A method for reducing residual stress in a dual-stage thermal shock combined aging cryogenic deformation component

Abstract

This invention relates to the field of residual stress control methods for structural components, and particularly to a method for reducing residual stress in cryogenically deformable structural components subjected to two-stage thermal vibration combined aging. The method includes: providing a residual stress reduction device; the method comprising: clamping the cryogenically deformable structural component to the center position of a thermal vibration platform using a pressure plate; pre-aging the cryogenically deformable structural component for 2-6 hours after heating the aging furnace to 157-177°C; raising the aging temperature to 217-257°C and applying vibration using a vibrator for 30-120 minutes at a frequency of 2 / 3-4 / 5 of the resonant frequency, maintaining the platform acceleration at 60-90g at the resonant frequency; and removing the cryogenically deformable structural component and air-cooling it. The above-mentioned method for reducing residual stress in cryogenically deformable structural components subjected to two-stage thermal vibration combined aging can effectively eliminate residual stress without affecting mechanical properties, and its hardness remains high.

Description

Technical Field

[0001] This invention relates to the field of residual stress control methods for components, and more particularly to a method for reducing residual stress in a dual-stage thermal vibration combined aging cryogenic deformation component. Background Technology

[0002] With the continuous development of my country's aerospace and defense industries, aerospace equipment and strategic weapons need to meet the important requirements of precision detection and precision guidance. Among them, aluminum alloy mirrors are the core imaging components of equipment such as airborne optoelectronic pods, missile-borne seekers, and spaceborne cameras. To achieve precise detection, aluminum alloy mirrors need to achieve sub-micron level surface accuracy, which places stringent requirements on the mirror blank for low residual stress.

[0003] By using ultra-low temperature multi-directional strong plastic deformation to form a high-density dislocation network, and suppressing grain coarsening during heat treatment, homogeneous micron-sized fine-grained aluminum mirror blanks can be prepared. However, the introduced high-density, non-uniformly distributed dislocations will lead to complex residual stress distribution, which will cause mirror deformation during subsequent processing / service. Traditional residual stress reduction methods struggle to balance low residual stress with high processing performance requirements in addressing the residual stress caused by ultra-low temperature strong rheological processes. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a method for reducing residual stress in a two-stage thermal shock composite aging cryogenic deformation component that can effectively eliminate residual stress without affecting mechanical properties.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by the present invention is as follows: a method for reducing residual stress in a dual-stage thermal vibration composite aging cryogenic deformation component, comprising: providing a residual stress reduction device, including a resonance platform, wherein the resonance platform is provided with an exciter and an aging furnace, the bottom of the aging furnace is provided with a through hole, the aging furnace is fixedly connected to the resonance platform through a guide column passing through the through hole in the bottom of the furnace, and a gap is reserved between the guide column and the side wall of the through hole; the aging furnace is provided with a thermal vibration platform for placing the cryogenic deformation component, the cryogenic deformation component is clamped onto the thermal vibration platform by a pressure plate, and the thermal vibration platform is fixed on the guide column;

[0006] The method includes:

[0007] The cryogenic deformation component is clamped to the center of the thermal vibration platform using a pressure plate;

[0008] After heating the aging furnace to 157-177℃, pre-aging the ultra-low temperature deformable components for 2-6 hours;

[0009] Increase the aging temperature to 217-257℃, apply vibration using a vibrator, vibrate for 30-120 minutes, vibrate at 2 / 3-4 / 5 of the resonant frequency, and maintain the thermal vibration platform acceleration at 60-90g.

[0010] Remove the ultra-low temperature deformed component and cool it down by air cooling.

[0011] In one embodiment, the vibration frequency is determined by using modal analysis with finite element simulation software, taking into account the geometry of the cryogenic deformation component.

[0012] In one embodiment, when the cryogenic deformation member is clamped to the center position of the thermal vibration platform by a pressure plate, a preload is applied to the cryogenic deformation member, and the preload is greater than 1 / 5 of the yield strength of the cryogenic deformation member.

[0013] In one embodiment, the gap between the guide post and the sidewall of the through hole is 1mm to 2mm.

[0014] In one embodiment, the bottom of the resonant platform is supported by a rubber pad, which is positioned at the resonant node of the platform.

[0015] In one embodiment, the material of the cryogenic deformation component is 6xxx aluminum alloy or 2xxx aluminum alloy.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: This application combines the stress relief stage with the aging heat treatment stage, eliminating the need for a separate residual stress reduction process, thus significantly improving component production efficiency. The cryogenic deformation component of this application is an aluminum alloy component subjected to deep cryogenic deformation at temperatures below -150℃. In conventional stress relief methods, the aging temperature generally does not exceed 200℃, because at this high temperature, the aging process leads to coarsening of the component's microstructure and loss of mechanical properties, resulting in reduced component hardness and strength, and deterioration of processing performance. This application employs a two-stage aging treatment. First, a low-temperature pre-aging process at 157-177℃ induces homogeneous nucleation in the GP region, providing nucleation sites for the precipitation of strengthening phases, effectively suppressing the coarsening of the component's microstructure and loss of mechanical properties in the traditional high-temperature aging process. Based on this, by combining high temperature short-time thermal shock composite aging, dynamic stress is introduced to promote rapid recovery of defects in high dislocation density areas, improve the uniformity of microstructure distribution, and alleviate local stress concentration, thereby significantly reducing the residual stress of the component under ultra-low temperature deformation. Using the residual stress reduction method of this application, the peak residual stress can be reduced to about 27 MPa, and the Vickers hardness of the material remains higher than 109 HV. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the residual stress reduction device of the present invention;

[0018] In the diagram, 1: aging furnace; 2: pressure plate; 3: ultra-low temperature deformation component; 4: thermal vibration platform; 5: guide column; 6: resonance platform; 7: vibrator;

[0019] Figure 2 This is a comparison diagram of dislocation morphology between the two-stage thermal shock composite aging of the present invention and ordinary aging;

[0020] Figure 3 This is a comparison diagram of the residual stress reduction effects of the two-stage thermal shock composite aging of the present invention and the comparative example;

[0021] Figure 4 This is a comparison chart of the Vickers hardness after the two-stage thermal shock composite aging of the present invention and the residual stress reduction of the comparative example. Detailed Implementation

[0022] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0024] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0025] Please combine Figure 1-4 A method for reducing residual stress in a dual-stage thermal vibration composite aging cryogenic deformation component includes a residual stress reduction device comprising a resonance platform 6, on which an exciter 7 and an aging furnace 1 are mounted. The bottom of the aging furnace 1 has a through hole, and the aging furnace 1 is fixedly connected to the resonance platform 6 via a guide post 5 passing through the through hole in the furnace bottom. A gap is reserved between the guide post 5 and the side wall of the through hole. The aging furnace 1 contains a thermal vibration platform 4 for placing the cryogenic deformation component 3. The cryogenic deformation component 3 is clamped onto the thermal vibration platform 4 via a pressure plate 2, and the thermal vibration platform 4 is fixed to the guide post 5.

[0026] The above methods specifically include:

[0027] S1. The cryogenic deformation component 3 is clamped to the center 4 of the thermal vibration platform by the pressure plate 2.

[0028] Specifically, cryogenic deformation component 3 refers to an aluminum alloy component subjected to deep cryogenic deformation at temperatures below -150℃. The material of the cryogenic deformation component is 6xxx or 2xxx aluminum alloy. In conventional stress relief methods, the aging temperature will not exceed 200℃. This is because high-temperature aging leads to coarsening of the strengthening phase, a decrease in density, and the accumulation of coarse phases near grain boundaries, resulting in reduced component hardness and strength, and deterioration of processing performance.

[0029] Preferably, when the cryogenic deformation component is clamped to the center position of the thermal vibration platform by the pressure plate, a preload is applied to the cryogenic deformation component, and the preload is greater than 1 / 5 of the yield strength of the cryogenic deformation component.

[0030] Preferably, the gap between the guide post and the sidewall of the through hole is 1mm to 2mm.

[0031] S2. After heating the aging furnace 1 to 157-177℃, pre-age the ultra-low temperature deformable component for 2-6 hours.

[0032] Preferably, the bottom of the resonance platform is supported by a rubber pad, which is placed at the resonance node of the platform.

[0033] In this application, a first-stage aging treatment is first performed at a low temperature of 157-177℃ followed by long aging (2-6h) to induce homogeneous nucleation in the GP region, providing nucleation sites for the precipitation of the strengthening phase, and effectively suppressing the coarsening of the microstructure and loss of mechanical properties of components in the traditional high-temperature aging process.

[0034] S3. Increase the aging temperature to 217-257℃, apply vibration using exciter 7, the vibration time is 30min~120min, the vibration frequency is 2 / 3~4 / 5 of the resonance frequency, and the acceleration of thermal vibration platform 4 is maintained at 60-90g.

[0035] Building upon S2, this method combines high-temperature short-time (217-257℃, 30-120 min) thermal vibration composite aging to introduce dynamic stress. This promotes rapid recovery of defects in high dislocation density areas, improves the uniformity of microstructure distribution, and alleviates local stress concentration, thereby significantly reducing the residual stress of the component during ultra-low temperature deformation. At the resonant frequency, the component will vibrate violently with extremely large amplitudes, which can damage the component and equipment. To obtain reasonable vibration, the vibration frequency is usually chosen to be lower than the resonant frequency, thus achieving reasonable acceleration, dynamic stress, and amplitude. Therefore, the vibration frequency is selected to be 2 / 3 to 4 / 5 of the resonant frequency.

[0036] S4. Remove the ultra-low temperature deformable component 3 and air-cool it down.

[0037] Preferably, the resonance frequency is determined by using finite element simulation software to perform modal analysis based on the geometry of the cryogenic deformation component 3. Using the residual stress reduction method of this application, the peak residual stress can be reduced to approximately 27 MPa, while the Vickers hardness of the material remains above 109 HV.

[0038] Example 1:

[0039] A method for reducing residual stress in a dual-stage thermal shock combined aging cryogenic deformation component includes the following steps:

[0040] S1: Clamping Components: Clamp the exciter 7 to one end of the resonance platform 6; clamp the cryogenic deformation component 3 to the center of the thermal vibration platform 4 via the pressure plate 2. The cryogenic deformation component 3 is made of 6061 aluminum alloy;

[0041] S2: Pre-aging: Heat the aging furnace 1 to 157°C and pre-age the ultra-low temperature deformable component 3 for 6 hours to avoid coarsening of the precipitated phase during the subsequent thermal shock aging process;

[0042] S3: Thermal vibration aging: Raise the aging temperature to 237℃, apply vibration after reaching the temperature, the vibration time is 120min, the vibration frequency is selected as 2 / 3 of the resonance frequency, and the platform acceleration needs to be maintained at 60g.

[0043] S4: Ultra-low temperature deformable component, air-cooled for cooling.

[0044] By employing low-temperature pre-aging to induce the dispersion of fine GP regions and β′′ phases, nucleation sites are provided for the subsequent formation of strengthening phases. Simultaneously, pre-precipitation reduces matrix supersaturation, thereby inhibiting the growth of precipitated phases during the secondary high-temperature aging stage, improving the strength of the treated component, and ensuring its machinability. Dynamic stress is introduced through coupled vibration; the superposition of cyclic load and residual stress promotes the transformation of local strain concentration areas, allowing for the full release of residual stress in the cryogenic deformation component. The peak stress of the cryogenic deformation component 3 using this method is reduced to 27.1 MPa, and the Vickers hardness is 109.1 HV.

[0045] Comparative Example 1 (Standard Delivery Time)

[0046] A method for reducing residual stress in conventionally aged cryogenic deformation components includes:

[0047] S1: Preheat the aging furnace to 177°C for 1.5 hours until the furnace temperature is uniform and stable.

[0048] S2: Place the ultra-low temperature deformation component for heat preservation for 10 hours. The ultra-low temperature deformation component is made of 6061 aluminum alloy.

[0049] S3: Low-temperature deformable component, cooled to room temperature by air.

[0050] The peak residual stress of the cryogenically deformed component treated with this method decreased only slightly from 66.6 MPa to 60.0 MPa, a very small reduction. While the Vickers hardness was 121.9 HV, which is relatively high, the residual peak stress was still significantly higher than that treated using the method described in this application. Even after conventional aging treatment, high-density dislocations still exist in the matrix of the cryogenically deformed component. These dislocations are difficult to recover at this temperature, and the unevenly distributed high-density dislocations are the main reason for the high residual stress.

[0051] Comparative Example 2 (Aging under hot and cold cycling)

[0052] A method for reducing residual stress in cryogenically deformable components subjected to thermal cycling includes the following steps:

[0053] S1: Preheat the aging furnace to 177°C for 1.5 hours until the furnace temperature is uniform and stable.

[0054] S2: Place the ultra-low temperature deformation component in the container for heat preservation for 1.5 hours. The ultra-low temperature deformation component is made of 6061 aluminum alloy.

[0055] S3: Ultra-low temperature deformable component. The component is rapidly cooled to -196℃ by immersion in liquid nitrogen and then kept at that temperature in liquid nitrogen for 0.5h.

[0056] S4: Repeat steps S1-S3 twice in a loop.

[0057] S5: The component is deformed at ultra-low temperature in liquid nitrogen, left to stand at room temperature, and then heated to room temperature.

[0058] After undergoing thermal cycling aging treatment, the peak residual stress of the cryogenic deformation component only decreased from 66.6 MPa to 59.8 MPa, a relatively small reduction, and the residual peak stress was still much higher than that of the treatment method described in this application. The Vickers hardness was 120.4 HV.

[0059] Comparative Example 3 (Single-level timeliness)

[0060] A method for reducing residual stress in high-temperature single-stage aged cryogenic deformation components includes the following steps:

[0061] S1: Preheat the aging furnace to 237℃ for 1.5 hours until the furnace temperature is uniform and stable.

[0062] S2: Place the ultra-low temperature deformation component in the container for heat preservation for 4 hours. The ultra-low temperature deformation component is made of 6061 aluminum alloy.

[0063] S3: Low-temperature deformable component, cooled to room temperature by air.

[0064] After high-temperature single-stage aging treatment, the peak residual stress of the cryogenic deformation component is 34.9 MPa, which is a large reduction in stress, but it is still lower than the 27.1 MPa of this application. The Vickers hardness of the cryogenic deformation component treated by this method is 92.3 HV, which greatly reduces the hardness of the cryogenic deformation component and affects the material properties and subsequent processing.

[0065] As can be seen from the above embodiments and comparative examples, the residual stress reduction method for low-temperature deformable components using the two-stage thermal shock composite aging method of this application can greatly eliminate the residual stress of low-temperature deformable components while maintaining a relatively high material hardness.

[0066] The above are merely preferred embodiments of the present invention. It should be noted that the present invention is not limited to the above embodiments. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for reducing residual stress in a dual-stage thermal shock composite aging cryogenic deformation component, characterized in that, The application relates to a residual stress relieving device. The device comprises a resonance platform, a vibration exciter and an aging furnace, the furnace bottom of the aging furnace is provided with a through hole, the aging furnace is fixedly connected with the resonance platform through guide columns penetrating through the through hole of the furnace bottom, and a gap is reserved between the guide columns and the side wall of the through hole; the aging furnace is provided with a thermal vibration platform for placing an ultralow-temperature deformed component, the ultralow-temperature deformed component is clamped to the thermal vibration platform through a pressing plate, and the thermal vibration platform is fixed on the guide columns; The ultralow-temperature deformed component is an aluminum alloy component subjected to cryogenic deformation at a temperature below-150 DEG C, The method comprises the following steps: clamping the ultralow-temperature deformed component to the center position of the thermal vibration platform through a pressing plate; preaging the ultralow-temperature deformed component for 2-6 hours after the aging furnace is heated to 157-177 DEG C; increasing the aging temperature to 217-257 DEG C, applying vibration through the vibration exciter, the vibration time is 30 minutes to 120 minutes, the vibration frequency is 2 / 3 to 4 / 5 of the resonance frequency, and the acceleration of the thermal vibration platform is maintained at 60-90g; taking out the ultralow-temperature deformed component and air cooling; the vibration frequency is determined by combining the geometric shape of the ultralow-temperature deformed component and using finite element simulation software to perform modal analysis.

2. The method of claim 1, wherein the method is characterized by: When the ultralow-temperature deformed component is clamped to the center position of the thermal vibration platform through the pressing plate, a pre-tightening force is applied to the ultralow-temperature deformed component, and the pre-tightening force is greater than 1 / 5 of the yield strength of the ultralow-temperature deformed component.

3. The dual-stage thermal-mechanical composite aging ultra-low strain member residual stress reduction method of claim 1, wherein, The gap reserved between the guide columns and the side wall of the through hole is 1mm-2mm.

4. The dual-stage thermal-mechanical composite aging ultra-low strain member residual stress reduction method of claim 1, wherein, The bottom of the resonance platform is supported through rubber pads, and the rubber pads are placed at the resonance node position of the platform.

5. The dual-stage thermal-mechanical composite age-forming ultra-low temperature structural member residual stress reduction method of claim 1, wherein, The material of the ultralow-temperature deformed component is 6xxx aluminum alloy or 2xxx aluminum alloy.

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