A nanocrystalline Ta-Ti-Cu alloy and its preparation method

Abstract

The present invention belongs to the field of tantalum alloy materials, and provides a nanocrystalline Ta-Ti-Cu alloy and a preparation method thereof. The chemical composition of the alloy is as follows (wt%): Cu: 1-12; Ti: 10-40; the balance is Ta. The preparation method of the alloy is as follows: using selective laser melting technology, the laser power is 500-800 W, the scanning speed is 1000-2500 mm·S-1, the interlayer deflection angle is 30-90°, and the energy density is 100-300 J·mm-3. The microstructure of the prepared alloy is a nanosized fine strip structure, and the width of the fine strip structure is between 80 and 150 nm. The tensile strength of the nanocrystalline Ta-Ti-Cu alloy is ≥1200 MPa, and the elongation is ≥12%, which can be applied in the fields of aerospace, medical materials, industry, etc.

Description

Technical Field

[0001] The present invention relates to the field of tantalum alloy materials, and particularly to a nanocrystalline Ta-Ti-Cu alloy and a preparation method thereof. Background Art

[0002] Tantalum and tantalum alloys have been applied to many high-tech fields such as aerospace, metallurgical chemistry, and biomedicine due to their excellent chemical stability, high-temperature mechanical properties, corrosion resistance, processing and forming capabilities, and excellent biological inertness and biocompatibility. Selective laser melting (SLM) is one of the fastest-developing and most widely used technologies in additive manufacturing (AM). Its characteristic is to rapidly melt and solidify metal powders, and then rapidly form metal parts with complex structures. The working principle of the SLM technology is to make a high-power laser beam melt metal powders layer by layer according to the forming requirements of the cross-section of the part to rapidly form metal components. The SLM technology has advantages such as grain refinement, avoiding segregation, energy conservation and environmental protection, and one-time forming of complex structural parts. Therefore, preparing titanium alloy components with complex structures by the SLM technology will have broad prospects in the fields of aerospace or medical devices.

[0003] However, the layer-by-layer deposition method of the SLM technology generates a unique complex thermal history composed of multiple non-steady-state horizontal and vertical thermal cycles, resulting in the microstructure of the tantalum alloy during the forming process being composed of needle-like martensite α' penetrating the primary columnar β grains, leading to poor mechanical properties of the material, especially poor plasticity, which greatly limits the application of the SLM technology in preparing titanium alloys in the fields of aerospace and medicine. Summary of the Invention

[0004] The purpose of the present invention is to provide a nanocrystalline Ta-Ti-Cu alloy and a preparation method thereof.

[0005] For the nanocrystalline Ta-Ti-Cu alloy provided by the present invention, by weight percentage, the chemical composition of the alloy is: Cu: 1-12%, Ti: 10-40%, and the balance is Ta.

[0006] Further, the weight percentage of Cu in the alloy is 3-9%.

[0007] For the nanocrystalline Ta-Ti-Cu alloy provided by the present invention, the microstructure of the alloy is a nanosized strip structure, and the width of the strip structure is 80-150 nm; when the alloy is used for 2 h under the condition that the temperature is less than or equal to 600 °C, the grains do not coarsen and grow; the tensile strength of the alloy is ≥1200 MPa, and the elongation is ≥12%.

[0008] The preparation method of the nanocrystalline Ta-Ti-Cu alloy provided by the present invention is as follows:

[0009] 1) Pre-set Ta-Ti-Cu alloy powder to form a layer to be processed;

[0010] 2) Selective laser melting is performed on the layer to be processed according to the printing process parameters to form a target layer;

[0011] 3) Steps 1)-2) are repeatedly executed to form a Ta-Ti-Cu alloy.

[0012] In the preparation method of the nanocrystalline Ta-Ti-Cu alloy provided by the present invention, during the selective laser melting process, the laser power is 500-800 W, the laser scanning speed is 1000-2500 mm / s, the laser scanning spacing is 30-120 μm, the interlayer deflection angle is 30-90°, and the energy density is 100-200 J·mm -3 .

[0013] The nanocrystalline Ta-Ti-Cu alloy provided by the present invention is applied in the fields of aerospace, medical devices, and industry, and the medical devices are oral and orthopedic implant medical devices.

[0014] The beneficial effects of the present invention are as follows:

[0015] (1) Different from the existing preparation methods of additive manufacturing tantalum and its alloys (Ta-Ti, pure Ta), the nanocrystalline Ta-Ti-Cu alloy and its additive manufacturing preparation method provided by the present invention do not have defects such as through-columnar crystal defects, and the microstructure is a nanoscale fine strip structure. (Ti acts as a solid solution of Cu element, solving the problem of immiscibility between Ta and Cu, improving the density of the additive manufacturing alloy, and making the material free of defects at the Ta-Cu interface).

[0016] (2) The Ta-Ti-Cu alloy of the present invention has excellent mechanical properties, achieving a strong-plasticity match, with a tensile strength ≥ 1200 MPa and an elongation ≥ 12%.

[0017] (3) The service condition of the nanocrystalline Ta-Ti-Cu alloy provided by the present invention is used at 600 °C and below for 2 hours, and the grains do not coarsen and grow, and can maintain excellent mechanical properties. Description of the Drawings

[0018] Figure 1 It is the transmission electron microscope image of the alloy in Example 7;

[0019] Figure 2 It is the transmission electron microscope image of the alloy in Comparative Example 2;

[0020] Figure 3Transmission electron microscope image of the alloy of Comparative Example 11. Detailed implementation manners

[0021] The present invention will be further described in detail below in conjunction with embodiments, but the implementation manners of the present invention are not limited thereto.

[0022] Embodiment:

[0023] A nanocrystalline Ta-Ti-Cu alloy, whose chemical composition is (by weight percentage): Cu: 1-12%; Ti: 10-40%; the balance is Ta. Examples 1-12 are Ta-Ti-Cu alloys prepared according to the chemical composition ranges provided by the present invention, the content of Cu element gradually increases, and the corresponding preparation processes are appropriately adjusted within the technical parameter ranges specified by the present invention. Examples 3-8 are the preferred Cu content ranges of the present invention. See Table 1 for details.

[0024] Table 1 Chemical compositions and preparation processes of examples

[0025]

[0026] Comparative example:

[0027] The chemical compositions of Comparative Examples 1-2 are lower than the lower limit of the chemical composition ranges provided by the present invention, and the chemical compositions of Comparative Examples 11-12 are higher than the upper limit of the chemical composition ranges provided by the present invention. The laser power of Comparative Example 3 is lower than the lower limit of the laser power range provided by the present invention; the laser power of Comparative Example 4 is higher than the upper limit of the range provided by the present invention; the scanning speed of Comparative Example 5 is lower than the lower limit of the range provided by the present invention; the scanning speed of Comparative Example 6 is higher than the upper limit of the range provided by the present invention; the interlayer deflection angle of Comparative Example 7 is lower than the lower limit of the range provided by the present invention; the interlayer deflection angle of Comparative Example 8 is higher than the upper limit of the range provided by the present invention; the energy densities of Comparative Examples 9 and 10 are respectively lower than or higher than the lower limit or upper limit of the ranges provided by the present invention. See Table 2 for details.

[0028] Table 2 Chemical compositions and preparation processes of comparative examples

[0029]

[0030] 1. Tensile property test

[0031] An Instron 8872 type tensile testing machine was used to test the room temperature tensile mechanical properties of the materials of the comparative examples and examples, and the tensile rate was 0.5 mm / min. Before the test, the materials were processed into standard tensile specimens with a threaded diameter of 10 mm, a gauge diameter of 5 mm, and a gauge length of 30 mm by a lathe. Three parallel samples were taken for each group of heat-treated (additive manufacturing materials) specimens. The mechanical properties obtained from the experiment included the tensile strength and elongation. See Table 3 for specific results.

[0032] 2. Grain size statistics

[0033] The electron backscatter diffraction (EBSD) analysis system of a scanning electron microscope was used to statistically analyze the phase volume fraction (grain size) of the samples before and after fatigue. The sample preparation method was as follows: first, the sample was mechanically polished to obtain a smooth and clean surface, and then the sample was placed in an electrolyte solution (6% perchloric acid + 30% butanol + 64% methanol) and electrochemically polished at -25°C for 20 s to remove the surface stress. When collecting EBSD data, the working voltage of the scanning electron microscope was 20 kV, the current was 18 nA, the step size was selected as 0.2 μm, the resolution of the scanning range was greater than 80%, and Channel 5 software was used to analyze the grain size. The specific results are shown in Tables 3 and 4.

[0034] Table 3 Mechanical properties and grain size of the materials in the examples and comparative examples

[0035]

[0036]

[0037] Table 4 Microstructural characteristics of the materials in the examples and comparative examples and microstructural changes after heat preservation at different temperatures for 2 h

[0038]

[0039] The transmission electron microscope images of the alloys in Example 7, Comparative Example 2, and Comparative Example 11 are as follows Figures 1 - 3 . It can be seen from the results in Tables 3 and 4 that Examples 1 to 12 all have a nanolath structure and have high strength and good plasticity. In Comparative Examples 1, 2, 11, and 12, since the Cu content range is not within the range required by the present invention, their mechanical properties are finally poor, or the microstructure is a coarse lath structure. In Comparative Examples 3 - 10, since the process parameters such as laser power and scanning speed are not within the range required by the present invention, the mechanical properties of the prepared materials are poor, and at the same time, a nanocrystalline lath structure is not obtained.

[0040] It can be seen from the results in Table 4 that Examples 3 - 8 have good thermal stability during aging at 600°C and below, and the lath size does not change significantly after aging. Since the original lath sizes of Examples 1, 2, 9 - 12 are larger than those of Examples 3 - 8, during aging at 600°C and below, the lath sizes grow to the range of 300 - 500 nm, and their thermal stability is slightly worse than that of Examples 3 - 8 of the present invention, but they are all better than Comparative Example 1. It can be seen from Table 4 that the laths in Comparative Example 1 are significantly coarsened and grown.

[0041] Although the present invention has been disclosed above in some embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the gist and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A nanocrystalline Ta-Ti-Cu alloy, characterized in that: The chemical composition of the alloy is, by weight percentage, Cu: 3-9%, Ti: 10-40%, and the balance is Ta; The tensile strength of the alloy is ≥1200MPa and the elongation is ≥12%; The microstructure of the alloy is a nano-sized fine strip structure with a width of 80 to 150 nm. When the alloy is used for 2 hours at a temperature less than or equal to 600°C, the grains do not coarsen and grow.

2. A method for preparing a nanocrystalline Ta-Ti-Cu alloy as claimed in claim 1, characterized in that: The preparation method is as follows: 1) Pre-setting Ta-Ti-Cu alloy powder to form a layer to be treated; 2) performing selective laser melting on the layer to be processed according to printing process parameters to form a target layer; 3) Repeat steps 1) to 2) to form a Ta-Ti-Cu alloy.

3. A method for preparing a nanocrystalline Ta-Ti-Cu alloy as claimed in claim 2, characterized in that: In the selective laser melting process, the laser power is 500-800W, the laser scanning speed is 1000-2500mm / s, the laser scanning spacing is 30-120μm, the interlayer deflection angle is 30-90°, and the energy density is 100-200J·mm -3 .

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