A method for preparing a wide-temperature-range constant-elasticity low-modulus titanium alloy based on an additive manufacturing technology

Abstract

A method for preparing a wide-temperature-range constant-elasticity low-modulus titanium alloy based on additive manufacturing technology, relates to the field of electron beam additive manufacturing technology, and the method comprises the following steps: step 1, preparing an electron beam powder with a particle size of 30-150 microns; step 2, establishing a three-dimensional model of a printed metal part; step 3, adjusting the printing process parameters and scanning strategy, using an electron beam device for additive manufacturing, and directly obtaining a high-precision wide-temperature-range constant-elasticity titanium alloy. The wide-temperature-range constant-elasticity characteristics of the alloy prepared by the method can be directly generated by controlling the additive manufacturing process parameters, without subsequent processing, and the room-temperature elastic modulus is 35-55 GPa, and the elastic modulus remains unchanged in the temperature range of-50 DEG C to 200 DEG C. The method has the advantages of simple process steps, low production cost and short processing cycle, and has good application prospect in the fields of national defense, aerospace, precision machinery and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electron beam additive manufacturing, in particular to a method for preparing wide-temperature-range constant-elasticity low-modulus titanium alloy based on additive manufacturing technology. BACKGROUND

[0002] Constant modulus alloys have been widely used in the fields of aerospace and precision machinery because of their function of keeping the elastic modulus unchanged within a certain temperature range. The parts used in general precision instruments are often complex in design, difficult to process, have many processing procedures and high manufacturing costs, and other problems, which limit the further development of the precision machinery field.

[0003] Additive manufacturing technology can directly print completed parts without molds based on computer-aided design system (CAD) models, and the manufacturing precision can reach ±20μm, which has extremely high processing precision. Moreover, it can form complex structural parts without the problem of processing dead angles in traditional processing methods.

[0004] Electron beam selective melting technology is an additive manufacturing technology using electron beam as heat source, and has several important process parameters such as scanning speed, electron beam current, defocus amount, line defocus and bottom plate temperature. The mechanical properties, phase content, phase composition and microstructure of the same metal parts processed by different processing technologies are different.

[0005] Therefore, by using the processing characteristics of additive manufacturing technology and controlling the process parameters to adjust the phase content, phase composition and microstructure of the parts, the purpose of directly preparing wide-temperature-range constant-elasticity low-modulus titanium alloy can be achieved. This method can not only reduce manufacturing costs, reduce processing procedures and shorten processing time, but also directly form high-precision parts. The constant modulus titanium alloy prepared by additive manufacturing technology can be directly and quickly formed without complicated processing procedures, and has excellent performance, which has good application prospects in the fields of national defense, aerospace, precision machinery and the like. SUMMARY

[0006] The purpose of the present application is to provide a method for preparing wide-temperature-range constant-elasticity low-modulus titanium alloy based on additive manufacturing technology. The wide-temperature-range constant-elasticity low-modulus titanium alloy prepared by the method has an elastic modulus in the range of 35-55Gpa at room temperature, and can keep the elastic modulus unchanged within the temperature range of-50℃-200℃.

[0007] The technical solution of the present application is as follows:

[0008] A method for preparing wide-temperature-range constant-elasticity low-modulus titanium alloy based on additive manufacturing technology, the specific steps are as follows:

[0009] Step 1: preparing an electron beam powder with a particle size of 30μm-150μm;

[0010] According to the type of alloy to be printed, spherical alloy powder with specified composition is prepared, and the alloy powder is prepared by gas atomization process or rotating electrode method. The powder particle size distribution range is 30μm to 150μm, and its powder characteristics must meet the particle size distribution, D10 is 48-52μm, D50 is 68-72μm, and D90 is 95-100μm. The bulk density is 2.4-3.0g / cm 3 , the tap density is 2.6~3.5g / cm 3 , Hall fluidity ≤30 (s / 50g), hollow powder rate does not exceed 0.5%.

[0011] Step 2: Create a 3D model of the printed metal part;

[0012] Use 3D modeling software to create a 3D model of the metal part, import the designed 3D model into the 3D model processing software for graphic optimization and subsequent support design; then transfer the optimized 3D model into the computer control system of the electron beam molten metal forming equipment, and use the electron beam additive manufacturing equipment for subsequent printing;

[0013] Step 3: Adjust the printing process parameters and scanning strategy, and use electron beam equipment for additive manufacturing;

[0014] Select the base plate according to the size of the printed model, preheat the base plate to the printing temperature, set the thickness of each layer of powder during the printing process, set the printing process parameters and scanning strategy for printing.

[0015] The scanning strategy is a layer-by-layer 90° printing method, meaning the melt pool lines between adjacent printed layers are perpendicular to each other. The base plate temperature range is 450°C to 550°C, the powder layer thickness is 50-70μm, preferably 70μm, the scanning speed is 1300-1500mm / s, the electron beam current is 7-9mA, the defocus is 10-15mA, and the line defocus is 0.1-0.2mm.

[0016] The above-mentioned method for preparing a titanium alloy with constant elasticity and low modulus over a wide temperature range based on additive manufacturing technology, wherein:

[0017] In step 1, the alloy powder needs to satisfy an electron concentration ratio e / a between 4.10 and 4.25.

[0018] In the step 2, the printing device is an electron beam selective melting device.

[0019] In step 2, the 3D modeling software used includes Solidworks, Creo, and UG.

[0020] In step 3, the input energy density E of the process parameter is 25-35 J / mm 3 , Where U is the electron beam emission voltage, I is the electron beam current, H is the powder thickness, L is the line defocus, and V is the scanning speed.

[0021] The constant modulus alloy prepared in step 3 does not require any subsequent processing and can be directly manufactured using additive manufacturing technology to produce an alloy with constant elastic properties. This constant modulus titanium alloy has a stable constant elastic modulus within the temperature range of -50°C to 200°C, a room temperature tensile strength of 670 to 750 MPa, and a density greater than 99%.

[0022] The design concept of the present invention:

[0023] The additive manufacturing process of the present invention features adjustable parameters, including scanning speed, electron beam current, focus deflection, line focus deflection, and baseplate temperature. By adjusting these parameters, the degree of powder melting, the post-solidification holding temperature, and the cooling rate of the part can be controlled. By controlling the molding temperature and cooling method, the microstructure, phase composition, and phase content of the alloy can be controlled.

[0024] For titanium alloys with an electron concentration ratio e / a between 4.10 and 4.25, the constant modulus characteristic is mainly related to the presence of a large amount of α" phase. By controlling its phase composition, that is, mainly consisting of β phase and α" phase, and at the same time controlling the phase content, the alloy can have a constant modulus characteristic within a certain temperature range.

[0025] Advantages and beneficial effects of the present invention:

[0026] 1. The constant modulus titanium alloy prepared by the method of the present invention has excellent performance. The room temperature elastic modulus measured by the resonance method is 35 to 55 GPa, which has an extremely low elastic modulus and maintains the elastic modulus unchanged in the temperature range of -50°C to 200°C. The tensile strength reaches 670 to 750 MPa, with excellent mechanical properties and broad application prospects.

[0027] 2. The present invention uses electron beam additive manufacturing to prepare the alloy. The additive manufacturing process is simple. Compared with constant modulus alloys manufactured by traditional processing techniques, it can directly form complex parts in one step with high manufacturing precision. This effectively solves the problem that traditional manufacturing processes require further processing.

[0028] 3. The present invention adopts electron beam additive manufacturing to prepare alloys. By utilizing the adjustability of the process, alloys with different properties can be formed at one time according to actual requirements, and alloys with constant modulus only in local areas can be manufactured. This is something that cannot be achieved by existing processing methods and has very wide application and research value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is the SEM scanning electron microscope image of the Ti-24Nb-4Zr-8Sn alloy powder.

[0030] Figure 2 Figures of the prepared constant modulus titanium alloy materials, where (a) is the sample diagram of Example 1, (b) is the sample diagram of Example 2, (c) is the sample diagram of Comparative Example 1, and (d) is the sample diagram of Comparative Example 2.

[0031] Figure 3 1 and 2 are modulus-temperature curves of constant modulus titanium alloy, wherein (a) is the modulus-temperature diagram of Example 1, and (b) is the modulus-temperature diagram of Example 2.

[0032] Figure 4 This is the modulus-temperature curve of the sample prepared in Comparative Example 2.

[0033] Figure 5 1 and 2 are metallographic organization diagrams of constant modulus titanium alloy materials, wherein (a) is the organization diagram of Example 1, and (b) is the organization diagram of Example 2. DETAILED DESCRIPTION

[0034] A method for preparing a titanium alloy with constant elasticity and low modulus over a wide temperature range based on additive manufacturing technology, the specific steps are as follows:

[0035] Step 1: Prepare electron beam powder with a particle size of 30 μm to 150 μm;

[0036] According to the type of alloy to be printed, spherical alloy powder with specified composition is prepared, and the alloy powder is prepared by gas atomization process or rotating electrode method. The metal powder particle size distribution range is 30μm to 150μm, and its powder characteristics meet the particle size distribution, D10 is 48 to 52, D50 is 68 to 72, and D90 is 95 to 100. The bulk density is 2.4 to 3.0g / cm 3 , the tap density is 2.6~3.5g / cm 3 , Hall fluidity ≤30 (s / 50g), hollow powder rate not exceeding 0.5%. The alloy powder satisfies the electron concentration ratio e / a between 4.10-4.25.

[0037] Step 2: Create a 3D model of the printed metal part;

[0038] Use 3D modeling software such as Solidworks, Creo, and UG to build a 3D model of metal parts, and import the designed 3D model into 3D model processing software such as Magics for graphic optimization and subsequent support design; then transfer the optimized 3D model into the computer control system of the electron beam molten metal forming equipment, and use electron beam additive manufacturing equipment for subsequent printing.

[0039] Step 3: Adjust the printing process parameters and scanning strategy, and use electron beam equipment for additive manufacturing;

[0040] Select the base plate according to the size of the printed model, preheat the base plate to the printing temperature, set the thickness of each layer of powder during the printing process, set the printing process parameters and scanning strategy for printing.

[0041] The scanning strategy is a layer-by-layer 90° printing method, meaning the melt pool lines between adjacent printed layers are perpendicular to each other. The base plate temperature range is 450°C to 550°C, the powder layer thickness is 50-70μm, preferably 70μm, the scanning speed is 1300-1500mm / s, the electron beam current is 7-9mA, the defocus is 10-15mA, and the line defocus is 0.1-0.2mm.

[0042] Example 1

[0043] In Example 1, Ti-24Nb-4Zr-8Sn (wt.%) (Ti2448) alloy powder was used as raw material, and its electron concentration ratio e / a was 4.15. The powder used for electron beam additive manufacturing was prepared by gas atomization process. The sphericity of the powder was as follows: Figure 1 shown.

[0044] The powder particle size distribution is D10 = 48.2 μm, D50 = 71.7 μm, and D90 = 109 μm. The bulk density is 2.964 g / cm 3 , the tap density is 3.33g / cm 3 , Hall fluidity 24 (s / 50g), particle size distribution test adopts GB / T 19077-2016 standard.

[0045] The printing model was designed using SolidWorks software, and the designed 3D model was imported into Magics processing software for graphic optimization and subsequent support design to meet printing requirements. The optimized 3D model was then transferred to the computer control system of the electron beam melting metal forming equipment for printing preparation and manufacturing using Arcam A1 electron beam melting equipment.

[0046] The printing process parameters and scanning strategy were adjusted. The scanning strategy was a 90° printing method with each layer deflected. That is, the molten pool lines between adjacent printing layers were perpendicular to each other. The process parameters were set as follows: preheating the base plate temperature to 450°C, the powder thickness of each layer was 70 μm, the electron beam scanning speed was set to 1400 mm / s, the electron beam current was 7 mA, the focus offset was 10 mA, the line focus offset was 0.15 mm, and the energy density was 28.6 J / mm. 3. Perform vacuum treatment. When the vacuum degree is less than 9×e^-3Pa, use the nine-point focusing method to adjust the electron beam focus so that the electron beam can accurately act on the powder bed to ensure the accuracy of the printed sample. Figure 2 As shown in (a).

[0047] The printed sample was measured using the Archimedean drainage method to a density of 99.6%. It was processed into a 60×8×1mm sheet and a dynamic thermomechanical analyzer (Q800) was used to obtain a curve showing the change in modulus of the sample with temperature. Liquid nitrogen was used to cool the equipment to explore the low-temperature zone. The temperature range was set to -100°C to 300°C, the heating rate was 5°C / min, and the vibration frequency was 1Hz. At the same time, its tensile properties and organization were also observed and characterized.

[0048] In this embodiment 1, the prepared alloy has a modulus of about 37 GPa at a temperature between -50°C and 200°C, and its modulus-temperature curve is as follows: Figure 3 (a) shows that the alloy has constant elasticity in a wide temperature range and has relatively excellent mechanical properties.

[0049] The metallographic observation of its microstructure shows that Figure 5 As shown in (a).

[0050] Example 2

[0051] The alloy types and preliminary preparations used are the same as those in Example 1, except that:

[0052] The process parameters were set as base plate temperature of 450°C, electron beam scanning speed of 1100 mm / s, electron beam current of 6 mA, and energy density of 31.2 J / mm 3 . Perform vacuum treatment. When the vacuum degree is less than 9×e^-3Pa, use the nine-point focusing method to adjust the electron beam focus so that the electron beam can accurately act on the powder bed to ensure the accuracy of the printed sample. Figure 2 (b) shown.

[0053] The printed sample was measured using the Archimedes drainage method to obtain a density of 99.4%. The sample was processed into a 45×6×1mm thin sheet and a dynamic thermomechanical analyzer (Q800) was used to obtain a curve showing the change in modulus of the sample with temperature. Liquid nitrogen was used to cool the device to explore the low-temperature zone. The temperature range was set to -100°C to 300°C, the heating rate was 5°C / min, and the vibration frequency was 1Hz. At the same time, its tensile properties and organization were also observed and characterized.

[0054] In Example 2, the prepared alloy maintains a modulus of approximately 37 GPa within a temperature range of -50°C to 200°C, and its modulus-temperature curve is shown in FIG. Figure 3 (b) This alloy has constant elasticity over a wide temperature range and excellent mechanical properties.

[0055] The metallographic observation of its microstructure shows that Figure 5 (b) shown.

[0056] Comparative Example 1

[0057] The alloy types and preliminary preparations used are the same as those in Example 1, except that:

[0058] The process parameters are set as follows: the base plate temperature is 700℃, the electron beam scanning speed is 500mm / s, the electron beam current is 7mA, and the energy density is 80.0J / mm 3 , the defocus amount is 10mA, and the linear defocus is 0.15mm. A vacuum process is performed. When the vacuum degree is less than 9×e^-3Pa, the electron beam focus is adjusted using the nine-point focusing method to ensure that the electron beam can accurately act on the powder bed, ensuring the accuracy of the printed sample.

[0059] The precision of the prepared samples is extremely poor, and it is impossible to effectively prepare high-precision samples. Figure 2 (c) shown.

[0060] Comparative Example 2

[0061] The alloy types and preliminary preparations used are the same as those in Example 1, except that:

[0062] The process parameters were set as base plate temperature of 450°C, electron beam scanning speed of 300 mm / s, electron beam current of 5 mA, and energy density of 95.2 J / mm 3 , the defocus amount is 10mA, and the linear defocus is 0.15mm. Vacuum treatment is carried out. When the vacuum degree is less than 9×e^-3, the nine-point focusing method is used to adjust the electron beam focus so that the electron beam can accurately act on the powder bed, ensuring the accuracy of the printed sample.

[0063] The precision of the prepared samples is extremely poor, and it is impossible to effectively prepare high-precision samples. Figure 2 (d) shown.

[0064] The printed samples were processed into 45×6×1mm sheets and analyzed using a dynamic thermomechanical analyzer (Q800) to obtain a curve showing the sample's modulus changing with temperature. Liquid nitrogen was used to cool the device, allowing for exploration of the low-temperature region. The temperature range was set between -100°C and 300°C, with a heating rate of 5°C / min and an oscillation frequency of 1Hz. The tensile properties and microstructure were also observed and characterized.

[0065] In this comparative example 2, the elastic modulus of the alloy prepared in this temperature range varies greatly and does not have the constant modulus characteristic. The curve is as follows Figure 4 shown.

Claims

1. A method for preparing a titanium alloy with constant elasticity and low modulus in a wide temperature range based on additive manufacturing technology, characterized in that The specific steps are as follows: Step 1: Prepare electron beam powder with a particle size of 30 μm to 150 μm; According to the type of alloy to be printed, spherical alloy powder with specified composition is prepared. The alloy powder is prepared by gas atomization process or rotating electrode method. The powder particle size distribution range is 30μm to 150μm. The powder characteristics must meet the particle size distribution requirements, D10 is 48-52μm, D50 is 68-72μm, and D90 is 95-100μm. The bulk density is 2.4-3.0g / cm 3 , the tap density is 2.6~3.5g / cm 3 , Hall fluidity ≤30 (s / 50g), hollow powder rate does not exceed 0.5%; Step 2: Create a 3D model of the printed metal part; Use 3D modeling software to create a 3D model of the metal part, import the designed 3D model into the 3D model processing software for graphic optimization and subsequent support design; then transfer the optimized 3D model into the computer control system of the electron beam molten metal forming equipment, and use the electron beam additive manufacturing equipment for subsequent printing; Step 3: Adjust the printing process parameters and scanning strategy, and use electron beam equipment for additive manufacturing; Select the base plate according to the size of the printed model, preheat the base plate to the printing temperature, set the thickness of each layer of powder during the printing process, set the printing process parameters and scanning strategy for printing.

2. The method for preparing a titanium alloy with constant elasticity and low modulus in a wide temperature range based on additive manufacturing technology according to claim 1, characterized in that In step 1, the alloy powder needs to satisfy an electron concentration ratio e / a between 4.10 and 4.

25.

3. The method for preparing a titanium alloy with constant elasticity and low modulus in a wide temperature range based on additive manufacturing technology according to claim 1, characterized in that In the step 2, the printing device is an electron beam selective melting device.

4. The method for preparing a titanium alloy with constant elasticity and low modulus in a wide temperature range based on additive manufacturing technology according to claim 1, characterized in that In step 2, the three-dimensional modeling software used is selected from one of Solidworks, Creo and UG.

5. The method for preparing a titanium alloy with constant elasticity and low modulus in a wide temperature range based on additive manufacturing technology according to claim 1, characterized in that In step 3, the input energy density E of the process parameter is 25-35 J / mm 3 , Where U is the electron beam emission voltage, I is the electron beam current, H is the powder thickness, L is the line defocus, and V is the scanning speed.

6. The method for preparing a titanium alloy with constant elasticity and low modulus in a wide temperature range based on additive manufacturing technology according to claim 1, characterized in that In step 3, the scanning strategy is a layer-by-layer 90° deflection printing method, the base plate temperature range is 450°C to 550°C, the powder thickness of each layer is 50 to 70 μm, the scanning speed is 1300 to 1500 mm / s, the electron beam current is 7 to 9 mA, the defocus amount is 10 to 15 mA, and the line defocus is 0.1 to 0.2 mm.

7. The method for preparing a titanium alloy with constant elasticity and low modulus in a wide temperature range based on additive manufacturing technology according to claim 1, characterized in that In step 3, the constant modulus titanium alloy prepared has a stable constant elastic modulus in the temperature range of -50°C to 200°C, the elastic modulus is 35 to 55GPa, the room temperature tensile strength of the alloy is in the range of 670 to 750MPa, and the density is greater than 99%.

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