阅读说明：本技术 一种Mg-Li基复合材料用增强体表面改性及其预制体制备方法 (Surface modification of reinforcement for Mg-Li-based composite material and preparation method of prefabricated body of reinforcement ) 是由 赵登川 王金良 宋相家 吴国清 于 2020-05-19 设计创作，主要内容包括：本发明公开了一种Mg-Li基复合材料用增强体表面改性及其预制体制备方法,属于复合材料及其制备技术领域。本发明的制备方法首先将超细增强体颗粒与基体合金元素颗粒进行长时复合球磨,使其表面被基体元素充分包覆,从而提高与基体合金间的润湿性；通过施加导引棒,对表面改性后的增强体颗粒进行多道次变径角挤压,实现超细粉体高密实度的压制成型与剪切变形一次进行,有效排除超细颗粒中的气体、改善基体元素对增强体颗粒的包覆效应以及提高颗粒的分散度等。工艺全程采用惰性气体保护,有效降低超细粉体氧化问题,获得高纯净度的增强体颗粒预制体,且制备工艺流程短,利于工业化生产。(The invention discloses reinforcement surface modification for an Mg-Li-based composite material and a preparation method of a prefabricated body of the reinforcement surface modification, and belongs to the technical field of composite materials and preparation thereof. The preparation method of the invention firstly carries out long-term composite ball milling on ultrafine reinforcement particles and matrix alloy element particles to ensure that the surfaces of the ultrafine reinforcement particles and the matrix alloy element particles are fully coated by matrix elements, thereby improving the wettability between the ultrafine reinforcement particles and the matrix alloy; by applying the guide rod, the surface-modified reinforcement particles are subjected to multi-pass variable-diameter-angle extrusion, so that the high-compactness press forming and the shearing deformation of the ultrafine powder are carried out at one time, the gas in the ultrafine particles is effectively removed, the coating effect of matrix elements on the reinforcement particles is improved, the dispersion degree of the particles is improved, and the like. The whole process of the process adopts inert gas protection, the problem of oxidation of superfine powder is effectively reduced, the high-purity reinforcement particle prefabricated body is obtained, the preparation process flow is short, and the industrial production is facilitated.)

1. A method for modifying the surface of a reinforcement for Mg-Li-based composite material and preparing a prefabricated body thereof is characterized in that:

firstly, mixing ultrafine reinforcement particles and matrix alloy element particles in proportion to form mixed powder, then carrying out composite ball milling for 2-8 h to obtain pre-composite powder, and carrying out inert gas protection in the ball milling process;

and secondly, placing a guide rod into a reducing angle extrusion die, then placing the pre-composite powder prepared in the first step on the guide rod, and carrying out multi-pass reducing angle extrusion forming to obtain the reinforcement prefabricated body.

2. The surface modification of a reinforcement for Mg-Li-based composite material and the method for producing a preform thereof according to claim 1, characterized in that: the inert gas is argon gas with the pressure of 0.1 MPa.

3. The surface modification of a reinforcement for Mg-Li-based composite material and the method for producing a preform thereof according to claim 1, characterized in that: the ultrafine reinforcement particles are intermetallic compound YAl₂The particle size distribution range is 0.01 to 1 μm.

4. The surface modification of a reinforcement for Mg-Li-based composite material and the method for producing a preform thereof according to claim 1, characterized in that: the matrix alloy element particles are pure Mg powder, and the particle size distribution range is 100-200 meshes.

5. The surface modification of a reinforcement for Mg-Li-based composite material and the method for producing a preform thereof according to claim 1, characterized in that: the mass ratio of the ultrafine reinforcement particles to the matrix alloy elements is 1: 1-2: 1.

6. The surface modification of a reinforcement for Mg-Li-based composite material and the method for producing a preform thereof according to claim 1, characterized in that: the guide rod is made of magnesium-lithium alloy.

7. The surface modification of a reinforcement for Mg-Li-based composite material and the method for producing a preform thereof according to claim 1, characterized in that: extruding and forming the reducing angle at the extrusion temperature of 25-300 ℃ for 1-3 times; the inner angle of the reducing angle extrusion die is adoptedφIs 90 to 120 degrees and has an external angleψ20-60 degrees, and the ratio of variation to diameter is 1.1: 1-6: 1; in the extrusion process, argon atmosphere protection is implemented around the reducing angle extrusion die.

8. The surface modification of the reinforcement for Mg-Li-based composite material and the method for producing the preform thereof according to claim 7, characterized in that: the extrusion temperature of the variable-diameter-angle extrusion molding is 100 ℃, and the extrusion pass is three times; inner angle of reducing angle extrusion dieφIs 90 degrees and an external angleψThe diameter-changing ratio is 1.1:1 at 20 degrees.

9. A reinforcement surface-modified preform for a Mg-Li-based composite material, characterized in that: the composite material is prepared by the method of any one of claims 1 to 8, the density of the prefabricated body reaches 98 percent, and the ultrafine reinforcement particles are uniformly embedded in the matrix alloy element powder.

Technical Field

The invention belongs to the technical field of composite materials and preparation thereof, and particularly relates to reinforcement surface modification for an Mg-Li-based composite material and a preparation method of a prefabricated body of the reinforcement surface modification.

Background

The Mg-Li alloy is used as the lightest metal structure material, has high specific strength, specific rigidity and excellent plasticity, and has wide application prospect in the fields of aerospace, military industry and the like. However, the magnesium-lithium alloy has the intrinsic properties of high component activity, low elastic modulus, strength attenuation caused by room-temperature overaging and the like, so that the engineering preparation and the wide application of the alloy are limited. Intermetallic compound YAl₂The particles are used as a reinforcement, and when the magnesium-lithium alloy is introduced, a transition type interface layer with a certain thickness is formed with the matrix alloy, the interface layer can effectively relieve stress concentration in the material deformation process, inhibit crack initiation at the interface in the material deformation process, and realize a strong pinning effect on the matrix alloy, so that the toughness of the magnesium-lithium alloy is improved. Particularly, when the particle size of the reinforcement is thinned to submicron or nanometer, the mechanical property of the composite material is greatly improved, and compared with a matrix alloy, the tensile strength can be improved by 250-350%. However, in the actual smelting preparation of the particle-reinforced magnesium-lithium-based composite material, because the chemical activity of matrix alloy elements Mg and Li is high and the smelting temperature is relatively high, ultrafine reinforcement particles cannot be effectively added into a Mg-Li alloy melt; in addition, as the reinforcement particle size decreases, its surface energy increases, prone to spontaneous condensation, and exhibits strong agglomeration characteristics in the matrix alloy, thereby deteriorating material properties. In this regard, how to ensure that the ultrafine reinforcement particles are effectively incorporated into the molten Mg-Li matrix alloy and improve the uniformity of its distribution is the preparation of ultra-light, high-strength YAl₂The key of the particle reinforced magnesium lithium based composite material.

The patent document with application number 201510179706.3 proposes a Mg-Li based composite material and a preparation method thereof, and the document proposes that ultrafine reinforcement YAl is prepared₂Carrying out surface modification on the particles and Mg powder by composite ball milling, and then pressing the pre-composite powder into the composite powder by multiple working procedures of cold pressing, hot extrusion and the likeAnd (3) prefabricating a block, and finally adding the reinforcement particles into the molten magnesium-lithium matrix alloy in the form of the prefabricated block to prepare the Mg-Li based composite material. Although the method solves the problem of adding superfine particles externally, the preparation process is relatively complicated, and particularly, the hot extrusion link needs 9-16 times, so that the time consumption is long, and the method is not favorable for large-scale production; the composite ball milling time is short (the longest time is 2 h), and Mg powder is difficult to realize on YAl₂Complete coating of the particles; in addition, the YAl is pressed by adopting the conventional unidirectional straight compact mode₂Mg pre-composite powder, hard YAl₂The particles are more easily agglomerated, and the particles can be bridged with each other to form a skeleton structure, so that air is remained in the prefabricated body, the melt is easily oxidized during smelting, local bumping is generated, the melt and the reinforcement are splashed, and potential safety hazards are brought to smelting.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, designs a short-flow high-efficiency preparation method, and produces YAl in a large scale₂the/Mg prefabricated body is ultra-light high-strength YAl₂The reinforced magnesium-lithium based composite material provides a reinforcement preform with high particle dispersion degree, high purity and high compactness. The preparation method specifically comprises the following steps.

Firstly, mixing ultrafine reinforcement particles and matrix alloy element particles in proportion to form mixed powder, then carrying out composite ball milling to form pre-composite powder, wherein the composite ball milling time is 2-8 h, and carrying out inert gas protection in the ball milling process.

And secondly, placing a guide rod into a reducing angle extrusion die, then placing the pre-composite powder prepared in the first step on the guide rod, and carrying out multi-pass reducing angle extrusion forming to obtain the reinforcement prefabricated body.

Optionally, the inert gas is 0.1MPa argon.

Optionally, the ultrafine reinforcement particles are an intermetallic YAl₂The particle size distribution range is 0.01 to 1 μm.

Optionally, the matrix alloy element particles are pure Mg powder, and the particle size distribution range is 100-200 meshes.

Optionally, the mass ratio of the ultrafine reinforcement particles to the matrix alloy elements is 1: 1-2: 1.

Optionally, the material of the guide rod is magnesium-lithium alloy.

Optionally, carrying out extrusion forming on the variable-diameter angle at the extrusion temperature of 25-300 ℃ for 1-3 times; the inner angle of the reducing angle extrusion die is adoptedφIs 90 to 120 degrees and has an external angleψ20-60 degrees, and the ratio of variation to diameter is 1.1: 1-6: 1; in the extrusion process, argon atmosphere protection is implemented around the reducing angle extrusion die.

Preferably, the extrusion temperature of the variable-diameter-angle extrusion molding is 100 ℃, and the extrusion pass is three times; inner angle of reducing angle extrusion dieφIs 90 degrees and an external angleψThe diameter-changing ratio is 1.1:1 at 20 degrees.

The invention also provides a prefabricated body for modifying the surface of the reinforcement for the Mg-Li-based composite material, which is prepared by the method, the compactness of the prefabricated body reaches 98 percent, and the ultrafine reinforcement particles are uniformly embedded in the matrix alloy element powder.

According to the invention, by adopting the reducing angle extrusion technology, the powdery reinforcement particles are pressed into the massive reinforcement preform, so that the gas in the powder is effectively discharged, the compactness of the preform and the dispersion degree of the reinforcement particles are improved, and the method has the following outstanding advantages.

(1) And long-time composite ball milling is beneficial to the surface modification of the reinforcement particles. By prolonging the composite ball milling time of the superfine reinforcement particles and the matrix alloy elements, the superfine reinforcement particles and the matrix alloy elements are repeatedly crushed → welded → crushed under the continuous impact action of a grinding ball, so that the reinforcement particles can be further refined, element diffusion can be generated between the reinforcement particles and matrix alloy element powder, the coating effect of the matrix alloy elements on the reinforcement particles is enhanced, and the agglomeration of the reinforcement particles in the smelting process of the composite material is reduced.

(2) The guide rod is used for guiding and is beneficial to the extrusion forming of the reducing angle of the superfine powder. Because the reducing angle extrusion die is a through channel, the powder can not be pressed and molded, a guide rod is arranged at the front end of the pressed powder, and a reverse acting force (relative extrusion force) is applied to the extruded powder, so that the superfine powder is pressed and molded; the guide rod is made of magnesium-lithium alloy, has good plasticity and is easy to deform, the powder formed by pressing can be guided to finish variable-diameter-angle extrusion while the powder is ensured to be formed, mutual permeation occurs between the magnesium-lithium guide rod and the pre-composite powder during extrusion, the plasticity of the powder is increased, and then multi-pass extrusion is realized.

(3) The powder forming and deformation are integrated, which is beneficial to the dispersion of the particles of the reinforcement. The variable-diameter angle extrusion powder technology of the invention integrates equal-diameter angle extrusion technology and conventional extrusion technology, realizes the integration of superfine powder molding and large plastic deformation, and performs the first extrusion, and then performs the compaction molding → shearing → stretching 3 times of plastic deformation on the superfine pre-composite powder to obtain a reinforcement prefabricated body; and (3) extruding in the subsequent pass, wherein the prefabricated body is subjected to upsetting → shearing → elongation for 3 times of plastic deformation and is continuously subjected to the coupling action of multidirectional forces such as extrusion, shearing and the like, so that the particles of the reinforcement body in the prefabricated body are distributed more uniformly.

(4) And multiple deformation means are combined, so that the compactness of the reinforcement prefabricated body is improved. The conventionally pressed reinforcement prefabricated body has low compactness and air remained in the reinforcement prefabricated body, and when the molten magnesium-lithium matrix alloy is added, the melt is locally subjected to bumping, so that the melt and the reinforcement are splashed, and element burning loss and smelting potential safety hazards are caused. The technology for extruding the powder with the variable diameter angle effectively destroys a skeleton structure formed by bridging among particles in the process of pressing the superfine powder by large plastic deformation such as pressing, shearing, elongation and the like, thereby reducing cavities and gases in a prefabricated body, and further improving the compactness of the prefabricated body to more than 98 percent.

(5) Short-flow operation is favorable for large-scale production of the reinforcement prefabricated body. The invention directly carries out reducing angle extrusion on the pre-compounded powder after the compound ball milling, saves the preforming links such as cold pressing, hot pressing and the like compared with the prior preparation technology, and realizes the short-flow preparation from the powder directly to the prefabricated body; in addition, the variable-diameter angle extrusion is adopted, so that continuous powder adding and continuous multi-time extrusion can be realized, and the large-scale mass production is facilitated.

Drawings

FIG. 1 is a flow chart of the surface modification of the reinforcement for the Mg-Li-based composite material and the preparation process of the preform thereof.

FIG. 2 is YAl in the preparation process of the present invention₂Complex of/MgMorphology of the particles after ball milling (SEM image).

FIG. 3 is a schematic view of reducing angle extrusion in the manufacturing process of the present invention.

FIG. 4 is YAl prepared by the present invention₂Phase analysis of the/Mg preform (XRD pattern).

FIG. 5 is YAl prepared by the present invention₂Microstructure image of/Mg preform (SEM image).

In the figure: 1-YAl₂Mg pre-composite powder; 2-a guide rod; 3-reducing angle extrusion die; 4-extruding the rod.

Detailed Description

For the purpose of enhancing the understanding of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and examples, which are only used for explaining the present invention and are not to be construed as limiting the scope of the present invention.

The invention provides a surface modification method of a reinforcement for an Mg-Li-based composite material and a preparation method of a prefabricated body of the reinforcement, and the preparation method comprises the following steps as shown in a flow chart of figure 1.

Firstly, mixing ultrafine reinforcement particles and matrix alloy element particles in proportion to form mixed powder, then carrying out composite ball milling to form pre-composite powder, wherein the composite ball milling time is 2-8 h, and carrying out inert gas protection in the ball milling process.

And secondly, placing a guide rod into a reducing angle extrusion die, then placing the pre-composite powder prepared in the first step on the guide rod, and carrying out multi-pass reducing angle extrusion forming to obtain the reinforcement prefabricated body.

The invention provides a prefabricated body for surface modification of a reinforcement for an Mg-Li-based composite material and a preparation method thereof, which prolong the composite ball milling time to at most 8 hours compared with the prior art and are beneficial to surface modification of the reinforcement and particle dispersion. The mode of guiding by the guide rod is beneficial to the variable-diameter-angle extrusion molding of the superfine powder, and after multi-pass extrusion, the superfine pre-composite powder is compacted and molded → sheared → elongated for 3 times of plastic deformation in each pass, so that the reinforcement prefabricated body with high compactness can be obtained. The ball milling time is properly prolonged, the preforming links such as cold pressing, hot pressing and the like in the subsequent preparation process are reduced, and the short-flow preparation from powder to a preform is realized; in addition, the variable-diameter angle extrusion is adopted, so that continuous powder adding and continuous multi-time extrusion can be realized, and the large-scale mass production is facilitated.

The whole preparation process adopts inert gas protection, and the inert gas is argon with the pressure of 0.1MPa, so that the oxidation of ultrafine reinforcement particles and matrix alloy elements is prevented.

The ultrafine reinforcement particles in the invention are intermetallic compound YAl₂The particle size distribution range is 0.01 to 1 μm. The matrix alloy element particles are pure Mg powder, and the particle size distribution range is 100-200 meshes. The mass ratio of the selected superfine reinforcement particles to the matrix alloy elements is 1: 1-2: 1. Furthermore, the material of the guide rod is magnesium-lithium alloy, and can be LA143 magnesium-lithium alloy or LA141 magnesium-lithium alloy.

Optionally, carrying out variable-diameter-angle extrusion molding at the extrusion temperature of 25-300 ℃ for 1-3 times; the inner angle of the reducing angle extrusion die is adoptedφIs 90 to 120 degrees and has an external angleψ20-60 degrees, and the ratio of variation to diameter is 1.1: 1-6: 1; in the extrusion process, argon atmosphere protection is implemented around the reducing angle extrusion die.

YAl prepared as described above₂the/Mg prefabricated body has pure components and reinforced YAl₂Basically, the single particles are independently distributed, the surface of the single particles is coated by Mg powder, particularly after the single particles are extruded at a variable diameter angle, the particles of the reinforcement body are distributed more uniformly, and the prefabricated body is more compact.

The invention also provides a prefabricated body for modifying the surface of the reinforcement for the Mg-Li-based composite material, the compactness of the prefabricated body reaches 98 percent, and the ultrafine reinforcement particles are uniformly embedded in the matrix alloy element powder.