A laser net near-forming TiB2 / Ti-based functionally gradient material and its preparation method

Abstract

The present invention discloses a laser net near forming TiB2 / Ti-based functionally gradient material and a preparation method thereof, belonging to the technical field of composite material preparation. The method for the TiB2 / Ti-based functionally gradient material includes: establishing a three-dimensional data model of the TiB2 / Ti-based functionally gradient material; putting Ti-6Al-4V powder and TiB2 ceramic powder with different mass percentages into the powder mixer of the laser near net forming equipment, sending them out through the powder distributor and the annular laser coaxial powder feeding nozzle, or placing the Ti-6Al-4V powder and the TiB2 ceramic powder in the powder feeders of the laser near net forming equipment respectively, and the powder feeders synchronously transport the Ti-6Al-4V titanium powder and the TiB2 ceramic powder to the powder mixer according to a ratio, and the mixed powder is sent out through the annular laser coaxial powder feeding nozzle. The finished material has a gradient performance from high strength and low plasticity to low plasticity and high strength, is more resistant to heavy load impact, and improves the service life.

Description

Technical Field

[0001] The present invention relates to a laser net near-forming TiB2 / Ti-based functionally graded material and a preparation method thereof, belonging to the technical field of composite material preparation. Background Art

[0002] Traditional methods such as smelting, chemical vapor deposition method, ion spraying method, etc. have a long preparation period, the thickness of the material is limited, and the powder metallurgy method cannot achieve continuous transition of material components, resulting in problems such as uneven distribution of reinforcing phases in the composite material due to composition segregation, which limits the production and application of composite materials.

[0003] Laser additive manufacturing technology can realize the composite of ceramic part materials to improve their damage tolerance, realize the combination of multi-scale structures and multi-materials printing of ceramic parts to broaden their functional application ranges, and realize flexible deployment of the organizational structure of ceramic parts. It has a short production cycle and can be used to process workpieces with complex shapes without molds. It has the characteristics of customization, lightweight, and rapidity, providing a new way for forming composite materials. However, there are interface stress problems caused by the combination of different material interfaces and sudden changes in performance parameters of the composite material, which are prone to cause interface failure and lead to defects such as uneven melting, balling, cracking, and low plasticity of the formed parts.

[0004] Existing additive manufacturing composite material technologies mainly focus on selective laser melting. However, the size of the formed workpieces prepared by this method is limited by the equipment. The volume effect problem of exponentially increasing the single-use amount of raw materials caused by the increase in the workpiece size will greatly increase the powder cost. The laser power of the laser net near-forming technology is large and the forming efficiency is high. The coaxial powder feeding process characteristics determine that its forming size is not limited, alleviating the contradiction between the surface quality and forming efficiency of selective laser melting workpieces and reducing the processing cost. Summary of the Invention

[0005] Aiming at the problems in the preparation of composite materials in the prior art, the purpose of the present invention is to provide a laser net near-forming TiB2 / Ti-based functionally graded material with high impact resistance. The functionally graded material is sequentially divided into three working areas from the outside to the inside: a high-strength area, a transition area, and a high-plasticity area; the height ratios of the high-strength area, the transition area, and the high-plasticity area are 1:2:1; the high-strength area is a 30wt.% TiB2 / Ti-6Al-4V composite material; the transition area is a 22.5wt.% TiB2 / Ti-6Al-4V composite material and a 15wt.% TiB2 / Ti-6Al-4V composite material, with a height ratio of 1:1; the high-plasticity area is a 7.5wt.% TiB2 / Ti-6Al-4V composite material.

[0006] Another object of the present invention is to provide a method for preparing the TiB2 / Ti-based functionally graded material with high impact resistance by laser net shape forming. The method for preparing the TiB2 / Ti-based functionally graded material with high impact resistance by laser net shape forming is as follows: The material forming process should be protected in an argon environment to avoid oxidation and reaction of the printed powder. According to the process requirements, strictly control the laser rate and scanning speed for selective area printing. After completing one selective area, proceed to print the next selective area. In this way, print four selective areas to complete the printing of the entire selective area of the impact-resistant functionally graded material. There are two specific preparation methods:

[0007] The specific steps of the first preparation method are as follows:

[0008] (1) Use modeling software to establish a three-dimensional data model of the TiB2 / Ti-based functionally graded material with high impact resistance, slice and layer the three-dimensional data model, plan the laser scanning path, and configure different metal powder contents in different regions.

[0009] (2) Put Ti-6Al-4V titanium powder and TiB2 ceramic powder into a planetary ball mill for mechanical ball milling in proportion to obtain different uniformly mixed xTiB2 / Ti-6Al-4V composite powders, where x is 7.5wt.%, 15wt.%, 22.5wt.%, 30wt.%.

[0010] (3) Put the uniformly mixed 7.5wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selective area for printing the plastic zone of the functionally graded material.

[0011] (4) Put the uniformly mixed 15wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selective area for printing the transition zone of the functionally graded material.

[0012] (5) Put the uniformly mixed 22.5wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selective area for printing the transition zone of the functionally graded material after mechanical ball milling.

[0013] (6) Put the uniformly mixed 30wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selective area for printing the strength zone of the functionally graded material, where x is 30wt.%.

[0014] The specific steps of the second preparation method are as follows:

[0015] (1) Place Ti-6Al-4V titanium powder and TiB2 ceramic powder in the powder distributor of the laser near-net shaping equipment respectively.

[0016] (2) The powder divider synchronously conveys Ti-6Al-4V titanium powder and TiB2 ceramic powder into the powder mixer in proportion and mixes them evenly to obtain xTiB2 / Ti-6Al-4V mixed powder, where x is 7.5wt.%, 15wt.%, 22.5wt.%, 30wt.%.

[0017] (3) It passes through the powder mixer and is sent out through the annular laser coaxial powder feeding nozzle. At the same time, the laser near-net shaping equipment scans the mixed powder according to the laser scanning path. The mixed powder forms TiB2 / Ti composite material through the processes of rapid melting and rapid solidification, gradually changes the composition ratio, and prepares TiB2 / Ti-based functionally gradient material.

[0018] Preferably, the purity of the Ti-6Al-4V is ≥99.9%, and the purity of the TiB2 powder is ≥99.9%.

[0019] Preferably, the particle size of the Ti-6Al-4V powder is 50 - 200μm, and the particle size of the TiB2 powder is 20 - 100μm.

[0020] Preferably, for the transmission laser scanning path of the laser near-net shaping equipment in Method 2, the specific parameters are: the powder feeding amount is continuously adjustable, ranging from 10 to 24g / min, the powder particle size is 50 - 200μm; the output power of the laser is 50 - 4000W; the spot diameter is Φ1.6mm; the focal length of the focusing lens is 0 - 25mm, and the protective atmosphere is argon, with the atmosphere flow rate being 16 - 20L / h.

[0021] Preferably, the present invention can also use high-speed camera imaging technology to characterize the gradually changing composition and structure of the gradient material in the whole volume, and can accurately detect the forming process and effect of the TiB2 / Ti-based material.

[0022] Preferably, the powder mixer in Method 2 is a carrier gas type powder mixer.

[0023] The laser near-net shaping principle of the present invention: The functionally gradient material is prepared and formed by using the laser near-net shaping technology. Utilizing the infinite stacking and rapid melting and solidification process of the tiny laser molten pool in three-dimensional space, the mixed powder undergoes in-situ reaction under the action of the laser beam, thereby preparing a TiB2 / Ti-based functionally gradient material with a gradient structure and high impact resistance; The laser near-net shaping of the TiB2 / Ti-based functionally gradient material can reduce and overcome the factors of mismatch in the performance between layers and interfaces at the material bonding part, relieve the contradiction that the material strength and toughness cannot be both obtained, realize the integration of structure and function, make the overall structure of the material present new design functions such as high specific strength, high specific stiffness and high temperature resistance, prepare a structural material with good impact resistance with large continuous changes in performance, and at the same time having both toughness and strength, and reduce the plastic deformation and cracking tendency of the TiB2 / Ti-based composite material under service conditions.

[0024] The reactions involved in the present invention include:

[0025] Ti + TiB2 → 2TiB

[0026] Only the Ti element in the Ti-6Al-4V powder undergoes the above in-situ chemical reaction with TiB2.

[0027] Principle of laser net-shape forming of TiB2 / Ti-based functionally graded materials: During the forming process, Ti powder can react in-situ with TiB2 powder to generate a new TiB phase. When a crack propagates to TiB particles after the material is impacted, transgranular fracture occurs and the crack deflects, increasing the crack propagation path, consuming more energy, and improving the toughness of the material. At the same time, the in-situ reaction releases a large amount of heat, which can increase the heat input during the forming process to a certain extent, effectively melting the powder and avoiding the generation of unmelted powder and pores. Meanwhile, the in-situ reaction occurs in the limited space of a tiny molten pool, and its rapid solidification conditions can minimize element segregation during the solidification of the molten pool. In addition, the high flexural strength of the Ti-based material can provide sufficient strength support for the TiB2 / Ti-based functionally graded material, maintaining a high bonding strength between the layers of the functionally graded material. A gradient nanostructure will form between the material layers, and its dual mechanisms of load transfer and multi-scale (micrometer → micro-nanometer → nanometer) interfacial shear coupling can strongly inhibit the interlayer lateral displacement generated by the transverse shear stress wave, significantly weakening the interlayer dissociation tendency, alleviating the accumulation of dynamic damage inside the material, increasing the residence time of the impact body inside the material, reducing and overcoming the factors of mismatch in the interlayer and interfacial properties at the bonding part of traditional composite materials, and mitigating the thermal stress generated by the difference in thermal physical properties of different materials. In addition, defects such as dislocations and stacking faults in the prepared TiB2 / Ti-based functionally graded material will consume more fracture energy during the crack propagation process, comprehensively improving the strength and toughness of the composite material.

[0028] The composite powder of xTiB2 / Ti-6Al-4V according to the present invention, where x is 7.5wt.%, 15wt.%, 22.5wt.%, 30wt.%, has relatively excellent dynamic mechanical properties, can better slow down the impact stress, relieve the stress concentration problem existing at the interface of the composite material, and has better impact resistance.

[0029] Advantages of the present invention

[0030] (1) The method of laser near-net shaping adopted in the present invention can enable the in-situ reaction of Ti powder and TiB2 powder to generate a new TiB phase, improving the strength and toughness of the composite material by causing crack deflection and whisker pulling out; the in-situ reaction occurring under the action of the laser can increase the heat input of the molten pool during laser preparation and forming, making the temperature field distribution in the molten pool more uniform, and avoiding the generation of material defects to a certain extent.

[0031] (2) The preparation process of the present invention can avoid the element segregation phenomenon during the solidification process of the molten pool to the greatest extent under the condition of rapid solidification, so that the impact resistance of the formed functional gradient material is significantly improved.

[0032] (3) The gradient nanocomposite structure formed between the layers of the TiB2 / Ti-based functional gradient material prepared by the present invention can alleviate the contradiction between the impact body and the toughness of the ceramic material, realize the integration of structure and function, and prepare a structural material with large continuous changes in performance and good impact resistance while having both toughness and strength.

[0033] (4) The TiB2 / Ti-based functional gradient material prepared by the present invention has defects such as dislocations and stacking faults, which consume more fracture energy during crack propagation, comprehensively improve the strength and toughness of the composite material, and greatly improve the impact performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of the high impact resistant functional gradient material of the present invention.

[0035] Figure 2 These are different partition diagrams of the high impact resistant functional gradient material described in the present invention.

[0036] Figure 3 This is a process flow chart of the powder feeding section of laser near-net forming of high impact-resistant functional gradient materials in Example 1.

[0037] Figure 4 This is the morphology of the xTiB2 / Ti-6Al-4V (x=30wt.%) composite powder after mechanical ball milling in Example 1.

[0038] Figure 5 This is the powder feeding process flow of embodiment 2 for laser near-net forming of functional gradient material with high impact resistance.

[0039] Figure 6 The raw material morphology diagram for preparing laser near-net-shape high impact resistance functional gradient material in Example 2, including (a) Ti-6Al-4V powder and (b) TiB2 powder. DETAILED DESCRIPTION

[0040] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0041] Example 1

[0042] A method for preparing a laser net-nearly formed TiB2 / Ti-based functionally gradient material (see Figure 3 ), the specific steps are as follows:

[0043] (1) Establish a three-dimensional data model of the TiB2 / Ti-based functionally graded material, use slicing software to slice and layer the three-dimensional data model, and plan the laser scanning path to generate a laser scanning program.

[0044] (2) Put Ti-6Al-4V titanium powder and TiB2 ceramic powder into a planetary ball mill for mechanical ball milling in proportion to obtain a uniformly mixed composite powder of xTiB2 / Ti-6Al-4V (x = 7.5, 15, 22.5, 30 wt.%). Among them, the purity of Ti-6Al-4V powder is ≥99.9%, and the purity of TiB2 powder is ≥99.9% (the powder morphology after ball milling is shown in Figure 4 ).

[0045] (3) Place the mixed powder in the carrier gas powder mixer of the laser near-net shaping equipment, select different areas for printing, and configure different areas with different metal powder contents.

[0046] (4) Put the uniformly mixed composite powder of xTiB2 / Ti-6Al-4V (x = 7.5 wt.%) after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the plastic zone of the functionally graded material.

[0047] (5) Put the uniformly mixed composite powder of xTiB2 / Ti-6Al-4V (x = 15 wt.%) after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the transition zone of the functionally graded material.

[0048] (6) Put the uniformly mixed composite powder of xTiB2 / Ti-6Al-4V (x = 22.5 wt.%) after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the transition zone of the functionally graded material that is uniformly mixed after mechanical ball milling.

[0049] (7) Put the uniformly mixed composite powder of xTiB2 / Ti-6Al-4V (x = 30 wt.%) after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the strength zone of the functionally graded material.

[0050] Example 2:

[0051] A preparation method of a laser net-shape near-formed TiB2 / Ti-based functionally graded material (see Figure 5 ), the specific steps are as follows:

[0052] (1) Establish a three-dimensional data model of the TiB2 / Ti-based functionally graded material, use slicing software to slice and layer the three-dimensional data model, and plan the laser scanning path to generate a laser scanning program.

[0053] (2) Place the Ti-6Al-4V powder and the TiB2 powder into the carrier gas powder mixer of the laser near-net shaping equipment respectively. The purity of the Ti-6Al-4V powder is ≥99.9%, and the purity of the TiB2 powder is ≥99.9% (for the powder morphology, see Figure 6 ).

[0054] (3) Place the Ti-6Al-4V titanium powder and the TiB2 ceramic powder into the powder feeder of the laser near-net shaping equipment respectively. Start the powder feeder and the laser. The powder feeder synchronously conveys the Ti-6Al-4V titanium powder and the TiB2 ceramic powder into the powder mixer in proportion and mixes them evenly to obtain the xTiB2 / Ti-6Al-4V (x = 7.5, 15, 22.5, 30 wt.%) mixed powder. The mixed powder passes through the powder mixer and is sent out through the annular laser coaxial powder feeding nozzle. At the same time, the laser near-net shaping equipment scans the mixed powder according to the laser scanning path. The mixed powder forms the TiB2 / Ti composite material through the processes of rapid melting and rapid solidification. Gradually change the component ratio to prepare the TiB2 / Ti-based functionally graded material. Protect it in a protective atmosphere environment. Strictly control the laser temperature for selective area printing according to the process requirements. Complete one selective area and then proceed to the next selective area for printing. In this way, four selective areas are printed to complete the entire selective area printing of the high impact-resistant functionally graded material, forming a ceramic-reinforced titanium-based functionally graded material with excellent impact resistance; the powder feeding amount is continuously adjustable, with a range of 10 - 24 g / min, the powder particle size is 50 - 200 μm; the output power of the laser is 50 - 4000 W; the spot diameter is Φ1.6 mm; the focal length of the focusing lens is 0 - 25 mm, and the protective atmosphere is argon.

[0055] The result analysis of Examples 1 and 2 is as follows:

[0056] Compared with the conventional TiB2 / Ti-6Al-4V impact-resistant composite materials, the TiB2 / Ti-6Al-4V functionally graded materials are considered to be materials with better protective performance and have good application prospects. At present, there is little research on the impact resistance of such materials, the gradient structure is single, and the overall material distribution is uneven; the TiB2 / Ti-6Al-4V composite functionally graded material prepared by the present invention has a large impact load resistance. Referring to the literature, the yield strength of ordinary TiB2 / Ti-6Al-4V composite materials is 1800 Mpa, while the yield strength of the material prepared by the present invention is expected to increase by 16.6%, reaching 2100-2149 MPa; based on the finite element simulation calculation, the maximum impact stress borne by the traditional TiB2 / Ti-6Al-4V composite material at the beginning of damage under low-speed impact is 1110 MPa, and its impact stress is 3800 MPa, while the maximum impact stress of the TiB2 / Ti-6Al-4V functionally graded material is 1040 Mpa, and its impact stress is 2150 Mpa, and it is expected to reduce the impact force by 6.3% - 43%; the material has many advantages such as high plastic stress at the bottom, can withstand structural loads, good interfacial shear coupling characteristics, and is easy to adhere to the metal surface, and has a small degree of damage and damage range when being impacted; the powder material can be changed according to different working conditions. For example, if the hardness is increased and the cost is reduced, the TiB2 content can be increased in the xTiB2 / Ti-6Al-4V (x ∈ 0-30 wt.%) powder; if the plasticity is increased, the TiB2 content in the plastic zone can be reduced.

Claims

1. A laser net near forming TiB2 / Ti-based functionally gradient material, characterized in that: The functional gradient material is sequentially divided into three working zones from the outside to the inside: a high-strength zone, a transition zone, and a high-plasticity zone; the height ratio of the high-strength zone, the transition zone, and the high-plasticity zone is 1:2:1; the high-strength zone is a 30wt.% TiB2 / Ti-6Al-4V composite material; the transition zone is a 22.5wt.% TiB2 / Ti-6Al-4V composite material and a 15wt.% TiB2 / Ti-6Al-4V composite material, with a height ratio of 1:1; the high-plasticity zone is a 7.5wt.% TiB2 / Ti-6Al-4V composite material.

2. The preparation method of the laser net near forming TiB2 / Ti-based functionally gradient material according to claim 1, characterized in that, Specifically, it includes the following steps: (1) Use modeling software to establish a three-dimensional data model of the TiB2 / Ti-based functional gradient material with high impact resistance, slice and layer the three-dimensional data model, plan the laser scanning path, and configure different metal powder contents in different regions; (2) Put Ti-6Al-4V titanium powder and TiB2 ceramic powder into a planetary ball mill for mechanical ball milling in proportion to obtain different uniformly mixed composite powders of xTiB2 / Ti-6Al-4V, where x is 7.5wt.%, 15wt.%, 22.5wt.%, 30wt.%; (3) Put the uniformly mixed 7.5wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the plastic zone of the gradient material; (4) Put the uniformly mixed 15wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the transition zone of the gradient material; (5) Put the uniformly mixed 22.5wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the transition zone of the gradient material after mechanical ball milling; (6) Put the uniformly mixed 30wt.% TiB2 / Ti-6Al-4V composite powder after mechanical ball milling into the first powder spraying box, and select the corresponding selected area for printing the strength zone of the gradient material, where x is 30wt.%.

3. The preparation method of the laser net near-forming TiB2 / Ti-based functionally gradient material according to claim 1, characterized in that Specifically, it includes the following steps: (1) Place Ti-6Al-4V titanium powder and TiB2 ceramic powder in the powder distributor of the laser near-net shaping equipment respectively; (2) The powder distributor synchronously conveys Ti-6Al-4V titanium powder and TiB2 ceramic powder in proportion to the mixer for uniform mixing to obtain xTiB2 / Ti-6Al-4V mixed powder, where x is 7.5wt.%, 15wt.%, 22.5wt.%, 30wt.%; (3) Send it through the mixer and out through the annular laser coaxial powder feeding nozzle. At the same time, the laser near-net shaping equipment scans the mixed powder according to the laser scanning path. The mixed powder forms a TiB2 / Ti composite material through the processes of rapid melting and rapid solidification, and gradually changes the composition ratio to prepare a TiB2 / Ti-based functional gradient material.

4. The preparation method of the laser net near forming TiB2 / Ti-based functionally gradient material according to claim 2 or 3, characterized in that, The particle size of the Ti-6Al-4V powder is 50 - 200μm, and the particle size of the TiB2 powder is 20 - 100μm.

5. The preparation method of the laser net near-forming TiB2 / Ti-based functionally gradient material according to claim 3, characterized in that, The transmission laser scanning path of the laser near-net shaping equipment, with specific parameters as follows: the powder feeding rate is continuously adjustable, ranging from 10 to 24 g / min, the powder particle size is 50 to 200 μm; the output power of the laser is 50 to 4000 W; the spot diameter is Φ1.6 mm; the focal length of the focusing lens is 0 to 25 mm, and the protective atmosphere is argon.

6. The preparation method of the laser net near-forming TiB2 / Ti-based functionally gradient material according to claim 5, characterized in that, The flow rate of the protective atmosphere is 16 to 20 L / h.

7. The preparation method of the laser net near-forming TiB2 / Ti-based functionally gradient material according to claim 3, characterized in that The powder mixer is a carrier gas type powder mixer.

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