A multi-stage heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching and a preparation method thereof

Abstract

The application discloses a super-high strength and toughness matched multistage heterogeneous laminated composite titanium alloy and a preparation method thereof, and belongs to the technical field of titanium-based composite materials. The titanium alloy comprises at least one group of alternately laminated first strengthening layers and first toughening layers, and the first strengthening layers and the first toughening layers are both composed of alternately laminated second strengthening layers and second toughening layers, and adjacent laminated layers have heterogeneous interface characteristics with composition transition or direct transition. The second strengthening layer is a metastable beta titanium alloy with precipitation strengthening characteristics, and the second toughening layer is a metastable beta titanium alloy with TWIP / TRIP toughening effect. The laminated composite titanium alloy is prepared by using an additive manufacturing method, the first layers are constructed by alternately depositing the second layers and differentiating in-situ heat treatment or rapid cooling between passes, and the corresponding heterogeneous interfaces are obtained by combining different powder flow rate control and layer-to-layer powder / silk replacement. The application realizes good matching and promotion of super-high strength and plasticity and toughness of the titanium alloy by coupling precipitation strengthening and TWIP / TRIP toughening effect.

Description

Technical Field

[0001] This invention relates to the field of titanium-based composite materials technology, and in particular to a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching and its preparation method. Background Technology

[0002] Due to the negative correlation between strength and plasticity / toughness caused by the classical deformation mechanism of dislocation movement in metallic materials, a significant increase in strength inevitably leads to a significant decrease in plasticity and toughness. Metastable β-titanium alloys, ideal for aerospace load-bearing structures, struggle to achieve a good balance and improvement in ultra-high strength, plasticity, and toughness. For example, typical commercial high-strength and high-toughness titanium alloys Ti-1023 and Ti-5553, widely used in the landing gear structures of Boeing 777 and Airbus A380, achieve service strengths exceeding 1200 MPa, but their fracture toughness only reaches slightly above 50 MPa·m. 1 / 2 The current technology is gradually failing to meet the leapfrog development needs of the new generation of aircraft, which are moving towards higher speeds, larger sizes, more complex structures, and improved fuel efficiency.

[0003] In recent years, numerous studies on the deformation mechanism of metastable β-titanium alloys have revealed the presence of twin-induced plasticity (TWIP) / transformation-induced plasticity (TRIP) effects, commonly found in austenitic steels and high-entropy alloys, in some titanium alloys. This results in higher work hardening capacity and improved plasticity and toughness, providing a new opportunity for the synergistic improvement and breakthrough of the strength, plasticity, and toughness of titanium alloys. However, because the critical shear stress for inducing phase transformation and mechanical twinning in TWIP / TRIP titanium alloys is relatively small, their yield strength is relatively low, approximately 420–750 MPa, which currently cannot meet the application requirements in the aerospace field. Furthermore, numerous studies on the coupling of precipitation strengthening and TWIP / TRIP toughening in metastable β titanium alloys based on composition design, microstructure optimization, and β phase stability regulation have shown that: (1) the TWIP / TRIP effect usually occurs in alloys with low β stability, while precipitation strengthening requires high β stability to precipitate the α phase; (2) with the formation and increase of precipitates in TWIP / TRIP titanium alloys, β-stabilizing elements are redistributed and enriched in the β matrix, further improving its stability and thus suppressing the TWIP / TRIP effect; (3) the formation of precipitates disrupts the continuity of the β matrix, hindering the long-range atomic movement required for mechanical twinning and stress-induced phase transformation, thereby further suppressing the TWIP / TRIP effect. Therefore, precipitation strengthening and TWIP / TRIP toughening are difficult to coexist in homogeneous metastable β titanium alloys and achieve ultra-high strength and toughness levels.

[0004] Mother-of-pearl from seashells is a composite biomaterial composed of hard aragonite calcium carbonate and soft biopolymers stacked in a regular pattern. Based on a unique "mud-brick" structure, it achieves a perfect combination of strength, toughness, and hardness, making its overall performance far exceed the mechanical sum of its individual basic units. In addition, the morphology of the bird feather skeleton exhibits a progressive, Russian nesting doll-like, iterative porous structure from macroscopic to microscopic levels, enabling it to meet the requirements of stiffness, toughness, and strength while maintaining an unimaginable ultra-lightweight design.

[0005] Therefore, drawing on the unique macro / micro structure of biomaterials such as mother-of-pearl from seashells and bird feather skeletons, which exhibits a perfect combination of strength and toughness, the inventors have provided a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching and its preparation method. Summary of the Invention

[0006] (1) Technical problems to be solved: This invention provides a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching and its preparation method, which solves the technical problem that precipitation strengthening and TWIP / TRIP toughening are difficult to coexist in metastable β titanium alloys and achieve ultra-high strength and toughness matching. It provides a new idea for the material development and selection of load-bearing structures for next-generation aircraft.

[0007] (2) Technical solution: To address the aforementioned technical problems, this invention provides a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching. It is a multi-level heterogeneous laminated structure, including at least one set of alternating stacked Level I strengthening layers and Level I toughening layers. The thickness of each Level I strengthening layer and Level I toughening layer is 1.0~5.0 mm, and they are all formed by alternating stacking of Level II strengthening layers and Level II toughening layers. Furthermore, there are heterogeneous interface features with compositional transition or direct transition between adjacent stacks. In the Level I reinforcement layer, the two outermost layers are both Level II reinforcement layers, with a thickness of 0.5~1.0 mm and a thickness of 0.1~0.5 mm for the Level II toughening layer; In the Class I toughening layer, the outermost two sides are Class II toughening layers, the thickness of the Class II toughening layer is 0.5~1.0mm, and the thickness of the Class II strengthening layer is 0.1~0.5mm; The Class II strengthening layer is a metastable β-titanium alloy with precipitation strengthening characteristics, exhibiting a microstructure morphology of fine α-phase dispersed in the β-phase matrix; The Class II toughening layer is a metastable β titanium alloy with TWIP / TRIP toughening effect, exhibiting a single metastable β phase microstructure.

[0008] Preferably, the metastable β-titanium alloy with precipitation strengthening characteristics is one or more of Ti-53331, TC18, and TB6; Metastable β-titanium alloys with TWIP / TRIP toughening effect are one or more of Ti-12Mo, Ti-7Mo-3Cr, and Ti-3Al-5Mo-7V-3Cr.

[0009] Preferably, the microstructure of fine α phase dispersed in the β phase matrix in the Level II reinforcement layer is formed and precipitated by in-situ heat treatment by applying a low-power energy beam preheating between each deposition pass of the additive manufacturing of the Level II reinforcement layer. In the Class II toughening layer, the single metastable β phase microstructure was obtained by increasing the cooling interval between each deposition pass in the additive manufacturing of the toughening layer and applying an inert gas flow for in-situ rapid cooling.

[0010] Preferably, the component transition interface is formed during the additive manufacturing process by controlling the continuous change of powder flow rate of adjacent reinforcing layer and toughening layer materials.

[0011] Preferably, the direct transition interface is formed during the additive manufacturing process through interlayer powder / filament exchange.

[0012] Preferably, the composite titanium alloy achieves a good match and improvement in ultra-high strength, plasticity, and toughness by simultaneously engaging deformation mechanisms such as stress-induced phase transformation, mechanical twinning, and dislocation slip during plastic deformation, combined with the effects of heterogeneous deformation-induced (HDI) strengthening at the layer interface and toughening by consuming fracture energy.

[0013] This invention also provides a method for preparing the above-mentioned ultra-high strength and toughness matched multi-level heterogeneous laminated composite titanium alloy, as follows: S1. Select a titanium alloy substrate made of the same material as the Class II reinforcement layer and preheat it to 150~200℃. S2. Under an inert gas protective atmosphere, additive manufacturing technology is used to alternately deposit a first-level strengthening layer and a first-level toughening layer according to the strategy of preferentially depositing the strengthening layer. During the deposition process, by controlling the powder flow rate of the strengthening layer and toughening layer materials, or based on the interlayer powder / wire exchange method, a composition transition interface or direct transition interface is formed between adjacent stacks to realize the preparation of multi-level heterogeneous stacked composite titanium alloy.

[0014] Preferably, in S2, the inert gas is high-purity argon.

[0015] Preferably, the additive manufacturing technology is one of selective laser melting, laser directional energy deposition, arc wire additive manufacturing, or electron beam wire additive manufacturing.

[0016] Preferably, when the selected additive manufacturing technology is laser-directed energy deposition, spherical alloy powder with a particle size range of 45~150μm, selected from the metastable β titanium alloy for the strengthening layer and toughening layer, is used as raw material. The process parameters are as follows: deposition laser power is 1500~3000W, scanning rate is 5~15mm / s, powder feeding rate is 200~500g / h, laser spot diameter is 3~7mm, and preheating laser power is 200~400W.

[0017] Preferably, when the selected additive manufacturing technology is selective laser melting, spherical alloy powder with a particle size range of 15~53μm of metastable β titanium alloy selected for the strengthening layer and toughening layer are used as raw materials. The process parameters are as follows: cladding laser power is 130~180W, scanning rate is 800~1300mm / s, powder thickness is 60~80μm, laser spot diameter is 0.06~0.1mm, scanning spacing is 80~130μm, and preheating laser power is 15~25W.

[0018] Preferably, when depositing the Level I reinforcement layer, the Level II reinforcement layer and the Level II toughening layer are deposited alternately until the total thickness reaches 1.0~5.0 mm, and the two outermost layers are both Level II reinforcement layers; the thickness of the Level II reinforcement layer is controlled at 0.5~1.0 mm, and the thickness of the Level II toughening layer is controlled at 0.1~0.5 mm. When depositing the Class I toughening layer, the Class II toughening layer and the Class II strengthening layer are deposited alternately until the total thickness reaches 1.0~5.0 mm, and the two outermost layers are both Class II toughening layers. The thickness of the Class II toughening layer is controlled at 0.5~1.0 mm, and the thickness of the Class II strengthening layer is controlled at 0.1~0.5 mm.

[0019] Preferably, between each deposition pass of the Level II reinforcement layer, a smaller power energy beam with 10-30% deposition energy beam power is used to preheat the deposited layer, thereby precipitating finely dispersed α phase based on in-situ heat treatment; Between each deposition pass of the Level II toughening layer, a cooling interval of 30-60 seconds was added, and an inert gas flow was applied for in-situ rapid cooling to obtain a single metastable β-phase microstructure.

[0020] (3) Beneficial effects: 1) This invention draws on the unique macro / micro structure of biomaterials such as mother-of-pearl and bird feather skeletons, which presents a perfect combination of strength and toughness. Metastable β titanium alloy with precipitation strengthening and TWIP / TRIP toughening effect is used as the basic unit. Through additive manufacturing technology, a Russian nesting doll-like multi-level heterogeneous laminated composite titanium alloy is designed and constructed. The heterogeneous interlayer interface with direct transition or composition transition is prepared, realizing the synergistic strengthening and toughening of titanium alloy based on structural biomimicry.

[0021] 2) The strengthening layer metastable β titanium alloy, through the interaction of finely dispersed α phase and moving dislocations, can effectively exert precipitation strengthening effect and improve the alloy strength to ultra-high strength level; the toughening layer TWIP / TRIP metastable β titanium alloy, based on the stress-induced phase transformation and mechanical twinning during plastic deformation, can not only alleviate excessive local stress concentration and reduce the risk of crack initiation, but also consume a large amount of fracture energy due to the continuous generation of phase boundaries and twin boundaries, which hinder crack propagation and change the propagation path. Furthermore, it can significantly improve the alloy's plasticity and toughness by changing the crystal orientation through twinning and stimulating dislocation slip.

[0022] 3) The phase interfaces, twin interfaces, and interlayer interfaces of the multilayer composite titanium alloy continuously generated during the plastic deformation process can significantly hinder dislocation movement and cause dislocation pile-up, and can also generate HDI strengthening by coordinating plastic deformation through "soft" and "hard" regions. In addition, the heterogeneous interlayer interfaces can effectively deflect, bridge, and passivate cracks, significantly extending their propagation paths and consuming a large amount of fracture energy, thereby further optimizing their toughness properties.

[0023] 4) The reinforcing layer and toughening layer selected in this invention are both metastable β-titanium alloys, with relatively small differences in their physicochemical properties, thus avoiding material compatibility issues at heterogeneous interfaces. Combined with the construction of the interface between heterogeneous layers with transitional composition, the risk of failure due to insufficient load-bearing and load transfer capacity caused by abrupt changes in interface properties is reduced, and load transfer and coordinated plastic deformation between the precipitation reinforcing layer and the TWIP / TRIP toughening layer can be effectively achieved.

[0024] 5) This invention achieves a good match and improvement in the ultra-high strength, plasticity, and toughness of titanium alloys by simultaneously activating deformation mechanisms such as stress-induced phase transformation, mechanical twinning, and dislocation slip during plastic deformation, combined with the strengthening effect of HDI at the heterostructure interface and the toughening effect of dissipating fracture energy. Specifically, this results in improved tensile strength. R m >1300MPa, elongation after fracture A >15%, fracture toughness K IC >65MPa·m 1 / 2 . Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a multi-level heterogeneous laminated composite titanium alloy structure with ultra-high strength and toughness matching according to the present invention. Figure 2 This is a schematic diagram of the structure of the first-level strengthening layer in a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching according to the present invention. Figure 3 This is a schematic diagram of the structure of the first-level toughening layer in a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching according to the present invention. Figure label: 1. Level I reinforcement layer; 2. Level I toughening layer; 3. Level II reinforcement layer; 4. Level II toughening layer. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0028] like Figure 1 As shown, the present invention provides a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching. It is a multi-level heterogeneous laminated structure, including at least one set of alternating stacked primary strengthening layer 1 and primary toughening layer 2. The thickness of each primary strengthening layer 1 and primary toughening layer 2 is 1.0~5.0mm, which is formed by alternating stacking of secondary strengthening layer 3 and secondary toughening layer 4, and the adjacent stacks have heterogeneous interface features of compositional transition or direct transition.

[0029] like Figure 2 As shown, in the Class I reinforcement layer 1, the two outermost layers are both Class II reinforcement layers 3, the thickness of Class II reinforcement layer 3 is 0.5~1.0mm, and the thickness of Class II toughening layer 4 is 0.1~0.5mm.

[0030] like Figure 3 As shown, in the Class I toughening layer 2, the outermost two sides are both Class II toughening layers 4, the thickness of Class II toughening layer 4 is 0.5~1.0mm, and the thickness of Class II strengthening layer 3 is 0.1~0.5mm.

[0031] The Level II strengthening layer 3 is a metastable β titanium alloy with precipitation strengthening characteristics, exhibiting a microstructure morphology of fine α phase dispersed in the β phase matrix; the Level II toughening layer 4 is a metastable β titanium alloy with TWIP / TRIP toughening effect, exhibiting a single metastable β phase microstructure morphology.

[0032] Example 1 This embodiment provides a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching, including 5 sets of alternating stacked primary strengthening layers and primary toughening layers. The thickness of each primary strengthening layer and primary toughening layer is 4.5 mm. It is formed by alternating stacking of secondary strengthening layers and secondary toughening layers. The thickness of each secondary strengthening layer and secondary toughening layer is 0.5 mm. The adjacent stacks have heterogeneous interface features with compositional transition.

[0033] The Level II strengthening layer is a metastable β titanium alloy Ti-55531 (nominal composition Ti-5Al-5Mo-5V-3Cr-1Zr) with precipitation strengthening characteristics, which exhibits a microstructure of fine α phase dispersed in the β phase matrix; the Level II toughening layer is a metastable β titanium alloy Ti-3Al-5Mo-7V-3Cr with TWIP / TRIP toughening effect, which exhibits a single metastable β phase microstructure.

[0034] The multi-level heterogeneous multilayer composite titanium alloy was prepared by laser-directed energy deposition additive manufacturing technology, as detailed below: (1) Using the above-mentioned metastable β titanium alloy spherical alloy powder with a particle size range of 45~150μm as raw material, select a titanium alloy substrate with the same material as the Class II reinforcement layer and preheat it to 150℃.

[0035] (2) The deposition process was carried out using process parameters of 1500W deposition laser power, 5mm / s scanning rate, 200g / h powder feeding rate, 5mm laser spot diameter and 300W preheating laser power.

[0036] (3) Under the protection of high-purity argon, following the strategy of preferentially depositing the strengthening layer, the second-level strengthening layer and the second-level toughening layer are deposited alternately, and the two outermost layers are both second-level strengthening layers to construct the first-level strengthening layer; then the second-level toughening layer and the second-level strengthening layer are deposited alternately, and the two outermost layers are both second-level toughening layers to construct the first-level toughening layer; by controlling the powder flow rate of the strengthening layer and the toughening layer material to form a heterogeneous interface of composition transition between adjacent stacks, the preparation of multi-level heterogeneous stacked composite titanium alloy is achieved through repeated iterations.

[0037] (4) Between each deposition pass of the strengthening layer, the deposited layer is preheated with a smaller energy beam of 300W with 20% deposition energy beam power, and finely dispersed α phase is precipitated based on in-situ heat treatment; between each deposition pass of the toughening layer, in-situ rapid cooling is carried out by increasing the cooling interval by 60s and applying high-purity argon gas flow to obtain a single metastable β phase structure.

[0038] This multi-level heterogeneous laminated composite titanium alloy achieves a good balance and enhancement of ultra-high strength, plasticity, and toughness by simultaneously engaging deformation mechanisms such as stress-induced phase transformation, mechanical twinning, and dislocation slip during plastic deformation, combined with the HDI strengthening effect at the heterogeneous laminate interface and the toughening effect of dissipating fracture energy. R m >1350MPa, elongation after fracture A >15%, fracture toughness K IC >65MPa·m 1 / 2 .

[0039] Example 2 The difference between this embodiment and Embodiment 1 lies in the toughening layer material, the design of each layer thickness, the preparation method, and the interlayer transition method. Its structure includes five sets of alternating stacked primary reinforcement layers and primary toughening layers. The thickness of the primary reinforcement layer is 4.3 mm, and the thickness of the primary toughening layer is 4.7 mm. These are formed by alternating stacking of secondary reinforcement layers and secondary toughening layers, with a heterogeneous interface feature between adjacent stacks. In the primary reinforcement layers, each secondary reinforcement layer has a thickness of 1.0 mm, and each secondary toughening layer has a thickness of 0.1 mm; in the primary toughening layers, each secondary reinforcement layer has a thickness of 0.1 mm, and each secondary toughening layer has a thickness of 0.5 mm.

[0040] The Level II strengthening layer is a metastable β titanium alloy Ti-55531 with precipitation strengthening characteristics, which exhibits a microstructure of fine α phase dispersed in the β phase matrix; the Level II toughening layer is a metastable β titanium alloy Ti-12Mo with TWIP / TRIP toughening effect, which exhibits a single metastable β phase microstructure.

[0041] The multi-level heterogeneous laminated composite titanium alloy was prepared by cladding using laser selective melting additive manufacturing technology, as detailed below: (1) Using the above-mentioned metastable β titanium alloy spherical alloy powder with a particle size range of 15~53μm as raw material, select a titanium alloy substrate of the same material as the Class II reinforcement layer and preheat it to 150℃.

[0042] (2) The process parameters of 150W cladding laser power, 1200mm / s scanning rate, 50μm powder thickness, 0.06mm laser spot diameter, 80μm scanning spacing and 15W preheating laser power were selected for cladding.

[0043] (3) Under the protection of high-purity argon, following the strategy of prioritizing the cladding of the strengthening layer, the second-level strengthening layer and the second-level toughening layer are clad alternately, and the outermost two layers are both second-level strengthening layers to construct the first-level strengthening layer; then the second-level strengthening layer and the second-level toughening layer are clad alternately, and the outermost two layers are both second-level toughening layers to construct the first-level toughening layer; the direct transition heterogeneous interface is obtained by the interlayer powder exchange method, and the preparation of multi-level heterogeneous stacked composite titanium alloy is achieved through repeated iterations.

[0044] (4) Between each cladding pass of the strengthening layer, the cladding layer is preheated with a smaller energy beam of 15W with 10% cladding energy beam power, and finely dispersed α phase is precipitated based on in-situ heat treatment; between each deposition pass of the toughening layer, in-situ rapid cooling is carried out by increasing the cooling interval by 60s and applying high-purity argon gas flow to obtain a single metastable β phase structure.

[0045] This multi-level heterogeneous laminated composite titanium alloy achieves a good balance and enhancement of ultra-high strength, plasticity, and toughness by simultaneously engaging deformation mechanisms such as stress-induced phase transformation, mechanical twinning, and dislocation slip during plastic deformation, combined with the HDI strengthening effect at the heterogeneous laminate interface and the toughening effect of dissipating fracture energy. R m >1300MPa, elongation after fracture A >20%, fracture toughness K IC >65MPa·m 1 / 2 .

[0046] Example 3 The difference between this embodiment and Embodiment 1 lies in the materials and thickness design of the reinforcing and toughening layers. The thickness of the Level I reinforcing layer is 3.4 mm, and the thickness of the Level I toughening layer is 3.5 mm. Within the Level I reinforcing layer, each Level II reinforcing layer has a thickness of 1.0 mm, and each Level II toughening layer has a thickness of 0.2 mm; within the Level I toughening layer, each Level II reinforcing layer has a thickness of 0.1 mm, and each Level II toughening layer has a thickness of 0.5 mm.

[0047] The Level II strengthening layer is a metastable β titanium alloy TC18 (nominal composition Ti-5Al-5Mo-5V-1Cr-1Fe) with precipitation strengthening characteristics, which exhibits a microstructure of fine α phase dispersed in the β phase matrix; the Level II toughening layer is a metastable β titanium alloy Ti-7Mo-3Cr with TWIP / TRIP toughening effect, which exhibits a single metastable β phase microstructure.

[0048] This multi-level heterogeneous laminated composite titanium alloy achieves a good balance and enhancement of ultra-high strength, plasticity, and toughness by simultaneously engaging deformation mechanisms such as stress-induced phase transformation, mechanical twinning, and dislocation slip during plastic deformation, combined with the HDI strengthening effect at the heterogeneous laminate interface and the toughening effect of dissipating fracture energy. R m >1300MPa A >15%, K IC >65MPa·m 1 / 2 .

[0049] Example 4 The difference between this embodiment and Embodiment 1 lies in the materials and thickness design of the reinforcing and toughening layers. The thickness of the Level I reinforcing layer is 2.1 mm, and the thickness of the Level I toughening layer is 2.6 mm. Within the Level I reinforcing layer, each Level II reinforcing layer has a thickness of 1.0 mm, and each Level II toughening layer has a thickness of 0.1 mm; within the Level I toughening layer, each Level II reinforcing layer has a thickness of 0.2 mm, and each Level II toughening layer has a thickness of 0.5 mm.

[0050] The Level II strengthening layer is a metastable β titanium alloy TB6 (nominal composition Ti-10V-2Fe-3Al) with precipitation strengthening characteristics, which exhibits a microstructure of fine α phase dispersed in the β phase matrix; the Level II toughening layer is a metastable β titanium alloy Ti-3Al-5Mo-7V-3Cr with TWIP / TRIP toughening effect, which exhibits a single metastable β phase microstructure.

[0051] This multi-level heterogeneous laminated composite titanium alloy achieves a good balance and enhancement of ultra-high strength, plasticity, and toughness by simultaneously engaging deformation mechanisms such as stress-induced phase transformation, mechanical twinning, and dislocation slip during plastic deformation, combined with the HDI strengthening effect at the heterogeneous laminate interface and the toughening effect of dissipating fracture energy. R m >1300MPa A >15%, K IC >65MPa·m 1 / 2 .

[0052] Therefore, this invention relates to a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness and its preparation method. Drawing inspiration from the unique macro / microstructures of biomaterials such as mother-of-pearl and bird feather skeletons, which exhibit a perfect combination of strength and toughness, this invention uses metastable β-titanium alloys with precipitation strengthening and TWIP / TRIP toughening effects as the basic unit. Through additive manufacturing technology, a Russian doll-like multi-level heterogeneous laminated composite titanium alloy is designed and constructed, and a direct transition or compositional transition heterogeneous interlayer structure is prepared. This composite titanium alloy achieves a good match and improvement in ultra-high strength, plasticity, and toughness by simultaneously engaging deformation mechanisms such as stress-induced phase transformation, mechanical twinning, and dislocation slip during plastic deformation, combined with the effects of heterogeneous deformation-induced (HDI) strengthening at the laminate interface and fracture energy dissipation toughening. Specifically, this results in improved tensile strength. R m >1300MPa, elongation after fracture A >15%, fracture toughness K IC >65MPa·m 1 / 2 This provides new ideas for the development and selection of materials for the load-bearing structures of next-generation aircraft.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching, characterized in that: The composite titanium alloy is a multi-level heterogeneous stacked structure, including at least one set of alternating stacked primary strengthening layers and primary toughening layers. The thickness of each primary strengthening layer and primary toughening layer is 1.0~5.0 mm. They are all formed by alternating stacking of secondary strengthening layers and secondary toughening layers, and there are heterogeneous interface features of compositional transition or direct transition between adjacent stacks. In the Level I reinforcement layer, the two outermost layers are both Level II reinforcement layers, with a thickness of 0.5~1.0 mm and a thickness of 0.1~0.5 mm for the Level II toughening layer; In the Class I toughening layer, the outermost two sides are Class II toughening layers, the thickness of the Class II toughening layer is 0.5~1.0mm, and the thickness of the Class II strengthening layer is 0.1~0.5mm; The Class II strengthening layer is a metastable β-titanium alloy with precipitation strengthening characteristics, exhibiting a microstructure morphology of fine α-phase dispersed in the β-phase matrix; The Class II toughening layer is a metastable β titanium alloy with TWIP / TRIP toughening effect, exhibiting a single metastable β phase microstructure.

2. The ultra-high strength and toughness matched multi-level heterogeneous laminated composite titanium alloy according to claim 1, characterized in that: Metastable β-titanium alloys with precipitation strengthening characteristics are one or more of Ti-53331, TC18, and TB6; Metastable β-titanium alloys with TWIP / TRIP toughening effect are one or more of Ti-12Mo, Ti-7Mo-3Cr, and Ti-3Al-5Mo-7V-3Cr.

3. The ultra-high strength and toughness matched multi-level heterogeneous laminated composite titanium alloy according to claim 2, characterized in that: In the Level II reinforcement layer, the fine α phase dispersed in the β phase matrix is ​​nucleated and precipitated by in-situ heat treatment generated by applying a low-power energy beam preheating between each deposition pass of the Level II reinforcement layer additive manufacturing. In the Class II toughening layer, the single metastable β-phase microstructure was obtained by increasing the cooling interval between each deposition pass in the additive manufacturing of the toughening layer and applying an inert gas flow for in-situ rapid cooling.

4. The ultra-high strength and toughness matched multi-level heterogeneous laminated composite titanium alloy according to claim 3, characterized in that: The composition transition interface is formed during additive manufacturing by continuously changing the powder flow rate of adjacent reinforcing and toughening layer materials.

5. The ultra-high strength and toughness matched multi-level heterogeneous laminated composite titanium alloy according to claim 4, characterized in that: Direct transition interfaces are formed during additive manufacturing through interlayer powder / filament exchange.

6. A method for preparing a multi-level heterogeneous laminated composite titanium alloy with ultra-high strength and toughness matching as described in any one of claims 1-5, characterized in that: S1. Select a titanium alloy substrate made of the same material as the Class II reinforcement layer and preheat it to 150~200℃. S2. Under an inert gas protective atmosphere, using additive manufacturing technology, the first-level reinforcement layer and the first-level toughening layer are deposited alternately according to the strategy of preferentially depositing the reinforcement layer. During the deposition process, by controlling the powder flow rate of the reinforcing layer and toughening layer materials, or by using an interlayer powder / wire exchange method, a compositional transition or direct transition interface is formed between adjacent layers, thereby realizing the preparation of multi-level heterogeneous laminated composite titanium alloys.

7. The preparation method according to claim 6, characterized in that: Additive manufacturing technology is one of laser selective melting, laser directional energy deposition, electric arc wire additive manufacturing, or electron beam wire additive manufacturing.

8. The preparation method according to claim 7, characterized in that: When depositing the Level I reinforcement layer, the Level II reinforcement layer and the Level II toughening layer are deposited alternately until the total thickness reaches 1.0~5.0 mm, and the two outermost layers are both Level II reinforcement layers; the thickness of the Level II reinforcement layer is controlled at 0.5~1.0 mm, and the thickness of the Level II toughening layer is controlled at 0.1~0.5 mm. When depositing the Class I toughening layer, the Class II toughening layer and the Class II strengthening layer are deposited alternately until the total thickness reaches 1.0~5.0 mm, and the two outermost layers are both Class II toughening layers. The thickness of the Class II toughening layer is controlled at 0.5~1.0 mm, and the thickness of the Class II strengthening layer is controlled at 0.1~0.5 mm.

9. The preparation method according to claim 8, characterized in that: Between each deposition pass of the Level II reinforcement layer, a smaller power energy beam with 10-30% deposition energy beam power is used to preheat the deposited layer, and finely dispersed α phase is precipitated based on in-situ heat treatment. Between each deposition pass of the Level II toughening layer, a cooling interval of 30-60 seconds was added, and an inert gas flow was applied for in-situ rapid cooling to obtain a single metastable β-phase microstructure.

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