A heat treatment method to improve the plasticity of Ti-5321 titanium alloy formed by laser cladding

Abstract

The present invention discloses a heat treatment method for improving the plasticity of laser-clad Ti-5321 titanium alloy. The laser-clad Ti-5321 titanium alloy is subjected to a multi-stage heat treatment to transform the coarse α-lamellae in the original structure into rod-shaped α-lamellae and ultrafine α-lamellae, so that the strength of the laser-clad Ti-5321 titanium alloy remains unchanged while the plasticity is improved. The present invention adopts a multi-stage heat treatment to regulate the original structure of the laser-clad titanium alloy by improving the size and morphology of the α-phase, effectively regulating the size, content and tissue type of the α-phase, so that the strength of the laser-clad Ti-5321 titanium alloy remains unchanged while the plasticity is improved, achieving a better strength-plasticity matching relationship, meeting the requirements of aerospace for high-strength and plastic titanium alloy materials, and the process flow is simple, easy to implement and operate, suitable for industrial production, and has good production and application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of metal heat treatment, and in particular relates to a heat treatment method for improving the plasticity of Ti-5321 titanium alloy formed by laser cladding. Background Art

[0002] Laser cladding is a near-net-shape additive manufacturing technology that combines surface enhancement and rapid prototyping techniques. It boasts advantages such as a wide range of process materials, high-complexity parts, optimized structures, fast build speeds, and a high cost-performance ratio. It is widely used in aerospace, military equipment, and marine vessels. Compared to traditional forming techniques such as casting, forging, and welding, it offers significant advantages in forming and repairing complex parts and has a wide range of applications.

[0003] The high-strength and toughness Ti-5321 (Ti-5Al-3Mo-3V-2Zr-2Cr-1Nb-1Fe) titanium alloy, designed and developed based on the high-strength Ti-1300 and TC21 alloys, combines high strength with high ductility and toughness. Due to its high Al and V content, Ti-5321 offers a wide range of microstructure control options. During the layer-by-layer laser cladding deposition process, the rapid cooling and heating of the laser and the complex thermal cycling characteristics result in poor ductility in the original basketweave microstructure of the laser-clad Ti-5321 titanium alloy, with an elongation of only 6.0%, failing to meet the high-performance titanium alloy requirements of the aerospace industry. Specific multiple heat treatments applied to the laser-clad Ti-5321 titanium alloy effectively eliminate residual stresses, improve ductility without changing strength, and create a microstructure that better matches strength and ductility, meeting the aerospace requirements for high-strength and ductile titanium alloys. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned existing technologies and provide a heat treatment method for improving the plasticity of Ti-5321 titanium alloy formed by laser cladding. This method uses a multi-stage heat treatment to control the original microstructure of the laser-clad titanium alloy by improving the size and morphology of the α phase. The original coarse α lamellar layers are transformed into rod-shaped α and ultrafine α lamellar layers. The size, content, and microstructure of the α phase are effectively controlled, resulting in the laser-clad Ti-5321 titanium alloy with unchanged strength and improved plasticity, thus solving the problem of low plasticity of laser-clad Ti-5321 titanium alloy components.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a heat treatment method for improving the plasticity of laser cladding formed Ti-5321 titanium alloy, characterized in that the laser cladding formed Ti-5321 titanium alloy is subjected to multi-stage heat treatment to transform the coarse lamellar layer α in the original structure into rod-shaped α and ultrafine lamellar layer α, so that the strength of the laser cladding formed Ti-5321 titanium alloy remains unchanged while the plasticity is improved.

[0006] The above-mentioned heat treatment method for improving the plasticity of laser cladding formed Ti-5321 titanium alloy is characterized in that the multi-stage heat treatment comprises the following steps:

[0007] Step 1: Heat the laser cladding formed Ti-5321 titanium alloy to 530°C to 540°C and keep it at this temperature for 6h to 8h, and then air-cool it to room temperature;

[0008] Step 2: heating the laser cladding formed Ti-5321 titanium alloy after air cooling in step 1 to 800° C. to 810° C. and keeping the temperature for 1 h to 2 h, and then air cooling to room temperature;

[0009] Step 3: Heat the laser cladding formed Ti-5321 titanium alloy after air cooling in step 2 to 570° C. to 580° C. and keep it at this temperature for 6 h to 8 h, and then air cool it to room temperature.

[0010] The above-mentioned heat treatment method for improving the plasticity of laser cladding formed Ti-5321 titanium alloy is characterized in that the strength of the laser cladding formed Ti-5321 titanium alloy remains unchanged after the multi-stage heat treatment, and the elongation is increased to more than 8%.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] 1. The present invention adopts multi-stage heat treatment based on the microstructure characteristics of laser cladding-formed Ti-5321 titanium alloy. By improving the size and morphology of the α phase, the original microstructure of the laser cladding-formed titanium alloy is regulated, and the original coarse α layer is transformed into rod-shaped α and ultrafine α layer. The size, content and microstructure type of the α phase are effectively regulated, so that the strength of the laser cladding-formed Ti-5321 titanium alloy remains unchanged while the plasticity is improved, meeting the requirements of aerospace for high-strength and high-plasticity titanium alloy materials.

[0013] 2. The tensile strength of the laser cladding formed Ti-5321 titanium alloy after multi-stage heat treatment of the present invention is increased from a maximum of 1104 MPa to more than 1171 MPa. While maintaining the original strength or slightly exceeding the original strength, the elongation is greatly improved from a maximum of 6.0% to more than 8%.

[0014] 3. The laser cladding formed Ti-5321 titanium alloy after multi-stage heat treatment of the present invention has a better matching relationship between strength and plasticity, and the process flow is simple, easy to implement and operate, suitable for industrial production, and has good production application prospects.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a microstructure diagram of the Ti-5321 titanium alloy formed by laser cladding in Example 1 of the present invention.

[0017] Figure 2 This is a low-magnification microstructure diagram of the Ti-5321 titanium alloy formed by laser cladding and subjected to multi-stage heat treatment in Example 1 of the present invention.

[0018] Figure 3 This is a high-magnification microstructure diagram of the laser-clad Ti-5321 titanium alloy after multi-stage heat treatment in Example 1 of the present invention. DETAILED DESCRIPTION

[0019] Example 1

[0020] This embodiment includes the following steps:

[0021] Step 1: Place the laser cladding formed Ti-5321 titanium alloy with a coarse flake layer α into a box-type resistance furnace, heat it to 530° C. and keep it at this temperature for 6 hours, and then air-cool it to room temperature;

[0022] Step 2: Place the laser cladding Ti-5321 titanium alloy formed in step 1 after air cooling in a box-type resistance furnace, heat it to 800°C and keep it at this temperature for 1 hour, and then air cool it to room temperature;

[0023] Step 3: Place the laser cladding formed Ti-5321 titanium alloy after air cooling in step 2 into a box-type resistance furnace, heat it to 580° C. and keep it at this temperature for 6 hours, and then air cool it to room temperature.

[0024] Figure 1 The microstructure of the Ti-5321 titanium alloy formed by laser cladding in this embodiment is shown in FIG. Figure 1 It can be seen that the original structure of laser cladding Ti-5321 titanium alloy contains coarse lamellar layer α.

[0025] Figure 2 and Figure 3 They are low-magnification and high-magnification microstructures of the Ti-5321 titanium alloy formed by laser cladding and subjected to multi-stage heat treatment in this embodiment, respectively. Figures 2 and 3 It can be seen that the microstructure of Ti-5321 titanium alloy formed by laser cladding after multi-stage heat treatment contains rod-like α and ultrafine lamellar α.

[0026] According to tests, the strength of the Ti-5321 titanium alloy formed by laser cladding in this embodiment after multi-stage heat treatment is 1171 MPa, and the elongation is 8.5%.

[0027] Example 2

[0028] This embodiment includes the following steps:

[0029] Step 1: Place the laser cladding formed Ti-5321 titanium alloy with a coarse flake layer α into a box-type resistance furnace, heat it to 540° C. and keep it at this temperature for 6 hours, and then air-cool it to room temperature;

[0030] Step 2: Place the laser cladding Ti-5321 titanium alloy formed in step 1 after air cooling in a box-type resistance furnace, heat it to 810°C and keep it at this temperature for 1 hour, and then air cool it to room temperature;

[0031] Step 3: Place the laser cladding formed Ti-5321 titanium alloy after air cooling in step 2 into a box-type resistance furnace, heat it to 580° C. and keep it at this temperature for 6 hours, and then air cool it to room temperature.

[0032] After testing, the microstructure of the laser cladding Ti-5321 titanium alloy in this embodiment after multi-stage heat treatment contains rod-shaped α and ultrafine lamellar α. The strength of the laser cladding Ti-5321 titanium alloy after multi-stage heat treatment is 1149 MPa and the elongation is 8.3%.

[0033] Example 3

[0034] This embodiment includes the following steps:

[0035] Step 1: Place the laser cladding formed Ti-5321 titanium alloy with a coarse flake layer α into a box-type resistance furnace, heat it to 535° C. and keep it at this temperature for 7 hours, and then air-cool it to room temperature;

[0036] Step 2: Place the laser cladding Ti-5321 titanium alloy formed in step 1 after air cooling in a box-type resistance furnace, heat it to 810°C and keep it at this temperature for 2 hours, and then air cool it to room temperature;

[0037] Step 3: Place the laser cladding formed Ti-5321 titanium alloy after air cooling in step 2 into a box-type resistance furnace, heat it to 570° C. and keep it at this temperature for 7 hours, and then air cool it to room temperature.

[0038] After testing, the microstructure of the laser cladding Ti-5321 titanium alloy in this embodiment after multi-stage heat treatment contains rod-shaped α and ultrafine lamellar α. The strength of the laser cladding Ti-5321 titanium alloy after multi-stage heat treatment is 1165 MPa and the elongation is 8.4%.

[0039] Example 4

[0040] This embodiment includes the following steps:

[0041] Step 1: Place the laser cladding formed Ti-5321 titanium alloy with a coarse flake layer α into a box-type resistance furnace, heat it to 540° C. and keep it at this temperature for 8 hours, and then air-cool it to room temperature;

[0042] Step 2: Place the laser cladding Ti-5321 titanium alloy formed in step 1 after air cooling in a box-type resistance furnace, heat it to 810°C and keep it at this temperature for 2 hours, and then air cool it to room temperature;

[0043] Step 3: Place the laser cladding formed Ti-5321 titanium alloy after air cooling in step 2 into a box-type resistance furnace, heat it to 580° C. and keep it at this temperature for 8 hours, and then air cool it to room temperature.

[0044] After testing, the microstructure of the laser cladding Ti-5321 titanium alloy in this embodiment after multi-stage heat treatment contains rod-shaped α and ultrafine lamellar α. The strength of the laser cladding Ti-5321 titanium alloy after multi-stage heat treatment is 1141 MPa and the elongation is 8.1%.

[0045] It can be seen from Examples 1 to 4 that compared with the laser cladding-formed Ti-5321 titanium alloy (tensile strength of up to 1104 MPa, elongation of up to 6.0%) that has not undergone the multi-stage heat treatment of the present invention, the strength of the laser cladding-formed Ti-5321 titanium alloy after multi-stage heat treatment of the present invention remains unchanged and the plasticity is improved. This is because the size and aspect ratio of the larger lamellar layers α in the laser cladding-formed Ti-5321 titanium alloy remain basically unchanged after heat treatment, so that the strength of the structure after heat treatment remains unchanged; while the content of large-sized lamellar layers α is reduced, and part of them is transformed into smaller ultrafine α. The ultrafine α and lamellar α are staggered to make the structure have better plasticity after heat treatment.

[0046] The above description 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 variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A heat treatment method for improving the plasticity of laser cladding formed Ti-5321 titanium alloy, characterized in that: A multi-stage heat treatment is performed on a laser cladding formed Ti-5321 titanium alloy to transform the coarse lamellar layer α in the original structure into rod-shaped α and ultrafine lamellar layer α, so that the strength of the laser cladding formed Ti-5321 titanium alloy remains unchanged while the plasticity is improved; the multi-stage heat treatment comprises the following steps: Step 1: Heat the laser cladding formed Ti-5321 titanium alloy to 530℃~540℃ and keep it at this temperature for 6h~8h, then air-cool it to room temperature; Step 2: heating the laser cladding formed Ti-5321 titanium alloy after air cooling in step 1 to 800°C~810°C and keeping the temperature for 1h~2h, and then air cooling to room temperature; Step 3: Heat the laser cladding formed Ti-5321 titanium alloy after air cooling in step 2 to 570° C.~580° C. and keep it at this temperature for 6 h~8 h, and then air cool it to room temperature.

2. A heat treatment method for improving the plasticity of laser cladding formed Ti-5321 titanium alloy according to claim 1, characterized in that: The strength of the laser cladding formed Ti-5321 titanium alloy after the multi-stage heat treatment remains unchanged, and the elongation is increased to more than 8%.

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