CN117165875A - Titanium alloy based on additive manufacturing and preparation method thereof - Google Patents

Abstract

The application discloses a titanium alloy based on additive manufacturing, which comprises the following components in percentage by mass: al:4% -5.5%, mo:4% -5.5%, V:4% -5.5%, cr:1% -1.5%, fe:1% -1.5%, B:0.03% -0.15%, and the balance is Ti; the structure of the titanium alloy is a basket structure, and TiB whiskers are discontinuously distributed at the grain boundary. The titanium alloy based on additive manufacturing has higher strength and plasticity. The application also discloses a preparation method of the titanium alloy based on additive manufacturing.

Description

A titanium alloy based on additive manufacturing and its preparation method

Technical field

The invention belongs to the field of metal alloys, and specifically relates to a titanium alloy based on additive manufacturing and a preparation method thereof.

Background technique

TC18 (Ti-5Al-5Mo-5V-1Cr-1Fe) is an indispensable structural titanium alloy in the aerospace field. TC18 has the characteristics of low forging temperature, high hardenability, high strength and high toughness, making it very suitable for use in the aerospace field. At present, TC18 has been used in different types of aircraft components: the main landing gear torsion arm of the Su-27 and the left and right brackets of the nose landing gear; the landing gear, fuselage parts and flap guide rails of the Il-76; the Il-86 and The landing gear parts, wing beams and beams of the IL-9; the landing gear parts, wing beams, beams, fasteners and springs of the An-124; the flap guide rails, pylons and landing gear parts of the Boeing-777, etc. In addition, TC18 is also used to manufacture large load-bearing components for mainline passenger aircraft and large transport aircraft, as well as engine fan disks and blades whose working environment is less than 350°C.

Although TC18 alloy has obvious advantages in manufacturing aircraft components, one problem caused by high strength is sensitivity to defects. The uneven microstructure and segregation caused by traditional smelting methods greatly reduce the utilization rate of cast TC18; in addition, As the main load-bearing structure of the aircraft, its design concept requires that the properties of the materials used need to be matched. However, an important issue that needs to be solved urgently in the development of metal material properties - the problem of strong plastic inversion also restricts the development of TC18 titanium alloy. How to achieve simultaneous improvement of strong plasticity is the focus of research on the modification of TC18 and many metal materials.

Introducing reinforcing materials into the metal matrix is one of the effective methods to improve mechanical properties, but there is still a trade-off dilemma between strength and ductility. In this kind of composite material, the reinforcements are concentrated at the grain boundaries, so too many reinforcements will cause them to form ceramic walls at the grain boundaries, hindering the coordinated deformation of the matrix and causing the material's plasticity to decline rapidly. However, when the reinforcement content is too low, its strength-increasing effect cannot be fully demonstrated. Therefore, it is hoped that by introducing only a relatively small amount of reinforcing agent, the evolution of the microstructure in the matrix alloy can be affected, thereby simultaneously improving the strength and plasticity of the matrix alloy.

Metal additive manufacturing technology is a rapid manufacturing and molding technology that integrates CAD technology and path algorithm theory. It can achieve rapid and free molding without molds, arbitrary composite manufacturing of multiple materials, and is fully digital and highly flexible. Additive manufacturing is based on 3D models. Software is used to calculate and process slices of the models, build a layer-by-layer printing path, and obtain the final alloy parts through layer-by-layer accumulation. Among them, laser metal deposition technology is achieved by using laser as the energy source and argon gas to synchronously feed powder. This technology has the advantages of atmosphere protection, easy operation, high molding efficiency, small size restrictions on molded parts, and can be used for material repair. In recent years, additive manufacturing technology, especially laser metal deposition (Laser Metal Deposition) technology, has been considered a promising technology for the production of complex geometric shapes required for titanium alloys used in the aerospace industry.

Therefore, this article mainly regulates the microstructure of titanium alloy and optimizes its mechanical properties by introducing an appropriate amount of reinforcing phase and combining it with laser metal deposition technology.

Contents of the invention

The present invention provides a titanium alloy based on additive manufacturing with higher strength and plasticity.

Specific embodiments of the present invention provide a titanium alloy based on additive manufacturing. The mass percentages of each component of the titanium alloy are: Al: Al: 4%-5.5%, Mo: 4%-5.5%, V: 4%-5.5%, Cr: 1%-1.5%, Fe: 1%-1.5%, B: 0.03%-0.15%, the balance is Ti;

The organizational structure of the titanium alloy is a basket structure, and TiB whiskers are discontinuously distributed at the grain boundaries.

Further, the size of the TiB whisker is less than 1 μm, and the TiB whisker is in the shape of a short rod.

Further, the raw materials for preparing the titanium alloy are nano-level B powder and micron-level TC18 powder.

Further, the average grain size of the titanium alloy is 20-110 μm.

By adjusting the mass proportion of nanoscale B powder in the mixed powder, the present invention causes the B element to react with the Ti element to form short rod-shaped TiB whiskers with a size less than 1 μm and form a discontinuous reinforcing phase at the titanium alloy grain boundary. The TiB whiskers The inhibition of grain growth can effectively refine the grains, thereby improving the tensile strength of titanium alloys; at the same time, due to the relatively small size of TiB whiskers, it can effectively passivate cracks and hinder crack expansion during the tensile fracture process of the alloy. , improve the elongation of titanium alloy; in addition, the discontinuous generation of TiB whiskers at the grain boundaries also eliminates part of the grain boundary α and enhances the cohesion of the grain boundaries, inhibiting intergranular fracture. Therefore, the purpose of synergistic improvement of strong plasticity of titanium alloy is achieved.

Further, when the mass ratio of the nanoscale B powder and the micron scale TC18 powder is 0-0.03%, the average grain size of the titanium alloy is 75-110 μm, the tensile strength is 1550-1660MPa, and the elongation is 2.5 -4.9%.

Further, when the mass ratio of the nanoscale B powder and the micron scale TC18 powder is 0.03%-0.05%, the average grain size of the titanium alloy is 50-75μm, the tensile strength is 1660-1720MPa, and the elongation is 4.5%-4.9%.

Further, when the mass ratio of the nanoscale B powder and the micron scale TC18 powder is 0.05%-0.15%, the average grain size of the titanium alloy is 20-50μm, the tensile strength is 1720-1770MPa, and the elongation is 4.5-4.9%.

The invention also provides a method for preparing the titanium alloy based on additive manufacturing, including:

Mix nanoscale B powder and micron TC18 powder according to the mass percentage of each component of the titanium alloy based on additive manufacturing to obtain a mixed powder;

The mixed powder is ball milled, dried and sieved;

The mixed powder obtained after sieving is deposited layer by layer on the substrate through laser additive manufacturing to obtain a multi-layer titanium alloy based on additive manufacturing.

Further, the process parameters of the laser additive manufacturing are: laser power is 800-1000W, scanning speed is 500-800mm/min, laser scanning path spacing is set to 40-60% of the cross-sectional size of the single-pass molten pool, slicing The layer thickness is set to 60-80% of the cross-sectional size of the single-pass molten pool, and the powder feeding rate is fixed at 3-5g/min. When the laser power is moderate, the width, height and depth of the molten pool formed by metal powder deposition are all moderate, and the appropriate powder feeding rate and scanning rate ensure that the time acting on the metal powder during the laser scanning process is moderate and the powder absorbs The laser energy is moderate, thereby forming a suitable powder melting range, and the surface of the cladding layer is smooth, which is conducive to subsequent pass overlapping, thereby affecting the geometry, density, and organizational structure of the material, making the material have excellent mechanical properties.

Further, the mixed powder is ball milled, wherein the ball milling process is: the material of the steel ball is 316L, the diameter of the steel ball is 3-6mm, the ball milling speed is 150-250r/min, and the ball milling time is 2 -4h. The appropriate ball milling speed enables the nanoscale B powder to evenly adhere to the surface of the TC18 powder, and the powder can maintain a good spherical shape without deformation.

Further, the mass ratio of the mixed powder to the steel ball is 1:3. The appropriate mass ratio enables the nanoscale B powder to evenly adhere to the surface of the TC18 powder.

Further, drying the mixed powder includes:

Put the ball-milled mixed powder into a vacuum drying box, evacuate until the pressure in the container is less than 1Pa, and dry at 100-120°C for 4-8 hours.

Further, the mixed powder is sieved multiple times through a sieve, and the mesh of the sieve is 80-200 mesh.

Further, before the mixed powder obtained after sieving is deposited layer by layer on the substrate through laser additive manufacturing, the substrate is polished and cleaned in sequence. A substrate with a smooth and bright surface is obtained by polishing and cleaning.

Further, the substrate is a TC4 substrate with a thickness of 10-20mm. Choosing a TC4 substrate with an appropriate thickness is more conducive to the effective deposition of metal powder and promotes a moderate molten pool width and molten pool depth, which in turn affects the geometry, density, structure and mechanical properties of the material formed.

Compared with the prior art, the beneficial effects of the present invention are:

The present invention uses an appropriate content of B element to make the Ti alloy formed have a basket structure, and TiB whiskers are discontinuously distributed at the grain boundaries, so that the Ti alloy formed has smaller size grains, higher tensile strength, and TiB whiskers. Whiskers can effectively passivate cracks, hinder crack expansion, and improve the ductility of titanium alloys during the tensile fracture process of the alloy. On the other hand, the generation of TiB whiskers also eliminates part of the grain boundary α and enhances the cohesion of the grain boundaries, inhibiting the grain boundary. fracture, thus achieving a synergistic improvement in the strong plasticity of titanium alloys.

The preparation method provided by the invention has universal applicability, the preparation process is simple, the production cycle is short, and the repeatability is high, and can be widely used to improve the mechanical properties of TC18 titanium alloy.

Description of drawings

Figure 1 is a block diagram of the laser printing forming block of titanium alloy based on additive manufacturing prepared in Examples 1-3 and Comparative Example 1 of the present invention;

Figure 2 is a grain morphology diagram of the titanium alloy based on additive manufacturing prepared in Examples 1-3 and Comparative Example 1 of the present invention;

Figure 3 is a statistical diagram of the grain size of titanium alloys based on additive manufacturing prepared in Examples 1-3 and Comparative Example 1 of the present invention;

Figure 4 is a backscattered electron (BSE) microstructure diagram of the titanium alloy based on additive manufacturing prepared in Examples 1-3 and Comparative Example 1 of the present invention;

Figure 5 is a backscattered electron (BSE) TiB whisker diagram of the titanium alloy based on additive manufacturing prepared in Examples 1-3 of the present invention;

Figure 6 is a graph showing the mechanical properties of high-strength titanium alloys based on additive manufacturing prepared in Examples 1-3 and Comparative Example 1 of the present invention.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all of the embodiments.

Example 1

TC18 powder and nanoscale B powder were obtained as powder raw materials for laser metal deposition. The particle size of TC18 powder was 50-150 μm.

The mass of TC18 powder is 199.98g, and the mass of nanoscale B powder is 0.02g, accounting for 0.03wt.%. Mix TC18 powder and nanoscale B powder, and put diameter 316L steel ball, the mass ratio of the steel ball to alloy powder is 3:1, and then the mixed powder is put into a stainless steel ball mill tank for ball milling, the ball milling speed is 200r/min, and the ball milling time is 5h.

Put the mixed powder obtained after ball milling into a vacuum drying box, evacuate until the pressure inside the box is less than 1Pa, the drying temperature is 120°C, and the drying time is 8 hours. After drying, use a sieve with an aperture of 100 mesh to screen the powder twice. , and then load the mixed powder into the powder feeder of the laser additive manufacturing equipment.

Take a 10*10cm TC4 substrate with a thickness of 10mm, polish the surface with sandpaper to expose a flat and bright upper surface, clean and dry it with ethanol after polishing, and then put it into the laser additive manufacturing equipment.

Set the laser power of laser metal deposition to 900W and the scanning speed to 600mm/min; pre-scan and print a single pass and measure the cross-sectional size of the molten pool. Set the path spacing to 1.38mm according to the single-pass molten pool size, and the slice layer thickness to 0.4mm, which is fixed. The powder feeding rate is 3g/min, and a multi-channel, multi-layered titanium alloy block without macro cracks is prepared.

Example 2

TC18 powder and nanoscale B powder were obtained as powder raw materials for laser metal deposition. The particle size of TC18 powder was 50-150 μm.

The mass of TC18 powder is 199.9g, and the mass of nanoscale B powder is 0.1g, accounting for 0.05wt.%. Mix TC18 powder and nanoscale B powder, and put diameter 316L steel ball, the mass ratio of the steel ball to alloy powder is 3:1, and then the mixed powder is put into a stainless steel ball mill tank for ball milling, the ball milling speed is 200r/min, and the ball milling time is 5h.

Put the mixed powder obtained after ball milling into a vacuum drying box, evacuate until the pressure inside the box is less than 1Pa, the drying temperature is 120°C, and the drying time is 8 hours. After drying, use a sieve with an aperture of 100 mesh to screen the powder twice. , and then load the mixed powder into the powder feeder of the laser additive manufacturing equipment.

Take a 10*10cm TC4 substrate with a thickness of 10mm, polish the surface with sandpaper to expose a flat and bright upper surface, clean and dry it with ethanol after polishing, and then put it into the laser additive manufacturing equipment.

Set the laser power of laser metal deposition to 900W and the scanning speed to 600mm/min; pre-scan and print a single pass and measure the cross-sectional size of the molten pool. Set the path spacing to 1.38mm according to the single-pass molten pool size, and the slice layer thickness to 0.4mm, which is fixed. The powder feeding rate is 3g/min, and a multi-channel, multi-layered titanium alloy block without macro cracks is prepared.

Example 3

TC18 powder and nanoscale B powder were obtained as powder raw materials for laser metal deposition. The particle size of TC18 powder was 50-150 μm.

The mass of TC18 powder is 199.7g, and the mass of nanoscale B powder is 0.3g, accounting for 0.15wt.%. Mix TC18 powder and nanoscale B powder, and put diameter 316L steel ball, the mass ratio of the steel ball to alloy powder is 3:1, and then the mixed powder is put into a stainless steel ball mill tank for ball milling, the ball milling speed is 200r/min, and the ball milling time is 5h.

Put the mixed powder obtained after ball milling into a vacuum drying box, evacuate until the pressure inside the box is less than 1Pa, the drying temperature is 120°C, and the drying time is 8 hours. After drying, use a sieve with an aperture of 100 mesh to screen the powder twice. , and then load the mixed powder into the powder feeder of the laser additive manufacturing equipment.

Take a 10*10cm TC4 substrate with a thickness of 10mm, polish the surface with sandpaper to expose a flat and bright upper surface, clean and dry it with ethanol after polishing, and then put it into the laser additive manufacturing equipment.

Set the laser power of laser metal deposition to 900W and the scanning speed to 600mm/min; pre-scan and print a single pass and measure the cross-sectional size of the molten pool. Set the path spacing to 1.38mm according to the single-pass molten pool size, and the slice layer thickness to 0.4mm, which is fixed. The powder feeding rate is 3g/min, and a multi-channel, multi-layered titanium alloy block without macro cracks is prepared.

Comparative example 1

Compared with the examples, the difference is that no nanoscale B powder is added in the comparative examples.

Performance comparison:

Referring to Figure 1, Figure 1 shows the macroscopic morphology of the titanium alloy block in Comparative Example 1 and Examples 1-3. TC18, TC18+0.03B, TC18+0.05B, and TC18+0.15B respectively correspond to Countermeasure 1 and Examples 1, 2, and 3. As can be seen from the figure, printing is done from bottom to top along the direction of metal deposition. The titanium alloy block exhibits layered characteristics.

Referring to Figure 2, Figure 2 shows the grain morphology diagrams of Comparative Example 1 and Examples 1-3. TC18, TC18+0.03B, TC18+0.05B, and TC18+0.15B correspond to Comparative Example 1 and Example 1 respectively. , 2, 3. It can be seen from the figure that the grain size of TC18 titanium alloy without adding nano-scale B powder is relatively large, and as the amount of nano-scale B powder added increases, the grain size of titanium alloy gradually becomes finer. When the addition amount of nano-scale B powder is 0.15wt.%, the grain size refinement effect is the most significant, and it can be clearly observed that the grain morphology gradually becomes spherical due to the addition of nano-scale B powder.

Referring to Figure 3, Figure 3 shows the grain size statistical diagram of Comparative Example 1 and Examples 1-3 and the change curve of the average grain size of titanium alloy, Figure 3 (a), Figure 3 (b), Figure 3 (c) and Figure 3 (d) represent the grain size statistical graphs of Comparative Example 1 and Examples 1-3 respectively, and Figure 3 (e) is a titanium alloy grain size change curve. As can be seen from Figure 3(a), Figure 3(b), Figure 3(c), and Figure 3(d), the average grain size of TC18 titanium alloy without adding nano-scale B powder is 110 μm. , and the grain size is very uneven. When the addition amount of nano-scale B powder is 0.03% wt., the average grain size of TC18+0.03B titanium alloy is 75 μm. When the addition amount of nano-scale B powder is 0.05% wt., the average grain size of TC18+0.05B titanium alloy is 50 μm, and the grain size distribution is relatively uniform. When the addition amount of nanoscale B powder is 0.15% wt., the average grain size of TC18+0.05B titanium alloy The size is 20 μm, and the grain size distribution is very uniform. About 90% of the grain sizes range from 10-30 μm. From Figure 3(e), it can be clearly seen that the average grain size of titanium alloy increases with the nanoscale B The amount of powder added gradually decreases, indicating that the addition of nanoscale B powder can effectively refine the grain size of TC18 titanium alloy and make it uniform.

Referring to Figure 4, Figure 4 shows the microstructure diagram of Comparative Example 1 and Examples 1-3. TC18, TC18+0.03B, TC18+0.05B, and TC18+0.15B correspond to Comparative Example 1 and Example 1 respectively. , 2, 3. It can be seen from the figure that the four titanium alloys all have a basket structure. The nano-scale B powder and the TC18 titanium alloy matrix generate TiB whiskers in situ, and the TiB whiskers are mainly distributed at the grain boundaries. This It shows that TiB whiskers effectively refine the grain size by inhibiting the growth of grains.

Referring to Figure 5, Figure 5 shows the TiB whisker diagrams of Examples 1-3. TC18+0.03B, TC18+0.05B, and TC18+0.15B correspond to Examples 1, 2, and 3 respectively. Obviously, the B element and The Ti element reacts to form short rod-shaped TiB whiskers with a size less than 1 μm and generates a discontinuous network reinforcement phase in situ at the titanium alloy grain boundaries. The inhibitory effect of this small-sized TiB whisker on grain growth can effectively refine grains, thereby improving the tensile strength of titanium alloys; at the same time, TiB whiskers can effectively passivate cracks, hinder crack expansion during the alloy tensile fracture process, and improve the ductility of titanium alloys; on the other hand, the generation of TiB whiskers also Part of the grain boundary α is eliminated, grain boundary cohesion is enhanced, and intergranular fracture is suppressed. Therefore, the addition of nanoscale B powder causes the discontinuous network reinforcement phase TiB whiskers to be generated in situ at the grain boundaries, achieving the purpose of synergistically improving the strong plasticity of titanium alloys.

Referring to Figure 6, Figure 6 shows the stress strain curves of Comparative Example 1 and Examples 1-3. Among them, the curve corresponding to TC18 is the stress-strain curve of Comparative Example 1; the curve corresponding to TC18+0.03B is the stress-strain curve of Example 1; the curve corresponding to TC18+0.05B is the stress-strain curve of Example 2; TC18+0.15 The curve corresponding to B is the stress-strain curve of Example 3. As shown in Figure 5, the tensile strength of TC18 titanium alloy without adding nano-scale B powder is 1550MPa, and the elongation is 2.5%. When the added amounts of nano-scale B powder are 0.03wt.%, 0.05wt.%, and 0.15 respectively wt.%, the tensile strength of titanium alloy is 1660MPa, 1720MPa, 1770MPa respectively, and the elongation is 4.9%, 4.9%, 4.5% respectively. Obviously, the tensile strength and elongation of TC18 titanium alloy increase with the nanoscale The increase in the amount of B powder added effectively achieves a synergistic improvement in strong plasticity.

Claims (10)

1. The titanium alloy based on additive manufacturing is characterized by comprising the following components in percentage by mass: al:4% -5.5%, mo:4% -5.5%, V:4% -5.5%, cr:1% -1.5%, fe:1% -1.5%, B:0.03% -0.15%, and the balance is Ti;

the structure of the titanium alloy is a basket structure, and TiB whiskers are discontinuously distributed at the grain boundary.

2. The additive manufacturing-based titanium alloy of claim 1, wherein the TiB whiskers are less than 1 μιη in size and are short rod-shaped.

3. The titanium alloy of claim 1, wherein the titanium alloy is prepared from nanoscale B powder and microscale TC18 powder.

4. The titanium alloy based on additive manufacturing according to claim 3, wherein the average grain size is 75-110 μm when the mass ratio of the nano-sized B powder to the micro-sized TC18 powder is 0-0.03%, the tensile strength of the titanium alloy is 1550-1660MPa, and the elongation is 2.5-4.9%.

5. The titanium alloy based on additive manufacturing according to claim 3, wherein the average grain size is 50-75 μm when the mass ratio of the nano-sized B powder to the micro-sized TC18 powder is 0.03% -0.05%, the tensile strength of the titanium alloy is 1660-1720MPa, and the elongation is 4.5% -4.9%.

6. The titanium alloy based on additive manufacturing according to claim 3, wherein the average grain size is 20-50 μm when the mass ratio of the nano-sized B powder to the micro-sized TC18 powder is 0.05% -0.15%, the tensile strength of the titanium alloy is 1720-1770MPa, and the elongation is 4.5-4.9%.

7. The titanium alloy of claim 1, wherein said titanium alloy has an average grain size of 20-110 μm.

8. A method of producing an additive manufacturing-based titanium alloy according to any one of claims 1 to 7, comprising:

batching the nano-scale B powder and the micro-scale TC18 powder according to the mass percentages of the components of the titanium alloy based on additive manufacturing according to any one of claims 1 to 8 to obtain mixed powder;

ball milling, drying and sieving the mixed powder;

and depositing the mixed powder obtained after sieving on a substrate layer by layer through laser additive manufacturing to obtain the multilayer titanium alloy based on additive manufacturing.

9. The method for preparing a titanium alloy based on additive manufacturing according to claim 8, wherein the technological parameters of the laser additive manufacturing are as follows: the laser power is 800-1000W, the scanning speed is 500-800mm/min, the path interval of laser scanning is set to 40-60% of the cross section size of the single-channel molten pool, the slice layer thickness is set to 60-80% of the cross section size of the single-channel molten pool, and the powder feeding speed is fixed to 3-5g/min.

10. The method for preparing a titanium alloy based on additive manufacturing according to claim 8, wherein the mixed powder is ball milled, wherein the ball milling process is as follows: the steel ball is made of 316L, the diameter of the steel ball is 3-6mm, the ball milling rotating speed is 150-250r/min, and the ball milling time is 2-4h.