A heat treatment method for high-ductility low-yield-strength aluminum alloy and application thereof

Abstract

The application discloses a high-ductility low-yield-strength aluminum alloy heat treatment method and application thereof, and belongs to the technical field of aluminum alloy preparation, and comprises the following steps: primary quenching: heating an aluminum alloy part to a quenching temperature, keeping warm, and then performing water quenching treatment and natural air cooling; primary aging: keeping warm after heating, and thus high-ductility low-yield-strength aluminum alloy is prepared; the heat treatment process is designed through 'high-temperature, short-time solid solution + water quenching + higher temperature, long-time single-stage aging', so that the ductility and energy absorption capacity of the aluminum alloy are maximally improved under the premise of a certain strength, and the yield strength is reduced; the radar mounting rack is changed from a dangerous rigid point to a controllable and efficient energy absorption element, actively participates in a whole vehicle pedestrian protection system in a collision accident, and has great practical application value.

Description

Technical Field

[0001] This application belongs to the field of aluminum alloy preparation technology, and in particular relates to a heat treatment method for aluminum alloys with high elongation and low yield strength and its application. Background Technology

[0002] With the continuous improvement of automotive intelligence, the application of in-vehicle environmental perception sensors is becoming increasingly widespread. These sensors usually need to be securely installed at the front or rear of the vehicle to achieve accurate detection of the surrounding environment. To ensure that the sensors maintain accurate position and stable performance under complex conditions such as vehicle vibration and impact, their mounting brackets are generally made of high-strength and rigid materials, such as die-cast aluminum alloys, and the overall support rigidity is ensured through a robust structural design.

[0003] However, this design philosophy, which emphasizes structural stability, contradicts increasingly stringent vehicle and pedestrian safety regulations and the "human-centered" safety concept. Specifically, radar mounting brackets located in the front bumper or grille area of ​​a vehicle are likely to come into direct contact with the lower limbs of pedestrians or children during a collision. The harder materials and rigid structures used to pursue sensor stability are not easily deformed or absorbed during a collision, which is equivalent to adding a local rigid protrusion "hard point" to the front of the vehicle. This will cause the collision force to be transmitted to the pedestrian's body more directly, hindering the normal energy absorption process of the front structure of the vehicle, which may increase the risk of lower leg fractures, thigh injuries, or more serious injuries to pedestrians.

[0004] Currently, industry research and optimization on vehicle pedestrian protection are mostly focused on the macro level, such as the design of the engine hood, windshield, and bumper system, as well as the design of cushioning materials. For newly added sensor accessories such as radar, how to coordinate their installation structure with the overall vehicle pedestrian protection performance has not received sufficient attention. A common solution is to add an independent energy-absorbing structure around the sensor or adjust its layout, but this may increase design complexity, cost, and space burden, which goes against the current trend of lightweight vehicle development.

[0005] In existing technologies, the treatment of aluminum alloys mostly employs a two-stage solution treatment: first, heating to 410-420 ℃ and holding for 1 hour, then heating to 460-490 ℃ and holding for 1 hour, followed by air cooling to below 300 ℃ and then spray cooling; a two-stage aging treatment: first heating to 150 ℃ and holding for 0.5 hours, then heating to 190-230 ℃ and holding for 1 hour; the tensile strength after heat treatment is greater than 240 MPa, the yield strength is greater than 180 MPa, and the elongation is around 6%; patent CN101724796B discloses a direct quenching heat treatment for aluminum alloy castings, which aims to eliminate the energy consumption associated with reheating to the aging temperature after room temperature quenching, and improve productivity by eliminating the room temperature quenching maintenance; however, its mechanical properties do not meet the requirements of the aforementioned application scenarios, the resulting aluminum alloy has a low elongation, around 4-6%, and a tensile strength of around 350 MPa. The resulting aluminum alloy castings have extremely high hardness, with a strength of around MPa.

[0006] Therefore, starting from the inherent material properties, a new solution is sought: that is, while ensuring that the radar mounting bracket has sufficient structural strength and rigidity under normal use conditions, the hardness and structural mechanical properties of the aluminum alloy are specifically modified so that it can effectively reduce the impact intensity on pedestrians and mitigate the degree of injury when encountering specific high-speed impact conditions such as pedestrian collisions. This is not only necessary to meet regulatory requirements, but also an important direction to improve the overall safety and ethical level of vehicles. Summary of the Invention

[0007] The purpose of this application is to provide a heat treatment method for aluminum alloys with high elongation and low yield strength and its application, so as to solve the technical problem that aluminum alloy parts in the prior art cannot simultaneously meet the requirements of high tensile strength, high elongation and low yield strength.

[0008] To achieve the above objectives, the technical solution adopted in this application is: to provide a heat treatment method for aluminum alloys with high ductility and low yield strength, specifically including the following steps:

[0009] First-stage quenching: The aluminum alloy parts are heated to the quenching temperature, held at that temperature, and then subjected to water quenching followed by natural air cooling; First-stage aging: The parts are heated and held at that temperature to obtain an aluminum alloy with high elongation and low yield strength.

[0010] In one embodiment,

[0011] The components of aluminum alloy parts include Si, Fe, Cu, Mn, Mg, Zn, Ti, and Al.

[0012] In one embodiment,

[0013] The content of Si is 9.0-11.5% by weight, the content of Fe is 0.1-0.25%, the content of Cu is 0.01-0.05%, the content of Mn is 0.4-0.8%, the content of Mg is 0.1-0.6%, the content of Zn is 0.01-0.07%, the content of Ti is 0.1-0.2%, and the balance is Al.

[0014] In one embodiment,

[0015] The quenching temperature is 418-422 ℃.

[0016] In one embodiment,

[0017] The holding time for primary quenching is 2 hours.

[0018] In one embodiment,

[0019] The interval between the completion of the first-stage quenching and the water quenching treatment was 20 seconds, and the water temperature was room temperature.

[0020] In one embodiment,

[0021] The temperature for first-stage aging is 208-212 ℃.

[0022] In one embodiment,

[0023] The heat preservation time for Level 1 aging is 4 hours.

[0024] In one embodiment,

[0025] High elongation and low yield strength aluminum alloys have an elongation greater than 10% and a yield strength of 120-150 MPa.

[0026] This application also provides an application of a high ductility and low yield strength aluminum alloy, wherein the high ductility and low yield strength aluminum alloy obtained by any of the methods in the above embodiments is used to make a radar bracket for use in automobile radar installation.

[0027] This application provides a heat treatment method for high-ductility, low-yield-strength aluminum alloys. This heat treatment process, designed with "high temperature, short-time solution treatment + water quenching + relatively high temperature, long-term single-stage aging," ensures that the aluminum alloy, while maintaining a certain strength, maximizes its ductility and energy absorption capacity, while simultaneously reducing its yield strength. In the first-stage quenching, the temperature of 418-422 ℃ is higher than the solution temperature of the main strengthening phases of the aluminum alloy. Holding at this temperature for 2 hours is sufficient to allow these second phases to completely dissolve into the aluminum matrix, forming a homogeneous α-Al supersaturated solid solution. Rapid cooling inhibits the diffusion of alloying elements and the re-precipitation of second phases, placing the material in a metastable, high-energy state, providing a foundation for subsequent aging treatment. In the first-stage aging treatment, the use of "high temperature, long-time" single-stage aging is key to achieving a combination of high ductility, low yield strength, and high tensile strength: the peak aging time for most high-strength aluminum alloys is typically between 150-180℃. When the aging process is carried out at ℃, a large number of fine, dispersed GP regions or intermediate phases will precipitate. These nanoscale precipitates can effectively hinder dislocation movement, resulting in high yield strength, but they will also significantly reduce the ductility and toughness of the material. Using a relatively high aging temperature will bring about the following changes:

[0028] 1. Larger precipitated phase size: Strong atomic diffusion capability, the driving force for precipitation is more inclined to form a stable phase or over-aged phase with a larger size and relatively sparse distribution, rather than an extremely dense strengthening phase;

[0029] 2. Lower yield strength: Larger precipitates have a weaker "pinning" effect on the movement of dislocations, and dislocations can more easily bypass or cut through these precipitates. This means that the material begins to undergo plastic deformation at lower stress, i.e., lower yield strength.

[0030] 3. High elongation: Larger precipitates and a relatively sparse distribution cause less damage to the material's plasticity. Dislocations have a longer path of freedom, allowing the material to withstand greater plastic deformation before fracture, thus achieving high elongation. High elongation is a direct indicator of the absorption of impact energy.

[0031] By carefully designing heat treatment conditions and sacrificing high yield strength to achieve high ductility, the radar mounting bracket is transformed from a dangerous rigid point into an elastic, controllable, and efficient energy-absorbing element. In a collision accident, it actively participates in the vehicle's pedestrian protection system, thereby significantly reducing the risk of injury to pedestrians without sacrificing the basic function of the radar mounting. This aligns with the concept of "structure-function integration" and has great practical application value. Detailed Implementation

[0032] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, this application will be further described in detail. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0033] Example 1

[0034] A heat treatment method for aluminum alloys with high ductility and low yield strength specifically includes the following steps:

[0035] First-stage quenching treatment: The aluminum alloy parts are placed in a quenching furnace and heated directly to 420 ℃ and held for 2 hours. Then, water quenching treatment is performed immediately within 20 seconds, followed by natural air cooling. Then, first-stage aging treatment is performed: the temperature is raised to 210 ℃ and held for 4 hours to obtain an aluminum alloy with high elongation and low yield strength.

[0036] The aluminum alloy parts, by weight percentage, contain 10.5% Si, 0.2% Fe, 0.025% Cu, 0.6% Mn, 0.3% Mg, 0.035% Zn, 0.15% Ti, with the balance being Al.

[0037] Example 2

[0038] The difference between this embodiment and Embodiment 1 is that, by weight percentage, the aluminum alloy parts contain 9.0% Si, 0.1% Fe, 0.01% Cu, 0.4% Mn, 0.1% Mg, 0.01% Zn, and 0.1% Ti, with the balance being Al. The remaining operations are the same, resulting in an aluminum alloy with high elongation and low yield strength.

[0039] Example 3

[0040] The difference between this embodiment and Embodiment 1 is that, by weight percentage, the aluminum alloy parts contain 11.5% Si, 0.25% Fe, 0.05% Cu, 0.8% Mn, 0.6% Mg, 0.07% Zn, and 0.2% Ti, with the balance being Al. The remaining operations are the same, resulting in an aluminum alloy with high elongation and low yield strength.

[0041] Example 4

[0042] The difference between this embodiment and Embodiment 1 is that the first-stage quenching treatment is performed: the aluminum alloy part is placed in a quenching furnace and heated directly to 418 ℃ and held for 2 hours, and then immediately subjected to water quenching within 20 seconds, followed by natural air cooling; then the first-stage aging treatment is performed: the part is heated to 208 ℃ and held for 4 hours, and the remaining operations are the same, resulting in an aluminum alloy with high elongation and low yield strength.

[0043] Example 5

[0044] The difference between this embodiment and Embodiment 1 is that the first-stage quenching treatment is performed: the aluminum alloy part is placed in a quenching furnace and heated directly to 422 ℃ and held for 2 hours, and then immediately subjected to water quenching within 20 seconds, followed by natural air cooling; then the first-stage aging treatment is performed: the part is heated to 212 ℃ and held for 4 hours, and the remaining operations are the same, to obtain an aluminum alloy with high elongation and low yield strength.

[0045] Example 6

[0046] The high elongation and low yield strength aluminum alloy obtained in Example 1 was used to make a radar bracket for installing radar in automobiles.

[0047] Comparative Example 1

[0048] First-stage quenching treatment: The aluminum alloy parts are placed in a quenching furnace and heated directly to 420 ℃ and held for 2 hours. Then, water quenching treatment is performed immediately within 20 seconds, followed by natural air cooling. Then, first-stage aging treatment is performed: the temperature is raised to 190 ℃ and held for 4 hours to obtain the aluminum alloy.

[0049] The aluminum alloy parts, by weight percentage, contain 10.5% Si, 0.2% Fe, 0.025% Cu, 0.6% Mn, 0.3% Mg, 0.035% Zn, 0.15% Ti, with the balance being Al.

[0050] Comparative Example 2

[0051] The difference between this comparative example and Comparative Example 1 is that the temperature of the first-stage aging treatment is 165 ℃, while the other operations are the same, and an aluminum alloy is obtained.

[0052] Comparative Example 3

[0053] The difference between this comparative example and Comparative Example 1 is that the temperature of the first-stage quenching treatment is 470 ℃ and the temperature of the first-stage aging treatment is 160 ℃. The other operations are the same, and an aluminum alloy is obtained.

[0054] Test case

[0055] The aluminum alloy parts obtained in Example 1 and Comparative Examples 1-3 were made into radar brackets and test bars, and their tensile strength, yield strength and elongation were tested respectively. The results are shown in Table 1.

[0056] Table 1 Mechanical property test data

[0057]

[0058] The high elongation and low yield strength aluminum alloy prepared in this application needs to meet certain standard requirements in order to be suitable for radar installation. The tensile strength needs to reach 180 MPa, the yield strength needs to reach 120-150 MPa, and the elongation needs to reach more than 10%. As can be seen from the test data in Table 1, the mechanical properties of the aluminum alloy can only meet the requirements if the conditions of Example 1 are strictly followed.

[0059] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0060] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A heat treatment method for aluminum alloys with high ductility and low yield strength, characterized in that, Specifically, the following steps are included: First-stage quenching: The aluminum alloy parts are heated to the quenching temperature, held at that temperature, and then subjected to water quenching and natural air cooling; First-stage aging: The parts are heated and held at that temperature to obtain an aluminum alloy with high elongation and low yield strength. The aluminum alloy components, by weight percentage, contain 9.0-11.5% Si, 0.1-0.25% Fe, 0.01-0.05% Cu, 0.4-0.8% Mn, 0.1-0.6% Mg, 0.01-0.07% Zn, 0.1-0.2% Ti, with the balance being Al. The quenching temperature is 418-422 ℃, and the holding time for the first-stage quenching is 2 h; The temperature for first-stage aging is 208-212 ℃; the holding time for first-stage aging is 4 h. The high elongation and low yield strength aluminum alloy has an elongation greater than 10% and a yield strength of 120-150 MPa.

2. The heat treatment method for high ductility and low yield strength aluminum alloy according to claim 1, characterized in that, The interval between the completion of the first-stage quenching and heat preservation and the water quenching treatment is 20 seconds, and the water temperature is room temperature.

3. An application of a high-ductility, low-yield-strength aluminum alloy, characterized in that, The high elongation and low yield strength aluminum alloy obtained by any of the methods in claims 1-2 is used to make a radar bracket for installing radar in automobiles.

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