KR102444652B1 - high volume reinforced aluminum composite and method of manufacturing the same - Google Patents

Abstract

The present invention provides a solid area ratio aluminum composite material capable of improving properties by ensuring interfacial stability and a method for manufacturing the same. According to an embodiment of the present invention, the method for manufacturing the high-volume aluminum composite includes: forming a titanium boride preform; disposing solid aluminum on the titanium boride preform; heating the aluminum to melt; pressurizing the molten aluminum using a gas so that the molten aluminum is impregnated into the titanium boride preform; and cooling the titanium boride preform impregnated with the molten aluminum to form an aluminum composite.

Description

High volume reinforced aluminum composite and method of manufacturing the same

The technical idea of the present invention relates to an aluminum composite material, and more particularly, to an aluminum composite material having a high area ratio and a manufacturing method thereof.

The demand for a lightweight material having a special performance in application fields such as automobile field, aerospace field, and defense industry field is increasing, and thus research on aluminum composite material is in progress. These aluminum composites are ceramic using silicon carbide (SiC), alumina (Al ₂ O ₃ ), boron carbide (B ₄ C), titanium carbide (TiC), titanium diboride (TiB ₂ ) or a combination thereof on an aluminum matrix. Manufactured by adding reinforcements. The aluminum composite material has excellent mechanical properties while maintaining a low density.

The production of aluminum composites is made in an ex-situ process in which reinforcement material is added from the outside of the base material. Compared with the in-situ method, the ex-situ method has advantages in that it is easy to control the volume ratio of the reinforcing material, and economical efficiency and productivity are excellent. However, in the ex-situ method, since the reinforcing material is physically attached to the base material, there is an unstable limit at the interface between the reinforcing material and the base material. have.

Korean Patent Publication No. 10-2001-0011347

The technical problem to be achieved by the technical idea of the present invention is to provide a solid area ratio aluminum composite material capable of improving properties by securing interfacial stability and a method for manufacturing the same.

However, these tasks are exemplary, and the technical spirit of the present invention is not limited thereto.

According to one aspect of the present invention, there is provided a solid area ratio aluminum composite material capable of improving properties by ensuring interfacial stability and a method for manufacturing the same.

According to an embodiment of the present invention, a method for manufacturing a high-volume aluminum composite includes: forming a titanium boride preform; disposing solid aluminum on the titanium boride preform; heating the aluminum to melt; pressurizing the molten aluminum using a gas so that the molten aluminum is impregnated into the titanium boride preform; and cooling the titanium boride preform impregnated with the molten aluminum to form an aluminum composite material.

According to an embodiment of the present invention, the forming of the titanium boride preform comprises the steps of forming a titanium boride compression material by compressing the titanium boride powder; and sintering the titanium boride compression material to form the titanium boride preform.

According to an embodiment of the present invention, the titanium boride powder may have an average particle size in the range of 2 μm to 3 μm.

According to an embodiment of the present invention, the compression of the titanium boride powder may be performed at a uniaxial pressure in the range of 60 MPa to 100 MPa.

According to an embodiment of the present invention, the sintering of the titanium boride compressed material may be performed in an inert gas atmosphere, at a temperature in the range of 900°C to 1100°C, for 10 minutes to 120 minutes.

According to an embodiment of the present invention, the heating and melting of the aluminum may be performed at a temperature in the range of 900°C to 1800°C in a vacuum atmosphere.

According to an embodiment of the present invention, the step of pressurizing the molten aluminum using a gas may be performed by injecting an inert gas having a pressure of 1 bar to 20 bar into the molten aluminum.

According to an embodiment of the present invention, the heating and melting of the aluminum and the pressing of the molten aluminum using a gas may be performed simultaneously.

According to an embodiment of the present invention, the aluminum may include pure aluminum or an aluminum alloy.

According to an embodiment of the present invention, the solid area ratio aluminum composite material is manufactured by the above-described method for manufacturing the solid area ratio aluminum composite material, and includes a titanium boride preform; and aluminum impregnated in the titanium boride preform.

According to an embodiment of the present invention, it has pores having a porosity of 20% by volume to 50% by volume, and at least some of the pores may be filled with the aluminum.

According to an embodiment of the present invention, the high-volume aluminum composite material may exhibit a mixed fracture behavior in which the brittle fracture of the titanium boride and the ductile fracture of aluminum are mixed.

According to an embodiment of the present invention, the solid area ratio aluminum composite material may have a density of 3.0 g/cm ³ to 4.2 g/cm ³ .

According to an embodiment of the present invention, the high-volume aluminum composite material may have a tensile strength of 100 MPa to 500 MPa, a compressive yield strength of 100 MPa to 600 MPa, and a Vickers hardness of 40 Hv to 250 Hv.

According to an embodiment of the present invention, the high-volume aluminum composite material may have a thermal expansion coefficient of 11 ppmK ^-1 to 17 ppmK ^-1 .

According to an embodiment of the present invention, the method for manufacturing the high-volume aluminum composite includes: forming a ceramic preform; disposing solid aluminum on the ceramic preform; heating the aluminum to melt; pressing the molten aluminum with a gas so that the molten aluminum is impregnated into the ceramic preform; and cooling the ceramic preform impregnated with the molten aluminum to form an aluminum composite.

According to an embodiment of the present invention, the ceramic preform may include at least one of Al ₂ O ₃ , B ₄ C, SiC, and TiC.

According to the technical idea of the present invention, it is to prepare a titanium boride-aluminum composite material uniformly dispersed and having a high volume fraction by using a melt pressure impregnation process. The present invention can be applied to manufacturing a metal matrix composite by applying a gas pressure at a high temperature of about 1000°C to 1800°C. In addition, the effect of the fine titanium boride reinforcement on the mechanical properties of the titanium boride-aluminum composite material was analyzed. When the titanium boride reinforcing material is uniformly dispersed in aluminum, the titanium boride-aluminum composite material may have an ideal microstructure having high hardness and high strength, which can be manufactured in a cost-effective melting process.

The present invention provides a titanium boride-reinforced aluminum metal matrix composite formed by using a titanium boride (TiB ₂ ) and aluminum (Al1050) alloy having improved properties. The aluminum composite is reinforced with fine titanium boride having a volume ratio of 60% or more. The aluminum composite material is manufactured using melt pressure impregnation using gas pressure at high temperature. Examining the microstructure of the titanium boride-aluminum composite formed by pressing at 1000° C. at 10 bar for 1 hour, it can be confirmed that the molten aluminum is effectively impregnated into the titanium boride preform having a high volume fraction, which has improved wettability and external It is analyzed to be due to gas pressurization. In addition, cracks, pores, and brittle intermetallic compounds were not found at the interface between the titanium boride and the aluminum.

In conclusion, the titanium boride-aluminum composite material has an excellent microstructure without bonds, and has improved mechanical properties such as hardness and strength. From these results, in the titanium boride-aluminum composite, it is analyzed that the load is effectively transferred from the aluminum matrix to the fine titanium boride reinforcement.

The titanium boride-aluminum composite material may be applied to various industrial fields such as automobile fields, aerospace fields, and defense industries.

The above-described effects of the present invention have been described by way of example, and the scope of the present invention is not limited by these effects.

1 is a flowchart illustrating a method of manufacturing a solid area ratio aluminum composite material according to an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating a method for manufacturing the solid area ratio aluminum composite material of FIG. 1 according to an embodiment of the present invention.
3 is a flowchart illustrating a method of manufacturing a solid area ratio aluminum composite material according to an embodiment of the present invention.
4 is a graph showing a contact angle between titanium boride and aluminum applied to a method for manufacturing a solid area ratio aluminum composite material according to an embodiment of the present invention.
5 is a photograph showing a contact form between titanium boride and aluminum applied to the manufacturing method of the solid area ratio aluminum composite material according to an embodiment of the present invention.
6 is a scanning electron microscope photograph showing a titanium boride powder for carrying out the manufacturing method of the solid area ratio aluminum composite material according to an embodiment of the present invention.
7 is a scanning electron microscope photograph showing a titanium boride preform formed by performing the manufacturing method of the solid area ratio aluminum composite material according to an embodiment of the present invention.
8 is a titanium boride formed by the method for manufacturing a solid-area aluminum composite material according to an embodiment of the present invention - are external photos according to the steps of the aluminum composite material.
9 is a scanning electron microscope photograph showing the microstructure of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.
10 is an EPMA mapping photograph of a titanium boride-aluminum composite material formed by the method of manufacturing a solid area aluminum composite material according to an embodiment of the present invention.
11 is a graph showing an X-ray diffraction pattern of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.
12 is a transmission electron microscope photograph showing the microstructure of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.
13 is a stress-strain graph at room temperature of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.
14 is a compressive stress-strain graph at room temperature of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.
15 is a scanning electron microscope photograph showing a fracture surface after a tensile test of a titanium boride-aluminum composite formed by the method for manufacturing a solid area aluminum composite according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, The scope of the technical idea is not limited to the following examples. Rather, these embodiments are provided so as to more fully and complete the present disclosure, and to fully convey the technical spirit of the present invention to those skilled in the art. In the present specification, the same reference numerals refer to the same elements throughout. Furthermore, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing drawn in the accompanying drawings.

The technical idea of the present invention is to provide a high-volume ratio aluminum composite material capable of improving properties by securing interfacial stability and a method for manufacturing the same.

Metal matrix composite (MMC) has excellent properties such as light weight, mechanical properties, functional properties, high temperature stability, abrasion resistance, and oxidation resistance, a lot of research is in progress. In such a metal matrix composite, the uniform dispersion of the reinforcement in the matrix and the interfacial stability between the reinforcement and the matrix are very important factors for the properties.

Among the metal matrix composites, various studies have been conducted as follows to compensate for interfacial defects in the aluminum composite. Urena et al. (Urena et al.) oxidized the surface of SiC reinforcements through heat treatment to improve the wettability of the reinforcement to the aluminum matrix. Rajan et al. (Rajan et al.) coated nickel (Ni) or copper (Cu) on the surface of the carbon/graphite, SiC, and Al ₂ O ₃ reinforcement to improve the wettability of the reinforcement to the aluminum matrix. Zhou et al. (Zhou et al.) performed nickel coating to improve the wettability of TiC and Al-Cu before preparing TiC _p -Al-Cu composites. However, even if these surface pretreatment processes improve the interfacial properties between the reinforcement and the matrix, there is a limitation in that the composition of the base metal is changed and additional time and cost are required.

According to Kou et al., the surface tension of aluminum decreases with increasing temperature. As the temperature increases, the wettability of TiB ₂ with aluminum increases. In particular, at a temperature of 1000° C. or higher, the wettability can be increased to enable spontaneous impregnation. Therefore, when the process temperature is increased, the wettability of the reinforcement and the matrix can be increased without performing a surface pretreatment process. However, a composite produced only by a spontaneous impregnation process may have unimpregnated pores between the reinforcement and the matrix. As a method for solving this problem, an additional pressing process may be performed to remove the impregnated pores.

In the present invention, titanium boride (TiB ₂ ) is selected as an exemplary among the ceramic reinforcement used to manufacture the aluminum composite material. The titanium boride has advantages of excellent Young's modulus, excellent hardness, high wettability to aluminum at high temperature, and high chemical stability to aluminum. However, this is exemplary and the technical spirit of the present invention is not limited thereto, and may include various ceramic reinforcement materials, for example, Al ₂ O ₃ , B ₄ C, SiC, TiC, and the like.

1 is a flowchart illustrating a method ( S100 ) of manufacturing a solid area ratio aluminum composite material according to an embodiment of the present invention.

Referring to Figure 1, the manufacturing method (S100) of the manufacturing method of the solid area ratio aluminum composite material, forming a titanium boride preform (S110); disposing solid aluminum on the titanium boride preform (S120); heating and melting the aluminum (S130); pressing the molten aluminum using a gas so that the molten aluminum is impregnated into the titanium boride preform (S140); and cooling the titanium boride preform impregnated with the molten aluminum to form an aluminum composite (S150).

FIG. 2 is a schematic diagram illustrating a method for manufacturing the solid area ratio aluminum composite material of FIG. 1 according to an embodiment of the present invention.

1 and 2 , first, forming the titanium boride (TiB ₂ ) preform (S110) includes compressing the titanium boride powder to form a titanium boride compression material; and sintering the compression material to form the titanium boride preform 110 .

The titanium boride powder may have an average particle size in the range of 2 μm to 3 μm. The compression of the titanium boride powder may be performed at a uniaxial pressure in the range of 60 MPa to 100 MPa. Compression of the titanium boride powder may be made at room temperature, for example, at a temperature in the range of 0°C to 40°C.

The sintering of the compression material may be performed in an inert gas atmosphere such as argon gas or nitrogen gas, for example, at a temperature in the range of 900°C to 1100°C, for example at 1000°C, for example, 10 minutes to 120 minutes. .

Next, the titanium boride preform 110 is charged into the crucible 190 . The crucible may be, for example, a magnesium oxide (MgO) crucible, but this is exemplary and the technical spirit of the present invention is not limited thereto. A solid aluminum 120 is disposed on the charged titanium boride preform 110 . That is, the solid aluminum 120 is charged in the crucible (190). Aluminum 120 may include pure aluminum or an aluminum alloy.

The step (S130) of heating and melting the aluminum is, for example, in a vacuum atmosphere ranging from 1.0 x 10 ^-1 torr to 5.0 x 10 ^-1 torr, for example, in a vacuum atmosphere of 2.8 x 10 ^-1 torr, for example. For example, at a temperature in the range of 900°C to 1800°C, for example, at a temperature of 1000°C. The heated temperature may be maintained until the aluminum is completely melted, for example, for 30 minutes to 2 hours, for example, for 1 hour. Accordingly, the solid aluminum 120 may be changed to the molten aluminum 130 .

The step of pressurizing the molten aluminum using a gas (S140) may be performed by injecting an inert gas having a pressure of 1 bar to 20 bar into the molten aluminum. The molten aluminum 130 may be impregnated into the titanium boride preform 110 by this gas pressure. It may be maintained at a heated temperature during the pressing step (S140).

The step S130 and the step S140 may be performed simultaneously.

In the forming of the aluminum composite material ( S150 ), the aluminum composite material 140 may be formed by cooling the titanium boride preform 110 impregnated with the molten aluminum 130 . The aluminum composite 140 may be referred to as a titanium boride-aluminum composite.

Therefore, the solid area ratio aluminum composite material, titanium boride preform; and aluminum impregnated in the titanium boride preform.

The titanium boride preform may have, for example, pores having a porosity of 20% by volume to 50% by volume, or, for example, pores having a porosity of 35% by volume. At least a portion of the pores may be filled with the aluminum.

The solid area aluminum composite material may have a density of 3.0 g/cm ³ to 4.2 g/cm ³ .

The high-volume aluminum composite material may have a tensile strength of 100 MPa to 500 MPa, a compressive yield strength of 100 MPa to 600 MPa, and a Vickers hardness of 40 Hv to 250 Hv.

The high-volume aluminum composite material may have a thermal expansion coefficient of 11 ppmK ^-1 to 17 ppmK ^-1 .

As described above, a method of heating and pressurizing a gas to impregnate a metal may be referred to as a liquid pressing infiltration (LPI) process. The melt pressure impregnation process may be performed simultaneously with a high temperature process of 1800 °C and a pressurization process of 20 bar.

The manufacturing method of the solid area ratio aluminum composite material may be applied to various ceramic reinforcement materials.

3 is a flowchart illustrating a method ( S200 ) of manufacturing a solid area ratio aluminum composite material according to an embodiment of the present invention.

Referring to Figure 3, forming a ceramic preform (S210); disposing solid aluminum on the ceramic preform (S220); heating and melting the aluminum (S230); pressing the molten aluminum using a gas so that the molten aluminum is impregnated into the ceramic preform (S240); and cooling the ceramic preform impregnated with the molten aluminum to form an aluminum composite (S250).

The ceramic preform may include at least one of Al ₂ O ₃ , B ₄ C, SiC, and TiC.

Experimental example

Hereinafter, preferred experimental examples are presented to help the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited by the following experimental examples.

Experimental method

Production of titanium boride-aluminum composites

Before preparing the titanium boride-aluminum composite, an experiment for optimizing process conditions was performed. For this optimization, the contact angle between titanium boride and aluminum according to temperature was measured.

The contact angle between titanium boride and aluminum was measured using a sessile drop method. The Cecil drop was a drop of liquid aluminum on a titanium boride plate of 20x20x2 mm ³ under a temperature of 700° C. to 1000° C. in a vacuum. As the liquid aluminum, Al1050 aluminum alloy (Portland aluminum, Portland, Australia) was used to minimize the effect of additional elements. Note that the aluminum described below refers to the Al1050 aluminum alloy.

Table 1 shows the chemical composition of the Al1050 aluminum alloy. In Table 1, the content of each element is expressed in wt%.

element Al Fe Cu Mg Mn Si Ti V Zn content 99.8 or higher 0.1
below 0.001
below 0.001
below 0.02
below 0.05
below 0.04
below 0.02
below 0.002
below

As a reinforcing material of the titanium boride-aluminum composite material, titanium boride (TiB ₂ ) powder (Kojundo Chemical Laboratory Co., Ltd., Saitama, Japan) was used. The titanium boride powder had an average particle size in the range of 2 μm to 3 μm. The titanium boride powder was compressed with a uniaxial pressure of 80 MPa to form a titanium boride compressed material, and then the titanium boride compressed material was sintered at 1000° C. for 60 minutes under an argon atmosphere to form a titanium boride preform. Accordingly, the titanium boride preform had a porous structure having a diameter of 50 mm and a height of 20 mm. The porosity of the titanium boride preform was calculated by measuring the volume and weight of the preform.

Then, a titanium boride-aluminum composite material was formed using a melt pressure impregnation process. Molten aluminum was impregnated into the titanium boride preform using hydrostatic pressure. Accordingly, aluminum may be filled in the pores of the titanium boride preform. In other words, in the titanium boride-aluminum composite material, titanium boride, which is a reinforcing material, may be uniformly dispersed in aluminum, which is a metal matrix.

The melt pressure impregnation process may be performed as follows. The titanium boride preform and the aluminum were charged into a magnesium oxide (MgO) crucible, and heated to 1000° C. in a vacuum atmosphere (2.8×10 ⁻¹ torr) at a heating rate of 10° C./min. After maintaining at the temperature for 1 hour, argon gas at a pressure of 10 bar was injected into the molten aluminum to impregnate the molten aluminum in the porous titanium boride preform, thereby preparing the titanium boride-aluminum composite. .

Characterization of titanium boride-aluminum composites

A scanning electron microscope (SEM, JSM-6610LV, JEOL, Tokyo, Japan), a transmission electron microscope (TEM, JEM-ARM200F, JEOL, Tokyo, Japan), the microstructure of the titanium boride-aluminum composite prepared by the melt pressure impregnation process ), and electron probe microanalyzer (EPMA, JXA-8530F, JEOL, Tokyo, Japan). Analysis was performed using an X-ray diffractometer (Cu Kα radiation at 30 kV and 250 mA) (XRD, D/Max-2500, Rigaku, Tokyo, Japan). In order to measure the relative density of the titanium boride-aluminum composite, the Archimedes method was used and compared with the theoretical density.

The coefficient of thermal expansion (CTE) of the titanium boride-aluminum composite was measured at a temperature of 400° C. at room temperature using a dilatometer (DIL 402C, NETZSCH, Selb, Germany).

Room temperature tensile and compressive properties of the titanium boride-aluminum composite were measured at a strain rate of 5×10 ⁻⁴ using a general-purpose tester (5882 model, INSTRON, Norwood, MA, USA). The hardness of the titanium boride-aluminum composite and the Al1050 aluminum alloy was measured by applying a load at 300 KgF for 10 seconds using a Vickers hardness measuring instrument (FM-700, Future-tech, Kanagawa, Japan).

Five tensile specimens, five compression specimens, and three Vickers hardness specimens were used to ensure reliability of characterization.

Results and analysis

Analysis of the contact angle between titanium boride and aluminum

In the case of manufacturing a metal matrix composite, it is very important to control process conditions such as temperature, atmosphere, and the like. Therefore, the wettability properties between titanium boride and aluminum were investigated while increasing the temperature in vacuum. Specifically, the contact angle between the titanium boride and the aluminum was measured while increasing the temperature from room temperature to 1000° C. in vacuum.

4 is a graph showing a contact angle between titanium boride and aluminum applied to a method for manufacturing a solid area ratio aluminum composite material according to an embodiment of the present invention.

5 is a photograph showing a contact form between titanium boride and aluminum applied to the manufacturing method of the solid area ratio aluminum composite material according to an embodiment of the present invention.

4 and 5 , contact angles and contact forms at 700° C., 800° C., 900° C., and 1000° C. in vacuum are shown. After disposing spherical aluminum on the titanium boride plate, the temperature was increased to measure the contact angle until the aluminum was completely melted and spread widely on the titanium boride plate.

At 700°C and 800°C, the contact angle between the titanium boride plate and the aluminum was 100 degrees or more until 6000 seconds had elapsed. From these results, it can be seen that it is difficult to spontaneously impregnate the molten aluminum into the inside of the titanium boride preform.

On the other hand, at 900°C and 1000°C, the contact angle between the titanium boride plate and the aluminum was 40 degrees or less. In particular, at 1000°C, the contact angle decreased to 90 degrees or less after 94 seconds had elapsed. This means that the wettability between the titanium boride and the aluminum is rapidly increased. From these results, it can be seen that at 1000° C., it is easy to impregnate the molten aluminum into the porous titanium boride in a relatively short time.

According to these results, the titanium boride-aluminum composite material was prepared by performing melt pressure impregnation at 1000 ℃.

Analysis of surface shape of titanium boride preform

When the reinforcing material is uniformly dispersed in the composite, it is possible to effectively impregnate the molten metal alloy, thereby improving the mechanical properties of the metal matrix composite. In order to prepare a homogeneous titanium boride-aluminum composite material uniformly dispersed in this way, a titanium boride preform was prepared in a porous structure. In addition, in order to effectively impregnate the molten aluminum by the subsequent melt pressure impregnation process, it is preferable that the titanium boride preform not only has a porous structure, but also that the titanium boride particles are weakly bonded without crystal growth.

6 is a scanning electron microscope photograph showing a titanium boride powder for carrying out the manufacturing method of the solid area ratio aluminum composite material according to an embodiment of the present invention.

Referring to Figure 6, titanium boride powder is shown. The titanium boride powder has a particle size in the range of 2 μm to 3 μm, and also includes relatively large particles of 5 μm and small fragments of various sizes.

7 is a scanning electron microscope photograph showing a titanium boride preform formed by performing the manufacturing method of the solid area ratio aluminum composite material according to an embodiment of the present invention.

Referring to FIG. 7 , a titanium boride preform is shown. The titanium boride preform was prepared by sintering titanium boride powder at 1000°C. The temperature of 1000° C. is very low compared to the sintering temperature of general titanium boride ceramics. Therefore, it is analyzed that the titanium boride preform has a relatively weakly bonded structure. The titanium boride preform has a porous microstructure composed of titanium boride particles having a size of 2 μm to 3 μm, and therefore it is analyzed that crystal growth does not occur during sintering at 1000°C. That is, the titanium boride particles are weakly bonded to each other, maintain their original shapes, and may have a porosity of about 35% by volume. Therefore, at the heating temperature, the molten aluminum can be effectively impregnated into the open pores uniformly formed in the titanium boride preform.

Referring to the internal photograph of FIG. 7 , as an external photograph of the titanium boride preform sintered at 1000° C., it can be seen that the titanium boride preform has a diameter of 50 mm and a height of 20 mm.

Microstructure of titanium boride-aluminum composites

8 is a titanium boride formed by the method for manufacturing a solid-area aluminum composite material according to an embodiment of the present invention - are external photos according to the steps of the aluminum composite material.

Referring to FIG. 8 , external photos according to stages of the titanium boride-aluminum composite are shown. In the case of melt pressure impregnation at 1000° C., it can be seen that aluminum is uniformly and completely impregnated in the titanium boride preform.

9 is a scanning electron microscope photograph showing the microstructure of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.

Referring to FIG. 9 , as shown in the interior photograph, after the molten aluminum was impregnated, the gray titanium boride preform was a silver titanium boride-aluminum composite, and a change in color occurred.

During the melt pressure impregnation process, molten aluminum was effectively impregnated into the porous titanium boride preform by applying a gas pressure, and the titanium boride particles were individually dispersed in the aluminum matrix without agglomeration.

The volume fraction of the titanium boride preform was analyzed using a scanning electron microscope image obtained from the central region and the side region of the titanium boride-aluminum composite material using an Image J program. The volume fraction of the titanium boride preform was found to be about 65%. As described above, since the porosity of the titanium boride preform is about 35%, it is analyzed that aluminum is effectively impregnated into the titanium boride preform.

In addition, in the titanium boride-aluminum composite prepared by the melt pressure impregnation process, the particle size of the titanium boride was similar to that of the titanium boride powder before being manufactured. Therefore, it is analyzed that crystal growth of the titanium boride particles did not occur while the melt pressure impregnation process was performed at a temperature of 1000°C.

10 is an EPMA mapping photograph of a titanium boride-aluminum composite material formed by the method of manufacturing a solid area aluminum composite material according to an embodiment of the present invention.

Referring to FIG. 10 , in the titanium boride-aluminum composite material, an aluminum region and a titanium boride region are clearly separated. Titanium and boron atoms were mostly observed only in titanium boride particles. Therefore, the titanium boride is uniformly dispersed without agglomeration while having a high volume ratio.

When the mapping photo for the aluminum was analyzed, the aluminum was impregnated in a micrometer-sized space provided between the titanium boride having an average particle size of 2 μm to 3 μm. In addition, the aluminum was effectively impregnated even in a narrow space of a sub-micrometer size between the titanium boride.

When the wettability between the ceramic reinforcement and the metal matrix is low, impregnation of the molten metal is more difficult when the ceramic reinforcement has a large volume fraction than when the volume fraction of the ceramic reinforcement is small. The reason is that the interfacial area between the ceramic reinforcing agent and the metal is increased, and it has a high surface energy. However, in the present invention, the process was performed at a temperature that can provide high wettability, for example, a process temperature of 1000° C., as described above in the wettability analysis, and as such, the boride by the high wettability between the titanium boride and aluminum A titanium boride-aluminum composite material having a large volume fraction of titanium may be prepared.

On the other hand, magnesium oxide was also confirmed in the microstructure of the titanium boride-aluminum composite material. The magnesium oxide is analyzed to be due to the reaction of magnesium, oxygen, and sub-elements of aluminum provided from a magnesium oxide crucible used for manufacturing. However, since the amount of the magnesium oxide is very small, the effect on the mechanical properties is analyzed to be negligible.

11 is a graph showing an X-ray diffraction pattern of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.

Referring to FIG. 11 , in the titanium boride-aluminum composite, only a peak corresponding to aluminum and a peak corresponding to titanium boride were observed. Magnesium oxide was found in the EPMA mapping photograph, but was not found in the X-ray diffraction pattern because it was very small. In general, titanium boride (TiB ₂ ) is thermodynamically stable compared to intermetallic compounds such as AlB ₂ and Al ₃ Ti and ceramics such as B ₄ C and TiC. Therefore, it is analyzed that the interfacial reaction between the titanium boride and the aluminum did not occur during the melt pressure impregnation.

12 is a transmission electron microscope photograph showing the microstructure of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.

Referring to FIG. 12 , it was observed that the interface between the titanium boride (TiB ₂ ) and aluminum (Al) does not include voids or defects and forms a very smooth boundary. The interface between the titanium boride and the aluminum is analyzed to have a semi-coherent characteristic. From these results, it is analyzed that molten aluminum is effectively impregnated into the titanium boride preform.

In addition, since the thermal expansion coefficient of the titanium boride is 6 ppmK ^-1 to 8 ppmK ^-1 , and the thermal expansion coefficient of the aluminum is 26 ppmK ^-1 to 28 ppmK ^-1 , although the thermal expansion coefficients of the two materials are significantly different, the manufacturing process During the period, it can be seen that the titanium boride particles are not broken and form a smooth interface.

Referring to the energy dispersive X-ray spectroscopy (EDS) element mapping photograph at the interface of FIG. 12 , whether chemical complexes are formed at the interface may be analyzed. Since the titanium boride is chemically very stable, it is expected not to form chemical complexes during the manufacturing process at 1000°C, which was confirmed by EDS analysis. That is, very brittle complexes such as Al ₃ Ti or AlB ₂ that can be formed by chemical reaction were not formed.

Therefore, the titanium boride-aluminum composite prepared by the melt pressure impregnation process has a smooth and excellent microstructure without brittle complexes, and is therefore expected to have superior mechanical properties compared to the case prepared by other ex-situ processes. .

Analysis of mechanical properties of titanium boride-aluminum composites

13 is a stress-strain graph at room temperature of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.

14 is a compressive stress-strain graph at room temperature of a titanium boride-aluminum composite material formed by the method for manufacturing a solid area aluminum composite material according to an embodiment of the present invention.

13 and 14, the titanium boride-aluminum (TiB ₂ - Al1050) composite material is indicated by a solid black line, and the Al1050 aluminum alloy as a comparative example is indicated by a red dotted line. The internal photos are photos of the test specimen of TiB ₂ -aluminum composite before and after the test.

13 and 14 , compared with the Al1050 aluminum alloy, the tensile strength and compressive strength of the titanium boride-aluminum composite material were greatly increased, and the elongation rate was decreased. This is due to the high strength and brittleness of the titanium boride. The elastic modulus calculated from the tensile stress-strain gradient was significantly increased compared to the Al1050 aluminum alloy, which is analyzed because the titanium boride has a high elastic modulus of 530 GPa.

In general, since ceramics have brittle properties, they exhibit fracture in the elastic deformation region during a tensile test at room temperature, making it difficult to measure tensile strength. Ceramic-reinforced metal matrix composites with a high volume fraction also exhibit the same fracture behavior as general ceramics. Therefore, in the stress-strain graph of a general metal matrix composite, it is common that fracture occurs in the elastic deformation region. However, the titanium boride-aluminum composite prepared by the melt pressure impregnation process exhibits slight plastic deformation during the tensile test, and in particular, a clear plastic deformation behavior in the compression test. This phenomenon is very interesting and requires precise analysis.

In the composite material, if the fine reinforcement is uniformly dispersed in the metal matrix and maintains a smooth interface state with the matrix, the tensile strength of the composite material can be increased without significantly lowering the elongation. From these results, it can be proved that the titanium boride-aluminum composite prepared by the melt pressure impregnation process has fine titanium boride particles dispersed in the aluminum metal matrix with the help of increased impregnation temperature and applied gas pressure, and a smooth interface is formed. .

Table 2 shows the mechanical and physical properties of TiB ₂ -aluminum composite and Al1050 aluminum alloy.

division density
(g/cm ³ ) UTS
(MPa) CYS
(MPa) Hardness
(Hv) CTE
(ppmK ^-1 ) TiB ₂ -Aluminum Composite 3.84 471.5 500.4 194.4 12.97 Al1050 aluminum alloy 2.71 67.1 59.4 23.2 26.28

Referring to Table 2, since the density of the titanium boride (TiB ₂ ) is 4.52 g/cm ³ , which is relatively higher than that of aluminum, the density of the titanium boride-aluminum composite material is increased by 1.4 times compared to the Al1050 aluminum alloy. However, the tensile strength (UTS) at room temperature of the titanium boride-aluminum composite material was 471.5 MPa, which was significantly increased by 7.0 times compared to the Al1050 aluminum alloy of 67.1 MPa. In addition, the compressive yield strength (CYS) and Vickers hardness (hardness) of the titanium boride-aluminum composite at room temperature were significantly increased by 8.4 times, respectively, compared to the Al1050 aluminum alloy.

The thermal expansion coefficient of the titanium boride-aluminum composite material was 12.97 ppmK ^-1 at a temperature between room temperature and 100 °C. This is 49% lower than the Al1050 aluminum alloy.

The properties of the composite material can be roughly estimated using the rule of mixtures (ROM) of Equation 1 below. According to this mixing law, the properties and composition of the mixed material can be predicted.

<Equation 1>

Most of the measured properties of the titanium boride-aluminum composite prepared using the melt pressure impregnation process were consistent with the values predicted by the mixing law.

However, the tensile strength of the titanium boride-aluminum composite material was very high compared to the value predicted by the mixing law of bulk titanium boride and aluminum. This phenomenon is very interesting and is analyzed to be related to the plastic deformation behavior shown in the stress-strain graph of the titanium boride-aluminum composite material. The tensile strength of bulk ceramics is very low due to the fracture behavior, and the strength of ceramics depends on the particle size and distribution of defects, so it does not have a standard value. Therefore, the effect of mixing the excellent microstructure and smooth interface of the titanium boride and the aluminum of the titanium boride-aluminum composite is analyzed.

When a tensile load is applied, failure usually begins at defects such as voids. In the case of the ceramic-reinforced metal matrix composite, when a tensile load is applied in the vertical direction to the composite having low strength aluminum, the composite is stretched, and fractures grow in the defects formed at the interface between the reinforcement and the matrix. If this interface is not smooth, the interface between the reinforcement and the matrix acts as a major location for forming defects such as voids. Therefore, in the case of a composite material having a low-quality interface, low mechanical properties are exhibited due to interfacial delamination.

15 is a scanning electron microscope photograph showing a fracture surface after a tensile test of a titanium boride-aluminum composite formed by the method for manufacturing a solid area aluminum composite according to an embodiment of the present invention.

Referring to Figure 15 (a), the fracture surface of the Al1050 aluminum alloy is shown. It can be seen that when a load is applied to the Al1050 aluminum alloy specimen in a vertical direction, rough dimples having a size of several tens of micrometers are formed and the Al1050 aluminum alloy specimen is destroyed.

15 (b) and (c), the fracture surface of the titanium boride-aluminum composite material is shown. Compared with the aluminum, it can be seen that the microstructure is very fine. This is due to the presence of fine titanium boride reinforcement and the formation of finer particles of the aluminum matrix.

Referring to (c) of Figure 15, a high-resolution photograph is shown to analyze the fracture surface of the titanium boride-aluminum composite material. It can be seen that very fine dimples are formed and the titanium boride particles are destroyed. It is analyzed that this fracture behavior is that the cracks formed on the soft aluminum matrix are transferred to the strong titanium boride particles.

Through this phenomenon, the titanium boride-aluminum composite manufactured by the melt pressure impregnation process exhibits a mixed fracture behavior in which the brittle fracture of the titanium boride and the ductile fracture of aluminum are mixed. In particular, it is destroyed without causing interfacial delamination at the interface between the titanium boride and the aluminum, and thus it can be seen that the load is effectively transferred from the soft aluminum matrix to the high-strength titanium boride reinforcing material.

In conclusion, the titanium boride-aluminum composite material manufactured through the aid of a temperature and gas pressure of 1000° C. using the melt pressure impregnation process was strengthened using a high volume fraction of fine titanium boride in aluminum, and the saddle was greatly increased. It shows strength and sufficient elongation.

conclusion

In the present invention, a titanium boride-aluminum composite material having improved mechanical properties and microstructure was prepared in order to compensate for the unstable interface of the composite material manufactured using the ex-situ method. Melting the titanium boride-aluminum composite with a fine titanium boride reinforcement uniformly dispersed in about 65% volume ratio by applying a gas pressure at a high temperature, taking advantage of the improved wettability between titanium boride and aluminum as the temperature is increased It was successfully prepared using the pressure impregnation process. At a high temperature of 1000°C, the aluminum alloy molten metal was well impregnated even in the sub-micro-sized regions between the titanium boride particles. No interfacial defects were found due to the excellent wettability and gas pressure between the titanium boride and aluminum matrix.

The density of the titanium boride-aluminum composite material was 3.84 g/cm ³ , which was 1.4 times that of the Al1050 aluminum alloy. Tensile strength, compressive yield strength, and Vickers hardness of the titanium boride-aluminum composite were 471.5 MPa, 500.4 MPa, and 194.4 Hv, respectively, and were 7.0 times, 8.4 times, and 8.4 times larger than that of the Al1050 aluminum alloy. The thermal expansion coefficient of the titanium boride-aluminum composite material was 12.97 ppmK ^-1 at a temperature between room temperature and 100° C., which is 49% lower than that of the Al1050 aluminum alloy.

Since there is no brittle intermetallic compound in the titanium boride-aluminum composite material and there are no interfacial defects, the load applied to the titanium boride-aluminum composite material is effectively transferred from the soft aluminum matrix to the high strength titanium boride reinforcement material, and thus ductile fracture and the mixed fracture behavior of brittle fracture. For this reason, the strength and elongation of the titanium boride-aluminum composite material were found to be very high compared to the conventional high volume fraction metal matrix composite prepared by other ex-situ methods.

Therefore, the titanium boride-aluminum composite material prepared by the melt pressure impregnation process has excellent mechanical and physical properties, and thus can be applied to various fields such as automobile field, aerospace field, and defense industry field.

The technical spirit of the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is the technical spirit of the present invention that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in the art to which this belongs.

Claims (17)

forming a titanium boride preform;
disposing solid aluminum on the titanium boride preform;
heating the aluminum to melt;
pressurizing the molten aluminum using a gas so that the molten aluminum is impregnated into the titanium boride preform; and
and cooling the titanium boride preform impregnated with the molten aluminum to form an aluminum composite;
The step of melting the aluminum by heating,
carried out at a temperature ranging from 900 ° C to 1800 ° C in a vacuum atmosphere,
The step of pressurizing the molten aluminum using a gas,
It is performed by injecting an inert gas at a pressure of 1 bar to 20 bar into the molten aluminum,
A method for manufacturing a high-volume aluminum composite. The method of claim 1,
Forming the titanium boride preform comprises:
compressing the titanium boride powder to form a titanium boride compressed material; and
Including; sintering the titanium boride compression material to form the titanium boride preform;
A method for manufacturing a high-volume aluminum composite. 3. The method of claim 2,
The titanium boride powder,
having an average particle size in the range of 2 μm to 3 μm,
A method for manufacturing a high-volume aluminum composite. 3. The method of claim 2,
The compression of the titanium boride powder is,
carried out with a uniaxial pressure ranging from 60 MPa to 100 MPa,
A method for manufacturing a high-volume aluminum composite. 3. The method of claim 2,
The sintering of the titanium boride compression material is,
carried out in an inert gas atmosphere, at a temperature in the range of 900°C to 1100°C, for 10 minutes to 120 minutes,
A method for manufacturing a high-volume aluminum composite. delete delete The method of claim 1,
The heating and melting of the aluminum and the pressing of the molten aluminum using a gas are performed simultaneously,
A method for manufacturing a high-volume aluminum composite. The method of claim 1,
The aluminum is
containing pure aluminum or aluminum alloy,
A method for manufacturing a high-volume aluminum composite. Claims 1 to 5, as a solid area ratio aluminum composite prepared by the method for producing the aluminum composite material according to any one of claims 8 and 9,
titanium boride preform; and
Including; aluminum uniformly dispersed and impregnated in the titanium boride preform;
having a density of 3.0 g/cm ³ to 4.2 g/cm ³ ,
having a tensile strength of 100 MPa to 500 MPa, a compressive yield strength of 100 MPa to 600 MPa, and a Vickers hardness of 40 Hv to 250 Hv,
having a coefficient of thermal expansion of 11 ppmK ^-1 to 17 ppmK ^-1 ,
A high-volume aluminum composite. 11. The method of claim 10,
The titanium boride preform,
Having pores having a porosity of 20% by volume to 50% by volume, at least a portion of the pores is filled with the aluminum,
A high-volume aluminum composite. 11. The method of claim 10,
The solid area ratio aluminum composite material,
Representing a mixed fracture behavior in which the brittle fracture of the titanium boride and the ductile fracture of aluminum are mixed,
A high-volume aluminum composite. delete delete delete forming a ceramic preform;
disposing solid aluminum on the ceramic preform;
heating the aluminum to melt;
pressing the molten aluminum with a gas so that the molten aluminum is impregnated into the ceramic preform; and
Including; cooling the ceramic preform impregnated with the molten aluminum to form an aluminum composite;
The ceramic preform comprises at least one of Al ₂ O ₃ , B ₄ C, SiC, and TiC,
A method for manufacturing a high-volume aluminum composite. delete

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