CN102061421A - In-situ submicron/nanometer particle-reinforced magnesium-matrix composite material and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of preparation of in-situ particle reinforced magnesium-based composite materials, in particular to a new synthetic system of Mg-TiO ₂ -B ₂ O ₃ and a high-strength anti-creep method prepared by melt direct reaction method + mechanical stirring + high-energy ultrasonic technology Variation in situ submicron/nano _TiB particles reinforced magnesium matrix composites. The present invention is realized through the following technical approach. Add the dried reactant TiO ₂ and B ₂ O ₃ powder to the magnesium alloy melt by mechanical stirring, and after adding the reactant, alternately apply high-energy ultrasonic and mechanical stirring to prepare a composite Materials; the technology is simple, especially suitable for the forming of complex parts. The synthetic reinforcement is a high-temperature thermodynamically stable ceramic phase, and the resulting reinforcement particles are small in size, with a scale range of submicron/nano level. The surface of the particles is pollution-free and combined with the matrix interface. good.

Description

An in-situ submicron/nanoparticle reinforced magnesium-based composite material and its preparation method

technical field

The invention relates to the technical field of preparation of in-situ particle reinforced magnesium-based composite materials, in particular to a new synthetic system of Mg-TiO ₂ -B ₂ O ₃ and a high-strength anti-creep method prepared by melt direct reaction method + mechanical stirring + high-energy ultrasonic technology Variation in situ submicron/nano _TiB particles reinforced magnesium matrix composites.

Background technique

Magnesium-based composites are another competitive light metal-based composite after aluminum-based composites. The main features are low density, high specific strength and specific stiffness, and also have good wear resistance, high temperature resistance, and impact resistance. properties, excellent shock absorption performance, good dimensional stability and casting performance, etc., are becoming the most promising composite material in the field of modern high-tech, in advanced electronic devices, aerospace vehicles, mobile communications, precision mechanical devices , medical devices and other fields have broad application prospects, and countries all over the world have invested heavily in research and development.

At present, the research work on particle-reinforced magnesium-based composites mainly focuses on the addition of particle-reinforced magnesium-based composites. However, since the reinforcing particles are added from the outside, there are problems such as poor wettability between the reinforcing particles and the matrix, surface contamination and easy A series of shortcomings such as the generation of fragile by-products, although the surface treatment and surface modification of the reinforced particles are carried out, the process is complicated and the effect is unsatisfactory, which eventually leads to high preparation costs, complicated processes, and poor wettability between the particles and the matrix. The disadvantages such as poor capacitance, unstable performance and low reliability limit the further development of this material.

However, for the particle-reinforced magnesium-based composites prepared by the in-situ endogenous method, since the reinforcement is a thermodynamically stable ceramic phase with high hardness and high elastic modulus generated in situ in the metal matrix, its content, size and distribution can be better It is controlled, eliminating the need for separate synthesis, treatment and addition of reinforcement phases, which has the advantages of simple process and low preparation cost. It is a promising synthesis technology and has absolute advantages in technology and economy; in situ The preparation technology has been developed to the present, and there are more than a dozen methods. However, due to the differences in performance between magnesium alloys and other alloys (aluminum alloys, titanium alloys), such as chemical activity, plasticity, and density, the in-situ preparation technology is used in magnesium-based composites. The application of materials is limited, resulting in the research and development of particle-reinforced magnesium-based composites prepared by in-situ endogenous method in its infancy, and the relevant research reports are not perfect enough. The primary problem at present is to further improve the composite materials. preparation process.

A search of existing technical literature found that there are many literature reports on the preparation technology of magnesium-based composite materials, such as Chinese patent 03116169.3 (named "Preparation of in-situ reinforced magnesium-based composite materials by mixed salt method"). The mixed salt is added to the magnesium melt at a higher temperature and stirred continuously for a long time to obtain an in-situ magnesium-based composite material. However, magnesium is easy to burn at high temperatures, and long-term strong mechanical mixing will lead to severe gas absorption of the melt. This preparation process has certain limitations, and the performance of the prepared composite material needs to be further improved; Chinese patent 200910082583.6 (named "with Melting furnace with mechanical stirring and high-energy ultrasonic treatment and its melting method"), this technology patent combines mechanical stirring and high-energy ultrasonic to melt metal and improve the wettability of composite materials and the distribution of particles. However, in the implementation process of this patented technology, mechanical stirring is carried out first and then high-energy ultrasonic treatment is carried out, which is effective for metal melt treatment and external particle reinforced metal matrix composites, and for in-situ melt reaction synthesis of metal matrix composites As far as the in-situ reaction of the melt is concerned, it mainly includes several processes such as the contact-diffusion of reactants and metal liquid, chemical reaction, and the diffusion of endogenous reinforcing particles. The effect of single application of mechanical stirring or high-energy ultrasound on the in-situ melt reaction is limited. This preparation process has certain limitations, and the performance of the prepared composite material needs to be further improved.

So far, the technology of synthesizing submicron/nanometer TiB ₂ particles reinforced magnesium matrix composites through the in-situ reaction of Mg-TiO ₂ -B ₂ O ₃ reaction system melt has not been reported. Therefore, this patented technology invented Mg-TiO A new synthesis system of ₂ -B ₂ O ₃ and the development of melt direct reaction method + mechanical stirring + high-energy ultrasonic technology prepared a new material of high-strength creep-resistant in-situ submicron/nano TiB ₂ particle-reinforced magnesium-based composite material.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art and provide a method for in-situ preparation of _TiB2 particle reinforced magnesium-based composite materials. The main invention is as follows: (1) Synthesize submicron/nanoparticles by melt direct reaction method Reinforced magnesium-based composite materials, because the reinforcement is a thermodynamically stable ceramic phase with high hardness and high elastic modulus generated in situ in the metal matrix, the surface of the particles is free from pollution, well combined with the matrix interface, and the process is simple, especially for complex parts Forming; (2) Invention of Mg-TiO ₂ -B ₂ O ₃ system to prepare submicron/nano TiB ₂ particle reinforced magnesium matrix composites. Because TiB ₂ ceramic particles have excellent characteristics such as high hardness, wear resistance, and good thermal stability, the lattice type of TiB ₂ and magnesium are both close-packed hexagonal structures, and their lattice arrangement is very similar to that of magnesium, so , as a reinforcing phase, TiB ₂ has great advantages in combining with magnesium. The reactants TiO ₂ and B ₂ O ₃ have low cost and wide sources, but because magnesium is chemically active, it is easy to oxidize and flammable etc. At the same time, the reactants TiO ₂ and B ₂ O ₃ emit a lot of heat during the reaction process, which makes the preparation difficult, and it is even more difficult to directly synthesize submicron/nano particles in the magnesium melt; for this reason, the present invention The technology adopts intermittent application of mechanical stirring and high-energy ultrasound to further disperse the reinforced particles and unreacted oxides generated by the reaction in the melt. After a period of reaction, stand still, remove slag, and cast.

The present invention is realized through the following technical approach. Add the dried reactant TiO ₂ and B ₂ O ₃ powder to the magnesium alloy melt by mechanical stirring, and after adding the reactant, alternately apply high-energy ultrasonic and mechanical stirring to prepare a composite Materials: The technology is simple, and the size of the reinforced particles generated is small, and the scale range is at the submicron/nano level. The process includes the addition and dispersion of reactants TiO ₂ and B ₂ O ₃ , and the diffusion and distribution of the reinforced particles generated by the reaction. After mixing TiO ₂ and B ₂ O ₃ powders evenly and adding them to the magnesium alloy melt at a certain temperature, the following chemical reaction occurs: B ₂ O ₃ +TiO ₂ +5Mg→TiB ₂ +5MgO, thus producing TiB ₂ submicron / nano-reinforced particles.

The present invention comprises the following steps:

(1) Mix TiO ₂ and B ₂ O ₃ powders evenly according to the ratio, and dry them in a drying oven for use;

(2) The magnesium alloy is melted under the protection of the mixed gas of SF ₆ and CO ₂ , and the heat preservation is homogenized;

(3) Add the mixed powder in step (1) to the magnesium melt in step (2) using a stirrer with graphite stirring blades, so that the reactants are uniformly dispersed in the melt;

(4) Treating the magnesium melt in step (3) with high-energy ultrasound, so that the reactants can be further dispersed in the melt and the chemical reaction of the melt can be accelerated;

(5) After mechanically stirring the magnesium melt in step (4), continue to apply high-energy ultrasound to the magnesium melt, so that the generated reinforcing particles are uniformly dispersed in the melt;

(6) After repeating steps (4) and (5) three times, let the magnesium melt stand still, remove the scum on the surface of the melt, and cast.

The drying temperature in step (1) is 180-200°C, and the drying time is 1h-2h; the stoichiometric ratio of the mixed powder TiO ₂ and B ₂ O ₃ is 1:1.03.

The smelting temperature in step (2) is 710-720° C., and the homogenization time for heat preservation is 10-20 minutes.

The stirrer with graphite stirring blades described in step (3) stirs the magnesium melt, the stirring speed is 200-1500rpm, and the stirring time is 3-5 minutes.

The power of the high-energy ultrasonic in step (4) is 800W-1200W, and the treatment time is 3-5 minutes.

The mechanical stirring speed described in step (5) is 200-1500 rpm, and the stirring time is 3-5 minutes.

The standing time described in step (6) is 10-15 minutes.

Compared with the existing preparation technology at present, the present invention adopts a new synthesis system of Mg-TiO ₂ -B ₂ O ₃ and develops a melt direct reaction method + mechanical stirring + high-energy ultrasonic technology to prepare a high-strength anti-creep in-situ Submicron/nano TiB ₂ particle-reinforced magnesium-based composite material, melt direct reaction method + mechanical stirring + high-energy ultrasonic technology not only improves the yield of reactants, but also effectively shortens the synthesis time; and the size of the synthesized particles is small , the interface with the matrix is clean and pollution-free, the wettability is good, the distribution in the matrix is uniform, and it has the advantages of simple preparation process and low cost. The in-situ TiB ₂ reinforced particle size prepared by the present invention is between 80nm and 1μm, the density of the composite material is between 1.8 and 2.1g/cm ³ , and its tensile strength is increased by more than 55% compared with the matrix alloy, which is the in-situ The preparation of magnesium-based composites reinforced with endogenous particles provides an effective method.

Description of drawings

Fig. 1 is the XRD figure of the composite material prepared by the present invention;

Fig. 2 is the SEM figure of the composite material prepared by Comparative Example Example 1;

Fig. 3 is the SEM figure of the composite material prepared by the embodiment of the present invention 2;

Fig. 4 is the SEM figure of the composite material prepared by the embodiment of the present invention 3;

Fig. 5 is an EDS diagram of the composite material prepared in Example 3 of the present invention.

Detailed ways

The embodiments of the present invention are described in detail below: the present embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation and specific operation process are provided, but the protection scope of the present invention is not limited to the following implementation example.

Example 1 (comparative example)

Composite materials prepared by continuous mechanical stirring + high-energy ultrasonic treatment

Mix TiO ₂ and B ₂ O ₃ powders evenly according to the stoichiometric ratio of 1:1.03, preheat at 200°C for 2 hours for use, heat the AZ91 alloy to 710°C to melt, keep warm for 20 minutes, and use graphite The agitator of the stirring blade stirs the magnesium melt, adds the mixed powder, and makes the powder evenly dispersed in the melt, the stirring speed is 800rpm, and the stirring time is 18 minutes; after standing for 2 minutes, the power applied to the magnesium alloy melt is 800W high-energy ultrasound, the action time is 18 minutes. After the magnesium melt is left to stand for 15 minutes, the slag is removed, refined and cast into a copper mold to form a magnesium-based composite material. It can be seen from Figure 2 that the prepared composite material has No reinforced particles with a round shape can be found, most of them are in the form of agglomerates and flocculents, and the shape of the particles is not obvious. The tensile strength of the composite material is only 273MPa.

Example 2

Composite material A prepared by intermittent mechanical stirring + high-energy ultrasonic treatment

Mix TiO ₂ and B ₂ O ₃ powders evenly according to the stoichiometric ratio of 1:1.03, preheat at 200°C for 2 hours for use, heat the AZ91 alloy to 710°C to melt, keep warm for 20 minutes, and use graphite The agitator of the stirring blade stirs the magnesium melt, adds the mixed powder, and disperses the powder evenly in the melt, the stirring speed is 200rpm, and the stirring time is 5 minutes; after standing for 2 minutes, the power applied to the magnesium alloy melt is 800W high-energy ultrasound, the action time is 5 minutes; after standing for 1 minute, the magnesium alloy melt is mechanically stirred, the stirring speed is 200rpm, and the stirring time is 5 minutes; after repeating the above steps 3 times, the magnesium alloy melt is statically stirred. After standing for 15 minutes, the slag was removed, refined and casted into a copper mold to form a magnesium matrix composite material reinforced with micron+submicron particles. The average size of the reinforced particles was 250nm, and the tensile strength was 320MPa. Figure 3 shows the prepared composite material SEM image.

Example 3

Composite material B prepared by intermittent mechanical stirring + high-energy ultrasonic treatment

The TiO ₂ and B ₂ O ₃ powders were mixed evenly according to the stoichiometric ratio of 1:1.03, and preheated at 200°C for 2 hours before use. Heat the AZ91 alloy to 720°C to melt, and keep it homogenized for 15 minutes. Utilize a stirrer with graphite stirring blades to stir the magnesium melt, add the mixed powder, and make the powder evenly dispersed in the melt, the stirring speed is 1500rpm, the stirring time is 3 minutes, after standing for 2 minutes, the magnesium alloy melting The body applies high-energy ultrasound with a power of 1200W, and the action time is 3 minutes. After standing for 1 minute, the magnesium alloy melt is mechanically stirred. The stirring speed is 1500rpm, and the stirring time is 3 minutes. After repeating the above steps 3 times, the After the magnesium melt was left to stand for 10 minutes, the slag was removed and refined and casted into a copper mold to form a magnesium-based composite material reinforced with submicron particles. The average size of the reinforced particles was 150 nm, and the tensile strength was 340 MPa. Figure 4 and Figure 5 SEM images and EDS images of the prepared composites.

Claims (9)

1. a particle reinforced magnesium base compound material is characterized in that: with TiO ₂And B ₂O ₃Powder joins in the magnesium alloy fused mass as reactant, forms Mg-TiO ₂-B ₂O ₃Synthetic system alternately applies high-energy ultrasonic and mechanical stirring and prepares described matrix material, the TiB of generation ₂Enhanced granule be close-packed hexagonal structure with magnesium, be the submicron enhanced granule, described TiB ₂The enhanced granule particle diameter is between 80nm～1 μ m.

2. the preparation method of a kind of particle reinforced magnesium base compound material as claimed in claim 1 is characterized in that: with the reactant TiO of drying treatment ₂And B ₂O ₃Powder utilizes churned mechanically mode to add magnesium alloy fused mass, behind the adding reactant, alternately applies high-energy ultrasonic and mechanical stirring, thus the preparation matrix material.

3. the preparation method of a kind of particle reinforced magnesium base compound material as claimed in claim 2 is characterized in that may further comprise the steps:

(1) with TiO ₂And B ₂O ₃Powder proportionally mixes, and oven dry is stand-by in loft drier;

(2) magnesium alloy is at SF ₆And CO ₂The protection of mixed gas is fusing down, and the insulation homogenizing;

(3) mixed powder in the step (1) is added in the magnesium melt in the step (2), utilizes the agitator that has the graphite agitating vane to stir the magnesium melt, mixed powder is uniformly dispersed in melt;

(4) utilize high-energy ultrasonic that the magnesium melt of step (3) is handled, thereby reactant further is uniformly dispersed in melt and quickens the melt chemical reaction;

(5) after the magnesium melt mechanical stirring to step (4), continue the magnesium melt is applied high-energy ultrasonic, make enhanced granule homodisperse in melt of generation;

(6) after repeating step (4) and (5) 3 times, the magnesium melt is left standstill, remove the scum silica frost of bath surface, casting.

4. preparation method as claimed in claim 3 is characterized in that: the bake out temperature described in the step (1) is 180～200 ℃, and the time is 1h～2h.

5. preparation method as claimed in claim 3 is characterized in that: the mixed powder TiO described in the step (1) ₂And B ₂O ₃Stoichiometric ratio be 1:1.03.

6. preparation method as claimed in claim 3 is characterized in that: the smelting temperature described in the step (2) is 710～720 ℃, and the insulation homogenization time is 10～20 minutes;

Preparation method as claimed in claim 3 is characterized in that: the agitator that has the graphite agitating vane described in the step (3) stirs the magnesium melt, and its stirring velocity is 200～1500rpm; Its churning time is 3～5 minutes.

7. preparation method as claimed in claim 4 is characterized in that: the high-energy ultrasonic power described in the step (4) is 800W～1200W, and the high-energy ultrasonic treatment time is 3～5 minutes.

8. preparation method as claimed in claim 4 is characterized in that: the mechanical stirring speed described in the step (5) is 200～1500rpm, and churning time is 3～5 minutes.

9. the synthetic TiB of melt in situ reaction as claimed in claim 1 ₂The preparation method of particle reinforced magnesium base compound material is characterized in that: the time of repose described in the step (6) 10～15 minutes.

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