CN1298879C - Process of preparing composite material with in situ particle inhancing magnesium base - Google Patents

Abstract

The invention discloses a process for preparing in-situ particle-reinforced magnesium-aluminum matrix composite material, which belongs to the field of materials. In the present invention, the reinforcement phase is firstly selected according to the wettability between the matrix and the reinforcement phase, and the aluminum-magnesium matrix composite material matrix with a particle weight percentage of 10 to 30% is prepared by the mixed salt method, and then the magnesium matrix material is smelted, and then selected Melt temperature, the aluminum-magnesium matrix composite material matrix is added to the magnesium melt, stirred, and finally the melt is left to stand before pouring and casting. The invention utilizes the mixed salt method to prepare the matrix of aluminum-magnesium based composite material, supplemented by stirring, remelts and dilutes the matrix of aluminum-magnesium based composite material, and prepares a reinforced phase with fine particles, uniform distribution, good interface bonding, and good The magnesium-based composites with mechanical and physical properties have opened up a new way for the preparation of magnesium-based composites and laid a good foundation for the wide application of magnesium-based composites in the industrial field.

Description

Preparation process of in-situ particle reinforced magnesium matrix composites

technical field

The invention relates to a process for preparing a particle-reinforced magnesium-based composite material, in particular to a process for preparing an in-situ reinforced magnesium-based composite material by using an aluminum-based composite material prefabricated matrix, and belongs to the field of materials.

Background technique

In recent years, due to concerns about the environment, energy and other issues, research on magnesium-based composites has become a hot spot in the field of materials. Magnesium-based composites are one of the lightest structural materials, and magnesium-based composites have high specific strength, specific stiffness, good castability and dimensional stability, good resistance to electromagnetic interference and shielding, and good damping properties. It has good vibration damping performance, little impact on the environment, no pollution, and its waste recycling rate is as high as 85%. It has broad application prospects in aerospace, automobile, computer, network, communication and other fields. Therefore, the development of magnesium-based composite materials is of great significance to energy saving and environmental protection. At present, the preparation of magnesium-based composite materials is mainly reinforced by adding particles or fibers. The particle size of the added reinforcement particles is large, the interface bonding is not good, and the mechanical properties of the material are relatively poor; the preparation process of fiber-reinforced composite materials is complicated and the cost is relatively high. In actual production and application restricted in. In-situ preparation of composite materials is a preparation method developed in recent years. It has the characteristics of fine particle size, good interface bonding, and high comprehensive performance of materials. It has achieved more success in the preparation of aluminum-based composite materials. After literature search, it was found that Chinese Patent Publication No.: 1441076, patent name: process for preparing in-situ reinforced magnesium-based composite materials by mixed salt method, this patent proposes a process for preparing magnesium-based composite materials by mixed salt method, and the process selects a suitable Reinforcement phase reaction system, particle volume fraction, melt temperature, and stirring time prepare a magnesium-based composite material with fine reinforcement phase particles, uniform distribution, good interface bonding, and good mechanical and physical properties. However, due to the relatively large activity of magnesium , easy to react with many substances, so the preparation of magnesium-based composites by the mixed salt method has strict requirements on the reinforcing phase system and the melt reaction temperature, which is not easy to control in actual production, so the preparation of magnesium-based composites by the mixed salt method exists. Certain restrictions.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a process for preparing particle in-situ reinforced magnesium-based composite materials. The present invention utilizes the mixed salt method to in-situ prepare the particle-reinforced aluminum-magnesium-based composite material prefabricated matrix, and then remelts and dilutes the aluminum-magnesium-based composite material prefabricated matrix into the magnesium melt to prepare the reinforced phase with fine particles and uniform distribution The prepared magnesium-based composite material has good interfacial bonding and superior mechanical and physical properties.

The present invention is achieved through the following technical solutions. The present invention first selects the reinforcement phase according to the wettability between the matrix and the reinforcement phase, and prepares an aluminum-magnesium matrix composite material matrix with a particle weight percentage of 10 to 30% by using a mixed salt method. Then smelting the magnesium matrix material, and then selecting the melt temperature, adding the aluminum-magnesium matrix composite material matrix into the magnesium melt, stirring, and finally pouring the melt after standing still, and casting.

Below the inventive method is further described, and processing step is as follows:

(1) The matrix of aluminum-magnesium matrix composites was prepared by mixed salt method. The mixed salt reaction system selects titanium salt, boron salt or zirconium salt to prepare _TiB2 or _ZrB2 grain-reinforced aluminum-magnesium matrix composite material, and the content of the reinforcement grain is 10-30% by weight. Firstly, pure aluminum is melted, and after melting, the temperature of the aluminum melt is kept at 750-850°C, and the pretreated mixed salt is added. The pretreatment of the mixed salt is to dry in the range of 150°C-250°C for 1-3 hours after mixing. After adding the mixed salt, stir, the stirring speed is 200-1000r/min, and the stirring time is 10-60min. After the stirring is completed, the reaction residue on the surface of the melt is scooped out. In order to increase the fluidity of the melt of the aluminum-based composite material, dry magnesium blocks are added in an amount of 5-10% by weight. In order to ensure the content of the reinforcement phase in the magnesium-based composite material, the particle content in the aluminum-magnesium-based composite material matrix must reach a certain value. %.

(2) Smelting of magnesium. Magnesium is extremely flammable, so magnesium smelting is also an important step. During the magnesium smelting process, flux protection or gas protection can be used, and 0.001% to 0.1% by weight of beryllium and 0.05% to 0.2% of calcium are added as flame retardant elements as required.

(3) After the magnesium ingot is melted, the temperature of the magnesium melt is selected, and the prefabricated matrix of the aluminum-magnesium matrix composite material is added into the magnesium melt and stirred.

The density of pure magnesium is relatively small, only 1.74g/cm ³ , and the reinforcing phase is generally ceramic particles. Settling is a critical step. The use of stirring can promote the full dispersion of particles, make the particles dispersed in the magnesium matrix, and prevent the re-agglomeration of particles and the occurrence of sedimentation. Moreover, stirring can promote the melting and dispersion of the aluminum-magnesium matrix composite prefabricated matrix in the magnesium melt, so stirring is a relatively important step. Stirring time intensity and time have a greater impact on the melting and dispersion of the aluminum-magnesium matrix composite matrix and the prevention of particle settlement. The greater the stirring intensity, the better the dispersion of the particles, but it also increases the chance of the particles colliding in the melt. Increase agglomeration, so choosing a suitable stirring speed is very important for the synthesis of materials; short stirring time, uneven dispersion of particles, obvious sedimentation phenomenon, reducing the yield of particles, but too long will increase the oxidation of the melt. The stirring speed selected in the present invention is 200-1000r/min. Stirring time is 10-30min. In the melting process of the prefabricated matrix of aluminum-magnesium matrix composite materials, the temperature of the magnesium melt is also critical. The melt temperature is low, and the matrix of the aluminum-magnesium matrix composite material melts slowly, and it is easy to sink in the lower part of the magnesium melt, which shortens the process time. Prolonged, reduced productivity. If the temperature of the magnesium melt is too high, the oxidation of magnesium will be increased, oxide inclusions will be increased, and the burning loss of magnesium will be increased. The temperature of the magnesium melt in this process is maintained at 720°C to 780°C.

(4) After the stirring is completed, the melt is left to stand, poured, and casted to obtain a magnesium-based composite material. The resting temperature of the melt is 700°C to 740°C, and the resting time is 5 to 20 minutes. Metal mold or sand mold can be used for casting.

Aluminum is the most important alloying element in magnesium alloys. The content of aluminum in magnesium alloys can reach about 12% by weight, and the melting point of aluminum is only 660 ° C. It is easy to melt and diffuse in magnesium, so the operation of melting aluminum in magnesium Relatively simple and easy to implement. Magnesium-aluminum magnesium alloys such as AZ61A, AZ80A, AZ91A, AM100A and other widely used alloys have higher specific strength and specific stiffness than the corresponding aluminum alloys. Moreover, compared with magnesium, aluminum is less active, and in-situ synthesis of many reinforcements can be easily realized in aluminum melts. The melt temperature can also be changed in a wide range, and the composition and quantity of the reinforcement phase can also be well controlled. .

Compared with the prior art, the present invention adds the aluminum-based composite material to the magnesium melt to prepare the magnesium-aluminum-based composite material. Firstly, the aluminum-magnesium-based composite material matrix is prepared by the mixed salt method, supplemented by stirring, and the aluminum-magnesium-based composite material is prepared. The remelting and dilution of the matrix of the magnesium-based composite material prepares a magnesium-based composite material with fine particles of the reinforcing phase, uniform distribution, good interface bonding, and good mechanical and physical properties, which opens up a new way for the preparation of magnesium-based composite materials , which laid a good foundation for the wide application of magnesium-based composites in the industrial field.

Detailed ways

In conjunction with the content of the technology of the present invention, the following examples are provided:

Example 1

Use pure aluminum as the prefabricated matrix material, KBF ₄ and K ₂ TiF ₆ as the mixed salt, and dry it at 150°C for 1 hour. The temperature of the aluminum melt was selected to be 750°C, stirred with a steel paddle at a speed of 200r/min for 10 minutes, and after the stirring was completed, 5% magnesium was pressed in with a bell jar, and an in _- situ reinforced aluminum- Magnesium matrix composite material matrix. When the magnesium melt temperature was maintained at 720°C, the aluminum-magnesium matrix composite material prefabricated matrix was added, the steel slurry was stirred at 200r/min, and the stirring time was _10min . Bit-reinforced magnesium-aluminum matrix composites. The tensile strength of the material is 343-352MPa, and the elongation is 3.8-4.0%.

Example 2

Use pure aluminum as the prefabricated matrix material, KBF ₄ and K ₂ TiF ₆ as the mixed salt, and dry it at 200°C for 2 hours. The temperature of the aluminum melt was selected to be 800°C, and the steel paddle was used to stir at a speed of 600r/min for 30 minutes. After the stirring was completed, 8% magnesium was pressed in with a bell jar, and the in _- situ reinforced aluminum- Magnesium matrix composite material matrix. When the magnesium melt temperature was maintained at 740°C, the aluminum-magnesium matrix composite material prefabricated matrix was added, the steel slurry was stirred at 600r/min, and the stirring time was _20min . Bit-reinforced magnesium-aluminum matrix composites. The tensile strength of the material is 363-378MPa, and the elongation is 4.1-4.8%.

Example 3

Use pure aluminum as the prefabricated matrix material, KBF ₄ and K ₂ ZrF ₆ as the mixed salt, and dry it at 200°C for 2 hours. The temperature of the aluminum melt was selected to be 800°C, stirred with a steel paddle at a speed of 600r/min for 40 minutes, and after the stirring was completed, 8% magnesium was pressed in with a bell jar, and an in _- situ reinforced aluminum- Magnesium matrix composite material matrix. When the magnesium melt temperature was maintained at 740°C, the aluminum-magnesium matrix composite material prefabricated matrix was added, the steel slurry was stirred at 600r/min, and the stirring time was _20min . Bit-reinforced magnesium-aluminum matrix composites. The tensile strength of the material is 333-342MPa, and the elongation is 3.9-4.3%.

Example 4

Use pure aluminum as the prefabricated matrix material, KBF ₄ and K ₂ TiF ₆ as the mixed salt, and dry it at 250°C for 3 hours. The temperature of the aluminum melt was selected to be 850°C, and the steel paddle was used to stir at a speed of 1000r/min for 60 minutes. After the stirring was completed, 10% magnesium was pressed in with a bell jar, and the TiB ₂ in-situ reinforced aluminum- Magnesium matrix composite material matrix. When the magnesium melt temperature was maintained at 780°C, the aluminum-magnesium matrix composite material prefabricated matrix was added, the steel slurry was stirred at 1000r/min, and the stirring time was _30min . Bit-reinforced magnesium-aluminum matrix composites. The tensile strength of the material is 308-321MPa, and the elongation is 3.7-4.2%.

Claims (3)

1. A process for preparing in-situ particle-reinforced magnesium-based composites, characterized in that, firstly, according to the wettability between the matrix and the reinforcing phase, TiB ₂ or ZrB ₂ are selected as the reinforcing phase, and titanium salt and boron salt or zirconium are used Salt and boron salt are used as mixed salts to prepare _TiB2 or _ZrB2 particle-reinforced aluminum-magnesium matrix composite materials. The steps are to first melt pure aluminum, and after melting, the temperature of the aluminum melt is kept at 750-850 ° C, and pretreatment is added After the mixed salt, the pretreatment of the mixed salt is to dry in the range of 150°C to 250°C for 1 to 3 hours after mixing, and then stir after adding the mixed salt. The stirring speed is 200 to 1000r/min, and the stirring time is 10 to 60min, after the stirring is finished, scoop out the reaction residue on the surface of the melt, add 5-10% by weight of dried magnesium ingots to increase the fluidity of the aluminum matrix composite melt, and prepare reinforcing particles by weight percentage by mixed salt method After making 10-30% of the aluminum-magnesium matrix composite material matrix, the magnesium matrix material is smelted, and the melt temperature is selected to be 720-780°C, and the aluminum-magnesium matrix composite material matrix is added to the magnesium melt, and stirred. The speed is 200-1000r/min, the stirring time is 10-30min, and finally the melt is left to stand before pouring and casting. 2. The process for preparing in-situ particle-reinforced magnesium-based composite materials according to claim 1, characterized in that: during the smelting of the magnesium matrix material: use flux protection or gas protection, and add 0.001% to 0.001% by weight 0.1% beryllium and 0.05% to 0.2% calcium are used as flame retardant elements. 3. The process for preparing in-situ particle-reinforced magnesium-based composite materials according to claim 1, characterized in that the resting temperature of the melt is 700°C-740°C, the resting time is 5-20min, and the pouring adopts Metal mold or sand mold.