CN111500905A - A kind of nano-ceramic modified high silicon aluminum alloy based on selective laser melting - Google Patents

Abstract

The invention discloses a modified high-silicon aluminum alloy based on selective laser melting of nano-ceramics, adopts a high-energy ball milling process to prepare nano-titanium diboride ceramic powder, and then separates the high-silicon aluminum alloy powder and nano-titanium diboride ceramic powder through a ball mill. Mix uniformly under the protection of inert gas to obtain nano-ceramic modified high-silicon aluminum alloy powder, and use selective laser melting and forming equipment to fuse the nano-ceramic modified high-silicon aluminum alloy powder layer by layer to form the target parts to be created. In the method of the invention, during the solidification process of the nano-titanium diboride modified high-silicon aluminum alloy melt, the nano-titanium diboride acts as a heterogeneous nucleation point, which hinders the growth of the precipitation silicon phase at the front of the solidification liquid phase, and makes the star-shaped primary silicon phase grow. Remarkably reduced, the edges and corners of the polygonal primary silicon phase are passivated, the edges are smooth, and the fibrous eutectic silicon structure is also significantly refined, which can effectively adjust the size, morphology and distribution of the primary silicon phase and eutectic silicon phase, and significantly improve the high silicon content. Mechanical properties of aluminum alloys.

Description

A kind of nano-ceramic modified high silicon aluminum alloy based on selective laser melting

technical field

The invention belongs to the field of high-silicon aluminum alloy materials, and in particular, the invention relates to a nano-ceramic modified high-silicon aluminum alloy based on selective laser melting.

Background technique

High-silicon aluminum alloys have the advantages of low density, high strength, good corrosion resistance, and low thermal expansion coefficient. Different from hypoeutectic and eutectic aluminum-silicon alloys, the silicon phase in the hypereutectic high-silicon aluminum alloy structure exists in two forms: primary silicon phase and eutectic silicon phase. With the increase of silicon content, the wear resistance and heat resistance of aluminum alloys are improved, but the size, morphology and distribution of primary silicon and eutectic silicon phases in the microstructure of the formed parts also have a significant effect on their mechanical properties. , especially in the traditional casting structure, the coarse lath-shaped primary crystal silicon phase seriously splits the continuity of the structure, and it is easy to generate stress concentration in the corners and sharp parts of the silicon phase and increase the crack initiation particles, which ultimately reduces the strength and elongation of the material. . Based on this, the nano-ceramic phase is added to the aluminum matrix to modify the structure, increase the heterogeneous nucleation particles during the solidification of the aluminum melt, and effectively adjust the morphology, size and distribution of the primary silicon phase and the eutectic silicon phase, and finally achieve an improved Material mechanical properties purpose. Among the common ceramic phases for aluminum alloy modification, titanium diboride has higher elastic modulus (560GPa) and hardness (35GPa), excellent heat resistance and wear resistance, and good wettability with aluminum matrix. , which makes titanium diboride an ideal structural modification material in high-silicon aluminum alloys.

From the point of view of processing technology, in order to achieve the purpose of refining grains, uniform structure and improving the mechanical properties of materials, rapid solidification methods, such as spray deposition and powder metallurgy, are usually used in the preparation of hypereutectic high-silicon aluminum alloys. The equipment and process are relatively complex, and the production cost is high, while the internal porosity of the parts made by the powder metallurgy process is high, and it is difficult to form parts with complex structures. As a new type of rapid solidification technology, selective laser melting technology is based on the local forming principle of layered manufacturing and accumulation and superposition, and according to the three-dimensional part model of computer-aided design, using high-energy laser heat source to select metal powder materials in a layer-by-layer manner. It can realize direct and precise manufacturing of complex structural metal components. In the process of selective laser melting and forming, the interaction time between the laser heat source and the pre-laid powder layer is extremely short, only about 0.5-20ms, so the molten material has a relatively high cooling rate, which is beneficial for the grain refinement of high-silicon aluminum alloys. conditions, and the powder particles are completely melted under the action of the high-energy laser beam, so that the metallurgical bonding between adjacent scanning tracks or layers is good, the forming quality of high-silicon aluminum alloy parts is improved, and the mechanical properties of the material are improved. Selective laser melting technology breaks through the constraints of traditional manufacturing processes, conforms to the "near net shape" design concept, effectively shortens the development and manufacturing cycle of new products, improves production efficiency, and can form parts with complex geometric structures, so the selective laser is used. The preparation of high-silicon aluminum alloy materials by melting technology has great potential for development.

SUMMARY OF THE INVENTION

In view of the problems existing in the current high-silicon aluminum alloy material preparation technology, and at the same time to meet the improvement requirements proposed above, the present invention provides a nano-ceramic modified high-silicon aluminum alloy based on selective laser melting technology, so as to significantly improve the high-silicon aluminum alloy. mechanical properties.

For achieving the above object, the technical scheme adopted by the present invention is as follows:

A modified high-silicon aluminum alloy based on selective laser melting of nano-ceramics, comprising the following steps:

(1) Nano-TiB ₂ ceramic powder was prepared by Pulverisette 6 single-pot planetary high-energy ball milling process;

(2) mixing the Al-20Si alloy powder with the nano-TiB ₂ ceramic powder prepared in step (1) through a QM series planetary ball mill under the protection of an inert gas to obtain a nano-TiB ₂ /Al-20Si composite powder;

(3) Use Soildworks software in the computer to establish a three-dimensional solid geometric model of the target part, then use Magics software to slice the model and plan the laser scanning path, discretize the three-dimensional solid into a series of two-dimensional data, save this file and Imported into the selective laser melting forming equipment;

(4) Selective laser melting and forming equipment melts the nano-TiB ₂ /Al-20Si composite powder in step (2) layer by layer according to the file saved in step (3) to form the target part to be created.

Preferably, in step (1), the raw material used is a polygonal micron TiB ₂ powder with a particle size distribution range of 1-5 μm and a purity greater than 99.9%.

Preferably, in step (1), the rotational speed of the high-energy ball milling is 250-300 rpm, and the ball-milling time is 20-25 h.

Preferably, in step (1), the particle size of the nano-TiB ₂ ceramic powder prepared by high-energy ball milling is 40-200 nm.

Preferably, in step (2), the Al-20Si alloy powder has a particle size distribution range of 12-31 μm, wherein the silicon content is 19.2-20 wt.%, the iron content is 0.05-0.15%, and the balance is aluminum.

Preferably, in step (2), the content of nano-TiB ₂ particles in the TiB ₂ /Al-20Si composite powder is 1-10 wt.%, most preferably 2 wt.%, if the content of nano-TiB ₂ particles is too low, its modified The effect is not good; if the content of nano-TiB ₂ particles is too high, the quality of laser forming will be reduced, which will affect the performance of composite materials.

Specifically, in step (2), the ball mill adopts QM series planetary ball mill to perform ball milling and powder mixing operation. This process adopts a ceramic tank, and the ball milling medium is ceramic grinding balls with diameters of 6 mm and 8 mm. The ball milling process parameters are set as: the ratio of ball to material is 2:1; at the same time, in order to prevent the temperature in the ball milling tank from being too high, the equipment operation mode during ball milling is selected as interval type, that is, the air cooling is suspended for 5 minutes after every 15 minutes of operation of the equipment. The ball milling process is required to be carried out under the protection of inert gas to prevent the aluminum alloy powder from being oxidized or contaminated.

Preferably, in step (2), the rotation speed of the ball milling used is 150-250 rpm, and the ball milling time is 3-5 h.

Specifically, step (4) uses a SLM-150 type selective laser melting equipment, which mainly includes a YLR-500 type fiber laser, a laser forming chamber, an automatic powder spreading system, a protective atmosphere device, a computer control circuit system and a cooling cycle system. Before forming, the sandblasted aluminum substrate is fixed on the worktable of the selective laser melting forming equipment and leveled, and then the forming cavity is sealed by a sealing device, evacuated and introduced into an inert gas protective atmosphere. The typical selective laser melting forming process 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 line by line according to the pre-designed scanning path, so that the powder layer rapidly melts- Solidification, thereby obtaining the first two-dimensional plane of the part; (b) the computer control system lowers the forming substrate by one powder layer thickness, on the contrary, makes the piston of the powder supply cylinder rise one powder layer thickness, and the powder spreading device re-lays a layer to be prepared. To process the powder, the laser beam scans the second powder layer according to the slicing information to obtain the second two-dimensional plane of the part; (c) Repeat the above steps, and the powder to be processed is formed layer by layer until the part is processed. Preferably, in step (4), the laser scanning speed of the selected area laser melting forming is 1800-2200 mm/s, the laser power is 450 W, the scanning distance is 50 μm, and the powder thickness is 50 μm, and the partitioned island scanning strategy is adopted. Determined after process optimization.

According to the structure and performance characteristics of high-silicon aluminum alloy materials, high-silicon aluminum alloy structural modifiers can be reasonably selected and appropriately added, and the preparation method combined with the cutting-edge laser additive manufacturing technology can effectively adjust the morphology of the silicon phase. , size and distribution state, and successfully prepared high-silicon aluminum alloy materials with excellent comprehensive properties.

Beneficial effects:

(1) In the present invention, the micron titanium diboride powder is used as the raw material, and the nano-TiB ₂ powder is prepared by the high-energy ball milling process, and the obtained nano-TiB ₂ and the Al-20Si powder are mixed and placed in a QM series planetary ball mill Ball milling and powder mixing are carried out in the process of ball milling, and the TiB ₂ /Al-20Si composite powder with uniform distribution of nano-TiB ₂ and good flow performance is finally obtained through the optimization of the ball milling process, which is suitable for selective laser melting and forming. The process is simple and cost-effective.

(2) Compared with the Al-20Si alloy powder, the laser absorption rate of the nano-TiB ₂ /Al-20Si powder is significantly increased, and the laser energy input of the powder bed increases during the selective laser melting forming process, so that the powder layer can be fully melted , so as to improve the forming quality of the parts.

(3) The present invention uses the selective laser melting technology to prepare high-silicon aluminum alloy materials, which not only shortens the production cycle, improves product production efficiency, but also can form parts with complex geometric shapes almost without subsequent machining processing. The cooling rate of the molten pool during selective laser melting and forming is extremely high, up to 10 ³ ～ 10 ⁸ K/s, which increases the supercooling degree of the high-silicon aluminum alloy melt, avoids the formation of coarse dendrites in the traditional processing technology, and improves the quality of the parts. mechanical properties.

(4) During the solidification process of TiB ₂ /Al-20Si melt, nano-TiB ₂ increases the heterogeneous nucleation points of silicon phase precipitation, hinders the growth of the precipitation silicon phase at the front of the solidification liquid phase, and reduces the star-shaped primary silicon phase obviously. The polygonal primary silicon phase has passivated edges and smooth edges, and the fibrous eutectic silicon structure is also significantly refined. The invention can effectively adjust the morphology and distribution state of the primary silicon phase and the eutectic silicon phase through the refinement and modification of the primary silicon phase and the eutectic silicon phase in the high _- silicon aluminum alloy structure, and significantly improve the Al- Mechanical properties of 20Si.

(5) The optimal laser power for selective laser melting and forming of high-silicon aluminum alloys was obtained through the prior process optimization, and the laser energy density was adjusted by changing the laser scanning speed. With the change of the laser energy input of the powder bed, the thermodynamic and dynamic characteristics of the molten pool formed by the interaction between the laser and the powder bed also change. By reasonably selecting the laser process parameters and adjusting the laser energy input, metallurgical defects such as spheroidization, pores and cracks can be reduced. Produced and obtained TiB ₂ /Al-20Si composite material with dense organization and good comprehensive properties.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the advantages of other aspects of the present invention will become clearer.

FIG. 1 is a TEM image of the nano-TiB ₂ prepared by the high-energy ball milling process in Example 1.

FIG. 2 is an SEM image of the TiB ₂ /Al-20Si composite powder prepared in Example 3. FIG.

FIG. 3 is a real photo of the sample of selective laser melting nano-TiB ₂ /Al-20Si composite material prepared in Example 3. FIG.

FIG. 4 is an SEM image of a sample of nano-TiB ₂ /Al-20Si composite material formed by selective laser melting in Example 3. FIG.

5 is a SEM image of the Al-20Si alloy sample formed by selective laser melting in Comparative Example 1.

FIG. 6 is the SEM image of the micro-TiB ₂ /AlSi10Mg composite sample formed by selective laser melting in Comparative Example 3. FIG.

Detailed ways

The present invention can be better understood from the following examples.

In the following examples, the used TiB ₂ powder raw material is polygonal micron TiB ₂ powder with a particle size distribution range of 1-5 μm and a purity greater than 99.9%. The particle size of the Al-20Si alloy powder is 12-31 μm, the silicon content is 19.2-20 wt.%, the iron content is 0.11%, and the balance is aluminum.

Example 1

(1) Nano-TiB ₂ ceramic powder was prepared by high-energy ball milling process. The high-energy ball-milling equipment was a Pulverisette 6 single-tank planetary high-energy ball mill. The ball-milling medium in the stainless steel ball mill was stainless steel balls with diameters of 6mm and 20mm, and the ball-to-material ratio was 10 :1. When the equipment is working, the stainless steel ball mill jar rotates at a fixed speed around its own axis, and at the same time revolves around a fixed axis parallel to its own axis. The ball milling speed is set to 250rpm, and the ball milling time is 25h. During the high-energy ball milling process, the balls and ceramic powder are ground The collision and impact between the two particles break the ceramic phase particles, thereby obtaining nano-TiB ₂ ceramic powder. The TEM image of the nano _- TiB2 powder prepared by this high-energy ball milling process is shown in Fig. 1.

(2) The nano-TiB ₂ ceramic powder prepared in step (1) is added to the Al-20Si alloy powder in a proportion of 1 wt. %, and the TiB ₂ /Al-20Si composite powder is prepared by ball milling and powder mixing. The QM series planetary ball mill is used for ball milling and powder mixing operation. The process uses a ceramic tank, and the ball milling medium is ceramic grinding balls with a diameter of 6mm and 8mm. The ball milling process parameters are set as: the ratio of ball to material is 2:1, the ball milling speed is 150rpm, and the ball milling time is 5h. At the same time, in order to prevent the temperature in the ball milling tank from being too high, the operation mode of the equipment during ball milling is the interval type, that is, the air cooling is suspended for 5 minutes after every 15 minutes of operation of the equipment. The ball milling process requires argon protection to prevent the aluminum alloy powder from being oxidized or contaminated.

(3) Modeling and slicing of target parts

Use Soildworks software in the computer to establish a 3D solid geometric model of the target part, and then use Magics software to perform layered slicing and scanning path planning for the 3D solid model, discretize the 3D solid into a series of 2D data, save this file and import it into the selection laser melting and forming equipment. The laser process parameters are set as follows: the laser power is 450W, the laser scanning speed is 1800mm/s, the scanning spacing is 50μm, the powder thickness is 50μm, the partitioned island scanning strategy is adopted, and the rotation angle of the laser scanning direction of the adjacent layers is 37 μm. °.

(4) Selective laser melting forming process

The nano-ceramic modified high-silicon aluminum alloy powder obtained in step (2) is used for selective laser melting forming. SLM-150 type selective laser melting equipment is used, the system mainly includes YLR-500 type fiber laser, laser forming chamber, automatic powder spreading system, protective atmosphere device, computer control circuit system and cooling circulation system. Before forming, the sandblasted aluminum substrate was fixed on the table of the selective laser melting forming equipment and leveled, and then the forming cavity was sealed by a sealing device, evacuated and passed into an argon protective atmosphere (the purity of argon is 99.999 %, the outlet pressure is 30mbar), to ensure that the _O2 content in the forming chamber is less than 10ppm. The typical selective laser melting forming process 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 line by line according to the pre-designed scanning path, so that the powder layer rapidly melts- Solidification, thereby obtaining the first two-dimensional plane of the part; (b) the computer control system lowers the forming substrate by one powder layer thickness, on the contrary, makes the piston of the powder supply cylinder rise one powder layer thickness, and the powder spreading device re-lays a layer to be prepared. To process the powder, the laser beam scans the second powder layer according to the slicing information to obtain the second two-dimensional plane of the part; (c) Repeat the above steps, and the powder to be processed is formed layer by layer until the part is processed.

After cooling, the forming substrate was taken out from the equipment, and the parts were separated from the substrate by a wire cutting process to obtain a nano-titanium diboride modified high-silicon aluminum alloy sample. According to the standard metallographic sample preparation method, the nano-titanium diboride modified high silicon aluminum alloy bulk sample was ground, polished and etched.

The obtained TiB ₂ /Al-20Si standard tensile sample is subjected to room temperature tensile test, and its tensile strength can reach 409MPa.

Example 2

(1) Nano-TiB ₂ ceramic powder was prepared by high-energy ball milling process. The high-energy ball-milling equipment was a Pulverisette 6 single-tank planetary high-energy ball mill. The ball-milling medium in the stainless steel ball mill was stainless steel balls with diameters of 6mm and 20mm, and the ball-to-material ratio was 10 :1. When the equipment is working, the stainless steel ball mill rotates at a fixed speed around its own axis, and at the same time revolves around a fixed axis parallel to its own axis. The ball milling speed is set to 280rpm and the ball milling time is 23h. During the high-energy ball milling process, the balls and ceramic powder are ground The collision and impact between the two particles break the ceramic phase particles, thereby obtaining nano-TiB ₂ ceramic powder.

(2) The nano-TiB ₂ ceramic powder prepared in step (1) is added to the Al-20Si alloy powder in a proportion of 10 wt. %, and the TiB ₂ /Al-20Si composite powder is prepared by ball milling and powder mixing. The QM series planetary ball mill is used for ball milling and powder mixing operation. The process uses a ceramic tank, and the ball milling medium is ceramic grinding balls with a diameter of 6mm and 8mm. The ball milling process parameters are set as: the ratio of ball to material is 2:1, the ball milling speed is 200rpm, and the ball milling time is 4h. At the same time, in order to prevent the temperature in the ball milling tank from being too high, the operation mode of the equipment during ball milling is the interval type, that is, the air cooling is suspended for 5 minutes after every 15 minutes of operation of the equipment. The ball milling process requires argon protection to prevent the aluminum alloy powder from being oxidized or contaminated.

(3) Modeling and slicing of target parts

Use Soildworks software in the computer to establish a 3D solid geometric model of the target part, and then use Magics software to perform layered slicing and scanning path planning for the 3D solid model, discretize the 3D solid into a series of 2D data, save this file and import it into the selection laser melting and forming equipment. The laser process parameters are set as follows: the laser power is 450W, the laser scanning speed is 2000mm/s, the scanning spacing is 50μm, the powder thickness is 50μm, the partitioned island scanning strategy is adopted, and the rotation angle of the laser scanning direction of the adjacent layers is 37 μm. °.

(4) Selective laser melting forming process

The nano-ceramic modified high-silicon aluminum alloy powder obtained in step (2) is used for selective laser melting forming. SLM-150 type selective laser melting equipment is used, the system mainly includes YLR-500 type fiber laser, laser forming chamber, automatic powder spreading system, protective atmosphere device, computer control circuit system and cooling circulation system. Before forming, the sandblasted aluminum substrate was fixed on the table of the selective laser melting forming equipment and leveled, and then the forming cavity was sealed by a sealing device, evacuated and passed into an argon protective atmosphere (the purity of argon is 99.999 %, the outlet pressure is 30mbar), to ensure that the _O2 content in the forming chamber is less than 10ppm. The typical selective laser melting forming process 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 line by line according to the pre-designed scanning path, so that the powder layer rapidly melts- Solidification, thereby obtaining the first two-dimensional plane of the part; (b) the computer control system lowers the forming substrate by one powder layer thickness, on the contrary, makes the piston of the powder supply cylinder rise one powder layer thickness, and the powder spreading device re-lays a layer to be prepared. To process the powder, the laser beam scans the second powder layer according to the slicing information to obtain the second two-dimensional plane of the part; (c) Repeat the above steps, and the powder to be processed is formed layer by layer until the part is processed.

After cooling, the forming substrate was taken out from the equipment, and the parts were separated from the substrate by a wire cutting process to obtain a nano-titanium diboride modified high-silicon aluminum alloy sample. According to the standard metallographic sample preparation method, the nano-titanium diboride modified high silicon aluminum alloy bulk sample was ground, polished and etched.

The obtained TiB ₂ /Al-20Si standard tensile sample is subjected to room temperature tensile test, and its tensile strength can reach 472MPa.

Example 3

(1) Nano-TiB ₂ ceramic powder was prepared by high-energy ball milling process. The high-energy ball-milling equipment was a Pulverisette 6 single-tank planetary high-energy ball mill. The ball-milling medium in the stainless steel ball mill was stainless steel balls with diameters of 6mm and 20mm, and the ball-to-material ratio was 10 :1. When the equipment is working, the stainless steel ball mill rotates at a fixed speed around its own axis, and at the same time revolves around a fixed axis parallel to its own axis. The ball milling speed is set to 300rpm and the ball milling time is 20h. During the high-energy ball milling process, the balls and ceramic powder are ground The collision and impact between the two particles break the ceramic phase particles, thereby obtaining nano-TiB ₂ ceramic powder.

(2) The nano-TiB ₂ ceramic powder prepared in step (1) is added to the Al-20Si alloy powder in a proportion of 2 wt.%, and the TiB ₂ /Al-20Si composite powder is prepared by ball milling and powder mixing. The QM series planetary ball mill is used for ball milling and powder mixing operation. The process uses a ceramic tank, and the ball milling medium is ceramic grinding balls with a diameter of 6mm and 8mm. The ball milling process parameters are set as: the ratio of ball to material is 2:1, the ball milling speed is 250rpm, and the ball milling time is 3h. At the same time, in order to prevent the temperature in the ball milling tank from being too high, the operation mode of the equipment during ball milling is the interval type, that is, the air cooling is suspended for 5 minutes after every 15 minutes of operation of the equipment. The ball milling process requires argon protection to prevent the aluminum alloy powder from being oxidized or contaminated. Figure 2 shows the SEM image of the nano-TiB ₂ /Al-20Si powder prepared by using the ball-milled powder.

(3) Modeling and slicing of target parts

Use Soildworks software in the computer to establish a 3D solid geometric model of the target part, and then use Magics software to perform layered slicing and scanning path planning for the 3D solid model, discretize the 3D solid into a series of 2D data, save this file and import it into the selection laser melting and forming equipment. The laser process parameters are set as follows: the laser power is 450W, the laser scanning speed is 2200mm/s, the scanning spacing is 50μm, the powder thickness is 50μm, the partitioned island scanning strategy is adopted, and the rotation angle of the laser scanning direction of the adjacent layers is 37 μm. °.

(4) Selective laser melting forming process

The nano-ceramic modified high-silicon aluminum alloy powder obtained in step (2) is used for selective laser melting forming. SLM-150 type selective laser melting equipment is used, the system mainly includes YLR-500 type fiber laser, laser forming chamber, automatic powder spreading system, protective atmosphere device, computer control circuit system and cooling circulation system. Before forming, the sandblasted aluminum substrate was fixed on the table of the selective laser melting forming equipment and leveled, and then the forming cavity was sealed by a sealing device, evacuated and passed into an argon protective atmosphere (the purity of argon is 99.999 %, the outlet pressure is 30mbar), to ensure that the _O2 content in the forming chamber is less than 10ppm. The typical selective laser melting forming process 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 line by line according to the pre-designed scanning path, so that the powder layer rapidly melts- Solidification, thereby obtaining the first two-dimensional plane of the part; (b) the computer control system lowers the forming substrate by one powder layer thickness, on the contrary, makes the piston of the powder supply cylinder rise one powder layer thickness, and the powder spreading device re-lays a layer to be prepared. To process the powder, the laser beam scans the second powder layer according to the slicing information to obtain the second two-dimensional plane of the part; (c) Repeat the above steps, the powder to be processed is formed layer by layer until the part is processed, as shown in Figure 3. The microstructure of the nano-TiB ₂ /Al-20Si composite sample prepared by this selective laser melting process is shown in Fig. 4 .

After cooling, the formed substrate is taken out from the equipment, and the parts are separated from the substrate by a wire cutting process to obtain a nano-titanium diboride modified high-silicon aluminum alloy sample. According to the standard metallographic sample preparation method, the nano-titanium diboride modified high silicon aluminum alloy bulk sample was ground, polished and etched. Figure 4 shows the microstructure of the nano-TiB ₂ /Al-20Si composite sample in this example.

The obtained TiB ₂ /Al-20Si standard tensile sample is subjected to room temperature tensile test, and its tensile strength can reach 494MPa.

Comparative Example 1

This comparative example relates to a preparation method of nano-ceramic modified high-silicon aluminum alloy based on selective laser melting. The specific steps are basically the same as those in Example 3, except that in steps (1) and (2) of this comparative example, The nano-TiB ₂ /Al-20Si composite powder was not prepared with nano-TiB ₂ as the raw material and the ball milling process was used, but the nearly spherical Al-20Si alloy powder prepared by gas atomization was used as the raw material for selective laser melting and forming. Its microstructure As shown in Figure 5. Comparing Fig. 4 and Fig. 5, it can be found that compared with the nano-TiB ₂ /Al-20Si composite, the number of star-shaped and polygonal primary silicon phases in the Al-20Si alloy structure is significantly increased and the dispersion is not uniform, showing an aggregated state, while The size of the fibrous eutectic silicon increases significantly, and stress concentration is likely to occur in the brittle silicon phase aggregation area or the polygonal edge of the larger-sized primary silicon phase, resulting in premature cracks and expansion, thereby reducing the mechanical properties of the material.

The Al-20Si alloy standard tensile sample prepared in step (3) is subjected to a room temperature tensile test, and its tensile strength can reach 357 MPa.

Comparative Example 2

This comparative example relates to a method for preparing a nano-ceramic modified high-silicon aluminum alloy based on selective laser melting. The specific steps are basically the same as those in Example 3, except that in step (2) of this comparative example, nano-TiB ₂ The content of TiB ₂ nanoparticles in the /Al-20Si composite powder is 25wt.%. In this comparative example, due to the excessive addition of nano-TiB ₂ ceramics, the nanoparticles agglomerated and the viscosity of the aluminum melt was significantly increased. During the subsequent solidification process, the gap between the powder particles lacked sufficient melt filling to form pore defects. As a result, the forming quality and performance of the sample were seriously reduced.

Comparative Example 3

This comparative example relates to a preparation method of nano-ceramic modified high-silicon aluminum alloy based on selective laser melting. The specific steps are basically the same as those in Example 3, except that in steps (1) and (2) of this comparative example, Using micron TiB ₂ and AlSi10Mg alloy powder as raw materials, a 2wt.% TiB ₂ /AlSi10Mg composite powder was prepared by ball milling process, and the selective laser melting was performed. The microstructure is shown in Figure 6. Comparing Fig. 4 and Fig. 6, it can be found that compared with the nano-TiB ₂ /Al-20Si composite, the eutectic silicon structure of the micro-TiB ₂ /AlSi10Mg composite is obviously coarsened, which is mainly because the micro-ceramic is relatively The microstructure of aluminum matrix composites has a weaker degree of refinement; at the same time, the larger size of the ceramic phase increases the tendency of stress concentration and fracture within the material. The silicon content of the aluminum alloy used in this example is relatively low (12.6 wt.% lower than the eutectic point of the aluminum-silicon alloy), and there is no uniform distribution of fine and massive primary silicon phase precipitation during the solidification of the aluminum alloy melt, thereby reducing the composite material. strength.

The tensile strength of TiB ₂ /AlSi10Mg composite was measured to be 444MPa by room temperature tensile test.

From Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that the tensile strength and mechanical properties of the nano-TiB ₂ /Al _- 20Si composite samples formed by selective laser melting are significantly increased. Refinement and modification of primary silicon phase and eutectic silicon phase in high silicon aluminum alloy structure. Compared with the Al-20Si alloy, the star-shaped primary silicon phase in the nano-TiB ₂ /Al-20Si composite material is obviously reduced, the edges and corners of the polygonal primary silicon phase are passivated, the edges are smooth, and the fibrous eutectic silicon structure is obviously refined. Nano-TiB ₂ is evenly distributed on the aluminum matrix, which has a dispersion strengthening effect on the high-silicon aluminum alloy matrix, and the wettability of TiB ₂ ceramics and aluminum alloys is good, so that the interface between the nano-TiB ₂ ceramic phase and the aluminum matrix is closely combined. The mechanical properties of the material are further improved.

The present invention provides an idea and method for modifying high-silicon aluminum alloy based on selective laser melting of nano-ceramics. There are many specific methods and approaches for realizing this technical solution. The above are only the preferred embodiments of the present invention. It should be noted that for For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims (8)

1. a nano-ceramic modified high-silicon aluminum alloy based on selective laser melting, is characterized in that, prepares by the following steps: (1) Nano-TiB ₂ ceramic powder was prepared by using Pulverisette 6 type single-pot planetary high-energy ball mill; (2) mixing the Al-20Si alloy powder with the nano-TiB ₂ ceramic powder prepared in step (1) through a QM series planetary ball mill under the protection of an inert gas to obtain a nano-TiB ₂ /Al-20Si composite powder; (3) Use Soildworks software in the computer to establish a three-dimensional solid geometric model of the target part, then use Magics software to slice the model and plan the laser scanning path, discretize the three-dimensional solid into a series of two-dimensional data, save this file and Imported into the selective laser melting forming equipment; (4) The selective laser melting and forming equipment fuses the nano-TiB ₂ /Al-20Si composite powder in step (2) layer by layer according to the file saved in step (3), and finally forms the target part to be created. 2. nano-ceramic modified high-silicon aluminum alloy based on selective laser melting according to claim 1, is characterized in that, in step ( ₁ ), the raw material used is polygonal micron TiB powder, and the particle size distribution range is in 1～5μm, the purity is more than 99.9%. 3 . The nano-ceramic modified high-silicon aluminum alloy based on selective laser melting according to claim 1 , wherein, in step (1), the high-energy ball milling rotational speed is 250-300 rpm, and the ball-milling time is 20-25 h. 4 . 4 . The nano-ceramic modified high-silicon aluminum alloy based on selective laser melting according to claim 3 , wherein in step (1), the particle size of the nano-TiB ₂ ceramic powder prepared by high-energy ball milling is 40-200 nm. 5 . 5 . The nano-ceramic modified high-silicon aluminum alloy based on selective laser melting according to claim 1 , wherein in step (2), the particle size distribution of the Al-20Si alloy powder ranges from 12 to 31 μm, wherein the silicon The content is 19.2-20 wt.%, the iron content is 0.05-0.15%, and the balance is aluminum. 6. The nano-ceramic modified high-silicon aluminum alloy based on selective laser melting according to claim 1, wherein in step (2), the TiB ₂ nanoparticles in the nano-TiB ₂ /Al-20Si composite powder are The content is 1-10 wt.%. 7 . The nano-ceramic modified high-silicon aluminum alloy based on selective laser melting according to claim 1 , wherein, in step (2), the ball milling speed is 150-250 rpm, and the ball-milling time is 3-5 h. 8 . 8 . The nano-ceramic modified high-silicon aluminum alloy based on selective laser melting according to claim 1 , wherein, in step (4), the laser scanning speed used in selective laser melting is 1800-2200 mm/s. 9 .

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