Multi-stage heat treatment method for improving hardness of RT1400 titanium alloy

Abstract

The invention discloses a multi-stage heat treatment method for improving the hardness of an RT1400 titanium alloy. The method comprises the following steps: 1, carrying out solution treatment on the RT1400 titanium alloy; secondly, the RT1400 titanium alloy subjected to solution treatment is subjected to pre-aging treatment; and thirdly, the RT1400 titanium alloy subjected to pre-aging treatment is sequentially subjected to first-stage aging treatment and second-stage aging treatment. Solution treatment is carried out at the temperature higher than the beta-phase transformation temperature of the RT1400 titanium alloy, the lamellar thickness of a beta-phase transformation structure is reduced, phase separation is carried out in the pre-aging treatment process, so that beta'presents fine dispersed particles and becomes a crystal core of a subsequent aging alpha phase, beta 'is decomposed to form an alpha + beta phase through first-stage aging treatment, and the alpha + beta phase is formed through second-stage aging treatment. And a secondary alpha phase is formed on a beta-phase matrix through long-time second-stage aging treatment, and a fine dispersed alpha phase is separated out, so that the strength and hardness of the RT1400 titanium alloy are improved, and the strong-plasticity matching of the RT1400 titanium alloy is kept.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of titanium alloys, and in particular to a multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy. Background Art

[0002] RT1400 titanium alloy is a new type of aviation structural β titanium alloy developed by Xi'an Rare Metal Materials Research Institute Co., Ltd. Its design goal is to obtain a new type of high-strength titanium alloy material with excellent strength, toughness and plasticity matching. The titanium alloy is composed of the following mass percentages: Al 4.2%~5.2%, V 2.5%~3.5%, Cr 1.1%~2.1%, Mo5.1%~6.1%, Fe 1.0%~2.0%, and the balance is Ti and inevitable impurity elements. After solution aging treatment, the room temperature tensile properties of RT1400 titanium alloy can reach 1500MPa, and the elongation can reach 7.8%, which has better comprehensive performance than the same type of near-β alloys.

[0003] β titanium alloy is widely used in aerospace, weapons and equipment, medical and chemical industries due to its high specific strength, good mechanical properties, biocompatibility and corrosion resistance. However, with the advancement of science and technology, people have put forward higher requirements on the performance of titanium alloys, especially in the fields of aerospace and weapons and equipment. The demand for weight reduction and lightweighting is becoming increasingly obvious. Replacing steel and high-temperature alloys with titanium alloys has become an important direction for the research and development of titanium alloys. However, there is a significant gap in hardness between titanium alloys and steel and high-temperature alloys. The hardness of existing high-strength titanium alloys is usually lower than 45HRC, such as TB2, Ti-15333, Ti-55531, etc., while the hardness of high-strength steel is usually greater than 50HRC, which greatly restricts the use of titanium alloys in wear-resistant environments.

[0004] The traditional way to improve the wear resistance of titanium alloys is to add a certain volume content of reinforcing phase (TiC, TiB, B4C, etc.) into the matrix, generate ceramic reinforcing phase particles in situ during the smelting process, and form a titanium-based composite material containing a ceramic reinforcing phase. However, this method has limited effect on improving the hardness of the material and significantly reduces the elongation, which limits the large-scale use of titanium-based composite materials. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy in view of the above-mentioned deficiencies of the prior art. The method adopts a multi-stage heat treatment process, so that phase separation and phase decomposition occur in sequence in the RT1400 titanium alloy structure, and fine dispersed α phase is precipitated in the β phase matrix, thereby improving the strength and hardness of the RT1400 titanium alloy, and at the same time improving the uniformity and stability of the RT1400 titanium alloy structure, solving the problem of limited improvement of the hardness of titanium alloy in the prior art.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy, characterized in that the method comprises the following steps: Step 1, solution treatment: performing solution treatment on the RT1400 titanium alloy; the solution treatment temperature is 870°C to 890°C, and the solution treatment time is 15min to 25min; Step 2, pre-aging treatment: pre-aging treatment is performed on the RT1400 titanium alloy after the solution treatment in step 1; the pre-aging treatment temperature is 360° C. to 400° C., and the pre-aging treatment time is 280 min to 320 min; Step 3, multi-stage aging treatment: the RT1400 titanium alloy after pre-aging treatment in step 2 is subjected to first-stage aging treatment and second-stage aging treatment in sequence; the first-stage aging treatment temperature is 410°C~440°C, and the first-stage aging treatment time is 280min~320min; the second-stage aging treatment temperature is 440°C~480°C, and the second-stage aging treatment time is 1420min~1460min.

[0007] The β phase transformation temperature of RT1400 titanium alloy is about 840°C. The present invention firstly performs a solution treatment above the β phase transformation temperature of RT1400 titanium alloy to increase the temperature and thus increase the solid solubility. After water cooling, the thickness of the lamellae of the β phase transformation structure is reduced, laying a foundation for subsequent grain refinement. Then, a pre-aging treatment is performed. The pre-aging treatment has a strong nucleation effect, and phase separation occurs during the pre-aging treatment: β M →β+β', β' appears as fine dispersed particles, becoming the crystallization core of the subsequent aging α phase; then the first stage aging treatment is carried out, at this time β' decomposes to form α+β phase, and then after a longer second stage aging treatment, a secondary α phase is formed in the β phase matrix, and fine dispersed α phase is precipitated, which improves the strength and hardness of RT1400 titanium alloy.

[0008] The above-mentioned multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy is characterized in that the cooling method of the solid solution treatment in step 1 is water cooling.

[0009] The above-mentioned multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy is characterized in that the cooling method of the pre-aging treatment in step 2 is air cooling.

[0010] The above-mentioned multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy is characterized in that the cooling method of the first-stage aging treatment in step three is air cooling.

[0011] The above-mentioned multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy is characterized in that the cooling method of the second-stage aging treatment in step three is air cooling.

[0012] The cooling methods after each level of treatment in the present invention are conventional methods, which are convenient for large-scale industrial production and reduce costs.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The present invention reduces the lamellar thickness of the β-phase transformation structure by performing a solution treatment above the β-phase transformation temperature of the RT1400 titanium alloy, combines a pre-aging treatment to provide a crystallization core for the subsequent aging α-phase, and then performs a multi-stage aging treatment to precipitate fine dispersed α-phase in the β-phase matrix, thereby improving the strength and hardness of the RT1400 titanium alloy.

[0014] 2. The present invention adopts multi-stage heat treatment, which not only improves the hardness of the RT1400 titanium alloy, but also performs overall modification on the deformed material. Through the multi-stage heat treatment process, the material itself undergoes plastic deformation due to the volume shrinkage effect, forming dislocation strengthening and precipitation strengthening, while refining the precipitated primary phase and secondary phase, thereby maintaining the plasticity of the RT1400 titanium alloy to a certain extent.

[0015] 3. The present invention can not only reduce the thermal stress generated during the heat treatment process by controlling the heat treatment process parameters, but also effectively improve the uniformity and stability of the RT1400 titanium alloy structure. In terms of microstructure, it can refine the grain size and hinder dislocation movement. In terms of macroscopic mechanical properties, it can effectively improve the hardness of the material and maintain the strength-plasticity matching of the RT1400 titanium alloy.

[0016] 4. The multi-stage heat treatment of the present invention can improve the hardness of the titanium alloy while maintaining a certain degree of strength and plasticity, so that the hardness value of the RT1400 titanium alloy reaches 50HRC, the strength can reach more than 1300MPa, and the elongation reaches more than 3%.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a process diagram for the multi-stage heat treatment of RT1400 titanium alloy of the present invention.

[0019] Figure 2 This is a low-magnification microstructure image of the RT1400 titanium alloy after multi-stage heat treatment in Example 1 of the present invention.

[0020] Figure 3 This is a high-magnification microstructure image of the RT1400 titanium alloy after multi-stage heat treatment in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] Example 1 like Figure 1 As shown, this embodiment includes the following steps: Step 1, solution treatment: performing solution treatment on the RT1400 titanium alloy; the solution treatment temperature is 880° C., the solution treatment time is 20 min, and the cooling method is water cooling; Step 2, pre-aging treatment: pre-aging treatment is performed on the RT1400 titanium alloy after the solution treatment in step 1; the pre-aging treatment temperature is 380° C., the pre-aging treatment time is 300 min, and the cooling method is air cooling; Step 3, multi-stage aging treatment: the RT1400 titanium alloy after pre-aging treatment in step 2 is subjected to first-stage aging treatment and second-stage aging treatment in sequence; the first-stage aging treatment temperature is 430°C, the first-stage aging treatment time is 300min, and the cooling method is air cooling; the second-stage aging treatment temperature is 460°C, the second-stage aging treatment time is 1440min, and the cooling method is air cooling.

[0022] Figure 2 and Figure 3 They are low-magnification and high-magnification microstructure images of the RT1400 titanium alloy after multi-stage heat treatment in this embodiment. Figure 2 and Figure 3 It can be seen that the RT1400 titanium alloy after multi-stage heat treatment has fine grains and the secondary α phase is evenly distributed.

[0023] Example 2 like Figure 1 As shown, this embodiment includes the following steps: Step 1, solution treatment: performing solution treatment on the RT1400 titanium alloy; the solution treatment temperature is 870° C., the solution treatment time is 25 min, and the cooling method is water cooling; Step 2, pre-aging treatment: pre-aging treatment is performed on the RT1400 titanium alloy after the solution treatment in step 1; the pre-aging treatment temperature is 360° C., the pre-aging treatment time is 280 min, and the cooling method is air cooling; Step 3, multi-stage aging treatment: the RT1400 titanium alloy after pre-aging treatment in step 2 is subjected to first-stage aging treatment and second-stage aging treatment in sequence; the first-stage aging treatment temperature is 410°C, the first-stage aging treatment time is 280min, and the cooling method is air cooling; the second-stage aging treatment temperature is 440°C, the second-stage aging treatment time is 1420min, and the cooling method is air cooling.

[0024] Example 3 like Figure 1 As shown, this embodiment includes the following steps: Step 1, solution treatment: performing solution treatment on the RT1400 titanium alloy; the solution treatment temperature is 890° C., the solution treatment time is 15 min, and the cooling method is water cooling; Step 2, pre-aging treatment: pre-aging treatment is performed on the RT1400 titanium alloy after the solution treatment in step 1; the pre-aging treatment temperature is 400° C., the pre-aging treatment time is 320 min, and the cooling method is air cooling; Step 3, multi-stage aging treatment: the RT1400 titanium alloy after pre-aging treatment in step 2 is subjected to first-stage aging treatment and second-stage aging treatment in sequence; the first-stage aging treatment temperature is 440°C, the first-stage aging treatment time is 320min, and the cooling method is air cooling; the second-stage aging treatment temperature is 480°C, the second-stage aging treatment time is 1460min, and the cooling method is air cooling.

[0025] Example 4 like Figure 1 As shown, this embodiment includes the following steps: Step 1, solution treatment: performing solution treatment on the RT1400 titanium alloy; the solution treatment temperature is 885°C, the solution treatment time is 20 minutes, and the cooling method is water cooling; Step 2, pre-aging treatment: pre-aging treatment is performed on the RT1400 titanium alloy after the solution treatment in step 1; the pre-aging treatment temperature is 370° C., the pre-aging treatment time is 310 min, and the cooling method is air cooling; Step 3, multi-stage aging treatment: the RT1400 titanium alloy after pre-aging treatment in step 2 is subjected to first-stage aging treatment and second-stage aging treatment in sequence; the first-stage aging treatment temperature is 425°C, the first-stage aging treatment time is 310min, and the cooling method is air cooling; the second-stage aging treatment temperature is 455°C, the second-stage aging treatment time is 1430min, and the cooling method is air cooling.

[0026] The mechanical properties and hardness of the RT1400 titanium alloy before and after the multi-stage heat treatment in Examples 1 to 4 of the present invention are compared, as shown in Table 1 below.

[0027]

[0028] It can be seen from Table 1 that compared with the RT1400 titanium alloy before treatment, the strength of the RT1400 titanium alloy after multi-stage heat treatment in Examples 1 to 4 of the present invention decreases less, the elongation decreases more, but the hardness value is significantly improved, and it is shown that the present invention effectively improves the hardness value of the RT1400 titanium alloy by performing multi-stage heat treatment on the RT1400 titanium alloy, and maintains the mechanical stability of the RT1400 titanium alloy to a certain extent.

[0029] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy, characterized in that: The method comprises the following steps: Step 1, solution treatment: performing solution treatment on the RT1400 titanium alloy; the solution treatment temperature is 870°C to 890°C, and the solution treatment time is 15min to 25min; Step 2, pre-aging treatment: pre-aging treatment is performed on the RT1400 titanium alloy after the solution treatment in step 1; the pre-aging treatment temperature is 360° C. to 400° C., and the pre-aging treatment time is 280 min to 320 min; Step 3, multi-stage aging treatment: the RT1400 titanium alloy after pre-aging treatment in step 2 is subjected to first-stage aging treatment and second-stage aging treatment in sequence; the first-stage aging treatment temperature is 410°C~440°C, and the first-stage aging treatment time is 280min~320min; the second-stage aging treatment temperature is 440°C~480°C, and the second-stage aging treatment time is 1420min~1460min.

2. A multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy according to claim 1, characterized in that: The cooling method of the solution treatment in step 1 is water cooling.

3. A multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy according to claim 1, characterized in that: The cooling method of the pre-aging treatment in step 2 is air cooling.

4. A multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy according to claim 1, characterized in that: The cooling method of the first-stage aging treatment in step three is air cooling.

5. A multi-stage heat treatment method for improving the hardness of RT1400 titanium alloy according to claim 1, characterized in that: The cooling method of the second-stage aging treatment in step three is air cooling.

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