Heat treatment method for regulating silicide precipitation in high-temperature titanium-based composite material

Abstract

The invention relates to a heat treatment method for regulating and controlling silicide precipitation in a high-temperature titanium-based composite material, which comprises a solid solution treatment step for completely carrying out solid solution on an Si element in a matrix, avoiding coarse silicide precipitation and simultaneously providing component conditions for subsequent silicide precipitation, and a heat treatment step for promoting the silicide to be dispersed and precipitated in the matrix so as to regulate and control silicide precipitation in a high-temperature titanium-based composite material. The aging treatment step is achieved, and the good ductility is still kept while the material strength is remarkably improved; the comprehensive mechanical property of the titanium-based composite material is improved, and the high-temperature use requirement of the titanium-based composite material is further met.

Description

Technical Field

[0001] The present invention relates to the field of preparation of metal matrix composites, and particularly to a heat treatment process for the precipitation of silicides in titanium matrix composites. Background Art

[0002] Titanium matrix composites have higher specific strength and specific stiffness compared to titanium alloys and are widely used in the aerospace field. Among them, high-temperature titanium matrix composites are often used to manufacture aerospace engines due to their high high-temperature strength, excellent high-temperature creep resistance, and good thermal stability. Si element is usually added to high-temperature titanium matrix composites to improve their mechanical properties. Due to the solubility difference of Si in α-Ti and β-Ti, it precipitates in the form of silicides along the α / β phase boundary. The silicides precipitated at the α / β phase boundary can pin dislocations, thus effectively hindering the movement of dislocations, which is beneficial to the improvement of the strength and creep resistance of titanium matrix composites.

[0003] However, the coarse silicide particles distributed along the grain boundaries are stress concentration points, which are prone to inducing the formation of microcracks, thereby reducing the ductility of titanium matrix composites. Heat treatment can regulate the morphology, size, volume fraction, and distribution of silicides in high-temperature titanium matrix composites, thereby improving the mechanical properties of high-temperature titanium matrix composites.

[0004] Chinese Patent No. CN118880207A discloses a thermomechanical method for regulating the precipitation size of silicides in silicon-containing titanium matrix composites. By simultaneously adjusting the two parameters of temperature and stress in the thermomechanical treatment process, the regulation of the precipitation size of silicides in titanium matrix composites is achieved, and the customized range of silicide precipitation size is broadened. Although this method can effectively regulate the size of silicides, it has not yet regulated the volume fraction of silicides. Document 1 "W. Jia, W. Zeng, H. Yu. Effect of aging on the tensile properties and microstructures of a near-alpha titanium alloy. Materials & Design, 2014, 58: 108-115." points out that with the increase of aging temperature and the prolongation of aging time, the size and volume fraction of silicides gradually increase, and the silicides have a strengthening effect on titanium alloys, but when the silicides grow, this strengthening effect will weaken.

[0005] In summary, the size and volume fraction of silicides have a significant impact on the mechanical properties of high-temperature titanium matrix composites. The larger the size of the silicides, the easier it is to initiate stress concentration, leading to premature fracture of the material and thus reducing the ductility and toughness of the material. While an increase in the volume fraction of silicides is beneficial to the improvement of the material strength, an excessive volume fraction may result in a decrease in the plasticity of the material. Therefore, how to regulate the size, volume fraction and distribution of silicides through heat treatment to further improve the comprehensive mechanical properties of high-temperature titanium matrix composites remains to be studied more deeply. Summary of the Invention

[0006] The object of the present invention is to avoid the deficiencies of the prior art and provide a heat treatment method for regulating the precipitation of silicides in high-temperature titanium matrix composites.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: A heat treatment method for regulating the precipitation of silicides in high-temperature titanium matrix composites, comprising the following steps: Step 1, solution treatment: used to completely dissolve Si elements in the matrix, avoid the precipitation of coarse silicides, and at the same time provide compositional conditions for the subsequent precipitation of silicides; Specifically: After keeping the high-temperature titanium matrix composite at a temperature 20 - 60 °C below the β transformation temperature for 0.5 - 2 h, it is cooled to room temperature, and thus a high-temperature titanium matrix composite with silicides completely dissolved in the matrix, that is, a solution-treated high-temperature titanium matrix composite without silicide precipitation, is obtained. Among them, the mass fraction of Si element in the titanium alloy matrix of the high-temperature titanium matrix composite is greater than or equal to 0.3%. Step 2, aging treatment: used to promote the dispersion precipitation of silicides in the matrix, so as to significantly improve the strength of the material while still maintaining a good elongation; Specifically: After keeping the solution-treated high-temperature titanium matrix composite at a temperature of 600 - 800 °C for 2 - 8 h, it is cooled to room temperature, and thus a high-temperature titanium matrix composite with silicide precipitation size of 4 - 110 nm and volume fraction of 0.10 - 1.70% is obtained.

[0008] Further, the silicides in the high-temperature titanium matrix composite with silicide precipitation are distributed at the α / β phase boundary or inside α-Ti.

[0009] Further, after the heat preservation in Step 1 is completed, the high-temperature titanium matrix composite sample is taken out of the furnace and water-cooled to room temperature.

[0010] Further, after the heat preservation in Step 2 is completed, the high-temperature titanium matrix composite sample is taken out of the furnace and air-cooled to room temperature.

[0011] Furthermore, the reinforcing phase of the high-temperature titanium matrix composite is B4C, and the mass fraction of the reinforcing phase is 0.05~0.4wt.%; the titanium alloy matrix of the high-temperature titanium matrix composite is Ti65 or Ti55 alloy.

[0012] Furthermore, the high-temperature titanium matrix composite is 0.2wt.% B4C / Ti65.

[0013] Furthermore, it also includes the step of preparing a metallographic specimen of the high-temperature titanium matrix composite.

[0014] Furthermore, the steps of preparing the metallographic specimen are specifically as follows: Cut a metallographic specimen from the high-temperature titanium matrix composite. After grinding and polishing the metallographic specimen, put it into absolute ethanol, clean it by ultrasonic vibration for 5~15 min and then dry it to ensure that there is no dirt and water stain on the surface of the specimen, thus obtaining the metallographic specimen.

[0015] The beneficial effects of the present invention are as follows: The present invention regulates the size, volume fraction and distribution of silicides in the high-temperature titanium matrix composite through heat treatment. Among them, solution treatment can completely dissolve Si element in the matrix, avoid the precipitation of coarse silicides, and provide compositional conditions for the precipitation of silicides in subsequent aging treatment. And aging treatment can promote the precipitation of nanoscale silicides in the matrix. While significantly improving the strength, it still maintains a good elongation rate, improves the comprehensive mechanical properties of the titanium matrix composite, and further meets its high-temperature use requirements. Description of the Drawings

[0016] Figure 1 It is the microstructural photograph of the 0.2wt.% B4C / Ti65 composite after solution treatment in the specific experimental example 1 of the present invention; Figure 2 It is the microstructural photograph of the 0.2wt.% B4C / Ti65 composite after aging treatment in the specific experimental example 1 of the present invention; Figure 3 It is the microstructural photograph of the 0.2wt.% B4C / Ti65 composite after aging treatment in the specific experimental example 2 of the present invention. Detailed Embodiments

[0017] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0018] Si element is usually added to the high-temperature titanium matrix composite to improve the high-temperature strength, creep resistance, etc. of the material. Si usually exists in the high-temperature titanium matrix composite in the form of solid solution or silicide. Si dissolved in the matrix can play a role in solid solution strengthening, while the precipitated silicide can play a role in precipitation strengthening.

[0019] However, when the silicide coarsens, the strengthening effect will be weakened and the plasticity of the material will decrease. Therefore, how to control the size, volume fraction and distribution of the silicide by heat treatment is of great significance for improving the properties of high-temperature titanium matrix composites.

[0020] To achieve the above object, the present invention provides the following specific embodiments: Example 1: A heat treatment method for regulating the precipitation of silicide in a high-temperature titanium matrix composite, comprising the following steps: Step 1: Keep the high-temperature titanium matrix composite at a temperature 20 - 60 °C below the β transformation temperature for 0.5 - 2 h, and then water-cool it to room temperature, thus obtaining a high-temperature titanium matrix composite with silicide completely dissolved in the matrix, that is, a solution-treated high-temperature titanium matrix composite without silicide precipitation; Among them, the mass fraction of Si element in the titanium alloy matrix of the high-temperature titanium matrix composite is greater than or equal to 0.3%; Step 2: Aging treatment: used to promote the dispersion precipitation of silicide in the matrix, so as to significantly improve the strength of the material while still maintaining a good elongation; Specifically: Keep the solution-treated high-temperature titanium matrix composite at a temperature of 600 - 800 °C for 2 - 8 h, and then air-cool it to room temperature, thus obtaining a high-temperature titanium matrix composite with the precipitation size of silicide being 4 - 110 nm and the volume fraction being 0.10 - 1.70%; and the silicide in the high-temperature titanium matrix composite with silicide precipitation is distributed at the α / β phase boundary or inside α-Ti.

[0021] Example 2: The same as Example 1, except that: the reinforcing phase of the high-temperature titanium matrix composite is B4C, and the mass fraction of the reinforcing phase is 0.05 - 0.4 wt.%; the titanium alloy matrix of the high-temperature titanium matrix composite is Ti65 alloy.

[0022] Example 3: The same as Example 1, except that: the reinforcing phase of the high-temperature titanium matrix composite is B4C, and the mass fraction of the reinforcing phase is 0.05 - 0.4 wt.%; the titanium alloy matrix of the high-temperature titanium matrix composite is Ti55 alloy.

[0023] Example 4: The same as Example 1, except that the high-temperature titanium matrix composite is 0.2 wt.% B4C / Ti65.

[0024] Example 5: The same as Example 1, except that: Step 3: It also includes the step of preparing a metallographic specimen of the high-temperature titanium matrix composite, specifically: cut a metallographic specimen from the high-temperature titanium matrix composite, after grinding and polishing the metallographic specimen, put it into absolute ethanol, use ultrasonic vibration to clean it for 5 - 15 min and then dry it, to ensure that there is no dirt and water stain on the surface of the specimen, thus obtaining the metallographic specimen.

[0025] As Figures 1-3 shown, in order to further illustrate the technical solution and technical effect of the present invention, the following specific examples are provided: Specific Example 1: As Figure 1 and Figure 2 shown, a heat treatment process method for regulating the precipitation of silicides in a high-temperature titanium matrix composite includes the following steps: Step 1: Prepare a 0.2wt.% B4C / Ti65 composite block by laser additive manufacturing technology, and measure the β transformation temperature of the 0.2wt.% B4C / Ti65 composite to be 1110 °C.

[0026] Step 2: Perform solution treatment on the 0.2wt.% B4C / Ti65 composite in Step 1: First, heat the heat treatment furnace to 1050 °C, then place the high-temperature titanium matrix composite in the heat treatment furnace and hold for 1 h. After the holding is completed, take out the high-temperature titanium matrix composite from the furnace and cool it in water, and then the solution-treated high-temperature titanium matrix composite is obtained; Step 3: Heat the heat treatment furnace to 700 °C, then place the solution-treated high-temperature titanium matrix composite in Step 2 in the heat treatment furnace and hold for 5 h. After the holding is completed, take out the high-temperature titanium matrix composite from the furnace and air-cool it to room temperature, and then the aged high-temperature titanium matrix composite is obtained.

[0027] Step 4: Cut a metallographic specimen of the 0.2wt.% B4C / Ti65 composite after solution and aging treatments. The preparation method of this metallographic specimen is as follows: After grinding and polishing the metallographic specimen, place it in absolute ethanol, clean it by ultrasonic vibration for 10 min and then dry it to ensure that the surface has no dirt and water stains, so as to obtain a surface-smooth metallographic specimen of the high-temperature titanium matrix composite after solution and aging treatments.

[0028] It can be seen from Figure 1 and Figure 2 that no silicides precipitate after solution treatment of the laser additive manufactured 0.2wt.% B4C / Ti65 composite at 1050 °C for 1 h; while silicides are observed to precipitate after aging at 700 °C for 5 h. The silicides mainly precipitate along the α / β phase boundary, the average size of the silicides is 60 nm, and the volume fraction is 1.1%. The incoherent interface between the silicides and the matrix will effectively hinder the movement of dislocations, resulting in an increase in the strength of the material, while the nanoscale silicides have little effect on the plasticity of the material.

[0029] Specific Experimental Example 2: As Figure 3 shown, the same as Specific Experimental Example 1, the difference is that this specific example includes the following steps: Step 1: Prepare a bulk 0.2wt.% B4C / Ti65 composite material using laser additive manufacturing technology, and measure that the β transformation temperature of the 0.2wt.% B4C / Ti65 composite material is 1110 °C.

[0030] Step 2: Conduct a solution treatment experiment on the 0.2wt.% B4C / Ti65 composite material described in Step 1. First, heat the heat treatment furnace to 1050 °C, then place the high-temperature titanium matrix composite material in the heat treatment furnace and hold it for 1 h. After the holding is completed, take out the high-temperature titanium matrix composite material from the furnace and cool it in water, and then the solution-treated high-temperature titanium matrix composite material is obtained. Step 3: Heat the heat treatment furnace to 800 °C, then place the solution-treated high-temperature titanium matrix composite material in Step 2 in the heat treatment furnace and hold it for 5 h. After the holding is completed, take out the high-temperature titanium matrix composite material from the furnace and air-cool it to room temperature, and then the aged high-temperature titanium matrix composite material is obtained.

[0031] Step 4: Cut a metallographic specimen of the 0.2wt.% B4C / Ti65 composite material after solution and aging treatments. The preparation method of this metallographic specimen is as follows: After grinding and polishing the metallographic specimen, place it in absolute ethanol, clean it by ultrasonic vibration for 10 min and then dry it to ensure that there is no dirt and water stain on the surface, so as to obtain a surface-smooth metallographic specimen of the high-temperature titanium matrix composite material after solution and aging treatments.

[0032] It can be seen from Figure 3 that: After aging the 0.2wt.% B4C / Ti65 composite material prepared by laser additive manufacturing at 800 °C for 5 h, the precipitation of silicides is observed. The silicides mainly precipitate along the α / β phase boundary and inside α-Ti. The average size of the silicides is 110 nm, and the volume fraction is 1.6%. The incoherent interface between the silicides and the matrix will effectively hinder the movement of dislocations, resulting in an increase in the strength of the material, while the silicides with nanoscale size have little effect on the plasticity of the material.

[0033] The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heat treatment method for regulating the precipitation of silicides in a high-temperature titanium matrix composite, characterized in that, It includes the following steps: Step 1, solution treatment: It is used to completely dissolve Si element in the matrix, avoid the precipitation of coarse silicides, and provide compositional conditions for the subsequent precipitation of silicides; Specifically: After holding the high-temperature titanium matrix composite at a temperature 20 - 60 °C below the β-transformation temperature for 0.5 - 2 h, it is cooled to room temperature, and thus a high-temperature titanium matrix composite with silicides completely dissolved in the matrix, that is, a solution-treated high-temperature titanium matrix composite without silicide precipitation, is obtained; Among them, the mass fraction of Si element in the titanium alloy matrix of the high-temperature titanium matrix composite is greater than or equal to 0.3%; Step 2, aging treatment: It is used to promote the dispersion precipitation of silicides in the matrix, so as to significantly improve the strength of the material while still maintaining a good elongation; Specifically: After holding the solution-treated high-temperature titanium matrix composite at a temperature of 600 - 800 °C for 2 - 8 h, it is cooled to room temperature, and thus a high-temperature titanium matrix composite with silicide precipitation size of 4 - 110 nm and volume fraction of 0.10 - 1.70% is obtained.

2. The heat treatment method for regulating the precipitation of silicides in a high-temperature titanium matrix composite according to claim 1, characterized in that, The silicides in the high-temperature titanium matrix composite with silicide precipitation are distributed at the α / β phase boundary or inside α-Ti.

3. The heat treatment method for regulating the precipitation of silicides in a high-temperature titanium matrix composite according to claim 1, characterized in that, After the heat preservation in Step 1 is completed, the high-temperature titanium matrix composite sample is taken out of the furnace and water-cooled to room temperature.

4. The heat treatment method for regulating the precipitation of silicides in the high-temperature titanium matrix composite according to claim 1, wherein, After the heat preservation in Step 2 is completed, the high-temperature titanium matrix composite sample is taken out of the furnace and air-cooled to room temperature.

5. The heat treatment method for regulating the precipitation of silicides in the high-temperature titanium matrix composite according to claim 1, wherein, The reinforcing phase of the high-temperature titanium matrix composite is B4C, and the mass fraction of the reinforcing phase is 0.05 - 0.4 wt.%; the titanium alloy matrix of the high-temperature titanium matrix composite is Ti65 or Ti55 alloy.

6. The heat treatment method for regulating the precipitation of silicides in a high-temperature titanium matrix composite according to claim 1, characterized in that, The high-temperature titanium matrix composite is 0.2 wt.% B4C / Ti65.

7. The heat treatment method for regulating the precipitation of silicides in the high-temperature titanium matrix composite according to any one of claims 1-6, characterized in that, It also includes the step of preparing a metallographic sample of the high-temperature titanium matrix composite.

8. The heat treatment method for regulating the precipitation of silicides in a high-temperature titanium matrix composite according to claim 7, characterized in that, The specific steps for preparing the metallographic sample are: cutting a metallographic sample from the high-temperature titanium matrix composite, after grinding and polishing the metallographic sample, putting it into absolute ethanol, cleaning it by ultrasonic vibration for 5 - 15 min and then drying it to ensure that there is no dirt and water stain on the sample surface, and thus the metallographic sample is obtained.

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