A method for laser fusion additive manufacturing of memory alloy fiber implanted aluminum alloy self-healing material

Abstract

The application relates to a laser wire additive manufacturing preparation method of memory alloy fiber implanting aluminum alloy self-healing materials. The method comprises the following steps: selecting an Al-Mg-Sc aluminum alloy as a base material; performing surface acid etching treatment on Ti-20Ta-10Zr memory alloy fibers; applying 1.0% tensile pre-strain to the treated memory alloy fibers; weaving the memory alloy fibers into a twill weaving structure; and alternately depositing an aluminum alloy layer and laying a memory alloy fiber layer by adopting a laser coaxial wire feeding method to prepare a multilayer composite material. The prepared composite material has excellent mechanical properties and a self-healing function. When subjected to external force damage, crack closure and material self-healing are realized through the shape memory effect of the memory alloy fibers. The method is simple in process, stable in material performance, suitable for industrialized production, and has a wide application prospect in the fields of aviation, aerospace, automobile industry and the like.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, and specifically to a method for preparing shape memory alloy fiber-reinforced aluminum alloy self-healing composite materials using a laser coaxial wire feeding method. Background Technology

[0002] With the rapid development of modern industry, especially in high-tech fields such as aerospace, automobile manufacturing, and electronics, the requirements for material performance are increasing. Among these, the demand for lightweight, high-strength materials is particularly urgent. Aluminum alloys, due to their low density, high specific strength, and good machinability, have always been one of the preferred materials in these fields. However, traditional aluminum alloys still have shortcomings in fatigue resistance and damage tolerance, which limits their use in some critical applications.

[0003] To overcome these shortcomings, researchers have begun exploring various composite material technologies. Among them, shape memory alloys (SMAs) have attracted widespread attention due to their unique shape memory effect and superelasticity. SMAs can recover their original shape after being deformed by external forces through heating or unloading, a property that offers the possibility of self-healing capabilities. However, effectively bonding SMAs to an aluminum alloy matrix has remained a technical challenge, with major difficulties including insufficient interfacial bonding strength, uneven distribution of SMAs, and oxidation problems during the fabrication process.

[0004] Traditional composite material preparation methods, such as powder metallurgy and casting, face numerous challenges when processing SMA-reinforced aluminum alloy composites. While powder metallurgy can achieve good component homogeneity, it struggles to control the orientation of SMA fibers and suffers from high porosity. Casting, on the other hand, easily leads to excessive oxidation of SMA fibers or adverse reactions with the matrix, affecting the overall material properties. Furthermore, these methods struggle to precisely control the spatial distribution of SMA fibers within the matrix, which is crucial for the material's self-healing capabilities.

[0005] In recent years, the development of additive manufacturing technology has provided new solutions to the aforementioned problems. Laser additive manufacturing, due to its advantages of precise control and high flexibility, has shown great potential in the field of composite material preparation. However, a method that can effectively combine SMA fibers and aluminum alloy matrices while achieving self-healing functionality is still lacking. Existing technologies still face challenges in processing SMA / aluminum alloy composites, including interfacial bonding, microstructure uniformity, and optimization of process parameters.

[0006] Therefore, developing a novel additive manufacturing method that can effectively combine SMA fibers with an aluminum alloy matrix to achieve self-healing properties while improving the overall mechanical properties of the composite material has significant theoretical and practical value. This will not only promote the development of high-performance lightweight composite materials but also provide new material solutions for high-end manufacturing industries such as aerospace and automotive manufacturing. Summary of the Invention

[0007] The purpose of this invention is to provide an additive manufacturing method for preparing shape memory alloy fiber reinforced aluminum alloy self-healing materials, in order to solve the technical problems existing in the prior art, such as insufficient interfacial bonding strength, uneven distribution of SMA fibers, degradation of SMA fiber properties, limitations of preparation process, and insufficient self-healing ability.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An additive manufacturing method for a shape memory alloy fiber-reinforced self-healing aluminum alloy material, characterized by the following steps:

[0010] First, Al-Mg-Sc aluminum alloy was selected as the matrix material, and Ti-Ta-Zr shape memory alloy was selected as the reinforcing fiber.

[0011] The first step involves surface treatment of the Ti-Ta-Zr memory alloy fibers. Controlled etching is performed using a mixed acid solution of HF and HNO3. This step aims to increase the surface roughness of the fibers, create microscopic mechanical interlocking conditions, and improve the interfacial bonding strength with the aluminum alloy matrix.

[0012] The second step involves applying a predetermined tensile pre-strain to the surface-treated shape memory alloy fibers. This step aims to activate the shape memory effect of the shape memory alloy, laying the foundation for its subsequent self-healing function.

[0013] The third step involves weaving the pretreated shape memory alloy fibers into a twill weave structure at a specific angle. The weaving density is controlled to ensure the volume fraction of the shape memory alloy fibers in the composite material reaches a predetermined proportion. This structural design provides stress closure capability in multiple directions while guaranteeing sufficient self-healing ability without unduly affecting the performance of the matrix alloy.

[0014] The fourth step involves preparing the composite material using a laser coaxial wire feeding additive manufacturing method. This step is performed in an inert atmosphere to prevent material oxidation and adverse reactions. The specific procedures are as follows:

[0015] First, the laser power, wire feed speed, and stage movement speed are set. Then, the first layer of aluminum alloy is deposited, followed immediately by the laying of a pre-treated shape memory alloy fiber mesh. Next, the next layer of aluminum alloy is deposited and the shape memory alloy fiber mesh is laid, alternating between these steps until the predetermined thickness is achieved. Throughout the manufacturing process, the laser power, wire feed speed, and process temperature are precisely controlled to ensure good material bonding and performance retention.

[0016] The fifth step involves post-processing the prepared composite material. Heat treatment is performed to optimize the microstructure of the matrix alloy. Subsequently, surface treatment is carried out to improve surface quality.

[0017] Preferably, the Al-Mg-Sc aluminum alloy is an Al-5Mg-0.3Sc alloy, which possesses excellent strength, toughness, and corrosion resistance. This alloy composition provides good matrix properties for the composite material and exhibits good compatibility with shape memory alloy fibers.

[0018] Preferably, the Ti-Ta-Zr memory alloy is a Ti-20Ta-10Zr alloy, which has a wide phase transformation temperature range and excellent superelasticity. This alloy composition ensures that the memory alloy fibers maintain their shape memory effect and superelasticity over a wide temperature range, thereby enhancing the self-healing ability and adaptability of the composite material.

[0019] Preferably, the etching time in the first step is 30 seconds, and the temperature is controlled at 20-25℃. This etching condition can effectively increase the surface roughness of the shape memory alloy fibers without excessively damaging them, thus providing good interface conditions for subsequent bonding with the aluminum alloy substrate.

[0020] Preferably, the pre-stretch strain in the second step is controlled at 1%. This pre-strain value can effectively activate the shape memory effect of the shape memory alloy without causing excessive deformation or damage to the fibers.

[0021] Preferably, the weaving angle in the third step is ±45°, and the volume fraction of the shape memory alloy fiber is controlled at 10%-20%. This weaving structure and fiber content can ensure that the composite material has sufficient self-healing ability without excessively affecting the performance of the matrix alloy, thus achieving the best balance of performance.

[0022] Preferably, in the fourth step, high-purity argon is used as the inert atmosphere, the laser power ranges from 1000 to 1500 W, the wire feed speed ranges from 5 to 10 m / min, and the stage movement speed ranges from 400 to 600 mm / min. The selection of these process parameters ensures good melting and bonding of the material during preparation, while minimizing oxidation and adverse reactions.

[0023] Preferably, the heat treatment temperature in step five is controlled at 350-400℃ for 2-4 hours, and the surface treatment can be achieved by sandblasting or polishing. This post-treatment process can effectively optimize the microstructure of the base alloy, release internal stress, and improve the surface quality of the material.

[0024] The beneficial effects of this invention are as follows: By adopting the above-mentioned technical solution, this invention significantly improves the interfacial bonding strength between shape memory alloy fibers and the aluminum alloy matrix. Tests show that in the prepared composite material, the interfacial shear strength between the shape memory alloy fibers and the aluminum alloy matrix is ​​increased by 40%-60%, and the tensile strength is increased by 20%-30% compared to the untreated composite material. Simultaneously, this invention achieves uniform distribution and directional arrangement of the shape memory alloy fibers. By employing a twill weave structure at a specific angle and a layer-by-layer laying method, the uniformity of the shape memory alloy fiber distribution throughout the component reaches over 90%, and the performance difference in different directions is reduced to within 10%. Furthermore, this invention effectively prevents oxidation and adverse reactions of the shape memory alloy fibers. Through laser coaxial fiber feeding additive manufacturing under an inert atmosphere, the oxide layer thickness on the surface of the prepared shape memory alloy fibers does not exceed 50 nm, and more than 95% of the phase transition enthalpy is retained, proving that its shape memory effect is essentially unaffected.

[0025] This invention also optimizes the self-healing function. The prepared composite material can self-heal cracks up to 100 μm wide at room temperature, and retains more than 80% self-healing efficiency after 100 fatigue cycles. In terms of overall performance, compared with materials prepared by traditional methods, the composite material of this invention has a 25% higher tensile strength, a 35% higher fracture toughness, and a fatigue life extended by more than 50%. Under the same stress level, its service life is 2-3 times that of ordinary aluminum alloys. Finally, the process of this invention has good flexibility and applicability, and can directly manufacture components with complex functional structures such as internal cooling channels and lightweight structures. Moreover, by adjusting the process parameters, a flexible balance can be achieved between strength and self-healing ability. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the layered structure of the shape memory alloy fiber-reinforced aluminum alloy composite material of the present invention.

[0027] Figure 2 This is a cross-sectional view of the distribution of shape memory alloy fibers in an aluminum alloy matrix according to the present invention.

[0028] Figure 3 This is a planar structural diagram of the shape memory alloy fiber mesh of the present invention.

[0029] The markings in the figure are: 1. Substrate, 2. Al-Mg-Sc deposited layer, 3. Ti-20Ta-10Zr shape memory alloy fiber. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments. Those skilled in the art should understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the invention.

[0031] This embodiment provides an additive manufacturing method for a shape memory alloy fiber-reinforced aluminum alloy self-healing material. Regarding raw material selection, this embodiment uses an Al-5Mg-0.3Sc alloy as the matrix material. The chemical composition (mass fraction) of this alloy is: Mg 5.0%, Sc 0.3%, Fe≤0.1%, Si≤0.1%, with the remainder being Al. This alloy was chosen as the matrix because the addition of magnesium significantly improves the strength and corrosion resistance of the aluminum alloy, the addition of the rare earth element Sc refines the grains and improves the high-temperature performance of the alloy, and it also possesses good weldability and formability, making it suitable for additive manufacturing. The reinforcement is a Ti-20Ta-10Zr alloy as the shape memory alloy fiber. The chemical composition (mass fraction) of this alloy is: Ta 20%, Zr 10%, with the remainder being Ti. The main consideration for choosing this alloy is its suitable phase transformation temperature range and excellent superelasticity, while maintaining good chemical stability. This composition ratio can provide sufficient strength and toughness while ensuring the shape memory effect.

[0032] In the actual preparation process, the shape memory alloy fibers first need to undergo surface treatment. The purpose of surface treatment is to clean the fiber surface, remove the surface oxide layer, and form an appropriate surface roughness to enhance the subsequent interfacial bonding strength with the substrate. The specific operation steps are as follows: First, prepare an acidic etching solution of 2% HF-5% HNO3 in a fume hood. During the preparation process, place a 1000ml beaker in an ice-water bath, add deionized water to the beaker to the 600ml mark, and then slowly add the hydrofluoric acid and nitric acid required by the calculation, while stirring with a glass rod.

[0033] Ti-20Ta-10Zr shape memory alloy fibers were immersed in a prepared etching solution for controlled etching. Temperature control during the etching process is crucial; the solution temperature needs to be stabilized at 22±1℃, which can be achieved using a water bath. The etching time was precisely controlled at 30 seconds using a timer. The accuracy of the time control directly affects the surface treatment effect; too short a time will result in insufficient surface treatment, while too long a time may over-etch the fibers, reducing their mechanical properties. After etching, the fibers were immediately removed using stainless steel tweezers and quickly immersed in prepared deionized water for the first rinse. This was followed by a second and third rinse with fresh water, each rinse lasting 1 minute.

[0034] After rinsing, the fibers need to undergo ultrasonic cleaning. The fibers are placed in a beaker containing anhydrous ethanol, and the beaker is then placed in an ultrasonic cleaner. The ultrasonic cleaning frequency is set to 40kHz, the power to 100W, and the cleaning time to 5 minutes. Ultrasonic cleaning effectively removes residual impurities and reaction products from the fiber surface, while also promoting surface activation. After cleaning, the fibers are removed and placed in a vacuum drying oven for drying. The drying process is controlled at 60℃, the vacuum level is maintained at -0.08MPa, and the drying time is 2 hours. This drying process thoroughly removes moisture and ethanol from the fiber surface, preparing it for subsequent processing.

[0035] Pre-strain treatment is a crucial step in the fabrication process, directly affecting the self-healing properties of shape memory alloy fibers. A universal testing machine was used to perform tensile pre-strain treatment on the fibers, with the pre-strain value set at 1%. Before pre-strain treatment, the testing machine was preheated for 20 minutes to ensure stable operation. The ends of the fiber were fixed to the clamps of the testing machine with moderate clamping force, preventing slippage during stretching while avoiding excessive clamping force that could cause localized fiber damage. The pre-strain rate was controlled at 1 mm / min, ensuring uniform deformation without causing localized stress concentration due to excessively rapid deformation. During the test, strain gauges were used to monitor the fiber's strain state in real time. When the 1% pre-strain value was reached, loading was immediately stopped, and the fiber was unloaded after maintaining this strain state for 1 minute.

[0036] Fiber braiding is a crucial process step in achieving uniform distribution of shape memory alloy fibers within the matrix. This embodiment employs a ±45° twill weave structure, which provides excellent self-healing properties while ensuring material isotropy. Figure 3 As shown, the planar structure of the shape memory alloy fiber mesh exhibits a continuous rhomboid shape, with each shape composed of multiple interwoven fiber threads, forming a high-strength, high-toughness network structure. The weaving process utilizes specialized weaving equipment to weave pre-strained fibers according to the design pattern. Special attention must be paid to controlling the fiber tension during weaving; maintaining appropriate tension ensures the stability of the woven structure without causing additional fiber deformation. By precisely controlling the weaving parameters, the volume fraction of the shape memory alloy fiber reaches 15%. After weaving, the mesh needs to be inspected to ensure there are no defects such as breaks or tangles.

[0037] Additive manufacturing is the core process of this invention. The manufacturing process takes place in a specially designed inert gas-protected chamber, filled with high-purity argon at atmospheric pressure. The laser power of the coaxial laser wire feeding system is set to 1200W, the laser spot diameter to 3mm, the wire feeding speed to 15mm / s, and the stage movement speed to 10mm / s. These parameters are based on extensive pre-experiment optimization results, ensuring good molten pool conditions and deposition quality. During the manufacturing process, inert gas (high-purity argon) is continuously introduced at a flow rate of 15L / min to prevent material oxidation. The substrate preheating temperature is set to 150℃, which reduces thermal stress and improves the quality of the deposited layer.

[0038] In actual deposition processes, such as Figure 1 As shown, an aluminum alloy layer with a thickness of approximately 0.8 mm is first deposited on the substrate as a transition layer. Then, aluminum alloy layer 2 is deposited alternately, followed by the laying of a shape memory alloy fiber mesh 3. The deposition thickness of each aluminum alloy layer is controlled to be approximately 0.5 mm, and after the fiber mesh is laid, it is ensured that it is completely immersed in the molten pool.

[0039] like Figure 2 As shown, in the cross-section of the composite material, the bottom substrate layer 1 is an aluminum alloy matrix. The upper multi-layered arc-shaped structure 2 represents the aluminum alloy layers, with shape memory alloy fibers embedded on top of each deposited layer. The cross-sections of these shape memory alloy fibers 3 exhibit a regularly distributed circular cross-section. This layered structure clearly demonstrates the alternating distribution of the aluminum alloy matrix and shape memory alloy fibers. The cross-sections of the shape memory alloy fibers can be observed on both sides of each arc-shaped structure, indicating that the fibers are distributed in a grid pattern within the aluminum alloy layers. This structural design helps to improve the overall strength and self-healing ability of the material.

[0040] During the deposition process, the state of the molten pool needs to be monitored in real time, including its size, shape, and stability. If instability or splashing is observed, process parameters should be adjusted promptly. After each deposition layer, a surface quality inspection must be performed to ensure there are no obvious defects. If defects are found, they must be repaired or remanufactured immediately.

[0041] Temperature control is crucial throughout the manufacturing process. Besides substrate preheating, interlayer temperatures must be controlled. After each layer is deposited, the temperature must be allowed to drop below 200°C before depositing the next layer. This prevents excessive heat input from degrading the shape memory alloy fibers. Simultaneously, precise positioning during layer transitions is essential to ensure good bonding between layers. After manufacturing, the sample is cooled to room temperature in the furnace. This slow cooling process helps release internal stress and improves the overall material properties.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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. The scope of protection of the present invention should be determined by the appended claims and is not limited to the description of the specific embodiments above.

Claims

1. A method for additive manufacturing a shape memory alloy fiber-reinforced self-healing aluminum alloy material, characterized in that, Includes the following steps: (1) Al-Mg-Sc aluminum alloy was selected as the matrix material; (2) The surface of Ti-20Ta-10Zr shape memory alloy fiber is subjected to acid etching treatment to enhance its wettability; (3) Apply a tensile pre-strain of 1.0% to the treated shape memory alloy fiber to improve its restoring force; (4) The shape memory alloy fibers are woven into a twill braided fiber web; (5) Using the laser coaxial filament melting method, the process temperature is controlled between 660℃ and 1400℃. By optimizing the fiber mesh structure parameters, aluminum alloy layers are deposited alternately and memory alloy fiber meshes are laid to prepare multilayer composite materials. The fiber mesh is made of two main fibers woven in parallel. Each main fiber is composed of multiple memory alloy fibers woven in parallel. The fiber mesh structure optimization includes setting the main fiber weaving angle to ±45° to achieve uniform stress distribution. The volume fraction of memory alloy fibers in the composite material is controlled at 10%-20%. The planar structure of the memory alloy fiber mesh presents a continuous rhombus shape. The overlap length of the main fiber intersection is designed to be no less than 10 times the diameter of the memory alloy fiber to enhance the interlayer connection strength. The overall mechanical properties of the composite material are improved through the above structural parameter optimization design. The prepared composite material is then post-treated. The post-treatment includes heat treatment. The heat treatment temperature is controlled at 350-400℃ and the time is 2-4 hours.

2. The preparation method according to claim 1, characterized in that, The acid etching process includes: (a) Immerse shape memory alloy fibers in a 2% HF-5% HNO3 aqueous solution; (b) Etch for 30 seconds at room temperature; (c) Wash with distilled water and dry.

3. The preparation method according to claim 1, characterized in that, The laser coaxial fuse method includes: (a) Depositing an Al-Mg-Sc aluminum alloy layer on a substrate; (b) Lay a layer of woven shape memory alloy fibers on the aluminum alloy layer; (c) Repeat steps (a) and (b) until the designed thickness is achieved.

4. The preparation method according to claim 1, characterized in that, The diameter of the Ti-20Ta-10Zr shape memory alloy fiber is 50μm.

5. The preparation method according to claim 1, characterized in that, The reinforcing effect of the shape memory alloy fiber on the matrix includes the following: when the matrix is ​​subjected to excessive load deformation or cracking, the crack encounters the shape memory alloy fiber during the matrix propagation process, resulting in interface debonding, matrix and fiber fracture, and fiber pull-out process, which makes the fracture energy higher than that of a single aluminum alloy, thereby playing a strengthening role.

6. The preparation method according to claim 1, characterized in that, The process temperature of the laser coaxial melting process is controlled between 660℃ and 1400℃ to ensure that the Ti-20Ta-10Zr shape memory alloy fiber completes the phase transformation from β phase to α'' phase within this temperature range, while ensuring that the aluminum alloy matrix is ​​fully melted and forms a good interfacial bond with the fiber.

7. The preparation method according to claim 1, characterized in that, The self-healing process of the composite material includes: when the material is damaged by external force and cracks are generated, by heating to a temperature close to the solidus line of the Al-Mg-Sc alloy, the phase transformation of the martensite α'' phase to the austenite β phase in the shape memory alloy is activated, and the recovery stress generated by the shape memory effect is used to close the crack, thereby realizing the self-healing of the material.

8. The preparation method according to claim 1, characterized in that, The composition of the Al-Mg-Sc aluminum alloy, by mass percentage, is: Mg: 4.0-6.0%, Sc: 0.2-0.8%, with the balance being Al and unavoidable impurities.

Images