A method for producing a low-modulus solid titanium alloy

Abstract

This invention discloses a method for preparing low-modulus solid titanium alloys, belonging to the field of materials manufacturing. The method employs electron beam selective melting technology, adjusting the contour parameters, base plate temperature, preheating parameters, and process parameters of the electron beam control system to prepare high-strength solid titanium alloys. <100> Oriented, low-elastic-modulus solid titanium alloys with a modulus of 30-35 GPa are prepared, resulting in alloys with a porosity of less than 1.5%, high dimensional accuracy, and high surface quality. The elastic modulus of the alloy obtained using the method provided in this invention is closer to that of human bone, which can greatly reduce the impact of the "stress shielding" effect. As a non-toxic, novel biomedical titanium alloy, it has good scientific research and application value.

Description

Technical Field

[0001] This invention belongs to the field of materials manufacturing, and specifically relates to a method for preparing a low-modulus solid titanium alloy. Background Technology

[0002] As a type of medical titanium alloy, Ti-Nb alloy has been widely welcomed due to its good biocompatibility. However, when it is implanted into the human body, the elastic modulus of Ti-Nb alloy (50-90 GPa) is higher than that of human bone (20-30 GPa), resulting in a "stress shielding" phenomenon. This leads to osteoporosis in human bones due to insufficient mechanical stimulation, resulting in poor mechanical properties of the bones and further increasing the risk of bone damage. Further reducing the elastic modulus can avoid the above risks. At present, the research and development of low modulus solid titanium alloys mainly includes the following methods: (1) changing the alloy composition to reduce the alloy modulus, adding elements such as Nb, Zr, Mo, and Ta to further reduce the elastic modulus on the basis of existing medical titanium alloys. (2) using appropriate heat treatment processes to reduce the elastic modulus by adjusting the phase composition. (3) adjusting the texture content and using anisotropy to reduce the elastic modulus.

[0003] Ti-Nb alloy is a typical β-Ti alloy. Studies have found that... <100> Orientation is the direction in which the elastic modulus of Ti-Nb alloys is lowest. Therefore, improving the elastic modulus of the prepared medical-grade Ti-Nb alloys... <100> The proportion of oriented grains forms a strong <100> Oriented alloys further reduce the elastic modulus. This is of great significance.

[0004] In alloys prepared using traditional processing techniques, the crystal orientation is generally disordered, making it difficult to form a single orientation and thus impossible to control the alloy's properties. Even in alloys prepared by rolling, the internal orientation is formed along the rolling direction and cannot be controlled, meaning it is impossible to obtain a single-oriented alloy.

[0005] Selective electron beam melting (SEBLM) is a type of additive manufacturing technology that uses an electron beam as an energy source to directly form metal parts in a high-vacuum environment. It features high energy density, high energy utilization, high purity, low residual stress, and fast forming speed. However, due to its process characteristics, SEBLM forms a large number of columnar crystals in the resulting alloy. Therefore, the process characteristics of SEBLM can be utilized to prepare strong... <100> Oriented low-modulus Ti-Nb alloys. Furthermore, electron beam selective melting technology can form complex three-dimensional models, enabling the integrated precision forming of complex structural parts using Ti-Nb alloys, which has broad application prospects.

[0006] However, the electron beam selective melting technology currently faces the following technical problems: (1) Ti-Nb alloys have high melting points and are difficult to melt. At present, electron beam selective melting technology lacks the process for preparing Ti-Nb alloys, and the process for forming high-density, high-dimensional-precision TiNb alloys urgently needs to be solved. (2) Electron beam selective melting technology lacks the process for preparing strong Ti-Nb alloys. <100> In the technique of orientation alloying, the Ti-Nb alloy prepared by electron beam selective melting under the general process window still contains a large number of non-orientation alloys. <100> For oriented grains, the elastic modulus is generally within the range of 35-55 GPa. How can the forming strength be controlled through process control? <100> The method to further reduce the modulus of oriented alloys is still unknown. (3) Among the currently published technical solutions, there is no suitable process window for electron beam selective melting technology to be used directly to prepare low modulus Ti-Nb alloys. The specific parameters need to be further studied and explored.

[0007] Research has shown that the crystal orientation of alloys prepared by selective electron beam melting can be controlled through process parameters, thus allowing for the control of the formation of the prepared alloy. <100> Orientation-based textures can theoretically achieve close approximations. <100> The alloy with the lowest single-crystal modulus. Summary of the Invention

[0008] This invention provides a method for preparing low-modulus solid titanium alloys, producing Ti-Nb alloys with high density, high dimensional accuracy, and high surface quality, thus solving the problem of relatively high elastic modulus of Ti-Nb alloys.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A method for preparing a low-modulus solid titanium alloy includes the following steps:

[0011] Step 1: Prepare high-purity raw materials and prepare metal powder;

[0012] Step 2: Adjust the metal powder ratio;

[0013] Step 3: Establish a data model along the X / Y / Z coordinate system;

[0014] Step 4: Extract two-dimensional data along the X / Y plane from the data model obtained in Step 3. The thickness of the two-dimensional data slice is consistent with the thickness of the powder layer, which is 70 μm.

[0015] Step 5: Adjust the contour parameters, base plate temperature, preheating parameters, and process parameters of the electron beam control system;

[0016] Step 6: Fill the powder hopper with the metal powder obtained in Step 1;

[0017] Step 7: Adjust the bottom support to keep the base plate parallel to the powder dispenser;

[0018] Step 8: Adjust the amount of powder taken;

[0019] Step 9: Evacuate the vacuum until the vacuum value is no greater than 9 × 10⁻⁶. -3 Pa;

[0020] Step 10: Focus the electron beam position;

[0021] Step 11: Adjust the base plate temperature until the predetermined temperature is reached, then start printing;

[0022] Step 12: Use a powder taker to take powder again, spread the powder evenly on the powder bed, preheat the powder bed evenly, scan the powder bed with an electron beam, and after scanning, use a contour process to remelt and correct the two-dimensional contour.

[0023] Step 13: The toner bed descends to a certain height, the toner dispenser re-spreads the toner, and the scanning strategy is to scan alternately in the X and Y directions to print a new layer;

[0024] Step 14: Repeat steps 12 and 13 until printing is complete;

[0025] Step 15: Lower the powder bed height until the bottom plate contacts the bottom metal, and then fill the molding chamber with inert gas;

[0026] Step 16: Remove the alloy parts and use a PRS device to perform surface treatment on the sample to blow away excess powder in order to improve the surface quality of the sample and obtain a low-modulus solid titanium alloy.

[0027] In step 1, the high-purity raw material is composed of titanium, niobium and oxygen, wherein the mass fraction of titanium:niobium is (2~3):1;

[0028] In step 5, the preheating parameters include Beam current, Line offset, Beam speed, and Number of repetitions; wherein, Beam current is 14-20mA; Line offset is 0.10-0.15mm; Beam speed is selected as 8000-15000mm / s; and Number of repetitions is 10-16 times.

[0029] In step 5, the process parameters include: Beam current, Line offset, Beam speed, and Focusoffset; wherein, Beam speed is generally 600~1500mm / s, Beam current is 6-7mA, Focusoffset is 10-12mA, and Line offset is 0.13~0.15mm.

[0030] In step 5, the contour parameters include Beam current, Line offset, Beam speed, and Focus offset; wherein, Beam speed is 500-650mm / s, Beam current is 7-10mA, Focus offset is 5-8mA, and Line offset is 0.15~0.2mm.

[0031] In step 5, the temperature of the base plate is selected as 400-450℃;

[0032] In step 7, the parallelism between the upper and lower surfaces of the base plate is less than 0.2mm, the length and width of the base plate are greater than 150mm, the thickness is 8~15mm, and the material is stainless steel.

[0033] In step 15, the powder bed must descend to contact the bottom metal until it can no longer descend;

[0034] In step 16, the low-modulus solid titanium alloy has an elastic modulus of 30-35 GPa along the Z-axis, contains columnar crystal structure along the Z-direction, and its preferred orientation is... <100> orientation.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. The process for preparing titanium-niobium alloys by selective electron beam melting has been elucidated. This invention employs selective electron beam melting technology, and by adjusting the contour parameters, substrate temperature, preheating parameters, and process parameters of the electron beam control system, titanium-niobium alloys with low elastic modulus, porosity below 1.5%, high dimensional accuracy, and high surface quality are prepared. The process window for preparing titanium-niobium alloys using selective electron beam melting technology has been elucidated.

[0037] 2. The titanium-niobium alloy prepared by this invention possesses strong... <100> The orientation and modulus range from 30-35 GPa, significantly reducing the alloy's elastic modulus. Compared to the elastic modulus of other medical titanium alloys, such as Ti-6Al-4V (101-110 GPa), Ti-13Nb-13Zr (79-84 GPa), and Ti-35.3Nb-5.1Ta-7.1Zr (52-55 GPa), it is closer to the elastic modulus of human bone, greatly reducing the impact of the "stress shielding" effect. As a non-toxic, novel biomedical titanium alloy, it has significant scientific research and application value.

[0038] 3. This study pioneered the idea of ​​using electron beam selective melting technology to control crystal orientation and obtain superior performance, and the results have been proven in the research. This has improved the ideas and provided reference schemes for using this technology to further obtain superior performance.

[0039] 4. This invention uses electron beam selective melting technology to prepare titanium-niobium alloys. The process parameters are simple to design and operate, and there are many process windows, which can prepare suitable titanium-niobium alloys in different process windows. Attached Figure Description

[0040] Figure 1 This is a diagram of the powder's shape.

[0041] Figure 2 Image of the sample prepared in Example 1;

[0042] Figure 3 Metallographic structure of the sample prepared in Example 1;

[0043] Figure 4 The image shows the electron backscatter diffraction analysis data of the sample prepared in Example 1.

[0044] Figure 5 Image showing the preparation of sample for Comparative Example 1;

[0045] Figure 6 Metallographic structure of the sample prepared for Comparative Example 1;

[0046] Figure 7 Image showing sample preparation for Comparative Example 2;

[0047] Figure 8 Metallographic structure of the sample prepared for Comparative Example 2. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0049] Example 1

[0050] A method for preparing a low-modulus solid titanium alloy, the specific operation steps of which are as follows:

[0051] Step 1: Prepare high-purity raw materials and prepare metal powder;

[0052] Step 2: Adjust the powder ratio;

[0053] Step 3: Establish a data model along the X / Y / Z coordinate system;

[0054] Step 4: Extract two-dimensional data along the X / Y plane from the data model obtained in Step 3; the thickness of the two-dimensional data slice and the powder layer thickness are 70 μm;

[0055] Step 5: Adjust the contour parameters, base plate temperature, preheating parameters, and process parameters;

[0056] Step 6: Fill the powder hopper with the metal powder obtained in Step 1;

[0057] Step 7: Adjust the bottom support to keep the base plate parallel to the powder dispenser;

[0058] Step 8: Adjust the amount of powder taken;

[0059] Step 9: Evacuate until the vacuum value reaches 9×10 -3 Pa;

[0060] Step 10: Focus the electron beam position;

[0061] Step 11: Heat the base plate to the preset temperature and then start printing;

[0062] Step 12: Use the powder taker to take powder again, spread the powder evenly on the powder bed, preheat the powder bed evenly, scan the powder bed with an electron beam, and after the scanning is completed, use the contour parameters to remelt and correct the two-dimensional contour.

[0063] Step 13: The toner bed descends to a certain height, the toner dispenser re-spreads the toner, the electron beam rotates 90° to scan, and a new layer is printed;

[0064] Step 14: Repeat steps 12 and 13 until printing is complete;

[0065] Step 15: Lower the powder bed height until the bottom plate contacts the bottom metal, and then fill the forming chamber with inert gas;

[0066] Step 16: Remove the alloy parts, perform surface treatment on the sample to blow away excess powder, and obtain the final low-modulus solid titanium alloy.

[0067] The Ti-Nb alloy used is a Ti-24Nb-4Zr-8Sn (wt.%) alloy, and the powder used in the electron beam selective melting equipment is prepared using a gas atomization process (e.g., Figure 1As shown in the figure, the particle size distribution of the powder is: D10 is 47.8 μm, D50 is 71.9 μm, and D90 is 108 μm.

[0068] The substrate is heated using preheating parameters. Once the substrate temperature reaches the predetermined temperature, the powder dispenser begins to evenly spread the powder onto the substrate, and printing begins.

[0069] After printing is complete, argon gas is introduced into the forming chamber for gas protection and to accelerate cooling.

[0070] The Magics software was used to optimize the graphics of the 3D model and design subsequent support, and then sliced ​​it. The set process parameters were input into the electron beam selective melting equipment to match the sliced ​​model, and then manufactured using the Arcam A1 electron beam melting equipment.

[0071] The selected preheating parameters are: Beam current 15mA; Line offset 0.10mm; Beam speed 10000mm / s; Number of repetitions 15.

[0072] The selected contour parameters are: Beam speed 500mm / s, beam current 8mA, focus offset 8mA, and line offset 0.15mm.

[0073] Process parameters were set as follows: substrate temperature 450℃, electron beam scanning speed 1100 mm / s, electron beam current 6 mA, and focus offset 12 mA. The vacuum level was less than 9 × 10⁻⁶. -3 Printing is performed in an environment with Pa. After sample preparation, as follows: Figure 2 As shown. The prepared sample has a smooth surface, high precision, and a density of 98.8%. The microstructure is as follows. Figure 3 As shown.

[0074] The alloy prepared using these parameters has been tested and found to have high strength. <100> Orientation, electron backscattering diffraction analysis data such as Figure 4 As shown. The elastic modulus was measured to be 33 GPa using the resonance method.

[0075] Comparative Example 1

[0076] The alloy types used and the preliminary preparations are the same as in Example 1.

[0077] Process parameters were set as follows: substrate temperature 500℃, electron beam scanning speed 3000 mm / s, electron beam current 10 mA, and focus offset 10 mA. This was achieved under a vacuum level less than 9 × 10⁻⁶.-3 Printing is performed in an environment with Pa. After sample preparation, as follows: Figure 5 As shown, the microstructure is as follows Figure 6 As shown, the prepared sample had extremely poor precision and numerous surface defects, rendering it unusable.

[0078] Comparative Example 2

[0079] The alloy types used and the preliminary preparations are the same as in Example 1.

[0080] Process parameters were set as follows: substrate temperature 500℃, electron beam scanning speed 600 mm / s, electron beam current 6 mA, and focus offset 12 mA. This was achieved under a vacuum level less than 9 × 10⁻⁶. -3 Printing is performed in an environment with Pa. After sample preparation, as follows: Figure 7 As shown, the microstructure is as follows Figure 8 As shown, the prepared sample exhibits severe protrusions and internal grain deformation, no longer resembling the typical columnar grains of electron beam selective melting, rendering it unusable.

Claims

1. A method for preparing a low-modulus solid titanium alloy, characterized in that, Includes the following steps: Step 1: Prepare high-purity raw materials and prepare metal powder; Step 2: Adjust the metal powder ratio; Step 3: Establish a data model along the X / Y / Z coordinate system; Step 4: Extract two-dimensional data along the X / Y plane from the data model obtained in Step 3. The thickness of the two-dimensional data slice is consistent with the thickness of the powder layer, which is 70 μm. Step 5: Adjust the contour parameters, base plate temperature, preheating parameters, and process parameters of the electron beam control system; the base plate temperature is 400~450℃. Step 6: Fill the powder hopper with the metal powder obtained in Step 1; Step 7: Adjust the bottom support to keep the base plate parallel to the powder dispenser; Step 8: Adjust the amount of powder taken; Step 9: Evacuate the vacuum until the vacuum value is no greater than 9 × 10⁻⁶. -3 Pa; Step 10: Focus the electron beam position; Step 11: Adjust the base plate temperature until the predetermined temperature is reached, then start printing; Step 12: Use a powder taker to take powder again, spread the powder evenly on the powder bed, preheat the powder bed evenly, scan the powder bed with an electron beam, and after scanning, use a contour process to remelt and correct the two-dimensional contour. Step 13: The toner bed descends to a certain height, the toner dispenser re-spreads the toner, and the scanning strategy is to scan alternately in the X and Y directions to print a new layer; Step 14: Repeat steps 12 and 13 until printing is complete; Step 15: Lower the powder bed height until the bottom plate contacts the bottom metal, and then fill the molding chamber with inert gas; Step 16: Remove the alloy parts and use a PRS device to perform surface treatment on the sample to blow away excess powder in order to improve the surface quality of the sample and obtain a low-modulus solid titanium alloy. In step 1, the high-purity raw material is composed of titanium, niobium and oxygen, wherein the mass fraction of titanium:niobium is (2~3):1; In step 5, the preheating parameters include beam current, scanning spacing, scanning speed, and number of scans; wherein, the beam current is 14-20mA; the scanning spacing is 0.10-0.15mm; the scanning speed is selected as 8000-15000mm / s; and the number of scans is 10-16. In step 5, the process parameters include: beam current, scanning spacing, scanning speed, and defocusing amount; wherein, the scanning speed is generally 600~1500mm / s, the beam current is 6-7mA, the defocusing amount is 10-12mA, and the scanning spacing is 0.13~0.15mm. In step 5, the contour parameters include beam current, scanning spacing, scanning speed, and defocusing amount; wherein, the scanning speed is 500-650mm / s, the beam current is 7-10mA, the defocusing amount is 5-8mA, and the scanning spacing is 0.15~0.2mm. In step 15, the powder bed must descend to contact the bottom metal until it can no longer descend.

2. The method for preparing a low-modulus solid titanium alloy according to claim 1, characterized in that, In step 7, the parallelism between the upper and lower surfaces of the base plate is less than 0.2mm, the length and width of the base plate are greater than 150mm, the thickness is 8~15mm, and the material is stainless steel.

3. The method for preparing a low-modulus solid titanium alloy according to claim 1, characterized in that, In step 16, the low-modulus titanium alloy has an elastic modulus of 30-35 GPa along the Z-axis, contains columnar crystal structure along the Z-direction, and its preferred orientation is... <100> orientation.

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