Magnesium alloy asymmetric extrusion equipment and method

Abstract

According to the magnesium alloy asymmetric extrusion equipment and method, a blank is extruded through a male die assembly and a female die assembly which are matched with each other, the male die assembly directly acts on the blank, the female die assembly comprises a female die outer ring and a die core embedded in the female die outer ring, and a die cavity is formed in the die core; the mold cavity comprises a flat cylindrical extrusion cavity and a forming channel hole, the length and thickness of the forming channel hole are both small, and the extrusion cavity and the forming channel hole are sequentially distributed in the extrusion direction of a blank, so that the blank can be extruded from the extrusion cavity to the forming channel hole and extruded through the forming channel hole to form a profile; wherein the forming channel holes are asymmetrically arranged, the length, the thickness and the cross section of the forming channel holes are asymmetrical, a strong shear strain field can be actively introduced into a magnesium alloy material through the asymmetrical offset design, the flowing state of magnesium alloy is changed, the defects, caused by the flow velocity difference, of the profile are reduced, and the yield of the asymmetrical magnesium alloy profile is increased.

Description

Technical Field

[0001] This application relates to the field of magnesium alloy plastic forming technology, and more specifically, to a magnesium alloy asymmetric extrusion equipment and method. Background Technology

[0002] Magnesium alloys, as a core choice for lightweight metallic structural materials, demonstrate strategic application prospects in aerospace, high-speed transportation, and other fields due to their excellent specific strength, damping performance, and electromagnetic shielding properties. However, the close-packed hexagonal crystal structure of magnesium alloys results in a lack of room-temperature slip systems, significantly limiting their plastic forming capabilities, particularly making it difficult to fabricate asymmetric magnesium alloy profiles. Therefore, during magnesium alloy extrusion or thermoforming, the significant differences in cross-sectional area across different parts of the asymmetric profile lead to marked inconsistencies in the metal flow velocity within the mold cavity. These velocity differences create a complex stress field distribution within the profile. When the residual stress exceeds the material's yield strength, warping and deformation occur, and even microcracks may develop in stress concentration areas, resulting in a low yield rate for the formed asymmetric magnesium alloy profiles.

[0003] In conclusion, how to improve the yield rate of asymmetric magnesium alloy profiles is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide an asymmetric extrusion apparatus and method for magnesium alloys to improve the yield of asymmetric magnesium alloy profiles.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] A magnesium alloy asymmetric extrusion apparatus for extruding magnesium alloy billets includes: a punch assembly and a die assembly that cooperate with each other; wherein the punch assembly is used to extrude the billet; the die assembly includes a die outer ring and a die core nested inside the die outer ring, the die core forming a die cavity, the die cavity including an extrusion cavity with a flat cylindrical structure and a forming channel hole, the length and thickness of the forming channel hole being smaller than the extrusion cavity, the extrusion cavity and the forming channel hole being distributed sequentially along the extrusion direction of the billet; the forming channel hole is asymmetrically arranged, specifically including: asymmetry in the length direction, with a deviation distance between the central axis of the forming channel hole and the central axis of the extrusion cavity; asymmetry in the thickness direction, with the forming channel hole having at least two parts with unequal thicknesses; and asymmetry in the cross-section, with the projection of the forming channel hole along the extrusion direction of the billet being asymmetric in at least one direction.

[0007] In some embodiments, the ratio of the deviation between the central axis of the forming channel hole and the central axis of the extrusion cavity is the asymmetric extrusion coefficient K, which satisfies: K=d / R, where d is the deviation distance between the central axis of the forming channel hole and the central axis of the extrusion cavity, in mm; and R is the radius of the extrusion cavity, in mm.

[0008] In some embodiments, the profile asymmetry coefficient is E, and the asymmetry extrusion coefficient K and the profile asymmetry coefficient E satisfy: K=E.

[0009] In some embodiments, the cross-section of the formed channel hole has an "I" shaped structure.

[0010] [P] In some embodiments, the forming channel holes of the I-shaped structure form an I-shaped profile, and the asymmetry coefficient E of the I-shaped profile satisfies: E =

[0011] In some embodiments, the cross-section of the formed channel hole is one of a single-sided stepped structure, a locally thickened structure, a T-shaped structure, or an L-shaped structure.

[0012] In some embodiments, the ratio of the cross-sectional area of ​​the forming channel hole to the cross-sectional area of ​​the extrusion cavity is 4 / 100.

[0013] In some embodiments, the mold core includes a first mold core and a second mold core, the first mold core and the second mold core are detachably fixedly connected, and the first mold core and the second mold core can be assembled to form the mold cavity; the first mold core has a first groove, the second mold core has a second groove, the first groove and the second groove are assembled to form the molding channel hole, and the first groove and the second groove have different thicknesses.

[0014] In some embodiments, the extrusion apparatus further includes a frame; the punch assembly includes an extrusion rod movably connected to the top surface of the frame, the other end of the extrusion rod away from the top surface of the frame is used to abut against an extrusion plate, and the extrusion plate is placed on the billet to directly act on the upper surface of the billet.

[0015] In some embodiments, the punch further includes a guide plate, which is fixedly connected to the extrusion rod; the frame is provided with a guide rod, and the guide plate and the guide rod are slidably engaged.

[0016] In some embodiments, the outer ring of the die is a frustum-shaped structure with a flat, round central through hole; the die assembly further includes a support frame for supporting the outer ring of the die; the support frame has a through hole, the outer ring of the die is fixedly connected to the through hole via a flange, and the axis of the outer ring of the die is aligned with the axis of the through hole.

[0017] A method for asymmetric extrusion of magnesium alloys, using the magnesium alloy asymmetric extrusion equipment described above, the extrusion method comprising: assembling a die; assembling the die core to form the die cavity; uniformly applying lubricant to the die cavity; placing a magnesium alloy billet into the die cavity and heating the billet to 200℃-450℃ using an external heating furnace; placing the heated billet and the die core into the outer ring of the die cavity; placing the extrusion plate on the top surface of the billet and driving the extrusion rod to uniformly extrude the extrusion plate at a speed v; uniformly extruding the billet through the forming channel hole to obtain a magnesium alloy asymmetric profile; and performing a stress-relief annealing process on the profile.

[0018] In some embodiments, the extrusion speed v ranges from 0.1 m / min to 20 m / min.

[0019] In some embodiments, the lubricant is a glass, graphite, or aluminum powder lubricant.

[0020] In some embodiments, the stress-relief annealing process includes: holding at 150℃-400℃ for 0.5-2 hours.

[0021] The magnesium alloy asymmetric extrusion equipment provided in this application extrudes a billet through a mutually cooperating punch assembly and die assembly. The punch assembly acts directly on the billet, and the die assembly includes an outer die ring and a die core nested within the outer die ring. The die core forms a mold cavity, which includes a flat cylindrical extrusion cavity and a forming channel hole. The length and thickness of the forming channel hole are smaller than those of the extrusion cavity, and the extrusion cavity and forming channel hole are sequentially distributed along the extrusion direction of the billet, allowing the billet to be extruded from the extrusion cavity into the forming channel hole and then extruded through the forming channel hole to form a profile. The forming channel hole is asymmetrically arranged, specifically including the length direction... The asymmetry design allows for the introduction of a strong shear strain field within the magnesium alloy material during extrusion. This alters the flow state of the magnesium alloy, creating an asymmetric flow velocity distribution. This effectively compensates for velocity differences during magnesium alloy extrusion, reducing defects in the profiles caused by velocity variations and improving the yield rate of asymmetric magnesium alloy profiles. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the magnesium alloy asymmetric extrusion equipment provided in the embodiments of this application;

[0024] Figure 2 A top view of the mold core provided in the embodiments of this application;

[0025] Figure 3 for Figure 2 Sectional view at point AA;

[0026] Figure 4 This is a schematic flowchart of the asymmetric extrusion method for magnesium alloys provided in an embodiment of this application.

[0027] Explanation of reference numerals in the attached figures:

[0028] 100-Frame;

[0029] 110 - Extrusion rod, 120 - Guide plate, 130 - Guide rod;

[0030] 210 - Outer ring of the die, 220 - Die core, 221 - Extrusion cavity, 222 - Forming channel hole, 230 - Support frame. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The terminology used in the following embodiments is for the purpose of describing specific embodiments only and is not intended to be a limitation of this application. As used in the specification and appended claims of this application, the singular expressions "a," "an," "the," "the," "the," and "this" are intended to also include expressions such as "one or more," unless the context clearly indicates otherwise.

[0033] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0034] The "multiple" mentioned in the embodiments of this application refers to two or more. It should be noted that in the description of the embodiments of this application, terms such as "first" and "second" are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance, nor should they be construed as indicating or implying order.

[0035] like Figure 1 As shown in the embodiment of this application, the magnesium alloy asymmetric extrusion equipment is used to extrude magnesium alloy billets into shapes. The extrusion equipment includes a punch assembly and a die assembly that cooperate with each other. The punch assembly is used to extrude the billet so that the billet is extruded through the die assembly to form a profile. The die assembly includes a die outer ring 210 and a die core 220 nested inside the die outer ring 210. The die core 220 forms a mold cavity, which includes an extrusion cavity 221 with a flat cylindrical structure and a forming channel hole 222. The length and thickness of the forming channel hole 222 are both smaller than those of the extrusion cavity 221. The extrusion cavity 221 and the forming channel hole 222 are distributed sequentially along the extrusion direction of the billet so that the billet can be extruded from the extrusion cavity 221 through the forming channel hole 222 and from the forming channel hole 222.

[0036] The forming channel hole 222 is asymmetrically designed, specifically including: asymmetry in the length direction, with a deviation distance between the central axis of the forming channel hole 222 and the central axis of the extrusion cavity 221; asymmetry in the thickness direction, with the forming channel hole 222 having at least two parts with unequal thicknesses; and asymmetry in the cross-section, with the projection of the forming channel hole 222 along the extrusion direction of the billet being asymmetrical in at least one direction. In this way, during the extrusion of magnesium alloy, the asymmetrical offset design can actively introduce a strong shear strain field into the magnesium alloy material, change the flow state of the magnesium alloy, and form an asymmetrical flow velocity distribution, thereby effectively compensating for the flow velocity difference during the magnesium alloy extrusion process, reducing the defects of the profile caused by the flow velocity difference, and improving the yield of asymmetrical magnesium alloy profiles.

[0037] In this application, the deviation ratio between the central axis of the forming channel hole 222 and the central axis of the extrusion cavity 221 is the asymmetric extrusion coefficient K, which satisfies the following:

[0038] K = d / R, where d is the deviation distance between the central axis of the forming channel hole 222 and the central axis of the extrusion cavity 221, in mm; and R is the radius of the extrusion cavity 221, in mm.

[0039] By setting an asymmetric extrusion coefficient K, a strong shear strain field is actively introduced into the magnesium alloy material during the extrusion process, which changes the flow state of the magnesium alloy and forms an asymmetric flow velocity distribution, thereby effectively compensating for the flow velocity differences during the magnesium alloy extrusion process.

[0040] The asymmetry coefficient of the formed asymmetric profile is E. In this application, the asymmetric extrusion coefficient K and the asymmetric coefficient E are set to satisfy: K=E, so as to better balance and reduce the defects of the profile caused by the difference in flow rate and improve the yield of asymmetric magnesium alloy profiles.

[0041] It should be noted that the profile asymmetry coefficient E is a geometric asymmetry coefficient specific to asymmetric profiles, obtained through quantitative calculation based on the asymmetric characteristics of the forming channel holes (length offset, thickness difference, cross-sectional asymmetry).

[0042] After obtaining the profile asymmetry coefficient E, structural parameters such as the size of the die core 220, the groove thickness of the first die core and the second die core, the offset, and the cross-sectional shape can be adjusted to make the asymmetric extrusion coefficient K correspond to the profile asymmetry coefficient E, thereby ensuring the extrusion molding of magnesium alloy billets, reducing profile defects caused by flow rate differences, and improving the yield of asymmetric magnesium alloy profiles.

[0043] like Figure 2 As shown, the cross-section of the forming channel hole 222 is in the shape of an "I" to form an asymmetric magnesium alloy profile. Through the asymmetric extrusion molding process, the defects of the profile caused by the flow rate difference are reduced, and the yield of the asymmetric magnesium alloy profile is improved.

[0044] Specifically, the I-shaped forming channel hole 222 forms an I-shaped profile, and the profile asymmetry coefficient E of the I-shaped asymmetric profile satisfies:

[0045] E= Unit: mm ； hm is the length of the connecting side of the I-shaped forming channel hole 222, in meters. m .

[0046] In this way, the asymmetric extrusion coefficient K of the die core 220 can be adjusted according to the specific profile asymmetry coefficient E to ensure that a strong shear strain field is introduced inside the magnesium alloy material, changing the flow state of the magnesium alloy and forming an asymmetric flow velocity distribution. This effectively compensates for the flow velocity difference during the magnesium alloy extrusion process, reduces the defects of the profile caused by the flow velocity difference, and improves the yield of asymmetric magnesium alloy profiles.

[0047] In other embodiments, the cross-sectional structure of the forming channel hole 222 can also be one of the following: a single-sided stepped structure, a locally thickened structure, a T-shaped structure, or an L-shaped structure. The asymmetry coefficient E of the profile with different asymmetric structures is obtained by quantitative calculation. The asymmetric extrusion coefficient K is adjusted to match the profile asymmetry coefficient E by the asymmetric offset design of the mold core 220, thereby improving the yield of asymmetric magnesium alloy profiles.

[0048] In this application, the extrusion ratio of the magnesium alloy profile is 4 / 100, that is, the ratio of the cross-sectional area of ​​the forming channel hole 222 to the cross-sectional area of ​​the extrusion cavity 221 is 4 / 100. By using a higher extrusion ratio, a profile with a finer and more uniform crystal structure is obtained, which improves the yield strength and tensile strength of the profile and further improves the mechanical properties of the profile.

[0049] Of course, in other embodiments, other extrusion ratios can be selected according to actual conditions. The range of selectable extrusion ratios is 1 / 70-1 / 10, for example, 1 / 15. This application embodiment does not limit this.

[0050] In this application, the mold core 220 includes a first mold core and a second mold core, and the first mold core and the second mold core are detachably fixedly connected so that the first mold core and the second mold core can be assembled to form a mold cavity.

[0051] Specifically, both the first and second mold cores are semi-flat cylindrical structures, with corresponding threaded holes and external threaded pins at the four corners of the first and second mold cores, respectively. The mating surfaces of the first and second mold cores have locating tapered holes. During assembly, the mating surfaces of the two mold cores are first arranged opposite each other so that the external threaded pins correspond to the threaded holes. Then, the tapered locating pins are hammered into the tapered locating holes. Finally, the external threaded pins are screwed into the threaded holes and fixed using tools such as an Allen wrench to achieve the assembly of the first and second mold cores.

[0052] The first and second mold cores are detachably fixedly connected, allowing for the formation of mold cavities of different sizes by selecting different sizes for assembly. This also facilitates the installation and replacement of the mold cores, thereby improving their applicability.

[0053] A first groove is formed in the first mold core, and a second groove is formed in the second mold core. The first groove and the second groove are joined together to form a forming channel hole 222. The thicknesses of the first groove and the second groove are different, so that the forming channel hole 222 has two parts with different thicknesses. This further actively introduces a strong shear strain field into the magnesium alloy material, changes the flow state of the magnesium alloy, and forms an asymmetric flow velocity distribution. This effectively compensates for the flow velocity difference during the magnesium alloy extrusion process, reduces the defects of the profile caused by the flow velocity difference, and improves the yield of asymmetric magnesium alloy profiles.

[0054] like Figure 1 As shown, the extrusion equipment provided in this application embodiment also includes a frame 100, which supports the punch assembly and the die assembly. The punch assembly includes an extrusion rod 110, which is movably connected to the top surface of the frame 100. Specifically, the extrusion rod 110 can be connected to a power device so that the extrusion rod 110 can slide with the frame 100. The other end of the extrusion rod 110 away from the top surface of the frame 100 is used to abut against the extrusion plate. The extrusion plate is placed on the top surface of the billet to directly act on the upper surface of the billet, so that the billet is subjected to uniform force and to ensure the uniformity of the extrusion force area.

[0055] like Figure 1 As shown, the punch assembly also includes a guide plate 120, which is fixedly connected to the extrusion rod 110. Guide rods 130 are provided around the frame 100. The guide plate 120 and the guide rods 130 are slidably engaged, so that the extrusion rod 110 can be stably linearly displaced under the action of the guide plate 120, thereby further improving the stability of the extrusion of the billet and improving the forming quality of the profile.

[0056] like Figure 1 As shown, the outer ring 210 of the die is a frustum-shaped structure with a flat oval central through hole, and the inner ring of the outer ring 210 of the die is matched with the outer ring of the mold core 220 to ensure the stability of the mold core 220 and to allow the formed profile to fall from the outer ring 210 of the die.

[0057] The die assembly also includes a support frame 230, which supports the outer ring 210 of the die. The support frame 230 has a through hole, and the outer ring 210 of the die is fixedly connected to the through hole through a flange, so that the axis of the outer ring 210 of the die is aligned with the axis of the through hole, thereby ensuring the fitting accuracy of the punch assembly and the die assembly.

[0058] This application also provides a method for asymmetric extrusion of magnesium alloys, employing the magnesium alloy asymmetric extrusion equipment as described above, specifically including:

[0059] S100, assembly mold.

[0060] The first and second mold cores of the mold core 220 are combined to form a mold cavity, and components such as the extrusion rod 110 and the outer ring 210 of the die are installed and fitted with the frame 100.

[0061] S200. Apply lubricant evenly inside the mold cavity.

[0062] A lubricant is evenly applied inside the mold cavity. The lubricant can be glass, graphite, or aluminum powder lubricant. The lubricant controls and optimizes the flow process of the magnesium alloy, reduces the friction between the magnesium alloy billet and the mold core 220, improves the uniformity of magnesium alloy flow, and further improves the profile forming quality.

[0063] S300: Place the magnesium alloy billet into the mold cavity and heat the billet to 200℃-450℃ using an external heating furnace.

[0064] Heating magnesium alloy billets achieves the following: Improved plasticity: Magnesium alloys have limited slip systems that can be activated at room temperature, resulting in poor plasticity and high brittleness. Direct large deformation processing such as extrusion or rolling easily leads to cracking. Heating to a certain temperature intensifies atomic thermal motion, activating more slip systems, making the material "softer" and able to withstand large, complex plastic deformations without cracking; Reduced deformation resistance: As temperature increases, the yield strength and flow stress of the metal decrease significantly. This means that the material can be deformed with less force, greatly reducing equipment load and energy consumption; Promoted dynamic recrystallization: During hot deformation, dynamic recrystallization occurs within the material. New, strain-free equiaxed grains replace the old, work-hardened deformed grains. This process can: Eliminate work hardening, allowing deformation to continue; Improved formability: Heating through the above methods improves the formability of magnesium alloys, thereby increasing the yield of profiles.

[0065] S400, extrusion molding of magnesium alloy.

[0066] S410. Place the heated blank and mold core 220 into the outer ring 210 of the die cavity.

[0067] S420. Place the extrusion plate on the top surface of the billet to be extruded, and drive the extrusion rod 110 to extrude the extrusion plate at a speed v. The speed v ranges from 0.1 m / min to 20 m / min and can be selected according to the actual situation.

[0068] S430, the billet is uniformly extruded into the forming channel hole 222 to obtain an asymmetric profile of magnesium alloy.

[0069] S500, stress-relief annealing process is applied to the obtained profiles.

[0070] The profile is kept at 150℃-400℃ for 0.5-2 hours to eliminate residual stress and ensure dimensional stability, thereby preventing deformation and cracking and improving yield.

[0071] The following three examples illustrate this in detail:

[0072] Specific Example 1: Mg-1.0Al-0.5Ca-0.3Mn (wt.%)

[0073] Magnesium alloy is placed into the mold cavity inside the assembled mold core 220 and heated to 200-450℃ by an external heating furnace. The heated billet and mold core 220 are placed into the outer ring 210 of the die, and the extrusion rod 110 is driven to extrude the billet at a speed of 15 m / min with an extrusion ratio of 1 / 15.

[0074] The extruded profiles are subjected to stress-relief annealing, which involves holding them at 200℃ for 0.5-2 hours to eliminate work hardening that occurs during plastic deformation.

[0075] The profile formed in Example 1 was tested, and the test results are shown in Table 1:

[0076] Table SEQ Table * ARABIC 1 Example 1 Profile Performance Test Results performance Grain size (μm) Yield strength (MPa) Tensile strength (MPa) Elongation (%) Before extrusion 67 121 165 8.1 After squeezing 2.7 271 295 20.1

[0077] As shown in Table 1, the extrusion process using the method described in this application significantly optimizes and enhances the comprehensive mechanical properties of magnesium alloys. The grain size is reduced from 67 μm to 2.7 μm. The intense plastic deformation and dynamic recrystallization during extrusion thoroughly break down and refine the coarse cast structure, resulting in a simultaneous increase in both strength and toughness of the profile. The yield strength increases from 121 MPa to 271 MPa, an increase of 124%, improving the profile's load-bearing capacity and deformation resistance. The tensile strength increases from 165 MPa to 295 MPa, an increase of 79%, allowing for a higher structural safety margin and improved reliability. The elongation increases from 8.1% to 20.1%, an increase of 148%, significantly improving the toughness of the profile. This results in a high-strength, high-toughness magnesium alloy asymmetric profile, greatly improving the yield rate of magnesium alloy asymmetric profiles.

[0078] Specific Example 2: Mg-1.2Al-1Ca-0.3Mn-0.5Zn (wt.%)

[0079] Magnesium alloy is placed into the mold cavity inside the assembled mold core 220 and heated to 450°C by an external heating furnace. The heated billet and mold core 220 are placed into the outer ring 210 of the die cavity, and the extrusion rod 110 is driven to extrude the billet at a speed of 21 m / min at a uniform speed with an extrusion ratio of 1 / 15.

[0080] The extruded profiles are subjected to stress-relief annealing, which involves holding them at 300℃ for 1 hour to eliminate work hardening that occurs during plastic deformation.

[0081] Then, artificial aging was performed at 200℃ for 1 hour to further optimize the profile performance.

[0082] It should be noted that artificial aging, also known as precipitation heat treatment, is a heat treatment process that artificially alters the microstructure of metallic materials through heating, thereby improving their mechanical properties (mainly strength and hardness). This heat treatment process actively controls the precipitation of strengthening phases in the alloy by heating and holding at a specific temperature, thus allowing the material to achieve the highest strength, hardness, and optimal overall performance in the shortest possible time.

[0083] Performance tests were conducted on Example 2, and the test structure is shown in Table 2:

[0084] Table SEQ Table * ARABIC 2 Example 2 Profile Performance Test Results performance Grain size (μm) Yield strength (MPa) Tensile strength (MPa) Elongation (%) Before extrusion 78 125 178 9.2 After squeezing 2.1 281 319 22.1

[0085] As shown in Table 2, the extrusion process described in this application significantly optimizes and enhances the comprehensive mechanical properties of magnesium alloys. The grain size is reduced from 78 μm to 2.1 μm. The intense plastic deformation and dynamic recrystallization during extrusion thoroughly break down and refine the coarse cast structure, resulting in a simultaneous increase in both strength and toughness of the profile. The yield strength increases from 125 MPa to 281 MPa, an increase of 125%, improving the profile's load-bearing capacity and deformation resistance. The tensile strength increases from 178 MPa to 319 MPa, an increase of 79%, allowing for a higher structural safety margin and improved reliability. The elongation increases from 9.2% to 22.1%, an increase of 140%, significantly improving the toughness of the profile. This results in a high-strength, high-toughness magnesium alloy asymmetric profile, greatly improving the yield rate of magnesium alloy asymmetric profiles.

[0086] Specific Example 3: Mg-2Sn-0.5Zn-0.3wMn (wt.%)

[0087] Magnesium alloy is placed into the mold cavity inside the assembled mold core 220 and heated to 200-450℃ by an external heating furnace. The heated billet and mold core 220 are placed into the outer ring 210 of the die, and the extrusion rod 110 is driven to extrude the billet at a speed of 15 m / min with an extrusion ratio of 1 / 15.

[0088] The extruded profiles are subjected to stress-relief annealing, which involves holding them at 200℃ for 0.5-2 hours to eliminate work hardening that occurs during plastic deformation.

[0089] The profile formed in Example 3 was tested, and the test structure is shown in Table 3:

[0090] Table SEQ Table \* ARABIC 3 Example 3 Profile Performance Test Results performance Grain size (μm) Yield strength (MPa) Tensile strength (MPa) Elongation (%) Before extrusion 61 132 175 7.2 After squeezing 2.1 294 331 20.1

[0091] As shown in Table 3, the extrusion process described in this application significantly optimizes and enhances the comprehensive mechanical properties of magnesium alloys. The grain size is reduced from 61 μm to 2.1 μm. The intense plastic deformation and dynamic recrystallization during extrusion thoroughly break down and refine the coarse cast structure, resulting in simultaneous improvements in both strength and toughness of the profile. The yield strength increases from 131 MPa to 294 MPa, an increase of 123%, enhancing the profile's load-bearing capacity and resistance to deformation. The tensile strength increases from 175 MPa to 331 MPa, an increase of 89%, allowing for a higher structural safety margin and improved reliability. The elongation increases from 7.2% to 20.1%, an increase of 179%, significantly improving the toughness of the profile. This results in a high-strength, high-toughness magnesium alloy asymmetric profile, greatly improving the yield rate of magnesium alloy asymmetric profiles.

[0092] As can be seen from the above, when magnesium alloys with different mass ratios are extruded into profiles using the extrusion method provided in this application, their yield strength, tensile strength, and elongation can be significantly improved. The extrusion method of this application, through its asymmetric offset design, can actively introduce a strong shear strain field into the magnesium alloy material, change the flow state of the magnesium alloy, and form an asymmetric flow velocity distribution. This effectively compensates for the flow velocity differences during the magnesium alloy extrusion process, reduces the defects in the profiles caused by the flow velocity differences, and improves the yield of asymmetric magnesium alloy profiles.

[0093] The above description of the embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A magnesium alloy asymmetric extrusion apparatus for extruding magnesium alloy billets, characterized in that, include: A mutually cooperating punch assembly and die assembly; The punch assembly is used to extrude the blank; The die assembly includes a die outer ring (210) and a die core (220) nested inside the die outer ring (210). A die cavity is formed inside the die core (220). The die cavity includes an extrusion cavity (221) with a flat cylindrical structure and a forming channel hole (222). The length and thickness of the forming channel hole (222) are both smaller than those of the extrusion cavity (221). The extrusion cavity (221) and the forming channel hole (222) are distributed sequentially along the extrusion direction of the blank. The forming channel hole (222) is asymmetrically arranged, specifically including: The longitudinal direction is asymmetrical, and there is a deviation distance between the central axis of the forming channel hole (222) and the central axis of the extrusion cavity (221); The thickness direction is asymmetrical, and the forming channel hole (222) has at least two parts with different thicknesses; The cross-section is asymmetrical, and the projection of the forming channel hole (222) along the extrusion direction of the blank is asymmetrical in at least one direction.

2. The magnesium alloy asymmetric extrusion equipment according to claim 1, characterized in that, The ratio of the deviation between the central axis of the forming channel hole (222) and the central axis of the extrusion cavity (221) is the asymmetric extrusion coefficient K, which satisfies: K=d / R, where d is the deviation distance between the central axis of the forming channel hole (222) and the central axis of the extrusion cavity (221), in mm; and R is the radius of the extrusion cavity (221), in mm.

3. The magnesium alloy asymmetric extrusion equipment according to claim 2, characterized in that, The profile asymmetry coefficient is E, and the asymmetric extrusion coefficient K and the profile asymmetry coefficient E satisfy the following: K=E.

4. The magnesium alloy asymmetric extrusion equipment according to claim 3, characterized in that, The cross-section of the formed channel hole (222) has an I-shaped structure.

5. The magnesium alloy asymmetric extrusion equipment according to claim 4, characterized in that, The forming channel hole (222) of the I-shaped structure forms an I-shaped profile, and the asymmetry coefficient E of the I-shaped profile satisfies: E= Kong (222) ） The length of the longer side, in mm; hm is the I-shaped forming channel hole (222). ） The length of the connecting edge, in mm.

6. The magnesium alloy asymmetric extrusion equipment according to claim 4, characterized in that, The cross-section of the formed channel hole (222) is one of the following: a single-sided stepped structure, a locally thickened structure, a T-shaped structure, or an L-shaped structure.

7. The magnesium alloy asymmetric extrusion equipment according to claim 1, characterized in that, The ratio of the cross-sectional area of ​​the forming channel hole (222) to the cross-sectional area of ​​the extrusion cavity (221) is 4 / 100.

8. The magnesium alloy asymmetric extrusion equipment according to claim 1, characterized in that, The mold core (220) includes a first mold core and a second mold core, the first mold core and the second mold core are detachably fixedly connected, and the first mold core and the second mold core can be assembled to form the mold cavity; The first mold core has a first groove, and the second mold core has a second groove. The first groove and the second groove are joined together to form the molding channel hole (222). The first groove and the second groove have different thicknesses.

9. The magnesium alloy asymmetric extrusion equipment according to claim 1, characterized in that, The extrusion equipment also includes a frame (100). The punch assembly includes an extrusion rod (110), which is movably connected to the top surface of the frame (100). The other end of the extrusion rod (110) away from the top surface of the frame (100) is used to abut against an extrusion plate, which is placed on the blank and used to directly act on the upper surface of the blank.

10. The magnesium alloy asymmetric extrusion equipment according to claim 9, characterized in that, The punch assembly also includes a guide plate (120), which is fixedly connected to the extrusion rod (110); The frame (100) is provided with a guide rod (130), and the guide plate (120) slides in cooperation with the guide rod (130).

11. The magnesium alloy asymmetric extrusion equipment according to claim 1, characterized in that, The outer ring (210) of the die cavity is a frustum-shaped structure with a flat, round central through hole; The die assembly also includes a support frame (230) for supporting the outer ring (210) of the die. The support frame (230) has a through hole, and the outer ring of the die (210) is fixedly connected to the through hole through a flange, and the axis of the outer ring of the die (210) is consistent with the axis of the through hole.

12. A method for asymmetric extrusion of magnesium alloys, characterized in that, The extrusion method, using the magnesium alloy asymmetric extrusion equipment as described in any one of claims 1-7, comprises: Assemble the mold, and assemble the mold core (220) to form the mold cavity; Apply lubricant evenly inside the mold cavity; The magnesium alloy billet is placed into the mold cavity and heated to 200℃-450℃ by an external heating furnace. The heated blank and the mold core (220) are placed into the outer ring (210) of the die cavity; The extrusion plate is placed on the top surface of the billet, and the extrusion rod (110) is driven to extrude the extrusion plate at a constant speed v. The billet is uniformly extruded from the forming channel hole (222) to obtain a magnesium alloy asymmetric profile; The profile is subjected to a stress-relief annealing process.

13. The asymmetric extrusion method for magnesium alloys according to claim 12, characterized in that, The extrusion speed v ranges from 0.1 m / min to 20 m / min.

14. The asymmetric extrusion method for magnesium alloys according to claim 12, characterized in that, The lubricant is a glass, graphite, or aluminum powder lubricant.

15. The asymmetric extrusion method for magnesium alloys according to claim 12, characterized in that, The stress-relief annealing process includes: holding at 150℃-400℃ for 0.5-2 hours.

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