CN112143925A - Preparation method of high-strength high-plasticity titanium-magnesium composite material - Google Patents

Abstract

The invention discloses a preparation method of a high-strength and high-plastic titanium-magnesium composite material. A spark plasma sintering method (SPS) is used to prepare a titanium-particle-reinforced magnesium-based composite material. In vivo, the interface with the matrix is more closely combined and the structure is denser. The metallographic structure shows that there is no second phase Mg ₁₇ Al ₁₂ in the magnesium matrix distributed along the grain boundary, which significantly reduces the internal stress of the grain and makes the grain before fracture. It can withstand large deformation and improve the plasticity of magnesium matrix composites. The titanium grain boundary is serrated, which increases the resistance of crack propagation, thereby inhibiting the occurrence of dislocations, weakening the interaction of dislocations, improving the macroscopic plastic deformation ability of the material, and giving full play to the strength of titanium particles in the magnesium matrix. toughening effect. Therefore, the magnesium-based composite material prepared by the present invention has both high strength and high plasticity. The preparation process of the invention is simple, the production time is short, and the cost is low, which is favorable for industrialized large-scale production.

Description

A kind of preparation method of high-strength and high-plastic titanium-magnesium composite material

technical field

The invention relates to the technical field of magnesium alloy composite materials, in particular to a preparation method of a high-strength and high-plasticity titanium-magnesium composite material.

Background technique

At present, with the transformation of my country's economy, the development of high-tech industries requires a large number of high-performance materials, and magnesium alloys have become the most promising lightweight structural materials due to their high specific strength and specific stiffness. For magnesium matrix composites, microstructure control is one of the most effective ways to strengthen and toughen materials. Ceramic particles are often used as reinforcements, which not only increase the hardness of the material, but also significantly reduce the plasticity of the material. This defect limits The application of magnesium matrix composites. Contrary to the ceramic reinforcement, the crystallographic and physical characteristics of titanium are closer to those of magnesium, and titanium is not prone to adverse interfacial reactions with the magnesium matrix to form a brittle interface reaction layer; if titanium particles are used as reinforcements, titanium , Magnesium is a hexagonal structure and the crystal planes are more closely combined, so that a better joint surface and fewer internal defects can be obtained. At the same time, the element titanium itself has excellent plasticity and strong stiffness, which is conducive to obtaining both strength and plasticity. Magnesium matrix composites.

In order to solve the above problems, scientists at home and abroad have also done a lot of work. For example, the invention patent CN200510027718.0 discloses a preparation method for preparing titanium particle reinforced magnesium matrix composite material by powder metallurgy, but through cold pressing sintering, the sintering process is complicated, the production efficiency is low, and the performance of the prepared material is not high, which limits the its scope of use. Invention patent CN201710807978.2 discloses a titanium particle as a reinforced magnesium-based composite material and a preparation method thereof. The composite material uses titanium particles as a reinforcing base and a magnesium alloy as a matrix. The metal powders are respectively weighed and mixed according to the proportions. It is dried in a vacuum environment, cold-pressed, solidified at high temperature and then annealed for many times. The production process is complex, the energy consumption is high, and it is not conducive to the large-scale production of enterprises. More importantly, the composite material prepared by the above method has a second phase Mg ₁₂ Al ₁₇ on the magnesium grain boundary, which is a hard and brittle phase, which will reduce the plasticity of the magnesium matrix to a certain extent and limit its application range.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of a high-strength and high-plastic titanium-magnesium composite material, which solves the problems of the complicated technological process, low production efficiency, high energy consumption and poor plasticity of the existing titanium-magnesium composite material. good question.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme: a preparation method of a high-plastic titanium-magnesium composite material, the steps are as follows:

1) The ingredients are based on mass percentage, including 5~15% of pure titanium powder, and the balance is magnesium alloy powder;

2) The ingredients are mechanically ball-milled in an argon atmosphere, using anhydrous ethanol as the ball-milling medium, and after ball-milling for a certain period of time, take out, vacuum-dry, and sieve to obtain powder; in this way, the ball-milling environment is argon, which can prevent magnesium to the greatest extent. Oxidation phenomenon of powder, eliminating the interference of external factors.

3) The powder obtained in step 2) is placed in a graphite mold and then sintered by current-activated discharge plasma in the process of pressurization to obtain a high-plastic titanium-magnesium composite material; the titanium grain boundary in the high-plastic titanium-magnesium composite material is a It is serrated and does not contain the second phase Mg ₁₇ Al ₁₂ distributed along the grain boundaries.

In this way, the titanium powder and magnesium powder in this ratio can directly make Ti through mechanical ball milling, and can be evenly distributed on the Mg matrix, and the alloy powder mixed uniformly after ball milling can minimize the accumulation of titanium particles on the grain boundary of the magnesium matrix. The sintering process is simple and time-consuming, and the strength and plasticity of the sintered products are higher.

Preferably, the particle size of the titanium powder is 20-37 μm; the particle size of the magnesium alloy powder is 50-74 μm. In this way, preselecting fine micron-sized titanium particles is beneficial to the sufficient alloying of alloying elements.

Preferably, the ball-to-material ratio is 10:1, the ball milling speed is 50 rpm, and the ball milling time is 2-3 h. In this way, the ball-to-material ratio is the ratio of the mass of the grinding ball (ball milling medium) to the mass of the material (total amount of element powder). It will reduce the ball milling effect; if the ball-to-material ratio is too large, the impact and friction in the ball mill will increase, which will increase the power consumption, and at the same time will increase the wear of the ball mill tank, damage the instrument, and the metal chips that fall off during ball milling will also be mixed into the material.

Preferably, during the spark plasma sintering, the temperature is raised to 450-550°C at a heating rate of 40-60°C/min, kept at a pressure of 55-80 MPa for 10-30min, and then cooled to room temperature at 50°C/min. In this way, the sintering pressure and temperature have a great influence on the density of the sintered body. Spark plasma sintering (SPS) is adopted. Compared with the traditional sintering method, this method uses the action of strong pulse current to promote the solidification of the material. It has the characteristics of fast heating rate and low sintering temperature, which can effectively reduce the sintering temperature of magnesium alloys. In addition, the sample has a short holding time at the high temperature stage, which can effectively solve the problem of the reduction of material density due to the Kirkendall effect. If the sintering pressure is too high, the particles will be deformed or broken, and the equipment will be more demanding; if the sintering pressure is too low, the density of the compact will be insufficient, and the densification of the sintered body will be difficult to complete, resulting in pores between the particles, and the sintered block will not be easy to achieve. forming. If the sintering temperature is too high or the holding time is too long, the grains will be coarse and the mechanical properties of the composite material will be reduced; if the sintering temperature is too low or the holding time is too short, the internal stress caused by the sintering process cannot be fully released; The composite material sintered block with fine grain and excellent performance can be obtained.

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

1. Among the magnesium-based composite materials prepared by the present invention, spark plasma sintering (SPS) is used for the first time to prepare titanium-particle-reinforced magnesium-based composite materials. The particle size of titanium is controllable, and the average particle size is about 13 μm. The control makes the micron-sized titanium particles distributed in the matrix, and the interface with the matrix is more closely combined and the structure is denser. Transmission electron microscopy shows that there is no second phase Mg ₁₇ Al ₁₂ in the magnesium matrix distributed along the grain boundary, so that the grains are not fractured before fracture. It can withstand a large amount of deformation, significantly reduce the stress inside the grain, and improve the plasticity of magnesium matrix composites. The titanium grain boundary is serrated, which increases the resistance of crack propagation, thereby inhibiting the occurrence of dislocations, weakening the interaction of dislocations, improving the macroscopic plastic deformation ability of the material, and giving full play to the strength of titanium particles in the magnesium matrix. toughening effect. Therefore, the magnesium-based composite material prepared by the present invention has both high strength and high plasticity.

2. Compared with the traditional hot pressing sintering method, the preparation process of the present invention is simple, the production time is short, and the cost is low, which is beneficial to industrialized large-scale production, and also solves the problems of high cost and long production process time in the cold pressing sintering method. , has good application prospects and economic benefits.

3. In the structure of the magnesium-based composite material of the present invention, the use of micron-sized titanium particles as the reinforcement of magnesium combined with the SPS method can effectively solve the problem of reduced material density due to the Kirkendall effect. It is more dense and uniform, the interface is more closely combined, and the interface reaction is weaker; compared with the hot-pressed sintered AZ91 composite material, the magnesium-based composite material prepared by the present invention has higher yield strength, compressive strength and ultimate compressive strength, The ultimate compressive strength can reach 442.2MPa, which significantly improves the stability of the material and has broad application prospects in the fields of automobile, energy and biomedicine.

Description of drawings

FIG. 1 is a microstructure diagram of the magnesium-based composite material prepared in Example 1. FIG.

FIG. 2 is a metallographic diagram of the magnesium-based composite material prepared in Example 1. FIG.

Detailed ways

The present invention will be further described in detail below in conjunction with the examples. In the following examples, the experimental methods are not specifically described, they are all routine operations, and the reagents used are common commercially available.

One, a kind of preparation method of high-strength and high-plasticity titanium-magnesium composite material

Example 1

1) Weigh 2.5g of Ti element powder with particle size <37 μm and 47.5g of AZ91 alloy powder with particle size <74 μm;

2) Load the raw materials weighed in step 1) into a ball mill, add 500g stainless steel balls, first evacuate and then fill with argon, repeat three times of evacuation and inflation, and then perform ball milling in an argon environment at a rotational speed of 50rpm, after ball milling for 2h, the powder is mixed uniformly to obtain mixed powder;

3) After placing the mixed powder obtained in step 2) in a graphite mold, spark plasma sintering was activated by current during the pressurization process, and the temperature was raised to 500°C at a heating rate of 50°C/min. The temperature is lowered to room temperature at 50° C./min to finally obtain a magnesium-based composite material, and the composite material is then made into a sample to obtain a prefabricated sample.

The Ti particle-reinforced AZ91 composite material obtained in this example was observed under an optical microscope, and the results are shown in FIG. 1 . It can be seen from the figure that the micron-sized titanium particles are white and distributed in the black magnesium matrix, and the shape and size of the titanium particles are irregular. The occurrence of dislocations is inhibited, the interaction of dislocations is weakened, the macroscopic plastic deformation ability of the material is improved, and the role of titanium particles in strengthening and toughening in the magnesium matrix is fully exerted.

Figure 2 shows the metallographic phase of the Ti particle-reinforced AZ91 composite obtained in this example. It can be seen from the figure that the black part is titanium particles, the white part is α magnesium, and there is no second phase Mg ₁₇ Al ₁₂ formed at the grain boundary of magnesium, thereby indirectly improving the plasticity of magnesium matrix composites.

Example 2

1) Weigh 5 g of Ti element powder with particle size <37 μm and 45 g of AZ91 alloy powder with particle size <74 μm;

2) Load the raw materials weighed in step 1) into a ball mill, add 500g stainless steel balls, first evacuate and then fill with argon, repeat three times of evacuation and inflation, and then perform ball milling in an argon environment at a rotational speed of 50rpm, after ball milling for 2h, the powder is mixed uniformly to obtain mixed powder;

3) After placing the mixed powder obtained in step 2) in a graphite mold, spark plasma sintering was activated by current during the pressurization process, and the temperature was raised to 500°C at a heating rate of 50°C/min. The temperature is lowered to room temperature at 50° C./min to finally obtain a magnesium-based composite material, and the composite material is then made into a sample to obtain a prefabricated sample.

Example 3

1) Weigh 7.5g of Ti element powder with particle size <37 μm and 42.5g of AZ91 alloy powder with particle size <74 μm;

2) Load the raw materials weighed in step 1) into a ball mill, add 500g stainless steel balls, first evacuate and then fill with argon, repeat three times of evacuation and inflation, and then perform ball milling in an argon environment at a rotational speed of 50rpm, after ball milling for 2h, the powder is mixed uniformly to obtain mixed powder;

3) After placing the mixed powder obtained in step 2) in a graphite mold, spark plasma sintering was activated by current during the pressurization process, and the temperature was raised to 500°C at a heating rate of 50°C/min. The temperature is lowered to room temperature at 50° C./min to finally obtain a magnesium-based composite material, and the composite material is then made into a sample to obtain a prefabricated sample.

2. Performance testing

1. The microstructure characteristics of the magnesium matrix composite material prefabricated samples prepared in Examples 1-3 were measured, and the results are shown in Table 1.

Table 1

It can be seen from Table 1 that the Ti particle reinforced AZ91 composite material prepared by the present invention has good compressive strength and elongation, wherein the compressive yield strength can reach more than 155 MPa, and the compressive strength can reach more than 437 MPa, which improves the The stability and wear resistance of the composite material; the compression plasticity can reach more than 21%, and the magnesium matrix composite material has a large amount of deformation, thereby ensuring its high plasticity.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (4)

1. a preparation method of high-strength and high-plastic titanium-magnesium composite material, is characterized in that, step is as follows: 1) The ingredients are based on mass percentage, including 5~15% of pure titanium powder, and the balance is magnesium alloy powder; 2) The ingredients are mechanically ball-milled in an argon atmosphere, using anhydrous ethanol as the ball-milling medium, and after ball-milling for a certain period of time, take out and vacuum dry and sieve to obtain powder; 3) After placing the powder obtained in step 2) in a graphite mold, electric current-activated discharge plasma sintering is performed to obtain a high-strength and high-plasticity titanium-magnesium composite material; the titanium crystal grains in the high-plasticity titanium-magnesium composite material are The boundaries are serrated and do not contain the second phase Mg ₁₇ Al ₁₂ distributed along the grain boundaries. 2 . The method for preparing a high-strength and high-plastic titanium-magnesium composite material according to claim 1 , wherein the particle size of the titanium powder is 20-37 μm; the particle size of the magnesium alloy powder is 50-74 μm. 3 . 3. The preparation method of the high-strength and high-plastic titanium-magnesium composite material according to claim 1, wherein the ball-to-material ratio is 5~10:1, preferably 10:1, and the ball milling speed is 50~100rpm, preferably 50 rpm, and the ball milling time is 2-3 h. 4. the preparation method of the high-strength and high-plastic titanium-magnesium composite material according to claim 1, is characterized in that, described spark plasma sintering is to keep under the pressure of 55～80MPa, preferably 80MPa, at 40～60 ℃/min The heating rate was increased to 450~550°C, kept for 10~30min, and then cooled to room temperature at 50°C/min.

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