WO2023245850A1 - 一种超声辅助铝合金板材激光冲击成形方法及系统 - Google Patents

一种超声辅助铝合金板材激光冲击成形方法及系统 Download PDF

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WO2023245850A1
WO2023245850A1 PCT/CN2022/114177 CN2022114177W WO2023245850A1 WO 2023245850 A1 WO2023245850 A1 WO 2023245850A1 CN 2022114177 W CN2022114177 W CN 2022114177W WO 2023245850 A1 WO2023245850 A1 WO 2023245850A1
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ultrasonic
aluminum alloy
shock
laser beam
laser
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PCT/CN2022/114177
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English (en)
French (fr)
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周建忠
缑延强
夏雪峰
李礼
李鹏飞
姜高强
孟宪凯
黄舒
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江苏大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
    • B23K26/356—Working by laser beam, e.g. welding, cutting or boring for surface treatment by shock processing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/0093—Working by laser beam, e.g. welding, cutting or boring combined with mechanical machining or metal-working covered by other subclasses than B23K
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/60—Preliminary treatment

Definitions

  • the invention relates to the field of metal plate forming processing, and specifically relates to an ultrasonic-assisted laser shock forming method and system for aluminum alloy plates.
  • Aluminum alloys are widely used in high-speed rail, aircraft and other machinery manufacturing fields due to their high strength, good toughness, plasticity, and excellent mechanical and processing properties, such as aircraft skins, high-speed rail carriages, etc.
  • the manufacturing requirements for complex curved surfaces of aluminum alloy plates are increasing.
  • cold stamping is the main method to achieve metal sheet forming. It has high production efficiency and is suitable for mass production. However, this forming technology has high requirements for mold accuracy, and the manufacturing process of the mold is complex, long cycle and expensive. , limiting the application of this method in the production of small batches of parts.
  • Cold stamping is only suitable for the forming of metal sheets with good plasticity such as low carbon steel and aluminum-copper alloys. It is not suitable for the forming of high-strength metal sheets such as hard aluminum alloys.
  • cold stamping is also difficult to achieve special curvatures. The required plate forming is prone to defects such as tensile cracks, which affects the service life of the formed components. Therefore, traditional processing methods are often difficult to meet the current high-precision plate forming requirements. It is necessary to find an advanced flexible precision forming technology to achieve rapid and efficient forming of aluminum alloy sheets, which is of great significance.
  • Laser forming technology is a new type of metal forming technology. It overcomes the shortcomings of traditional forming processes such as poor flexibility, high mold costs, and long production cycles. It has shown broad application prospects in many fields such as automobiles, aviation, and defense industries. Among them, laser shock forming (LSF) has the characteristics of ultra-high pressure, high energy, and high strain rate. It is a composite forming technology that integrates material modification, strengthening and forming. Its principle is to use high-energy short-pulse laser The mechanical effect of interacting with physical materials and inducing the generation of high-amplitude shock waves or stress waves promotes macroscopic plastic deformation of the sheet.
  • LSF laser shock forming
  • the ideal sheet deformation can be obtained; by setting the appropriate forming trajectory, impact area and pulse number, local or large-area forming of the sheet can be achieved.
  • the plastic deformation of a single laser shock forming sheet is very small, the forming efficiency is low, and it is difficult to adapt to large-area macroforming of high-strength aluminum alloy sheets, which greatly limits the application of laser shock forming technology in the field of metal sheet forming. effective application. Therefore, improved research on laser shock forming technology is needed.
  • the prior art discloses a method and device for plate forming.
  • the patent uses CO2 continuous laser to heat and pretreat the plate to improve the plastic forming ability of the plate and increase the amount of laser impact forming deformation of the plate.
  • the disadvantages of this method are: the temperature of laser heating is relatively high, which can easily cause thermal damage to the plate, and the heating is uneven, and the stress distribution is difficult to control, which will form harmful residual tensile stress on the surface of the plate.
  • the prior art discloses a multi-point laser shock forming device and forming method, which uses several independent single pulse lasers to perform multi-point synchronous laser shock forming, effectively avoiding breakage that is easily produced during single spot impact forming. damage phenomenon, significantly improving the processing efficiency of laser shock forming, and making it easy to achieve precise forming of complex curved surfaces.
  • the present invention provides an ultrasonic-assisted laser shock forming method and system for aluminum alloy plates.
  • the ultrasonic-assisted laser shock forming technology is used to realize flexible moldless forming of aluminum alloy plates.
  • the ultrasonic shock generates high-frequency vibrations.
  • the acoustic softening effect can effectively improve the plastic forming ability of aluminum alloy sheets and realize the macroscopic plastic forming of high-strength aluminum alloy sheets by laser shock.
  • the ultrasonic effect effectively enhances the ability of laser shock to induce dynamic recrystallization inside the matrix material.
  • the coupling mechanism can effectively reduce surface defects of laser shock forming workpieces.
  • the surface quality of aluminum alloy sheets is also improved while achieving macroscopic shaping.
  • the present invention achieves the above technical objectives through the following technical means.
  • An ultrasonic-assisted laser shock forming method for aluminum alloy plates includes the following steps:
  • the surface of the aluminum alloy plate is divided into concave surface and convex surface;
  • the pulsed laser beam and the ultrasonic shock wave are moved synchronously according to the traveling path to obtain an aluminum alloy plate with a curved curvature.
  • the method also includes the following steps: pretreating the surface of the aluminum alloy plate to make the surface roughness value ⁇ 5 ⁇ m.
  • the surface of the aluminum alloy plate is pre-treated, specifically: the surface of the plate is ground and polished with sandpaper of different particle sizes, and the treated surface is ultrasonically cleaned and dried using an anhydrous ethanol solution.
  • the pulsed laser beam remains perpendicular to the inner concave surface
  • the ultrasonic shock wave remains perpendicular to the outer convex surface
  • the pulse laser beam is generated by a nanosecond pulse laser
  • the spot diameter of the pulse laser beam is 3 to 10 mm
  • the pulse frequency of the pulse laser beam is 1 to 10 Hz
  • the pulse width of the pulse laser beam is 10 ⁇ 20ns
  • the pulse energy of the pulsed laser beam is 3 ⁇ 20J
  • the spot overlap rate of the pulsed laser beam is 20% ⁇ 80%.
  • the ultrasonic shock wave is generated by an ultrasonic generator, and the vibration frequency of the ultrasonic shock wave is 20 to 40 kHz; the ultrasonic impact head striker amplitude of the ultrasonic generator ranges from 20 to 100 ⁇ m, and the striker diameter ranges from 3 to 10 mm.
  • a system for ultrasonic-assisted aluminum alloy plate laser shock forming method including an ultrasonic generator, a pulse laser and a controller; the ultrasonic generator is used to generate ultrasonic shock waves, and the pulse laser is used to generate a pulse laser beam;
  • the ultrasonic-assisted aluminum alloy plate laser impact forming method of the present invention uses the high-frequency vibration energy generated by ultrasonic impact to significantly reduce the flow stress and deformation resistance of the material in the impact area, so that the material has good plastic deformation ability and improves It has reached the forming limit of laser shock aluminum alloy sheets; at the same time, the ultrasonic shock stress bending forming mechanism can effectively reduce the energy required for laser shock forming, improve the efficiency of laser shock forming, and increase the deformation amount of the sheet during single laser shock plastic forming.
  • the application of laser shock in the forming of high-strength aluminum alloy sheets has been expanded.
  • the ultrasonic-assisted laser shock forming method of aluminum alloy plates according to the present invention utilizes the coupling effect of ultra-high strain rate of laser shock and high-frequency vibration of ultrasonic shock to reduce dislocation activation energy and reduce the impact of dislocation pinning. Reduce the amount of stress rebound during plate forming and improve the forming accuracy and efficiency of aluminum alloy plates; ultrasonic impact and laser impact process parameters are accurately controllable, and all process parameters can be set in the computer, making it easy to achieve large-scale industrial production , has a wide range of industrial application prospects.
  • Figure 1 is a schematic diagram of the ultrasonic-assisted laser shock forming method of aluminum alloy plates according to the present invention.
  • Figure 2 is a path diagram of ultrasonic-assisted laser shock forming of aluminum alloy plates according to Embodiment 1 of the present invention.
  • Figure 3 is a diagram showing the actual forming effect of an aluminum alloy plate according to Embodiment 1 of the present invention.
  • Figure 4 is an outline view of formed aluminum alloy plates according to various embodiments of the present invention.
  • Figure 5 is a surface hardness diagram of formed aluminum alloy plates according to various embodiments of the present invention.
  • Figure 6 is a diagram of residual stress on the surface of formed aluminum alloy plates according to various embodiments of the present invention.
  • first and second are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as “first” and “second” may explicitly or implicitly include one or more of these features.
  • “plurality” means two or more than two, unless otherwise explicitly and specifically limited.
  • connection In the present invention, unless otherwise clearly stated and limited, the terms “installation”, “connection”, “connection”, “fixing” and other terms should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. , or integrally connected; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two components.
  • connection connection
  • fixing and other terms should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. , or integrally connected; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two components.
  • the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
  • the ultrasonic-assisted laser shock forming method of aluminum alloy plates according to the present invention includes the following steps:
  • the surface of the aluminum alloy plate is divided into a concave surface 6 and an convex surface 7; the pulse laser beam 1 is used to impact the concave surface 6, and the convex surface 7 is assisted at the corresponding position of the laser impact Apply ultrasonic shock wave 2; Coat the concave surface 6 with 40-60 ⁇ m black paint as the absorption layer, and use 2 mm thick running water as the constraint layer;
  • the pulse laser beam 1 and the ultrasonic shock wave 2 are moved synchronously according to the traveling path.
  • the pulse laser beam 1 remains perpendicular to the concave surface 6, and the ultrasonic shock wave 2 remains perpendicular to the convex surface 7, thereby obtaining an aluminum alloy plate with a curved curvature. .
  • the ultrasonic-assisted aluminum alloy plate laser shock forming method of the present invention is a moldless forming method of high-strength aluminum alloy plates.
  • Ultrasonic shock is introduced into the laser shock forming process to assist the aluminum alloy plate forming.
  • the high-frequency vibration generated by ultrasonic impact can effectively reduce the deformation resistance and deformation resistance of the material and improve the plastic forming ability of the plate.
  • the formed aluminum alloy material prepared by the ultrasonic-assisted laser shock process produces more effective grain refinement and a uniform residual compressive stress-affected layer, which significantly improves the mechanical properties and fatigue resistance of the formed workpiece; in addition, the ultrasonic field Adding effective suppression of the depth of pits produced by laser shock on the surface of the plate improves the quality of the surface of the formed plate.
  • the coupling effect of the ultra-high strain rate of laser shock and the high-frequency vibration of ultrasonic shock reduces the dislocation activation energy of the material and reduces the dislocation
  • the pinning effect is weakened, and the amount of sheet forming stress rebound is reduced, which improves the forming accuracy and efficiency of aluminum alloy sheets.
  • the 2024 aviation aluminum alloy plate is selected as the research object below, and the present invention is described in detail with reference to the drawings and three specific embodiments.
  • the ultrasonic-assisted laser shock forming method of aluminum alloy plates described in Embodiment 1 includes the following specific steps:
  • Example 1 The actual effect of the aviation aluminum alloy formed plate prepared in Example 1 is shown in Figure 3.
  • the contour curves of the aluminum alloy plate formed by different laser shock processes are shown in Figure 4.
  • the maximum deformation of the formed aluminum alloy plate is The depth is only 1.78mm, while the maximum deformation depth of the aluminum alloy plate formed by ultrasonic-assisted laser shock in Example 1 is 2.83mm, which is approximately 59% higher than the maximum deformation depth of the aluminum alloy plate formed by single laser shock. This result shows that ultrasonic shock effectively softens the matrix material and improves the plastic deformation ability of the material, allowing the laser shock to obtain a greater plate deformation.
  • Example 1 The surface hardness of the formed aluminum alloy plate is shown in Figure 5.
  • the surface hardness of the ultrasonic-assisted laser shock formed aluminum alloy plate is 189HV, which is approximately 45.4% higher than the surface hardness of the untreated aluminum alloy plate of 130HV.
  • the surface hardness of the aluminum alloy plate formed by single laser shock is 167HV, which is increased by about 13.2%.
  • the residual stress on the surface of the formed aluminum alloy plate is shown in Figure 6.
  • the residual stress on the surface of the aluminum alloy plate formed by ultrasonic-assisted laser shock in Example 1 is -191MPa.
  • the laser shock process parameters in the second embodiment are set as follows: laser pulse energy is 15J, spot diameter is 5mm, pulse frequency is 5Hz, pulse width is 15ns, overlap rate is 20%, during laser shock forming Spray 50 ⁇ m thick black paint on one side as the absorption layer.
  • the ultrasonic-assisted process parameters are set as follows: the operating frequency is 30 kHz, the amplitude is 50 ⁇ m, and the impact head striker diameter is 5 mm.
  • the deformation profile curve of the aviation aluminum alloy plate prepared in Example 2 is shown in Figure 4. It can be seen from the figure that the maximum deformation depth of the aluminum alloy plate formed by ultrasonic-assisted laser impact forming under the above process parameters is 3.41mm. Compared with the embodiment The maximum deformation depth of an aluminum alloy plate formed by ultrasonic-assisted laser shock is 2.83mm, which is an increase of about 20.5%.
  • the surface hardness of the formed aluminum alloy plate in Example 2 is shown in Figure 5.
  • the surface hardness of the formed aluminum alloy plate is 201HV, which is approximately 6.3% higher than the surface hardness of the formed aluminum alloy plate prepared in Example 1, which is 189HV.
  • the surface residual stress of the formed aluminum alloy plate prepared in Example 2 is shown in Figure 6.
  • the surface residual stress of the formed aluminum alloy plate is -207MPa, which is an increase of approximately 8.4% compared to the surface residual stress of -191MPa of the formed aluminum alloy plate in Example 1. Since the second embodiment uses larger laser shock and ultrasonic-assisted process parameters, the deformation amount, surface hardness, and residual stress are all effectively improved compared to the first embodiment.
  • the laser shock process parameters in the third embodiment are set as follows: laser pulse energy is 20J, spot diameter is 10mm, pulse frequency is 10Hz, pulse width is 20ns, overlap rate is 80%, during laser shock forming Spray 60 ⁇ m thick black paint on one side as the absorption layer.
  • the ultrasonic-assisted process parameters are set as follows: the operating frequency is 40 kHz, the amplitude is 70 ⁇ m, and the impact head striker diameter is 10 mm.
  • the deformation profile curve of the aviation aluminum alloy plate in Example 3 is shown in Figure 4. It can be seen from the figure that the maximum deformation depth of the aluminum alloy plate formed by ultrasonic-assisted laser shock in Example 3 is 3.79mm. Compared with the formed aluminum alloy in Example 1 The maximum deformation depth of the plate is 2.83 mm, which is an increase of about 33.9%. Compared with the maximum deformation depth of the formed aluminum alloy plate in Example 2, which is 3.41 mm, it is an increase of about 11.1%. As shown in Figure 5, the surface hardness of the formed aluminum alloy plate prepared in Example 3 is 203HV. As shown in Figure 6, the surface residual stress of the formed aluminum alloy plate prepared in Example 3 is -206MPa.
  • Embodiment 3 further increases the process parameters of laser shock and ultrasonic assistance. Affected by the saturation effect, the surface hardness and residual stress of the prepared formed sample are similar to those in Embodiment 2, but the maximum deformation depth of the formed plate is better than that in Embodiment 1 and Embodiment 2. In the second embodiment, greater plastic deformation was obtained.
  • the system of the ultrasonic-assisted laser shock forming method of aluminum alloy plates according to the present invention includes an ultrasonic generator, a pulse laser and a controller; the ultrasonic generator is used to generate ultrasonic shock waves 2, and the pulse laser is used to generate a pulse laser beam 1 ;
  • the pulse laser beam 1 acts on the concave surface 6 of the aluminum alloy plate, and the ultrasonic shock wave 2 acts on the convex surface 7 of the aluminum alloy plate at the corresponding position of the laser impact; the water outlet 5 is located on the concave surface 6 , used to form a flow constraint layer.
  • the controller controls the ultrasonic shock wave 2 and the pulse laser beam 1 to move synchronously.

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Abstract

一种超声辅助铝合金板材激光冲击成形方法及系统，方法包括如下步骤：根据板材弯曲成形要求将铝合金板材表面分为内凹表面（6）和外凸表面（7）；利用脉冲激光束（1）冲击所述内凹表面（6），且在激光冲击的对应位置上的外凸表面（7）处辅助施加超声冲击波（2）；按照行进路径同步移动脉冲激光束（1）和超声冲击波（2），得到具有弯曲曲率的铝合金板材。利用超声辅助激光冲击成形技术实现铝合金板材的柔性无模成形，超声冲击高频振动产生的声软化效应，可以有效提高铝合金板材的塑性成形能力，实现激光冲击对高强度铝合金板材的宏观塑性成形。

Description

一种超声辅助铝合金板材激光冲击成形方法及系统 技术领域
本发明涉及金属板材成形加工领域，具体涉及一种超声辅助铝合金板材激光冲击成形方法及系统。
背景技术
铝合金由于其强度高，韧性、塑性好，且具有优良的力学和加工性能，在高铁、飞机等机械制造业领域应用广泛，如飞机蒙皮、高铁车厢等。随着装备的发展与进步，为了满足装备高性能使用要求，铝合金板材复杂曲面的制造要求日益增多。
当前冷冲压成形是实现金属板材成形的主要方法，其生产效率较高，适用于大批量生产，但该成形技术对模具精度具有较高的要求，而模具的制造工序复杂、周期长、费用昂贵，限制了这种方法在小批量零件的生产中的应用。冷冲压成形仅适用于低碳钢、铝铜合金等塑性好的金属板材的成形，不适用于硬质铝合金等高强度金属板材的成形加工，此外，冷冲压成形也很难实现具有特殊曲率要求的板材成形，容易产生拉伸裂纹等缺陷，影响成形构件的使用寿命。因此，传统的加工手段，往往难以满足当前高精度板件成形的要求，需要寻找一种先进的柔性精密成形技术，实现铝合金板料的快速高效成形，具有重要的意义。
激光成形技术是一种新型的金属成形技术，它克服了传统成形工艺柔性差，模具费用大，生产周期长的缺点，在汽车、航空、国防工业等许多领域展现出了广泛的应用前景。其中，激光冲击成形(Laser shock forming，LSF)具有超高压、高能、高应变率等特征，是一种集材料改性强化和成形于一体的复合成形技术，其原理是利用高能量短脉冲激光与物质材料相互作用，诱导产生高幅冲击波或应力波的力学效应促使板料产生宏观塑性变形。通过选择合适的激光脉冲能量、脉冲宽度、光斑大小与搭接率，可获得理想的板料变形量；通过设置合适的成形轨迹、冲击区域与脉冲次数，可实现板材的局部或大面积成形。对于硬质铝合金，单次激光冲击成形板料塑性变形量很小，成形效率较低，难以适应高强度铝合金板材大面积宏观成形，这极大地限制了激光冲击成形技术在金属板材成形领域的有效应用。因此，需要对激光冲击成形技术进行改进研究。例如，现有技术公开了一种板材成形的方法和装置，该专利采用CO 2连续激光对板材进行加热预处理，提高板材塑性成形能力，增大板材激光冲击成形变形量。该方法的缺点是：激光加热的温度较高，容易对板材形成热伤害，且加热不均匀，其应力分布难以控制，会在板材表面形成有害的残余拉应力。又如，现有技术公开一种多点激光冲击成形装置及成形方法，采用若干个相互独立的单个脉冲激光器，进行多点同步 激光冲击成形，有效避免了单个光斑冲击成形时极易产生的断裂损伤现象，显著提高激光冲击成形的加工效率，易于实现复杂曲面的精确成形。但多脉冲激光器共同作用，该加工方法所需成本过高，在实际生产中局限性较大，且受限于搭接率的缺失，单点激光冲击形成的凹凸痕迹难以磨灭，成形工件表面质量较差。
发明内容
针对现有技术中存在的不足，本发明提供了一种超声辅助铝合金板材激光冲击成形方法及系统，利用超声辅助激光冲击成形技术实现铝合金板材的柔性无模成形，超声冲击高频振动产生的声软化效应，可以有效提高铝合金板材的塑性成形能力，实现激光冲击对高强度铝合金板材的宏观塑性成形；同时，超声效应有效增强了激光冲击在基体材料内部诱导产生动态再结晶的能力，对等离子冲击波在基体材料内部产生的应力也具有有效的调控，因此，可进一步增强激光冲击对材料产生的力学增益；此外，超声冲击产生的高频振动与激光冲击产生的超高应变率的耦合作用机制能够有效的减少激光冲击成形工件的表面缺陷，铝合金板材在实现宏观塑形成形的同时表面质量也得到了提高。
本发明是通过以下技术手段实现上述技术目的的。
一种超声辅助铝合金板材激光冲击成形方法，包括如下步骤：
根据板材弯曲成形要求将铝合金板材表面分为内凹表面和外凸表面；
利用脉冲激光束冲击所述内凹表面，且在激光冲击的对应位置上的外凸表面处辅助施加超声冲击波；
按照行进路径同步移动脉冲激光束和超声冲击波，得到具有弯曲曲率的铝合金板材。
进一步，还包括如下步骤：对铝合金板材表面进行预处理，使表面粗糙度值≤5μm。
进一步，所述铝合金板材表面进行预处理，具体为：通过不同粒径的砂纸对板材表面进行打磨后抛光，并使用无水乙醇溶液对处理后表面进行超声清洗并烘干。
进一步，所述内凹表面上涂覆吸收层和约束层，所述吸收层厚度为40～60μm，所述流水约束层厚度约为2mm。
进一步，在行进路径中，所述脉冲激光束保持垂直作用于内凹表面，且超声冲击波保持垂直作用于外凸表面。
进一步，所述脉冲激光束通过纳秒脉冲激光器产生，所述脉冲激光束的光斑直径为3～10mm，所述脉冲激光束的脉冲频率为1～10Hz，所述脉冲激光束的脉冲宽度为10～20ns，所述脉冲激光束的脉冲能量为3～20J，所述脉冲激光束的光斑搭接率为20％～80％。
进一步，所述超声冲击波通过超声波发生器产生，所述超声冲击波的振动频率20～40kHz；所述超声波发生器的超声冲击头撞针振幅范围20～100μm，撞针直径范围3～10mm。
一种超声辅助铝合金板材激光冲击成形方法的系统，包括超声波发生器、脉冲激光器和控制器；所述超声波发生器用于产生超声冲击波，所述脉冲激光器用于产生脉冲激光束；
所述脉冲激光束作用在铝合金板材的内凹表面，且超声冲击波作用在激光冲击的对应位置上的铝合金板材的外凸表面处；
所述控制器控制超声冲击波和脉冲激光束同步移动。
本发明的有益效果在于：
1.本发明所述的超声辅助铝合金板材激光冲击成形方法，采用超声冲击产生的高频振动能大幅降低了冲击作用区材料的流动应力与变形阻力，使材料具有良好的塑性变形能力，提高了激光冲击铝合金板材的成形极限；同时，超声冲击应力弯曲成形机制能有效减小激光冲击成形所需要的能量，提高了激光冲击成形效率，增大了单一激光冲击塑性成形的板材变形量，扩展了激光冲击在高强度铝合金板材成形领域的应用。
2.本发明所述的超声辅助铝合金板材激光冲击成形方法，超声冲击诱导的高频振动会促进原子点阵出现周期性密集与疏松，促使激光冲击波传播过程中位错胞、位错墙等微观结构快速向低能态转变，使得亚晶界以及大角度晶界形成，动态再结晶能力提高，在基体材料内部诱导产生更加细化的晶粒、更高的位错密度、更大的残余压应力幅值及更深的有益影响层厚度，进而有效增强了激光冲击对材料的强化效果；超声场的加入还可以有效减弱激光冲击在板材表面产生的凹坑深度，提高成形板材表面的精度，同时基体表层和深度方向残余应力分布不匀的问题也得到了有效改善，实现了基体材料内部应力的有益调控，提高了成形铝合金板材的力学性能与使用寿命。
3.本发明所述的超声辅助铝合金板材激光冲击成形方法，利用激光冲击超高应变率与超声冲击高频振动产生的耦合作用，降低位错激活能，减轻位错钉扎作用的影响，使板材成形的应力回弹量减小，提高铝合金板材的成形精度和效率；超声冲击与激光冲击工艺参数精确可控，且所有工艺参数均可在计算机中进行设置，易于实现大规模工业化生产，具有较为广泛的工业应用前景。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，下面描述中的附图是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，显而易见地还可以根据这些附图获得其他的附图。
图1为本发明所述的超声辅助铝合金板材激光冲击成形方法原理图。
图2为本发明实施例一超声辅助铝合金板材激光冲击成形行进路径图。
图3为本发明实施例一铝合金板材实际成形效果图。
图4为本发明各实施例成形铝合金板材轮廓图。
图5为本发明各实施例成形铝合金板材表面硬度图。
图6为本发明各实施例成形铝合金板材表面残余应力图。
图中：
1-脉冲激光束；2-超声冲击波；3-超声冲击头；4-吸收层；5-出水口；6-内凹表面；7-外凸表面。
具体实施方式
下面结合附图以及具体实施例对本发明作进一步的说明，但本发明的保护范围并不限于此。
下面详细描述本发明的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，旨在用于解释本发明，而不能理解为对本发明的限制。
在本发明的描述中，需要理解的是，术语“中心”、“纵向”、“横向”、“长度”、“宽度”、“厚度”、“上”、“下”、“轴向”、“径向”、“竖直”、“水平”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。在本发明的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
在本发明中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本发明中的具体含义。
如图1所示，本发明所述的超声辅助铝合金板材激光冲击成形方法，包括如下步骤：
采用不同粒径的砂纸对铝合金板材表面进行打磨抛光，使表面粗糙度值≤5μm，将处理后的板材表面放置在无水乙醇溶液中进行超声清洗，烘干后备用；
根据板材弯曲成形要求将铝合金板材表面分为内凹表面6和外凸表面7；利用脉冲激光束1冲击所述内凹表面6，且在激光冲击的对应位置上的外凸表面7处辅助施加超声冲击波2； 在内凹表面6涂覆40～60μm黑漆作为吸收层，使用2mm厚的流水作为约束层；
按照行进路径同步移动脉冲激光束1和超声冲击波2，所述脉冲激光束1保持垂直作用于内凹表面6，且超声冲击波2保持垂直作用于外凸表面7，得到具有弯曲曲率的铝合金板材。
本发明所述的超声辅助铝合金板材激光冲击成形方法，是一种高强度铝合金板材的无模成形方法，在激光冲击成形工艺中引入超声冲击辅助铝合金板材成形。超声冲击产生的高频振动能有效减小材料的变形阻力与变形抗力，提高板材的塑性成形能力。在超声辅助下激光冲击工艺制备的成形铝合金材料内部产生了更加有效的晶粒细化与均匀的残余压应力影响层，显著提高了成形工件的力学性能与抗疲劳强度；此外，超声场的加入有效抑制激光冲击在板材表面产生的凹坑深度，提高了成形板材表面的质量，而激光冲击超高应变率与超声冲击高频振动的耦合作用，使得材料的位错激活能降低，位错钉扎作用减弱，板材成形应力回弹量减小，提高了铝合金板材的成形精度和效率。
为使本发明的目的、技术方案和优点更加清楚，下面选取2024航空铝合金板材作为研究对象，结合附图和三个具体实施例对本发明进行详细的描述。
实施例一：
实施例一所述的超声辅助铝合金板材激光冲击成形方法，包括如下具体步骤：
(1)使用不同粒径的砂纸对尺寸为40mm×20mm×1mm的2024航空铝合金板材表面进行打磨抛光，使其表面粗糙度值≤5μm，采用无水乙醇溶液对处理后表面进行超声清洗并烘干；
(2)采用Nd:YAG高重频大能量纳秒脉冲激光器进行激光冲击，激光脉冲能量为6J，光斑直径为3mm，脉冲频率1Hz，脉冲宽度10ns，搭接率为50％，在内凹表面喷涂40μm厚的黑漆为吸收层4，以2mm的流水为约束层；
(3)在航空铝合金板材激光冲击相对位置处同步施加超声冲击，冲击头撞针直径选用3mm，工作频率为20kHz，振幅为20μm，脉冲激光束与超声冲击头始终垂直作用于板材两侧对称位置，运动路径重合，具有同步性，激光冲击与超声冲击的工作行进路径如图2所示；
(4)在超声辅助下对铝合金板材进行激光冲击成形，得到具有弯曲曲率的铝合金板材。
实施例一制备的航空铝合金成形板材实际效果如图3所示，不同激光冲击工艺成形的铝合金板材轮廓曲线如图4所示，在激光冲击塑性成形机制下，成形铝合金板材的最大变形深度仅为1.78mm，而实施例一利用超声辅助激光冲击成形的铝合金板材最大变形深度为2.83mm，相比于单一激光冲击成形铝合金板材最大变形深度提高了约59％。这一结果表明，超声冲击有效软化了基体材料，提高了材料的塑性变形能力，使得激光冲击获得了更大的板材变形量。实施例一成形铝合金板材表面硬度如图5所示，超声辅助激光冲击成形铝合金板 材的表面硬度为189HV，相比未经处理的铝合金板材表面硬度130HV，提高了约45.4％，相比单一激光冲击成形的铝合金板材表面硬度167HV，提高了约13.2％。成形铝合金板材表面残余应力如图6所示，实施例一超声辅助激光冲击成形铝合金板材表面的残余应力为-191MPa，相比未处理铝合金板材的表面残余应力-11MPa，提高了约16倍，相比经过单一激光冲击成形的铝合金板材表面残余应力-166MPa，提高了约15.1％，极大提高了航空铝合金成形构件的使用寿命。
实施例二：
在实施例一的基础上，实施例二中的激光冲击工艺参数设置为：激光脉冲能量为15J，光斑直径为5mm，脉冲频率5Hz，脉冲宽度15ns，搭接率为20％，在激光冲击成形一侧喷涂50μm厚的黑漆为吸收层。
实施例二中超声辅助工艺参数设置为：工作频率为30kHz，振幅为50μm，冲击头撞针直径选用5mm。
实施例二制备的航空铝合金板材变形轮廓曲线如图4所示，从图中可以看出，在上述工艺参数下超声辅助激光冲击成形铝合金板材最大变形深度为3.41mm，相比于实施例一超声辅助激光冲击成形铝合金板材最大变形深度2.83mm，提高了约20.5％。实施例二成形铝合金板材的表面硬度如图5所示，成形后的铝合金板材表面硬度为201HV，相比实施例一制备的成形铝合金板材表面硬度189HV，提高了约6.3％。实施例二制备的成形铝合金板材表面残余应力如图6所示，成形铝合金板材表面残余应力为-207MPa，相比实施例一成形铝合金板材表面残余应力-191MPa，提高了约8.4％。由于实施例二选用了更大的激光冲击与超声辅助工艺参数，相较于实施例一的变形量、表面硬度、残余应力都的得到了有效的提高。
实施例三：
在实施例一的基础上，实施例三中的激光冲击工艺参数设置为：激光脉冲能量为20J，光斑直径为10mm，脉冲频率10Hz，脉冲宽度20ns，搭接率为80％，在激光冲击成形一侧喷涂60μm厚的黑漆为吸收层。
实施例三中超声辅助工艺参数设置为：工作频率为40kHz，振幅为70μm，冲击头撞针直径选用10mm。
实施例三航空铝合金板材变形轮廓曲线如图4所示，从图中可以看出，实施例三超声辅助激光冲击成形铝合金板材最大变形深度为3.79mm，相比于实施例一成形铝合金板材最大变形深度2.83mm，提高了约33.9％，相比于实施例二成形铝合金板材最大变形深度3.41mm，提高了约11.1％。如图5所示，实施例三制备的成形铝合金板材表面硬度为203HV，如图所6示，实施例三制备的成形铝合金板材表面残余应力为-206MPa。实施例三进一步增加了激光冲击与超声辅助的工艺参数，受饱和效应的影响，制备成形试样的表面硬度与残余应力与实 施例二相似，但成形板材的最大变形深度优于实施例一与实施例二，获得了更大塑形变形量。
本发明所述的超声辅助铝合金板材激光冲击成形方法的系统，包括超声波发生器、脉冲激光器和控制器；所述超声波发生器用于产生超声冲击波2，所述脉冲激光器用于产生脉冲激光束1；
所述脉冲激光束1作用在铝合金板材的内凹表面6，且超声冲击波2作用在激光冲击的对应位置上的铝合金板材的外凸表面7处；所述出水口5位于内凹表面6处，用于形成流动的约束层。所述控制器控制超声冲击波2和脉冲激光束1同步移动。
应当理解，虽然本说明书是按照各个实施例描述的，但并非每个实施例仅包含一个独立的技术方案，说明书的这种叙述方式仅仅是为清楚起见，本领域技术人员应当将说明书作为一个整体，各实施例中的技术方案也可以经适当组合，形成本领域技术人员可以理解的其他实施方式。
上文所列出的一系列的详细说明仅仅是针对本发明的可行性实施例的具体说明，它们并非用以限制本发明的保护范围，凡未脱离本发明技艺精神所作的等效实施例或变更均应包含在本发明的保护范围之内。

Claims (8)

  1. 一种超声辅助铝合金板材激光冲击成形方法，其特征在于，包括如下步骤：
    根据板材弯曲成形要求将铝合金板材表面分为内凹表面(6)和外凸表面(7)；
    利用脉冲激光束(1)冲击所述内凹表面(6)，且在激光冲击的对应位置上的外凸表面(7)处辅助施加超声冲击波(2)；
    按照行进路径同步移动脉冲激光束(1)和超声冲击波(2)，得到具有弯曲曲率的铝合金板材。
  2. 根据权利要求1所述的超声辅助铝合金板材激光冲击成形方法，其特征在于，还包括如下步骤：对铝合金板材表面进行预处理，使表面粗糙度值≤5μm。
  3. 根据权利要求2所述的超声辅助铝合金板材激光冲击成形方法，其特征在于，所述铝合金板材表面进行预处理，具体为：通过不同粒径的砂纸对板材表面进行打磨后抛光，并使用无水乙醇溶液对处理后表面进行超声清洗并烘干。
  4. 根据权利要求1所述的超声辅助铝合金板材激光冲击成形方法，其特征在于，所述内凹表面(6)上涂覆吸收层(4)和约束层，所述吸收层(4)厚度为40～60μm，所述流水约束层厚度约为2mm。
  5. 根据权利要求1所述的超声辅助铝合金板材激光冲击成形方法，其特征在于，在行进路径中，所述脉冲激光束(1)保持垂直作用于内凹表面(6)，且超声冲击波(2)保持垂直作用于外凸表面(7)。
  6. 根据权利要求1所述的超声辅助铝合金板材激光冲击成形方法，其特征在于，所述脉冲激光束(1)通过纳秒脉冲激光器产生，所述脉冲激光束(1)的光斑直径为3～10mm，所述脉冲激光束(1)的脉冲频率为1～10Hz，所述脉冲激光束(1)的脉冲宽度为10～20ns，所述脉冲激光束(1)的脉冲能量为3～20J，所述脉冲激光束(1)的光斑搭接率为20％～80％。
  7. 根据权利要求1所述的超声辅助铝合金板材激光冲击成形方法，其特征在于，所述超声冲击波(2)通过超声波发生器产生，所述超声冲击波(2)的振动频率20～40kHz；所述超声波发生器的超声冲击头(3)撞针振幅范围20～100μm，撞针直径范围3～10mm。
  8. 一种根据权利要求1-7任一项所述的超声辅助铝合金板材激光冲击成形方法的系统，其特征在于，包括超声波发生器、脉冲激光器和控制器；所述超声波发生器用于产生超声冲击波(2)，所述脉冲激光器用于产生脉冲激光束(1)；
    所述脉冲激光束(1)作用在铝合金板材的内凹表面(6)，且超声冲击波(2)作用在激光冲击的对应位置上的铝合金板材的外凸表面(7)处；
    所述控制器控制超声冲击波(2)和脉冲激光束(1)同步移动。
PCT/CN2022/114177 2022-06-22 2022-08-23 一种超声辅助铝合金板材激光冲击成形方法及系统 WO2023245850A1 (zh)

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