Heat treatment plasticization method for laser additive manufacturing of near-alpha titanium matrix composites

Abstract

This invention relates to a heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials. The method involves heating a vacuum heat treatment furnace to 500–800°C, then placing the near-α titanium-based composite material sample inside the furnace. Under vacuum or argon atmosphere, the temperature is increased at a rate of 10–15°C / min to a temperature 20–100°C below the β-transformation temperature of the near-α titanium-based composite material sample. After holding at this temperature for 0.5–2 hours, the sample is removed from the furnace and air-cooled to room temperature, thus obtaining the heat-treated plasticized near-α titanium-based composite material. This invention can increase the room temperature elongation of the composite material by 115%–135% while reducing the ultimate tensile strength by 4–7%, achieving a balance between strength and plasticity in laser additive manufacturing of near-α titanium-based composite materials.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composite material preparation, and specifically to the heat treatment plasticizing process of titanium matrix composite materials. Background Technology

[0002] With the rapid development of aerospace technology, aircraft are moving at increasingly higher speeds, leading to a greater demand for lightweight, high-strength, and heat-resistant alloy materials. High-temperature titanium alloys are increasingly used in the manufacture of aerospace engines and high-temperature hot-section components for aircraft. However, traditional high-temperature titanium alloys have a thermal barrier temperature, which cannot meet the needs of the rapidly evolving aerospace field.

[0003] Titanium-based composite materials refer to composite materials in which a high specific modulus, high strength, high hardness and good high-temperature performance reinforcing phase is added to a titanium or titanium alloy matrix. Compared with titanium alloys, titanium-based composite materials have higher strength and excellent high-temperature performance and corrosion resistance.

[0004] Currently, laser additive manufacturing technology boasts advantages such as high forming speed, short production cycle, high precision, good surface quality, and near-net-shape forming without molds, making its development prospects in the aerospace field increasingly evident. However, the addition of reinforcing phases, while increasing strength, often comes at the cost of reduced plasticity, which limits the service conditions of titanium-based composites. Therefore, improving the plasticity of laser additively manufactured titanium-based composites has become a research hotspot.

[0005] Chinese invention patent CN114774818B discloses a heat treatment process for improving the microstructure of Ti65 alloy castings. Compared with traditional heat treatment, this invention process ultimately yields a bimodal microstructure, with a significantly improved room temperature elongation. However, due to differences in preparation processes and the substantial differences in microstructure and mechanical properties between titanium alloys and titanium-based composites, this heat treatment process may not be suitable for laser additive manufacturing of near-α titanium-based composites.

[0006] Reference 1, "H.Li,D.Jia,Z.Yang, et al. Effect of heat treatment on microstructure evolution and mechanical properties of selective laser melted Ti–6Al–4V and TiB / Ti–6Al–4V composite: A comparative study[J].MaterialsScience and Engineering A,2021,801:140415," describes the preparation of 2 vol.% TiB / Ti6Al4V composite materials using laser additive manufacturing technology. Heat treatment improved the plasticity of the composite material, but reduced its strength to some extent.

[0007] In summary, most current methods for improving the plasticity of laser additive manufacturing titanium-based composites involve subsequent heat treatment. However, the increase in plasticity is often accompanied by a decrease in strength. The greater the increase in plasticity, the more significant the decrease in strength. How to significantly improve the plasticity of titanium-based composites with minimal or no strength loss has become an urgent problem to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials that can significantly improve the plasticity of titanium-based composite materials with minimal strength loss.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials, comprising the following steps:

[0010] The near-α titanium-based composite material sample is heated to 500-800℃ in a vacuum heat treatment furnace. Then, the sample is placed in the vacuum heat treatment furnace and heated to 20-100℃ below the β transformation temperature of the sample at a heating rate of 10-15℃ / min under vacuum or argon atmosphere. After holding at this temperature for 0.5-2h, the sample is removed from the furnace and air-cooled to room temperature, thus obtaining the heat-treated plasticized near-α titanium-based composite material.

[0011] The near-α titanium-based composite material is a titanium-based composite material with a lamellar structure prepared by laser additive manufacturing technology. The matrix structure of the near-α titanium-based composite material after heat treatment and plasticization is a mixture of equiaxed α and lamellar α, wherein the aspect ratio is less than or equal to 3 and is equiaxed α, and the aspect ratio is greater than 3 and is lamellar α. The volume fraction of equiaxed α is 25-40%.

[0012] Furthermore, it also includes the preparation of metallographic specimens of the near-α titanium-based composite material after heat treatment and plasticization:

[0013] Cut a sample of the heat-treated and plasticized near-α titanium-based composite material, and grind the cut sample on sandpaper of grades 240#, 400#, 600#, 800#, 1000#, 1200#, 1500#, and 2000#. After polishing, place the sample in anhydrous ethanol for ultrasonic cleaning for 5-15 minutes and blow dry to ensure that the surface is free of dirt and water stains. This yields a metallographic sample of the heat-treated and plasticized near-α titanium-based composite material with a smooth surface, which is used to observe the microstructure of the near-α titanium-based composite material sample.

[0014] Furthermore, the metallographic specimen is a block specimen with length, width, and height dimensions of 3–15 mm.

[0015] Furthermore, the vacuum environment refers to a vacuum degree of less than or equal to 500 Pa in the heat treatment furnace; the argon environment refers to argon gas being introduced into the vacuum environment until the furnace pressure reaches 1 atm, and the argon gas flow rate is controlled at 1 to 2 L / min.

[0016] Furthermore, the near-α titanium-based composite material sample is a block sample with a length of 50–100 mm, a width of 10–40 mm, and a height of 10–40 mm.

[0017] Furthermore, the reinforcing phase of the near-α titanium-based composite material is B4C, and the mass fraction of the reinforcing phase is 0.05 to 0.4 wt.%; the titanium alloy matrix of the near-α titanium-based composite material is Ti6242, Ti65, or Ti55 alloy.

[0018] Furthermore, the near-α titanium-based composite material is 0.2 wt.% B4C / Ti65, and the β transition temperature is 1110 °C.

[0019] Furthermore, the heat treatment plasticization method for the near-α titanium-based composite material, consisting of 0.2 wt.% B4C / Ti65, is as follows:

[0020] The near-α titanium-based composite material sample was heated to 800℃ in a vacuum heat treatment furnace and then placed in the furnace. Under vacuum or argon atmosphere, the temperature was increased to 1025-1075℃ at a heating rate of 10℃ / min. After holding at this temperature for 1 hour, the sample was removed from the furnace and air-cooled until room temperature, thus obtaining the heat-treated and plasticized near-α titanium-based composite material.

[0021] The beneficial effects of this invention are as follows: Compared with traditional heat treatment, this invention uses high-temperature heat treatment based on the Ti-C phase diagram, which dissolves the TiC reinforcing phase and allows C to re-dissolve in the matrix, improving solid solution strengthening and thus enhancing strength. It can also alleviate the strength reduction caused by coarse matrix structure. It can increase the room temperature elongation of the composite material by 115%–135% while reducing the ultimate tensile strength by 4–7%. This achieves a strong-plasticity match in laser additive manufacturing of near-α titanium-based composite materials. Attached Figure Description

[0022] Figure 1 This is a micrograph of the 0.2 wt.% B4C / Ti65 composite material produced by laser additive manufacturing without heat treatment in specific experimental example 1 of this invention;

[0023] Figure 2 This is a micrograph of the 0.2 wt.% B4C / Ti65 composite material produced by laser additive manufacturing in Experimental Example 1 of this invention after heat treatment;

[0024] Figure 3 The table shows the room temperature tensile engineering stress-engineering strain curves of 0.2wt.% B4C / Ti65 composite material manufactured by laser additive manufacturing in Experiment Example 1 of this invention before and after heat treatment.

[0025] Figure 4 This is a microstructure photograph of the 0.2 wt.% B4C / Ti65 composite material produced by laser additive manufacturing in Experimental Example 2 of this invention after heat treatment. Detailed Implementation

[0026] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0027] The addition of hard and brittle ceramic reinforcing phases often improves the strength of titanium-based composites to a certain extent, but the plasticity of the composites is also severely affected. The material has poor room temperature plasticity, and the contradiction between strength and plasticity will greatly limit the further development of titanium-based composites.

[0028] The key to engineering applications lies in achieving high plasticity while maintaining high strength in titanium-based composites, especially those prepared by laser additive manufacturing. This invention employs effective heat treatment to regulate the microstructure of the reinforcing phase and the matrix, thereby further improving the comprehensive mechanical properties of titanium-based composites.

[0029] To achieve the above objectives, the present invention provides the following specific embodiments:

[0030] Example 1: A heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials, comprising the following steps:

[0031] The near-α titanium-based composite material sample is heated to 500-800℃ in a vacuum heat treatment furnace. Then, the sample is placed in the vacuum heat treatment furnace and heated to 20-100℃ below the β transformation temperature of the sample at a heating rate of 10-15℃ / min under vacuum or argon atmosphere. After holding at this temperature for 0.5-2h, the sample is removed from the furnace and air-cooled to room temperature, thus obtaining the heat-treated plasticized near-α titanium-based composite material.

[0032] The vacuum environment refers to a vacuum degree of less than or equal to 500 Pa in the heat treatment furnace; the argon environment refers to the introduction of argon gas into the vacuum environment until the furnace pressure reaches 1 atm, and the argon gas flow rate is controlled at 1–2 L / min. The reinforcing phase of the near-α titanium-based composite material is B4C, with a mass fraction of 0.05–0.4 wt.%; the titanium alloy matrix of the near-α titanium-based composite material is Ti6242, Ti65, or Ti55 alloy. The near-α titanium-based composite material samples are block samples, with a length of 50–100 mm, a width of 10–40 mm, and a height of 10–40 mm.

[0033] The near-α titanium-based composite material is a titanium-based composite material with a lamellar structure prepared by laser additive manufacturing technology. The matrix structure of the near-α titanium-based composite material after heat treatment and plasticization is a mixture of equiaxed α and lamellar α, wherein the aspect ratio is less than or equal to 3 and is equiaxed α, and the aspect ratio is greater than 3 and is lamellar α. The volume fraction of equiaxed α is 25-40%.

[0034] It also includes the preparation of metallographic specimens of the near-α titanium-based composite material after heat treatment and plasticization:

[0035] A sample of the heat-treated and plasticized near-α titanium-based composite material was cut and progressively polished on 240#, 400#, 600#, 800#, 1000#, 1200#, 1500#, and 2000# sandpaper. After polishing, the sample was ultrasonically cleaned with anhydrous ethanol for 5–15 minutes and then dried to ensure the surface was free of contaminants and water stains. This yielded a metallographic sample of the heat-treated and plasticized near-α titanium-based composite material with a smooth surface, used for observing the microstructure of the near-α titanium-based composite material. The metallographic sample was a block-shaped sample with dimensions of 3–15 mm (length, width, and height).

[0036] Example 2: Same as Example 1, except that the near-α titanium-based composite material is 0.2 wt.% B4C / Ti65, the β transition temperature is 1110℃, and its heat treatment plasticization method is as follows:

[0037] The near-α titanium-based composite material sample was heated to 800℃ in a vacuum heat treatment furnace and then placed in the furnace. Under vacuum or argon atmosphere, the temperature was increased to 1025-1075℃ at a heating rate of 10℃ / min. After holding at this temperature for 1 hour, the sample was removed from the furnace and air-cooled until room temperature, thus obtaining the heat-treated and plasticized near-α titanium-based composite material.

[0038] Specific Experimental Example 1: A heat treatment plasticizing process for laser additive manufacturing of near-α titanium-based composite materials, including the following steps:

[0039] Step 1: A 0.2 wt.% B4C / Ti65 composite material block sample was prepared using laser additive manufacturing technology. The size of the block sample was 65 × 15 × 15 mm. The β transition temperature of the 0.2 wt.% B4C / Ti65 composite material was measured to be 1110℃.

[0040] Step 2: Perform heat treatment tests on the 0.2 wt.% B4C / Ti65 composite material sample produced by laser additive manufacturing in Step 1. First, heat the vacuum heat treatment furnace to 800°C, then place the sample in the vacuum heat treatment furnace. Under an argon atmosphere, the vacuum heat treatment furnace is heated to 1025°C at a heating rate of 10°C / min and held at that temperature for 1 hour. After the holding period, remove the sample from the furnace and air-cool it to room temperature.

[0041] Step 3: Cut a metallographic sample of the 0.2 wt.% B4C / Ti65 composite material produced by laser additive manufacturing. The metallographic sample is 5 mm long, 5 mm wide, and 3 mm high. The preparation method of the metallographic sample is as follows: After grinding and polishing the metallographic sample, it is placed in anhydrous ethanol and ultrasonically cleaned for 10 minutes, then dried to ensure that the surface is free of dirt and water stains, thus obtaining a smooth titanium-based composite metallographic sample.

[0042] The microstructure of the 0.2 wt.% B4C / Ti65 composite material before and after heat treatment is as follows: Figure 1 and Figure 2 As shown.

[0043] Figure 1 and Figure 2 The results show that the matrix microstructure of the 0.2 wt.% B4C / Ti65 composite material manufactured by laser additive manufacturing is lamellar. The B4C reinforcing phase reacts in situ with the Ti65 alloy to generate TiB and TiC reinforcing phases. After heat treatment, the aspect ratio of the α phase decreases, and the volume fraction of equiaxed α phase increases. The microstructure is a mixture of equiaxed α and lamellar α phases, with an equiaxed α volume fraction of 27.7%, which is beneficial to improving the plasticity of the composite material. The TiB reinforcing phase is whisker-like and maintains good stability without change during heat treatment. The TiC reinforcing phase is dissolved in the matrix, enhancing the solid solution strengthening effect.

[0044] Step 4: Process three plate-shaped tensile specimens on the heat-treated laser additive manufacturing 0.2wt.% B4C / Ti65 composite material specimen, and conduct room temperature tensile tests on an Instron 3382 electronic universal testing machine. Take the average value as the tensile value of the specimen.

[0045] Table 1 shows the room temperature tensile properties of the 0.2 wt.% B4C / Ti65 composite material in Experiment Example 1, both before and after heat treatment. The room temperature tensile stress-strain curves before and after heat treatment are shown in Table 1. Figure 3 As shown:

[0046] Table 1 shows the room temperature tensile properties of the 0.2 wt.% B4C / Ti65 composite material in Experiment Example 1.

[0047]

[0048] From Table 1 and Figure 3 The analysis revealed that the ultimate tensile strength of the untreated titanium-based composite material was 1205.23 MPa, with an elongation of 5.44%. After heat treatment, the ultimate tensile strength of the titanium-based composite material formed in this specific experimental example was 1154.19 MPa, with an elongation of 12.01%. Compared to the untreated titanium-based composite material, the elongation of the titanium-based composite material formed in this embodiment increased by 120%, while the ultimate tensile strength decreased by only 4.4%, achieving a good match between strength and plasticity of the titanium-based composite material.

[0049] This invention demonstrates that it can effectively improve the plasticity of near-α titanium-based composite materials manufactured by laser additive manufacturing with minimal strength loss.

[0050] Specific Experiment Example 2: Same as Specific Experiment Example 1, except that this example includes the following steps:

[0051] Step 1: A 0.2 wt.% B4C / Ti65 composite material block sample was prepared using laser additive manufacturing technology. The size of the block sample was 65 × 15 × 15 mm. The β transition temperature of the 0.2 wt.% B4C / Ti65 composite material was measured to be 1110℃.

[0052] Step 2: Perform heat treatment tests on the 0.2 wt.% B4C / Ti65 composite material sample produced by laser additive manufacturing as described in Step 1. First, heat the vacuum heat treatment furnace to 800°C, then place the sample in the vacuum heat treatment furnace. Under an argon atmosphere, the vacuum heat treatment furnace is heated to 1075°C at a heating rate of 10°C / min and held at that temperature for 1 hour. After the holding period, remove the sample from the furnace and air-cool it to room temperature.

[0053] Step 3: Cut a metallographic sample of the 0.2 wt.% B4C / Ti65 composite material produced by laser additive manufacturing. The metallographic sample is 5 mm long, 5 mm wide, and 3 mm high. The preparation method of the metallographic sample is as follows: After grinding and polishing the metallographic sample, it is placed in anhydrous ethanol and ultrasonically cleaned for 10 minutes, then dried to ensure that the surface is free of dirt and water stains, thus obtaining a smooth titanium-based composite metallographic sample.

[0054] The microstructure of the 0.2 wt.% B4C / Ti65 composite material after heat treatment is as follows: Figure 4 As shown.

[0055] Figure 4 This indicates that after heat treatment, the aspect ratio of the α phase decreases, and the volume fraction of equiaxed α phase increases. The microstructure is a mixture of equiaxed α and lamellar α phases. The volume fraction of equiaxed α phase is 37.8%, which is beneficial to improving the plasticity of the composite material. The TiB reinforcing phase is whisker-like and maintains good stability without change during heat treatment. The TiC reinforcing phase is dissolved in the matrix, which enhances the solid solution strengthening effect.

[0056] Step 4: Process three plate-shaped tensile specimens on the heat-treated laser additive manufacturing 0.2wt.% B4C / Ti65 composite material specimen, and conduct room temperature tensile tests on an Instron 3382 electronic universal testing machine. Take the average value as the tensile value of the specimen.

[0057] The room temperature tensile properties of the 0.2 wt.% B4C / Ti65 composite material in Experiment Example 2, both before and after heat treatment, are shown in Table 2.

[0058] Table 2. Room temperature tensile properties of the 0.2 wt.% B4C / Ti65 composite material in Example 2

[0059]

[0060] The analysis in Table 2 shows that the ultimate tensile strength of the untreated titanium-based composite material is 1205.23 MPa, and the elongation is 5.44%. After heat treatment, the tensile strength of the titanium-based composite material formed in this specific experimental example is 1139.81 MPa, and the elongation is 12.76%. Compared with the untreated titanium-based composite material, the elongation of the titanium-based composite material formed in this embodiment is increased by 134%, while the ultimate tensile strength is only reduced by 5.7%, achieving a good match between the strength and plasticity of the titanium-based composite material.

[0061] This invention demonstrates that it can effectively improve the plasticity of near-α titanium-based composite materials manufactured by laser additive manufacturing with minimal strength loss.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials, characterized in that, Includes the following steps: The near-α titanium-based composite material sample is heated to 500~800℃ in a vacuum heat treatment furnace. Then, the sample is placed in the vacuum heat treatment furnace and heated to 20~100℃ below the β transformation temperature of the near-α titanium-based composite material sample at a heating rate of 10~15℃ / min under vacuum or argon atmosphere. After holding at this temperature for 0.5~2h, the sample is removed from the furnace and air-cooled until room temperature, thus obtaining the heat-treated plasticized near-α titanium-based composite material. The near-α titanium-based composite material is a titanium-based composite material with a lamellar structure prepared by laser additive manufacturing technology. The matrix structure of the near-α titanium-based composite material after heat treatment and plasticization is a mixture of equiaxed α and lamellar α, wherein the aspect ratio is less than or equal to 3 and is equiaxed α, and the aspect ratio is greater than 3 and is lamellar α. The volume fraction of equiaxed α is 25-40%. The reinforcing phase of the near-α titanium-based composite material is B4C, and the mass fraction of the reinforcing phase is 0.05~0.4wt.%; the titanium alloy matrix of the near-α titanium-based composite material is Ti6242, Ti65, or Ti55 alloy.

2. The heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials as described in claim 1, characterized in that, It also includes the preparation of metallographic specimens of the near-α titanium-based composite material after heat treatment and plasticization: Cut a sample of the heat-treated and plasticized near-α titanium-based composite material, and grind the cut sample on sandpaper of grades 240#, 400#, 600#, 800#, 1000#, 1200#, 1500#, and 2000#. After polishing, place the sample in anhydrous ethanol for ultrasonic cleaning for 5-15 minutes and blow dry to ensure that the surface is free of dirt and water stains. This yields a metallographic sample of the heat-treated and plasticized near-α titanium-based composite material with a smooth surface, which is used to observe the microstructure of the near-α titanium-based composite material sample.

3. The heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials as described in claim 2, characterized in that, The metallographic specimen is a block-shaped specimen with length, width and height dimensions of 3~15mm.

4. The heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials as described in claim 1, characterized in that, The vacuum environment refers to a vacuum degree of less than or equal to 500 Pa in the heat treatment furnace; the argon environment refers to the introduction of argon into the vacuum environment until the furnace pressure reaches 1 atm, and the argon flow rate is controlled at 1~2 L / min.

5. The heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials as described in claim 1, characterized in that, The near-α titanium-based composite material sample is a block sample with a length of 50-100 mm, a width of 10-40 mm, and a height of 10-40 mm.

6. The heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials as described in claim 5, characterized in that, The near-α titanium-based composite material is 0.2 wt.% B4C / Ti65 with a β transition temperature of 1110℃.

7. The heat treatment plasticization method for laser additive manufacturing of near-α titanium-based composite materials as described in claim 6, characterized in that, The heat treatment plasticization method for the near-α titanium-based composite material (0.2 wt.% B4C / Ti65) is as follows: The near-α titanium-based composite material sample was heated to 800℃ in a vacuum heat treatment furnace and then placed in the furnace. Under vacuum or argon atmosphere, the temperature was increased to 1025~1075℃ at a heating rate of 10℃ / min. After holding at this temperature for 1 hour, the sample was removed from the furnace and air-cooled until room temperature, thus obtaining the heat-treated and plasticized near-α titanium-based composite material.

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