A high-strength magnesium alloy sheet and its preparation method

Abstract

This application discloses an ultra-high strength magnesium alloy sheet and its preparation method, belonging to the field of metallic materials. Through the technical solution provided in the embodiments of this application, a magnesium alloy sheet with specific composition and microstructure can be prepared using a method of restricted free bending deformation and width-limited rolling. Experiments have demonstrated that the prepared magnesium alloy sheet possesses high yield strength and tensile strength, providing a wider range of applications for magnesium alloys.

Description

Technical Field

[0001] This application relates to the field of metallic materials, and in particular to an ultra-high strength magnesium alloy sheet and its preparation method. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials, are increasingly being used to replace traditional high-density metals. Furthermore, magnesium alloys possess numerous advantages, including high specific stiffness, high specific strength, damping and vibration reduction properties, electromagnetic shielding performance, and good electrical and thermal conductivity, making them widely used in industries such as automotive, aerospace, electronics, and biomedicine.

[0003] Magnesium alloys can be divided into wrought magnesium alloys and cast magnesium alloys. Wrought magnesium alloys exhibit significantly superior overall mechanical properties compared to cast magnesium alloys. Therefore, the development of wrought magnesium alloys is of great significance for the widespread application of magnesium alloys. Among them, rolled magnesium alloys, as an important component of wrought magnesium alloys, are the main materials for manufacturing high-performance shell components. Using magnesium alloy sheets to manufacture aircraft skins and panels, as well as automobile bodies and engine compartments, can achieve lightweighting in the aerospace and automotive industries by reducing their weight.

[0004] However, the low strength of magnesium alloys hinders their widespread use as structural materials. Summary of the Invention

[0005] This application provides an ultra-high strength magnesium alloy sheet and its preparation method, which can obtain magnesium alloy sheets with high strength. The technical solution is as follows:

[0006] On the one hand, an ultra-high strength magnesium alloy sheet is provided, which is obtained by restricting free bending deformation and width-limited rolling of magnesium alloy ingots, wherein the magnesium alloy ingots include Mg, Al, Mn, Zn, Cu, Ni, Si, Fe and other impurities;

[0007] The composition, measured by mass percentage, is as follows: Al: 2.8%–3.5%, Mn: 0.6%–1.0%, Zn: 0.91%–0.98%, Cu: 0–0.0011%, Ni: 0–0.0007%, Si: 0–0.013%, Fe: 0–0.0059%, other impurities <0.2%, and the balance being Mg.

[0008] In one possible implementation, the magnesium alloy ingot contains 2.8% to 3.2% Al by mass, 0.7% to 0.95% Mn by mass, 0.95% to 0.98% Zn by mass, and 0.0025% to 0.0058% Fe by mass.

[0009] In one possible implementation, the magnesium alloy ingot contains 3% Al by mass, 0.75% to 0.9% Mn by mass, 0.97% Zn by mass, and 0.005% to 0.0058% Fe by mass.

[0010] In one possible implementation, the mass percentage of Mn in the magnesium alloy ingot is 0.85%.

[0011] In one possible implementation, the mass percentage of Fe in the magnesium alloy ingot is 0.0054%.

[0012] On the one hand, a method for preparing ultra-high strength magnesium alloy sheet is provided, for producing the aforementioned magnesium alloy sheet, the method comprising:

[0013] The ingredients are batched according to the preset mass percentage of each component, and then heated, melted, refined, and cast to obtain magnesium alloy ingots.

[0014] The magnesium alloy ingot is heated and then extruded to obtain a magnesium alloy extruded slab.

[0015] The magnesium alloy extruded slab is hot-rolled to obtain a magnesium alloy hot-rolled plate, and the magnesium alloy hot-rolled plate is air-cooled, oil-cooled, or water-cooled to room temperature.

[0016] The cooled hot-rolled magnesium alloy sheet is placed in a restricted free bending die, and pressure is applied to the hot-rolled magnesium alloy sheet in the restricted free bending die by a press to perform restricted free bending deformation on the hot-rolled magnesium alloy sheet;

[0017] The magnesium alloy hot-rolled plate, after being subjected to restricted free bending, is placed into a width-limiting rolling die. The lower edge of the rolling mill is used to perform width-limiting rolling on the magnesium alloy hot-rolled plate perpendicular to the bending direction within the width-limiting rolling die, thereby obtaining a one-pass rolled magnesium alloy sheet.

[0018] The magnesium alloy sheet is rotated 90° along the normal direction in one pass and the above steps of restricted free bending deformation and width-limited rolling are repeated to obtain the final magnesium alloy sheet.

[0019] In one possible implementation, the step of placing the cooled hot-rolled magnesium alloy sheet into a restricted free bending die, and applying pressure to the hot-rolled magnesium alloy sheet within the restricted free bending die using a press, wherein the restricted free bending deformation of the hot-rolled magnesium alloy sheet includes any of the following:

[0020] The cooled hot-rolled magnesium alloy sheet is placed in a restricted free bending die, and pressure is applied directly to the hot-rolled magnesium alloy sheet in the restricted free bending die by a press at room temperature to perform restricted free bending deformation on the hot-rolled magnesium alloy sheet;

[0021] The cooled hot-rolled magnesium alloy sheet is placed in a restricted free bending die, and the free bending die is placed in a heating furnace for heating. The heating temperature of the heating furnace is 100℃~250℃, and the free bending die is held in the heating furnace for 10min~20min. Pressure is applied to the heated hot-rolled magnesium alloy sheet in the free bending die by a press to perform restricted free bending deformation on the hot-rolled magnesium alloy sheet.

[0022] In one possible implementation, the compression displacement of the press is 5% of the width of the hot-rolled magnesium alloy plate in the compression direction; the bending height for restrictive free bending deformation of the hot-rolled magnesium alloy plate is 2 to 5 times the thickness of the hot-rolled magnesium alloy plate.

[0023] In one possible implementation, the hot-rolled magnesium alloy sheet, after being subjected to restricted free bending, is placed into a width-limiting rolling die, and the sheet is subjected to width-limiting rolling along the lower edge of the mill in a direction perpendicular to the bending direction within the width-limiting rolling die, thereby obtaining a single-pass rolled magnesium alloy sheet according to any of the following:

[0024] The magnesium alloy hot-rolled plate after restricted free bending is placed into a width-limiting rolling die, and the width-limiting rolling is performed directly through the lower edge of the rolling mill at room temperature in the bending direction of the magnesium alloy hot-rolled plate perpendicular to the width-limiting rolling die to obtain a one-pass rolled magnesium alloy plate.

[0025] The hot-rolled magnesium alloy sheet, after being subjected to restricted free bending, is placed into a width-limiting rolling die. The width-limiting rolling die is then placed in a heating furnace for heating at a temperature of 100℃ to 250℃. The width-limiting rolling die is held in the heating furnace for 10 to 20 minutes. The width-limiting rolling is then performed by rolling the hot-rolled magnesium alloy sheet perpendicular to the bending direction within the width-limiting rolling die through the lower edge of the rolling mill, thereby obtaining a one-pass rolled magnesium alloy sheet.

[0026] In one possible implementation, the mill's downward pressure during the width-limiting rolling process is 5%.

[0027] The technical solution provided in this application, employing a method of restricted free bending deformation and width-limited rolling, enables the preparation of a magnesium alloy sheet with a specific composition and microstructure. Experiments have demonstrated that the prepared magnesium alloy sheet possesses high yield strength and tensile strength, providing broader application scenarios for magnesium alloys. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating a method for preparing an ultra-high strength magnesium alloy sheet according to an embodiment of this application;

[0030] Figure 2 This is a schematic diagram of a restricted free bending die provided in an embodiment of this application;

[0031] Figure 3 This is a schematic diagram of a width-limiting rolling die provided in an embodiment of this application;

[0032] Figure 4 This is a scanning electron microscope image of a magnesium alloy sheet (Mn 0.85 wt.%) with the optimal composition prepared at room temperature according to the embodiments of this application;

[0033] Figure 5 This is a transmission electron microscope image of a magnesium alloy sheet (Mn 0.85 wt.%) with the optimal composition prepared at room temperature according to an embodiment of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0035] In this application, the terms "first," "second," etc., are used to distinguish identical or similar items with essentially the same function. It should be understood that there is no logical or temporal dependency between "first," "second," and "n," nor is there any limitation on the quantity or execution order.

[0036] To provide a clearer explanation of the technical solutions provided in the embodiments of this application, some terms involved in the embodiments of this application will be explained below.

[0037] Magnesium alloys are alloys composed of magnesium as the base and other elements added. Their characteristics include: low density, high strength, high elastic modulus, good heat dissipation and vibration damping, greater impact load capacity than aluminum alloys, and good resistance to corrosion from organic substances and alkalis.

[0038] Rolling: a metal processing technique in which a metal billet is passed through the gap between a pair of rotating rolls (of various shapes), and the material's cross-section is reduced and its length is increased due to the compression of the rolls.

[0039] A press is a sophisticated, general-purpose press. It is characterized by its wide range of applications and high production efficiency. Presses can be widely used in processes such as cutting, punching, blanking, bending, riveting, and forming. They process metal parts by applying strong pressure to metal blanks, causing plastic deformation and fracture.

[0040] A mold is a tool used to shape a blank into a part with a specific shape and size under the action of external force. It is widely used in blanking, die forging, cold heading, extrusion, powder metallurgy pressing, pressure casting, and compression molding or injection molding of engineering plastics, rubber, ceramics, and other products. A mold has a specific contour or internal cavity shape. Using the contour shape with cutting edges allows the blank to be separated according to the contour line (blanking). Using the internal cavity shape allows the blank to obtain a corresponding three-dimensional shape.

[0041] In related technologies, methods for strengthening and toughening magnesium alloys include refining grains through large plastic deformation or alloying with rare earth elements, followed by solution treatment and age hardening. Large plastic deformation processing usually requires high temperatures (typically in the range of 423K to 623K), is complex and inefficient, and currently achieves limited strengthening effects. While rare earth alloying has some strengthening effect, the addition of rare earth elements significantly increases raw material costs, and the increased density of high rare earth content magnesium alloys partially offsets the advantages of magnesium alloys as lightweight materials. Furthermore, the preparation and processing of high rare earth content magnesium alloys are complex.

[0042] Furthermore, Mg-Al magnesium alloys are most commonly used at room temperature. Among them, AZ31 has good plastic deformation capacity and is the preferred raw material for the production of magnesium alloy sheets. However, the absolute strength of magnesium alloys is generally low. Typically, the tensile strength and yield strength of AZ31 magnesium alloy are approximately 200MPa to 300MPa. Improving the strength of magnesium alloys is of paramount importance.

[0043] After introducing the terms used in the embodiments of this application, the preparation method of the ultra-high strength magnesium alloy sheet provided in the embodiments of this application will be described below. (See also...) Figure 1 The method includes the following steps.

[0044] S101. The ingredients are batched according to the preset mass percentage of each component, and then heated, melted, refined and cast to obtain magnesium alloy ingots.

[0045] In some embodiments, the magnesium alloy ingot comprises multiple components, including Mg, Al, Mn, Zn, Cu, Ni, Si, Fe, and other impurities. Specifically, by mass percentage, Al: 2.8%–3.5%, Mn: 0.6%–1.0%, Zn: 0.91%–0.98%, Cu: 0–0.0011%, Ni: 0–0.0007%, Si: 0–0.013%, Fe: 0–0.0059%, other impurities <0.2%, and the balance being Mg. Besides the process, the composition design of the magnesium alloy ingot is one of the factors contributing to the high strength of the magnesium alloy sheet prepared using the magnesium alloy sheet provided in the embodiments of this application. Heating and melting are means of fusing multiple raw materials into an alloy; refining is to remove impurities from the alloy; and casting is used for the initial shaping of the alloy to facilitate subsequent processing. It should be noted that the other impurities in the above components are unavoidable impurities introduced during the heating, melting, refining, and casting processes. With the development of science and technology, the content of other impurities can be continuously reduced, and this application does not limit this. In some embodiments, the magnesium alloy ingot used in this application is a rare earth-free magnesium alloy, which has a lower cost.

[0046] In one possible implementation, the raw materials for each component are proportioned according to a preset percentage, and the proportioned raw materials are placed in a crucible. The crucible is heated to melt the raw materials. After the raw materials in the crucible have melted, they are refined. After refining, the mixture is cast to obtain a magnesium alloy ingot.

[0047] The crucible can be a graphite crucible, a ceramic crucible, a quartz crucible, or other types of crucibles; this application does not limit the types of crucibles used. The crucible can be heated using electromagnetic heating or heat conduction; this application does not limit the types of heating used.

[0048] In this implementation method, the raw materials of each component are directly mixed according to the preset percentage of each component, which makes it convenient to adjust the percentage of raw material composition according to the preparation results or preparation strategy, and the preparation of magnesium alloy ingots has a high degree of autonomy.

[0049] In one possible implementation, the target mass of the desired additional component is determined based on the existing magnesium alloy mass, the mass percentage of each component in the existing magnesium alloy, and a preset mass percentage of each component. The target mass of the target component is placed in a crucible. The crucible is heated to melt the raw materials in the crucible, including the existing magnesium alloy and the target component. After the raw materials in the crucible have melted, they are refined. After refining, the materials are cast to obtain a magnesium alloy ingot.

[0050] The target component is the combination whose mass percentage needs to be increased in the magnesium alloy ingot. In the case of the existing magnesium alloy being AZ31 (or my country's MB2), the target component is Mn. Accordingly, increasing the target component is to increase the Mn content in the existing magnesium alloy.

[0051] In this implementation, magnesium alloy ingots can be prepared using existing magnesium alloys, resulting in high preparation efficiency.

[0052] It should be noted that any of the above-described embodiments can be used to prepare magnesium alloy ingots, and the embodiments of this application do not limit this.

[0053] S102. The magnesium alloy ingot is heated and then extruded to obtain a magnesium alloy extruded slab.

[0054] Extrusion refers to a pressure processing method in which a punch or die applies pressure to a blank placed in a die, causing it to flow plastically, thereby obtaining a part corresponding to the shape of the die hole or the shape of the punch and die. The heating temperature of the magnesium alloy ingot is set by the technician according to the actual situation, and this application embodiment does not limit this. Extruding the magnesium alloy ingot to obtain a magnesium alloy extruded slab facilitates subsequent further processes.

[0055] In one possible implementation, the magnesium alloy ingot is heated. The extrusion pressure is determined based on the temperature of the magnesium alloy ingot. The magnesium alloy ingot is then extruded at this pressure to obtain the magnesium alloy extruded slab.

[0056] The relationship between the temperature of the magnesium alloy ingot and the extrusion pressure is set by technicians according to the actual situation, and this application embodiment does not limit this.

[0057] In this implementation, the extrusion pressure is determined based on the temperature of the magnesium alloy ingot, making the extrusion pressure more compatible with the temperature of the magnesium alloy ingot, resulting in a better extrusion effect on the magnesium alloy ingot.

[0058] S103. The magnesium alloy extruded slab is hot-rolled to obtain a magnesium alloy hot-rolled plate, and the magnesium alloy hot-rolled plate is air-cooled, oil-cooled, or water-cooled to room temperature.

[0059] Hot rolling refers to a process in which the rolls are heated to a preset temperature before rolling. This preset temperature is set by technicians according to actual conditions, and this application does not limit this. Air cooling refers to using air to cool the heated workpiece, which can save energy and costs; oil cooling is a cooling method between air cooling and water cooling. Its principle is to use the different thermal conductivity of oil to slowly cool the workpiece at an average speed. Oil cooling is slower, but faster than air cooling, and the cooling effect is also better than air cooling; water cooling uses cooling water to quickly and uniformly cool the workpiece, which can significantly increase the hardness of the material. Water cooling is faster and has a stronger cooling effect.

[0060] In one possible implementation, the magnesium alloy extruded sheet is placed in a rolling mill, and the magnesium alloy extruded sheet is hot-rolled by the mill's rollers to obtain a hot-rolled magnesium alloy sheet. The hot-rolled magnesium alloy sheet is then air-cooled, oil-cooled, or water-cooled to room temperature.

[0061] S104. The cooled magnesium alloy hot-rolled plate is placed in a restricted free bending die, and pressure is applied to the magnesium alloy hot-rolled plate in the restricted free bending die by a press to perform restricted free bending deformation on the magnesium alloy hot-rolled plate.

[0062] Among them, the restricted free bending die is used for free bending deformation, see [reference needed]. Figure 2 A schematic diagram of a restricted free bending die is provided. The bending die (full name: restricted free bending die) 200 includes a detachable upper cover 201, a cavity 202, and a lower cover 203. In some embodiments, the outer dimensions of the cavity 202 are 100mm × 100mm × 20mm, and the inner dimensions are 100mm × 100mm × 10mm. When an external force is applied to the upper cover 201 and the lower cover 203, the hot-rolled magnesium alloy sheet can be freely bent within the enclosed space formed by the upper cover 201, the cavity 202, and the lower cover 203. In some embodiments, the press is a hydraulic press.

[0063] In one possible implementation, a cooled hot-rolled magnesium alloy sheet is placed in a restricted free bending die, and pressure is applied directly to the hot-rolled magnesium alloy sheet in the restricted free bending die by a press at room temperature to perform restricted free bending deformation on the hot-rolled magnesium alloy sheet.

[0064] For example, a cooled hot-rolled magnesium alloy sheet is placed into a restricted free-bending die. The restricted free-bending die for holding the hot-rolled magnesium alloy sheet is then placed on a press. At room temperature, the press applies a preset pressure to the restricted free-bending die to bend the hot-rolled magnesium alloy sheet laterally, resulting in the restricted free-bending hot-rolled magnesium alloy sheet.

[0065] The preset pressure is related to the dimensions of the restrictive free bending die and the hot-rolled magnesium alloy plate, for example, 3 MPa. In some embodiments, the preset pressure is positively correlated with the dimensions of the restrictive free bending die and the hot-rolled magnesium alloy plate.

[0066] For example, a cooled hot-rolled magnesium alloy sheet is placed into the cavity of a restrictive free bending die, and the upper and lower covers of the die are connected to the cavity. The restrictive free bending die containing the hot-rolled magnesium alloy sheet is placed on a press, and the press punch is moved to the upper cover of the restrictive free bending die. At room temperature, the press punch applies a preset pressure to the restrictive free bending die to bend the hot-rolled magnesium alloy sheet laterally until the downward compression displacement of the punch reaches the preset compression displacement, thus obtaining the hot-rolled magnesium alloy sheet after restrictive free bending.

[0067] The preset compression displacement is positively correlated with the dimensions of the hot-rolled magnesium alloy plate and is set by technicians according to actual conditions; this application embodiment does not limit this setting. In some embodiments, the preset compression displacement of the press is 5% of the width of the hot-rolled magnesium alloy plate in the compression direction. The bending height for restrictive free bending deformation of the hot-rolled magnesium alloy plate is 2 to 5 times the thickness of the hot-rolled magnesium alloy plate.

[0068] It should be noted that the above embodiments involve directly subjecting the hot-rolled magnesium alloy sheet to restricted free bending deformation at room temperature. In addition to the above embodiments, this application also provides another method for subjecting the hot-rolled magnesium alloy sheet to restricted free bending deformation, as detailed in the following embodiments.

[0069] In one possible implementation, a cooled hot-rolled magnesium alloy sheet is placed into a restricted free-bending die, which is then placed in a heating furnace for heating at a temperature of 100°C to 250°C. The free-bending die is held in the heating furnace for 10 to 20 minutes. Pressure is then applied to the heated hot-rolled magnesium alloy sheet within the free-bending die using a press to perform restricted free-bending deformation on the sheet.

[0070] For example, a cooled hot-rolled magnesium alloy sheet is placed into a restricted free-bending die. The die is then placed in a heating furnace at a temperature of 150°C to 200°C, and held for 10 minutes to raise the temperature of both the die and the hot-rolled magnesium alloy sheet within it. After heating, the die is placed on a press. A preset pressure is applied to the die to bend the hot-rolled magnesium alloy sheet laterally, resulting in the restricted-free-bending magnesium alloy sheet.

[0071] The preset pressure is related to the dimensions of the restricted free bending die and the hot-rolled magnesium alloy plate, for example, 3 MPa.

[0072] For example, a cooled hot-rolled magnesium alloy sheet is placed into the cavity of a restrictive free bending die, and the upper and lower covers of the restrictive free bending die are connected to the cavity. The restrictive free bending die containing the hot-rolled magnesium alloy sheet is then placed in a heating furnace for heating at 200°C. The restrictive free bending die is held in the furnace for 10 minutes to raise the temperature of the restrictive free bending die and the hot-rolled magnesium alloy sheet within it to 200°C. If the temperature of the restrictive free bending die and the hot-rolled magnesium alloy sheet within it has not reached 200°C after 10 minutes, the restrictive free bending die is placed back into the heating furnace for heating until the temperature of the restrictive free bending die and the hot-rolled magnesium alloy sheet within it reaches 200°C. After heating is complete, the restrictive free bending die containing the hot-rolled magnesium alloy sheet is placed on a press, and the punch of the press is moved to the upper cover of the restrictive free bending die. The punch of the control press applies a preset pressure to the restricted free bending die to make the hot-rolled magnesium alloy sheet bend laterally until the downward compression displacement of the punch reaches the preset compression displacement, thus obtaining the hot-rolled magnesium alloy sheet after restricted free bending.

[0073] In some embodiments, when controlling the heating furnace to heat up, the heating furnace is controlled to heat to a set temperature at preset temperature intervals. After the temperature of the heating furnace reaches the set temperature, it is maintained for a preset time before the free bending mold is heated. The preset temperature interval and preset time are set by technicians according to the actual situation, such as setting the preset temperature interval to 5°C and the preset time to 1 hour, etc. The embodiments of this application do not limit this.

[0074] S105. The hot-rolled magnesium alloy plate after restricted free bending is placed into a width-limiting rolling die, and the bending direction of the hot-rolled magnesium alloy plate perpendicular to the width-limiting rolling die is limited by the lower edge of the rolling mill to obtain a one-pass rolled magnesium alloy plate.

[0075] Among them, the width-limiting rolling die is used for width-limiting rolling, see [link / reference]. Figure 3 A schematic diagram of a width-limiting rolling die is provided. The rolling die (full name: width-limiting rolling die) 300 includes a grooved base 301 and a cover plate 302. The base 301 and cover plate 302 are connected by screws. The magnesium alloy hot-rolled plate, after being restricted and freely bent, can be embedded in the groove of the base 301 and pass through the rolling mill together with the width-limiting rolling die. Correspondingly, the size of the cover plate 302 matches the groove of the base 301 so that the cover plate 302 can be embedded in the groove of the base 301 during the width-limiting rolling process. In some embodiments, the composition of the base 301 is 5CrMnMo, and the composition of the cover plate 302 is 430 stainless steel. The dimensions of the base 301 are 200mm × 106mm × 20mm, the dimensions of the groove are 200mm × 86mm × 4mm, and the dimensions of the cover plate 302 are 200mm × 86mm × 1mm. The lower edge of the rolling mill refers to the lower roller of the rolling mill.

[0076] In one possible implementation, the hot-rolled magnesium alloy sheet after restricted free bending is placed into a width-limiting rolling die, and the sheet is directly rolled at room temperature through the lower edge of the mill in a direction perpendicular to the bending direction of the hot-rolled magnesium alloy sheet within the width-limiting rolling die to obtain a one-pass rolled magnesium alloy sheet.

[0077] For example, the hot-rolled magnesium alloy sheet, after being subjected to restricted free bending, is placed into a groove in the base of a width-limiting rolling die. The cover plate of the width-limiting rolling die is then placed on the groove to cover the hot-rolled magnesium alloy sheet. The cover plate and base of the width-limiting rolling die are connected using screws. After adjusting the mill's reduction to the preset reduction, the mill is started. The connected width-limiting rolling die is placed into the mill, and the lower edge of the mill performs width-limiting rolling on the hot-rolled magnesium alloy sheet perpendicular to the bending direction within the width-limiting rolling die, resulting in a one-pass rolled magnesium alloy sheet.

[0078] The preset reduction amount is set by technicians according to the actual situation, and this application embodiment does not limit this. In some embodiments, the reduction amount of the rolling mill during the width-limiting rolling process is 5%, where 5% refers to 5% of the thickness of the magnesium alloy hot-rolled plate in the width-limiting rolling die.

[0079] It should be noted that the above embodiments involve directly performing width-limiting rolling on hot-rolled magnesium alloy plates at room temperature. In addition to the above embodiments, this application also provides another method for performing width-limiting rolling on hot-rolled magnesium alloy plates, as detailed in the following embodiments.

[0080] In one possible implementation, the hot-rolled magnesium alloy sheet, after being constrained and freely bent, is placed into a width-limiting rolling die. The die is then placed in a heating furnace for heating at a temperature of 100°C to 250°C. The die is held in the furnace for 10 to 20 minutes. Width-limiting rolling is then performed by rolling the hot-rolled magnesium alloy sheet perpendicular to the bending direction within the die along the lower edge of the mill, resulting in a one-pass rolled magnesium alloy sheet.

[0081] For example, the magnesium alloy hot-rolled sheet, after being constrained and freely bent, is placed into a groove in the base of a width-limiting rolling die. The cover plate of the width-limiting rolling die is then placed on the groove to cover the magnesium alloy hot-rolled sheet. The cover plate and base of the width-limiting rolling die are connected using screws. The width-limiting rolling die is then placed in a heating furnace for heating at a temperature of 150°C to 200°C. The die is held in the furnace for 10 minutes to increase the temperature of the die and the magnesium alloy hot-rolled sheet within it. After heating, the mill's reduction is adjusted to a preset reduction. The mill roll temperature is raised to 150°C to 200°C, and the mill is started. The connected width-limiting rolling die is placed in the mill, and the width-limiting rolling is performed on the magnesium alloy hot-rolled sheet perpendicular to the bending direction within the die through the lower edge of the mill, resulting in a one-pass rolled magnesium alloy sheet.

[0082] For example, the magnesium alloy hot-rolled sheet, after being subjected to restricted free bending, is placed into a groove in the base of a width-limiting rolling die. The cover plate of the width-limiting rolling die is then placed on the groove to cover the magnesium alloy hot-rolled sheet. The cover plate and base of the width-limiting rolling die are connected using screws. The width-limiting rolling die is then placed in a heating furnace for heating at a temperature of 200°C. The width-limiting rolling die is held in the heating furnace for 10 minutes to raise the temperature of the width-limiting rolling die and the magnesium alloy hot-rolled sheet within it to 200°C. If the temperature of the width-limiting rolling die and the magnesium alloy hot-rolled sheet within it has not reached 200°C after 10 minutes, the width-limiting rolling die is placed back in the heating furnace for heating until the temperature of the width-limiting rolling die and the magnesium alloy hot-rolled sheet within it reaches 200°C. After heating is complete, the reduction of the rolling mill is adjusted to the preset reduction. The rolling mill roll temperature is raised to 200°C and then the rolling mill is started. The connected width-limiting rolling die is placed in the rolling mill. The width-limiting rolling is performed on the magnesium alloy hot-rolled plate perpendicular to the bending direction of the width-limiting rolling die through the lower edge of the rolling mill to obtain a one-pass rolled magnesium alloy plate.

[0083] In some embodiments, after the roll temperature is raised to the set temperature, the roll temperature is maintained at the set temperature for a preset time before the mill is started, so as to ensure the roll temperature is stable and prevent the temperature of the magnesium alloy hot-rolled plate in the width-limiting rolling die from dropping too quickly during the rolling process. The preset time is set by the technician according to the actual situation, such as setting the preset time to 1 hour, etc. This application embodiment does not limit this.

[0084] S106. After rotating the rolled magnesium alloy sheet 90° along the normal direction, place it into a restricted free bending die. Apply pressure to the rolled magnesium alloy sheet in the restricted free bending die using a press to achieve restricted free bending deformation of the rolled magnesium alloy sheet.

[0085] This single-pass rolled magnesium alloy sheet, also known as a single-pass deformed sheet, undergoes a second deformation process (S106 and S107) to improve its performance. Compared to hot-rolled magnesium alloy sheets, single-pass deformed sheets shorten in the RD (Rolling Direction) and lengthen in the TD (Transverse Direction) (the direction perpendicular to RD on the sheet's plane). The second deformation process shortens the single-pass deformed sheet along the TD direction and lengthens it along the RD direction, ensuring that the thickness of the magnesium alloy sheet remains unchanged. After rotating the single-pass rolled magnesium alloy sheet 90° along the normal direction, the initial width of the magnesium alloy sheet can be considered as its length before rotation, and its length as its width before rotation, ensuring consistency with the single-pass deformation when placing the die.

[0086] In one possible implementation, if the first-pass rolled magnesium alloy sheet is prepared at room temperature, the first-pass rolled magnesium alloy sheet is rotated 90° along the normal direction and placed in a restricted free bending die. At room temperature, pressure is applied directly to the first-pass rolled magnesium alloy sheet in the restricted free bending die by a press to perform restricted free bending deformation on the first-pass rolled magnesium alloy sheet.

[0087] For example, if the magnesium alloy sheet is prepared at room temperature, the sheet is rotated 90° along the normal direction and placed into a restrictive free bending die. The restrictive free bending die is then placed on a press. At room temperature, the press applies a preset pressure to the restrictive free bending die to bend the magnesium alloy sheet laterally, resulting in the restricted free bending magnesium alloy sheet.

[0088] For example, if the magnesium alloy sheet is prepared at room temperature, the sheet is rotated 90° along the normal direction and placed into the cavity of a restrictive free bending die. The upper and lower covers of the restrictive free bending die are connected to the cavity. The restrictive free bending die containing the sheet is placed on a press, and the press punch is moved to the upper cover of the die. At room temperature, the press punch applies a preset pressure to the restrictive free bending die to laterally bend the magnesium alloy sheet until the downward compression displacement of the punch reaches the preset compression displacement, thus obtaining the restricted free bending magnesium alloy sheet.

[0089] In one possible implementation, if the magnesium alloy sheet is prepared after heating, the sheet is rotated 90° along the normal direction and placed into a restrictive free bending die. The die is then placed in a heating furnace at a temperature of 100°C to 250°C, and held for 10 to 20 minutes. Pressure is applied to the heated magnesium alloy sheet within the die using a press to induce a restricted free bending deformation.

[0090] For example, when the magnesium alloy sheet is prepared after heating in a single pass, the sheet is rotated 90° along the normal direction and placed into a restrictive free bending die. The restrictive free bending die containing the sheet is then placed in a heating furnace at a temperature of 150°C to 200°C. The die is held in the furnace for 10 minutes to increase the temperature of both the die and the sheet within it. After heating, the die is placed on a press. A preset pressure is applied to the die to laterally bend the sheet, resulting in the restricted free bending of the single pass magnesium alloy sheet.

[0091] For example, if the magnesium alloy sheet is prepared after heating in a single pass, the sheet is rotated 90° along the normal direction and placed into the cavity of a restrictive free bending die. The upper and lower covers of the restrictive free bending die are then connected to the cavity. The restrictive free bending die containing the sheet is placed in a heating furnace for heating at 200°C. The mold is held in the furnace for 10 minutes to raise the temperature of the mold and the sheet to 200°C. If the temperature of the mold and the sheet does not reach 200°C after 10 minutes, the mold is placed back in the furnace for heating until the temperature reaches 200°C. After heating is complete, a restrictive free bending die for a single-pass rolled magnesium alloy sheet is placed on a press, and the press punch is moved to the upper cover of the restrictive free bending die. The press punch is controlled to apply a preset pressure to the restrictive free bending die to bend the single-pass rolled magnesium alloy sheet laterally until the downward compression displacement of the punch reaches the preset compression displacement, thus obtaining the single-pass rolled magnesium alloy sheet after restrictive free bending.

[0092] S107. The magnesium alloy sheet after restricted free bending is placed into the width-limiting rolling die, and the width is limited by the lower edge of the rolling mill to roll the magnesium alloy sheet in the pass perpendicular to the bending direction of the width-limiting rolling die, so as to obtain the final magnesium alloy sheet.

[0093] In some embodiments, the final magnesium alloy sheet is also referred to as a second-stage deformed sheet.

[0094] In one possible implementation, if the magnesium alloy sheet is prepared at room temperature, the magnesium alloy sheet after restricted free bending is placed into a width-limiting rolling die, and the width-limiting rolling is performed directly through the lower edge of the mill at room temperature on the bending direction of the magnesium alloy sheet perpendicular to the width-limiting rolling die to obtain the final magnesium alloy sheet.

[0095] For example, if the magnesium alloy sheet for this pass is prepared at room temperature, the sheet, after being subjected to restricted free bending, is placed into a groove in the base of a width-limiting rolling die. The cover plate of the width-limiting rolling die is then placed on the groove to cover the sheet. The cover plate and the base are connected using screws. After adjusting the mill reduction to the preset reduction, the mill is started. The connected width-limiting rolling die is placed into the mill, and the sheet is subjected to width-limiting rolling along the lower edge of the mill, perpendicular to the bending direction of the magnesium alloy sheet within the die, to obtain the final magnesium alloy sheet.

[0096] In one possible implementation, if the magnesium alloy sheet is prepared at room temperature, the sheet, after being subjected to restricted free bending, is placed into a width-limiting rolling die. The die is then placed in a heating furnace at a temperature of 100°C to 250°C, and held for 10 to 20 minutes. Width-limiting rolling is then performed by the lower edge of the mill along the bending direction of the magnesium alloy sheet, perpendicular to the width-limiting rolling die, to obtain the final magnesium alloy sheet.

[0097] For example, when the magnesium alloy sheet for this pass is prepared at room temperature, the magnesium alloy sheet, after being subjected to restricted free bending, is placed into a groove in the base of the width-limiting rolling die. The cover plate of the width-limiting rolling die is then placed on the groove to cover the magnesium alloy sheet. The cover plate of the width-limiting rolling die and the base are connected using screws. The width-limiting rolling die is then placed in a heating furnace for heating at a temperature of 150°C to 200°C. The width-limiting rolling die is held in the heating furnace for 10 minutes to increase the temperature of the width-limiting rolling die and the magnesium alloy sheet rolled in it. After heating is complete, the reduction of the rolling mill is adjusted to the preset reduction. The rolling mill roll temperature is raised to 150℃~200℃ and then the rolling mill is started. The connected width-limiting rolling die is placed in the rolling mill. The width-limiting rolling is performed on the bending direction of the magnesium alloy sheet in one pass through the lower edge of the rolling mill, which is perpendicular to the width-limiting rolling die, to obtain the final magnesium alloy sheet.

[0098] For example, if the magnesium alloy sheet being rolled in one pass is prepared at room temperature, the sheet, after being subjected to restricted free bending, is placed into a groove in the base of a width-limiting rolling die. The cover plate of the width-limiting rolling die is then placed on the groove to cover the sheet. The cover plate and base are connected using screws. The width-limiting rolling die is then placed in a heating furnace at a temperature of 200°C. The die is held in the furnace for 10 minutes to raise the temperature of the die and the magnesium alloy sheet within it to 200°C. If the temperature of the die and the sheet does not reach 200°C after 10 minutes, the die is placed back in the furnace for heating until the temperature reaches 200°C. After heating is complete, the reduction of the rolling mill is adjusted to the preset reduction. The rolling mill roll temperature is raised to 200°C and then the rolling mill is started. The connected width-limiting rolling die is placed in the rolling mill. The width-limiting rolling is performed on the bending direction of the magnesium alloy sheet in one pass through the lower edge of the rolling mill, which is perpendicular to the width-limiting rolling die, to obtain the final magnesium alloy sheet.

[0099] To provide a clearer explanation of the preparation method of the ultra-high strength magnesium alloy sheet provided in the embodiments of this application, the above S104-S107 will be explained below through two specific examples.

[0100] Example 1 (Prepared at room temperature): The RD, TD, and ND (normal) directions of a hot-rolled magnesium alloy sheet are 91 mm, 86 mm, and 3 mm, respectively. The hot-rolled magnesium alloy sheet is placed in a restricted free-bending die, and pressure is applied along the RD direction of the sheet using a press to cause it to bend laterally, shortening the RD direction from 91 mm to 86 mm. The applied pressure is 3 MPa. See also... Figure 2 The diagram shows a schematic before and after transverse bending. The magnesium alloy hot-rolled sheet, after restricted free bending, is placed in the groove of a width-limiting rolling die (groove width is 86mm). Width-limiting rolling is performed on the magnesium alloy hot-rolled sheet perpendicular to the bending direction (i.e., the TD direction) within the width-limiting rolling die by the lower edge of the mill. The rolling linear speed is 100mm / s, causing the magnesium alloy hot-rolled sheet to elongate along the TD direction from 86mm to 91mm, with a strain of approximately 5%. This yields a one-pass rolled magnesium alloy sheet with lengths of 86mm in the RD direction, 91mm in the TD direction, and 3mm in the ND direction. This one-pass rolled magnesium alloy sheet is also referred to as a one-pass deformed sheet. See also... Figure 3The diagram shows the changes before and after the width-limited rolling process. The deformed sheet is then placed again in a restricted free-bending die and, along with the die, onto a press. It is compressed along the TD direction of the original sheet (hot-rolled magnesium alloy sheet) at a compressive stress of 3 MPa, causing the sheet to bend laterally, reducing its horizontal length in the TD direction from 91 mm to 86 mm. The bent sheet is then placed in the groove of a width-limited rolling die and rolled along the RD direction of the original sheet (hot-rolled magnesium alloy sheet) at a rolling speed of 100 mm / s. This causes the sheet to elongate along the RD direction, increasing its length from 86 mm to 91 mm, with a strain of approximately 5%. A magnesium alloy sheet with lengths of 91 mm, 86 mm, and 3 mm in the RD, TD, and ND directions is obtained. This magnesium alloy sheet is the final sheet and is also referred to as the second-pass deformed sheet.

[0101] Example 2 (Preparation by Heating): A restricted free bending die and a width-limiting rolling die are placed in a heating furnace. The furnace is heated to 200°C at a rate of 5°C per minute and held for 1 hour. The rolling mill rolls are also heated to 200°C and held for 1 hour. The RD, TD, and ND (normal) directions of the magnesium alloy hot-rolled plate are 91 mm, 86 mm, and 3 mm, respectively. The magnesium alloy hot-rolled plate is placed in the restricted free bending die. After holding the magnesium alloy hot-rolled plate at 200°C for 10 minutes along with the restricted free bending die, pressure is applied to the RD direction of the magnesium alloy hot-rolled plate in the restricted free bending die using a press to cause the magnesium alloy hot-rolled plate to bend laterally, shortening the RD direction from 91 mm to 86 mm. The applied pressure is 3 MPa. The magnesium alloy hot-rolled plate, after being subjected to restricted free bending, is placed in the groove of a width-limiting rolling die (groove width is 86mm). The magnesium alloy hot-rolled plate is held at 200℃ for 10 minutes along with the width-limiting rolling die. Then, the plate is subjected to width-limiting rolling along the lower edge of the rolling mill in the bending direction (i.e., the TD direction of the magnesium alloy hot-rolled plate) perpendicular to the width-limiting rolling die. The rolling linear speed is 100mm / s, which causes the magnesium alloy hot-rolled plate to elongate along the TD direction, increasing its length from 86mm to 91mm, with a strain of about 5%. This results in a one-pass rolled magnesium alloy plate with lengths of 86mm, 91mm, and 3mm in the RD, TD, and ND directions, respectively. This one-pass rolled magnesium alloy plate is also called a one-pass deformed plate. The hot-rolled magnesium alloy sheet is placed again in a restricted free bending die. The sheet, along with the die, is held at 200°C for 10 minutes. Then, it is placed on a press and compressed along the TD direction of the original sheet (hot-rolled magnesium alloy sheet) with a compressive stress of 3 MPa, causing the sheet to bend laterally, reducing its horizontal length in the TD direction from 91 mm to 86 mm. The sheet, along with the width-limiting rolling die, is held at 200°C for 10 minutes and then rolled along the RD direction of the original sheet (hot-rolled magnesium alloy sheet) at a rolling mill with a rolling speed of 100 mm / s, causing the sheet to elongate along the RD direction from 86 mm to 91 mm, with a strain of approximately 5%. This yields a magnesium alloy sheet with lengths of 91 mm in the RD direction, 86 mm in the TD direction, and 3 mm in the ND direction. This magnesium alloy sheet is the final magnesium alloy sheet, also known as the second-pass deformed sheet.

[0102] In the embodiments of this application, the mass percentage of each component in the magnesium alloy ingot is as follows: Al: 2.8% to 3.5%, Mn: 0.6% to 1.0%, Zn: 0.91% to 0.98%, Cu: 0 to 0.0011%, Ni: 0 to 0.0007%, Si: 0 to 0.013%, Fe: 0 to 0.0059%, other impurities <0.2%, and the balance is Mg.

[0103] During the research and development process, magnesium alloy plates with good performance were also able to be prepared when the mass percentage of Al in the magnesium alloy ingot was 2.8% to 3.2%, the mass percentage of Mn was 0.7% to 0.95%, the mass percentage of Zn was 0.95% to 0.98%, and the mass percentage of Fe was 0.0025% to 0.0058%.

[0104] Furthermore, when the mass percentage of Al in the magnesium alloy ingot is 3%, the mass percentage of Mn is 0.75% to 0.9%, the mass percentage of Zn is 0.97%, and the mass percentage of Fe is 0.005% to 0.0058%, the performance of the magnesium alloy sheet prepared by the above embodiment is further improved.

[0105] Ultimately, with the following mass percentages of components in the magnesium alloy ingot: Al: 3%, Mn: 0.85%, Zn: 0.97%, Cu: 0–0.0011%, Ni: 0–0.0007%, Si: 0–0.013%, Fe: 0.0054%, other impurities <0.2%, and the balance being Mg (hereinafter referred to as the optimal component ratio), the magnesium alloy sheet prepared using the above-described embodiment achieved optimal performance. Table 1 below shows a comparison of the performance of magnesium alloy sheets prepared using different processes under the aforementioned optimal component ratio.

[0106] Table 1

[0107] sample Yield strength YS / MPa Tensile strength UTS / MPa Elongation FE / % Magnesium alloy sheet before deformation 200 303 8.2 Magnesium alloy sheet after room temperature deformation 485 543 4.4 Magnesium alloy sheet deformed at 200℃ 375 446.1 8.6

[0108] In Table 1, the magnesium alloy sheet before deformation refers to the magnesium alloy sheet that has not undergone the restricted free bending deformation and width-limited rolling provided in the embodiments of this application; the magnesium alloy sheet after deformation at 200℃ refers to the magnesium alloy sheet that has undergone restricted free bending deformation and width-limited rolling at 200℃; and the magnesium alloy sheet after room temperature deformation refers to the magnesium alloy sheet that has undergone restricted free bending deformation and width-limited rolling at room temperature. The component ratios of the magnesium alloy sheet before deformation, the magnesium alloy sheet after deformation at 200℃, and the magnesium alloy sheet after room temperature deformation are all the above-mentioned optimal component ratios. As can be seen from Table 1, under the optimal component ratio, the yield strength of the magnesium alloy sheet after room temperature deformation reaches 485 MPa, and the tensile strength reaches 543 MPa. Compared with the magnesium alloy sheet before deformation, the yield strength of the magnesium alloy sheet increased by 285 MPa (142.5%) and the tensile strength increased by 240 MPa (79%) through the technical solution provided in the embodiments of this application. With the increase of deformation temperature, the strength and toughness of magnesium alloy sheet are significantly improved. The tensile strength, yield strength and elongation of magnesium alloy sheet after deformation at 200℃ are increased from the original 303MPa, 200MPa and 8.2% to 446.1MPa, 375MPa and 8.6%, respectively.

[0109] The performance of the magnesium alloy sheet prepared according to the embodiments of this application will be compared with that of the AZ31 magnesium alloy sheet of related technologies. In the comparison, the magnesium alloy sheet used is the magnesium alloy sheet with the above-mentioned optimal composition ratio. The Mn content (0.85 wt.%) in the magnesium alloy sheet provided by the embodiments of this application is significantly higher than the Mn content (0.3 wt.%) in AZ31, where wt.% represents the mass percentage. Table 2 shows a performance comparison between AZ31 and the magnesium alloy sheet using the above-mentioned optimal composition. The performance shown in Table 2 was obtained at room temperature using the preparation method of the magnesium alloy sheet provided by the embodiments of this application. That is, the performance corresponding to AZ31 in Table 2 below was directly measured by subjecting AZ31 to the restricted free bending deformation and width-limited rolling provided by the embodiments of this application. For comparison, the preparation process of the magnesium alloy sheet with the optimal composition is the same as that of AZ31.

[0110] Table 2

[0111]

[0112] In Table 2, after room temperature deformation, the tensile strength of AZ31 in the RD direction significantly increased to 528.2 MPa, while the tensile strength in the TD direction was 397.3 MPa. Although the performance of AZ31 in the TD direction improved after room temperature deformation, the difference in strength and plasticity between the RD and TD directions remained significant, and this anisotropy limited its application scenarios. For the magnesium alloy sheet with the optimal composition after room temperature deformation, the anisotropy of strength and plasticity in the RD and TD directions was reduced. Its tensile strength in the RD direction was 543 MPa, yield strength was 485 MPa, and elongation was 4.4%; the tensile strength in the TD direction was 502.2 MPa, yield strength was 455 MPa, and elongation was 5.5%. The magnesium alloy sheet with the optimal composition showed significantly improved performance in both the RD and TD directions, and its isotropy was superior to that of the AZ31 magnesium alloy with lower Mn content. Therefore, increasing the Mn content from 0.36 wt.% to 0.85 wt.% can bring about a leap in the performance of magnesium alloy sheets.

[0113] As can be seen from Tables 1 and 2, the preparation method and component ratio provided in the embodiments of this application have resulted in the preparation of magnesium alloy plates with good performance.

[0114] The following will combine Figure 4 and Figure 5 The principle behind this performance leap will be explained.

[0115] Figure 4 Scanning electron microscope image of magnesium alloy sheet (Mn 0.85 wt.%) prepared at room temperature with optimal composition, see [link to image]. Figure 4 The optimal magnesium alloy sheet composition (0.85 wt.%) contains a large number of dispersed nano-sized spherical second phase particles with a size of approximately 20 nm. Analysis revealed that the precipitated phase is Al-Mn. The presence of the nano-sized Al-Mn phase effectively inhibits the activation of basal slip, which is beneficial to improving the yield strength of the restricted free bending width-limited rolled magnesium alloy sheet. In addition, the increased Mn content lowers the cross-slip energy barrier of the restricted free bending width-limited rolled magnesium alloy sheet during room temperature deformation, reduces the difference in critical shear stress between non-basal slip and basal slip, increases the activation of various types of non-basal slip systems, and dislocation strengthening increases the tensile strength of the deformed magnesium alloy sheet. AZ31, due to its lower Mn content (0.36 wt.%), has little or no Al-Mn phase precipitates; therefore, the sheet with a higher Mn content (0.85 wt.%) exhibits higher strength than ordinary AZ31.

[0116] also, Figure 5 This is a transmission electron microscope image of a magnesium alloy sheet (Mn 0.85 wt.%) prepared at room temperature with the optimal composition. See also Figure 5After restricted free bending deformation and width-limited rolling, a large number of pre-twins and dislocations were formed in the magnesium alloy sheet with the optimal composition (Mn 0.85 wt.%). As the Mn content increased from 0.36 wt.% to 0.85 wt.%, the "pinning" effect of the nanoscale Al-Mn phase became increasingly obvious during room temperature stretching of the magnesium alloy sheet with the optimal composition (Mn 0.85 wt.%), hindering dislocation movement and grain boundary sliding, while suppressing the detwinization process, resulting in a further significant improvement in the strength of the sheet.

[0117] Therefore, the increased Mn content in the magnesium alloy, combined with the effects of a large number of nanoscale second phases (Al-Mn phase), dislocations, and twins after restricted free bending deformation and width-limited rolling, gives the magnesium alloy sheet in the embodiments of this application ultra-high strength.

[0118] All of the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments of this application, and will not be described in detail here.

[0119] The technical solution provided in this application, employing a method of restricted free bending deformation and width-limited rolling, enables the preparation of a magnesium alloy sheet with a specific composition and microstructure. Experiments have demonstrated that the prepared magnesium alloy sheet possesses high yield strength and tensile strength, providing broader application scenarios for magnesium alloys.

[0120] In summary, 1. The technical solution provided in this application reduces the deformation temperature of magnesium alloys. By using the magnesium alloy sheet and the preparation method of the magnesium alloy sheet provided in this application, magnesium alloys can be deformed in a temperature range of 25℃ (room temperature) to 250℃, while the deformation temperature of magnesium alloys in the prior art is usually 275℃ to 400℃, which greatly saves costs and energy consumption.

[0121] 2. The method for preparing magnesium alloy plates provided in this application is simple and easy to operate. It can significantly improve the strength and toughness of magnesium alloy plates by using only two small deformation passes (each pass is only about 5%).

[0122] 3. By using the magnesium alloy sheet and the preparation method of the magnesium alloy sheet provided in the embodiments of this application, the yield strength of the magnesium alloy sheet can be increased by 285 MPa and the tensile strength can be increased by 240 MPa, resulting in an ultra-high strength magnesium alloy sheet.

[0123] 4. Using the magnesium alloy sheet and the preparation method of the magnesium alloy sheet provided in the embodiments of this application, as the Mn content in the magnesium alloy sheet increases (the best is 0.85 wt.%), the anisotropy of the magnesium alloy sheet properties weakens, and the tensile strength in different directions increases to more than 500 MPa and the yield strength increases to more than 450 MPa.

[0124] 5. By using the magnesium alloy sheet and the preparation method of the magnesium alloy sheet provided in the embodiments of this application, the strength and plasticity of the magnesium alloy can be controlled by changing the temperature of the restricted free bending deformation and the width-limited rolling, so as to obtain an ultra-high strength magnesium alloy sheet or a magnesium alloy sheet with high strength and high plasticity.

[0125] The above are merely optional embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing an ultra-high strength magnesium alloy sheet material, characterized by, The method includes: The ingredients are batched according to the preset mass percentage of each component, and then heated, melted, refined, and cast to obtain magnesium alloy ingots. The magnesium alloy ingot contains Mg, Al, Mn, Zn, Cu, Ni, Si, Fe, and other impurities; The composition, measured by mass percentage, is as follows: Al: 2.8%–3.5%, Mn: 0.6%–1.0%, Zn: 0.91%–0.98%, Cu: 0–0.0011%, Ni: 0–0.0007%, Si: 0–0.013%, Fe: 0–0.0059%, other impurities <0.2%, and the balance being Mg. The magnesium alloy ingot is heated and then extruded to obtain a magnesium alloy extruded slab. The magnesium alloy extruded slab is hot-rolled to obtain a magnesium alloy hot-rolled plate, and the magnesium alloy hot-rolled plate is air-cooled, oil-cooled, or water-cooled to room temperature. The cooled hot-rolled magnesium alloy sheet is placed in a restricted free bending die, and pressure is applied to the hot-rolled magnesium alloy sheet in the restricted free bending die by a press to perform restricted free bending deformation on the hot-rolled magnesium alloy sheet; The magnesium alloy hot-rolled plate, after being subjected to restricted free bending, is placed into a width-limiting rolling die. The lower edge of the rolling mill is used to perform width-limiting rolling on the magnesium alloy hot-rolled plate perpendicular to the bending direction within the width-limiting rolling die, thereby obtaining a one-pass rolled magnesium alloy sheet. The magnesium alloy sheet is rotated 90° along the normal direction in one pass and the above steps of restricted free bending deformation and width-limited rolling are repeated to obtain the final magnesium alloy sheet. The step of placing the cooled hot-rolled magnesium alloy sheet into a restricted free bending die, and applying pressure to the hot-rolled magnesium alloy sheet within the restricted free bending die using a press, wherein the restricted free bending deformation of the hot-rolled magnesium alloy sheet includes any of the following: The cooled hot-rolled magnesium alloy sheet is placed in a restricted free bending die, and pressure is applied directly to the hot-rolled magnesium alloy sheet in the restricted free bending die by a press at room temperature to perform restricted free bending deformation on the hot-rolled magnesium alloy sheet; The cooled hot-rolled magnesium alloy sheet is placed into a restricted free bending die, and the free bending die is placed in a heating furnace for heating at a temperature of 100℃ to 250℃. The free bending die is held in the heating furnace for 10 min to 20 min. Pressure is applied to the heated hot-rolled magnesium alloy sheet in the free bending die using a press to perform restricted free bending deformation on the hot-rolled magnesium alloy sheet. The compression displacement of the press is 5% of the width of the hot-rolled magnesium alloy plate in the compression direction; The reduction in pressure of the rolling mill during the width-limited rolling process is 5%; The bending height for the restricted free bending deformation of the magnesium alloy hot-rolled plate is 2 to 5 times the thickness of the magnesium alloy hot-rolled plate; The magnesium alloy hot-rolled sheet, after being subjected to restricted free bending, is placed into a width-limiting rolling die, and the width is limited by rolling the magnesium alloy hot-rolled sheet perpendicular to the bending direction within the width-limiting rolling die through the lower edge of the rolling mill, resulting in a single-pass rolled magnesium alloy sheet, which includes any of the following: The magnesium alloy hot-rolled plate after restricted free bending is placed into a width-limiting rolling die, and the width-limiting rolling is performed directly through the lower edge of the rolling mill at room temperature in the bending direction of the magnesium alloy hot-rolled plate perpendicular to the width-limiting rolling die to obtain a one-pass rolled magnesium alloy plate. The hot-rolled magnesium alloy sheet, after being subjected to restricted free bending, is placed into a width-limiting rolling die. The width-limiting rolling die is then placed in a heating furnace for heating at a temperature of 100℃ to 250℃. The width-limiting rolling die is held in the heating furnace for 10 to 20 minutes. The width-limiting rolling is then performed by rolling the hot-rolled magnesium alloy sheet perpendicular to the bending direction within the width-limiting rolling die through the lower edge of the rolling mill, thereby obtaining a one-pass rolled magnesium alloy sheet.

2. The method of claim 1, wherein, The magnesium alloy ingot contains 2.8%–3.2% Al by mass, 0.7%–0.95% Mn by mass, 0.95%–0.98% Zn by mass, and 0.0025%–0.0058% Fe by mass.

3. The method of claim 2, wherein, The magnesium alloy ingot contains 3% Al by mass, 0.75%–0.9% Mn by mass, 0.97% Zn by mass, and 0.005%–0.0058% Fe by mass.

4. The method of claim 3, wherein, The mass percentage of Mn in the magnesium alloy ingot is 0.85%.

5. The method of claim 3, wherein, The mass percentage of Fe in the magnesium alloy ingot is 0.0054%.

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