A high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy and its preparation method

Abstract

A high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy and a preparation method thereof, relate to the technical field of magnesium alloys, and particularly to a high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy and a preparation method thereof. In order to solve the problems of poor strength, thermal conductivity and corrosion resistance of existing magnesium alloys. The present invention adds appropriate alloying elements and utilizes simple alloy melting, extrusion and thermal deformation to obtain a high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy with excellent comprehensive performance. The prepared high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy coordinates the problems of poor corrosion resistance and mismatch between strength and thermal conductivity of magnesium alloys. In addition, the preparation method provided by the present invention has simple equipment requirements, short process flow, convenient operation, high preparation efficiency, low cost, and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloys, and in particular to a high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy and a preparation method thereof. Background Art

[0002] As the lightest metal structural material currently used in engineering applications, magnesium alloys offer high specific strength and stiffness, excellent thermal conductivity, and electromagnetic shielding properties, holding broad application prospects in 5G communications, new energy vehicles, aerospace, and other fields. However, with the rapid development of these fields, the number and density of electronic components have increased significantly, leading to a significant increase in the heat generated during equipment operation. Therefore, materials with high thermal conductivity are needed to dissipate excess heat in a timely manner. Furthermore, these materials must also possess high strength, corrosion resistance, and lightweight properties.

[0003] Pure magnesium has a thermal conductivity of up to 158 W / (m·K), but its mechanical properties are relatively poor. The tensile strength of cast pure magnesium is only approximately 11.5 MPa, and that of deformed pure magnesium is only around 20 MPa, which is insufficient for practical applications. Alloying can significantly improve the mechanical properties of magnesium alloys, but this can lead to varying degrees of reduction in their thermal conductivity. Currently, commonly used commercial magnesium alloys such as AZ81 have a room-temperature thermal conductivity of 51 W / (m·K) and a tensile strength of 275 MPa, while WE43 has a room-temperature thermal conductivity of 51 W / (m·K) and a tensile strength of 250 MPa. Because magnesium alloys have a very low standard electrode potential (-2.38 V vs. NHE), they are chemically very active, and the potential of common secondary phases in magnesium alloys is higher than that of the magnesium matrix, making them susceptible to intense microgalvanic corrosion. Furthermore, the surface film formed during the oxidation process of magnesium alloys is loose and porous, resulting in poor stability. Consequently, magnesium alloys have poor corrosion resistance, which severely restricts their widespread use and development.

[0004] Therefore, it is of great application value to select appropriate alloying elements and preparation processes, regulate its microstructure, improve its thermal conductivity and corrosion resistance while increasing the strength of magnesium alloy, and realize the integration of magnesium alloy structure and function. Summary of the Invention

[0005] In order to solve the problems of poor strength, thermal conductivity and corrosion resistance of existing magnesium alloys, the present invention provides a high-strength, high-thermal-conductivity and corrosion-resistant magnesium alloy and a preparation method thereof.

[0006] The high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy of the present invention is a Mg-Mn-Ce-Ca alloy, wherein the content of Mn is 1.0-3.0 wt.%, the content of Ce is 1.5-3.0 wt.%, the content of Ca is 0.01-1.0 wt.%, and the balance is Mg.

[0007] The preparation method of the high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy of the present invention is carried out according to the following steps:

[0008] 1. Weigh the raw materials according to the mass ratio of the elements in the Mg-Mn-Ce-Ca alloy and pretreat the raw materials;

[0009] The raw materials are pure Mg ingots, Mg-Mn master alloys, Mg-Ce master alloys and Mg-Ca master alloys;

[0010] The process of pre-treating the raw materials is as follows: grinding the raw materials with sandpaper to remove surface oxide scale and impurities;

[0011] 2. Preheating the raw materials after the treatment in step 1, then smelting them under a protective atmosphere, and obtaining alloy ingots after cooling;

[0012] The temperature of the preheat treatment is 250-350°C;

[0013] The protective atmosphere gas is a mixture of SF6 and CO2, with SF6 accounting for 2% to 3% of the mixed gas;

[0014] The smelting process is as follows: firstly, a pure Mg ingot is melted, and then a Mg-Mn master alloy and a Mg-Ce master alloy are added. After the alloy is completely melted, the alloy is kept warm for 20 minutes. Then, the temperature is lowered to 720° C., and a Mg-Ca master alloy is added. After the alloy is completely melted, the alloy is stirred and kept warm to obtain a magnesium alloy melt. Finally, the magnesium alloy melt is water-cooled in a protective atmosphere to form an ingot, thereby completing the smelting process.

[0015] The melting temperature of the pure Mg ingot is 700-760°C;

[0016] The time of standing and keeping warm is 10 to 20 minutes;

[0017] The stirring time after complete melting is 3 to 5 minutes;

[0018] 3. preparing the alloy ingot obtained in step 2 into a cylindrical billet for extrusion, extruding and deforming the cylindrical billet, and finally water-cooling the billet to obtain a high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy;

[0019] The method also includes preheating the cylindrical billet and the extrusion die before the extrusion deformation; the preheating temperature is 300-450°C and the time is 10-30 minutes;

[0020] The extrusion ratio of the extrusion deformation is (10-30):1, and the extrusion rate is 0.1-5 mm / s.

[0021] The principles and beneficial technical effects of the present invention are as follows:

[0022] 1. The present invention, by adding appropriate alloying elements, utilizes simple alloy melting and extrusion hot deformation to produce a high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy with excellent overall performance. This alloy addresses the issues of poor corrosion resistance and mismatched strength and thermal conductivity found in magnesium alloys. Furthermore, the preparation method provided by the present invention requires simple equipment, has a short process flow, is easy to operate, has high production efficiency, and is low in cost, making it suitable for large-scale production.

[0023] 2. The magnesium alloy prepared by the present invention has a tensile yield strength of 370-430 MPa and a tensile strength of 380-440 MPa. It also has excellent thermal conductivity and corrosion resistance. Its room temperature thermal conductivity is 120-135 W / (m·K). After immersion in a 3.5 wt.% NaCl aqueous solution at room temperature for 30 days, the corrosion rate obtained in a hydrogen evolution experiment is 0.06-0.4 mm / y. The performance of this alloy can effectively meet the performance requirements of components such as 5G communications, radar, and 3C products, and has broad application prospects in aerospace, automotive, electronics and other fields.

[0024] 3. The present invention adds low-cost rare earth elements Ce and alkaline earth elements Ca to the Mg-Mn alloy. Adding Mn can reduce the content of impurities such as Fe and Ni in the magnesium alloy and improve the corrosion resistance of the magnesium alloy. Mn has a very low solid solubility in the magnesium alloy and does not react with Mg. During the thermal deformation process, it can dynamically precipitate elemental manganese particles to prevent dislocation movement, thereby refining the magnesium alloy grains and improving the mechanical properties of the alloy. Ce has a low solid solubility in magnesium and has a very small effect on the reduction of the thermal conductivity of the magnesium alloy. The Ce element can refine the grains and easily form a second phase with alloying elements or impurity elements, which can strengthen the alloy, purify the matrix, and reduce the corrosion potential of the second phase. In addition, the rare earth oxides formed during the corrosion process can well fill the loose and porous surface film layer of the magnesium alloy, enhance the density of the corrosion product film, and thus improve the corrosion resistance of the magnesium alloy. The solid solubility of Ca in the Mg matrix is ​​only 0.82 wt.%, which has minimal impact on the thermal conductivity of magnesium alloys. Ca refines grain size, weakens texture strength, and improves the mechanical properties of the alloy. Ca can cause magnesium alloys to form a continuously or dispersed second phase. The Mg2Ca phase has a lower corrosion potential than the magnesium matrix and acts as an anode, preferentially corroding, thus reducing the corrosion rate of the matrix. The addition of Ca can also alter the structure of the corrosion product film, improving its density and stability, thereby enhancing its protective effect on the matrix.

[0025] 4. In the present invention, by selecting appropriate contents of alloying elements Mn, Ce, and Ca, and regulating the microstructure of the alloy through casting, extrusion, and other processes, the content of solute atoms in the matrix is ​​reduced, a large number of nanoscale second phases are dynamically precipitated, the alloy grains are refined, and a bimodal grain distribution is formed. Extrusion deformation causes a large amount of Mg-Ce phases and Ca-containing phases in the alloy to be broken into fine particles and evenly distributed. Therefore, the alloy has high strength while maintaining high thermal conductivity. The large amount of broken fine Mg-Ce phases and Ca-containing phases can act as anodes for galvanic corrosion and preferentially dissolve during the corrosion process, thereby protecting the magnesium matrix. In addition, the corrosion products formed by the alloying elements Ce and Ca during the corrosion process can effectively fill the loose and porous surface film layer of the magnesium alloy, enhance the density and stability of the corrosion product film, and thus improve its protective effect on the alloy matrix. Therefore, the alloy also has excellent corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope micrograph of the as-cast Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step 3 of Example 1;

[0027] Figure 2 This is the scanning electron microscope structure of the extruded Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step 5 of Example 1;

[0028] Figure 3 This is the hydrogen evolution amount-time curve of the extruded Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step 5 of Example 1;

[0029] Figure 4 This is the tensile engineering stress-engineering strain curve of the extruded Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step five of Example 1. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any reasonable combination of the specific implementation methods.

[0031] Specific embodiment 1: In this embodiment, the high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy is a Mg-Mn-Ce-Ca alloy, wherein the Mn content is 1.0-3.0 wt.%, the Ce content is 1.5-3.0 wt.%, the Ca content is 0.01-1.0 wt.%, and the balance is Mg.

[0032] This embodiment has the following beneficial effects:

[0033] 1. This embodiment, by adding appropriate alloying elements, utilizes simple alloy melting and extrusion hot deformation to produce a high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy with excellent overall performance. This alloy addresses the issues of poor corrosion resistance and mismatched strength and thermal conductivity found in magnesium alloys. Furthermore, the preparation method provided by this embodiment requires simple equipment, has a short process flow, is easy to operate, has high production efficiency, and is low in cost, making it suitable for large-scale production.

[0034] 2. The magnesium alloy prepared in this embodiment has a tensile yield strength of 370-430 MPa and a tensile strength of 380-440 MPa. It also has excellent thermal conductivity and corrosion resistance, with a room temperature thermal conductivity of 120-135 W / (m·K). After immersion in a 3.5 wt.% NaCl aqueous solution at room temperature for 30 days, the corrosion rate obtained in a hydrogen evolution experiment was 0.06-0.4 mm / y. The performance of this alloy can effectively meet the performance requirements of components such as 5G communications, radar, and 3C products, and has broad application prospects in aerospace, automotive, electronics, and other fields.

[0035] 3. This embodiment adds low-cost rare earth elements Ce and alkaline earth elements Ca to the Mg-Mn alloy. Adding Mn can reduce the content of impurities such as Fe and Ni in the magnesium alloy and improve the corrosion resistance of the magnesium alloy. Mn has a very low solid solubility in the magnesium alloy and does not react with Mg. During the thermal deformation process, it can dynamically precipitate elemental manganese particles to prevent dislocation movement, thereby refining the magnesium alloy grains and improving the mechanical properties of the alloy. Ce has a low solid solubility in magnesium and has a very small effect on the reduction of the thermal conductivity of the magnesium alloy. The Ce element can refine the grains and easily form a second phase with alloying elements or impurity elements, which can strengthen the alloy, purify the matrix, and reduce the corrosion potential of the second phase. In addition, the rare earth oxides formed during the corrosion process can well fill the loose and porous surface film layer of the magnesium alloy, enhance the density of the corrosion product film, and thus improve the corrosion resistance of the magnesium alloy. The solid solubility of Ca in the Mg matrix is ​​only 0.82 wt.%, which has minimal impact on the thermal conductivity of magnesium alloys. Ca refines grain size, weakens texture strength, and improves the mechanical properties of the alloy. Ca can cause magnesium alloys to form a continuously or dispersed second phase. The Mg2Ca phase has a lower corrosion potential than the magnesium matrix and acts as an anode, preferentially corroding, thus reducing the corrosion rate of the matrix. The addition of Ca can also alter the structure of the corrosion product film, improving its density and stability, thereby enhancing its protective effect on the matrix.

[0036] 4. In this embodiment, by selecting the appropriate content of alloying elements Mn, Ce, and Ca, and using casting, extrusion and other processes to regulate the microstructure of the alloy, the content of solute atoms in the matrix is ​​reduced, a large number of nano-scale second phases are dynamically precipitated, the grains of the alloy are refined, and a bimodal grain distribution is formed. Extrusion deformation causes a large amount of Mg-Ce phases and Ca-containing phases in the alloy to be broken into fine particles and evenly distributed. Therefore, the alloy has high strength while maintaining high thermal conductivity. The large amount of broken fine Mg-Ce phases and Ca-containing phases can act as anodes for galvanic corrosion and preferentially dissolve during the corrosion process, thereby protecting the magnesium matrix. In addition, the corrosion products formed by the alloying elements Ce and Ca during the corrosion process can well fill the loose and porous surface film layer of the magnesium alloy, enhance the density and stability of the corrosion product film, and thus improve its protective effect on the alloy matrix. Therefore, the alloy also has excellent corrosion resistance.

[0037] Specific embodiment 2: The preparation method of the high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy in this embodiment is carried out according to the following steps:

[0038] 1. Weigh the raw materials according to the mass ratio of the elements in the Mg-Mn-Ce-Ca alloy and pretreat the raw materials;

[0039] 2. Preheating the raw materials after the treatment in step 1, then smelting them under a protective atmosphere, and obtaining alloy ingots after cooling;

[0040] The temperature of the preheat treatment is 250-350°C;

[0041] The smelting process is as follows: firstly, a pure Mg ingot is melted, and then a Mg-Mn master alloy and a Mg-Ce master alloy are added. After the alloy is completely melted, the alloy is kept warm for 20 minutes. Then, the temperature is lowered to 720° C., and a Mg-Ca master alloy is added. After the alloy is completely melted, the alloy is stirred and kept warm to obtain a magnesium alloy melt. Finally, the magnesium alloy melt is water-cooled in a protective atmosphere to form an ingot, thereby completing the smelting process.

[0042] 3. preparing the alloy ingot obtained in step 2 into a cylindrical billet for extrusion, extruding and deforming the cylindrical billet, and finally water-cooling the billet to obtain a high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy;

[0043] The method also includes preheating the cylindrical billet and the extrusion die before the extrusion deformation; the preheating temperature is 300-450°C and the time is 10-30 minutes;

[0044] The extrusion ratio of the extrusion deformation is (10-30):1, and the extrusion rate is 0.1-5 mm / s.

[0045] 1. This embodiment, by adding appropriate alloying elements, utilizes simple alloy melting and extrusion hot deformation to produce a high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy with excellent overall performance. This alloy addresses the issues of poor corrosion resistance and mismatched strength and thermal conductivity found in magnesium alloys. Furthermore, the preparation method provided by this embodiment requires simple equipment, has a short process flow, is easy to operate, has high production efficiency, and is low in cost, making it suitable for large-scale production.

[0046] 2. The magnesium alloy prepared in this embodiment has a tensile yield strength of 370-430 MPa and a tensile strength of 380-440 MPa. It also has excellent thermal conductivity and corrosion resistance, with a room temperature thermal conductivity of 120-135 W / (m·K). After immersion in a 3.5 wt.% NaCl aqueous solution at room temperature for 30 days, the corrosion rate obtained in a hydrogen evolution experiment was 0.06-0.4 mm / y. The performance of this alloy can effectively meet the performance requirements of components such as 5G communications, radar, and 3C products, and has broad application prospects in aerospace, automotive, electronics, and other fields.

[0047] 3. This embodiment adds low-cost rare earth elements Ce and alkaline earth elements Ca to the Mg-Mn alloy. Adding Mn can reduce the content of impurities such as Fe and Ni in the magnesium alloy and improve the corrosion resistance of the magnesium alloy. Mn has a very low solid solubility in the magnesium alloy and does not react with Mg. During the thermal deformation process, it can dynamically precipitate elemental manganese particles to prevent dislocation movement, thereby refining the magnesium alloy grains and improving the mechanical properties of the alloy. Ce has a low solid solubility in magnesium and has a very small effect on the reduction of the thermal conductivity of the magnesium alloy. The Ce element can refine the grains and easily form a second phase with alloying elements or impurity elements, which can strengthen the alloy, purify the matrix, and reduce the corrosion potential of the second phase. In addition, the rare earth oxides formed during the corrosion process can well fill the loose and porous surface film layer of the magnesium alloy, enhance the density of the corrosion product film, and thus improve the corrosion resistance of the magnesium alloy. The solid solubility of Ca in the Mg matrix is ​​only 0.82 wt.%, which has minimal impact on the thermal conductivity of magnesium alloys. Ca refines grain size, weakens texture strength, and improves the mechanical properties of the alloy. Ca can cause magnesium alloys to form a continuously or dispersed second phase. The Mg2Ca phase has a lower corrosion potential than the magnesium matrix and acts as an anode, preferentially corroding, thus reducing the corrosion rate of the matrix. The addition of Ca can also alter the structure of the corrosion product film, improving its density and stability, thereby enhancing its protective effect on the matrix.

[0048] 4. In this embodiment, by selecting the appropriate content of alloying elements Mn, Ce, and Ca, and using casting, extrusion and other processes to regulate the microstructure of the alloy, the content of solute atoms in the matrix is ​​reduced, a large number of nano-scale second phases are dynamically precipitated, the grains of the alloy are refined, and a bimodal grain distribution is formed. Extrusion deformation causes a large amount of Mg-Ce phases and Ca-containing phases in the alloy to be broken into fine particles and evenly distributed. Therefore, the alloy has high strength while maintaining high thermal conductivity. The large amount of broken fine Mg-Ce phases and Ca-containing phases can act as anodes for galvanic corrosion and preferentially dissolve during the corrosion process, thereby protecting the magnesium matrix. In addition, the corrosion products formed by the alloying elements Ce and Ca during the corrosion process can well fill the loose and porous surface film layer of the magnesium alloy, enhance the density and stability of the corrosion product film, and thus improve its protective effect on the alloy matrix. Therefore, the alloy also has excellent corrosion resistance.

[0049] Specific embodiment three: This embodiment differs from specific embodiment two in that: the raw materials in step one are pure Mg ingots, Mg-Mn master alloys, Mg-Ce master alloys and Mg-Ca master alloys.

[0050] Specific embodiment 4: The difference between this embodiment and specific embodiment 2 is that: the process of pre-treating the raw materials in step 1 is: grinding the raw materials with sandpaper to remove surface oxide scale and impurities.

[0051] Specific embodiment 5: The difference between this embodiment and specific embodiment 2 is that: the process of pre-treating the raw materials in step 1 is: grinding the raw materials with sandpaper to remove surface oxide scale and impurities.

[0052] Specific embodiment 6: This embodiment differs from specific embodiment 2 in that: the temperature of melting the pure Mg ingot in step 2 is 700-760°C.

[0053] Specific embodiment seven: This embodiment differs from specific embodiment two in that the time for standing and keeping warm in step two is 10 to 20 minutes.

[0054] Specific embodiment eight: This embodiment differs from specific embodiment two in that the stirring time after complete melting in step two is 3 to 5 minutes.

[0055] Specific embodiment 9: This embodiment differs from specific embodiment 2 in that: before the extrusion deformation in step 2, the cylindrical billet for extrusion and the extrusion die are also preheated; the preheating temperature is 350° C. and the time is 15 minutes.

[0056] Specific embodiment ten: This embodiment differs from the specific embodiment two in that the extrusion ratio of the extrusion deformation in step two is 18:1, and the extrusion rate is 0.1 mm / s.

[0057] Example 1:

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

[0059] 1. Weigh the raw materials according to the mass ratio of the elements in the Mg-Mn-Ce-Ca alloy and pretreat the raw materials;

[0060] The high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy is a Mg-Mn-Ce-Ca alloy, wherein the content of Mn is 1.89 wt.%, the content of Ce is 2.48 wt.%, the content of Ca is 0.06 wt.%, and the balance is Mg.

[0061] The raw materials are pure Mg ingot, Mg-3wt.%Mn master alloy, Mg-30wt.%Ce master alloy, and Mg-15wt.%Ca master alloy;

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

[0063] 2. Preheating the raw materials after the treatment in step 1, then smelting them under a protective atmosphere, and obtaining alloy ingots after cooling;

[0064] The temperature of the preheating treatment is 300°C; the preheating is carried out in a box-type resistance furnace;

[0065] The protective atmosphere gas is a mixture of SF6 and CO2, with SF6 accounting for 2.4% of the mixed gas;

[0066] The smelting process comprises the following steps: firstly melting a pure Mg ingot, then adding a Mg-3wt.% Mn master alloy and a Mg-30wt.% Ce master alloy, maintaining the temperature for 20 minutes after complete melting, then cooling the temperature to 720°C, adding a Mg-15wt.% Ca master alloy, stirring after complete melting, and allowing the temperature to stand to obtain a magnesium alloy melt; finally, water-cooling the magnesium alloy melt in a protective atmosphere to form an ingot, thereby completing the smelting; and skimming the magnesium alloy melt before each addition of the master alloy.

[0067] The melting temperature of the pure Mg ingot is 700°C;

[0068] The time of standing and keeping warm is 15min;

[0069] The stirring time after complete melting is 4 minutes;

[0070] 3. The alloy ingot obtained in step 2 is prepared into a cylindrical billet with a height of 25 mm and a diameter of 45 mm for extrusion, the cylindrical billet is extruded and deformed, and finally water-cooled to obtain a high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy;

[0071] The extrusion deformation also includes a preheating step of the cylindrical billet and the extrusion die; the preheating temperature is 350°C and the time is 15 minutes;

[0072] The extrusion ratio of the extrusion deformation is 18:1, and the extrusion rate is 0.1 mm / s.

[0073] At 25°C, the extruded Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in this embodiment has a yield strength of 425.2 MPa, a tensile strength of 431.7 MPa, and a thermal conductivity of 120.0 W / (m·K). The corrosion rate obtained in a hydrogen evolution experiment after immersion in a 3.5 wt.% NaCl solution for 30 days is 0.06 mm / y. The corrosion resistance of the alloy far exceeds that of pure Mg, and its comprehensive performance exceeds that of most magnesium alloys. Figure 1 This is the scanning electron microscope micrograph of the as-cast Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step 2 of Example 1; Figure 1 It can be seen that the microstructure of the cast Mg-1.89Mn-2.48Ce-0.06Ca alloy is mainly composed of α-Mg matrix and eutectic structure along the grain boundaries, and the eutectic structure is approximately in the form of a continuous network. Figure 2 This is the scanning electron microscope structure of the extruded Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step 3 of Example 1; Figure 2 It can be seen that after extrusion, the eutectic phase in the alloy is broken into fine particles and distributed in a streamlined manner along the extrusion direction, which can play the role of second phase strengthening and improve the strength of the alloy. Figure 3 This is the hydrogen evolution amount-time curve of the extruded Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step 3 of Example 1; Figure 3 It can be seen that the amount of hydrogen evolution gradually increases with time, but the increase is very small. The average corrosion rate over 30 days is calculated to be 0.06 mm / y. Figure 4 This is the tensile engineering stress-engineering strain curve of the extruded Mg-1.89Mn-2.48Ce-0.06Ca alloy prepared in step 3 of Example 1.

[0074] Example 2:

[0075] This embodiment differs from Example 1 in that the high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy is a Mg-Mn-Ce-Ca alloy, wherein the Mn content is 1.26 wt.%, the Ce content is 2.65 wt.%, the Ca content is 0.08 wt.%, and the balance is Mg. The remaining components are the same as in Example 1.

[0076] The extruded Mg-1.26Mn-2.65Ce-0.08Ca alloy prepared in this embodiment has a yield strength of 423.7 MPa, a tensile strength of 436.5 MPa, and a thermal conductivity of 121.3 W / (m·K). The corrosion rate obtained from the hydrogen evolution experiment after immersion in 3.5 wt.% NaCl solution for 30 days is 0.39 mm / y.

[0077] Example 3:

[0078] This embodiment differs from Example 2 in that the extrusion process includes a preheating step of the cylindrical billet and the extrusion die before extrusion deformation; the preheating temperature is 400°C and the time is 15 minutes; the extrusion ratio is 18:1, and the extrusion rate is 0.1 mm / s. The remaining steps are the same as in Example 1.

[0079] The extruded Mg-1.26Mn-2.65Ce-0.08Ca alloy prepared in this embodiment has a yield strength of 378.3 MPa, a tensile strength of 382.2 MPa, and a thermal conductivity of 132.9 W / (m·K). The corrosion rate obtained from the hydrogen evolution experiment after immersion in 3.5 wt.% NaCl solution for 30 days is 0.35 mm / y.

[0080] Example 4:

[0081] This embodiment differs from Example 1 in that the high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy is a Mg-Mn-Ce-Ca alloy, wherein the Mn content is 1.26 wt.%, the Ce content is 2.47 wt.%, the Ca content is 0.03 wt.%, and the balance is Mg. The remaining components are the same as in Example 1.

[0082] The extruded Mg-1.26Mn-2.47Ce-0.03Ca alloy prepared in this embodiment has a yield strength of 403.7 MPa, a tensile strength of 414.2 MPa, and a thermal conductivity of 124.6 W / (m·K). The corrosion rate obtained from the hydrogen evolution experiment after immersion in 3.5 wt.% NaCl solution for 30 days is 0.30 mm / y.

[0083] Example 5:

[0084] This embodiment differs from Example 1 in that the high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy is a Mg-Mn-Ce-Ca alloy, wherein the Mn content is 1.02 wt.%, the Ce content is 2.54 wt.%, the Ca content is 0.15 wt.%, and the balance is Mg. The remaining components are the same as in Example 1.

[0085] The extruded Mg-1.02Mn-2.54Ce-0.15Ca alloy prepared in this embodiment has a yield strength of 388.0 MPa, a tensile strength of 391.9 MPa, and a thermal conductivity of 128.7 W / (m·K). The corrosion rate obtained from the hydrogen evolution experiment after immersion in 3.5 wt.% NaCl solution for 30 days is 0.38 mm / y.

Claims

1. A high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy, characterized by: The high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy is a Mg-Mn-Ce-Ca alloy, wherein the content of Mn is 1.0-3.0 wt.%, the content of Ce is 1.5-3.0 wt.%, the content of Ca is 0.01-0.15 wt.%, and the balance is Mg; The Ca element can make the magnesium alloy form a second phase with continuous or dispersed distribution, and the corrosion potential of the Mg2Ca phase is lower than that of the magnesium matrix. It is corroded preferentially as an anode, which can reduce the corrosion rate of the matrix. During the corrosion process, the corrosion products formed by the alloying elements Ce and Ca fill the loose and porous surface film of the magnesium alloy, enhancing the density and stability of the corrosion product film, thereby improving the protection of the alloy matrix; The preparation method of the high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy is carried out according to the following steps:

1. Weigh the raw materials according to the mass ratio of the elements in the Mg-Mn-Ce-Ca alloy and pretreat the raw materials; 2. Preheating the raw materials after the treatment in step 1, then smelting them under a protective atmosphere, and obtaining alloy ingots after cooling; The temperature of the preheat treatment is 250-350°C; The smelting process is as follows: first, a pure Mg ingot is melted, and then a Mg-Mn master alloy and a Mg-Ce master alloy are added. After the alloy is completely melted, the alloy is kept warm for 20 minutes. Then, the temperature is lowered to 720° C., and a Mg-Ca master alloy is added. After the alloy is completely melted, the alloy is stirred and kept warm to obtain a magnesium alloy melt. Finally, the magnesium alloy melt is water-cooled in a protective atmosphere to form an ingot, thereby completing the smelting process.

3. preparing the alloy ingot obtained in step 2 into a cylindrical billet for extrusion, extruding and deforming the cylindrical billet, and finally water-cooling the billet to obtain a high-strength, high-thermal-conductivity, and corrosion-resistant magnesium alloy; The method also includes preheating the cylindrical billet and the extrusion die before the extrusion deformation; the preheating temperature is 300-450°C and the time is 10-30 minutes; The extrusion deformation has an extrusion ratio of (10-30):1 and an extrusion rate of 0.1-5 mm / s. The extrusion deformation causes a large amount of Mg-Ce phases and Ca-containing phases in the alloy to be broken into fine particles and evenly distributed. The large amount of broken fine Mg-Ce phases and Ca-containing phases can serve as anodes for galvanic corrosion and preferentially dissolve during the corrosion process, thereby protecting the magnesium matrix.

2. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: The raw materials in step 1 are pure Mg ingots, Mg-Mn master alloys, Mg-Ce master alloys and Mg-Ca master alloys.

3. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: The process for pre-treating the raw materials in step 1 is: grinding the raw materials with sandpaper to remove surface oxide scale and impurities.

4. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: The protective atmosphere gas in step 2 is a mixture of SF6 and CO2, with SF6 accounting for 2% to 3% of the mixed gas.

5. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: The temperature of melting the pure Mg ingot in step 2 is 700-760°C.

6. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: The time for standing and keeping warm in step 2 is 10 to 20 minutes.

7. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: The stirring time after complete melting in step 2 is 3 to 5 minutes.

8. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: Step 2 includes a preheating step of the cylindrical billet and the extrusion die before the extrusion deformation; the preheating temperature is 350° C. and the time is 15 minutes.

9. The high-strength, high-thermal-conductivity, corrosion-resistant magnesium alloy according to claim 1, characterized in that: The extrusion ratio of the extrusion deformation in step 2 is 18:1, and the extrusion rate is 0.1 mm / s.

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