CN110863160A

CN110863160A - SIALON whisker reinforced aluminum matrix composite material and preparation method thereof

Info

Publication number: CN110863160A
Application number: CN201911093867.5A
Authority: CN
Inventors: 曾宇平; 张晨旭; 尹金伟; 左开慧; 夏咏峰; 姚冬旭; 梁汉琴
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2019-11-11
Filing date: 2019-11-11
Publication date: 2020-03-06

Abstract

The invention relates to a SIALON whisker reinforced aluminum-based composite material and a preparation method thereof.

Description

SIALON whisker reinforced aluminum matrix composite material and preparation method thereof

Technical Field

The invention relates to a reinforced aluminum matrix composite material taking SIALON whiskers as a reinforcement and a preparation method thereof, belonging to the field of preparation of new materials.

Background

The aluminum matrix composite has a series of advantages of small density, high specific strength and specific stiffness, small thermal expansion coefficient, good heat conductivity, excellent wear resistance and the like, and has potential application prospect and wide market. Ceramic materials have high hardness and strength and are the most widely used reinforcing phase materials. Among these, ceramic particles and whiskers are the most common type of ceramic reinforcing phase. While the raw materials for ceramic particles are relatively low in cost, they have a number of internal defects, have limited reinforcing effects on the matrix material, and generally also reduce the ductility and processability of the composite. In the case of ceramic whiskers, the ceramic whiskers have a typical single crystal structure, have no defects such as holes, dislocations and grain boundaries, and have density and strength close to theoretical values. In addition, the ceramic whisker is similar to short fiber in appearance, and the reinforcing effect of the whisker can be more prominent due to the larger length-diameter ratio. Wherein, the SIAlON crystal whisker not only has the density similar to that of aluminum, but also has high strength and rigidity. Therefore, the SIAlON whisker is an ideal reinforcing phase material in the aluminum matrix composite. For the aluminum matrix composite, the stirring casting method is a preparation process which is simple to operate, low in cost, capable of preparing large-size materials and extremely suitable for industrial production. However, the disadvantages of the conventional stir casting method are also significant. The main reason is that the size of the reinforcing phase is mostly in the micron order, and macroscopic stirring not only can easily cause agglomeration, but also can cause gas and impurities to be involved in the high-speed stirring process, so that the performance of the casting is greatly reduced.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide an enhanced aluminum matrix composite material taking SIAlON whiskers as a reinforcing phase and a preparation method thereof, which effectively solve the problem of poor distribution uniformity of ceramic in a metal matrix, improve the compactness of the material and realize good interface bonding of two phases.

In one aspect, the invention provides a SIALON whisker reinforced aluminum-based composite material, which takes SIALON whiskers as a reinforcing phase and pure aluminum or aluminum-based alloy as a matrix phase, and the SIALON whiskers are uniformly distributed in the pure aluminum or aluminum alloy matrix.

In the aluminum-based composite material provided by the invention, the reinforcing phase SIALON whiskers are uniformly distributed in the aluminum-based material and are tightly combined with the aluminum-based material, so that the mechanical property of the aluminum-based composite material is greatly improved. The obtained SIALON whisker reinforced aluminum matrix composite material has the advantages of high strength, high hardness, wear resistance, low expansion and the like.

Preferably, the SIALON whisker accounts for 1-40% by mass, and the matrix phase accounts for 60-99% by mass; preferably, the SIALON whisker accounts for 5-20% by mass, and the matrix phase accounts for 80-95% by mass.

Preferably, the diameter of the SIAlON whisker is 0.1-1 μm, the length is 1-5 μm, and the length-diameter ratio of the whisker is 1-50.

On the other hand, the invention also provides a preparation method of the above SIALON whisker reinforced aluminum matrix composite material, which comprises the following steps:

(1) adding the SIALON whiskers into a crucible filled with a pure aluminum melt or an aluminum alloy melt, and then pre-dispersing the SIALON whiskers in an aluminum matrix by adopting a mechanical stirring method to obtain a mixed solution;

(2) introducing an ultrasonic stirring rod into the obtained mixed solution for ultrasonic stirring treatment, pouring the mixed solution into a mold, contacting the bottom of the mold with an ultrasonic device in the melt solidification process (aiming at preventing non-uniform sedimentation of whiskers at the initial stage of melt solidification), and continuing ultrasonic treatment until the mixed solution is completely solidified to obtain a block;

(3) in order to further improve the compactness and the mechanical property of the composite material, the obtained block is extruded by adopting a hot extrusion process, so that the SIALON whisker reinforced aluminum matrix composite material is obtained.

In the invention, a method of combining mechanical stirring with ultrasonic stirring is adopted, firstly, macroscopic pre-dispersion of the SIALON whiskers in the aluminum melt is realized, and then the melt is mixed from a microscopic angle through cavitation and acoustic flow effects generated in the aluminum melt by high-intensity ultrasound, so that SIALON whisker aggregates can be effectively crushed, and the wettability of the whiskers and an aluminum matrix can be improved. In addition, bubbles in the melt can be effectively removed by ultrasonic stirring, so that a more uniform and stable tissue is obtained. The method of combining mechanical stirring and ultrasonic stirring can effectively reduce the production time of materials, improve the production efficiency and save the cost.

Preferably, the temperature of the pure aluminum melt or the aluminum alloy melt is 800-1100 ℃, and preferably 850-1000 ℃.

Preferably, the speed of the mechanical stirring is 200-500 r/min, and the time is 0.5-5 hours; preferably, the speed of the mechanical stirring is 300-400 r/min, and the time is 2-3 hours.

Preferably, the ultrasonic stirring rod is made of Nb-Zr; the frequency of ultrasonic stirring treatment is 80-150 kHz, and the time is 10-30 minutes.

Preferably, the ultrasonic treatment is performed by contacting a plurality of ultrasonic vibration rods made of Nb — Zr with the bottom outside the mold (e.g., crucible) and indirectly transmitting the ultrasonic waves through the mold until the ultrasonic vibration rods are completely solidified; the frequency of the ultrasonic wave is 100-150 kHz. On one hand, the introduction of ultrasonic treatment in the solidification process can accelerate the atom movement in the melt, so that the temperature field in the crucible is more uniform; on the other hand, the method can also effectively avoid the precipitation of the SIALON whiskers in the solidification process, and particularly prevent the non-uniform sedimentation of the whiskers in the early solidification stage. In addition, the ultrasonic wave can also play a role in refining aluminum matrix grains to a certain extent, and is favorable for improving the mechanical property of the material.

Preferably, the temperature of the extrusion treatment is 400-500 ℃; the extrusion ratio of the extrusion treatment is (1-8): 1, preferably 2:1, 4:1 or 8:1, and both the compactness and the mechanical property of the material are improved. The extrusion ratio is the ratio of the cross-sectional area of the extrusion cylinder cavity to the total cross-sectional area of the extruded product, also called the extrusion coefficient, and the volume is unchanged before and after extrusion.

Has the advantages that:

in the invention, under the molten state of matrix metal, the SIALON whisker is pre-dispersed by mechanical stirring, the further dispersion of the whisker in the matrix is realized by an ultrasonic stirring method, then the crystal whisker is poured into a mould, the ultrasonic wave is introduced again in the solidification process of the crystal whisker, and finally the obtained casting is subjected to hot extrusion treatment, so that the uniformly dispersed SIALON whisker reinforced aluminum matrix composite material is obtained;

in the invention, the SIALON crystal whisker has extremely high hardness and strength and excellent chemical stability; secondly, the SIALON crystal whisker has a certain length-diameter ratio and can better play a role in stress transfer; in addition, the crystal structure of the SIALON whisker contains Al atoms, and the compatibility with an aluminum matrix is better. In conclusion, the SIALON whisker is an ideal aluminum-based reinforcement material. Practical verification shows that the aluminum matrix composite with 20 wt% of whisker content has the strength improved by 113MPa to the maximum extent and the improvement amplitude up to 91.9% compared with a pure aluminum matrix;

the invention uses the liquid phase stirring method assisted by ultrasound, and the method has the characteristics of high production efficiency and is suitable for popularization and application.

Drawings

FIG. 1 is a scanning electron microscope photograph of SIALON whiskers used in examples 1-5 of the present invention;

FIG. 2 is a TEM image of the interface between the reinforcing phase and the matrix phase of the reinforced Al-based composite material obtained in example 1;

FIG. 3 is a surface polishing topography of the enhanced aluminum-based composite material prepared in example 1 of the present invention.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

In the present disclosure, the SIALON whisker-reinforced aluminum-based composite material uses SIALON whisker as a reinforcing phase and pure aluminum or an aluminum-based alloy as a matrix phase. Wherein, the diameter of the SIAlON whisker can be 0.1-1 μm, the length can be 1-5 μm, and the length-diameter ratio of the whisker can be 1-50.

As a preferable scheme, the SIALON whiskers in the composite material account for 1-40% by mass, and the matrix phase accounts for 60-99% by mass. If the content of the SIALON whiskers is too low, the enhancement effect is not obvious enough; if the SIALON whisker content is too high, the whisker agglomeration phenomenon is easily caused, thereby reducing the mechanical properties of the material, such as strength reduction or ductility reduction. More preferably, the SIALON whisker accounts for 5-20% by mass, and the matrix phase accounts for 80-95% by mass. The composite material with the composition has more excellent mechanical property.

In one embodiment of the invention, a certain amount of SIALON whiskers are added into pure aluminum or an aluminum alloy melt, mechanical stirring is adopted to realize pre-dispersion of the SIALON whiskers in an aluminum matrix, ultrasonic stirring is used for further dispersion, the mixture is poured into a mold, ultrasonic treatment is applied again in the solidification process of the mixture, and finally the uniformly dispersed SIALON whisker reinforced aluminum matrix composite material is obtained. The following is an exemplary description of the preparation method of the SIALON whisker reinforced aluminum matrix composite.

The SIALON whisker is prepared according to the prior art (for example, see Yuesheng and the like, β -the research on the induction synthesis and growth mechanism of the SIALON whisker, artificial crystal science, 2011 5 th, Ben Peng and the like, synthesis of β -the SiAlON whisker and the research on the microstructure thereof by using coal gangue as a raw material, silicate notification, 2010 1 st and the like).

Adding the SIALON whiskers into a pure aluminum melt or an aluminum alloy melt in proportion, and mechanically stirring for 0.5-5 hours at a rotating speed of 200-500 r/min to realize pre-dispersion of the SIALON whiskers in an aluminum matrix. Wherein the mechanical stirring speed is 300-400 r/min, and the stirring time is 2-3 h. Heating a pure aluminum ingot or an aluminum alloy ingot to 800-1100 ℃ (preferably 850-1000 ℃) until complete melting to form a melt. The atmosphere is inert atmosphere, and can be protective atmosphere such as argon, helium and the like.

And introducing an ultrasonic stirring rod made of Nb-Zr into the melt after mechanical stirring, and further carrying out ultrasonic stirring treatment on the SIALON whiskers in the melt. Wherein, the parameters of the ultrasonic stirring treatment comprise: the ultrasonic treatment time is 10-30 min, and the ultrasonic frequency is 80-150 kHz. The atmosphere is inert atmosphere, and can be protective atmosphere such as argon, helium and the like.

The dross on the surface of the melt is removed, and the obtained aluminum melt containing the SIALON whiskers is poured into a mold (such as a crucible) and solidified. And in the solidification process of the melt, the bottom outside the mold is contacted with a plurality of ultrasonic rods, the ultrasonic frequency is controlled to be 100-150 kHz, and the ultrasonic is turned off until the melt of the aluminum matrix composite is completely solidified, so that the block is obtained. The atmosphere is inert atmosphere, and can be protective atmosphere such as argon, helium and the like.

Preheating the solidified block at 400-500 ℃ by adopting a hot extrusion process, and then carrying out hot extrusion treatment (namely extrusion treatment), wherein the hot extrusion temperature and the preheating temperature are kept consistent at 400-500 ℃, and finally obtaining the enhanced aluminum-based composite material. During the hot extrusion process, the extrusion ratio can be controlled to be 2:1, 4:1, or 8: 1. The time of the preheating treatment may be 30 minutes. The atmosphere is inert atmosphere, and can be protective atmosphere such as argon, helium and the like.

In the invention, a universal testing machine is adopted to test the ultimate tensile strength, the ultimate compression strength and the bending strength of the SIALON whisker reinforced aluminum matrix composite.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

Firstly, 1800g of pure aluminum ingot is heated to 950 ℃ by using an electromagnetic heating device to be melted (the pure aluminum ingot comprises more than or equal to 99.9 mass percent of Al and less than or equal to 0.1 mass percent of O, and the pure aluminum ingot used in the following examples 2 to 5 is the same as the pure aluminum ingot used in the example 1), at the moment, mechanical stirring is started, the rotating speed is 350r/min, then 200g of SIALON crystal whisker is added into an aluminum melt in batches, and the stirring is continued for 3 hours; then, placing an ultrasonic stirring rod made of Nb-Zr material in the melt, wherein the ultrasonic frequency is set to be 100kHz, and the ultrasonic time is 30 min; removing surface scum, pouring the molten aluminum matrix composite into a steel mold, introducing ultrasonic at the bottom of the outer side of the crucible, wherein the ultrasonic frequency is 100kHz, and performing ultrasonic until the material is solidified; and finally, preheating the poured sample to 500 ℃, preserving heat for 30min, then placing the sample in a hot extrusion die at 500 ℃, carrying out hot extrusion treatment with the extrusion ratio of 4:1, and obtaining the SIALON whisker reinforced aluminum matrix composite material with the whisker content of 10% by mass after extrusion.

Comparative example 1

This comparative example differs from example 1 in that: the raw materials do not contain SIALON crystal whiskers, and the raw materials are not subjected to any mechanical stirring and ultrasonic stirring treatment, but only subjected to hot extrusion treatment.

The vickers hardness, ultimate tensile strength, ultimate compressive strength, and bending strength test data of the reinforced aluminum matrix composites obtained in example 1 and comparative example 1 are shown in table 1, and the interface between the reinforcing phase and the matrix phase of the reinforced aluminum matrix composites is shown in fig. 2. The distribution state of whiskers in the composite material is shown in fig. 3.

Example 2

Firstly, 1600g of pure aluminum ingot is heated to 1000 ℃ by using an electromagnetic heating device to be melted, mechanical stirring is started at the moment, the rotating speed is 350r/min, then 400g of SIALON crystal whisker is added into an aluminum melt in several times, and the stirring is continuously carried out for 3 hours; then, placing an ultrasonic stirring rod made of Nb-Zr material in the melt, wherein the ultrasonic frequency is set to be 100kHz, and the ultrasonic time is 30 min; removing surface scum, pouring the molten aluminum matrix composite into a steel mold, introducing ultrasonic at the bottom of the outer side of the crucible, wherein the ultrasonic frequency is 100kHz, and performing ultrasonic until the material is solidified; and finally, preheating the poured sample to 500 ℃, preserving heat for 30min, then placing the sample in a hot extrusion die at 500 ℃, carrying out hot extrusion treatment with the extrusion ratio of 4:1, and obtaining the SIALON whisker reinforced aluminum matrix composite material with the whisker content of 20% by mass after extrusion.

The data of the detection of vickers hardness, ultimate tensile strength, ultimate compressive strength, and bending strength of the SIALON whisker-reinforced aluminum matrix composite material obtained in example 2 are shown in table 1.

Example 3

Firstly, heating 1800g of pure aluminum ingot to 800 ℃ by using an electromagnetic heating device to melt the ingot, starting mechanical stirring at the time, controlling the rotating speed to be 400r/min, then adding 200g of SIALON whiskers into an aluminum melt in batches, and continuously stirring for 3 hours; then, placing an ultrasonic stirring rod made of Nb-Zr material in the melt, wherein the ultrasonic frequency is set to be 100kHz, and the ultrasonic time is 30 min; removing surface scum, pouring the molten aluminum matrix composite into a steel mold, introducing ultrasonic at the bottom of the outer side of the crucible, wherein the ultrasonic frequency is 100kHz, and performing ultrasonic until the material is solidified; and finally, preheating the poured sample to 500 ℃, preserving heat for 30min, then placing the sample in a hot extrusion die at 500 ℃, carrying out hot extrusion treatment with the extrusion ratio of 2:1, and obtaining the SIALON whisker reinforced aluminum matrix composite material with the whisker content of 10% by mass after extrusion.

The data of the detection of vickers hardness, ultimate tensile strength, ultimate compressive strength, and bending strength of the SIALON whisker-reinforced aluminum matrix composite material obtained in example 3 are shown in table 1.

Example 4

Firstly, heating 1800g of pure aluminum ingot to 800 ℃ by using an electromagnetic heating device to melt the ingot, starting mechanical stirring at the time, controlling the rotating speed to be 400r/min, then adding 200g of SIALON whiskers into an aluminum melt in batches, and continuously stirring for 3 hours; then, placing an ultrasonic stirring rod made of Nb-Zr material in the melt, wherein the ultrasonic frequency is set to be 100kHz, and the ultrasonic time is 30 min; removing surface scum, pouring the molten aluminum matrix composite into a steel mold, introducing ultrasonic at the bottom of the outer side of the crucible, wherein the ultrasonic frequency is 100kHz, and performing ultrasonic until the material is solidified; and finally, preheating the poured sample to 500 ℃, preserving heat for 30min, then placing the sample in a hot extrusion die at 500 ℃, carrying out hot extrusion treatment with the extrusion ratio of 8:1, and obtaining the SIALON whisker reinforced aluminum matrix composite material with the whisker content of 10% by mass after extrusion.

The data of the detection of vickers hardness, ultimate tensile strength, ultimate compressive strength, and bending strength of the SIALON whisker-reinforced aluminum matrix composite material obtained in example 4 are shown in table 1.

Example 5

Firstly, heating 1800g of pure aluminum ingot to 950 ℃ by using an electromagnetic heating device to melt the ingot, starting mechanical stirring at the time, controlling the rotating speed to be 400r/min, then adding 200g of sialon whisker into an aluminum melt in batches, and continuously stirring for 3 hours; then, placing an ultrasonic stirring rod made of Nb-Zr material in the melt, wherein the ultrasonic frequency is set to be 150kHz, and the ultrasonic time is 30 min; removing surface scum, pouring the molten aluminum matrix composite into a steel mold, introducing ultrasonic at the bottom of the outer side of the crucible, wherein the ultrasonic frequency is 150kHz, and performing ultrasonic until the material is solidified; and finally, preheating the poured sample to 500 ℃, preserving heat for 30min, then placing the sample in a hot extrusion die at 500 ℃, carrying out hot extrusion treatment with the extrusion ratio of 8:1, and obtaining the SIALON whisker reinforced aluminum matrix composite material with the whisker content of 10% by mass after extrusion.

The data of the detection of vickers hardness, ultimate tensile strength, ultimate compressive strength, and bending strength of the SIALON whisker-reinforced aluminum matrix composite material obtained in example 5 are shown in table 1.

Example 6

The preparation process of the SIALON whisker reinforced aluminum matrix composite material prepared in this example 6 is substantially the same as that of example 1, except that: the content of SIALON whiskers was 30 wt%.

Example 7

The preparation process of the SIALON whisker reinforced aluminum matrix composite material obtained in this example 7 is substantially the same as that of example 1, except that: the content of SIALON whiskers is 40 wt%.

Comparative example 2

The preparation process of the SIALON whisker reinforced aluminum matrix composite material prepared in the comparative example 2 is basically the same as that of the embodiment 1, and the difference is that: the content of SIALON whiskers was 50 wt%.

Comparative example 3

The preparation process of the SIALON whisker reinforced aluminum matrix composite material prepared in the comparative example 3 is basically the same as that of the example 1, and the difference is that: only an ultrasonic device at the bottom outside the crucible is not introduced, and ultrasonic treatment is not performed.

Comparative example 4

The preparation process of the SIALON whisker reinforced aluminum matrix composite material prepared in the comparative example 4 is basically the same as that of the example 1, and the difference is that: without any ultrasound process.

Table 1 shows the measured data of the Vickers hardness, ultimate tensile strength, ultimate compressive strength, and flexural strength of the reinforced aluminum matrix composites obtained in examples 1 to 7 and comparative examples 1 to 4:

. The meaning of the frequency 1 in the table 1 is that an ultrasonic stirring rod made of Nb-Zr material is placed in the melt, and the ultrasonic frequency is set; the frequency 2 means a value set by placing an ultrasonic device at the bottom outside the crucible and continuing the ultrasonic treatment.

As can be seen from table 1, the addition of the SIALON whisker obviously strengthens the pure aluminum matrix in the examples, and the material strength is obviously improved; the composite material treated by high-temperature melting and high-frequency ultrasonic stirring has the best performance.

As can be seen from FIG. 2, the SIALON whisker reinforcing phase and the matrix phase are tightly combined, no obvious interfacial reaction exists between the two phase interfaces, and the defect that the ductility of the material is reduced by the reaction product is overcome. As can be seen from FIG. 3, the SIALON whiskers are uniformly distributed inside the matrix.

Claims

1. The composite material is characterized in that the composite material takes SIALON whiskers as a reinforcing phase and pure aluminum or aluminum-based alloy as a matrix phase, and the SIALON whiskers are uniformly distributed in the pure aluminum or aluminum alloy matrix.

2. The SIALON whisker reinforced aluminum-based composite material as recited in claim 1, wherein the SIALON whisker accounts for 1-40% by mass, and the matrix phase accounts for 60-99% by mass; preferably, the SIALON whisker accounts for 5-20% by mass, and the matrix phase accounts for 80-95% by mass.

3. The SIALON whisker reinforced aluminum-based composite material as claimed in claim 1 or 2, wherein the SIALON whiskers have a diameter of 0.1 to 1 μm, a length of 1 to 5 μm, and an aspect ratio of the whiskers of 1 to 50.

4. A method of making a SIALON whisker reinforced aluminum matrix composite material as claimed in any one of claims 1 to 3, comprising:

(2) introducing an ultrasonic stirring rod into the obtained mixed solution for ultrasonic stirring treatment, pouring the mixed solution into a mold, contacting the bottom of the mold with an ultrasonic device in the melt solidification process, and continuing to perform ultrasonic treatment until the mixed solution is completely solidified to obtain a block;

(3) and extruding the obtained block by adopting a hot extrusion process to obtain the SIALON whisker reinforced aluminum matrix composite.

5. The method according to claim 4, wherein the temperature of the pure aluminum melt or the aluminum alloy melt is 800 to 1100 ℃, preferably 850 to 1000 ℃.

6. The method according to claim 4 or 5, wherein the mechanical stirring is performed at a speed of 200 to 500 rpm for 0.5 to 5 hours; preferably, the speed of the mechanical stirring is 300-400 r/min, and the time is 2-3 hours.

7. The preparation method according to any one of claims 4 to 6, wherein the material of the ultrasonic stirring rod is Nb-Zr material; the frequency of ultrasonic stirring treatment is 80-150 kHz, and the time is 10-30 minutes.

8. The method for preparing the alloy material according to any one of claims 4 to 7, wherein the ultrasonic treatment is carried out by contacting a plurality of ultrasonic vibration rods made of Nb-Zr with the bottom outside the mold, and indirectly transmitting the ultrasonic waves through the mold until the solidification is completed; the frequency of the ultrasonic wave is 100-150 kHz.

9. The method according to any one of claims 4 to 8, wherein the temperature of the extrusion treatment is 400 to 500 ℃; the extrusion ratio of the extrusion treatment is (1-8): 1, preferably 2:1, 4:1 or 8: 1.