Gradient heat treatment method of Ti60-Ti2AlNb gradient titanium alloy

Abstract

The invention discloses a gradient heat treatment method of a Ti60-Ti2AlNb gradient titanium alloy, which comprises the following steps: determining laser heat treatment process parameters and a scanning strategy according to heat treatment requirements of a Ti60 alloy area, a Ti2AlNb alloy area and a transition area in the Ti60-Ti2AlNb gradient titanium alloy; in the protective atmosphere, gradient laser scanning is conducted on a corresponding area of the Ti60-Ti2AlNb gradient titanium alloy, a gradient temperature field is formed, and gradient heat treatment of the Ti60-Ti2AlNb gradient titanium alloy is achieved. And the Ti60-Ti2AlNb gradient titanium alloy subjected to gradient heat treatment is cooled and then subjected to aftertreatment, and the Ti60-Ti2AlNb gradient titanium alloy subjected to gradient heat treatment is obtained. The local temperature fields with different thermal cycle characteristics are applied by regulating and controlling laser scanning, and the structure and performance improvement effect which is more flexible and efficient compared with conventional heat treatment is achieved.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology for metallic materials, and relates to a gradient heat treatment method for Ti60-Ti2AlNb gradient titanium alloy. Background Technology

[0002] Gradient titanium alloys, by connecting two or more titanium alloys with their own performance characteristics through a specific compositional transition path, can meet the performance requirements of different parts of the same component, ensuring the full performance of integral bladed disk (IBD) components for aero-engines. For IBD components, the disk requires high high-temperature creep resistance and damage tolerance, and can be prepared using Ti60 alloy, which has good creep resistance and low density; the blade requires high yield strength and low crack propagation rate, and can be prepared using Ti2AlNb alloy, which has better fracture toughness and high-temperature performance. Therefore, by gradually transitioning between two titanium alloys through a specific compositional path, the integral forming of the disk and blades can be achieved while fully utilizing the characteristics and performance advantages of each alloy, meeting lightweight design principles, and improving the thrust-to-weight ratio of aero-engines.

[0003] The compositional and microstructural evolution of the transition zone in gradient materials is complex, and elemental miscibility can lead to the formation of harmful intermetallic phases. Therefore, optimizing the microstructure evolution and phase precipitation behavior of the transition zone in gradient alloys through appropriate heat treatment processes is essential for improving the overall mechanical properties of gradient components. However, different alloys have different optimal heat treatment regimes, and conventional heat treatment methods cannot simultaneously meet the customized requirements of gradient alloy heat treatment, hindering the practical application of gradient titanium alloys.

[0004] Chinese invention patent CN 111575470 B discloses a gradient heat treatment apparatus and method for rod-shaped materials. This invention includes upper and lower heating zones formed by heating elements controlled by independent power supplies. An annular radiation screen is placed between the heating zones to ensure heat transfer along the sample's axial direction, and a closed heat insulation plate prevents heat loss from the sample's ends, ensuring precise temperature control of the upper and lower heating zones, thereby achieving gradient heat treatment of the rod-shaped material. However, in this apparatus, the temperature field in the middle of the sample can only be formed through heat conduction, resulting in an approximately linear temperature distribution along the axial direction, which cannot achieve highly customized gradient heat treatment.

[0005] Chinese invention patent CN 112522494 B discloses a method for gradient heat treatment of rod-shaped materials with dual structures and dual properties. This method places one end of the rod with oriented columnar crystal structure inside a graphite heating body, and the other end with fine-grained structure on a water-cooled copper disk. A heat insulation device is installed in the transition zone between the fine-grained and columnar crystal structures to prevent radiative heating of the lower fine-grained structure by the graphite heating body. This method mainly controls the temperature of the hot zone of the sample through the graphite heating body and the temperature of the cold zone through the water-cooled copper disk. The temperature distribution between the hot and cold zones is still passively formed under heat transfer conditions, thus also suffering from insufficient freedom in temperature control.

[0006] Chinese patent application CN 118497647 A discloses a method for deforming gradient titanium alloys using gradient heat treatment. This method utilizes electromagnetic coil induction heating. By adjusting the moving speed of the gradient structure sample as it enters the heating coil and the induction heating power, different initial temperatures are obtained at different locations on the gradient titanium alloy. Combined with subsequent forging processes, this allows the gradient titanium alloy to undergo hot deformation within an optimal temperature range, thus optimizing its performance. However, this method relies heavily on the sample moving speed and induction heating power for temperature control in different regions, making precise control of the heating area difficult and resulting in low temperature control accuracy.

[0007] In summary, current methods for gradient heat treatment struggle to simultaneously achieve both free customization of the heating zone and precise control of the temperature field. Summary of the Invention

[0008] The purpose of this invention is to provide a gradient heat treatment method for Ti60-Ti2AlNb gradient titanium alloys, which solves the problem that existing technologies cannot simultaneously achieve free customization of the heating zone and precise control of the temperature field.

[0009] To achieve the above objectives, the present invention employs the following technical solution: A gradient heat treatment method for Ti60-Ti2AlNb gradient titanium alloy, comprising: Based on the heat treatment requirements of the Ti60 alloy region, Ti2AlNb alloy region and transition region in Ti60-Ti2AlNb gradient titanium alloy, the laser heat treatment process parameters and scanning strategy are determined. According to the determined laser heat treatment process parameters and scanning strategy, gradient laser scanning is performed on the corresponding regions of Ti60-Ti2AlNb gradient titanium alloy in a protective atmosphere to form a gradient temperature field and realize the gradient heat treatment of Ti60-Ti2AlNb gradient titanium alloy. After cooling, the Ti60-Ti2AlNb gradient titanium alloy after gradient heat treatment is subjected to post-treatment to obtain the Ti60-Ti2AlNb gradient titanium alloy after gradient heat treatment.

[0010] Furthermore, the Ti60-Ti2AlNb gradient titanium alloy is prepared by additive manufacturing of Ti60 alloy, transition zone and Ti2AlNb alloy, and the transition zone is formed by direct connection, linear transition or intermediate layer transition.

[0011] Furthermore, the laser heat treatment process parameters and scanning strategies are designed and optimized by finite element simulation of the dynamic evolution of the temperature field during laser scanning, so that the thermal history conditions provided by laser scanning are in line with the heat treatment requirements of the Ti60 alloy region, Ti2AlNb alloy region and transition region in Ti60-Ti2AlNb gradient titanium alloy.

[0012] Furthermore, when performing laser heat treatment on the Ti60 alloy region, a translational scanning mode is adopted, the scanning strategy is to scan along the short side in an S-shape, scan on one or both sides, repeat the scan once, the spot diameter is 4mm, the preheating temperature is 0~400℃, the laser power is 150~220W, the scanning speed is 8~10mm / s, and the scanning track spacing is 0.4~0.5mm.

[0013] Furthermore, when performing laser heat treatment on the transition zone, a translational scanning mode is adopted, with the scanning strategy being an S-shaped scan along the short side, single-sided or double-sided scanning, repeated scanning once, a spot diameter of 4 mm, a preheating temperature of 0~400℃, a laser power of 150~250W, a scanning speed of 5~10 mm / s, and a scanning track spacing of 0.3~0.5 mm.

[0014] Furthermore, when performing laser heat treatment on the Ti2AlNb alloy region, a translational scanning mode is adopted, the scanning strategy is to scan along the short side in an S-shape, scan on one or both sides, repeat the scan once, the spot diameter is 4 mm, the preheating temperature is 0~400℃, the laser power is 180~250W, the scanning speed is 5~10 mm / s, and the scanning track spacing is 0.25~0.5 mm.

[0015] Furthermore, the Ti60-Ti2AlNb gradient titanium alloy is pretreated before laser scanning. The pretreatment process includes: Use sandpaper to remove the oxide scale from the surface of the Ti60-Ti2AlNb gradient titanium alloy, and then use anhydrous ethanol to clean the surface of the Ti60-Ti2AlNb gradient titanium alloy.

[0016] Furthermore, the protective atmosphere is an argon atmosphere with a purity of 99.99%.

[0017] Further post-treatment includes annealing at a temperature of 600-800℃ for 4-6 hours.

[0018] Furthermore, before annealing, an anti-oxidation coating is applied to the surface of the Ti60-Ti2AlNb gradient titanium alloy. The anti-oxidation coating is MP90 anti-oxidation and decarburization coating.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a gradient heat treatment method for Ti60-Ti2AlNb gradient titanium alloys. By considering the heat treatment requirements of the Ti60 alloy region, Ti2AlNb alloy region, and transition region within the Ti60-Ti2AlNb gradient titanium alloy, and by designing and optimizing the laser scanning process parameters and scanning strategy through finite element simulation of the dynamic evolution of the temperature field during laser scanning, corresponding temperature field conditions can be formed for different parts of the Ti60-Ti2AlNb gradient titanium alloy parts. This allows for flexible control of the heating region of the gradient titanium alloy structure and precise regulation of the temperature field, achieving microstructure and property improvement approximately equivalent to conventional heat treatment. Then, in a protective atmosphere, gradient laser scanning is performed on the corresponding regions of the Ti60-Ti2AlNb gradient titanium alloy to form a specific gradient temperature field. The thermal cycling conditions formed by laser scanning can achieve high-frequency, multi-cycle heat treatment effects. This promotes the full precipitation of strengthening phases within the Ti60-Ti2AlNb gradient material under shorter high-temperature residence times, overcoming the problems of high thermal inertia, difficulty in achieving high-frequency and large-temperature-span thermal cycling, and low heat treatment efficiency associated with traditional heat treatment. After laser scanning, the Ti60-Ti2AlNb gradient titanium alloy is cooled and then post-treated to remove internal residual stress and stabilize the microstructure, ultimately obtaining a gradient heat-treated Ti60-Ti2AlNb gradient titanium alloy. This invention achieves gradient heat treatment of the gradient titanium alloy by flexibly controlling the temperature field applied by the laser to different regions. It overcomes the limitation of traditional heat treatment processes that rely on a single temperature field, leading to inconsistent performance of gradient parts. This invention enables customized heat treatment for different parts of the Ti60-Ti2AlNb gradient part, fully utilizing the performance potential of different alloys, resulting in different microstructures in different regions of the part, and improving the overall mechanical properties of the gradient titanium alloy structure.

[0020] Furthermore, by controlling process parameters such as laser power, scanning rate, and channel spacing in the scanned area, the heating area of ​​the gradient titanium alloy structure can be flexibly controlled, while achieving precise temperature field regulation. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This diagram illustrates a typical connection method for additive manufacturing gradient titanium alloys according to the present invention.

[0023] Figure 2 This is the phase diagram related to the Ti60 alloy of the present invention.

[0024] Figure 3 This is the phase diagram related to the Ti-Al alloy of the present invention.

[0025] Figure 4 This is the Ti-22Al-xNb phase diagram of the present invention.

[0026] Figure 5 This is a temperature field diagram formed under the simulated laser process parameters and scanning strategy of the present invention.

[0027] Figure 6 This is a schematic diagram of the sample specifications and scanning strategy of the present invention.

[0028] Figure 7 This is a comparison image of the microstructure before and after laser heat treatment in Example 1 of the present invention.

[0029] Figure 8 This is a graph showing the room temperature tensile properties of the samples before and after laser heat treatment in Example 1 of the present invention.

[0030] Figure 9 This is a graph showing the room temperature tensile properties of the samples before and after laser heat treatment in Example 2 of the present invention.

[0031] Figure 10 This is a graph showing the room temperature tensile properties of the samples before and after laser heat treatment in Example 3 of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0033] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0034] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0035] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0036] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings: In gradient titanium alloys, the heat treatment requirements differ across different regions. Ti60-Ti2AlNb gradient titanium alloys prepared by additive manufacturing typically exhibit microstructure inhomogeneity. For the transition region where the composition of the Ti60 alloy is close to that of Ti60, annealing is usually used to improve microstructure inhomogeneity and reduce the precipitation of α-lamellar silicides. For Ti2AlNb alloys and the transition region with compositions close to Ti2AlNb, the precipitated phases are mainly α, β / B2, α2, and O phases. β / B2 is the matrix phase, while the α2 phase has a close-packed hexagonal structure with fewer slip systems and is the main brittle and hard phase precipitated in this region. The O phase has an ordered orthogonal structure and exhibits better plasticity than the α2 phase, making it the main strengthening phase in this region. By optimizing the proportions of the α2 and O phases in the transition region, a microstructure of β / B2 phase + lath-like O phase + a small amount of fine needle-like α2 phase can be formed, improving the mechanical properties of the transition region. According to the Ti-22Al-xNb phase diagram, the precipitation temperature of the α2 phase is relatively high. Combined with the characteristics of additive manufacturing processes, the high-temperature α2 phase is easily retained to room temperature during rapid cooling, leading to insufficient precipitation of the strengthening O phase. Therefore, for Ti2AlNb and the transition region with compositions close to Ti2AlNb, high-temperature solution treatment is usually required to partially dissolve the α2 phase, followed by aging in the O phase region to ensure complete precipitation. In summary, traditional heat treatment methods struggle to balance the heat treatment requirements of Ti60-Ti2AlNb gradient titanium alloys, and prolonged high-temperature holding in traditional heat treatment furnaces leads to microstructure coarsening, which is detrimental to mechanical properties. This invention, however, by controlling process parameters such as laser power, scanning rate, and channel spacing in the scanned area, can flexibly control the heating region of the gradient titanium alloy structure and achieve precise temperature field regulation. Furthermore, by shortening the residence time in the high-temperature zone through laser scanning heat treatment, and providing high-frequency, multi-cycle thermal cycling conditions, it not only helps to obtain a high-performance microstructure, but also promotes the full precipitation of the O phase in the transition zone and Ti2AlNb region, thereby improving the overall mechanical properties of the gradient structure.

[0040] This invention provides a gradient heat treatment method for Ti60-Ti2AlNb gradient titanium alloys, specifically including the following steps: Step 1: Based on the heat treatment requirements of the Ti60 alloy region, Ti2AlNb alloy region, and transition region in the Ti60-Ti2AlNb gradient titanium alloy, determine reasonable laser heat treatment process parameters and scanning strategies.

[0041] The present invention applies to Ti60-Ti2AlNb gradient titanium alloys prepared by additive manufacturing methods, which, from one end to the other, include a Ti60 alloy region, a transition region, and a Ti2AlNb alloy region connected sequentially. The transition region of the Ti60-Ti2AlNb gradient titanium alloy is formed by direct connection, linear transition, or intermediate layer transition, such as... Figure 1 As shown. Accordingly, the transition region includes a connection region formed by directly connecting the Ti60 and Ti2AlNb alloys, a gradient composition region formed by linearly transitioning the Ti60 and Ti2AlNb alloys, and a composition region formed by transitioning the Ti60 and Ti2AlNb alloys through an intermediate layer.

[0042] In step 1, the heat treatment requirements for the Ti60 alloy region, the Ti2AlNb alloy region, and the transition region mainly lie in the Ti60 alloy phase diagram (e.g., ...). Figure 2 (as shown), Ti-Al phase diagram (as shown) Figure 3 (as shown) and Ti-Al-xNb phase diagram (as shown) Figure 4 Design the corresponding heat treatment regime (as shown).

[0043] Determining reasonable laser heat treatment process parameters and scanning strategies mainly involves adjusting relevant parameters and strategies to change the temperature field generated by the laser action, so that the thermal history conditions provided by laser scanning fit the heat treatment requirements of different regions of Ti60-Ti2AlNb gradient titanium alloy.

[0044] Preferably, the process parameters include spot diameter, laser power, laser scanning speed, laser scanning track spacing, and scanning strategy.

[0045] Preferably, the laser heat treatment process parameters and scanning strategy are designed and optimized by finite element simulation of the dynamic evolution of the temperature field during laser scanning.

[0046] Step 2: Place the Ti60-Ti2AlNb gradient titanium alloy inside the laser scanning chamber.

[0047] Step 2 includes a series of intermediate steps in placing the part in the laser scanning chamber, including: Ti60-Ti2AlNb gradient titanium alloy pretreatment, substrate placement, Ti60-Ti2AlNb gradient titanium alloy placement, laser scanning program setting, substrate preheating, and protective gas filling.

[0048] Preferably, during the pretreatment stage of the Ti60-Ti2AlNb gradient titanium alloy, sandpaper is used to remove the oxide scale on the surface of the parts, and then anhydrous ethanol is used to clean it to prevent the oxide scale from being too thick and affecting the laser absorption rate.

[0049] Preferably, the laser scanning program is first set up according to the position of the Ti60-Ti2AlNb gradient titanium alloy, establishing a coordinate axis, and then strictly following the determined laser process parameters and scanning strategy.

[0050] Preferably, the substrate preheating conditions are set strictly in accordance with the determined laser process parameters and scanning strategy.

[0051] Preferably, high-purity argon gas with a purity of 99.99% is continuously introduced as a protective gas until the oxygen content is below 1000ppm before operation begins.

[0052] Step 3: According to the determined laser heat treatment process parameters and scanning strategy, use laser scanning to form a specific gradient temperature field in the corresponding region of Ti60-Ti2AlNb gradient titanium alloy, thereby realizing the gradient heat treatment of Ti60-Ti2AlNb gradient titanium alloy.

[0053] In step 3, the gradient heat treatment of the Ti60-Ti2AlNb gradient titanium alloy is achieved by performing corresponding laser scanning heat treatment on different regions of the Ti60-Ti2AlNb gradient titanium alloy through the laser scanning program set in step 2.

[0054] Preferably, when performing laser scanning heat treatment on the Ti60 alloy region, a translational scanning mode is adopted, the scanning strategy is to scan along the short side in an S-shape, scan on one or both sides, repeat the scan once, the spot diameter is 4 mm, the substrate preheating temperature is 0~400℃, the laser power is 150~220W, the scanning speed is 8~10 mm / s, and the scanning track spacing is 0.4~0.5 mm.

[0055] Preferably, when performing laser scanning heat treatment in the intermediate transition zone, a translational scanning mode is adopted, the scanning strategy is to scan along the short side in an S-shape, scan on one or both sides, repeat the scan once, the spot diameter is 4 mm, the substrate preheating temperature is 0~400℃, the laser power is 150~250W, the scanning speed is 5~10 mm / s, and the scanning track spacing is 0.3~0.5 mm.

[0056] Preferably, when performing laser scanning heat treatment on the Ti2AlNb alloy region, a translational scanning mode is adopted, the scanning strategy is to scan along the short side in an S-shape, scan on one or both sides, repeat the scan once, the spot diameter is 4 mm, the substrate preheating temperature is 0~400℃, the laser power is 180~250W, the scanning speed is 5~10 mm / s, and the scanning track spacing is 0.25~0.5 mm.

[0057] Step 4: Cool the laser-scanned Ti60-Ti2AlNb gradient titanium alloy and perform post-processing.

[0058] In step 4, the post-processing includes annealing the Ti60-Ti2AlNb gradient titanium alloy after laser scanning heat treatment to stabilize the internal structure and eliminate the internal stress applied by laser scanning.

[0059] For annealing, the furnace temperature can be raised to 600~800℃ first, and then the Ti60-Ti2AlNb gradient titanium alloy after corresponding laser heat treatment can be placed in the furnace and held for 4~6 hours.

[0060] Preferably, since it is inconvenient to perform vacuuming operation after the annealing furnace reaches a high temperature, in order to prevent the Ti60-Ti2AlNb gradient titanium alloy from oxidizing at high temperature, the surface of the Ti60-Ti2AlNb gradient titanium alloy can be covered with an anti-oxidation coating before being sent into the annealing furnace. The anti-oxidation coating is MP90 anti-oxidation and decarburization coating.

[0061] The present invention will be further described in detail below through specific embodiments: Example 1: This embodiment describes laser partitioning heat treatment of Ti60-Ti2AlNb gradient titanium alloy parts with a composition transition path of (Ti60→Ti2AlNb). The parts are 50mm long, 10mm wide, and 5mm high.

[0062] Step 1: Determine the heat treatment requirements for the Ti60 alloy region, the Ti2AlNb alloy region, and the transition region.

[0063] In this embodiment, the heat treatment requirements for the Ti60-Ti2AlNb gradient titanium alloy parts mainly consider the Ti60 and Ti2AlNb portions. The connection zone formed by directly connecting the Ti60 and Ti2AlNb alloys is relatively small and can be ignored. For the Ti60 portion, the provided temperature range should be 1000℃ to control the dispersed precipitation of silicides; for the Ti2AlNb portion, the provided temperature range should be 1100℃ to allow α2 to dissolve back.

[0064] Step 2: Determine reasonable laser heat treatment process parameters based on relevant heat treatment requirements.

[0065] The temperature field during laser scanning was simulated using ABAQUS software to determine relevant process parameters. Combined with the actual dimensions of the part, a suitable laser scanning strategy was optimized to provide thermal history conditions approximately equivalent to conventional heat treatment. Figure 5 As shown. A translational scanning mode is used, with a scanning strategy of scanning along the short side in an S-shape, double-sided scanning, and one repeated scan. Figure 6 As shown. For the Ti60 part, the laser power is 180W, the laser scanning speed is 10 mm / s, and the channel spacing is 0.5mm; for the Ti2AlNb part, the laser power is 200W, the laser scanning speed is 5 mm / s, and the channel spacing is 0.5mm.

[0066] Step 3: Place the Ti60-Ti2AlNb gradient titanium alloy parts inside the laser scanning chamber.

[0067] (1) Part pretreatment Use sandpaper to polish the oxide scale on Ti60-Ti2AlNb gradient titanium alloy parts and clean them with anhydrous ethanol to prevent the oxide scale from being too thick and affecting the laser absorption rate.

[0068] (2) Place the substrate The substrate is placed on the worktable of the laser scanning chamber.

[0069] (3) Place the parts Then place the parts on the pre-installed substrate.

[0070] (4) Establish a coordinate system and set the laser scanning program. Determine the origin and coordinate system based on the location of the part, and set the laser scanning program according to the laser scanning strategy designed in step 2.

[0071] (5) Fill with protective gas High-purity argon gas with a purity of 99.99% was introduced as a protective gas until the oxygen content in the scanning chamber was below 1000 ppm.

[0072] Step 4: Use a laser to scan the corresponding area of ​​the part to form a corresponding temperature field.

[0073] Following the established process parameters and scanning strategy, laser scanning was used to scan the areas to be processed in the Ti60-Ti2AlNb gradient titanium alloy parts, establishing the thermal history conditions determined in step 2. Starting with the Ti60 portion, the Ti60 portion and then the Ti2AlNb portion were scanned sequentially. After the front side of the part was scanned, it was allowed to cool to room temperature, and the reverse side was scanned using the same scanning strategy and sequence.

[0074] Step 5: After the laser-scanned parts have cooled, post-processing is performed.

[0075] After the Ti60-Ti2AlNb gradient titanium alloy under laser scanning heat treatment is cooled, the parts are treated with MP90 anti-oxidation and decarburization coating for anti-oxidation treatment. Then, the parts are subjected to isothermal annealing at 600℃ / 4h / AC to stabilize the internal structure and eliminate the internal stress applied by laser scanning.

[0076] The microstructure of the transition zone of the Ti60-Ti2AlNb gradient titanium alloy obtained in this embodiment after gradient heat treatment is as follows: Figure 7 As shown, by changing the laser scanning process parameters and scanning strategy, the precipitated phases and microstructure in different regions were controlled. The microstructure of Ti60 and regions with compositions close to Ti60 was more uniform compared to the deposited state, and the silicide precipitation between the α-lamellae was more dispersed, achieving the expected microstructure control effect. For Ti2AlNb and regions with compositions close to Ti2AlNb, more O phase precipitated around and inside the α2 laths, reducing the proportion of α2 phase in the transition zone, suppressing the formation of bulk α2 phase, and promoting the increase of O phase content. This is beneficial for improving the room temperature plasticity of this region and optimizing the overall mechanical properties of the gradient material. Figure 8It can be seen that the tensile strength of the sample after gradient heat treatment in this embodiment is 949.8 MPa and the elongation is 4.4%. Compared with the deposited Ti60-Ti2AlNb gradient titanium alloy with a tensile strength of 917.3 MPa and an elongation of 2.6%, both the strength and plasticity are improved.

[0077] Example 2: The difference between this embodiment and Embodiment 1 is that: This embodiment describes laser partitioning heat treatment of Ti60-Ti2AlNb gradient titanium alloy parts with a composition transition path of (Ti60→Ti60-20wt%Ti2AlNb→Ti60-40wt%Ti2AlNb→Ti60-60wt%Ti2AlNb→Ti60-80wt%Ti2AlNb→Ti2AlNb). The parts are 50mm long, 10mm wide, and 5mm high.

[0078] In step 1, the heat treatment requirements for Ti60-Ti2AlNb gradient parts are considered in the following categories: Ti60 alloy region, 20wt%Ti2AlNb and Ti60-40wt%Ti2AlNb composition region, Ti60-60wt%Ti2AlNb and Ti60-80wt%Ti2AlNb composition region, and Ti2AlNb alloy region. For the Ti60 alloy region, the provided temperature range should be 1000℃ to control the dispersed precipitation of silicides between α Widmanstätten clusters; for the 20wt%Ti2AlNb and Ti60-40wt%Ti2AlNb composition regions, the provided temperature range should be 1000℃ to improve the uniformity of α laths; for the Ti60-60wt%Ti2AlNb and Ti60-80wt%Ti2AlNb composition regions, the provided temperature range should be 1050℃ to allow the precipitated α2 phase to dissolve back; for the Ti2AlNb portion, the provided temperature range should be 1100℃ to allow the precipitated α2 phase to dissolve back.

[0079] In step 2, for the Ti60 alloy region, the laser power was determined to be 180W, the laser scanning speed to be 10 mm / s, and the channel spacing to be 0.5mm; for the Ti60-20wt%Ti2AlNb and Ti60-40wt%Ti2AlNb composition regions, the laser power was determined to be 180W, the laser scanning speed to be 10 mm / s, and the channel spacing to be 0.4mm; for the Ti60-60wt%Ti2AlNb and Ti60-80wt%Ti2AlNb composition regions, the laser power was determined to be 200W, the laser scanning speed to be 10 mm / s, and the channel spacing to be 0.4mm; and for the Ti2AlNb alloy region, the laser power was determined to be 200W, the laser scanning speed to be 5 mm / s, and the channel spacing to be 0.5mm.

[0080] In step 4, starting from the Ti60 alloy region, the Ti60 alloy region, the 20wt%Ti2AlNb, Ti60-40wt%Ti2AlNb, Ti60-60wt%Ti2AlNb, Ti60-80wt%Ti2AlNb composition regions and the Ti2AlNb alloy region are scanned sequentially.

[0081] from Figure 9 As can be seen, the Ti60-Ti2AlNb gradient titanium alloy obtained in this embodiment after gradient heat treatment has a tensile strength of 1019.4 MPa and an elongation of 3.6%. Compared with the deposited Ti60-Ti2AlNb gradient titanium alloy with a tensile strength of 922.8 MPa and an elongation of 4.4%, the plasticity remains basically unchanged while the strength is improved.

[0082] Example 3: The difference between this embodiment and Embodiment 1 is that: This embodiment performs laser partitioned heat treatment on Ti60-Ti2AlNb gradient titanium alloy parts with a composition transition path of (Ti60→Ti2AlNb+Nb→Ti2AlNb), where Ti2AlNb+Nb is an added intermediate layer with a specific composition of Ti-(14.7~17.3at%)Al-(41.3~50at%)Nb. In this embodiment, it is Ti-16.6Al-43.6Nb(at%). The part is 50mm long, 10mm wide, and 5mm high.

[0083] In step 1, the heat treatment requirements for Ti60-Ti2AlNb gradient titanium alloy parts are considered in three categories: the Ti60 alloy region, the Ti-16.6Al-43.6Nb(at%) interlayer region, and the Ti2AlNb alloy region. For the Ti60 alloy region, the provided temperature range should be around 1000℃ to control the dispersed precipitation of silicides between α Widmanstätten clusters; for the Ti-16.6Al-43.6Nb(at%) interlayer region, the provided temperature range should be around 1080℃ to allow the precipitated α2 phase to dissolve back and promote the α2→O transformation; for the Ti2AlNb alloy region, the provided temperature range should be around 1100℃ to allow the precipitated α2 phase to dissolve back.

[0084] In step 2, for the Ti60 alloy region, the laser power was determined to be 180W, the laser scanning speed to be 10 mm / s, and the channel spacing to be 0.5mm; for the Ti-16.6Al-43.6Nb(at%) intermediate layer region, the laser power was determined to be 200W, the laser scanning speed to be 10 mm / s, and the channel spacing to be 0.3mm; for the Ti2AlNb alloy region, the laser power was determined to be 200W, the laser scanning speed to be 5mm / s, and the channel spacing to be 0.5mm.

[0085] In step 4, starting from the Ti60 alloy region, the Ti60 alloy region, the Ti2AlNb+Nb intermediate layer region, and the Ti2AlNb alloy region are scanned sequentially.

[0086] from Figure 10 As can be seen, the Ti60-Ti2AlNb gradient titanium alloy obtained in this embodiment after gradient heat treatment has a tensile strength of 1059.4 MPa and an elongation of 5.5%, which are improved in both strength and plasticity compared to the deposited Ti60-Ti2AlNb gradient titanium alloy with a tensile strength of 1006.1 MPa and an elongation of 3.5%.

[0087] Example 4: The difference between this embodiment and Embodiment 2 is as follows: In this embodiment, the Ti60-Ti2AlNb gradient titanium alloy part is 96mm long, 20mm wide, and 5mm high.

[0088] In step 2, for the Ti60 region, the laser power is 220W, the laser scanning speed is 10 mm / s, and the channel spacing is 0.5mm; for the Ti60-20wt%Ti2AlNb and Ti60-40wt%Ti2AlNb composition regions, the laser power is 220W, the laser scanning speed is 10 mm / s, and the channel spacing is 0.4mm; for the Ti60-60wt%Ti2AlNb and Ti60-80wt%Ti2AlNb composition regions, the laser power is 250W, the laser scanning speed is 10 mm / s, and the channel spacing is 0.4mm; for the Ti2AlNb region, the laser power is 250W, the laser scanning speed is 5 mm / s, and the channel spacing is 0.5mm.

[0089] In step 4, after the front side of the part is scanned, the part is cooled and the back side is not scanned.

[0090] The Ti60-Ti2AlNb gradient titanium alloy obtained in this embodiment after gradient heat treatment has a tensile strength of 921.9 MPa and an elongation of 5.6%.

[0091] Example 5: The difference between this embodiment and Embodiment 2 is as follows: In step 2, for the Ti60 and Ti60-20wt%Ti2AlNb and Ti60-40wt%Ti2AlNb composition regions, the laser power is 150W, the laser scanning speed is 10 mm / s, and the channel spacing is 0.5mm; for the Ti2AlNb and Ti60-60wt%Ti2AlNb and Ti60-80wt%Ti2AlNb composition regions, the laser power is 180W, the laser scanning speed is 10 mm / s, and the channel spacing is 0.25mm.

[0092] In step 3, after placing the part on the substrate, the substrate is preheated to 200°C and kept at that temperature until the laser heat treatment process is completed.

[0093] The Ti60-Ti2AlNb gradient titanium alloy obtained in this embodiment after gradient heat treatment has a tensile strength of 860.0 MPa and an elongation of 5.0%.

[0094] Examples 1-3 of this invention provide laser scanning gradient heat treatment under three typical connection methods of gradient titanium alloys, indicating that the gradient heat treatment method of Ti60-Ti2AlNb gradient titanium alloys provided by this invention is not limited to the connection method of gradient parts.

[0095] Embodiments 2 and 4 of this invention provide laser scanning gradient heat treatment of Ti60-Ti2AlNb gradient titanium alloys with different specifications and sizes, indicating that the gradient heat treatment method of Ti60-Ti2AlNb gradient titanium alloys provided by this invention can adjust the laser scanning parameters and strategies according to the temperature field simulation calculation based on the specifications and sizes of the parts, and is not limited to the specifications and sizes of the gradient parts.

[0096] Embodiments 2 and 5 of this invention provide laser scanning gradient heat treatment of Ti60-Ti2AlNb gradient titanium alloys under different laser scanning process parameters and related strategies. This indicates that the gradient heat treatment method for Ti60-Ti2AlNb gradient titanium alloys provided by this invention mainly involves combining the part size and heat treatment requirements, and designing laser scanning process parameters and related strategies under corresponding thermal history conditions based on simulation calculations. These parameters and strategies can be transformed in various ways to achieve approximately equivalent thermal history conditions, rather than being limited to fixed laser scanning process parameters and related strategies.

[0097] In summary, this invention provides a method for achieving gradient heat treatment of Ti60-Ti2AlNb gradient titanium alloy by laser scanning. By simulating relevant temperature fields, the process parameters and scanning strategies of laser scanning are designed and optimized, which can create corresponding temperature field conditions for different parts of the part. This enables flexible control of the heating area of ​​the gradient titanium alloy structure and precise regulation of the temperature field, achieving an improvement in microstructure and properties that is approximately equivalent to conventional heat treatment.

[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gradient heat treatment method for Ti60-Ti2AlNb gradient titanium alloy, characterized in that, include: Based on the heat treatment requirements of the Ti60 alloy region, Ti2AlNb alloy region and transition region in Ti60-Ti2AlNb gradient titanium alloy, the laser heat treatment process parameters and scanning strategy are determined. According to the determined laser heat treatment process parameters and scanning strategy, gradient laser scanning is performed on the corresponding regions of Ti60-Ti2AlNb gradient titanium alloy in a protective atmosphere to form a gradient temperature field and realize the gradient heat treatment of Ti60-Ti2AlNb gradient titanium alloy. After cooling, the Ti60-Ti2AlNb gradient titanium alloy after gradient heat treatment is subjected to post-treatment to obtain the Ti60-Ti2AlNb gradient titanium alloy after gradient heat treatment.

2. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, The Ti60-Ti2AlNb gradient titanium alloy is prepared by additive manufacturing of Ti60 alloy, transition zone and Ti2AlNb alloy. The transition zone is formed by direct connection, linear transition or intermediate layer transition.

3. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, The laser heat treatment process parameters and scanning strategy are designed and optimized by finite element simulation of the dynamic evolution of the temperature field during laser scanning, so that the thermal history conditions provided by laser scanning are in line with the heat treatment requirements of the Ti60 alloy region, Ti2AlNb alloy region and transition region in Ti60-Ti2AlNb gradient titanium alloy.

4. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, When performing laser heat treatment on the Ti60 alloy region, a translational scanning mode is adopted, the scanning strategy is to scan along the short side in an S-shape, scan on one or both sides, repeat the scan once, the spot diameter is 4mm, the preheating temperature is 0~400℃, the laser power is 150~220W, the scanning speed is 8~10mm / s, and the scanning track spacing is 0.4~0.5mm.

5. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, When performing laser heat treatment on the transition zone, a translational scanning mode is adopted. The scanning strategy is to scan along the short side in an S-shape, with single-sided or double-sided scanning. The number of repeated scans is 1, the spot diameter is 4mm, the preheating temperature is 0~400℃, the laser power is 150~250W, the scanning speed is 5~10mm / s, and the scanning track spacing is 0.3~0.5mm.

6. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, When performing laser heat treatment on the Ti2AlNb alloy region, a translational scanning mode is adopted, the scanning strategy is to scan along the short side in an S-shape, scan on one or both sides, repeat the scan once, the spot diameter is 4 mm, the preheating temperature is 0~400℃, the laser power is 180~250W, the scanning speed is 5~10 mm / s, and the scanning track spacing is 0.25~0.5 mm.

7. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, The Ti60-Ti2AlNb gradient titanium alloy was pretreated before laser scanning. The pretreatment process included: Use sandpaper to remove the oxide scale from the surface of the Ti60-Ti2AlNb gradient titanium alloy, and then use anhydrous ethanol to clean the surface of the Ti60-Ti2AlNb gradient titanium alloy.

8. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, The protective atmosphere is an argon atmosphere with a purity of 99.99%.

9. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 1, characterized in that, Post-treatment includes annealing at a temperature of 600-800℃ for 4-6 hours.

10. The gradient heat treatment method for a Ti60-Ti2AlNb gradient titanium alloy according to claim 9, characterized in that, Before annealing, an anti-oxidation coating is applied to the surface of the Ti60-Ti2AlNb gradient titanium alloy. The anti-oxidation coating is MP90 anti-oxidation and decarburization coating.

Images