CN116904795A - (TiC+Ti)/Mg layered composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a (TiC+Ti)/Mg layered composite material and a preparation method thereof. The preparation method of the composite material comprises the following steps: the method of freezing casting and in-situ generation is adopted to prepare a layered porous TiC ceramic skeleton, and the magnesium alloy is completely immersed into the ceramic skeleton by combining air pressure infiltration, so as to obtain the (TiC+Ti)/Mg composite material with a layered structure. The invention benefits from a plurality of toughening mechanisms such as multi-crack expansion, crack passivation and deflection, and the pulling-out of the metal layer and the ceramic sheet caused by the layered structure, and the composite material has good compressive strength, bending strength, tensile strength, fracture toughness, wear resistance and damping performance. The composite material is expected to be applied to the fields of aerospace, automobiles, communication and the like with high requirements on high-performance light wear-resistant materials.

Description

A (TiC+Ti)/Mg layered composite material and its preparation method

Technical areas:

The invention relates to the technical field of magnesium-based composite materials, and specifically relates to a (TiC+Ti)/Mg layered composite material and a preparation method thereof.

Background technique:

Magnesium and its magnesium alloys are one of the lightest structural materials. They have high specific strength, specific stiffness, good dimensional stability, vibration damping, anti-electromagnetic interference and shielding properties. They are widely used in aerospace, automobiles, communications, electronics, etc. fields are receiving more and more attention. However, its shortcomings such as low absolute strength, limited plasticity, and insufficient stiffness limit its application range. In recent years, people have improved their overall properties by introducing reinforcing phases into Mg and its alloys. Studies have shown that the strength of magnesium and its alloys is improved when an appropriate amount of hard ceramic particles are added. However, when the content of ceramic particles is too high, the toughness of magnesium-based composites decreases sharply, which is not conducive to the preparation of high-strength magnesium-based composites and limits the application of magnesium-based composites with high ceramic content. Therefore, it is necessary to find a new method to adjust the strengthening relationship between ceramic particles and aluminum matrix to solve the high strength and toughness matching problem of ceramic particle reinforced magnesium matrix composites.

With the development of bionic materials, a promising method has been provided to solve this problem-imitating shell structures. Nacre, composed of brittle minerals (95 vol%) and small amounts of biopolymers (5 vol%), was found to exhibit unprecedented strength and fracture toughness at least an order of magnitude higher than its components, which can be attributed to its complex " Brick and mud "layered structure." A large number of studies have shown that metal matrix composites with high ceramic content (20-30vol%) that imitate the nacreous structure of shells have both good strength and toughness. Among the many methods of imitating shell structures, "freeze casting" has gained more and more attention due to its advantages such as simple operation, low cost, and the ability to control the microstructure of porous materials. In recent years, domestic and foreign scholars have begun to apply freeze casting to prepare magnesium-based imitation shell materials. Among the many ceramic particle reinforced phases, TiC has the advantages of high hardness, high melting point and excellent wear resistance. These advantages make it an extremely advantageous reinforcing phase in magnesium-based composites with imitated shell structure. It is also about the use of freeze casting. There are few reports on the preparation of (TiC+Ti)/Mg layered composites by infiltration method. The patent of this invention uses a certain proportion of TiH ₂ and graphite powder to prepare a layered porous preform through freeze casting, synthesizes Ti and TiC through in-situ sintering, and adjusts the proportion of TiH ₂ and graphite powder to obtain different ratios. of Ti and TiC, and then infiltrate the magnesium melt into the preform to obtain a (TiC+Ti)/Mg layered composite material. The composite material can have comprehensive mechanical properties of high strength, high toughness and high wear resistance by regulating the ratio of TiC and Ti generated by the reaction, as well as good damping properties.

Contents of the invention:

The present invention solves the problem of poor toughness of magnesium-based composite materials with high ceramic content, and provides a (TiC+Ti)/Mg layered composite material and a preparation method thereof. The invention benefits from a variety of enhanced properties caused by the layered structure. The toughness mechanism enables the composite material to have good mechanical properties by regulating the ratio of TiC and Ti generated by the reaction. The composite material can be used in aerospace, automotive, communications and other fields where there is a greater demand for high-performance lightweight structural materials.

The invention provides a method for preparing (TiC+Ti)/Mg layered composite materials, which includes the following steps: using a unidirectional freezing mold to freeze a slurry composed of TiH ₂ powder, graphite powder, ammonium polyacrylate and neutral silica sol , by adjusting the ratio of TiH ₂ and graphite powder, in-situ sintering was used to prepare (TiC+Ti) porous ceramic skeletons with different proportions, and air pressure infiltration was used to completely immerse the magnesium matrix into the porous ceramic skeleton to obtain a layered structure (TiC+ Ti)/Mg composites.

During the infiltration process, the ceramic sheets of the porous ceramic skeleton remain basically intact, and the interlayer pores are completely filled with molten magnesium alloy, forming a layered structure. The composite material can be endowed with good strength and toughness by regulating the ratio of TiC and Ti produced by the reaction.

Preferably, the preparation method specifically includes the following steps:

(1) Powder mixing: Pour TiH ₂ powder and graphite powder into a container, then add water, ammonium polyacrylate and neutral silica sol, fill with high-purity argon gas, and ball-mill for 1-3 hours to obtain a slurry with uniformly dispersed particles. ;

(2) Freezing: Place the one-way freezing mold in a freezing container at -30°C-(-35°C), then pour the slurry obtained in step (1) and freeze for 1.0-1.5 hours, and then demould to obtain blocks with alternating layers of ceramic and ice;

(3) Low-temperature drying: After low-temperature drying in a low-temperature dryer for 24-48 hours, the dried green body is obtained;

(4) Sintering: The green body is sintered under the protection of inert gas to obtain a layered porous ceramic skeleton;

(5) Impregnation: Put the layered porous ceramic skeleton and magnesium alloy into the graphite mold in sequence, then put the mold into the vacuum reaction vessel, first evacuate to below 10Pa at normal temperature, raise the temperature to 750℃-850℃, and Insulate the temperature, and then pass high-purity argon gas into the vacuum furnace to allow the molten metal to penetrate into the ceramic skeleton to obtain a layered structure (TiC+Ti)/Mg composite material.

The present invention adopts freeze casting and in-situ generation methods to prepare a layered porous (TiC+Ti) ceramic skeleton. Combined with air pressure infiltration, the magnesium alloy is completely immersed in the ceramic skeleton to obtain a layered structure of (TiC+Ti)/Mg composite materials.

Preferably, the one-way freezing mold includes a constant-temperature freezing container. The bottom of the constant-temperature freezing container is provided with a heat-conducting liquid and a metal column. The metal column is immersed in the heat-conducting liquid. The top of the metal column is provided with a metal plate. The top of the metal plate is A polytetrafluoroethylene tube is provided for placing the slurry.

Further preferably, the heat transfer liquid is alcohol, and the material of the metal pillar and metal plate is copper. The constant temperature freezing container is a constant temperature freezer.

Preferably, the specific steps of step (1) are: pour a certain proportion of TiH ₂ powder and graphite powder into a ball mill tank, then add water, ammonium polyacrylate and neutral silica sol, fill with high-purity argon gas and ball mill for 2 hours. , to obtain a slurry with uniformly dispersed particles. The conditions for low-temperature drying in step (3) are low temperature (ie, temperature <-60°C) and low pressure (ie, pressure <10 Pa).

Preferably, the total volume of TiH ₂ powder and graphite powder described in step (1) accounts for 20%-50% of the total volume of the slurry, ammonium polyacrylate accounts for 1%-1.5% of the total volume of the slurry, and neutral silica sol Accounting for 0.8%-1% of the total volume of the slurry. Further preferably, the total volume of the TiH ₂ powder and graphite powder accounts for 28%-30% of the total volume of the water-based slurry.

Preferably, the mass ratio of the TiH ₂ powder and graphite powder is 4-8:1. Further preferably, the mass ratio of TiH ₂ powder and graphite powder is 30-35:6 (5:1-35:6).

Preferably, the specific steps of step (4) are: first put the low-temperature dried green body into a vacuum sintering furnace, and then extract the air in the sintering furnace. When the vacuum gauge value reaches below -0.1MPa, continue to the vacuum furnace. Pour in inert gas with a purity of 99.9%, keep the gas pressure at 0MPa, carry out normal pressure sintering, raise the temperature at a rate of 8-12°C/min, and keep it at 500°C for 25-35 minutes, 1000°C for 0.8-1.2 hours, and 1500°C. °C for 1-1.5 hours, and finally reduce the temperature to 300 °C at a cooling rate of 8-12 °C/min and then cool it in the furnace to obtain a layered porous ceramic skeleton. The inert gas is argon.

Preferably, the mass ratio of the layered porous ceramic framework and the magnesium alloy described in step (5) is 3:7-8.

The present invention also protects the (TiC+Ti)/Mg layered composite material obtained by the above preparation method. The ceramic content of the composite is 28%-50%.

The invention also protects the application of the (TiC+Ti)/Mg layered composite material in the fields of aerospace, automobile or communication.

Compared with the prior art, the present invention has the following advantages:

(1) Compared with existing layered composite materials, the present invention uses an environmentally friendly freeze-casting method to construct a ceramic skeleton. The ceramics can be controlled by adjusting factors such as freezing temperature, additives, ceramic content, powder particle size, and sintering temperature. The lamellar morphology of the skeleton can be adjusted to regulate the comprehensive performance of the composite material to meet the material selection under various working conditions.

(2) The present invention benefits from various toughening mechanisms caused by the layered structure, such as multi-crack propagation, crack passivation and deflection, and the pull-out of metal layers and ceramic sheets. By regulating the ratio of TiC and Ti generated by the reaction, the composite material has excellent compressive strength, flexural strength, tensile strength and fracture toughness, as well as good wear resistance and damping properties.

(3) The present invention uses in-situ autogenous technology to prepare TiC+Ti ceramic skeleton. Compared with other methods, the in-situ autogenous reinforcement and the matrix have good interfacial bonding and wettability, making the metal matrix composite material excellent and stable. performance. The reaction equation is as follows:

TiH ₂ →Ti+H ₂ ; Ti+C → TiC

The decomposition process of TiH ₂ occurs in the range of 620°C to 720°C, because the decomposed Ti is highly active and can easily react with graphite powder to form TiC after being kept at 1500°C for 1-1.5 hours. When too _much TiH2 is added, the decomposed Ti will wrap and bind the TiC particles generated by the bonding reaction, which not only improves the wettability of the ceramic skeleton and the magnesium alloy, but also enhances the strength of the ceramic skeleton, eventually leading to the fracture of the composite material. Resilience is improved.

Picture description:

Figure 1 is a flow chart of the preparation process of the (TiC+Ti)/Mg layered composite material of the present invention.

Figure 2 is a schematic structural diagram of the one-way freezing mold proposed by the present invention.

Figure 3 is the microscopic morphology of the fracture of the ceramic skeleton after sintering in step (4) in Example 1, in which (a) is the longitudinal fracture and (b) is the transverse fracture.

Figure 4 is an XRD pattern of the (TiC+Ti)/Mg layered composite material prepared in Example 1.

Figure 5 is an OM diagram of the (TiC+Ti)/Mg layered composite material prepared in Example 1, in which (a) is the longitudinal fracture and (b) is the transverse fracture.

Figure 6 is a schematic structural diagram of the sample undergoing mechanical testing, in which (a) is the bending test and (b) is the fracture test.

Figure 7 is a dimensional drawing of the tensile specimen.

Figure 8 is the damping-strain curve of AZ91D magnesium alloy and prepared composite materials.

Explanation of reference signs: 1. Constant temperature freezer; 2. Teflon tube; 3. Slurry; 4. Copper plate; 5. Copper column; 6. Alcohol.

Detailed ways:

The following examples further illustrate the present invention, rather than limiting the present invention.

Unless otherwise defined, all technical terms used below have the same meanings as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present invention. Unless otherwise specified, the experimental materials and reagents in this article are all conventional commercial products in this technical field.

The one-way freezing mold used in the following embodiments includes a constant temperature freezing container. The bottom of the constant temperature freezing container is provided with a thermal conductive liquid and a metal column. The metal column is immersed in the thermal conductive liquid. A metal plate is provided on the top of the metal column, and a metal plate is provided on the top of the metal plate. Place PTFE tube 2 of slurry 3. The preferred thermal conductive liquid in the present invention is alcohol 6, the metal in the metal plate and metal column is thermal conductive metal, the preferred metal plate in the present invention is a copper plate 4, the metal column is a copper column 5, and the constant temperature freezing container is a constant temperature freezer 1.

The heat in the slurry in the one-way freezing mold proposed by the present invention is conducted to the copper pillars 5 through the copper plate 4, the alcohol 6 accelerates the heat dissipation, and the temperature difference between the upper and lower parts of the copper plate 4 forms a vertical temperature gradient. When used, the mold is first cryogenically frozen to -30°C-(-35°C), and the slurry 3 is placed in the polytetrafluoroethylene tube 2. The copper plate 4 and the copper pillar 5 are connected and together with the alcohol 6 form a thermal conductive module to form a one-way temperature gradient.

The materials used in the following examples include _TiH powder, graphite powder, ammonium polyacrylate, neutral silica sol, deionized water and magnesium alloy. The specific information is shown in Table 1.

Table 1 Specific information on materials used

Example 1

A preparation method of (TiC+Ti)/Mg layered composite material, including the following steps:

(1) Powder mixing: Weigh 25g TiH ₂ powder and 6g graphite powder and pour them into the ball mill tank, then add 22mL deionized water, 0.3g ammonium polyacrylate and 0.2g neutral silica sol, and then fill the ball mill with high-purity argon 2 hours.

(2) Freezing: First place the one-way freezing mold (Figure 2) in a -35°C refrigerator for 30 minutes, then pour in the stirred slurry and freeze for 1 hour. After demoulding, the ceramic layer and ice layer are alternately arranged. block.

(3) Low-temperature drying: Place the block into a freeze-drying device and freeze-dry in a low-temperature, low-pressure (<-65°C, <10Pa) environment. The drying time is 48 hours.

(4) Sintering: First put the green body into the vacuum sintering furnace, and then extract the air in the sintering furnace. When the vacuum gauge value reaches below -0.1MPa, continue to pass argon gas with a purity of 99.9% into the vacuum furnace to maintain The air pressure is 0MPa, and sintering is performed under normal pressure. The sintering curve is: heating at a rate of 8°C/min, holding at 500°C for 30 minutes, 1000°C for 1 hour, and 1500°C for 1.2 hours, and finally lowering the temperature to 100°C at a cooling rate of 8°C/min. The furnace is cooled, and finally a porous ceramic skeleton with a certain strength is obtained.

(5) Impregnation: Put the porous ceramic skeleton and magnesium alloy with a mass ratio of 3:7 into the graphite mold in sequence, and put the mold into a vacuum furnace. First, evacuate to below 10Pa at room temperature, heat to 800°C at 5°C/min, and keep warm for 15 minutes. Then high-purity argon gas is introduced into the vacuum furnace to form a high pressure above the molten metal, while the internal pores of the ceramic skeleton below are still in a vacuum state. The pressure difference between the inside and outside is used to make the molten metal penetrate into the ceramic skeleton, and the temperature and pressure are maintained for 5 minutes. The temperature was lowered to room temperature at 10°C/min to obtain a (TiC+Ti)/Mg layered composite material.

The prepared composite material was cut and polished, and performance testing and microscopic morphology observation were performed:

(1) Mechanical properties: Use a wire EDM machine to cut the composite material into specimens of different sizes. In compression and bending, the sample sizes are 4mm×4mm×8mm and 3mm×4mm×20mm respectively. The sample for the fracture toughness test is 2mm × 4mm × 22mm. A notch is opened in the middle of the sample, the width of the notch is 0.3mm, and the depth of the notch is 2mm. (Figure 6). The tensile specimen is a 140mm×20mm×10mm sheet specimen (as shown in Figure 7). The INSTRON3369 electronic universal material testing machine was used to conduct compression, bending, tensile and fracture tests on composite materials.

All samples were ground and polished before testing, and the loading rate of the compression test was: 0.5mm/min. The loading rate of bending and fracture is: 0.1mm/min, and the experimental span is 10mm.

Compressive strength (σ _C ) and flexural strength (σ _f ) are calculated according to the following formulas:

Where P _IC is the maximum applied load, A is the cross-sectional area of the compression specimen. S is the span; b is the specimen width; h is the specimen thickness.

The crack initiation toughness (K _IC ) of the material can be calculated according to the following formula:

P _IC is the maximum load when the sample breaks; a is the notch depth; S is the support span; B is the thickness of the specimen, and W is the width of the specimen.

(2) Friction and wear performance: Use an electric discharge wire cutting machine to cut the composite material into 10mm×10mm×5mm rectangular parallelepipeds. A 20-min linear reciprocating friction and wear test was conducted on the cross section (TS) and the longitudinal section (LS). Wear tests were conducted on the longitudinal section (LS) in the directions parallel to the lamellar growth (hereinafter referred to as LS-P) and perpendicular to the lamellar growth (hereinafter referred to as LS-V). The applied load in the experiment was 10N, and the linear reciprocating distance and speed were 5mm and 8mm/s respectively.

The wear rate can be calculated by the following formula:

Where A is the wear cross-sectional area, L is the wear length, F is the load, and S is the sliding distance.

(3) Damping performance: Use a DMAQ850 dynamic thermomechanical analyzer to test the damping performance of the sample at room temperature, with a frequency of 1Hz and a sample size of 30mm×3mm×1mm.

(4) Micromorphology: Use the SUPRA55 scanning electron microscope produced by the German ZEISS company to observe the micromorphology of the porous ceramic skeleton: a parallel ordered layered structure is observed on the longitudinal section parallel to the temperature gradient (Figure 3.a ), and it was observed on the cross section that the lamellae showed a locally ordered but overall chaotic morphology (Figure 3.b); X-ray diffractometer (XRD; BrukerAXS) was used to analyze the (TiC+Ti)/Mg layered composite material For phase composition analysis, the diffraction angle range is 20-80°, and the scanning speed is 5°/min. The results show (Figure 4): In the XRD pattern of the composite material, the diffraction peaks of TiC, Mg and Mg ₁₇ Al ₁₂ were found, indicating that TiC was synthesized in situ and there were no other impurities in the prepared composite material; using The XD30M series metallographic optical microscope produced by Ningbo Sunny Instrument Co., Ltd. observed the metallographic phase of the sample: the white part is the magnesium alloy and the dark gray part is the ceramic layer. On the longitudinal section, it is observed that the metal layer and the ceramic layer are parallel to each other. They are arranged alternately in an orderly manner (Figure 5.a), while the lamellae on the cross-section are partially ordered and overall disordered (Figure 5.b).

The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2. The damping performance is shown in Figure 8.

Example 2

Same as Example 1, except that:

Change step (1) to: weigh 36g TiH ₂ powder and 6g graphite powder and pour them into the ball mill tank, then add 26mL deionized water, 0.32g ammonium polyacrylate and 0.22g neutral silica sol, and then fill with high-purity argon Balloon grinding for 2 hours.

Consistent with the testing method in Example 1, the prepared composite material was cut and polished, and mechanical properties were tested and micromorphology was observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2. The damping performance is shown in Figure 8.

Example 3

Same as Example 1, except that:

Change step (1) to: weigh 48g TiH ₂ powder and 6g graphite powder into the ball mill tank, then add 33mL deionized water, 0.35g ammonium polyacrylate and 0.24g neutral silica sol, and then fill with high-purity argon Balloon grinding for 2 hours.

Consistent with the testing method in Example 1, the prepared composite material was cut and polished, and mechanical properties were tested and micromorphology was observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2. The damping performance is shown in Figure 8.

Example 4

Same as Example 1, except that:

Change step (1) to: weigh 48g TiH ₂ powder and 1g graphite powder into the ball mill tank, then add 33mL deionized water, 0.35g ammonium polyacrylate and 0.24g neutral silica sol, and then fill with high-purity argon Balloon grinding for 2 hours.

Consistent with the testing method in Example 1, the prepared composite material was cut and polished, and mechanical properties were tested and micromorphology was observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2.

Example 5

Same as Example 1, except that:

Change step (1) to: weigh 25g TiH ₂ powder and 6g graphite powder and pour them into the ball mill tank, then add 9.64mL deionized water, 0.3g ammonium polyacrylate and 0.2g neutral silica sol, and then fill in high-purity Argon balloon grinding for 2 hours.

Consistent with the testing method in Example 1, the prepared composite material was cut and polished, and mechanical properties were tested and micromorphology was observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2.

Example 6

Same as Example 3, except that:

Change step (2) to: first place the one-way freezing mold (Picture 2) in a -30°C refrigerator for 30 minutes, then pour in the stirred slurry and freeze for 1 hour. After demoulding, the ceramic layer and ice layer are obtained Alternating blocks.

Consistent with the testing method in Example 1, the prepared composite material was cut and polished, and mechanical properties were tested and micromorphology was observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2.

Example 7

Same as Example 3, except that:

Change the sintering curve in step (4) to: heating at a rate of 10°C/min, holding at 500°C for 30 minutes, 1000°C for 1 hour, 1500°C for 1.5 hours, and finally cooling at a rate of 10°C/min. Lower the temperature to 500°C and then cool in the furnace.

Consistent with the testing method in Example 1, the prepared composite material was cut and polished, and mechanical properties were tested and micromorphology was observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2.

Comparative example 1

Processing magnesium alloys includes the following steps:

Weigh 200g of magnesium alloy (AZ91D) into a graphite mold, and place the mold into a vacuum furnace. First, evacuate to below 10Pa at room temperature, heat to 800°C at 5°C/min, and keep warm for 15 minutes. Then, high-purity argon gas was introduced into the vacuum furnace, kept at temperature and pressure for 5 min, and then cooled to room temperature at 10°C/min.

Consistent with the testing method in Example 1, the prepared material was cut and polished, and mechanical properties tested and micromorphology observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2.

Comparative example 2

A preparation method of non-layered (TiC+C)/Mg composite material, including the following steps:

Weigh 35g TiH ₂ powder and 6g graphite powder, pour them into a ball mill tank, and grind them for 2 hours. The mixed powder is then pressed and then sintered. The mixing and sintering of the powder are carried out under the protection of high-purity argon gas. Then preheat the prefabricated block at 300°C for 30 minutes, then add it to 300g of magnesium alloy (AZ91D) melt, keep warm, and stir to melt the prefabricated block and disperse it in the magnesium melt, then refine, keep warm, let stand, and pour to prepare Non-layered (TiC+C) particle-reinforced magnesium-based composite materials were produced.

Consistent with the testing method in Example 1, the prepared composite material was cut and polished, and mechanical properties were tested and micromorphology was observed. The test results of the ceramic content, compressive strength, flexural strength, tensile strength and fracture toughness of the composite material are shown in Table 2.

Table 2 Performance test results

Judging from the test results, the (TiC+Ti)/Mg layered composite material (Example 3) with a ceramic content of 30% has the best flexural strength. The difference in performance can be attributed to the fact that when sufficient TiH ₂ is added, the full reaction between TiH ₂ and graphite powder is ensured, and more TiC ceramic reinforcement phases are synthesized in situ. The reinforcement phase plays an effective role in supporting and reducing wear. function, thus improving the compressive strength, flexural strength and wear resistance of the composite material. Especially when the ceramic content reaches 50%, the compressive strength is the highest and the wear rate is the lowest (Example 5). When too much _TiH2 is added, the remaining Ti will wrap and bond the TiC particles generated by the reaction, improving the wettability of the ceramic skeleton and the magnesium alloy, which is beneficial to reducing infiltration defects in the composite material, thereby improving its fracture toughness. Especially when the Ti content is extremely high, its tensile strength and fracture toughness are optimal (Example 4). Compared with Example 6, a lower freezing temperature can obtain a finer ceramic sheet layer, which enhances the compressive strength, flexural strength and fracture toughness of the material. Compared with Example 7, slow temperature rise can prevent the deformation of the ceramic sheet and ensure that the multiple mechanisms of the layered structure can play a toughening role. Compared with the magnesium alloy matrix treated by the same process (Comparative Example 1), the compressive strength, flexural strength, tensile strength and fracture toughness of the present invention are greatly improved. In Comparative Example 2, a non-layered structure (TiC+C)/Mg composite material was prepared using a stirring method. After testing, it was found that the compressive strength, flexural strength, tensile strength, fracture toughness and wear resistance of the high ceramic content layered composite material of the present invention are better than those of the low ceramic content non-layered (TiC+Al)/Mg Composite material embodies the advantages of imitation shell layered structure.

Among metallic materials, pure magnesium exhibits excellent damping properties, but its poor mechanical properties hinder its application. Therefore, it is necessary to explore a method to improve the mechanical properties of magnesium alloys while ensuring good damping properties. The present invention provides a way to achieve this goal - (TiC+Ti)/Mg layered composite materials. From the damping-strain diagram (Fig. 8), in the strain amplitude-independent stage, the damping performance of Examples 1-3 and Comparative Example 1 is almost the same, while in the strain amplitude-related stage, the damping performance of Comparative Example 1 is better than that of Example 1 -3 has a higher degree of improvement, while the critical strain amplitude of Example 1-3 is higher than that of Comparative Example 1, and the damping performance of Examples 1-3 is almost the same. It shows that under low strain (0.1%), the composite material has higher strength than magnesium alloy and also has excellent damping performance.

In summary, the present invention benefits from various toughening mechanisms caused by the layered structure, such as multi-crack propagation, crack passivation and deflection, and pull-out of metal layers and ceramic sheets. By regulating the properties of TiC and Ti generated by the reaction, Proportionally, the present invention has good compressive strength, flexural strength, tensile strength and fracture toughness. Its strength has been greatly improved compared to the magnesium alloy matrix, while maintaining excellent fracture toughness, wear resistance and damping properties. The composite material is expected to be used in aerospace, new energy vehicles, electronic communications and other fields where there is a greater demand for high-performance lightweight wear-resistant materials.

The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present invention. It should be pointed out that for those skilled in the art, several improvements can be made to the present invention without departing from the principles of the present invention. and modifications, these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (10)

1. A method for preparing a (TiC+Ti)/Mg layered composite material, which is characterized in that it includes the following steps: using a unidirectional freezing mold to freeze a compound composed of TiH ₂ powder, graphite powder, ammonium polyacrylate and neutral silica sol Using the slurry, by adjusting the ratio of TiH ₂ and graphite powder, in-situ sintering is used to prepare (TiC+Ti) porous ceramic skeletons with different proportions, and air pressure infiltration is used to completely immerse the magnesium matrix into the porous ceramic skeleton to obtain a layered structure. (TiC+Ti)/Mg composite material. 2. The preparation method according to claim 1, characterized in that it specifically includes the following steps: (1) Powder mixing: Pour TiH ₂ powder and graphite powder into a container, then add water, ammonium polyacrylate and neutral silica sol, fill with high-purity argon gas, and ball-mill for 1-3 hours to obtain a slurry with uniformly dispersed particles. ; (2) Freezing: Place the one-way freezing mold in a freezing container at -30℃-(-35℃), then pour the slurry obtained in step (1) and freeze for 1.0-1.5 hours. After demoulding, the ceramic layer and blocks of alternating layers of ice; (3) Low-temperature drying: After low-temperature drying in a low-temperature dryer for 24-48 hours, the dried green body is obtained; (4) Sintering: The green body is sintered under the protection of inert gas to obtain a layered (TiC+Ti) porous ceramic skeleton; (5) Impregnation: Put the layered (TiC+Ti) porous ceramic skeleton and magnesium alloy into the mold in sequence, then put the mold into the vacuum reaction vessel, first evacuate to below 10Pa at normal temperature, and raise the temperature to 750°C -850°C and heat preservation, and then pass high-purity argon gas into the vacuum furnace to allow the molten metal to penetrate into the ceramic skeleton to obtain a layered structure (TiC+Ti)/Mg composite material. 3. The preparation method according to claim 1 or 2, characterized in that the one-way freezing mold includes a constant temperature freezing container, the bottom of the constant temperature freezing container is provided with a thermally conductive liquid and a metal column, and the metal column is immersed in the thermally conductive liquid. , a metal plate is provided on the top of the metal column, and a polytetrafluoroethylene tube for placing the slurry is provided on the top of the metal plate. 4. The preparation method according to claim 3, characterized in that the thermal conductive liquid is alcohol, and the material of the metal pillar and the metal plate is copper. 5. The preparation method according to claim 1 or 2, characterized in that the total volume of the TiH powder and graphite powder described in step (1) accounts for 20%-50% of the total volume _of the water-based slurry, and the polyacrylic acid Ammonium accounts for 1%-1.5% of the total volume of the slurry, and neutral silica sol accounts for 0.8%-1% of the total volume of the slurry. 6. The preparation method according to claim 5, characterized in that the mass ratio of the TiH ₂ powder and graphite powder is 4-8:1. 7. The preparation method according to claim 2, characterized in that the specific steps of step (4) are: first put the low-temperature dried green body into a vacuum sintering furnace, then extract the air in the sintering furnace, and place it on the vacuum table. When the value reaches below -0.1MPa, continuously pass inert gas with a purity of 99.9% into the vacuum furnace, keep the gas pressure at 0MPa, perform sintering at normal pressure, raise the temperature at a rate of 8-12℃/min, and keep it at 500℃ for 25 -35 minutes, 1000°C for 0.8-1.2 hours, 1500°C for 1-1.5 hours, and finally the temperature is lowered to 200°C at a cooling rate of 8-12°C/min and then cooled in the furnace to obtain a layered porous ceramic skeleton. 8. The preparation method according to claim 2, characterized in that the mass ratio of the layered porous ceramic skeleton and magnesium alloy in step (5) is 3:7-8. 9. The (TiC+Ti)/Mg layered composite material obtained by the preparation method according to claim 1 or 2. 10. Application of the (TiC+Ti)/Mg layered composite material according to claim 9 in the fields of aerospace, automobile or communication.