JP2742634B2 - Aluminum borate whisker having a nitrided layer on the surface and composite material using the whisker as a reinforcing material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material, and more particularly to an aluminum borate whisker having a nitrided layer on the surface and a composite material using the whisker as a reinforcing material.

[0002]

2. Description of the Related Art As one of Al-based composite materials, for example, "Interface in Whisker Reinforced Aluminum-Based Composite Material" distributed on April 23, 1990 at the Committee on Wetability of the Committee on Composite Materials of the Japan Institute of Light Metals. As described in the article entitled "Structure", aluminum borate whisker (alumina-boria whisker) is used as a reinforcing material, and A6061 alloy or J
Al-based composite materials using an Al alloy such as the IS standard AC8A alloy as a matrix are already known.

[0003] Aluminum borate whiskers are 9A.
There are two types represented by l ₂ O ₃ · 2B ₂ O ₃ and 2Al ₂ O ₃ · B ₂ O _3, and the aluminum borate whisker represented by the former chemical formula has strength and elasticity. The whisker is excellent in heat resistance and chemical resistance, and is therefore excellent as a reinforcing material for composite materials. Also, aluminum borate whiskers are very inexpensive reinforcing materials. Therefore, according to the aluminum borate whisker reinforced Al-based composite material, for example, a composite material that is much cheaper than a composite material using SiC whiskers as a reinforcing material is used. Obtainable.

[0004]

However, it has been found that in a composite material using aluminum borate whiskers as a reinforcing material and an aluminum alloy as a matrix, sufficient strength cannot be obtained depending on the type of aluminum alloy used. did.

The inventors of the present application have conducted detailed experimental studies on the cause of insufficient strength of aluminum borate whisker reinforced Al-based composite materials depending on the type of Al alloy used, and as a result, B was found to be Mg. The aluminum oxide borate whiskers (9Al ₂
O ₃ · 2B ₂ O ₃₎ in B ₂ O ₃ reacts with Mg in the Al alloy according to _{B 2 O 3 + 3Mg → 3MgO} + 2B, thereby spinel (MgO · Al ₂ O ₃ on the surface of the whiskers) layer is generated In addition, the strength of the whisker is greatly reduced and the strength of the composite material is reduced, and it is also possible to avoid a reduction in the strength of the composite material by forming a nitride layer on the surface of the aluminum borate whisker. I found it.

The present invention provides an aluminum borate whisker and a high-strength boric acid capable of improving the strength of a composite material as compared with the prior art, based on the knowledge obtained as a result of an experimental study conducted by the present inventors. An object is to provide an aluminum whisker reinforced light metal composite material.

[0007]

According to the present invention, there is provided an aluminum borate whisker having a nitrided layer on its surface and an aluminum borate whisker having a nitrided layer on its surface according to the present invention. This is achieved by a composite material with a light metal alloy as the matrix.

[0008]

According to the whisker of the present invention, the aluminum borate whisker has on its surface a nitrided layer that is stable even for a molten Al alloy containing Mg and the like. _{Since the} reaction between ₂ O ₃ and Mg in the matrix is suppressed, the formation of the spinel layer and the decrease in the strength of the whiskers due to the spinel layer are avoided, whereby the decrease in the strength of the aluminum borate whisker reinforced light metal composite material is prevented. Is prevented.

According to the composite material of the present invention, an aluminum borate whisker having a nitrided layer on the surface which is stable against a molten Al alloy containing Mg is used as a reinforcing material. B in Whisker
_{Since the} reaction between ₂ O ₃ and Mg in the matrix is suppressed, the formation of the spinel layer and the reduction in the strength of the whiskers due to the formation of the spinel layer do not occur, thereby obtaining a high-strength aluminum borate whisker reinforced light metal composite material. Can be

[0010]

According to the results of an experimental study conducted by the inventor of the present invention, the presence of a nitrided layer on the surface of aluminum borate whiskers is greater than the case without a nitrided layer. The performance of the aluminum borate whisker can be improved, and thus the strength of the composite material can be improved, but especially the average thickness of the nitrided layer is 0.05 μm
In the case described above, the effect of forming the nitride layer is remarkable.
Even if the average thickness of the nitride layer is set to a value exceeding 0.3 μm, the effect of increasing the thickness of the nitride layer is not so large, and conversely, the cost of the whisker increases.

Therefore, in the aluminum borate whisker and composite material of the present invention, the average thickness of the nitrided layer is 0.05
μm or more, especially 0.1 to 0.3 μm.

A method for producing an aluminum borate whisker having a nitrided layer on its surface and a method for producing a preform of aluminum borate whisker having a nitrided layer on its surface are described in the patent application of the same applicant as the present applicant. This is described in detail in Japanese Patent Application No. 3-93712 and drawings.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

[0014]Example 1  First, aluminum borate whisker (Shikoku Chemical Industry Co., Ltd.
Company-made "Arbolex G", whisker diameter 0.5-1μ
m, whisker length 10-30 μm) with hydrocarbon gas
1 in a mixed gas with Monia gas (1:20 by volume)
Heated to 400 ° C. Figure 1 shows that nitriding is
A nitride layer 11 having a thickness of 0.1 μm
Showing a cross section of aluminum borate whisker 10
It is a formula diagram, 10A is substantially only aluminum borate
Is shown. The nitride layer 11 and aluminum borate
The interface between the system-only part is actually very complex
It is supposed to be.

Next, as shown in FIG. 2, the aluminum borate whisker 10 having the nitrided layer formed on the surface is introduced into distilled water 12, and distilled water and propeller 14 are used until the whisker is sufficiently defibrated. After stirring the whiskers, the whiskers are transferred into a molding jig and subjected to compression molding to form a molded body having a size of 100 × 38 × 16 mm, and the molded body together with the jig is kept at −50 ° C. , And the state was maintained until the moisture in the molded body was sufficiently frozen.

Next, the compact is removed from the jig, and thereafter, as shown in FIG. 3, the inner dimensions are 38 × 16 mm, the length is 140 mm, the ends are open at both ends, and the weight 16 is provided at one end. The molded body 20 formed as described above was filled in a case 18 made of stainless steel (JIS standard SUS304) provided integrally. Next, the formed body was heated by a heater together with the case to sufficiently dry the formed body, thereby forming a formed body composed of aluminum borate whiskers having a nitrided layer on the surface and having a whisker volume ratio of 30%.

Next, after pre-heating the molded body together with the case to 600 ° C. for 1 hour, the molded body 20 is placed together with the case in a mold 24 of a high-pressure casting apparatus 22 as shown in FIG. Plunger 2 in which a molten metal 26 of Al alloy (JIS 2024) is poured and the molten metal is fitted into a mold.
8 and pressurized at a pressure of about 1000 kgf / cm ² , and the pressurized state was maintained until the molten metal was completely solidified. After the molten metal is completely solidified, the mold 2 is
The solidified body is taken out of the solidified body 4, and the solidified body is subjected to a machining process to cut out a composite material made of an Al alloy composite-reinforced with an aluminum borate whisker having a nitrided layer on the surface, and subjected to a heat treatment T6. gave.

For the purpose of comparison, a composite material was formed in the same manner and under the same conditions as in the embodiment except that an aluminum borate whisker having no nitrided layer on the surface was used. Heat treatment was applied.

Next, a bending test piece was formed from each composite material, and a three-point bending test was performed on each test piece at room temperature with a distance between supporting points of 40 mm. The results of these tests are shown in FIG.
FIG. 5 shows that the strength of the composite material can be significantly improved by forming a nitrided layer on the surface of the aluminum borate whisker.

[0020]Example 2  Al alloy with a hot water temperature of 850 ° C (A
1-5wt% Cu-1.5wt% Mg)
The thickness of the nitride layer is set to 0 μm and 0.15 μm,
Example 1 except that the volume ratio of the ska was set to 25%
Form a composite material in the same manner and conditions as in
Perform T6 heat treatment on the composite material and bend it from each composite material
Specimens were formed, and each specimen was the same as in Example 1.
A three-point bending test was performed under one procedure and condition.

FIG. 6 shows the results of these tests. FIG. 6 shows that even when the composition of the Al alloy as the matrix is different from the composition of the Al alloy of Example 1, the strength of the composite material is significantly improved by forming a nitrided layer on the surface of the aluminum borate whisker. You can see that you can do it.

[0022]Example 3  Mg alloy with hot water temperature of 700 ° C (J
The molten metal of IS standard AZ91) is used, and the thickness of the nitride layer is
0 μm and 0.08 μm, and the volume ratio of whisker is
Same as Example 1 except that it was set to 25%
Form composite materials according to the procedure and conditions, and for each composite material
T6 heat treatment to form bending test pieces from each composite material
Then, for each test piece, the same procedure as in Example 1 and
A three-point bending test was performed under the conditions.

FIG. 7 shows the results of these tests. FIG. 7 shows that the strength of the composite material can be significantly improved by forming a nitride layer on the surface of aluminum borate whiskers even when the matrix is an Mg alloy.

[0024]Example 4  Al alloy with a hot water temperature of 750 ° C (A
1-4.5 wt% Cu-2 wt% Mg) is used,
Aluminum borate with a 0.1μm thick nitride layer on the surface
When the volume ratio of whisker becomes 15-45% (every 5%)
Except for the set points, the same procedure as in the first embodiment and
A composite material is formed under the conditions, and each composite material is subjected to T6 heat treatment.
To form a bending test piece from each composite material.
For the piece, 3
A point bending test was performed.

The lower limit of molding is 15%, and the volume ratio is 15%.
%, It was difficult to maintain the shape of the molded body.

FIG. 8 shows the results of these tests. From FIG. 8, in order to obtain a composite material having excellent strength, the volume ratio of aluminum borate whiskers having a nitrided layer on the surface is 15
It turns out that it is preferable that it is -40%.

When the nitrided layer on the whisker surface in each of the above embodiments was analyzed by an X-ray diffraction method, the nitrided layer mainly contained A
It was confirmed that 1N was contained.

When the interface of the whiskers in each of the composite materials formed in each of the above embodiments was observed by a TEM method, the composite material using aluminum borate whiskers having no nitrided layer on the surface as a reinforcing material was observed. In the above, spinel is present at the whisker interface, and it is presumed that the performance of the whisker has been impaired by the formation of the spinel.On the other hand, aluminum borate whisker having a nitrided layer on the surface is used as a reinforcing material. In this composite material, it was confirmed that no spinel was present at the whisker interface.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to these embodiments, and various other embodiments may be included within the scope of the present invention. It will be clear to those skilled in the art that is possible.

[0030]

As is clear from the above description, according to the whisker of the present invention, the aluminum borate whisker has a nitrided layer on the surface that is stable against molten Al alloy and the like. B in aluminum borate whiskers
_{Since the} reaction between ₂ O ₃ and Mg in the matrix is suppressed, formation of a spinel layer and a decrease in the strength of whiskers due to the formation of the spinel layer are avoided, thereby reducing the strength of the aluminum borate whisker reinforced light metal composite material. Can be prevented.

According to the composite material of the present invention, the molten Al
Aluminum borate whiskers having a nitrided layer on the surface that is stable against alloys and the like are used as a reinforcing material, and the nitrided layer suppresses the reaction between B ₂ O _{3 in} aluminum borate whiskers and Mg in the matrix. Therefore, there is no generation of the spinel layer and no reduction in the strength of the whiskers due to the formation of the spinel layer, whereby a high-strength aluminum borate whisker reinforced Al-based composite material can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross section of an aluminum borate whisker having a nitrided layer on its surface.

FIG. 2 is an explanatory view showing a fibrillation step of aluminum borate whiskers.

FIG. 3 is a longitudinal sectional view showing a molded body of aluminum borate whiskers accommodated in a case.

FIG. 4 is a longitudinal sectional view showing a high-pressure casting step performed using the aluminum borate whisker compact shown in FIG. 3;

FIG. 5 is a graph showing the flexural strength of the composite materials of Example 1 and Comparative Example.

FIG. 6 is a graph showing the bending strength of the composite materials of Example 2 and Comparative Example.

FIG. 7 is a graph showing the bending strength of the composite materials of Example 3 and Comparative Example.

FIG. 8 is a graph showing the relationship between the volume ratio of aluminum borate whiskers and the bending strength of the composite material.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Aluminum borate whisker which has a nitride layer on the surface 11 ... Nitride layer 10A ... Aluminum borate 12 ... Distilled water 14 ... Propeller 16 ... Weight 18 ... Case 20 ... Molded body 22 ... High pressure casting apparatus 24 ... Mold 26 ... Al Molten alloy 28 ... Plunger 30 ... Knockout pin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masataka Suzuki 30 Soya, Hadano-shi, Kanagawa Prefecture Toshiba Ceramics Co., Ltd. Central Research Laboratory (72) Inventor Nobuhisa Kurono 1-1-11 Tsukisancho Minato-ku Nagoya-shi (72) Inventor Hidenori Yamaoka 1-1-11 Tsukisancho, Minato-ku, Nagoya-shi, Aichi Prefecture In-house STK Ceramics Research Institute (72) Inventor Hajime Saito 1-11-11 Tsukisancho, Minato-ku, Nagoya-shi, Aichi Prefecture Inside the STK Ceramics Research Institute, Inc. (72) Inventor Hajime Yamashita 30 Soya, Hadano-shi, Kanagawa Prefecture, Toshiba Ceramics Corporation Central Research Laboratory

Claims (2)

(57) [Claims] 1. An aluminum borate whisker having a nitrided layer on its surface. 2. A composite material comprising aluminum borate whiskers having a nitrided layer on the surface as a reinforcing material and a light alloy as a matrix.