Preparation method of homogeneous magnesium alloy with high thermal conductivity
Through vacuum smelting and segmented homogenization treatment combined with multi-directional forging, the problem of difficult to take into account both the thermal conductivity and structural uniformity of magnesium alloys is solved, and the improvement of high thermal conductivity and uniformity is achieved.
Patent Information
- Application Number
- CN202411617236.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-13
- Publication Date
- 2025-02-18
AI Technical Summary
Magnesium alloys are difficult to take into account both high thermal conductivity and radial uniformity, and the prior art cannot simultaneously improve the uniformity of their thermal conductivity and tissue properties.
Magnesium alloys are prepared through a vacuum smelting furnace, and the forging temperature and direction are controlled, dynamic recrystallization is promoted, and grain size and dislocation density are regulated.
The high thermal conductivity and uniformity of the structural properties of magnesium alloys are achieved, which significantly improves its thermal conductivity and slows down the existence of anisotropy.
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Figure CN119464801A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing a magnesium alloy. Background Art
[0002] Magnesium alloys are widely used in aviation, automobile, shipbuilding, electronics and other fields due to their excellent properties such as low density, high specific strength, good corrosion resistance, dimensional stability and formability, and have become one of the most promising light metals in the field of structural applications. However, its shortcomings such as few movable slip systems at room temperature, poor ductility and low absolute strength have greatly limited the application of magnesium alloys. Alloying is one of the common ways to improve the performance of magnesium alloys. Among them, rare earth elements have the advantages of refining grains, weakening textures and improving strength, making them commonly used alloying elements. However, the atomic radius of rare earth elements is quite different from that of magnesium, and the severe deformation of the lattice of the magnesium matrix greatly reduces the thermal conductivity of magnesium alloys. The thermal conductivity of the commonly used rare earth magnesium alloys Mg-Zn-Y and Mg-Zn-Gd alloys is 55W / (m·K) and 40W / (m·K), respectively, which is much lower than the thermal conductivity of pure magnesium 158W / (m·K). To this end, researchers generally improve the mechanical properties of magnesium alloys while improving their thermal conductivity through extrusion, forging and rolling, but the thermal conductivity often shows anisotropy. Summary of the invention
[0003] The present invention aims to solve the technical problem that the high thermal conductivity and isotropic uniformity of magnesium alloys cannot be satisfied at the same time, and to provide a method for preparing a homogeneous high thermal conductivity magnesium alloy.
[0004] The preparation method of the homogeneous high thermal conductivity magnesium alloy of the present invention is carried out according to the following steps:
[0005] 1. Preparation of magnesium alloy by vacuum melting furnace:
[0006] S1. Prepare raw materials according to the weight percentage of each element in the magnesium alloy, wherein the zinc element in the magnesium alloy is 0-6%, the gadolinium element is 0-2%, the yttrium element is 0-2%, and the balance is magnesium; the raw materials are magnesium blocks, zinc particles, Mg-Gd master alloys and Mg-Y master alloys; place the polished magnesium blocks and zinc particles at the bottom of the crucible, and place the Mg-Gd master alloy and the Mg-Y master alloy in the charging bin, the crucible and the charging bin are both located in a vacuum melting furnace, and the furnace door is closed;
[0007] S2, the furnace starts to be evacuated until the pressure inside the furnace is 50Pa~51Pa, and then the furnace starts to be evacuated for the second time until the pressure inside the furnace is 40Pa~41Pa, and then the evacuation is stopped; finally, SF6 gas is filled into the furnace as a protective gas until the pressure inside the furnace is 0.013MPa~0.015MPa;
[0008] S3, heating the smelting furnace to 720℃~730℃, and keeping the temperature for 10min~15min after the magnesium block and zinc particles in the crucible are completely melted, and then heating the smelting furnace to 780℃~790℃, and then pushing the Mg-Gd master alloy and Mg-Y master alloy in the charging bin into the crucible and keeping the temperature for 30min~35min, and then slowly lowering the stirring paddle below the metal liquid level, setting the speed to 250rpm~260rpm, and stirring for 3min~5min; after the stirring is completed, the stirring paddle remains in place, and after keeping the temperature at 780℃~790℃ for 10min~12min, the stirring paddle is removed, and then the temperature of the smelting furnace is reduced to 680℃~690℃ and kept for 1h~1.5h, and a filter iron sheet is installed at the casting port to skim off the slag floating on the molten metal to ensure the cleanliness of the melt;
[0009] S4, preheating the casting mold at 250° C. to 260° C., casting the molten metal obtained in S3 into the preheated casting mold, naturally cooling to room temperature, and taking out the magnesium alloy ingot from the casting mold;
[0010] 2. subjecting the magnesium alloy ingot obtained in step 1 to a stepwise homogenization treatment at 360° C. to 510° C.;
[0011] 3. The magnesium alloy ingot after homogenization treatment is subjected to multi-directional forging. The direction of each forging is vertically downward, and the pressure and holding time of each forging are the same:
[0012] S1. Process the magnesium alloy ingot after homogenization treatment in step 2 into a forging block of standard rectangular sample size, and polish the surface of the forging block with sandpaper until the surface is clean; first, keep the forging block in a muffle furnace at 400℃~410℃ for 50min~55min, and then forge it for the first time at 400℃~410℃, and load the press to 250KN~255KN at a rate of 5KN / s and keep the pressure for 300s~305s; immediately water quench it after forging, and then put it into a muffle furnace at 400℃~41 Keep the forging block in a muffle furnace at 0℃ for 50min~55min, then rotate the forging block counterclockwise or clockwise 90° in the vertical plane, then forge it for the second time at 400℃~410℃, water quench it again after forging, then put it in a muffle furnace at 400℃~410℃ for 50min~55min, then rotate the forging block counterclockwise or clockwise 90° in the vertical plane, then forge it for the third time at 400℃~410℃, and water quench it after taking it out;
[0013] S2. Place the forging block after three forging passes into a muffle furnace and keep it at 300℃~310℃ for 50min~55min, then rotate it 90° counterclockwise or clockwise in the vertical plane, then rotate it 90° counterclockwise or clockwise in the horizontal plane, then place it into a press and forge it for the fourth time at 300℃~310℃, water quench, then keep it at 300℃~310℃ for 50min~55min, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the fifth time at 300℃~310℃, water quench, then keep it at 300℃~310℃ for 50min~55min, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the sixth time at 300℃~310℃, take it out and water quench it;
[0014] S3, the forging block after six forging passes is placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, the forging block after keeping warm is first rotated 90° counterclockwise or clockwise in the vertical plane, then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging for the seventh time at 350℃~355℃, water quenched, placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, then the forging block is rotated 90° counterclockwise or clockwise in the vertical plane, and then forged for the eighth time at 350℃~355℃, water quenched, placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, rotated 90° counterclockwise or clockwise in the vertical plane, and then forged for the ninth time at 350℃~355℃, taken out and water quenched;
[0015] S4. Place the forged block after nine passes of forging in a muffle furnace and keep it at 300℃~310℃ for 50min~55min. After keeping it warm, first rotate the forged block counterclockwise or clockwise 90° in the vertical plane, then rotate it counterclockwise or clockwise 90° in the horizontal plane, then place it in a press and forge it for the tenth time at 300℃~310℃, water quench, then place the forged block in a muffle furnace and keep it at 350℃~355℃ for 50min~55min. After keeping it warm, first rotate the forged block counterclockwise or clockwise in the vertical plane, then rotate it counterclockwise or clockwise in the horizontal plane, then place it in a press and forge it for the tenth time at 300℃~310℃, water quench, then place the forged block in a muffle furnace and keep it at 350℃~355℃ for 50min~55min. Rotate 90°, then rotate 90° counterclockwise or clockwise in the horizontal plane, then put it into the press for the eleventh forging at 350℃~355℃, water quench, then put the forging block into the muffle furnace and keep it at 400℃~410℃ for 50min~55min, the forging block after keeping is first rotated 90° counterclockwise or clockwise in the vertical plane, then rotated 90° counterclockwise or clockwise in the horizontal plane, then put it into the press for the twelfth forging at 400℃~410℃, take it out and water quench it to obtain magnesium alloy. The forging block prepared by this method achieves the synergistic improvement of uniformity of organizational properties and thermal conductivity.
[0016] The present invention uses a vacuum melting furnace to cast the magnesium alloy, thereby avoiding defects such as pores or a large amount of oxides generated due to contact with air during the casting process, and reducing impurities in the magnesium alloy.
[0017] The present invention controls the temperature and accumulated strain in different directions during the forging process through segmented forging, which is beneficial to the dynamic recrystallization process and alleviates the anisotropy of performance.
[0018] The present invention uses temperature-raising forging to promote the growth of dynamic recrystallization grains through accumulated dislocations, consumes a large number of dislocations, reduces the dislocation density inside the alloy, and achieves an improvement in the thermal conductivity of the magnesium alloy.
[0019] The present invention designs a method for preparing a homogeneous high thermal conductivity magnesium alloy, which promotes dynamic recrystallization by controlling the forging temperature and direction of the Mg-Zn-Gd-Y alloy, increases the cumulative strain in different directions, and alleviates the anisotropy thereof. At the same time, the dynamic recrystallization grain size and dislocation density are regulated by combining constant temperature, cooling and heating forging, thereby achieving a significant improvement in thermal conductivity while ensuring the uniformity of the magnesium alloy structure. Therefore, the preparation method of the Mg-Zn-Gd-Y alloy is a solution to achieve high thermal conductivity of the magnesium alloy and mitigate anisotropy. The thermal conductivity of the obtained magnesium alloy forging block is 131.43W / (m·K) in the direction perpendicular to the final forging direction, and is 124.76W / (m·K) in the direction parallel to the final forging direction. It can be seen that the thermal conductivity of the material of the present invention is very small in different directions, and the performance is relatively excellent. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 The process flow chart of multi-directional forging of magnesium alloy ingot in step 3 of experiment 1;
[0021] Figure 2 This is the SEM microstructure of the magnesium alloy finally obtained in Test 1;
[0022] Figure 3 This is a comparison diagram of the thermal conductivity of the magnesium alloy finally obtained in experiment 1 in the direction perpendicular to the final forging direction and parallel to the final forging direction. DETAILED DESCRIPTION
[0023] Specific implementation method 1: This implementation method is a method for preparing a homogeneous high thermal conductivity magnesium alloy, which is specifically carried out according to the following steps:
[0024] 1. Preparation of magnesium alloy by vacuum melting furnace:
[0025] S1. Prepare raw materials according to the weight percentage of each element in the magnesium alloy, wherein the zinc element in the magnesium alloy is 0-6%, the gadolinium element is 0-2%, the yttrium element is 0-2%, and the balance is magnesium; the raw materials are magnesium blocks, zinc particles, Mg-Gd master alloys and Mg-Y master alloys; place the polished magnesium blocks and zinc particles at the bottom of the crucible, and place the Mg-Gd master alloy and the Mg-Y master alloy in the charging bin, the crucible and the charging bin are both located in a vacuum melting furnace, and the furnace door is closed;
[0026] S2, the furnace starts to be evacuated until the pressure inside the furnace is 50Pa~51Pa, and then the furnace starts to be evacuated for the second time until the pressure inside the furnace is 40Pa~41Pa, and then the evacuation is stopped; finally, SF6 gas is filled into the furnace as a protective gas until the pressure inside the furnace is 0.013MPa~0.015MPa;
[0027] S3, heating the smelting furnace to 720℃~730℃, and keeping the temperature for 10min~15min after the magnesium block and zinc particles in the crucible are completely melted, and then heating the smelting furnace to 780℃~790℃, and then pushing the Mg-Gd master alloy and Mg-Y master alloy in the charging bin into the crucible and keeping the temperature for 30min~35min, and then slowly lowering the stirring paddle below the metal liquid level, setting the speed to 250rpm~260rpm, and stirring for 3min~5min; after the stirring is completed, the stirring paddle remains in place, and after keeping the temperature at 780℃~790℃ for 10min~12min, the stirring paddle is removed, and then the temperature of the smelting furnace is reduced to 680℃~690℃ and kept for 1h~1.5h, and a filter iron sheet is installed at the casting port to skim off the slag floating on the molten metal to ensure the cleanliness of the melt;
[0028] S4, preheating the casting mold at 250° C. to 260° C., casting the molten metal obtained in S3 into the preheated casting mold, naturally cooling to room temperature, and taking out the magnesium alloy ingot from the casting mold;
[0029] 2. subjecting the magnesium alloy ingot obtained in step 1 to a stepwise homogenization treatment at 360° C. to 510° C.;
[0030] 3. The magnesium alloy ingot after homogenization treatment is subjected to multi-directional forging. The direction of each forging is vertically downward, and the pressure and holding time of each forging are the same:
[0031] S1. Process the magnesium alloy ingot after homogenization treatment in step 2 into a forging block of standard rectangular sample size, and polish the surface of the forging block with sandpaper until the surface is clean; first, keep the forging block in a muffle furnace at 400℃~410℃ for 50min~55min, and then forge it for the first time at 400℃~410℃, and load the press to 250KN~255KN at a rate of 5KN / s and keep the pressure for 300s~305s; immediately water quench it after forging, and then put it into a muffle furnace at 400℃~41 Keep the forging block in a muffle furnace at 0℃ for 50min~55min, then rotate the forging block counterclockwise or clockwise 90° in the vertical plane, then forge it for the second time at 400℃~410℃, water quench it again after forging, then put it in a muffle furnace at 400℃~410℃ for 50min~55min, then rotate the forging block counterclockwise or clockwise 90° in the vertical plane, then forge it for the third time at 400℃~410℃, and water quench it after taking it out;
[0032] S2. Place the forging block after three forging passes into a muffle furnace and keep it at 300℃~310℃ for 50min~55min, then rotate it 90° counterclockwise or clockwise in the vertical plane, then rotate it 90° counterclockwise or clockwise in the horizontal plane, then place it into a press and forge it for the fourth time at 300℃~310℃, water quench, then keep it at 300℃~310℃ for 50min~55min, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the fifth time at 300℃~310℃, water quench, then keep it at 300℃~310℃ for 50min~55min, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the sixth time at 300℃~310℃, take it out and water quench it;
[0033] S3, the forging block after six forging passes is placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, the forging block after keeping warm is first rotated 90° counterclockwise or clockwise in the vertical plane, then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging for the seventh time at 350℃~355℃, water quenched, placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, then the forging block is rotated 90° counterclockwise or clockwise in the vertical plane, and then forged for the eighth time at 350℃~355℃, water quenched, placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, rotated 90° counterclockwise or clockwise in the vertical plane, and then forged for the ninth time at 350℃~355℃, taken out and water quenched;
[0034] S4. Place the forged block after nine passes of forging in a muffle furnace and keep it at 300℃~310℃ for 50min~55min. After keeping it warm, first rotate the forged block counterclockwise or clockwise 90° in the vertical plane, then rotate it counterclockwise or clockwise 90° in the horizontal plane, then place it in a press and forge it for the tenth time at 300℃~310℃, water quench, then place the forged block in a muffle furnace and keep it at 350℃~355℃ for 50min~55min. After keeping it warm, first rotate the forged block counterclockwise or clockwise in the vertical plane, then rotate it counterclockwise or clockwise in the horizontal plane, then place it in a press and forge it for the tenth time at 300℃~310℃, water quench, then place the forged block in a muffle furnace and keep it at 350℃~355℃ for 50min~55min. The forging block is rotated 90°, and then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging at 350°C-355°C for the eleventh time, water quenched, and then placed in a muffle furnace for insulation at 400°C-410°C for 50min-55min. The forging block after insulation is first rotated 90° counterclockwise or clockwise in the vertical plane, and then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging at 400°C-410°C for the twelfth time, and then taken out for water quenching to obtain a magnesium alloy.
[0035] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that: before step 1, to ensure the vacuum degree during smelting, the furnace wall is wet-wiped once with an industrial dust-free cloth, and then dry-wiped once to ensure that the furnace body is clean, dust-free and free of water stains. The rest is the same as specific implementation method 1.
[0036] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the Mg-Gd master alloy in step 1 is Mg-30Gd. Other aspects are the same as specific implementation method 1 or 2.
[0037] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the Mg-Y master alloy in step 1 is Mg-30Y. The rest is the same as specific embodiments 1 to 3.
[0038] Specific implementation method 5: This implementation method is different from specific implementation method 4 in that the step-by-step homogenization process described in step 2 is divided into three stages, and the specific steps are as follows:
[0039] The first stage is kept at 360°C for 2 hours; the second stage is kept at 430°C for 6 hours; the third stage is kept at 510°C for 16 hours. The rest is the same as the fourth embodiment.
[0040] The present invention is verified by the following tests:
[0041] Experiment 1: This experiment is a method for preparing a homogeneous high thermal conductivity magnesium alloy, which is specifically carried out in the following steps:
[0042] 1. Preparation of magnesium alloy by vacuum melting furnace:
[0043] S1. Prepare raw materials according to the weight percentage of each element in the magnesium alloy, wherein the zinc element is 5%, the gadolinium element is 1%, the yttrium element is 1%, and the balance is magnesium; the raw materials are magnesium blocks, zinc particles, Mg-Gd master alloys and Mg-Y master alloys; the polished magnesium blocks and zinc particles are placed at the bottom of the crucible, and the Mg-Gd master alloys and Mg-Y master alloys are placed in the charging bin, the crucible and the charging bin are both placed in a vacuum melting furnace, and the furnace door is closed; the Mg-Gd master alloy is Mg-30Gd; the Mg-Y master alloy is Mg-30Y;
[0044] S2, the furnace starts to be evacuated until the pressure inside the furnace is 50Pa, and then the furnace starts to be evacuated for the second time until the pressure inside the furnace reaches 40Pa and then stops evacuating; finally, SF6 gas is filled into the furnace as a protective gas until the pressure inside the furnace reaches 0.013MPa;
[0045] S3, heating the smelting furnace to 720°C, and keeping the temperature for 10 minutes after the magnesium block and zinc particles in the crucible are completely melted, and then heating the smelting furnace to 780°C, and then pushing the Mg-Gd master alloy and Mg-Y master alloy in the charging bin into the crucible and keeping the temperature for 30 minutes, and then slowly lowering the stirring paddle below the metal liquid level, setting the speed to 250rpm, and stirring for 3 minutes; after the stirring is completed, the stirring paddle remains in place, and after keeping the temperature at 780°C for 10 minutes, the stirring paddle is removed, and then the temperature of the smelting furnace is lowered to 680°C and kept for 1 hour, and a filter iron sheet is installed at the casting port to skim off the slag floating on the metal liquid to ensure the cleanliness of the melt;
[0046] S4, preheating the casting mold at 250° C., casting the molten metal obtained in S3 into the preheated casting mold, naturally cooling to room temperature, and taking out the magnesium alloy ingot from the casting mold;
[0047] Before step 1, to ensure the vacuum degree during smelting, use industrial dust-free cloth to wet wipe the furnace wall once, and then dry wipe the furnace wall once to ensure that the furnace body is clean, dust-free and free of water stains;
[0048] 2. The magnesium alloy ingot obtained in step 1 is subjected to a stepwise homogenization treatment at 360°C to 510°C, which is divided into three stages. The specific steps are as follows: the first stage is kept at 360°C for 2 hours; the second stage is kept at 430°C for 6 hours; the third stage is kept at 510°C for 16 hours;
[0049] 3. The magnesium alloy ingot after homogenization treatment is subjected to multi-directional forging. The direction of each forging is vertically downward, and the pressure and holding time of each forging are the same. Figure 1 As shown, letters A, B and C represent a surface of the forging block respectively, and the letters representing the two opposite surfaces in each forging block are the same. The arc arrow represents the rotation of the forging block, but does not represent the direction of rotation;
[0050] S1. Process the magnesium alloy ingot after homogenization treatment in step 2 into a forging block (30mm×30mm×60mm) of standard rectangular sample size, and polish the surface of the forging block with sandpaper until the surface is clean; first, keep the forging block in a muffle furnace at 400°C for 50 minutes, and then perform the first forging at 400°C, and load the press to 250KN at a rate of 5KN / s and maintain the pressure for 300s; immediately perform water quenching after forging, and then place it in a muffle furnace at 400°C for 50 minutes, and then rotate the forging block in a vertical plane counterclockwise or clockwise by 90°, and then perform the second forging at 400°C, and then perform water quenching again after forging, and then place it in a muffle furnace at 400°C for 50 minutes, and then rotate the forging block in a vertical plane counterclockwise or clockwise by 90°, and then perform the third forging at 400°C, and then take it out and perform water quenching;
[0051] S2. Place the forging block after three forging passes into a muffle furnace and keep it at 300°C for 50 minutes, then rotate it 90° counterclockwise or clockwise in the vertical plane, then rotate it 90° counterclockwise or clockwise in the horizontal plane, then place it into a press and forge it for the fourth time at 300°C, water quench, then keep it at 300°C for 50 minutes, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the fifth time at 300°C, water quench, then keep it at 300°C for 50 minutes, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the sixth time at 300°C, take it out and water quench it;
[0052] S3, the forging block after six forging passes is placed in a muffle furnace at 350°C and kept warm for 50 minutes, the forging block after keeping warm is first rotated 90° counterclockwise or clockwise in the vertical plane, then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging at 350°C for the seventh time, water quenched, placed in a muffle furnace at 350°C and kept warm for 50 minutes, then the forging block is rotated 90° counterclockwise or clockwise in the vertical plane, and then forged at 350°C for the eighth time, water quenched, placed in a muffle furnace at 350°C and kept warm for 50 minutes, rotated 90° counterclockwise or clockwise in the vertical plane, and then forged at 350°C for the ninth time, and then taken out and water quenched;
[0053] S4. Place the forged block after nine passes of forging in a muffle furnace and keep it at 300°C for 50 minutes. After keeping it warm, first rotate the forged block 90° counterclockwise or clockwise in the vertical plane, then rotate it 90° counterclockwise or clockwise in the horizontal plane, and then place it in a press for the tenth forging at 300°C, water quench, and then place the forged block in a muffle furnace and keep it at 350°C for 50 minutes. After keeping it warm, first rotate the forged block 90° counterclockwise or clockwise in the vertical plane, and then rotate it 90° counterclockwise or clockwise in the horizontal plane. 0°, then rotate 90° counterclockwise or clockwise in the horizontal plane, and then put it into a press for the eleventh forging at 350°C, water quench, and then put the forging block into a muffle furnace and keep it at 400°C for 50 minutes. The forging block after keeping warm is first rotated 90° counterclockwise or clockwise in the vertical plane, and then rotated 90° counterclockwise or clockwise in the horizontal plane, and then put it into a press for the twelfth forging at 400°C, and then take it out and quench it in water to obtain a magnesium alloy.
[0054] Figure 2 This is the SEM microstructure diagram of the magnesium alloy finally obtained in Experiment 1. Figure (a) is perpendicular to the final forging direction, and Figure (b) is parallel to the final forging direction. FD represents the final forging direction, and TD represents the direction perpendicular to the final forging direction. It can be seen from the figure that the structure of the magnesium alloy in the directions perpendicular to and parallel to the terminal is relatively uniform.
[0055] Figure 3 This is a comparison chart of the thermal conductivity of the magnesium alloy obtained in the test 1 in the directions perpendicular to the final forging and parallel to the final forging. It can be seen from the figure that the thermal conductivity of the magnesium alloy in the direction perpendicular to the final forging is 131.43W / (m·K), and the thermal conductivity parallel to the final forging is 124.76W / (m·K). The difference in thermal conductivity in the two directions is very small, and both are relatively excellent.
Claims
1. A method for preparing a homogeneous high thermal conductivity magnesium alloy, characterized in that The preparation method of the homogeneous high thermal conductivity magnesium alloy is carried out according to the following steps:
1. Preparation of magnesium alloy by vacuum melting furnace: S1. Prepare raw materials according to the weight percentage of each element in the magnesium alloy, wherein the zinc element in the magnesium alloy is 0-6%, the gadolinium element is 0-2%, the yttrium element is 0-2%, and the balance is magnesium; the raw materials are magnesium blocks, zinc particles, Mg-Gd master alloys and Mg-Y master alloys; place the polished magnesium blocks and zinc particles at the bottom of the crucible, and place the Mg-Gd master alloy and the Mg-Y master alloy in the charging bin, the crucible and the charging bin are both located in a vacuum melting furnace, and the furnace door is closed; S2, the furnace starts to be evacuated until the pressure inside the furnace is 50Pa~51Pa, and then the furnace starts to be evacuated for the second time until the pressure inside the furnace is 40Pa~41Pa, and then the evacuation is stopped; finally, SF6 gas is filled into the furnace as a protective gas until the pressure inside the furnace is 0.013MPa~0.015MPa; S3, heating the smelting furnace to 720℃~730℃, and keeping the temperature for 10min~15min after the magnesium block and zinc particles in the crucible are completely melted, and then heating the smelting furnace to 780℃~790℃, and then pushing the Mg-Gd master alloy and Mg-Y master alloy in the charging bin into the crucible and keeping the temperature for 30min~35min, and then slowly lowering the stirring paddle below the metal liquid level, setting the speed to 250rpm~260rpm, and stirring for 3min~5min; after the stirring is completed, the stirring paddle remains in place, and after keeping the temperature at 780℃~790℃ for 10min~12min, the stirring paddle is removed, and then the temperature of the smelting furnace is reduced to 680℃~690℃ and kept for 1h~1.5h, and a filter iron sheet is installed at the casting port to skim off the slag floating on the molten metal to ensure the cleanliness of the melt; S4, preheating the casting mold at 250° C. to 260° C., casting the molten metal obtained in S3 into the preheated casting mold, naturally cooling to room temperature, and taking out the magnesium alloy ingot from the casting mold; 2. subjecting the magnesium alloy ingot obtained in step 1 to a stepwise homogenization treatment at 360° C. to 510° C.; 3. The magnesium alloy ingot after homogenization treatment is subjected to multi-directional forging, and the direction of each forging is vertically downward, and the pressure and holding time of each forging are the same: S1. Process the magnesium alloy ingot after homogenization treatment in step 2 into a forging block of standard rectangular sample size, and polish the surface of the forging block with sandpaper until the surface is clean; first, keep the forging block in a muffle furnace at 400℃~410℃ for 50min~55min, and then forge it for the first time at 400℃~410℃, and load the press to 250KN~255KN at a rate of 5KN / s and keep the pressure for 300s~305s; immediately water quench it after forging, and then put it into a muffle furnace at 400℃~41 Keep the forging block in a muffle furnace at 0℃ for 50min~55min, then rotate the forging block counterclockwise or clockwise 90° in the vertical plane, then forge it for the second time at 400℃~410℃, water quench it again after forging, then put it in a muffle furnace at 400℃~410℃ for 50min~55min, then rotate the forging block counterclockwise or clockwise 90° in the vertical plane, then forge it for the third time at 400℃~410℃, and water quench it after taking it out; S2. Place the forging block after three forging passes into a muffle furnace and keep it at 300℃~310℃ for 50min~55min, then rotate it 90° counterclockwise or clockwise in the vertical plane, then rotate it 90° counterclockwise or clockwise in the horizontal plane, then place it into a press and forge it for the fourth time at 300℃~310℃, water quench, then keep it at 300℃~310℃ for 50min~55min, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the fifth time at 300℃~310℃, water quench, then keep it at 300℃~310℃ for 50min~55min, then rotate the forging block 90° counterclockwise or clockwise in the vertical plane, then forge it for the sixth time at 300℃~310℃, take it out and water quench it; S3, the forging block after six forging passes is placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, the forging block after keeping warm is first rotated 90° counterclockwise or clockwise in the vertical plane, then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging for the seventh time at 350℃~355℃, water quenched, placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, then the forging block is rotated 90° counterclockwise or clockwise in the vertical plane, and then forged for the eighth time at 350℃~355℃, water quenched, placed in a muffle furnace at 350℃~355℃ and kept warm for 50min~55min, rotated 90° counterclockwise or clockwise in the vertical plane, and then forged for the ninth time at 350℃~355℃, taken out and water quenched; S4. Place the forged block after nine passes of forging in a muffle furnace and keep it at 300℃~310℃ for 50min~55min. After keeping it warm, first rotate the forged block counterclockwise or clockwise 90° in the vertical plane, then rotate it counterclockwise or clockwise 90° in the horizontal plane, then place it in a press and forge it for the tenth time at 300℃~310℃, water quench, then place the forged block in a muffle furnace and keep it at 350℃~355℃ for 50min~55min. After keeping it warm, first rotate the forged block counterclockwise or clockwise in the vertical plane, then rotate it counterclockwise or clockwise in the horizontal plane, then place it in a press and forge it for the tenth time at 300℃~310℃, water quench, then place the forged block in a muffle furnace and keep it at 350℃~355℃ for 50min~55min. The forging block is rotated 90°, and then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging at 350°C-355°C for the eleventh time, water quenched, and then placed in a muffle furnace for insulation at 400°C-410°C for 50min-55min. The forging block after insulation is first rotated 90° counterclockwise or clockwise in the vertical plane, and then rotated 90° counterclockwise or clockwise in the horizontal plane, and then placed in a press for forging at 400°C-410°C for the twelfth time, and then taken out for water quenching to obtain a magnesium alloy.
2. The method for preparing a homogeneous high thermal conductivity magnesium alloy according to claim 1, characterized in that Before step 1, to ensure the vacuum degree during smelting, use an industrial dust-free cloth to wet wipe the furnace wall once, and then dry wipe the furnace wall once to ensure that the furnace body is clean, dust-free and free of water stains.
3. The method for preparing a homogeneous high thermal conductivity magnesium alloy according to claim 1, characterized in that The Mg-Gd master alloy described in step 1 is Mg-30Gd.
4. The method for preparing a homogeneous high thermal conductivity magnesium alloy according to claim 1, characterized in that The Mg-Y master alloy described in step 1 is Mg-30Y.
5. The method for preparing a homogeneous high thermal conductivity magnesium alloy according to claim 1, characterized in that The stepwise homogenization process described in step 2 is divided into three stages, and the specific steps are as follows: the first stage is kept at 360°C for 2 hours; the second stage is kept at 430°C for 6 hours; and the third stage is kept at 510°C for 16 hours.