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

Abstract

The invention provides a high-thermal-conductivity and high-corrosion-resistance magnesium alloy plate and a preparation method thereof, and belongs to the technical field of magnesium alloy plate preparation. The magnesium alloy plate comprises the following components in percentage by mass: 0.4-2.0% of Mn, 0.2-3% of Ce and the balance of Mg and inevitable impurities, and the development of the high-heat-conductivity and high-corrosion-resistance magnesium alloy plate is realized by regulating and controlling an alloy microstructure through metal mold water-cooling casting, homogenizing heat treatment and rolling deformation. The prepared magnesium alloy plate has excellent heat conduction performance and good corrosion resistance, a new material and a manufacturing method are provided for development of the high-heat-conduction and high-corrosion-resistance magnesium alloy plate, and the usability of the magnesium alloy plate is greatly expanded.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy sheet preparation technology, and particularly relates to a high thermal conductivity and high corrosion resistance magnesium alloy sheet and its preparation method. Background Technology

[0002] With continuous industrial development and the exacerbation of energy shortages and the greenhouse effect, lightweight materials have become a crucial development direction. Magnesium alloys, with their high specific strength and specific stiffness, are the lightest metallic structural materials, possessing excellent electromagnetic shielding properties, machinability, and recyclability, making them promising for applications in aerospace, transportation, and 3C electronics. As sophisticated equipment and structures continue to evolve across various fields, electronic components are trending towards smaller footprints, higher integration, and more severe and complex service environments. This necessitates higher requirements for materials in terms of thermal conductivity and corrosion resistance.

[0003] While pure magnesium has a high thermal conductivity of 157 W / (m·K), its mechanical properties are poor, necessitating alloying and plastic deformation. However, the introduction of alloying elements increases electron and phonon scattering due to the presence of solute atoms and a second phase within the magnesium matrix, significantly reducing thermal conductivity. Currently, the room temperature thermal conductivity of AZ91 rolled magnesium alloy is only 61 W / (m·K). Furthermore, magnesium has a low standard electrode potential of -2.37 V, making it highly susceptible to oxidation. The natural oxide film (MgO / Mg(OH)2) formed on the magnesium surface is porous and cannot effectively isolate corrosive media. The second phase formed after the addition of alloying elements also creates strong galvanic corrosion with the magnesium matrix, further exacerbating the risk of corrosion failure. Therefore, the low thermal conductivity and poor corrosion resistance of magnesium alloys, with the inability to synergistically improve both, have become the core bottleneck restricting their large-scale application in high-end equipment.

[0004] In existing technologies, researchers have largely focused on optimizing single properties to improve the performance of magnesium alloys: some approaches retain thermal conductivity by reducing the amount of alloying elements added, but sacrifice corrosion resistance and mechanical strength; others improve corrosion resistance by introducing multiple alloying elements, but this leads to a significant decrease in thermal conductivity. Regarding processing technology, due to the poor room temperature formability of magnesium alloys, most high thermal conductivity or high corrosion resistance magnesium alloys rely on extrusion processes. However, extrusion processes suffer from low production efficiency, limited sheet size, and high manufacturing costs. Furthermore, extruded sheets exhibit a single texture orientation, which is unfavorable for the subsequent processing and forming of complex structural components. Therefore, there is an urgent need to develop a technical solution that balances composition optimization and process innovation. This solution should achieve a synergistic improvement in the thermal conductivity and corrosion resistance of magnesium alloys by precisely selecting alloying elements, optimizing proportioning parameters, and combining efficient heat treatment and rolling processes, while simultaneously addressing the challenges of formability and large-scale production. Summary of the Invention

[0005] To address the problems of low thermal conductivity and poor corrosion resistance in existing magnesium alloys, this invention proposes a high thermal conductivity and high corrosion resistance magnesium alloy sheet and its preparation method. This invention uses the addition of two alloying elements, Mn and Ce, and a specific element composition ratio to prepare a high thermal conductivity and high corrosion resistance magnesium alloy sheet through metal mold casting, homogenization heat treatment, and multi-pass rolling technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention proposes a high thermal conductivity and high corrosion resistance magnesium alloy sheet, which comprises, by mass percentage: Mn 0.4~2.0wt.%, Ce 0.2~3wt.%, with the balance being Mg and unavoidable impurities.

[0007] Preferably, the alloy comprises, by mass percentage: Mn 0.52~1.65wt.%, Ce 1.54~2.12wt.%, with the balance being Mg and unavoidable impurities; more preferably, the unavoidable impurities include Fe, wherein the Fe content in the high thermal conductivity and high corrosion resistance magnesium alloy sheet is ≤0.02wt.

[0008] This invention also proposes a method for preparing the above-mentioned high thermal conductivity and high corrosion resistance magnesium alloy sheet, comprising the following steps: (1) Using pure magnesium, Mg-Mn master alloy and Mg-Ce master alloy as raw materials, prepare and clean the materials according to the mass percentages mentioned above; (2) Preheat the cleaned raw materials and then melt them in a protective atmosphere; (3) Remove slag from the melt obtained by smelting, and then prepare alloy ingots by water cooling process in a protective atmosphere; (4) The alloy ingot obtained in step (3) is prepared into a billet and subjected to homogenization heat treatment; (5) The billet after homogenization heat treatment in step (4) is preheated, and then the billet is subjected to multiple rolling deformations and finally air cooling treatment to obtain the high thermal conductivity and high corrosion resistance magnesium alloy plate.

[0009] Further, in step (2), the smelting step is as follows: pure magnesium is heated to 680~760℃ to melt, then Mg-Mn master alloy and Mg-Ce master alloy are added until completely melted, the temperature is maintained for 30 minutes and then stirred, and after stirring, the melt is cooled to 680~705℃ and left to stand for 10~20 minutes.

[0010] Furthermore, in step (4), the temperature of the homogenization heat treatment is 450~520℃, and the holding time is 2~12 hours.

[0011] Furthermore, in step (4), the thickness of the blank is 10~30mm.

[0012] Furthermore, in step (5), the preheating time of the billet is 10~35min, and the preheating temperature is 340~460℃.

[0013] Furthermore, in step (5), in the multi-pass rolling, the deformation amount of the first pass is 10%, and the deformation amount of subsequent passes gradually increases, with an increment of 5%, and the cumulative deformation amount is 60~90%; the rolling speed is 0.5~3m / s.

[0014] Furthermore, in step (5), during the multi-pass hot rolling process, annealing is performed between adjacent passes. When the thickness exceeds 5 mm, annealing is performed for 15 minutes; when the thickness is 3.5~5 mm, annealing is performed for 10 minutes; and when the thickness is less than 3.5 mm, annealing is performed for 5 minutes. The annealing temperature is 290~350℃.

[0015] For example, a method for preparing a high thermal conductivity and high corrosion resistance magnesium alloy sheet according to the present invention specifically includes the following steps: (1) Using pure magnesium, Mg-Mn master alloy and Mg-Ce master alloy as raw materials, prepare and clean them according to Mn 0.4~2.0wt.%, Ce 0.2~3wt.%, with the balance being Mg and unavoidable impurities; (2) Preheat the cleaned raw materials to 200~300℃, and then melt them in a protective atmosphere (composed of a mixture of CO2 and SF6, with SF6 volume percentage of 1.0~4.0%). The melting steps are as follows: heat pure magnesium to 680~760℃ to melt, then add Mg-Mn master alloy and Mg-Ce master alloy until completely melted, keep warm for 30 minutes and then stir for 2~6 minutes. After stirring, cool the melt to 680~705℃ and let it stand for 10~20 minutes. (3) Remove slag from the melt obtained by smelting, and then remove the oxide layer on the surface of the alloy ingot by water cooling process in a protective atmosphere to prepare the alloy ingot; (4) The alloy ingot obtained in step (3) is prepared into a billet with a thickness of 10~30mm and subjected to homogenization heat treatment at 450~520℃ for 2~12 hours; (5) The billet after homogenization heat treatment in step (4) is preheated to 340~460℃ and held for 10~35min. Then the billet is subjected to multi-pass rolling deformation. In the multi-pass rolling, the deformation amount of the first pass is 10%, and the deformation amount of the subsequent passes gradually increases by 5%, with a cumulative deformation amount of 60~90%. The rolling speed is 0.5~3m / s. Annealing is performed between adjacent passes. When the thickness exceeds 5mm, annealing is performed for 15 minutes. When the thickness is 3.5~5mm, annealing is performed for 10 minutes. When the thickness is less than 3.5mm, annealing is performed for 5 minutes. The annealing temperature is 290~350℃. After the multi-pass rolling is completed, air cooling is performed to obtain the high thermal conductivity and high corrosion resistance magnesium alloy plate.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: 1. This invention selects high thermal conductivity and high corrosion resistance alloying elements and, through smelting, homogenization heat treatment, and rolling deformation processes, achieves the preparation of high thermal conductivity and high corrosion resistance magnesium alloy plates. In the high thermal conductivity and high corrosion resistance magnesium alloy plates of this invention, Mn has low solubility in magnesium, which can purify Fe in the magnesium matrix and promote the dynamic precipitation of the alloy during hot deformation, forming a dispersed α-Mn nano-precipitate phase. On the one hand, it reduces the solute atom content in the matrix, improves thermal conductivity, fully precipitates and pins dislocations, refines grains, and strengthens the alloy. On the other hand, it can increase the electrode potential of the alloy and improve the oxide film, making it denser, thereby improving the corrosion resistance of the alloy. Ce has low solid solubility and exhibits rare earth texture that weakens the basal texture, which can reduce the influence of solute atoms on thermal conductivity and improve the thermal conductivity of the alloy. The Ce-containing oxide film, due to its increased density and chemical stability, significantly enhances its barrier effect against corrosive media, which is beneficial to improving the corrosion resistance of the magnesium alloy.

[0017] 2. The rolled magnesium alloy sheet prepared by this invention achieves a room temperature thermal conductivity of 146.8 W / (m·K) and a hydrogen evolution corrosion rate of 0.193 mm / y in a 3.5 wt.% NaCl solution. It exhibits excellent thermal conductivity and good corrosion resistance. The resulting sheet meets the thermal conductivity and corrosion resistance requirements of structural components in fields such as satellite radar and transportation, and has broad application prospects. This invention enables large-scale production and provides technical guidance for the development of high thermal conductivity and high corrosion resistance magnesium alloy sheets.

[0018] 3. This invention employs homogenization heat treatment at 450-520℃ and hot rolling at 350-450℃. By controlling the temperature and deformation process, the precipitation and recrystallization behavior of the alloy are influenced, resulting in the full precipitation of Mn and Ce elements. This reduces the solute atomic content in the matrix and creates a high density of small-angle grain boundaries, thus promoting improved thermal conductivity. Furthermore, multi-pass hot rolling improves the formability of the sheet metal. The hot rolling process partially breaks down the magnesium rare-earth intermetallic compound phases, providing energy to promote dynamic precipitation. It also constructs a multi-scale phase structure with refined eutectic phase size, dispersed distribution, and abundant dispersed nano-precipitates. This reduces the alloy's galvanic corrosion tendency and increases its electrode potential, promoting the formation of a denser oxide film and synergistically improving the alloy's thermal conductivity and corrosion resistance. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Metallographic diagram of the high thermal conductivity and high corrosion resistance magnesium alloy prepared in Example 2; Figure 2 The image shows a SEM image of the high thermal conductivity and high corrosion resistance magnesium alloy prepared in Example 2. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] This invention provides a high thermal conductivity and high corrosion resistance magnesium alloy sheet, comprising, by mass percentage: Mn 0.4~2.0 wt.%, Ce 0.2~3 wt.%, with the balance being Mg and unavoidable impurities.

[0026] Preferably, by mass percentage, it includes: Mn 0.52~1.65wt.%, Ce 1.54~2.12wt.%, with the balance being Mg and unavoidable impurities; more preferably, the unavoidable impurities include Fe, and the content of Fe in the high thermal conductivity and high corrosion resistance magnesium alloy sheet is ≤0.02wt.%.

[0027] To overcome the bottleneck of balancing thermal conductivity and corrosion resistance in existing magnesium alloys, this invention precisely selects Mn and Ce dual alloying elements and limits their compatibility. In the technical solution of this invention, Mn has low solubility in magnesium, which can remove harmful Fe impurities from the matrix through purification, while promoting the dynamic precipitation of dispersed α-Mn nanophases during hot deformation. This reduces the scattering of electrons / phonons by solute atoms (lowering thermal conductivity resistance) and also pins dislocations and refines grains (strengthening the alloy). Ce has low solid solubility and a texture-weakening effect, which can reduce the negative impact of solute atoms on thermal conductivity. At the same time, its oxide film has higher density and chemical resistance. The alloy exhibits excellent stability and effectively isolates it from corrosive media. The synergistic effect of two elements avoids the limitations of single elements (e.g., adding only Mn provides limited corrosion resistance, while adding only Ce results in insufficient mechanical properties). By using a ratio of 0.4~2.0 wt.% Mn to 0.2~3 wt.% Ce, a triple synergy of solute atom regulation, precipitated phase dispersion, and oxide film density is achieved. This addresses the antagonistic relationship between thermal conductivity and corrosion resistance in magnesium alloys from the compositional source, providing a foundation for subsequent process control. The resulting alloy achieves a room temperature thermal conductivity exceeding 140 W / (m·K) and a corrosion rate in 3.5 wt.% NaCl solution below 0.36 mm / y, far surpassing commercial magnesium alloys such as AZ91 and WE43. Furthermore, Fe is a typical harmful impurity in magnesium alloys, with a standard electrode potential much higher than Mg. It forms a strong galvanic corrosion with the Mg matrix, and Fe also forms Fe-Mg compounds, exacerbating solute atom scattering and reducing thermal conductivity. This invention reduces corrosion initiation and thermal conductivity obstacles at the source by limiting Fe to ≤0.02wt.% and combining it with the purification effect of Mn (Mn reacts with Fe to form stable compounds that precipitate).

[0028] This invention also proposes a method for preparing the above-mentioned high thermal conductivity and high corrosion resistance magnesium alloy sheet, comprising the following steps: (1) Using pure magnesium, Mg-Mn master alloy and Mg-Ce master alloy as raw materials, prepare and clean them according to the mass percentage; (2) Preheat the cleaned raw materials and then melt them in a protective atmosphere; (3) Remove slag from the melt obtained by smelting, and then prepare alloy ingots by water cooling process in a protective atmosphere; (4) The alloy ingot obtained in step (3) is prepared into a billet and subjected to homogenization heat treatment; (5) The billet after homogenization heat treatment in step (4) is preheated, and then the billet is rolled and deformed in multiple passes. Finally, it is air-cooled to obtain a high thermal conductivity and high corrosion resistance magnesium alloy plate.

[0029] In step (2) of this embodiment, the smelting process is as follows: pure magnesium is heated to 680-760℃ to melt, then Mg-Mn master alloy and Mg-Ce master alloy are added until completely melted, held at this temperature for 30 minutes, and then stirred. After stirring, the melt is cooled to 680-705℃ and allowed to stand for 10-20 minutes. Below 680℃, pure magnesium is difficult to completely melt, and above 760℃, Mg volatilization and oxidation are aggravated, affecting the accuracy of the composition. Holding and stirring for 30 minutes ensures that the Mg-Mn and Mg-Ce master alloys are completely melted, resulting in a uniform distribution of the composition and avoiding local element enrichment. Cooling to 680-705℃ and allowing it to stand reduces the melt viscosity, facilitating the rise of bubbles and impurities, improving melt purity, and preventing defects such as porosity and inclusions in the ingot. Through this smelting process, a uniform and highly pure alloy melt can be obtained, laying the foundation for the subsequent ingot quality and final performance. If the temperature or time parameters deviate (such as excessively high temperature causing Mg to volatilize), the actual content of Mn and Ce will be insufficient, and a sufficient amount of precipitated phase will not be formed, resulting in a decrease in thermal conductivity and corrosion resistance.

[0030] In step (4) of this embodiment, the homogenization heat treatment temperature is 450~520℃, and the holding time is 2~12 hours. The core function of homogenization heat treatment is to eliminate ingot composition segregation and promote element diffusion. The temperature of 450~520℃ is close to the recrystallization temperature of magnesium, which can allow Mn and Ce elements to diffuse fully without causing excessive grain growth. Below 450℃, diffusion is insufficient and segregation cannot be eliminated. Above 520℃, the grains are coarse, which affects the subsequent rolling formability. Holding for 2~12 hours can ensure complete element diffusion, making the ingot structure more uniform, creating conditions for the dynamic precipitation of α-Mn and Ce-containing phases in the subsequent rolling process, thereby eliminating ingot defects, improving the formability in the rolling process, and promoting the dispersed distribution of precipitated phases. Homogenization is a key process step for performance synergy.

[0031] In step (4) of this embodiment, the thickness of the billet is 10~30mm. This thickness ensures sufficient homogenization and uniform rolling deformation, resulting in a plate with consistent thickness and uniform structure, thus avoiding performance fluctuations caused by improper billet thickness.

[0032] In step (5) of this embodiment, the preheating time of the billet is 10~35 min, and the preheating temperature is 340~460℃. The preheating treatment in this embodiment can ensure the smooth progress of multi-pass hot rolling, avoid rolling defects (such as cracks and delamination), and maintain the fine-grained structure of the billet, providing a guarantee for subsequent precipitate control.

[0033] In step (5) of this embodiment, during multi-pass rolling, the deformation amount of the first pass is 10%, and the deformation amount of subsequent passes gradually increases by 5%, with a cumulative deformation amount of 60-90%. The rolling speed is 0.5-3 m / s. During multi-pass hot rolling, annealing is performed between adjacent passes. Annealing is performed for 15 minutes when the thickness exceeds 5 mm, for 10 minutes when the thickness is 3.5-5 mm, and for 5 minutes when the thickness is less than 3.5 mm. The annealing temperature is 290-350℃. In this embodiment, multi-pass rolling can achieve microstructure optimization while ensuring formability, reducing solute atom scattering (improving thermal conductivity) and reducing galvanic corrosion tendency (improving corrosion resistance), thus achieving optimal overall performance of the sheet metal.

[0034] All raw materials used in the embodiments of the present invention were purchased commercially. The Mg-Mn master alloy was Mg-5Mn (wt.%) master alloy, and the Mg-Ce master alloy was Mg-30Ce (wt.%) master alloy. The pure magnesium, Mg-5Mn (wt.%) master alloy and Mg-30Ce (wt.%) master alloy were purchased from Shanxi Yinguang Huasheng Magnesium Industry Co., Ltd. and Shanxi Bada Magnesium Industry Co., Ltd., respectively.

[0035] The technical solution of the present invention will be further illustrated by the following embodiments.

[0036] Examples 1-5 (1) Using pure magnesium, Mg-Mn master alloy and Mg-Ce master alloy as raw materials, prepare and clean them according to Examples 1 to 5 in Table 1; (2) Preheat the cleaned raw materials to 250°C, and then melt them in a protective atmosphere (composed of a mixture of CO2 and SF6, with SF6 accounting for 2.0% by volume). The melting steps are as follows: heat pure magnesium to 720°C to melt, then add Mg-Mn master alloy and Mg-Ce master alloy until completely melted, keep warm for 30 minutes and then stir for 4 minutes. After stirring, cool the melt to 690°C and let it stand for 10 minutes. (3) Remove slag from the melt obtained by smelting, and then remove the oxide layer on the surface of the alloy ingot by water cooling process in a protective atmosphere to prepare the alloy ingot; (4) The alloy ingot obtained in step (3) is prepared into a billet with a thickness of 10~20mm and subjected to homogenization heat treatment at 500℃ for 12 hours; (5) The billet after homogenization heat treatment in step (4) is preheated to 400℃ and held for 30 minutes. Then the billet is subjected to multi-pass rolling deformation. In the multi-pass rolling, the deformation amount of the first pass is 10%, and the deformation amount of the subsequent passes gradually increases by 5%, with a cumulative deformation amount of 90%. The rolling speed is 0.5~3m / s. Annealing is performed between adjacent passes. When the thickness exceeds 5mm, annealing is performed for 15 minutes. When the thickness is 3.5~5mm, annealing is performed for 10 minutes. When the thickness is less than 3.5mm, annealing is performed for 5 minutes. The annealing temperature is 350℃. After the multi-pass rolling is completed, air cooling is performed to obtain high thermal conductivity and high corrosion resistance magnesium alloy plate.

[0037] The metallographic structure and scanning electron microscope (SEM) images of the high thermal conductivity and high corrosion resistance magnesium alloy prepared in Example 2 are shown below. Figure 1 and Figure 2 As can be seen, after a cumulative rolling deformation of 90%, the Mg-Mn-Ce alloy forms a second phase distributed in bands along the rolling direction. This second phase is effectively broken up and refined, exhibiting a dispersed distribution. This microstructure ensures the continuity of the heat conduction channels while avoiding strong scattering of electron transport by coarse or continuous second phases. Sufficient dynamic precipitation of the alloy reduces the solute atom content, which is beneficial for maintaining the alloy's high thermal conductivity. Simultaneously, Mn elements purify impurities such as Fe and reduce the driving force of micro-galvanic corrosion, while Ce elements form a rare-earth second phase with a small potential difference and thermal stability, promoting the formation of a dense and stable corrosion product film, significantly inhibiting the occurrence of localized corrosion. The synergistic effect of the strong deformation texture and the fine, uniformly distributed second phase enables the alloy to maintain excellent thermal conductivity and corrosion resistance even under high deformation conditions.

[0038] Table 1. Elemental composition of high thermal conductivity and high corrosion resistance magnesium alloy plates in Examples 1-5 (balance: Mg and unavoidable impurities). Comparative Example 1 The preparation method is the same as in Example 1, except that the materials are prepared according to the elemental composition of Comparative Example 1 in Table 2.

[0039] Comparative Example 2 The preparation method is the same as in Example 1, except that the materials are prepared according to the elemental composition of Comparative Example 2 in Table 2.

[0040] Comparative Example 3 The preparation method is the same as in Example 1, except that the materials are prepared according to the elemental composition of Comparative Example 3 in Table 2.

[0041] Comparative Example 4 The preparation method is the same as in Example 1, except that the materials are prepared according to the elemental composition of Comparative Example 4 in Table 2.

[0042] Comparative Example 5 The preparation method is the same as in Example 1, except that the materials are prepared according to the elemental composition of Comparative Example 5 in Table 2, and the homogenization step is omitted. Specifically: (1) Using pure magnesium, Mg-Mn master alloy and Mg-Ce master alloy as raw materials, prepare and clean them according to Comparative Example 5 in Table 2; (2) Preheat the cleaned raw materials to 250°C, and then melt them in a protective atmosphere (composed of a mixture of CO2 and SF6, with SF6 accounting for 2.0% by volume). The melting steps are as follows: heat pure magnesium to 720°C to melt, then add Mg-Mn master alloy and Mg-Ce master alloy until completely melted, keep warm for 30 minutes and then stir for 4 minutes. After stirring, cool the melt to 690°C and let it stand for 10 minutes. (3) Remove slag from the melt obtained by smelting, and then remove the oxide layer on the surface of the alloy ingot by water cooling process in a protective atmosphere to prepare the alloy ingot; (4) The alloy ingot obtained in step (3) is prepared into a billet with a thickness of 10~20mm. The billet is then preheated to 400℃ and held for 30min. The billet is then subjected to multi-pass rolling deformation. In the multi-pass rolling, the deformation amount of the first pass is 10%, and the deformation amount of subsequent passes gradually increases by 5%, with a cumulative deformation amount of 90%. The rolling speed is 0.5~3m / s. Annealing is performed between adjacent passes. When the thickness exceeds 5mm, annealing is performed for 15 minutes. When the thickness is 3.5~5mm, annealing is performed for 10 minutes. When the thickness is less than 3.5mm, annealing is performed for 5 minutes. The annealing temperature is 350℃. After the multi-pass rolling is completed, air cooling is performed to obtain a high thermal conductivity and high corrosion resistance magnesium alloy plate.

[0043] Table 2 Elemental composition of high thermal conductivity and high corrosion resistance magnesium alloy plates of Comparative Examples 1-5 (balance is Mg and unavoidable impurities) Performance testing 1. Thermal conductivity test The magnesium alloy plates obtained in Examples 1-5 and Comparative Examples 1-5 were used to measure the thermal conductivity of the alloys using a laser thermal conductivity meter. Circular samples with a diameter of 12.7 mm and a thickness of 2 mm were prepared. The thermal conductivity test results are shown in Table 3.

[0044] Table 3. Thermal conductivity test results of magnesium alloy plates in each embodiment and comparative example. As shown in Table 3, the magnesium alloy sheet prepared in the embodiments of this invention exhibits excellent thermal conductivity, ranging from 141.3 to 146.8 W / (m·K). In contrast, in Comparative Examples 1-4, the excessively high Ce content leads to an increase in the number of solute atoms in the matrix, enhancing the scattering of electrons and phonons, hindering their free movement within the Mg lattice, and reducing their mean free path, thereby lowering the thermal conductivity of the magnesium alloy. Comparative Example 5, lacking homogenization treatment before rolling, exhibits reduced dynamic precipitation behavior during the rolling process, resulting in an increased number of solute atoms in the matrix and a decrease in the alloy's thermal conductivity.

[0045] 2. Immersion test in 3.5 wt.% NaCl solution The magnesium alloy plates prepared in Examples 1-5 and Comparative Examples 1-5 were immersed in a 3.5 wt.% NaCl solution. The corrosion rate results are shown in Table 4.

[0046] Table 4 Results of NaCl solution immersion test As shown in Table 4, the high thermal conductivity and high corrosion resistance magnesium alloy prepared in the embodiments of the present invention exhibits a corrosion rate as low as 0.193 mm / y in the salt spray immersion test, demonstrating excellent corrosion resistance, lower than that of ultrapure magnesium. In contrast, the Ce content in Comparative Examples 1-4 exceeds the suitable range, and the coarse and excessively large volume of the second phase exacerbates the galvanic corrosion effect between the second phase and the matrix, accelerating corrosion and exceeding a corrosion rate of 0.5 mm / y. Comparative Example 5, due to the lack of homogenization treatment, has a high Mg content... 12 Both the Ce phase and the α-Mn phase are irregular in shape and relatively coarse and continuous. Their distribution is extremely uneven after rolling, which will aggravate the galvanic corrosion of the alloy and reduce the uniformity of the surface oxide film, thus significantly reducing the corrosion resistance.

[0047] Comparative Example 6 (containing only Mn element (no Ce)) Same as Example 2, except that Ce element is removed from the composition, Mn content is maintained at 1.05 wt.% (same as Example 2), Fe content is 0.009 wt.%, and the balance is Mg and unavoidable impurities. The preparation process is completely consistent with Example 2.

[0048] Comparative Example 7 (containing only Ce element (no Mn)) Same as Example 2, except that Mn element is removed from the composition, Ce content is maintained at 1.86 wt.% (same as Example 2), Fe content is 0.009 wt.%, and the balance is Mg and unavoidable impurities. The preparation process is completely consistent with Example 2.

[0049] Comparative Example 8 Same as Example 2, except that Al element is used to replace Ce, Al content is 1.86 wt.% (consistent with Ce content in Example 2), Mn content is 1.05 wt.%, Fe content is 0.009 wt.%, and the remaining components and preparation process are completely the same.

[0050] Comparative Example 9 Same as Example 2, except that the multi-pass rolling in step (5) is replaced by an extrusion process with an extrusion temperature of 350°C and an extrusion ratio of 10:1. The rest of the process is completely the same as in Example 2.

[0051] Comparative Example 10 Same as Example 2, except that the raw materials are prepared according to the following elemental composition: Mn content is 1.26 wt.%, Ce content is 2.65 wt.%, Ca content is 0.08 wt.%, and the balance is Mg. The rest of the process is completely the same as in Example 2.

[0052] Comparative Example 11 Same as Example 2, except that the multi-pass rolling is specifically as follows: The billet after homogenization heat treatment in step (4) is preheated to 500℃ and held for 25 minutes. Then the billet is subjected to multi-pass rolling deformation. In the multi-pass rolling, the deformation amount of the first pass is 30%, and the deformation amount of subsequent passes gradually increases by 10%, with a cumulative deformation amount of 55%. The rolling speed is 4.5 m / s. Annealing is performed between adjacent passes. When the thickness exceeds 5 mm, annealing is performed for 15 minutes. When the thickness is 3.5~5 mm, annealing is performed for 10 minutes. When the thickness is less than 3.5 mm, annealing is performed for 5 minutes. The annealing temperature is 500℃. After the multi-pass rolling is completed, air cooling is performed to obtain a high thermal conductivity and high corrosion resistance magnesium alloy plate.

[0053] Performance testing The test methods are consistent with those described above. The thermal conductivity test results of the magnesium alloy plates in Comparative Examples 6 to 11 are shown in Table 5, and the NaCl solution immersion test results are shown in Table 6.

[0054] Table 5. Thermal conductivity test results of magnesium alloy plates Table 6 Results of NaCl solution immersion test The core innovation of this invention lies in constructing a compositional system with Mn and Ce as essential synergistic elements, and matching it with a precisely controlled rolling process. Mn is crucial for ensuring the alloy's corrosion resistance (Comparative Example 7 demonstrates that its absence leads to significant degradation in corrosion resistance), while Ce is a unique element that forms the conductive pathway of the Mg-Ce phase, improves thermal conductivity, and synergistically enhances corrosion resistance (Comparative Examples 6 and 8 respectively demonstrate that Ce deficiency or substitution with Al leads to a decrease in thermal conductivity and corrosion resistance). In terms of compositional design, this invention avoids interference from harmful elements such as Ca by precisely controlling the content of Mn and Ce and the total number of solute atoms (Comparative Example 10), achieving optimal performance. In terms of process design, a strictly limited rolling temperature range (Comparative Example 11 demonstrates that exceeding the temperature leads to grain coarsening and a decrease in corrosion resistance) ensures a fine and uniform grain structure and favorable substructure, thereby translating the compositional advantages into excellent overall performance of the sheet metal. Therefore, this invention successfully solves the problem of simultaneously achieving high thermal conductivity and high corrosion resistance in magnesium alloy sheets, representing a significant technological advancement and necessity compared to conventional processes (Comparative Example 9).

[0055] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high thermal conductivity and high corrosion resistance magnesium alloy sheet, characterized in that, It includes, by mass percentage: Mn 0.4~2.0 wt.%, Ce 0.2~3 wt.%, with the balance being Mg and unavoidable impurities.

2. The high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 1, characterized in that, It includes, by mass percentage: Mn 0.52~1.65wt.%, Ce 1.54~2.12wt.%, with the balance being Mg and unavoidable impurities.

3. The high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 2, characterized in that, The unavoidable impurities include Fe, and the content of Fe in the high thermal conductivity and high corrosion resistance magnesium alloy sheet is ≤0.02wt.%.

4. A method for preparing a high thermal conductivity and high corrosion resistance magnesium alloy sheet according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Using pure magnesium, Mg-Mn master alloy and Mg-Ce master alloy as raw materials, prepare and clean the materials according to the mass percentages mentioned above; (2) Preheat the cleaned raw materials and then melt them in a protective atmosphere; (3) Remove slag from the melt obtained by smelting, and then prepare alloy ingots by water cooling process in a protective atmosphere; (4) The alloy ingot obtained in step (3) is prepared into a billet and subjected to homogenization heat treatment; (5) The billet after homogenization heat treatment in step (4) is preheated, and then the billet is subjected to multiple rolling deformations and finally air cooling treatment to obtain the high thermal conductivity and high corrosion resistance magnesium alloy plate.

5. The method for preparing high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 4, characterized in that, In step (2), the smelting process is as follows: pure magnesium is heated to 680~760℃ to melt, then Mg-Mn master alloy and Mg-Ce master alloy are added until completely melted, the mixture is kept at the temperature for 30 minutes and then stirred. After stirring, the melt is cooled to 680~705℃ and left to stand for 10~20 minutes.

6. The method for preparing the high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 4, characterized in that, In step (4), the temperature of the homogenization heat treatment is 450~520℃, and the holding time is 2~12 hours.

7. The method for preparing high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 4, characterized in that, In step (4), the thickness of the blank is 10~30mm.

8. The method for preparing high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 4, characterized in that, In step (5), the preheating time of the billet is 10~35min, and the preheating temperature is 340~460℃.

9. The method for preparing the high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 4, characterized in that, In step (5), the deformation amount of the first pass in the multi-pass rolling is 10%, and the deformation amount of subsequent passes gradually increases by 5%, with a cumulative deformation amount of 60~90%; the rolling speed is 0.5~3m / s.

10. The method for preparing the high thermal conductivity and high corrosion resistance magnesium alloy sheet according to claim 9, characterized in that, In step (5), during the multi-pass hot rolling process, annealing is performed between adjacent passes. When the thickness exceeds 5 mm, annealing is performed for 15 minutes; when the thickness is 3.5~5 mm, annealing is performed for 10 minutes; and when the thickness is less than 3.5 mm, annealing is performed for 5 minutes. The annealing temperature is 290~350℃.

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