High-strength, high-thermal-conductivity and high-corrosion-resistance magnesium alloy and preparation method of rolled plate thereof

Abstract

The invention discloses a high-strength, high-thermal-conductivity and high-corrosion-resistance magnesium alloy and a preparation method of a rolled plate thereof, and relates to a magnesium alloy and a preparation method of a rolled plate thereof. In order to solve the problems that an existing magnesium alloy plate is low in absolute strength, low in heat conductivity and poor in corrosion resistance, the high-heat-conductivity, high-strength and high-corrosion-resistance rolled magnesium alloy and the preparation method of the rolled plate of the high-heat-conductivity, high-strength and high-corrosion-resistance rolled magnesium alloy are provided. An innovative deformation method of asynchronous gradient rolling is developed, the structure of the alloy is regulated and controlled, the heat-conducting property, the mechanical property and the corrosion resistance of the magnesium alloy are synergistically improved, meanwhile, the formability of the plate is considered, and the prepared high-heat-conductivity, high-strength and high-corrosion-resistance rolled magnesium alloy plate meets the use requirements of aerospace, transportation and military industry national defense.

Description

Technical Field

[0001] This invention relates to a magnesium alloy and a method for preparing the rolled sheet thereof. Background Technology

[0002] As modern industry evolves towards greater precision and integration, resource constraints and environmental challenges are driving structural materials into a new stage of multi-dimensional performance synergistic optimization. Magnesium-based alloys, as a typical representative of lightweight metals, boast top-tier strength and rigidity parameters among engineering materials, while also exhibiting excellent electromagnetic barrier properties and machinability, making them irreplaceable in aerospace frame components, new energy vehicle power systems, and microelectronic packaging. Current technological development exhibits a dual evolutionary trend: on the one hand, highly integrated devices require components to achieve a three-in-one function of mechanical load-bearing, heat dissipation, and environmental protection within limited space; on the other hand, complex operating environments force materials to achieve breakthrough synergistic improvements in tensile strength, thermal conductivity, and corrosion resistance while maintaining their lightweight advantages. This signifies that the research and development of new magnesium alloys has entered a critical stage of tackling composite performance challenges involving high strength, high thermal conductivity, and high corrosion resistance, requiring cross-scale synergistic innovation at both the microstructure control and preparation levels.

[0003] Magnesium alloys, as the lightest metallic structural materials, are the preferred material for lightweighting high-end equipment. Pure magnesium, with its hexagonal close-packed (HCP) structure where free electrons dominate thermal conduction, exhibits an intrinsic thermal conductivity of 157 W / (m·K). However, its restricted basal slip system results in a room temperature yield strength generally below 100 MPa, requiring alloying to activate non-basal slip or twinning strengthening mechanisms. However, microstructural evolution induced by alloy design significantly alters the material's transport properties: first-principles calculations show that every 1 at.% of dissolved atoms can reduce the thermal conductivity of the magnesium matrix by 15-20%. Experiments confirm that the mean free path of electrons in AZ91 rolled sheet is reduced by 62% compared to pure magnesium, leading to a room temperature thermal conductivity of 61 W / (m·K). Furthermore, the thermal conductivity of WE43 alloy containing Y / RE elements is further reduced to 51 W / (m·K) due to the rare-earth phase interface scattering effect. Regarding corrosion behavior, according to the mixed potential theory, the magnesium matrix (-2.37 V) and β-Mg... 17 Al 12 A potential difference of 1.17 V between phases (-1.20 V) forms a macroscopic electrical couple, accelerating the corrosion kinetics process. The porosity of the oxide film on the surface of typical magnesium alloys is as high as 25-40%, and its equivalent corrosion current density can be 5-8 times that of pure magnesium. This antagonistic effect of strength enhancement and functional degradation makes it difficult for existing magnesium alloy systems to meet the synergistic indicators of tensile strength (≥300 MPa), thermal conductivity (≥120 W / (m·K)) and corrosion rate (≤0.4 mm / y) required for advanced equipment, becoming a key material science challenge restricting its application in fields such as aerospace thermal control components and high-power electronic packaging.

[0004] Although existing research has achieved a better match between thermal conductivity, mechanical properties and corrosion resistance, the developed magnesium alloys are mostly extruded bars or profiles, making it difficult to prepare wide-width plates. There is still no plate that meets the above comprehensive performance requirements, which cannot meet the current demand for high-strength, high-thermal-conductivity and high-corrosion-resistant magnesium alloy plates. Summary of the Invention

[0005] To address the problems of low absolute strength, low thermal conductivity, and poor corrosion resistance in existing magnesium alloy sheets, this invention proposes a method for preparing high thermal conductivity, high strength, and high corrosion resistance rolled magnesium alloy and its rolled sheets. By optimizing the alloying elements and their content, controlling element and phase distribution through heat treatment, and developing an innovative asynchronous gradient rolling deformation method, the microstructure of the alloy is controlled. This achieves a synergistic improvement in the thermal conductivity, mechanical properties, and corrosion resistance of the magnesium alloy, while also ensuring the formability of the sheet. The resulting high thermal conductivity, high strength, and high corrosion resistance rolled magnesium alloy sheets meet the application requirements of aerospace, transportation, and military defense.

[0006] This invention relates to a high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy, which is a Mg-Ce-Mn-Zn-Ca alloy with the following elemental composition by mass percentage: Ce: 0.1~2.5%, Mn: 0.2~1.5%, Zn: 0.5~4.0%, Ca: 0.05~0.5%, and the balance being Mg. By designing specific elemental composition ratios, high-thermal-conductivity, high-strength, and high-corrosion-resistant rolled magnesium alloy sheets are prepared through metal mold casting, homogenization heat treatment, and reverse temperature field rolling techniques.

[0007] The method for preparing high thermal conductivity, high strength, and high corrosion resistance rolled magnesium alloy sheet of the present invention is carried out according to the following steps:

[0008] 1. Weigh the raw materials according to the mass percentage of the elements in the Mg-Mn-Ce-Ca-Zn alloy, and grind and clean the raw materials.

[0009] 2. Preheat the raw materials processed in step one, and then melt them in a protective atmosphere;

[0010] The smelting process is as follows: industrial pure magnesium is heated to 690~760℃ to melt, then Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy are added. After complete melting, the mixture is held at the temperature for 30 minutes, stirred and cooled to 690~710℃, then allowed to stand for 10~20 minutes, and finally alloy ingots are prepared by water cooling process in a protective atmosphere.

[0011] 3. Cut the magnesium alloy ingot into billets and perform homogenization heat treatment;

[0012] The homogenization heat treatment temperature is 420~520℃, and the holding time is 2~16 hours;

[0013] 4. Preheat the billet, then perform asynchronous temperature gradient rolling deformation treatment. Annealing is performed between adjacent passes during the process. After the asynchronous temperature gradient rolling deformation treatment is completed, air cooling is performed to obtain the plate.

[0014] The asynchronous temperature gradient rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10~20%, and the deformation amount of subsequent passes gradually increasing by 5~10%, with a cumulative deformation amount of 60~97%. The rolling speed is 0.5~5.5m / s, and the speed ratio of the upper roll to the lower roll is 1.1~1.3:1. During the rolling process, a tensile stress of 50~60% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet, and the application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device.

[0015] The annealing temperatures between adjacent passes are as follows: the first two passes are 400~460℃, the next two passes are 370~400℃, and the subsequent passes are 340~370℃.

[0016] The annealing time between adjacent passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3.5~5 mm, and 5 minutes for billet thickness of less than 3.5 mm.

[0017] The principles and beneficial effects of this invention are as follows:

[0018] This invention, based on the Mg-Ce-Mn-Ca-Zn alloy system, optimizes alloying elements to achieve beneficial effects such as high strength, high thermal conductivity, and high corrosion resistance. It also optimizes smelting, homogenization, and an innovative asynchronous temperature gradient rolling process, successfully developing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy sheets. Specifically, the use of low-solid-solubility Mn to purify the matrix and promote the dynamic precipitation of dispersed α-Mn nanophases reduces solute atoms, improving thermal conductivity while enhancing strength and corrosion resistance through precipitation strengthening and grain refinement. Ce further reduces the influence of solutes, promotes dynamic recrystallization, and possesses a significant texture-weakening effect, making it particularly suitable for asynchronous rolling. During asynchronous rolling, the different linear speeds of the upper and lower rolls generate strong additional shear strain in the rolling deformation zone. This shear strain, superimposed on the compressive strain of traditional rolling, causes significant shearing in the core of the sheet, leading to stronger grain breakage and lattice rotation, thus optimizing the sheet's uniform plastic deformation capability. Furthermore, Ce is a typical reactive element, tending to segregate at the metal / oxide film interface and grain boundaries of the oxide film, forming CeO2 / Ce2O3 (with high chemical stability and low ion mobility) within the oxide film. This fills the loose pores of the MgO film, enhancing the barrier effect and strengthening the oxide film's density. Zn, as a highly efficient grain refiner, significantly refines the microstructure and inhibits grain growth during rolling, greatly improving strength and plasticity through grain refinement strengthening. Trace amounts of Ca assist in grain refinement and form thermally stable grain boundary phases, contributing to grain boundary strengthening. The synergistic effect of the multi-element combination generates a second phase, promoting dynamic precipitation, reducing the atomic content within the solute, and promoting dynamic recrystallization of the alloy, pinning dislocations, and improving alloy strength.

[0019] 2. The magnesium alloy sheet prepared by this invention exhibits a tensile yield strength of 310-330 MPa, a tensile strength of 350-380 MPa, an elongation of 4.0-7.0%, and a room temperature thermal conductivity of 135-145 W / (m·K). Simultaneously, the hydrogen evolution corrosion rate after immersion in a 3.5 wt.% NaCl solution for 15 days is 0.265-0.379 mm / y. It possesses high strength, high thermal conductivity, and good corrosion resistance. The resulting sheet meets the strength, thermal conductivity, and corrosion resistance requirements of key structural and functional components in aerospace and 3C electronics industries, demonstrating broad application prospects. This invention enables large-scale production and provides technical guidance for the development of high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy sheets.

[0020] 3. This invention achieves multi-scale synergistic control of alloy microstructure through innovative methods such as homogenization heat treatment at 420~520℃ and asynchronous rolling with a cooling temperature gradient: Homogenization heat treatment (420~520℃) promotes partial dissolution and Ostwald ripening and spheroidization of the continuous network eutectic phase at grain boundaries, forming micron-sized isolated particles and improving compositional segregation, significantly reducing deformation resistance; Asynchronous rolling with strong shear strain further breaks the spherical phase into strip-shaped fragments (micron-sized) oriented along the rolling direction, while inducing dynamic precipitation of nano-sized strengthening phases to construct a multi-scale spatial configuration of "strip-shaped broken eutectic phase - dispersed nano-phase" coexistence; and through sufficient dynamic precipitation, the solute atom content in the matrix is ​​reduced, improving the thermal conductivity of the alloy. Gradient cooling treatment utilizes a non-uniform thermal stress field to drive dislocation recombination combined with strong shear strain, forming a uniformly densely distributed small-angle grain boundary network and high-density dislocation walls. Triple regulation and coupling achieve cross-scale strengthening through "micron phase support - nano phase pinning - grain boundary / dislocation retardation", simultaneously improving the alloy's strength, thermal conductivity and corrosion resistance, breaking through the traditional bottleneck of the inversion of strength and plasticity in magnesium alloys.

[0021] 4. This invention utilizes the strong shear strain unique to asynchronous rolling with a differential speed ratio of 1.1-1.3, which facilitates the breakage and dispersed distribution of the second phase, which is difficult to break using conventional rolling methods, under strong shear strain, resulting in a weakened texture under plane strain. A cooling temperature gradient of 460℃~340℃ is set during the inter-pass annealing process to construct a grain boundary type with a high proportion of small-angle grain boundaries, refining the multi-scale phase structure of broken eutectic phases, dispersed distribution, and a large amount of nano-precipitates. This reduces the alloy's galvanic corrosion tendency and increases the electrode potential, while Ce and Ca elements promote the formation of a denser oxide film. Furthermore, tensile stress of 50-60% of the yield strength is applied to both sides of the rolled plate to maintain excellent plate shape. This achieves a synergistic improvement in high thermal conductivity, high strength, and high corrosion resistance, while ensuring excellent plate formability. Attached Figure Description

[0022] Figure 1 The image shows the as-cast metallographic structure of the Mg-Ce-Mn-Zn-Ca alloy prepared in Example 3.

[0023] Figure 2 SEM image of the rolled microstructure of the Mg-Ce-Mn-Zn-Ca alloy prepared in Example 3. Detailed Implementation

[0024] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0025] Specific implementation method one: The high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy in this implementation method is a Mg-Ce-Mn-Zn-Ca alloy, with the following elemental composition by mass percentage: Ce: 0.1~2.5%, Mn: 0.2~1.5%, Zn: 0.5~4.0%, Ca: 0.05~0.5%, and the balance being Mg.

[0026] This embodiment, based on the Mg-Ce-Mn-Ca-Zn alloy system, achieves beneficial effects of high strength, high thermal conductivity, and high corrosion resistance by optimizing alloying elements. Furthermore, it optimizes smelting, homogenization, and an innovative asynchronous temperature gradient rolling process, successfully developing a high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy sheet. Specifically, the use of low-solid-solubility Mn to purify the matrix and promote the dynamic precipitation of dispersed α-Mn nanophases reduces solute atoms, improving thermal conductivity while enhancing strength and corrosion resistance through precipitation strengthening and grain refinement. Ce further reduces the influence of solutes, promotes dynamic recrystallization, and possesses a significant texture-weakening effect, making it particularly suitable for asynchronous rolling. During asynchronous rolling, the different linear speeds of the upper and lower rolls generate strong additional shear strain in the rolling deformation zone. This shear strain, superimposed on the compressive strain of traditional rolling, causes significant shearing in the core of the sheet, leading to stronger grain breakage and lattice rotation, thus optimizing the sheet's uniform plastic deformation capability. Furthermore, Ce is a typical reactive element, tending to segregate at the metal / oxide film interface and grain boundaries of the oxide film, forming CeO2 / Ce2O3 (with high chemical stability and low ion mobility) within the oxide film. This fills the loose pores of the MgO film, enhancing the barrier effect and strengthening the oxide film's density. Zn, as a highly efficient grain refiner, significantly refines the microstructure and inhibits grain growth during rolling, greatly improving strength and plasticity through grain refinement strengthening. Trace amounts of Ca assist in grain refinement and form thermally stable grain boundary phases, contributing to grain boundary strengthening. The synergistic effect of the multi-element combination generates a second phase, promoting dynamic precipitation, reducing the atomic content within the solute, and promoting dynamic recrystallization of the alloy, pinning dislocations, and improving alloy strength.

[0027] Specific Implementation Method Two: The preparation method of high thermal conductivity, high strength, and high corrosion resistance rolled magnesium alloy sheet in this implementation method is carried out according to the following steps:

[0028] 1. Weigh the raw materials according to the mass percentage of the elements in the Mg-Mn-Ce-Ca-Zn alloy, and grind and clean the raw materials.

[0029] 2. Preheat the raw materials processed in step one, and then melt them in a protective atmosphere;

[0030] The smelting process is as follows: industrial pure magnesium is heated to 690~760℃ to melt, then Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy are added. After complete melting, the mixture is held at the temperature for 30 minutes, stirred and cooled to 690~710℃, then allowed to stand for 10~20 minutes, and finally alloy ingots are prepared by water cooling process in a protective atmosphere.

[0031] 3. Cut the magnesium alloy ingot into billets and perform homogenization heat treatment;

[0032] The homogenization heat treatment temperature is 420~520℃, and the holding time is 2~16 hours;

[0033] 4. Preheat the billet, then perform asynchronous temperature gradient rolling deformation treatment. Annealing is performed between adjacent passes during the process. After the asynchronous temperature gradient rolling deformation treatment is completed, air cooling is performed to obtain the plate.

[0034] The asynchronous temperature gradient rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10~20%, and the deformation amount of subsequent passes gradually increasing by 5~10%, with a cumulative deformation amount of 60~97%. The rolling speed is 0.5~5.5m / s, and the speed ratio of the upper roll to the lower roll is 1.1~1.3:1. During the rolling process, a tensile stress of 50~60% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet, and the application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device.

[0035] The annealing temperatures between adjacent passes are as follows: the first two passes are 400~460℃, the next two passes are 370~400℃, and the subsequent passes are 340~370℃.

[0036] The annealing time between adjacent passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3.5~5 mm, and 5 minutes for billet thickness of less than 3.5 mm.

[0037] This embodiment, based on the Mg-Ce-Mn-Ca-Zn alloy system, achieves beneficial effects of high strength, high thermal conductivity, and high corrosion resistance by optimizing alloying elements. Furthermore, it optimizes smelting, homogenization, and an innovative asynchronous temperature gradient rolling process, successfully developing a high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy sheet. Specifically, the use of low-solid-solubility Mn to purify the matrix and promote the dynamic precipitation of dispersed α-Mn nanophases reduces solute atoms, improving thermal conductivity while enhancing strength and corrosion resistance through precipitation strengthening and grain refinement. Ce further reduces the influence of solutes, promotes dynamic recrystallization, and possesses a significant texture-weakening effect, making it particularly suitable for asynchronous rolling. During asynchronous rolling, the different linear speeds of the upper and lower rolls generate strong additional shear strain in the rolling deformation zone. This shear strain, superimposed on the compressive strain of traditional rolling, causes significant shearing in the core of the sheet, leading to stronger grain breakage and lattice rotation, thus optimizing the sheet's uniform plastic deformation capability. Furthermore, Ce is a typical reactive element, tending to segregate at the metal / oxide film interface and grain boundaries of the oxide film, forming CeO2 / Ce2O3 (with high chemical stability and low ion mobility) within the oxide film. This fills the loose pores of the MgO film, enhancing the barrier effect and strengthening the oxide film's density. Zn, as a highly efficient grain refiner, significantly refines the microstructure and inhibits grain growth during rolling, greatly improving strength and plasticity through grain refinement strengthening. Trace amounts of Ca assist in grain refinement and form thermally stable grain boundary phases, contributing to grain boundary strengthening. The synergistic effect of the multi-element combination generates a second phase, promoting dynamic precipitation, reducing the atomic content within the solute, and promoting dynamic recrystallization of the alloy, pinning dislocations, and improving alloy strength.

[0038] 2. The magnesium alloy sheet prepared in this embodiment exhibits a tensile yield strength of 310-330 MPa, a tensile strength of 350-380 MPa, an elongation of 4.0-7.0%, and a room temperature thermal conductivity of 135-145 W / (m·K). Simultaneously, the hydrogen evolution corrosion rate after immersion in a 3.5 wt.% NaCl solution for 15 days is 0.265-0.379 mm / y. It possesses high strength, high thermal conductivity, and good corrosion resistance. The resulting sheet meets the strength, thermal conductivity, and corrosion resistance requirements of key structural and functional components in aerospace and 3C electronics industries, demonstrating broad application prospects. This embodiment enables large-scale production and provides technical guidance for the development of high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy sheets.

[0039] 3. This embodiment achieves multi-scale synergistic control of the alloy microstructure through innovative methods such as homogenization heat treatment at 420~520℃ and asynchronous rolling with a cooling temperature gradient: Homogenization heat treatment (420~520℃) promotes partial dissolution and Ostwald ripening and spheroidization of the continuous network eutectic phase at grain boundaries, forming micron-sized isolated particles and improving compositional segregation, significantly reducing deformation resistance; Asynchronous rolling with strong shear strain further breaks the spherical phase into strip-shaped fragments (micron-sized) oriented along the rolling direction, while inducing dynamic precipitation of nano-sized strengthening phases to construct a multi-scale spatial configuration of "strip-shaped broken eutectic phase - dispersed nano-phase" coexistence; and through sufficient dynamic precipitation, the solute atom content in the matrix is ​​reduced, improving the thermal conductivity of the alloy. Gradient cooling treatment utilizes a non-uniform thermal stress field to drive dislocation recombination combined with strong shear strain to form a uniformly densely distributed small-angle grain boundary network and high-density dislocation walls. Triple regulation and coupling achieve cross-scale strengthening through "micron phase support - nano phase pinning - grain boundary / dislocation retardation", simultaneously improving the alloy's strength, thermal conductivity and corrosion resistance, breaking through the traditional bottleneck of the inversion of strength and plasticity in magnesium alloys.

[0040] 4. This embodiment utilizes the strong shear strain unique to asynchronous rolling with a differential speed ratio of 1.1-1.3, which facilitates the breakage and dispersed distribution of the second phase, which is difficult to break using conventional rolling methods, under strong shear strain, resulting in a weakened texture under plane strain. A cooling temperature gradient of 460℃~340℃ is set during the inter-pass annealing process to construct a grain boundary type with a high proportion of small-angle grain boundaries, refining the multi-scale phase structure of broken eutectic phases, dispersed distribution, and a large amount of nano-precipitates. This reduces the alloy's galvanic corrosion tendency and increases the electrode potential, while Ce and Ca elements promote the formation of a denser oxide film. Furthermore, tensile stress of 50-60% of the yield strength is applied to both sides of the rolled plate to maintain excellent plate shape. This achieves a synergistic improvement in high thermal conductivity, high strength, and high corrosion resistance, while ensuring excellent plate formability.

[0041] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the raw materials mentioned in step one are industrial pure magnesium, Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy.

[0042] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two in that the protective atmosphere described in step two is composed of a mixture of CO2 and SF6, with the volume percentage of SF6 in the mixture being 2.0~4.5%.

[0043] Specific Implementation Method 5: This implementation method differs from Specific Implementation Method 2 in that the thickness of the blank in step 3 is 10~30mm.

[0044] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Two in that the preheating temperature in step four is 340~460℃, and the preheating time is 10~35min.

[0045] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Two in that the asynchronous temperature gradient rolling deformation process described in step four is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by an increment of 10%, resulting in a cumulative deformation amount of 90%. The rolling speed is 2 m / s, and the speed ratio of the upper roll to the lower roll is 1.2:1. During the rolling process, a tensile stress of 55% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet, and the application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device.

[0046] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Two in that the annealing temperature between adjacent passes in step four is as follows: the annealing temperature for the first two passes is 430°C, the annealing temperature for the next two passes is 390°C, and the annealing temperature for the subsequent passes is 365°C.

[0047] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Two in that the annealing time between adjacent passes in step four is as follows: annealing for 15 minutes when the billet thickness is 5mm or more, annealing for 10 minutes when the billet thickness is 3.5~5mm, and annealing for 5 minutes when the billet thickness is less than 3.5mm.

[0048] Specific Implementation Method 10: This implementation method differs from Specific Implementation Method 2 in that the homogenization heat treatment in step 3 is performed at a temperature of 500°C for 12 hours.

[0049] Example 1:

[0050] The preparation method of the high thermal conductivity, high strength, and high corrosion resistance rolled magnesium alloy sheet in this embodiment is carried out according to the following steps:

[0051] 1. Weigh the raw materials according to the mass percentage of the elements in the Mg-Mn-Ce-Ca-Zn alloy, and grind and clean the raw materials.

[0052] The raw materials are industrial pure magnesium, Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy;

[0053] The high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy is a Mg-Ce-Mn-Zn-Ca alloy with the following elemental composition by mass percentage: Ce: 2.1%, Mn: 1.3%, Zn: 2.2%, Ca: 0.2%, and the balance being Mg.

[0054] 2. Preheat the raw materials processed in step one, and then melt them in a protective atmosphere;

[0055] The smelting process is as follows: industrial pure magnesium is heated to 730°C to melt, and then Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy are added. After complete melting, the mixture is kept at the temperature for 30 minutes, stirred to cool the melt to 700°C, and then allowed to stand for 15 minutes. Finally, the alloy ingot is prepared by water cooling process in a protective atmosphere.

[0056] The protective atmosphere consists of a mixture of CO2 and SF6, wherein the volume percentage of SF6 in the mixture is 3%.

[0057] 3. Cut the magnesium alloy ingot into billets and perform homogenization heat treatment;

[0058] The thickness of the blank is 30mm;

[0059] The homogenization heat treatment was performed at a temperature of 500°C for 12 hours.

[0060] 4. Preheat the billet, then perform asynchronous temperature gradient rolling deformation treatment. Annealing is carried out between adjacent passes during the process. After the asynchronous temperature gradient rolling deformation treatment is completed, air cooling is performed to obtain the plate.

[0061] The asynchronous temperature gradient rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 10% each time, resulting in a cumulative deformation amount of 90%. The rolling speed is 2 m / s, and the speed ratio of the upper roll to the lower roll is 1.2:1. During the rolling process, a tensile stress of 55% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet, and the application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device.

[0062] The annealing temperatures between adjacent passes are as follows: the first two passes are 430℃, the next two passes are 390℃, and the subsequent passes are 365℃.

[0063] The annealing time between adjacent passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3.5~5 mm, and 5 minutes for billet thickness of less than 3.5 mm.

[0064] The preheating temperature is 400℃ and the preheating time is 20 minutes.

[0065] Examples 2 through 5 were set up. The difference between Examples 2 through 5 and Example 1 is the composition of the high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy. Other process parameters are the same as in Example 1. The composition of the magnesium alloy in Examples 2 through 5 is shown in Table 1.

[0066] Table 1

[0067]

[0068] Table 2

[0069]

[0070] Figure 1 The image shows the as-cast metallographic structure of the Mg-Ce-Mn-Zn-Ca alloy prepared in Example 3. It can be seen that the second phase in the alloy exhibits a semi-continuous network distribution. The structure of the second phase is free of pores, and there are no casting defects or inclusions. Figure 2 SEM image of the rolled microstructure of the Mg-Ce-Mn-Zn-Ca alloy prepared in Example 3. Figure 2 As shown, the Mg-Ce-Mn-Zn-Ca alloy prepared in Example 3 contains a large number of precipitated, dispersed multi-scale phase structures.

[0071] Comparative Examples 1 through 5 were also set up, and the composition of the magnesium alloys in Comparative Examples 1 through 5 is shown in Table 2. The preparation methods of the magnesium alloy plates in Comparative Examples 1, 3, and 4 were the same as those in Example 1.

[0072] The preparation method of the magnesium alloy sheet in Comparative Example 2 is as follows:

[0073] 1. Weigh the raw materials according to the mass percentage of the elements in the Mg-Mn-Ce-Ca-Zn alloy, and grind and clean the raw materials.

[0074] The raw materials are industrial pure magnesium, Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy;

[0075] The high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy is a Mg-Ce-Mn-Zn-Ca alloy with the following elemental composition by mass percentage: Ce: 2.1%, Mn: 1.3%, Zn: 2.2%, Ca: 0.2%, and the balance being Mg.

[0076] 2. Preheat the raw materials processed in step one, and then melt them in a protective atmosphere;

[0077] The smelting process is as follows: industrial pure magnesium is heated to 730°C to melt, and then Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy are added. After complete melting, the mixture is kept at the temperature for 30 minutes, stirred to cool the melt to 700°C, and then allowed to stand for 15 minutes. Finally, the alloy ingot is prepared by water cooling process in a protective atmosphere.

[0078] The protective atmosphere consists of a mixture of CO2 and SF6, wherein the volume percentage of SF6 in the mixture is 3%.

[0079] 3. Cut the magnesium alloy ingot into billets;

[0080] The thickness of the blank is 30mm;

[0081] 4. Preheat the billet, then perform asynchronous temperature gradient rolling deformation treatment. Annealing is carried out between adjacent passes during the process. After the asynchronous temperature gradient rolling deformation treatment is completed, air cooling is performed to obtain the plate.

[0082] The asynchronous temperature gradient rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 10% each time, resulting in a cumulative deformation amount of 90%. The rolling speed is 2 m / s, and the speed ratio of the upper roll to the lower roll is 1.2:1. During the rolling process, a tensile stress of 55% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet, and the application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device.

[0083] The annealing temperatures between adjacent passes are as follows: the first two passes are 430℃, the next two passes are 390℃, and the subsequent passes are 365℃.

[0084] The annealing time between adjacent passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3.5~5 mm, and 5 minutes for billet thickness of less than 3.5 mm.

[0085] The preheating temperature is 400℃ and the preheating time is 20 minutes.

[0086] The preparation method of the magnesium alloy sheet in Comparative Example 5 is as follows:

[0087] 1. Weigh the raw materials according to the mass percentage of the elements in the Mg-Mn-Ce-Ca-Zn alloy, and grind and clean the raw materials.

[0088] The raw materials are industrial pure magnesium, Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy;

[0089] The high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy is a Mg-Ce-Mn-Zn-Ca alloy with the following elemental composition by mass percentage: Ce: 2.1%, Mn: 1.3%, Zn: 2.2%, Ca: 0.2%, and the balance being Mg.

[0090] 2. Preheat the raw materials processed in step one, and then melt them in a protective atmosphere;

[0091] The smelting process is as follows: industrial pure magnesium is heated to 730°C to melt, and then Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy are added. After complete melting, the mixture is kept at the temperature for 30 minutes, stirred to cool the melt to 700°C, and then allowed to stand for 15 minutes. Finally, the alloy ingot is prepared by water cooling process in a protective atmosphere.

[0092] The protective atmosphere consists of a mixture of CO2 and SF6, wherein the volume percentage of SF6 in the mixture is 3%.

[0093] 3. Cut the magnesium alloy ingot into billets and perform homogenization heat treatment;

[0094] The thickness of the blank is 30mm;

[0095] The homogenization heat treatment was performed at a temperature of 500°C for 12 hours.

[0096] 4. Preheat the billet, then perform asynchronous temperature gradient rolling deformation treatment. Annealing is carried out between adjacent passes during the process. After the asynchronous temperature gradient rolling deformation treatment is completed, air cooling is performed to obtain the plate.

[0097] The asynchronous temperature gradient rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 10%, with a cumulative deformation amount of 90%. The rolling speed is 2 m / s, and the speed ratio of the upper roll to the lower roll is 2:1. During the rolling process, a tensile stress of 55% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet. The application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device.

[0098] The annealing temperatures between adjacent passes are as follows: the first two passes are 430℃, the next two passes are 390℃, and the subsequent passes are 365℃.

[0099] The annealing time between adjacent passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3.5~5 mm, and 5 minutes for billet thickness of less than 3.5 mm.

[0100] The preheating temperature is 400℃ and the preheating time is 20 minutes.

[0101] The results of the tensile mechanical property tests are shown in Table 3:

[0102] Table 3

[0103]

[0104] The thermal conductivity test results are shown in Table 4: The magnesium alloys prepared in Examples 1-5 and Comparative Examples 1-5 were used. The thermal conductivity of the alloys was measured using a laser thermal conductivity meter. The sample size was φ12.7 mm and the thickness was 2 mm. The test results are shown in Table 4.

[0105] The magnesium alloy sheets prepared in Examples 1-5 exhibited excellent thermal conductivity, ranging from 130-145 W / (m·K). However, in Comparative Example 1, the Mn content was too high. In Comparative Examples 3 and 4, the excessive Ce content led to an increase in solute atoms within the matrix, enhancing scattering and hindering the free movement of electrons and phonons within the Mg lattice, thus reducing thermal conductivity. In Comparative Example 2, the lack of homogenization treatment resulted in reduced dynamic precipitation during rolling and an increase in solute atoms, similarly leading to a decrease in thermal conductivity. In Comparative Example 5, the upper and lower roll speed ratio was 2:1, resulting in an excessive speed difference that increased the adiabatic shear bands within the sheet structure, easily causing stress concentration and material instability and fracture. Furthermore, the high density of dislocations and numerous grain boundaries near the shear bands enhanced electron scattering, further reducing thermal conductivity.

[0106] The results of the immersion test in 3.5 wt.% NaCl solution are shown in Table 5:

[0107] The test results above show that the high thermal conductivity and high corrosion resistance magnesium alloys prepared in Examples 1-5 exhibit excellent corrosion resistance with corrosion rates between 0.277 and 0.411 mm / y in salt spray immersion tests, lower than that of ultrapure magnesium. In Comparative Example 1, the Mn, 3, and Ce content in Comparative Example 4 exceeds the suitable range. The coarse and excessively large volumetric second phase exacerbates the galvanic corrosion effect with the matrix, accelerating corrosion and increasing the corrosion rate to over 0.5 mm / y. In Comparative Example 2, due to the lack of homogenization, the phase size is large, and stress concentration after rolling is more likely to occur, leading to alloy failure and exacerbating the alloy's corrosion tendency. In Comparative Example 5, due to the large difference in the upper and lower roll speed ratio, the phase distribution after rolling is extremely uneven and introduces defects, exacerbating the galvanic corrosion of the alloy. Furthermore, the uniformity of the surface oxide film formed deteriorates, resulting in a significant decrease in corrosion resistance.

[0108] Table 4

[0109] Table 5

[0110]

Claims

1. A high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy, characterized in that: The high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy is a Mg-Ce-Mn-Zn-Ca alloy with the following elemental composition by mass percentage: Ce: 0.1~2.5%, Mn: 0.2~1.5%, Zn: 0.5~4.0%, Ca: 0.05~0.5%, and the balance being Mg.

2. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates as described in claim 1, characterized in that: The preparation method of high thermal conductivity, high strength and high corrosion resistance rolled magnesium alloy sheet is carried out according to the following steps:

1. Weigh the raw materials according to the mass percentage of the elements in the Mg-Mn-Ce-Ca-Zn alloy, and grind and clean the raw materials.

2. Preheat the raw materials processed in step one, and then melt them in a protective atmosphere; The smelting process is as follows: industrial pure magnesium is heated to 690~760℃ to melt, then Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy are added. After complete melting, the mixture is held at the temperature for 30 minutes, stirred and cooled to 690~710℃, then allowed to stand for 10~20 minutes, and finally alloy ingots are prepared by water cooling process in a protective atmosphere.

3. Cut the magnesium alloy ingot into billets and perform homogenization heat treatment; The homogenization heat treatment temperature is 420~520℃, and the holding time is 2~16 hours; 4. Preheat the billet, then perform asynchronous temperature gradient rolling deformation treatment. Annealing is performed between adjacent passes during the process. After the asynchronous temperature gradient rolling deformation treatment is completed, air cooling is performed to obtain the plate. The asynchronous temperature gradient rolling deformation process is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10~20%, and the deformation amount of subsequent passes gradually increasing by 5~10%, with a cumulative deformation amount of 60~97%. The rolling speed is 0.5~5.5m / s, and the speed ratio of the upper roll to the lower roll is 1.1~1.3:

1. During the rolling process, a tensile stress of 50~60% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet, and the application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device. The annealing temperatures between adjacent passes are as follows: the first two passes are 400~460℃, the next two passes are 370~400℃, and the subsequent passes are 340~370℃. The annealing time between adjacent passes is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3.5~5 mm, and 5 minutes for billet thickness of less than 3.5 mm.

3. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The raw materials mentioned in step one are industrial pure magnesium, Mg-Ca master alloy, Mg-Zn master alloy, Mg-Mn master alloy and Mg-Ce master alloy.

4. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The protective atmosphere described in step two consists of a mixture of CO2 and SF6, with the volume percentage of SF6 in the mixture being 2.0 to 4.5%.

5. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The thickness of the blank in step three is 10~30mm.

6. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The preheating temperature in step four is 340~460℃, and the preheating time is 10~35min.

7. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The asynchronous temperature gradient rolling deformation process described in step four is as follows: multiple rolling passes are performed, with the deformation amount of the first pass being 10%, and the deformation amount of subsequent passes gradually increasing by 10%, with a cumulative deformation amount of 90%. The rolling speed is 2 m / s, and the speed ratio of the upper roll to the lower roll is 1.2:

1. During the rolling process, a tensile stress of 55% of the yield strength of the billet is applied to the billet. The direction of the tensile stress is parallel to the extension direction of the billet, and the application of the tensile stress is achieved by pulling the two ends of the billet through a tensioning device.

8. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The annealing temperatures between adjacent passes in step four are as follows: the first two passes are annealed at 430°C, the next two passes are annealed at 390°C, and the subsequent passes are annealed at 365°C.

9. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The annealing time between adjacent passes in step four is as follows: 15 minutes for billet thickness of 5 mm or more, 10 minutes for billet thickness of 3.5~5 mm, and 5 minutes for billet thickness of less than 3.5 mm.

10. The method for preparing high-strength, high-thermal-conductivity, and high-corrosion-resistant magnesium alloy plates according to claim 2, characterized in that: The homogenization heat treatment in step three is performed at a temperature of 500℃ for 12 hours.

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