JP2822200B2 - Ceramics for aluminum alloy diffusion bonding - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride ceramic used in connection with an aluminum alloy.

2. Description of the Related Art In recent years, the fields of application of ceramics are expanding more and more, while, on the other hand, the excellent properties of ceramics, such as heat insulation and heat resistance, and the properties of metals, such as high toughness and high thermal conductivity, In order to simultaneously utilize both conductivity and the like, composite members and composite parts in which ceramic and metal are joined have been used in various fields.

By the way, adhesives have conventionally been used for joining ceramics and metals. However, it is difficult to obtain sufficient joining strength when an adhesive is used. There is a problem that peeling easily occurs at the joint surface due to a difference in thermal expansion coefficient.

In order to bond ceramics and metal firmly, it is desirable that bonding at the atomic level be performed at the bonding interface, that is, so-called metal bonding is performed. However, since ceramics are nonmetallic, direct bonding between them is required. It has been difficult to perform metal bonding.

Therefore, recently, diffusion bonding of ceramics and metal has been considered as a method of obtaining relatively high bonding strength. One of the methods is to use a silicon nitride (Si ₃ N ₄ ) -based ceramic and an aluminum alloy. Diffusion bonding is considered.

Problems to be Solved by the Invention Silicon nitride-based ceramics generally contain various sintering aids in addition to silicon nitride as a main component, but conventionally, as described above, silicon nitride-based ceramics The fact is that the type and amount of the sintering aid that affects the bonding strength in the case of diffusion bonding of aluminum and an aluminum alloy are not sufficiently considered. That is, according to experiments and studies by the present inventors, it is clear that the bonding strength when diffusion bonding silicon nitride-based ceramics and an aluminum alloy greatly differs depending on the type and amount of a sintering aid contained in the ceramics. It has been found that mechanical properties (fracture toughness, Young's modulus, hardness, etc.) of silicon nitride ceramics may be inferior if bonding strength is increased more than necessary. However, since these points have not been sufficiently studied, silicon nitride ceramics that have sufficiently excellent mechanical properties at the same time as being capable of being diffusion bonded with an aluminum alloy with sufficiently high bonding strength have not been put to practical use. It was.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a silicon nitride-based ceramic which can be diffusion-bonded to an aluminum alloy with high bonding strength without deteriorating mechanical properties.

Means for Solving the Problems The inventors of the present invention have been eager to find a compounding of a sintering aid that can increase the bonding strength in diffusion bonding with an aluminum alloy without lowering the mechanical properties as described above. As a result of experiments and studies, it was found that it is effective to simultaneously use specific amounts of yttria (Y ₂ O ₃ ), alumina (Al ₂ O ₃ ), and zirconia (ZrO ₂ ) as sintering aids. The present invention has been made.

Specifically, the ceramics for aluminum alloy diffusion bonding of the present invention contain silicon nitride as a main component, and as sintering aids, 0.5 mol% or more of yttria, 0.5 mol% or more of alumina, and 1.0 mol% or more of It is characterized in that zirconia is contained in a total amount of 6 mol% or more and 30 mol% or less.

Effect In the ceramics for aluminum alloy diffusion bonding of the present invention, a specific amount of yttria, alumina and zirconia is used as a sintering aid mainly with silicon nitride (Si ₃ N ₄ ). The reasons for limiting the components of the assistant will be described.

Yttria (Y ₂ O ₃ ): Yttria is mixed with silicon nitride powder and sintered under pressure to increase the density of silicon nitride ceramics, improve sinterability, and improve the bonding strength with aluminum alloys. It is a sintering aid that is effective for increasing. Yttria is 0.
If the amount is less than 5 mol%, these effects are small. Therefore, the amount of yttria (single amount) is set to 0.5 mol% or more.

Alumina (Al ₂ O ₃ ): Alumina is mixed with silicon nitride powder in combination with itria and sintered under pressure to improve the density sinterability and heat resistance after sintering, and join with aluminum alloy It is an effective sintering aid for increasing the strength. 0.5 mol of alumina
%, The effect is small. Therefore, the added amount of alumina is set to 0.5 mol% or more.

Zirconia (ZrO ₂ ): By adding 1.0 mol% or more of zirconia, the fracture toughness value and the grain boundary strength are improved, and the bonding strength when diffusion bonding is performed with an aluminum alloy. By sintering zirconia with alumina and yttria, a tougher dispersed phase is obtained, which contributes to improvement in heat resistance and toughness.

Further, when the total amount of these sintering aids is less than 6 mol%, the sinterability is reduced, and the bonding strength when diffusion bonding with an aluminum alloy is also reduced. 30 mol% in total
If the ratio exceeds 1, the inherent properties of the silicon nitride-based ceramic itself, that is, the strength and hardness at a high temperature, decrease. Therefore, the total addition amount of yttria, alumina, and zirconia as sintering aids is set to 6 mol% or more and 30 mol% or less.

As described above, silicon nitride-based ceramics containing a specific amount of yttria, alumina, and zirconia as a sintering aid have excellent bonding strength when diffusion-bonded to an aluminum alloy, and at the same time, the mechanical properties of the ceramics themselves are also high. Excellent.

In joining such ceramics to an aluminum alloy, the surfaces to be joined to each other may be smoothed, then superposed, and pressurized and heated in a vacuum atmosphere. The heating temperature during this bonding is preferably about 300 to 650 ° C.

The aluminum alloy to be joined is not particularly limited, but may be an Al-Si type, Al-Mn- (Si)
System, Al-Cu system, Al-Li system, Al-Ti system alloy and the like can be used.

Example Ceramics having the components shown in No. 1 to No. 12 in Table 1 were sintered by hot pressing. The conditions for hot pressing are as follows: sintering temperature 1650 ~ 1750 ℃, press pressure up to 20MP
a, The pressure holding time was 1 hour, and the atmosphere was a nitrogen atmosphere of 1 MPa. FIG. 1 shows a detailed hot press temperature-pressure (load) -time pattern. The relative density of the obtained ceramic sintered body is 0.98 or more. After sintering, the dimensions of the ceramic were processed to 28 mm x 13 mm x 20 mm, and the surface to be joined was finished to a mirror surface by lapping to obtain a test material.

About each test material, the joining strength with the aluminum alloy was examined as follows. That is, a JIS 2219 alloy (Al-6tw% Cu) was used as an aluminum alloy to be joined, its dimensions were 28 mm × 13 mm × 3 mm, and the surface to be joined with the ceramic was mirror-finished in advance by lapping.
Then, an aluminum alloy is sandwiched between the two ceramics, and in an atmosphere having a degree of vacuum of 7 × 10 ⁻⁵ Torr,
Heating and pressurizing were performed under the conditions of a temperature of 620 ° C. and a load (joining pressure) of 4 MPa to perform joining. FIG. 2 shows a detailed temperature-pressure-time pattern at the time of the joining.

From the sandwich-like joining member obtained as described above, a joining strength test piece 1 having a shape and dimensions as shown in FIG.
Was cut out. In Fig. 3, 2 and 3 are ceramics,
4 is an aluminum alloy.

The test piece 1 was subjected to a four-point bending test using a four-point bending test jig as shown in FIG. 4, and the bending strength was examined as the bonding strength. In FIG. 4, 5 is an upper jig, 6 is a lower jig, and 7 is a round bar as a bending fulcrum. Table 2 shows the results of the bending test.

As shown in Table 2, each of the joining members using the ceramics of the present invention (Examples of the present invention) exhibited extremely high bending strength. In this four-point bending test, cracking when exceeding the bending strength of any of the joining members occurred starting from the joint surface between the ceramic and the aluminum alloy. Therefore, the value of the bending strength in this bending test was the same as that of the ceramic. It is related to the bonding strength with the aluminum alloy. Therefore, from the results shown in Table 2, it is clear that the ceramics of the present invention have remarkably excellent bonding strength with the aluminum alloy. It has been confirmed that each of the ceramics itself of the present invention has excellent mechanical properties equal to or higher than those of conventional ordinary silicon nitride ceramics.

Effects of the Invention According to the ceramics for aluminum alloy diffusion bonding of the present invention, mechanical properties are impaired by appropriately adjusting the blending of a sintering aid as a silicon nitride ceramic used by diffusion bonding with an aluminum alloy. Without
It has become possible to obtain high bonding strength with an aluminum alloy. Therefore, the ceramic of the present invention is most suitable for a composite member joined with an aluminum alloy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature-pressure-time curve at the time of hot pressing of the ceramics in the embodiment, FIG. 2 is a diagram showing a temperature-pressure-time curve at the time of joining in the embodiment, and FIG.
FIG. 4 is a perspective view showing a test piece for a four-point bending test in the example, and FIG. 4 is a front view showing a jig for the four-point bending test in the example.

Continuation of front page (56) References JP-A-64-51378 (JP, A) JP-A-64-5975 (JP, A) JP-A-63-162574 (JP, A) JP-A-63-60163 (JP) JP-A-59-26975 (JP, A) JP-A-58-95655 (JP, A) JP-A-55-116670 (JP, A) JP-A-55-113674 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 37/02 C04B 35/58 102

Claims (1)

(57) [Claims] 1. A method according to claim 1, which comprises silicon nitride as a main component and a sintering aid.
0.5 mol% or more of yttria, 0.5 mol% or more of alumina, and 1.0 mol% or more of zirconia, in their total amount
A ceramic for aluminum alloy diffusion bonding, characterized in that the content is 6 mol% or more and 30 mol% or less.