JP2742633B2 - Aluminum borate whisker having Si3N4 coating and composite material using the whisker as reinforcement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite material, and more particularly to an aluminum borate whisker having a Si ₃ N ₄ coating layer 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 is B ₂ O ₃ + 3Mg →
Reacts with Mg in the Al alloy in accordance with 3MgO + 2B, and thereby spinel (MgO.Al ₂ O)
₃ ) The strength of the whisker is greatly reduced as the layer is formed, and the strength of the composite material is reduced.
In addition, it has been found that by forming a Si ₃ N ₄ coating layer on the surface of aluminum borate whiskers, a decrease in the strength of the composite material can be avoided.

The present invention provides an aluminum borate whisker and a high-strength aluminum borate whisker reinforced light metal composite capable of improving the strength of a composite material based on the knowledge obtained as a result of an experimental study conducted by the inventor of the present invention. It is intended to provide materials.

[0007]

Above-mentioned object, according order to achieve the above, according to the present invention, Si ₃ N ₄ aluminum borate whiskers, characterized in that it has a coating layer, and Si ₃ N ₄ boric acid having a coating layer This is achieved by a composite material with aluminum whiskers as reinforcement and a light alloy as matrix.

[0008]

According to whiskers of the present invention, the aluminum borate whiskers are coated with a stable Si ₃ N ₄ coating layer against molten Al alloy containing Mg, Si ₃ N
₄ B ₂ O in the aluminum borate whiskers with a covering layer
_{Since the} reaction between ₃ and Mg in the matrix is suppressed, the formation of the spinel layer and the decrease in the strength of the whiskers caused by the spinel layer are avoided, whereby the decrease in the strength of the aluminum borate whisker reinforced light metal composite material is prevented. You.

According to the composite material of the present invention, an aluminum borate whisker coated with a Si ₃ N ₄ coating layer that is stable against a molten Al alloy containing Mg is used as a reinforcing material. _The reaction between B ₂ O ₃ in the aluminum borate whiskers and Mg in the matrix is suppressed by the ₃ N ₄ coating layer, so that the formation of the spinel layer and the decrease in the strength of the whiskers due to this are prevented. A high strength aluminum borate whisker reinforced light metal composite is obtained.

[0010]

According to the results of the present inventors experimental studies conducted [Supplemental Description of the means for solving the problems], Si ₃ if there is Si ₃ N ₄ coating layer on the surface of the aluminum borate whiskers
As compared with the case having no N ₄ coating layer can improve the performance of the aluminum borate whiskers, and therefore it is possible to increase the strength of the composite material, in particular Si ₃ N ₄
When the thickness of the coating layer is 0.1 μm or more, the effect of forming the coating layer is remarkable. Even if the thickness of the Si ₃ N ₄ coating layer is set to 0.8 μm or more, the effect of increasing the thickness of the coating layer is not so large, and conversely, the cost of whiskers increases.

Therefore, in the aluminum borate whisker and composite material of the present invention, the thickness of the Si ₃ N ₄ coating layer is set to 0.1 μm or more, particularly 0.15 to 0.8 μm.

[0012] For Si ₃ N ₄ process for the production of a preform of the aluminum borate whiskers having a manufacturing method and Si ₃ N ₄ coating layers of aluminum borate whiskers having a coating layer, Applicants have the same applicant and It is described in detail in the specification and drawings of Japanese Patent Application No. 3-93712 filed in the present application.

[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) and fumed silica
Are mixed at a predetermined ratio, and the mixture is mixed with hydrocarbon gas and air.
Heated to 1400 ° C in a mixed gas with ammonia gas,
This results in aluminum borate as shown in FIG.
0.4 μm thick Si_ThreeN_FourCoating
Layer 11 was formed.

Next, as shown in FIG. 2, the aluminum borate whisker 10A on which the Si ₃ N ₄ coating layer is formed is put into the distilled water 12, and the whisker is distilled by the propeller 14 until the whisker is sufficiently defibrated. After stirring the water and the whiskers, the whiskers are transferred into a molding jig to perform compression molding to form a molded body having a size of 100 × 38 × 16 mm, and the molded body is kept at −50 ° C. together with the jig. And kept in that state until the water 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 Si ₃ N ₄ coating layer 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 from the solid body 4, and the solidified body is machined to cut out a composite material made of an Al alloy composite-reinforced with an aluminum borate whisker having a Si ₃ N ₄ coating layer, and heat-treated the composite material. T6 was applied.

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 Si ₃ N ₄ coating layer was used. On the other hand, T6 heat treatment was performed.

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.
From FIG. 5, Si ₃ on the surface of the aluminum borate whiskers
It is understood that the strength of the composite material can be greatly improved by forming the N ₄ coating layer.

[0020]Example 2  Al alloy with a hot water temperature of 850 ° C (A
1-5wt% Cu-1.5wt% Mg)
Si_ThreeN_FourSet the thickness of the coating layer to 0, 0.1, 0.5 μm.
Except that the whisker volume ratio is set to 25%.
In the same manner and conditions as in Example 1, the composite material
Is formed, and a T6 heat treatment is applied to each composite material,
Bending test pieces were formed from the materials, and examples were given for each test piece.
Perform a three-point bending test under the same conditions and conditions as in 1.
Was.

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 greatly increased by forming the Si ₃ N ₄ coating layer on the surface of the aluminum borate whisker. It can be seen that it can be improved.

[0022]Example 3  Mg alloy with hot water temperature of 700 ° C (J
Melt of IS standard AZ91) is used and Si_ThreeN_FourCoating
The layer thickness is set to 0 μm and 0.5 μm,
Example 1 except that the volume ratio was set to 25%
Form a composite material in the same manner and under the same conditions as
Specimen is subjected to T6 heat treatment, and a bending test piece is prepared from each composite material.
And the same requirements as in Example 1 were used for each test piece.
A three-point bending test was performed under various conditions and conditions.

As a result, the flexural strength of the composite material using the aluminum borate whisker having no Si ₃ N ₄ coating layer as a reinforcing material is 270 MPa, whereas the aluminum borate whisker having the Si ₃ N ₄ coating layer has a bending strength of 270 MPa. The flexural strength of the composite material used as a reinforcing material is 450 MPa. Therefore, even when the matrix is a Mg alloy, the strength of the composite material can be greatly increased by forming a Si ₃ N ₄ coating layer on the surface of aluminum borate whiskers. It can be seen that it can be improved.

[0024]Example 4  Al alloy (A
1-5wt% Cu-2wt% Mg)
_ThreeN_FourWhen the thickness of the coating layer is 0, 0.05 to 0.5 μm (0.
The volume ratio of whisker is 25%
And the same procedure as in the first embodiment, except that
The composite material is formed under various conditions, and T6 heat is applied to each composite material.
Process to form a bending test piece from each composite material.
For the test piece, in the same manner and conditions as in Example 1.
A three-point bending test was performed.

As a result, to obtain a high-strength composite material, it is necessary to form S on the surface of aluminum borate whiskers.
The thickness of the i ₃ N ₄ coating layer is 0.1 μm or more, especially 0.15 μm.
It was recognized that the thickness was preferably not less than μm.

[0026]Example 5  Al alloy with a hot water temperature of 750 ° C (A
1-4.5 wt% Cu-2 wt% Mg) is used,
0.4 μm thick Si_ThreeN_FourBoric acid having a coating layer
Luminium whisker volume ratio is 15-45% (5%
And the same requirements as in Example 1 except that
A composite material is formed under the conditions and conditions, and T
6 heat treatment to form a bending test piece from each composite material,
The same procedure and conditions as in Example 1 for each test piece
A three-point bending test was performed.

FIG. 7 shows the results of these tests. According to FIG. 7, in order to obtain a composite material having excellent strength, it is necessary to use Si ₃ N ₄
It is understood that the volume ratio of the aluminum borate whisker having the coating layer is preferably 15 to 40%.

When the interface of the whiskers in each composite material formed in each of the above embodiments was observed by a TEM method, aluminum borate whiskers having no Si ₃ N ₄ coating layer were used as a reinforcing material. In the composite material, spinel exists at the whisker interface, and it is estimated that the performance of the whisker is impaired by the formation of the spinel.
In the composite material using the aluminum borate whisker having the i ₃ N 4 coating layer as a reinforcing 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 is coated with a Si ₃ N ₄ coating layer that is stable even for a molten Al alloy or the like. Since the Si ₃ N ₄ coating layer suppresses the reaction between B ₂ O _{3 in} aluminum borate whiskers and Mg in the matrix, it avoids formation of a spinel layer and a decrease in whisker strength caused by this. This can prevent the strength of the aluminum borate whisker reinforced light metal composite material from decreasing.

According to the composite material of the present invention, the molten Al
Aluminum borate whiskers coated with a Si ₃ N ₄ coating layer, which is stable against alloys and the like, are used as a reinforcing material, and B ₂ O ₃ in the aluminum borate whiskers and the matrix in the matrix are used by the Si ₃ N ₄ coating layer. Is suppressed from being formed, and the formation of the spinel layer and the reduction in the strength of the whiskers caused by the formation of the spinel layer are not caused, whereby a high-strength aluminum borate whisker reinforced Al-based composite material can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a cross section of an aluminum borate whisker having a Si ₃ N ₄ coating layer.

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 bending strength of two types of composite materials having different thicknesses of the Si ₃ N ₄ coating layer.

FIG. 6 is a graph showing the bending strength of three types of composite materials having different thicknesses of the Si ₃ N ₄ coating layer.

FIG. 7 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]

10 ... aluminum borate whiskers 11 ... Si ₃ N ₄ coating layers 10A ... Si ₃ N ₄ aluminum borate whiskers 12 having a coating layer ... distilled water 14 ... propeller 16 ... governor weight 18 ... Case 20 ... molded body 22 ... high-pressure casting Apparatus 24: Mold 26: Melt of Al alloy 28: Plunger 30: Knockout pin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuhisa Kurono 1-1-11 Tsukisancho, Minato-ku, Nagoya-shi, Aichi Pref. Within the STK Ceramics Research Institute Co., Ltd. (72) Inventor Hidenori Yamaoka Nagoya-shi, Aichi 1-1-11 Tsukisancho, Minato-ku, within the STK Ceramics Research Institute, Inc. (72) Inventor Hajime Saito 1-11, Tsukisancho, Minato-ku, Nagoya-shi, Aichi, Japan STK Ceramics, Inc. (72) Inventor Masataka Suzuki 30 Soya, Hadano-shi, Kanagawa Prefecture, Central Research Laboratories (72) Inventor Hajime Yamashita 30 Soya, Hadano-shi, Kanagawa Prefecture, Central Research Center of Toshiba Ceramics Co., Ltd.

Claims (2)

(57) [Claims] 1. An aluminum borate whisker having a Si ₃ N ₄ coating layer. 2. A composite material comprising aluminum borate whiskers having a Si ₃ N ₄ coating layer as a reinforcing material and a light alloy as a matrix.