A tc4-al2o3 gradient composite material and a preparation method thereof

Abstract

The application discloses a TC4-Al2O3 gradient composite material and a preparation method thereof. The functional gradient composite material is prepared by using powder shock wave treatment, powder grading technology and hot isostatic pressing sintering technology. The preparation process comprises the following steps: powder shock wave treatment, raw material mixing, pressing forming, degreasing and pre-sintering, and sintering. The material is uniformly shrunk, has no deformation and cracking, and has the properties of titanium alloy and ceramic on two sides respectively, and has no interface problem, and has the potential for use under extreme conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material preparation, and particularly relates to a preparation of TC4-Al2O3 gradient composite material. BACKGROUND

[0002] Functional gradient material (FGM) refers to two-component materials along a certain direction, the structure or composition of each component changes in a gradient, and the performance also changes with the change of the structure or composition. Functional materials have special properties in structure / composition, which can realize the characteristics of two materials on one material. The two sides of the material have different characteristics, such as one side is metal and the other side is ceramic. The middle part is a plate material gradually changing from metal to ceramic, which can have the dual characteristics of metal and ceramic materials. It has the hardness and corrosion resistance, high temperature resistance of ceramic, and also has the strength and toughness of metal. And because the middle layer is a continuous transition, there is no obvious interface, and the interface problem can be avoided. During use, it is not easy to produce cracking and other problems, and it has great advantages compared with traditional layered composite materials. For example, in the field of aerospace, the combustion chamber of the engine, one side needs to contact high-temperature gas, so the material on this side needs to have the ability of high-temperature resistance and corrosion resistance, and ceramic material is often used. The other side needs to be in contact with cooling liquid to reduce temperature and has high specific strength, so metal is often used as the material on this side. However, the physical properties such as strength and thermal expansion coefficient of metal and ceramic are quite different, and in the process of use, cracking, deformation, peeling and other phenomena often occur at the interface connection. Therefore, the way of combining two homogeneous materials with large performance difference together is not suitable for such extreme conditions. Titanium alloy has high specific strength, Al2O3 ceramic has high strength, high heat resistance, high corrosion resistance, oxidation resistance and other properties. Ti / Al2O3 gradient composite material made of the two has continuous composition / structure change and no interface problem, and can meet the use requirements in extreme environments such as large temperature difference and ultra-high temperature. It is expected to be used as a new generation of aerospace aircraft body, combustion chamber wall, turbine engine, high-efficiency gas turbine and other parts of heat-resistant materials.

[0003] Powder metallurgy is an important method for the preparation of functionally graded materials, and the basic process is to place the mixed powder layer by layer, and then to obtain a dense sintered body of the graded material by pressing and sintering. The method is relatively simple, has free composition design, and has small shape limitation, but the asynchronous sintering shrinkage widely exists in the sintering process. The reasons for the uneven shrinkage are related to the particle characteristics of the raw material powder, the material structure and the sintering atmosphere. According to the particle composition of the sintered body, the reasons for the asynchronous sintering shrinkage can be divided into two categories: sintering of powders of different particle sizes of the same material and sintering of powders of different materials. The asynchronous sintering shrinkage of powders of different materials mainly exists in the preparation process of functionally graded materials and composite materials, such as metal-ceramic co-sintered body. The sintering temperature of powders of different materials is obviously different, and the order of reaching the sintering temperature is different, which leads to asynchronous shrinkage, and there are interface problems between different layers if the shrinkage is uneven. In addition, the characteristics of powders of different materials are quite different, such as the difference in thermal expansion coefficient, and when cooling and shrinking, due to the uneven shrinkage at the interface between different materials, a large residual stress is generated, which causes defects.

[0004] Due to the layer-by-layer laying of the powder, there is a difference in the sintering temperature between each layer, and there is a difference in the physical properties of the material, so there is inevitably a difference in the shrinkage between the layers, which further causes deformation and cracking problems. Therefore, the main problem in the preparation of graded material parts by powder metallurgy process at present is the non-uniform shrinkage caused by the sintering of the sintered body of the non-homogeneous powder. SUMMARY

[0005] In order to solve the problems in the prior art, the present application uses shock wave powder processing powder technology, particle grading, and hot isostatic pressing sintering technology to solve the deformation and cracking problems between the gradients of the gradient composite material, and provides a TC4-Al2O3 gradient composite material and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A TC4-Al2O3 gradient composite material, characterized in that the composition (TC4) 100-x -(Al2O3) x is (TC4) 20 -(Al2O3) 80 is (TC4) 80 -(Al2O3) 20 transition;

[0008] The TC4-Al2O3 and (TC4) 100-x -(Al2O3) x , Al2O3 is a mixture containing 2-3% TiO2 and 2-4% (CaO-MgO-SiO2) sintering aid, and TC4 is TC4 titanium alloy;

[0009] The CaO-MgO-SiO2 sintering aid has a mass ratio of 20:23:57.

[0010] A preparation method of a TC4-Al2O3 gradient composite material, characterized by a preparation process comprising powder shock wave treatment, raw material mixing, pressing forming, debinding and pre-sintering, and sintering in sequence.

[0011] The powder shock wave treatment comprises placing Al2O3 raw material powder in a recovery container and performing shock wave treatment at a pressure of 10-15 GPa.

[0012] The raw material mixing comprises uniformly mixing Al2O3 raw material powder of different particle sizes with TC4 titanium alloy powder and a sintering aid in a proportion, wherein the mass ratio of the components is (TC4) 20 -(Al2O3) 80 , (TC4) 30 -(Al2O3) 70 , (TC4) 40 -(Al2O3) 60 , (TC4) 50 -(Al2O3) 50 , (TC4) 60 -(Al2O3) 40 , (TC4) 70 -(Al2O3) 30 , (TC4) 80 -(Al2O3) 20 , and 2-4% paraffin is further mixed into each proportion of powder.

[0013] Preferably, the Al2O3 raw material powder has a purity of >99% and particle sizes of 100-300 nm, 0.5-1 μm, and 1-3 μm, and the TC4 titanium alloy powder has a purity of >99% and a particle size of 50-150 μm.

[0014] Preferably, in the (TC4) 20 -(Al2O3) 80、 , the Al2O3 raw material powder has a particle size of 100-300 nm, in the (TC4) 30 -(Al2O3) 70、 , the Al2O3 raw material powder has a particle size of 0.5-1 μm, in the (TC4) 40 -(Al2O3) 60 , the Al2O3 raw material powder has a particle size of 1-3 μm, in the (TC4) 50 -(Al2O3) 50 , the Al2O3 raw material powder has a particle size of 50-150 μm, in the (TC4) 60 -(Al2O3) 40 , the Al2O3 raw material powder has a particle size of 0.5-1 μm, and in the (TC4) 70 -(Al2O3)30 (TC4) 80 -(Al2O3) 20 The Al2O3 raw material powder has a particle size of 1-3 μm.

[0015] In a preferred embodiment, the forming process is as follows: the alloy powders with different proportions are first pressed into blanks at 30-40 MPa in a forming machine at the same mass ratio, and then the blanks with increasing TC4 content are stacked in turn on the bottom to be isostatic pressed at 100-150 MPa. 20 -(Al2O3) 80

[0016] In a preferred embodiment, the debinding and pre-sintering are as follows: the formed green body is placed in a debinding furnace, vacuum is drawn to below 10-3 Pa, high-purity nitrogen / argon is introduced, the temperature is raised to 400-500 °C at a rate of 1-3 °C / min, and the temperature is maintained for 60-180 min to complete debinding, then vacuum is drawn, the temperature is raised to 900-1000 °C at a rate of 3-5 °C / min, and the temperature is maintained for 30-60 min to complete pre-sintering.

[0017] In a preferred embodiment, the sintering is hot isostatic sintering, and the specific process is as follows: the pre-sintered product is placed in a bag, the temperature is raised to 1350-1400 °C at a rate of 3-6 °C / min, the temperature is maintained for 60-90 min, and the pressure is 50-70 MPa.

[0018] Principle and advantages

[0019] ​The sintering temperature of the layers with different proportions is different, and the sintering temperature of the metal end gradually increases to the ceramic end, the layer that reaches the sintering temperature first will shrink, and the layer that does not reach the sintering temperature will not shrink, at this time, internal stress is generated between the shrinkage layer and the non-shrinkage layer, which is easy to cause cracking. According to the sintering theory, the shrinkage mainly occurs in the second stage of sintering neck growth, the specific surface area of large particle powder is relatively small compared with small particle powder, the contact points of powder are less, the sintering neck is less formed, the surface energy is lower, the sintering driving force is smaller, and it is more difficult to make the sintering neck grow through the transfer of matter, so the particle grading technology can be used to adjust the particle size of each layer to change the sintering temperature of each layer, so that the sintering temperature of each layer is as close as possible, and the defect problem caused by sintering shrinkage is reduced. The sintering temperature of TC4 is about 1300 DEG C, and the sintering temperature of pure Al2O3 commonly used in industry can reach 1700 DEG C, and research shows that the sintering temperature can be significantly reduced by using ultra-fine Al2O3 powder, and when the particle size is refined to 20 nm, the sintering temperature can even be reduced to 1000 DEG C, so the application selects nano and micro Al2O3 powder as raw material to reduce the sintering temperature of the Al2O3-rich layer, and the particle size distribution decreases with the increase of Al2O3 content. In addition, the Al2O3 raw powder is treated by shock wave, so that the crystal lattice is distorted, the powder energy is increased, the internal defects (such as dislocation) of the powder are increased, and the diffusion rate of matter at the crystal defects is higher, so the shock wave treatment can improve the sintering activity of the powder and further reduce the sintering temperature. Furthermore, a certain sintering aid, such as TiO2, Ba2O3, CaO alkali metal oxide, etc., is added, the lattice of TiO2 is similar to that of Al2O3, but the radius of its ion is larger than that of Al 3+ ion, so that the lattice is distorted after solid solution, the lattice is activated, the sintering temperature is reduced, and the sintering is easier, and CaO-MgO-SiO2 and MgO-Al2O3-SiO2 can form glass phase in the sintering process, which can also reduce the sintering temperature. The purpose of isostatic sintering is to apply pressure during sintering, which is more conducive to the densification of the material and the application of compressive stress on the surface, which can effectively reduce the risk of cracking.

[0020] Compared with the prior art, the application solves the problem of deformation and cracking caused by uneven shrinkage between layers by using shock wave treatment powder technology, powder grading technology and hot isostatic sintering technology, and provides a preparation method of TC4-Al2O3 gradient composite material, the material shrinks uniformly without obvious deformation and cracking, the high TC4 side of the material has the strength and toughness of titanium alloy, the high Al2O3 side has the characteristics of ceramic such as wear resistance, corrosion resistance and high strength, and has good market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Process flow diagram

[0022] Figure 2Material pressing stack schematic diagram DETAILED DESCRIPTION

[0023] The method of the present application is further described below in connection with three examples. EXAMPLE

[0024] A TC4-Al2O3 gradient composite material and a preparation method thereof, the process being as follows:

[0025] Powder shock wave treatment: Al2O3 raw material powders with particle sizes of 300 nm, 0.5 μm and 1 μm respectively were subjected to shock wave treatment, the powders were placed in a recovery box, and the powders were treated by shock wave caused by detonation of explosives using a detonator, the shock pressure being 13.8 GPa.

[0026] Raw material mixing: Al2O3 raw material powders with different particle sizes were mixed with TC4 powder and sintering aids in proportion, wherein the mass of sintering aid TiO2 was 2% of the Al2O3 raw material powder, and the mass of CaO-MgO-SiO2 was 2% of the Al2O3 raw material powder, when mixing, the TC4 powder was mixed with the Al2O3 raw material powder with a particle size of 300 nm, the TC4 powder was mixed with the Al2O3 raw material powder with a particle size of 0.5 μm, and the TC4 powder was mixed with the Al2O3 raw material powder with a particle size of 1 μm. 20 -(Al2O3) 80、 (TC4) 30 -(Al2O3) 70、 (TC4) 40 -(Al2O3) 60 The Al2O3 raw material powder had a particle size of 300 nm, the TC4 powder was mixed with the Al2O3 raw material powder. 50 -(Al2O3) 50 , the TC4 powder was mixed with the Al2O3 raw material powder. 60 -(Al2O3) 40 The Al2O3 raw material powder had a particle size of 0.5 μm, the TC4 powder was mixed with the Al2O3 raw material powder. 70 -(Al2O3) 30 , the TC4 powder was mixed with the Al2O3 raw material powder. 80 -(Al2O3) 20 The Al2O3 raw material powder had a particle size of 1 μm, and 2% of paraffin was mixed into each kind of mixed powder.

[0027] Pressing forming: the alloy powders with different proportions were first pressed into blanks in a forming machine at 30 MPa, then the (TC4) 20 -(Al2O3) 80 was placed at the bottom, and the blanks with increasing TC4 content were stacked in sequence on top, and isostatic pressing was performed at 150 MPa.

[0028] Degreasing and pre-sintering: the green body after forming was placed in a degreasing furnace, vacuum was extracted to 10 -3After Pa, pass high-purity nitrogen / argon, 1 ℃ / min to 400 ℃, and keep for 90 min to complete the degreasing, then vacuumize, and heat to 900 ℃ at 3 ℃ / min, keep for 60 min to complete the pre-sintering.

[0029] Sintering: place the pre-sintered product in a jacket, heat to 1400 ℃ at 3 ℃ / min, keep for 90 min, and perform hot isostatic sintering at a pressure of 70 MPa. Embodiment

[0030] A TC4-Al2O3 gradient composite material and a preparation method thereof, the process being as follows:

[0031] Powder shock wave treatment: Al2O3 raw material powders with particle sizes of 100 nm, 0.5 μm and 1 μm are subjected to shock wave treatment respectively, the powders are placed in a recovery box, and the shock wave caused by detonation of a detonator is used to treat the powders, and the shock pressure is 10 GPa.

[0032] Raw material mixing: the Al2O3 raw material powders with different particle sizes are mixed with TC4 powder and sintering aids in proportion, wherein the mass of the sintering aid TiO2 is 3% of the Al2O3 raw material powders, and the mass of CaO-MgO-SiO2 is 3% of the Al2O3 raw material powders, when mixing, the TC4 powder is placed at the bottom, and the Al2O3 raw material powders are stacked on the TC4 powder in order of increasing particle size. 20 -(Al2O3) 80、 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder. 30 -(Al2O3) 70、 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder. 40 -(Al2O3) 60 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder. 50 -(Al2O3) 50 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder. 60 -(Al2O3) 40 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder. 70 -(Al2O3) 30 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder. 80 -(Al2O3) 20 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder.

[0033] Pressing forming: the alloy powders with different proportions are first pressed into blanks in a forming machine at 40 MPa, then the TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder. 20 -(Al2O3) 80 The TC4 powder is placed at the bottom, and the TC4 powder with increasing TC4 content is stacked in order on the TC4 powder.

[0034] Debinding and pre-sintering: the formed green body is placed in a debinding furnace, vacuumed to 10 -3 After the temperature is raised to 500℃ at a rate of 1℃ / min, the debinding is completed after 90min, then vacuumed, and the temperature is raised to 1000℃ at a rate of 3℃ / min, and the pre-sintering is completed after 30min.

[0035] Sintering: the pre-sintered product is placed in a package, the temperature is raised to 1350℃ at a rate of 3℃ / min, and the sintering is completed after 60min under a pressure of 50MPa by hot isostatic pressing. Example

[0036] A TC4-Al2O3 gradient composite material and a preparation method thereof, the process being as follows:

[0037] Powder shock wave treatment: Al2O3 raw material powders with particle sizes of 300nm, 1μm and 3μm are treated by shock wave, respectively, the powders are placed in a recovery box, and the powders are treated by the shock wave caused by the detonation of explosives, and the shock pressure is 15GPa.

[0038] Raw material mixing: the Al2O3 raw material powders with different particle sizes are mixed with TC4 powder and sintering additives in proportion, wherein the mass of the sintering additive TiO2 is 3% of the Al2O3 raw material powders, and the mass of CaO-MgO-SiO2 is 4% of the Al2O3 raw material powders, and when the materials are mixed, the TC4 20 -(Al2O3) 80、 (TC4) 30 -(Al2O3) 70、 (TC4) 40 -(Al2O3) 60 The particle size of the Al2O3 raw material powder in the middle is 300nm, the TC4 50 -(Al2O3) 50 , the TC4 60 -(Al2O3) 40 The particle size of the Al2O3 raw material powder in the middle is 1μm, the TC4 70 -(Al2O3) 30 , the TC4 80 -(Al2O3) 20 The particle size of the Al2O3 raw material powder in the middle is 3μm, and 3% of paraffin is mixed into each kind of powder in proportion.

[0039] Pressing forming: the alloy powders with different proportions are first pressed into blanks in a forming machine at a pressure of 30MPa, then the (TC4) 20 -(Al2O3) 80 is placed at the bottom, and the TC4-containing blanks with increasing contents are stacked on the bottom in turn, and the isostatic pressing is completed at a pressure of 130MPa.

[0040] Defatting and pre-sintering: the shaped green body is placed in a defatting furnace, vacuumed to 10 -3 After the temperature is raised to 450℃ at a rate of 3℃ / min, the defatting is completed after 90min of heat preservation, then vacuumed, and the temperature is raised to 900℃ at a rate of 3℃ / min, and the pre-sintering is completed after 60min of heat preservation.

[0041] Sintering: the pre-sintered product is placed in a package, the temperature is raised to 1400℃ at a rate of 3℃ / min, and the sintering is completed after 80min of heat preservation under a pressure of 70MPa.

[0042] Comparative Example 1

[0043] The comparative example uses the same method as Example 2, except that the powder is not subjected to shock wave treatment, and the result is that the Al2O3-rich ceramic end pores are large and not dense.

[0044] Comparative Example 2

[0045] The comparative example uses the same method as Example 2, except that the particle size of the Al2O3 raw material powder used is different, and the results are as follows.

[0046]

[0047] Comparative Example 3

[0048] The comparative example uses the same method as Example 2, except that the addition amount of TiO2 and CaO-MgO-SiO2 sintering aids is different, and the results are as follows.

[0049]

[0050] Comparative Example 4

[0051] The comparative example uses the same method as Example 2, except that the lamination method before isostatic pressing is different, and the results are that the shrinkage difference between layers is large, and the material deforms and cracks.

[0052] Comparative Example 5

[0053] The comparative example uses the same method as Example 2, except that pressureless sintering is used, and the results are that the material deforms and cracks, and is not dense.

[0054] The above examples are only the preferred implementation methods of the present application, and therefore cannot limit the scope of implementation of the present application, and other equivalent changes, modifications, substitutions and combinations made in accordance with the principles and content of the present application still belong to the protection scope of the present application.

Claims

1. A method for preparing a TC4-Al2O3 gradient composite material, characterized in that Its components (TC4) 100-x -(Al2O3) x By mass fraction from (TC4) 80 -(Al2O3) 20 To (TC4) 20 -(Al2O3) 80 Transition, the preparation process is powder shock wave processing, raw material mixing, pressing forming, debinding and pre-sintering, hot isostatic pressing sintering; TC4-Al2O3 and (TC4) 100-x -(Al2O3) x In the formula, Al2O3 is a mixture containing 2-3% TiO2 and 2-4% (CaO-MgO-SiO2) sintering aids, and TC4 is TC4 titanium alloy. The mass ratio of the CaO-MgO-SiO2 sintering aid is 20:23:57; In the preparation process: 1) the powder shock wave treatment is to place Al2O3 raw material powder in a recovery container and perform shock wave treatment at a pressure of 10-15 GPa; 2) The raw material is mixed by mixing Al2O3 raw material powder with different particle sizes, TC4 titanium alloy powder and sintering aid in proportion, and the mass ratio of each component is (TC4) 80 - (Al2O3) 20 , (TC4) 70 - (Al2O3) 30 , (TC4) 60 - (Al2O3) 40 , (TC4) 50 - (Al2O3) 50 , (TC4) 40 - (Al2O3) 60 , (TC4) 30 - (Al2O3) 70 , (TC4) 20 - (Al2O3) 80 , and then 2-4% paraffin is mixed into each proportion of powder; 3) said (TC4) 20 - (Al203) 80 , (TC4) 30 - (Al203) 70 , (TC4) 40 - (Al203) 60 The Al203 raw material powder particle size in (TC4) 50 - (Al203) 50 , (TC4) 60 - (Al203) 40 The Al203 raw material powder particle size in (TC4) 70 - (Al203) 30 , (TC4) 80 - (Al203) 20 The Al203 raw material powder particle size in (TC4) 1-3 μm; 4) The compression molding process is to compress different proportions of alloy powder into blanks in the forming machine at the same mass ratio of 30-40 MPa, and then stack the TC4 content increasing compacts on the bottom in turn to isostatic pressing at 100-150 MPa. 20 - (Al2O3) 80 is placed at the bottom, and the TC4 content increasing compacts are stacked in turn to isostatic pressing at 100-150 MPa. 5) the hot isostatic pressing sintering process is to place the pre-sintered product in a package, heat to 1350-1400℃ at a temperature increasing rate of 3-6℃ / min, keep for 60-90 min, and the pressure is 50-70 MPa.

2. The method for preparing TC4-Al2O3 gradient composite material according to claim 1, characterized in that, The purity of Al2O3 raw material powder is greater than 99%, the particle size is 100-300 nm, 0.5 m-1 μm and 1-3 μm respectively, the purity of TC4 titanium alloy powder is greater than 99%, and the particle size is 50-150 μm.

3. The method of claim 1, wherein the TC4-Al2O3 gradient composite material is prepared by the following steps of: After the forming, the green body is placed in a degreasing furnace, vacuumed to 10 -3 After the temperature is raised to 400-500℃ at a rate of 1-3℃ / min, the degreasing is completed after 60-180min. Then, vacuum is applied, the temperature is raised to 900-1000℃ at a rate of 3-5℃ / min, and the pre-sintering is completed after 30-60min. ​

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