High-strength high-thermal-conductivity wrought magnesium alloy added with mixed rare earth and preparation method thereof

Abstract

The application relates to a high-strength and high-thermal-conductivity deformed magnesium alloy added with mixed rare earth and a preparation method thereof. The deformed magnesium alloy is Mg-xZn-0.5Mn-yRE, wherein x is 0.5-3 wt.%, y is less than 0.5 wt.%, and RE is composed of any La and Ce in a mixed ratio, and RE is added through Mg-30La / Ce mixed rare earth intermediate alloy (the mass ratio of La / Ce in the intermediate alloy is any value). The preparation method comprises the following steps: (1) batching; (2) alloy smelting; (3) homogenization treatment; and (4) extrusion deformation. The alloy has a room-temperature thermal conductivity of no less than 120 W / (m*K), a tensile strength of no less than 250 MPa, and an elongation of no less than 13%. The Mg-30La / Ce mixed rare earth can improve the thermal conductivity and mechanical properties of Mg-Zn-Mn, and the cost is lower than that of binary rare earth intermediate alloy and rare earth metal.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metals, specifically relating to thermally conductive deformable magnesium alloys and their preparation methods. Background Technology

[0002] With the continuous development of aerospace, new energy vehicles, 3C products, and other fields, the demand for lightweight heat dissipation structural materials is increasing. Magnesium has a density of 1.74 g / cm³. 3 Magnesium is 2 / 3 the weight of aluminum and 1 / 5 the weight of copper, making it the lightest metallic structural material. Simultaneously, its thermal conductivity is 156 W / (m·K), making it a next-generation lightweight thermal conductive material. However, magnesium has poor mechanical properties. Alloying is an effective way to improve mechanical properties, but alloying often leads to a decrease in thermal conductivity. For example, the thermal conductivity of commercial magnesium alloys AZ91 is only 58 W / (m·K), AS21 has a thermal conductivity of 68 W / (m·K), and WE43 has a thermal conductivity of 51 W / (m·K).

[0003] Casting thermally conductive magnesium alloys requires a balance between thermal conductivity and strength, typically necessitating complex alloy compositions (quaternary or higher-order systems). For example, Mg-Al alloys, by adding various rare earth elements such as Mg-3Al-3Ce-0.25Mn-1.55La-0.6Zn-0.15Ca, yielded die-cast samples [a high thermal conductivity die-cast magnesium alloy for automotive inverter housings, CN109136699B] with a thermal conductivity of ~110 W / (m·K) and tensile strength of ~220 MPa. However, the alloy composition is extremely complex, making its preparation extremely difficult. In applications where high mechanical strength is not required, such as heat sink casings, cast thermally conductive magnesium alloys often exhibit thermal conductivity exceeding 130 W / (m·K). For example, the thermal conductivity of low-tin-content cast Mg-2Sn-2.3La alloy reaches 149 W / (m·K) [Journal of Materials Research and Technology, 2022, 17: 1380-1389]. Die-cast rare-earth magnesium alloys, with rare-earth elements as the main alloying elements, have low thermal conductivity (W / (m·K) for non-La and Ce series alloys), but their strength is limited to ~220 MPa, typically only 50-80 W / (m·K), with a strength of ~100 MPa [Journal of Materials Research and Technology, 2022, 17: 1380-1389]. Science & Technology, 2017, 33: 1240-1248; Su Chuangye, Research on thermal conductivity mechanism of magnesium alloy based on solid solution atoms and second phase. Shanghai Jiaotong University, 2019; Ying Tao, Research on thermal conductivity behavior of pure magnesium and binary magnesium alloy. Harbin Institute of Technology, 2015.], while the thermal conductivity of La and Ce series is slightly better, reaching 90-110 W / (m·K). For example, Mg-5La-3Al-0.3Mn deformed magnesium alloy, rare earth La element exists as the main alloying element, its room temperature thermal conductivity is 117.4 W / (m·K), and its tensile strength can reach 332.2 MPa [Materials. 2022; 15(3): 1078]. It is evident that existing cast high-strength, high-thermal-conductivity magnesium alloys often require complex composition design, and their preparation and processing composition control is difficult; cast thermally conductive magnesium alloys with rare earth as the main alloy (addition amount of 1-5%) are difficult to balance thermal conductivity and strength, and their performance is still some distance from practical application.

[0004] In applications such as 5G base stations and automotive components, where high thermal conductivity and mechanical properties are required, deformed thermally conductive magnesium alloys such as Mg-Zn and Mg-Mn alloys are often used. [Analysis of the market size and development prospects of the magnesium alloy industry in 2022, Zhongyan Puhua] For example, after solution treatment at 643K for 12h, rolling at 673K, annealing at 673K ​​for 1h, and aging at 693K for 4h + 448K for 24h, the room temperature thermal conductivity of the Mg-2Zn-Zr alloy is 132.1 W / (m·K) and the tensile strength is 279 MPa [Journal of Alloys and Compounds 722(2017)772-777]; after solution treatment at 643K for 12h, extrusion at 623K, annealing at 673K ​​for 1.5h, and aging at 448K for 20h, the room temperature thermal conductivity of the Mg-5Zn-1Mn alloy is 122 W / (m·K) and the tensile strength is 321 MPa. [Research on High Thermal Conductivity Mg-Zn-Mn Alloys and Their Properties [D]. Beijing General Research Institute of Nonferrous Metals]. Deformed thermally conductive magnesium alloys with trace amounts of rare earth have been a research focus in recent years. The addition of rare earth as a microalloying element (<0.5%) can purify the melt and improve the mechanical properties of the alloy, while not significantly reducing the thermal conductivity of the alloy [Journal of Materials Science & Technology 33(2017)1240-1248]. For example, adding 0.5 wt.% rare earth element Ce to a Mg-0.9Mn alloy, followed by semi-continuous casting with a 40 Hz magnetic field, homogenization annealing at 500℃ for 24 h, extrusion at 150℃, and rolling four times at 200℃, increases the tensile strength from 320 MPa to 335 MPa, but the thermal conductivity decreases by only 10 W / (m·K) from 140 W / (m·K) [A high-strength, high-thermal-conductivity magnesium alloy and its preparation method, CN 114182147 B]; adding 0.3 wt.% rare earth element Ce to a Mg-0.5Mn alloy, followed by T4 (693 K / 12 h) + extrusion (673 K) treatment, increases the tensile strength from 295.1 MPa to 320.9 MPa, while maintaining a room temperature thermal conductivity of around 139 W / (m·K) [Journal of Alloys and Compounds] 661(2016)402-410].Adding 0.1 wt.% to 0.41 wt.% of rare earth Ce to the Mg-2Zn-0.41Mn alloy increases the tensile strength from 254.5 MPa to 287.7 MPa, and slightly improves its room temperature thermal conductivity from 131.7 W / (m·K) to 138.3 W / (m·K) [A thermally conductive magnesium alloy and its preparation method, CN104152769B]; adding 0.1 to 0.5 wt.% of rare earth Sm to the Mg-2.5Zn-0.15Zr alloy increases the tensile strength from 295.1 MPa to 312.6 to 316.7 MPa, and slightly improves its room temperature thermal conductivity from 118.1 W / (m·K) to 121.2 W / (m·K) [A high thermal conductivity rare earth magnesium alloy and its preparation method, CN107130158B]. Adding trace amounts of rare earth elements to other multi-element deformable magnesium alloys results in improved mechanical and thermal conductivity. For example, a Mg-1.6%Zn-0.6%Cu-0.5%Y alloy, after homogenization annealing at 400℃ for 12 hours, extrusion forming, solution treatment at 380℃ for 3 hours, and aging at 150℃ for 8 hours, exhibits a room temperature thermal conductivity of 141.04 W / (m·K) and a tensile strength of 260 MPa [A high thermal conductivity, high strength, and high toughness magnesium alloy material and a hot deformation heat treatment process, CN 114517268 A]; a Mg-4.2Zn-0.5Mn-0.4Ca-0.25La alloy, after homogenization treatment at 450℃ for 4 hours, pre-compression deformation of 30% along the x / y / z directions at 450℃, and extrusion at 350℃, exhibits a tensile strength of 313 MPa and a thermal conductivity of 140 W / (m·K). [A low-cost, high thermal conductivity, ultra-high ductility magnesium alloy and its preparation method, CN 111218597 A]. Compared with cast thermally conductive magnesium alloys, wrought thermally conductive magnesium alloys have a relatively simple composition, but the deformation process is complex. Rare earth elements are added as microalloying elements to wrought magnesium alloys (~0.5%) in small amounts, so high-purity binary master alloys such as Mg-Ce, Mg-La, and Mg-Y, as well as high-purity rare earth metals, are often required. However, rare earth elements are prone to co-occurrence, so high-purity binary master alloys and high-purity rare earth metals are expensive.

[0005] To address the aforementioned problems, this invention proposes a high-strength, high-thermal-conductivity wrought magnesium alloy with added mixed rare earth elements and its preparation method. Specifically, it employs the addition of a mixed rare earth master alloy Mg-La / Ce, which not only enhances the mechanical and thermal conductivity properties of the wrought magnesium alloy but also significantly reduces the preparation cost of the thermally conductive wrought alloy compared to adding a binary master alloy or rare earth metals. Summary of the Invention

[0006] The purpose of this invention is to provide a high-strength, high-thermal-conductivity wrought magnesium alloy with added mixed rare earth elements and its preparation method, which not only improves its thermal conductivity and mechanical properties but also significantly reduces the alloy preparation cost. The wrought magnesium alloy is Mg-xZn-0.5Mn-yRE, where x is 0.5–3 wt.%, y < 0.5 wt.%, and RE is composed of any La and Ce mixing ratio, added via a Mg-30La / Ce mixed rare earth master alloy (the La / Ce mass ratio in the master alloy is arbitrary). The wrought magnesium alloy exhibits a room-temperature thermal conductivity ≥120 W / (m·K), a tensile strength ≥250 MPa, and an elongation ≥13%.

[0007] Its preparation process includes the following steps:

[0008] (1) Ingredients: Weigh pure magnesium, pure zinc, Mg-10Mn, and Mg-30La / Ce mixed rare earth magnesium intermediate alloy according to the stoichiometric ratio, and preheat the raw materials by heating them to 150°C in a vacuum drying oven.

[0009] (2) Alloy smelting: ① Heat the crucible to 400℃, introduce a mixed gas of 1 vol.% SF6 and CO2, put pure magnesium into the crucible, sprinkle a layer of solvent to prevent local overheating, and heat evenly to above 700℃ until completely melted; continue to heat to 720℃, add pure Zn according to the composition ratio, and stir for 2 minutes; heat to 750℃, add Mg-10Mn and Mg-30La / Ce master alloys, the La / Ce mass ratio of the master alloys can be arbitrary, stir the melt for 3-5 minutes, cover the surface of the solution with an appropriate amount of solvent and keep warm for 20 minutes until the master alloys are completely melted. ② Heat to 750℃, introduce argon gas, add 2% of the melt mass of RJ-5 refining agent to start refining, mechanically stir for 5-10 minutes until the liquid surface has a mirror luster, remove the scum on the liquid surface, and lightly sprinkle the covering agent; let stand at 750℃ for 20 minutes and then remove the slag to complete the refining process. ③ When the alloy melt cools down to 710℃, pour the magnesium alloy melt into a fully preheated mold, cool it to an appropriate temperature, open the mold and take out the ingot.

[0010] (3) Homogenization treatment: Place the ingot prepared in the above steps into a box-type resistance furnace, slowly heat it to 400°C, keep it at that temperature for 10 hours, and then take out the ingot and air cool it to room temperature.

[0011] (4) Extrusion deformation: Remove the oxide scale from the surface of the ingot before extrusion and preheat the ingot to 390°C; set the extrusion temperature to 390°C, the extrusion ratio to 19:1, and the extrusion rate to 2 mm / s to obtain magnesium alloy rods.

[0012] This invention presents a high-strength, high-thermal-conductivity wrought magnesium alloy with added rare earth elements and its preparation method. In the application of Mg-Zn-Mn wrought thermally conductive magnesium alloys, this significantly improves mechanical properties without reducing thermal conductivity, and allows for the continued use of the original deformation processing procedure. This rare earth addition method is not only applicable to Mg-Zn-Mn but can also be extended to other wrought magnesium alloy systems, such as Mg-Mn and Mg-Al. Attached Figure Description

[0013] Figure 1 The results are the microstructure analysis results of alloys in Examples 1, 2, 4, and 5.

[0014] Figure 2 The X-ray diffraction analysis results are for the phase composition of alloys in Examples 1, 2, 4, and 5.

[0015] Figure 3 The tensile curves are for alloys in Examples 1, 2, 4, and 5. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments and accompanying drawings. The following embodiments are all implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0017] Table 1 shows the ICP composition test results of the embodiment, and Table 2 shows the mechanical property test results obtained by thermal conductivity and tensile tests of the embodiment.

[0018] Example 1. Mg-0.5Zn-0.5Mn wrought magnesium alloy

[0019] The preparation method described in this embodiment is performed according to the following steps:

[0020] (1) Ingredients: Weigh pure magnesium, pure zinc and Mg-10Mn according to the stoichiometric ratio of Mg-0.5Zn-0.5Mn, and preheat the raw materials by heating them to 150°C in a vacuum drying oven.

[0021] (2) Alloy smelting: ① Heat the crucible to 400℃, introduce a mixed gas of 1 vol.% SF6 and CO2, put pure magnesium into the crucible, sprinkle a layer of solvent to prevent local overheating, and heat evenly to above 700℃ until completely melted; continue to heat to 720℃, add pure Zn according to the composition ratio, and stir for 2 minutes; heat to 750℃, add Mg-10Mn, stir the melt for 3-5 minutes, cover the surface of the solution with an appropriate amount of solvent and keep warm for 20 minutes until the intermediate alloy is completely melted. ② Heat to 750℃, introduce argon gas, add 2% of the melt mass of RJ-5 refining agent to start refining, mechanically stir for 5-10 minutes until the liquid surface shows a mirror luster, remove the scum on the liquid surface, and lightly sprinkle the covering agent; let stand at 750℃ for 20 minutes and then remove the slag to complete the refining process. ③ When the alloy melt cools down to 710℃, pour the magnesium alloy melt into a fully preheated mold, cool it to an appropriate temperature, open the mold and take out the ingot.

[0022] (3) Homogenization treatment: Place the ingot prepared in the above steps into a box-type resistance furnace, slowly heat it to 400°C, keep it at that temperature for 10 hours, and then take out the ingot and air cool it to room temperature.

[0023] (4) Extrusion deformation: Remove the oxide scale from the surface of the ingot before extrusion and preheat the ingot to 390°C; set the extrusion temperature to 390°C, the extrusion ratio to 19:1, and the extrusion rate to 2 mm / s to obtain magnesium alloy rods.

[0024] The Mg-0.5Zn-0.5Mn wrought alloy obtained in this embodiment has the following microstructure: Figure 1 As shown; the phase composition is as follows Figure 2 As shown; room temperature stretch curve as shown Figure 3 As shown, its tensile strength is 246.2 MPa, its yield strength is 166 MPa, and its elongation is 13.1%; its room temperature thermal conductivity is 138.5 W / (m·K); its properties are listed in Table 2.

[0025] Example 2. Mg-1.5Zn-0.5Mn wrought magnesium alloy

[0026] The process for preparing the deformed magnesium alloy in this embodiment is the same as in Example 1. The difference lies in the alloy composition: Mg-1.5Zn-0.5Mn.

[0027] The Mg-1.5Zn-0.5Mn alloy obtained in this embodiment has the following microstructure: Figure 1 As shown; the phase composition is as follows Figure 2 As shown; room temperature stretch curve as shown Figure 3 As shown, the tensile strength is 268.4 MPa, the yield strength is 171.9 MPa, and the elongation is 15.9%; its room temperature thermal conductivity is 124.9 W / (m·K); the properties are listed in Table 2.

[0028] Example 3. Mg-3Zn-0.5Mn wrought magnesium alloy

[0029] The process for preparing the deformed magnesium alloy in this embodiment is the same as in Example 1. The difference lies in the alloy composition: Mg-3Zn-0.5Mn.

[0030] The Mg-3Zn-0.5Mn alloy obtained in this embodiment has a room temperature thermal conductivity of 118.7 W / (m·K); room temperature tensile properties: tensile strength of 271.2 MPa, yield strength of 182 MPa, and elongation of 15.3%; the properties are listed in Table 2.

[0031] Example 4. Mg-0.5Zn-0.5Mn-0.5La / Ce wrought magnesium alloy (La / Ce mass ratio in the alloy is 1:2)

[0032] Its preparation process includes the following steps:

[0033] (1) Batching: Weigh pure magnesium, pure zinc, Mg-10Mn, and Mg-30La / Ce mixed rare earth magnesium master alloy according to the stoichiometric ratio of Mg-0.5Zn-0.5Mn-0.5La / Ce. Dry and preheat the raw materials in a vacuum drying oven at 150°C.

[0034] (2) Alloy smelting: ① Heat the crucible to 400℃, introduce a mixed gas of 1 vol.% SF6 and CO2, put pure magnesium into the crucible, sprinkle a layer of solvent to prevent local overheating, and heat evenly to above 700℃ until completely melted; continue to heat to 720℃, add pure Zn according to the composition ratio, and stir for 2 minutes; heat to 750℃, add Mg-10Mn and Mg-30La / Ce master alloy (the mass ratio of La / Ce in the master alloy is 1:2), stir the melt for 3-5 minutes, cover the surface of the solution with an appropriate amount of solvent and keep warm for 20 minutes until the master alloy is completely melted. ② Heat to 750℃, introduce argon gas, add 2% of the melt mass of RJ-5 refining agent to start refining, mechanically stir for 5-10 minutes until the liquid surface has a mirror luster, remove the scum on the liquid surface, and lightly sprinkle the covering agent; let stand at 750℃ for 20 minutes and then remove the slag to complete the refining process. ③ When the alloy melt cools down to 710℃, pour the magnesium alloy melt into a fully preheated mold, cool it to an appropriate temperature, open the mold and take out the ingot.

[0035] (3) Homogenization treatment: Place the ingot prepared in the above steps into a box-type resistance furnace, slowly heat it to 400°C, keep it at that temperature for 10 hours, and then take out the ingot and air cool it to room temperature.

[0036] (4) Extrusion deformation: Remove the oxide scale from the surface of the ingot before extrusion and preheat the ingot to 390°C; set the extrusion temperature to 390°C, the extrusion ratio to 19:1, and the extrusion rate to 2 mm / s to obtain magnesium alloy rods.

[0037] The Mg-0.5Zn-0.5Mn-0.5La / Ce alloy obtained in this embodiment (with a La / Ce mass ratio of 1:2, i.e., La is 0.164wt% and Ce is 0.329wt.%) has the following microstructure: Figure 1 As shown; the phase composition is as follows Figure 2 As shown; room temperature stretch curve as shown Figure 3 As shown, the tensile strength is 248 MPa, the yield strength is 169 MPa, and the elongation is 13.5%; its room temperature thermal conductivity is 139.6 W / (m·K); compared with the sample Example 1 without mixed rare earth, its thermal conductivity increased by 1 W / (m·K) and its strength increased by 1 MPa; the performance is shown in Table 2.

[0038] Example 5. Mg-1.5Zn-0.5Mn-0.5La / Ce wrought magnesium alloy (La / Ce mass ratio in the alloy is 1:2)

[0039] The alloy preparation process in this embodiment is the same as in Example 4. The difference is that the alloy composition is Mg-1.5Zn-0.5Mn-0.5La / Ce, and rare earth elements are added through Mg-30La / Ce (the mass ratio of La / Ce in the intermediate alloy is 1:2).

[0040] The Mg-1.5Zn-0.5Mn-0.5La / Ce alloy obtained in this embodiment (with a La / Ce mass ratio of 1:2, i.e., La is 0.163wt% and Ce is 0.326wt.%) has the following microstructure: Figure 1 As shown; its phase composition is as follows Figure 2 As shown; room temperature stretch curve as shown Figure 3 As shown, the tensile strength is 275.2 MPa, the yield strength is 194 MPa, and the elongation is 16.5%; its room temperature thermal conductivity is 130.2 W / (m·K); compared with the sample Example 2 without mixed rare earth, its thermal conductivity increased by 5 W / (m·K) and its strength increased by 7 MPa; the performance is shown in Table 2.

[0041] Example 6. Mg-3Zn-0.5Mn-0.5La / Ce wrought magnesium alloy (La / Ce mass ratio in the alloy is 1:2)

[0042] The alloy preparation process in this embodiment is the same as in Example 4. The difference lies in the alloy composition: Mg-3Zn-0.5Mn-0.5La / Ce, and the rare earth elements are added through Mg-30La / Ce (the mass ratio of La / Ce in the intermediate alloy is 1:2).

[0043] The Mg-3Zn-0.5Mn-0.5La / Ce alloy obtained in this embodiment (with a La / Ce mass ratio of 1:2, i.e., La is 0.161wt% and Ce is 0.321wt.%) has a room temperature thermal conductivity of 122.8 W / (m·K); room temperature tensile properties: tensile strength of 280.5 MPa, yield strength of 201.5 MPa, and elongation of 16.2%. Compared with the sample Example 3 without mixed rare earth elements, its thermal conductivity increased by 4 W / (m·K) and its strength increased by 9 MPa, as shown in Table 2.

[0044] Example 7. Mg-1.5Zn-0.5Mn-0.5La / Ce wrought magnesium alloy (La / Ce mass ratio in the alloy is 1:1)

[0045] The alloy preparation process in this embodiment is the same as in Example 4. The difference lies in the alloy composition: Mg-1.5Zn-0.5Mn-0.5La / Ce, and rare earth elements are added through Mg-30La / Ce (the mass ratio of La / Ce in the intermediate alloy is 1:1).

[0046] The Mg-1.5Zn-0.5Mn-0.5La / Ce alloy obtained in this embodiment (with a La / Ce mass ratio of 1:1, i.e., La 0.242 wt.% and Ce 0.254 wt.%) has the following microstructure: Figure 1 As shown, the XRD results are as follows Figure 2 As shown in Table 2, its room temperature thermal conductivity is 130.1 W / (m·K); tensile strength is 276 MPa, yield strength is 195.6 MPa, and elongation is 16.6%. Compared with Example 2, the thermal conductivity increased by 5 W / (m·K) and the strength increased by 7 MPa.

[0047] Example 8. Mg-1.5Zn-0.5Mn-0.5La / Ce wrought magnesium alloy (La / Ce mass ratio in the alloy is 2:1)

[0048] The alloy preparation process in this embodiment is the same as in Example 4. The difference lies in the alloy composition: Mg-1.5Zn-0.5Mn-0.5La / Ce, and rare earth elements are added through Mg-30La / Ce (the mass ratio of La / Ce in the intermediate alloy is 2:1).

[0049] The Mg-1.5Zn-0.5Mn-0.5La / Ce alloy obtained in this embodiment (with a La / Ce mass ratio of 2:1, i.e., La is 0.320 wt.% and Ce is 0.157 wt.%) has a room temperature thermal conductivity of 129.8 W / (m·K), a tensile strength of 277.2 MPa, a yield strength of 196.5 MPa, and an elongation of 16.9%. Compared with Example 2, the thermal conductivity increased by 5 W / (m·K) and the strength increased by 9 MPa, as shown in Table 2.

[0050] Example 9. Mg-1.5Zn-0.5Mn-0.2La / Ce wrought magnesium alloy (La / Ce mass ratio in the alloy is 1:2)

[0051] The alloy preparation process in this embodiment is the same as in Example 4. The difference lies in the alloy composition: Mg-1.5Zn-0.5Mn-0.2La / Ce, and rare earth elements are added through Mg-30La / Ce (the mass ratio of La / Ce in the intermediate alloy is 1:2).

[0052] The Mg-1.5Zn-0.5Mn-0.2La / Ce alloy obtained in this embodiment (with a La / Ce mass ratio of 1:2, i.e., La is 0.065wt.% and Ce is 0.126wt.%) has a room temperature thermal conductivity of 126.2 W / (m·K), a tensile strength of 270 MPa, a yield strength of 187 MPa, and an elongation of 16%. Compared with Example 2, the thermal conductivity increased by 1 W / (m·K) and the strength increased by 1 MPa, as shown in Table 2.

[0053] Example 10. Mg-1.5Zn-0.5Mn-0.35La / Ce wrought magnesium alloy (La / Ce mass ratio in the alloy is 1:2)

[0054] The smelting and preparation process of the alloy in this embodiment is the same as that in Example 4. The difference lies in the alloy composition: Mg-1.5Zn-0.5Mn-0.35La / Ce, and rare earth elements are added through Mg-30La / Ce (the mass ratio of La / Ce in the intermediate alloy is 1:2).

[0055] The Mg-1.5Zn-0.5Mn-0.35La / Ce alloy obtained in this embodiment (with a La / Ce mass ratio of 1:2, i.e., La is 0.110 wt.% and Ce is 0.229 wt.%) has a room temperature thermal conductivity of 128.1 W / (m·K), a tensile strength of 271.8 MPa, a yield strength of 190 MPa, and an elongation of 16.2%. Compared with Example 2, the thermal conductivity increased by 3 W / (m·K) and the strength increased by 3 MPa, as shown in Table 2.

[0056] Table 1 Alloy composition of the examples

[0057]

[0058] Table 2 Thermal conductivity and mechanical properties of the examples

[0059]

Claims

1. A high-strength, high-thermal-conductivity deformable magnesium alloy with added rare earth elements, characterized in that: The deformed magnesium alloy is Mg-xZn-0.5Mn-yRE, where x is 0.5-3 wt.%, 0 < y < 0.5 wt.%, and RE is composed of any mixing ratio of La and Ce; and RE is added through a Mg-30La / Ce master alloy, and the mass ratio of La / Ce in the master alloy is any value; the preparation method of the high-strength and high-thermal-conductivity deformed magnesium alloy added with mixed rare earths is the following steps: (1) Batching: Weigh pure magnesium, pure zinc, Mg-10Mn, and Mg-30La / Ce master alloy according to the stoichiometric ratio, and heat the raw materials in a vacuum drying oven to 150 °C for drying and preheating; (2) Alloy melting: ① Heat the crucible to 400 °C, introduce a mixed gas of 1 vol.% SF6 and CO2, put pure magnesium into the crucible, sprinkle a layer of flux to prevent local overheating, and uniformly heat to above 700 °C until completely melted; continue to heat up to 720 °C, add pure Zn according to the composition ratio, and stir for 2 minutes; heat up to 750 °C, add Mg-10Mn and Mg-30La / Ce master alloy, the mass ratio of La / Ce in the master alloy is any value, stir the melt for 3-5 minutes, cover the surface of the solution with an appropriate amount of flux and keep it warm for 20 min until the master alloy is completely melted; ② Heat up to 750 °C, introduce argon, add 2% of the melt mass of RJ-5 refining agent to start refining, mechanically stir for 5-10 minutes until the liquid surface shows a mirror-like luster, remove the floating slag on the liquid surface, and gently sprinkle the covering agent; after standing for 20 min at 750 °C, skim the slag to complete the refining process; ③ When the alloy melt cools down to 710 °C, pour the magnesium alloy melt into a fully preheated mold, cool to an appropriate temperature, and open the mold to take out the ingot; (3) Homogenization treatment: Put the ingot prepared in the above step into a box-type resistance furnace, slowly heat it up to 400 °C with the furnace, keep it warm for 10 h, take out the ingot and air-cool it to room temperature; (4) Extrusion deformation: Remove the oxide scale on the surface of the ingot before extrusion, and preheat the ingot to 390 °C; set the extrusion temperature to 390 °C, the extrusion ratio to 19:1, and the extrusion rate to 2 mm / s to obtain a magnesium alloy bar.

2. The high-strength, high-thermal-conductivity deformable magnesium alloy according to claim 1, characterized in that, The room-temperature thermal conductivity of the deformed magnesium alloy is ≥1,20 W / (m·K), the tensile strength is ≥250 MPa, and the elongation is ≥13%.

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