CN111057892A

CN111057892A - Particulate reinforcement α -Al2O3/ZrB2In-situ synthesis method of reinforced aluminum-based composite material

Info

Publication number: CN111057892A
Application number: CN201811203179.5A
Authority: CN
Inventors: 张大山; 朱和国; 李成鑫; 孙晓东; 薛云飞
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2018-10-16
Filing date: 2018-10-16
Publication date: 2020-04-24
Anticipated expiration: 2038-10-16
Also published as: CN111057892B

Abstract

The invention discloses a particle reinforced α -Al₂O₃/ZrB₂The in-situ synthesis method of the reinforced aluminum-based composite material comprises the steps of preparing a reaction sintered sample, drying, putting the sample into a microwave reaction furnace, vacuumizing, heating by microwave until the in-situ reaction occurs, continuously preserving the heat for a period of time, cooling, and taking out from the microwave furnace to obtain α -Al₂O₃/ZrB₂A reinforced aluminum matrix composite block. The invention takes microwave as heating source and Al and ZrO₂Pressing the B powder as a raw material into a prefabricated blank, and sintering to obtain an aluminum-based composite material taking α -Al2O3/ZrB2 as a reinforcement;the method is simple and convenient to operate, energy-saving and efficient, and the consumed energy is only 1/2 of the conventional method; when the volume fraction of the reinforcement is 20%, the particles of the reinforcement are fine and uniformly distributed, the compactness of a sample is improved by 11.2%, the microhardness is improved by 8%, the particles of the reinforcement are generated by thermal explosion reaction, and the surface is clean and well combined with a matrix.

Description

Particulate reinforcement α -Al2O3/ZrB2In-situ synthesis method of reinforced aluminum-based composite material

Technical Field

The invention relates to a method for synthesizing α -Al by microwave thermal explosion in-situ reaction₂O₃/ZrB₂A method for reinforcing an aluminum-based composite material belongs to the field of material preparation.

Background

The microwave thermal explosion in-situ reaction synthesis of composite material is a technology for heating a sample by microwave instead of a traditional heat source to cause the sample to generate chemical reaction to generate a reinforcement in situ. Usually, the designed reaction system is firstly ball-milled and dried, and then the mixed powder is pressed into a blank. Then placing the mixture in a vacuum microwave reaction oven to heat by microwaves, and reacting to generate the required reinforcement. In the traditional sintering process, the temperature of the surface, the interior and the central area of the material has large gradient, so that the crystal grains are easy to be uneven, and the interior has more defects. Microwave sintering penetrates into the material by means of microwave electromagnetic field radiation, the whole material is heated due to medium loss, the temperature difference of each part is small, a uniform structure is easy to obtain, the material performance is obviously improved, and the defect that the traditional sintering structure is not uniform is overcome. And because the microwave sintering speed is very fast, the growth of crystal grains can be effectively prevented to obtain a fine crystal structure. The method of using microwave sintering also has the advantages of high efficiency and energy saving. The microwave is used as a heat source to heat the sample, so that the reaction temperature and the reaction activation energy can be obviously reduced.

Document 1 adopts slurry dip-coating combined with in-situ reaction process to successfully prepare ZrB on the surface of C/C composite material₂The SiC coating has cracks due to violent reaction, and has the phenomena of Si residue and uneven distribution of reinforcing phases. (Zhou navy, inorganic materials bulletin, 2013.5, vol.28, No 3)

Document 2 uses a carbon reduction method for ZrO₂、B₄C. C powder is used as raw material, and is subjected to carbothermic reduction reaction in the atmosphere of inert gas (Ar) when ZrB₂When the formation rate is high, the particle size increases, which affects the performance.（Zhao Hong，Journalof American Ceramic Society，1999，78（9））。

Disclosure of Invention

The invention aims to provide particle reinforced α -Al₂O₃/ZrB₂An in-situ synthesis method of reinforced aluminum-based composite material. The method is simple to operate, safe, reliable, energy-saving, time-saving and environment-friendly, the particles are generated by in-situ reaction, the surface is pollution-free, the interface is clean, the strength of the matrix can be obviously improved, and the compactness and hardness of the composite material are improved.

The technical solution for realizing the purpose of the invention is as follows:

α -Al synthesized by microwave thermal explosion in-situ reaction₂O₃/ZrB₂A method of reinforcing an aluminum matrix composite comprising the steps of:

(1) preparing a reaction sample: weighing powder, mixing, ball-milling, drying, and pressing into a blank as a sample, wherein the powder is aluminum powder, zirconium dioxide powder and boron powder, the volume fraction of the reinforcement is determined to be 20%, and the mass ratio of the powder is as follows: al: ZrO (ZrO)₂: b is 19.41: 5.67: 1;

(2) sample loading and vacuumizing: placing the sample in a vacuum microwave reaction furnace, and vacuumizing;

(3) reaction synthesis: heating a sample by using microwaves as a heat source, and performing thermal explosion reaction at 810-900 ℃;

(4) keeping the temperature, namely heating and keeping the temperature for a period of time after the reaction, taking out the sample after the sample is cooled along with the furnace to obtain α -Al₂O₃/ZrB₂A reinforced aluminum matrix composite.

Further, in the step (1), the mass ratio of ball powder during ball milling is 5: 1, the ball milling speed is 250p.r.m, and the ball milling time is 2 h.

Further, in the step (1), the drying temperature is 100-110 ℃, the drying time is 2 hours, and the pressing pressure is 10 MPa.

Further, in the step (2), after the sample is placed in a vacuum microwave reaction oven, vacuumizing is carried out to 10 DEG^-1pa。

Further, in the step (4), the temperature is raised to 1000 ℃, and the temperature is maintained for 5 minutes.

Compared with the prior art, the invention has the following remarkable advantages:

(1) the process is simple to operate, safe, reliable, energy-saving, time-saving and environment-friendly, energy consumption is greatly reduced, and energy is saved by 50%.

(2) The particles of the reinforcement prepared by the process are fine and uniformly distributed, the compactness of a sample is improved by 11.2 percent, the microhardness is improved by 8 percent, the particles of the reinforcement are generated by thermal explosion reaction, and the surface is clean and is well combined with a matrix.

Drawings

FIG. 1 is an XRD pattern of a microwave vacuum sintered sample.

Fig. 2 is SEM images of the microwave vacuum-sintered sample (a) and the induction vacuum-sintered sample (b).

Detailed Description

The present invention will be described in more detail with reference to the following examples and the accompanying drawings.

α -Al of the invention₂O₃/ZrB₂The microwave thermal explosion in-situ reaction synthesis method of the reinforced aluminum-based composite material specifically comprises the following steps:

(1) preparing a reaction sample: mixing Al and ZrO₂Mixing with B powder and ball milling, wherein Al and ZrO₂And B according to the chemical reaction formula: 3ZrO 2₂+4Al+6B→2α-Al₂O₃+3ZrB₂And α -Al₂O₃And ZrB₂The occupied volume fraction is determined as 20 percent, and the mass ratio of the powder is as follows: al: ZrO (ZrO)₂: b is 19.41: 5.67: 1. the mass ratio of the ball powder is 5: 1, the rotating speed is 250p.r.m, the ball milling time is 2 hours, and then the ball-milled powder is dried for 1 hour at the temperature of 100-110 ℃ and extruded into a blank to prepare a reaction sample.

(2) Sample loading and vacuumizing: loading the pressed compact sample into a reaction device, ensuring the top monitoring hole to clearly observe the whole reaction process, putting the reaction device into a vacuum furnace, and vacuumizing to 10 DEG C^－1Pa or so.

(3) Reaction synthesis and heat preservation: adjusting microwave input power, controlling heating rate, recording temperature change in the vacuum microwave reaction furnace,when the sample is subjected to thermal explosion reaction, the temperature rises suddenly to exceed the temperature set by the program, the microwave stops working, when the temperature of the sample after heat release is finished is close to or lower than the continuously-rising set temperature, the microwave resumes working again, the sample is kept for 5min after reaching the sintering temperature of 1000 ℃, the reaction sample is taken out after the furnace is cooled to 60 ℃, and α -Al is obtained₂O₃/ZrB₂Reinforced aluminum-based composite material

Example (b): microwave sintering of Al-ZrO₂-B reaction system

(1) Al powder and ZrO powder for preparing reaction samples₂The mass ratio of the powder to the powder B is 19.41: 5.67: 1, then they were placed in a ball mill jar, at a rate of 5: 1, ball-milling and mixing for 2 hours at the rotating speed of 250p.r.m, and then extruding into a blank at the pressure of 10MPa to prepare a blank sample;

(2) loading and vacuumizing, putting the pressed blank sample into a microwave vacuum reaction furnace, and vacuumizing to 10 DEG^-1Pa；

(3) Setting the microwave input power at 2000w, the heating rate at 33 deg.C/min, 40 deg.C/min, 50 deg.C/min and 66 deg.C/min, heating to compact sample for thermal explosion reaction at 848 deg.C, 877 deg.C, 891 deg.C and 938 deg.C, heating to sintering temperature of 1000 deg.C by microwave action after the sample thermal explosion reaction is finished, maintaining for 5min, stopping power input, cooling to 60 deg.C, and taking out the reaction sample to obtain α -Al₂O₃/ZrB₂A reinforced aluminum matrix composite.

TABLE 120% α -Al₂O₃/ZrB₂Performance comparison of traditional sintering mode sample of reinforced aluminum-based composite material and sintering sample of microwave vacuum oven

TABLE 1

	Average density (g/cm)³）	Average microhardness (HV 0.5)
			Sample with heating rate of 33 ℃/min	2.91	58.34
Sample with heating rate of 40 ℃/min	3.07	61.40
			Sample with heating rate of 50 ℃/min	3.01	61.21
Sample with heating rate of 66 ℃/min	2.93	59.65
			Sintering sample of traditional induction vacuum furnace	2.68	55.98
Ratio of improvement in average performance	11.2%	8%

Table 1 shows 20% α -Al₂O₃/ZrB₂And comparing the performance of the reinforced aluminum-based composite material sample in the traditional sintering mode with that of the microwave vacuum furnace sintering sample. The microwave vacuum furnace sintering method has the advantages that the reaction process is short, the coarsening of the structure is inhibited, the density of the material is improved, and compared with the conventional sintering method, the average density of a sample can be improved by 11.2 percent, and the microhardness can be improved by about 8 percent.

FIG. 1 is an XRD pattern of a microwave vacuum sintered sample, and it can be seen that α -Al was obtained by this method₂O₃/ZrB₂Two kinds of reinforced aluminum-base composite material and no other impurity.

Fig. 2 is SEM images of the microwave vacuum-sintered sample (a) and the induction vacuum-sintered sample (b). It can be seen through comparison that the sample reinforcement body sintered by microwave vacuum is fine and uniformly distributed, so that the sample reinforcement body heated by induction vacuum is different in size and non-uniformly distributed.

Claims

1. Particulate reinforcement α -Al₂O₃/ZrB₂The in-situ synthesis method of the reinforced aluminum-based composite material is characterized by comprising the following steps:

(1) weighing powder, mixing, ball-milling, drying, and pressing into a blank as a sample, wherein the powder is aluminum powder, zirconium dioxide powder and boron powder, the volume fraction of the reinforcement is determined to be 20%, and the mass ratio of the powder is as follows: al: ZrO (ZrO)₂: b is 19.41: 5.67: 1;

(2) placing the sample in a vacuum microwave reaction furnace, and vacuumizing;

(3) heating a sample by using microwaves as a heat source, and performing thermal explosion reaction at 810-900 ℃;

(4) after the reaction, heating and preserving heat for a period of time, taking out the sample after the sample is cooled along with the furnace to obtain α -Al₂O₃/ZrB₂A reinforced aluminum matrix composite.

2. The method of claim 1, wherein in the step (1), the mass ratio of the ball powder during ball milling is 5: 1, the ball milling speed is 250p.r.m, and the ball milling time is 2 h.

3. The method according to claim 1, wherein in the step (1), the drying temperature is 100 to 110 ℃, the drying time is 2 hours, and the pressing pressure is 10 MPa.

4. As claimed inThe method of claim 1, wherein in the step (2), the sample is placed in a vacuum microwave reaction oven and then is vacuumized to 10 degrees^-1pa。

5. The method of claim 1, wherein in step (4), the temperature is raised to 1000 ℃ and maintained for 5 minutes.