Novel titanium alloy material based on double-laser fusion forging and preparation method of novel titanium alloy material

Abstract

The invention belongs to the technical field of laser welding, and particularly relates to a novel titanium alloy material based on double-laser fusion forging and a preparation method of the novel titanium alloy material. Novel titanium alloy powder based on double-laser melt forging is prepared from, by mass, 0.03%-0.09% of C, 5%-8% of Al, 2%-5% of V, 0.2%-0.5% of Zr, 0.2%-0.3% of Nb, 0.1%-0.5% of Fe, 0.01%-0.05% of N, 0.02%-0.05% of Ce and the balance Ti. According to the method, precise time sequence matching of main laser cladding and auxiliary laser dynamic forging is combined with alloy powder, so that cladding-grain refinement-stress reconstruction cooperative regulation and control are achieved, a superfine double-state structure is obtained in a repairing area, in-situ repairing of a TC4-DT material structural part at the position of the R area of the aircraft frame beam is achieved, and the in-situ repairing effect of the TC4-DT material structural part at the position of the R area of the aircraft frame beam is achieved. According to the repaired performance index, the original position of the component is repaired through the double-laser melting forging technology under the condition that a traditional high-temperature furnace heat treatment technology is not needed, so that the beta area achieves the metallographic structure performance the same as that obtained after traditional high-temperature furnace heat treatment, and particularly the damage tolerance is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser welding, and particularly relates to a new type of titanium alloy material based on double laser forging and a preparation method thereof. Background Art

[0002] During the manufacturing and maintenance of aircraft, the integrity of aircraft frame beam structural components is of crucial importance. Under the action of random loads and during long-term service, the accumulation of material damage will lead to a decrease in structural strength and ultimately result in structural failure. Fatigue failure is one of the main forms of aircraft structural failure, and if it occurs during use, it will cause catastrophic consequences. In known fatigue tests, cracks have been exposed at multiple fatigue-weak parts in the R area of the frame beam ribs. The R area of the aircraft frame beam (i.e., the transition area where the frame beam is connected to the skin) is a key part of the aircraft structure and bears complex stress loads; the R area is a stress concentration area, and the weight and size of the main load-bearing frame beam components on the aircraft are generally large and cannot be easily moved. When cracks occur, these parts cannot be disassembled, replaced, or repaired, and must be repaired in place.

[0003] According to the existing domestic technical conditions, the in-situ repair of aircraft frame beams mainly uses the argon arc welding process; when cracks occur, if the cracks are large, the fractured part is cut off, a welding repair block is processed, and the vacancy is filled by welding to perform in-situ repair; if the cracks are small, the repair is directly carried out using the repair welding process. However, in either case, due to the large heat input of argon arc welding, it is easy to cause deformation of typical thin structural components such as aircraft frame beams during in-situ repair, affecting their use accuracy. In the traditional argon arc welding process, due to the large heat input, there are still limitations. Mainly, TC4 has high thermal sensitivity and is prone to generating coarse grains at high temperatures, resulting in a decrease in the mechanical properties of the repair area; moreover, TC4 is prone to generating residual stress during argon arc welding, affecting the fatigue performance of the repair area.

[0004] Since the current aircraft frame beams use TC4-DT titanium alloy material, which is a new type of titanium alloy material with a high heat damage tolerance achieved through heat treatment. The high heat damage tolerance can not only extend the structural life but also ensure safety redundancy. If the heat damage tolerance in the R area is insufficient, cracks may penetrate the skin within the design life, leading to catastrophic accidents. Moreover, the high heat damage tolerance allows for a longer inspection interval (such as extending from 1000 flight hours to 2000 hours), reducing the time for out-of-service maintenance. For the TC4-DT new type of titanium alloy material with a high heat damage tolerance achieved through heat treatment, although argon arc welding can ensure that the material composition of the repaired part is TC4-DT, it cannot reach the performance indicators that the material should have, and the repaired structural components have deficiencies in key performance such as damage tolerance. In addition, the current laser cladding method with a small heat input also has limitations because it cannot provide subsequent heat treatment means and is also difficult to meet the repair requirements of TC4-DT materials and cannot effectively repair the damaged parts.

[0005] Therefore, there is an urgent need for a new alloy material and process method to solve the in-situ repair problem of the TC4-DT material structure at the R area of the aircraft frame beam, improve the performance indicators after repair, and ensure the flight safety of the aircraft. Summary of the Invention

[0006] In view of the above technical problems, the present invention proposes a new titanium alloy material based on dual-laser melt forging and its preparation method. Through the precise timing matching of main laser cladding and auxiliary laser dynamic forging combined with alloy powder, the present invention realizes the synergistic regulation of "cladding - grain refinement - stress reconstruction", enables the repair area to obtain an ultrafine bimodal structure, realizes the in-situ repair of the TC4-DT material structure at the R area of the aircraft frame beam, and enables the performance indicators after repair to reach the same metallographic structure performance as that after traditional high-temperature furnace heat treatment (solution + tempering) at the original position of the component through the dual-laser melt forging process without the need for traditional high-temperature furnace heat treatment process, especially significantly improving the damage tolerance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions.

[0008] A new titanium alloy powder based on dual-laser melt forging, comprising the following components in mass percentage: 0.03%-0.09% C, 5%-8% Al, 2%-5% V, 0.2%-0.5% Zr, 0.2%-0.3% Nb, 0.1%-0.5% Fe, 0.01%-0.05% N, 0.02-0.05% Ce, and the balance is Ti.

[0009] A preparation method of a new titanium alloy material based on dual-laser melt forging, comprising the following steps: Step 1, cleaning the damaged area of the TC4-DT material structure at the R area of the base material aircraft frame beam; Step 2, performing a dual-laser melt forging timing coupling process on the cleaned base material: using the above alloy powder to start a pre-set continuous laser on the base material in Step 1 for cladding to form a relatively uniform molten pool prototype, starting a post-set pulsed laser, and controlling the interval time between the two lasers to be 1-6 ms, and obtaining a new titanium alloy material based on dual-laser melt forging after in-situ repair of the base material.

[0010] Further, in Step 1, the cleaning treatment is to remove impurities such as oil stains and oxide layers on the surface.

[0011] Furthermore, a pre - placed continuous laser with a power set at 1300 - 1500 W, a scanning speed of 10 - 30 mm / s, and a spot diameter of 2 - 3 mm; a post - placed pulsed laser with a pulse frequency of 10–50 kHz, a pulse width of 10 - 40 ns, and a spot size of φ 0.4 - 2 mm (focused spot); the two lasers are rigidly synchronized for cladding to ensure that the molten pool formed by the first laser is at an appropriate temperature and state for the second laser to perform effective hot forging.

[0012] Furthermore, during the double - laser hot - forging process in step 2, the temperature, shape, and size of the molten pool are monitored in real - time, and the laser power and scanning speed are adjusted through a feedback control system to ensure the stability and consistency of the hot - forging process.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0014] 1. The present invention uses two lasers, which act on the damaged area of the R - region of the aircraft frame beam in a specific time sequence. The first high - energy - density continuous laser first rapidly pre - heats and preliminarily clads the damaged area. With a lower energy density and a faster scanning speed, the TC4 - DT filling material is preliminarily fused with the base material to form a relatively uniform molten - pool prototype, laying a foundation for the subsequent hot - forging process. Immediately afterwards, within the process window period when the clad material is not solidified and is still in a molten state, the second high - energy - density pulsed laser performs a secondary scan on the molten pool. At this time, the laser energy not only further melts the molten pool but also applies sufficient pressure to the molten pool, simulating the forging process, promoting the material flow and densification inside the molten pool. Through post - placed forging, dislocation multiplication and dynamic recrystallization occur, and the residual stress changes from tensile stress to compressive stress, realizing the reconstruction of tissue stress. The tissue grains are refined, and a fine equiaxed crystal structure is formed by triggering the continuous dynamic recrystallization mechanism, forcing the cracks that may initiate and expand to frequently turn at the grain boundaries, consuming more energy to inhibit crack expansion. Moreover, a compressive stress layer is formed on the surface layer through post - placed pulsed - laser forging, delaying crack initiation.

[0015] 2. The present invention has developed a TC4 - DT titanium - alloy filling alloy powder suitable for the double - laser hot - forging process. A small amount of trace elements, such as niobium (Nb) and zirconium (Zr), are added to the composition of the powder. Niobium can effectively improve the strength and high - temperature stability of the titanium alloy, while zirconium helps to improve the toughness and processing performance of the material, especially the Nb - Zr synergistic mechanism: (1) β - phase synergistic stabilization: The Nb - Zr composite solid solution reduces the free energy of the β - phase. Even under rapid laser cooling (>10 3It still retains 30%-40% of the metastable β phase at 1000 K / s; (2) Nano-precipitation synergistic regulation: During the hot forging stage, Nb segregates at the β-phase grain boundaries, and Zr enriches at the α / β interfaces, jointly inducing coherent nano-precipitation phases (Nb3Ti + ZrTi3), strengthening the interfaces and hindering crack propagation; (3) Oxygen trap effect: The Nb-Zr-O complex preferentially captures free oxygen, avoids oxygen-induced embrittlement, and enhances the high-temperature oxidation resistance of the repaired area (no significant oxidation weight gain below 800 °C); By precisely controlling the contents of these trace elements, the filler material can better fuse with the base material during the double-laser hot forging process and improve the performance of the overall structure after repair.

[0016] 3. Improvement of damage tolerance: Through the time-sequence coupling process of double-laser hot forging, the thermal damage tolerance of the repaired new titanium alloy material is increased by 30%-50% compared with the traditional GTAW repair method, and it can more effectively resist the initiation and propagation of cracks, greatly improving the safety and reliability of aircraft frame beam structural components.

[0017] 4. Stress reconstruction and grain size improvement: The forging effect during the double-laser hot forging process makes the stress distribution in the repaired part more uniform, and the stress state changes from surface tensile stress to surface compressive stress state. At the same time, the grains are refined, and the grain size is reduced by 2-3 grades compared with the traditional repair method. The fine equiaxed grain boundaries consume a large amount of energy for crack initiation, effectively delaying the initiation and propagation of cracks while increasing the material strength, and greatly improving the comprehensive mechanical properties of the material.

[0018] 5. In-situ repair advantages: This process can directly repair in-situ on the aircraft frame beam without disassembling large structural components, greatly shortening the maintenance cycle and reducing the maintenance cost. Moreover, the thermal impact on the surrounding base material during the repair process is small, avoiding the degradation of the base material performance caused by excessive heating. In particular, it opens up a new path for the engineering application of high-end titanium alloys. Specific implementation manners

[0019] The technical solutions in the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] A new type of titanium alloy powder based on double-laser hot forging includes the following components in mass percentages: 0.03%-0.09% C, 5%-8% Al, 2%-5% V, 0.2%-0.5% Zr, 0.2%-0.3% Nb, 0.1%-0.5% Fe, 0.01%-0.05% N, 0.02-0.05% Ce, and the balance is Ti.

[0021] A preparation method of a new type of titanium alloy material based on double laser melting forging, comprising the following steps: Step 1, cleaning the damaged area of the TC4-DT material structure in the R area of the base material aircraft frame beam; Step 2, performing a double laser melting forging timing coupling process on the cleaned base material: using the above alloy powder to start a pre-set continuous laser for cladding on the base material in Step 1 to form a relatively uniform molten pool prototype, then starting the post-set pulsed laser, controlling the interval time between the two lasers to be 1-6 ms, and obtaining a new type of titanium alloy material based on double laser melting forging after in-situ repair of the base material.

[0022] Further, in Step 1, the cleaning process is to remove impurities such as oil stains and oxide layers on the surface.

[0023] Further, for the pre-set continuous laser, the power is set to 1300-1500 W, the scanning speed is 10-30 mm / s, and the spot diameter is 2-3 mm; for the post-set pulsed laser, the pulse frequency is 10–50 kHz, the pulse width is 10-40 ns, and the spot size is φ 0.4-2 mm (focused spot); the two lasers are rigidly synchronously clad to ensure that the molten pool formed by the first laser is at an appropriate temperature and state for the second laser to perform effective melting forging.

[0024] Further, during the double laser melting forging process in Step 2, the temperature, shape and size of the molten pool are monitored in real time, and the laser power and scanning speed are adjusted through a feedback control system to ensure the stability and consistency of the melting forging process.

[0025] Example 1

[0026] A new type of titanium alloy powder based on double laser melting forging, comprising the following components in mass percentage: 0.03% C, 5% Al, 2% V, 0.2% Zr, 0.3% Nb, 0.2% Fe, 0.03% N, 0.02 Ce, and the balance is Ti.

[0027] A preparation method of a new type of titanium alloy material based on double laser melting forging, specifically the following steps: 1. Preparation work: Select an aircraft with damage in the frame beam R area, and the damaged material is TC4-DT titanium alloy; use professional detection equipment to determine the scope and depth of the damaged area; prepare a double laser melting forging equipment that meets the requirements of the invention, and load the above-developed new type of titanium alloy material into the powder feeding device; conduct a comprehensive inspection and debugging of the optical path, control system, powder feeding system, etc. of the equipment to ensure the normal operation of the equipment.

[0028] 2. Cleaning treatment of the damaged area: Adopt a method combining chemical cleaning and mechanical grinding to thoroughly clean the surface impurities of the damaged part in the R area of the aircraft frame beam until the metal luster is exposed; use a high-precision measuring instrument to measure the size of the damaged area after cleaning to provide accurate data for subsequent laser scanning path planning.

[0029] 3. Dual-laser melting and forging repair: According to the shape and size of the damaged area, use automated programming software to generate the scanning paths of the dual lasers, start the dual-laser melting and forging equipment, and perform repair operations according to the set process parameters. The front continuous laser has a power setting of 1300W, a scanning speed of 15mm / s, and a spot diameter of 2mm; the rear pulsed laser has a pulse frequency of 10kHz, a pulse width of 20ns, a spot size of φ2mm (focused spot), and the interval time between the two laser beams is controlled at 2ms for rigid synchronous cladding; during the melting and forging process, use an infrared thermometer to monitor the temperature of the molten pool in real time to ensure that the temperature is stable within a suitable range; if the temperature fluctuates, the automatic feedback control system will adjust the laser power in a timely manner.

[0030] Performance detection: Conduct a comprehensive performance detection on the repaired R area of the aircraft frame beam. Use fracture toughness testing equipment to evaluate the damage tolerance performance. Test results: Conduct fracture toughness tests on the forging area, and the KIC value reaches 85MPa・m¹ / ²; conduct fracture toughness tests on the transition area, and the KIC value reaches 72.5MPa・m¹ / ²; conduct fracture toughness tests on the HAZ area, and the KIC value reaches 60.5MPa・m¹ / ²; conduct fracture toughness tests on the substrate area, and the KIC value reaches 52MPa・m¹ / ², enabling the design of a fracture toughness gradient. And use X-ray diffraction residual stress testing: The residual compressive stress is 300MPa on the surface layer and gradually transitions to a tensile stress of 100MPa in the substrate, and the stress relaxation rate is 11%. A reasonable stress gradient is constructed inside the material. The detection results show that the performance indicators of the repaired TC4-DT material all reach or exceed the level of the original base material, and the damage tolerance is significantly improved compared with traditional argon arc welding repair, proving the effectiveness of the process method of the present invention.

[0031] Example 2

[0032] A new type of titanium alloy powder based on dual-laser melting and forging, including the following components by mass percentage: 0.07%C, 6%Al, 4.5%V, 0.4%Zr, 0.2%Nb, 0.1% Fe, 0.02% N, 0.02Ce, and the balance is Ti.

[0033] A preparation method of a new type of titanium alloy material based on dual-laser melting and forging is as follows: 1. Preparation: Select an aircraft with damage in the frame beam R area, and the damaged material is TC4-DT titanium alloy; use professional detection equipment to determine the scope and depth of the damaged area; prepare a dual-laser forging equipment that meets the requirements of the invention, and load the above-developed new titanium alloy material into the powder feeding device; conduct a comprehensive inspection and debugging of the optical path, control system, powder feeding system, etc. of the equipment to ensure the normal operation of the equipment.

[0034] 2. Cleaning of the damaged area: Adopt a method combining chemical cleaning and mechanical grinding to thoroughly clean the surface impurities of the damaged part in the frame beam R area of the aircraft until the metal luster is exposed; use a high-precision measuring instrument to measure the size of the damaged area after cleaning to provide accurate data for the subsequent laser scanning path planning.

[0035] 3. Dual-laser forging repair: According to the shape and size of the damaged area, use automated programming software to generate the scanning path of the dual-laser, start the dual-laser forging equipment, and perform repair operations according to the set process parameters. The front continuous laser has a power setting of 1380W, a scanning speed of 16mm / s, and a spot diameter of 2.4mm; the rear pulsed laser has a pulse frequency of 20kHz, a pulse width of 20ns, a spot size of φ2mm (focused spot), and the interval time between the two laser beams is controlled at 1.5ms for rigid synchronous cladding; during the forging process, use an infrared thermometer to monitor the temperature of the molten pool in real time to ensure that the temperature is stable within a suitable range; if the temperature fluctuates, the automatic feedback control system will adjust the laser power in a timely manner.

[0036] Performance detection: Conduct a comprehensive performance detection on the repaired frame beam R area of the aircraft, and use a fracture toughness test equipment to evaluate the damage tolerance performance. Test results: Conduct a fracture toughness test on the forging area, and the KIC value reaches 88MPa・m¹ / ²; conduct a fracture toughness test on the transition area, and the KIC value reaches 75MPa・m¹ / ²; conduct a fracture toughness test on the HAZ area, and the KIC value reaches 65MPa・m¹ / ²; conduct a fracture toughness test on the substrate area, and the KIC value reaches 52MPa・m¹ / ², which can achieve the design of fracture toughness gradient; and use X-ray diffraction residual stress test: The residual compressive stress is 320MPa on the surface layer, gradually transitioning to a tensile stress of 95MPa towards the substrate, and the stress relaxation rate is 11%. A reasonable stress gradient is built inside the material. The detection results show that the performance indicators of the repaired TC4-DT material all reach or exceed the level of the original base material, and the damage tolerance is significantly improved compared with the traditional argon arc welding repair, which proves the effectiveness of the process method of the present invention.

[0037] Comparative example 1.

[0038] A preparation method of a conventional titanium alloy material based on double laser forging, the equipment, substrate and process steps of which are exactly the same as those in Example 1, but the key elements Zr and Nb are removed from the alloy powder, and the specific components are as follows: 0.03% C, 5% Al, 2% V, 0.2% Fe, 0.03% N, 0.02% Ce, and the balance is Ti (Comparative Example 1: containing 0.2% Zr, 0.3% Nb).

[0039] The preparation method, steps 1-3 are exactly the same as those in Example 1, including: Damage area detection and cleaning (chemical cleaning + mechanical grinding); double laser parameter setting (front continuous laser 1300W, rear pulse laser 10kHz / 20ns, interval time 2ms, synchronous cladding); real-time molten pool temperature monitoring and feedback regulation.

[0040] Performance detection: Comprehensive performance detection is carried out on the repaired R area of the aircraft frame beam. The damage tolerance performance is evaluated by using fracture toughness testing equipment. The test results: The fracture toughness of the forging area is tested, and the KIC value reaches 62 MPa・m¹ / ². The fracture toughness of the transition area is tested, and the KIC value reaches 48 MPa・m¹ / ². The fracture toughness of the HAZ area is tested, and the KIC value reaches 40 MPa・m¹ / ². The fracture toughness of the substrate area is tested, and the KIC value reaches 35 MPa・m¹ / ². A fracture toughness gradient design can be achieved; and X-ray diffraction residual stress testing is used: The residual compressive stress is 120 MPa on the surface layer and gradually transitions to a tensile stress of 180 MPa in the substrate, and the stress relaxation rate is 28%.

[0041] Failure mechanism analysis: (1) Lack of Zr / Nb synergistic effect: Zr: Forms stable ZrO2 by adsorbing oxygen, reducing the oxygen content in the molten pool (measured 0.015% → 0.08%), and avoiding the formation of α2 brittle phase; Nb: Dissolves in β-Ti to inhibit the precipitation of ω phase and improve the thermal stability of β phase (the proportion of ω phase in Comparative Example 2 > 15%).

[0042] (2) Grain boundary weakening: When Zr / Nb is not added, the β grains grow abnormally (the Hall-Petch effect fails), and the coarsening of the α phase at the grain boundary leads to brittle fracture.

Claims

1. A new type of titanium alloy powder based on double laser melting forging, characterized in that, It includes the following components by mass percentage: 0.03% - 0.09% C, 5% - 8% Al, 2% - 5% V, 0.2% - 0.5% Zr, 0.2% - 0.3% Nb, 0.1% - 0.5% Fe, 0.01% - 0.05% N, 0.02 - 0.05% Ce, and the balance is Ti.

2. A preparation method of a new type of titanium alloy material based on double laser forging, characterized in that, It includes the following steps: Step 1: Clean the damaged area of the TC4-DT material structure in the R area of the base material aircraft frame beam. Step 2: Perform a double-laser forge timing coupling process on the cleaned base material: Use the above alloy powder to start a pre - continuous laser for cladding on the base material in Step 1 to form a relatively uniform molten pool prototype, then start the post - pulse laser, and control the interval time between the two lasers at 1 - 6 ms. After in - situ repair of the base material, a new titanium alloy material based on double - laser forging is obtained.

3. The novel titanium alloy powder based on double laser forging according to claim 1, wherein In Step 1, the cleaning treatment is to remove impurities such as oil stains and oxide layers on the surface.

4. The novel titanium alloy powder based on dual laser forging according to claim 1, wherein The pre - continuous laser has a power setting of 1300 - 1500 W, a scanning speed of 10 - 30 mm / s, and a spot diameter of 2 - 3 mm; the post - pulse laser has a pulse frequency of 10 - 50 kHz, a pulse width of 10 - 40 ns, and a spot size of φ 0.4 - 2 mm; the two lasers are rigidly synchronously clad.

5. The novel titanium alloy powder based on double laser forging according to claim 1, characterized in that During the double - laser forging process in Step 2, the temperature, shape, and size of the molten pool are monitored in real time.