JPH05302135A - Al alloy matrix for si3n4 coated aluminum borate whisker reinforced composite - Google Patents

Abstract

PURPOSE:To improve the strength of an Al alloy composite using Si3N4 coated aluminum borate whiskers as a reinforcing material. CONSTITUTION:The objective Al alloy matrix for a composite uses aluminum borate whiskers having an Si3N4 coated layer on the surface as a reinforcing material. This Al alloy matrix contains, by weight, 3 to 6% Cu and 2.2 to 4% Mg or 3 to 6% Cu, 2.2 to 4% Mg, 0.4 to 0.8% Mn and 0.2 to 0.6% Fe.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to composite materials, and more particularly to aluminum alloy matrices for aluminum borate whisker reinforced composite materials having a Si ₃ N ₄ coating.

[0002]

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

In the specification and drawings of Japanese Patent Application No. 3-190591, which is a joint application between the applicant of the present application and the other two applicants, B has a smaller oxide formation tendency than Mg. aluminum borate whisker (9Al ₂ O ₃ · 2B
B ₂ O ₃ in ₂ O ₃ ) reacts with Mg in the Al alloy according to B ₂ O ₃ + 3Mg → 3MgO + 2B, thereby forming a spinel (MgO.Al ₂ O ₃ ) layer on the surface of the whisker, and The strength of the composite material may be significantly reduced, and the strength of the composite material may be reduced. It is effective to form a Si ₃ N ₄ coating layer on the surface of the aluminum borate whiskers in order to prevent the occurrence of such a problem. Has already been disclosed.

[0004] Thus Si ₃ N ₄ coating layer formed on the aluminum borate whiskers (Si is At a present ₃ on the surface
According to) that N ₄ coated aluminum borate whiskers, Si ₃ N ₄ coating layer is stable to the molten Al alloy containing Mg, Si ₃ N ₄ B boric acid in the aluminum whiskers by coating layer _{Since the} reaction between ₂ O ₃ and Mg in the matrix is suppressed, the formation of the spinel layer and the resulting reduction in the strength of the whiskers are avoided,
This makes it possible to prevent the strength of the aluminum borate whisker reinforced light metal composite material from decreasing.

[0005]

However, in the composite material using the high performance Si ₃ N ₄ coated aluminum borate whiskers as the reinforcing material and the Al alloy as the matrix as described above,
In order to improve the strength as much as possible, what composition of Al alloy is most suitable as the matrix has not been sufficiently studied.

The inventor of the present invention has conducted various experimental studies on what composition of the Al alloy is most suitable as the Al alloy matrix to be composite strengthened by the Si ₃ N ₄ coated aluminum borate whiskers. It has been found that preferably contains a predetermined amount of Cu and Mg, and further preferably contains a predetermined amount of Mn and Fe.

The present invention is based on the knowledge obtained as a result of the experimental study conducted by the inventor of the present application, to provide an Al alloy matrix having an optimum composition for a composite material using Si ₃ N ₄ coated aluminum borate whiskers as a reinforcing material. It is intended to be provided.

[0008]

According to the present invention, there is provided an Al alloy matrix for a composite material, which comprises aluminum borate whiskers having a Si ₃ N ₄ coating layer as a reinforcing material. 6 wt% Cu and 2-4 wt% M
An Al alloy matrix containing g and an Al alloy matrix for a composite material having an aluminum borate whisker having a Si ₃ N ₄ coating layer as a reinforcing material.
% Cu, 2.2-4 wt% Mg, 0.4-0.8 wt%
Of Mn, Al alloy matrix containing 0.2-0.6 wt% Fe.

[0009]

According to the present invention, the Al alloy matrix is 3 to
6 wt% Cu and 2-4 wt% Mg, or 3-6 wt% Cu, 2.2-4 wt% Mg, 0.4-0.8 wt% M
Since n, 0.2 to 0.6 wt% of Fe is contained, the reason is not clear, but as described in detail later, Si ₃ N _{4 is used.}
Strength, such as bending strength, of the coated aluminum borate whisker reinforced Al alloy composite is improved.

[0010]

According to the results of the present inventors experimental studies conducted [Supplemental Description of the means for solving the problems], the Si ₃ N ₄ coated aluminum borate whiskers of the composite strengthen the Al alloy matrix of the present invention Si ₃ N ₄ The thickness of the coating layer is 0.05μ
If it is less than m, the effect of forming the coating layer is insufficient, and conversely, if the thickness of the Si ₃ N ₄ coating layer exceeds 0.6 μm, the strength of the aluminum borate whisker itself decreases,
Therefore, the strength of the composite material decreases. Therefore, A of the present invention
The thickness of the Si ₃ N ₄ coated aluminum borate whiskers Si ₃ N ₄ coating layers of the composite, reinforced the l alloy matrix is preferably set to 0.05 to 0.6 .mu.m.

Further, according to the results of the experimental research conducted by the inventor of the present invention, when the volume ratio of the Si ₃ N ₄ -coated aluminum borate whiskers which strengthens the Al alloy matrix of the present invention is less than 15%, The effect of composite strengthening by whiskers is insufficient, and conversely, when the volume ratio of whiskers exceeds 45%, the strength of the composite material decreases. Therefore, A of the present invention
The volume ratio of the Si ₃ N ₄ -coated aluminum borate whiskers that compositely strengthen the 1-alloy matrix is preferably set to 15 to 45%.

[0012] Si ₃ N ₄ for the production method and Si ₃ N ₄ preform manufacturing method of the coated aluminum borate whiskers coated aluminum borate whiskers, Japanese Patent Application according to Applicants same applicant filed and 3-937
No. 12 and the drawings are detailed.

[0013]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Example 1 First, aluminum borate whiskers ("Arborex G" manufactured by Shikoku Kasei Co., Ltd., whisker diameter 0.5-1 μm)
, Whisker length 10 to 30 μm) and fumed silica are mixed at a predetermined ratio, and the mixture is heated to 1400 ° C. in a mixed gas of hydrocarbon gas and ammonia gas,
As a result, a Si ₃ N ₄ coating layer 11 having a thickness of 0.4 μm was formed on the surface of the aluminum borate whiskers 10 as shown in FIG.

Then, as shown in FIG. 2, the Si ₃ N ₄ -coated aluminum borate whiskers 10A thus formed are put into distilled water 12 and the propeller 14 propels the distilled water and the distilled water until the whiskers are sufficiently defibrated. After stirring the whiskers, the whiskers are moved into a molding jig and compression molded to form a molded body having a size of 100 × 38 × 16 mm, and the molded body together with the jig is kept in a freezer at −50 ° C. And kept in that state until the water content in the molded body was sufficiently frozen.

Then, the molded body was taken out from the jig, and as shown in FIG. 3, the inner dimension was 38 × 16 mm, the length was 140 mm, the both ends were open, and the weight 16 was provided at one end. Was integrally provided in a case 18 made of stainless steel (JIS standard SUS304) with the molded body 20 formed as described above. Then, the molded body is heated together with the case by a heater to be sufficiently dried, thereby forming a molded body made of aluminum borate whiskers having a Si ₃ N ₄ coating layer and having a whisker volume ratio of 30%. ..

Next, after the molded body is preheated together with the case to 600 ° C. for 1 hour, the molded body 20 together with the case is placed in the mold 24 of the high-pressure casting apparatus 22 as shown in FIG. Al alloy (Al-2 to 8 wt% Cu-0
~ 5wt% Mg, Cu content and Mg content is 0.5wt%
The molten metal 26 was poured into the mold and pressurized with a plunger 28 fitted in the mold 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 solidified body is taken out from the mold 24 by the knockout pin 30, and the solidified body is machined to form an Al alloy that has been composite-reinforced with a Si ₃ N ₄ coated aluminum borate whisker. The composite material was cut out and subjected to heat treatment T6.

Next, a bending test piece was formed from each composite material, and each test piece was subjected to a three-point bending test at a room distance of 40 mm and room temperature. The results of these tests are shown in FIG.
In FIG. 5, the alternate long and short dash line, the solid line, and the broken line indicate the points at which the bending strengths are 850 MPa, 900 MPa, and 950 MPa, or the lines connecting the points estimated to be these values from the test results. There is. From FIG. 5, the Cu content of the Al alloy as the matrix is 3 to 6 wt%, especially 3
Preferably, the Mg content is 2.2.
It is understood that it is preferably 4% by weight, particularly 2.5 to 3.5% by weight.

[0019]Example 2  Al alloy as the matrix metal (Al-4 wt% Cu-
0.1 to 1 wt% (every 0.1 wt%) M in 3 wt% Mg)
n-added Al alloy and Al alloy (Al-4 wt% C
u-3wt% Mg) 0.1-1wt% (every 0.1wt%)
Except that the Al alloy with Fe added was used.
A composite material is formed under the same procedure and conditions as in the case of Example 1.
Then, T6 heat treatment is applied to each composite material,
Bending test pieces were formed, and in the case of Example 1 for each test piece,
A three-point bending test was carried out under the same procedure and conditions as in the case.

The results of these tests are shown in FIGS. 6 and 7. From FIGS. 6 and 7, the Mn content of the Al alloy as the matrix is 0.4 to 0.8 wt%, particularly 0.5 to 0.
7 wt% is preferable, Fe content is 0.2 ~
It can be seen that it is preferably 0.6% by weight, particularly 0.3 to 0.5% by weight.

Although not shown in the figure, an Al alloy (Al-3 wt% Cu-2 wt% Mg) is used as the matrix metal.
Alloy and Al alloy in which 0.1 to 1 wt% (every 0.1 wt%) of Mn is added to Al (Al-4 wt% Cu-3 wt% M
The same results as those shown in FIGS. 6 and 7 were obtained when an Al alloy containing 0.1 to 1 wt% (every 0.1 wt%) Fe was added to g). ..

Example 3 As a matrix metal, an Al alloy (Al-4 wt% Cu-
3 wt% Mg-0.2 wt% Fe) to 0.1-1 wt% (0.
0.1 to 1 wt% (every 0.1 wt%) of Mn is added to an Al alloy (Al-4 wt% Cu-3 wt% Mg-0.6 wt% Fe) to which Mn of 1 wt% is added. Al alloy, Al alloy (Al-4 wt% Cu-3 wt% Mg-
0.1 wt% to 0.4 wt% Mn) (every 0.1 wt%)
Alloy with added Fe, Al alloy (Al-4wt%
Cu-3wt% Mg-0.8wt% Mn) 0.1-1wt%
A composite material was formed under the same procedure and conditions as in Example 1 except that an Al alloy containing Fe (0.1 wt%) was used, and each composite material was subjected to T6 heat treatment. A bending test piece was formed from each composite material, and a three-point bending test was performed on each test piece under the same procedure and conditions as in Example 1.

As a result, the Mn content of the Al alloy as the matrix is preferably 0.4 to 0.8 wt% and the Fe content is preferably 0.2 to 0.6 wt%, and the Mn content is particularly 0. 0.5-0.7 wt% and Fe content 0.3-
It has been found that 0.5 wt% is preferable.

Example 4 Al-4 wt% Cu-3 wt% Mg as matrix metal
A having a composition of -0.6 wt% Fe-0.4 wt% Mn
A composite material was formed under the same conditions and conditions as in Example 1 except that the 1-alloy was used, and each composite material was subjected to T6 heat treatment to form a rotary bending fatigue test piece from each composite material. Then, each test piece was subjected to a rotary bending fatigue test in which the fatigue strength was measured 10 ⁷ times at room temperature and 200 ° C. under the condition of a rotation speed of 7,000 rpm.

As a result, the fatigue strengths at room temperature and 200 ° C. are about 280 MPa and about 220 MPa, respectively, which is about 10 to 30% higher than the standard fatigue strength of the silicon carbide whisker reinforced Al alloy composite material. I understand.

[Relationship between Thickness of Si ₃ N ₄ Coating Layer and Bending Strength] A at a temperature of 780 ° C. as a molten matrix metal
alloy (Al-4.5 wt% Cu-2.5 wt% Mg-0.
6 wt% Mn-0.4 wt% Fe) is used,
The thickness of the ₃ N ₄ coating layer is 0, 0.05 to 0.5 μm (0.
1 μm), and a composite material is formed under the same procedure and conditions as in Example 1, and T6 is applied to each composite material.
A heat treatment was performed to form a bending test piece from each composite material, and each test piece was subjected to a three-point bending test under the same procedure and conditions as in Example 1.

The results of these tests are shown in FIG. From FIG. 8, it is understood that the thickness of the Si ₃ N ₄ coating layer formed on the surface of the aluminum borate whiskers is preferably 0.05 to 0.6 μm in order to obtain a high-strength composite material. When the thickness of the Si ₃ N ₄ coating layer was 0.7 μm or more, the whisker compact could not maintain its shape, and it was substantially impossible to form a bending test piece.

[Relationship Between Volume Ratio of Whiskers and Bending Strength]
Al alloy with a hot water temperature of 750 ° C (Al
-5 wt% Cu-3 wt% Mg) is used, and Si ₃
The volume ratio of N ₄ coated aluminum borate whiskers is 15-
A composite material was formed under the same procedure and conditions as in Example 1 except that the content was set to 45% (every 5%), each composite material was subjected to T6 heat treatment, and a bending test was performed from each composite material. A piece was formed, and a three-point bending test was performed on each test piece under the same procedures and conditions as in Example 1. When the whisker volume ratio was less than 15%, it was difficult to form a whisker compact.

The results of these tests are shown in FIG. From FIG. 9, in order to obtain a composite material having excellent strength, Si ₃ N ₄
Volume ratio of coated aluminum borate whiskers is 15-40
It turns out that it is preferable that it is%. As a molten metal for the matrix metal, an Al alloy (Al-4.5
wt% Cu-2.5 wt% Mg-0.6 wt% Mn-0.4 wt
The same result as that shown in FIG. 9 was obtained when the molten metal of (% Fe) was used.

When the interface of whiskers in each composite material formed in each of the above-mentioned Examples was observed by the TEM method, it was confirmed that spinel did not exist at the interface of whiskers.

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

[0032]

As is apparent from the above description, according to the present invention, the Al alloy matrix contains 3 to 6 wt% of Cu.
And 2.2-4 wt% Mg, or 3-6 wt% Cu,
2.2-4 wt% Mg, 0.4-0.8 wt% Mn,
Since it contains 0.2 to 0.6 wt% Fe, it is possible to improve the strength such as the bending strength of the Si ₃ N ₄ -coated aluminum borate whisker reinforced Al alloy composite material as described above.

Further, according to the present invention, the price is about 1/10 of that of silicon carbide whiskers, which is considered to have the highest performance as a reinforcing material for fiber reinforced metal composite materials, in comparison with Si ₃ N _4. With the coated aluminum borate whiskers, a composite material having strength equal to or higher than that of the composite material using the aluminum borate whiskers as a reinforcing material can be produced, and a high-performance composite material having extremely excellent cost performance can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a cross section of a Si ₃ N ₄ coated aluminum borate whisker.

FIG. 2 is an explanatory view showing a defibrating process of whiskers.

FIG. 3 is a vertical sectional view showing a whisker molded body housed in a case.

FIG. 4 is a vertical cross-sectional view showing a high-pressure casting process performed using the whisker compact shown in FIG.

FIG. 5 is a graph showing the bending strength of a composite material with the Cu content of the Al alloy matrix on the horizontal axis and the Mg content on the vertical axis.

FIG. 6 is a graph showing the relationship between the Mn content of an Al alloy matrix and the bending strength of a composite material.

FIG. 7 is a graph showing the relationship between the Fe content of the Al alloy matrix and the bending strength of the composite material.

FIG. 8 is a graph showing the relationship between the thickness of the Si ₃ N ₄ coating layer and the bending strength of the composite material.

FIG. 9 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 coated aluminum borate whiskers 12 ... distilled water 14 ... propeller 16 ... governor weight 18 ... Case 20 ... molded body 22 ... a high-pressure casting apparatus 24 ... Mold 26 ... Molten aluminum alloy 28 ... Plunger 30 ... Knockout pin

Claims (2)

[Claims] 1. An Al alloy matrix for a composite material, which is reinforced by an aluminum borate whisker having a Si ₃ N ₄ coating layer, comprising ₃ to 6 wt% Cu and 2.2 to 4 wt%.
Al alloy matrix containing Mg. 2. An Al alloy matrix for a composite material comprising an aluminum borate whisker having a Si ₃ N ₄ coating layer as a reinforcing material, comprising 3 to 6 wt% Cu, 2.2 to 4 wt% Mg, and 0. 4-0.8 wt% Mn, 0.2-0.6 wt%
Al alloy matrix containing Fe.