Additive manufacturing and structure refining method for submicron in-situ TiC reinforced titanium-based composite material

Abstract

The invention discloses an additive manufacturing and structure refining method for a submicron in-situ TiC reinforced titanium-based composite material, and belongs to the field of additive manufacturing of titanium-based composite materials. According to the method, superfine TiC powder with the particle size smaller than 10 micrometers and Ti6Al4V spherical powder with the particle size ranging from 45 micrometers to 100 micrometers are subjected to ball milling and mixing, fine TiC powder particles are evenly inlaid on the surfaces of large Ti6Al4V powder particles, and the superfine TiC / Ti6Al4V powder is prepared. Superfine TiC / Ti6Al4V powder is used as a raw material, a TiC / Ti6Al4V composite material sample is prepared through a laser melting deposition method, a submicron in-situ TiC reinforced phase is formed in a microstructure, meanwhile, original beta Ti grains in a Ti6Al4V matrix and alpha Ti grains in the Ti6Al4V matrix are refined, and finally the mechanical property of the TiC / Ti6Al4V composite material is improved.

Description

Technical Field

[0001] The invention belongs to the field of additive manufacturing of titanium-based composite materials, and in particular relates to an additive manufacturing and tissue refinement method of a submicron-level in-situ TiC-reinforced titanium-based composite material. Background Art

[0002] As one of the most widely used aviation alloys, Ti6Al4V titanium alloy faces the challenge of being difficult to meet the requirements of higher combat performance. Its low hardness, strength and other properties limit its wider application under some extreme conditions. By developing excellent titanium matrix composites (TMCs), components can withstand greater loads and stresses to ensure safety and reliability. Titanium carbide (TiC) has the advantages of high hardness, good stability, density similar to titanium, and good compatibility with titanium alloys. Therefore, many scholars use TiC as a reinforcement to strengthen Ti6Al4V alloy and prepare TiC / Ti6Al4V composites with superior performance.

[0003] However, the extremely high melting point (3160°C) and hardness (Mohs 9.0-9.5) of TiC make it extremely difficult to prepare TMCs using traditional processing techniques such as forging, casting, and machining. Laser melting deposition (LMD) is an additive manufacturing technology that uses a high-energy laser beam to melt one or more raw materials (powder or wire) and deposit them on a substrate along a certain path to eventually form a sample with certain geometric dimensions. Thanks to its high energy density and high forming freedom, LMD can easily melt refractory materials and form them into a predetermined geometric shape without the need for a large amount of post-processing, and has been proven to be an effective method for preparing TMCs.

[0004] When using LMD technology to prepare TiC / Ti6Al4V composite materials, the raw materials used are usually powders with a particle size of tens of microns. This particle size range can ensure good fluidity of the powder. However, LMD is a process of rapid melting and solidification of materials, in which the cooling rate of the molten pool can reach 10 4 ~10 6℃ / s, a large number of studies have shown that TiC powders of tens of microns cannot be completely melted or dissolved in such a short-lived molten pool. As a result, a large amount of undissolved TiC is distributed in the microstructure of the solidified material, and the size is usually tens of microns. These large-sized and irregularly shaped TiC particles have an adverse effect on the mechanical properties of TMCs. Since the undissolved TiC contains the original defects existing in the TiC raw material powder itself, and TiC is inherently hard and brittle, and has a large gap in elastic modulus with Ti6Al4V (TiC elastic modulus is about 280GPa, Ti6Al4V elastic modulus is about 110GPa), it is easy to produce strong stress concentration inside and at the interface of the undissolved TiC, forming original cracks, thereby accelerating failure, which is not conducive to improving the mechanical properties of the composite material.

[0005] In addition, the dissolved TiC forms an in-situ TiC phase during the cooling and solidification of the molten pool. For TiC / Ti6Al4V composites with high TiC content (>5 vol.%), the in-situ TiC phase usually exists in the form of large-sized granular / dendritic primary TiC (several microns to tens of microns), which is also not conducive to the improvement of performance to a certain extent. Summary of the invention

[0006] The purpose of the present invention is to provide a method for additive manufacturing and microstructure refinement of a submicron in-situ TiC-reinforced titanium-based composite material. The method uses ultrafine TiC powder as a carbon source and a laser melting deposition method to prepare a TiC / Ti6Al4V composite material, achieves complete dissolution of the TiC powder, forms a submicron-level fine in-situ TiC reinforcement phase, and promotes the grain refinement of the Ti6Al4V matrix, ultimately improving the mechanical properties of the TiC / Ti6Al4V composite material.

[0007] The invention provides a submicron in-situ TiC reinforced titanium-based composite material, which consists of a titanium-based alloy and a TiC reinforcement phase; the composite material comprises an α+β type dual-phase titanium alloy and a TiC reinforcement phase; the TiC reinforcement phase is dispersed in a titanium-based alloy matrix in the form of short rods or particles, the length of the short rod-shaped TiC reinforcement phase is 0.3-1.6 μm, the width is 0.1-0.8 μm, and the particle size of the granular TiC reinforcement phase is 0.1-1.0 μm.

[0008] The present invention further provides a method for additive manufacturing and microstructure refinement of a submicron-level in-situ TiC-reinforced titanium-based composite material, comprising the following steps:

[0009] Step 1: Add TiC powder and titanium-based powder into a ball mill; the mass of the TiC powder X, the mass of the titanium-based powder Y, and the volume fraction of the TiC powder a% satisfy the relationship: X / Y = aρ TiC / (100-a)ρ0

[0010] Among them, ρ TiC is the density of TiC powder; ρ0 is the density of titanium-based powder;

[0011] Step 2: Add stainless steel grinding balls into the ball mill described in step 1 and perform ball milling;

[0012] Step 3: After ball milling and mixing, the powder obtained in step 1 is dried;

[0013] Step 4: Place the dried powder into a powder feeder tank of a laser melting deposition system to obtain a dense titanium-based composite material with well-controlled reinforcement distribution and structural uniformity.

[0014] Furthermore, in step 1, the titanium-based powder is made of α+β dual-phase titanium alloy powder with a particle size of 45 to 100 μm.

[0015] Furthermore, in step 1, the particle size of the TiC powder is less than 10 μm; and the volume fraction of the TiC powder is 1% to 5%.

[0016] Furthermore, in step 2, the mass ratio of the stainless steel grinding balls to the mixed powder in step 1 is 2.5 to 4:1; the stainless steel grinding balls are mixed with three different diameters D1, D2, and D3 in the range of 3 to 8 mm; the diameters of the stainless steel grinding balls are D1>D2>D3, and the masses of the stainless steel grinding balls with different diameters meet M D1 <M D2 <M D3 .

[0017] Furthermore, in step 2, the sum of the volumes of the TiC powder, Ti6Al4V powder and stainless steel grinding balls added to the ball mill shall not exceed 2 / 3 of the volume of the ball mill.

[0018] Furthermore, in the ball milling process of step 2, the rotation speed of the ball mill is 180 to 220 r / min. -1 , the ball milling time is 8 to 12 hours.

[0019] Furthermore, in the drying process of step 3, the drying temperature is 100-120° C. and the drying time is 2-3 hours.

[0020] Furthermore, in step 4, the laser power is 1800-2400W, and the scanning speed is 300-900mm·min -1 .

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention provides a method for additive manufacturing and microstructure refinement of a submicron-level in-situ TiC-reinforced titanium-based composite material, in which ultrafine TiC powder particles with a particle size of less than 10 μm are uniformly embedded on the surface of Ti6Al4V spherical powder by a ball milling method, which helps to improve the microstructure uniformity of the laser melt-deposited TiC / Ti6Al4V composite material;

[0023] (2) The present invention provides a method for additive manufacturing and microstructure refinement of a submicron in-situ TiC-reinforced titanium-based composite material, using ultrafine TiC powder with a particle size of less than 10 μm as a carbon source, eliminating undissolved TiC particles during the additive manufacturing process of the TiC / Ti6Al4V composite material, and forming a large number of dispersed submicron in-situ TiC reinforcement phases, which helps to improve the mechanical properties of the composite material;

[0024] (3) The present invention provides a method for additive manufacturing and microstructure refinement of a submicron in-situ TiC-reinforced titanium-based composite material. Ultrafine TiC powder with a particle size of less than 10 μm provides a large number of nucleation points for Ti6Al4V matrix grains, which helps to refine βTi and αTi grains and improve the mechanical properties of the composite material.

[0025] (4) The present invention provides a method for additive manufacturing and microstructure refinement of submicron in-situ TiC-reinforced titanium-based composite materials, which can be used for but not limited to the laser melting deposition preparation process of titanium-based composite materials with Ti6Al4V as the matrix, and can be extended to the field of additive manufacturing of other titanium-based composite materials or metal-based composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process of preparing ultrafine TiC / Ti6Al4V powder by ball milling in Example 1; wherein: 1-Ti6Al4V spherical powder; 2-ultrafine TiC powder; 3-stainless steel ball; 4-ball mill; 5-TiC / Ti6Al4V powder; 6-TiC component in TiC / Ti6Al4V powder; 7-Ti6Al4V component in TiC / Ti6Al4V powder;

[0027] Figure 2 The microstructures of the Ti6Al4V titanium alloy and the submicron TiC / Ti6Al4V composite material in Example 1 show the grain morphologies of TiC, βTi and αTi;

[0028] Figure 3 The microhardness statistics of Ti6Al4V titanium alloy and submicron TiC / Ti6Al4V composite material in Example 1;

[0029] Figure 4The tensile properties test curves of the Ti6Al4V titanium alloy and the submicron TiC / Ti6Al4V composite material in Example 1;

[0030] Figure 5 This is the microstructure of the submicron TiC / Ti6Al4V composite material in Example 2. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings.

[0032] In order to make the technical solution and implementation of the present invention clearer, a further detailed description is given here by taking the preparation of TiC / Ti6Al4V composite material by laser melting deposition as an example.

[0033] The present invention provides a method for additive manufacturing and microstructure refinement of a submicron in-situ TiC-reinforced titanium-based composite material. The method comprises ball-milling and mixing ultrafine TiC powder and Ti6Al4V spherical powder to prepare TiC / Ti6Al4V powder, which is used for LMD to prepare TiC / Ti6Al4V composite materials, so as to achieve complete dissolution of TiC powder, form a submicron-level fine in-situ TiC reinforcement phase, and promote the grain refinement of Ti6Al4V matrix, and finally improve the mechanical properties of TiC / Ti6Al4V composite materials; the specific steps are as follows:

[0034] S1. Ultrafine TiC powder with a particle size of less than 10 μm Xg and spherical Ti6Al4V powder with a particle size of 45 to 100 μm Yg are placed in a ball mill to prepare TiC / Ti6Al4V powder with a TiC volume fraction of a vol.%; the relationship between the mass X of the TiC powder, the mass Y of the Ti6Al4V powder, and the TiC volume fraction a% is: X / Y=aρ TiC / (100-a)ρ Ti6Al4V , where ρ TiC About 4.93g·mm -3 ,ρ Ti6Al4V About 4.51 g·mm -3 , the TiC volume fraction is 1 vol.%~5 vol.%.

[0035] S2, put 2.5 (X + Y) ~ 4 (X + Y) g of stainless steel balls into the ball mill described in S1 (i.e., the ball-to-material ratio is 2.5 ~ 4:1) to mix TiC / Ti6Al4V powder; the stainless steel balls described in S2 are mixed with three different sizes, and the mass ratio of stainless steel balls with different diameters is m (8mm) :m (5mm) :m (3mm) =2:3:5; the sum of the volumes of the TiC powder, Ti6Al4V powder and stainless steel balls added to the ball mill shall not exceed 2 / 3 of the volume of the ball mill;

[0036] S3, ball milling the TiC powder and Ti6Al4V powder described in S1 to prepare TiC / Ti6Al4V powder; the ball milling jar rotates at a speed of 180 to 220 r·min -1 , the ball milling time is 8 to 12 hours.

[0037] S4, drying the TiC / Ti6Al4V powder in S3; the oven insulation temperature is 100-120° C., and the insulation time is 2-3 hours;

[0038] S5. Put the dried TiC / Ti6Al4V powder described in S4 into a powder feeder tank of a laser melting deposition system to prepare a TiC / Ti6Al4V composite material sample.

[0039] Embodiment 1:

[0040] S1. 1.09 g of ultrafine TiC powder with a particle size of less than 10 μm and 98.91 g of Ti6Al4V spherical powder with a particle size of 45 to 100 μm are placed in a ball mill to prepare TiC / Ti6Al4V powder with a TiC volume fraction of 1 vol.%;

[0041] S2, put 300g stainless steel balls into the ball mill described in S1 (ball to material ratio is 3:1), where m (8mm) :m (5mm) :m (3mm) =60g:90g:150g, for mixing TiC / Ti6Al4V powder;

[0042] S3, the TiC powder and Ti6Al4V powder described in S1 are subjected to 200 r·min -1 , ball milling for 12 hours to prepare TiC / Ti6Al4V powder;

[0043] S4, drying the TiC / Ti6Al4V powder described in S3 at 110° C. for 2 h;

[0044] S5. Put the dried TiC / Ti6Al4V powder described in S4 into the powder feeder of the laser melting deposition system to prepare TiC / Ti6Al4V composite material samples, wherein the laser melting deposition process parameters are: laser power 2100 W, scanning speed 600 mm / min.

[0045] Depend on Figure 1 It can be seen that the ultrafine TiC powder is evenly embedded on the surface of Ti6Al4V spherical powder through ball milling mixing;

[0046] Depend on Figure 2It can be seen that compared with the Ti6Al4V alloy prepared by the same process, the TiC / Ti6Al4V composites prepared by adding ultrafine TiC powder all formed submicron-scale in-situ TiC phase, the βTi grains were significantly refined, and the αTi grains were equiaxed.

[0047] Depend on Figure 3 It can be seen that compared with the Ti6Al4V alloy prepared by the same process, the TiC / Ti6Al4V composite prepared by adding ultrafine TiC powder has higher microhardness;

[0048] Depend on Figure 4 It can be seen that compared with the Ti6Al4V alloy prepared by the same process, the TiC / Ti6Al4V composite material prepared by adding ultrafine TiC powder has higher tensile strength.

[0049] Embodiment 2:

[0050] The laser melting deposition process parameters were changed to: laser power 2400 W, scanning speed 450 mm / min; the other steps were the same as in Example 1.

[0051] Depend on Figure 5 It can be seen that submicron-scale in-situ TiC phase is also formed in the TiC / Ti6Al4V composite material after changing the process parameters.

[0052] It can be seen that the method proposed in the present invention can effectively prepare submicron in-situ TiC reinforced titanium-based composite materials, achieve the refinement of βTi grains and αTi grains and improve the mechanical properties.

[0053] The present invention provides a method for additive manufacturing and organization refinement of a submicron in-situ TiC-reinforced titanium-based composite material. Since ultrafine TiC powder particles smaller than 10 μm have poor fluidity, it is difficult to evenly and stably transport them to a molten pool of laser melting deposition directly through a powder feeder. Therefore, the present invention uses a ball milling method to evenly embed ultrafine TiC powder particles with a particle size smaller than 10 μm on the surface of Ti6Al4V spherical powder to prepare an integrated TiC / Ti6Al4V composite powder. At the same time, the uniformity of TiC distribution and the fluidity of the composite powder are improved, large-sized undissolved TiC particles are eliminated in the additive manufacturing process of the TiC / Ti6Al4V composite material, the risk of cracking caused by stress concentration is reduced, and a large number of dispersed submicron in-situ TiC reinforcement phases are formed. These dispersed TiC reinforcement phases can provide a large number of nucleation points for titanium alloy grains, thereby obtaining fine βTi and αTi grains, and improving the mechanical properties of the composite material by using the fine grain strengthening and second phase strengthening principles. The method provided by the present invention can be used for, but not limited to, the laser melting deposition preparation process of titanium-based composite materials with Ti6Al4V as the matrix, and can be extended to the field of additive manufacturing of other titanium-based composite materials or metal-based composite materials.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A submicron in-situ TiC reinforced titanium-based composite material, characterized in that: The composite material comprises a titanium-based alloy and a TiC reinforcement phase; the composite material phases comprise an α+β type dual-phase titanium alloy and a TiC reinforcement phase; the TiC reinforcement phase is dispersed in the titanium-based alloy matrix in the form of short rods or particles, the length of the short rod-shaped TiC reinforcement phase is 0.3 to 1.6 μm, the width is 0.1 to 0.8 μm, and the particle size of the granular TiC reinforcement phase is 0.1 to 1.0 μm.

2. A method for additive manufacturing and microstructure refinement of submicron in-situ TiC reinforced titanium-based composite materials, characterized in that: The following steps are involved: Step 1: Add TiC powder and titanium-based powder into a ball mill; the mass of the TiC powder X, the mass of the titanium-based powder Y, and the volume fraction of the TiC powder a% satisfy the relationship: X / Y = aρ TiC / (100-a)ρ0 Among them, ρ TiC is the density of TiC powder; ρ0 is the density of titanium-based powder; Step 2: Add the grinding balls into the ball mill described in step 1 and perform ball milling; Step 3: After ball milling and mixing, the powder obtained in step 2 is dried; Step 4: placing the dried powder into a powder feeder tank of a laser melting deposition system; the laser melting deposition process parameters are as follows: laser power of 1800-2400 W, scanning speed of 300-900 mm / min, powder feeding rate of 5-15 g / min, to obtain a dense, uniformly distributed reinforcement structure and submicron-level in-situ TiC-reinforced titanium-based composite material.

3. The additive manufacturing and microstructure refinement method of a submicron in-situ TiC reinforced titanium-based composite material according to claim 2, characterized in that: In the step 1, the titanium-based powder is made of α+β dual-phase titanium alloy powder with a particle size of 45 to 100 μm.

4. The additive manufacturing and microstructure refinement method of a submicron in-situ TiC-reinforced titanium-based composite material according to claim 2, characterized in that: In the step 1, the particle size of the TiC powder is 0 to 10 μm; and the volume fraction of the TiC powder is 1% to 5%.

5. The additive manufacturing and microstructure refinement method of a submicron in-situ TiC reinforced titanium-based composite material according to claim 2, characterized in that: In step 2, the mass ratio of the grinding balls to the mixed powder in step 1 is 2.5 to 4:1; the grinding balls are a mixture of three stainless steel balls with different diameters D1, D2, and D3 within a range of 3 to 8 mm; the diameters of the stainless steel grinding balls are D1>D2>D3, and the corresponding masses of the stainless steel grinding balls with different diameters meet M D1 <M D2 <M D3 .

6. The additive manufacturing and microstructure refinement method of a submicron in-situ TiC reinforced titanium-based composite material according to claim 2, characterized in that: In the step 2, the total volume of the TiC powder, Ti6Al4V powder and grinding balls added to the ball mill shall not exceed 2 / 3 of the volume of the ball mill.

7. The additive manufacturing and microstructure refinement method of a submicron in-situ TiC reinforced titanium-based composite material according to claim 2, characterized in that: In the ball milling process of step 2, the rotation speed of the ball mill is 180 to 220 r / min -1 , the ball milling time is 8 to 12 hours.

8. The additive manufacturing and microstructure refinement method of submicron in-situ TiC reinforced titanium-based composite material according to claim 2, characterized in that: The drying process in step 3 has a drying temperature of 100 to 120° C. and a drying time of 2 to 3 hours.

Images