A titanium-aluminum alloy part having a backbone reinforcement structure and a method of making the same

Abstract

The application discloses a titanium-aluminum alloy part with a skeleton reinforced structure and a preparation method thereof. A skeleton structure is designed in the part based on a three-dimensional structure model of the part, and a skeleton model of the part is obtained. The structure model of the part and the skeleton model of the part are nested together, slicing software is used to implement layering and slicing, and printing data with a nested relationship is obtained. The printing data is imported into a 3D printer, printing process parameters are set respectively, printing is started, and an electromagnetic induction coil current around a forming plane is started at the same time, so that an electromagnetic field environment wrapping the printing forming plane is created, and a printing blank is obtained after completion. The printing blank is subjected to heat treatment and machining, and a finished product is prepared. The titanium-aluminum alloy part with the skeleton reinforcement has a tensile strength and elongation which are both improved by more than 30% compared to the performance of an ordinary 3D printed part. The method is suitable for high-performance manufacturing of high-strength, brittle and refractory alloy parts, and has the characteristics of high efficiency and excellent performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal additive manufacturing, and particularly relates to a titanium-aluminum alloy part with a framework reinforcing structure and a preparation method thereof. BACKGROUND

[0002] TiAl intermetallic compound has excellent high-temperature creep and oxidation resistance in the range of 700-850 DEG C, and has the characteristics of high elastic modulus and low density, is considered as an ideal substitute for nickel-based high-temperature alloy, is the first choice material for super-high speed aircraft and advanced aero-engine, has been gradually applied in the fields of aerospace, automobile industry and the like, and is a research hotspot of lightweight high-temperature alloy material. However, TiAl alloy has poor plasticity at room temperature, and it is difficult to manufacture TiAl alloy parts with excellent mechanical properties and complex shape and structure by traditional methods such as casting, extrusion, forging and powder metallurgy, and the production cost is relatively high. At present, only GE company in the United States uses electron beam 3D printing technology to prepare Ti48Al2Cr2Nb alloy blades to replace the original high-temperature alloy blades, and the mechanical properties completely meet the use requirements of the engine, realizes the weight reduction of about 200 kg of a single engine, significantly improves the engine thrust and reduces the fuel consumption by 15%, achieves remarkable results, and realizes large-scale manufacturing and application. With the gradual mass production of C919 and other domestic large aircraft, the domestic Changjiang series commercial aviation engine puts forward an urgent demand for TiAl alloy low-pressure turbine blades, and it is urgent to track, innovate and break through in the 3D printing research of TiAl alloy parts.

[0003] In order to solve the problems existing in the traditional processing method of TiAl alloy parts, additive manufacturing technology is introduced, which can quickly and efficiently realize the preparation of TiAl alloy parts. Additive manufacturing, commonly known as 3D printing, is an advanced manufacturing technology based on digital model. It can manufacture parts by slicing the part model and "from bottom to top" melting and accumulating materials. It has the characteristics of high material utilization, high processing efficiency, and the ability to process complex parts. The 3D printed parts have fine grains, uniform structure, and excellent mechanical properties. It has obvious advantages in manufacturing gradient / difficult / machining materials, thin-walled / lattice / complex structure parts. At present, 3D printing technology has been widely used in the field of manufacturing key parts of engines. TiAl alloy material is not suitable for selective laser melting forming method due to its intrinsic brittleness, while electron beam selective melting technology (EBM) can realize high temperature preheating above 1000℃ in the processing chamber. After melting and sintering a layer, real-time annealing is carried out, which can effectively inhibit the generation of cracks in TiAl alloy during printing. The prepared TiAl alloy parts have fine grains and uniform structure, which can effectively solve the problems of composition segregation, mechanical property degradation, and low yield of traditional casting, forging, and machining of TiAl materials. It has the advantages of short production process and high production efficiency. However, the plasticity of TiAl alloy parts prepared by ordinary 3D printing method is still low, which can easily cause damage during part assembly and maintenance. Therefore, it is urgent to strengthen the room temperature performance of TiAl alloy to improve its plasticity, so as to promote the application of TiAl alloy parts. SUMMARY

[0004] In order to overcome the defects of the prior art, the present application is aimed at the technical problems of composition segregation, mechanical property degradation, low yield, and low plasticity of TiAl alloy materials prepared by ordinary 3D printing. By designing and manufacturing a skeleton structure inside the TiAl alloy part, the skeleton structure can effectively strengthen the overall strength, enhance the tensile strength and elongation of TiAl alloy material. This method is very suitable for high-performance manufacturing of high-strength, brittle, and difficult-to-machine TiAl alloy parts, and has the characteristics of high efficiency and excellent performance.

[0005] In order to achieve the above-mentioned application purpose, the present application provides a preparation method of a titanium-aluminum alloy part with a skeleton reinforced structure, which comprises the following steps:

[0006] The three-dimensional structure model of the part is taken as a basis and as a design space of the skeleton structure, a skeleton structure is designed inside the part to obtain a part skeleton model; a suitable machining allowance is added to the part structure model; the part structure model and the part skeleton model are nested together, slicing software is used to implement slicing to obtain printing data with a nested relationship.

[0007] After the printing data is imported into a 3D printer, printing process parameters are set for the data of the part structure and the data of the skeleton structure respectively, printing is started, and an electromagnetic induction coil current around the forming plane is selectively turned on to create an electromagnetic field environment wrapping the printing forming surface, and a printed blank of the TiAl alloy part is obtained after completion; the printed blank is subjected to necessary heat treatment and machining to obtain a TiAl alloy part with a skeleton reinforced structure.

[0008] In the above technical solution, further, the part skeleton model uses three-dimensional design software to implement skeleton structure design, and the designed skeleton structure is one of a dot matrix, a unit cell, a topological optimization structure, or other structural shapes.

[0009] Further, the features of the TiAl alloy part printing data include: the part structure model and the part skeleton model are simultaneously imported into data processing software to form a part structure and a skeleton structure with a nested relationship, but this is not to combine the two into one through Boolean operation, and then use data processing software to implement slicing of the nested model to obtain printing data of the nested model. The slicing layer thickness of the nested model is 0.03-0.3 mm.

[0010] Further, the features of the TiAl alloy part 3D printing process parameters include: the particle size distribution of the spherical TiAl alloy powder used is 0.045-0.2 mm, the 3D printer used is an electron beam selective melting device, and the main process parameters are: the vacuum degree of the processing chamber is ≤0.3 Pa, the slicing thickness is set to 0.03-0.3 mm, the scanning size of the substrate is set to a square plane with a side length of 80-210 mm, the preheating temperature is set to 1000-1350°C, the preheating cycle number is set to 3-15 times, the electron beam focusing current is set to 10-48 mA, and the scanning speed is set to (1000-6000) × 10 3 mm / s. Start printing while turning on the electromagnetic induction coil current around the forming plane to create an electromagnetic field environment wrapping the printing forming surface, and obtain a TiAl alloy part with a skeleton reinforced structure after completion.

[0011] Further, the features of the electromagnetic field environment created during the 3D printing of the TiAl alloy part include: the current voltage parameters loaded in the electromagnetic induction coil are: voltage 0-60 kV, current 0-103 A, the time of current action is 0-1s; the current pause time is 0-1s, when the current pause time is 0s, the current is steady current; when the pause is not 0s, the current is pulse current.

[0012] Further, the heat treatment of the TiAl alloy part comprises: 0-1 times of hot isostatic pressing treatment, the process is: after the package treatment, the pressure is 50-200MPa, the temperature is 950-1350℃, the holding and pressure maintaining time is 1-5h, and the pressure transmission medium is inert gas. Then 1-15 times of ordinary heat treatment cycle is adopted, the process is: the furnace body vacuum degree is ≤1×10 -2 Pa, the temperature rising and falling rate is 5-25℃ / min, the holding temperature is 800-1350℃, the holding time is 1-10h, and the temperature is lowered to room temperature, and the part is taken out.

[0013] Further, the machining of the TiAl alloy part comprises: the cutting speed is 500-1500r / min, the feed rate is 300-1000mm / min, the cutting width is 4-10mm, and the cutting depth is 0.1-0.6mm. The cutter used is a special titanium alloy milling cutter with a coating, and the coating material is TiN. Finally, a TiAl alloy part with a skeleton reinforced structure is obtained.

[0014] A TiAl alloy part with a skeleton reinforced structure prepared by the above method.

[0015] The atomic percentage of the TiAl alloy part material is: aluminum 40-54%, niobium 0-12%, X 0-10%, Y 0-4%, Z 0-1%, and Re 0-0.5%; wherein, X is one or more elements of Cr, V, Mn and Ta, Y is one or more elements of W, Mo and Zr, Z is one or more elements of C, B, Si and N, Re is a rare earth element, and the balance is Ti and unavoidable impurities, and the percentage of 0 indicates that the element is not contained.

[0016] Further, the skeleton of the TiAl alloy part material is of the same material grade as the rest of the part, and the oxygen content of the microstructure of the skeleton structure is 20-40% lower than that of the microstructure of the rest of the part, and the grain size is reduced by 20-30%.

[0017] Compared with the prior art, the beneficial effects of the present application are:

[0018] The application designs and manufactures a framework structure inside a TiAl alloy part, the framework is consistent with the material grade of the rest, but the microstructure of the framework structure has lower oxygen content and finer grains than the microstructure of the rest, because in the printing forming process of the part, the auxiliary electromagnetic field environment can activate the forming surface of the printed part, help the TiAl alloy molten pool obtain electromagnetic field assistance, promote the liquid phase flow in the molten pool to fill the pores and form a dense structure, and at the same time help to break the grains and reduce anisotropy, thereby improving the overall performance of the material. The tensile strength and elongation of the framework reinforced TiAl alloy material are both improved by more than 30% compared with ordinary 3D printed parts. Therefore, in the TiAl alloy part, the framework structure can play a good overall strengthening effect. The method is very suitable for high-performance manufacturing of TiAl alloy parts with high strength, high brittleness and difficult processing, and has the remarkable characteristics of high efficiency and excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A flowchart of a preparation method of a titanium-aluminum alloy part with a framework reinforced structure. DETAILED DESCRIPTION

[0020] The application will be further described below in conjunction with specific examples, but in no way limits the application. To avoid redundancy, the raw materials in the following examples are commercially available unless otherwise specified; the methods used are conventional unless otherwise specified.

[0021] A preparation method of a titanium-aluminum alloy part with a framework reinforced structure, comprising the following steps:

[0022] Based on the three-dimensional structure model of the part, and as the design space of the framework structure, a framework structure is designed inside the part to obtain a part framework model; an appropriate machining allowance is added to the part structure model; the part structure model and the part framework model are nested together, and slicing software is used to implement layering and slicing to obtain printing data with a nested relationship.

[0023] After the printing data is imported into the 3D printer, the printing process parameters are set for the data of the part structure and the data of the framework structure respectively, the printing is started, and the current of the electromagnetic induction coil around the forming plane is selectively turned on to create an electromagnetic field environment wrapping the printing forming surface, and the TiAl alloy part is obtained after the printing is completed; the printing blank is subjected to necessary heat treatment and machining to obtain a TiAl alloy part with a framework reinforced structure.

[0024] In the technical solution, further, the design features of the TiAl alloy part skeleton model include: taking the three-dimensional structure of the part as the basis and as the design space of the skeleton structure, using a three-dimensional design software to implement the structural design of the skeleton, the designed skeleton structure being a structure with a lattice, a unit cell, a topological optimization structure or other structure shape, and obtaining a part skeleton model. A suitable machining allowance is added to the structure model of the TiAl alloy part.

[0025] Further, the features of the TiAl alloy part printing data include: importing the part structure model and the part skeleton model into a data processing software at the same time to form a part structure and a skeleton structure with a nested relationship, but this is not to integrate the two through Boolean operation, and then using the data processing software to implement layer slicing on the nested model to obtain the printing data of the nested model. The slicing layer thickness of the nested model is 0.03-0.3mm.

[0026] Further, the features of the TiAl alloy part 3D printing process parameters include: the particle size distribution of the spherical TiAl alloy powder used is 0.045-0.2mm, the 3D printer used is an electron beam selective melting device, and the main process parameters are: the vacuum degree of the processing chamber is ≤0.3Pa, the slicing thickness is set to 0.03-0.3mm, the scanning size of the substrate is set to a square plane with a side length of 80-210mm, the preheating temperature is set to 1000-1350℃, the preheating cycle number is set to 3-15 times, the electron beam focusing current is set to 10-48mA, and the scanning speed is set to (1000-6000)×10 3 mm / s. The printing process parameters are set for the part structure and the skeleton structure respectively. Start printing while turning on the electromagnetic induction coil current around the forming plane to create an electromagnetic field environment wrapping the printing forming surface, and obtain a TiAl alloy part printing blank with a skeleton reinforced structure after completion.

[0027] Further, the features of the created electromagnetic field environment in the TiAl alloy part 3D printing process include: the current voltage parameters loaded in the electromagnetic induction coil are: voltage 0-60kV, current 0-10 3 A, current acting time 0-1s; current pause time 0-1s, when the current pause time is 0s, the current is a steady current; when the pause is not 0s, the current is a pulse current.

[0028] Further, the features of the TiAl alloy part heat treatment include: first, 0-1 times of hot isostatic pressing treatment, process: after the package treatment, pressure 50-200MPa, temperature 950-1350℃, holding and pressure 1-5h, pressure transmission medium is inert gas. Then, 1-15 times of ordinary heat treatment cycle, process: furnace body vacuum degree ≤1×10 -2Pa, the temperature rising and falling rate is 5-25℃ / min, the holding temperature is 800-1350℃, the holding time is 1-10h, the temperature is decreased to room temperature, and the part is taken out.

[0029] Further, the machining features of the TiAl alloy part include: a cutting speed of 500-1500r / min, a feed rate of 300-1000mm / min, a cutting width of 4-10mm, and a cutting depth of 0.1-0.6mm. A special titanium alloy milling cutter with a coating is used, and the coating material is TiN. Finally, a TiAl alloy part with a skeleton reinforced structure is obtained.

[0030] A TiAl alloy part with a skeleton reinforced structure prepared by the above method.

[0031] The atomic percentage of the TiAl alloy part material is: aluminum 40-54%, niobium 0-12%, X 0-10%, Y 0-4%, Z 0-1%, and Re 0-0.5%; wherein X is one or more of Cr, V, Mn, and Ta, Y is one or more of W, Mo, and Zr, Z is one or more of C, B, Si, and N, Re is a rare earth element, and the balance is Ti and unavoidable impurities. A percentage of 0 indicates that the element is not present.

[0032] Further, the skeleton of the TiAl alloy part material is of the same material grade as the rest of the part, and the oxygen content of the microstructure of the skeleton structure is 20-40% lower than that of the microstructure of the rest of the part, and the grain size is reduced by 20-30%.

[0033] Embodiment

[0034] Preferably, the following is further illustrated by specific embodiments. A TiAl alloy part with a skeleton reinforced structure and a method for preparing the same, as shown in Figure 1 includes the following steps:

[0035] First, according to the three-dimensional structure model of the turbine part, the three-dimensional structure model is used as the design space of the skeleton structure, and a skeleton structure is designed inside the turbine part using UGNX12 three-dimensional model design software. The skeleton structure adopts a diamond lattice point array form, the small beam diameter is 1.5mm, the small beam length is 3mm, the diamond lattice point array structure is generated inside the structure part with a wall thickness of ≥3mm, a part skeleton model is obtained, and a.stl file is exported. A machining allowance of 1.5mm is added to the position surface of the turbine part and other parts.

[0036] The part model and the skeleton model (.stl file) are imported into the 3D printing data processing software BuildAssembler3 at the same time to form a part structure and a skeleton structure with a nested relationship, but this is not to synthesize the two by Boolean operation into one, and then use the software to implement layer slicing on the nested model to obtain the printing data (.abf file) of the nested model. The slice layer thickness of the model is 0.09mm.

[0037] The printing data (.abf file) is imported into the electron beam selective melting 3D printer Arcam A2X. The composition of the spherical TiAl alloy powder used is Ti48Al2Cr2Nb0.5B, the particle size distribution is 0.050-0.150mm, and the average particle size is 0.095mm. 3D printing is carried out, and printing process parameters are set for the part structure and the skeleton structure respectively. The printing process parameters for the part structure are: the vacuum degree of the processing chamber is ≤0.3Pa, the slice thickness is set to 0.09mm, the scanning size of the substrate is set to a square plane with a side length of 170mm, the preheating temperature is set to 1020℃, the preheating cycle number is set to 5 times, the electron beam focusing current is set to 40mA, and the scanning speed is 5000×10 3 mm / s. The printing process parameters for the skeleton structure are: the vacuum degree of the processing chamber is ≤0.3Pa, the slice thickness is set to 0.09mm, the scanning size of the substrate is set to a square plane with a side length of 170mm, the preheating temperature is set to 1020℃, the preheating cycle number is set to 5 times, the electron beam focusing current is set to 46mA, and the scanning speed is 5000×10 3 mm / s. Start printing while turning on the electromagnetic induction coil current around the forming plane to create an electromagnetic field environment wrapping the printing forming surface. The current voltage parameters loaded in the electromagnetic induction coil are: voltage is 380V, current is 100A, current acting time is 0.25s, current pause time is 0.1s, and current is pulse current. After printing, a TiAl alloy turbine printing blank with a skeleton reinforced structure is obtained.

[0038] The 3D printed TiAl alloy turbine part blank is subjected to necessary heat treatment and machining. The heat treatment process is: no hot isostatic pressing treatment, 5 ordinary heat treatment cycles are adopted, and the specific process is: the furnace body vacuum degree is ≤1×10 -2Pa, the heating and cooling rate is 15℃ / min, the holding temperature is 1250℃, the holding time is 2h, the temperature is decreased to room temperature, and the part is taken out; the key process parameters for machining are: the cutting speed is 700mm / min, the feeding amount is 500mm / min, the cutting width is 7mm, and the cutting depth is 0.2mm; the cutter used is a special titanium alloy milling cutter with a coating, and the coating material is TiN; the sequence of heat treatment and machining can be exchanged according to actual needs, and finally a TiAl alloy turbine part with a skeleton reinforced structure is obtained.

[0039] A mechanical tensile sample (R7) with a skeleton reinforced structure is printed by adopting the same skeleton reinforced structure design and 3D printing process parameters as the TiAl turbine part, and a room temperature tensile test and a microstructure SEM detection are carried out. The results show that the tensile strength of the sample with the skeleton reinforced structure is (1080±20) MPa, and the elongation is (1.1±0.1) %, which are both increased by more than 30% compared with the sample without the skeleton reinforced structure (824MPa and 0.73%). The SEM results show that the grain size of the skeleton part is 120μm, which is reduced by more than 25% compared with the grain size (165μm) of the other parts. At the same time, the energy spectrum analysis shows that the oxygen content of the skeleton part is 620ppm, which is reduced by more than 35% compared with the oxygen content (894ppm) of the other parts. Therefore, the titanium aluminum alloy part prepared by the present application establishes a skeleton reinforced structure in the part, which can greatly improve the mechanical properties of the part, and is conducive to promoting the popularization and application of the TiAl alloy part.

[0040] For any person skilled in the art, many possible changes and modifications or equivalent embodiments of the technical solutions of the present application can be made by using the technical content disclosed above without departing from the scope of the technical solutions of the present application. Therefore, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application, which does not deviate from the content of the technical solutions of the present application, should still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A method of making a titanium aluminide alloy part having a skeletal reinforcement structure, characterized by, The method comprises the following steps: A skeleton structure is designed in the part based on the three-dimensional structure model of the part, and the part skeleton model is obtained; a machining allowance is added to the part structure model; the part structure model and the part skeleton model are nested together, and slicing software is used to implement slicing, so that printing data with a nested relationship is obtained; After the printing data is imported into the 3D printer, printing process parameters are set for the data of the part structure and the data of the skeleton structure, and the printing is started, and at the same time, the current of the electromagnetic induction coil around the forming plane is selectively turned on to create an electromagnetic field environment wrapping the printing forming surface, and a printed blank of the TiAl alloy part is obtained after completion; The printed blank is subjected to heat treatment and machining to obtain a TiAl alloy part with a skeleton reinforced structure; The skeleton structure designed by the three-dimensional design software has a lattice, a unit cell or a topological optimization structure; The TiAl alloy part printing data features include: the part structure model and the part skeleton model are simultaneously imported into the data processing software to form a part structure and a skeleton structure with a nested relationship, and then the data processing software is used to implement slicing on the nested model to obtain printing data of the nested model; the slicing layer thickness of the nested model is 0.03-0.3 mm; The TiAl alloy part 3D printing process parameter characteristics include: the particle size distribution of the spherical TiAl alloy powder used is 0.045-0.2 mm, the 3D printer used is an electron beam selective melting device, and the main process parameters are: the vacuum degree of the processing bin is ≤0.3 Pa, the slice thickness is set to 0.03-0.3 mm, the scanning size of the substrate is set to a square plane with a side length of 80-210 mm, the preheating temperature is set to 1000-1350℃, the preheating cycle number is set to 3-15 times, the electron beam focusing current is set to 10-48 mA, and the scanning speed is(1000-6000)×10 3 mm / s. The electromagnetic field environment characteristics created in the 3D printing process of the TiAl alloy part include: the current voltage parameters loaded in the electromagnetic induction coil are: the voltage is 0-60 kV, the current is 0-10 3 A, the current action time is 0-1 s, and the current pause time is 0-1 s; when the current pause time is 0 s, the current is a steady current, and when the pause is not 0 s, the current is a pulse current; The heat treatment features of the TiAl alloy part include: 0-1 times of hot isostatic pressing treatment, process: after the package treatment, the pressure is 50-200 MPa, the temperature is 950-1350 DEG C, the holding and pressure maintaining time is 1-5 h, and the pressure transmission medium is inert gas; and then 1-15 times of ordinary heat treatment cycle, process: the furnace body vacuum degree is less than or equal to 1*10 -2 Pa, the temperature rising and falling rate is 5-25 DEG C / min, the holding temperature is 800-1350 DEG C, the holding time is 1-10 h, the temperature is lowered to room temperature, and the part is taken out. The TiAl alloy part machining features include: the cutting speed is 500-1500 r / min, the feed rate is 300-1000 mm / min, the cutting width is 4-10 mm, and the cutting depth is 0.1-0.6 mm; the cutting tool used is a special titanium alloy milling cutter with a coating, and the coating material is TiN; and finally a TiAl alloy part with a skeleton reinforced structure is obtained.

2. A titanium aluminum alloy part with a skeleton reinforced structure prepared by the method of claim 1.

3. The titanium aluminide alloy part having a backbone reinforcement structure of claim 2, wherein, The atomic percentage of the titanium aluminum alloy part material is: aluminum 40%-54%, niobium 0-12%, X 0-10%, Y 0-4%, Z 0-1%, and Re 0-0.5%; wherein X is one or more elements of Cr, V, Mn, and Ta, Y is one or more elements of W, Mo, and Zr, Z is one or more elements of C, B, Si, and N, Re is a rare earth element, and the balance is Ti and unavoidable impurities.

4. The titanium aluminide alloy part having a backbone reinforcement structure of claim 3, wherein, The skeleton of the titanium aluminum alloy part material is of the same material grade as the rest of the part, and the microstructure of the skeleton structure has an oxygen content 20%-40% lower and a grain size 20%-30% smaller than those of the microstructure of the rest of the part.

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