Device and method for preparing fine-grained magnesium alloy rod by asymmetric multi-directional shear extrusion

Abstract

The present application belongs to the field of light metal plastic forming, and particularly relates to a device and method for preparing fine-grained magnesium alloy rod by asymmetric multi-directional shear extrusion. The wedge block combination in the present application can combine multi-directional shear extrusion deformation and differential speed torsional deformation, effectively weaken the magnesium alloy basal plane texture, and improve the mechanical properties of the magnesium alloy. While the magnesium alloy material is subjected to torsional extrusion in the torsional extrusion deformation zone, the sectional area of the channel gradually decreases, and the angle of the channel deflection is different, so that the frictional force of the magnesium alloy material on the surface of the convex and concave dies at the contact position is different, and the degree of torsional deformation is also different, so that the material realizes differential speed torsional deformation, and the grain refinement effect of the magnesium alloy rod is more remarkable. When the magnesium alloy material passes through the large and small concave dies, the deformation degrees of the magnesium alloy material are different due to the particularity of the structure, so that the grain refinement is effectively realized. At the same time, the flowability of the magnesium alloy material is also different, causing differential speed flow to deflect the c-axis, thereby weakening the texture.

Description

Technical Field

[0001] This invention belongs to the field of light metal plastic forming technology, specifically relating to a processing device for preparing fine-grained, weakly textured high-performance magnesium alloy rods by asymmetric multi-directional shear extrusion and an extrusion method using the device. Background Technology

[0002] Magnesium and magnesium alloys have a low density, approximately two-thirds that of aluminum alloys and less than one-quarter that of steel. They possess high specific strength and high specific stiffness, making them the lightest engineering structural materials currently available. Furthermore, they offer advantages such as good damping and vibration reduction, ease of machining, and recyclability. In recent years, with the global energy and resource crises, lightweight magnesium alloys and their lightweight components have been widely used in aerospace, transportation, and electronic communications, becoming the third most widely used metal structural material after steel and aluminum alloys. Compared to metals like aluminum, iron, and copper, which are heavily reliant on exports, my country has abundant magnesium reserves, ranking first in the world in both production and exports, giving it a significant domestic advantage and a robust supply chain. Therefore, developing magnesium alloy raw materials and processing technologies, and promoting the coordinated and sustainable development of my country's magnesium and magnesium alloy industry, holds significant socio-economic value and strategic importance.

[0003] The demand for magnesium alloy structural materials in the lightweighting field is increasing year by year. Compared with castings and die-cast products, magnesium alloys, after plastic processing such as extrusion and rolling, have a fine-grained structure and high strength and toughness in mechanical properties, which are different from the as-cast structure. They can meet the requirements of more complex or harsh load-bearing conditions, such as cyclic stress or multi-directional loading, and are currently a hot topic in scientific research and industrial development. However, because basal slip is easily initiated during the deformation of magnesium alloys, strong basal textures are easily generated, such as the rolled plate texture on the basal surface and the extruded wire texture in the extrusion direction. Therefore, weakening the basal texture to reduce the growth of medullary nuclei is an effective method to reduce tensile and compressive asymmetry. Conventional plastic processing such as extrusion and rolling is difficult to achieve texture weakening and control. Severe plastic deformation techniques (SPD) such as reciprocating extrusion (CEC), equal-diameter angular extrusion (ECAP), and multi-directional coarsening (MAF) are beneficial for obtaining relatively dispersed weak basal textures. These texture weakening techniques all employ controlled strain path changes during plastic deformation to achieve grain orientation dispersion. However, in engineering applications, these processes typically suffer from complex process paths and limitations in dimensional specifications. For equal-diameter angular extrusion, the extruded material often experiences a sharp drop in tensile and compressive yield strength due to excessive tilting of the basal texture, which is detrimental to the manufacture of high-strength magnesium materials. Therefore, inventing an effective device and method for weakening the deformation texture and refining the grains of magnesium alloys is crucial for expanding the application range of magnesium alloys. Summary of the Invention

[0004] This invention aims to solve the above-mentioned problems by providing an asymmetric multi-directional shear extrusion processing apparatus for preparing fine-grained, weak-textured high-performance magnesium alloy bars, and a method for using this apparatus to extrude weak-textured magnesium alloy bars. Through this apparatus and processing method, the magnesium alloy billet undergoes continuous multi-directional shear-torsional extrusion deformation during processing, causing the c-axis of the magnesium alloy to deflect, thereby achieving weakened texture and grain refinement, improving the room-temperature mechanical properties of the magnesium alloy, and expanding the application range of magnesium alloys.

[0005] This invention is achieved through the following technical solution:

[0006] An apparatus for preparing fine-grained magnesium alloy bars by asymmetric multi-directional shear extrusion includes a vertical extruder, a feed channel die, a large concave die, a straight channel die, a small concave die, a discharge channel die, an external die frame, and a power unit, wherein:

[0007] The vertical extrusion press includes a base, a top seat, and a column fixed between the base and the top seat; a power unit is installed at the center of the top seat, an extrusion telescopic head is installed at the bottom of the power unit, a pressure block is fixed at the end of the extrusion telescopic head, an extrusion punch is fixed at the bottom of the pressure block, and the lower end of the extrusion punch is flat; a lifting handle for controlling the movement of the extrusion telescopic head is installed on the column, a pad is fixed at the center of the base, and a discharge port that runs vertically through the pad and the base is provided;

[0008] The inner cavity of the feeding channel mold is provided with an extrusion channel. The inner cavity of the large concave mold below the feeding channel mold is provided with a diameter reduction channel that communicates with the extrusion channel. The bottom of the inner cavity of the large concave mold is provided with a large wedge block assembly. The large wedge block assembly is formed by stacking four wedge-shaped long plates end to end. The upper surface of the wedges has an arc and slopes towards the center of the assembly. The corners of the large wedge block assembly are rounded. The middle part of the large wedge block assembly has a quadrilateral through hole. The four wedge-shaped long plates have different heights.

[0009] The straight channel mold is located below the large concave mold. The inner cavity of the straight channel mold is a through hole with a certain height. The size of the through hole on the upper surface of the straight channel mold is the same as the cross-sectional area of ​​the quadrilateral through hole of the large wedge block assembly above. The cross-sectional area of ​​the through hole on the lower surface of the straight channel mold is larger than the cross-sectional area of ​​the cavity of the small concave mold located below it.

[0010] The position of the small concave mold is offset from that of the large concave mold by a certain angle, which is no more than 90°. The small concave mold consists of two parts. The upper part is composed of a twisted diameter reduction channel (the four sides of the channel are deflected at different angles to form a twisted structure). This twisted diameter reduction channel is connected to the cavity of the straight channel mold. The lower part of the small concave mold is provided with a small wedge block assembly with a structure similar to that of the large wedge block assembly.

[0011] The discharge channel mold cavity is a straight channel that communicates with the cavity of the small concave mold, and the straight channel communicates with the discharge port.

[0012] The external mold frame includes a die fixing frame mounted on a pad block. A heating sleeve is provided on the inner wall of the die fixing frame. The feed channel mold, large die mold, straight channel mold, small die mold, and discharge channel mold are stacked sequentially from top to bottom on the pad block inside the die fixing frame.

[0013] The extrusion punch, feed channel die, large concave die, straight channel die, small concave die, and discharge channel die together constitute the torsional extrusion space. From top to bottom, the torsional extrusion space consists of the extrusion pushing zone, the multi-directional shear deformation zone, the torsional extrusion deformation zone, the small multi-directional shear deformation zone, and the discharge zone. In the extrusion pushing zone, the magnesium alloy billet advances continuously under the extrusion of the extrusion punch, reaching the multi-directional shear deformation zone. When the magnesium alloy billet contacts the four highest points of the four wedge-shaped structures connected end-to-end in the wedge block assembly, the contact time differs due to the inconsistent heights of the four wedge blocks, resulting in differential flow and varying degrees of deformation. Simultaneously, the wedge blocks exhibit a downward-sloping surface at a certain angle longitudinally and a downward-sloping, arc-shaped ramp laterally. When the billet passes through these structures, it will flow laterally and longitudinally, undergoing shear deformation. Since the structures are connected end to end, a vertical area will appear at the intersection of the two wedges. To avoid dead zones, the corners are rounded, and the billet will also undergo a certain degree of shear deformation at this point. In addition, since the height and slope angle of the four wedges are different, the degree of deformation of the billet at each wedge is also different. At the same time, the core of the billet flows towards the central quadrilateral hole, reducing the size of the billet and causing diameter reduction deformation. The plastic and shear deformation of magnesium alloy billets refines the grain structure. During shear deformation, the c-axis of the grains tilts under the shear force, weakening the basal texture. Under the action of the extrusion die, the magnesium alloy billet continues to flow downwards into the torsional extrusion deformation zone. When the magnesium alloy billet reaches the torsional extrusion deformation zone, it undergoes torsional extrusion at different torsional angles through the die channel. The torsional deformation causes the c-axis of the grains to tilt again, further weakening the basal texture and intensifying the deformation of the magnesium alloy. At the same time, the cross-sectional area of ​​the torsional extrusion channel gradually decreases, generating differential shear deformation, which further refines the grain structure. After extruding from the torsional extrusion deformation zone, it enters the small multi-directional shear deformation zone, with a deformation mode similar to that in the large multi-directional shear deformation zone. After extruding from the small multi-directional shear deformation zone, it enters the discharge zone and is finally extruded through the through hole to obtain a high-performance magnesium alloy rod. This device can realize the preparation of fine-grained, weakly textured high-performance magnesium alloys through asymmetric multi-directional shear extrusion deformation.

[0014] Furthermore, the extrusion punch, die, and dies are all made of 4Cr5MoSiV1 hot work die steel.

[0015] Furthermore, the surface roughness of the extrusion punch is Ra 0.08~0.16μm, the surface roughness of the large die is Ra 0.4~0.8μm, and the surface roughness of the small die is Ra 0.08~0.16μm. The asymmetrical distribution of surface roughness of the torsional extrusion channel creates a difference in the frictional force generated between the extrusion process and the billet, further promoting differential flow of the billet and generating shear extrusion deformation to weaken its base surface texture.

[0016] A method for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion includes the following steps:

[0017] S1. Pretreatment of magnesium alloy billet:

[0018] S1-1. Use 600-grit sandpaper to polish the surface of the magnesium alloy block blank to remove oil stains, and then use 800-grit, 1000-grit, and 1200-grit sandpaper in sequence until the surface of the magnesium alloy block blank is smooth.

[0019] S1-2. Mix acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stir until homogeneous to prepare a cleaning solution.

[0020] S1-3. Immerse the magnesium alloy block blank prepared in step S1-1 into the cleaning solution prepared in step S1-2, place the cleaning tank on an ultrasonic cleaner and ultrasonically clean the magnesium alloy block blank for 60 minutes, then take out the magnesium alloy block blank and clean it with anhydrous ethanol, and finally dry it with a hair dryer.

[0021] S1-4. Coat the surface of the magnesium alloy block blank prepared in step S1-3 with graphite oil solution for later use.

[0022] S2. Preheating of magnesium alloy billet: Set the heating temperature of the vacuum atmosphere heating furnace to 450℃. After the furnace temperature reaches the set temperature, put the magnesium alloy billet into the heating furnace and keep it at that temperature for 3 hours.

[0023] S3. Lubrication, assembly, and preheating of the asymmetric multi-directional shear extrusion deformation forming device:

[0024] S3-1, Lubrication: Apply graphite oil solution to the surface of the large concave die, the small concave die cavity, and the extrusion punch.

[0025] S3-2, Assembly:

[0026] First, install and fix the pad block on the base of the vertical extruder, then fix the die fixing frame on the base, and then install the heating jacket on the inner surface of the die fixing frame. Then, from bottom to top, place the discharge channel mold, small die mold, straight channel mold, large die mold, and feed channel mold in the die fixing frame and fix them with four long screws. Control the extrusion punch to move down and be placed in the top cavity of the feed channel mold to ensure that the cavities of the extrusion punch and the feed channel mold are in close vertical contact.

[0027] S3-3. Preheating: Control the temperature of the heating jacket to 300~500℃, and keep it warm for 2~4 hours after reaching the set temperature, so that it can be used in the next step.

[0028] S4. Asymmetric multi-directional shear extrusion molding: The extrusion punch, the feeding channel die, the large concave die, the straight channel die, the small concave die, and the discharge channel die together form a torsional extrusion space; the torsional extrusion space includes five areas arranged from top to bottom: the extrusion pushing area I, the multi-directional shear deformation area II, the torsional extrusion deformation area III, the small multi-directional shear deformation area IV, and the discharge area V;

[0029] S4-1. Remove the extrusion punch from the extrusion pushing zone I, allowing the magnesium alloy block billet to fill the extrusion pushing zone I, and then push the extrusion punch into the extrusion pushing zone I.

[0030] Operating the vertical extrusion press, the magnesium alloy billet advances continuously in the extrusion pushing zone I under the extrusion punch, reaching the shear deformation zone II. The magnesium alloy billet continues to be extruded downwards, and the channel gradually narrows during the extrusion process. Through the large concave die, when the magnesium alloy billet contacts the large wedge-shaped block assembly, it undergoes lateral and longitudinal flow, resulting in shear deformation. Shear deformation also occurs at the rounded corners where the two wedges intersect. Furthermore, because the height and slope angle of the four wedges are different, the degree of deformation at each wedge is also different. Simultaneously, the core of the magnesium alloy billet flows towards the central quadrilateral hole, reducing the size of the billet and causing diameter reduction deformation. The plastic deformation and shear deformation of the magnesium alloy billet refine the grain structure. During shear deformation, under the action of shear force, the grains tilt towards the slope surface of the wedges, weakening the basal texture. Under the action of the extrusion punch, the magnesium alloy billet continues to... The magnesium alloy billet flows downwards, first passing through a straight-channel die, and then entering the torsional extrusion deformation zone III. When the magnesium alloy billet reaches the torsional extrusion deformation zone III, it undergoes torsional extrusion at different torsional angles through the die channel. The torsional deformation causes the c-axis of the grains to deflect again in the torsional direction, thereby further weakening the basal texture and intensifying the deformation of the magnesium alloy. At the same time, the cross-sectional area of ​​the torsional extrusion deformation zone III gradually decreases, generating differential shear deformation, and the grain structure will be further refined. After extruding from the torsional extrusion deformation zone III, it enters the small multi-directional shear deformation zone IV, and the deformation mode is similar to that of the large multi-directional shear deformation zone II. Under the structural action of the small wedge block assembly, the magnesium alloy billet grains are refined again, and the c-axis deflects at the inclined surface of the small wedge block assembly. After extruding from the small multi-directional shear deformation zone IV, it enters the discharge zone V and is finally extruded through the discharge port. The magnesium alloy billet undergoes a final deformation through the discharge channel die and is then discharged to obtain a high-performance magnesium alloy rod. During the torsional extrusion forming process, the heating jacket temperature is controlled at 300~500℃.

[0031] S4-2. Take out the magnesium alloy rod obtained in step S4-1, polish its surface with sandpaper, clean the magnesium alloy rod with the cleaning solution prepared in step S1-2, clean it a second time with anhydrous ethanol, and dry it with a hair dryer to obtain a fine-grained weak-textured magnesium alloy rod that can be used directly.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The wedge block assembly in this invention can combine multi-directional shear extrusion deformation and differential torsional deformation, effectively weakening the texture of the magnesium alloy base surface and improving the mechanical properties of the magnesium alloy;

[0034] 2. While the magnesium alloy material is being torsional extruded in the torsional extrusion deformation zone, the cross-sectional area of ​​the channel gradually decreases, and the different deflection angles of the channel cause the frictional force on the surface of the punch and die at the contact point of the magnesium alloy material to be different, as well as the degree of torsional deformation to be different. This enables the material to achieve differential torsional deformation, resulting in a more significant grain refinement effect for the magnesium alloy rod.

[0035] 3. When magnesium alloy materials pass through dies of varying sizes, their deformation varies due to the unique structure of the dies, effectively refining the grains. This also results in varying flowability of the magnesium alloy material, causing differential flow that deflects the c-axis, thereby weakening the texture. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the main structure of the mold of the present invention;

[0037] Figure 2 This is a top view of the mold of the present invention. Figure 1 ;

[0038] Figure 3 This is a top view of the mold of the present invention. Figure 2 ;

[0039] Figure 4 This is a three-dimensional schematic diagram of the mold of the present invention;

[0040] Figure 5 A schematic diagram showing the dimensions and angles of a large concave mold.

[0041] Figure 6 A schematic diagram showing the dimensions and angles of a small concave mold;

[0042] Figure 7 A schematic diagram showing the dimensions and angles of the straight channel and the large concave mold section;

[0043] Figure 8 Dimensions and angles of the small concave mold and the discharge channel mold are shown in the diagram. Figure 1 ;

[0044] Figure 9 Dimensions and angles of the small concave mold and the discharge channel mold are shown in the diagram. Figure 2 ;

[0045] Figure 10 This is the front view of the wedge block assembly;

[0046] Figure 11 This is a top view of the wedge block assembly;

[0047] Figure 12 A three-dimensional view of the wedge block assembly;

[0048] Figure 13 This is a schematic diagram showing the gradual shaping of the billet within the channel area.

[0049] In the diagram: 1-Electrical control box; 2-Wire; 3-Base; 4-Long screw; 5-Discharge port; 6-Column; 7-Top seat; 8-Pressure motor; 9-Extrusion telescopic head; 10-Pressure block; 11-Lifting handle; 12-Extrusion punch; 13-Magnesium alloy block blank; 14-Feeding channel mold; 15-Die fixing frame; 16-Heating jacket; 17-Large die; 18-Large wedge block assembly; 19-Straight channel mold; 20-Small die; 21-Small wedge block assembly; 22-Discharge channel mold; 23-Small screw; 24-Padded block; 25-Display screen; 26-Indicator light; 27-Power switch; 28-Heating jacket controller; 29-Pressure motor controller;

[0050] Ⅰ-Extrusion pushing zone; Ⅱ-Multi-directional shear deformation zone; Ⅲ-Torsion extrusion deformation zone; Ⅳ-Small multi-directional shear deformation zone; Ⅴ-Discharge zone. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0052] An apparatus for preparing fine-grained, weakly textured high-performance magnesium alloy rods by asymmetric multi-directional shear extrusion, comprising:

[0053] The system includes a vertical extruder, a feed channel die 14, a large concave die 17, a straight channel die 19, a small concave die 20, a discharge channel die 22, an external die frame, and a power unit, wherein:

[0054] The vertical extruder includes a base 3, a top seat 7, and a column 6 fixed between the base 3 and the top seat 7. A power unit is installed at the center of the top seat 7, and an extrusion telescopic head 9 is installed at the bottom of the power unit. A pressure block 10 is fixed at the end of the extrusion telescopic head 9, and an extrusion punch 12 is fixed at the bottom of the pressure block 10. The lower end of the extrusion punch 12 is flat. A lifting handle 11 for controlling the movement of the extrusion telescopic head 9 is installed on the column 6. A pad 24 is fixed at the center of the base 3, and a discharge port 5 is formed between the pad 24 and the base 3.

[0055] The upper part of the feeding channel mold 14 is provided with an extrusion channel. The four inclination angles of the channel are β1, β2, β3, and β4, respectively, with an inclination angle range of 90°≤β≤150°. The channel length is h1, the height is 50-100mm, and the lengths of the four sides are l. 0-1 l 0-2 l 0-3 l 0-4The length is 100-200mm, and the channel width is w2, which is also 100-200mm. The large concave mold 17 is provided with a diameter reduction channel that contacts the bottom forming device. The height h2 of the diameter reduction channel is 30-40mm, and the four inclination angles of the channel are δ1, δ2, δ3, and δ4, with an angle of 90°≤δ≤150°. The bottom forming device is composed of four wedge-shaped long plates stacked end to end. The height of one side of the four wedge-shaped long plates is h. 5-1 h 5-2 h 5-3 h 5-4 The height is 15-30mm, and the lengths of the four wedges are l respectively. 1-1 l 1-2 l 1-3 l 1-4 The length is 100-150mm, and the width of the four wedge-shaped blocks is w. 0-1 w 0-2 w 0-3 w 0-4 The width is 30-50mm, and due to the different heights at both ends of the wedge plate, the angles on both sides are also different. The four angles on the side with the highest height of the four wedge blocks are ε1, ε2, ε3, and ε4, with an angle of 5°≤ε≤10°. The angles on the side with the lower height of the four wedge blocks are μ1, μ2, μ3, and μ4, with an angle of 0°≤μ≤5°. The upper surface of the wedge has a curved slope shape (this structure is called the large wedge block assembly 18), and the corners of the forming device are all rounded with a rounding radius of 2-5mm to avoid dead zones during forming. Furthermore, the middle part of the device formed by stacking the four wedge blocks end to end has a quadrilateral structure. After the first deformation, the length and width of the blank are reduced, thereby achieving diameter reduction, which facilitates the second forming of the blank.

[0056] The straight channel mold 19 is a channel that facilitates a second deformation of the blank after the first deformation. It is a through hole with a certain height, h3, ranging from 15-30mm. The angles of the four sides of the through hole are α1, α2, α3, and α4, with an angle of 90°≤α≤150°. The size of the through hole on the upper surface of this mold is the same as the cross-sectional area of ​​the bottom through hole of the upper large concave mold. The size of the cross-sectional area of ​​the through hole on the lower surface of the straight channel mold can be freely adjusted according to actual needs, but it must be larger than the cross-sectional area of ​​the small concave mold.

[0057] The small concave mold 20 is similar to the large concave mold 17, but the position of the small concave mold 20 is deflected relative to the large concave mold 17 (equivalent to being coaxial but deflected by a certain angle), and the angle of deflection is no greater than 90°. The small concave mold consists of two parts. The upper part is composed of a twisted channel, and its upper surface is in contact with the lower end surface of the straight channel mold. The lower half of the small concave mold is similar in structure to the forming device of the large concave mold (it has a small wedge block assembly 21). The outermost heights of the four wedge blocks of the small wedge block assembly 21 are h respectively. 6-1 h 6-2 h 6-3 h 6-4 The height is 5-15mm. The outermost angles of the four wedges are λ1, λ2, λ3, and λ4, with an angle of 5°≤λ≤10°. The innermost angles of the four wedges are Φ1, Φ2, Φ3, and Φ4, with an angle of 0°≤Φ≤5°. The lengths of the four wedges are l. 2-1 l 2-2 l 2-3 l 2-4 The length is 60-80mm, and the widths of the four wedges are w respectively. 1-1 w 1-2 w 1-3 w 1-4 The width is 20-30mm. The height of the deflection channel is h4, and the deflection (tilt) angles of the four sides of the twist channel are γ1, γ2, γ3, and γ4, with an angle of 90°≤γ≤150°. The four tilt angles are different from each other.

[0058] The discharge channel mold 22 is a through hole. The upper end of the through hole is the same size as the middle channel formed by the four small wedge-shaped block assemblies 21, and the lower end is the same size as the discharge port. The four sides of the discharge channel have angles of θ1, θ2, θ3, and θ4, respectively, with an angle of 90°≤θ≤150°. Its upper surface is in contact with the lower surface of the small concave mold. After the second deformation is completed, the material is discharged through the discharge channel mold. The four sides of the finished product after discharge are l... 3-1 l 3-2 l 3-3 l 3-4 The length is 30-50mm, and the final shaping is completed.

[0059] The external mold frame includes a concave mold fixing frame 15 mounted on the base. The concave mold fixing frame 15 is fixed by small screws 23. A heating sleeve 16 is provided on the inner wall of the concave mold fixing frame. A pad 24 placed on the base is placed inside the concave mold fixing frame.

[0060] The power mechanism is a pressure motor 8 that drives the extrusion die.

[0061] Furthermore, the torsional extrusion space, from top to bottom, consists of extrusion pushing zone I, multi-directional shear deformation zone II, torsional extrusion deformation zone III, small multi-directional shear deformation zone IV, and discharge zone V. In extrusion pushing zone I, the magnesium alloy billet 13 advances continuously under the extrusion of the extrusion punch 12, with an advance height of h1 of 50-100mm, reaching multi-directional shear deformation zone II. The magnesium alloy billet 13 continues to be extruded downwards to a depth of h2 of 30-40mm. During the extrusion process, the channel gradually narrows, with angles δ1, δ2, δ3, and δ4, where the angle is 90°≤δ≤150°. Through the extrusion of the large concave die 17, the magnesium alloy billet 13 contacts the four highest points h of the four wedge-shaped structures of the large wedge-shaped block assembly 18. 5-1 h 5-2 h 5-3 h 5-4When the diameter is 15-30mm, the different heights of the four wedges result in different contact times, causing differential flow and varying degrees of deformation. Simultaneously, the wedges exhibit a downward-sloping surface at a certain angle in the longitudinal direction and a downward-sloping, curved slope in the transverse direction. The four angles on the side with the highest height of the four wedge blocks are ε1, ε2, ε3, and ε4, with an angle of 5°≤ε≤10°. The angles on the side with the lower height of the four wedge blocks are μ1, μ2, μ3, and μ4, with an angle of 0°≤μ≤5°. When the magnesium alloy billet 13 passes through these structures, it will undergo lateral and longitudinal flow and shear deformation. Since they are connected end to end, a vertical area will appear at the intersection of two wedge blocks. To avoid dead zones, the corners are rounded with a radius of 2-5mm. The billet will also undergo a certain degree of shear deformation at this point. In addition, since the height and slope angle of the four wedge blocks are different, the degree of deformation of the billet at each wedge block is also different. At the same time, the core of the billet flows towards the central quadrilateral hole, reducing the size of the billet and causing diameter reduction deformation. The plastic deformation and shear deformation of the magnesium alloy billet 13 refine the grain structure. During shear deformation, under the action of shear force, the grains tilt along the c-axis at the inclined surface of the large wedge-shaped block assembly 18, weakening the basal texture. Under the action of the extrusion punch 12, the magnesium alloy billet continues to flow downward, first passing through the straight channel die 19, a channel designed to facilitate the second deformation of the billet after the first deformation. This channel is a through hole with a certain height, h3, ranging from 15-30 mm. The angles of the four sides of the through hole are α1, α2, α3, and α4, with an angle of 90°≤α≤150°. The size of the through hole on the upper surface of this die is the same as the cross-sectional area of ​​the bottom through hole of the upper large concave die. The size of the cross-sectional area of ​​the through hole on the lower surface of the die can be freely adjusted according to actual needs, but it must be larger than the cross-sectional area of ​​the small concave die. Subsequently, the material enters the torsional extrusion deformation zone III. When the magnesium alloy billet 13 flows into the torsional extrusion deformation zone III, it undergoes torsional extrusion at different torsional angles through the die channel. The torsional angles are γ1, γ2, γ3, and γ4, with an angle of 90°≤γ≤150°. The torsional deformation causes the grain c-axis to deflect, thereby further weakening the basal texture and intensifying the deformation of the magnesium alloy. At the same time, the cross-sectional area of ​​the small concave die gradually decreases, generating differential shear deformation, which further refines the grain structure. After extruding the torsional extrusion deformation zone III, the material enters the small multi-directional shear deformation zone IV, with a deformation mode similar to that of the large multi-directional shear deformation zone II. Under the structural action of the small wedge block assembly 21, the billet has a structure in which the outermost heights of the four wedge blocks are h respectively. 6-1 h 6-2 h 6-3 h 6-4The height is 5-15mm. The outermost angles of the four wedges are λ1, λ2, λ3, and λ4, with an angle of 5°≤λ≤10°. The innermost angles of the four wedges are Φ1, Φ2, Φ3, and Φ4, with an angle of 0°≤Φ≤5°. The lengths of the four wedges are l. 2-1 l 2-2 l 2-3 l 2-4 The length is 60-80mm, and the widths of the four wedges are w respectively. 1-1 w 1-2 w 1-3 w 1-4 The width is 20-30mm. The magnesium alloy billet 13 is further refined in grain size, and deflection occurs at the inclined surface of the small wedge block assembly 21 along the c-axis. After being extruded from the small multi-directional shear deformation zone IV, it enters the discharge zone V and is finally extruded from the discharge port 5. Since the upper end of the through hole is the same size as the middle channel formed by the four small wedge block assemblies 21, and the lower end is the same size as the discharge port, the angles of the discharge channel are θ1, θ2, θ3, and θ4, with an angle of 90°≤θ≤150°. Its upper surface is in contact with the lower surface of the small concave mold. After the second deformation is completed, the billet through the discharge channel mold undergoes the last deformation and is then discharged. The four sides of the finished product after discharge are l 3-1 l 3-2 l 3-3 l 3-4 The length is 30-50mm. A high-performance magnesium alloy rod is obtained. This device can realize the preparation of fine-grained, weakly textured high-performance magnesium alloys through asymmetric multi-directional shear extrusion deformation.

[0062] Furthermore, the extrusion punch 12, large die 17, small die 20 and pad 24 are all made of 4Cr5MoSiV1 hot work die steel.

[0063] Furthermore, the surface roughness of the extrusion punch 12 is Ra0.08~0.16μm, the surface roughness of the large die 17 is Ra0.4~0.8μm, and the surface roughness of the small die 20 is Ra0.08~0.16. Due to the uneven distribution of roughness on each surface, the friction force generated between the extrusion process and the billet is different, which further promotes the differential flow of the billet and generates shear extrusion deformation to weaken its base surface texture.

[0064] In this specific embodiment, before preparing fine-grained, weakly textured magnesium alloys through asymmetric multi-directional shear extrusion deformation, the materials and chemical reagents required for the preparation process are carefully selected:

[0065] 1. Magnesium alloy billet: rectangular block billet, material selected is AZ31, containing 96% magnesium, 3% aluminum and 1% zinc;

[0066] 2. Sandpaper: Solid.

[0067] 3. Graphite oil solution: a viscous liquid;

[0068] 4. Anhydrous ethanol: Liquid, purity 99.5%;

[0069] 5. Acetone: Liquid, 99% purity.

[0070] A method for preparing fine-grained, weakly textured high-performance magnesium alloy rods by asymmetric multi-directional shear extrusion includes the following steps:

[0071] S1. Pretreatment of magnesium alloy billet:

[0072] S1-1. Use 600-grit sandpaper to polish the surface of the magnesium alloy billet to remove oil stains, and then use 800-grit, 1000-grit, and 1200-grit sandpaper in sequence until the surface of the magnesium alloy rod is smooth.

[0073] S1-2. Mix acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stir until homogeneous to prepare a cleaning solution.

[0074] S1-3. Immerse the magnesium alloy block blank prepared in step S1-1 into the cleaning solution prepared in step S1-2, place the cleaning tank on an ultrasonic cleaner and ultrasonically clean the magnesium alloy block blank for 60 minutes, then take out the magnesium alloy block blank and clean it with anhydrous ethanol, and finally dry it with a hair dryer.

[0075] S1-4. Coat the surface of the magnesium alloy block blank prepared in step S1-3 with graphite oil solution for later use.

[0076] S2. Preheating of magnesium alloy billet: Set the heating temperature of the vacuum atmosphere heating furnace to 450℃. After the furnace temperature reaches the set temperature, put the magnesium alloy billet into the heating furnace and keep it at that temperature for 3 hours.

[0077] S3. Lubrication, assembly, and preheating of the asymmetric multi-directional shear extrusion deformation forming device:

[0078] S3-1, Lubrication: Apply graphite oil solution to the surface of the large concave mold 17, the small concave mold 20, and the surface of the extrusion punch 12;

[0079] S3-2, Assembly:

[0080] First, install and fix the pad 24 on the middle working platform of the vertical extruder. Then, fix the die fixing frame 15 on the working table with small screws 23. Next, install the heating sleeve 16 on the inner surface of the die fixing frame. Then, from bottom to top, place the discharge channel mold 22, small die mold 20, large die mold 17, and straight channel mold 19 in the die fixing frame 15 and fix them with four long screws 4. Control the extrusion punch mold 12 to move down and be placed in the top cavity of the die mold cavity to ensure that the extrusion punch mold 12 and the die mold cavity are in close vertical contact.

[0081] S3-3. Preheating: Control the temperature of the heating jacket to 300~500℃, and keep it warm for 2~4 hours after reaching the set temperature, so that it can be used in the next step.

[0082] S4. Asymmetric multi-directional shear extrusion molding: The extrusion punch 12, the feeding channel 14, the large concave die 17, the straight channel 19, the small concave die 20, and the discharge channel 22 together form a torsional extrusion space; the torsional extrusion space includes five areas arranged from top to bottom: the extrusion pushing area I, the multi-directional shear deformation area II, the torsional extrusion deformation area III, the small multi-directional shear deformation area IV, and the discharge area V;

[0083] S4-1. Withdraw the extrusion punch 12 from the channel, allowing the magnesium alloy block billet to fill the extrusion pushing zone I. Then, push the extrusion punch 12 back into the channel; operate the vertical extrusion press.

[0084] In the extrusion pushing zone I, the magnesium alloy billet 13 advances continuously under the extrusion punch 12, with an advance height of h1 of 50-100mm, reaching the multi-directional shear deformation zone II. The magnesium alloy billet 13 continues to be extruded downward to a depth of h2 of 30-40mm. During the extrusion process, the channel gradually narrows, with angles δ1, δ2, δ3, and δ4, where the angle is 90°≤δ≤150°. It is then extruded through the large concave die 17, and the lengths of the four wedge blocks are l. 1-1 l 1-2 l 1-3 l 1-4 The length is 100-150mm, and the width of the four wedge-shaped blocks is w. 0-1 w 0-2 w 0-3 w 0-4 The width is 30-50mm. The magnesium alloy block blank 13 contacts the four highest points h of the four wedge-shaped structures of the large wedge-shaped block assembly 18, which are connected end to end. 5-1 h 5-2 h 5-3 h 5-4When the diameter is 15-30mm, the different heights of the four wedges result in different contact times, causing differential flow and varying degrees of deformation. Simultaneously, the wedges exhibit a downward-sloping surface at a certain angle in the longitudinal direction and a downward-sloping, curved slope in the transverse direction. The four angles on the side with the highest height of the four wedge blocks are ε1, ε2, ε3, and ε4, with an angle of 5°≤ε≤10°. The angles on the side with the lower height of the four wedge blocks are μ1, μ2, μ3, and μ4, with an angle of 0°≤μ≤5°. When the magnesium alloy billet 13 passes through these structures, it will undergo lateral and longitudinal flow and shear deformation. Since they are connected end to end, a vertical area will appear at the intersection of two wedge blocks. To avoid dead zones, the corners are rounded with a radius of 2-5mm. The billet will also undergo a certain degree of shear deformation at this point. In addition, since the height and slope angle of the four wedge blocks are different, the degree of deformation of the billet at each wedge block is also different. At the same time, the core of the billet flows towards the central quadrilateral hole, reducing the size of the billet and causing diameter reduction deformation. The plastic deformation and shear deformation of the magnesium alloy billet 13 refine the grain structure. During shear deformation, under the action of shear force, the grains tilt towards the wedge-shaped slope surface, weakening the basal texture. Under the action of the extrusion punch 12, the magnesium alloy billet continues to flow downward, first passing through the straight channel die 19, which is a channel for the billet to undergo a second deformation after the first deformation. This channel has a certain height of h3, with a height of 15-30mm, and the angles of the through holes are α1, α2, α3, and α4, with an angle of 90°≤α≤150°. The size of the through hole on the upper surface of this die is the same as the cross-sectional area of ​​the bottom through hole of the upper large concave die. The size of the cross-sectional area of ​​the through hole on the lower surface of the die can be freely adjusted according to actual needs, but it must be larger than the area of ​​the small concave die forming device. Subsequently, the magnesium alloy billet 13 enters the torsional extrusion deformation zone III. When the billet flows into zone III, it undergoes torsional extrusion at different torsional angles through the die channel. These angles are γ1, γ2, γ3, and γ4, with a range of 90° ≤ γ ≤ 150°. The torsional deformation causes the c-axis of the grains to deflect again in the torsional direction, further weakening the basal texture and intensifying the deformation of the magnesium alloy. Simultaneously, the cross-sectional area of ​​the torsional extrusion channel gradually decreases, generating differential shear deformation, which further refines the grain structure. After extruding from zone III, the billet enters the small multi-directional shear deformation zone IV, with a deformation mode similar to that of zone II. Under the structural action of the small wedge block assembly, the billet's structure consists of four wedge blocks with outermost heights h... 6-1 h 6-2 h 6-3 h 6-4The height is 5-15mm. The outermost angles of the four wedges are λ1, λ2, λ3, and λ4, with an angle of 5°≤λ≤10°. The innermost angles of the four wedges are Φ1, Φ2, Φ3, and Φ4, with an angle of 0°≤Φ≤5°. The lengths of the four wedges are l. 2-1 l 2-2 l 2-3 l 2-4 The length is 60-80mm, and the widths of the four wedges are w respectively. 1-1 w 1-2 w 1-3 w 1-4 The width is 20-30mm. The grains of the magnesium alloy billet are further refined, and the c-axis deflects at the inclined surface of the small wedge block assembly 21. After extruding the small multi-directional shear deformation zone IV, it enters the discharge zone V and is finally extruded through the discharge port 5. Since the upper end of the through hole is the same size as the middle channel formed by the four small wedge block assemblies 21, and the lower end is the same size as the discharge port, the angles of the discharge channel are θ1, θ2, θ3, and θ4, with an angle of 90°≤θ≤150°. Its upper surface is in contact with the lower surface of the small concave die. The billet deforms towards different angles of the channel. After the second deformation, the billet through the discharge channel die undergoes a final deformation and is then discharged. The four sides of the finished product after discharge are l 3-1 l 3-2 l 3-3 l 3-4 The length is 30-50mm. A high-performance magnesium alloy rod is obtained. During the torsion extrusion molding process, the heating wire temperature is controlled at 300~500℃.

[0085] S4-2. Take out the magnesium alloy rod obtained in step S4-1, polish its surface with sandpaper, clean the magnesium alloy rod with the cleaning solution prepared in step S1-2, clean it a second time with anhydrous ethanol, and dry it with a hair dryer to obtain a fine-grained weak-textured magnesium alloy rod that can be used directly.

[0086] A specific embodiment of the apparatus and process for preparing fine-grained, weakly textured magnesium alloy rods by asymmetric multi-directional shear extrusion comprises the following steps:

[0087] (1) Install the upper torsional extrusion die and the outer die frame on the vertical extruder. The connection relationship of each part must be correct, and the operation should be carried out in sequence.

[0088] (2) Polish the outer surface of the AZ31 magnesium alloy block blank with 600 grit sandpaper to remove oil stains, and then polish it with 1000, 1200 and 2500 grit sandpaper in sequence to ensure that the surface is clean and smooth; place the polished magnesium alloy block blank in a mixture of acetone and anhydrous ethanol with a volume ratio of 3:2 for ultrasonic cleaning for 30 minutes, then clean it with alcohol and dry it with a hair dryer;

[0089] (3) Turn on the vacuum atmosphere heating furnace to preheat the magnesium alloy billet. The preset temperature is 400℃. When the preset temperature is reached, continue to keep the magnesium alloy billet in the heating furnace for 3 hours.

[0090] (4) Turn on the extrusion mold cavity heating device (heating jacket) to heat the extrusion mold cavity I, II, III, IV and V areas. The heating temperature is preset to 400℃. After reaching the preset temperature, continue to keep it warm for 3 hours.

[0091] (5) Remove the extrusion punch 12 from the extrusion channel, apply high-temperature graphite oil solution to the surface of the magnesium alloy block blank 13 for lubrication, so that the magnesium alloy block blank 13 fills the extrusion pushing area I, and then push the extrusion punch 12 into the extrusion channel.

[0092] (6) In this invention, the extrusion punch 12 and the large and small dies are all made of 4Cr5MoSiV1 hot work die steel. The surface roughness of the extrusion punch 12 is Ra0.08~0.16μm, the surface roughness of the large die 17 is Ra0.4~0.8μm, and the surface roughness of the small die 20 is Ra0.16~0.4μm.

[0093] (7) Turn on the motor of the vertical extruder, set the pressure to 400MPa, and turn on the motor at the same time. The vertical extruder pushes the extrusion punch 9 downward, and its traveling speed is V1=70mm / min; in the extrusion pushing zone I, the magnesium alloy block billet 13 is continuously advanced under the extrusion of the extrusion punch 12, and the advancing height is h1=50mm. When it reaches the multi-directional shear deformation zone II, the magnesium alloy block billet 13 continues to be extruded to a depth of h2=30mm. During the extrusion process, the channel gradually narrows, and the angles are δ1, δ2, δ3, and δ4, all of which are 120°. It is extruded by the large concave die 17, and the lengths of the four wedge blocks are l 1-1 l 1-2 l 1-3 l 1-4 The length is 150mm, and the width of the four wedge-shaped blocks is w. 0-1 w 0-2 w 0-3 w 0-4 The 30mm wide magnesium alloy block blank 13 contacts the four highest points h of the four wedge-shaped structures of the large wedge-shaped block assembly 18, which are connected end to end.5-1 h 5-2 h 5-3 h 5-4 The diameters of the four wedges are 15, 18, 21, and 24 mm respectively. Due to the inconsistent heights of the four wedges, the contact times differ, resulting in differential flow and varying degrees of deformation. Furthermore, the longitudinal direction of each wedge is a downward-sloping surface at a certain angle, while the transverse direction is a downward-sloping surface with a certain curvature. The four wedges on the side with the highest height have four angles: ε1, ε2, ε3, and ε4, with angles of 5°, 6°, 7°, and 8° respectively. The four wedges on the side with the lowest height have angles: μ1, μ2, μ3, and μ4, with angles of 1°, 2°, 3°, and 4° respectively. When the magnesium alloy billet 13 passes through these structures, it will experience lateral and longitudinal flow and shear deformation. Since the wedges are connected end to end, a vertical area will appear at the intersection of two wedges. To avoid dead zones, the corners are rounded with a radius of 3mm. The billet will also experience some shear deformation at this point. In addition, since the height and slope angle of the four wedges are different, the degree of deformation of the billet at each wedge is also different. At the same time, the core of the billet flows towards the central quadrilateral hole, reducing the size of the billet and causing diameter reduction deformation. The plastic deformation and shear deformation of the magnesium alloy billet 13 refine the grain structure. During shear deformation, under the action of shear force, the grains tilt towards the surface of the wedge-shaped block slope, weakening the basal texture. Under the action of the extrusion punch 12, the magnesium alloy billet continues to flow downwards, first passing through the straight channel die 19, which is a channel for the billet to undergo a second deformation after the first deformation. This channel has a certain height of h3, a height of 20mm, and through holes with angles of α1, α2, α3, and α4, all at 90°. The size of the through hole on the upper surface of this die is the same as the cross-sectional area of ​​the bottom through hole of the upper large concave die. The size of the cross-sectional area of ​​the through hole on the lower surface of the die can be freely adjusted according to actual needs, but it must be larger than the area of ​​the small concave die. Subsequently, it enters the torsional extrusion deformation zone III. When the magnesium alloy billet 13 flows into the torsional extrusion deformation zone III, it undergoes torsional extrusion at different torsional angles through the die channel. The torsional angles are γ1, γ2, γ3, and γ4, all at 135°. Torsional deformation causes the c-axis of the grains to deflect again in the torsional direction, further weakening the basal texture and intensifying the deformation of the magnesium alloy. Simultaneously, the cross-sectional area of ​​the small die gradually decreases, resulting in differential shear deformation, which further refines the grain structure. After extrusion torsional extrusion deformation zone III, the material enters small multi-directional shear deformation zone IV, with a deformation mode similar to that of multi-directional shear deformation zone II. Under the structural action of the small wedge block assembly, the billet's structure consists of four wedge blocks with outermost heights h... 6-1 h 6-2 h 6-3 h 6-4The heights are 5, 8, 11, and 13 mm. The outermost angles of the four wedges are λ1, λ2, λ3, and λ4, with angles of 5°, 6°, 7°, and 8°. The innermost angles of the four wedges are Φ1, Φ2, Φ3, and Φ4, with angles of 1°, 2°, 3°, and 4°. The lengths of the four wedges are l. 2-1 l 2-2 l 2-3 l 2-4 The length is 60mm, and the widths of the four wedges are w respectively. 1-1 w 1-2 w 1-3 w 1-4 The width is 20mm. The grains of the magnesium alloy billet are further refined, and the c-axis deflects at the inclined surface of the small wedge block assembly 21. After being extruded from the small multi-directional shear deformation zone IV, it enters the discharge zone V and is finally extruded from the discharge port 5. Since the upper end of the through hole is the same size as the middle channel formed by the four small wedge block assemblies 21, and the lower end is the same size as the discharge port, the angles of the discharge channel are θ1, θ2, θ3, and θ4, with an angle of 90°. Its upper surface is in contact with the lower surface of the small concave die. The billet deforms towards different angles of the channel. After the second deformation, the billet through the discharge channel die undergoes a final deformation and is then discharged. The four sides of the finished product after discharge are l 3-1 l 3-2 l 3-3 l 3-4 Each rod is 35mm in length. A high-performance magnesium alloy rod was obtained.

[0094] (8) Take out the magnesium alloy rod material, polish its surface with sandpaper, then place it in a mixture of acetone and anhydrous ethanol in a volume ratio of 3:2 for ultrasonic cleaning, and finally clean it with alcohol and dry it with a hair dryer in cold air.

[0095] Conclusion: The apparatus and process for preparing fine-grained, weakly textured magnesium alloy bars by asymmetric multi-directional shear extrusion according to the present invention significantly reduces the average grain size of the magnesium alloy billet compared to conventional magnesium alloys. At the same time, the combination of large and small wedge blocks allows for different degrees of deformation of the billet. Its special structure allows a single deformation to include shearing, differential speed, and torsion, which can effectively weaken the basal texture compared to the initial magnesium alloy billet, and effectively improve the mechanical properties of the magnesium alloy.

[0096] Materials and chemical reagents used: AZ31 magnesium alloy block blank, with length L=160mm, width W=160mm, and height H=100mm; sandpaper: SiC, 600 mesh, 2 sheets; 1000 mesh, 2 sheets; 1200 mesh, 2 sheets; 2500 mesh, 2 sheets; high-temperature graphite oil solution: C, 500g; anhydrous ethanol: CH3CH2OH, 1200ml; acetone: C3H6O, 800ml.

[0097] The principle of obtaining fine-grained, weakly textured magnesium alloy rods through the above steps is described in detail below with reference to the accompanying drawings:

[0098] 1) Dimensional parameters of the large and small wedge block assembly: The height of one side of the four wedge-shaped plates of the large wedge block assembly is h. 5-1 h 5-2 h 5-3 h 5-4 The height is 15-30mm, and the lengths of the four wedges are l respectively. 1-1 l 1-2 l 1-3 l 1-4 The length is 100-150mm, and the width of the four wedge-shaped blocks is w. 0-1 w 0-2 w 0-3 w 0-4 The wedges are 30-50mm wide, and due to the different heights at both ends, their angles also differ. The four angles on the side with the highest wedge are ε1, ε2, ε3, and ε4, with an angle range of 5° ≤ ε ≤ 10°. The angles on the side with the lower height are μ1, μ2, μ3, and μ4, with an angle range of 0° ≤ μ ≤ 5°. The upper surface of the wedges exhibits a curved slope, and all edges of the forming device are rounded with a radius of 2-5mm to prevent dead zones during forming. The outermost heights of the four wedges in the small wedge block assembly are h... 6-1 h 6-2 h 6-3 h 6-4 The height is 5-15mm. The outermost angles of the four wedges are λ1, λ2, λ3, and λ4, with an angle of 5°≤λ≤10°. The innermost angles of the four wedges are Φ1, Φ2, Φ3, and Φ4, with an angle of 0°≤Φ≤5°. The lengths of the four wedges are l. 2-1 l 2-2 l 2-3 l 2-4 The length is 60-80mm, and the widths of the four wedges are w respectively. 1-1 w 1-2 w 1-3 w 1-4The structure, with a width of 20-30mm, features four wedges of varying sizes. This causes the billet to deform at different speeds, resulting in a differential flow. Furthermore, the parameters and degrees of deformation vary. The discharge channel is formed by connecting the four wedges end-to-end, causing the channel cross-sectional area to gradually decrease. Additionally, the different surface roughness of the die cavity leads to varying friction between the punch and die surfaces at the contact point. These two factors cause uneven flow velocity of the magnesium alloy billet near these surfaces during deformation, resulting in differential shearing and torsional deformation. This causes the c-axis of the magnesium alloy billet grains to deflect at the inclined surface of the wedges, weakening the basal texture of the magnesium alloy billet and refining the grains.

[0099] 2) Torsional extrusion deformation zone within the small die: The torsion angles on each side are γ1, γ2, γ3, and γ4, with an angle of 90°≤γ≤150°. The varying torsion angles cause the c-axis of the grains to deflect again in the torsion direction, further weakening the basal texture and intensifying the deformation of the magnesium alloy. Simultaneously, the cross-sectional area of ​​the torsion extrusion channel gradually decreases, generating differential shear deformation, further refining the grain structure to obtain a fine-grained, weak-texture, high-performance magnesium alloy.

[0100] By utilizing the above two principles, the magnesium alloy billet is subjected to a large amount of shearing, torsion, extrusion deformation to obtain high-performance magnesium alloy rods with weak basal texture.

[0101] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An apparatus for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion, characterized in that, The components include a vertical extruder, a feed channel die (14), a large die (17), a straight channel die (19), a small die (20), a discharge channel die (22), an external die frame, and a power unit, wherein: The vertical extruder includes a base (3), a top seat (7), and a column (6) fixed between the base (3) and the top seat (7); a power unit is installed at the center of the top seat (7), an extrusion telescopic head (9) is installed at the bottom of the power unit, a pressure block (10) is fixed at the end of the extrusion telescopic head (9), an extrusion punch (12) is fixed at the bottom of the pressure block (10), and the lower end of the extrusion punch (12) is flat; a lifting handle (11) for controlling the movement of the extrusion telescopic head (9) is installed on the column (6), a pad (24) is fixed at the center of the base (3), and a discharge port (5) that runs vertically through the pad (24) and the base (3) is provided. The inner cavity of the feed channel mold (14) is provided with an extrusion channel. The inner cavity of the large concave mold (17) below the feed channel mold (14) is provided with a diameter reduction channel that communicates with the extrusion channel. The bottom of the inner cavity of the large concave mold (17) is provided with a large wedge block assembly (18). The large wedge block assembly (18) is formed by stacking four wedge-shaped long plates one end to the other. The upper surface of the wedges is curved and sloped towards the center of the assembly. The corners of the large wedge block assembly (18) are rounded. The middle part of the large wedge block assembly (18) has a quadrilateral through hole. The four wedge-shaped long plates have different heights. The straight channel mold (19) is located below the large concave mold (17). The inner cavity of the straight channel mold (19) is a through hole with a certain height. The size of the through hole on the upper surface of the straight channel mold (19) is the same as the cross-sectional area of ​​the quadrilateral through hole of the large wedge block assembly (18) above. The cross-sectional area of ​​the through hole on the lower surface of the straight channel mold (19) is larger than the cross-sectional area of ​​the cavity of the small concave mold (20) located below it. The position of the small concave mold (20) is offset from that of the large concave mold (17) by a certain angle not greater than 90°; the small concave mold (20) is composed of two parts, the upper part is composed of a twisted diameter reduction channel, which is connected to the cavity of the straight channel mold (19); the lower part of the small concave mold (20) is provided with a small wedge block assembly (21) with a structure similar to that of the large wedge block assembly (18). The inner cavity of the discharge channel mold (22) is a straight channel that communicates with the cavity of the small concave mold (20), and the straight channel communicates with the discharge port (5); The external mold frame includes a die fixing frame (15) installed on the pad (24), and a heating sleeve (16) is provided on the inner wall of the die fixing frame (15). The feed channel mold (14), the large die mold (17), the straight channel mold (19), the small die mold (20), and the discharge channel mold (22) are stacked sequentially from top to bottom on the pad (24) inside the die fixing frame (15). The extrusion channel of the feed channel mold (14) has four sides with inclination angles of β1, β2, β3, and β4, respectively, with an inclination angle range of 90°≤β≤150°. The channel length is h1, the height is 50-100mm, and the lengths of the four sides are l1, β2, β3, and β4, respectively. 0-1 l 0-2 l 0-3 l 0-4 The length is 100-200mm, the channel width is w2, and the width is 100-200mm; the diameter reduction channel height h2 of the large concave mold (17) is 30-40mm, and the four sides of the channel have inclination angles of δ1, δ2, δ3, and δ4, respectively, with an angle of 90°≤δ≤150°.

2. The apparatus for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion as described in claim 1, characterized in that, The large wedge block assembly (18) has four wedge-shaped plates with a height of h on one side. 5-1 h 5-2 h 5-3 h 5-4 The height is 15-30mm, and the lengths of the four wedges are l respectively. 1-1 l 1-2 l 1-3 l 1-4 The length is 100-150mm, and the width of the four wedge-shaped blocks is w. 0-1 w 0-2 w 0-3 w 0-4 The width is 30-50mm, and the angles on both sides are different due to the different heights at both ends of the wedge plate. The four angles on the side with the highest height of the four wedge blocks are ε1, ε2, ε3, and ε4, with an angle of 5°≤ε≤10°. The angles on the side with the lower height of the four wedge blocks are μ1, μ2, μ3, and μ4, with an angle of 0°≤μ≤5°. The upper surface of the wedge has an arc-shaped slope, and the corners of the assembly are all rounded with a radius of 2-5mm.

3. The apparatus for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion as described in claim 2, characterized in that, The height of the through hole in the straight channel mold (19) is h3, which is 15-30mm. The angles of the four sides of the through hole are α1, α2, α3, and α4, which are 90°≤α≤150°.

4. The apparatus for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion as described in claim 3, characterized in that, The position of the small concave mold (20) is deflected relative to the large concave mold (17) by a certain angle not exceeding 90°; the outermost heights of the four wedge blocks of the small wedge block assembly (21) are h respectively. 6-1 h 6-2 h 6-3 h 6-4 The height is 5-15mm. The outermost angles of the four wedges are λ1, λ2, λ3, and λ4, with an angle of 5°≤λ≤10°. The innermost angles of the four wedges are Φ1, Φ2, Φ3, and Φ4, with an angle of 0°≤Φ≤5°. The lengths of the four wedges are l. 2-1 l 2-2 l 2-3 l 2-4 The length is 60-80mm, and the widths of the four wedges are w respectively. 1-1 w 1-2 w 1-3 w 1-4 The width is 20-30mm; the height of the torsion channel is h4; the torsion angles of the four sides of the torsion channel are γ1, γ2, γ3, and γ4, and the angles are 90°≤γ≤150° and are all different.

5. The apparatus for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion as described in claim 4, characterized in that, The discharge channel of the discharge channel mold (22) has angles of θ1, θ2, θ3, and θ4, respectively, with an angle of 90°≤θ≤150°. The four side lengths of the finished product after discharge are l 3-1 l 3-2 l 3-3 l 3-4 The length is 30-50mm.

6. The apparatus for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion as described in any one of claims 1-5, characterized in that, The extrusion punch (12), large die (17), small die (20) and pad (24) are all made of 4Cr5MoSiV1 hot work die steel.

7. The apparatus for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion as described in any one of claims 1-5, characterized in that, The surface roughness of the extrusion punch (12) is Ra0.08~0.16μm, the surface roughness of the large die (17) is Ra0.4~0.8μm, the surface roughness of the small die (20) is Ra0.08~0.16μm, and the power device is a pressure motor (8) that drives the extrusion die.

8. A method for preparing fine-grained magnesium alloy rods by asymmetric multi-directional shear extrusion, characterized in that, Includes the following steps: S1. Pretreatment of magnesium alloy billet: S1-1. Use 600-grit sandpaper to polish the surface of the magnesium alloy block blank (13) to remove oil stains, and then use 800-grit, 1000-grit, and 1200-grit sandpaper in sequence until the surface of the magnesium alloy block blank (13) is smooth. S1-2. Mix acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stir until homogeneous to prepare a cleaning solution. S1-3. Immerse the magnesium alloy block blank (13) prepared in step S1-1 into the cleaning solution prepared in step S1-2, place the cleaning tank on an ultrasonic cleaner and ultrasonically clean the magnesium alloy block blank (13) for 60 minutes, then take out the magnesium alloy block blank (13) and clean it with anhydrous ethanol, and finally dry it with a hair dryer. S1-4. Coat the surface of the magnesium alloy block blank (13) prepared in step S1-3 with graphite oil solution and save it for later use. S2. Preheating of magnesium alloy billet: Set the heating temperature of the vacuum atmosphere heating furnace to 450℃. After the furnace temperature reaches the set temperature, put the magnesium alloy billet (13) into the heating furnace and keep it warm for 3 hours. S3. Lubrication, assembly, and preheating of the asymmetric multi-directional shear extrusion deformation forming device: S3-1, Lubrication: Apply graphite oil solution to the surface of the large concave mold (17), the small concave mold (20), and the surface of the extrusion punch (12); S3-2, Assembly: First, install and fix the pad (24) on the base (3) of the vertical extruder, then fix the die fixing frame (15) on the base (3), then install the heating jacket (16) on the inner surface of the die fixing frame (15), and then place the discharge channel mold (22), small die mold (20), straight channel mold (19), large die mold (17), and feed channel mold (14) in the die fixing frame (15) from bottom to top. Use four long screws (4) to install and fix them, control the extrusion punch mold (12) to go down and place it in the top cavity of the feed channel mold (14) to ensure that the mold cavities of the extrusion punch mold (12) and the feed channel mold (14) are in close vertical contact. S3-3, Preheating: Control the temperature of the heating jacket (16) to 300~500℃, and keep it warm for 2~4 hours after reaching the set temperature, so that it can be used in the next step; S4. Asymmetric multi-directional shear extrusion molding: The extrusion punch (12), the feeding channel die (14), the large concave die (17), the straight channel die (19), the small concave die (20), and the discharge channel die (22) together form a torsional extrusion space; the torsional extrusion space includes five areas arranged from top to bottom: the extrusion pushing area I, the multi-directional shear deformation area II, the torsional extrusion deformation area III, the small multi-directional shear deformation area IV, and the discharge area V; S4-1. Remove the extrusion punch (12) from the extrusion pushing zone I, so that the magnesium alloy block blank (13) fills the extrusion pushing zone I, and then push the extrusion punch (12) into the extrusion pushing zone I. Operating the vertical extruder, the magnesium alloy billet (13) in the extrusion pushing zone I is continuously advanced under the extrusion punch (12) and reaches the multi-directional shear deformation zone II. The magnesium alloy billet (13) continues to be extruded downwards. During the extrusion process, the channel gradually narrows. When the magnesium alloy billet (13) is extruded by the large concave die (17), it will undergo lateral and longitudinal flow and shear deformation when it comes into contact with the large wedge block assembly (18). A certain amount of shear deformation also occurs at the rounded corner where the two wedge blocks intersect. Since the height and slope angle of the four wedges are different, the degree of deformation of the magnesium alloy billet (13) at each wedge is also different. At the same time, the core of the magnesium alloy billet (13) flows towards the central quadrilateral hole, reducing the size of the magnesium alloy billet (13) and causing diameter reduction deformation. The plastic deformation and shear deformation generated by the magnesium alloy billet (13) refine the grain structure. During the shear deformation process, under the action of shear force, the c-axis of the grains tilts towards the slope surface of the wedge, weakening the basal texture. In the extrusion punch (12) Under the action of the die, the magnesium alloy billet (13) continues to flow downward, first through the straight channel die (19), and then into the torsional extrusion deformation zone III. When the magnesium alloy billet (13) flows into the torsional extrusion deformation zone III, it is subjected to torsional extrusion at different torsional angles through the die channel. The torsional deformation causes the c-axis of the grains to deflect again in the torsional direction, thereby further weakening the basal texture and intensifying the deformation of the magnesium alloy. At the same time, the cross-sectional area of ​​the torsional extrusion deformation zone III gradually decreases, generating differential shear deformation, and the grain structure will be further refined. Then it enters the small multi-directional shear deformation zone IV; under the structural action of the small wedge block assembly (21), the magnesium alloy billet (13) is refined again, and the c-axis deflects at the inclined surface of the small wedge block assembly (21); after being extruded from the small multi-directional shear deformation zone IV, it enters the discharge zone V and is finally extruded from the discharge port (5). The magnesium alloy billet (13) passing through the discharge channel mold (22) undergoes the last deformation and is then discharged to obtain a high-performance magnesium alloy rod; during the torsion extrusion molding process, the temperature of the heating jacket (16) is controlled at 300~500℃; S4-2. Take out the magnesium alloy rod obtained in step S4-1, polish its surface with sandpaper, clean the magnesium alloy rod with the cleaning solution prepared in step S1-2, clean it a second time with anhydrous ethanol, and dry it with a hair dryer to obtain a fine-grained weak-textured magnesium alloy rod that can be used directly.

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