Titanium alloy special for PBF additive manufacturing and preparation method and application thereof

Abstract

The application belongs to the technical field of in-situ additive manufacturing, and discloses a PBF additive manufacturing special titanium alloy and a preparation method and application thereof, the method comprising the following steps: (1) uniformly mixing pure titanium powder and other elements required for preparing a customized titanium alloy in the form of intermediate alloy powder or single-element powder to obtain titanium alloy raw material powder; (2) uniformly mixing a low-melting-point polymer with the titanium alloy raw material powder, then adding anhydrous ethanol solution for common ball milling, obtaining a wet mixture, and then obtaining the titanium alloy. The application uses pure titanium powder as the base material of a new component titanium alloy, mixes with intermediate alloy or element single-element powder required for the customized target titanium alloy, and uses diluted low-melting-point polymer solution as an aid to prepare additive manufacturing special titanium alloy powder with high homogeneity, good particle size consistency and good fluidity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field related to in-situ additive manufacturing, and more particularly relates to a titanium alloy special for PBF additive manufacturing and a preparation method and application thereof. BACKGROUND

[0002] Titanium and titanium alloy have high specific strength, good corrosion resistance, excellent biocompatibility and other characteristics, and have broad application prospects in the fields of aerospace, ocean engineering, petroleum chemical industry, biological medicine and the like. Additive manufacturing technology has the advantages of clean energy and high degree of digital information, and is different from traditional forming methods, and is an ideal preparation technology for processing titanium alloy and other high reactivity difficult-to-machine metal materials. As one of the important raw materials for titanium alloy additive manufacturing technology, it is an urgent task to design and develop titanium alloy powder with diversified composition to meet the needs of different scenarios.

[0003] Common vacuum induction melting gas atomization method (VIGA) and plasma rotating electrode atomization method (PREP) can obtain pre-alloyed spherical powder of target titanium alloy composition, but these methods require pre-preparation of target titanium alloy mother liquor, and high requirements are put forward for the production equipment of the melting mother liquor. For new composition titanium alloy design that needs to frequently change components, huge capital cost and time cost seriously restrict the development and research of multi-component titanium alloy.

[0004] In-situ alloying additive manufacturing is a low-cost and high-efficiency method for titanium alloy design, which can arbitrarily change the components and mass percentage of the target alloy, and then quickly prepare microstructure and mechanical property samples through additive manufacturing, and quickly complete the development of new composition titanium alloy. However, due to the differences in the characteristics of various component powders, the in-situ alloying powder usually has problems such as unevenness and poor flowability, which leads to pores, inclusions or element segregation in the parts manufactured by additive manufacturing, and ultimately affects the mechanical properties of titanium alloy, indirectly increases the development cost, and hinders the potential of in-situ additive manufacturing in the design and development of new composition titanium alloy. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the present application provides a titanium alloy special for PBF additive manufacturing and a preparation method and application thereof, which uses pure titanium powder as the base material of new composition titanium alloy, mixes with intermediate alloy or elemental powder required for customizing target titanium alloy, and uses diluted low-melting polymer solution as an aid to prepare additive manufacturing special titanium alloy powder with high homogeneity, good particle size consistency and good flowability, solving the technical problems of poor printability of traditional in-situ alloying powder with customized composition, uneven microstructure of PBF additive manufacturing titanium alloy and many particles of refractory elements.

[0006] To achieve the above object, according to one aspect of the present application, a preparation method of a PBF additive manufacturing special titanium alloy is provided, which comprises the following steps:

[0007] (1) mixing pure titanium powder and other elements required for preparing the customized titanium alloy in the form of intermediate alloy powder or single-element powder to obtain titanium alloy raw material powder;

[0008] (2) mixing the low-melting-point polymer with the titanium alloy raw material powder, then adding anhydrous ethanol solution for joint ball milling, obtaining a wet mixture by ball milling, and further obtaining the titanium alloy.

[0009] Further, the low-melting-point polymer powder is one or more of polyvinyl alcohol, polyethylene wax and stearic acid.

[0010] Further, the mixing is performed by rotating the mixer for 8h; the mixing is performed by planetary ball milling, the ball diameter is 8mm, the ball-to-material mass ratio is 5:1, the rotating speed is 1.5m / s-3m / s, and the mixing time is 5h-24h.

[0011] Further, the low-melting-point polymer is stearic acid powder, and the mass percentage of the stearic acid powder in the mixture of the stearic acid powder and the anhydrous ethanol solution is 2.5%.

[0012] Further, the rotating speed of the ball milling mixing is 2m / s, the mixing time is 8h, the mixture is vacuum dried for 3h at a temperature of 100℃.

[0013] Further, the low-melting-point polymer comprises polyethylene wax and stearic acid powder, and the mass percentages of the polyethylene wax and the stearic acid powder in the mixture formed by the polyethylene wax, the stearic acid powder and the anhydrous ethanol solution are 2.5% and 1% respectively.

[0014] Further, the low-melting-point polymer comprises polyvinyl alcohol and stearic acid powder, and the mass percentages of the polyvinyl alcohol and the stearic acid powder in the mixture formed by the polyvinyl alcohol, the stearic acid powder and the anhydrous ethanol solution are 2.5% and 1% respectively.

[0015] The present application also provides a PBF additive manufacturing special titanium alloy prepared by the preparation method of the PBF additive manufacturing special titanium alloy as described above.

[0016] The present application also provides an application of the PBF additive manufacturing special titanium alloy as described above in the preparation of a titanium alloy part.

[0017] Further, the laser power used in the additive manufacturing of the titanium alloy part is 200W-350W, the scanning speed is 900mm / s-1800mm / s, and the scanning interval is 75μm.

[0018] Overall, compared with the prior art, the PBF additive manufacturing special titanium alloy provided by the application and the preparation method and application thereof mainly have the following beneficial effects:

[0019] 1. The preparation method has great inclusiveness for the component composition of the titanium alloy in terms of customized composition. The component powder can not only have refractory elements with high melting points, but also can have a particle size requirement of 1-40 pm, which is relatively easy to obtain on the market. Compared with some schemes of adding metal or non-metal particles in Ti-based to prepare composite materials, the advantages are obvious. Since the in-situ generated intermetallic compound cannot be solid-soluted in the matrix, only low-melting-point and nano-sized strengthening elements such as C and N can be selected. However, it is extremely difficult to prepare nano-sized powder of some metal elements or intermediate alloys, and the price is expensive.

[0020] 2. The low-melting-point polymer solution suspends the irregular small-size powder, the powder of different particle sizes is separated in the suspension area of the solution, so that the small-size powder is more easily close to the powder with similar particle size, thereby increasing the ball milling contact area between the powders with similar particle size. From a macroscopic point of view, the cold welding effect in the ball milling process can be significantly improved, and uniform alloying of the same particle size between components can be completed.

[0021] 3. The low-melting-point polymer solution suspends the irregular small-size powder, the powder of different particle sizes is separated in the suspension area of the solution, so that the small-size powder is more easily close to the powder with similar particle size, thereby increasing the ball milling contact area between the powders with similar particle size. From a macroscopic point of view, the cold welding effect in the ball milling process can be significantly improved, and uniform alloying of the same particle size between components can be completed.

[0022] 4. By controlling the viscosity of the polymer solution, the liquid suspension effect of the solution on the irregular small-size powder can be changed, the polymerization of each component of the titanium alloy matrix with different compositions and different sizes can be controlled, and the dispersion degree of one or more elements can be controlled, thereby providing a new idea for flexible design of titanium alloy composition.

[0023] 5.PBF additive manufacturing is a technology with certain requirements for the flowability of powder materials, and the powder with smaller particle size gap has more advantages in the manufacturing process. The alloy powder prepared by the present application has uniform composition and good particle size consistency, is easier to pass the flowability test, has better printability, and is different from other additive manufacturing methods such as binder jetting additive manufacturing, which can only prepare porous titanium alloy parts with fixed composition and low melting point. PBF additive manufacturing can obtain full-dense, customizable composition homogeneous titanium alloy parts. After using the alloy powder prepared by the present application, the microstructure is also significantly improved, and common defects such as pores, inclusions and refractory particles are greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a flow chart of a preparation method of a PBF additive manufacturing special titanium alloy provided by the present application;

[0025] Figure 2 (a) and (b) in are respectively the preparation principle schematic diagram of the original method and the preparation method of the PBF additive manufacturing special spherical titanium alloy powder provided by the present application;

[0026] Figure 3 is the SEM image of the spherical titanium alloy powder prepared in Comparative Example 1;

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

[0028] Figure 5 is the SEM image of the spherical titanium alloy powder prepared in Example 2;

[0029] Figure 6 is the SEM image of the spherical titanium alloy powder prepared in Example 3;

[0030] Figure 7 (a), (b), (c) and (d) in are respectively the comparison diagram of the microstructure uniformity of the titanium alloy prepared by PBF additive manufacturing of each example;

[0031] Figure 8 is the flowability comparison schematic diagram of the spherical titanium alloy powder prepared in each example. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0033] The present application improves the printability of the in-situ alloying powder of the customized composition by adding a low-melting polymer additive, and further optimizes the microstructure uniformity of the laser powder bed fusion (PBF, Powder Bed Fusion) titanium alloy, which relates to the field of in-situ alloying additive manufacturing, to solve the problems of poor printability of the in-situ alloying powder of the customized composition, and poor microstructure uniformity of the PBF manufactured titanium alloy caused by poor quality powder. In addition, by the method of in-situ alloying, pure titanium powder is used as the base material of the titanium alloy, and the intermediate alloy powder or elemental powder required for the target titanium alloy is added according to the customized composition, and the low-melting polymer additive is used to increase the ball milling contact area between the same diameter powders in the solution, to prepare high-quality spherical PBF additive manufacturing alloy powder with high homogeneity, good particle size consistency and good flowability, to solve the key technical problems of poor printability of the in-situ alloying powder of the customized composition, poor microstructure uniformity of the PBF additive manufacturing titanium alloy, and many particles of refractory elements.

[0034] Please refer to Figure 1 and Figure 2 The present application provides a preparation method of PBF additive manufacturing special titanium alloy, which mainly includes the following steps:

[0035] Step one, mix the pure titanium powder and other elements required for preparing the customized titanium alloy in the form of intermediate alloy powder or elemental powder to obtain titanium alloy raw powder.

[0036] The mass percentage of the pure titanium powder in the titanium alloy raw powder is greater than 80%, the particle size of the pure titanium powder is not greater than 53 μm, and the powder with a particle size of more than 40 μm must be near-spherical. The intermediate alloy powder or elemental powder can be irregularly shaped powder or near-spherical powder, with an average particle size of not greater than 10 μm and not less than 1 μm.

[0037] Step two, mix the low-melting polymer with the titanium alloy raw powder, then add anhydrous ethanol solution for common ball milling, obtain a wet mixture by ball milling, and then obtain a titanium alloy.

[0038] The low-melting polymer powder is one or more of polyvinyl alcohol, polyethylene wax and stearic acid. The addition amount of the low-melting polymer powder and the anhydrous ethanol solution can be controlled according to different alloy compositions and powder particle sizes, to adjust the consistency of the polymer colloid, and then change the liquid suspension effect of the solution on the irregular small-size powder. Mixing is carried out by a mixer at a low speed for 8 hours; the ball milling adopts a planetary ball milling method, the ball milling bead diameter is 8 mm, the ball-to-material mass ratio is 5:1, the rotation speed is 1.5 m / s-3 m / s, and the mixing time is 5 h-24 h. The wet mixture after ball milling is dried and sieved to obtain a titanium alloy with uniform composition and good particle size consistency.

[0039] The application further provides a PBF additive manufacturing special titanium alloy prepared by the preparation method of the PBF additive manufacturing special titanium alloy.

[0040] The application further provides application of the PBF additive manufacturing special titanium alloy in preparation of a titanium alloy part, wherein the titanium alloy is used as raw material to obtain the titanium alloy part through additive manufacturing. The laser power of the additive manufacturing is 200 W-350 W, the scanning speed is 900 mm / s-1800 mm / s, and the scanning interval is 75 μm; by controlling the appropriate power and scanning speed, the powder can be quickly melted without being easy to form inclusions, the laser power is 250 W-300 W, the scanning speed is 1000 mm / s-1600 mm / s, and the scanning interval is 60 μm.

[0041] The application is further described in detail in the following examples.

[0042] Comparative Example 1

[0043] Please refer to Figure 3 Comparative Example 1 mainly includes the following steps:

[0044] (1) The titanium powder with an average particle size of 53 μm and the non-spherical Mo and Zr elemental powder with an average particle size of 10 μm are mixed according to the required proportion of the target titanium alloy.

[0045] (2) The raw material powder in step (1) is ball-milled and mixed, the rotating speed is 2 m / s, the mixing time is 8 h, the mixture is vacuum (1.0E-3 MPa or below) dried for 3 h, and the temperature is 100 DEG C. The powder is passed through a 200 mesh sieve, the minimum particle size of the titanium alloy powder is 2 μm, the average particle size is 35 μm, the flowability is poor, and the flowability test cannot be passed through the Hall flowmeter.

[0046] (3) The titanium alloy powder obtained in step (2) is used for additive manufacturing of a titanium alloy part, the laser power is 250 W, the scanning speed is 1200 mm / s, and the scanning interval is 60 μm. In the preferred embodiment. The prepared part has uneven microstructure, and the unmelted inclusion rate is 30%.

[0047] Example 1

[0048] Please refer to Figure 4 Example 1 of the application mainly includes the following steps:

[0049] (1) The titanium powder with an average particle size of 53 μm and the non-spherical Mo and Zr elemental powder with an average particle size of 10 μm are mixed according to the required proportion of the target titanium alloy.

[0050] (2) The stearic acid powder, anhydrous ethanol solution and the raw material powder of step (1) are ball-milled at a rotation speed of 2 m / s for 8 h, and the mixture is vacuum-dried (under 1.0E-3 MPa) at 100°C for 3 h. The powder is sieved through a 200-mesh screen, and the minimum particle size of the titanium alloy powder is 10 μm and the average particle size is 45 μm. The flowability test by a Hall flowmeter is 42.47 s / 50 g. The mass percentage of the stearic acid powder in the mixture of the stearic acid powder and the anhydrous ethanol solution is 2.5%.

[0051] (3) The titanium alloy powder obtained in step (2) is used for additive manufacturing of a titanium alloy part, with a laser power of 250 W, a scanning speed of 1200 mm / s and a scanning interval of 60 μm. In the preferred embodiment, the prepared part has a uniform microstructure, and the unmelted inclusion rate is 16%.

[0052] Example 2

[0053] Referring to Figure 5 , Example 2 of the present application mainly includes the following steps:

[0054] (1) The titanium powder with an average particle size of 53 μm and the non-spherical Mo and Zr elemental powder with an average particle size of 10 μm are mixed in the required proportions for the target titanium alloy.

[0055] (2) The polyethylene wax, stearic acid powder, anhydrous ethanol solution and the raw material powder of step (1) are ball-milled at a rotation speed of 2 m / s for 8 h, and the mixture is vacuum-dried (under 1.0E-3 MPa) at 100°C for 3 h. The powder is sieved through a 200-mesh screen, and the minimum particle size of the titanium alloy powder is 10 μm and the average particle size is 55 μm. The flowability test by a Hall flowmeter is 39.74 s / 50 g. The mass percentage of the polyethylene wax and the stearic acid powder in the mixture of the polyethylene wax, the stearic acid powder and the anhydrous ethanol solution is 2.5% and 1%, respectively.

[0056] (3) The titanium alloy powder obtained in step (2) is used for additive manufacturing of a titanium alloy part, with a laser power of 250 W, a scanning speed of 1200 mm / s and a scanning interval of 60 μm. In the preferred embodiment, the prepared part has a uniform microstructure, and the unmelted inclusion rate is 7%.

[0057] Example 3

[0058] Referring to Figure 6 , Figure 7 and Figure 8 , Example 3 of the present application mainly includes the following steps:

[0059] (1) The titanium powder with an average particle size of 53 μm and the non-spherical Mo and Zr elemental powder with an average particle size of 10 μm are mixed in the required proportions for the target titanium alloy.

[0060] (2) Polyvinyl alcohol and stearic acid powder, anhydrous ethanol solution, and the raw material powder of step (1) are ball-mixed at a rotation speed of 2 m / s for 8 h. The mixture is vacuum-dried (1.0E-3 MPa or less) for 3 h at a temperature of 100°C. The powder is sieved through a 200-mesh screen, and the titanium alloy powder has a minimum particle size of 20 μm and an average particle size of 55 μm. The flowability test by a Hall flowmeter is 37.41 s / 50 g. In the mixture, the mass percentages of polyvinyl alcohol and stearic acid powder are 2.5% and 1%, respectively.

[0061] (3) The titanium alloy powder obtained in step (2) is used to additively manufacture a titanium alloy part, with a laser power of 250 W, a scanning speed of 1200 mm / s, and a scanning interval of 60 μm. In the preferred embodiment, the prepared part has a uniform microstructure, and the unmelted inclusion rate is 3%.

[0062] From Figure 3 It can be seen that the titanium alloy powder prepared in the comparative example is loose, irregular, and has obvious unevenness. From Figure 4 It can be seen that the titanium alloy powder prepared in the present example is loose and irregular, but part of the powder has a tendency to aggregate with each other. From Figure 5 It can be seen that the powder of about 50 μm has a clear separation from the fine powder, but the overall powder particle size still cannot maintain good uniformity. From Figure 6 It can be seen that the powder of about 50 μm and the fine powder are separated from each other, and the small-size powder aggregates into powder groups with a size close to 50 μm. The overall powder particle size shows good uniformity and a uniform distribution.

[0063] From Figure 5 It can be seen that, from the uniformity of the molten pool, the addition of the low-melting-point polymer additive makes the ball-mixed mixture powder more uniformly distributed. Not only the Ti element powder is uniformly distributed, but also the Mo and Zr elements are uniformly dispersed, basically reaching the required standard of PBF additive manufacturing powder. Figure 6 is a comparison of the flowability of the titanium alloy powder prepared in each embodiment. Under the auxiliary action of the polymer solution on the fine powder suspension layer, the particle size of the ball-mixed mixture powder tends to be uniform, and the flowability is obviously improved, basically meeting the requirements of additive manufacturing on powder flowability

[0064] Those skilled in the art will readily understand that the above description is only of the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of producing a PBF additive manufacturing specialty titanium alloy, characterized by, The method comprises the following steps: (1) mixing pure titanium powder with intermediate alloy powder or elemental powder of other elements required for preparing a customized titanium alloy to obtain titanium alloy raw material powder; (2) mixing a low-melting-point polymer with the titanium alloy raw material powder, then adding anhydrous ethanol solution for joint ball milling, obtaining a wet mixture after ball milling, and obtaining a titanium alloy with uniform composition and good particle size consistency after drying and screening the wet mixture; The low-melting-point polymer is stearic acid powder, and the mass percentage of the stearic acid powder in the mixture of the stearic acid powder and the anhydrous ethanol solution is 2.5%; or the low-melting-point polymer comprises polyethylene wax and stearic acid powder, and the mass percentages of the polyethylene wax and the stearic acid powder in the mixture formed by the polyethylene wax, the stearic acid powder and the anhydrous ethanol solution are 2.5% and 1% respectively; or the low-melting-point polymer comprises polyvinyl alcohol and stearic acid powder, and the mass percentages of the polyvinyl alcohol and the stearic acid powder in the mixture formed by the polyvinyl alcohol, the stearic acid powder and the anhydrous ethanol solution are 2.5% and 1% respectively.

2. The method of producing a PBF additive manufacturing specialized titanium alloy of claim 1, wherein: The mixing is performed by rotating a mixer for 8 hours; the ball milling is performed by using a planetary ball milling mixer, the ball diameter is 8 mm, the ball-to-material mass ratio is 5:1, the rotating speed is 1.5 m / s-3 m / s, and the mixing time is 5 h-24 h.

3. The method of producing a PBF additive manufacturing specialized titanium alloy of claim 1, wherein: The rotating speed of the ball milling mixer is 2 m / s, the mixing time is 8 h, the mixture is vacuum-dried for 3 h at a temperature of 100°C.

4. A PBF additive manufacturing dedicated titanium alloy characterized in that: The PBF additive manufacturing special titanium alloy is prepared by using the preparation method of the PBF additive manufacturing special titanium alloy according to any one of claims 1-3.

5. Use of the PBF additive manufacturing special titanium alloy according to claim 4 in the preparation of a titanium alloy part.

6. Use of the PBF additive manufacturing specialized titanium alloy of claim 5 in the manufacture of a titanium alloy part, characterized by: The laser power used in additive manufacturing of the titanium alloy part is 200 W-350 W, the scanning speed is 900 mm / s-1800 mm / s, and the scanning interval is 75 μm.

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