A magnesium-based composite material, its preparation method and application

Abstract

The present invention discloses a magnesium-based composite material, its preparation method and application, belonging to the technical field of magnesium-based materials. The composite material comprises a magnesium-based matrix and reinforcing phases, and the reinforcing phases include a hard-core reinforcing phase and a soft-core reinforcing phase; the composition of the magnesium-based matrix contains at least Mg and Al; the hard-core reinforcing phase includes a Ti reinforcing phase, and the soft-core reinforcing phase includes an AlCuMg reinforcing phase. The composite material uses dual heterogeneous structure metal reinforcing particles, introducing a hard-core reinforcing phase and a soft-core reinforcing phase formed in-situ on the surface, which can effectively improve the interfacial bonding force between the reinforcing particles and the matrix, thereby improving the mechanical properties of the composite material, such as tensile strength, yield strength and elongation, etc. Its preparation includes: mixing Ti powder coated with Cu powder on the surface with magnesium-based matrix powder, and then carrying out ball milling, hot pressing sintering, homogenization heat treatment and hot extrusion. This method is simple and easy to operate, and is suitable for industrial production. The composite material can be used in the fields of aerospace, rail transit or 3C.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium-based materials, and in particular, to a magnesium-based composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Particle-reinforced magnesium-based composites are of great technical significance to the automotive and aerospace industries due to their light weight and good comprehensive properties. However, interfacial failure is one of the main limiting factors affecting the strength and plasticity of magnesium-based composites. During the plastic deformation of the matrix, since stress will concentrate at the interface between the particles and the matrix, pores can rapidly nucleate at the interface and coalesce into cracks, resulting in premature failure of the particle-reinforced magnesium-based composites. To prevent interfacial failure, it is necessary to limit the plastic strain of the metal matrix, but this conflicts with the requirement of high ductility.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The purpose of the present application is to provide a magnesium-based composite material, a preparation method thereof, and an application thereof to solve or improve the above technical problems.

[0005] The present application can be implemented as follows:

[0006] In a first aspect, the present application provides a magnesium-based composite material, which includes a magnesium-based matrix and a reinforcing phase. The reinforcing phase includes a hard-core reinforcing phase and a soft-core reinforcing phase;

[0007] Among them, the composition of the magnesium-based matrix contains at least Mg and Al; at least part of the soft-core reinforcing phase is located on the outer surface of the hard-core reinforcing phase. The hard-core reinforcing phase includes a Ti reinforcing phase, and the soft-core reinforcing phase includes an AlCuMg reinforcing phase.

[0008] In an optional embodiment, in the magnesium-based composite material, the volume fraction of the hard-core reinforcing phase is 3-50%; the volume fraction of the soft-core reinforcing phase is 2-10%;

[0009] And / or, by mass percentage, the magnesium-based matrix contains 3-10% of Al and 0.5-1% of Zn, and the balance is Mg.

[0010] In a second aspect, the present application provides a preparation method of a magnesium-based composite material as described in the foregoing embodiment, including the following steps: mixing Ti powder coated with Cu powder on the surface with magnesium-based matrix powder to obtain composite powder; successively performing ball milling, hot press sintering, heat treatment, and hot extrusion on the composite powder to enable the Cu powder to react with the magnesium-based matrix to generate a soft-core reinforcing phase.

[0011] In an optional embodiment, the preparation of the Ti powder coated with Cu powder on the surface includes: coating Cu powder on the surface of the Ti powder by means of electro-explosion deposition.

[0012] In an alternative embodiment, the conditions for electro-explosion deposition include: an initial voltage of 5 - 10 Kv and a deposition distance of 20 - 30 mm.

[0013] In an alternative embodiment, the mass of the Cu powder is 2 - 10% of the Ti powder.

[0014] In an alternative embodiment, the Ti powder is micron-sized; preferably, the average particle size of the Ti powder is 10 - 30 μm.

[0015] In an alternative embodiment, the Cu powder is nano-sized; preferably, the average particle size of the Cu powder is 10 - 100 nm.

[0016] In an alternative embodiment, the mixing of the Ti powder surface-coated with Cu powder and the magnesium-based matrix powder is carried out under the conditions of 20 - 40 r / min for 5 - 8 h.

[0017] In an alternative embodiment, the mass of the Ti powder surface-coated with Cu powder is 5 - 20% of the magnesium-based matrix powder.

[0018] In an alternative embodiment, the conditions for ball milling include: a ball milling speed of 50 - 80 r / min, a ball-to-material ratio of 1:1 - 3:1, and a ball milling time of 3 - 5 h.

[0019] In an alternative embodiment, the conditions for hot press sintering include: a sintering temperature of 400 - 500 °C, a sintering pressure of 20 - 40 MPa, and a heat preservation time of 30 - 60 min.

[0020] In an alternative embodiment, the heating rate is 4 - 6 °C / min.

[0021] In an alternative embodiment, the conditions for heat treatment include: a heat treatment temperature of 350 - 400 °C and a heat treatment time of 30 - 60 min.

[0022] In an alternative embodiment, the conditions for hot extrusion include: an extrusion ratio of 20:1 - 40:1 and an extrusion speed of 0.3 - 0.8 m / min.

[0023] In a third aspect, the present application provides an application of a magnesium-based composite material as described in the foregoing embodiments, such as for preparing aerospace products, rail transit products, or 3C field products.

[0024] The beneficial effects of the present application include:

[0025] The magnesium-based composite material provided by this application uses dual heterogeneous structure metal reinforcing particles, introducing a hard-core reinforcing phase region and a soft-core reinforcing phase region, which can effectively improve the interfacial bonding force between the reinforcing particles and the matrix, thereby improving the mechanical properties of the composite material, such as tensile strength, yield strength, and elongation. Its preparation method is simple and easy to operate, and is suitable for industrial production. The obtained composite material can be used to prepare aerospace products, rail transit products, or products in the 3C field. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0027] Figure 1 It is the microstructure morphology diagram of the magnesium-based composite material obtained in Example 1;

[0028] Figure 2 It is the microstructure diagram of the magnesium-based composite material obtained in Example 1;

[0029] Figure 3 It is the fracture morphology diagram of the magnesium-based composite material obtained in Example 1;

[0030] Figure 4 It is the fracture morphology diagram of the magnesium-based material obtained in Comparative Example 1;

[0031] Figure 5 It is the fracture morphology diagram of the magnesium-based composite material obtained in Comparative Example 2;

[0032] Figure 6 It is the stress-strain curves of the magnesium-based materials of Example 1, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0034] The magnesium-based composite material provided by this application, its preparation method, and applications will be specifically described below.

[0035] This application proposes a magnesium-based composite material, which includes a magnesium-based matrix and a reinforcing phase. The reinforcing phase includes a hard-core reinforcing phase and a soft-core reinforcing phase.

[0036] Among them, the composition of the magnesium-based matrix contains at least Mg and Al, that is, in addition to Mg and Al, the used magnesium-based matrix may also contain other components.

[0037] In some embodiments, by mass percentage, the magnesium-based matrix may contain 3-10% of Al and 0.5-1% of Zn, and the balance is Mg.

[0038] In this application, at least part of the soft-core reinforcing phase is located on the outer surface of the hard-core reinforcing phase. The hard-core reinforcing phase includes a Ti reinforcing phase, and the soft-core reinforcing phase includes an AlCuMg reinforcing phase.

[0039] The above-mentioned AlCuMg reinforcing phase is formed by the reaction of Cu with Mg and Al in the magnesium-based matrix, preferably formed by the in-situ reaction of Cu with Mg and Al in the magnesium-based matrix.

[0040] In some embodiments, all of the soft-core reinforcing phases are located on the outer surface of the hard-core reinforcing phase.

[0041] In other embodiments, part of the soft-core reinforcing phase is located on the outer surface of the hard-core reinforcing phase (this part of the soft-core reinforcing phase can be understood as being located at the grain boundaries of the magnesium-based matrix), and the remaining soft-core reinforcing phase enters the interior of the grains of the magnesium-based matrix. That is, in the latter embodiment, the soft-core reinforcing phase is distributed in both the grain boundaries and the interior of the grains of the magnesium-based matrix.

[0042] The above-mentioned soft-core reinforcing phase located in the interior of the grains of the magnesium-based matrix can hinder the movement of dislocations, resulting in the formation of a large number of dislocation cells; the soft-core reinforcing phase located at the grain boundaries of the magnesium-based matrix can generate a large number of twins near the grain boundaries. All regions of the soft-core reinforcing phase can buffer the stress concentration caused by the difference between the reinforcing particles and the matrix, significantly improving the strength and plasticity of the composite material.

[0043] For reference, in the magnesium-based composite material, the volume fraction of the hard-core reinforcing phase can be 3-50%, such as 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc., and can also be any other value within the range of 3-50%.

[0044] In the magnesium-based composite material, the volume fraction of the soft-core reinforcing phase can be 2-10%, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., and can also be any other value within the range of 2-10%.

[0045] It should be noted that in the magnesium-based composite material, the other volume except for the hard-core reinforcing phase and the soft-core reinforcing phase corresponds to the volume of the unreacted magnesium-based matrix.

[0046] Continuing from the above, the magnesium-based composite material provided by this application uses dual heterogeneous structure metal reinforcing particles (where "dual heterogeneous" refers to Cu and Ti), introducing a hard core reinforcing phase and a soft core reinforcing phase formed in situ on the surface, which can effectively improve the interfacial bonding force between the reinforcing particles and the matrix, thereby improving the mechanical properties of the composite material, such as tensile strength, yield strength, and elongation.

[0047] Correspondingly, this application provides a preparation method for the above magnesium-based composite material, which may include the following steps: mixing Ti powder coated with Cu powder on the surface with magnesium-based matrix powder to obtain composite powder; sequentially performing ball milling, hot press sintering, heat treatment, and hot extrusion on the composite powder to enable the Cu powder to react with the magnesium-based matrix to generate a soft core reinforcing phase.

[0048] By coating the surface of the primary heterogeneous Ti particles with secondary Cu particles, the primary reinforcing Ti particles are metallic elements that are immiscible with the Mg matrix, and the secondary reinforcing Cu reacts in situ with the magnesium matrix to form a second phase (AlCuMg phase). Among them, the internal reinforcing Ti particles are the hard core region, and the surface AlCuMg phase is the soft core region. The plastic strain borne by the soft core region is smaller than that of the hard core region to prevent premature interfacial failure. The dual heterogeneous structure produces a unique double-layer heterogeneous deformation that can induce strengthening and hardening to produce high strength and high plasticity.

[0049] For reference, the preparation of Ti powder coated with Cu powder on the surface may include: using the electro-explosion deposition method to coat Cu powder on the surface of Ti powder.

[0050] Coating in this way can achieve metallurgical bonding and improve the firmness of the coating. Chemical deposition may easily generate impurities and affect the effect.

[0051] Among them, the initial voltage of electro-explosion deposition can be 5 - 10 Kv, such as 5 Kv, 6 Kv, 7 Kv, 8 Kv, 9 Kv, or 10 Kv, etc., or any other arbitrary value within the range of 5 - 10 Kv.

[0052] The deposition distance of electro-explosion deposition can be 20 - 30 mm, such as 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, or 30 mm, etc., or any other arbitrary value within the range of 20 - 30 mm.

[0053] If the deposition voltage is too low, it is impossible to achieve the coating of nanoscale Cu on the surface of Ti; if the deposition voltage is too high, it will cause the powder to burn and unable to form a preset coating layer. If the deposition distance is too far, it is easy to result in too low deposition efficiency; if the deposition distance is too close, it is easy to cause uneven coating.

[0054] The mass of the Cu powder may be 2-10% of the Ti powder, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., or any other value within the range of 2-10%.

[0055] Through the above-mentioned quality, Cu particles can be coated discontinuously on the surface of Ti particles (that is, not all surfaces of Ti particles are coated with Cu particles), so that Cu particles react in situ with the magnesium matrix to generate a discontinuously distributed second phase. It should be emphasized that if the amount of nano Cu particles used is too much, Cu will easily agglomerate at the interface of the composite material, affecting the interface bonding; and if the amount of Cu is too much, the corrosion performance of the material will be reduced. If the amount of nano Cu particles used is too little, the interface bonding will deteriorate.

[0056] In the present application, the Ti powder is in micron size. In some embodiments, the average particle size of the Ti powder may be 10-30 μm, such as 10 μm, 15 μm, 20 μm, 25 μm or 30 μm.

[0057] The Cu powder is nanometer-sized. In some embodiments, the average particle size of the Cu powder may be 10-100 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0058] It should be noted that if the Ti powder is nanometer-level, it will be difficult to disperse; if the Ti powder is micrometer-level, the deformation ability is poor, resulting in poor mechanical properties and poor interface bonding. The present application uses nanometer-level Cu powder to modify the surface of micrometer-level Ti powder, and the nanometer activity is high, which is conducive to the reaction at the interface and improves the interface bonding ability.

[0059] For reference, in the present application, the mixing of Ti powder coated with Cu powder on the surface and magnesium-based matrix powder can be carried out at 20-40 r / min (such as 20 r / min, 25 r / min, 30 r / min, 35 r / min or 40 r / min, etc.) for 5-8 h (such as 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h or 8 h, etc.). The process can be exemplarily carried out in a double cone mixer.

[0060] In the present application, the mass of the Ti powder coated with Cu powder on the surface can be 5-20% of the magnesium-based matrix powder, such as 5%, 8%, 10%, 12%, 15%, 18% or 20%, etc., or any other value within the range of 5-20%.

[0061] Within this dosage range, a phase with good interface bonding can be stably formed, and the effect of the Ti reinforcement phase can be ensured.

[0062] In this application, the rotation speed of ball milling can be 50 - 80 r / min, such as 50 r / min, 55 r / min, 60 r / min, 65 r / min, 70 r / min, 75 r / min or 80 r / min, etc., or any other arbitrary value within the range of 50 - 80 r / min.

[0063] The ball - to - material ratio can be 1:1 - 3:1, such as 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, etc., or any other arbitrary value within the range of 1:1 - 3:1.

[0064] It should be noted that by controlling the ball - to - material ratio within the above range, the components can be effectively mixed evenly. If the high - energy ball milling process is adopted, the powder with surface coating is easily knocked off by the grinding balls, resulting in the failure of the coated powder to form a double - heterogeneous structure of hard core and soft core, ultimately affecting the mechanical properties.

[0065] The ball milling time can be 3 - 5 h, such as 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc., or any other arbitrary value within the range of 3 - 5 h.

[0066] In this application, by first mechanically mixing the Ti powder coated with Cu powder on the surface with the magnesium - based matrix powder, the Ti powder coated with Cu powder on the surface can be slightly adhered to the surface of the magnesium - based matrix. Subsequently, through the ball milling process, the Ti powder coated with Cu powder can be combined with the magnesium - based matrix more evenly and firmly.

[0067] In addition, in the magnesium - based composite material, the reinforcement plays a role in supporting most of the externally applied loads, while the matrix plays a role in connecting, transmitting and distributing the loads to each reinforcement, thereby improving the performance of the magnesium alloy as a whole. The interface is the bridge between the reinforcement and the magnesium matrix, and the strength of the interface bonding has a very crucial impact on the mechanical properties of the magnesium - based composite material. Generally speaking, the two key factors determining the interface bonding strength are: the wettability between the reinforcement and the matrix material and the interface reaction situation.

[0068] Regarding the wettability between the reinforcement and the matrix material, adding alloying elements, applying an external energy field and surface modification of the reinforcement can improve the wettability. In this application, the ball milling method is adopted. During the ball milling process, the hard balls impact, grind and stir the composite powder, causing changes in the microstructure, structure and properties of the material, which can improve the wettability while also improving the particle distribution. Moreover, Ti is chemically active and often forms oxides on its surface easily, resulting in a high oxygen content at the interface of the final composite material and affecting the mechanical properties. Coating the surface with nano - Cu can solve this technical problem and reduce the oxygen content of the composite material.

[0069] In this application, the sintering temperature of hot-press sintering can be 400 - 500 °C, such as 400 °C, 420 °C, 450 °C, 480 °C or 500 °C, etc., and can also be any other value within the range of 400 - 500 °C.

[0070] The sintering pressure can be 20 - 40 MPa, such as 20 MPa, 25 MPa, 30 MPa, 35 MPa or 40 MPa, etc., and can also be any other value within the range of 20 - 40 MPa.

[0071] The heat preservation time can be 30 - 60 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, etc.

[0072] The heating rate during the above hot-press sintering process can be 4 - 6 °C / min, such as 4 °C / min, 4.5 °C / min, 5 °C / min, 5.5 °C / min or 6 °C / min, etc.

[0073] The above hot-press sintering process is carried out in a sintering furnace with a protective atmosphere (such as argon atmosphere, etc.). After sintering is completed, it can be cooled to room temperature with the furnace.

[0074] If the hot-press sintering temperature is too high, it is easy to cause the grains to grow too large and reduce its mechanical properties; if the hot-press sintering temperature is too low, it is easy to cause the elements not to diffuse yet and the AlCuMg phase at the interface cannot be formed. If the hot-press sintering pressure is too high, it will cause premature fracture failure due to stress concentration in the material; if the hot-press sintering pressure is too low, it is easy to cause more pores in the material and it is difficult to form a dense composite material. If the hot-press sintering time is too long, it is easy to cause the grains to grow too large and reduce its mechanical properties; if the hot-press sintering time is too short, it is easy to cause the elements not to diffuse yet and the AlCuMg phase at the interface cannot be formed. By controlling the heating rate within 4 - 6 °C / min in this application, it is beneficial to the uniform diffusion of elements.

[0075] In this application, the temperature of heat treatment can be 350 - 400 °C, such as 350 °C, 360 °C, 370 °C, 380 °C, 390 °C or 400 °C, etc., and can also be any other value within the range of 350 - 400 °C.

[0076] The time of heat treatment can be 30 - 60 min, such as 30 min, 40 min, 50 min or 60 min, etc., and can also be any other value within the range of 30 - 60 min.

[0077] It should be noted that after hot-press sintering, problems such as segregation and non-uniform structure usually easily occur in the structure. Through heat treatment, it is beneficial to relieve the composition segregation and can also play a certain role in solid solution strengthening.

[0078] In the present application, the extrusion ratio of hot extrusion can be 20:1-40:1, such as 20:1, 25:1, 30:1, 35:1 or 40:1, or any other value within the range of 20:1-40:1.

[0079] The extrusion speed may be 0.3-0.8 m / min, such as 0.3 m / min, 0.4 m / min, 0.5 m / min, 0.6 m / min, 0.7 m / min or 0.8 m / min, or any other value within the range of 0.3-0.8 m / min.

[0080] It should be noted that magnesium alloys have poor plasticity and require later deformation to improve their plasticity and strength. The larger the extrusion ratio, the deeper the degree of organizational deformation, the finer the grains, and the stronger the deformation coordination ability, thereby improving strength and plasticity. If the extrusion rate is too fast, severe deformation will occur, but the organization will not have time to coordinate the deformation, which will lead to stress concentration and material cracking; if the extrusion rate is too slow, the pretreatment temperature will be reduced during the extrusion process, and the deformation ability will deteriorate.

[0081] In line with the above, the preparation method of the magnesium-based composite material provided in the present application has at least the following characteristics:

[0082] (1) The high strength and plasticity of metal Ti are brought into play, avoiding the failure behavior of interface fracture along the particle boundary caused by the non-reaction between the reinforcement phase Ti and the Mg matrix; the high ductility of metal Cu is brought into play, avoiding the problem of poor corrosion resistance of Cu / Mg-based composite materials.

[0083] (2) The powder metallurgy preparation method can make the in-situ reaction process and interface products more controllable than the casting method, and can form a hard-core Ti reinforcement phase and a discontinuous soft-core AlCuMg reinforcement phase at the phase interface, thereby improving the interface bonding strength.

[0084] (3) The interface hard core Ti reinforcement phase region has higher strength and plasticity, and the interface soft core AlCuMg reinforcement phase region is distributed at the grain boundary and in the grain of the magnesium alloy matrix. The impediment of dislocation movement in the grain leads to the formation of a large number of dislocation cells; a large number of twins are generated near the grain boundary. The soft core region can buffer the stress concentration caused by the difference between the reinforcement particles and the matrix, so that the strength and plasticity of the composite material are significantly improved.

[0085] (4) In magnesium alloys, since there are no reinforcing particles to hinder the extension and expansion of cracks, the fracture form is mainly delamination fracture. In titanium particle reinforced magnesium-based composites, titanium particles can hinder the expansion of cracks, but titanium and magnesium do not react, the interface bonding is weak, and the cracks tear along the edge of the particles and the matrix. In double heterogeneous structure metal particle reinforced magnesium-based composites, there is a composition gradient between the reinforcement phase and the matrix, and the fracture mode is a large number of dislocation cells entangled and entangled, causing micropore aggregation fracture.

[0086] (5) Appropriate interfacial reactions are beneficial to improving the wetting between the reinforcement and the matrix, forming a stable interfacial structure, and thus generating a stronger interfacial bond. According to the strength of the interfacial bond with the magnesium matrix, the interfacial reactions are classified into the following three categories: First, there is no interfacial reaction, such as traditional Ti particle-reinforced Mg alloys. In this case, the wetting between the reinforcement and the magnesium matrix is poor, and the interfacial bond strength is weak. Second, there is a strong interfacial reaction. A strong interfacial reaction will lead to the destruction of the integrity of the reinforcement. The reaction products are also prone to aggregate at the interface to form a brittle layer, and cracks are formed under the action of load, resulting in a sharp decline in the performance of the composite material. Third, it is the weak interfacial reaction in this application. Discontinuous AlCuMg phases are formed at the interface, and there are more reaction products than in the case of no interfacial reaction. At this time, the integrity of the reinforcement is good, and the formed reaction products can effectively transfer the load received by the matrix to the reinforcement to improve the strength of the composite material. And it can prevent cracking caused by stress concentration and improve the plasticity of the material.

[0087] In addition, this application also provides an application of the above magnesium matrix composite material, for example, it can be used to prepare aerospace products, rail transit products, or products in the 3C field, etc.

[0088] The features and properties of the present invention will be further described in detail below in conjunction with the embodiments.

[0089] Example 1

[0090] This example provides a magnesium matrix composite material, and its preparation method includes:

[0091] S1: Using the electro-explosion deposition method, Cu powder is coated on the surface of Ti powder to obtain Ti powder with Cu powder coated on its surface.

[0092] Among them, the average particle size of Ti powder is 20 μm, the average particle size of Cu powder is 80 nm, and the mass of Cu powder is 2 wt% of Ti powder. The voltage of electro-explosion deposition is 8 Kv, and the deposition distance is 25 mm.

[0093] S2: The Ti powder with Cu powder coated on its surface and the magnesium matrix powder are mixed in a double-cone mixer at a condition of 30 r / min for 8 h to obtain composite powder.

[0094] Among them, the magnesium matrix powder is commercial AZ91 magnesium alloy powder (containing 9 wt% of Al and 1 wt% of Zn, and the balance is Mg), and the mass of the Ti powder with Cu powder coated on its surface is 5 wt% of the magnesium matrix powder.

[0095] S3: The above composite powder is put into a ball mill and ball-milled for 4 h at a ball-to-material ratio of 2:1 and a ball-milling speed of 60 r / min.

[0096] S4: The materials obtained by ball milling are placed in a sintering furnace with an argon atmosphere, heated to 500 °C at a heating rate of 5 °C / min, and hot press sintered under a pressure condition of 30 MPa for 1 h, and then cooled to room temperature with the furnace.

[0097] S5: The sintered parts obtained by hot press sintering and the extrusion die are placed in a furnace and heated to 400 °C, and held for 1 h for heat treatment.

[0098] S6: The samples obtained by heat treatment are hot extruded. Among them, the extrusion ratio is 30:1 and the extrusion speed is 0.8 m / min to obtain a Cu-coated Ti particle-reinforced magnesium matrix composite.

[0099] Example 2

[0100] The difference between this example and Example 1 is that in S2, the magnesium matrix uses AZ31 magnesium alloy powder (containing 3 wt% Al and 1 wt% Zn, and the balance is Mg).

[0101] Example 3

[0102] The difference between this example and Example 1 is that in S3, the ball-to-material ratio is 3:1.

[0103] Example 4

[0104] The difference between this example and Example 1 is that in S4, the hot press sintering temperature is 480 °C.

[0105] Example 5

[0106] This example provides a magnesium matrix composite, and its preparation method includes:

[0107] S1: By means of electro-explosive deposition, Cu powder is coated on the surface of Ti powder to obtain Ti powder with Cu powder coated on the surface.

[0108] Among them, the average particle size of Ti powder is 10 μm, the average particle size of Cu powder is 10 nm, and the mass of Cu powder is 5 wt% of Ti powder. The voltage of electro-explosive deposition is 5 Kv and the deposition distance is 20 mm.

[0109] S2: The Ti powder with Cu powder coated on the surface and the magnesium matrix powder are mixed in a double-cone mixer at 20 r / min for 6 h to obtain composite powder.

[0110] Among them, the magnesium matrix powder is commercial AZ91 magnesium alloy powder, and the mass of the Ti powder with Cu powder coated on the surface is 10 wt% of the magnesium matrix powder.

[0111] S3: The above composite powder is put into a ball mill and ball milled for 5 h at a ball-to-material ratio of 1:1 and a ball milling speed of 50 r / min.

[0112] S4: Put the material obtained by ball milling into a sintering furnace with an argon atmosphere, heat it up to 400 °C at a heating rate of 4 °C / min, and perform hot pressing sintering for 40 min under a pressure condition of 20 MPa, and then cool it to room temperature with the furnace.

[0113] S5: Put the sintered part obtained by hot pressing sintering and the extrusion die into the furnace and heat it up to 350 °C, and keep it warm for 40 min for heat treatment.

[0114] S6: Perform hot extrusion on the sample obtained by heat treatment. Among them, the extrusion ratio is 20:1, and the extrusion speed is 0.5 m / min to obtain a Cu-coated Ti particle-reinforced magnesium matrix composite.

[0115] Example 6

[0116] This example provides a magnesium matrix composite, and its preparation method includes:

[0117] S1: Adopt the electro-explosion deposition method to coat Cu powder on the surface of Ti powder to obtain Ti powder with Cu powder coated on its surface.

[0118] Among them, the average particle size of Ti powder is 30 μm, the average particle size of Cu powder is 50 nm, and the mass of Cu powder is 10 wt% of Ti powder. The voltage of electro-explosion deposition is 10 Kv, and the deposition distance is 30 mm.

[0119] S2: Put the Ti powder with Cu powder coated on its surface and the magnesium matrix powder into a double-cone mixer and mix them for 5 h under the condition of 40 r / min to obtain composite powder.

[0120] Among them, the magnesium matrix powder is commercial AZ91 magnesium alloy powder, and the mass of the Ti powder with Cu powder coated on its surface is 20 wt% of the magnesium matrix powder.

[0121] S3: Put the above composite powder into a ball mill and perform ball milling for 3 h with a ball-to-material ratio of 3:1 and a ball milling speed of 80 r / min.

[0122] S4: Put the material obtained by ball milling into a sintering furnace with an argon atmosphere, heat it up to 450 °C at a heating rate of 6 °C / min, and perform hot pressing sintering for 30 min under a pressure condition of 40 MPa, and then cool it to room temperature with the furnace.

[0123] S5: Put the sintered part obtained by hot pressing sintering and the extrusion die into the furnace and heat it up to 380 °C, and keep it warm for 30 min for heat treatment.

[0124] S6: Hot-extrude the samples obtained from heat treatment. Among them, the extrusion ratio is 40:1 and the extrusion speed is 0.3 m / min to obtain a Cu-coated Ti particle-reinforced magnesium matrix composite material.

[0125] Comparative Example 1

[0126] The difference between this comparative example and Example 1 lies in that instead of using Ti powder coated with Cu powder on the surface, pure commercial AZ91 magnesium alloy powder is directly mixed in a double-cone mixer and the subsequent steps S4 to S6 are carried out in sequence. That is, the finally obtained material does not contain a reinforcing phase.

[0127] Comparative Example 2

[0128] The difference between this comparative example and Example 1 lies in that there is no S1, and the Ti powder coated with Cu powder in S2 is replaced with the Ti powder in S1 of Example 1. That is, in the finally obtained composite material, the reinforcing phase is only the Ti reinforcing phase.

[0129] Comparative Example 3

[0130] The difference between this comparative example and Example 1 lies in that the preparation method selects the stir-casting method.

[0131] Specifically: Heat the magnesium alloy to 600 °C, add the composite reinforcing particles into the magnesium alloy melt, stir for 5 min at a stirring speed of 800 r / min, and then cast and form.

[0132] Comparative Example 4

[0133] The difference between this comparative example and Example 1 lies in that the mass of the Ti powder coated with Cu powder is 30% of the magnesium matrix powder.

[0134] Comparative Example 5

[0135] The difference between this comparative example and Example 1 lies in that high-energy ball milling is used in S3 and the ball-to-material ratio is 10:1.

[0136] Comparative Example 6

[0137] The difference between this comparative example and Example 1 lies in that in S1, the average particle size of the Ti powder is 500 nm.

[0138] Comparative Example 7

[0139] The difference between this comparative example and Example 1 lies in that in S1, the mass of the Cu powder is 1% of the Ti powder.

[0140] Comparative Example 8

[0141] The difference between this comparative example and Example 1 lies in that in S1, the mass of the Cu powder is 20% of the Ti powder.

[0142] Comparative Example 9

[0143] The difference between this comparative example and Example 1 is that: in S1, the voltage of electro-explosion deposition is 2 Kv.

[0144] Comparative Example 10

[0145] The difference between this comparative example and Example 1 is that: in S1, the voltage of electro-explosion deposition is 15 Kv.

[0146] Comparative Example 11

[0147] The difference between this comparative example and Example 1 is that: the composite powder obtained in S2 is directly subjected to hot pressing and sintering without undergoing the S3 process.

[0148] Comparative Example 12

[0149] The difference between this comparative example and Example 1 is that: the Ti powder with a Cu powder coating on its surface obtained in S1 and the magnesium-based matrix powder are directly ball-milled in S3 without undergoing the S2 process.

[0150] Comparative Example 13

[0151] The difference between this comparative example and Example 1 is that: in S4, the temperature of hot pressing and sintering is 650 °C.

[0152] Comparative Example 14

[0153] The difference between this comparative example and Example 1 is that: in S4, the temperature of hot pressing and sintering is 350 °C.

[0154] Comparative Example 15

[0155] The difference between this comparative example and Example 1 is that: in S4, the pressure of hot pressing and sintering is 15 MPa.

[0156] Comparative Example 16

[0157] The difference between this comparative example and Example 1 is that: in S4, the pressure of hot pressing and sintering is 45 MPa.

[0158] Comparative Example 17

[0159] The difference between this comparative example and Example 1 is that: the sintered part obtained in S4 is directly subjected to hot extrusion in S6 without undergoing S5.

[0160] Comparative Example 18

[0161] The difference between this comparative example and Example 1 is that: in S6, the hot extrusion speed is 1.2 m / min.

[0162] Test Example

[0163] ①. The magnesium-based composites obtained from Example 1 and Comparative Examples 1-2 were subjected to structural and property comparisons, and the results are as follows. Figures 1 to 6 as shown.

[0164] Figure 1 and Figure 2 Corresponding to Example 1, it can be seen from Figure 1 that for the magnesium-based composite prepared by using micron Ti particles coated with nano Cu on the surface as the reinforcement phase, a transition layer was formed around the Ti particles. After intense hot extrusion, the Ti particles remained spherical, proving that the stress on the composite was relatively uniform, and the coating layer played a role in transmitting the load and buffered the mechanical property differences between the reinforcing particles and the matrix. Figure 2 shows the microstructure (distribution of internal dislocations and twins) of the magnesium-based composite reinforced with nano Cu-coated micron Ti. It can be seen from Figure 2 that there are a large number of dislocations and twins around the AlCuMg phase, and their synergistic effect helps to further improve the mechanical properties of the composite.

[0165] Figure 3 is the fracture morphology of the magnesium-based composite provided in Example 1. It can be observed from Figure 5 that the soft-core AlCuMg phase helps the hard-core Ti phase to stably exist in the magnesium matrix.

[0166] Figure 4 is the fracture morphology of the magnesium-based material provided in Comparative Example 1. It can be directly observed from Figure 3 that there is delamination fracture and the plasticity of the material is poor.

[0167] Figure 5 is the fracture morphology of the magnesium-based composite provided in Comparative Example 2. It can be observed from Figure 4 that there are pits where the Ti particles are pulled out, indicating weak interfacial bonding.

[0168] Figure 6 For the magnesium-based materials of Example 1 (corresponding to AZ91+Cu@Ti), Comparative Example 1 (corresponding to AZ91), and Comparative Example 2 (corresponding to AZ91+Ti), the stress-strain curves at room temperature were obtained according to the standard of GBT32498-2016 Test Method for Tensile Test of Metal Matrix Composites at Room Temperature. It can be seen from Figure 6 that the strength, especially the plasticity, of the dual-heterostructure particle-reinforced magnesium-based composite corresponding to Example 1 was greatly improved compared with Comparative Examples 1 and 2.

[0169] ②. Performance testing

[0170] The mechanical properties of the magnesium-based composites obtained from Examples 1-6 and Comparative Examples 1-18 were tested with reference to "GB / T 1177 2018", and the results are shown in Table 1.

[0171] Table 1 Results of Mechanical Properties

[0172]

[0173]

[0174] As can be seen from Table 1, for the composite material composition, compared with the pure magnesium alloy material, the magnesium matrix composite material reinforced with micron Ti particles can improve the strength and plasticity of the composite material to a certain extent, but the plasticity still cannot reach the application standard. And the Cu-coated Ti particle-reinforced magnesium matrix composite material designed and prepared in this application can controllably form a hard-core Ti reinforcement phase region and an in-situ reaction soft-core AlCuMg reinforcement phase region at the interface, and the strength and plasticity of the obtained magnesium matrix composite material are significantly improved. For the powder metallurgy preparation method, when choosing an excessive amount of nano-Cu-coated micron Ti particles, Cu is prone to agglomerate at the interface of the composite material, affecting the interface bonding situation. And when using the high-energy ball milling process, the surface-coated powder is easily knocked off by the grinding balls, resulting in the detachment and failure of the coated powder, and a dual heterogeneous structure of hard core and soft core cannot be formed, ultimately affecting the mechanical properties.

[0175] In summary, the magnesium matrix composite material provided in this application uses dual heterogeneous structure metal reinforcement particles, introduces a hard-core reinforcement phase region and a soft-core reinforcement phase region formed in-situ on the surface, which can effectively improve the interfacial bonding force between the reinforcement particles and the matrix, thereby improving the mechanical properties of the composite material, such as tensile strength, yield strength, and elongation. Its preparation method is simple and easy to operate, and is suitable for industrial production. The obtained composite material can be used to prepare aerospace products, rail transit products, or products in the 3C field.

[0176] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A magnesium-based composite material, characterized in that, the magnesium-based composite material comprises a magnesium-based matrix and reinforcing phases, and the reinforcing phases include hard-core reinforcing phases and soft-core reinforcing phases; wherein, the composition of the magnesium-based matrix contains at least Mg and Al; the hard-core reinforcing phase includes a Ti reinforcing phase, and the soft-core reinforcing phase includes an AlCuMg reinforcing phase; the AlCuMg reinforcing phase is formed by in-situ reaction of Cu particles with the magnesium-based matrix, part of the soft-core reinforcing phase is located on the outer surface of the hard-core reinforcing phase and at the grain boundaries of the magnesium-based matrix, and the remaining soft-core reinforcing phase enters the grains of the magnesium-based matrix; in the magnesium-based composite material, the volume fraction of the hard-core reinforcing phase is 3-50%; the volume fraction of the soft-core reinforcing phase is 2-10%; the preparation of the magnesium-based composite material includes: mixing Ti powder coated with Cu powder on the surface with magnesium-based matrix powder to obtain composite powder; successively performing ball milling, hot pressing sintering, heat treatment and hot extrusion on the composite powder to enable the Cu powder to react with the magnesium-based matrix to generate soft-core reinforcing phases; the preparation of the Ti powder coated with Cu powder on the surface includes: using an electro-explosion deposition method to coat Cu powder on the surface of the Ti powder; the conditions of the electro-explosion deposition include: the initial voltage is 5-10 kV, and the deposition distance is 20-30 mm; the mass of the Cu powder is 2-10% of the mass of the Ti powder; the average particle size of the Ti powder is 10-30 μm; the average particle size of the Cu powder is 10-100 nm.

2. The magnesium-based composite material according to claim 1, characterized in that, by mass percentage, the magnesium-based matrix contains 3-10% of Al and 0.5-1% of Zn, and the balance is Mg.

3. A preparation method of the magnesium-based composite material according to claim 1 or 2, characterized in that, comprises the following steps: mixing Ti powder coated with Cu powder on the surface with magnesium-based matrix powder to obtain composite powder; successively performing ball milling, hot pressing sintering, heat treatment and hot extrusion on the composite powder to enable the Cu powder to react with the magnesium-based matrix to generate the soft-core reinforcing phases; the preparation of the Ti powder coated with Cu powder on the surface includes: using an electro-explosion deposition method to coat Cu powder on the surface of the Ti powder; the conditions of the electro-explosion deposition include: the initial voltage is 5-10 kV, and the deposition distance is 20-30 mm.

4. The preparation method according to claim 3, characterized in that, the mixing of the Ti powder coated with Cu powder on the surface and the magnesium-based matrix powder is carried out under the condition of 20-40 r / min for 5-8 h.

5. The preparation method according to claim 4, characterized in that, the mass of the Ti powder coated with Cu powder on the surface is 5-20% of the mass of the magnesium-based matrix powder.

6. The preparation method according to claim 3, characterized in that, the conditions of the ball milling include: the ball milling speed is 50-80 r / min, the ball-to-material ratio is 1:1-3:1, and the ball milling time is 3-5 h.

7. The preparation method according to claim 3, characterized in that, The conditions for hot-press sintering include: the sintering temperature is 400 - 500 °C, the sintering pressure is 20 - 40 MPa, and the heat preservation time is 30 - 60 min.

8. The preparation method according to claim 7, characterized in that, the heating rate is 4 - 6 °C / min.

9. The preparation method according to claim 3, characterized in that, the conditions for heat treatment include: the heat treatment temperature is 350 - 400 °C, and the heat treatment time is 30 - 60 min.

10. The preparation method according to claim 3, characterized in that, the conditions for hot extrusion include: the extrusion ratio is 20:1 - 40:1, and the extrusion speed is 0.3 - 0.8 m / min.

11. An application of the magnesium-based composite material according to claim 1 or 2, characterized in that, the magnesium-based composite material is used for preparing aerospace products, rail transit products or products in the 3C field.

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