Mg-Ce-Zr cast magnesium alloy and preparation method thereof
By designing the composition and heat treatment process of Mg-Ce-Zr series cast magnesium alloys, the problems of insufficient strength and thermal conductivity of cast magnesium alloys have been solved, achieving a balance of high strength, high thermal conductivity and low density, which is suitable for the material requirements of complex structural parts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BAOTOU RESEARCH INSTITUTE OF RARE EARTHS
- Filing Date
- 2026-02-10
- Publication Date
- 2026-05-12
AI Technical Summary
Existing cast magnesium alloys are insufficient in terms of both high strength and high thermal conductivity, and their high density makes it difficult to meet the material and processing requirements of complex structural parts.
Magnesium alloys based on the Mg-Ce-Zr system are produced by adding 0.5-2.5% Ce and 0.35-0.55% Zr, combined with specific heat treatment processes. The preparation methods include melting, stirring, settling, refining, casting, and aging treatment. The solid solubility of alloying elements and the formation of the second phase are controlled, and the grains are refined to improve strength and thermal conductivity.
It achieves high strength (205~240MPa tensile strength, 130~160MPa yield strength) and high thermal conductivity (thermal conductivity greater than 125 W/(m•K) at 20~200℃), while maintaining low density characteristics by controlling the density within the range of 1.751~1.780g/cm3.
Smart Images
Figure CN122013010A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of magnesium alloy materials technology, and relates to a Mg-Ce-Zr cast magnesium alloy and its preparation method. Background Technology
[0002] With the rapid development of electronic technology, the electronics industry is moving towards miniaturization, integration, and high performance, which has led to a significant increase in the total power density and heat generation of electronic devices. Heat dissipation problems are becoming increasingly prominent, especially for complex structural components of heat dissipation systems in products such as aerospace devices, portable electrical appliances, communication equipment, and transportation vehicles that are sensitive to weight reduction requirements. These systems require materials with low density, high specific strength and specific stiffness, as well as high thermal conductivity and good formability. Therefore, magnesium alloys have gained attention due to their relatively low density and high thermal conductivity.
[0003] Magnesium alloys can be divided into cast magnesium alloys and wrought magnesium alloys. Wrought magnesium alloys, produced through deformation processes such as extrusion, rolling, and forging, have higher strength and better mechanical properties than cast magnesium alloys. However, they suffer from drawbacks such as high processing costs and limited forming shapes, which restricts their widespread application as magnesium alloy parts with complex shapes or intricate structures. Cast magnesium alloys, on the other hand, have good formability and low cost, but their strength is slightly insufficient. Therefore, developing a cast magnesium alloy that combines high strength and high thermal conductivity would meet the material and processing requirements for complex structural components in the aforementioned heat dissipation system.
[0004] Pure magnesium has the highest thermal conductivity of 158 W / (m•K), but its as-cast yield strength and tensile strength are only 2.5 MPa and 11.5 MPa, respectively. The mechanical properties of magnesium alloys are generally improved by adding alloying elements. However, according to thermal conductivity theory, adding alloying elements to the magnesium matrix reduces the thermal conductivity of the material. Therefore, obtaining cast magnesium alloys with high thermal conductivity and high strength is a dilemma or requires a balance. Existing research shows that when alloying elements exist in the magnesium matrix as a second phase, their negative impact on thermal conductivity is far less than when they exist as dissolved atoms. Therefore, while meeting the strength requirements of the alloy, adding as few alloying elements as possible, and ensuring that the alloy forms a stable second phase rather than being dissolved in the magnesium matrix, can maintain high strength while maintaining high thermal conductivity. Furthermore, since most alloying elements have a higher density than magnesium, maintaining the low density of magnesium alloys also requires adding as few alloying elements as possible.
[0005] Currently, most cast magnesium alloys possessing both high strength and high thermal conductivity are magnesium-zinc alloys, such as those specified in patents CN100513606C, CN102719716A, CN101709418A, and CN114351020A. In these alloys, zinc (Zn) is the primary element used for solid solution strengthening to improve the mechanical properties of the magnesium alloy. Other alloying elements balance strength enhancement with minimizing their impact on thermal conductivity. To maintain high strength, the Zn content is mostly above 1.0%, with some exceeding 10%. Although some alloys have a Zn content of less than 1.0%, they also incorporate other rare earth elements and the heavy metal th. In summary, the high strength and high thermal conductivity of existing cast magnesium alloys, due to their higher Zn content or total alloy mass, result in varying degrees of increased density. Summary of the Invention
[0006] In view of the above-mentioned technical status, the present invention provides a Mg-Ce-Zr cast magnesium alloy and its preparation method, so as to achieve at least one of the following objectives: the cast magnesium alloy has high thermal conductivity, or has both high strength and high thermal conductivity, or has both high strength and high thermal conductivity, while the magnesium alloy density can be controlled to a minimum level.
[0007] It is mainly achieved through the following technical solutions:
[0008] On the one hand, the present invention provides a Mg-Ce-Zr cast magnesium alloy, wherein the composition of the magnesium alloy by weight percentage is: 0.5~2.5% Ce, 0.35~0.55% Zr, and the balance being magnesium and unavoidable impurities.
[0009] Furthermore, the composition of the magnesium alloy, by weight percentage, is: 1.0~2.0% Ce, 0.40~0.50% Zr, with the balance being magnesium and unavoidable impurities.
[0010] On the other hand, the present invention also provides a method for preparing the above-mentioned magnesium alloy, comprising the following steps: (1) According to the chemical composition of magnesium alloy, the raw materials are magnesium ingot, Mg-Ce master alloy and Mg-Zr master alloy, and the raw materials are preheated; (2) Melt the preheated magnesium ingot under a protective gas and at 680-720°C to obtain molten magnesium; (3) Add preheated Mg-Ce master alloy to magnesium liquid under protective gas and 700-800℃ conditions. After it is completely melted, raise the temperature to 740-780℃ and add Mg-Zr master alloy. Stir, let it stand for the first time, then refine and remove slag, and let it stand for the second time to cool down. (4) When the furnace temperature drops to 700~720℃, pour it into a custom iron mold and then air cool it to room temperature to obtain a primary magnesium alloy ingot; (5) Heat the primary magnesium alloy ingot to 500~530℃, hold for 5~8 hours, and then quench; (6) Heat the quenched magnesium alloy to 200~230℃ and hold for 10~20 hours, then cool it to room temperature with the furnace.
[0011] Furthermore, in step (1), the Mg-Ce master alloy is a Mg-25wt.%Ce master alloy and the Mg-Zr master alloy is a Mg-25wt.%Zr master alloy.
[0012] Furthermore, in step (1), the preheating temperature is 150-350℃ and the preheating time is 2-6h.
[0013] Furthermore, in step (3), the stirring time is 60-120 min, the first settling time is 60-90 min, and the refining and slag removal are carried out using 99.99% pure argon gas with a flow rate of 80-150 cm³. 3 / min.
[0014] Furthermore, in steps (2) and (3), the protective gas consists of SF6 and N2, with a volume ratio of SF6 to N2 of 1:300 to 800.
[0015] Furthermore, the volume ratio of SF6 to N2 is 1:350 to 650.
[0016] Furthermore, in step (5), quenching involves immersing the heat-preserved primary magnesium alloy ingot in boiling water for cooling.
[0017] Furthermore, the magnesium alloy has a tensile strength of 205~240MPa, a yield strength of 130~160MPa, an elongation of more than 10%, and a thermal conductivity of more than 125 W / (m•K) at 20~200℃.
[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention selects Ce, a rare earth element with a similar atomic radius to magnesium. Ce can refine grains, purify the melt, and improve fluidity and heat resistance in magnesium alloys. Ce, a rare earth element with a solid solubility exceeding that of magnesium, can also form a second phase Mg at grain boundaries. 17 Ce2 and CeMg 12 It has a relatively small negative impact on thermal conductivity, while improving strength by pinning grain boundaries.
[0019] 2. This invention selects Zr, an element that can refine the grains of magnesium alloys to improve their mechanical properties. During solidification, zirconium first precipitates as α-Zr particles. These α-Zr particles have a similar crystal structure to the magnesium matrix, both being close-packed hexagonal lattices with very similar lattice constants. Therefore, they can become high-quality heterogeneous nucleation cores for magnesium grains. These zirconium atoms dissolved in the magnesium matrix are key to the grain refining effect. They can effectively inhibit grain growth and increase the recrystallization temperature of the alloy.
[0020] 3. The rare earth elements Ce and Zr selected in this invention have extremely low solid solubility in the magnesium matrix. Ce forms a second phase outside of the low solid solubility, and the content of Zr is controlled within the low solid solubility range, so a second phase cannot be formed. Therefore, the negative impact of Ce and Zr on thermal conductivity is relatively small, which can maintain the high thermal conductivity characteristics of magnesium to the greatest extent. At the same time, the second phase of Ce and the grain refinement of Zr can both play a role in improving the strength of magnesium alloy, so that high strength and high thermal conductivity can be balanced.
[0021] 4. The Ce and Zr selected in this invention have densities lower than those of Zn, and the total content of Ce and Zr in the magnesium alloy is less than 1.0%. Therefore, the lowest theoretical density of the Mg-Ce-Zr cast magnesium alloy of this invention can reach 1.751 g / cm³. 3 Its density is between 1.751 and 1.780 g / cm³. 3 Within this range, it can also maintain the low-density characteristics of magnesium to the greatest extent.
[0022] 5. This invention achieves high strength and high thermal conductivity in Mg-Ce-Zr cast magnesium alloys through composition design and specific heat treatment processes. The tensile strength is 205~240MPa, the yield strength is 130~160MPa, the elongation is greater than 10%, and the thermal conductivity at 20~200℃ is greater than 125 W / (m•K). Attached Figure Description
[0023] Figure 1 The image shows the microstructure of the Mg-Ce-Zr cast magnesium alloy from Example 1. Figure 2 The tensile curves of the Mg-Ce-Zr cast magnesium alloys in Examples 1-4 are shown. Figure 3 The graphs show the variation of thermal conductivity of magnesium alloys in Examples 1-4 and Comparative Examples 1-2 from 20 to 200°C. Detailed Implementation
[0024] The following detailed description of a Mg-Ce-Zr cast magnesium alloy and its preparation method, with reference to specific embodiments, is provided. These embodiments are for illustrative purposes only, and the present invention is not limited to these embodiments.
[0025] On the one hand, the present invention provides a Mg-Ce-Zr cast magnesium alloy, wherein the composition of the magnesium alloy by weight percentage is: 0.5~2.5% Ce, 0.35~0.55% Zr, and the balance being magnesium and unavoidable impurities.
[0026] First, this invention selects Ce, a rare earth element with a similar atomic radius to magnesium and low solid solubility (0.75% by mass) in magnesium. Specifically, Ce in magnesium alloys can refine grains, purify the melt, and improve fluidity and heat resistance; Ce with high solid solubility can also form a second phase at grain boundaries, having a relatively small negative impact on thermal conductivity, while simultaneously increasing strength by pinning grain boundaries.
[0027] Secondly, this invention selects Zr, an element that can refine the grains of magnesium alloys to improve their mechanical properties. Specifically, zirconium has extremely low solid solubility in magnesium, only 0.58% by mass at the peritectic temperature of 654℃. During solidification, zirconium first precipitates as α-Zr particles. These α-Zr particles have a similar crystal structure to the magnesium matrix, both being close-packed hexagonal lattices with very similar lattice constants (α-Zr: a=0.323nm, c=0.514nm; Mg: a=0.321nm, c=0.521nm), thus serving as excellent heterogeneous nucleation sites for magnesium grains. These zirconium atoms dissolved in the magnesium matrix are key to grain refinement, effectively inhibiting grain growth and increasing the recrystallization temperature of the alloy.
[0028] It should be noted that, due to the extremely low solid solubility of rare earth elements Ce and Zr in the magnesium matrix, Ce forms a second phase outside of its low solid solubility, and Zr content is controlled within the low solid solubility range to prevent the formation of a second phase. Therefore, the negative impact of Ce and Zr on thermal conductivity is relatively small, maximizing the preservation of magnesium's high thermal conductivity. Simultaneously, the second phase of Ce and the grain refinement of Zr both contribute to improving the strength of the magnesium alloy, thus achieving a balance between high strength and high thermal conductivity. Furthermore, Ce has a density of 6.77 g / cm³. 3 The density of Zr is 6.49 g / cm³. 3 All of them have a density lower than that of Zn (7.14 g / cm³). 3 Furthermore, this invention contains only Ce and Zr alloying elements outside the Mg matrix. The total content of Ce and Zr in the magnesium alloy is less than 1.0%, so the minimum theoretical density of the Mg-Ce-Zr cast magnesium alloy of this invention can reach 1.751 g / cm³. 3 Its density is between 1.751 and 1.780 g / cm³. 3 Within this range, it can also maintain the low-density characteristics of magnesium to the greatest extent.
[0029] Furthermore, the composition of the magnesium alloy is optimized, and by weight percentage, it is: 1.0~2.0% Ce, 0.40~0.50% Zr, with the balance being magnesium and unavoidable impurities.
[0030] On the other hand, the present invention also provides a method for preparing the above-mentioned magnesium alloy, comprising the following steps: (1) The equipment used is an electric resistance furnace. The raw materials are magnesium ingots, Mg-Ce master alloy and Mg-Zr master alloy according to the chemical composition of magnesium alloy, and the raw materials are preheated. (2) Melt the preheated magnesium ingot under a protective gas and at 680-720°C to obtain molten magnesium; (3) Add the preheated Mg-Ce master alloy under protective gas and 700-800℃ conditions. After it is completely melted, raise the temperature to 740-780℃ and add the Mg-Zr master alloy. Stir and let it stand for the first time. Then refine and remove slag. Let it stand for the second time to cool down. (4) When the furnace temperature drops to 700~720℃, pour it into a custom iron mold and then air cool it to room temperature to obtain a primary magnesium alloy ingot; (5) Heat the primary magnesium alloy ingot to 500~530℃, then hold it at this temperature for 5~8 hours, and then quench it; (6) Heat the quenched magnesium alloy to 200~230℃ and hold for 10~20 hours, then cool it to room temperature with the furnace.
[0031] It should be noted that in step (1), the raw materials include magnesium ingots, magnesium-cerium master alloys, and magnesium-zirconium master alloys, such as Mg-25wt.%Ce master alloy and Mg-25wt.%Zr master alloy. When preparing the raw materials, the burn-off rate needs to be considered. Specifically, the burn-off rate for Mg ingots is 96%, for Mg-25wt.%Ce it is 95%, and for Mg-25wt.%Zr it is 40%. The preheating temperature is 150–350℃, and the preheating time is 2–6 hours.
[0032] Specifically, in step (3), under protective gas and at 700-800℃, preheated Mg-Ce master alloy is added. After it is completely melted, the temperature is raised to 740-780℃, and Mg-Zr master alloy is added and stirred for 60-120 minutes. The mixture is then allowed to stand for 60-90 minutes for the first time, followed by refining and slag removal, and then a second cooling and standing period. The refining and slag removal is carried out using 99.99% pure argon gas at a flow rate of 80-150 cm³. 3 The refining process continues at a rate of / min until no slag floats to the surface. Preheating the alloy prevents moisture from being introduced into the raw materials, which could cause alloy splashing or even explosions, and also increases the alloy melting speed.
[0033] In steps (2) and (3), the protective gas consists of SF6 and N2, with a volume ratio of SF6 to N2 of 1:300 to 800, such as 1:350 to 650. Gas protection ensures smooth alloy melting and reduces oxide inclusions, thereby improving alloy quality.
[0034] In step (4), the alloy temperature is reduced during casting, the alloy solidification time is shorter, the grains can be refined, the hydrogen absorption phenomenon of the alloy is weakened at a lower temperature, and the wear on the alloy mold can be reduced at the same time.
[0035] Specifically, in step (5), quenching involves immersing the heated primary magnesium alloy ingot in boiling water for cooling. Step (6) is an aging process. In step (5), by controlling the temperature, holding time, and quenching treatment after the process, the solid solution atoms are rapidly locked into the magnesium matrix. In step (6), by controlling the temperature and holding time, the solid solution atoms are dispersed and distributed.
[0036] The tensile properties of the Mg-Ce-Zr cast magnesium alloy of this invention were determined according to GB / T 228.1-2021. The thermal conductivity of the Mg-Ce-Zr cast magnesium alloy was measured using a NETZSCH LFA427 laser thermal conductivity meter. The tensile strength was 205~240 MPa, the yield strength was 130~160 MPa, the elongation was greater than 10%, and the thermal conductivity at 20~200℃ was greater than 125 W / (m•K). This invention achieves both high strength and high thermal conductivity in the Mg-Ce-Zr cast magnesium alloy through compositional design and a specific heat treatment process.
[0037] The following are several specific embodiments and comparative examples of the present invention.
[0038] Example 1 A Mg-Ce-Zr cast magnesium alloy, wherein the composition of the magnesium alloy by weight percentage is: 1.13% Ce, 0.47% Zr, with the balance being magnesium and unavoidable impurities.
[0039] A method for preparing the above-mentioned magnesium alloy includes the following steps: (1) The equipment used is a 3.5Kg resistance furnace. According to the chemical composition of magnesium alloy, the raw materials are 3.412Kg of magnesium ingot, 0.167Kg of Mg-Ce master alloy and 0.110Kg of Mg-Zr master alloy, and the raw materials are preheated. The raw materials include magnesium ingots with a purity of 99.98%, Mg-25wt.%Ce master alloy, and Mg-25wt.%Zr master alloy. During batching, the raw material burn-off rate is calculated based on 96% for Mg ingots, 95% for Mg-25wt.%Ce, and 40% for Mg-25wt.%Zr. The preheating temperature is 200℃, and the preheating time is 3 hours.
[0040] (2) Melt the preheated magnesium ingot under a protective gas and at 720°C to obtain molten magnesium; (3) Add the preheated Mg-Ce master alloy under protective gas and 740℃ conditions. After it is completely melted, raise the temperature to 760℃ and add the Mg-Zr master alloy. Stir and let it stand for the first time. Then refine and remove slag. Let it stand for the second time to cool down. Add Mg-Zr master alloy and stir for 90 min, let stand for 60 min, then refine and remove slag, and let stand to cool. Refining and slag removal are carried out using 99.99% pure argon gas at a flow rate of 100 cm³ / min. 3 / min, until no slag floats to the surface and refining is complete.
[0041] In steps (2) and (3), the protective gas consists of SF6 and N2, with a volume ratio of SF6 to N2 of 1:500.
[0042] (4) When the furnace temperature drops to 700°C, pour it into a custom-made iron mold and then air cool it to room temperature to obtain a primary magnesium alloy ingot; (5) Heat the primary magnesium alloy ingot to 520°C, then hold it at this temperature for 6 hours, and then put the held primary magnesium alloy ingot into boiling water to cool and quench it. (6) Heat the quenched magnesium alloy to 225°C and hold for 16 hours, then cool it to room temperature in the furnace.
[0043] Figure 1 These are microstructure images of the Mg-Ce-Zr cast magnesium alloy in this embodiment, where (b) is an enlarged view of the area within the yellow box in (a), and (c) and (d) are EDS surface scans of the area within the yellow box in (a). Figure 1 As can be seen, the black part is the magnesium matrix, Ce exists as a second phase at the grain boundaries of the magnesium matrix, while Zr is dissolved in the magnesium matrix.
[0044] The tensile properties of the Mg-Ce-Zr cast magnesium alloy of this embodiment were determined in accordance with GB / T 228.1-2021. The thermal conductivity of the Mg-Ce-Zr cast magnesium alloy of this embodiment was determined using a NETZSCH LFA427 laser thermal conductivity meter. The test results are shown in Table 1. Figure 2 This includes the tensile curve of the magnesium alloy in this embodiment. Figure 3 The figure includes a graph showing the change in thermal conductivity of the magnesium alloy in this embodiment from 20 to 200°C.
[0045] Example 2 A Mg-Ce-Zr cast magnesium alloy, wherein the composition of the magnesium alloy by weight percentage is: 0.94% Ce, 0.36% Zr, with the balance being magnesium and unavoidable impurities.
[0046] A method for preparing the above-mentioned magnesium alloy, wherein the raw material ratio in step (1) is: 3.456 kg of magnesium ingot, 0.139 kg of Mg-Ce master alloy and 0.084 kg of Mg-Zr master alloy; step (5) heating the primary magnesium alloy ingot to 500°C, then holding it at this temperature for 5 hours, and then quenching the held primary magnesium alloy ingot in boiling water; (6) heating the quenched magnesium alloy to 200°C and holding it for 10 hours, and then cooling it to room temperature in the furnace; the rest is exactly the same as in Example 1. The tensile properties and thermal conductivity are also determined by the same method as in Example 1, and the results are shown in Table 1. Figure 2 This includes the tensile curve of the magnesium alloy in this embodiment. Figure 3 The figure includes a graph showing the change in thermal conductivity of the magnesium alloy in this embodiment from 20 to 200°C.
[0047] Example 3 A Mg-Ce-Zr cast magnesium alloy, wherein the composition of the magnesium alloy by weight percentage is: 2.34% Ce, 0.51% Zr, with the balance being magnesium and unavoidable impurities.
[0048] A method for preparing the above-mentioned magnesium alloy, wherein the raw material ratio in step (1) is: 3.230 kg of magnesium ingot, 0.345 kg of Mg-Ce master alloy and 0.119 kg of Mg-Zr master alloy; step (5) heating the primary magnesium alloy ingot to 510°C, then holding it at this temperature for 7 hours, and then quenching the held primary magnesium alloy ingot in boiling water; (6) heating the quenched magnesium alloy to 210°C and holding it for 14 hours, and then cooling it to room temperature in the furnace; the rest is exactly the same as in Example 1. The tensile properties and thermal conductivity are also determined by the same method as in Example 1, and the results are shown in Table 1. Figure 2 This includes the tensile curve of the magnesium alloy in this embodiment. Figure 3 The figure includes a graph showing the change in thermal conductivity of the magnesium alloy in this embodiment from 20 to 200°C.
[0049] Example 4 A Mg-Ce-Zr cast magnesium alloy, wherein the composition of the magnesium alloy by weight percentage is: 0.73% Ce, 0.52% Zr, with the balance being magnesium and unavoidable impurities.
[0050] A method for preparing the above-mentioned magnesium alloy, wherein the raw material ratio in step (1) is: 3.463 kg of magnesium ingot, 0.108 kg of Mg-Ce master alloy and 0.121 kg of Mg-Zr master alloy; step (5) heating the primary magnesium alloy ingot to 530°C, then holding it at this temperature for 8 hours, and then quenching the held primary magnesium alloy ingot in boiling water; (6) heating the quenched magnesium alloy to 220°C and holding it for 20 hours, and then cooling it to room temperature in the furnace; the rest is exactly the same as in Example 1. The methods for determining tensile properties and thermal conductivity are also exactly the same as in Example 1, and the results are shown in Table 1. Figure 2 This includes the tensile curve of the magnesium alloy in this embodiment. Figure 3 The figure includes a graph showing the change in thermal conductivity of the magnesium alloy in this embodiment from 20 to 200°C.
[0051] Comparative Example 1 The composition of the Mg-Ce-Zr cast magnesium alloy in this comparative example is exactly the same as that in Example 1. Except for the heating at 520°C and the holding time of step (5) being 10 hours, the other steps in the preparation method are exactly the same as those in Example 1. The methods for determining tensile properties and thermal conductivity are also exactly the same as those in Example 1, and the results are shown in Table 1. Figure 3 The figure includes a curve showing the change in thermal conductivity of the magnesium alloy in this comparative example from 20 to 200℃.
[0052] Comparative Example 2 The composition of the Mg-Ce-Zr cast magnesium alloy in this comparative example is exactly the same as that in Example 1. The preparation method is exactly the same as in Example 1, except that the heating in step (6) is 225°C and the holding time is 24 hours. The tensile properties and thermal conductivity are also measured in the same way as in Example 1. The results are shown in Table 1. Figure 3 The figure includes a curve showing the change in thermal conductivity of the magnesium alloy in this comparative example from 20 to 200℃.
[0053] Table 1. Process, properties, and microstructure of the examples and comparative examples.
[0054] From Table 1 and Figure 2 As can be seen, the tensile strength of Examples 1-4 is all in the range of 205-240 MPa, the yield strength is all in the range of 130-160 MPa, and the elongation is all greater than 10%. Furthermore, the tensile strength and yield strength increase with the increase of the total Ce and Zr content in the magnesium alloy, which is consistent with the conclusion that adding alloying elements can improve the mechanical properties of magnesium alloys. The quenching holding time of Comparative Example 1 was 10 h, which is outside the 5-8 h range of this invention; the aging holding time of Comparative Example 2 was 24 h, which is outside the 10-20 h range of this invention; the tensile strength of Comparative Examples 1 and 2 is below 200 MPa, and the elongation is below 10%.
[0055] From Table 1 and Figure 3 As can be seen, the thermal conductivity of Examples 1-4 at 20-200℃ is greater than 125 W / (m•K), and the thermal conductivity decreases with increasing total Ce and Zr content in the magnesium alloy, which is consistent with the theory that adding alloying elements to a magnesium matrix reduces the thermal conductivity of the material. In contrast, the thermal conductivity of Comparative Examples 1 and 2 is lower than 125 W / (m•K). It should be noted that the thermal conductivity of Examples 1-3 and Comparative Examples 1-2 is approximately negatively correlated with temperature, while the thermal conductivity of Example 4 is approximately positively correlated with temperature. This is because the limiting solid solubility of Ce in magnesium alloys is 0.75%. In Example 4, the Ce element did not exceed the limiting solid solubility. As the temperature increases, the vibration of electrons and phonons in magnesium alloys intensifies, and the thermal conductivity of the alloy increases. In Examples 1-3 and Comparative Examples 1-2, the Ce element exceeded the limiting solid solubility. As the temperature increases, the number of Ce atoms dissolved in the magnesium matrix reaches saturation, and the lattice distortion also reaches its maximum, thereby hindering the vibration of electrons and phonons. Moreover, this effect is greater than the vibration of electrons and phonons caused by the increase in temperature. Therefore, the overall performance is that the thermal conductivity of magnesium alloys decreases with increasing temperature.
[0056] The above description of the present invention represents only some embodiments, but the present invention is not limited to the specific implementations described above. The specific implementations described above are illustrative and not restrictive. All specific extensions using the materials and methods of the present invention, without departing from the spirit and scope of the claims, are within the protection scope of the present invention.
Claims
1. A Mg-Ce-Zr based cast magnesium alloy, characterized in that, The composition of the magnesium alloy, by weight percentage, is: 0.5-2.5% Ce, 0.35-0.55% Zr, with the balance being magnesium and unavoidable impurities.
2. The magnesium alloy according to claim 1, characterized in that, The composition of the magnesium alloy, by weight percentage, is: 1.0~2.0% Ce, 0.40~0.50% Zr, with the balance being magnesium and unavoidable impurities.
3. A method for preparing a magnesium alloy as described in any one of claims 1 or 2, characterized in that, The preparation method includes the following steps: (1) According to the chemical composition of magnesium alloy, the raw materials are magnesium ingot, Mg-Ce master alloy and Mg-Zr master alloy, and the raw materials are preheated; (2) Melt the preheated magnesium ingot under a protective gas and at 680-720°C to obtain molten magnesium; (3) Add preheated Mg-Ce master alloy to magnesium liquid under protective gas and 700-800℃ conditions. After it is completely melted, raise the temperature to 740-780℃ and add Mg-Zr master alloy. Stir, let it stand for the first time, then refine and remove slag, and let it stand for the second time to cool down. (4) When the furnace temperature drops to 700~720℃, pour it into a custom iron mold and then air cool it to room temperature to obtain a primary magnesium alloy ingot; (5) Heat the primary magnesium alloy ingot to 500~530℃, hold for 5~8 hours, and then quench; (6) Heat the quenched magnesium alloy to 200~230℃ and hold for 10~20 hours, then cool it to room temperature with the furnace.
4. The preparation method according to claim 3, characterized in that, In step (1), the Mg-Ce master alloy is a Mg-25wt.%Ce master alloy and the Mg-Zr master alloy is a Mg-25wt.%Zr master alloy.
5. The preparation method according to claim 3, characterized in that, In step (1), the preheating temperature is 150-350℃ and the preheating time is 2-6h.
6. The preparation method according to claim 3, characterized in that, In step (3), the stirring time is 60-120 min, the first settling time is 60-90 min, and the refining and slag removal is carried out using 99.99% pure argon gas with a flow rate of 80-150 cm³. 3 / min.
7. The preparation method according to claim 3, characterized in that, In steps (2) and (3), the protective gas is composed of SF6 and N2, and the volume ratio of SF6 to N2 is 1:300 to 800.
8. The preparation method according to claim 7, characterized in that, The volume ratio of SF6 to N2 is 1:350 to 650.
9. The preparation method according to claim 3, characterized in that, In step (5), the quenching process involves immersing the heat-preserved primary magnesium alloy ingot in boiling water for cooling.
10. The magnesium alloy according to any one of claims 1 or 2, or the magnesium alloy prepared by the preparation method according to any one of claims 3 to 9, characterized in that, The magnesium alloy has a tensile strength of 205~240MPa, a yield strength of 130~160MPa, an elongation of more than 10%, and a thermal conductivity of more than 125 W / (m•K) at 20~200℃.