low-energy ball milling, placing them in a mold, and hot-pressing sintering.

[0014] Furthermore, the low-energy ball milling conditions are as follows: under argon protection, the ball-to-material ratio is 5-10:1, the ball milling speed is 180-240 rpm, and the ball milling time is 4-8 hours.

[0015] Furthermore, the hot-pressing sintering conditions are as follows: when the vacuum degree reaches 10... -2 The temperature is gradually increased in stages, and the pressure is gradually increased in stages when the temperature reaches 600-900℃. When the temperature and pressure reach 1100-1300℃ and 20-30MPa respectively, the temperature and pressure are maintained for 1-2 hours.

[0016] Furthermore, the hot-pressing sintering conditions are as follows: when the vacuum degree reaches 10... -2The temperature is gradually increased in stages, and the pressure is gradually increased in stages when the temperature reaches 700-800℃. When the temperature and pressure reach 1200-1300℃ and 25-30MPa respectively, the temperature and pressure are maintained for 1-2 hours.

[0017] Furthermore, the mass percentage of Si in the silicon-titanium-based composite material is greater than or equal to 0.3%.

[0018] Furthermore, the silicide precipitates in the titanium-based composite material have a size of 0.17–0.32 μm.

[0019] Furthermore, the thermomechanical treatment time is 13 to 78 hours.

[0020] This invention achieves precise control over the size of silicide precipitation in titanium-based composite materials by simultaneously adjusting two parameters, temperature and stress, in the thermomechanical processing, thus broadening the customizable range for silicide precipitation size. The final effects of this invention are as follows:

[0021] (1) High flexibility of thermomechanical treatment process. The thermomechanical treatment process involved in this invention has two process parameters, temperature and stress, which solves the problem of single process parameter (temperature) in traditional heat treatment control technology. Taking the process parameters in the embodiment as an example, under the condition that the temperature process parameter is the same, different thermomechanical treatment processes can be designed by changing the stress process parameter.

[0022] (2) Silicide precipitation size is customizable. By adjusting the combination of temperature and stress parameters in the thermomechanical processing, the precipitation size of silicides can be precisely controlled, while simultaneously improving the precipitation behavior of silicides distributed along the α / β phase interface. Dislocations formed in titanium-based composites during thermomechanical processing can serve as precipitation sites for silicides, improving the interfacial precipitation behavior of silicides. For example... Figure 2 As shown, a large amount of silicide precipitated along dislocation lines was observed within the α phase. By controlling the amount of deformation in the thermomechanical processing, the dislocation density within the material can be precisely controlled, thereby regulating the precipitate size of the silicides. Figure 3 As shown, although the thermomechanical processing parameters differ, the dislocation density inside the materials is almost equal under the same deformation, and the size of the precipitated silicides is also nearly equal. Compared with titanium-based composite materials that have undergone conventional heat treatment at 650℃ (such as...), Figure 1 As shown, thermomechanical processing can refine the size of silicides and improve their interfacial distribution characteristics. Furthermore, compared to traditional thermal processing techniques, thermomechanical processing can broaden the customizable range of silicide precipitation sizes. By adjusting temperature and stress process parameters, silicides with sizes ranging from 0.17 to 0.32 μm can be customized.

[0023] (3) The thermomechanical treatment process has controllable time consumption. Since the effects of increased temperature and increased stress on the high-temperature creep behavior of titanium-based composite materials are equivalent, the time cost of obtaining the desired silicide size can be further reduced by optimizing the thermomechanical treatment process parameters. Taking the process parameters in the embodiment as an example, if silicides of the same size are precipitated, the thermomechanical treatment process with parameters of 650℃-200MPa requires 78 hours, while the process with parameters of 650℃-250MPa requires only 13 hours. The corresponding thermomechanical treatment curve (strain-time curve) is shown below. Figure 4 As shown. Attached Figure Description

[0024] Figure 1 Images of sintered discontinuous reinforced titanium matrix composites after conventional heat treatment at 650℃; (a) SEM secondary electron image; (b) frequency histogram of silicide size distribution and average particle size.

[0025] Figure 2 Distribution characteristics of silicides inside discontinuous reinforced titanium matrix composites after thermomechanical treatment; where (a) is a bright-field TEM image; (b) and (c) are the surface distribution diagrams of Si and Zr elements, respectively.

[0026] Figure 3 Size characteristics of silicides inside discontinuous reinforced titanium matrix composites after treatment with different thermomechanical process parameters; (a) and (d) are SEM secondary electron images after treatment with different thermomechanical process parameters; (b) and (e) are corresponding EBSD average orientation difference distribution maps and dislocation density maps; (c) and (f) are corresponding silicide size distribution frequency histograms and average particle size maps.

[0027] Figure 4 Curves of different thermomechanical treatment processes; where (a) is a curve of thermomechanical treatment process parameters of 650℃-200MPa; and (b) is a curve of thermomechanical treatment process parameters of 650℃-250MPa. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the spirit of the contents disclosed in the present invention will be described in detail below. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0029] The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0030] Example 1:

[0031] (1) Small-sized TiB2 powder (~5μm) and Si powder (~3μm) were ball-milled with large-sized spherical Ti55 alloy powder (~120μm) and ball-milled under argon protection. The ball-to-material ratio was 5:1, the ball milling speed was 200rpm, and the ball milling time was 5h.

[0032] (2) Select a graphite mold (including matching sleeve and gasket) with appropriate diameter and height, and apply BN coating to the inner surface of the graphite sleeve and the surface of the graphite gasket that contacts the ball milling powder to avoid chemical reaction between the matrix powder and the graphite mold.

[0033] (3) Place the graphite mold filled with ball milled powder in a hot press sintering furnace and perform vacuum degassing at room temperature until the vacuum degree reaches 10. -2 The temperature was gradually increased stepwise at 800℃, and the pressure was gradually increased stepwise at 800℃. When the temperature and pressure reached 1300℃ and 25MPa, the temperature and pressure were held for 1.5 hours to obtain the sintered discontinuous reinforced titanium matrix composite material.

[0034] (4) Cut the sintered discontinuous reinforced titanium matrix composite material into a size suitable for thermomechanical processing, grind the front and sides of the sample to eliminate cutting marks, and measure its cross-sectional area.

[0035] (5) Install the sample into the thermomechanical testing machine, and fix the upper, middle and lower thermocouples around the sample in sequence using ceramic binding wires. Before starting the thermomechanical treatment, zero the displacement and load of the testing machine.

[0036] (6) The sample is heated to 650°C under a preload (5% of the specified load), and held at that temperature for 15 minutes before the load is applied (adjusted according to the cross-sectional area of ​​the sample in step (4)). The deformation is monitored in real time after the stress is loaded to 200 MPa and stabilized, and this is used as the requirement for thermomechanical treatment process.

[0037] (7) When the deformation reaches 3%, unload and air-cool the sample to obtain a discontinuous reinforced titanium matrix composite material that meets the expected silicide size.

[0038] This embodiment, by adjusting the combination of temperature and stress parameters in the thermomechanical processing, can precisely control the precipitation size of silicides and improve the precipitation behavior of silicides along the α / β phase interface. Dislocations formed in the titanium-based composite material during thermomechanical processing can serve as precipitation sites for silicides, improving the interfacial precipitation behavior of silicides. Figure 2 As shown, a large amount of silicide precipitated along dislocation lines was observed within the α phase. By controlling the amount of deformation in the thermomechanical processing, the dislocation density within the material can be precisely controlled, thereby regulating the precipitate size of the silicides. Figure 3As shown, although the thermomechanical processing parameters differ, the dislocation density inside the materials is almost equal under the same deformation, and the size of the precipitated silicides is also nearly equal. Compared with titanium-based composite materials that have undergone conventional heat treatment at 650℃ (such as...), Figure 1 As shown, thermomechanical processing can refine the size of silicides and improve their interfacial distribution characteristics. Furthermore, compared to traditional thermal processing techniques, thermomechanical processing can broaden the customizable range of silicide precipitation sizes. By adjusting temperature and stress process parameters, silicides with sizes ranging from 0.17 to 0.32 μm can be customized.

[0039] Since the effects of increased temperature and increased stress on the high-temperature creep behavior of titanium-based composites are equivalent, the process flow to obtain the desired silicide size can be shortened by optimizing the thermomechanical processing parameters, further reducing the time cost of this process. Figure 3 It is known that the precipitation size of silicides is controlled by the dislocation density inside the titanium-based composite material, and the dislocation density can be regulated by controlling the amount of deformation in the thermomechanical processing. Figure 3 The corresponding thermomechanical curves (strain-time curves) are as follows: Figure 4 As shown, when the thermomechanical processing parameters are 650℃-200MPa, it takes 78 hours to reach the specified deformation (3%), while when the thermomechanical processing parameters are 650℃-250MPa, it only takes 13 hours. This demonstrates that increasing stress can effectively shorten the time for titanium-based composite materials to reach the specified deformation, thereby shortening the time to reach the specified dislocation density and effectively reducing the time cost of obtaining the expected silicide precipitation size.

[0040] Example 2:

[0041] (1) Small-sized TiB2 powder (~5μm) and Si powder (~3μm) were ball-milled with large-sized spherical Ti55 alloy powder (~120μm) and ball-milled under argon protection. The ball-to-material ratio was 5:1, the ball milling speed was 200rpm, and the ball milling time was 5h.

[0042] (2) Select a graphite mold (including matching sleeve and gasket) with appropriate diameter and height, and apply BN coating to the inner surface of the graphite sleeve and the surface of the graphite gasket that contacts the ball milling powder to avoid chemical reaction between the matrix powder and the graphite mold.

[0043] (3) Place the graphite mold filled with ball milled powder in a hot press sintering furnace and perform vacuum degassing at room temperature until the vacuum degree reaches 10. -2 The temperature was gradually increased stepwise at 800℃, and the pressure was gradually increased stepwise at 800℃. When the temperature and pressure reached 1300℃ and 25MPa, the temperature and pressure were held for 1.5 hours to obtain the sintered discontinuous reinforced titanium matrix composite material.

[0044] (4) Cut the sintered discontinuous reinforced titanium matrix composite material into a size suitable for thermomechanical processing, grind the front and sides of the sample to eliminate cutting marks, and measure its cross-sectional area.

[0045] (5) Install the sample into the thermomechanical testing machine, and fix the upper, middle and lower thermocouples around the sample in sequence using ceramic binding wires. Before starting the thermomechanical treatment, zero the displacement and load of the testing machine.

[0046] (6) The sample is heated to 650°C under a preload (5% of the specified load), and held at that temperature for 15 minutes before the load is applied (adjusted according to the cross-sectional area of ​​the sample in step (4)). The deformation is monitored in real time after the stress is applied to 250 MPa and stabilized, and this is used as the requirement for thermomechanical treatment process.

[0047] (7) When the deformation reaches 3%, unload and air-cool the sample to obtain a discontinuous reinforced titanium matrix composite material that meets the expected silicide size.

Claims

1. A thermomechanical method for controlling the precipitation size of silicides in silicon-titanium-based composite materials, characterized in that... It is done in the following steps: (1) Cut the sintered discontinuous reinforced silicon-titanium matrix composite material and grind the front and side surfaces of the cut material; (2) Place the polished material in a thermomechanical machine to make the temperature distribution of the material uniform along the deformation direction; (3) Under the conditions of temperature 650℃ + pressure 150MPa, temperature 650℃ + pressure 200MPa, temperature 650℃ + pressure 250MPa, temperature 700℃ + pressure 150MPa, temperature 700℃ + pressure 200MPa or temperature 750℃ + pressure 150MPa, thermomechanical treatment is carried out. After the deformation reaches 3%, the thermomechanical treatment is stopped, the equipment is unloaded and cooled by air cooling, and the process is completed. The silicon-containing titanium-based composite material is a sintered discontinuous reinforced titanium-based composite material obtained by ball milling and hot pressing TiB2 powder with a particle size of 5μm, Si powder with a particle size of 3μm, and spherical Ti55 alloy powder with a particle size of 120μm as raw materials; the mass percentage of Si element in the silicon-containing titanium-based composite material is greater than or equal to 0.3%.

2. The thermomechanical method for controlling the precipitation size of silicides in silicon-titanium-based composite materials according to claim 1, characterized in that... The sintered discontinuous reinforced silicon-titanium-based composite material is obtained by mixing raw materials, performing low-energy ball milling, placing them in a mold, and hot-pressing sintering.

3. The thermomechanical method for controlling the precipitation size of silicides in silicon-titanium-based composite materials according to claim 2, characterized in that... The low-energy ball milling conditions are as follows: under argon protection, the ball-to-material ratio is 5~10:1, the ball milling speed is 180~240 rpm, and the ball milling time is 4~8 h.

4. The thermomechanical method for controlling the precipitation size of silicides in silicon-titanium-based composite materials according to claim 1, characterized in that... The hot pressing sintering conditions are as follows: when the vacuum degree reaches 10... -2 The temperature is gradually increased in stages, and the pressure is gradually increased in stages when the temperature reaches 600~900℃. When the temperature and pressure reach 1100~1300℃ and 20~30MPa respectively, the temperature and pressure are maintained for 1~2 hours.

5. A thermomechanical method for controlling the precipitation size of silicides in a silicon-titanium-based composite material according to claim 1 or 4, characterized in that... The hot pressing sintering conditions are as follows: when the vacuum degree reaches 10... -2 The temperature is gradually increased in stages, and the pressure is gradually increased in stages when the temperature reaches 700~800℃. When the temperature and pressure reach 1200~1300℃ and 25~30MPa respectively, the temperature and pressure are maintained for 1~2 hours.

6. The thermomechanical method for controlling the precipitation size of silicides in silicon-titanium-based composite materials according to claim 1, characterized in that... The silicide precipitates in the titanium-based composite material have a size of 0.17~0.32μm.

7. The thermomechanical method for controlling the precipitation size of silicides in silicon-titanium-based composite materials according to claim 1, characterized in that... The thermomechanical treatment time is 13~78h.

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