Method for preparing submicron dispersion reinforced light alloy based on oxygen-induced in-situ laser

Abstract

The invention discloses a method for preparing a submicron dispersion reinforced light alloy based on oxygen-induced in-situ laser, and aims to solve the problems that (Y, Zr) Ox can be used as a reinforcing phase to reinforce light alloys such as aluminum alloys and magnesium alloys, so that the mechanical property of the material is improved, but the problems that the reinforcing phase is agglomerated, the powder fluidity is reduced and the interface bonding is relatively weak are easily caused by directly adding a fine reinforcing phase. According to the method, by regulating and controlling the oxygen content of a cavity in the laser forming process, in-situ generation of a submicron (Y, Zr) Ox reinforcement phase distributed in a dispersed mode in the alloy is induced. And (Y, Zr) Ox separated out in situ can be used as a heterogeneous nucleation point, so that the grain refinement of a matrix is promoted, and fine isometric crystals are formed. And meanwhile, the (Y, Zr) Ox distributed in a dispersed mode can effectively hinder dislocation movement, the dispersion strengthening effect is achieved, and the mechanical property of the alloy is improved.

Description

Technical Field

[0001] The present invention belongs to the field of laser additive manufacturing process innovation, and specifically relates to a method for preparing submicron dispersion-reinforced light alloy based on oxygen-induced in-situ laser. Background Art

[0002] High-strength aluminum alloys, magnesium alloys and other light alloys have the characteristics of low density, high specific strength and good corrosion resistance, and are often used in aerospace, automobile and ship transportation and other fields. Laser additive manufacturing technology has the characteristics of layer-by-layer melting, strong designability and high forming freedom. It can realize the rapid manufacturing of complex parts and provide an effective way for the efficient forming of complex structures of light alloys. The strength of laser additively manufactured light alloys is still difficult to meet the use requirements of harsh environments such as aerospace. At present, premixed micron / nano ceramic particles are mostly used to prepare metal-based composites for light alloy strengthening. However, the difficulty of dispersing fine ceramic particles increases the cost of material preparation, and the interface bonding between the added ceramics and the matrix is ​​weak, which makes the improvement of the mechanical properties of light alloys limited, thus limiting the further development and application of light alloys.

[0003] The in-situ reinforcement phase is formed by in-situ reaction in the laser molten pool. The in-situ reinforcement phase is dispersed and distributed along with the melt flow, and no complex pretreatment such as ball milling and coating is required. The agglomeration problem of the added particles is avoided, and the preparation cost is reduced. The in-situ reinforcement phase and the light alloy matrix react in-situ in the molten pool, and the interface is clean and pollution-free. The bonding strength is much higher than that of physically mixed added particles. Summary of the invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is that the laser additive manufacturing of light alloys such as aluminum alloys and magnesium alloys has problems such as uneven dispersion of the reinforcement phase and weak interface bonding due to the direct addition of the reinforcement phase, resulting in limited improvement in material strength and difficulty in meeting the stringent requirements of the aerospace field for high-performance lightweight materials. A method for preparing submicron dispersion-reinforced light alloys based on oxygen-induced in-situ laser is provided, thereby improving the mechanical properties of laser additive manufacturing light alloys.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing submicron dispersion-reinforced light alloy based on oxygen-induced in-situ laser, comprising the following steps: (1) Establish a 3D solid geometric model of the part, slice the model, plan the laser scanning path, discretize the 3D solid into a series of 2D data, save and import it into the laser powder bed fusion forming equipment; (2) The laser powder bed fusion forming equipment melts and solidifies the light alloy powder layer by layer according to the data imported in step (1) and adjusts the oxygen content in the cavity during the laser forming process, so that the oxygen in the cavity reacts with the Y element and the Zr element in the light alloy to form oxides, and finally forms the target three-dimensional solid part.

[0006] As one option, in step (2), the light alloy powder is an aluminum alloy powder with a Mg content of 4.3-5.1 wt.%, a Y content of 0.80-1.30 wt.%, a Zr content of 0.3-0.7 wt.%, and the balance being Al.

[0007] Preferably, the aluminum alloy powder has a particle size of 16-49 μm.

[0008] Preferably, the oxygen content of the aluminum alloy powder in the cavity during laser forming is 70-150 ppm.

[0009] Preferably, during laser forming of aluminum alloy powder, the laser power used by the laser powder bed fusion forming equipment is 300-400 W and the scanning speed is 700-1100 mm / s.

[0010] As another option, in step (2), the light alloy powder is a magnesium alloy powder, the Y content is 3.0-3.6 wt.%, the total content of rare earth elements Nd and Gd is 2.8-3.3 wt.%, the Zr content is 0.4-0.6 wt.%, and the balance is Mg.

[0011] Preferably, the magnesium alloy powder has a particle size of 23-50 μm.

[0012] Preferably, the oxygen content of the magnesium alloy powder in the cavity during laser forming is 15-40 ppm.

[0013] Preferably, during the laser forming of magnesium alloy powder, the laser power used by the laser powder bed fusion forming equipment is 120-180 W and the scanning speed is 300-500 mm / s.

[0014] Furthermore, the laser forming process of the present invention is as follows: (a) the powder spreading device evenly spreads the powder to be processed on the forming substrate, and the laser beam scans the slicing area layer by layer according to a pre-designed scanning path, so that the powder layer is quickly melted, and the first two-dimensional plane of the part to be formed is obtained after solidification; (b) the computer control system causes the forming substrate to drop a powder layer thickness, and the powder supply cylinder piston rises a certain powder layer thickness, and the powder spreading device re-spreads a layer of powder to be processed, and the high-energy laser beam completes the second layer of powder scanning according to the slicing information to obtain the second two-dimensional plane of the part to be formed; (c) repeat step (b), and the powder to be processed is formed layer by layer until the part to be formed is completed.

[0015] The above parameters are the optimal parameters. According to the characteristics of different aluminum alloys and magnesium alloys in terms of microstructure and properties, the process parameters of the laser additive manufacturing process can be reasonably adjusted and optimized, especially the control of the oxygen content in the cavity during the forming process. Aluminum alloy and magnesium alloy materials with good forming quality and excellent comprehensive properties have been successfully prepared.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) During the laser additive manufacturing process of the present invention, the oxygen content in the cavity during the laser forming process is regulated to induce the in-situ formation of sub-micron (Y, Zr)O x , where x = 1.5 - 2.0. The sub-micron (Y, Zr)O x can serve as heterogeneous nucleation sites, promoting the refinement of the matrix grains and the formation of equiaxed grains, and reducing the tendency of hot cracks; the dispersed (Y, Zr)O x particles hinder the movement of dislocations, improving the strength of the alloy. Finally, light alloys with good forming quality and excellent comprehensive properties are prepared.

[0018] (2) The present invention only needs to simply change the oxygen content in the cavity during the laser additive manufacturing process without damaging its original functions and structures. Only by appropriately adjusting the oxygen content in the cavity on the basis of the existing forming process, the operation is simple, the production cost can be effectively controlled, and the forming quality and mechanical properties of the light alloys prepared by laser additive manufacturing can be improved.

[0019] (3) In the present invention, the laser powder bed fusion technology is used to prepare light alloys, shortening the production cycle, improving the production efficiency of products, and almost no subsequent machining treatment is required to form parts with complex geometric shapes. Description of the Drawings

[0020] The following further specific description of the present invention will be made in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0021] Figure 1 It is the OM diagram of the magnesium alloy prepared by laser powder bed fusion in Example 1.

[0022] Figure 2 It is the SEM diagram of the magnesium alloy prepared by laser powder bed fusion in Example 1.

[0023] Figure 3 It is the XRD pattern of the magnesium alloy prepared by laser powder bed fusion in Example 1.

[0024] Figure 4 It is the OM diagram of the aluminum alloy prepared by laser powder bed fusion in Example 2.

[0025] Figure 5 OM image of aluminum alloy prepared by laser powder bed fusion in Comparative Example 1.

[0026] Figure 6 OM image of aluminum alloy prepared by laser powder bed fusion in Comparative Example 2.

[0027] Figure 7 For Comparative Example 3, SEM image of Y 2 O 3 / Mg-based composite powder. Specific embodiments

[0028] The present invention can be better understood according to the following embodiments.

[0029] In the following embodiments, in the aluminum alloy powder, the Mg content is 4.3 - 5.1 wt.%, the Y content is 0.80 - 1.30 wt.%, the Zr content is 0.3 - 0.7 wt.%, the balance is Al, and the particle size is 16 - 49 μm. In the magnesium alloy powder, the Y content is 3.0 - 3.6 wt.%, the total content of rare earth elements Nd and Gd is 2.8 - 3.3 wt.%, the Zr content is 0.4 - 0.6 wt.%, the balance is Mg, and the particle size is 23 - 50 μm.

[0030] The preparation method of the present invention for oxygen-induced in-situ laser preparation of submicron dispersion-strengthened light alloys uses Y 2 O 3 or ZrO 2 which can be directly added as a reinforcing phase to aluminum alloys and magnesium alloys to improve the mechanical properties of the materials. However, directly adding fine oxide reinforcing phases easily leads to problems such as agglomeration of the reinforcing phase, weak interfacial bonding, and limited performance improvement. The present invention induces in-situ generation of submicron (Y, Zr)O x in the alloy by regulating the oxygen content in the cavity during the laser forming process, which is dispersed in the matrix and can serve as heterogeneous nucleation sites, promoting the refinement of the matrix grains and the formation of fine equiaxed grains, and reducing the tendency of solidification cracks in high-strength aluminum alloys and magnesium alloys. The finely dispersed oxides can hinder the movement of dislocations, improve the strength of the alloy, and ultimately achieve the purpose of improving the forming quality and mechanical properties of the alloy. Example 1

[0031] (1) Establish a three-dimensional solid geometric model of the target part in the computer, perform layer slicing on the three-dimensional solid model, and set the laser scanning path. The laser process parameters are set as the laser power of 150 W and the scanning speed of 400 mm / s.

[0032] (2) Laser powder bed fusion forming process: (a) Control the oxygen content in the chamber at 15 - 40 ppm. The powder spreading device evenly spreads the powder to be processed on the forming substrate. The laser beam scans the sliced area layer by layer according to the pre-designed scanning path, causing the powder layer to rapidly melt / solidify, thereby obtaining the first two-dimensional plane of the part to be formed; (b) The computer control system lowers the forming substrate by one powder layer thickness, while the piston of the powder supply cylinder rises by a certain powder layer thickness. The powder spreading device re-lays a layer of powder to be processed, and the high-energy laser beam completes the scanning of the second layer of powder according to the slice information to obtain the second two-dimensional plane of the part to be formed; (c) Repeat step (b) until the powder to be processed is formed layer by layer until the part to be formed is processed.

[0033] (3) After cooling, take out the forming substrate from the equipment, and use wire cutting process to separate the part from the substrate to obtain a magnesium alloy part. Polish, polish and corrode the magnesium alloy bulk specimen according to the standard metallographic specimen preparation method. No solidification cracks were observed in the magnesium alloy prepared by laser powder bed fusion, only a small amount of pores ( Figure 1 ) were observed, and the relative density was 99.8%. It can be seen from Figure 2 that white submicron particles uniformly distributed in the laser-formed magnesium alloy matrix, enriched with Y, Zr, and O elements, can be determined as in-situ generated (Y, Zr)O x , where x = 1.5 - 2.0. After XRD phase analysis ( Figure 3 ), the diffraction peaks of the oxide were identified, corresponding to the precipitation of (Y, Zr)O x in the matrix. The tensile properties of the prepared standard tensile specimens were tested, and the tensile strength was 341 MPa. Example 2

[0034] (1) Establish a three-dimensional solid geometric model of the target part in the computer, slice the three-dimensional solid model, and set the laser scanning path. The laser process parameters are set as laser power of 350 W and scanning speed of 900 mm / s.

[0035] (2) Laser powder bed fusion forming process: (a) Control the oxygen content in the chamber at 70 - 150 ppm. The powder spreading device evenly spreads the powder to be processed on the forming substrate. The laser beam scans the sliced area layer by layer according to the pre-designed scanning path, causing the powder layer to rapidly melt / solidify, thereby obtaining the first two-dimensional plane of the part to be formed; (b) The computer control system lowers the forming substrate by one powder layer thickness, while the piston of the powder supply cylinder rises by a certain powder layer thickness. The powder spreading device re-lays a layer of powder to be processed, and the high-energy laser beam completes the scanning of the second layer of powder according to the slice information to obtain the second two-dimensional plane of the part to be formed; (c) Repeat step (b) until the powder to be processed is formed layer by layer until the part to be formed is processed.

[0036] (3) After cooling, take out the formed substrate from the equipment, and use wire cutting process to separate the parts from the substrate to obtain aluminum alloy parts. Polish, polish and corrode the aluminum alloy bulk specimen according to the standard metallographic specimen preparation method. The formed quality of the aluminum alloy prepared by laser powder bed fusion is relatively high, and only a small amount of pores ( Figure 4 ) are observed, and the relative density is 99.7%. The laser-formed aluminum alloy matrix forms uniformly distributed submicron (Y, Zr)O x , where x = 1.5 - 2.0. Tensile property tests are carried out on the prepared standard tensile specimens, and the tensile strength is 425 MPa. Example 3

[0037] (1) Establish a three-dimensional solid geometric model of the target part in the computer, perform layer slicing on the three-dimensional solid model, and set the laser scanning path. The laser process parameters are set as laser power of 400 W and scanning speed of 1000 mm / s.

[0038] (2) Laser powder bed fusion forming process: (a) Control the oxygen content in the cavity to be 70 - 150 ppm. The powder spreading device evenly spreads the powder to be processed on the forming substrate, and the laser beam scans the sliced area layer by layer according to the pre-designed scanning path, causing the powder layer to rapidly melt / solidify, thereby obtaining the first two-dimensional plane of the part to be formed; (b) The computer control system makes the forming substrate descend by a powder layer thickness, while the piston of the powder supply cylinder rises by a certain powder layer thickness. The powder spreading device re-lays a layer of powder to be processed, and the high-energy laser beam completes the scanning of the second layer of powder according to the slicing information to obtain the second two-dimensional plane of the part to be formed; (c) Repeat step (b), and the powder to be processed is formed layer by layer until the part to be formed is processed.

[0039] (3) After cooling, take out the formed substrate from the equipment, and use wire cutting process to separate the parts from the substrate to obtain aluminum alloy parts. Polish, polish and corrode the aluminum alloy bulk specimen according to the standard metallographic specimen preparation method. The pores of the aluminum alloy prepared by laser powder bed fusion slightly increase, and the relative density drops to 99.5%. The uniformly distributed submicron oxide particles in the laser-formed aluminum alloy matrix also increase, and the strengthening effect is improved. Tensile property tests are carried out on the prepared standard tensile specimens, and the tensile strength is 428 MPa.

[0040] It can be seen from Examples 1, 2, and 3 that by regulating the oxygen content and process parameters in the cavity during laser forming, in-situ generation of submicron (Y, Zr)O in the alloy is induced x, where x = 1.5 - 2.0, is dispersed in the matrix, which can reduce the tendency of solidification crack formation in high-strength aluminum alloys and magnesium alloys. The finely dispersed oxides can hinder the movement of dislocations, increase the strength of the alloy, and ultimately achieve the purpose of improving the forming quality and mechanical properties of the alloy. Comparative Example 1

[0041] This comparative example has the same steps and laser process parameters as Example 2, except that the oxygen content in the cavity is below 20 ppm. In this comparative example, the aluminum alloy bulk specimen was polished, polished, and corroded according to the standard metallographic specimen preparation method. A small amount of microcracks were observed in the aluminum alloy prepared by laser powder bed fusion ( Figure 5 ), and it still had a high density of 99.6%. Since the oxygen content was always controlled below 20 ppm, no oxide formation was observed in the sample. In this case, the promoting effect of oxides on grain refinement and the formation of equiaxed grains was weakened, so a small amount of microcracks were formed in the laser-formed aluminum alloy. At the same time, the dispersion strengthening effect of the fine oxides on the matrix was weakened, and the tensile strength of the laser-formed aluminum alloy was only 378 MPa. This is because the microcracks can act as crack sources during the tensile process to promote the generation and propagation of cracks, causing early fracture failure of the material. Comparative Example 2

[0042] This comparative example has the same steps as Example 2, except that the oxygen content in the cavity is greater than 400 ppm. Since the oxygen content in the cavity was controlled at a high level, the aluminum alloy was over-oxidized, and a dense oxide film formed on the surface of the molten aluminum alloy powder, significantly reducing the wetting and spreading effect of the melt and increasing the porosity ( Figure 6 ), resulting in a decrease in the density of the laser-formed aluminum alloy to 96.3%. Due to the excessive oxygen content in the cavity, the oxides in the laser-formed aluminum alloy increased in number and size, and some of them aggregated. The strengthening effect of these large-sized brittle oxides was significantly weakened, and the tensile strength of the material did not change significantly, being 413 MPa. Comparative Example 3

[0043] This comparative example has the same steps as Example 1, except that sub-micron Y 2 O 3 ceramic particles were directly added to the alloy powder as the reinforcing phase. In this comparative example, due to the van der Waals force, during the powder preparation process, the sub-micron oxide ceramic particles agglomerated ( Figure 7 ), making it difficult to distribute evenly on the surface of the alloy powder. During the laser forming process, these oxides did not completely melt and were still difficult to disperse evenly in the matrix, significantly reducing the strengthening effect of the oxides on the alloy.

[0044] The present invention discloses a method for preparing submicron dispersion-strengthened light alloys based on oxygen-induced in-situ laser. The above only expresses several preferred embodiments of the present invention, and its description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser, characterized in that: The steps include: (1) Establish a 3D solid geometric model of the part, slice the model, plan the laser scanning path, discretize the 3D solid into a series of 2D data, save and import it into the laser powder bed fusion forming equipment; (2) The laser powder bed fusion forming equipment melts and solidifies the light alloy powder layer by layer according to the data imported in step (1) and adjusts the oxygen content in the cavity during the laser forming process, so that the oxygen in the cavity reacts with the Y element and the Zr element in the light alloy to form oxides, and finally forms the target three-dimensional solid part.

2. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser preparation according to claim 1 is characterized in that: In step (2), the light alloy powder is an aluminum alloy powder, with a Mg content of 4.3-5.1 wt.%, a Y content of 0.80-1.30 wt.%, a Zr content of 0.3-0.7 wt.%, and the balance being Al.

3. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 2 is characterized in that: The aluminum alloy powder has a particle size of 16-49 μm.

4. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 1, characterized in that: In step (2), the light alloy powder is a magnesium alloy powder, wherein the Y content is 3.0-3.6 wt.%, the total content of rare earth elements Nd and Gd is 2.8-3.3 wt.%, the Zr content is 0.4-0.6 wt.%, and the balance is Mg.

5. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 4 is characterized in that: The magnesium alloy powder has a particle size of 23-50 μm.

6. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 2, characterized in that: The oxygen content in the cavity during laser forming of aluminum alloy is 70~150 ppm.

7. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 4 is characterized in that: The oxygen content in the cavity during magnesium alloy laser forming is 15~40 ppm.

8. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 2, characterized in that: In step (2), during the laser forming of the aluminum alloy, the laser power used by the laser powder bed fusion forming equipment is 300-400 W and the scanning speed is 700-1100 mm / s.

9. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 4, characterized in that: In step (2), during the laser forming of the magnesium alloy, the laser power used by the laser powder bed fusion forming equipment is 120-180 W and the scanning speed is 300-500 mm / s.

10. The method for preparing submicron dispersion-enhanced light alloy based on oxygen-induced in-situ laser according to claim 1, characterized in that: Laser forming process: (a) The powder spreading device evenly spreads the powder to be processed on the forming substrate, and the laser beam scans the slicing area layer by layer according to the pre-designed scanning path, so that the powder layer melts quickly and obtains the first two-dimensional plane of the part to be formed after solidification; (b) The computer control system makes the forming substrate drop by a powder layer thickness, and the piston of the powder supply cylinder rises a certain powder layer thickness. The powder spreading device re-spreads a layer of powder to be processed, and the high-energy laser beam completes the second layer of powder scanning according to the slicing information to obtain the second two-dimensional plane of the part to be formed; (c) Repeat step (b), and the powder to be processed is formed layer by layer until the part to be formed is completed.

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