A high-strength, high-ductility and high-thermal-conductivity magnesium alloy extrusion and its preparation method

Abstract

A high-strength, high-plasticity, and high-thermal-conductivity magnesium alloy extruded material and its preparation method belong to the technical field of non-ferrous metal materials. The preparation method provided by the present invention adopts medium-temperature pre-deformation to form a solute enrichment zone in the matrix, and then performs low-temperature extrusion forming. In this way, deformation precipitation is promoted, which not only improves the thermal conductivity of the alloy but also greatly enhances its mechanical properties, enabling the preparation of a high-thermal-conductivity extruded material with high strength and high plasticity characteristics. The thermal conductivity of the magnesium alloy extruded material prepared by this method is 140-150 W·m ‑1 ·K ‑1 , the tensile strength is 320-360 MPa, the yield strength is 260-300 MPa, and the elongation is 15%-25%.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-ferrous metal materials, and relates to a magnesium alloy extruded material with high strength, high plasticity and high thermal conductivity and a preparation method thereof. Background Art

[0002] Magnesium alloys, as the lightest metal structural materials at present, have received great attention and have been gradually widely used in civilian and military fields. The thermal conductivity of pure magnesium is 158 W·m -1 ·K -1 , which is second only to pure copper and pure aluminum among metal materials, and its density is lower, only 2 / 3 of that of aluminum and 1 / 5 of that of copper. It can achieve lightweight in some fields with special requirements for both mechanical properties and heat dissipation performance, such as 3C electronic products, automobile engine casings, and some high-power LED radiators for tunnels, etc., and has special and broad development advantages.

[0003] Mg-Zn series magnesium alloys have excellent mechanical properties. When Zn element is dissolved into the matrix, while improving the mechanical properties, it will also reduce the electrical and thermal conductivity of the alloy. The addition of Cu element has a significant impact on the microstructure and thermophysical properties. Cu can refine the grain size of magnesium alloys, and with the increase of Cu content, the content of MgZnCu phase in as-cast Mg-Zn-Cu alloys increases. The high electrical conductivity of the MgZnCu network structure and the network formed by the eutectic structure provide favorable heat transfer channels. Therefore, the electrical / thermal conductivity of the alloy will also increase, and the plasticity and age hardening effect will also be improved.

[0004] Studies have shown that low-solubility rare earth elements such as La, Ce, and Nd can form high-temperature resistant second phases. When the alloy is deformed, these second phases can not only pin the grain boundaries, but also promote the occurrence of dynamic recrystallization as heterogeneous nucleation points, refine the grains, and thus improve the mechanical properties of the alloy; at the same time, the addition of low-solubility rare earth elements to the matrix and the content is relatively low, and the influence on the thermal conductivity of the alloy is not obvious.

[0005] Extrusion deformation is a common deformation method in magnesium alloys. After extrusion deformation, the mechanical properties of magnesium alloys will be improved. Due to the high deformation temperature sensitivity of magnesium alloys, higher strength can be obtained when extruded at a lower temperature; at the same time, low-temperature extrusion helps to promote the precipitation of solute atoms in the alloy, further improving the mechanical properties of the alloy. Summary of the Invention

[0006] The purpose of the present invention is to provide a magnesium alloy extruded material with high strength, high plasticity and high thermal conductivity and a preparation method thereof, which is beneficial to expanding the application of magnesium alloys.

[0007] The mechanical properties of magnesium alloys are highly sensitive to the extrusion temperature, and good strength and plasticity can be obtained at low extrusion temperatures. Since there are many defects (dislocations, stacking faults, etc.) in the extruded alloy, the thermal conductivity of the as-cast alloy is usually higher than that of the extruded alloy. Based on previous research, it was found that "deformation-induced precipitation behavior" occurs during the extrusion of this alloy, and the solute Zn atoms in the matrix precipitate to form a precipitate phase, which not only improves the strength of the alloy but also enhances the thermal conductivity. Therefore, the preparation method of the present invention uses medium-temperature pre-deformation to form a solute enrichment region in the matrix, and then performs low-temperature extrusion forming to promote deformation precipitation in this way. This not only improves the thermal conductivity of the alloy but also significantly enhances its mechanical properties, enabling the preparation of high-thermal-conductivity extruded materials with high strength and high plasticity characteristics.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A high-strength, high-plasticity, and high-thermal-conductivity magnesium alloy extruded material, the components of which are calculated by weight percentage, including: Zn 0.5 wt.% - 4 wt.%, Cu 0.2 wt.% - 4 wt.%, RE 0.1 wt.% - 0.8 wt.%, and the balance is Mg and unavoidable impurities;

[0010] Wherein RE is a light rare earth element with low solid solubility, selected from one of La, Ce, Sm, and Nd.

[0011] The thermal conductivity of the high-strength, high-plasticity, and high-thermal-conductivity magnesium alloy extruded material is 140 - 150 W·m -1 ·K -1 .

[0012] The tensile strength of the high-strength, high-plasticity, and high-thermal-conductivity magnesium alloy extruded material is 320 - 360 MPa, the yield strength is 260 - 300 MPa, and the elongation is 15% - 25%.

[0013] A preparation method of a high-strength, high-plasticity, and high-thermal-conductivity magnesium alloy extruded material, comprising the following steps:

[0014] Step 1. Melting and casting: After completely melting the Mg ingot, add Zn blocks and raise the temperature, add Cu blocks to it, keep warm, and then raise the furnace temperature; add the intermediate alloy Mg-RE and continue to keep warm, turn on the gas for refining to obtain a magnesium alloy melt; cast the magnesium alloy melt, and start electromagnetic stirring at the same time as casting until casting is completed to obtain a magnesium alloy ingot.

[0015] Step 2. Extrusion method: Homogenize the magnesium alloy ingot, then remove the surface oxide to obtain a billet; pre-deform the billet, and then perform low-temperature extrusion forming to obtain a magnesium alloy extruded material.

[0016] In step 1, after adding Zn, the temperature is raised to 700 - 710°C; after adding Cu blocks, it is held for 10 - 15 minutes, and then the furnace temperature is raised to 740 - 750°C; after adding the master alloy, it is held for 10 - 15 minutes, and the furnace temperature is controlled at 720 - 730°C; the casting temperature is 710 - 720°C.

[0017] In step 1, the gases introduced are CO₂ and SF₆ protective gases, where the ratio of CO₂ to SF₆ is 40:1, and the flow rate is 5 - 20 ml / min.

[0018] During the electromagnetic stirring process, the electromagnetic frequency is 15 - 30 Hz.

[0019] In step 1, both the melting and casting steps are carried out in a protective gas atmosphere.

[0020] In step 2, the homogenization process includes: holding the magnesium alloy ingot at 380 - 420°C for 10 - 12 hours, and then air-cooling it to room temperature to complete the homogenization process.

[0021] The method for removing surface oxides is turning on a lathe.

[0022] The pre-deformation temperature is 250 - 350°C.

[0023] In step 2, the extrusion process is as follows: holding the pre-deformed ingot blank at 150 - 250°C for 1 - 3 hours, and then extruding it on a vertical extruder. The extrusion speed is 0.5 - 3 mm / s. During hot extrusion, the temperatures of the extrusion cylinder and the die are 170 - 270°C, and the extrusion ratio is (12 - 20):1.

[0024] The present invention has the following innovative features and beneficial effects:

[0025] (1) Currently, most high-strength magnesium alloys rely on the addition of high-solid-solubility elements to form solid-solution strengthening and precipitation strengthening effects. High strength often leads to poor plasticity; at the same time, solid-solution solutes also reduce the thermal conductivity. The alloy extruded material in this application has the characteristics of both high strength, high plasticity, and high thermal conductivity. The thermal conductivity can reach 140 - 150 W·m -1 ·K -1 , approaching the thermal conductivity of pure magnesium (158 W·m -1 ·K -1 ); at the same time, the mechanical properties of this magnesium alloy are excellent, with a tensile strength of 320 - 360 MPa, a yield strength of 260 - 300 MPa, and an elongation of 15% - 25%.

[0026] (2) The high performance of the alloy extruded material prepared by the present invention is obtained not only by alloy design, but also the preparation method is different from the prior art. The magnesium alloy used in the present invention forms G.P. zones (solute enrichment zones) at medium temperature, and the alloy has good formability at low temperature, and has the characteristics of deformation precipitation. In view of this characteristic, the present invention adopts a method of first pre-deforming and then extruding to prepare the extruded material. In this way, the precipitation of solutes promotes the reduction of solute atoms in the matrix and the increase of precipitation phases, and can improve the thermal conductivity and mechanical properties at the same time. Description of the Drawings

[0027] Figure 1 It is a scanning micrograph of the as-cast alloy in Example 1.

[0028] Figure 2 It is an EDS spectrum of the as-cast alloy in Example 1.

[0029] Figure 3 It is a TEM photo of the extruded alloy in Example 1.

[0030] Figure 4 It is the stress-strain curve of the extruded alloy in Examples 1-5.

[0031] Figure 5 It is a scanning micrograph of the pre-deformed alloy in Example 6. Detailed Description of the Invention

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the examples and the drawings. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] The technical solutions of the present invention will be described in detail below in conjunction with the examples and the drawings, but the protection scope is not limited thereto.

[0034] Example 1

[0035] (1) Composition Design

[0036] In terms of mass percentage, the elemental composition of the high thermal conductivity magnesium alloy with high strength and high plasticity in this example includes the following components: Zn 2 wt.%, Cu 2 wt.%, Ce 0.4 wt.%, and the balance is Mg and unavoidable impurities.

[0037] (2) Preparation Method

[0038] Put the raw material Mg ingot in a resistance furnace to melt. After the Mg ingot is completely melted, add Zn blocks and raise the temperature. When the temperature reaches 700 °C, add the preheated Cu blocks and keep the temperature for 15 min. Raise the furnace temperature to 750 °C, add the preheated Mg-Ce master alloy, and keep the temperature for 15 min. Control the furnace temperature at 730 °C, turn on the CO2 and SF6 protective gases, and evenly sprinkle the No. 5 solvent for refining. After the refining is completed, start to stand still until the casting temperature (720 °C). Use an electromagnetic semi-continuous casting system to cast the magnesium alloy melt. At the same time as the casting starts, turn on the electromagnetic system to stir the magnesium alloy melt and the ingot electromagnetically. The electromagnetic frequency is 25 Hz until the casting is completed to obtain a magnesium alloy ingot.

[0039] All the above melting processes involving contact and treatment of the melt are carried out under the protective atmosphere of CO2 and SF6. During the casting process, CO2 and SF6 protective gases are also introduced into the mold.

[0040] Carry out homogenization treatment on the ingot in a heat treatment furnace. The process is 400 °C × 10 h, and then take it out of the furnace and air-cool it to room temperature.

[0041] Turn the surface oxide of the homogenized magnesium alloy ingot by turning, and then carry out pre-deformation (forging). The pre-deformation temperature is 300 °C.

[0042] Carry out low-temperature extrusion deformation on the pre-deformed ingot. The extrusion temperature is 150 °C, the extrusion ratio is 16:1, and the extrusion speed is 0.6 m / s.

[0043] For the alloy described in Example 1, its conductivity is 20.21 Ms / m, thermal conductivity is 141.37 W·m -1 ·K -1 , the tensile strength is 341 MPa, the yield strength is 292 MPa, and the elongation is 21.2%. Its stress-strain curve is as Figure 4 shown.

[0044] The SEM microstructure of the as-cast alloy in this example is as Figure 1 shown, and the EDS spectrum is as Figure 2 shown. In the as-cast alloy, there is a continuously network-distributed second phase. After detection, it can be known that this phase is the Ce-rich MgZnCu phase. After the alloy is extruded and deformed, its TEM microstructure is as Figure 3 shown. There are micron-sized recrystallized grains in the alloy, which play a role in fine-grain strengthening, improving the mechanical properties of the alloy. The MgZnCu phase is distributed at the grain boundaries and within the grains, inhibiting the growth of recrystallized grains; at the same time, the MgZnCu phase also provides a favorable channel for heat transfer, improving the thermal conductivity of the alloy.

[0045] Example 2

[0046] (1) Composition design

[0047] In terms of mass percentage, the elemental composition of the high thermal conductivity magnesium alloy with high strength and high plasticity in this example includes the following components: Zn 3 wt.%, Cu 3.5 wt.%, Ce 0.4 wt.%, and the balance is Mg and inevitable impurities.

[0048] (2) Preparation method

[0049] Put the raw material Mg ingot in an electric resistance furnace to melt. After the Mg ingot is completely melted, add Zn blocks and raise the temperature. When the temperature rises to 700 °C, add the preheated Cu blocks and keep warm for 15 min. Raise the furnace temperature to 750 °C, add the preheated Mg-Ce master alloy, and keep warm for 15 min. Control the furnace temperature at 730 °C, turn on the CO2 and SF6 protective gases, evenly sprinkle the No. 5 solvent for refining. After the refining is completed, start to stand still until the casting temperature (720 °C). Use an electromagnetic semi-continuous casting system to cast the magnesium alloy melt. At the same time as the casting starts, turn on the electromagnetic system to perform electromagnetic stirring on the magnesium alloy melt and the ingot. The electromagnetic frequency is 25 Hz until the casting is completed to obtain a magnesium alloy ingot.

[0050] All the above melting processes involving contact and treatment of the melt are carried out under a protective atmosphere of CO2 and SF6. The CO2 and SF6 protective gases are also introduced into the mold during the casting process.

[0051] Perform homogenization treatment on the ingot in a heat treatment furnace. The process is 400 °C × 10 h, and then take it out of the furnace and air-cool to room temperature;

[0052] Turn off the surface oxides of the homogenized magnesium alloy ingot by turning, and then perform pre-deformation (forging). The pre-deformation temperature is 300 °C.

[0053] Perform low-temperature extrusion deformation on the pre-deformed ingot. The extrusion temperature is 150 °C, the extrusion ratio is 16:1, and the extrusion speed is 0.6 m / s;

[0054] For the alloy described in Example 2, its electrical conductivity is 20.75 Ms / m, and its thermal conductivity is 143.28 W·m -1 ·K -1 , the tensile strength is 362 MPa, the yield strength is 313 MPa, and the elongation is 17.3%. Its stress-strain curve is as Figure 4 shown.

[0055] Example 3

[0056] (1) Composition design

[0057] In terms of mass percentage, the elemental composition of the high thermal conductivity magnesium alloy with high strength and high plasticity in this example includes the following components: Zn 4 wt.%, Cu 4 wt.%, Ce 0.4 wt.%, and the balance is Mg and inevitable impurities.

[0058] (2) Preparation method

[0059] Put the raw material Mg ingot into a resistance furnace to melt. After the Mg ingot is completely melted, add Zn blocks and raise the temperature. When the temperature rises to 700 °C, add the preheated Cu blocks and keep the temperature for 15 min. Raise the furnace temperature to 750 °C, add the preheated Mg-Ce master alloy, and keep the temperature for 15 min. Control the furnace temperature at 730 °C, turn on the CO2 and SF6 protective gases, evenly sprinkle the No. 5 solvent for refining. After the refining is completed, start to stand still until the casting temperature (720 °C). Use an electromagnetic semi-continuous casting system to cast the magnesium alloy melt. At the same time as the casting starts, turn on the electromagnetic system to stir the magnesium alloy melt and the ingot electromagnetically. The electromagnetic frequency is 25 Hz until the casting is completed to obtain a magnesium alloy ingot.

[0060] All the above melting processes involving contact and treatment of the melt are carried out under the protective atmosphere of CO2 and SF6. The CO2 and SF6 protective gases are also introduced into the mold during the casting process.

[0061] Perform homogenization treatment on the ingot in a heat treatment furnace. The process is 400 °C × 10 h, and then take it out of the furnace and air-cool it to room temperature;

[0062] Turn the surface oxide of the homogenized magnesium alloy ingot by turning, and then perform pre-deformation (forging). The pre-deformation temperature is 300 °C.

[0063] Perform low-temperature extrusion deformation on the pre-deformed ingot. The extrusion temperature is 150 °C, the extrusion ratio is 16:1, and the extrusion speed is 0.6 m / s;

[0064] For the alloy described in Example 3, its conductivity is 20.85 Ms / m, and its thermal conductivity is 146.54 W·m -1 ·K -1 , the tensile strength is 361 MPa, the yield strength is 322 MPa, and the elongation is 14.9%. Its stress-strain curve is as Figure 4 shown.

[0065] Example 4

[0066] (1) Composition design

[0067] In terms of mass percentage, the element composition of the high thermal conductivity magnesium alloy with high strength and high plasticity in this example includes the following components: Zn 1 wt.%, Cu 1 wt.%, Ce 0.4 wt.%, and the balance is Mg and unavoidable impurities.

[0068] (2) Preparation method

[0069] Put the raw material Mg ingot in a resistance furnace to melt. After the Mg ingot is completely melted, add Zn blocks and raise the temperature. When the temperature reaches 700 °C, add the preheated Cu blocks and keep the temperature for 15 min. Raise the furnace temperature to 750 °C, add the preheated Mg-Ce master alloy, and keep the temperature for 15 min. Control the furnace temperature at 730 °C, turn on the CO2 and SF6 protective gases, and evenly sprinkle the No. 5 solvent for refining. After the refining is completed, start to stand still until the casting temperature (720 °C). Use an electromagnetic semi-continuous casting system to cast the magnesium alloy melt. At the same time as the casting starts, turn on the electromagnetic system to stir the magnesium alloy melt and the ingot electromagnetically. The electromagnetic frequency is 25 Hz until the casting is completed to obtain a magnesium alloy ingot.

[0070] All the above melting processes involving contact and treatment of the melt are carried out under the protective atmosphere of CO2 and SF6. During the casting process, CO2 and SF6 protective gases are also introduced into the mold.

[0071] Homogenize the ingot in a heat treatment furnace. The process is 400 °C × 10 h, and then take it out of the furnace and air-cool it to room temperature.

[0072] Turn the surface oxide of the homogenized magnesium alloy ingot by turning, and then carry out pre-deformation (forging). The pre-deformation temperature is 300 °C.

[0073] Carry out low-temperature extrusion deformation on the pre-deformed ingot. The extrusion temperature is 150 °C, the extrusion ratio is 16:1, and the extrusion speed is 0.6 m / s.

[0074] For the alloy described in Example 4, its electrical conductivity is 20.25 Ms / m, thermal conductivity is 142.32 W·m -1 ·K -1 , the tensile strength is 331 MPa, the yield strength is 272 MPa, and the elongation is 23%. Its stress-strain curve is as Figure 4 shown.

[0075] Example 5

[0076] (1) Composition design

[0077] In terms of mass percentage, the elemental composition of the high thermal conductivity magnesium alloy with high strength and high plasticity in this example includes the following components: Zn 1.5 wt.%, Cu 1 wt.%, Ce 0.4 wt.%, and the balance is Mg and unavoidable impurities.

[0078] (2) Preparation method

[0079] Put the raw material Mg ingot in a resistance furnace to melt. After the Mg ingot is completely melted, add Zn blocks and raise the temperature. When the temperature reaches 700 °C, add the preheated Cu blocks and keep warm for 15 min. Raise the furnace temperature to 750 °C, add the preheated Mg-Ce master alloy and keep warm for 15 min. Control the furnace temperature at 730 °C, turn on the CO2 and SF6 protective gases, evenly sprinkle the No. 5 solvent for refining. After the refining is completed, start to stand still until the casting temperature (720 °C). Use an electromagnetic semi-continuous casting system to cast the magnesium alloy melt. When the casting starts, turn on the electromagnetic system to stir the magnesium alloy melt and the ingot electromagnetically. The electromagnetic frequency is 25 Hz until the casting is completed to obtain a magnesium alloy ingot.

[0080] All the above melting processes involving contact and treatment of the melt are carried out under the protective atmosphere of CO2 and SF6. During the casting process, CO2 and SF6 protective gases are also introduced into the mold.

[0081] Carry out homogenization treatment on the ingot in a heat treatment furnace. The process is 400 °C × 10 h, and then take it out of the furnace and air-cool it to room temperature.

[0082] Turn the surface oxide of the homogenized magnesium alloy ingot by turning, and then carry out pre-deformation (forging). The pre-deformation temperature is 300 °C.

[0083] Carry out low-temperature extrusion deformation on the pre-deformed ingot. The extrusion temperature is 150 °C, the extrusion ratio is 16:1, and the extrusion speed is 0.6 m / s.

[0084] For the alloy described in Example 5, its conductivity is 20.23 Ms / m, the thermal conductivity is 141.56 W·m -1 ·K -1 , the tensile strength is 337 MPa, the yield strength is 280 MPa, and the elongation is 21.5%. Its stress-strain curve is as Figure 4 shown.

[0085] Example 6

[0086] (1) Composition design

[0087] In terms of mass percentage, the elemental composition of the high thermal conductivity magnesium alloy with high strength and high plasticity in this example includes the following components: Zn 1.5 wt.%, Cu 1 wt.%, Ce 0.4 wt.%, and the balance is Mg and unavoidable impurities.

[0088] (2) Preparation method

[0089] Put the raw material Mg ingot in a resistance furnace to melt. After the Mg ingot is completely melted, add Zn blocks and raise the temperature. When the temperature reaches 700 °C, add the preheated Cu blocks and keep the temperature for 15 min. Raise the furnace temperature to 750 °C, add the preheated Mg-Ce master alloy and keep the temperature for 15 min. Control the furnace temperature at 730 °C, turn on the CO2 and SF6 protective gases, evenly sprinkle the No. 5 solvent for refining. After the refining is completed, start to stand still until the casting temperature (720 °C). Use an electromagnetic semi-continuous casting system to cast the magnesium alloy melt. At the same time as the casting starts, turn on the electromagnetic system to stir the magnesium alloy melt and the ingot electromagnetically at an electromagnetic frequency of 25 Hz until the casting is completed to obtain a magnesium alloy ingot.

[0090] All the above melting processes involving contact and treatment of the melt are carried out under the protective atmosphere of CO2 and SF6. The CO2 and SF6 protective gases are also introduced into the mold during the casting process.

[0091] Carry out homogenization treatment on the ingot in a heat treatment furnace with the process of 400 °C × 10 h, and then take it out of the furnace and air-cool it to room temperature.

[0092] Turn the surface oxide of the homogenized magnesium alloy ingot by turning, and then carry out pre-deformation.

[0093] In this example, the extrusion pre-deformation method is adopted, with a pre-deformation temperature of 280 °C and an extrusion ratio of 6:1.

[0094] The microstructure morphology of this pre-deformation scan is as Figure 5 shown. In this alloy, there are obvious solute enrichment regions (G.P. zones). Conduct electrical and thermal conductivity and mechanical property tests on the magnesium alloys prepared in Examples 1 to 5, and the results are shown in Table 1:

[0095] Table 1. Electrical and thermal conductivity and mechanical properties of Mg-xZn-xCu-0.4Ce alloy

[0096]

Claims

1. A high-strength, high-ductility, and high-thermal-conductivity magnesium alloy extruded material, characterized in that, The components, by weight percentage, include: 0.5 wt.% to 1.5 wt.% of Zn, 0.2 wt.% to 1 wt.% of Cu, 0.1 wt.% to 0.8 wt.% of RE, and the balance is Mg and unavoidable impurities; wherein RE is a light rare earth element with low solid solubility and is selected from one of La, Ce, Sm, and Nd; The thermal conductivity of the magnesium alloy extruded material is 140 to 150 W·m -1 ·K -1 ; the tensile strength of the magnesium alloy extruded material is 320 MPa to 360 MPa, the yield strength is 260 MPa to 300 MPa, and the elongation is 15% to 25%; A method for preparing a high-strength, high-plasticity, and high-thermal-conductivity magnesium alloy extruded material, characterized by comprising the following steps: Step 1. Melting and casting: After completely melting the Mg ingot, add Zn blocks and raise the temperature, then add Cu blocks and keep warm, and then raise the furnace temperature; add the master alloy Mg-RE and continue to keep warm, turn on the gas for refining to obtain a magnesium alloy melt; cast the magnesium alloy melt, and start electromagnetic stirring simultaneously during casting until casting is completed to obtain a magnesium alloy ingot; Step 2. Extrusion method: Homogenize the magnesium alloy ingot, and then remove the surface oxide to obtain an ingot blank; pre-deform the ingot blank, and then extrude it at a low temperature to obtain a magnesium alloy extruded material; In the said Step 1, after adding Zn, raise the temperature to 700 °C to 710 °C; keep warm for 10 min to 15 min after adding Cu blocks, and raise the furnace temperature to 740 °C - 750 °C; keep warm for 10 min to 15 min after adding the master alloy, and control the furnace temperature at 720 °C to 730 °C; the casting temperature is 710 °C to 720 °C; In the said Step 1, the gas turned on is a CO2 and SF6 protective gas, where the ratio of CO2 to SF6 is 40:1, and the flow rate is 5 ml / min to 20 ml / min; During the electromagnetic stirring process, the electromagnetic frequency is 15 Hz to 30 Hz; The pre-deformation temperature is 250 °C to 350 °C; The extrusion speed is 0.5 mm / s to 3 mm / s.

2. The high-strength, high-ductility, and high-thermal-conductivity magnesium alloy extruded material according to claim 1, characterized in that, In the said Step 1, both the melting and casting steps are carried out in a protective gas atmosphere.

3. The high-strength, high-ductility, and high-thermal-conductivity magnesium alloy extruded material according to claim 1, characterized in that, In the said Step 2, the homogenization process includes: keeping the magnesium alloy ingot at 380 °C to 420 °C for 10 h to 12 h, and then air-cooling it to room temperature to complete the homogenization process; The method for removing the surface oxide is lathe machining.

4. The high-strength, high-ductility, and high-thermal-conductivity magnesium alloy extruded material according to claim 1, characterized in that, In the said Step 2, the extrusion process is as follows: Keep the pre-deformed ingot blank at 150 °C to 250 °C for 1 to 3 h, and then extrude it on a vertical extruder. During hot extrusion, the temperature of the extrusion cylinder and the die is 170 °C to 270 °C, and the extrusion ratio is (12 - 20):1.

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