An aluminum-based composite material with ultra-high strength and its preparation method

Abstract

This invention discloses an aluminum-based composite material with ultra-high strength and its preparation method. Using pure aluminum, industrial pure Mg, AlZr master alloy, AlSc master alloy, and AlMn master alloy as raw materials, Al-Mn-Mg-Sc-Zr alloy powder is prepared using a vacuum atomization system. Nano-TiN and Al-Mn-Mg-Sc-Zr mixed powders are prepared by ultrasonic dispersion and mechanical vibration mixing to achieve uniform distribution of nano-TiN on the alloy powder surface. The composite material is formed using laser powder bed melting technology, resulting in a uniform and fine equiaxed crystal structure. The aluminum-based composite powder prepared by this method is suitable for laser additive manufacturing technology, and the formed samples have a dense structure and are free of cracks. The yield strength of the formed samples is 570-580 MPa, and the elongation after fracture is 2%-8%. After simple heat treatment, the yield strength of the samples reaches 670-700 MPa, and the elongation after fracture is 1%-5%.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing materials technology, and in particular to an aluminum-based composite material with ultra-high strength and its preparation method. Background Technology

[0002] With the rapid development of modern industry, the demand for high-performance, complex-shaped metal components is increasing across various fields. However, traditional machining processes for producing complex-shaped metal components often involve cumbersome post-processing steps. This inevitably increases the production cycle and cost of parts, and may even lead to situations where they are difficult to process, which to some extent limits the progress of modern industry.

[0003] Additive manufacturing technology breaks the constraints of traditional processing techniques on the shape and structure of parts, enriching and improving the manufacturing process system. Among them, laser powder bed fusion (LPBF) technology uses a laser beam to rapidly melt metal powder and then directly solidify it into shape, with a cooling rate of up to 10... 4 -10 6 K / s. This rapid cooling process results in significant temperature undercooling, which greatly refines the alloy's microstructure. Furthermore, under rapid cooling conditions, the limiting solid solubility of alloying elements increases significantly, allowing for the production of supersaturated solid solutions far exceeding the alloy's solubility, thus improving the mechanical properties of the parts. Thanks to these excellent process characteristics, LPBF technology has been widely applied in industries such as aerospace and advanced transportation.

[0004] Aluminum alloys are important structural materials, widely used in aerospace, automotive, and shipbuilding industries due to their high specific strength, good impact resistance, good ductility, and corrosion resistance. With the development of modern industry, higher demands are placed on the comprehensive performance of aluminum alloy materials, while single aluminum alloy materials are insufficient to support components in increasingly harsh working environments. Aluminum-based composite materials, due to their high specific strength, excellent wear resistance, and corrosion resistance, are now widely used in many industrial sectors, including automotive and aerospace.

[0005] Currently, research on LPBF-formed aluminum alloy composites generally focuses on ceramic particle-reinforced aluminum matrix materials. Ceramic particles typically have extremely high melting points, thus maintaining stable physicochemical properties during LPBF melting. Furthermore, the extremely fast melting and solidification rates of LPBF technology can, to some extent, prevent particle agglomeration, allowing the reinforcing particles to be uniformly distributed in the matrix, resulting in aluminum matrix composites with uniform microstructure and excellent properties. Currently, the reinforcing phases used in LPBF-formed particle-reinforced aluminum matrix composites mainly include TiB2, SiC, and TiN, while the matrix materials mainly include Al-Si-Mg, Al-Cu alloys, and Al-Zn alloys.

[0006] For the base material, Al-Si aluminum alloys have excellent LPBF formability and a wide process window. The resulting alloys have a unique submicron cellular microstructure and high Si solid solubility, which makes the mechanical properties of the alloys significantly better than those of cast alloys of the same composition. However, the yield strength of such LPBF forming alloys is often lower than 300 MPa and the elongation is lower than 10%.

[0007] While the addition of reinforcing particles can improve material strength, their mechanical properties are still not comparable to those of wrought aluminum alloys due to the limited strength of the matrix material. 2xxx, 6xxx, and 7xxx series high-strength aluminum alloys are commonly used in the aerospace field; however, the high concentration of alloying elements and wide solidification temperature range make these alloys prone to hot cracking during SLM forming, deteriorating their mechanical properties. Although existing research indicates that the addition of fine reinforcing particles can increase nucleation points during alloy solidification, reducing or eliminating hot cracking during LPBF forming and improving formability, their strength remains far lower than that of traditional forged high-strength alloys. Summary of the Invention

[0008] This invention addresses the problems existing in existing LPBF aluminum-based composite materials by providing an aluminum-based composite material with ultra-high strength and its preparation method. This invention is applicable to LPBF and utilizes a laser powder bed melting process for forming, resulting in a composite material with a uniform and fine equiaxed grain structure. The aluminum-based composite powder prepared by this method is suitable for laser additive manufacturing technology, and the formed samples have a dense structure free of cracks and defects. The yield strength of the formed samples is 570-580 MPa, and the elongation after fracture is 2%-8%. After simple heat treatment, the yield strength of the samples reaches 670-700 MPa, and the elongation after fracture is 1%-5%.

[0009] This invention is achieved through the following technical solution:

[0010] A method for preparing an aluminum-based composite material with ultra-high strength includes a composite powder preparation step and a laser forming step;

[0011] Composite powder preparation steps: The following components were prepared: 4.59 wt.% Mn, 3.00 wt.% Mg, 0.71 wt.% Sc, 0.47 wt.% Zr, <0.1 wt.% Fe, with the remainder being Al. Al-Mn-Mg-Sc-Zr alloy powder was prepared by vacuum melting and Ar gas atomization. TiN was then uniformly mixed with the alloy powder using ultrasonic dispersion and mechanical vibration. The average diameter of TiN was 80-110 nm, the addition amount was 0-5 wt.%, the ultrasonic frequency was 30 kHz, and the mixing time was 2 h, thus completing the preparation of the composite powder.

[0012] Laser forming steps: During the forming process, the laser power is 200-250W, the scanning speed is 1000-1400mm / s, the scanning spacing is 100μm, the layer thickness is 30μm, the scanning strategy is interlayer rotation of 67°, the substrate temperature is 180-200℃, and the forming atmosphere is 99.9%Ar, thus completing the preparation of aluminum-based composite materials.

[0013] In the laser forming process, the density of the formed composite material reaches 99.8%, the sample heat treatment temperature is 300-325℃, the heating rate is 10℃ / min, and the holding time is 2-6h.

[0014] Before the laser forming step, the composite powder needs to be dried at 80°C for 8 hours.

[0015] The aluminum-based composite material of the present invention has a yield strength of 570-580 MPa and an elongation after fracture of 2%-8% when measured at 25°C.

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

[0017] This invention provides a simple process for preparing particle-reinforced aluminum-based composite materials for laser additive manufacturing, achieving uniform distribution of TiN nanoparticles on the alloy surface. Simultaneously, the laser-formed samples are dense and crack-free, with a fine microstructure consisting entirely of equiaxed crystals with an average grain size of 0.2-3 μm. Benefiting from the ultrafast cooling rate of laser forming, alloying elements Mn and Mg are supersaturated and dissolved in α-Al. Some TiN particles melt and decompose at high temperatures, forming high-density L12 particles that significantly improve the material's mechanical properties, achieving a yield strength of ~580 MPa. After heat treatment, Sc, Zr, and Ti elements from TiN decomposition precipitate out secondary, further enhancing the material's mechanical properties, with a yield strength reaching 670-700 MPa, demonstrating broad application prospects. Its excellent mechanical properties mainly stem from:

[0018] (1) Due to the microalloying effect of Sc and Zr elements, efficient nucleation particles are provided for the nucleation of α-Al grains, resulting in a significant refinement of the grain structure in the formed sample.

[0019] (2) The supersaturated solid solution of Mn and Mg elements significantly improves the solid solution strengthening effect.

[0020] (3) The melting, decomposition and re-precipitation of TiN nanoparticles greatly increases the density of the precipitated phase, thereby significantly improving the strengthening effect of the second phase. Attached Figure Description

[0021] Figure 1 Example 1, wherein, Figure 1 (a) is the CT scan result. Figure 1 (b) is a metallographic electron microscope image.

[0022] Figure 2 Example 1, wherein, Figure 2 (a) is a 50 μm SEM image. Figure 2 (b) is a 2 μm SEM image.

[0023] Figure 3 Example 1: Sample tensile curve, wherein, Figure 3 (a) Morphological sample. Figure 3 (b) Aging sample curve.

[0024] Figure 4 Example 2: Metallographic electron microscope image.

[0025] Figure 5 Example 2, wherein, Figure 5 (a) is a 50 μm SEM image. Figure 5 (b) is a 2 μm SEM image.

[0026] Figure 6 Example 2: Sample tensile curve, wherein, Figure 6 (a) Morphological sample curve. Figure 6 (b) Aging sample curve.

[0027] Figure 7 Example 3: Metallographic electron microscope image.

[0028] Figure 8 Example 3, wherein, Figure 8 (a) is a 50 μm SEM image. Figure 8 (b) is a 2 μm SEM image.

[0029] Figure 9 Example 3: Sample tensile curve.

[0030] Figure 10 Comparative metallographic electron microscope Figure 10 (a) Metallographic electron microscopy Figure 10 (b) comparison.

[0031] Figure 11 Comparative example, where, Figure 11 (a) is a 50 μm SEM image. Figure 11 (b) and Figure 11 (c) are SEM images at 2 μm.

[0032] Figure 12 Tensile curves of comparative samples. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to specific embodiments.

[0034] Example 1:

[0035] 1.5 wt.% nano-TiN was ultrasonically dispersed and mechanically vibrated and mixed with gas-atomized Al-Mn-Mg-Sc-Zr alloy powder for 2 hours to ensure uniform distribution of TiN particles on the surface of the alloy powder. The final measured powder composition was: Mn: 3.83 wt.%, Mg: 2.34 wt.%, Sc: 0.60 wt.%, Zr: 0.41 wt.%, Fe: 0.14 wt.%, TiN: 1.53 wt.%, with the remainder being Al.

[0036] The forming parameters are: laser power 250W, scanning speed 1000mm / s, scanning spacing 100μm, layer thickness 30μm, scanning strategy is interlayer rotation 67°, substrate temperature 200℃, and forming atmosphere is 99.9%Ar.

[0037] The formed sample had a density of 99.9%. The sample was processed into tensile specimens with dimensions of 30×7×1.5mm. Mechanical property testing showed that its hardness was 165HV. 0.3 The yield strength was 588 MPa, and the elongation after fracture was 8.1%. After aging at 325℃ for 2 hours, the yield strength of the molded sample reached 667 MPa, and the elongation after fracture reached 8.3%.

[0038] Example 2:

[0039] 3.0 wt.% nano-TiN was ultrasonically dispersed and mechanically vibrated and mixed with gas-atomized Al-Mn-Mg-Sc-Zr alloy powder for 2 hours to ensure uniform distribution of TiN particles on the surface of the alloy powder. The final measured powder composition was: Mn: 4.14 wt.%, Mg: 2.02 wt.%, Sc: 0.59 wt.%, Zr: 0.42 wt.%, Fe: 0.19 wt.%, TiN: 3.14 wt.%, with the remainder being Al.

[0040] The forming parameters are: laser power 200W, scanning speed 1200mm / s, scanning spacing 100μm, layer thickness 30μm, scanning strategy is interlayer rotation 67°, substrate temperature 200℃, and forming atmosphere is 99.9%Ar.

[0041] The formed sample had a density of 99.8%. The sample was processed into tensile specimens with dimensions of 30×7×1.5mm. Mechanical property testing showed that its hardness was 174HV. 0.3The yield strength was 583 MPa, and the elongation after fracture was 2.8%. After aging at 325℃ for 6 hours, the strength of the formed sample was further improved to 701 MPa, and the elongation after fracture was 1.3%.

[0042] Example 3:

[0043] 4.5 wt.% nano-TiN was ultrasonically dispersed and mechanically vibrated and mixed with gas-atomized Al-Mn-Mg-Sc-Zr alloy powder for 2 hours to ensure uniform distribution of TiN particles on the alloy powder surface. The final measured powder composition was: Mn: 3.96 wt.%, Mg: 1.99 wt.%, Sc: 0.54 wt.%, Zr: 0.39 wt.%, Fe: 0.13 wt.%, TiN: 4.45 wt.%, with the remainder being Al. The forming parameters were: laser power 200 W, scanning speed 1400 mm / s, scanning spacing 100 μm, layer thickness 30 μm, scanning strategy of interlayer rotation 67°, substrate temperature 200 °C, and forming atmosphere of 99.9% Ar.

[0044] The formed sample had a density of 99.8%. The sample was processed into tensile specimens with dimensions of 30×7×1.5mm. Mechanical property testing showed that its hardness was 176HV. 0.3 The yield strength is 575 MPa and the elongation after fracture is 2.3%.

[0045] Comparative Example

[0046] This comparative example uses laser additive manufacturing technology to form an Al-Mn-Mg-Sc-Zr alloy, and compares its microstructure and properties with those of the composite materials in the examples. The process includes the following steps:

[0047] LPBF (Liquid Laser-Based Burning) technology was used to directly form gas-atomized alloy powder. The final powder composition was determined to be: Mn: 4.14 wt.%, Mg: 2.26 wt.%, Sc: 0.66 wt.%, Zr: 0.47 wt.%, Fe: 0.14 wt.%, with the remainder being Al. The forming parameters were: laser power 300 W, scanning speed 800 mm / s, scanning spacing 100 μm, layer thickness 30 μm, scanning strategy of 67° interlayer rotation, substrate temperature 200℃, and forming atmosphere of 99.9% Ar. The formed sample had a density of 99.2%. Tensile specimens with dimensions of 30 × 7 × 1.5 mm were processed, and mechanical property testing showed a hardness of 151 HV. 0.3 The yield strength is 442 MPa and the elongation after fracture is 5.1%.

[0048] Compared to the examples, the comparative examples show coarser grains, composed of equiaxed crystals of approximately 1 μm and columnar crystals of 2-8 μm. The equiaxed crystals are located at the molten pool boundary, while the columnar crystals are located in the center of the molten pool. In contrast, the comparative examples all contain fine equiaxed crystals, indicating that the TiN nanoparticles promote the transformation of columnar crystals in the center of the molten pool into equiaxed crystals. Furthermore, the samples in the examples all exhibit ultra-high strength, indicating that the addition of TiN particles is beneficial for improving mechanical properties.

[0049] As described above, the present invention can be implemented well.

[0050] The implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an aluminum-based composite material with ultra-high strength, characterized in that... This includes the composite powder preparation step and the laser forming step; Composite powder preparation steps: Materials were prepared with the following composition: 4.59 wt.% Mn, 3.00 wt.% Mg, 0.71 wt.% Sc, 0.47 wt.% Zr, <0.1 wt.% Fe, and the remainder Al. Al-Mn-Mg-Sc-Zr alloy powder was prepared by vacuum melting and Ar gas atomization. TiN and the alloy powder were then uniformly mixed using ultrasonic dispersion and mechanical vibration. The average diameter of TiN was 80-110 nm, the addition amount was 0-5 wt.%, the ultrasonic frequency was 30 kHz, and the mixing time was 2 h, thus completing the preparation of the composite powder. Laser forming steps: During the forming process, the laser power is 200-250W, the scanning speed is 1000-1400mm / s, the scanning spacing is 100μm, the layer thickness is 30μm, the scanning strategy is interlayer rotation of 67°, the substrate temperature is 180-200℃, and the forming atmosphere is 99.9%Ar, thus completing the preparation of aluminum-based composite materials.

2. The method for preparing the ultra-high strength aluminum-based composite material according to claim 1, characterized in that, In the laser forming process, the density of the formed composite material reaches 99.8%, the sample heat treatment temperature is 300-325℃, the heating rate is 10℃ / min, and the holding time is 2-6h.

3. The method for preparing the ultra-high strength aluminum-based composite material according to claim 1, characterized in that, Before the laser forming step, the composite powder needs to be dried at 80°C for 8 hours.

4. An aluminum-based composite material, characterized in that... It is obtained by the preparation method described in any one of claims 1-3.

5. The aluminum-based composite material according to claim 4, characterized in that, The yield strength of this aluminum-based composite material was measured at 25℃ to be 570-580 MPa, and the elongation after fracture was 2%-8%.

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