CN114749678A - Preparation method for gamma-based high-temperature TiAl composite material coaxial powder feeding 3D printing - Google Patents

Preparation method for gamma-based high-temperature TiAl composite material coaxial powder feeding 3D printing Download PDF

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CN114749678A
CN114749678A CN202210218687.0A CN202210218687A CN114749678A CN 114749678 A CN114749678 A CN 114749678A CN 202210218687 A CN202210218687 A CN 202210218687A CN 114749678 A CN114749678 A CN 114749678A
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CN114749678B (en
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梁永锋
薛辉
林均品
郭英超
王雪
佟欣桓
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University of Science and Technology Beijing USTB
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Abstract

A preparation method of gamma-based high-temperature TiAl composite material coaxial powder feeding 3D printing. With Si3N4The in-situ authigenic micro-nano particle mesh-coated synergistically-enhanced TiAl-based composite material is prepared by ball-milling and mixing silicon source and nitrogen source with prealloyed powder Ti-55Al-7.5Nb with high Al content and 3D printing. Micro-nano particles are dispersed in the composite material matrixGrade Ti2AlN and Ti5Si3A reinforcing phase. Micron-sized Ti2AlN and Ti5Si3The reinforcing phase is 5-10 mu m and Ti with nano-scale5Si3The reinforcing phase is 50 nm-100 nm, both reinforcing phases have reinforcing effect on the TiAl-based composite material, wherein the nano Ti5Si3The reinforcing phase is almost precipitated in the grain boundary of the gamma crystal grains of the matrix and plays a role of pinning the grain boundary. The precipitation coexistence of two reinforcing phases with different scales further improves the high-temperature structure stability of the gamma-based TiAl composite material, solves the problems of high energy consumption, serious environmental pollution and the like of the TiAl alloy prepared by the traditional process, solves the problem of the degradation of the high-temperature structure of the TiAl alloy widely applied at present, can be widely realized in industry, and has wide application prospect.

Description

Preparation method for gamma-based high-temperature TiAl composite material coaxial powder feeding 3D printing
Technical Field
The invention belongs to the field of TiAl and preparation of metal matrix composite materials thereof, and particularly relates to in-situ synthesized Ti5Si3And Ti2The preparation method of the AlN multiphase synergistic gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing.
Background
With the proposal of carbon neutralization by carbon peak, the energy, traffic and aviation industries also face great challenges, and structural materials occupy a very important position in the industries, especially for high-temperature structural materials applied to aerospace, for aerospace materials, high temperature resistance and light weight are always targets pursued by researchers at home and abroad. TiAl alloy is a novel intermetallic compound structural material, and is gradually paid attention and favored by people due to the fact that TiAl alloy has lower density (the weight reduction effect is 40-50 percent compared with nickel-based high-temperature alloy), high strength, high modulus, combustion resistance and excellent high-temperature oxidation resistance and fatigue resistance. In 2006, the american general company announced that cast TiAl alloys were applied to the two-stage blades of the low-pressure turbine of the GEnx engine of the latest boeing 787 civil aircraft, with a single engine weighing 200 pounds less, and then to the engines of other boeing civil aircraft. Similarly, airbus 320 aircraft engines were equipped with low pressure turbine blades made of TNM wrought TiAl alloys, and were used formally in 2016. The R-R company also plans to use TiAl alloys to produce grade 1-6 low pressure turbine blades for Trent series engines. In addition, the Euramerican national application of TiAl alloy in the manufacture of automobile turbo and exhaust valves has greatly improved the starting performance and dynamic response performance of automobile engines, greatly improved the automobile fuel efficiency, and reduced the emission of carbon dioxide. The TiAl alloy supercharging turbine and the exhaust valve for the vehicle have obvious application effect and huge market. In the past 20 years, a great deal of results are obtained in the research of TiAl alloy at home and abroad, and the application of TiAl in the aspect of aerospace is promoted to be developed to a certain extent.
However, most of the TiAl alloys currently used are of a dual-phase structure, the GE company mainly uses Ti-48Al-2Cr-2Nb (except for special marks, all are in atomic fraction), and the airmen mainly use TNM alloys, that is, most of the alloy structures currently used are alpha2A/gamma full lamellar or near lamellar tissue mainly composed of gamma-TiAl and alpha2-Ti3Al two-phase composition. The dual-phase structure can generate the structure degradation phenomenon in the long-time use at high temperature, namely, part of the structure grows up grains and generates solid phase transformation, and the high-temperature creep property is sharply reduced. Most of TiAl alloys applied at present are formed by casting or plastic deformation, and cast TiAl grains are coarse and have serious structure segregation, thus seriously influencing the later use. Although the microstructure of the deformation structure is fine and relatively uniform, the deformation processing of the TiAl alloy is extremely complex, and the procedures of casting ingot, hot isostatic pressing, sheath extrusion, high-temperature forging and the like are required, and the high-temperature forging requires an expensive forging machine and a forging die, so that the procedures are complex, a large amount of manpower and material resources are required, and the energy consumption is very serious.
In order to solve the problems of high energy consumption, serious environmental pollution and the like of the TiAl alloy prepared by the traditional process and simultaneously solve the problem of degradation of the high-temperature structure of the TiAl alloy widely applied at present, a novel TiAl-based composite material and a preparation and processing technology thereof are urgently needed to be designed, the material does not generate phase change in the high-temperature use process, the tissue degradation phenomenon is avoided, the corresponding preparation and processing technology is suitable for brittle TiAl alloy materials on the one hand, and the process requirement of low carbon and environmental protection on the other hand is met.
Disclosure of Invention
In view of the above, the invention provides a coaxial powder feeding 3D printing preparation method of a γ -based high-temperature Nb-TiAl composite material, so as to solve the above technical problems. In the TiAl alloy, different room-temperature microstructures can be obtained by adjusting the percentage of Al element. Compared with the traditional TiAl alloy, the invention adjusts the atomic ratio fraction of Al to be more than 50 percent. According to a Ti-Al binary phase diagram, theoretically, when the content of Al element is more than 50%, the structure of the alloy under equilibrium solidification is a single-phase gamma-phase structure, and when the alloy is heated to the use temperature of 700-800 ℃ again, even more than 1000 ℃, the alloy cannot pass through a dual-phase region, namely the alloy still is a single-phase structure at high temperature, so that great possibility is brought to the stability of the structure at high temperature and the use of TiAl alloy at higher temperature. However, in the conventional casting method, for casting an alloy with an Al element atomic ratio of more than 50%, a large amount of segregation is formed, so that the alloy forms a large amount of cracks and cannot be formed. Meanwhile, although the monophasic structure cannot be subjected to phase transition to cause tissue degradation, the monophasic structure is not restrained by other phases and can grow large and thick in the cooling process, so that the performance is deteriorated.
In order to solve the technical problems, the invention adopts the technical scheme that:
a preparation method of gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing is characterized in that Si is used3N4For the source of Si and N, Si is added3N4And after the in-situ authigenic micro-nano particles are uniformly mixed with Ti-55Al-7.5Nb alloy powder through low-temperature, low-speed and long-time mechanical ball milling, carrying out laser coaxial powder feeding additive manufacturing on the mixed powder through a low-carbon and environment-friendly 3D printing preparation technology, and cooling to obtain the in-situ authigenic micro-nano particle synergetic reinforced Ti-55Al-7.5 Nb-based composite material. The matrix and the dispersed second phase precipitated at the grain boundary play a certain strengthening role relative to the matrix, and the precipitated phase distributed at the grain boundary plays a good role in pinning the grain boundary relative to the matrix structure, so that the structure is further stabilized.
The preparation method for the gamma-based high-temperature TiAl composite material coaxial powder feeding 3D printing comprises the following steps:
(1) preparing pre-alloyed powder: firstly, preparing a Ti-55Al-7.5Nb round bar ingot by a suspension smelting method, and then preparing prealloy powder with the diameter of 100-180 mu m by a rotary electrode method;
(2) preparing mixed powder raw materials: si is added in an atomic ratio of 0.2 to 1% of the element N3N4Mixing the pre-alloyed powder prepared in the step (1) with silicon and nitrogen sources;
(3) ball milling and mixing powder at low temperature: placing the mixed powder prepared in the step (2) into a ball milling tank of a ball mill, filling argon for protection, mechanically milling the mixed powder at low temperature (5-10 ℃) for 550min at the rotation speed of the ball mill of 160-200r/min to obtain mixed powder, and then preserving the heat of 180-220 ℃ in a vacuum drying box for 12-24 h;
(4)3D printing: and placing the mixed powder into a powder feeder of coaxial powder feeding equipment for 3D printing, and carrying out laser synchronous in-situ heating on the substrate before printing the composite powder to enable the substrate to reach a red hot state and then starting powder feeding and printing. Continuous printing is adopted in printing, and the printing power is 1600-2400W.
Furthermore, in the step (1), the atomic ratio content of Al element in the alloy is 50% -60%, and the content of Nb element is 2% -10%.
Further, Si in the step (2)3N4The content of (A) is 0.2% -2%.
Further, the rotating speed of the ball mill in the step (3) is 100-300 r/min.
Further, the operation temperature of the ball mill in the step (3) is set to be-10-50 ℃.
Further, the mechanical ball milling time of the ball mill in the step (3) is 300-800 min.
Further, the printing speed in the step (4) is 6-12 mm/s.
Further, the powder feeding rate of printing in the step (4) is 4 g/min-12 g/min.
Further, the preparation method of the mixed powder comprises the following steps: the Ti-55Al-7.5Nb prealloying powder is firstly made into a round rod with the diameter of 100mm through a suspension smelting furnace, and then is made into prealloying powder particles with the diameter of 100-180 mu m through a rotating electrode. Prepared by a rotary electrode processThe prealloyed powder hardly contains argon pores, so that the density of the composite material formed in the later additive manufacturing process is higher, and the mechanical property is ensured. In the process of mechanical ball milling and mixing, the rotating speed of a ball mill is 120 r/min-180 r/min, the mixing time is not less than 480min, argon is filled into a ball milling tank for protection, and the ball milling environment temperature is set to be less than 10 ℃. By controlling the rotating speed and the ball milling time of the ball mill, Si is promoted3N4The Ti and TiAl alloy powder are uniformly mixed, so that two reinforcing phases Ti are further ensured2AlN and Ti5Si3The phases are uniformly separated out, and simultaneously, the powder deformation and oxidation caused by overhigh rotating speed and high temperature of the ball mill are avoided, so that the generation of the separated phases and the performance of a composite material matrix are influenced.
In the invention, Si is mixed with3N4Uniformly mixing with TiAl prealloyed powder, and printing by adopting a laser additive manufacturing method (3D printing) to obtain the gamma-based high Nb-TiAl composite material3N4Unstable at high temperature (complete decomposition at more than 1800 ℃), by first making Si3N4The high-strength Ti-55Al-7.5Nb prealloy powder is uniformly mixed with Ti-55Al-7.5Nb prealloy powder to ensure that precipitated phases are uniformly precipitated, then 3D printing is carried out on the mixed powder, and the characteristics of small molten pool, high heating and cooling speed, difficulty in large-area segregation and the like in laser additive manufacturing are utilized to enable matrix alloy to be rapidly solidified from a liquid state to form fine equiaxed grains, and meanwhile, a certain amount of N element is dissolved into the matrix in a solid solution mode to achieve the effect of solid solution strengthening. The nitrogen atoms in the mixed powder diffuse along crystal planes and are dissolved in the interstitial positions of the gamma phase as Ti2The dispersion precipitation of the AlN phase provides a prerequisite. Precipitating micro-nano nitride Ti when the maximum solid solubility of gamma phase is reached in the cooling process2AlN, micro-nano nitride Ti2AlN is taken as a reinforcing phase and is dispersed and distributed in the Ti-55Al-7.5 Nb-based composite material. The Si element has smaller solid solubility in TiAl and reacts with the Ti element to generate Ti5Si3Interface energy with TiAl phase interface is larger, Ti is in solidification process5Si3Distributed at the crystal boundary of Ti-55Al-7.5Nb grains to form the wrapping of matrix TiAl phase, and finally the in-situ synthesized Ti is obtained2AlN/Ti5Si3The TiAl-based composite material with the synergistically enhanced reticular crystal boundary distribution plays a role in pinning the TiAl alloy crystal boundary and inhibiting the growth of TiAl crystal grains. The characteristic of rapid solidification in laser additive manufacturing is combined, a stable structure of a fine gamma single-phase matrix is formed, and the high-temperature stability of the TiAl-based composite material is improved.
According to the coaxial powder feeding 3D printing preparation method of the gamma-based high-temperature Nb-TiAl composite material, the atomic ratio of N element in the mixed powder is 0.2-1.0%. With Si3N4The content is increased, when the content of N is less than 0.6 percent, most of N element is dissolved into TiAl matrix in a solid way, and Ti is basically not contained2Formation of AlN phase but with a certain content of Ti5Si3And (4) generating. A small amount of Ti5Si3TiAl crystal grains cannot be coated, and a composite material coated in a net shape cannot be formed, so that the content of the TiAl crystal grains needs to be increased to about 1.0%. But too high Si3N4Is not favorable for obtaining Ti with fine grain size and dispersed distribution2AlN phase, and hence Si in the mixed powder by controlled adjustment3N4Content of (2) to realize in-situ self-generated micro-nano Ti2The regulation and control of the AlN particle content is beneficial to obtaining the TiAl-based composite material with uniform tissue and excellent performance.
According to the coaxial powder feeding 3D printing preparation method of the gamma-based high-temperature Nb-TiAl composite material, the additive manufacturing environment is under the protection of argon, and the oxygen content is lower than 50 ppm. The substrate is made of TC4 material, and is heated in a laser in-situ preheating mode before printing is started, so that 3D printing is started after the substrate is partially reddened. The purpose of laser in-situ heating is to enable TiAl to be formed in a higher temperature environment, and TiAl is easy to crack through a cold-brittle transition temperature in the process of solidification from a liquid phase to a solid phase, so that the TiAl alloy cannot be formed. The substrate is heated in situ by laser to keep the forming temperature above the ductile-brittle transition temperature, and is cooled slowly after printing. The laser beam of the high-energy beam can increase the temperature of the liquid phase after the powder is melted to enable Si3N4Fully decomposed and reacted with TiAl to generate second phase particles, and the characteristic of rapid cooling of a micro-molten pool can inhibit Ti2AlN and Ti5Si3The crystal grains of the phase grow up, and the effect of micro-nano pinning matrix crystal grains is achieved. By adopting the 3D printing process, Si can be fully decomposed3N4Increase Ti2AlN and Ti5Si3The generation amount of the phase is simultaneously utilized, and the characteristic of rapid solidification of an additive manufacturing molten pool is utilized, so that Ti is avoided2AlN and Ti5Si3The second phase grows rapidly to obtain a dispersed phase with fine, dispersed and high volume fraction content, and the performance of the novel gamma-based high Nb-TiAl composite material reinforced by the in-situ authigenic micro-nano particles is further improved.
According to the coaxial powder feeding 3D printing preparation method of the gamma-based high Nb-TiAl composite material, the in-situ authigenic micro-nano particles are synergistically enhanced, and micro-nano-scale Ti is dispersed in the Ti-55Al-7.5 Nb-based composite material2AlN and Ti5Si3And (4) a reinforcing phase. Micron-sized Ti2AlN and Ti5Si3The reinforcing phase is usually 5-10 μm of Ti with nano-scale5Si3The reinforcing phase is usually 50 nm-100 nm, both reinforcing phases have the reinforcing effect on the TiAl-based composite material, wherein the nano-scale Ti5Si3The reinforcing phase is almost precipitated in the grain boundary of the gamma crystal grains of the matrix and plays a role of pinning the grain boundary. The precipitation coexistence of two reinforcing phases with different scales further improves the high-temperature stability of the gamma-based high Nb-TiAl composite material, and brings great possibility for the gamma-based high Nb-TiAl composite material to be used at higher temperature.
Compared with the prior art, the invention has the following advantages:
1. the invention utilizes Si3N4Unstable property of complete decomposition after a temperature of more than 1800 ℃ to make Si3N4Ball-milling and uniformly mixing the powder and Ti-55Al-7.5Nb prealloyed powder at a low temperature, then carrying out laser 3D printing, so that after the mixed powder is melted by high-energy beam laser, N element is dissolved in the gap position of gamma phase in a solid-liquid phase solidification process, meanwhile, other N elements react with TiAl, and micro-nano nitride Ti is formed in a cooling process2AlN is evenly precipitated and is dispersed and distributed in the gamma-based high Nb-TiAl composite material as a reinforcing phase. Si element reacts with Ti element in TiAl to generateMicro-and nano-sized Ti5Si3The material is distributed in the crystal boundary of the gamma crystal grains of the substrate, plays a certain pinning effect on the crystal grains of the substrate, inhibits the growth of the crystal grains in the high-temperature use process, and can improve the high-temperature use performance of the TiAl-based composite material. The room temperature compression performance of the obtained in-situ authigenic micro-nano particle reinforced TiAl-based composite material reaches 1.5 GPa.
2. The single-phase gamma-based high-Nb-TiAl composite material is prepared by innovatively adopting the prealloyed powder with high Al fraction for the first time and performing additive manufacturing, so that the TiAl alloy can be used at a higher temperature and has quite high structural stability.
3. The invention adopts Si3N4The powder is used as two additive element sources, the powder is commercial product powder, the cost is low, the adopted ball milling powder mixing and 3D printing process is energy-saving and environment-friendly, the repeatability of the method is ensured, and the application value of the method is improved.
4. The additive manufacturing technology adopted by the invention belongs to a near-forming process, complex front and back processing processes are not needed, the produced workpiece can be industrially applied through simple heat treatment and surface processing, and the application value of the additive manufacturing technology is improved through a simple and energy-saving process under the large background of carbon peak-to-peak carbon neutralization.
The technical solution of the present invention is further described in detail by the accompanying drawings and examples.
Drawings
FIG. 1 is a phase diagram of a Ti-Al binary alloy used in example 1 of the present invention.
FIG. 2 is a graphical representation of the morphology of the Ti-55Al-7.5Nb prealloyed spherical powder used as the starting material in example 1 of the present invention.
FIG. 3 is a graph of the grain size distribution of the Ti-55Al-7.5Nb prealloyed powder used as the starting material in example 1 of the present invention.
FIG. 4 is an XRD diffraction pattern of the raw material Ti-55Al-7.5Nb prealloyed powder used in example 1 of the present invention.
FIG. 5 shows Si as a raw material used in example 1 of the present invention3N4A pattern of the nanopowder.
FIG. 6 is a drawing of the present inventionRaw material Si for example 13N4XRD diffraction pattern of nanopowder.
Fig. 7 is a schematic diagram of laser 3D printing according to embodiment 1 of the present invention.
FIG. 8 is an SEM histogram of the novel gamma-based Ti-55Al-7.5Nb composite material of example 1 after 3D printing and forming.
Fig. 9 is an EBSD image of a novel gamma-based Ti-55Al-7.5Nb composite material of example 1 of the present invention after 3D printing and forming.
FIG. 10 shows Ti in the novel gamma-based Ti-55Al-7.5Nb composite material of example 1 of the present invention2TEM topography of AlN.
FIG. 11 shows the nano Ti content in the novel gamma-based Ti-55Al-7.5Nb composite material in example 1 of the invention5Si3TEM morphology distribution at grain boundaries.
Detailed Description
The preparation method of the embodiment uses Si3N4The Ti-55Al-7.5Nb prealloying powder with the total amount of 200g and Si with the corresponding proportion are used as a silicon source and a nitrogen source3N4Placing the mixed powder (the atomic ratio of N element is 1%) in a ball milling tank of a ball mill, filling argon for protection, mechanically milling and mixing for 480min at low temperature (5 ℃) under the condition that the rotating speed of the ball mill is 180r/min to obtain mixed powder, then preserving heat for 24h in a vacuum drying oven (200 ℃), and obtaining the novel gamma-based high Nb-TiAl composite material through laser 3D printing.
FIG. 1 is a phase diagram of the Ti-Al binary alloy used in the present embodiment, wherein two solidification paths are shown, wherein path 1 is the atomic ratio of the TiAl alloy in the conventional manner, and the solidification manner is also shown as a two-phase structure at room temperature, and path 2 is the composition ratio of the alloy used in the present embodiment, and it can be seen from the diagram that the TiAl alloy only passes through a single-phase gamma phase during the solidification process. That is to say, the novel alloy can not generate solid phase transformation and tissue degradation in the using process. However, the prior alloy forming method is mainly a traditional method such as casting, and a large amount of segregation can cause cracks due to slow cooling speed in the casting process, so that the alloy with high Al fraction can not be formed, and the component design and formability of the novel alloy are possible due to the occurrence of the laser additive technology.
Fig. 2 and 3 are SEM morphology and grain distribution diagrams of the Ti-55Al-7.5Nb prealloyed powder of this example, respectively, and it can be seen from fig. 2 that all the powder particles are spherical, and some of the powder particles are accompanied by some satellite powder, and a small amount of satellite powder is helpful for the adhesion between the powders, so as to improve the compactness of the alloy. As can be seen from FIG. 3, the grain diameters are basically distributed between 100 μm and 180 μm, which meets the requirements of the laser coaxial powder feeding process. FIG. 4 is an XRD diffraction pattern of the prealloyed powder, from which it can be seen that the alloy powder is primarily gamma phase and contains a small amount of alpha2And (4) phase(s).
FIGS. 5 and 6 are Si for providing Si and N sources, respectively, for this example3N4SEM morphology and XRD diffraction pattern of nanopowder. From FIG. 5, Si can be seen3N4The particles are of uniform size, substantially less than 100nm, so that after mixing with the prealloyed powder they can be dispersed uniformly into the liquid phase by laser heating to complete the decomposition. As can be seen from FIG. 6, the purity of the powder is relatively high, no other impurity phase exists, and the powder contains two different crystal forms of Si3N4。
Pre-alloyed Ti-55Al-7.5Nb powder prepared by a rotary electrode and Si3N4Mixing the nanometer powder according to a specific proportion, placing the mixture in a ball milling tank for ball milling and mixing the powder, wherein the rotating speed of a ball milling tank is 180r/min, the ball milling time is 480min, and ball milling is carried out at a low temperature of below 5 ℃. After the ball milling and powder mixing are completed, the powder is taken out and dried for 24 hours at the temperature of 200 ℃ in a vacuum drying oven, and then laser 3D printing is carried out by adopting the method shown in figure 7. As can be seen from fig. 7, the printing substrate used in this embodiment is Ti-6Al-4V (TC4 alloy), and the substrate is subjected to laser synchronous in-situ heating before the composite powder is printed, so that the substrate is heated to a red hot state, and then the powder feeding printing is started. Continuous printing is adopted for printing, the printing power is 2400W, the printing speed is 7mm/s, and the powder feeding rate is 5 g/min.
The SEM backscatter structure of the printed novel gamma-based Ti-55Al-7.5Nb composite material is shown in FIG. 8. As can be seen from FIG. 8, the matrix is single-phase equiaxial grains with a grain size of about 50-80 μmDark black fine rod-like second phases are uniformly dispersed in the silicon carbide material, bright white second phase particles are distributed along the grain boundary, and a certain pinning effect is achieved on the grain boundary. In order to confirm the phase of the dispersion distribution and the grain boundary distribution particles, the microstructure of the particles is characterized by an EBSD means. As shown in FIG. 9, it can be seen from the EBSD result that the particles in the interior of the dispersion-distributed grains are Ti2AlN particles and Ti particles at grain boundaries5Si3Phase, Ti dispersed inside equiaxed grains2The AlN particles play a role in strengthening a matrix and play a role in heterogeneous nucleation in the solidification process, so that Al segregation is greatly reduced, and the mechanical property of the composite material can be improved. And Ti at grain boundaries5Si3The particles are tightly pinned at the gamma crystal boundary, so that the pinning effect is realized on the growth of crystal grains in the subsequent use process of the material, and the effect of stabilizing the structure is very good. To further confirm the structure and characteristics of the precipitated phases, this example was characterized by transmission, and FIGS. 10 and 11 are graphs of Ti under TEM2AlN and Ti5Si3The micro-topography of (a). From FIG. 10, Ti can be seen2AlN is substantially precipitated inside the crystal grains, and as can be seen from FIG. 11, not only Ti5Si3The particle size of (2) is micron-sized as in fig. 8, and there are a large number of nano-sized (around 100 nm) particles pinned at the grain boundary. The novel gamma-based Ti-55Al-7.5Nb composite material of the embodiment has micro-nano double-level in-situ authigenic particles, has a synergistic pinning effect on matrix gamma grains, can stabilize an alloy structure, and improves the high-temperature stability of the TiAl alloy and the composite material thereof.

Claims (10)

1. A preparation method of gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing is characterized in that Si is used3N4For Si and N sources, Si3N4After being uniformly mixed with Ti-55Al-7.5Nb alloy powder through mechanical ball milling at low temperature and low speed for a long time, the mixed powder is subjected to laser coaxial powder feeding additive manufacturing through a low-carbon environment-friendly 3D printing preparation technology, and the in-situ authigenic micro-nano particle synergetic reinforced Ti-55Al-7.5 Nb-based composite material is obtained after cooling; dispersed second phase matrix separated from matrix and grain boundaryThe grain boundary strengthening effect is achieved, and simultaneously, the precipitates distributed at the grain boundary play a good role in pinning the grain boundary relative to the matrix structure, so that the structure is further stabilized.
2. The preparation method of the gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 1, which is characterized by comprising the following steps:
(1) preparing pre-alloyed powder: firstly, preparing a Ti-55Al-7.5Nb round bar ingot by a suspension smelting method, and then preparing prealloy powder with the diameter of 100-180 mu m by a rotary electrode method;
(2) preparing mixed powder raw materials: si is added in an atomic ratio of 0.2 to 1% of the element N3N4Mixing the pre-alloyed powder prepared in the step (1) with silicon and nitrogen sources;
(3) ball milling and mixing powder at low temperature: placing the mixed powder prepared in the step (2) into a ball milling tank of a ball mill, filling argon for protection, mechanically milling the mixed powder at the low temperature of 5-10 ℃ for 550min under the condition that the rotation speed of the ball mill is 160-200r/min to obtain mixed powder, and then preserving the heat of 180-220 ℃ for 12-24 h in a vacuum drying oven;
(4)3D printing: placing the mixed powder into a powder feeder of coaxial powder feeding equipment for 3D printing, and carrying out laser synchronous in-situ heating on the substrate before printing the composite powder to enable the substrate to reach a red hot state, and then starting powder feeding and printing; continuous printing is adopted in printing, and the printing power is 1600-2400W.
3. The preparation method of the gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 2, wherein in the step (1), the atomic ratio content of Al element in the alloy is 50% -60%, and the content of Nb element is 2% -10%.
4. The preparation method of gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 2, wherein Si in the step (2)3N4The content of (A) is 0.2% -2%.
5. The preparation method of the gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 2, wherein the rotation speed of the ball mill in the step (3) is 100-300 r/min.
6. The preparation method of the gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 2, wherein the operation temperature of the ball mill in the step (3) is set to be-10-50 ℃.
7. The preparation method of the gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 2, wherein the ball milling time of the ball mill in the step (3) is 300-800 min.
8. The preparation method of the gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 2, wherein the printing speed in the step (4) is 6-12 mm/s.
9. The preparation method of the gamma-based high-temperature TiAl composite material for coaxial powder feeding 3D printing according to claim 2, wherein the powder feeding rate in the step (4) is 4g/min to 12 g/min.
10. The preparation method for the gamma-based high-temperature TiAl composite material coaxial powder feeding 3D printing, which is characterized in that the preparation method of the mixed powder comprises the following steps: preparing Ti-55Al-7.5Nb prealloying powder into a round rod with the diameter of 100mm through a suspension smelting furnace, and preparing prealloying powder particles with the diameter of 100-180 mu m through a rotating electrode; the prealloyed powder prepared by the rotary electrode method hardly contains argon pores, so that the density of the composite material formed in the later additive manufacturing process is higher, and the mechanical property is ensured; in the process of mechanical ball milling and mixing, the rotating speed of a ball mill is 120 r/min-180 r/min, the mixing time is not less than 480min, argon gas is filled into a ball milling tank for protection, and meanwhile, the ball milling environment temperature is set to be less than 10 ℃; the rotation speed and the ball milling time of the ball mill are controlled to promote Si3N4And TiAThe uniform mixing of the alloy powder further ensures two reinforcing phases Ti2AlN and Ti5Si3The phases are uniformly separated out, and simultaneously, the powder deformation and oxidation caused by overhigh rotating speed and high temperature of the ball mill are avoided, so that the generation of the separated phases and the performance of a composite material matrix are influenced.
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