Heat treatment method of high-strength and high-conductivity magnesium-aluminum alloy

Abstract

The invention relates to the technical field of magnesium-aluminum alloy heat treatment, and discloses a high-strength and high-conductivity magnesium-aluminum alloy heat treatment method which comprises the following steps: step 1, surface cleaning treatment: carrying out surface cleaning treatment on a magnesium-aluminum alloy workpiece to remove oil stains, impurities and an oxide layer on the surface; secondly, preheating treatment is conducted, specifically, the cleaned magnesium-aluminum alloy workpiece is put into a heating furnace, the temperature is slowly increased to 200 DEG C at the temperature increasing speed of 10 DEG C / min, and heat preservation is conducted for 1-2 hours at the temperature; thirdly, the temperature is rapidly increased to the solid solution temperature, and after preheating treatment is completed. Precipitated phase distribution is optimized through two-stage aging treatment, a precipitated phase is preliminarily formed through low-temperature short-time aging, then the precipitated phase is uniformly grown through high-temperature long-time aging, local aggregation is avoided, meanwhile, solution treatment and quenching cooling are optimized, uniform dissolution of solute atoms is ensured, the alloy strength and hardness are improved, and the service life of the alloy is prolonged. And the fatigue resistance and the crack propagation resistance are remarkably improved through uniform precipitated phase distribution.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment of magnesium-aluminum alloys, and in particular to a heat treatment method for high-strength and high-conductivity magnesium-aluminum alloys. Background Art

[0002] Magnesium-aluminum alloys have broad application prospects in aerospace, automobile manufacturing, electronics and other fields due to their excellent properties such as low density, high strength, good electrical conductivity and thermal conductivity. However, in order to further improve their comprehensive performance and meet the needs of high-end applications, the development of high-strength and high-conductivity magnesium-aluminum alloys has become the focus of current research. By optimizing the alloy composition and preparation process, high-strength and high-conductivity magnesium-aluminum alloys can improve their strength and electrical conductivity while maintaining the low density advantage of magnesium alloys, making them show great application potential in the fields of high-performance structural materials and electronic materials. In the production process of magnesium-aluminum alloys, heat treatment is an indispensable key link. By controlling the heating, insulation and cooling processes of the alloy, heat treatment can effectively regulate the microstructure of the alloy, thereby optimizing its mechanical and physical properties. Through solution treatment, the alloying elements can be fully dissolved in the matrix to form a supersaturated solid solution, laying the foundation for subsequent aging treatment. Aging treatment further improves the strength and hardness of the alloy by controlling the formation and distribution of precipitated phases.

[0003] During the heat treatment process of magnesium-aluminum alloys, the uneven distribution of precipitated phases is a significant technical problem. Specifically, the precipitated phases may locally aggregate in certain areas of the alloy, resulting in significant differences in the density of the precipitated phases within the alloy. This uneven distribution will cause the following problems: in areas with higher precipitate density, the strength and hardness of the alloy will increase, but at the same time, stress concentration points will be formed due to the aggregation of precipitated phases, reducing the alloy's fatigue resistance and crack propagation resistance. In areas with lower precipitate density, the strength and hardness of the alloy are relatively insufficient, resulting in instability in the overall mechanical properties.

[0004] In order to solve the above problems, this application proposes a heat treatment method for high-strength and high-conductivity magnesium-aluminum alloy. Summary of the Invention

[0005] The present invention proposes a heat treatment method for high-strength and high-conductivity magnesium-aluminum alloys, which solves the problem in related technologies that the mechanical properties of magnesium-aluminum alloys deteriorate due to uneven distribution of precipitated phases during heat treatment. Specifically, the problem is manifested in the dual contradiction of stress concentration caused by the aggregation of precipitated phases in local areas and insufficient strength in low-density areas, resulting in spatial instability of the overall performance of the material.

[0006] The present invention provides a heat treatment method for a high-strength and high-conductivity magnesium-aluminum alloy, comprising the following steps:

[0007] Step 1: Surface cleaning: Clean the surface of the magnesium-aluminum alloy workpiece to remove oil, impurities and oxide layer on the surface;

[0008] Step 2: Preheating: Place the cleaned magnesium-aluminum alloy workpiece into a heating furnace, slowly heat it to 200°C at a heating rate of 10°C / min, and keep it at this temperature for 1-2 hours;

[0009] Step 3: Rapidly heat the workpiece to the solution temperature: After the preheating treatment is completed, rapidly heat the workpiece to the solution temperature of 400°C at a heating rate of 20°C / min;

[0010] Step 4: Solution heat preservation treatment: keep the alloy at the solution temperature for 10 to 15 hours to allow the solute atoms in the alloy to fully dissolve into the matrix and form a uniform supersaturated solid solution;

[0011] Step 5: Quenching and cooling: After the solution heat preservation is completed, the workpiece is immediately taken out of the heating furnace and quickly placed in the quenching medium for quenching and cooling;

[0012] Step 6: Cold treatment after quenching: Place the quenched workpiece in cold water and continue to cool it to room temperature;

[0013] Step 7: Double-stage aging treatment: Place the quenched workpiece into a heating furnace for double-stage aging treatment;

[0014] Step 8. Slow cooling treatment after aging: After the aging treatment is completed, the workpiece is taken out of the heating furnace and slowly cooled to room temperature.

[0015] As a further optimization solution of the present invention, the surface cleaning process in step 1 specifically includes:

[0016] S1. Soak the magnesium-aluminum alloy workpiece in a chemical cleaning agent for 10 to 30 minutes at a temperature of 40°C to 60°C.

[0017] S2. Use ultrasonic cleaning equipment to perform ultrasonic cleaning on the immersed workpiece, with an ultrasonic frequency of 20kHz-40kHz and a cleaning time of 5 minutes-15 minutes;

[0018] S3. Rinse the workpiece after ultrasonic cleaning with deionized water for 3 minutes to 8 minutes at a water temperature of 20°C to 30°C.

[0019] As a further optimization solution of the present invention, the preheating treatment in step 2 specifically includes:

[0020] S1. Place the cleaned magnesium-aluminum alloy workpiece in the preheating area of the heating furnace so that the distance between the workpiece and the heating element is uniform;

[0021] S2. Slowly increase the temperature of the heating furnace from room temperature to 200°C at a heating rate of 10°C / min. During the heating process, the atmosphere in the furnace is maintained as an inert gas with a gas flow rate of 10 L / min-20 L / min.

[0022] S3. Keep the workpiece at 200℃ for 1-2 hours. During the holding period, regularly monitor the surface temperature of the workpiece to ensure that the difference between the surface temperature of the workpiece and the temperature inside the furnace does not exceed ±5℃.

[0023] As a further optimization solution of the present invention, the rapid heating to the solution temperature in step 3 specifically includes:

[0024] S1. After the preheating treatment is completed, the rapid heating program of the heating furnace is started, and the temperature of the workpiece is raised to the solution temperature of 400°C at a heating rate of 20°C / min;

[0025] S2. During the heating process, the internal temperature of the workpiece is monitored in real time by a thermocouple to ensure that the internal temperature difference of the workpiece does not exceed ±3°C;

[0026] S3. When the workpiece temperature reaches 400°C, maintain this temperature for 10-20 minutes.

[0027] As a further optimization solution of the present invention, the solution heat preservation treatment in step 4 specifically includes:

[0028] S1. Keep the workpiece at a solution temperature of 400°C for 10-15 hours. During the holding period, the furnace atmosphere is kept inert gas with a gas flow rate of 5L / min-15L / min.

[0029] S2. Regularly detect the phase structure inside the workpiece by X-ray diffractometer;

[0030] S3. During the insulation process, record the temperature and insulation time of the workpiece every 2 hours.

[0031] As a further optimization solution of the present invention, the quenching cooling in step 5 specifically includes:

[0032] S1. After the solution treatment and holding is completed, the workpiece is immediately taken out of the heating furnace and placed in a pre-prepared quenching tank;

[0033] S2, the quenching tank is filled with a quenched polyvinyl alcohol aqueous solution with a concentration of 5%-10% and a temperature of 10°C-20°C;

[0034] S3. Completely immerse the workpiece in the polyvinyl alcohol aqueous solution, and allow the workpiece to remain in the polyvinyl alcohol aqueous solution for 10 seconds to 30 seconds.

[0035] As a further optimization solution of the present invention, the cold treatment after quenching in step 6 specifically includes:

[0036] S1. Take the quenched workpiece out of the quenching tank and immediately put it into cold water to continue cooling;

[0037] S2. The cooling water temperature is 5°C-15°C, and the workpiece stays in the cooling water for 3 minutes-8 minutes to cool the workpiece to room temperature;

[0038] S3. During the cooling process, stir the cooling water regularly.

[0039] As a further optimization solution of the present invention, the double-stage aging treatment in step seven specifically includes:

[0040] S1. Place the quenched workpiece into a heating furnace and heat it to the first-stage aging temperature of 150-180°C at a heating rate of 5°C / min;

[0041] S2. Keep the temperature at the first aging temperature for 3 hours to 5 hours. During the holding period, the gas in the furnace is kept as inert gas with a gas flow rate of 3L / min-8L / min;

[0042] S3. After the insulation is completed, the temperature of the workpiece is raised to the second-stage aging temperature of 200°C-230°C at a heating rate of 10°C / min, and is kept at this temperature for 8 hours to 12 hours. During the insulation period, the gas in the furnace is kept as inert gas with a gas flow rate of 3L / min-8L / min.

[0043] As a further optimization solution of the present invention, the slow cooling treatment after aging in step eight specifically includes:

[0044] S1. After the aging treatment is completed, turn off the heating power of the heating furnace, open the furnace door, and allow the workpiece to cool naturally in the furnace;

[0045] S2. During the cooling process, the gas in the furnace is kept as inert gas with a gas flow rate of 2L / min-5L / min;

[0046] S3. When the temperature of the workpiece drops to room temperature, the workpiece is taken out of the heating furnace for subsequent performance testing and processing.

[0047] As a further optimization solution of the present invention, the slow cooling treatment after aging in step eight further includes:

[0048] S1. After the workpiece is slowly cooled to room temperature, the surface of the workpiece is sandblasted. The sandblasting medium is alumina sand with a particle size of 80-120 mesh, the sandblasting pressure is 0.3MPa-0.5MPa, and the sandblasting time is 3 minutes to 8 minutes;

[0049] S2. After sandblasting, use compressed air to blow the workpiece surface to remove the remaining sandblasting medium;

[0050] S3. Surface quality inspection of the workpiece after purging is carried out, and the surface roughness reaches Ra1.6μm-Ra3.2μm.

[0051] The above technical solution of the present invention has the following beneficial technical effects:

[0052] By first aging at a lower temperature for a short time to allow the initial formation of the precipitate phase, and then aging at a higher temperature for a longer time to allow the precipitate phase to further grow and be evenly distributed, this staged aging treatment method avoids excessive aggregation of the precipitate phase in local areas and ensures that the precipitate phase is evenly distributed within the alloy. After the aging treatment is completed, a slow cooling method is adopted to further stabilize the distribution of the precipitate phase and avoid the re-aggregation or deformation of the precipitate phase caused by rapid cooling. This treatment method makes the size and distribution of the precipitate phase within the alloy more uniform, thereby improving the overall performance of the alloy;

[0053] By optimizing the solution treatment and quenching cooling steps, the solute atoms in the alloy are ensured to be fully dissolved and form a uniform supersaturated solid solution. In the subsequent two-stage aging treatment, the precipitates are evenly distributed and of moderate size, thereby improving the strength and hardness of the alloy. Due to the uniform distribution of the precipitates, stress concentration points caused by localized aggregation of the precipitates are avoided. This uniform distribution of the precipitates improves the fatigue resistance and crack propagation resistance of the alloy, significantly extending the service life of the alloy under complex working conditions. Through surface cleaning, preheating and slow cooling steps, the temperature uniformity and structural stability of each part of the alloy during the heat treatment process are ensured, which reduces the difference in mechanical properties between different regions of the alloy and makes the overall mechanical properties more stable.

[0054] By controlling the heating rate and holding time of preheat treatment, solution treatment and aging treatment, unnecessary energy consumption and time waste are reduced. The preheat treatment adopts a slow heating rate of 10℃ / min to avoid thermal stress caused by rapid heating, while shortening the holding time and improving production efficiency. Rapid quenching cooling and cold water cooling treatment are adopted to ensure that the workpiece is cooled to room temperature in a short time, reducing residual thermal stress after quenching. This efficient cooling method not only improves production efficiency, but also reduces the risk of workpiece deformation or cracking due to improper heat treatment. Adding surface sandblasting after slow cooling treatment after aging not only improves the surface quality of the workpiece, but also improves the efficiency of subsequent processing. The surface roughness of the workpiece after sandblasting is moderate, reducing the number of subsequent processing steps and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a schematic flow chart of a heat treatment method for a high-strength and high-conductivity magnesium-aluminum alloy proposed in the present invention. DETAILED DESCRIPTION

[0056] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0057] like Figure 1 As shown, the present invention proposes a heat treatment method for a high-strength and high-conductivity magnesium-aluminum alloy, comprising the following steps:

[0058] Step 1: Surface cleaning: Clean the surface of the magnesium-aluminum alloy workpiece to remove oil, impurities and oxide layer on the surface;

[0059] Step 2: Preheating: Place the cleaned magnesium-aluminum alloy workpiece into a heating furnace, slowly heat it to 200°C at a heating rate of 10°C / min, and keep it at this temperature for 1-2 hours;

[0060] Step 3: Rapidly heat the workpiece to the solution temperature: After the preheating treatment is completed, rapidly heat the workpiece to the solution temperature of 400°C at a heating rate of 20°C / min;

[0061] Step 4: Solution heat preservation treatment: keep the alloy at the solution temperature for 10 to 15 hours to allow the solute atoms in the alloy to fully dissolve into the matrix and form a uniform supersaturated solid solution;

[0062] Step 5: Quenching and cooling: After the solution heat preservation is completed, the workpiece is immediately taken out of the heating furnace and quickly placed in the quenching medium for quenching and cooling;

[0063] Step 6: Cold treatment after quenching: Place the quenched workpiece in cold water and continue to cool it to room temperature;

[0064] Step 7: Double-stage aging treatment: Place the quenched workpiece into a heating furnace for double-stage aging treatment;

[0065] Step 8: Slow cooling after aging: After aging, remove the workpiece from the heating furnace and slowly cool it to room temperature.

[0066] In actual operation, the present invention selects professional industrial cleaning agents for surface cleaning, completely immerses the magnesium-aluminum alloy workpiece in the cleaning agent, and gently shakes the workpiece to ensure the cleaning effect. When processing a batch of small magnesium-aluminum alloy parts, the parts are placed in a cleaning tank filled with cleaning agents. During preheating, a heating furnace of appropriate size is selected, and the workpiece is placed in a position where it is evenly heated in the furnace. The heating device is turned on and the heating rate is set to 10°C / min. After the temperature rises to 200°C, the temperature control system in the furnace is used to maintain the temperature for about 1.5 hours. When the temperature is rapidly raised to the solid solution temperature, the rapid heating function of the heating furnace is started, and the temperature change is closely monitored. When the temperature reaches 400°C, it is ready to enter the solid solution holding stage. During the temperature treatment stage, the solution heat preservation treatment can use heating equipment that can accurately control the temperature and gas, and the heat preservation is about 12 hours. During this period, the temperature stability is ensured by the control system of the equipment. When quenching and cooling, prepare the quenching tank and quenching medium in advance. Once the solution heat preservation is completed, quickly use the clamp to take out the workpiece and put it into the quenching tank. For cold treatment after quenching, prepare a cold water tank, put the quenched workpiece into it, and stir the cold water continuously to speed up the cooling speed until the workpiece reaches room temperature. During the two-stage aging treatment, adjust the heating furnace's heating rate and holding time according to the actual situation, and carry out two-stage aging treatment as required. For slow cooling treatment after aging, turn off the power of the heating furnace, open the furnace door and let the workpiece cool naturally to room temperature in the furnace.

[0067] In this embodiment, the surface cleaning process in step 1 specifically includes:

[0068] S1. Soak the magnesium-aluminum alloy workpiece in a chemical cleaning agent for 10 to 30 minutes at a temperature of 40°C to 60°C.

[0069] S2. Use ultrasonic cleaning equipment to perform ultrasonic cleaning on the immersed workpiece, with an ultrasonic frequency of 20kHz-40kHz and a cleaning time of 5 minutes-15 minutes;

[0070] S3. Rinse the workpiece after ultrasonic cleaning with deionized water for 3 minutes to 8 minutes at a water temperature of 20°C to 30°C.

[0071] Taking the processing of a batch of medium-sized magnesium-aluminum alloy plates as an example, choose a chemical cleaning agent specifically for magnesium-aluminum alloys, mix the cleaning agent into a cleaning liquid according to the proportion, and pour it into the soaking tank. Put the plate into the soaking tank, set the soaking temperature to 50℃, and soak for 20 minutes. After the soaking is completed, transfer the plate to the cleaning tank of the ultrasonic cleaning equipment, adjust the ultrasonic frequency to 30kHz, and clean for 10 minutes. Finally, rinse the plate with deionized water through the spray device for about 7 minutes, keeping the water temperature at 25℃. After rinsing, wipe the moisture on the surface of the plate with a clean towel.

[0072] In this embodiment, the preheating treatment in step 2 specifically includes:

[0073] S1. Place the cleaned magnesium-aluminum alloy workpiece in the preheating area of the heating furnace so that the distance between the workpiece and the heating element is uniform;

[0074] S2. Slowly increase the temperature of the heating furnace from room temperature to 200°C at a heating rate of 10°C / min. During the heating process, the atmosphere in the furnace is maintained as an inert gas with a gas flow rate of 10 L / min-20 L / min.

[0075] S3. Keep the workpiece at 200℃ for 1-2 hours. During the holding period, regularly monitor the surface temperature of the workpiece to ensure that the difference between the surface temperature of the workpiece and the temperature inside the furnace does not exceed ±5℃.

[0076] For example, if you're processing a magnesium-aluminum alloy mechanical part, place the part on a rack in the preheating area of the furnace, ensuring a consistent distance between the part and the heating element. Connect the inert gas supply, start the furnace, set the heating rate, and adjust the inert gas flow rate to 15 L / min. During the heating process, monitor the temperature in real time using a temperature sensor inside the furnace and a thermocouple mounted on the part surface. Once the temperature reaches 200°C, maintain it for 1.5 hours. Record the part surface temperature and the furnace temperature every 15 minutes. If the temperature difference exceeds ±5°C, adjust the heating power promptly.

[0077] In this embodiment, the rapid heating to the solution temperature in step 3 specifically includes:

[0078] S1. After the preheating treatment is completed, the rapid heating program of the heating furnace is started, and the temperature of the workpiece is raised to the solution temperature of 400°C at a heating rate of 20°C / min;

[0079] S2. During the heating process, the internal temperature of the workpiece is monitored in real time by a thermocouple to ensure that the internal temperature difference of the workpiece does not exceed ±3°C;

[0080] S3. When the workpiece temperature reaches 400°C, maintain this temperature for 10-20 minutes.

[0081] In actual production, when the preheating treatment is completed, the rapid heating button of the heating furnace is quickly started to heat the heating furnace at a rate of 20℃ / min. A thermocouple is embedded inside the workpiece, and the temperature changes inside the workpiece are observed in real time through a temperature monitor. If the temperature difference is close to ±3℃, the temperature can be balanced by adjusting the heating power in different areas of the heating furnace. When the temperature reaches 400℃, the timing device is turned on and the temperature is maintained for 15 minutes to prepare for the subsequent solid solution insulation treatment.

[0082] In this embodiment, the solution heat preservation treatment in step 4 specifically includes:

[0083] S1. Keep the workpiece at a solution temperature of 400°C for 10-15 hours. During the holding period, the furnace atmosphere is kept inert gas with a gas flow rate of 5L / min-15L / min.

[0084] S2. Regularly detect the phase structure inside the workpiece by X-ray diffractometer;

[0085] S3. During the insulation process, record the temperature and insulation time of the workpiece every 2 hours.

[0086] For the solution heat preservation treatment of large magnesium-aluminum alloy structural parts, the structural parts are placed in a large heating furnace, inert gas is introduced and the flow rate is adjusted to 10L / min, the temperature is maintained at 400°C, and the heat preservation is carried out for 13 hours. Every 3 hours, different positions of the structural parts are inspected using an X-ray diffractometer to observe the changes in phase structure. At the same time, a special person is arranged to record the temperature and cumulative heat preservation time in the heating furnace every 2 hours to ensure that the solution heat preservation treatment process meets the process requirements.

[0087] In this embodiment, the quenching cooling in step 5 specifically includes:

[0088] S1. After the solution treatment and holding is completed, the workpiece is immediately taken out of the heating furnace and placed in a pre-prepared quenching tank;

[0089] S2, the quenching tank is filled with a quenched polyvinyl alcohol aqueous solution with a concentration of 5%-10% and a temperature of 10°C-20°C;

[0090] S3. Completely immerse the workpiece in the polyvinyl alcohol aqueous solution, and allow the workpiece to remain in the polyvinyl alcohol aqueous solution for 10 seconds to 30 seconds.

[0091] When the solution holding time is over, use a special high-temperature fixture to quickly remove the workpiece from the heating furnace and quickly place it in the quenching tank. The quenching tank is pre-prepared with an 8% polyvinyl alcohol aqueous solution. The solution temperature is controlled at 15°C by a refrigeration device. The workpiece is completely immersed in the solution, the timing is started, and the workpiece is taken out after 20 seconds to complete the quenching cooling process.

[0092] In this embodiment, the cold treatment after quenching in step 6 specifically includes:

[0093] S1. Take the quenched workpiece out of the quenching tank and immediately put it into cold water to continue cooling;

[0094] S2. The cooling water temperature is 5°C-15°C, and the workpiece stays in the cooling water for 3 minutes-8 minutes to cool the workpiece to room temperature;

[0095] S3. During the cooling process, stir the cooling water regularly.

[0096] After taking the workpiece out of the quenching tank, quickly place it in a cooling tank filled with cooling water. The cooling tank is equipped with a refrigeration device and an agitator. The cooling water temperature is controlled at 10°C. Turn on the agitator and set the stirring frequency to 30 revolutions per minute. Let the workpiece stay in the cooling water for about 5 minutes. During this period, the workpiece temperature is continuously monitored until the workpiece cools to room temperature.

[0097] In this embodiment, the double-stage aging treatment in step seven specifically includes:

[0098] S1. Place the quenched workpiece into a heating furnace and heat it to the first-stage aging temperature of 150-180°C at a heating rate of 5°C / min;

[0099] S2. Keep the temperature at the first aging temperature for 3 hours to 5 hours. During the holding period, the gas in the furnace is kept as inert gas with a gas flow rate of 3L / min-8L / min;

[0100] S3. After the insulation is completed, the temperature of the workpiece is raised to the second-stage aging temperature of 200°C-230°C at a heating rate of 10°C / min, and is kept at this temperature for 8 hours to 12 hours. During the insulation period, the gas in the furnace is kept as inert gas with a gas flow rate of 3L / min-8L / min.

[0101] Taking the processing of electronic components of magnesium-aluminum alloy as an example, the components are placed in a small heating furnace, the heating rate is set to 5℃ / min, the temperature is raised to 160℃, inert gas is introduced, the flow rate is adjusted to 5L / min, and the temperature is kept warm for 4 hours. After the insulation is completed, the heating rate is adjusted to 10℃ / min, the temperature is raised to 210℃, inert gas is introduced again, the flow rate is still 5L / min, and the temperature is kept warm for 10 hours to complete the double-stage aging treatment.

[0102] In this embodiment, the slow cooling treatment after aging in step eight specifically includes:

[0103] S1. After the aging treatment is completed, turn off the heating power of the heating furnace, open the furnace door, and allow the workpiece to cool naturally in the furnace;

[0104] S2. During the cooling process, the gas in the furnace is kept as inert gas with a gas flow rate of 2L / min-5L / min;

[0105] S3. When the temperature of the workpiece drops to room temperature, the workpiece is taken out of the heating furnace for subsequent performance testing and processing.

[0106] When the double-stage aging treatment is completed, turn off the power of the heating furnace, slowly open the furnace door, connect the inert gas supply device, and adjust the gas flow to 3L / min. During the cooling process, use an infrared thermometer to measure the workpiece temperature every 30 minutes. When the workpiece temperature drops to room temperature, use tools to carefully remove the workpiece and place it in the designated area, waiting for performance testing and subsequent processing.

[0107] In this embodiment, the slow cooling treatment after aging in step eight further includes:

[0108] S1. After the workpiece is slowly cooled to room temperature, the surface of the workpiece is sandblasted. The sandblasting medium is alumina sand with a particle size of 80-120 mesh, the sandblasting pressure is 0.3MPa-0.5MPa, and the sandblasting time is 3 minutes to 8 minutes;

[0109] S2. After sandblasting, use compressed air to blow the workpiece surface to remove the remaining sandblasting medium;

[0110] S3. Surface quality inspection of the workpiece after purging is carried out, and the surface roughness reaches Ra1.6μm-Ra3.2μm.

[0111] When the workpiece cools to room temperature, it is transferred to the working chamber of the sandblasting equipment. 100-mesh alumina sand is selected as the sandblasting medium, the sandblasting pressure is adjusted to 0.4 MPa, and the sandblasting is performed for 5 minutes. After the sandblasting is completed, the surface of the workpiece is blown all around with a compressed air gun to remove residual sand particles. Finally, the surface of the workpiece is inspected using a surface roughness measuring instrument to ensure that the surface roughness is within the range of Ra1.6μm-Ra3.2μm. If it does not meet the standard, sandblast again or adjust the process according to the situation.

[0112] The specific working principle of the present invention is as follows:

[0113] Use chemical cleaning agent soaking, ultrasonic cleaning and deionized water rinsing to remove oil, impurities and oxide layer on the surface of magnesium-aluminum alloy workpieces to prevent them from affecting the subsequent heat treatment effect, ensure the clean surface of the workpiece, make the heat transfer uniform and the organizational transformation consistent during subsequent treatment, and lay the foundation for improving overall performance. Then slowly heat up to 200℃ at 10℃ / min and keep it warm for 1-2 hours, and maintain an inert gas atmosphere in the furnace. Slow heating can reduce thermal stress and prevent the workpiece from deformation or cracking due to rapid temperature changes. Keeping warm can make the temperature of each part of the workpiece uniform, preparing for the subsequent rapid heating to the solution temperature. The inert gas can prevent the workpiece from being oxidized during the heating process.

[0114] After preheating, the temperature is rapidly raised to 400℃ at a rate of 20℃ / min and maintained at this temperature for 10-20 minutes. Rapid heating can shorten the time to reach the solution temperature, reduce energy consumption and the risk of grain growth. Maintaining it for a certain time can allow all parts of the workpiece to fully reach the solution temperature, ensuring consistent results of subsequent solution treatment. Then, the workpiece is kept at the solution temperature of 400℃ for 10-15 hours in an inert gas atmosphere. This process allows the solute atoms in the alloy to fully dissolve into the matrix, forming a uniform supersaturated solid solution, providing a good organizational foundation for subsequent aging treatment. During the holding period, the phase structure is detected by X-ray diffractometer to monitor the internal organizational changes of the alloy in real time. The temperature and time are recorded every 2 hours to facilitate precise control of the solution process.

[0115] After the solution heat preservation is completed, the workpiece is quickly placed in a quenching tank of 10℃-20℃, 5%-10% concentration of polyvinyl alcohol aqueous solution and kept for 10-30 seconds. Rapid cooling can retain the supersaturated solid solution state at high temperature to room temperature, inhibit the precipitation of solute atoms, form a metastable supersaturated solid solution structure, and create conditions for aging strengthening;

[0116] After quenching, place the workpiece in 5℃-15℃ cold water and continue to cool to room temperature. Stir regularly during cooling. Further cooling can eliminate residual thermal stress after quenching and stabilize the workpiece size and structure. Stirring can make cooling more uniform and prevent uneven structure and performance due to local cooling differences. Then heat it to 150℃-180℃ at 5℃ / min and keep it for 3-5 hours. Then heat it to 200℃-230℃ at 10℃ / min and keep it for 8-12 hours. Maintain an inert gas atmosphere throughout the process. Aging at a lower temperature for a short time promotes the initial formation of the precipitate phase. Aging at a higher temperature for a long time allows the precipitate phase to grow further and be evenly distributed, avoiding local aggregation, thereby improving the strength and hardness of the alloy and enhancing fatigue resistance and crack growth resistance.

[0117] After aging, turn off the power of the heating furnace, open the furnace door to allow the workpiece to cool naturally in the furnace, maintain an inert gas atmosphere, and perform surface sandblasting after cooling to room temperature. Slow cooling can stabilize the distribution of the precipitated phase and prevent the precipitated phase from re-aggregating or deforming due to rapid cooling. Surface sandblasting can improve the surface quality of the workpiece and improve the efficiency of subsequent processing, so that the surface roughness can reach Ra1.6μm-Ra3.2μm to meet different processing requirements.

[0118] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A heat treatment method for high-strength and high-conductivity magnesium-aluminum alloy, characterized in that: The following steps are involved: Step 1: Surface cleaning: Clean the surface of the magnesium-aluminum alloy workpiece to remove oil, impurities and oxide layer on the surface; Step 2: Preheating: Place the cleaned magnesium-aluminum alloy workpiece into a heating furnace, slowly heat it to 200°C at a heating rate of 10°C / min, and keep it at this temperature for 1-2 hours; Step 3: Rapidly heat the workpiece to the solution temperature: After the preheating treatment is completed, rapidly heat the workpiece to the solution temperature of 400°C at a heating rate of 20°C / min; Step 4: Solution heat preservation treatment: keep the alloy at the solution temperature for 10 to 15 hours to allow the solute atoms in the alloy to fully dissolve into the matrix and form a uniform supersaturated solid solution; Step 5: Quenching and cooling: After the solution heat preservation is completed, the workpiece is immediately taken out of the heating furnace and quickly placed in the quenching medium for quenching and cooling; Step 6: Cold treatment after quenching: Place the quenched workpiece in cold water and continue to cool it to room temperature; Step 7: Double-stage aging treatment: Place the quenched workpiece into a heating furnace for double-stage aging treatment; Step 8. Slow cooling treatment after aging: After the aging treatment is completed, the workpiece is taken out of the heating furnace and slowly cooled to room temperature.

2. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 1, characterized in that: The surface cleaning process in step 1 specifically includes: S1. Soak the magnesium-aluminum alloy workpiece in a chemical cleaning agent for 10 to 30 minutes at a temperature of 40°C to 60°C. S2. Use ultrasonic cleaning equipment to perform ultrasonic cleaning on the immersed workpiece, with an ultrasonic frequency of 20kHz-40kHz and a cleaning time of 5 minutes-15 minutes; S3. Rinse the workpiece after ultrasonic cleaning with deionized water for 3 minutes to 8 minutes at a water temperature of 20°C to 30°C.

3. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 2, characterized in that: The preheating treatment in step 2 specifically includes: S1. Place the cleaned magnesium-aluminum alloy workpiece in the preheating area of the heating furnace so that the distance between the workpiece and the heating element is uniform; S2. Slowly increase the temperature of the heating furnace from room temperature to 200°C at a heating rate of 10°C / min. During the heating process, the atmosphere in the furnace is maintained as an inert gas with a gas flow rate of 10 L / min-20 L / min. S3. Keep the workpiece at 200℃ for 1-2 hours. During the holding period, regularly monitor the surface temperature of the workpiece to ensure that the difference between the surface temperature of the workpiece and the temperature inside the furnace does not exceed ±5℃.

4. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 3, characterized in that: The rapid heating to the solution temperature in step 3 specifically includes: S1. After the preheating treatment is completed, the rapid heating program of the heating furnace is started, and the temperature of the workpiece is raised to the solution temperature of 400°C at a heating rate of 20°C / min; S2. During the heating process, the internal temperature of the workpiece is monitored in real time by a thermocouple to ensure that the internal temperature difference of the workpiece does not exceed ±3°C; S3. When the workpiece temperature reaches 400°C, maintain this temperature for 10-20 minutes.

5. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 4, characterized in that: The solution heat preservation treatment in step 4 specifically includes: S1. Keep the workpiece at a solution temperature of 400°C for 10-15 hours. During the holding period, the furnace atmosphere is kept inert gas with a gas flow rate of 5L / min-15L / min. S2. Regularly detect the phase structure inside the workpiece by X-ray diffractometer; S3. During the insulation process, record the temperature and insulation time of the workpiece every 2 hours.

6. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 5, characterized in that: The quenching cooling in step 5 specifically includes: S1. After the solution treatment and holding is completed, the workpiece is immediately taken out of the heating furnace and placed in a pre-prepared quenching tank; S2, the quenching tank is filled with a quenched polyvinyl alcohol aqueous solution with a concentration of 5%-10% and a temperature of 10°C-20°C; S3. Completely immerse the workpiece in the polyvinyl alcohol aqueous solution, and allow the workpiece to remain in the polyvinyl alcohol aqueous solution for 10 seconds to 30 seconds.

7. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 6, characterized in that: The cold treatment after quenching in step 6 specifically includes: S1. Take the quenched workpiece out of the quenching tank and immediately put it into cold water to continue cooling; S2. The cooling water temperature is 5°C-15°C, and the workpiece stays in the cooling water for 3 minutes-8 minutes to cool the workpiece to room temperature; S3. During the cooling process, stir the cooling water regularly.

8. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 7, characterized in that: The double-stage aging treatment in step seven specifically includes: S1. Place the quenched workpiece into a heating furnace and heat it to the first-stage aging temperature of 150-180°C at a heating rate of 5°C / min; S2. Keep the temperature at the first aging temperature for 3 hours to 5 hours. During the holding period, the gas in the furnace is kept as inert gas with a gas flow rate of 3L / min-8L / min; S3. After the insulation is completed, the temperature of the workpiece is raised to the second-stage aging temperature of 200°C-230°C at a heating rate of 10°C / min, and is kept at this temperature for 8 hours to 12 hours. During the insulation period, the gas in the furnace is kept as inert gas with a gas flow rate of 3L / min-8L / min.

9. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 8, characterized in that: The slow cooling treatment after aging in step eight specifically includes: S1. After the aging treatment is completed, turn off the heating power of the heating furnace, open the furnace door, and allow the workpiece to cool naturally in the furnace; S2. During the cooling process, the gas in the furnace is kept as inert gas with a gas flow rate of 2L / min-5L / min; S3. When the temperature of the workpiece drops to room temperature, the workpiece is taken out of the heating furnace for subsequent performance testing and processing.

10. The heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy according to claim 9, characterized in that: The slow cooling treatment after aging in step eight further includes: S1. After the workpiece is slowly cooled to room temperature, the surface of the workpiece is sandblasted. The sandblasting medium is alumina sand with a particle size of 80-120 mesh, the sandblasting pressure is 0.3MPa-0.5MPa, and the sandblasting time is 3 minutes to 8 minutes; S2. After sandblasting, use compressed air to blow the workpiece surface to remove the remaining sandblasting medium; S3. Surface quality inspection of the workpiece after purging is carried out, and the surface roughness reaches Ra1.6μm-Ra3.2μm.

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