CN117626076A - Magnesium-based composite material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a magnesium-based composite material, a preparation method and application thereof, and belongs to the technical field of magnesium-based materials. The composite material comprises a magnesium-based matrix and a reinforcing phase, wherein the reinforcing phase comprises a hard core reinforcing phase and a soft core reinforcing phase; the magnesium-based matrix comprises at least Mg and Al; the hard core reinforcement phase comprises a Ti reinforcement phase and the soft core reinforcement phase comprises an AlCuMg reinforcement phase. The composite material uses double heterostructure metal reinforced particles, and introduces a hard core reinforced phase and a soft core reinforced phase formed on the surface in situ, so that the interfacial binding force between the reinforced particles and a matrix can be effectively improved, and the mechanical properties of the composite material, such as tensile strength, yield strength, elongation and the like, are improved. The preparation method comprises the following steps: mixing Ti powder coated with Cu powder on the surface with magnesium-based matrix powder, and performing ball milling, hot-pressing sintering, homogenization heat treatment and hot extrusion. The method is simple, easy to operate and suitable for industrial production. The composite material can be used in the fields of aerospace, rail transit or 3C.

Description

A kind of magnesium-based composite material and its preparation method and application

Technical field

The present invention relates to the technical field of magnesium-based materials, and specifically to a magnesium-based composite material and its preparation method and application.

Background technique

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, interface failure is one of the main limiting factors affecting the strength and plasticity of magnesium-based composites. During the plastic deformation process of the matrix, since the stress will be concentrated at the interface between the particles and the matrix, pores can quickly nucleate and coalesce into cracks at the interface, leading to premature failure of particle-reinforced magnesium matrix composites. To prevent interface failure, it is necessary to limit the plastic strain of the metal matrix, but this conflicts with the requirement of high ductility.

In view of this, the present invention is proposed.

Contents of the invention

The purpose of this application is to provide a magnesium-based composite material and its preparation method and application to solve or improve the above technical problems.

This application can be implemented as follows:

In a first aspect, this 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;

Among them, the components of the magnesium-based matrix contain at least Mg and Al; at least part of the soft-core reinforcement phase is located on the outer surface of the hard-core reinforcement phase, the hard-core reinforcement phase includes a Ti reinforcement phase, and the soft-core reinforcement phase includes an AlCuMg reinforcement phase.

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

And/or, based on mass percentage, the magnesium-based matrix contains 3-10% Al and 0.5-1% Zn, with the balance being Mg.

In a second aspect, the present application provides a method for preparing a magnesium-based composite material according to the aforementioned embodiment, including the following steps: mixing Ti powder with Cu powder on the surface and magnesium-based matrix powder to obtain a composite powder; Ball milling, hot pressing sintering, heat treatment and hot extrusion are performed in sequence to generate a soft-core reinforcement phase between the Cu powder and the magnesium-based matrix.

In an optional embodiment, the preparation of the Ti powder whose surface is coated with Cu powder includes: using an electric explosion deposition method to coat the surface of the Ti powder with Cu powder.

In an optional embodiment, the conditions for electroexplosion deposition include: initial voltage is 5-10Kv, and deposition distance is 20-30mm.

In an optional embodiment, the mass of Cu powder is 2-10% of the Ti powder.

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

In an optional embodiment, the Cu powder is nanoscale; preferably, the average particle size of the Cu powder is 10-100 nm.

In an optional embodiment, the Ti powder coated with Cu powder on the surface is mixed with the magnesium-based matrix powder for 5-8 hours at 20-40 r/min.

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

In an optional embodiment, the ball milling conditions 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 hours.

In an optional embodiment, the conditions for hot press sintering include: sintering temperature of 400-500°C, sintering pressure of 20-40MPa, and holding time of 30-60 minutes.

In an optional embodiment, the heating rate is 4-6°C/min.

In an optional embodiment, the heat treatment conditions include: the heat treatment temperature is 350-400°C, and the heat treatment time is 30-60 minutes.

In an optional embodiment, the hot extrusion conditions include: the extrusion ratio is 20:1-40:1, and the extrusion speed is 0.3-0.8m/min.

In a third aspect, this application provides an application of the magnesium-based composite material according to the aforementioned embodiment, such as for the preparation of aerospace products, rail transit products or products in the 3C field.

The beneficial effects of this application include:

The magnesium-based composite material provided by this application uses double heterostructure metal reinforced particles, and introduces a hard-core reinforced phase region and a soft-core reinforced phase region, which can effectively improve the interface bonding force between the reinforced particles and the matrix, thereby improving the mechanical properties of the composite material. Such as tensile strength, yield strength and elongation, etc. The preparation method is simple, easy to operate and suitable for industrial production. The obtained composite materials can be used to prepare aerospace products, rail transit products or products in the 3C field.

Description of drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the drawings required to be used 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 do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a structural morphology diagram of the magnesium-based composite material obtained in Example 1;

Figure 2 is a microstructure diagram of the magnesium-based composite material obtained in Example 1;

Figure 3 is a fracture morphology diagram of the magnesium-based composite material obtained in Example 1;

Figure 4 is a fracture morphology diagram of the magnesium-based material obtained in Comparative Example 1;

Figure 5 is a fracture morphology diagram of the magnesium-based composite material obtained in Comparative Example 2;

Figure 6 is the stress strain curve of the magnesium-based materials of Example 1, Comparative Example 1 and Comparative Example 2.

Detailed ways

In order 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 described clearly and completely below. If the specific conditions are not specified in the examples, the conditions should be carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.

The magnesium-based composite material provided by this application and its preparation method and application will be described in detail below.

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.

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

In some embodiments, the magnesium-based matrix may contain 3-10% Al and 0.5-1% Zn by mass percentage, with the balance being Mg.

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

The above-mentioned AlCuMg reinforcement phase is generated by the reaction between Cu and Mg and Al in the magnesium-based matrix, preferably by the in-situ reaction between Cu and Mg and Al in the magnesium-based matrix.

In some embodiments, all of the soft-core reinforcement phase is located on the outer surface of the hard-core reinforcement phase.

In other embodiments, part of the soft-core reinforcement phase is located on the outer surface of the hard-core reinforcement phase (this part of the soft-core reinforcement phase can be understood as being located at the grain boundary of the magnesium-based matrix), and the remaining soft-core reinforcement phase enters the grain boundary of the magnesium-based matrix. Within the crystal. That is, in the latter embodiment, the soft-core reinforcement phase is distributed simultaneously in the grain boundaries and within the grains of the magnesium-based matrix.

The above-mentioned soft-core reinforcement phase located in the crystals of the magnesium-based matrix can hinder dislocation movement and lead to the formation of a large number of dislocation cells; the soft-core reinforcement phase located at the grain boundaries of the magnesium-based matrix can generate a large number of twins near the grain boundaries. All soft core reinforcement phase areas can buffer the stress concentration caused by the difference between the reinforcement particles and the matrix, significantly improving the strength and plasticity of the composite material.

As a reference, in magnesium-based composites, the volume fraction of the hard core reinforcement phase can be 3-50%, such as 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35 %, 40%, 45% or 50%, etc., can also be any other value in the range of 3-50%.

In magnesium-based composites, the volume fraction of the soft core reinforcement phase can be 2-10%, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., also Can be any other value in the range 2-10%.

It should be noted that in the magnesium-based composite material, other volumes other than the hard-core reinforcement phase and the soft-core reinforcement phase correspond to the volume of the unreacted magnesium-based matrix.

Following the above, the magnesium-based composite material provided by this application uses double heterostructure metal reinforced particles (wherein double heterogeneous refers to Cu and Ti), introducing a hard core reinforcement phase and a soft core reinforcement phase formed in situ on the surface, which can effectively improve the Enhance the interface bonding force between particles and matrix, thereby improving the mechanical properties of composite materials, such as tensile strength, yield strength and elongation.

Accordingly, the present application provides a method for preparing the above-mentioned magnesium-based composite material, which may include the following steps: mixing Ti powder with Cu powder on the surface and magnesium-based matrix powder to obtain composite powder; ball milling the composite powder in sequence , hot pressing sintering, heat treatment and hot extrusion, so that the Cu powder and the magnesium-based matrix generate a soft core reinforcement phase.

By coating the surface of primary heterogeneous Ti particles with secondary Cu particles, the primary reinforced Ti particles are metal elements immiscible with the Mg matrix, and the secondary reinforced Cu reacts with the magnesium matrix in situ to generate a second phase (AlCuMg phase) . Among them, the internal reinforced Ti particles are the hard core area, and the surface AlCuMg phase is the soft core area. The soft core area carries smaller plastic strains than the hard core area to prevent premature interface failure. The dual heterostructure produces unique double-layer heterogeneous deformation that can induce strengthening and hardening to produce high strength and high plasticity.

As a reference, the preparation of Ti powder whose surface is coated with Cu powder may include: using an electric explosion deposition method to coat Cu powder on the surface of the Ti powder.

Using this method for coating can achieve metallurgical bonding and improve the firmness of the coating. Chemical deposition may easily generate impurities, affecting the effect.

Among them, the initial voltage of electric explosion deposition can be 5-10Kv, such as 5Kv, 6Kv, 7Kv, 8Kv, 9Kv or 10Kv, etc., or it can be any other value in the range of 5-10Kv.

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

If the deposition voltage is too low, nanoscale Cu coating on the Ti surface cannot be achieved; if the deposition voltage is too high, the powder will burn and the preset coating layer cannot be formed. If the deposition distance is too far, the deposition efficiency may be too low; if the deposition distance is too close, the coating may be uneven.

The mass of the above-mentioned Cu powder can be 2-10% of the Ti powder, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., or it can be 2-10% Any other value within the % range.

Through the above 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), thereby causing the Cu particles to react in situ with the magnesium matrix to generate discontinuous distribution of Second phase. It should be emphasized that if too much nano-Cu particles are used, Cu will easily agglomerate at the interface of the composite material, affecting the interface bonding; and too much Cu will also reduce the corrosion performance of the material. If the amount of nano-Cu particles used is too small, it will lead to poor interface bonding.

In this application, the Ti powder is micron-sized. 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, etc.

Cu powder is nanoscale. 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, etc.

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

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

In this application, the mass of 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., It can also be any other value in the range of 5-20%.

According to this dosage range, it can not only stably form a phase with better interface bonding, but also ensure the effect of Ti-reinforced phase.

In this application, the rotation speed of the ball mill can be 50-80r/min, such as 50r/min, 55r/min, 60r/min, 65r/min, 70r/min, 75r/min or 80r/min, etc., or it can be 50- Any other value within the range of 80r/min.

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 value within the range of 1:1-3:1 value.

It should be noted that by controlling the ball-to-material ratio within the above range, each component can be effectively mixed uniformly. If a high-energy ball milling process is used, the surface-coated powder will easily fall off when hit by the grinding ball, causing the coated powder to break away and fail, failing to form a dual heterogeneous structure of hard core and soft core, ultimately affecting the mechanical properties.

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

In this application, the Ti powder coated with Cu powder on the surface and the magnesium-based matrix powder are mechanically mixed first, so that the Ti powder coated with Cu powder on the surface can be slightly adhered to the surface of the magnesium-based matrix, and then through the ball milling process, the Ti powder can be slightly adhered to the surface of the magnesium-based matrix. The Ti powder coated with Cu powder is more uniformly and firmly combined with the magnesium-based matrix.

In addition, in magnesium-based composite materials, the reinforcements play the role of supporting most of the external loads, while the matrix plays the role of connecting, transmitting and distributing the load 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 bond plays a critical impact on the mechanical properties of magnesium-based composites. Generally speaking, the two key factors that determine the interface bonding strength are: the wettability of the reinforcement and the matrix material and the interface reaction.

Regarding the wettability between the reinforcement and the matrix material, adding alloy elements, external energy fields and surface modification of the reinforcement can improve the wettability. This application adopts the ball milling method. During the ball milling process, the hard balls impact, grind and stir the composite powder, causing changes in the organization, structure and properties of the material, which can improve the wettability and particle distribution at the same time. Moreover, Ti is active in nature, and oxides are often easily generated on the surface, resulting in high oxygen content at the interface of the final composite material, affecting the mechanical properties. Surface coating with nano-Cu can solve this technical problem and reduce the oxygen content of composite materials.

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, or any other value within the range of 400-500°C.

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

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

The temperature rise 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.

The above hot pressing sintering process is carried out in a sintering furnace with a protective atmosphere (such as argon atmosphere, etc.). After the sintering is completed, the furnace is cooled to the temperature.

If the hot-pressing sintering temperature is too high, it will easily cause the grains to grow too large and reduce their mechanical properties; if the hot-pressing sintering temperature is too low, it will easily lead to elements not yet diffusing and the AlCuMg phase at the interface unable to form. If the hot-pressing sintering pressure is too high, stress concentration within the material will lead to premature fracture and failure; if the hot-pressing sintering pressure is too low, it will easily produce more holes in the material, making it difficult to form a dense composite material. If the hot-pressing sintering time is too long, the grains may grow too large and reduce their mechanical properties; if the hot-pressing sintering time is too short, the elements may not have diffused and the AlCuMg phase at the interface cannot be formed. This application is conducive to the uniform diffusion of elements by controlling the heating rate at 4-6°C/min.

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

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

It should be noted that the structure after hot-pressing sintering is usually prone to problems such as segregation and uneven structure. Heat treatment can help alleviate component segregation and also play a certain solid solution enhancement role.

In this 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, etc., or it can also be 20:1-40:1. Any other value within the range of 40:1.

The extrusion speed can be 0.3-0.8m/min, such as 0.3m/min, 0.4m/min, 0.5m/min, 0.6m/min, 0.7m/min or 0.8m/min, etc. It can also be 0.3-0.8 Any other value within the m/min range.

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 structural deformation, the finer the grains, and the stronger the deformation coordination ability, thereby improving the 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 during the extrusion process will decrease and the deformation ability will decrease. Difference.

Following the above, the preparation method of magnesium-based composite materials provided in this application has at least the following characteristics:

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

(2) Using the powder metallurgy preparation method, the interface in-situ reaction process and interface products are 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 to improve the interface bonding force .

(3) The interface hard core Ti reinforced phase region has high strength and plasticity, and the interface soft core AlCuMg reinforced phase region is distributed in the grain boundaries and within the grains of the magnesium alloy matrix. Impeding dislocation movement within the grain leads to the formation of a large number of dislocation cells; a large number of twins are generated near the grain boundaries. The soft core area can buffer the stress concentration caused by the difference between the reinforced particles and the matrix, significantly improving the strength and plasticity of the composite material.

(4) In magnesium alloys, because there are no reinforcing particles to hinder the extension and expansion of cracks, the fracture mode is mainly delamination fracture; titanium particles strengthen magnesium-based composites, and titanium particles can hinder the expansion of cracks, but titanium does not react with magnesium. The interface bonding is weak, and cracks are torn along the edges of particles and matrix; double heterostructure metal particles reinforce magnesium-based composites, and there is a composition gradient between the reinforcement phase and the matrix. The fracture mode is a large number of dislocation cells entangled and entangled, causing micropore aggregation and fracture. .

(5) Appropriate interfacial reaction is conducive to improving the wettability between the reinforcement and the matrix, forming a stable interface structure, thereby producing a stronger interface bond. According to the strength of the interface with the magnesium matrix, the interface reactions are divided into the following three categories: First, there is no interface reaction, such as the traditional Ti particle reinforced Mg alloy. In this case, the wettability between the reinforcement and the magnesium matrix is poor, and the interface bonding strength is weak. The second is strong interface reaction. Strong interfacial reactions can lead to damage to the integrity of the reinforcement. The reaction products also tend to gather at the interface to form a brittle layer, which can form cracks under load, causing a sharp decline in the performance of the composite material. The third one is the weak interface reaction in this application. A discontinuous AlCuMg phase is formed at the interface, and the reaction products are more than those without interface reaction. At this time, the integrity of the reinforcement is better, and the reaction product formed can effectively transfer the load on the matrix to the reinforcement to improve the strength of the composite material. And it can prevent cracking due to stress concentration and improve the plasticity of the material.

In addition, this application also provides an application of the above-mentioned magnesium-based composite material, which can be used, for example, to prepare aerospace products, rail transit products or products in the 3C field.

The features and performance of the present invention will be described in further detail below with reference to examples.

Example 1

This embodiment provides a magnesium-based composite material, and its preparation method includes:

S1: Use the electric explosion deposition method to coat the surface of the Ti powder with Cu powder to obtain Ti powder with the surface coated with Cu powder.

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 2wt% of Ti powder. The voltage of electric explosion deposition is 8Kv, and the deposition distance is 25mm.

S2: Mix the Ti powder with Cu powder on the surface and the magnesium matrix powder in a double cone mixer at 30 r/min for 8 hours to obtain a composite powder.

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

S3: Put the above composite powder into a ball mill and conduct ball milling for 4 hours with a ball-to-material ratio of 2:1 and a ball milling speed of 60r/min.

S4: Put the material obtained by ball milling into a sintering furnace with an argon atmosphere, heat it up to 500°C at a heating rate of 5°C/min, and hot-press and sinter it under a pressure of 30MPa for 1 hour, and then cool to room temperature in the furnace.

S5: Put the sintered part obtained by hot pressing and sintering into the furnace together with the extrusion die, heat it to 400°C, and keep it warm for 1 hour for heat treatment.

S6: Hot-extrude the sample obtained by heat treatment. Among them, the extrusion ratio is 30:1 and the extrusion speed is 0.8m/min, and a Cu-coated Ti particle-reinforced magnesium-based composite material is obtained.

Example 2

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

Example 3

The difference between this embodiment and Embodiment 1 is that in S3, the ball-to-material ratio is 3:1.

Example 4

The difference between this embodiment and Embodiment 1 is that in S4, the temperature of hot pressing sintering is 480°C.

Example 5

This embodiment provides a magnesium-based composite material, and its preparation method includes:

S1: Use the electric explosion deposition method to coat the surface of the Ti powder with Cu powder to obtain Ti powder with the surface coated with Cu powder.

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 electric explosion deposition is 5Kv, and the deposition distance is 20mm.

S2: Mix the Ti powder with Cu powder on the surface and the magnesium matrix powder in a double cone mixer at 20 r/min for 6 hours to obtain a composite powder.

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

S3: Put the above composite powder into a ball mill and conduct ball milling for 5 hours with a ball-to-material ratio of 1:1 and a ball milling speed of 50r/min.

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 hot-press and sinter it under a pressure of 20MPa for 40 minutes, and then cool to room temperature in the furnace.

S5: Put the sintered part obtained by hot pressing and sintering into the furnace together with the extrusion die, heat it to 350°C, and keep it warm for 40 minutes for heat treatment.

S6: Hot-extrude the heat-treated sample. Among them, the extrusion ratio is 20:1 and the extrusion speed is 0.5m/min, and a Cu-coated Ti particle-reinforced magnesium-based composite material is obtained.

Example 6

This embodiment provides a magnesium-based composite material, and its preparation method includes:

S1: Use the electric explosion deposition method to coat the surface of the Ti powder with Cu powder to obtain Ti powder with the surface coated with Cu powder.

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 electric explosion deposition is 10Kv, and the deposition distance is 30mm.

S2: Mix the Ti powder with Cu powder on the surface and the magnesium matrix powder in a double cone mixer at 40 r/min for 5 hours to obtain a composite powder.

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

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

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 hot-press and sinter it under a pressure of 40MPa for 30 minutes, and then cool to room temperature in the furnace.

S5: Put the sintered part obtained by hot pressing and sintering into the furnace together with the extrusion die, heat it to 380°C, and keep it warm for 30 minutes for heat treatment.

S6: Hot-extrude the heat-treated sample. Among them, the extrusion ratio is 40:1, the extrusion speed is 0.3m/min, and a Cu-coated Ti particle-reinforced magnesium-based composite material is obtained.

Comparative example 1

The difference between this comparative example and Example 1 is that Ti powder coated with Cu powder on the surface is not used, but pure AZ91 commercial magnesium alloy powder is directly mixed in a double cone mixer, and subsequent S4 to S6 are performed in sequence. step. That is, the final resulting material contains no reinforcing phase.

Comparative example 2

The difference between this comparative example and Example 1 is that there is no S1, and the Ti powder whose surface is coated with Cu powder in S2 is replaced with the Ti powder in S1 of Example 1. That is to say, in the final composite material, the reinforcing phase is only the Ti reinforcing phase.

Comparative example 3

The difference between this comparative example and Example 1 is that the preparation method is stir casting.

Specifically: the magnesium alloy is heated to 600°C, the composite reinforced particles are added to the magnesium alloy melt, the stirring time is 5 minutes, the stirring speed is 800r/min, and then poured into shape.

Comparative example 4

The difference between this comparative example and Example 1 is that the mass of the Ti powder whose surface is coated with Cu powder is 30% of the magnesium-based matrix powder.

Comparative example 5

The difference between this comparative example and Example 1 is that S3 adopts high-energy ball milling, and the ball-to-material ratio is 10:1.

Comparative example 6

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

Comparative example 7

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

Comparative example 8

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

Comparative example 9

The difference between this comparative example and Example 1 is that in S1, the voltage of electric explosion deposition is 2Kv.

Comparative example 10

The difference between this comparative example and Example 1 is that in S1, the voltage of electric explosion deposition is 15Kv.

Comparative example 11

The difference between this comparative example and Example 1 is that the composite powder obtained in S2 was directly hot-pressed and sintered without performing the S3 process.

Comparative example 12

The difference between this comparative example and Example 1 is that the Ti powder whose surface is coated with Cu powder and the magnesium-based matrix powder obtained in S1 are directly ball-milled in S3, and the S2 process is not performed.

Comparative example 13

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

Comparative example 14

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

Comparative example 15

The difference between this comparative example and Example 1 is that in S4, the pressure of hot press sintering is 15MPa.

Comparative example 16

The difference between this comparative example and Example 1 is that in S4, the pressure of hot press sintering is 45MPa.

Comparative example 17

The difference between this comparative example and Example 1 is that the sintered part obtained in S4 was directly subjected to hot extrusion in S6, and S5 was not performed.

Comparative example 18

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

Test example

①. Conduct structural comparison and performance comparison on the magnesium-based composite materials obtained in Example 1 and Comparative Examples 1-2. The results are shown in Figures 1 to 6.

Figures 1 and 2 correspond to Example 1. It can be seen from Figure 1 that micron Ti particles with nano-Cu surface coating are selected as the reinforcing phase to prepare the magnesium-based composite material, and a transition layer is formed around the Ti particles. After intense hot extrusion, the Ti particles are still spherical, which proves that the composite material is relatively uniformly stressed, and the coating layer plays a role in transmitting the load and buffering the difference in mechanical properties between the reinforced particles and the matrix. Figure 2 shows the microstructure (distribution of internal dislocations and twins) of nano-Cu coated micron Ti-reinforced magnesium-based composites. It can be seen from Figure 2 that there are a large number of dislocations and twins around the AlCuMg phase, which is synergistic. It helps to further improve the mechanical properties of composite materials.

Figure 3 shows the fracture morphology of the magnesium-based composite material provided in Example 1. From Figure 5, it can be observed that the soft-core AlCuMg phase helps the hard-core Ti phase to stably exist in the magnesium matrix.

Figure 4 shows the fracture morphology of the magnesium-based material provided in Comparative Example 1. From Figure 3, it can be directly observed that delamination fracture occurs, and the material has poor plasticity.

Figure 5 shows the fracture morphology of the magnesium-based composite material provided in Comparative Example 2. From Figure 4, it can be observed that the holes where the Ti particles are pulled out are weak, and the interface bonding is weak.

Figure 6 shows 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). They were tested at room temperature according to GBT32498-2016 metal matrix composite tensile test. The stress-strain curve at normal temperature is obtained according to the method standard. As can be seen from Figure 6, the strength, especially the plasticity, of the double heterostructure particle-reinforced magnesium-based composite material corresponding to Example 1 has been greatly improved compared to Comparative Examples 1 and 2. .

②、Performance test

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

Table 1 Mechanical property results

As can be seen from Table 1, regarding the composition of composite materials, compared with pure magnesium alloy materials, the use of micron Ti particles to reinforce magnesium-based composite materials can improve the strength and plasticity of composite materials to a certain extent, but the plasticity still does not meet the application standards. . In this application, the Cu-coated Ti particle-reinforced magnesium-based composite material is designed and prepared. The interface can be controlled to form a hard-core Ti reinforcement phase region and an in-situ reaction soft-core AlCuMg reinforcement phase region. The resulting magnesium-based composite material has excellent strength and plasticity. have significantly improved. For the powder metallurgy preparation method, excessive nano-Cu is selected to coat micron Ti particles. Cu is easy to agglomerate at the interface of the composite material, affecting the interface bonding. However, using the high-energy ball milling process, the surface-coated powder is easily struck and fallen off by the grinding ball, causing the coated powder to break away and fail, failing to form a dual heterogeneous structure of hard core and soft core, ultimately affecting the mechanical properties.

To sum up, the magnesium-based composite material provided by this application uses double heterostructure metal reinforced particles, introduces a hard core reinforced phase region and a soft core reinforced phase region formed in situ on the surface, which can effectively improve the interface bonding between the reinforced particles and the matrix. force, thereby improving the mechanical properties of composite materials, such as tensile strength, yield strength and elongation. The preparation method is simple, easy to operate and suitable for industrial production. The obtained composite materials can be used to prepare aerospace products, rail transit products or products in the 3C field.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A magnesium-based composite material, characterized in that the magnesium-based composite material comprises a magnesium-based matrix and a reinforcing phase, the reinforcing phase comprising a hard core reinforcing phase and a soft core reinforcing phase;

wherein the magnesium-based matrix comprises at least Mg and Al; at least a portion of the soft-core reinforcement phase is located on an outer surface of the hard-core reinforcement phase, the hard-core reinforcement phase comprising a Ti reinforcement phase, and the soft-core reinforcement phase comprising an AlCuMg reinforcement phase.

2. The magnesium-based composite material according to claim 1, wherein the volume fraction of the hard core reinforcing phase in the magnesium-based composite material is 3-50%; the volume fraction of the soft-core reinforcing phase is 2-10%;

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

3. A method of preparing a magnesium-based composite material according to claim 1 or 2, comprising the steps of: mixing Ti powder coated with Cu powder on the surface with magnesium-based matrix powder to obtain composite powder; and sequentially performing ball milling, hot-pressing sintering, heat treatment and hot extrusion on the composite powder to enable the Cu powder and the magnesium-based matrix to generate the soft core reinforcing phase.

4. A production method according to claim 3, wherein the production of the Ti powder surface-coated with Cu powder comprises: coating Cu powder on the surface of Ti powder by adopting an electro-explosion deposition mode;

preferably, the conditions of the electro-explosive deposition include: the initial voltage is 5-10Kv, and the deposition distance is 20-30mm;

preferably, the mass of the Cu powder is 2-10% of the Ti powder;

preferably, the Ti powder is of micron order; more preferably, the Ti powder has an average particle size of 10 to 30 μm;

preferably, the Cu powder is nano-scale; more preferably, the average particle size of the Cu powder is 10-100nm.

5. The method according to claim 3, wherein the mixing of the Ti powder coated with Cu powder on the surface with the magnesium-based matrix powder is performed under the condition of 20-40r/min for 5-8 hours;

preferably, the mass of the Ti powder surface-coated with the Cu powder is 5-20% of that of the magnesium-based matrix powder.

6. The method of claim 3, wherein the ball milling conditions include: the ball milling rotating speed is 50-80r/min, the ball-material ratio is 1:1-3:1, and the ball milling time is 3-5h.

7. A method of preparing according to claim 3, wherein the hot press sintering conditions include: the sintering temperature is 400-500 ℃, the sintering pressure is 20-40MPa, and the heat preservation time is 30-60min;

preferably, the rate of temperature rise is 4-6deg.C/min.

8. A method of preparing according to claim 3, wherein the conditions of the heat treatment include: the heat treatment temperature is 350-400 ℃, and the heat treatment time is 30-60min.

9. A method of preparing according to claim 3, wherein the conditions of hot extrusion include: the extrusion ratio is 20:1-40:1, and the extrusion speed is 0.3-0.8m/min.

10. Use of a magnesium-based composite material according to claim 1 or 2 for the preparation of aerospace products, rail traffic products or 3C field products.