Processing method of TC4 particle reinforced low-rare-earth magnesium-based composite board

Abstract

The invention discloses a processing method of a TC4 particle reinforced low-rare-earth magnesium-based composite board, which comprises the following steps: selecting TC4 particles as a reinforcement body, combining a stirring casting process and an asymmetric extrusion processing process, and based on the principles of temperature asymmetry, strain asymmetry and the like, introducing shear stress, constructing an asymmetric stress state in a deformation process, promoting the TC4 particles to flow in multiple directions, and forming the low-rare-earth magnesium-based composite board. The particle dispersion uniformity is improved, crystal grains are further refined, meanwhile, tilting of the crystal grains is promoted, and the basal texture is weakened; and meanwhile, according to the material design, high-plasticity magnesium alloy with low rare earth content is adopted as a matrix, and the low-rare earth magnesium-based composite material plate with the strength remarkably improved and the plasticity maintained is finally prepared through the action of activating a non-basal slip system by rare earth elements.

Description

Technical Field

[0001] The present invention belongs to the technical field of deformation processing of magnesium-based composite materials, and specifically relates to an asymmetric extrusion processing method and product of a TC4 particle reinforced low-rare earth magnesium-based composite material plate. Background Art

[0002] Magnesium alloys have advantages such as low density and high specific strength, making them widely used in fields such as automobiles, aerospace, and electronic equipment. However, their low absolute strength and poor processing properties hinder their further application. The performance of magnesium alloys can be improved by adding reinforcements to the magnesium matrix to prepare magnesium-based composites. Magnesium-based composites utilize the high hardness, high melting point, and high corrosion resistance of the reinforcements (discontinuous components) to synergize with the matrix (continuous components), thereby further improving the strength, heat resistance, and corrosion resistance of the magnesium alloy on the basis of its original excellent properties. The above-mentioned excellent properties make magnesium-based composites have a huge application market and research value, and have broad application prospects in industries such as aerospace, automobile industry, and portable equipment.

[0003] The matrix of magnesium-based composite materials can be pure magnesium or magnesium alloys. When the matrix of the composite material is pure magnesium, the structure of the composite material prepared with the reinforcement is relatively simple, which facilitates the study of the reinforcement mechanism, but the material performance is greatly limited. When the matrix of the composite material is a cast magnesium alloy, taking the most widely used AZ series magnesium alloy as an example, the alloy has high specific strength, good corrosion resistance, and good castability, but the strength is not high enough and the plasticity is slightly reduced, which limits the wide application of this magnesium-based composite material. However, after adding a specific content of rare earth elements, the strength, plasticity, and corrosion resistance of the magnesium alloy are improved, which can expand the application field. Ceramic particles have high strength, hardness, and melting point, which can improve the strength of composite materials, but will lead to a decrease in the plasticity of magnesium-based composite materials. This is because ceramic particles have poor wettability with the matrix and low bonding strength at the interface. When the ceramic material is loaded, the accumulated stress is difficult to release, resulting in cracks and reduced plasticity. Titanium and its alloy particles, compared to other reinforcements, have high strength, hardness, elastic modulus, and good plasticity. They have good wettability with molten magnesium, which improves the interface bonding ability. The load transfer process can better release stress through their own plastic deformation, thereby improving the comprehensive mechanical properties of rare earth magnesium alloys. However, the traditional symmetrical extrusion of composite materials easily causes the reinforcement to be streamlined along the extrusion direction, which limits the performance improvement of the composite material. At the same time, traditional symmetrical deformed magnesium-based composite materials generally have the characteristics of strong texture, which makes magnesium-based composite products have poor room temperature formability and difficult processing and forming. This has also become a major obstacle to the industrial application of deformed magnesium-based composite materials.

[0004] Therefore, how to synergistically improve the mechanical properties of magnesium-based composites through innovations in raw material components and processes is a problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a processing method for TC4 particle reinforced low rare earth magnesium-based composite plates, to solve the above-mentioned defects of existing magnesium-based composite materials, and to provide new products with lightweight, high specific strength and cost control.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for processing a TC4 particle reinforced low-rare-earth magnesium-based composite plate comprises the following steps:

[0008] S1. Mixing the following ingredients by mass percentage: 2-10 wt.% of TC4 spherical powder and the balance of Mg-Gd-Zr alloy ingot; stirring and casting the TC4 titanium alloy powder particles and the Mg-Gd-Zr alloy ingot under a protective gas to obtain a composite material ingot;

[0009] S2, placing the composite material ingot in step S1 in a heat treatment furnace for homogenization treatment at a temperature of 400-500° C. for 20-24 hours;

[0010] S3. Polish the homogenized composite ingot obtained in step S2 to remove the oxide layer on the surface of the ingot, place the composite ingot and the asymmetric extrusion mold in a furnace for preheating for 1-2 hours, and then perform asymmetric extrusion at 400-430° C. with an extrusion rate of 1.5-3 m / min and an extrusion ratio of 25-51:1, and then air-cool to room temperature.

[0011] Furthermore, in step S1, the mass percentages of the components in the Mg-Gd-Zr alloy ingot are: 1.8-2.2 wt.% Gd, 0.3-0.7% Zr, and the balance being Mg and unavoidable impurities.

[0012] Furthermore, in step S1, the stirring casting under protective gas is specifically as follows: under protective gas CO2-SF6 with a ratio of 99:1, semi-solid stirring for 6 minutes, ultrasonic treatment for 10 minutes, and rapid and uniform water cooling to room temperature.

[0013] Furthermore, in step S2, the homogenization treatment is specifically as follows: placing the composite material in a crucible, adding graphite to the crucible to cover and isolate the air, then placing it in a heat treatment furnace, heating it to 450-500°C at a heating rate of 10-20°C / min, keeping it warm for 20-24 hours, and water quenching the sample after homogenization treatment.

[0014] Furthermore, in step S3, the asymmetric extrusion die is a triangular lateral gradient die, and the triangle is an isosceles triangle with three internal angles of 50°, 50° and 80°, that is, the triangular asymmetric design of the mold cavity is that the hypotenuse is 50° to the transverse direction, and a transverse shear force is introduced to obtain an asymmetric stress-strain field, thereby breaking the streamlined segregation of TC4 particles and achieving a dispersed distribution of particles.

[0015] Furthermore, in step S1, titanium alloy particles are added to the magnesium melt in a manner of being wrapped with aluminum foil. The specific method is to pre-spread a certain amount of titanium alloy particles evenly between multiple layers of ultra-thin aluminum foil to form a "sandwich"-like laminated structure, and then the laminated structure is tightly wound into a compact block preform to ensure that the aluminum foil completely wraps and seals the internal titanium alloy particle layer; the preform must be kept intact before being added to the magnesium melt, and its function is to use the aluminum foil to isolate the air and inhibit the pre-oxidation of the titanium alloy particles at high temperatures.

[0016] Furthermore, in step S1, the cooling is water quenching. Compared to slow cooling methods such as air cooling and furnace cooling, water quenching achieves an extremely high cooling rate. This rapid solidification process can effectively inhibit the excessive growth of matrix grains, while greatly limiting the sinking of reinforcement particles and possible adverse interfacial reactions with the matrix, thereby obtaining a cast composite material with a dense microstructure.

[0017] Furthermore, the particle size of the TC4 powder particles is 15-53 μm.

[0018] Furthermore, the processing method of the present invention comprises the following specific steps:

[0019] S1. Put the polished Mg-Gd-Zr alloy (components: 1.8-2.2wt.% Gd, 0.3-0.7% Zr, balance Mg, total rare earth content of 1-3wt.%) into a crucible, place the crucible in a resistance furnace and heat it to completely melt the alloy, and introduce protective gas throughout the process; then weigh TC4 titanium alloy powder particles and place them in a drying oven for preheating, and the titanium alloy particles are added to the magnesium melt in the form of aluminum foil wrapping. The specific method is to pre-spread a certain amount of titanium alloy particles evenly between multiple layers of ultra-thin aluminum foil to form a "sandwich"-shaped laminated structure, and then tightly wind the laminated structure into a compact block preform to ensure that the aluminum foil completely wraps and seals the internal titanium alloy particle layer; the preform must be kept intact before the magnesium melt is added, and its function is to use the aluminum foil to isolate the air and inhibit the pre-oxidation of the titanium alloy particles at high temperatures. When the Mg-Gd-Zr alloy melt is cooled to a semi-solid temperature, TC4 particles are added and stirred. After stirring, ultrasonic treatment is performed, and then the sample is quickly taken out and uniformly water-cooled to room temperature to obtain a composite material ingot;

[0020] S2. Place the composite material ingot in a heat treatment furnace for homogenization treatment, heat it to 450-500° C. at a heating rate of 10-20° C. / min, keep it at that temperature for 20-24 hours, and water quench the sample after homogenization treatment.

[0021] S3. A transverse gradient asymmetric extrusion die is used to perform asymmetric extrusion deformation on the composite material. The triangular asymmetric design of the die cavity shows that the hypotenuse is 50° to the transverse direction. The transverse shear force is introduced to obtain an asymmetric stress-strain field, thereby breaking the streamlined segregation of TC4 particles and obtaining a deformed magnesium-based composite extruded sheet with dispersed particles.

[0022] In summary, the asymmetric extruded low-rare earth magnesium-based composite material sheet prepared by the above method has a yield strength of 110MPa-260MPa, a tensile strength of 180MPa-270MPa, and a plasticity of 7%-40%. It is mainly used in fields with strict requirements on lightweight, specific strength and cost control. Specific application scenarios include non-main load-bearing structural parts in the aerospace field (such as brackets, shells, internal frames), high-end equipment and vehicles (such as battery pack shells, steering knuckles, wheels of new energy vehicles, and lightweight components of high-speed trains and drones), lightweight and high-strength casings and heat dissipation components of electronic products, and equipment components in the military field that need to take into account both concealment (low radar cross-section) and impact resistance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention uses TC4 particles as reinforcement, combines the stirring casting process with the asymmetric extrusion processing technology, and introduces shear stress based on the principles of temperature asymmetry and strain asymmetry to establish an asymmetric stress state during the deformation process, promote multi-directional flow of TC4 particles, improve the uniformity of particle dispersion, further refine the grains, promote grain tilting, and weaken the basal texture; at the same time, the material design uses a high-plasticity magnesium alloy with a low rare earth content as the matrix, and activates the non-basal slip system through the action of rare earth elements, ultimately producing a low-rare earth magnesium-based composite material plate with significantly improved strength and maintained plasticity.

[0025] 2. The method of the present invention uses TC4 (Ti-6Al-4V alloy) particles as reinforcements. Compared with ceramic particles, TC4 particles have better wettability with the magnesium matrix, improve the interface bonding ability, and avoid or reduce the generation of defects and internal stress at the interface. TC4 particle reinforcements can also better coordinate deformation and more effectively transfer loads. The transfer process can release stress through its own plastic deformation, so that the residual stress generated at the interface is less, thereby improving the mechanical properties of the composite material. Although magnesium-based composites have a good performance improvement compared to magnesium alloys, in the traditional symmetrical extrusion process of magnesium-based composites, the particle reinforcement is streamlined along the deformation direction, the particle dispersion uniformity is poor, and the prepared material always has anisotropy, a strong basal texture and poor room temperature formability, resulting in low production efficiency, reduced yield and high cost, which is not conducive to the widespread application of magnesium-based composites. Therefore, an attempt is made to use a new asymmetric extrusion processing method to solve this problem.

[0026] 3. The processing method of the present invention adds titanium alloy particles to a magnesium melt in the form of a stack of aluminum foil-coated titanium alloy particles, which can avoid burning of the titanium alloy particles during the addition process. Semi-solid stirring and ultrasonic treatment of the magnesium-based composite melt can initially prevent large-scale agglomeration of TC4 particles. Rapid cooling of the magnesium-based composite melt after ultrasonic treatment can prevent sedimentation of the TC4 particles, thereby obtaining a composite ingot. Asymmetric extrusion is performed on the low-rare earth magnesium-based composite ingot, resulting in significantly different flow rates at different locations during extrusion. The asymmetric extrusion die can change the deformation path of the metal, creating strain gradients and flow rate gradients, thereby introducing shear stress and promoting multidirectional flow of the particle reinforcement. It can also tilt the grains, thereby weakening the composite texture and improving the formability and mechanical properties of the magnesium-based composite. At the same time, asymmetric extrusion produces a large deformation of the material, which can refine the grains. Moreover, by activating the non-basal slip system through rare earth elements, the asymmetric extruded magnesium-based composite sheet maintains a certain plasticity, further improving the strength of the composite.

[0027] 4. The asymmetric extrusion processing and preparation process is simple, with less energy consumption and short production time. The low rare earth magnesium alloy has low cost, which is conducive to industrial large-scale production. The plate can have outstanding reprocessing capabilities and multi-scenario utilization characteristics, and has good application prospects and economic benefits.

[0028] 5. The low-rare earth magnesium-based composite material prepared by the present invention has higher strength than the traditional symmetrically extruded low-rare earth matrix alloy, and is particularly suitable for fields with strict requirements on lightweight, specific strength and cost control. Specific application scenarios include non-main load-bearing structural parts in the aerospace field (such as brackets, shells, internal frames), high-end equipment and vehicles (such as battery pack shells, steering knuckles, wheels of new energy vehicles, and lightweight components of high-speed trains and drones), lightweight and high-strength casings and heat dissipation components of electronic products, and equipment components in the military field that need to take into account both concealment (low radar cross-section) and impact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of an asymmetric die for asymmetric extrusion processing of TC4 particle reinforced low rare earth magnesium-based composite plates;

[0030] Figure 2 This is a microstructure diagram of the asymmetric extrusion-processed TC4 particle reinforced low-rare earth magnesium-based composite material plate prepared in Example 1;

[0031] Figure 3 This is a microstructure diagram of the asymmetric extrusion-processed TC4 particle reinforced low-rare earth magnesium-based composite material plate prepared in Example 2;

[0032] Figure 4 This is a microstructure diagram of the asymmetric extrusion-processed TC4 particle reinforced low rare earth magnesium alloy plate prepared in Comparative Examples 1 and 2;

[0033] Figure 5 These are the pole figures of the asymmetric extruded magnesium alloy plate prepared in Comparative Example 2 and the asymmetric extruded magnesium-based composite material plate prepared in Example 2. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with specific examples, but the embodiments of the present invention are not limited thereto.

[0035] Example 1

[0036] A method for processing a TC4 particle reinforced low-rare-earth magnesium-based composite plate comprises the following steps:

[0037] S1. Ingredients are prepared by mass percentage: 4 wt.% of TC4 (Ti-6Al-4V) granular powder with a particle size of 15-53 μm, and the balance is Mg-2Gd-0.5Zr alloy ingot. The TC4 spherical powder and the Mg-2Gd-0.5Zr alloy ingot are semi-solid stirred for 6 minutes under a protective gas of CO2-SF6 with a ratio of 99:1, ultrasonically treated for 10 minutes, and rapidly and uniformly water-cooled to room temperature to obtain a composite material ingot. The titanium alloy particles are added to the magnesium melt in a manner of being wrapped with aluminum foil. Specifically, a certain amount of titanium alloy particles are uniformly spread between multiple layers of ultra-thin aluminum foil in advance to form a "sandwich"-shaped laminated structure. The laminated structure is then tightly wound into a compact block preform to ensure that the aluminum foil completely wraps and seals the internal titanium alloy particle layer. The preform must remain intact before being added to the magnesium melt. Its function is to use the aluminum foil to isolate the air and inhibit the pre-oxidation of the titanium alloy particles at high temperatures.

[0038] S2. Place the composite material ingot obtained in step S1 in a crucible, add graphite to the crucible to cover it and isolate it from the air, then place it in a heat treatment furnace, heat it to 450°C at a heating rate of 10°C / min, keep it warm for 24 hours, and water quench the homogenized composite material to obtain a sample.

[0039] S3. Polishing the composite material ingot obtained in step S2 to remove the oxide layer on the surface of the ingot, placing the composite material ingot and the asymmetric extrusion mold in a furnace for preheating for 2 hours, and then performing asymmetric extrusion at a higher extrusion temperature of 430° C., an extrusion rate of 1 m / min, an extrusion ratio of 30:1, and air cooling to room temperature.

[0040] like Figure 1 As shown, the asymmetric extrusion die is a triangular lateral gradient die, including an extrusion rod 1, a die sleeve 2, an extrusion die 4 and an extrusion plate 5. In the figure, 3 is the blank, V is the flow rate, V is the flow rate, and V is the flow rate. ED - Flow velocity in the extrusion direction, V TD - Transverse flow velocity.

[0041] Among them, the triangular asymmetric design of the mold cavity is that the hypotenuse is 50° to the transverse direction (that is, the triangle of the asymmetric extrusion mold is an isosceles triangle, and the three internal angles are 50°, 50° and 80° respectively), that is, the transverse shear force is introduced to obtain an asymmetric stress-strain field, thereby breaking the streamlined segregation of TC4 particles and achieving a dispersed distribution of particles. A special triangular shape is designed in the extrusion mold to achieve an asymmetric stress-strain field, so that the flow rate of the material in different parts during extrusion is significantly different. The asymmetric extrusion mold is designed with a triangular geometric structure (asymmetric diversion angle) in the upper and lower die openings, so that the magnesium-based composite material is subjected to the synergistic effect of differential shear stress fields and multi-directional compressive stress fields in the extrusion deformation zone.

[0042] Working principle: During the asymmetric extrusion process of preparing low rare earth magnesium-based composite material plates, the extrusion rod 1 pushes the blank 3 (containing the matrix and the reinforcement phase) placed in the die sleeve under pressure. The blank 3 flows through the triangular extrusion die 4 fixed at the outlet end of the die sleeve 2. Through the multi-directional stress field design, the final extruded plate 5 is extruded from the orifice of the extrusion die 4. The core of its working principle is to use the triangular shape of the die structure to impose differentiated constraints on the material flow. V is determined by the pushing speed of the extrusion rod and the die opening area; V ED It is mainly controlled by the angle of the bevel of the extrusion die 4 and the material extrusion ratio; TD The multi-directional stress characteristics of the designed extrusion die 4 generate an uneven shear stress field and flow resistance gradient in the extrusion direction, forcing the material to produce a controllable differential flow (i.e., lateral velocity difference) on the cross section, thereby coordinating deformation, improving particle distribution uniformity, and regulating texture. Specifically, when the material flows through the die, additional shear deformation is generated due to asymmetric boundary constraints, resulting in a gradient plastic flow of the metal along the transverse direction of the plate, inducing a strong continuous shear strain accumulation. On the one hand, this process promotes the diffuse distribution of reinforcement particles, and on the other hand, it refines the matrix grains by inducing dynamic recrystallization, while weakening the basal texture strength, and ultimately synergistically improves the strong-plastic matching and forming performance of the low rare earth magnesium-based composite material plate.

[0043] Example 2

[0044] A method for processing a TC4 particle reinforced low-rare-earth magnesium-based composite plate comprises the following steps:

[0045] S1. Ingredients are prepared by mass percentage: 4 wt.% of TC4 (Ti-6Al-4V) granular powder with a particle size of 15-53 μm, and the balance is a Mg-2Gd-0.5Zr alloy ingot. The TC4 spherical powder and the Mg-2Gd-0.5Zr alloy ingot are stirred in a semi-solid state for 6 minutes under a protective gas atmosphere of CO2-SF6 in a ratio of 99:1, ultrasonically treated for 10 minutes, and rapidly and uniformly cooled to room temperature with water to obtain a composite ingot.

[0046] Among them, titanium alloy particles are added to the magnesium melt in the form of aluminum foil wrapping. The specific method is to evenly spread a certain amount of titanium alloy particles between multiple layers of ultra-thin aluminum foil in advance to form a "sandwich"-like laminated structure, and then the laminated layer is tightly wound into a compact block preform to ensure that the aluminum foil completely wraps and seals the internal titanium alloy particle layer; the preform must be kept intact before being added to the magnesium melt. Its function is to use the aluminum foil to isolate the air and inhibit the pre-oxidation of titanium alloy particles at high temperatures.

[0047] S2. Place the composite material ingot obtained in step S1 in a crucible, add graphite to the crucible to cover it and isolate it from the air, then place it in a heat treatment furnace, heat it to 450°C at a heating rate of 10°C / min, keep it warm for 24 hours, and water quench the homogenized composite material to obtain a sample.

[0048] S3. Polish the composite material ingot obtained in step S2 to remove the oxide layer on the surface of the ingot, place the composite material ingot and the asymmetric extrusion mold in a furnace for preheating for 2 hours, and then perform asymmetric extrusion at a low extrusion temperature of 400°C, an extrusion rate of 1 m / min, an extrusion ratio of 30:1, and air cool to room temperature.

[0049] like Figure 1 As shown, the asymmetric extrusion die is a triangular-shaped transverse gradient die. The triangular asymmetric design of the die cavity exhibits a 50° angle between the hypotenuse and the transverse direction. This introduces transverse shear force to create an asymmetric stress-strain field, thereby breaking the streamlined segregation of TC4 particles and achieving a dispersed distribution of particles. A special triangular shape is designed within the extrusion die to achieve an asymmetric stress-strain field, resulting in significantly different flow rates at different locations during extrusion. The extrusion structure and principle are the same as in Example 1.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that TC4 (Ti-6Al-4V) particle powder is not added.

[0052] Comparative Example 2

[0053] The difference from Example 2 is that TC4 (Ti-6Al-4V) particle powder is not added.

[0054] Performance Testing

[0055] The asymmetric extrusion processed low rare earth magnesium based composite material plates prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to organizational characteristics testing. The microstructure diagram and pole figure of the corresponding asymmetric extrusion processed low rare earth magnesium based composite material plates are shown in FIG. Figures 2 to 5 As shown by Figure 2 and Figure 3 It can be seen that TC4 particles are dispersed in the matrix, indicating that the lateral shear stress introduced by asymmetric extrusion promotes the multi-directional flow of particles and breaks the streamlined segregation of particles. Figure 4 and Figure 2 and Figure 3 By comparison, we can find Figure 2 and Figure 3 The grains of the magnesium-based composite material are finer, indicating that the introduction of TC4 particles can promote dynamic recrystallization and further achieve grain refinement. Figure 5It can be seen that the maximum strength of the macroscopic texture of the magnesium-based composite material prepared by asymmetric extrusion is significantly lower, indicating that asymmetric extrusion causes the c-axis to tilt, thereby achieving texture weakening.

[0056] The test results of the present invention are shown in Table 1.

[0057] Table 1 Room temperature mechanical properties of low rare earth magnesium based composite materials prepared in Examples 1-2 and Comparative Examples 1-2

[0058]

[0059] As can be seen from the test results in Table 1, the asymmetric extrusion-processed low-rare earth magnesium-based composite materials prepared according to the method of the present invention in Examples 1 and 2 all have higher strength than those of Comparative Examples 1 and 2, respectively. Example 2 achieves outstanding yield strength and tensile strength of 251 MPa and 262 MPa, respectively, which are higher than the yield strength and tensile strength of the low-rare earth magnesium alloy sheet in Comparative Example 2, and much higher than the yield strength (80-110 MPa) and tensile strength (160-200 MPa) of the traditional symmetrically extruded Mg-Gd-Zr low-rare earth magnesium alloy reported in the literature. In addition, Example 2 can maintain an elongation of 7.1%. This shows that the asymmetric extrusion processing method of the present invention can improve the dispersibility of titanium alloy particles in the low-rare earth magnesium-based composite material and weaken the texture, so that the prepared low-rare earth magnesium-based composite material sheet has a significantly improved tensile strength while maintaining a certain elongation, achieving excellent comprehensive mechanical properties and effectively improving the potential for further application of low-rare earth magnesium-based composite materials in complex mechanical scenarios.

[0060] Similarly, in the aluminum foil-coated TC4 particle lamination processing methods of Examples 1 and 2, the TC4 particle size can be 15 to 53 μm, the aluminum foil thickness can be 0.01 to 0.02 mm, the width can be 200 to 300 mm, and the thickness of the titanium powder spread on the aluminum foil can be 0.2 to 0.5 mm, without affecting the performance of the resulting low-rare-earth magnesium-based composite material. Furthermore, during the preparation process, the mass ratio of TC4 particles to magnesium melt in the aluminum foil-coated titanium alloy particle lamination can be selected within the range of 2:98 to 10:90, the asymmetric extrusion temperature can be 400 to 430°C, the extrusion ratio can be 25 to 51:1, and the extrusion rate can be 1.5 to 3 m / min. Performance testing shows that the low-rare-earth magnesium-based composite material prepared under these conditions also has the same performance as the products of Examples 1 and 2.

[0061] In summary, the present invention provides an asymmetric extrusion processing method and product for TC4 particle-reinforced low-rare-earth magnesium-based composite material sheet materials. This processing method adds titanium alloy particles to a magnesium melt in the form of a stack of aluminum foil-coated titanium alloy particles, which can avoid burning of the titanium alloy particles during the addition process. Semi-solid stirring and ultrasonic treatment of the magnesium-based composite material melt can initially prevent large-scale agglomeration of TC4 particles. Rapid cooling of the ultrasonically treated magnesium-based composite material melt can prevent sedimentation of the TC4 particles, thereby obtaining a composite material ingot. Asymmetric extrusion of the low-rare-earth magnesium-based composite material ingot results in significantly different flow rates at different locations during extrusion. The asymmetric extrusion die can change the deformation path of the metal, creating strain gradients and flow rate gradients, thereby introducing shear stress and promoting multidirectional flow of the particle reinforcement. It can also tilt the grains, thereby weakening the composite material texture and improving the formability and mechanical properties of the low-rare-earth magnesium-based composite material sheet materials. Asymmetric extrusion also produces a large deformation of the material, which can refine the grains and further improve the overall mechanical properties of the composite material sheet materials. The asymmetric extruded low-rare earth magnesium-based composite material plate prepared by the present invention has higher strength than the low-rare earth alloy plate while maintaining a certain plasticity. Among them, Example 2 obtains outstanding yield strength and tensile strength, which are 251 MPa and 262 MPa, respectively, which are much higher than the strength of the low-rare earth magnesium alloy plate in Comparative Example 2 and the strength of the traditional symmetrically extruded Mg-Gd-Zr low-rare earth magnesium alloy reported in the literature, and Example 2 can maintain an elongation of 7.1%.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for processing a TC4 particle reinforced low rare earth magnesium-based composite plate, comprising the following steps: S1. Mixing the following ingredients by mass percentage: 2-10 wt.% of TC4 spherical powder and the balance of Mg-Gd-Zr alloy ingot; stirring and casting the TC4 titanium alloy powder particles and the Mg-Gd-Zr alloy ingot under a protective gas to obtain a composite material ingot; S2, placing the composite material ingot in step S1 in a heat treatment furnace for homogenization treatment at a temperature of 400-500° C. for 20-24 hours; S3. Polishing the composite material ingot obtained in step S2 to remove the oxide layer on the surface of the ingot, placing the composite material ingot and the asymmetric extrusion mold in a furnace for preheating for 1-2 hours, and then performing asymmetric extrusion at 400-430°C with an extrusion rate of 1.5-3m / min and an extrusion ratio of 25-51:1, and air cooling to room temperature.

2. The processing method according to claim 1, wherein In step S1 , the mass percentages of the components in the Mg—Gd—Zr alloy ingot are: 1.8-2.2 wt.% Gd, 0.3-0.7% Zr, and the balance is Mg and unavoidable impurities.

3. The processing method according to claim 1, wherein: In step S1, the stirring casting under protective gas is specifically as follows: under protective gas CO2-SF6 with a ratio of 99:1, semi-solid stirring for 6 minutes, ultrasonic treatment for 10 minutes, and rapid and uniform water cooling to room temperature.

4. The processing method according to claim 1, wherein: In step S2, the homogenization treatment is specifically as follows: placing the composite material in a crucible, adding graphite to the crucible to cover and isolate the air, then placing it in a heat treatment furnace, heating it to 450-500°C at a heating rate of 10-20°C / min, keeping it warm for 20-24 hours, and water quenching the sample after homogenization treatment.

5. The processing method according to claim 1, wherein: In step S3, the asymmetric extrusion die is a triangular lateral gradient die, and the triangle is an isosceles triangle with three internal angles of 50°, 50° and 80°, that is, the triangular asymmetric design of the mold cavity is that the hypotenuse is 50° to the transverse direction, and a transverse shear force is introduced to obtain an asymmetric stress-strain field, thereby breaking the streamlined segregation of TC4 particles and achieving a dispersed distribution of particles.

6. The processing method according to claim 1, wherein: In step S1, titanium alloy particles are added to the magnesium melt in the form of aluminum foil wrapping. The specific method is to evenly spread a certain amount of titanium alloy particles between multiple layers of ultra-thin aluminum foil in advance to form a "sandwich"-like laminated structure, and then the laminated structure is tightly wound into a compact block preform to ensure that the aluminum foil completely wraps and seals the internal titanium alloy particle layer.

7. The processing method according to claim 1, wherein: In the step S1, the cooling is water quenching cooling.

8. The processing method according to claim 1, wherein: The particle size of the TC4 powder particles is 15-53 μm.

9. The processing method according to claim 1, wherein: The steps include: S1. Place the polished Mg-Gd-Zr alloy (components: 1.8-2.2wt.% Gd, 0.3-0.7% Zr, balance Mg, total rare earth content of 1-3wt.%) into a crucible, place the crucible into a resistance furnace and heat it to completely melt the alloy, and introduce a protective gas throughout the entire process; then weigh TC4 titanium alloy powder particles and place them in a drying oven for preheating. When the Mg-Gd-Zr alloy melt cools to a semi-solid temperature, add TC4 particles and begin stirring. After stirring, perform ultrasonic treatment, and then quickly take out the sample and evenly water-cool it to room temperature to obtain a composite material ingot; S2. Place the composite material ingot in a heat treatment furnace for homogenization treatment, heat it to 450-500°C at a heating rate of 10-20°C / min, keep it at that temperature for 20-24 hours, and water quench the homogenized sample; S3. A transverse gradient asymmetric extrusion die is used to perform asymmetric extrusion deformation on the composite material. The triangular asymmetric design of the die cavity shows that the hypotenuse is 50° to the transverse direction. The transverse shear force is introduced to obtain an asymmetric stress-strain field, thereby breaking the streamlined segregation of TC4 particles and obtaining a deformed magnesium-based composite extruded sheet with dispersed particles.

10. The TC4 particle reinforced low rare earth magnesium based composite plate prepared by the processing method according to any one of claims 1 to 9, characterized in that: The yield strength is 110MPa-260MPa, the tensile strength is 180MPa-270MPa, and the plasticity is 7%-40%. It is used in fields with strict requirements on lightweight, specific strength and cost control.

Images