In-situ synthesis gradient Ti2AlC / Ti composite material and preparation method thereof

Abstract

The invention provides an in-situ synthesis gradient net-shaped Ti2AlC / Ti composite material and a preparation method thereof, the microstructure of the Ti2AlC / Ti composite material comprises a Ti matrix and a net-shaped Ti2AlC reinforced phase distributed in the Ti matrix, and in the thickness direction of the composite material, the volume fraction of the net-shaped Ti2AlC reinforced phase is distributed in a gradient decreasing mode from top to bottom. The composite material has excellent strength and toughness, and no obvious interface transition layer exists between layers.

Description

Technical Field

[0001] The present invention relates to the technical field of gradient composite materials, and specifically to an in-situ self-generated gradient Ti 2 AlC / Ti composite material and a preparation method thereof. Background Art

[0002] Titanium metal and titanium alloys have become indispensable and important materials in the weapon field due to their low density, high specific strength, and strong corrosion resistance. However, the hardness, strength, plasticity, and toughness of homogeneous titanium cannot meet the usage requirements in the armored vehicle field. Based on the composite technology, the synergistic complementary advantages between the reinforcement and the matrix can be realized. MAX phase Ti 2 AlC is added as a reinforcement to solve the above problems. The MAX phase Ti 2 AlC as a reinforcement not only has the dual characteristics of metal and ceramic, but also is different from traditional hard and high-strength ceramic reinforcements. The MAX phase Ti 2 AlC as a reinforcement can effectively solve the problem of strong plastic inversion due to its special layered structure.

[0003] However, the traditional uniformly dispersed Ti 2 AlC / Ti composite material has the problem of insufficient room temperature plasticity and toughness, which limits its application in the armored vehicle protection field. At the same time, due to the different performance characteristics required for the back bullet surface and the front bullet surface of the armored vehicle plate, that is, the front bullet surface requires high strength of the material, and the back bullet surface requires good plasticity of the material. This requires that both sides of a composite material need to meet different performance requirements at the same time. The Chinese patent with the application number CN200810136852.8 discloses a single-component discontinuous fiber-reinforced titanium matrix composite material. While its strength is improved, its plasticity will decrease significantly. Therefore, it is difficult for a homogeneous single material to meet the requirements of both high strength and high toughness at the same time.

[0004] Therefore, how to design the microstructure of Ti 2 AlC / Ti composite material, give full play to the synergistic complementary potential of the reinforcement and the matrix, and meet the two-sided nature of a plate is one of the key topics discussed in this field. Summary of the Invention

[0005] To solve the above problems, the purpose of the present invention is to provide an in-situ self-generated gradient reticular Ti 2 AlC / Ti composite material and a preparation method thereof. This composite material has excellent strength and toughness, and there is no obvious interfacial transition layer between layers.

[0006] To achieve the above purpose, the specific scheme adopted by the present invention is as follows: On the one hand, the present invention provides an in-situ self-generated gradient Ti 2 AlC / Ti composite material, Ti2 The microstructure of the AlC / Ti composite includes a Ti matrix and network-shaped Ti distributed in the Ti matrix 2 AlC reinforcement phases. Along the thickness direction of the composite material, the network-shaped Ti 2 The volume fraction of the AlC reinforcement phase decreases in a gradient from top to bottom

[0007] Furthermore, the composite material includes an upper layer, a middle layer, and a lower layer in sequence from top to bottom along the thickness direction. The volume fraction of the network-shaped Ti 2 AlC reinforcement phase in the upper layer is 13 - 50%, the volume fraction of the network-shaped Ti 2 AlC reinforcement phase in the middle layer is 4 - 30%, and the volume fraction of the network-shaped Ti 2 AlC reinforcement phase in the lower layer is 2 - 20%

[0008] Furthermore, the volume fraction of the network-shaped Ti 2 AlC reinforcement phase in the upper layer is 24.87%, the volume fraction of the network-shaped Ti 2 AlC reinforcement phase in the middle layer is 17.6%, and the volume fraction of the network-shaped Ti 2 AlC reinforcement phase in the lower layer is 13.62%

[0009] Furthermore, the volume fraction of the network-shaped Ti 2 AlC reinforcement phase in each layer is affected by the mass ratio of raw materials and the particle size of spherical titanium powder at the same time. The mass fraction of spherical titanium powder in the raw materials used from top to bottom gradually decreases, while the particle size of spherical carbon powder gradually increases

[0010] On the other hand, the present invention provides a method for preparing an in-situ self-generated gradient Ti 2 AlC / Ti composite material, which is characterized by mainly including the following steps (1), Weigh spherical titanium powders of different particle size grades (2), Carry out low-energy ball milling on graphene solution, flaky aluminum powder and spherical titanium powders of different particle size grades respectively to obtain a variety of Ti@(Al - C) composite powders (3), Use each Ti@(Al - C) composite powder for cold isostatic pressing to obtain a plurality of blanks (4), Stack the blanks in the order that the particle size grade of titanium powder in the blanks gradually increases from top to bottom (5), Carry out cold isostatic pressing on the stacked blanks again to obtain a pressed blank (6), Place the pressed blank in a graphite mold, then place it in a spark plasma sintering furnace for sintering, and then cool it with the furnace to obtain the product

[0011] Furthermore, the composite material is formed by pressing three kinds of Ti@(Al-C) composite powders. Among them, in the Ti@(Al-C) composite powder used for the upper layer, the particle size of the spherical titanium powder is 0-20 μm; in the Ti@(Al-C) composite powder used for the middle layer, the particle size of the spherical titanium powder is 30-60 μm, and in the Ti@(Al-C) composite powder used for the lower layer, the particle size of the spherical titanium powder is 100-150 μm.

[0012] Furthermore, in step (3), the pressure of cold isostatic pressing is 80-110 MPa, and the pressure is maintained for 5-10 min.

[0013] Furthermore, in step (5), the pressure of cold isostatic pressing is 50-100 MPa, and the pressure is maintained for 3-5 min.

[0014] Furthermore, in step (6), the discharge plasma sintering process is set as follows: heating to 1100-1300 °C at a pressure of 45 MPa and a heating rate of 100 °C / min, and the holding time is 10 min.

[0015] Beneficial effects

[0016] (1) In the present invention, preliminary gradient configuration design is carried out on the composite powder, and then an in-situ self-generated Ti-based composite material with gradient distribution is prepared by using SPS sintering technology. The volume fraction of the network-like Ti2AlC reinforcement phase decreases gradually from top to bottom. The existence of the network structure improves the overall coordinated deformation ability of the material, passivates cracks, and hinders crack propagation, while improving the strength and solving the problem of the plasticity and toughness of the material. The gradient microstructure control meets the application of titanium in the field of armored vehicles, and solves the requirements for different performance characteristics of the back bullet surface and the front bullet surface, that is, the front bullet surface requires high strength of the material, and the back bullet surface requires good plasticity of the material.

[0017] (2) In the in-situ self-generated gradient Ti 2 AlC / Ti composite material, the volume fraction of the network-like Ti2AlC reinforcement phase decreases gradually from top to bottom. Taking the three-layer gradient composite material as an example, in the upper layer, due to the relatively high volume fraction of the Ti 2 AlC reinforcement phase, this layer of material has relatively high strength and hardness, which is particularly important for the front bullet surface of the armored vehicle, because the front bullet surface directly faces the impact and requires higher strength and hardness to resist bullets and absorb bullet energy. With the increase of the volume fraction of the Ti 2 AlC reinforcement phase, the plasticity and toughness of the middle layer are improved, and at the same time, a good balance between strength, hardness and plasticity and toughness is still maintained. This layer plays a transitional role, which can not only support the upper layer material, but also absorb the bullet impact force and provide a certain extension space for the lower layer material. In the lower layer, Ti 2The volume fraction of the AlC reinforcement phase is the lowest, making the material in this layer have extremely high plasticity and toughness, capable of absorbing and dispersing impact energy, effectively reducing the formation and propagation of cracks. This design enables the back face of the armored vehicle to resist internal impacts and deformations, protecting the vehicle structure and the safety of the crew.

[0018] (3) In the thickness direction of the composite material, from top to bottom, the mass fraction of spherical titanium powder gradually decreases. Since titanium is one of the main components of Ti 2 AlC, the decrease in the mass fraction of spherical titanium powder will result in a gradual decrease in the formation amount or content of Ti 2 AlC from the upper layer to the lower layer. This makes the volume fraction of the Ti 2 AlC reinforcement phase relatively high in the upper layer and relatively low in the lower layer. At the same time, in the thickness direction of the composite material, from top to bottom, the particle size of spherical carbon powder gradually increases. The change in particle size will affect the diffusion rate of carbon in the material and the reaction kinetics with titanium and aluminum, thus affecting the formation efficiency and microstructure of Ti 2 AlC. A larger particle size of spherical titanium powder may slow down the reaction rate, resulting in a certain degree of inhibition of the formation of Ti 2 AlC in the lower layer. Since the mass fraction of spherical titanium powder is relatively high and the particle size of carbon powder is relatively small in the upper layer, it is beneficial to form more Ti 2 AlC reinforcement phase, so the upper layer may have higher strength and hardness. With the decrease in the mass fraction of spherical titanium powder and the increase in the particle size of spherical titanium powder, from the upper layer to the lower layer, the volume fraction of Ti 2 AlC gradually decreases, which helps to improve the toughness of the material.

[0019] (4) When preparing the composite material in the present invention, a mixed powder containing titanium powders with different particle sizes is first prepared, and then different mixed powders are respectively pressed into billets, and then the billets are stacked together in sequence, and then cold isostatic pressing is carried out to obtain a pressed billet, and finally SPS sintering is carried out. Among them, by adjusting the pressing parameters, the close contact and uniform distribution between powder particles can be ensured, thereby improving the overall performance of the material. The spark plasma sintering (SPS) technology has the advantages of fast heating rate, short sintering time, and low energy consumption. In step (6), by setting reasonable pressure and heating rate and holding at 1100 - 1300 °C for 10 min, it can be ensured that the material reaches high densification in a short time while retaining a good microstructure.

[0020] (5) In the present invention, the mixed powder is first pressed into a blank and then sintered, rather than directly laying the mixed powder in the graphite mold of the plasma discharge sintering equipment. Through the pressing process, the gaps between the mixed powder particles are effectively compressed, making the pressed blank have a higher density. In the subsequent sintering process of this high-density blank, the contact area between the powder particles increases, which is beneficial to the formation and growth of sintering necks, thereby improving the density of the final sintered body. At the same time, sintering after pressing into a blank can make the pore distribution in the sintered body more uniform, reducing the performance differences caused by uneven pore distribution. In addition, the pressing process can also eliminate the stress concentration points in the powder to a certain extent, improving the mechanical properties and fatigue resistance of the sintered body.

[0021] (6) The in-situ self-generated gradient Ti 2 AlC / Ti composite material has broad application prospects in high-end fields such as armored vehicles, aerospace, and medical devices due to its excellent mechanical properties and gradient microstructure regulation ability. Especially in the field of armored vehicles, this material can meet the requirements of different performance characteristics for the bullet-facing surface and the back bullet-facing surface, improving the vehicle's protection ability and survival ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the preparation flow chart for preparing the composite material of the present invention.

[0023] Figure 2 It is the schematic diagram of the preparation method for preparing the composite material of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention discloses an in-situ self-generated gradient Ti 2 AlC / Ti composite material and its preparation method. The microstructure of this Ti 2 AlC / Ti composite material includes a Ti matrix and a network-like Ti 2 AlC reinforcement phase distributed in the Ti matrix. Along the thickness direction of the composite material, the volume fraction of the network-like Ti 2 AlC reinforcement phase decreases in a gradient from top to bottom.

[0025] The composite material includes an upper layer, a middle layer, and a lower layer in sequence from top to bottom along the thickness direction. The volume fraction of the network-like Ti 2 AlC reinforcement phase in the upper layer is 13 - 50%, the volume fraction of the network-like Ti 2 AlC reinforcement phase in the middle layer is 4 - 30%, and the volume fraction of the network-like Ti 2 AlC reinforcement phase in the lower layer is 2 - 20%.

[0026] In each layer, the network-like Ti 2The volume fraction of the AlC reinforcement is affected by both the mass ratio of raw materials and the particle size of spherical titanium powder. Along the thickness direction of the composite material, the mass fraction of spherical titanium powder in the raw materials used decreases gradually from top to bottom, while the particle size of spherical carbon powder increases gradually.

[0027] An in-situ self-generated gradient Ti 2 Preparation method of AlC / Ti composite material, please refer to Figure 1-2 , which mainly includes the following steps: Step (1): Weigh spherical titanium powders with different particle size grades; Step (2): Uniformly disperse graphene into deionized water, and at the same time add dodecylbenzenesulfonic acid. A monolayer uniformly dispersed graphene solution is obtained through ultrasonic dispersion, and monolayer graphene nanosheets are obtained after drying; Put spherical Al powder into a ball milling tank, and at the same time add zirconia as the ball milling medium to obtain flaky Al powder through high-energy ball milling; The graphene solution and flaky aluminum powder are respectively subjected to low-energy ball milling with titanium powders of different particle size grades to obtain a variety of Ti@(Al-C) composite powders; In this step, monolayer graphene nanosheets and flaky aluminum powder are uniformly coated on the surface of titanium powder through low-energy ball milling to form Ti@(Al-C) composite powders; Low-energy ball milling ensures the uniformity and dispersion of the composite powders, providing favorable conditions for the sintering process in the subsequent steps; The addition of graphene can significantly improve the electrical conductivity and thermal conductivity of the composite material, and in-situ self-generated reactions occur with flaky aluminum powder and titanium powder during sintering to generate Ti2AlC reinforcement; Step (3): Use each Ti@(Al-C) composite powder for cold isostatic pressing. The pressure of cold isostatic pressing is 80 - 110 MPa, and the pressure is maintained for 5 - 10 min to obtain a plurality of blanks. The powder particles are closely contacted and embedded with each other through high pressure to form blanks with certain strength and density. This step provides a good foundation for the subsequent gradient stacking and sintering processes; Step (4): Stack the blanks in the order of gradually increasing particle size grade of titanium powder from top to bottom. By stacking blanks with different particle size grades in the order of gradually increasing from top to bottom, a Ti2AlC / Ti composite material with a gradient distribution along the thickness direction can be formed. This gradient distribution helps to improve the overall coordinated deformation ability of the material and at the same time meet the requirements of different performance characteristics of materials in fields such as armored vehicles; Step (5): Perform cold isostatic pressing on the stacked blanks again. The pressure of cold isostatic pressing is 50 - 100 MPa, and the pressure is maintained for 3 - 5 min to obtain a pressed blank. This step further compacts and solidifies the stacked blanks to ensure tight bonding between layers and avoid defects such as delamination or cracks during the sintering process; By performing cold isostatic pressing again, the density and strength of the pressed blank can be improved, providing better conditions for the subsequent sintering process; Step (6): Place the compacted blank in a graphite mold, then place it in a spark plasma sintering furnace for sintering. Heat it to 1100 - 1300 °C at a pressure of 45 MPa and a heating rate of 100 °C / min, hold for 10 min, and then cool it in the furnace to obtain the product. By placing the compacted blank in a graphite mold and sintering it in an SPS furnace, the titanium powder, aluminum powder, and graphene in the Ti@(Al-C) composite powder can undergo in-situ self-generation reactions at high temperatures to form Ti 2 AlC reinforcement phase, and tightly combine with the Ti matrix to form a Ti 2 AlC / Ti composite material with a gradient distribution.

[0028] It should be noted that in step (2), the thickness of the graphene nanosheets used is 3 - 10 nm, and the sheet diameter is 5 - 10 μm. The ultrasonic dispersion power is 840 W, and the ultrasonic dispersion time is 100 min.

[0029] Furthermore, in step (2), the preparation of flaky Al powder is achieved by wet milling with absolute ethanol, using zirconia balls as the milling medium with a ball diameter of 5 mm. The specific experimental parameters are a ball-to-material ratio of 20:1, a rotation speed of 300 r / min, and a milling time of 20 h.

[0030] Furthermore, in step (2), the composite powder is achieved by dry milling, using zirconia balls as the milling medium with a ball diameter of 5 mm. The specific experimental parameters are a ball-to-material ratio of 10:1, a rotation speed of 100 - 120 r / min, and a milling time of 10 - 12 h.

[0031] The technical solution of the present invention will be elaborated in detail below in conjunction with specific embodiments.

[0032] Example 1

[0033] A preparation method of in-situ self-generated gradient Ti 2 AlC / Ti composite material mainly includes the following steps: (1) Raw material preparation Prepare Ti@(Al-C) composite powder A: Weigh spherical titanium powder with a particle size of 0 - 20 μm, and perform low-energy ball milling on the spherical titanium powder, graphene nanosheets, and flaky Al powder according to a mass ratio of 29:1:1 to obtain Ti@(Al-C) composite powder A; Prepare Ti@(Al-C) composite powder B: Weigh spherical titanium powder with a particle size of 30 - 60 μm, and perform low-energy ball milling on the spherical titanium powder, graphene nanosheets, and flaky Al powder according to a mass ratio of 29:2:2 to obtain Ti@(Al-C) composite powder B; Preparation of Ti@(Al-C) composite powder C: Weigh spherical titanium powder with a particle size of 100 - 150 μm, and perform low-energy ball milling on the spherical titanium powder, graphene nanosheets, and flaky Al powder according to a mass ratio of 29:3:3 to obtain Ti@(Al-C) composite powder C; (2), Press the blank Press the Ti@(Al-C) composite powder A into the first blank by cold isostatic pressing; the pressing parameter is 80 MPa; Press the Ti@(Al-C) composite powder B into the second blank by cold isostatic pressing; the pressing parameter is 80 MPa; Press the Ti@(Al-C) composite powder C into the third blank by cold isostatic pressing; the pressing parameter is 80 MPa; (3), Stack the third blank, the second blank, and the first blank together from bottom to top in sequence; (4), Perform cold isostatic pressing on the stacked blanks again, with the pressing parameter of 100 MPa to obtain the pressed blank; (5), Place the pressed blank in a graphite mold, place it in a spark plasma sintering equipment for sintering. The specific parameters of SPS sintering are: heat to 1200 °C at a pressure of 45 MPa and a heating rate of 100 °C / min, and keep the temperature for 10 min.

[0034] Example 2

[0035] The difference between this example and Example 1 is that in step (1), the mass ratio of spherical titanium powder, graphene nanosheets, and flaky Al powder in the Ti@(Al-C) composite powder A is 29:5:5; the mass ratio of spherical titanium powder, graphene nanosheets, and flaky Al powder in the Ti@(Al-C) composite powder B is 29:7:7; the mass ratio of spherical titanium powder, graphene nanosheets, and flaky Al powder in the Ti@(Al-C) composite powder C is 29:9:9.

[0036] Example 3 The difference between this embodiment and Example 1 is that in step (1), the mass ratio of spherical titanium powder, graphene nanosheets, and flaky Al powder in the Ti@(Al-C) composite powder A is 58:1:1; the mass ratio of spherical titanium powder, graphene nanosheets, and flaky Al powder in the Ti@(Al-C) composite powder B is 29:1:1; the mass ratio of spherical titanium powder, graphene nanosheets, and flaky Al powder in the Ti@(Al-C) composite powder C is 58:3:3.

[0037] Comparative example

[0038] The difference between this embodiment and Example 1 is that: (1) Step one only includes the Ti@(Al-C) composite powder A, and the obtained is a traditional uniformly composite material.

[0039] The volume fraction, strength, and toughness of Ti 2 AlC in the composite materials obtained in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0040] Table 1 Volume fraction of Ti 2 AlC, test results of the strength and toughness of the products in the composite materials obtained in Examples 1-3 and Comparative Example 1

[0041] As can be seen from Table 1, the higher the volume fraction of Ti 2 AlC, the higher the strength of the material and the worse the plasticity. However, after exceeding a certain value, the strength will gradually decrease. An armored vehicle requires both high hardness and strength, as well as good plastic toughness. Therefore, it is necessary to comprehensively control the volume fraction of Ti 2 AlC in each layer to achieve an optimal solution (such as Example 1).

[0042] The above are only the preferred embodiments of the present invention, and do not impose any formal restrictions on the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An in-situ self-generated gradient Ti2AlC / Ti composite material, characterized in that: The microstructure of the Ti2AlC / Ti composite material includes a Ti matrix and a network Ti2AlC reinforcement phase distributed in the Ti matrix. Along the thickness direction of the composite material, the volume fraction of the network Ti2AlC reinforcement phase is distributed in a gradient decreasing manner from top to bottom.

2. The in-situ self-generated gradient Ti2AlC / Ti composite material according to claim 1, characterized in that: The composite material comprises an upper layer, an intermediate layer and a lower layer in order from top to bottom along the thickness direction, the volume fraction of the network Ti2AlC reinforcement phase in the upper layer is 13-50%, the volume fraction of the network Ti2AlC reinforcement phase in the intermediate layer is 4-30%, and the volume fraction of the network Ti2AlC reinforcement phase in the lower layer is 2-20%.

3. The in-situ self-generated gradient Ti2AlC / Ti composite material according to claim 2, characterized in that: The volume fraction of the network Ti2AlC reinforcement phase in the upper layer is 24.87%, the volume fraction of the network Ti2AlC reinforcement phase in the middle layer is 17.6%, and the volume fraction of the network Ti2AlC reinforcement phase in the lower layer is 13.62%.

4. The in-situ self-generated gradient Ti2AlC / Ti composite material according to claim 2, characterized in that: The volume fraction of the network Ti2AlC reinforcement phase in each layer is affected by the mass ratio of the raw materials and the particle size of the spherical titanium powder. Along the thickness direction of the composite material, the mass fraction of the spherical titanium powder in the raw materials used gradually decreases from top to bottom, while the particle size of the spherical carbon powder gradually increases.

5. A method for preparing an in-situ self-generated gradient Ti2AlC / Ti composite material, characterized in that: The main steps are as follows: (1) Weigh spherical titanium powder of different particle sizes; (2) Low-energy ball milling of graphene solution and flaky aluminum powder with spherical titanium powder of different particle sizes to obtain a variety of Ti@(Al-C) composite powders; (3) Using each Ti@(Al-C) composite powder to perform cold isostatic pressing to obtain a plurality of blanks; (4) stacking the blanks in the order of increasing particle size of titanium powder in the blanks from top to bottom; (5) cold isostatic pressing is performed again on the stacked blanks to obtain pressed blanks; (6) Place the pressed blank in a graphite mold, then place it in a spark plasma sintering furnace for sintering, and then cool it in the furnace to obtain a product.

6. The method for preparing an in-situ self-generated gradient Ti2AlC / Ti composite material according to claim 5, characterized in that: The composite material is formed by pressing three kinds of Ti@(Al-C) composite powders, wherein the particle size of the spherical titanium powder in the Ti@(Al-C) composite powder used in the upper layer is 0-20μm; the particle size of the spherical titanium powder in the Ti@(Al-C) composite powder used in the middle layer is 30-60μm; and the particle size of the spherical titanium powder in the Ti@(Al-C) composite powder used in the lower layer is 100-150μm.

7. The method for preparing an in-situ self-generated gradient Ti2AlC / Ti composite material according to claim 5, characterized in that: In step (3), the cold isostatic pressing pressure is 80-110 MPa, and the pressure is maintained for 5-10 min.

8. The method for preparing an in-situ self-generated gradient Ti2AlC / Ti composite material according to claim 5, characterized in that: In step (5), the cold isostatic pressing pressure is 50-100 MPa, and the pressure is maintained for 3-5 minutes.

9. The method for preparing an in-situ self-generated gradient Ti2AlC / Ti composite material according to claim 5, characterized in that: In step (6), the spark plasma sintering process is set as follows: heating to 1100-1300° C. at a pressure of 45 MPa and a heating rate of 100° C. / min, and holding time of 10 min.

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