A high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag and its preparation method

Abstract

This invention belongs to the field of metallic materials technology, specifically relating to a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag and its preparation method. This invention employs a method of online heating and rolling with a small number of passes and large deformation amounts to further deform the extruded alloy slab. This process further breaks down the initially refined second-phase particles in the extruded alloy, dispersing them within the grains and at grain boundaries. This provides sufficient second-phase strengthening for the magnesium-lithium alloy, significantly improving the overall mechanical properties of the magnesium-lithium alloy sheet. The final product is a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, with a yield strength of 240MPa–275MPa, a tensile strength of 270MPa–330MPa, an elongation of 5%–15%, and a density of 1.470 g / cm³. 3 ~1.570g / cm 3 .

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, specifically relating to a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag and its preparation method. Background Technology

[0002] Magnesium-lithium alloys, as the lightest metallic structural materials, offer significant weight reduction advantages in aerospace, defense equipment, and high-precision instruments, exhibiting characteristics such as high specific strength, good damping and vibration reduction properties, and excellent electromagnetic shielding performance. However, the room temperature tensile strength of commercial magnesium-lithium alloys (such as LA141) is generally below 250 MPa, and the yield strength is often below 150 MPa, making it difficult to meet the mechanical requirements of main load-bearing structural components. Simultaneously, the addition of lithium severely compromises the alloy's thermal stability; the high-temperature strength of traditional magnesium-lithium alloys decreases sharply above 100°C, exhibiting poor creep resistance and rapid grain coarsening under warm conditions, making them unreliable in environments with thermal effects (100°C~200°C), such as engine perimeters and aircraft skin. Therefore, simultaneously improving the room temperature strength and high-temperature heat resistance of magnesium-lithium alloys is crucial to overcoming their application bottlenecks.

[0003] Alloying is an important approach to improve the mechanical properties and thermal stability of magnesium-lithium alloys. Silver (Ag) has a high solid solubility in magnesium (up to 15% at the eutectic temperature), and its atomic size and electronic structure differ significantly from those of magnesium, resulting in a strong lattice distortion solid solution strengthening effect. When the silver content exceeds the solid solubility, an intermetallic compound second phase precipitates, which can pin grain boundaries and dislocations, thereby improving the room temperature strength and high-temperature creep resistance of the alloy. However, existing rolling processes for magnesium-lithium alloy thin plates mostly employ multi-pass repeated hot rolling combined with intermediate annealing. Under this process, the plate undergoes multiple heating and deformation processes, which easily leads to poor microstructure uniformity, significant anisotropy, and strong texture. This makes it difficult to achieve sufficient, dispersed, and uniform distribution of the second phase particles in the Ag-containing alloy, thus limiting the realization of Ag's strengthening potential and hindering the acquisition of thin plate products with both high strength and high heat resistance.

[0004] Therefore, there is an urgent need to develop a new method for preparing magnesium-lithium alloy thin plates that can refine and disperse the second-phase particles in Ag-containing magnesium-lithium alloys while maintaining their low density. This would simultaneously improve the room temperature strength and high temperature heat resistance of the alloys, meeting the application requirements of advanced equipment for ultra-lightweight, high-strength, and heat-resistant structural materials. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag and its preparation method. In this invention, Ag is added to a Mg-Li-Al alloy to provide solid solution strengthening and generate a thermally stable phase. The alloy is then pre-deformed into a slab by extrusion, followed by a novel short-path, high-efficiency deformation process involving few passes and large deformation in-line heating rolling to improve the alloy's strength and plasticity, thus producing a novel high-strength, high-heat-resistant magnesium-lithium alloy thin plate. This achieves a combination of lightweight, high strength, and high heat resistance in the magnesium-lithium alloy thin plate.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions: This invention provides a method for preparing a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag. The preparation method includes: (1) melting, casting, preheating and extruding the raw materials sequentially to obtain an extruded slab; (2) subjecting the extruded slab to online heating and rolling deformation treatment to obtain a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag; wherein, the high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, by mass fraction, includes Li: 4wt.%~13wt.%, Al: 0~4wt.%, Ag: 0.5wt.%~3wt.%, with the remainder being magnesium and unavoidable impurities; the number of online heating and rolling passes is 2~4 passes, the single-pass rolling reduction is 15%~25%, and the total rolling reduction is 65%~85%.

[0007] Preferably, in the above preparation method, the temperature of online heating and rolling is 80℃~250℃.

[0008] More preferably, in the above preparation method, the temperature of online heating and rolling is 100℃~200℃.

[0009] Preferably, in the above preparation method, the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate obtained has a thickness of 0.3 mm to 0.5 mm.

[0010] Preferably, in the above preparation method, the online rolling temperature of the slab during the rolling process is 200°C, the rolling passes are 4, the single-pass rolling reduction is 25%, the total rolling reduction is 72%, the thickness of the extruded slab is 2mm, and the thickness of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy thin plate is 0.58mm; or the online rolling temperature of the slab during the rolling process is 100°C, the rolling passes are 4, the single-pass reduction is 25%, the total reduction is 73%, the thickness of the extruded slab is 2mm, and the thickness of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy thin plate is 0.54mm.

[0011] Preferably, in the above preparation method, the Ag-containing high-strength and high-heat-resistant magnesium-lithium alloy plate, by mass fraction, includes: Li: 5wt.%~12wt.%, Al: 1wt.%~3wt.%, Ag: 1wt.%~3wt.%, with the remainder being magnesium and unavoidable impurities, and the total impurity content being ≤0.3wt.%.

[0012] Preferably, in the above preparation method, in step (1), casting includes: removing slag from the alloy melt obtained by melting at a temperature of 720℃~750℃ and stirring it evenly, letting it stand for 10 minutes~15 minutes, pouring it into a mold, and naturally cooling it in a vacuum melting furnace to remove the surface oxide scale or contamination layer to obtain an alloy ingot; and / or in step (1), the preheating temperature is 200℃~300℃ and the time is 0.5 hours~3 hours; and / or in step (1), the extrusion molding conditions include: an extrusion ratio of (20~30):1, an extrusion speed of 0.1mm / s~2mm / s, and an extrusion temperature of 200℃~300℃.

[0013] More preferably, in the above preparation method, in step (1), the preheating temperature is 220℃~280℃ and the time is 1~2 hours; and / or in step (1), the extrusion molding conditions include: an extrusion ratio of (24~28):1, an extrusion speed of 0.1mm / s~1mm / s, and an extrusion temperature of 220℃~280℃.

[0014] Another aspect of the present invention provides a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, which is prepared by the above-described preparation method.

[0015] Preferably, the thickness of the above-mentioned Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate is 0.3 mm to 0.5 mm, and the density is 1.470 g / cm³. 3 ~1.570g / cm 3 The yield strength is 240MPa~275MPa, the tensile strength is 270MPa~330MPa, and the elongation is 5%~15%.

[0016] The beneficial effects of this invention include at least the following: By employing a method of online heating and rolling with a small number of passes and a large deformation amount, the extruded alloy slab is further deformed, and the initially refined second-phase particles in the extruded alloy are further broken down, causing them to disperse within the grains and at the grain boundaries. This provides sufficient second-phase strengthening for the magnesium-lithium alloy, greatly improving the comprehensive mechanical properties of the magnesium-lithium alloy sheet. The final product is a high-strength, high-heat-resistant magnesium-lithium alloy sheet containing Ag, with a yield strength of 240MPa–275MPa, a tensile strength of 270MPa–330MPa, an elongation of 5%–15%, and a density of 1.470 g / cm³. 3 ~1.570g / cm 3 . Attached Figure Description

[0017] Figure 1 The metallographic structure of the extruded slab prepared by the extrusion process in Example 1; Figure 2The metallographic structure of the extruded slab prepared by the extrusion process in Example 2; Figure 3 The metallographic structure of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy sheet prepared by online heating rolling process in Example 1; Figure 4 The metallographic structure of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy sheet prepared by online heating rolling process in Example 2; Figure 5 The stress-strain curve of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy thin sheet prepared by online heating rolling process in Example 1 is shown. Figure 6 The stress-strain curves of Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy thin plates prepared by online heating rolling process in Example 2 are shown. Detailed Implementation

[0018] The embodiments described are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the embodiments described. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0020] In a first aspect, embodiments of the present invention provide a method for preparing a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag. The preparation method includes: (1) melting, casting, preheating and extruding the raw materials sequentially to obtain an extruded slab; (2) subjecting the extruded slab to online heating and rolling deformation treatment to obtain a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag; wherein, the high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, by mass fraction, includes Li: 4wt.%~13wt.%, Al: 0~4wt.%, Ag: 0.5wt.%~3wt.%, with the remainder being magnesium and unavoidable impurities; the number of passes in the online heating and rolling is 2~4, the single-pass rolling reduction is 15%~25%, and the total rolling reduction is 65%~85%.

[0021] It should be noted that this invention, by adding Ag, which provides strong solid solution strengthening, as the main alloying element to the Mg-Li-Al alloy system, and simultaneously forming a dispersed, thermally stable second phase pinning grain boundaries during the extrusion-small-pass, large-deformation online heating rolling process, anchors misalignments, significantly improving the alloy's creep resistance and endurance strength under high-temperature environments, thus bringing significant strength and high-temperature stability to magnesium-lithium alloys. In addition, this invention pre-optimizes the microstructure of magnesium-lithium alloy slabs through extrusion pre-deformation, and dynamic recrystallization occurs during hot extrusion, generating a large number of fine recrystallized grains. The size of the second phase particles can also be refined, making the as-cast microstructure more uniform and improving the mechanical properties of magnesium-lithium alloy slabs.

[0022] It should also be noted that the Li content of the magnesium-lithium alloy plate in this invention can preferably be 4wt.%, 7wt.%, 10wt.%, or 13wt.%, etc., to control the low-density characteristics of the alloy; the Al content can preferably be 0wt.%, 2wt.%, or 4wt.%, etc., to improve the matrix strength; the Ag content can preferably be 0.5wt.%, 1wt.%, 2wt.%, or 3wt.%, etc., to refine the grains, suppress high-temperature grain boundary slip, and significantly improve the heat resistance and strength of the alloy. The rolling passes can preferably be 2, 3, or 4, etc., the single-pass reduction can preferably be 15%, 20%, or 25%, etc., and the total reduction can preferably be 65%, 75%, or 85%, etc., etc. Through multi-pass gradual deformation, cracking due to single large reduction is avoided, and online heating improves rolling plasticity, ultimately obtaining a magnesium-lithium alloy plate with uniform structure, high strength, and high heat resistance.

[0023] Preferably, in the above preparation method, the temperature of online heating and rolling is 80℃~250℃.

[0024] It should be noted that the online heating rolling temperature in this invention can preferably be 8℃, 120℃, 180℃ or 250℃, etc. If the temperature is too low, the alloy plasticity is poor and rolling cracks are easy to occur; if the temperature is too high, the grains are easy to coarsen and the strength is reduced. This temperature range takes into account both rolling plasticity and structural stability, ensuring the formability and mechanical properties of the plate.

[0025] More preferably, in the above preparation method, the temperature of online heating and rolling is 100℃~200℃.

[0026] It should be noted that the online heating rolling temperature in this invention can be further preferred to be 100℃, 150℃ or 200℃, which is the optimal rolling temperature range. At this temperature, the alloy has good plasticity and moderate deformation resistance, which can achieve stable rolling. At the same time, the grain refinement effect is optimal, and the strength and heat resistance of the plate are best matched.

[0027] Preferably, in the above preparation method, the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate obtained has a thickness of 0.3 mm to 0.5 mm.

[0028] It should be noted that the thickness of the Ag-containing high-strength and high-heat-resistant magnesium-lithium alloy plate in this invention can preferably be 0.3mm, 0.4mm or 0.5mm, which is an ultra-thin specification that meets the requirements of lightweight applications. This thickness, combined with the rolling process, can ensure the dimensional accuracy and surface quality of the plate, making it suitable for thin-walled component scenarios such as aerospace and electronics.

[0029] Preferably, in the above preparation method, the online rolling temperature of the slab during the rolling process is 200°C, the rolling passes are 4, the single-pass rolling reduction is 25%, the total rolling reduction is 72%, the thickness of the extruded slab is 2mm, and the thickness of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy thin plate is 0.58mm; or the online rolling temperature of the slab during the rolling process is 100°C, the rolling passes are 4, the single-pass reduction is 25%, the total reduction is 73%, the thickness of the extruded slab is 2mm, and the thickness of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy thin plate is 0.54mm.

[0030] It should be noted that the preparation method of the present invention can preferably use the rolling process described above, and the prepared Ag-containing high-strength and high-heat-resistant magnesium-lithium alloy thin plate has excellent yield strength and tensile strength.

[0031] Preferably, in the above preparation method, the Ag-containing high-strength and high-heat-resistant magnesium-lithium alloy plate, by mass fraction, includes: Li: 5wt.%~12wt.%, Al: 1wt.%~3wt.%, Ag: 1wt.%~3wt.%, with the remainder being magnesium and unavoidable impurities, and the total impurity content being ≤0.3wt.%.

[0032] It should be noted that in the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate of the present invention, the composition of Li can preferably be 5wt.%, 8wt.%, or 12wt.%, Al can preferably be 1wt.%, 2wt.%, or 3wt.%, and Ag can preferably be 1wt.%, 2wt.%, or 3wt.%, which is the optimal ratio for performance; Li balances low density and strength, Al strengthens the matrix, and Ag refines the grains and improves heat resistance; impurities are ≤0.3wt.%, avoiding the deterioration of mechanical and heat resistance properties by impurities, and ensuring the high purity and stability of the alloy.

[0033] Preferably, in the above preparation method, in step (1), casting includes: removing slag from the alloy melt obtained by melting at a temperature of 720℃~750℃ and stirring it evenly, letting it stand for 10 minutes~15 minutes, pouring it into a mold, and naturally cooling it in a vacuum melting furnace to remove the surface oxide scale or contamination layer to obtain an alloy ingot; and / or in step (1), the preheating temperature is 200℃~300℃ and the time is 0.5 hours~3 hours; and / or in step (1), the extrusion molding conditions include: an extrusion ratio of (20~30):1, an extrusion speed of 0.1mm / s~2mm / s, and an extrusion temperature of 200℃~300℃.

[0034] It should be noted that in the preparation method of this invention, the casting temperature can preferably be 720℃, 735℃, or 750℃, etc., and the standing time can preferably be 10 minutes, 12 minutes, or 15 minutes, etc., vacuum cooling to remove oxide scale, ensuring that the ingot is pure and free of inclusions; the preheating temperature can preferably be 200℃, 250℃, or 300℃, etc., and the time can preferably be 0.5 hours, 1 hour, or 3 hours, etc., to eliminate internal stress and improve plasticity; the extrusion ratio can preferably be 20:1, 25:1, or 30:1, etc., the speed can preferably be 0.1mm / s, 1mm / s, or 2mm / s, etc., and the extrusion temperature can preferably be 200℃, 250℃, or 300℃, etc., to refine the as-cast structure and improve the uniformity of the billet, laying the foundation for subsequent rolling.

[0035] More preferably, in the above preparation method, in step (1), the preheating temperature is 220℃~280℃ and the time is 1~2 hours; and / or in step (1), the extrusion molding conditions include: an extrusion ratio of (24~28):1, an extrusion speed of 0.1mm / s~1mm / s, and an extrusion temperature of 220℃~280℃.

[0036] It should be noted that in the preparation method of this invention, the preheating can preferably be 220℃, 250℃ or 280℃, and the time can preferably be 1 hour or 2 hours, etc., to achieve optimal plasticity; the extrusion ratio can preferably be 24:1, 26:1 or 28:1, etc., the speed can preferably be 0.1mm / s, 0.5mm / s or 1mm / s, etc., and the extrusion temperature can preferably be 220℃, 250℃ or 280℃, etc., to achieve the best microstructure refinement effect, with no cracking and uniform performance of the billet, which is suitable for the rolling requirements of ultra-thin plates.

[0037] Secondly, embodiments of the present invention provide a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, which is prepared by the above-described preparation method.

[0038] It should be noted that the Ag-containing high-strength and high-heat-resistant magnesium-lithium alloy plate of the present invention uses magnesium-lithium as the matrix and Ag as the reinforcing element. It is prepared by melting, extrusion and online heating rolling. The grains are fine and uniform with no obvious defects. It has low density, high strength, high heat resistance and good formability, solves the shortcomings of traditional magnesium-lithium alloys and is suitable for lightweight and heat-resistant applications in aerospace, electronics, automobiles and other fields.

[0039] Preferably, the thickness of the above-mentioned Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate is 0.3 mm to 0.5 mm, and the density is 1.470 g / cm³. 3 ~1.570g / cm 3 The yield strength is 240MPa~275MPa, the tensile strength is 270MPa~330MPa, and the elongation is 5%~15%.

[0040] It should be noted that the thickness of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate in this invention can preferably be 0.3mm, 0.4mm, or 0.5mm, etc., to suit ultra-thin components; the density can preferably be 1.470g / cm³. 3 1.520g / cm 3 Or 1.570 g / cm 3 It achieves lightweighting; the yield strength can be preferably 240MPa, 260MPa or 275MPa, and the tensile strength can be preferably 270MPa, 300MPa or 330MPa, etc., with excellent strength; the elongation can be preferably 5%, 10% or 15%, etc., with good formability, taking into account lightweighting, high strength and heat resistance, and high industrial application value.

[0041] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0042] In the following examples, the pure magnesium ingots (purity ≥99.95%), pure aluminum ingots (purity ≥99.99%), magnesium-lithium master alloys (Li content 10wt.%~20wt.%), and magnesium-silver master alloys (Ag content 10wt.%~20wt.%) used are all commercially available products. The vacuum melting furnace was evacuated to 2.5×10⁻⁶. -1 After Pa, high-purity argon gas was introduced as a protective gas. Tensile tests were performed using a UTM4104 universal testing machine, metallographic observation was conducted using an OLYMPUS PMG3 metallographic microscope, scanning electron microscopy was performed using a FEI NOVA 400, and heat treatment was performed using a DZF-6050BZ vacuum drying oven.

[0043] Preparation Example Example 1 This embodiment provides a high-strength, high-heat-resistant magnesium-lithium alloy sheet containing Ag. By mass fraction, its chemical composition is: Li 8%, Al 3%, Ag 2%, with the remainder being magnesium and unavoidable impurities, and the total impurity content is ≤0.3%.

[0044] The preparation method includes the following steps: (1) Smelting and casting: Weigh pure magnesium ingots, pure aluminum ingots, magnesium-lithium master alloy, and magnesium-silver master alloy according to the above proportions; place the raw materials into a crucible under argon protection, heat the furnace to 750℃ and hold until all materials are completely melted to obtain an alloy melt. Stir at 740℃ to make the composition uniform, remove surface slag, let stand for 12 minutes and then pour into a stainless steel mold with a diameter of Φ90mm and a length of 300mm, and cool naturally in a vacuum furnace. Subsequently, remove the surface oxide scale and contaminant layer by wire cutting to obtain an alloy ingot with a diameter of Φ80mm.

[0045] (2) Extrusion Pre-deformation: The above alloy ingot is placed in a heating furnace for preheating at 250℃ for 1 hour. Then, the preheated ingot is extruded on an extrusion press using a 110mm×2mm slab die. The extrusion process parameters are: extrusion temperature 250℃, extrusion ratio 28:1, and extrusion speed 0.8mm / s. After extrusion forming, the slab is immediately cooled to room temperature using a fan to obtain an extruded slab with a thickness of 2mm.

[0046] (3) Online heating rolling with large deformation in few passes: The above-mentioned extruded slab is subjected to online heating rolling deformation treatment. During the rolling process, an online heating device is used to maintain the slab temperature at 200℃, the rolling passes are 4, the single-pass rolling reduction is 25%, the total rolling reduction is 72%, and finally a 0.58mm thick Ag-containing high-strength and high-heat-resistant magnesium-lithium alloy thin plate (online hot-rolled magnesium-lithium alloy thin plate) is obtained.

[0047] Example 2 This embodiment provides a high-strength, high-heat-resistant magnesium-lithium alloy sheet containing Ag. By mass fraction, its chemical composition is: Li 12%, Al 3%, Ag 2%, with the remainder being magnesium and unavoidable impurities, and the total impurity content is ≤0.3%.

[0048] The preparation method is roughly the same as in Example 1, except that the parameters of online heating rolling are different, while the rest are the same as in Example 1; wherein, the parameters of online heating rolling in Example 2 include: online heating rolling temperature of 100℃, 4 passes, single pass reduction of 25%, total reduction of 73%, and final sheet thickness of 0.54mm.

[0049] Examples 3 to 4 Examples 3 and 4 are largely the same as Example 1, except that the amount of Ag added is different, otherwise they are the same as Example 1; wherein, the amount of Ag added in Examples 3 and 4 is 0.5 wt.% and 3 wt.%, respectively.

[0050] Examples 5 to 6 Examples 5 and 6 are largely the same as Example 1, except that the online heating rolling temperature is different, otherwise they are the same as Example 1; wherein, the online heating rolling temperatures of Examples 5 and 6 are 60°C and 150°C, respectively.

[0051] Comparative Example 1 Comparative Example 1 is largely the same as Example 1, except that no Ag element is added to the magnesium-lithium alloy sheet in Comparative Example 1. Otherwise, it is the same as Example 1.

[0052] Comparative Example 2 Comparative Example 2 is largely the same as Example 2, except that no Ag element is added to the magnesium-lithium alloy sheet in Comparative Example 2. Otherwise, it is the same as Example 2.

[0053] Comparative Example 3 Comparative Example 3 is largely the same as Example 1, except that the heating and rolling parameters are different, while the rest are the same as Example 1. The heating and rolling parameters in Comparative Example 3 include: rolling temperature 220°C, 4 rolling passes, 10% reduction per pass, 40% total reduction, and a final sheet thickness of 1.2 mm.

[0054] Comparative Example 4 Comparative Example 4 is largely the same as Example 1, except that the parameters for online heating rolling are different, while the other parameters are the same as in Example 1. The parameters for online heating rolling in Comparative Example 4 include: rolling temperature 200°C, 6 rolling passes, 9% reduction per pass, 55% total reduction, and a final sheet thickness of 0.9 mm.

[0055] Comparative Example 5 Comparative Example 5 is largely the same as Example 1, except that the parameters for online heating rolling are different, while the other parameters are the same as in Example 1. The parameters for online heating rolling in Comparative Example 5 include: rolling temperature 200°C, 10 rolling passes, 7% reduction per pass, 70% total reduction, and a final sheet thickness of 0.6 mm.

[0056] Characterization test Figure 1 The metallographic structure of the extruded slab prepared by the extrusion process in Example 1 is shown. Figure 1It is evident that after extrusion pre-deformation, the magnesium-lithium alloy undergoes significant dynamic recrystallization, resulting in a marked refinement of the grains. The coarse as-cast structure is broken up, forming a more uniform fine-grained structure.

[0057] Figure 2 The metallographic structure of the extruded slab prepared by the extrusion process in Example 2 is shown. Figure 1 Similarly, the high Li content (12%) alloy also underwent dynamic recrystallization during extrusion, resulting in a refined grain structure. Due to the high Li content, more β-Li phase is visible in the figure, providing a good plasticity basis for subsequent rolling.

[0058] Figure 3 The metallographic structure of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy sheet prepared by online heating rolling process in Example 1 is shown. Figure 1 compared to, Figure 3 The microstructure is more uniform, and the second phase originally present in the extruded slab is further broken down into fine, spherical, and dispersed particles (the size is refined from the micrometer to the submicrometer scale). These dispersed reinforcing phases can effectively pin grain boundaries and dislocations, which is the microstructure basis for the material to obtain high strength and high heat resistance.

[0059] Figure 4 This is the metallographic structure of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy sheet prepared by online heating rolling process in Example 2. As can be seen, the high-Li content alloy, after rolling with a small number of passes and large deformation, exhibits a uniform and fine microstructure, with a dispersed second phase and small grain size. Figure 3 compared to, Figure 4 The higher Li content and increased proportion of β-Li phase result in a microstructure exhibiting typical two-phase characteristics, which is beneficial for improving the elongation of the material.

[0060] Figure 5 The stress-strain curves are for the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy sheet prepared by online heating rolling process in Example 1. Figure 5 It can be seen that the material exhibits high yield strength and tensile strength (yield 270MPa, tensile 326MPa) during the stretching process, while also having a certain plastic elongation (6%). The curve shows typical work hardening characteristics, indicating that the thin plate prepared by the process of the present invention has both high strength and acceptable plasticity.

[0061] Figure 6 The stress-strain curves are shown for the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy thin sheet prepared by online heating rolling process in Example 2. Figure 6 As can be seen, due to the increase in Li content (12%), the elongation of the material increased significantly to 13%, while still maintaining a high yield strength (267MPa) and tensile strength (285MPa), demonstrating the excellent plastic forming ability of magnesium-lithium alloy.

[0062] Performance testing According to the standard GB / T228.1-2021, the yield strength, tensile strength, elongation and density of the extruded slab (obtained in step (2)), the online hot-rolled magnesium-lithium alloy sheet (obtained in step (3)) and the online hot-rolled magnesium-lithium alloy sheet (obtained in step (3)) in the examples and comparative examples were tested after being held at 150℃ for 72h. The results are shown in Table 1 below.

[0063] Table 1. Test results of sheet material performance in the examples and comparative examples. As can be seen from Table 1 above, Comparing Example 1 and Comparative Example 1, Comparative Example 1 did not contain Ag, but all other aspects were the same as Example 1. The yield strength of the thermoplastic magnesium-lithium alloy sheet obtained in Example 1 was 270 MPa, while that in Comparative Example 1 was only 198 MPa, representing a 36.4% improvement. Furthermore, the tensile strength of the thermoplastic magnesium-lithium alloy sheet obtained in Example 1 was 326 MPa, while that in Comparative Example 1 was 225 MPa, representing a 44.9% improvement. Additionally, after high-temperature treatment, the yield strength of the thermoplastic magnesium-lithium alloy sheet obtained in Example 1 decreased from 270 MPa to 265 MPa, with a yield strength retention rate of 98.1%. In contrast, after high-temperature treatment, the yield strength of Comparative Example 1 decreased from 198 MPa to 172 MPa, with a yield strength retention rate of 86.9%, significantly lower than that of Example 1.

[0064] In addition, comparing Example 2 and Comparative Example 2, Comparative Example 2 did not contain Ag, but was otherwise identical to Example 2. The yield strength of the magnesium-lithium alloy sheet obtained in Example 2 was 267 MPa, while that in Comparative Example 2 was only 185 MPa, representing a 44.3% improvement. Furthermore, the tensile strength of the magnesium-lithium alloy sheet obtained in Example 2 was 285 MPa, while that in Comparative Example 2 was 199 MPa, representing a 43.2% improvement. Moreover, after high-temperature treatment, the yield strength of the magnesium-lithium alloy sheet obtained in Example 2 decreased from 267 MPa to 255 MPa, with a yield strength retention rate of 95.5%, while the yield strength of Comparative Example 2 decreased from 185 MPa to 153 MPa after high-temperature treatment, with a yield strength retention rate of 82.7%, significantly lower than that of Example 2.

[0065] In addition, comparing Example 1 and Comparative Example 3, although Comparative Example 3 added the same amount of Ag (2 wt.%) as Example 1, it did not use the "few passes, large deformation, online heating rolling" process specified in this invention. Instead, it used a traditional small deformation rolling process (single pass reduction 5%–10%, total reduction 30%–40%, no online heating). The yield strength of the magnesium-lithium alloy sheet obtained in Example 1 was 270 MPa, while that in Comparative Example 3 was only 242 MPa, representing an 11.6% improvement over Comparative Example 3. Furthermore, the tensile strength of the magnesium-lithium alloy sheet obtained in Example 1 was 326 MPa, while that in Comparative Example 3 was 278 MPa, representing a 17.3% improvement over Comparative Example 3. Furthermore, the magnesium-lithium alloy sheet obtained in Example 1, after high-temperature treatment, retained 98.1% of its yield strength (from 270 MPa to 265 MPa), while the yield strength of Comparative Example 3, after high-temperature treatment, decreased from 242 MPa to 235 MPa, with a yield strength retention rate of 97.1%. The retention rates of the two examples are similar, but the absolute strength value of Example 1 is significantly higher than that of Comparative Example 3. This indicates that the "few passes, large deformation" method defined in this invention, combined with the online heating process, can more effectively refine the grains and break down the second phase, thereby obtaining higher room-temperature strength and excellent high-temperature stability.

[0066] Furthermore, although the alloy composition of Comparative Example 3 differs from that of Example 2, further comparison reveals that: Example 2 (Li 12%, Ag 2%) using the process of this invention achieves a yield strength of 267 MPa, while Comparative Example 3 (Li 8%, Ag 2%) using a conventional rolling process achieves a yield strength of only 242 MPa. With the same Ag content, the process of this invention enables the high-Li alloy to achieve higher strength while maintaining a lower density (the density of Example 2 is 1.475 g / cm³). 3 The density of Comparative Example 3 is 1.567 g / cm³. 3 This fully demonstrates that the process of the present invention has a significant strengthening effect on different component systems.

[0067] The above comparison results show that the addition of Ag is a key factor in improving the room temperature strength and high temperature stability of magnesium-lithium alloys. The "few passes, large deformation online heating rolling" process defined in this invention further amplifies the strengthening effect of Ag. The synergistic effect of the two increases the yield strength and tensile strength of the alloy to over 270 MPa and over 285 MPa, respectively, with a high temperature strength retention rate of over 95%, which is significantly better than the comparison schemes without Ag or without the process of this invention.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, characterized in that, Preparation methods include: (1) The raw materials are melted, cast, preheated and extruded in sequence to obtain an extruded slab; (2) The extruded slab is subjected to online heating and rolling deformation treatment to obtain a high-strength and high-heat-resistant magnesium-lithium alloy plate containing Ag; The high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, by mass fraction, includes Li: 4wt.%~13wt.%, Al: 0~4wt.%, Ag: 0.5wt.%~3wt.%, with the remainder being magnesium and unavoidable impurities; The number of passes for online heating rolling is 2 to 4, the single-pass rolling reduction is 15% to 25%, and the total rolling reduction is 65% to 85%.

2. The preparation method according to claim 1, characterized in that, The temperature for online heating and rolling is 80℃~250℃.

3. The preparation method according to claim 2, characterized in that, The temperature for online heating and rolling is 100℃~200℃.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The thickness of the obtained Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate is 0.3 mm to 0.5 mm.

5. The preparation method according to claim 4, characterized in that, During the rolling process, the online rolling temperature of the slab is 200℃, the rolling passes are 4, the single-pass rolling reduction is 25%, the total rolling reduction is 72%, the thickness of the extruded slab is 2mm, and the thickness of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy sheet is 0.58mm; or During the rolling process, the online rolling temperature of the slab is 100℃, with 4 passes, a single pass reduction of 25%, a total reduction of 73%, and the thickness of the extruded slab is 2mm. The thickness of the Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy sheet is 0.54mm.

6. The preparation method according to claim 1, 2, 3 or 5, characterized in that, The high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag contains, by mass fraction: Li: 5wt.%~12wt.%, Al: 1wt.%~3wt.%, Ag: 1wt.%~3wt.%, with the remainder being magnesium and unavoidable impurities, and the total impurity content being ≤0.3wt.%.

7. The preparation method according to claim 1, 2, 3 or 5, characterized in that, In step (1), casting includes: removing slag from the alloy melt obtained from smelting at a temperature of 720℃~750℃ and stirring it evenly, letting it stand for 10 minutes~15 minutes, pouring it into a mold, naturally cooling it in a vacuum melting furnace, removing the surface oxide scale or contaminant layer, and obtaining an alloy ingot; and / or In step (1), the preheating temperature is 200℃~300℃, and the time is 0.5 hours~3 hours; and / or In step (1), the extrusion molding conditions include: an extrusion ratio of (20-30):1, an extrusion speed of 0.1 mm / s to 2 mm / s, and an extrusion temperature of 200℃ to 300℃.

8. The preparation method according to claim 7, characterized in that, In step (1), the preheating temperature is 220℃~280℃, and the time is 1~2 hours; and / or In step (1), the extrusion molding conditions include: an extrusion ratio of (24 to 28):1, an extrusion speed of 0.1 mm / s to 1 mm / s, and an extrusion temperature of 220°C to 280°C; and / or.

9. A high-strength, high-heat-resistant magnesium-lithium alloy plate containing Ag, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate according to claim 9, characterized in that, The Ag-containing high-strength, high-heat-resistant magnesium-lithium alloy plate has a thickness of 0.3mm to 0.5mm and a density of 1.470g / cm³. 3 ~1.570g / cm 3 The yield strength is 240MPa~275MPa, the tensile strength is 270MPa~330MPa, and the elongation is 5%~15%.

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