A method for adjusting the strength and toughness matching of powder TC21 titanium alloy

Abstract

This invention provides a method for adjusting the strength and toughness matching of powdered TC21 titanium alloy, comprising: preparing spherical TC21 titanium alloy powder; loading the spherical TC21 titanium alloy powder into a sample sleeve, tapping and compacting the powder, evacuating the sample sleeve for degassing and sealing; subjecting the sealed sample sleeve to hot isostatic pressing (HIP); removing the HIP sample sleeve to obtain powdered TC21 titanium alloy; and subjecting the powdered TC21 titanium alloy to double annealing to obtain reinforced powdered TC21 titanium alloy. This invention creatively proposes a method for fine control of TC21 powder, a method for controlling the HIP process regime, and a method for adjusting the strength and toughness under different double annealing regimes, achieving comprehensive performance matching adjustment of powdered TC21 material. This provides a new technical path for the manufacturing of TC21 titanium alloy components and lays the material and process foundation for the upgrading of aerospace weaponry.

Description

Technical Field

[0001] This invention belongs to the field of special forming technology of titanium alloys, and specifically relates to a method for adjusting the strength and toughness matching of powder TC21 titanium alloy. Background Technology

[0002] Titanium alloys, characterized by low density, high specific strength, excellent corrosion resistance, and superior high / low temperature performance, combine the performance and characteristics required for aerospace products, earning them the reputation of "space metal" and "all-around metal." They have become one of the key materials widely used in the aerospace field. The level of application of titanium and its alloys in aerospace equipment has become an important indicator of the equipment's sophistication and performance.

[0003] In the modern aerospace industry, equipment design principles have gradually shifted from traditional static strength design to damage tolerance design. Guided by this design philosophy, the development of titanium alloys has also progressed from low strength, medium strength, high strength to high strength and high toughness. TC21 titanium alloy is a backbone material for my country's new aerospace equipment. In the future, TC21 high-strength and high-toughness titanium alloys and other new high-strength and high-toughness titanium alloys will gradually replace TC4 and TA15 titanium alloys, becoming the mainstream titanium alloy grades.

[0004] Currently, the manufacturing of TC21 high-strength and high-toughness titanium alloys all adopt forging technology, which has many problems such as large machining allowance, poor machining accuracy, long cycle time and high cost. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the inventors have conducted intensive research and provided a method for adjusting the strength and toughness matching of powder TC21 titanium alloy. The powder TC21 titanium alloy material manufactured by hot isostatic pressing can fully achieve the standard performance of forgings, and the strength and fracture toughness can be matched and adjusted.

[0006] The technical solution provided by this invention is as follows:

[0007] In a first aspect, a method for adjusting the strength-toughness matching of powder TC21 titanium alloy includes:

[0008] Preparation of TC21 titanium alloy spherical powder;

[0009] TC21 titanium alloy spherical powder is loaded into the sample sleeve, the powder is tapped and vibrated to compact it, and the sample sleeve is evacuated for degassing and sealing.

[0010] The sealed sample sleeve is subjected to hot isostatic pressing treatment.

[0011] After removing the sample cladding from hot isostatic pressing, powdered TC21 titanium alloy was obtained.

[0012] Double annealing treatment was performed on powdered TC21 titanium alloy to obtain reinforced powdered TC21 titanium alloy.

[0013] In a second aspect, a powdered TC21 titanium alloy is prepared by the strength and toughness matching adjustment method of the powdered TC21 titanium alloy described in the first aspect.

[0014] The present invention provides a method for adjusting the strength and toughness matching of powder TC21 titanium alloy, which has the following characteristics:

[0015] Beneficial effects:

[0016] (1) The present invention provides a method for adjusting the strength and toughness matching of powder TC21 titanium alloy. Compared with the forging method, the TC21 titanium alloy material manufactured by hot isostatic pressing fully meets the forging standard in GJB2744, and can also achieve high strength and high fracture toughness of TC21 titanium alloy.

[0017] (2) The present invention provides a method for adjusting the strength and toughness matching of powder TC21 titanium alloy. The TC21 titanium alloy manufactured by hot isostatic pressing has a uniform and fine microstructure, free from internal defects such as porosity, inclusions, and segregation, and exhibits good dimensional stability. This method can achieve near-net-shape forming of complex components. Subsequently, this technology can be used to directly manufacture complex TC21 components, which will significantly improve material utilization, shorten the production cycle, and provide a new technical approach for the manufacturing of complex TC21 titanium alloy components. Attached Figure Description

[0018] Figure 1 A flowchart of a method for adjusting the strength-toughness matching of powder TC21 titanium alloy;

[0019] Figure 2 The image shows the morphology of the TC21 titanium alloy powder prepared in the examples. Detailed Implementation

[0020] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0021] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0022] This invention provides a method for adjusting the strength-toughness matching of powder TC21 titanium alloy, such as... Figure 1 As shown, it includes:

[0023] Step (1): Prepare TC21 titanium alloy spherical powder by plasma rotating electrode method, and detect the composition, particle size, inclusions and morphology to obtain TC21 titanium alloy spherical powder that meets the requirements.

[0024] The composition of TC21 titanium alloy spherical powder must meet the requirements of TC21 titanium alloy chemical composition in GB / T 3620.1, with the oxygen content requirement being further tightened to be controlled between 0.10% and 0.15%; there must be no inclusions larger than 106μm, and no more than one inclusion smaller than 106μm per 100g of powder; the powder morphology must be spherical, near-spherical, and ellipsoidal particles, and the proportion of non-spherical particles such as flakes, strips, ellipsoids, and dumbbells must not exceed 2%.

[0025] Powder particle size directly affects material properties and tap density. Strictly controlling the spherical powder particle size range of TC21 titanium alloy to 15–106 μm is crucial, as finer powder helps improve the performance of the formed powder titanium alloy. Then, the powder particle size is further subdivided into 15–45 μm, 45–75 μm, and 75–106 μm, with the required powder ratio for each of the three particle size distribution ranges being (1±0.1):(1±0.1):(1±0.1). This will improve the tap density of the powder after loading.

[0026] Step (2): Load TC21 titanium alloy spherical powder into the prepared cylindrical sample sleeve and tap to compact the powder. After loading, insert the degassing stainless steel tube into the reserved degassing hole of the sleeve, then place the sample sleeve into the high-temperature furnace, connect the degassing steel tube to the vacuum unit, and perform degassing under high temperature. After degassing is completed, seal the steel tube to ensure high vacuum inside the cylindrical sample sleeve after loading.

[0027] The cylindrical sample sheath mainly consists of an outer sheath, a lower bottom, an upper bottom, and a degassing stainless steel tube. The thickness of the outer sheath, the lower bottom, and the upper bottom is 2–4 mm.

[0028] Step (3) involves hot isostatic pressing of the cylindrical sample sleeve sealed in step (2).

[0029] Unlike traditional titanium alloys, the properties of TC21 titanium alloy are primarily controlled through heat treatment. The hot isostatic pressing (HIP) temperature directly affects the microstructure before heat treatment. Through extensive experimentation, the HIP temperature range for powdered TC21 titanium alloy was optimized. The β-transformation temperature Tβ of spherical TC21 titanium alloy powder was tested. β The hot isostatic pressing holding temperature of TC21 titanium alloy is (T β -30℃~(T) β -10℃), the hot isostatic pressing holding pressure requirement is ≥120MPa, and the hot isostatic pressing holding time requirement is 2~4h.

[0030] After the hot isostatic pressing and holding period is completed, compared with the slow furnace cooling of conventional titanium alloys, in order to ensure the grain size of powder TC21 titanium alloy, the cooling rate of TC21 sample encased in the hot isostatic press is controlled. The cooling rate is (15~20)℃ / min, and the sample can be taken out of the furnace when the temperature is below 200℃.

[0031] Step (4): Remove the sleeve of the cylindrical sample after hot isostatic pressing to obtain a cylindrical sample of powder TC21.

[0032] (5) The TC21 powder cylindrical specimens were subjected to double annealing treatment, and then tensile specimens and fracture toughness specimens were processed.

[0033] The microstructure of hot isostatically pressed TC21 titanium alloy is completely different from that of conventional forging, possessing its own unique characteristics. Therefore, its double annealing regime also differs from that of forged titanium alloys. Through extensive experimental accumulation, a double annealing regime based on the microstructure of powder TC21 titanium alloy has been summarized. Depending on the performance requirements, different double annealing regimes can be used to achieve different combinations of tensile strength and fracture toughness in powder TC21 titanium alloy, thereby enabling the matching and adjustment of strength and fracture toughness.

[0034] When the room temperature tensile strength Rm of TC21 titanium alloy is required to be ≥1200MPa, the double annealing regime adopted is as follows: first stage: 850±20℃, 1~2h, air cooling; second stage: 550±20℃, 4~6h, air cooling.

[0035] When the room temperature tensile strength Rm of TC21 titanium alloy is required to be 1100-1200 MPa, and the fracture toughness K... IC At 50–70 MPa·m 1 / 2 The double annealing process used is as follows: first stage: 900±20℃, 1~2h, air cooling; second stage: 600±20℃, 4~6h, air cooling.

[0036] When the fracture toughness K of TC21 titanium alloy is required IC ≥70MPa·m 1 / 2 The double annealing process used is as follows: first stage: 950±20℃, 1~2h, air cooling; second stage: 650±20℃, 4~6h, air cooling.

[0037] (6) The tensile properties and fracture toughness of the powdered TC21 titanium alloy were tested to obtain the properties of the powdered TC21 titanium alloy.

[0038] Example

[0039] Example 1

[0040] A method for preparing powdered TC21 titanium alloy includes the following steps:

[0041] (1) Production and testing of TC21 titanium alloy spherical powder

[0042] TC21 titanium alloy spherical powder was obtained by plasma rotating electrode powder preparation. The powder composition, particle size, inclusions, and morphology were analyzed. The composition of the TC21 titanium alloy powder is shown in Table 1, with an oxygen content of 0.13%. The morphology of the TC21 titanium alloy powder was also analyzed, and typical morphologies are shown in [Table 1]. Figure 2 The powder exhibits extremely high sphericity, with irregularly shaped particles such as flakes, strips, and dumbbells comprising no more than 2%. Inclusion testing of the TC21 titanium alloy powder revealed the absence of inclusions larger than 106 μm. Furthermore, inclusions smaller than 106 μm were absent in all three 100g samples, indicating very high powder purity. Finally, particle size analysis of the TC21 titanium alloy powder revealed a particle size distribution range of 15–106 μm, with 15–45 μm accounting for 34.1%, 45–75 μm for 32.8%, and 75–106 μm for 33.1%.

[0043] Table 1. Composition of TC21 Titanium Alloy Powder

[0044] element Al Mo Cr Zr Nb GB / 3620.1 5.2～6.8 2.2～3.3 0.9～2.0 1.6～2.5 1.7～2.3 Measured value 6.28 2.75 1.58 2.12 1.91 element Fe N H O Ti GB / 3620.1 ≤0.15 ≤0.05 ≤0.015 0.15 Bal. Measured value 0.022 0.007 0.0049 0.13 Bal.

[0045] (2) Process the cylindrical sample sleeve and complete welding, powder filling and high-temperature degassing.

[0046] A cylindrical specimen sheath is fabricated using 304 stainless steel. The outer sheath, lower base, and upper base are all made of 3mm thick sheet metal. The outer sheath is rolled and welded into a cylinder with an inner diameter of 150mm and a height of 400mm. A degassing hole is pre-drilled on the upper base for inserting a degassing stainless steel tube. First, the outer sheath and lower base are argon-arc welded. Then, precisely controlled TC21 titanium alloy spherical powder is loaded into the sheath, compacted, and the upper base is installed. After argon-arc welding, the degassing stainless steel tube is inserted and then argon-arc welded together. The entire cylindrical specimen sheath is then placed in a high-temperature furnace, with the degassing stainless steel tube connected to a vacuum unit. The furnace is maintained at 600℃, and the vacuum level is required to be better than 3*10. -3 Pa, heat treatment time is 6 hours. After degassing, sealing welding is performed to obtain a complete cylindrical sample sleeve.

[0047] (3) Hot isostatic pressing treatment of cylindrical specimens

[0048] The β transformation temperature T of the TC21 titanium alloy spherical powder in test step (1) β T βThe temperature was 955℃. For this experiment, the hot isostatic pressing (HIP) temperature was 930℃, the pressure was 140MPa, and the holding time was 3 hours. After the HIP holding period, to ensure the grain size of the TC21 titanium alloy powder, the cooling rate of the TC21 sample encasing it in the HIP was controlled at 20℃ / min, and the sample was removed from the furnace at a temperature below 200℃.

[0049] (4) Remove the cylindrical sample sleeve.

[0050] The cylindrical sample casing was completely removed by machining to obtain a cylindrical sample of powder TC21 with a diameter of 120 mm and a height of 360 mm.

[0051] (5) Double annealing of TC21 titanium alloy cylindrical samples

[0052] The microstructure of hot isostatically pressed TC21 titanium alloy is completely different from that of conventional forging, possessing its own unique characteristics. Therefore, its double annealing regime also differs from that of forged titanium alloys. Depending on the performance requirements, different annealing regimes can yield different combinations of room temperature strength and fracture toughness in TC21 titanium alloy, thus enabling the matching and adjustment of strength and fracture toughness. The cylindrical specimen was divided into three sections along its height, each 120 mm high, numbered 1#, 2#, and 3#. Three different double annealing regimes were then applied: Regulation 1: 850℃, 1h, air cooling + 550℃, 4h, air cooling; Regulation 2: 900℃, 1h, air cooling + 600℃, 4h, air cooling; Regulation 3: 950℃, 1h, air cooling + 650℃, 4h, air cooling.

[0053] (6) Strength and fracture toughness testing of powder TC21 titanium alloy

[0054] Three tensile specimens and three fracture toughness specimens were machined from three powder TC21 titanium alloy samples (numbered 1#, 2#, and 3#) with different annealing regimes. Tests were performed according to GB / T 228 and GB / T 4161, and the resulting properties of the powder TC21 titanium alloy are shown in Table 2. The table shows that by using different double annealing regimes, the strength and fracture toughness of the powder TC21 titanium alloy can be adjusted to achieve different levels of matching. Its performance meets the TC21 titanium alloy forging standard specified in GJB2744-2019, demonstrating excellent overall performance.

[0055] Table 2 Properties of TC21 powder after double annealing

[0056]

[0057]

[0058] Comparative Examples 1-2

[0059] Comparative Example 1～2 Consistent with Example 1, the double annealing process was the same as for Sample #2, except that the hot isostatic pressing (HIP) holding temperatures were 900℃ and 960℃, exceeding the required HIP holding temperature of 925~945℃. The strength and fracture toughness tests of the powdered TC21 titanium alloy are shown in Table 3.

[0060] Table 3 Properties of TC21 powder after double annealing

[0061]

[0062] Comparative Examples 3-4

[0063] Comparative Example 3～4 Consistent with Example 1, the double annealing process was the same as that for Sample #2, except that the cooling rates after hot isostatic pressing were 10°C / min and 25°C / min, exceeding the required cooling rate of (15-20)°C / min. The strength and fracture toughness tests of the powdered TC21 titanium alloy are shown in Table 3.

[0064] Table 4 Properties of TC21 powder after double annealing

[0065]

[0066]

[0067] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0068] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for adjusting the strength and toughness matching of powder TC21 titanium alloy, characterized in that, include: Preparation of TC21 titanium alloy spherical powder; TC21 titanium alloy spherical powder is loaded into the sample sleeve, the powder is tapped and vibrated to compact it, and the sample sleeve is evacuated for degassing and sealing. The sealed sample sleeve is subjected to hot isostatic pressing treatment. After removing the sample cladding from hot isostatic pressing, powdered TC21 titanium alloy was obtained. Double annealing treatment was performed on powdered TC21 titanium alloy to obtain reinforced powdered TC21 titanium alloy. In the step of performing hot isostatic pressing on the sealed sample enclosure, the hot isostatic pressing holding temperature is (T β -30℃) ~ (T β -10℃), the hot isostatic pressing holding pressure requirement is ≥120MPa, and the hot isostatic pressing holding time requirement is 2~4h, where T β The β-transformation temperature of TC21 titanium alloy spherical powder; In the step of performing double annealing treatment on powdered TC21 titanium alloy to obtain reinforced powdered TC21 titanium alloy, when the room temperature tensile strength Rm of TC21 titanium alloy is required to be >1200MPa, the double annealing regime is as follows: first stage: 850±20℃, 1~2h, air cooling; second stage: 550±20℃, 4~6h, air cooling. In the step of performing double annealing treatment on powdered TC21 titanium alloy to obtain reinforced powdered TC21 titanium alloy, when the room temperature tensile strength Rm of TC21 titanium alloy is required to be 1100~1200MPa and the fracture toughness K is required to be [missing information]. IC At 50~70 MPa·m 1 / 2 The double annealing process used was as follows: first stage: 900±20℃, 1~2h, air cooling; second stage: 600±20℃, 4~6h, air cooling. In the step of performing double annealing treatment on powdered TC21 titanium alloy to obtain reinforced powdered TC21 titanium alloy, when the fracture toughness K of TC21 titanium alloy is required... IC ≥70MPa·m 1 / 2 The double annealing process used is as follows: first stage: 950±20℃, 1~2h, air cooling; second stage: 650±20℃, 4~6h, air cooling.

2. The method for adjusting the strength and toughness matching of powder TC21 titanium alloy according to claim 1, characterized in that, In the step of preparing TC21 titanium alloy spherical powder, the composition of the obtained TC21 titanium alloy spherical powder must meet the requirements of the chemical composition of TC21 titanium alloy in GB / T 3620.1, wherein the oxygen content is required to be controlled at 0.10%~0.15%; it is required that there be no inclusions with a size larger than 106μm, and no more than one inclusion with a size smaller than 106μm per 100g of powder.

3. The method for adjusting the strength and toughness matching of powder TC21 titanium alloy according to claim 1, characterized in that, In the steps of loading TC21 titanium alloy spherical powder into the sample sleeve, tapping and compacting the powder, evacuating the sample sleeve for degassing and sealing, the TC21 titanium alloy spherical powder is subdivided into 15~45μm, 45~75μm and 75~106μm particle sizes, and the powder ratio of the three particle size distribution ranges is required to be (1±0.1):(1±0.1):(1±0.1).

4. The method for adjusting the strength and toughness matching of powder TC21 titanium alloy according to claim 1, characterized in that, In the steps of loading TC21 titanium alloy spherical powder into the sample sleeve, tapping and compacting the powder, evacuating the sample sleeve for degassing, and sealing, the sample sleeve mainly includes an outer sleeve skin, a lower sleeve bottom, a upper sleeve bottom, and a degassing stainless steel tube. The thickness of the outer sleeve skin, the lower sleeve bottom, and the upper sleeve bottom is 2~4mm.

5. The method for adjusting the strength and toughness matching of powder TC21 titanium alloy according to claim 1, characterized in that, In the step of hot isostatic pressing of the sealed sample sleeve, the cooling rate of the sample sleeve after hot isostatic pressing is (15~20)℃ / min, and the temperature is below 200℃ when it is taken out of the furnace.

6. A powdered TC21 titanium alloy, prepared by the method for adjusting the strength and toughness matching of powdered TC21 titanium alloy as described in any one of claims 1 to 5.

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