A titanium alloy, its preparation method and application

Abstract

The present invention belongs to the technical field of alloy materials, and specifically relates to a titanium alloy and its preparation method and application. The titanium alloy provided by the present invention comprises the following elemental components in mass percentage: 4-6% Al, 0.55-0.75% Si, and the balance Ti. In the present invention, Al, as an α-stable metal element of the Ti alloy, plays a role in solid solution strengthening, improving the specific strength, low-temperature and high-temperature strength of the Ti alloy. In order to prevent the formation of the α2(Ti3Al) phase and cause material brittleness, the present application limits the mass content of Al in the titanium alloy to be below 6 wt%. At the same time, a trace amount of Si element in the titanium alloy can also form solid solution strengthening and dispersion strengthening effects, improving the strength of the titanium alloy. However, too much content of the Si element will also cause a significant decrease in the plasticity of the alloy. Under the combined action of the above specific contents of Al, Si, and Ti, the present application improves the strength and toughness of the titanium alloy and significantly improves the mechanical properties of the titanium alloy.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials, and particularly relates to a titanium alloy and its preparation method and application. Background Art

[0002] Titanium alloys not only have excellent properties such as high specific strength, good heat and corrosion resistance, non-magnetism, and resistance to ultra-low temperature, but also have unique functions such as superconductivity, good biocompatibility, shape memory, and hydrogen storage. They are widely used in the fields of aerospace, military, and civil applications. Titanium materials were initially applied to the aerospace field where there is an urgent need for high-strength and low-density materials and have become one of the "spines" in this field. Subsequently, they have gradually been widely used in fields such as ships, automobiles, and energy. Currently, the theme of the development of the automotive industry is safety, energy conservation, and environmental protection. Automobile lightweighting is the main measure to improve fuel utilization efficiency and reduce exhaust emissions and has received extensive attention from major automobile manufacturers.

[0003] Titanium alloys have a low thermal conductivity, a small elastic modulus, high chemical activity, and are prone to oxidation and hydrogen embrittlement. They belong to difficult-to-deform materials and have high requirements for the processing environment and process. In the process of plastic forming of titanium alloys, two aspects of shape and performance need to be considered. Not only should the dimensions meet the usage requirements, but also the properties such as strength and plasticity should be ideal enough. Existing titanium alloys are difficult to simultaneously take into account both the strength and plasticity aspects of performance. Summary of the Invention

[0004] In view of this, the present invention provides a titanium alloy and its preparation method and application. The titanium alloy provided by the present invention has both strength and plasticity and has good mechanical properties.

[0005] In order to solve the above technical problems, the present invention provides a titanium alloy, comprising the following elemental components by mass percentage:

[0006] Al 4 - 6%;

[0007] Si 0.55 - 0.75%;

[0008] Ti balance.

[0009] Preferably, the titanium alloy comprises the following elemental components by mass percentage:

[0010] Al 4.1 - 5%;

[0011] Si 0.6 - 0.7%;

[0012] Ti balance.

[0013] Preferably, the density of the titanium alloy is above 99.9%.

[0014] The present invention also provides a preparation method of the above-mentioned titanium alloy, comprising the following steps:

[0015] Mix titanium powder, aluminum powder and silicon powder to obtain a mixed material;

[0016] Perform 3D printing on the mixed material to obtain the titanium alloy.

[0017] Preferably, the average particle size of the titanium powder, aluminum powder and silicon powder is 15 - 53 μm.

[0018] Preferably, the mixing is carried out under the condition of mechanical stirring, the rotation speed of the mechanical stirring is 60 - 90 r / min, and the time of the mechanical stirring is 1.5 - 2.5 h.

[0019] Preferably, after mixing, it further includes: drying the mixed system to obtain a mixed material; the drying temperature is 90 - 110 °C, and the time is 1.8 - 2.2 h.

[0020] Preferably, the 3D printing includes selective laser melting printing.

[0021] Preferably, when the equipment for selective laser melting printing is BLT - S210, the printing parameters are as follows: laser power 155 w, scanning speed 1200 mm / s, layer thickness 0.03 mm, scanning spacing 0.1 mm, scanning rotation increment 67°.

[0022] The present invention also provides the application of the above - mentioned titanium alloy or the titanium alloy prepared by the above - mentioned preparation method in the fields of aviation, aerospace and deep - sea exploration.

[0023] The present invention provides a titanium alloy, including the following elemental components by mass percentage: 4 - 6% Al, 0.55 - 0.75% Si and the balance Ti. In the present invention, Al, as a Ti alloy α - stabilizing metal element, plays a role in solid - solution strengthening, improving the specific strength, low - temperature and high - temperature strength of the Ti alloy. In order to prevent the formation of the α2(Ti3Al) phase and cause material brittleness, the present application limits the mass content of Al in the titanium alloy to be below 6 wt%. At the same time, a small amount of Si element in the titanium alloy can also form solid - solution strengthening and dispersion strengthening effects to improve the strength of the titanium alloy, but too much content of the Si element will also cause a significant decrease in the plasticity of the alloy. Under the combined action of the above - mentioned specific contents of Al, Si and Ti, the present application improves the strength and toughness of the titanium alloy and significantly improves the mechanical properties of the titanium alloy. Description of the Drawings

[0024] Figure 1 It is the stress - strain curve diagram of the titanium alloy in Examples 1 - 2 and Comparative Examples 1 - 4;

[0025] Figure 2 It is the SEM diagram of the titanium alloy prepared in Example 1;

[0026] Figure 3 SEM image of the titanium alloy prepared in Example 2;

[0027] Figure 4 SEM image of the titanium alloy prepared in Comparative Example 1;

[0028] Figure 5 SEM image of the titanium alloy prepared in Comparative Example 1;

[0029] Figure 6 SEM images of the fracture surfaces of the samples after tensile fracture of the titanium alloys in Examples 1-2 and Comparative Examples 1-2, where (a) is the fracture surface morphology of the sample in Comparative Example 1; Figure (b) is the fracture surface morphology of the sample in Example 1; Figure (c) is the fracture surface morphology of the sample in Example 2; Figure (d) is the fracture surface morphology of the sample in Comparative Example 2;

[0030] Figure 7 Analysis and comparison chart of the microhardness results of the titanium alloys in Examples 1-2 and Comparative Examples 1, 2, and 4. Detailed implementation manner

[0031] The present invention provides a titanium alloy, comprising the following elemental components in mass percentage:

[0032] Al 4-6%;

[0033] Si 0.55-0.75%;

[0034] The balance is Ti.

[0035] In terms of mass percentage, the titanium alloy provided by the present invention comprises 4-6% Al, preferably 4.1-5%.

[0036] In terms of mass percentage, the titanium alloy provided by the present invention comprises 0.55-0.75% Si, preferably 0.6-0.7%.

[0037] In terms of mass percentage, the titanium alloy provided by the present invention comprises the balance Ti.

[0038] In the present invention, the relative density of the titanium alloy is preferably above 99.9%.

[0039] The present invention improves the strength and toughness of the titanium alloy under the solid solution strengthening effect and dispersion strengthening effect of specific contents of aluminum and silicon.

[0040] The present invention also provides a preparation method of the titanium alloy described in the above technical solution, comprising the following steps:

[0041] Mix titanium powder, aluminum powder, and silicon powder to obtain a mixed material;

[0042] 3D print the mixed material to obtain the titanium alloy.

[0043] In the present invention, titanium powder, aluminum powder and silicon powder are mixed to obtain a mixed material. In the present invention, the titanium powder is preferably spherical; the average particle size of the titanium powder is preferably 15 - 53 μm, more preferably 20 - 40 μm. In the present invention, the aluminum powder is preferably spherical; the average particle size of the aluminum powder is preferably 15 - 53 μm, more preferably 25 - 50 μm. In the present invention, the silicon powder is preferably spherical; the average particle size of the silicon powder is preferably 15 - 53 μm, more preferably 23 - 48 μm.

[0044] In the present invention, the mixing is preferably carried out under the condition of mechanical stirring; the rotation speed of the mechanical stirring is preferably 60 - 90 r / min, more preferably 70 - 80 r / min; the time of the mechanical stirring is preferably 1.5 - 2.5 h, more preferably 2 h.

[0045] In the present invention, after mixing, it preferably further includes: drying the mixed system to obtain a mixed material. In the present invention, the drying temperature is preferably 90 - 110 °C, more preferably 100 °C; the drying time is preferably 1.8 - 2.2 h, more preferably 2 h. In the present invention, the drying is preferably carried out in a vacuum dryer. Drying in the present invention can improve the fluidity of the mixed material, which is beneficial to the subsequent 3D printing.

[0046] After obtaining the mixed material, the present invention 3D prints the mixed material to obtain the titanium alloy. In the present invention, the 3D printing preferably includes selective laser melting (SLM). The present invention has no special requirements for the process conditions of the selective laser melting, as long as the density of the titanium alloy can reach more than 99.9%. In the examples of the present invention, the printing parameters when the equipment for selective laser melting is BLT - S210 are as follows: laser power 155 w, scanning speed 1200 mm / s, layer thickness 0.03 mm, scanning spacing 0.1 mm, scanning rotation increment 67°. In the present invention, the rapid melting and non - equilibrium solidification process of selective laser melting results in a large number of microstructures in the Ti - Al - Si titanium alloy, such as dislocations, twins and stacking faults, etc., which further improves the mechanical properties of the titanium alloy.

[0047] The present invention prepares titanium alloy by 3D printing, which can avoid the macroscopic segregation of elements that occurs in the traditional casting method and is conducive to the homogenization of alloy components. Since 3D printing manufactures products by layer-by-layer stacking, it can produce shaped parts with exquisite and complex structures; the utilization rate of raw materials in 3D printing can be close to 100% (excluding supports), avoiding waste of materials and energy and saving costs; and 3D printing is an integrated printing assembly, effectively avoiding the deterioration of the performance of the assembled parts caused by the assembly error between samples.

[0048] The present invention prepares titanium alloy materials by the in-situ alloying method of the SLM additive manufacturing technology, which has the following advantages: (1) The SLM technology can control the mixing amount of powders to regulate the component ratio of the alloy within a large range and quickly realize the alloy component design; (2) The laser heat source adopted by the SLM technology has a large output energy density, which can quickly melt refractory metal powders and rapidly solidify them in a short time, greatly reducing the macroscopic segregation of alloy elements and making the alloy components more uniform.

[0049] The present invention also provides the application of the titanium alloy described in the above technical solution or the titanium alloy prepared by the preparation method described in the above technical solution in the fields of aviation, aerospace and deep-sea exploration.

[0050] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0051] Example 1

[0052] Spherical titanium powder with an average particle size of 20 μm, spherical aluminum powder with an average particle size of 25 μm, and spherical silicon powder with an average particle size of 23 μm are mechanically stirred at a rotation speed of 80 r / min for 2 h and then placed in a vacuum dryer to be dried at 100 °C for 2 h to obtain a mixed material; the mass percentage content of aluminum in the mixed coating is 4.1%, and the mass percentage content of silicon is 0.6%.

[0053] Using the mixed material as the raw material, laser selective melting printing is carried out by a BLT-S210 device to obtain a titanium alloy; the printing parameters of the BLT-S210 device are: laser power 155 w, scanning speed 1200 mm / s, layer thickness 0.03 mm, scanning spacing 0.1 mm, and scanning rotation increment 67°.

[0054] Example 2

[0055] Prepare the titanium alloy according to the method of Example 1, the difference is that the mass percentage content of aluminum in the mixed material is 5%, and the mass percentage content of silicon is 0.7%.

[0056] Comparative Example 1

[0057] The titanium alloy was prepared according to the method of Example 1, except that the mass percentage of aluminum in the mixed material was 3.5% and the mass percentage of silicon was 0.5%.

[0058] Comparative Example 2

[0059] The titanium alloy was prepared according to the method of Example 1, except that the mass percentage of aluminum in the mixed material was 6.1% and the mass percentage of silicon was 0.8%.

[0060] Comparative Example 3

[0061] Titanium alloy TC4 was used as a comparative example.

[0062] Comparative Example 4

[0063] Pure titanium (CP-Ti) was used as a comparative example.

[0064] At room temperature (25 °C), the tensile strength and elongation at break of the titanium alloys in Examples 1-2 and Comparative Examples 1-4 were detected according to GB / T228.1-2010. Each test sample was tested in parallel 3 times, and the results are listed in Table 1.

[0065] Table 1 Mechanical properties of titanium alloys in Examples 1-2 and Comparative Examples 1-4

[0066]

[0067]

[0068] According to the data in Table 1, the stress-strain curves of the titanium alloys in Examples 1-2 and Comparative Examples 1-4 were plotted, as Figure 1 shown. Combining Table 1 and Figure 1 it can be seen that the titanium alloy provided by the present invention has both good tensile strength and elongation at break, and has excellent mechanical properties.

[0069] The longitudinal sections of the titanium alloys in Examples 1-2 and Comparative Examples 1-2 were detected by scanning electron microscopy to obtain SEM images, as Figures 2 - 5 shown, where Figure 2 is the SEM image of the titanium alloy prepared in Example 1, Figure 3 is the SEM image of the titanium alloy prepared in Example 2, Figure 4 is the SEM image of the titanium alloy prepared in Comparative Example 1, Figure 5 is the SEM image of the titanium alloy prepared in Comparative Example 1. It can be seen from the SEM images that at a lower magnification, the molten pool morphology of the laser can be seen, and at a higher magnification, acicular α phases can be seen. This feature conforms to the typical microstructural characteristics of titanium alloys prepared by selective laser melting. From Figures 2 - 5It can be seen that the titanium alloys obtained by selective laser melting printing all exhibit high density, no obvious metallurgical defects are observed, and no unmelted powders of Al and Si are observed in the alloys, indicating that Al and Si elements form a good solid solution in the alloys.

[0070] The fracture surface morphology of the samples after tensile fracture of the titanium alloys in Examples 1-2 and Comparative Examples 1-2 was observed using a scanning electron microscope (SEM), and the SEM images were obtained as Figure 6 shown, where (a) is the fracture surface morphology diagram of the sample in Comparative Example 1; Figure (b) is the fracture surface morphology diagram of the sample in Example 1; Figure (c) is the fracture surface morphology diagram of the sample in Example 2; Figure (d) is the fracture surface morphology diagram of the sample in Comparative Example 2. It can be Figure 6 seen that the titanium alloys of the four compositions all exhibit the characteristics of ductile fracture, and there are a large number of dimples on the fracture surface. With the increase of Al and Si elements, the dimples of the alloy gradually become shallower, and some cleavage facets appear, which is related to the decrease in ductility caused by solid solution strengthening.

[0071] The present invention tested the hardness of the titanium alloys in Examples 1-2 and Comparative Examples 1, 2, and 4:

[0072] Hardness test process: First, the titanium alloy specimens in Examples 1-2 and Comparative Examples 1, 2, and 4 were coarsely ground with 180#, 600#, and 1000# metallographic sandpapers, and then finely ground with 2000# fine sandpaper until the scratches on the specimens were in the same direction and the depth was relatively shallow. The polished specimens were polished using a silica suspension. The Vickers hardness of the specimens was measured using a hardness tester of model THV-50DP, and the parameters were set as follows: the load was 0.2 kgf, and the load time was 10 s. To reduce measurement errors, 10 groups of Vickers hardness values were measured for each sample, and the hardness value of the sample was the average value after removing the highest and lowest hardness values.

[0073] Analysis of the microhardness results of the titanium alloy specimens in Examples 1-2 and Comparative Examples 1, 2, and 4 is as Figure 7 shown. It can be Figure 7 seen that the microhardness value of the alloy increases with the increase of the content of Al and Si elements. The hardness value of CP-Ti (Comparative Example 4) is 145 HV; the microhardness value of Comparative Example 1 is 290 HV; the microhardness value of Example 1 is 336 HV; the microhardness value of Example 2 is 342 HV; the microhardness value of Comparative Example 2 is 396 HV. There are two reasons for the increase in the hardness of the alloy. On the one hand, solute elements dissolve into the Ti matrix, which has a solid solution strengthening effect on the alloy, resulting in an increase in hardness; on the other hand, due to the extremely fast cooling rate of the SLM-formed alloy, there are a large number of high dislocation densities in the microstructure, resulting in an increase in hardness.

[0074] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A titanium alloy, characterized in that, Composed of the following elemental components by mass percentage: Al 4.1～5％； Si 0.6 - 0.7%; Ti balance; The relative density of the titanium alloy is above 99.9%.

2. The preparation method of the titanium alloy according to claim 1, comprising the following steps: Mix titanium powder, aluminum powder and silicon powder to obtain a mixed material; Perform 3D printing on the mixed material to obtain the titanium alloy.

3. The preparation method according to claim 2, wherein The average particle size of the titanium powder, aluminum powder and silicon powder is 15 - 53 μm.

4. The preparation method according to claim 2 or 3, characterized in that, The mixing is carried out under the condition of mechanical stirring, the rotation speed of the mechanical stirring is 60 - 90 r / min, and the time of the mechanical stirring is 1.5 - 2.5 h.

5. The preparation method according to claim 4, characterized in that, After the mixing, it further includes: drying the mixed system to obtain a mixed material; the drying temperature is 90 - 110 °C, and the time is 1.8 - 2.2 h.

6. The preparation method according to claim 2, wherein The 3D printing includes selective laser melting printing.

7. The preparation method according to claim 6, characterized in that, When the equipment used for the selective laser melting printing is BLT - S210, the printing parameters are as follows: laser power 155 W, scanning speed 1200 mm / s, layer thickness 0.03 mm, scanning spacing 0.1 mm, scanning rotation increment 67°.

8. The application of the titanium alloy according to claim 1 or the titanium alloy prepared by the preparation method according to any one of claims 2 - 7 in the fields of aviation, aerospace and deep - sea exploration.

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