阅读说明：本技术 一种加工性能优良的Al合金基复合材料及其制备方法 (Al alloy-based composite material with excellent processability and preparation method thereof ) 是由 汤文明 常浩 陈国栋 聂强强 于 2020-06-19 设计创作，主要内容包括：本发明公开了一种加工性能优良的Al合金基复合材料及其制备方法,选取平均粒径(<I>d</I><Sub><I>50</I></Sub>)为10-20 um的SiC粉体(SiCp),直径50-100μm、厚度约为50-100 nm的纳米石墨片(GNPs)及平均粒径(<I>d</I><Sub><I>50</I></Sub>)为10-30 um的6061Al合金粉体为原料,包括如下制备步骤：(1)GNPs分散；(2)混料；(3)干燥；(4)压制成形；(5)热压烧结；(6)磨削加工。相对于常规的高体分SiCp/Al基复合材料,该复合材料的力学、热学性能优异,机加工性能显著改善,且加工后复合材料的性能保持率高,因而,可替代前者,在电子封装材料领域展现广阔的应用前景。(The invention discloses an Al alloy-based composite material with excellent processing performance and a preparation method thereof, wherein the average grain diameter (A) is selected d 50 ) SiC powder (SiCp) of 10-20 um, Graphite Nanoplatelets (GNPs) having a diameter of 50-100 μm and a thickness of about 50-100nm, and an average particle diameter: ( d 50 ) 6061Al alloy powder of 10-30 um as raw materialThe preparation method comprises the following preparation steps: (1) dispersing GNPs; (2) mixing materials; (3) drying; (4) pressing and forming; (5) hot pressing and sintering; (6) and (5) grinding. Compared with the conventional high-volume-fraction SiCp/Al-based composite material, the composite material has excellent mechanical and thermal properties, the machining performance is obviously improved, and the performance retention rate of the machined composite material is high, so that the composite material can replace the former and has a wide application prospect in the field of electronic packaging materials.)

1. An Al alloy based composite material with excellent processing performance and a preparation method thereof are characterized in that: the method comprises the following steps:

(1) dispersion of GNPs: weighing 5-15wt% of GNPs, placing in absolute ethyl alcohol, and then performing ultrasonic dispersion for 30-60 min until the GNPs are uniformly and stably suspended in the absolute ethyl alcohol and no obvious precipitation phenomenon exists;

(2) mixing materials: weighing 48.4-36.1wt% of SiCp and the balance of Al alloy powder, adding the SiCp and the balance of Al alloy powder into the graphite flake suspension prepared in the step (1), and mechanically stirring by using an electric stirrer;

(3) and (3) drying: after the materials are mixed, placing the mixed slurry of the Al alloy powder, SiCp and GNPs prepared in the step (2) in a constant-temperature drying box, and preserving the heat for 2-3h at the temperature of 60-80 ℃ to completely volatilize the absolute ethyl alcohol;

(4) pressing and forming: uniformly smearing hexagonal BN (boron nitride) absolute ethyl alcohol mixed liquor inside a graphite mould, wrapping carbon paper after the graphite mould is completely dried, filling the mixed material prepared in the step (3) into an inner cavity of the mould, applying axial pressure of 30-60MPa in a one-way mode, and maintaining the pressure for 1-2min for prepressing and forming;

(5) hot-pressing and sintering: putting the pressed compact obtained in the step (4) into a vacuum hot-pressing sintering furnace for sintering at the sintering temperature of 560 ℃ and 620 ℃ for 0.2-1h to obtain the 5-15wt% GNPs/48.4-36.1 wt% SiCp/Al alloy composite material;

(6) grinding: and (4) grinding the composite material prepared in the step (5) by using a surface grinding machine, wherein the rotating speed of a grinding wheel of the grinding machine is 1400-1500rpm, the feed amount of each cutter is 2-4 mu m, and the feed speed of a workbench is 0.8-1.2 m/min.

2. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: in the step (1), the diameter of the GNPs is 50-100 μm, the thickness is 50-100nm, and the absolute ethanol solvent required by ultrasonic dispersion is 60-100 ml by taking 1g of the GNPs as a reference.

3. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: the average particle diameter of SiCp in the step (2)d ₅₀ Is 10-20 μm.

4. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: in the step (2), an electric stirrer is used for stirring, the rotating speed is 100-.

5. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: in the step (4), the thickness of the carbon paper wrapped by the graphite mold is 0.1mm, and 5-10g of hexagonal BN powder is added into 50-100ml of absolute ethanol solution to prepare suspension.

6. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: in the step (5), the mixed powder is filled into a graphite mold, and then sintered in a hot-pressing sintering furnace, wherein the sintering temperature is set to 560 ℃ and 620 ℃, the vacuum degree is less than 1Pa, and the specific sintering process comprises the following steps: heating the sample to 300-500 ℃ at 5-10 ℃ per min, applying 30-50MPa pressure, heating to the set temperature at the rate of 3-5 ℃ per min, keeping the temperature for 0.2-1h, stopping heating and unloading, and cooling to room temperature along with the furnace.

7. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: the sintering pressure in the step (5) is preferably 50 MPa.

8. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: the grinding wheel in the step (6) is a 800-mesh grinding wheel, and the size of the grinding wheel is phi 355mm multiplied by 50 mm.

9. The Al alloy-based composite material with excellent processability as claimed in claim 1, wherein: in the GNPs/SiCp/Al alloy based composite material, the content of the GNPs is 5-15wt%, the content of the SiCp is 48.4-36.1wt%, and the balance is Al alloy.

Technical Field

The invention relates to a preparation method of a metal-based composite material, in particular to an Al alloy-based composite material with excellent processing performance and a preparation method thereof, belonging to the field of new materials and preparation processes thereof.

Background

The high-volume-fraction SiCp/Al-based composite material serving as a typical representative of a third-generation electronic packaging material has the performance advantages of high specific strength, high specific stiffness, controllable thermal conductivity, controllable thermal expansion coefficient and the like, but also has the defects of poor machining performance, extremely high machining cost, obvious performance reduction of the machined material and the like, and limits the application of the high-volume-fraction SiCp/Al-based composite material in the field of packaging of microelectronic and power electronic devices.

Carbon materials, such as carbon fibers, carbon nanotubes, graphene and GNPs, have excellent thermal conductivity and extremely low thermal expansion coefficient, can effectively reduce the thermal mismatching of metals such as Cu, Al and the like with semiconductor and ceramic substrates, and become an ideal reinforcing phase of the metal-based electronic packaging composite material. In particular, GNPs having a size between that of natural graphite flakes and graphene have high thermal conductivity, negative thermal expansion coefficient, low density and hardness with excellent self-lubricating properties. Therefore, the combination of the low thermal expansion coefficient, high thermal conductivity and excellent lubricity of GNPs, the high strength of SiCp and the excellent formability and processing performance of Al alloy is expected to develop an Al-based electronic packaging hybrid composite material with excellent comprehensive performance, and the problem of low processability of a high-volume SiCp/Al-based composite material is solved.

The powder metallurgy method is a relatively advanced material preparation method, and can be implemented by uniformly mixing reinforcing phase with metal matrix powder in any proportion, adding composite powder into metal or graphite mould to make compression, and finally adopting the processes of normal pressure, hot pressing or hot isostatic pressing, etc. under the protection of vacuum or inert atmosphere to make the prepared pressed compact be sintered and formed. The normal pressure sintering is a traditional powder metallurgy method, and has the advantages of simple process and equipment, but has the main defects that when the content of a reinforcing phase in a composite material is higher, the composite material is difficult to sinter and densify under the assistance of external conditions such as pressure and the like, contains a large number of microstructure defects, and has obvious influence on the performance of the composite material. In contrast, vacuum hot-pressing sintering is to place loose or pre-pressed composite material powder in a mold with a certain shape, and apply uniaxial pressure to the composite material while heating and sintering the composite material. Compared with the normal pressure sintering, the method has the advantage that the densification of the composite material is realized by the rearrangement of particles and the plastic flow of the contact part of the particles because the composite material powder is in a thermoplastic state during the hot pressing. Meanwhile, due to the fact that pressure is applied in the sintering process, the method is beneficial to the occurrence of the processes of atomic diffusion mass transfer and flow mass transfer in the composite material, the sintering temperature of the composite material is reduced, the sintering time is shortened, not only can the growth of crystal grains of the metal matrix be inhibited, but also the generation of harmful interface reaction products can be obviously inhibited. Therefore, the microstructure of the composite material is obviously improved, and the performance of the composite material is greatly improved.

Turning and grinding are important precision machining methods in the field of machining. Turning is generally suitable for the processing of low fraction SiCp/Al composites having SiCp content below 20 wt%. For the high-fraction SiCp/Al-based composite material, turning is not applicable any more, and a diamond grinding wheel is required to be used for grinding. However, because the SiCp has high hardness, when the SiCp content in the composite material is high, the SiCp is connected into a continuous matrix, the grinding efficiency is low, and meanwhile, during grinding, the SiCp in the composite material is easy to break, fall off or debond from Al alloy, so that the machined surface of the composite material has high roughness and low surface quality; and the performance of the composite material is obviously reduced after processing, and the retention rate of the performance is low compared with that before processing.

Therefore, the invention develops an Al alloy-based composite material with excellent processing performance and a preparation method thereof, namely, a novel method for designing the components of the composite material by partially replacing SiCp with GNPs is adopted to prepare the novel GNPs/SiCp/Al alloy-based composite material on the premise of keeping the volume percentage of the Al alloy in the composite material unchanged basically. On one hand, GNPs with low strength and excellent self-lubricating property are adopted to replace part of SiCp with high hardness and difficult processing; on the other hand, the GNPs are used for isolating the SiCp from each other to ensure that the SiCp is discontinuously distributed, so that the processing performance of the GNPs/SiCp/Al alloy-based composite material is remarkably improved, and meanwhile, the surface quality of the composite material and the retention rate of the performance after processing are greatly improved. The novel material design idea of the GNPs/SiCp/Al alloy-based composite material is original in the patent of the invention and is not published at home and abroad.

Disclosure of Invention

The invention aims to provide an Al alloy-based composite material with excellent processing performance and a preparation method thereof, and aims to solve the technical problems of improving the organization structure of the GNPs/SiCp/Al alloy-based composite material and improving the grinding processing performance by optimizing the process.

The method comprises the steps of firstly carrying out ultrasonic dispersion on GNPs, then mixing the GNPs with Al alloy powder and SiCp according to a certain proportion, and mixing the materials in a mechanical stirring and synchronous ultrasonic mode. After the mixed powder is dried, the GNPs/SiCp/Al alloy-based composite material with reasonable microstructure and excellent comprehensive performance is prepared by adopting a hot pressing technology, the processing performance of the novel electronic packaging composite material is improved, and the development of related industries is promoted.

In the GNPs/SiCp/Al alloy based composite material, the content of the GNPs is 5-15wt%, the content of the SiCp is 36.1-48.4wt%, and the balance is Al alloy.

An Al alloy based composite material with excellent processing performance and a preparation method thereof, comprising the following steps:

(1) dispersion of GNPs: weighing 5-15wt% of GNPs powder, placing the powder in absolute ethyl alcohol, and then performing ultrasonic dispersion for 30-60 min until the GNPs are uniformly and stably suspended in the absolute ethyl alcohol and no obvious precipitation phenomenon exists;

(2) mixing materials: weighing a certain amount of Al alloy powder and SiCp, adding the Al alloy powder and the SiCp into the graphite flake turbid liquid prepared in the step (1), mechanically stirring by using an electric stirrer, and synchronously carrying out ultrasonic treatment;

(3) and (3) drying: after the materials are mixed, placing the mixed slurry of the Al alloy powder, SiCp and GNPs prepared in the step (2) in a constant-temperature drying box, and preserving the heat for 2-3h at the temperature of 60-80 ℃ to completely volatilize the absolute ethyl alcohol;

(4) pressing and forming: uniformly smearing hexagonal BN (boron nitride) absolute ethyl alcohol suspension in the inner cavity of a graphite mould, pasting a layer of carbon paper in the inner cavity of the mould after the suspension is completely dried, filling the mixed powder of GNPs, SiCp and Al alloy powder prepared in the step (3) into the inner cavity of the mould, applying axial pressure of 30-60MPa in a one-way mode, and maintaining the pressure for 1-2min for prepressing and forming;

(5) hot-pressing and sintering: and (4) placing the pressed compact pre-pressed in the step (4) into a vacuum hot-pressing sintering furnace for sintering, wherein the sintering temperature is 560-: heating the sample to 300-500 ℃ at 5-10 ℃/min, applying 30-50MPa pressure, heating to the set temperature at the rate of 3-5 ℃/min, keeping the temperature for 0.2-1h, stopping heating and unloading, and cooling to room temperature along with the furnace;

(6) grinding: and (4) grinding the composite material prepared in the step (5) by using a surface grinding machine, wherein the rotating speed of a grinding wheel of the grinding machine is 1400-1500rpm, the feed amount of each cutter is 2-4 mu m, and the feed speed of a workbench is 0.8-1.2 m/min.

In the step (1), the diameter of the GNPs is 50-100 μm, and the thickness is 50-100 nm.

The average grain diameter of the Al alloy powder in the step (2)d ₅₀ 10-30 um, wherein the Al alloy powder is 6 series Al alloy powder with Si content of 0.5-3 wt% and Mg content of 0.5-3 wt%.

In the step (5), the sintering pressure is preferably 50 MPa.

Compared with the SiCp/Al-based composite material, the electronic packaging GNPs/SiCp/Al alloy-based composite material prepared by the process has the beneficial effects that the intensity of the GNPs/SiCp/Al alloy-based composite material prepared by partially replacing SiCp with GNPs with the weight of not more than 10 percent is reduced, but the thermal conductivity is increased, the thermal expansion coefficient in the X-Y direction is reduced, the mechanical and thermal properties of the 5 percent GNPs/48.4 percent SiCp/Al alloy-based composite material prepared under the sintering pressure of 50MPa are excellent, the density is more 98.9 percent, the bending strength is 267MPa, the thermal conductivity in the X-Y, Z direction is 198W/(m.K) and 125W/(m.K), and the CTE in the X-Y, Z direction is 9.0 and 12.5 × 10 respectively^-6/° C (RT-100 ℃). Meanwhile, the damage degree of the grinding processing to the surface structure of the composite material is reduced, and the surfaceThe roughness is reduced by 22.7 percent relative to a 54 percent SiCp/Al alloy based composite material ground by the same process, the thermal conductivity of the composite material in the Z direction is 120W/(m.K) after grinding, the thermal conductivity is reduced by only 1.9 percent relative to the thermal conductivity before processing, and the thermal expansion coefficient in the X-Y direction is 9.4 × 10^-6The temperature rises by only 3.3% compared to that before processing. After the 54wt% SiCp/Al-based composite material is ground, the thermal conductivity is reduced by 6%, and the thermal expansion coefficient is increased by 6.1%. Therefore, compared with a high-volume-fraction SiCp/Al-based composite material, the metal-based composite material has excellent comprehensive performance, the machining performance is obviously improved, the retention rate of the performance of the processed composite material is high, and the metal-based composite material can replace the SiCp/Al-based composite material and show wide application prospects in the field of electronic packaging materials.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) photograph of the microstructure (1a) and fracture morphology (1b) of a 590 ℃ and 50MPa sintered 5wt% GNPs/48.4 wt% SiCp/6061 Al-based composite material of example 1 and its magnified images (1a ') and (1 b').

FIG. 2 is a Scanning Electron Microscope (SEM) photograph of the microstructure (2a) and fracture morphology (2b) of the 590 ℃ and 50MPa sintered 10wt% GNPs/42.2 wt% SiCp/6061 Al-based composite material of example 2 and its magnified images (2a ') and (2 b').

FIG. 3 is a Scanning Electron Microscope (SEM) photograph of the microstructure (3a) and fracture morphology (3b) of the 590 ℃ and 50MPa sintered 15wt% GNPs/36.1 wt% SiCp/6061 Al-based composite material of example 3 and its magnified images (3a ') and (3 b').

FIG. 4 is a graph showing the surface morphology of the composite materials of example 1, example 2 and example 3 of example 4 after grinding, respectively, (4a) 54wt% SiCp/6061Al based composite material; (4b) 5wt% GNPs/48.4 wt% SiCp/6061Al based composite material; (4c) 10wt% GNPs/42.2 wt% SiCp/6061Al based composite material; (4d) 15wt% GNPs/36.1 wt% SiCp/6061Al based composite material.

Detailed Description

The invention will be further explained and explained with reference to the drawings and the specific embodiments.