CN108486431A - Selective laser melting process Al-Si-Mg line aluminium alloys composition and molded part preparation method - Google Patents

Abstract

The invention discloses an Al-Si-Mg series aluminum alloy composition for selective laser melting technology, which comprises: Si 7-15%, Mg 0.8-3%, Mn 1.2-2%, Zr 0.5-1.5% by mass percentage , and the balance is composed of aluminum. The aluminum alloy molded parts are obtained through master alloy smelting, metal powder preparation, aluminum alloy molded parts preparation and heat treatment process steps. The invention greatly improves the solubility of alloy elements in the aluminum matrix through the selective laser melting manufacturing technology, and greatly improves the mechanical properties of the aluminum alloy by increasing the concentration of the second phase strengthening particles in the aluminum alloy. The Al-Si-Mg aluminum alloy composition of the present invention is prepared by selective laser melting technology to obtain the maximum yield strength σ _0.2 of the aluminum alloy up to 380MPa, the tensile strength _σb up to 520MPa, and the plastic deformation rate of the alloy exceeds 8%. . It is suitable for preparing complex structural parts with high mechanical performance requirements through selective laser melting technology.

Description

Preparation of Al-Si-Mg-based Aluminum Alloy Composition and Molded Parts by Selective Laser Melting Technology method

technical field

The invention relates to the technical field of new materials, in particular to a series of Al-Si-Mg series aluminum alloy compositions with high tensile strength and high plastic deformation rate for selective laser melting technology.

Background technique

As the cast aluminum alloy with the largest output and consumption, Al-Si alloy has the advantages of good wear resistance and corrosion resistance, low thermal expansion coefficient, high specific strength, and good thermal conductivity, which makes Al-Si alloy widely used in pistons and engine blocks. , cylinder liners, hubs, bearings, bearing bushes, crankcases and other auto parts. In the Al-Si-Mg alloy, Mg and Si elements are partially dissolved in the aluminum matrix during the solidification process of the aluminum alloy, and some are precipitated as the Mg ₂ Si phase. Since the Mg ₂ Si formed as the primary phase is relatively coarse in size, it is mostly sharp-edged shape, split the matrix, and reduce the mechanical properties of the material. After the Al-Si-Mg alloy undergoes late solution and aging treatment, the Mg ₂ Si phase can be dispersed and precipitated in the aluminum alloy matrix, and there is a certain strain field between the precipitated phase and the matrix, and these strain fields become obstacles to dislocation movement Thereby playing the role of precipitation strengthening. However, due to the limited solid solubility of Mg in the Al-Si alloy during the solution treatment of traditional castings, the precipitation concentration of Mg ₂ Si particles in the later aging treatment process is limited, thereby limiting the further improvement of the mechanical properties of the Al-Si-Mg alloy. promote.

Rapid prototyping technology is a new processing technology that integrates computer-aided technology and laser and electron beam processing. It can solve some defects exposed in the casting process in a targeted manner, and meet the forming processing requirements of special parts that are difficult or impossible to process in the casting process. Selected area laser melting technology is a kind of rapid prototyping technology, which is called the main development trend in the field of rapid prototyping in the future, and its application in metal forming will bring a breakthrough leap in the manufacturing industry.

The selective laser melting molding process is divided into two stages: rapid heating and rapid cooling: firstly, the laser beam interacts with the metal powder, and because the metal powder absorbs the energy of the laser beam, the temperature rises suddenly and exceeds the melting point of the metal to form a molten pool. , the molten metal is in liquid phase equilibrium, the metal atoms can move freely, and the alloy elements are evenly distributed; when the laser beam is removed, the temperature of the molten pool drops at a rate of 10 ³ -10 ⁶ K/s due to the disappearance of the heat source. During this process, the diffusion and movement of metal atoms and alloying elements is limited, which inhibits the growth of grains and the segregation of alloying elements. The solidified metal structure has fine grains and uniform distribution of alloying elements, which can greatly improve the strength and toughness of the material. . In addition, due to the rapid solidification behavior of the molten pool, the solid solubility of the alloying atoms in the Al-Si-Mg aluminum alloy is greatly improved, so that a high concentration of Mg can be obtained during the later aging heat treatment of the aluminum alloy. ₂ Si particles can effectively improve the strength of aluminum alloy. However, the composition of aluminum alloys currently used in selective laser melting technology is still dominated by traditional casting alloys, which cannot reflect the process characteristics of melt quenching in selective laser melting technology and further improve the performance of Al-Si-Mg aluminum alloys. At this stage, although the strength and plasticity of aluminum alloys formed by selective laser melting are much higher than those of cast aluminum alloys (the yield strength of aluminum alloys formed by selective laser melting is about 200-320MPa, and the tensile strength is about 340-500MPa), there are still relatively large Room for improvement.

Contents of the invention

The technical problem to be solved by the present invention is: to overcome the shortcomings of the limited content of the second phase particles in the traditional casting Al-Si-Mg series aluminum alloy, and to realize the second phase particle content in the Al-Si-Mg series aluminum alloy by using the selective laser melting technology. The increase of the particle content leads to the improvement of the mechanical properties. Finally, a series of Al-Si-Mg series aluminum alloys for selective laser melting technology with excellent mechanical properties will be provided. The mechanical properties of this alloy are significantly better than those obtained by traditional casting and selective laser melting forming technology. mechanical properties.

In order to achieve the above object, the technical scheme adopted by the present invention to realize the object is as follows:

An Al-Si-Mg aluminum alloy composition for selective laser melting technology, the composition and content are: Si 7-15%, Mg 0.8-3%, Mn 1.2-2%, Zr 0.5- 1.5%, the balance is composed of aluminum, and the total mass percentage is 100%.

Wherein, the purity of the aluminum is 99.99% pure aluminum.

Said Si, Mg, Mn and Zr are simple substances or aluminum-based master alloys. Si, Mg, Mn, Zr are pressed into pure aluminum with a bell jar.

In order to achieve the above object, another technical solution adopted by the present invention to realize the object is as follows:

A method for preparing an Al-Si-Mg series aluminum alloy molding for selective laser melting technology, comprising the following steps:

S1: Master alloy smelting: preheat the crucible to 520±5°C, place pure aluminum in the crucible, continue to heat up to 1100±5°C, press the Al-Zr master alloy into the pure aluminum after the pure aluminum is melted, And stir for 30 minutes, after stirring evenly, reduce the melt temperature to 750±5°C, then add Mg and Mn simple substances, and stir for 30 minutes to obtain an alloy melt with uniform composition;

S2: Powder preparation: After the alloy melt is evenly melted, open the valve at the bottom of the crucible, the alloy melt flows out through an alumina conduit with an inner diameter of 5mm, and falls freely. form metal powder;

S3: Preparation of aluminum alloy forming parts:

1) Use CAD to establish a three-dimensional model of the required molding parts and convert it into a data format that can be cut;

2) Cut the 3D model together with the support body into multiple layers with a thickness of 0.04mm and then import it into the SLM equipment;

3) Spread a layer of 0.04mm metal powder on a detachable substrate as described in step S2;

4) Laser scanning step 3) The geometric shape of the cross-section of the metal powder layer is 4 times. During the scanning process, the laser spot is 0.1mm, the laser power is 200-400W, and the laser scanning rate is 400-2000mm/s;

5) The substrate is dropped to a thickness of 0.04mm, and a new layer of metal powder is spread on the base surface; the geometric shape of the cross-section of the newly laid metal powder layer is scanned by laser 1-2 times, and the laser spot is 0.1mm during the scanning process. The laser power is: 200-300W, the laser scanning rate is: 800-1300mm/s, and the scanning direction is rotated 60 degrees clockwise with the scanning direction of the previous layer;

6) repeating step 5) multiple times until the end of the entire program operation to obtain the aluminum alloy molding, the number of repetitions is determined by the size of the molding;

S4: heat treatment:

The aluminum alloy formed part obtained in step S3 is heat-treated at 150° C. for 6-24 hours to obtain an Al-Si-Mg series aluminum alloy formed part for selective melting technology.

Further preferably, the metal powder in step S2 has a diameter of 15-60 microns.

Further preferably, the atomization pressure in step S2 is 10 MPa.

Advantage and beneficial effect of the present invention are:

(1) Relying on the selective laser manufacturing technology, by increasing the content of Mg element and Zr element in the Al-Si-Mg series aluminum alloy, the concentration of the second phase strengthening Mg ₂ Si and Al ₃ Zr particles in the aluminum alloy is increased to realize the Al- Effective improvement of mechanical properties of Si-Mg aluminum alloy;

(2) By adding Mn and Zr elements, the formability of Al-Si-Mg aluminum alloys in selective laser melting can be increased at the same time, so that the density of the aluminum alloys exceeds 99.9%, and the Al-Si-Mg aluminum alloys can be effectively avoided. generation of cracks.

Detailed ways

In order to make the purpose, technical scheme and advantages of the present invention more clear, the following three terms will be Al _90.5 Si ₇ Mg _0.8 Mn _1.2 Zr _0.5 , Al ₈₆ Si ₁₀ Mg _1.5 Mn _1.5 Zr ₁ , Al _78.5 Si ₁₅ Mg ₃ Mn ₂ Zr _1.5 An alloy composition is taken as an example for further detailed description. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Example 1:

1. Composition and content of aluminum alloy composition:

Al _90.5 Si ₇ Mg _0.8 Mn _1.2 Zr _0.5

2. Preparation steps of aluminum alloy forming parts:

(1) Master alloy smelting:

After preheating the crucible to 520±5°C, place the pure aluminum in the crucible, continue to heat up to 1100±5°C, press the Al-Zr master alloy into the pure aluminum after the pure aluminum is melted, and stir for 30 minutes, After stirring evenly, reduce the melt temperature to 750±5°C, then add Mg and Mn simple substances, and stir for 30 minutes to obtain a uniform alloy melt;

(2) Powder preparation:

After the alloy melt is evenly melted, open the valve at the bottom of the crucible, and the alloy melt flows out through an alumina conduit with an inner diameter of 5 mm, and falls freely. The melting pressure is 10MPa, and the powder of 15-60 microns is finally screened for standby;

(3) Preparation of aluminum alloy forming parts:

1) Use CAD to establish a three-dimensional model of the required molding parts and convert it into a data format that can be cut;

2) Cut the 3D model together with the support body into multiple layers with a thickness of 0.04mm and then import it into the SLM equipment;

3) Lay a layer of 0.04mm metal powder as described in step (2) on a detachable substrate;

4) Laser scanning step 3) The geometric shape of the cross section of the metal powder layer is 4 times. During the scanning process, the laser spot is 0.1mm, the laser power is 200W, and the laser scanning rate is 1100mm/s;

5) The substrate is lowered by a layer with a thickness of 0.04mm, and a new layer of metal powder is spread on the base surface; the geometric shape of the cross-section of the newly laid metal powder layer is scanned by laser once, and the laser spot is 0.1mm during the scanning process. It is: 200W, the laser scanning rate is: 1100mm/s, and the scanning direction is rotated 60 degrees clockwise with the scanning direction of the previous layer;

6) repeating step 5) multiple times until the end of the entire program operation to obtain the aluminum alloy molding, the number of repetitions is determined by the size of the molding;

(4) Heat treatment:

The aluminum alloy formed part obtained in step (3) is heat-treated at 150° C. for 6 hours to obtain an Al-Si-Mg aluminum alloy for selective melting technology.

Three, the mechanical performance test and beneficial effect of the present embodiment

1. Mechanical performance test:

Use X-ray diffractometer (XRD) and transmission electron microscope (TEM) to detect the structure of aluminum alloy samples; use metallographic microscope (OM) scanning electron microscope (SEM) to observe the microstructure of aluminum alloy samples; apply universal mechanical test Machine testing the strength of aluminum alloy samples.

2. Beneficial effects:

The compactness of the formed part obtained through this embodiment is 99.95%, and its mechanical performance index is as follows: the maximum tensile strength σ _b is 380 MPa, the yield strength σ _0.2 is 300 MPa, and the plastic deformation rate is 22%. The plastic deformation rate of this embodiment is greater than that of the existing casting and selective laser melting Al-Si-Mg aluminum alloys.

Example 2:

1. Composition and content of aluminum alloy composition:

Al ₈₆ Si ₁₀ Mg _1.5 Mn _1.5 Zr ₁

2. Preparation steps of aluminum alloy forming parts:

(1) Master alloy smelting

With embodiment 1.

(2) Powder preparation

With embodiment 1.

(3) Preparation of aluminum alloy forming parts:

The steps of selective laser melting (SLM) to prepare aluminum alloy are as follows:

1) Use CAD to establish a three-dimensional model of the required molding parts and convert it into a data format that can be cut;

2) Cut the 3D model together with the support body into multiple layers with a thickness of 0.04mm and then import it into the SLM equipment;

3) Lay a layer of 0.04mm metal powder as described in step (2) on a detachable substrate;

4) Laser scanning step 3) The geometric shape of the cross-section of the metal powder layer is 4 times. During the scanning process, the laser spot is 0.1mm, the laser power is 250W, and the laser scanning rate is 900mm/s;

5) The substrate is lowered by a layer with a thickness of 0.04mm, and a new layer of metal powder is spread on the base surface; the geometric shape of the cross-section of the newly laid metal powder layer is scanned by laser once, and the laser spot is 0.1mm during the scanning process. It is: 250W, the laser scanning rate is: 900mm/s, and the scanning direction is rotated 60 degrees clockwise with the scanning direction of the previous layer;

6) repeating step 5) multiple times until the end of the entire program operation to obtain the aluminum alloy molding, the number of repetitions is determined by the size of the molding;

(4) Heat treatment:

The above alloy was aged at 150° C. for 12 hours.

Three, the mechanical performance test and beneficial effect of the present embodiment

1. Mechanical performance test:

Use X-ray diffractometer (XRD) and transmission electron microscope (TEM) to detect the structure of aluminum alloy samples; use metallographic microscope (OM) scanning electron microscope (SEM) to observe the microstructure of aluminum alloy samples; apply universal mechanical test Machine testing the strength of aluminum alloy samples.

2. Beneficial effects:

The compactness of the formed part obtained through this embodiment is 99.92%, and its mechanical performance index is as follows: the maximum tensile strength σ _b is 480 MPa, the yield strength σ _0.2 is 340 MPa, and the plastic deformation rate is 15%. The yield strength of this embodiment is greater than that of the existing casting and selective laser melting Al-Si-Mg aluminum alloys.

Example 3:

1. Composition and content of aluminum alloy composition:

Al _78.5 Si ₁₅ Mg ₃ Mn ₂ Zr _1.5

2. Preparation steps of aluminum alloy forming parts:

(1) Master alloy smelting

With embodiment 1.

(2) Powder preparation

With embodiment 1.

(3) Preparation of aluminum alloy forming parts:

The steps of selective laser melting (SLM) to prepare aluminum alloy are as follows:

1) Use CAD to establish a three-dimensional model of the required molding parts and convert it into a data format that can be cut;

2) Cut the 3D model together with the support body into multiple layers with a thickness of 0.04mm and then import it into the SLM equipment;

3) Lay a layer of 0.04mm metal powder as described in step (2) on a detachable substrate;

4) Laser scanning step 3) The geometric shape of the cross-section of the metal powder layer is 4 times. During the scanning process, the laser spot is 0.1mm, the laser power is 300W, and the laser scanning rate is 1000mm/s;

5) The substrate is lowered by a layer with a thickness of 0.04mm, and a new layer of metal powder is spread on the base surface; the geometric shape of the cross-section of the newly laid metal powder layer is scanned twice by laser, and the laser spot is 0.1mm during the scanning process. It is: 300W, the laser scanning rate is: 1000mm/s, and the scanning direction is rotated 60 degrees clockwise with the scanning direction of the previous layer;

6) repeating step 5) multiple times until the end of the entire program operation to obtain the aluminum alloy molding, the number of repetitions is determined by the size of the molding;

(4) Heat treatment:

The above alloy was aged at 150° C. for 24 hours.

Three, the mechanical performance test and beneficial effect of the present embodiment

1. Mechanical performance test:

Use X-ray diffractometer (XRD) and transmission electron microscope (TEM) to detect the structure of aluminum alloy samples; use metallographic microscope (OM) scanning electron microscope (SEM) to observe the microstructure of aluminum alloy samples; apply universal mechanical test Machine testing the strength of aluminum alloy samples.

2. Beneficial effects:

The density of the molded part obtained through this embodiment is 99.96%, and its mechanical performance index is as follows: the maximum tensile strength σ _b is 520MPa, the yield strength _σ0.2 is 380MPa, and the plastic deformation rate is 8%. Both the yield strength and the tensile strength of this embodiment are greater than the yield strength of the existing cast and selective laser melting Al-Si-Mg aluminum alloys.

The above are only preferred specific implementation modes of the present invention. Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, any person familiar with the technical field can make various corresponding equivalent changes and deformations according to the present invention , should belong to the scope of protection of the appended claims of the present invention.

Claims (6)

1. An Al-Si-Mg series aluminum alloy composition for selective laser melting technology, characterized in that: by mass percentage, the composition and content are: Si 7-15%, Mg 0.8-3%, Mn 1.2- 2%, Zr 0.5-1.5%, the balance is composed of aluminum, and the total mass percentage is 100%. 2. The Al-Si-Mg aluminum alloy composition for selective laser melting technology according to claim 1, characterized in that: the purity of the aluminum is 99.99% pure aluminum. 3 . The Al-Si-Mg aluminum alloy composition for selective laser melting technology according to claim 1 , wherein the Si, Mg, Mn, and Zr are simple substances or aluminum-based master alloys. 4. A method for preparing an Al-Si-Mg series aluminum alloy molding for selective laser melting technology, characterized in that: comprising the following steps: S1. Master alloy melting: After preheating the crucible to 520±5°C, place the pure aluminum in the crucible, continue to heat up to 1100±5°C, press the Al-Zr master alloy into the pure aluminum after the pure aluminum is melted, and stir for 30 minutes, After stirring evenly, reduce the melt temperature to 750±5°C, then add Mg and Mn simple substances, and stir for 30 minutes to obtain a uniform alloy melt; S2. Powder preparation: After the alloy melt is evenly melted, open the valve at the bottom of the crucible, the alloy melt flows out through the alumina conduit with an inner diameter of 5mm, falls freely, and the liquid flows through the high-pressure nitrogen atomizer and breaks into fine droplets, which form metal powder after solidification; S3. Preparation of aluminum alloy molded parts: 1) Use CAD to establish a three-dimensional model of the required molding parts and convert it into a data format that can be cut; 2) Cut the 3D model together with the support body into multiple layers with a thickness of 0.04mm and then import it into the SLM equipment; 3) Spread a layer of 0.04mm metal powder on a detachable substrate as described in step S2; 4) Laser scanning step 3) The geometric shape of the cross-section of the metal powder layer is 4 times. During the scanning process, the laser spot is 0.1mm, the laser power is 200-400W, and the laser scanning rate is 400-2000mm/s; 5) The substrate is dropped to a thickness of 0.04mm, and a new layer of metal powder is spread on the base surface; the geometric shape of the cross-section of the newly laid metal powder layer is scanned by laser 1-2 times, and the laser spot is 0.1mm during the scanning process. The laser power is: 200-300W, the laser scanning rate is: 800-1300mm/s, and the scanning direction is rotated 60 degrees clockwise with the scanning direction of the previous layer; 6) repeating step 5) multiple times until the end of the entire program operation to obtain the aluminum alloy molding, the number of repetitions is determined by the size of the molding; S4. Heat treatment: The aluminum alloy formed part obtained in step S3 is heat-treated at 150° C. for 6-24 hours to obtain an Al-Si-Mg series aluminum alloy formed part for selective melting technology. 5. The preparation method according to claim 4, characterized in that the metal powder in step S2 has a diameter of 15-60 microns. 6. The preparation method according to claim 4, characterized in that the atomization pressure in step S2 is 10 MPa.