In-situ composite titanium carbide reinforced titanium-based alloy and preparation method thereof

Abstract

The invention discloses an in-situ composite titanium carbide reinforced titanium-based alloy and a preparation method thereof. The in-situ composite titanium carbide reinforced titanium-based alloy comprises the following chemical components in percentage by mass: 0 < = N < = 0.010%, 0 < = H < = 0.015%, 0 < = O < = 0.2%, 0.10-0.40% of C and the balance of Ti and inevitable impurities. The preparation method comprises the following steps: mixing the titanium powder and the graphite powder, and carrying out metal laser powder bed fusion printing. According to the invention, through in-situ synthesis of nano TiC particles, the size and morphology of the TiC particles are regulated and controlled, so that the mechanical property of the titanium-based alloy is greatly improved. The titanium-based alloy with high strength and excellent elongation is obtained by using a trace interstitial element C, and is independent of solid solution strengthening, second-phase dispersion strengthening or work hardening ways of expensive rare metals such as V, Mo, Nb and the like, so that green and low-cost preparation of the titanium alloy is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy materials, and in particular relates to an in-situ composite titanium carbide reinforced titanium-based alloy and a preparation method thereof. Background Art

[0002] Titanium alloys are used as core structural materials in high-end fields such as aerospace and biomedicine due to their low density, high specific strength, corrosion resistance and biocompatibility. At present, common titanium alloys are divided into three categories: α titanium alloy (HCP), β titanium alloy (BCC), and α-β duplex titanium alloy (HCP-BCC). However, traditional high-strength and toughness titanium alloys rely on solid solution strengthening of rare metals such as V, Mo, and Nb, or precipitation strengthening after complex hot working processes, resulting in high costs, increased energy consumption, and waste of strategic resources. Therefore, the development of a plain titanium alloy that does not rely on rare metal alloying and can balance strength and plasticity has become a key challenge to achieve green and low-cost production.

[0003] Titanium carbide (TiC) combines the excellent properties of both metals and ceramics (such as high hardness, high elastic modulus, self-lubricity, and high-temperature stability), making it an ideal hard phase for reinforcing titanium-based composites. However, TiC powder prepared by traditional carbonization-reduction methods suffers from defects such as pores, cracks, and non-equilibrium phases, resulting in low density and high brittleness of the reinforced titanium-based composites, making them unsuitable for industrial application. Ex-situ synthesis methods, which introduce prefabricated TiC particles into a titanium matrix through mechanical mixing, can reduce sintering temperatures but face challenges such as uneven distribution of the reinforcing phase, interfacial impurity contamination, and complex processes. Furthermore, the weak bonding between the TiC particles and the matrix can easily induce stress concentration, leading to interfacial debonding or premature failure during service. In-situ synthesis methods, which directly generate TiC by triggering a reaction between titanium and a carbon source with a high-energy heat source, can achieve a clean and thermodynamically stable interface. However, due to insufficient dynamic control of the reaction process (lack of composition design and process parameter regulation), the TiC grain size is large, the interfacial bonding is unstable, and stress concentration is easily generated at the interface, which in turn reduces the overall mechanical properties of the material. In addition, the preparation of TiC-reinforced titanium-based alloys by additive manufacturing technology has also received widespread attention, but the lack of regulation of TiC size and morphology makes it difficult to control the bonding between the reinforcement phase and the interface, resulting in easy failure of the material. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides an in-situ composite titanium carbide reinforced titanium-based alloy and a preparation method thereof. The in-situ composite titanium carbide reinforced titanium-based alloy provided by the present invention does not rely on expensive rare metal solid solution strengthening such as Mo, Nb, Ta, Zr, and W, but synthesizes a large amount of nano-TiC phases in situ in the matrix that have a coherent relationship with the matrix to obtain a titanium carbide reinforced titanium-based alloy. The present invention uses only a trace amount of C element to in-situ synthesize a TiC phase that has a coherent interface with the matrix, which greatly improves the comprehensive mechanical properties of the material. At the same time, the present invention helps to achieve the simple design of high-strength and toughness titanium alloys, as well as green and low-cost preparation.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] On the one hand, the present invention provides an in-situ composite titanium carbide reinforced titanium-based alloy, whose chemical composition, by mass percentage, includes: 0≤N≤0.010%, 0≤H≤0.015%, 0≤O≤0.2%, C: 0.10%~0.40%, and the balance is Ti and unavoidable impurities.

[0007] As a preferred embodiment, the in-situ composite titanium carbide reinforced titanium-based alloy is prepared by a metal laser powder bed melting process; the raw materials for preparing the in-situ composite titanium carbide reinforced titanium-based alloy by the metal laser powder bed melting process include titanium powder and graphite powder.

[0008] As a preferred embodiment, the particle size of the titanium powder is 15 to 53 μm.

[0009] As a preferred embodiment, the particle size of the graphite powder is 1 to 8 μm.

[0010] In another aspect, the present invention provides a method for preparing the above-mentioned in-situ composite titanium carbide reinforced titanium-based alloy, comprising the following steps:

[0011] Titanium powder and graphite powder are mixed and then subjected to metal laser powder bed melting printing to obtain the in-situ composite titanium carbide reinforced titanium-based alloy.

[0012] As a preferred embodiment, the particle size of the titanium powder is in the range of 15 to 53 μm.

[0013] As a preferred embodiment, the particle size of the graphite powder is 1 to 8 μm.

[0014] As a preferred embodiment, the mass of the graphite powder is 0.10% to 0.40% of the total mass of the raw materials for preparing the in-situ composite titanium carbide reinforced titanium-based alloy.

[0015] As a preferred embodiment, in the metal laser powder bed fusion printing, the laser power is 160 to 200 W; the scanning speed is 900 to 1100 mm / s; and the pass spacing is 80 to 120 μm.

[0016] In some specific embodiments, the powder thickness of the metal laser powder bed fusion printing is 30 μm.

[0017] As a preferred embodiment, the protective atmosphere of the metal laser powder bed fusion printing is high-purity argon.

[0018] In the technical solution of the present invention, the above raw material powder can obtain high-density titanium-based alloy formed parts through metal laser powder bed fusion printing technology, and the TiC particles generated in situ by graphite powder and part of titanium powder form a coherent interface with the titanium matrix, and the mismatch degree is ≤1%.

[0019] The technical effects of the present invention are as follows:

[0020] (1) The present invention does not require expensive rare metal elements for alloying. Instead, a trace amount of interstitial element C (0.1 wt.% to 0.4 wt.%) is introduced into pure titanium using low-cost graphite powder, and nano-TiC particles are synthesized in situ using metal laser powder bed fusion printing technology. The size and morphology of the TiC particles are regulated by process parameters so that the TiC particles have a coherent relationship with the matrix, effectively strengthening the titanium-based alloy, improving the material strength while maintaining excellent plasticity, and achieving a significant improvement in the mechanical properties of the titanium-based alloy. At the same time, the preparation cost of the high-strength and toughness titanium alloy is greatly reduced, and the consumption of strategic resources is reduced.

[0021] (2) The present invention introduces the interstitial element C into pure titanium and combines it with the rapid cooling characteristics of the metal laser powder bed melting process to obtain a titanium-based alloy with needle-shaped α'+ blocky α+ equiaxed TiC phase. In addition, scanning electron microscopy and transmission electron microscopy were used to observe that nano-sized TiC second phases were dispersed in the titanium matrix, which played an effective dispersion strengthening role. At the same time, the in-situ synthesized equiaxed nano-TiC phase obtained through process control has a coherent interface relationship with the titanium matrix (mismatch ≤ 1%), which can relieve stress concentration and avoid crack initiation during plastic deformation, providing good plasticity for the titanium alloy.

[0022] (3) The present invention adopts a metal laser powder bed melting process, which reduces material waste, lowers preparation costs, and can also prepare components with complex shapes.

[0023] (4) The titanium-based alloy obtained by the present invention has excellent mechanical properties: room temperature tensile strength ≥800 MPa, room temperature yield strength ≥700 MPa, and room temperature elongation ≥15.0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a physical picture of the in-situ composite titanium carbide reinforced titanium-based alloy formed part prepared in Example 1 of the present invention;

[0025] Figure 2 The microstructure SEM and TEM images of the in-situ composite titanium carbide reinforced titanium-based alloy formed part prepared in Example 3 of the present invention;

[0026] Figure 3 This is the room temperature tensile stress-strain curve of the in-situ composite titanium carbide reinforced titanium-based alloy formed part prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0027] The following embodiments are merely some of the embodiments of the present invention, rather than all of them. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0028] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0029] The invention provides an in-situ composite titanium carbide particle reinforced titanium-based alloy, the chemical composition of which is as follows by mass percentage: 0≤N≤0.012%, 0≤H≤0.015%, 0≤O≤0.2%, C: 0.10%-0.40%, and the balance being Ti and inevitable impurities.

[0030] The composition design of the present invention is based on the following principles:

[0031] Carbon, as an interstitial solid solution atom in titanium, can improve the overall strength of titanium alloys. When the solubility limit (~0.1wt.%) is exceeded, TiC particles will precipitate. In traditional casting and forging processes, TiC phase can achieve strength improvement, but it will damage the plasticity, toughness and weldability of titanium alloys. Therefore, carbon is generally considered to be an impurity element in titanium alloys. The metal laser powder bed melting process adopted by the present invention can synthesize TiC phase in situ from raw material powder, achieving interface cleanliness and thermodynamic stability (compared to non-in situ synthesis methods). In addition, the research results found that the micron-scale non-equiaxed TiC phase has poor bonding with the matrix interface, which significantly reduces the load transfer efficiency, causes stress concentration and crack initiation during plastic deformation, and greatly reduces the plasticity of titanium alloys. Therefore, the present invention avoids excessive precipitation and growth of TiC phase by reducing the interstitial element C content, and through process parameter regulation, increases the cooling rate, and regulates the size and morphology of the TiC phase. The nano-scale TiC phase synthesized in situ has a coherent interface relationship with the matrix. Taking all factors into consideration, the carbon content of the titanium alloy of the present invention is controlled at 0.1wt.%-0.4wt.%, and the process parameters include laser power of 160-200W, scanning speed of 900-1100mm / s, pass spacing of 80-120μm, and protective atmosphere of high-purity argon (99.99%).

[0032] Example 1

[0033] The chemical composition of the in-situ composite titanium carbide reinforced titanium-based alloy in this embodiment includes, by mass percentage:

[0034] C: 0.10%, O: 0.16%, H: 0.011%, N: 0.008%, and the balance is Ti and inevitable impurities.

[0035] The preparation method of the in-situ composite titanium carbide reinforced titanium-based alloy is as follows: titanium powder with an average particle size of 23 μm and graphite powder with a particle size of 3 μm are mixed and then subjected to metal laser powder bed fusion printing, where the mass of the graphite powder is 0.10% of the total mass of the raw material powder; the printing process is carried out in a high-purity argon environment, and the specific process parameters are: laser power 160W, scanning speed 900 mm / s, pass spacing 100 μm, and powder coating thickness 30 μm.

[0036] Figure 1 This is a photo of the in-situ composite titanium carbide reinforced titanium-based alloy formed part obtained in this example. Microstructural observation reveals the initial precipitation of an equiaxed TiC phase. The TiC has an average length of 20 nm, an average width of 10 nm, and a volume fraction of 3.7%. It forms a coherent interface with the matrix, with a mismatch of 0.3%. The formed part was processed into tensile bars and tested for room temperature mechanical properties: tensile strength of 804 MPa, yield strength of 702 MPa, and elongation at break of 23.3%.

[0037] Example 2

[0038] The chemical composition of the in-situ composite titanium carbide reinforced titanium-based alloy in this embodiment includes, by mass percentage:

[0039] C: 0.17%, O: 0.15%, H: 0.012%, N: 0.007%, and the balance is Ti and inevitable impurities.

[0040] The preparation method of the in-situ composite titanium carbide reinforced titanium-based alloy is as follows: titanium powder with an average particle size of 25 μm and graphite powder with a particle size of 2 μm are mixed and then subjected to metal laser powder bed fusion printing, where the mass of the graphite powder is 0.17% of the total mass of the raw material powder; the printing process is carried out in a high-purity argon environment, and the specific process parameters are: laser power 200 W, scanning speed 1100 mm / s, pass spacing 90 μm, and powder thickness 30 μm.

[0041] Microstructural observation of the in-situ composite titanium carbide reinforced titanium-based alloy formed part produced in this example revealed an increased number of TiC phase precipitations, dispersed throughout the matrix. The TiC phase exhibited an equiaxed morphology, with an average length of 80 nm, an average width of 50 nm, and a volume fraction of 14.6%. The TiC phase formed a coherent interface with the matrix, with a mismatch of 0.5%. The formed part was processed into tensile bars for room temperature mechanical property testing, demonstrating a tensile strength of 836 MPa, a yield strength of 731 MPa, and an elongation at break of 20.1%.

[0042] Example 3

[0043] The chemical composition of the in-situ composite titanium carbide reinforced titanium-based alloy in this embodiment includes, by mass percentage, C: 0.36%, O: 0.17%, H: 0.012%, N: 0.008%, and the remainder is Ti and unavoidable impurities.

[0044] The preparation method of the in-situ composite titanium carbide reinforced titanium-based alloy is as follows: titanium powder with an average particle size of 32 μm and graphite powder with a particle size of 3 μm are mixed and then subjected to metal laser powder bed fusion printing, where the mass of the graphite powder accounts for 0.36% of the total mass of the raw material powder; the printing process is carried out in a high-purity argon environment, and the specific process parameters are: laser power 180W, scanning speed 1000 mm / s, pass spacing 110 μm, and powder coating thickness 30 μm.

[0045] The microstructure of the in-situ composite titanium carbide reinforced titanium-based alloy formed parts prepared in this embodiment was observed. The results are as follows: Figure 2 As shown: Among them, Figure 2 (a) is a scanning electron microscope (SEM) image of the formed part, showing a large number of dispersed equiaxed TiC particles in its microstructure. Figure 2 (b) is a bright field transmission electron micrograph (BF-TEM) of the formed part. Figure 2 (b1) is Figure 2 (b) The enlarged image in the white rectangular box, Figure 2 (b2) Yes Figure 2 The selected area electron diffraction pattern (SAED) in the white dashed box in (b1) is Figure 2 (b3) Yes Figure 2 High-resolution transmission electron micrograph (HRTEM) of the white dashed box in (b1), Figure 2 (b4) Yes Figure 2 (b3) is the inverse Fourier transform image. The TEM image and the corresponding selected area electron diffraction (SAED) pattern revealed equiaxed TiC dispersed in the matrix. The average length of TiC was 200 nm, the average width was 80 nm, the volume fraction was 30.6%, and the interface with the matrix was a coherent interface with a mismatch of 0.8%. The formed part was processed into a tensile bar to test the room temperature mechanical properties: the tensile strength was 906 MPa, the yield strength was 784 MPa, the elongation after fracture was 16.1%, and the stress-strain curve was as shown in the figure. Figure 3 shown.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An in-situ composite titanium carbide reinforced titanium-based alloy, characterized in that: The chemical composition of the in-situ composite titanium carbide reinforced titanium-based alloy includes, by mass percentage, 0≤N≤0.010%, 0≤H≤0.015%, 0≤O≤0.2%, C: 0.10% to 0.40%, and the balance being Ti and unavoidable impurities.

2. The in-situ composite titanium carbide reinforced titanium-based alloy according to claim 1, characterized in that: The in-situ composite titanium carbide reinforced titanium-based alloy is prepared by a metal laser powder bed melting process; the raw materials for preparing the in-situ composite titanium carbide reinforced titanium-based alloy by the metal laser powder bed melting process include titanium powder and graphite powder.

3. The in-situ composite titanium carbide reinforced titanium-based alloy according to claim 2, characterized in that: The particle size of the titanium powder is 15 to 53 μm.

4. The in-situ composite titanium carbide reinforced titanium-based alloy according to claim 2, characterized in that: The particle size of the graphite powder is 1 to 8 μm.

5. The method for preparing the in-situ composite titanium carbide reinforced titanium-based alloy according to claim 1, characterized in that: The following steps are involved: Titanium powder and graphite powder are mixed and then subjected to metal laser powder bed melting printing to obtain the in-situ composite titanium carbide reinforced titanium-based alloy.

6. The preparation method according to claim 5, characterized in that The particle size of the titanium powder ranges from 15 to 53 μm.

7. The preparation method according to claim 5, characterized in that The particle size of the graphite powder is 1 to 8 μm.

8. The preparation method according to claim 5, characterized in that The mass of the graphite powder is 0.10% to 0.40% of the total mass of the raw materials for preparing the in-situ composite titanium carbide reinforced titanium-based alloy.

9. The preparation method according to claim 5, characterized in that In the metal laser powder bed fusion printing, the laser power is 160 to 200 W; the scanning speed is 900 to 1100 mm / s; and the pass spacing is 80 to 120 μm.

10. The preparation method according to claim 5, characterized in that The protective atmosphere of the metal laser powder bed fusion printing is high-purity argon.

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