Additive manufacturing high-strength magnesium-based composite material and preparation method thereof

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly relates to an additive manufacturing high-strength magnesium-based composite material and a preparation method thereof, and the additive manufacturing high-strength magnesium-based composite material comprises a matrix made of rare earth magnesium alloy composed of Mg and rare earth, and a reinforcement formed by mixing TiB2 with micron particle size and nano particle size. By adopting the method disclosed by the invention, the high-strength and high-plasticity magnesium-based composite material of which the room-temperature tensile strength is 250-455MPa and the percentage elongation after fracture is 1-10% can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and specifically relates to a laser additively manufactured high-strength magnesium-based composite material and a preparation method thereof. Background Art

[0002] Rare earth magnesium alloys have many excellent comprehensive properties, such as low density, high specific strength and high specific modulus, and are widely used in aerospace, automotive and medical industries. Adding particle reinforcements to rare earth magnesium alloys can not only increase the nucleation core and improve the nucleation rate, but also enrich and pin the grain boundaries at the grain boundaries to prevent grain growth, further improving the strength and modulus of magnesium alloys without affecting the density.

[0003] At present, there are mainly two methods for preparing rare earth magnesium-based composite materials. 1. Traditional casting process: The casting process can produce magnesium-based composite materials with high uniformity of component distribution, but it is generally limited to magnesium-based composite materials with no rare earth or low rare earth content. Magnesium-based composite materials with medium and high rare earth content have poor melt fluidity during the casting process, and a large amount of rare earth elements are segregated during the solidification process, which will seriously deteriorate the mechanical properties. 2. Hot extrusion or rolling molding process: Hot extrusion or rolling molding process can prepare high-strength and high-modulus magnesium-based composite materials by refining the grains. However, the plasticity of medium and high rare earth content magnesium alloy ingots is extremely poor, and it is difficult to carry out further hot extrusion or rolling treatment.

[0004] Additive manufacturing can achieve the preparation of high rare earth content, high performance rare earth magnesium-based composites, but existing research is mostly limited to the research of magnesium-based composites with no rare earth or low rare earth content, and there are no reports on high rare earth content magnesium-based composites. Summary of the invention

[0005] In order to solve the problem of low strength and poor plasticity of medium- and high-rare earth content magnesium-based composite materials obtained by traditional casting technology in the prior art, the present invention provides a magnesium-based composite material with micro-nano mixed TiB2 particles as reinforcement and Mg-Gd-Y-Zr alloy powder as matrix and a laser additive manufacturing method thereof, which is simple and easy to operate. The specific scheme is as follows:

[0006] An additively manufactured high-strength magnesium-based composite material comprises a rare earth magnesium alloy composed of Mg and rare earth as a matrix, and a reinforcement formed by a mixture of micron-sized and nano-sized TiB2; in terms of mass percentage, the reinforcement accounts for 1-5% of the entire composite material; the rare earth accounts for 8-20% of the entire composite material.

[0007] Furthermore, the room temperature tensile strength is 250-455 MPa, and the elongation after break is 1-10%.

[0008] Furthermore, the rare earth includes Gd and Y; in the matrix, the Gd content is 6-18w.t.%, the Y content is 1-3w.t.%, the Zr content is 0.2-1w.t.%, and the balance is Mg.

[0009] Furthermore, in the reinforcement, the mass ratio of micron-sized and nano-sized TiB2 is 0.5-3:1; the micron-sized particle is 1-10 μm, and the nano-sized particle is 50-500 nm.

[0010] A method for preparing the above-mentioned additively manufactured high-strength magnesium-based composite material comprises the following steps:

[0011] S1: raw material powder preparation: preparing rare earth magnesium alloy rods into powder to obtain rare earth magnesium alloy powder;

[0012] S2: powder preparation and powder mixing; vacuum drying the rare earth magnesium alloy powder and nano-sized and micron-sized TiB2 particles, and then mechanically mixing them for 1 to 4 hours to obtain a mixed powder;

[0013] S3: Deposition: under the protection of inert gas, the mixed powder is deposited onto a clean magnesium alloy substrate according to a preset model;

[0014] S4: Heat treatment: subjecting the deposited product to solution aging heat treatment or stress relief annealing heat treatment.

[0015] Furthermore, the magnesium alloy powder described in S1 is prepared by a rotating plasma electrode atomization method or an argon gas atomization method.

[0016] Furthermore, the clean magnesium alloy substrate in S3 is obtained by polishing the magnesium alloy substrate clean with a steel brush and wiping the surface oil with acetone.

[0017] Furthermore, the laser power of the deposition in S3 is 0.5-3KW, the scanning speed is 400-1000mm / min, and the powder feeding rate is 10-50g / min.

[0018] Furthermore, the solution temperature of the solution aging heat treatment in S4 is 400-510° C., the solution time is 0.5-4 h, and the aging temperature is 200-250° C., and the aging time is 4-64 h. The adjustment is made according to the total rare earth content.

[0019] Furthermore, the stress relief annealing heat treatment in S4 is performed at a temperature of 200 to 300° C. and for a time of 4 to 6 hours.

[0020] By adopting the above scheme, the method of the present invention has the following advantages:

[0021] 1. The present invention effectively suppresses the agglomeration and segregation of rare earth atoms and particle reinforcement phases through the extraordinary metallurgical process characteristics of the small molten pool of laser additive manufacturing technology, obtains a two-phase composite material with uniform distribution of particle reinforcement phase, and significantly refines the grains to obtain an alloy material with excellent tensile strength and plasticity.

[0022] 2. The magnesium-based composite material of the present invention has a room temperature tensile strength of 250-455 MPa and a post-break elongation of 1-10%, and has the characteristics of high strength and high plasticity.

[0023] 3. The total rare earth content in the magnesium-based composite material of the present invention can reach an extremely high 8-20%. Under the premise of high rare earth content, the material can still be guaranteed to have excellent mechanical properties.

[0024] 4. The present invention uses reinforcements with micron and nanometer particle sizes to make the distribution between raw materials more uniform, the contact between rare earth and reinforcement more uniform, the contact area larger, inhibit the agglomeration and segregation between rare earth and reinforcement, and improve the mechanical properties of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope photograph of the microstructure of Example 1.

[0026] Figure 2 is the room temperature tensile stress-strain curve of Example 1.

[0027] Figure 3 This is a scanning electron microscope photograph of the microstructure of Example 2.

[0028] Figure 4 This is the room temperature tensile stress-strain curve of Example 2.

[0029] Figure 5 This is a scanning electron microscope photograph of the microstructure of Example 3.

[0030] Figure 6 This is the room temperature tensile stress-strain curve of Example 3. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1:

[0033] S1: Preparation of raw material powder; the components of the rare earth magnesium alloy GW123K include, by mass percentage, Gd: 12.1%, Y: 2.9%, Zr: 0.4%, and Mg: balance; the GW123K rare earth magnesium alloy is made into powder by argon atomization method to obtain rare earth magnesium alloy powder;

[0034] S2: powder preparation and powder mixing; weigh and prepare the rare earth magnesium alloy powder and TiB2 particle powder in a ratio of 95:5, wherein the ratio of nano-sized and micron-sized TiB2 particles is 2:3; fully mix the raw materials through a mixer, vacuum dry the rare earth magnesium alloy powder and nano-sized and micron-sized TiB2 particles, and then mechanically mix them for 2 hours to obtain a mixed powder;

[0035] S3: Deposition; the magnesium alloy substrate was polished clean with a steel brush and the surface oil was wiped with acetone to obtain a clean magnesium alloy substrate; to avoid oxidation of the powder and the alloy, under the protection of inert gas, according to the preset model, the laser power was set to 1.5KW, the scanning speed was 800mm / min, and the powder feeding rate was 15g / min, and the mixed powder was deposited on the clean magnesium alloy substrate;

[0036] S4: heat treatment; setting the solution temperature to 500°C and the solution time to 1.5h; setting the aging temperature to 200°C and the aging time to 24h to obtain a high-strength magnesium-based composite material.

[0037] Depend on Figure 1 It can be seen that the grains of the obtained composite material are relatively small, the material is uniform, and no obvious agglomeration and segregation occur.

[0038] Depend on Figure 2 It can be seen that the room temperature tensile strength of the obtained composite material is 453 MPa, and the elongation after break is 4.1%, which indicates that the composite material prepared by the method of the present invention achieves a good match between high strength and high plasticity.

[0039] Embodiment 2:

[0040] S1: Preparation of raw material powder; the components of the rare earth magnesium alloy GW63K, in terms of mass percentage, include: Gd: 5.9%, Y: 3.1%, Zr: 0.4%, Mg: balance; GW63K rare earth magnesium alloy is made into powder by argon atomization method to obtain rare earth magnesium alloy powder;

[0041] S2: powder preparation and mixing; weigh and prepare the rare earth magnesium alloy powder and TiB2 particle powder in a ratio of 97:3, wherein the nano-sized and micron-sized TiB2 particles each account for half; fully mix the raw materials through a mixer, vacuum dry the rare earth magnesium alloy powder and the nano-sized and micron-sized TiB2 particles, and then mechanically mix them for 1 hour to obtain a mixed powder;

[0042] S3: Deposition; the magnesium alloy substrate was polished clean with a steel brush and the surface oil was wiped with acetone to obtain a clean magnesium alloy substrate; to avoid oxidation of the powder and the alloy, under the protection of inert gas, according to the preset model, the laser power was set to 1KW, the scanning speed was 600mm / min, and the powder feeding rate was 15g / min, and the mixed powder was deposited on the clean magnesium alloy substrate;

[0043] S4: heat treatment; setting the solution temperature to 500°C and the solution time to 1.5h; obtaining a high-strength magnesium-based composite material.

[0044] Depend on Figure 3 It can be seen that the obtained composite material has fine grains, the content of particle phase is slightly reduced, and no obvious agglomeration and segregation are observed.

[0045] Compared with Example 1, in Example 2, the content of the reinforcing phase is reduced from 5% to 3%, and the rare earth content in the rare earth magnesium alloy powder is reduced from 15.4% to 9.0%, accounting for 8.73% of the total, and no aging heat treatment is continued. Figure 4 It can be seen that the room temperature tensile strength of the obtained composite material is 253 MPa, and the elongation after break is 8.9%. The strength is reduced but the plasticity is significantly improved, indicating that the rare earth content and the content of the reinforcing phase, especially the heat treatment process, have a significant effect on the mechanical strength of the material.

[0046] Embodiment 3:

[0047] S1: Preparation of raw material powder; the components of the rare earth magnesium alloy GW183K, in terms of mass percentage, include: Gd: 18.2%, Y: 3.1%, Zr: 0.5%, Mg: balance; GW183K rare earth magnesium alloy is made into powder by argon atomization method to obtain rare earth magnesium alloy powder;

[0048] S2: powder preparation and powder mixing; weigh and prepare the rare earth magnesium alloy powder and TiB2 particle powder in a ratio of 95:5, wherein the ratio of nano-sized and micron-sized TiB2 particles is 3:2; fully mix the raw materials through a mixer, vacuum dry the rare earth magnesium alloy powder and nano-sized and micron-sized TiB2 particles, and then mechanically mix them for 2 hours to obtain a mixed powder;

[0049] S3: Deposition; the magnesium alloy substrate was polished clean with a steel brush and the surface oil was wiped with acetone to obtain a clean magnesium alloy substrate; to avoid oxidation of the powder and the alloy, under the protection of inert gas, according to the preset model, the laser power was set to 1.5KW, the scanning speed was 1000mm / min, and the powder feeding rate was 20g / min, and the mixed powder was deposited on the clean magnesium alloy substrate;

[0050] S4: heat treatment; setting the solution temperature to 500°C and the solution time to 2h; setting the aging temperature to 200°C and the aging time to 20h to obtain a high-strength magnesium-based composite material.

[0051] Depend on Figure 5 It can be seen that the grains of the obtained composite material have only grown a small amount, and the particle phase and rare earth atoms have only slight agglomeration and segregation.

[0052] Compared with Example 1, the rare earth atom content in the rare earth magnesium alloy powder in Example 3 is increased to 21.3%, and the total heat treatment time is shorter. Figure 6 It can be seen that the room temperature tensile strength of the obtained composite material is 424 MPa, and the elongation after break is 1.3%, indicating that the method of the present invention can prepare a rare earth magnesium alloy composite material with a total rare earth content exceeding 20%. Although the plasticity of the material is reduced, it can still achieve a higher strength.

[0053] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. An additively manufactured high-strength magnesium-based composite material, characterized in that: It includes a rare earth magnesium alloy composed of Mg and rare earth as a matrix, and a reinforcement composed of a mixture of micron-sized and nano-sized TiB2; in terms of mass percentage, the reinforcement accounts for 1-5% of the composite material as a whole; the rare earth accounts for 8-20% of the composite material as a whole.

2. The additively manufactured high-strength magnesium-based composite material according to claim 1, characterized in that: The room temperature tensile strength is 250-455 MPa, and the elongation after break is 1-10%.

3. The additively manufactured high-strength magnesium-based composite material according to claim 1, characterized in that: The rare earth includes Gd and Y. In the matrix, the content of Gd is 6-18w.t.%, the content of Y is 1-3w.t.%, the content of Zr is 0.2-1w.t.%, and the balance is Mg.

4. The additively manufactured high-strength magnesium-based composite material according to claim 1, characterized in that: In the reinforcement, the mass ratio of TiB2 with micron particle size and nano particle size is 0.5-3:1, the micron particle size is 1-10 μm, and the nano particle size is 50-500 nm.

5. A method for preparing a high-strength magnesium-based composite material by additive manufacturing according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: raw material powder preparation: preparing rare earth magnesium alloy rods into powder to obtain rare earth magnesium alloy powder; S2: powder preparation and powder mixing; vacuum drying the rare earth magnesium alloy powder and nano-sized and micron-sized TiB2 particles, and then mechanically mixing them for 1 to 4 hours to obtain a mixed powder; S3: Deposition: under the protection of inert gas, the mixed powder is deposited onto a clean magnesium alloy substrate according to a preset model; S4: Heat treatment: the deposited product is subjected to stress relief annealing heat treatment or solution aging heat treatment.

6. The method for preparing a high-strength magnesium-based composite material by additive manufacturing according to claim 5, characterized in that: The magnesium alloy powder described in S1 is prepared by a rotating plasma electrode atomization method or an argon gas atomization method.

7. The method for preparing a high-strength magnesium-based composite material by additive manufacturing according to claim 5, characterized in that: The clean magnesium alloy substrate described in S3 is obtained by grinding the magnesium alloy substrate clean with a steel brush and wiping the surface oil with acetone.

8. The method for preparing a high-strength magnesium-based composite material by additive manufacturing according to claim 5, characterized in that: The laser power of the deposition in S3 is 0.5-3KW, the scanning speed is 400-1000mm / min, and the powder feeding rate is 10-50g / min.

9. The method for preparing a high-strength magnesium-based composite material by additive manufacturing according to claim 5, characterized in that: The solution temperature of the solution aging heat treatment in S4 is 400-510°C, the solution time is 0.5-4h, the aging temperature is 200-250°C, and the aging time is 4-64h.

10. The method for preparing a high-strength magnesium-based composite material by additive manufacturing according to claim 5, characterized in that: The stress relief annealing heat treatment in step S4 is performed at a temperature of 200 to 300° C. for a period of 4 to 6 hours.

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