CN115261658A - Additive manufacturing method of high-performance titanium-aluminum alloy with fine-grain full-lamellar structure - Google Patents

Additive manufacturing method of high-performance titanium-aluminum alloy with fine-grain full-lamellar structure Download PDF

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CN115261658A
CN115261658A CN202211000921.9A CN202211000921A CN115261658A CN 115261658 A CN115261658 A CN 115261658A CN 202211000921 A CN202211000921 A CN 202211000921A CN 115261658 A CN115261658 A CN 115261658A
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aluminum alloy
titanium
fine
laser
lamellar structure
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CN115261658B (en
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梁耀健
朱逸超
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Beijing Institute of Technology BIT
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/045—Alloys based on refractory metals
    • C22C1/0458—Alloys based on titanium, zirconium or hafnium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/25—Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/36—Process control of energy beam parameters
    • B22F10/364—Process control of energy beam parameters for post-heating, e.g. remelting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/36—Process control of energy beam parameters
    • B22F10/366—Scanning parameters, e.g. hatch distance or scanning strategy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/50—Treatment of workpieces or articles during build-up, e.g. treatments applied to fused layers during build-up
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

The invention relates to an additive manufacturing method of a high-performance titanium-aluminum alloy with a fine-grain full-lamellar structure, belonging to the field of goldBelongs to the technical field of additive manufacturing. Pouring titanium-aluminum alloy powder into a powder storage tank of a powder feeding device, setting the laser scanning speed in the laser deposition process to be 5-15 times of the diameter of a laser spot per second, setting the layering thickness to be 1-10% of the diameter of the laser spot, setting the interlayer fixed spacing to be 50-100% of the diameter of the laser spot, and selecting the titanium-aluminum alloy powder with the volume power density of 100-5000W/mm 3 Then operating a laser deposition program, and performing cyclic deposition on the substrate layer by layer to form the high-performance titanium-aluminum alloy with the required shape and the fine-grain full-lamellar structure. The method disclosed by the invention is simple to operate, has the capability of forming samples of any size, realizes the simultaneous implementation of preparation and tissue regulation, does not need subsequent treatment for tissue regulation, can greatly shorten the production period and reduce the cost, and the prepared titanium-aluminum alloy with the fine-grain full-lamellar structure has good mechanical properties.

Description

Additive manufacturing method of high-performance titanium-aluminum alloy with fine-grain full-lamellar structure
Technical Field
The invention relates to an additive manufacturing method of a high-performance titanium-aluminum alloy with a fine-grain full-lamellar structure, and belongs to the technical field of metal additive manufacturing.
Background
The titanium-aluminum alloy has a plurality of excellent performances such as high specific strength, high creep resistance, oxidation resistance and the like, is an excellent high-temperature structural material, and has great application potential in the field of aeroengine materials. General electric company of America is in GEnx TM The titanium-aluminum alloy is used as a blade material in the compressor of the turbine engine, so that the fuel efficiency of the engine is improved, and the overall carbon emission is reduced.
Investment casting is a common preparation method of titanium-aluminum alloy, but the solidification speed of the process is slow, so that the prepared titanium-aluminum alloy is generally alpha of coarse grains 2 The structure has good high-temperature creep resistance, fracture toughness and fatigue performance, but has poor room-temperature tensile plasticity and still has the problem of use safety to a certain extent. The hot deformation processing of the titanium-aluminum alloy is also widely concerned for refining the structure and improving the plasticity, and the fine spherical gamma crystal grains + alpha can be prepared by high-temperature thermal deformation and proper heat treatment 2 The room temperature plasticity of the titanium-aluminum alloy can be improved by adopting a bimodal structure of/gamma sheet layer group', but the high temperature creep resistance of the bimodal structure is poor, so that the application of the bimodal structure above 750 ℃ is limited. Moreover, the titanium-aluminum alloy has high ductile-brittle transition temperature, deformation processing is usually carried out at the temperature of over 1200 ℃, the requirement on equipment is strict, the preparation cost is high, and the popularization is difficult.
The results of the research show that: the fully lamellar structure lamellar groups/crystal grain sizes are refined, the room temperature plasticity can be improved on the premise of not changing the structure performance advantages, and the potential of the titanium-aluminum alloy can be further developed. However, as mentioned above, the existing preparation method still cannot prepare the titanium-aluminum alloy component with the complex shape and the fine-grained full-lamellar structure, so that the mechanical properties of the titanium-aluminum alloy in practical application are often compromised to the room temperature and the high temperature, and the performance potential of the series of materials cannot be fully exerted.
Disclosure of Invention
Aiming at the problem of the size of a full lamellar structure lamellar group/crystal grain in the prior refined titanium-aluminum alloy, the invention provides an additive manufacturing method of a High-performance titanium-aluminum alloy with fine-grain full lamellar structure, which adopts a High-sweeping-speed laser deposition (HLD) technology in the additive manufacturing technology, optimizes the process conditions of laser deposition based on the thermal characteristics of the gradual and layer-by-layer forming of the HLD technology and the characteristics of solid-state phase change of the titanium-aluminum alloy, and forms special in-situ thermal cycle in the laser deposition process to ensure that the titanium alloy layer deposited in advance is at the alpha-phase transition line temperature T α The method has the advantages that the preparation and the structure regulation are carried out simultaneously, the method has the capability of forming samples with any size, the production period can be greatly shortened, and the cost can be reduced.
The purpose of the invention is realized by the following technical scheme.
A method for additive manufacturing of a high-performance titanium-aluminum alloy with a fine-grained full-lamellar structure is disclosed, wherein eutectoid transformation of the titanium-aluminum alloy is realized by multiple thermal cycles formed by a high-sweep laser deposition process to obtain the titanium-aluminum alloy with the fine-grained full-lamellar structure, and the method specifically comprises the following steps:
pouring titanium-aluminum alloy powder into a powder storage tank of a powder feeding device, setting the laser scanning speed in the laser deposition process to be 5-15 times of the diameter of a laser spot per second, setting the layering thickness to be 1-10% of the diameter of the laser spot, setting the interlayer fixed spacing to be 50-100% of the diameter of the laser spot, and selecting the titanium-aluminum alloy powder with the volume power density of 100-5000W/mm 3 Then the laser deposition program is operated, and the required deposition is formed on the substrate by the way of the layer-by-layer circulation depositionThe shaped high-performance titanium-aluminum alloy with fine-grained full-lamellar structure.
The high-performance titanium-aluminum alloy with the fine-grain full lamellar structure prepared by the method has the fine-grain full lamellar groups of gamma-TiAl and alpha with the average size of less than 100 mu m 2 -Ti 3 Al two-phase full lamellar structure. In addition, the alpha phase transition line temperature T α Is the equilibrium/mutual transformation temperature between the alpha phase and the alpha + gamma phase in the titanium-aluminum alloy.
The components of the titanium-aluminum alloy powder include, but are not limited to, titanium-aluminum as a base component and other element components. The titanium-aluminum alloy powder is preferably spherical powder with the granularity range of 0.04-0.20 mm.
The diameter size of the laser spot is related to the size of the laser molten pool, and the diameter of the laser spot is preferably 2-6 mm.
Preferably, the laser scanning speed is set to be 15-50 mm/s, and the layering thickness is set to be 0.06-0.3 mm, so that better cyclic heat treatment can be carried out on the deposited sample in the printing preparation process.
Preferably, a coaxial powder feeding device is adopted to convey the titanium-aluminum alloy powder, wherein the flow rate of carrier gas is 3-10L/min.
The high-performance titanium-aluminum alloy with fine-grain full-lamellar structure prepared by the method comprises but is not limited to Ti-45Al-8Nb titanium-aluminum alloy or Ti-48Al-2Cr-2Nb titanium-aluminum alloy.
Has the advantages that:
(1) According to the invention, the self-existing repeated cyclic heating characteristic in 3D printing and the eutectoid reaction solid-state phase change characteristic in the titanium-aluminum alloy are combined, and the thermal cycle in 3D printing can promote multiple rapid eutectoid reactions of the titanium-aluminum alloy by optimizing the preparation process parameters, so that the tissue refinement is realized, and the preparation of the fine-grain full-lamella titanium-aluminum alloy is realized.
(2) In order to realize the rapid cyclic heat treatment for many times, the invention provides a constant high-scanning-speed laser deposition strategy, the method mainly realizes the rapid cyclic heating for many times of the deposited titanium-aluminum alloy by increasing the laser scanning speed and reducing the layered thickness, and in order to realize the aim, a proper preparation process window is obtained after experimental research on a series of process parameters, namely, the laser scanning speed is 5-15 times of the diameter of a laser spot per second, and the layered thickness is 1-10% of the diameter of the laser spot. If the scanning speed is reduced or the layering thickness is increased, the alloy cannot undergo multiple times of circulating heat treatment, so that a fine-grain full-lamellar structure cannot be formed; however, further increases in scanning speed or decreases in lamination thickness lead to poor sample shaping capability and reduced sample shaping efficiency.
(3) The method has simple operation, has the capability of forming samples with any size, realizes the simultaneous preparation and tissue regulation, does not need subsequent treatment for tissue regulation, can greatly shorten the production period and reduce the cost, and the fine-grain full-lamellar groups in the prepared titanium-aluminum alloy are gamma-TiAl and alpha with the average size of less than 100 mu m 2 -Ti 3 Al two-phase full lamellar structure.
(4) The tensile yield strengths of the Ti-45Al-8Nb titanium-aluminum alloy with the fine-grain full-lamellar structure prepared by the method at room temperature, 750 ℃, 850 ℃ and 900 ℃ are 653MPa, 550MPa, 460MPa and 435MPa respectively; the tensile yield strengths of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy with the fine-grain full-lamellar structure, which is prepared by the method, at room temperature, 700 ℃, 800 ℃ and 850 ℃ are respectively 517MPa, 470MPa, 480MPa and 405MPa. The two titanium-aluminum alloys with the fine-grain full-lamellar structure have good mechanical properties.
Drawings
FIG. 1 is a schematic diagram illustrating the principle of in-situ thermal cycling formed during laser deposition by the high-sweep-rate laser deposition technique according to the present invention.
FIG. 2 is a schematic diagram showing a comparison of the thermal cycle frequency in the phase change region at a low scan speed and a high scan speed, respectively, during laser deposition.
FIG. 3 is a metallographic structure chart of Ti-45Al-8Nb titanium-aluminum alloy prepared in example 1.
FIG. 4 is a graph of room temperature quasi-static tensile of the Ti-45Al-8Nb titanium-aluminum alloy prepared in example 1.
FIG. 5 is a graph of high temperature tensile yield strength versus temperature for the Ti-45Al-8Nb titanium aluminum alloy prepared in example 1.
FIG. 6 is a metallographic structure drawing of a Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in example 2.
FIG. 7 is a graph of room temperature quasi-static tensile of the Ti-48Al-2Cr-2Nb titanium aluminide alloy prepared in example 2.
FIG. 8 is a graph of high temperature tensile yield strength versus temperature for the Ti-48Al-2Cr-2Nb titanium aluminum alloy prepared in example 2.
FIG. 9 is a metallographic structure diagram of a Ti-45Al-8Nb titanium-aluminum alloy prepared by a conventional casting method in comparative example 1.
FIG. 10 is a metallographic structure drawing showing a Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by a conventional casting method in comparative example 2.
FIG. 11 is a comparison graph of room temperature quasi-static tensile properties of Ti-45Al-8Nb titanium-aluminum alloy and Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by the conventional casting method in comparative example 1 and comparative example 2, respectively.
FIG. 12 is a metallographic structure of Ti-45Al-8Nb titanium-aluminum alloy prepared by a conventional low-sweep laser deposition method in comparative example 3.
FIG. 13 is a graph of room temperature quasi-static tensile properties of Ti-45Al-8Nb titanium-aluminum alloy prepared by conventional low-sweep laser deposition method in comparative example 3.
FIG. 14 is a metallographic structure of Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by a conventional low-sweep laser deposition method in comparative example 4.
FIG. 15 is a graph showing the room temperature quasi-static tensile properties of Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by the conventional low-sweep laser deposition method in comparative example 4.
Detailed Description
The present invention is further illustrated by the following detailed description, wherein the processes are conventional unless otherwise specified, and the starting materials are commercially available from a public source without further specification.
Example 1
The specific steps for preparing the Ti-45Al-8Nb titanium-aluminum alloy by adopting the high-sweeping-speed laser deposition technology are as follows:
(1) Spherical Ti-45Al-8Nb titanium-aluminum alloy powder with the grain diameter of 0.04-0.2 mm is put into a vacuum drying oven with the temperature of 120 ℃ for drying for 4 hours, and is poured into a powder storage tank of a coaxial powder feeding device for standby after the temperature is reduced to room temperature;
(2) The diameter of a laser spot in the laser deposition process is set to be 3mm, the laser scanning speed is 10 times of the diameter of the laser spot per second (namely the laser scanning speed is 30 mm/s), the layering thickness is 3.3% of the diameter of the laser spot (namely the layering thickness is 0.1 mm), the interlayer fixed spacing is 70% of the diameter of the laser spot, and the selected volume power density reaches 467W/mm 3 The laser power (namely the laser power is 1400W), then a laser deposition program is operated, a laser beam runs along a preset scanning track and technological parameters, spherical Ti-45Al-8Nb titanium-aluminum alloy powder is sprayed to the center of a molten pool generated by the laser beam through carrier gas (the carrier gas is high-purity argon gas with the purity of more than 99.99%) with the flow rate of 5L/min in a coaxial powder feeding device to form deposition channels which are metallurgically combined with a substrate, a deposition layer with the thickness of a slice is formed by overlapping and accumulating of each deposition channel, a laser processing head is used for raising the height of one slice layer and then depositing the next layer, a plurality of previously deposited deposition layers are heated when the next layer is deposited (the principle refers to figure 1), the metallurgical combination of two adjacent deposition layers is realized, meanwhile, other deposition layers are subjected to multiple times of ultra-fast temperature rise and reduction to achieve the effect of tissue refinement, and the high-performance Ti-45Al-8Nb titanium-aluminum alloy with fine-grain full-lamella structure is formed by performing cyclic deposition on the substrate channel by channel and layer by layer.
The Ti-45Al-8Nb titanium-aluminum alloy prepared in the example 1 is subjected to structural morphology characterization, wherein the structural morphology is mainly used for sheet cluster size analysis, a metallographic sample is prepared by a metallographic sample preparation technology, and the sheet cluster size is counted by a GBT6394-2002 method. As can be seen from the metallographic structure diagram of FIG. 3, the Ti-45Al-8Nb titanium-aluminum alloy prepared in example 1 has γ -TiAl and α 2 -Ti 3 The Al two-phase fine-grain full lamellar structure has the average size of lamellar groups of 51 mu m, and compared with the Ti-45Al-8Nb titanium-aluminum alloy prepared by the traditional casting method in the comparative example 1 (the size of lamellar groups is obviously larger than 100 mu m, as shown in figure 9), the size of lamellar groups is obviously refined.
The Ti-45Al-8Nb titanium-aluminum alloy prepared in the example 1 is subjected to mechanical property test, wherein the mechanical properties mainly comprise room temperature quasi-static tensile property and high temperature quasi-static tensile property. The results of the room temperature quasi-static tensile property test are shown in FIG. 4, the tensile yield strength is 653MPa, the room temperature elongation is 1.2%, and the tensile strength is 805MPa. The high-temperature quasi-static tensile property test result is shown in figure 5, and the tensile yield strength of the titanium-aluminum alloy at high temperature of 750 ℃, 850 ℃ and 900 ℃ respectively reaches 550MPa, 460MPa and 435MPa. It can be seen that the mechanical properties of the Ti-45Al-8Nb titanium-aluminum alloy prepared in example 1 by the high-sweep laser deposition technique are significantly improved compared with the Ti-45Al-8Nb titanium-aluminum alloy prepared in comparative example 1 by the conventional casting method (the room-temperature quasi-static tensile strength is only 550MPa, and the room-temperature elongation is less than 0.5%, as shown in FIG. 11) and the Ti-45Al-8Nb titanium-aluminum alloy prepared in comparative example 3 by the conventional low-sweep laser deposition technique (the tensile strength is 600MPa, and the room-temperature elongation is less than 1%, as shown in FIG. 13).
Through the structure analysis and the mechanical property test of the Ti-45Al-8Nb titanium-aluminum alloy prepared by the high-sweep-rate laser deposition technology, the novel method is proved to be capable of realizing the refinement of the size of the Ti-45Al-8Nb titanium-aluminum alloy sheet lamination, so that the high strength and the high plasticity of the alloy at room temperature are maintained, and the high-temperature tensile property of the alloy can be obviously improved.
Example 2:
the specific steps for preparing the Ti-48Al-2Cr-2Nb titanium-aluminum alloy by adopting the high-sweep-rate laser deposition technology are as follows:
(1) Spherical Ti-48Al-2Cr-2Nb titanium-aluminum alloy powder with the grain diameter of 0.04-0.20 mm is put into a vacuum drying oven with the temperature of 120 ℃ for drying for 4 hours, and is poured into a powder storage tank of a coaxial powder feeding device for standby after the temperature is reduced to room temperature;
(2) Setting the diameter of a laser spot in the laser deposition process to be 3mm, setting the laser scanning speed to be 13.3 times of the diameter of the laser spot per second (namely, the laser scanning speed is 40 mm/s), setting the lamination thickness to be 7% of the diameter of the laser spot (namely, the lamination thickness is 0.2 mm), setting the interlayer fixed spacing to be 75% of the diameter of the laser spot, and selecting the volume power density to reach 200W/mm 3 Then a laser deposition program is operated, a laser beam runs along a preset scanning track and technological parameters, and the spherical Ti-48Al-2Cr-2Nb titanium-aluminum alloy powder is processed by the same processCarrier gas with the flow rate of 5L/min (the carrier gas is high-purity argon with the purity of more than 99.99%) in the axial powder feeding device is sprayed to the center of a molten pool generated by a laser beam to form deposition channels which are metallurgically bonded with a substrate, a deposition layer with the thickness of a slice is formed by overlapping and accumulating the deposition channels, a laser processing head is raised to the height of one slice layer and then carries out deposition of the next layer, a plurality of previously deposited deposition layers are heated when the deposition of the next layer is carried out (the principle of which refers to figure 1), the metallurgical bonding of two adjacent deposition layers is realized, other deposition layers can be subjected to multiple times of ultra-fast heating and cooling to achieve the effect of tissue refinement, and the high-performance Ti-48Al-2Cr-2Nb titanium aluminum alloy with the required shape and fine-grained full-lamellar structure is formed by cyclic deposition on the substrate channel by channel and layer by layer.
By using the same structural morphology characterization method as that of example 1, it can be known from the metallographic structure diagram of FIG. 6 that the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in example 2 has γ -TiAl and α 2 -Ti 3 The Al two-phase fine-grain full lamellar structure has the average size of lamellar groups of 55 mu m, and compared with the Ti-48Al-2Cr-2Nb titanium-aluminum alloy (the size of lamellar groups is obviously more than 100 mu m, as shown in figure 10) prepared by adopting the traditional casting method in the comparative example 2, the size of lamellar groups is obviously refined.
By adopting the same mechanical property test method as that of the example 1, according to the room temperature quasi-static tensile property test result of fig. 7, the tensile yield strength of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in the example 2 is 517MPa, the room temperature elongation is 0.9%, and the tensile strength is 608MPa; according to the high-temperature quasi-static tensile property test result of FIG. 8, the tensile yield strengths of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in example 2 at the high temperatures of 700 ℃, 750 ℃ and 800 ℃ reach 470MPa, 480MPa and 405MPa respectively. It can be seen that the mechanical properties of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in example 2 by the high-sweep-rate laser deposition technique are significantly improved compared with the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in comparative example 2 by the conventional casting method (the room-temperature quasi-static tensile strength is less than 400MPa, and the room-temperature elongation is less than 0.6%, as shown in FIG. 11) and the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in comparative example 4 by the conventional low-sweep-rate laser deposition technique (the tensile strength is 600MPa, and the room-temperature elongation is 0.7%, as shown in FIG. 15).
Through the structure analysis and the morphology test of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by the high-sweep-rate laser deposition technology, the novel method is proved to be capable of realizing the refinement of the size of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy sheet layer, so that the high-temperature tensile property of the alloy can be obviously improved while the high strength and the high plasticity of the alloy at room temperature are maintained.
Comparative example 1
The Ti-45Al-8Nb titanium-aluminum alloy is prepared by adopting a traditional casting method and comprises the following specific steps:
polishing the Ti, al and Nb metal raw materials with the purity higher than 99.5 percent, and weighing each raw material in a balance weight manner according to the nominal composition of alloy design, wherein the precision during weighing needs to be controlled within +/-0.1 g; putting the weighed metal raw materials into a water-cooled copper crucible of an induction melting furnace, vacuumizing the furnace, introducing high-purity argon, performing alloying melting, keeping for 5min after the metal raw materials are completely melted into a liquid state, and then solidifying and cooling to finish the preparation of the Ti-45Al-8Nb titanium-aluminum alloy as-cast sample.
By using the same texture and morphology characterization method as in example 1, it was found that the lamellar clusters of Ti-45Al-8Nb titanium-aluminum alloy prepared in comparative example 1 also have γ -TiAl and α 2 -Ti 3 The fully lamellar structure of the two phases of Al, but the size of lamellar clusters is more than 100 μm, is a remarkable coarse-grained structure, and meanwhile, a remarkable interdendritic segregation phenomenon exists, as shown in FIG. 9.
The same mechanical property test method as that of example 1 is adopted to test that the tensile strength of the Ti-45Al-8Nb titanium-aluminum alloy prepared in comparative example 1 is less than 550MPa, and the elongation is less than 0.5%, as shown in FIG. 11.
Comparative example 2
The specific steps for preparing the Ti-48Al-2Cr-2Nb titanium-aluminum alloy by adopting the traditional casting method are as follows:
polishing the Ti, al, cr and Nb metal raw materials with the purity higher than 99.5 percent, and weighing each raw material in a balance weight manner according to the nominal composition of alloy design, wherein the weighing precision needs to be controlled within +/-0.1 g; putting the weighed metal raw materials into a water-cooled copper crucible of an induction melting furnace, vacuumizing the furnace, introducing high-purity argon, performing alloying melting, keeping the metal raw materials for 5min after the metal raw materials are completely melted into a liquid state, and then solidifying and cooling to finish the preparation of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy as-cast sample.
By using the same texture and morphology characterization method as in example 1, it was found that the lamellar clusters of Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared in comparative example 2 also have γ -TiAl and α 2 -Ti 3 The full lamellar structure of the two phases of Al is shown in FIG. 10, but the size of lamellar clusters is more than 100 μm, which is a clear coarse-grained structure, and meanwhile, the inter-dendritic segregation phenomenon is also clear.
By adopting the same mechanical property test method as that of the example 1, the tensile strength of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by the comparative example 2 is less than 400MPa, and the elongation is less than 0.6 percent, which is shown in figure 11.
Comparative example 3
The method for preparing the Ti-45Al-8Nb titanium-aluminum alloy by adopting the low-sweep-rate laser deposition technology comprises the following specific steps of:
(1) Spherical Ti-45Al-8Nb titanium-aluminum alloy powder with the grain diameter of 0.04-0.2 mm is put into a vacuum drying oven with the temperature of 120 ℃ for drying for 4 hours, and is poured into a powder storage tank of a coaxial powder feeding device for standby after the temperature is reduced to room temperature;
(2) Setting the diameter of a laser spot in the laser deposition process to be 3mm, setting the laser scanning speed to be 3 times of the diameter of the laser spot per second (namely, the laser scanning speed is 9 mm/s), setting the lamination thickness to be 15 percent of the diameter of the laser spot (namely, the lamination thickness is 0.45 mm), setting the interlayer fixed spacing to be 70 percent of the diameter of the laser spot, and selecting the volume power density to reach 300W/mm 3 The laser power (namely the laser power is 1200W), then a laser deposition program is operated, a laser beam runs along a preset scanning track and technological parameters, spherical Ti-45Al-8Nb titanium-aluminum alloy powder is sprayed to the center of a molten pool generated by the laser beam through carrier gas (the carrier gas is high-purity argon with the purity of more than 99.99 percent) with the flow rate of 5L/min in a coaxial powder feeding device to form deposition channels which are combined with substrate metallurgy, a deposition layer with the slice thickness is formed by overlapping and accumulating of each deposition channel, and a laser processing head is raised up to a slice layer immediatelyAnd depositing the next layer to finish the preparation of the blocky Ti-45Al-8Nb titanium-aluminum alloy.
By adopting the same structural morphology characterization method as that of the embodiment 1 and observing the structural morphology of the Ti-45Al-8Nb titanium-aluminum alloy prepared by adopting the low-sweep-rate laser deposition technology, the obvious blocky gamma-TiAl structures, gamma-TiAl and alpha exist in the sample 2 -Ti 3 The lamellar structure of Al alternating, as shown in fig. 12, is clearly different from the full lamellar structure of example 1. Comparing the samples passing through the phase change interval (T) at different sweep speeds L And T α Between, T L Referring to phase line temperature of the material), it can be found that the frequency of the heat treatment at the high scanning speed is several times that at the low scanning speed (refer to the schematic diagram 2), and samples with different microstructures are obtained through different degrees of heat cycle treatment.
By adopting the same mechanical property test method as that of the embodiment 1, room temperature quasi-static mechanical property tests of the Ti-45Al-8Nb titanium-aluminum alloy prepared by adopting the low-sweep-speed laser deposition technology show that the yield is 400MPa, the tensile strength is 600MPa, and the elongation is less than 1%, and as shown in figure 13, the mechanical property is obviously lower than that of the Ti-45Al-8Nb titanium-aluminum alloy prepared by adopting the high-sweep-speed laser deposition technology in the embodiment 1.
Comparative example 4
The specific steps for preparing the Ti-48Al-2Cr-2Nb titanium-aluminum alloy by adopting the low-sweep-speed laser deposition technology are as follows:
(1) Spherical Ti-48Al-2Cr-2Nb titanium-aluminum alloy powder with the particle size of 0.04-0.2 mm is put into a vacuum drying oven with the temperature of 120 ℃ for drying for 4 hours, and is poured into a powder storage tank of a coaxial powder feeding device for standby after the temperature is reduced to room temperature;
(2) Setting the diameter of a laser spot in the laser deposition process to be 3mm, setting the laser scanning speed to be 3 times of the diameter of the laser spot per second (namely, the laser scanning speed is 9 mm/s), setting the lamination thickness to be 15 percent of the diameter of the laser spot (namely, the lamination thickness is 0.45 mm), setting the interlayer fixed spacing to be 70 percent of the diameter of the laser spot, and selecting the volume power density to reach 300W/mm 3 Laser power of 1200W, then a laser deposition program is run, the laser beam follows a predetermined scanning track and the process parametersThe operation is carried out, spherical Ti-48Al-2Cr-2Nb titanium-aluminum alloy powder is sprayed to the center of a molten pool generated by a laser beam through carrier gas (the carrier gas is high-purity argon with the purity of more than 99.99 percent) with the flow rate of 5L/min in a coaxial powder feeding device to form deposition channels which are metallurgically combined with a substrate, a deposition layer with the thickness of a slice is formed by overlapping and accumulating each deposition channel, a laser processing head is raised by the height of one slice layer and then the next layer is deposited, and therefore the preparation of the blocky Ti-48Al-2Cr-2Nb titanium-aluminum alloy is completed.
By adopting the same structural morphology characterization method as that of the embodiment 1 and observing the structural morphology of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by adopting the low-sweep-rate laser deposition technology, the samples have obvious massive gamma-TiAl phase structures, gamma-TiAl and alpha 2 -Ti 3 The lamellar structure of Al alternating, as shown in fig. 14, is significantly different from the full lamellar structure of example 2.
By adopting the same mechanical property test method as that of the embodiment 1, room temperature quasi-static mechanical property tests of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by adopting the low-scanning-speed laser deposition technology show that the yield is 450MPa, the tensile strength is 600MPa, and the elongation is 0.7 percent, and as shown in figure 15, the mechanical property is obviously lower than that of the Ti-48Al-2Cr-2Nb titanium-aluminum alloy prepared by adopting the high-scanning-speed laser deposition technology in the embodiment 2.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. A material additive manufacturing method of a high-performance titanium-aluminum alloy with a fine-grain full-lamellar structure is characterized by comprising the following steps of: the method realizes eutectoid transformation of the titanium-aluminum alloy by utilizing multiple thermal cycles formed in the high-scanning-rate laser deposition process to obtain the titanium-aluminum alloy with fine-grain full-lamellar structure, and specifically comprises the following steps,
pouring titanium-aluminum alloy powder into a powder storage tank of a powder feeding device, and setting the laser scanning speed in the laser deposition process to be laser facula per second5-15 times of the diameter, the layering thickness is 1-10% of the diameter of the laser spot, the interlayer fixed spacing is 50-100% of the diameter of the laser spot, and the selected volume power density reaches 100-5000W/mm 3 Then operating a laser deposition program, and performing cyclic deposition on the substrate layer by layer to form the high-performance titanium-aluminum alloy with the required shape and a fine-grain full-lamellar structure;
wherein the fine-grain fully lamellar structure refers to gamma-TiAl and alpha with the average size of less than 100 mu m 2 -Ti 3 Al two-phase fully lamellar structure.
2. The additive manufacturing method of high performance titanium aluminum alloy with fine grain full-sheet structure according to claim 1, wherein: the titanium-aluminum alloy powder is spherical powder with the granularity range of 0.04-0.20 mm.
3. The additive manufacturing method of high performance titanium aluminum alloy with fine grain full-sheet structure according to claim 1, wherein: the diameter of the laser spot is 2-6 mm.
4. The method of additive manufacturing of high performance titanium aluminum alloy with fine crystalline full lamellar structure according to claim 3, characterized in that: setting the laser scanning speed to be 15-50 mm/s and the lamination thickness to be 0.06-0.3 mm.
5. The additive manufacturing method of high performance titanium aluminum alloy with fine grain full-sheet structure according to claim 1, wherein: and conveying the titanium-aluminum alloy powder by adopting a coaxial powder conveying device, wherein the flow rate of carrier gas is 3-10L/min.
6. The method of additive manufacturing of a high performance titanium aluminium alloy with fine crystalline full lamellar structure according to any of claims 1 to 5, characterized in that: the prepared high-performance titanium-aluminum alloy with the fine-grain full-lamellar structure is Ti-45Al-8Nb titanium-aluminum alloy or Ti-48Al-2Cr-2Nb titanium-aluminum alloy.
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