High-strength high-thermal-conductivity magnesium alloy plate and preparation method thereof

Abstract

A high-strength and high-thermal-conductivity magnesium alloy plate and a preparation method thereof relate to a high-strength and high-thermal-conductivity rolled magnesium alloy and a preparation method thereof.The magnesium alloy comprises the following components by mass percentage: 1.0-7.0% of element Zn, 0.2-2.0% of element Mn and 1.5-7.0% of element X, the element X is one or more than two of yttrium, gadolinium, neodymium or erbium, and the balance is Mg.The high-strength and high-thermal-conductivity magnesium alloy plate is obtained by taking pure Mg ingot, Mg-Zn intermediate alloy, Mg-Mn intermediate alloy and Mg-X intermediate alloy as raw materials, smelting into high-quality cast ingot, and then carrying out homogenization heat treatment and hot rolling deformation.The rolled magnesium alloy prepared by the method has a tensile yield strength of 340-370 MPa, a tensile strength of 360-400 MPa, an elongation of 5-10%, and a room-temperature thermal conductivity of 130-140 W / (m*K), and has excellent mechanical properties and thermal conductivity, and can be used as a structural material of electronic devices such as aerospace, satellite radar antenna, etc.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy properties, and in particular to a high-strength, high-thermal-conductivity rolled magnesium alloy and its preparation method. Background Technology

[0002] Magnesium alloys are the lightest metallic structural materials, possessing high specific stiffness and strength, good hot formability, excellent electromagnetic shielding performance, and high thermal conductivity. They are currently the most promising lightweight metallic structural materials for applications in aerospace, deep space exploration, military defense, transportation, and consumer electronics. Furthermore, critical aerospace equipment contains complex, high-power electronic components, and overheating of these devices frequently leads to malfunctions. Therefore, the structural materials used in these components must not only be lightweight and high-strength but also possess high thermal conductivity. Thus, the manufacturing technology of high-strength, high-thermal-conductivity magnesium alloy materials and their products plays a crucial role in achieving lightweighting of such equipment, improving system operational stability and service life, and has significant application value.

[0003] In high-end aerospace equipment, such as satellite radar antenna backplates, high-strength, high-thermal-conductivity magnesium alloy sheets are required. Currently, commercially available AZ91 rolled sheets have a room-temperature thermal conductivity of 61 W / (m·K) and a tensile strength of 285 MPa, while WE43 rolled sheets have a room-temperature thermal conductivity of 51 W / (m·K) and a tensile strength of 260 MPa. Analysis of the strengthening and toughening mechanisms of magnesium alloys and the key factors affecting their thermal conductivity reveals an inverse relationship between strength and thermal conductivity. Almost all major strengthening mechanisms, such as grain refinement, solid solution strengthening, and dislocation strengthening, tend to reduce thermal conductivity. This is related to the scattering of electrons by atoms in solid solutions and the role of dislocations and grain boundaries as lattice defects. Therefore, there is a bottleneck problem in the synergistic improvement of thermal conductivity and mechanical properties. Currently developed magnesium alloy sheets still struggle to simultaneously meet the application goals of high strength and high thermal conductivity in terms of both thermal conductivity and mechanical properties. Therefore, developing alloying methods, controlling element and phase distribution through heat treatment, and controlling the microstructure, mechanical properties, and thermal conductivity of the alloy through rolling deformation in order to achieve synergistic improvement of both, and preparing high-strength, high-thermal-conductivity rolled magnesium alloy plates is of great significance for aerospace, transportation, and military defense. Summary of the Invention

[0004] This invention addresses the problems of low strength and difficulty in synergistically improving thermal conductivity and mechanical properties in existing magnesium alloys by proposing a high-strength, high-thermal-conductivity magnesium alloy sheet and its preparation method.

[0005] The high-strength, high-thermal-conductivity magnesium alloy sheet of this invention is a Mg-Zn-X-Mn alloy, wherein the Zn element content is 1.0% to 7.0%, the Mn element content is 0.2% to 2.0%, the X element content is 1.5% to 7.0%, Mg is the balance, and the X element is one or more of yttrium, gadolinium, neodymium, and erbium;

[0006] The preparation method of the high-strength, high-thermal-conductivity magnesium alloy sheet of the present invention is carried out according to the following steps:

[0007] 1. Weigh the raw materials according to the mass percentage of each element in the Mg-Zn-X-Mn alloy and perform cleaning pretreatment;

[0008] The raw materials are pure Mg ingots, Mg-Zn master alloys, Mg-X master alloys, and Mg-Mn master alloys;

[0009] The method for pre-treating the raw materials is as follows: sanding with sandpaper to remove surface impurities and oxide scale;

[0010] 2. The raw materials processed in step one are preheated, then melted under a protective atmosphere, cooled to obtain an alloy ingot, and finally the oxide layer on the surface of the alloy ingot is removed and homogenized heat treatment is performed.

[0011] The temperature of the preheating treatment is 290–450°C;

[0012] The protective atmosphere is a mixture of CO2 and SF6, wherein the volume ratio of SF6 in the mixture is 1.5% to 3.5%.

[0013] The smelting process is as follows: first, pure Mg ingots and Mg-Zn master alloys are melted at 690℃~760℃, then Mg-X master alloys and Mg-Mn master alloys are added. After complete melting, the mixture is kept at the temperature for 30 minutes and then stirred. After stirring, the temperature is lowered to 680℃ and allowed to stand for 10~20 minutes. The magnesium alloy melt is then water-cooled under a protective atmosphere to form an alloy ingot.

[0014] The stirring time is 3 to 5 minutes;

[0015] The homogenization treatment is carried out at a temperature of 450–520°C for 2–12 hours.

[0016] 3. Prepare the alloy obtained in step 2 into a billet, roll and deform the billet, and finally air cool it to complete the process.

[0017] The thickness of the blank is 10-30 mm;

[0018] The process before rolling deformation also includes a preheating step for the billet and the rolls; the preheating temperature of the billet is 290-450℃, the preheating temperature of the rolls is 200-350℃, and the preheating time for both is 10-35 minutes.

[0019] The rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 5%, with a cumulative deformation amount of 60-97%; the rolling speed is 0.5-6 m / s; annealing is performed between passes, with the annealing temperature being the same as the preheating temperature of the billet.

[0020] The annealing time between passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3-5 mm, and 5 minutes for billet thickness of less than 3 mm.

[0021] The principles and beneficial effects of this invention are as follows:

[0022] 1. This invention preferentially uses high-strength and high-thermal-conductivity alloying elements. Through smelting, homogenization heat treatment, and rolling deformation processes, a high-strength and high-thermal-conductivity rolled magnesium alloy with excellent mechanical and thermal properties is achieved. By designing the alloy composition so that the main second phase is a thermally conductive W phase (such as Mg3Zn3RE2), and by controlling the alloy microstructure through hot rolling deformation to a bimodal microstructure composed of elongated deformed grains and fine recrystallized grains, and by promoting dynamic precipitation to reduce the solute atom content in the matrix, the bottleneck problem of difficulty in synergistically improving strength and thermal conductivity is overcome. Furthermore, the technology is mature and can be mass-produced, providing technical guidance for the development of high-strength and high-thermal-conductivity magnesium alloy sheets.

[0023] 2. The rolled magnesium alloy prepared by this invention has a tensile yield strength of 340–370 MPa, a tensile strength of 360–400 MPa, an elongation of 5%–10%, and a room temperature thermal conductivity of 130–140 W / (m·K), while also exhibiting excellent mechanical and thermal properties. This invention represents a breakthrough in the preparation technology of high-strength, high-thermal-conductivity rolled magnesium alloy sheets. The resulting sheets meet the mechanical and thermal conductivity requirements of structural components in aerospace, deep space exploration, military defense, transportation, and 3C products, and have broad application prospects.

[0024] 3. In this invention, the added Zn has a solid solubility of up to 6.2 wt.%, resulting in significant solid solution aging strengthening. It exhibits less lattice distortion due to having the same extranuclear electrons as Mg, and can form a unique W-phase intermetallic compound with rare earth atoms, thus having a relatively small negative impact on the thermal conductivity of magnesium alloys. The added Mn element has low solid solubility and a +2 valence, exhibiting a strong dynamic nano-precipitation effect. Rare earth element X has a unique extranuclear electronic structure, resulting in a significant solid solution aging effect and the formation of rare earth textures to improve mechanical properties. The added Zn element forms a W-phase (Mg3Zn3RE2) with Mg and X elements, which is beneficial for solute atom precipitation. Furthermore, the dynamic precipitation of Mn element reduces the solute atom content in the matrix, thereby improving thermal conductivity.

[0025] 4. This invention utilizes homogenization heat treatment at 450-520℃ and hot rolling at 290-450℃ to regulate the microstructure and properties of the Mg-Zn-X-Mn alloy. The multi-pass hot rolling process ensures smooth forming of the alloy sheet. The hot rolling process partially breaks down the W phase and optimizes its distribution, promoting the precipitation of nano-precipitates such as MgZn2, Mg4Zn7, and Mg5Gd, facilitating the reduction of Zn and Gd solute atoms, and introducing high-density dislocations and grain boundaries. Therefore, the rolled Mg-Zn-X-Mn alloy exhibits excellent mechanical and thermal conductivity properties. Attached Figure Description

[0026] Figure 1 Metallographic diagram of the as-cast alloy prepared in Example 1;

[0027] Figure 2 Metallographic diagram of the rolled alloy prepared in Example 1;

[0028] Figure 3 The tensile engineering stress-engineering strain curve of the rolled alloy prepared in Example 1 is shown. Detailed Implementation

[0029] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0030] Specific implementation method one: The high-strength and high thermal conductivity magnesium alloy plate of this implementation method is a Mg-Zn-X-Mn alloy, wherein the Zn element content is 1.0% to 7.0%, the Mn element content is 0.2% to 2.0%, the X element content is 1.5% to 7.0%, Mg is the balance, and the X element is one or more of yttrium, gadolinium, neodymium, and erbium.

[0031] This embodiment has the following beneficial effects:

[0032] 1. This embodiment selects high-strength, high-thermal-conductivity alloying elements, and achieves high-strength, high-thermal-conductivity rolled magnesium alloys with excellent mechanical and thermal properties through smelting, homogenization heat treatment, and rolling deformation processes. By designing the alloy composition so that the main second phase is a thermally conductive W phase (such as Mg3Zn3RE2), and by controlling the alloy microstructure through hot rolling deformation to a bimodal microstructure composed of elongated deformed grains and fine recrystallized grains, and promoting dynamic precipitation to reduce the solute atom content in the matrix, it overcomes the bottleneck problem of difficulty in synergistically improving strength and thermal conductivity. Furthermore, the technology is mature and can be mass-produced, providing technical guidance for the development of high-strength, high-thermal-conductivity magnesium alloy sheets.

[0033] 2. The rolled magnesium alloy prepared in this embodiment has a tensile yield strength of 340–370 MPa, a tensile strength of 360–400 MPa, an elongation of 5%–10%, and a room temperature thermal conductivity of 130–140 W / (m·K). It also exhibits excellent mechanical and thermal properties. This represents a breakthrough in the preparation technology of high-strength, high-thermal-conductivity rolled magnesium alloy sheets. The resulting sheets meet the mechanical and thermal conductivity requirements of structural components in aerospace, deep space exploration, military defense, transportation, and 3C products, and have broad application prospects.

[0034] 3. In this embodiment, the added Zn has a solid solubility of up to 6.2 wt.%, and the solid solution aging strengthening is significant. The lattice distortion caused by the same extranuclear electrons as Mg is small, and it can form a unique W-phase intermetallic compound with rare earth atoms. Therefore, it has a small negative impact on the thermal conductivity of magnesium alloy. The added Mn element has a low solid solubility and a +2 valence, and has a strong dynamic nano-precipitation effect. The rare earth element X has a unique extranuclear electronic structure, and its solid solution aging effect is significant. It can form rare earth texture to improve mechanical properties. The added Zn element forms a W phase (Mg3Zn3RE2) with Mg and X elements, which is conducive to the precipitation of solute atoms. Furthermore, the dynamic precipitation of Mn element reduces the solute atom content in the matrix and improves thermal conductivity.

[0035] 4. In this embodiment, homogenization heat treatment at 450-520℃ and hot rolling at 290-450℃ can control the microstructure and properties of the Mg-Zn-X-Mn alloy. Multi-pass hot rolling ensures smooth forming of the alloy sheet. The hot rolling process partially breaks down the W phase and optimizes the phase distribution, promoting the precipitation of nano-precipitates such as MgZn2, Mg4Zn7, and Mg5Gd, facilitating the reduction of Zn and Gd solute atoms, and introducing high-density dislocations and grain boundaries. Therefore, the rolled Mg-Zn-X-Mn alloy exhibits excellent mechanical and thermal conductivity properties.

[0036] Specific Implementation Method Two: The preparation method of the high-strength, high-thermal-conductivity magnesium alloy sheet in this implementation method is carried out according to the following steps:

[0037] 1. Weigh the raw materials according to the mass percentage of each element in the Mg-Zn-X-Mn alloy and perform cleaning pretreatment;

[0038] 2. The raw materials processed in step one are preheated, then melted under a protective atmosphere, cooled to obtain an alloy ingot, and finally the oxide layer on the surface of the alloy ingot is removed and homogenized heat treatment is performed.

[0039] The smelting process is as follows: first, pure Mg ingots and Mg-Zn master alloys are melted at 690℃~760℃, then Mg-X master alloys and Mg-Mn master alloys are added. After complete melting, the mixture is kept at the temperature for 30 minutes and then stirred. After stirring, the temperature is lowered to 680℃ and allowed to stand for 10~20 minutes. The magnesium alloy melt is then water-cooled under a protective atmosphere to form an alloy ingot.

[0040] The homogenization treatment is carried out at a temperature of 450–520°C for 2–12 hours.

[0041] 3. Prepare the alloy obtained in step 2 into a billet, roll and deform the billet, and finally air cool it to complete the process.

[0042] The process before rolling deformation also includes a preheating step for the billet and the rolls; the preheating temperature of the billet is 290-450℃, the preheating temperature of the rolls is 200-350℃, and the preheating time for both is 10-35 minutes.

[0043] The rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 5%, with a cumulative deformation amount of 60-97%; the rolling speed is 0.5-6 m / s; annealing is performed between passes, with the annealing temperature being the same as the preheating temperature of the billet.

[0044] The annealing time between passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3-5 mm, and 5 minutes for billet thickness of less than 3 mm.

[0045] 1. This embodiment selects high-strength, high-thermal-conductivity alloying elements, and achieves high-strength, high-thermal-conductivity rolled magnesium alloys with excellent mechanical and thermal properties through smelting, homogenization heat treatment, and rolling deformation processes. By designing the alloy composition so that the main second phase is a thermally conductive W phase (such as Mg3Zn3RE2), and by controlling the alloy microstructure through hot rolling deformation to a bimodal microstructure composed of elongated deformed grains and fine recrystallized grains, and promoting dynamic precipitation to reduce the solute atom content in the matrix, it overcomes the bottleneck problem of difficulty in synergistically improving strength and thermal conductivity. Furthermore, the technology is mature and can be mass-produced, providing technical guidance for the development of high-strength, high-thermal-conductivity magnesium alloy sheets.

[0046] 2. The rolled magnesium alloy prepared in this embodiment has a tensile yield strength of 340–370 MPa, a tensile strength of 360–400 MPa, an elongation of 5%–10%, and a room temperature thermal conductivity of 130–140 W / (m·K). It also exhibits excellent mechanical and thermal properties. This represents a breakthrough in the preparation technology of high-strength, high-thermal-conductivity rolled magnesium alloy sheets. The resulting sheets meet the mechanical and thermal conductivity requirements of structural components in aerospace, deep space exploration, military defense, transportation, and 3C products, and have broad application prospects.

[0047] 3. In this embodiment, the added Zn has a solid solubility of up to 6.2 wt.%, and the solid solution aging strengthening is significant. The lattice distortion caused by the same extranuclear electrons as Mg is small, and it can form a unique W-phase intermetallic compound with rare earth atoms. Therefore, it has a small negative impact on the thermal conductivity of magnesium alloy. The added Mn element has a low solid solubility and a +2 valence, and has a strong dynamic nano-precipitation effect. The rare earth element X has a unique extranuclear electronic structure, and its solid solution aging effect is significant. It can form rare earth texture to improve mechanical properties. The added Zn element forms a W phase (Mg3Zn3RE2) with Mg and X elements, which is conducive to the precipitation of solute atoms. Furthermore, the dynamic precipitation of Mn element reduces the solute atom content in the matrix and improves thermal conductivity.

[0048] 4. In this embodiment, homogenization heat treatment at 450-520℃ and hot rolling at 290-450℃ can control the microstructure and properties of the Mg-Zn-X-Mn alloy. Multi-pass hot rolling ensures smooth forming of the alloy sheet. The hot rolling process partially breaks down the W phase and optimizes the phase distribution, promoting the precipitation of nano-precipitates such as MgZn2, Mg4Zn7, and Mg5Gd, facilitating the reduction of Zn and Gd solute atoms, and introducing high-density dislocations and grain boundaries. Therefore, the rolled Mg-Zn-X-Mn alloy exhibits excellent mechanical and thermal conductivity properties.

[0049] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the raw materials mentioned in step one are pure Mg ingots, Mg-Zn master alloys, Mg-X master alloys, and Mg-Mn master alloys.

[0050] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two in that the method for pre-treating the raw materials in Step One is to use sandpaper to polish and remove surface impurities and oxide scale.

[0051] Specific Implementation Method 5: This implementation method differs from Specific Implementation Method 2 in that the temperature of the preheating treatment in step 2 is 290-450℃.

[0052] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Two in that the protective atmosphere gas mentioned in step two is a mixture of CO2 and SF6, and the volume ratio of SF6 in the mixture is 1.5% to 3.5%.

[0053] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Two in that the stirring time in step two is 3 to 5 minutes.

[0054] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Two in that the thickness of the blank in step three is 10-30mm.

[0055] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Two in that: in the Mg-Zn-X-Mn alloy described in Step One, the Zn element content is 1.0% to 7.0%, the Mn element content is 0.2% to 2.0%, the X element content is 1.5% to 7.0%, Mg is the balance, and the X element is one or more of yttrium, gadolinium, neodymium, and erbium.

[0056] Specific Implementation Method 10: This implementation method differs from Specific Implementation Method 2 in that the smelting process described in step 2 is as follows: First, pure Mg ingots and Mg-Zn master alloys are melted at 760℃, then Mg-X master alloys and Mg-Mn master alloys are added. After complete melting, the mixture is kept at the temperature for 30 minutes and then stirred. After stirring, the temperature is lowered to 680℃ and allowed to stand for 15 minutes. The magnesium alloy melt is then water-cooled under a protective atmosphere to form an alloy ingot.

[0057] Example 1

[0058] The preparation method of the high-strength, high-thermal-conductivity magnesium alloy sheet in this embodiment is carried out according to the following steps:

[0059] 1. Weigh the raw materials according to the mass percentage of each element in the Mg-Zn-Gd-Mn alloy and perform cleaning pretreatment;

[0060] In the Mg-Zn-Gd-Mn alloy, the Zn element content is 4.82%, the Mn element content is 0.43%, the Gd element content is 5.56%, and the balance is Mg;

[0061] The raw materials are pure Mg ingots, Mg-30wt.%Zn master alloy, Mg-30wt.%Gd master alloy and Mg-5wt.%Mn master alloy;

[0062] The method for pre-treating the raw materials is as follows: sanding with sandpaper to remove surface impurities and oxide scale;

[0063] 2. The raw materials processed in step one are preheated, then melted under a protective atmosphere, cooled to obtain an alloy ingot, and finally the oxide layer on the surface of the alloy ingot is removed and homogenized heat treatment is performed.

[0064] The temperature of the preheating treatment is 390°C;

[0065] The protective atmosphere is a mixture of CO2 and SF6, wherein the volume percentage of SF6 in the mixture is 2.6%.

[0066] The smelting process is as follows: first, pure Mg ingots and Mg-Zn master alloy are melted at 760℃, then Mg-Gd master alloy and Mg-Mn master alloy are added, and after complete melting, the mixture is kept at the temperature for 30 minutes and then stirred. After stirring, the temperature is lowered to 680℃ and left to stand for 15 minutes. The magnesium alloy melt is then water-cooled under a protective atmosphere to form an alloy ingot.

[0067] The stirring time is 5 minutes;

[0068] The homogenization process was carried out at a temperature of 500°C for 7 hours.

[0069] 3. Prepare the alloy obtained in step 2 into a billet, roll and deform the billet, and finally air cool it to complete the process.

[0070] The thickness of the blank is 10 mm;

[0071] The process before rolling deformation also includes a preheating step for the billet and the rolls; the preheating temperature of the billet is 390°C, the preheating temperature of the rolls is 260°C, and the preheating time for both is 30 minutes.

[0072] The rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 5% each time, with a cumulative deformation amount of 70%; the rolling speed is 2 m / s; annealing is performed between passes, and the annealing temperature is the same as the preheating temperature of the billet.

[0073] The annealing time between passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3-5 mm, and 5 minutes for billet thickness of less than 3 mm.

[0074] The rolled Mg-4.82Zn-5.56Gd-0.43Mn alloy obtained in this embodiment has a yield strength of 341.9 MPa, a tensile strength of 384.8 MPa, an elongation of 6.5%, and a thermal conductivity of 135.6 W / (m·K). The mechanical properties and thermal conductivity are synergistically improved, far exceeding those of commercial magnesium alloys such as AZ series and WE43.

[0075] Figure 1Metallographic image of the as-cast alloy prepared in Example 1; from Figure 1 It can be seen that the microstructure of the as-cast Mg-4.82Zn-5.56Gd-0.43Mn alloy mainly consists of an α-Mg matrix and a semi-continuous network eutectic second phase W-Mg3Zn3Gd2, and the W phase has a lamellar structure. Figure 2 The image shows the metallographic structure of the rolled alloy prepared in Example 1; from Figure 2 It can be seen that after rolling, the semi-continuous network second phase in the alloy is broken into fine particles with an approximate strip-like distribution. The alloy exhibits a bimodal grain structure: composed of coarse strip-shaped deformed grains and fine recrystallized grains, with the recrystallized grain size being approximately 1 μm. Within the coarse deformed grains, there are fine strip-shaped twins undergoing coordinated deformation along the shear direction, which significantly improves the mechanical properties of the alloy. Figure 3 The image shows the tensile stress-strain curve of the rolled alloy prepared in Example 1. The alloy contains roughly equal amounts of Zn and Gd, forming the W phase. Hot rolling further promotes dynamic precipitation, significantly reducing the solute atom content in the Mg matrix and improving the alloy's thermal conductivity. The addition of Mn further promotes dynamic precipitation. In summary, this achieves a synergistic improvement in both the mechanical and thermal properties of the magnesium alloy.

[0076] Example 2:

[0077] The difference between this embodiment and embodiment 1 is that the preheating temperature of the billet before rolling deformation in step three is 420℃ and the time is 30min; the cumulative deformation amount during rolling deformation is 90% and the rolling speed is 2m / min, and the rest is the same as in embodiment 1.

[0078] The rolled Mg-4.82Zn-5.56Gd-0.43Mn alloy obtained in this embodiment has a yield strength of 330.2 MPa, a tensile strength of 371.6 MPa, an elongation of 8.6%, and a thermal conductivity of 137.3 W / (m·K).

[0079] Example 3:

[0080] The difference between this embodiment and Embodiment 2 is that in the Mg-Zn-Gd-Mn alloy, the Zn content is 5.16 wt.%, the Gd content is 5.27 wt.%, the Mn content is 0.38 wt.%, and the balance is Mg. Everything else is the same as in Embodiment 2.

[0081] The extruded Mg-5.16Zn-5.27Gd-0.38Mn alloy prepared in this embodiment has a yield strength of 332.2 MPa, a tensile strength of 373.6 MPa, an elongation of 8.5%, and a thermal conductivity of 136.8 W / (m·K).

[0082] Example 4:

[0083] The difference between this embodiment and Embodiment 3 is that in the Mg-Zn-Gd-Mn alloy, the Zn content is 4.69 wt.%, the Gd content is 4.93 wt.%, the Mn content is 0.45 wt.%, and the balance is Mg. Everything else is the same as in Embodiment 3.

[0084] The rolled Mg-4.69Zn-4.93Gd-0.45Mn alloy prepared in the example has a yield strength of 348.6 MPa, a tensile strength of 392.8 MPa, an elongation of 5.4%, and a thermal conductivity of 132.8 W / (m·K).

[0085] Example 5:

[0086] The difference between this embodiment and Embodiment 4 is that in the Mg-Zn-Gd-Mn alloy, the Zn content is 5.62 wt.%, the Gd content is 5.83 wt.%, the Mn content is 0.50 wt.%, and the balance is Mg. Everything else is the same as in Embodiment 4.

[0087] The rolled Mg-5.62Zn-5.83Gd-0.50Mn alloy prepared in the example has a yield strength of 350.4 MPa, a tensile strength of 398.9 MPa, an elongation of 4.2%, and a thermal conductivity of 130.6 W / (m·K).

Claims

1. A high-strength, high-thermal-conductivity magnesium alloy sheet, characterized in that: The high-strength, high-thermal-conductivity magnesium alloy sheet is a Mg-Zn-X-Mn alloy, wherein the Zn element content is 1.0%~7.0%, the Mn element content is 0.2%-2.0%, the X element content is 1.5%~7.0%, Mg is the balance, and the X element is gadolinium; The preparation method of high-strength, high-thermal-conductivity magnesium alloy sheet is carried out according to the following steps:

1. Weigh the raw materials according to the mass percentage of each element in the Mg-Zn-X-Mn alloy and perform cleaning pretreatment; 2. The raw materials processed in step one are preheated, then melted under a protective atmosphere, cooled to obtain an alloy ingot, and finally the oxide layer on the surface of the alloy ingot is removed and homogenized heat treatment is performed. The smelting process is as follows: first, pure Mg ingots and Mg-Zn master alloys are melted at 690℃~760℃, then Mg-X master alloys and Mg-Mn master alloys are added. After complete melting, the mixture is kept at the temperature for 30 minutes and then stirred. After stirring, the temperature is lowered to 680℃ and allowed to stand for 10~20 minutes. The magnesium alloy melt is then water-cooled under a protective atmosphere to form an alloy ingot. The homogenization process is carried out at a temperature of 450~520℃ for 2~12 hours.

3. Prepare the alloy obtained in step 2 into a billet, roll and deform the billet, and finally air cool it to complete the process. The process before rolling deformation also includes a preheating step for the billet and the rolls; the preheating temperature of the billet is 290~450℃, the preheating temperature of the rolls is 200~350℃, and the preheating time is 10~35min for both. The rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 5%, with a cumulative deformation amount of 60~97%; the rolling speed is 0.5~6m / s; annealing is performed between passes, and the annealing temperature is the same as the preheating temperature of the billet. The annealing time between passes is as follows: 15 minutes for billet thickness greater than 5 mm, 10 minutes for billet thickness of 3-5 mm, and 5 minutes for billet thickness less than 3 mm. The prepared rolled magnesium alloy has a tensile yield strength of 340~370MPa, a tensile strength of 360~400MPa, an elongation of 5%~10%, and a room temperature thermal conductivity of 130~140W / (m·K).

2. The high-strength, high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The raw materials mentioned in step one are pure Mg ingots, Mg-Zn master alloys, Mg-X master alloys, and Mg-Mn master alloys.

3. The high-strength, high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The method for cleaning and pre-treating the raw materials mentioned in step one is to use sandpaper to remove surface impurities and oxide scale.

4. The high-strength, high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The preheating temperature in step two is 290~450℃.

5. The high-strength, high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The protective atmosphere in step two is a mixture of CO2 and SF6, with the volume ratio of SF6 in the mixture being 1.5% to 3.5%.

6. The high-strength, high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The stirring time in step two is 3 to 5 minutes.

7. The high-strength, high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The thickness of the billet prepared from the alloy obtained in step two is 10~30mm.

8. The high-strength, high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The smelting process described in step two is as follows: first, pure Mg ingots and Mg-Zn master alloys are melted at 760℃, then Mg-X master alloys and Mg-Mn master alloys are added. After complete melting, the mixture is kept at the temperature for 30 minutes and then stirred. After stirring, the temperature is lowered to 680℃ and allowed to stand for 15 minutes. The magnesium alloy melt is then water-cooled under a protective atmosphere to form an alloy ingot.

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