JPH06128608A - Method of manufacturing gradient composition material - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method of sintering a gradient composition material using two or more kinds of powders having significantly different melting points and specific gravities. [Composition] A homogeneous mixture of two or more kinds of powders is first heated at a temperature not higher than the melting point of the powder having a high melting point and not lower than the melting point of the powder having a low melting point, and then the powder having a low melting point forms a liquid phase. While the high powders are in the solid phase, the difference in their specific gravities creates a graded composition and sinters as it is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a gradient composition material by using two or more kinds of powders,
In particular, the present invention relates to a method of sintering a gradient composition material using powders having significantly different melting points and specific gravities.

[0002]

2. Description of the Related Art Gradient composition materials have a heat resistance and mechanical properties which are obtained by continuously grading the composition (or giving a gradient to the concentration of each component) as shown in the schematic diagram of FIG. It is intended to make the functions such as strength and thermal conductivity superior to those of the single composition material. As described above, as a method for producing a gradient composition material, there is a method in which the volume mixture ratio of two or more kinds of powders is appropriately changed to prepare a powder mixture having a gradient composition, and then the obtained mixture is sintered. Typical examples thereof are shown in FIGS.

In the method shown in FIG. 3, several kinds of uniformly mixed powder sheets S ₁ , S ₂ , ..., S _n having different powder mixing volume ratios are prepared in advance, and these are mixed to form a gradient of components. It is a method of obtaining an FGM product P by laminating several stages and sintering the obtained laminated body L having a gradient composition by hot isotropic pressing (hereinafter abbreviated as HIP) or hot pressing.

The method of FIG. 4 is to produce a powder mixture having a gradient composition by utilizing the difference in specific gravities by applying vibration when mixing two kinds of powders. For example, Ni powder 1
When mixing Al ₂ O ₃ powder 4 with Ni powder 1
It was loaded into a vibrating sieve 2 of 00 mesh, and the sieve was vibrated to allow Ni powder to pass through the eyes of the sieve to a diameter of 2 below the sieve.
It is made to drop on the Al ₂ O ₃ powder 4 which has been charged in advance at the bottom of the cylinder cell 3 having a height of 0 mm and a height of 40 mm. The cylinder cell 3 is attached to the vibrating device 6 via the mounting base 5.
Since it is placed on the upper surface, the vibration causes the Ni powder 1 to gradually penetrate into the Al ₂ O ₃ powder 4 to form a powder mixture having a predetermined gradient composition. Then, the powder mixture is sintered by HIP or hot pressing.

As described above, in the prior art, it is fundamental to prepare a powder mixture having a desired gradient composition in a powder mixture state before sintering, and sintering is performed without breaking the gradient composition. Is normal. Therefore, the sintering temperature is set to a temperature equal to or lower than the melting point so that the powder having a low melting point is not melted.

[0006]

According to the conventional method, a powder mixed material having a graded composition is prepared using powders having significantly different melting points, and then the temperature usually used (that is,
When sintered at a temperature lower than the melting point of the powder having a low melting point), the powder having a high melting point does not sinter sufficiently, and the material strength of the obtained sintered body is insufficient, or in the worst case, a powder having a high melting point. The powder remains unsintered in the part with a large volume ratio of
There is a problem that it does not function as a material.

Therefore, in order to produce a gradient composition material by sintering by the conventional method, a material having a close melting point must be selected as a powder to be used so that a powder having a high melting point can be sufficiently sintered. There is an upper limit. In order to avoid this problem, if the sintering temperature is raised and the melting point is higher than the melting point of the powder, the powder will melt and
Since it becomes a liquid phase and flows, another problem that the gradient composition of the initial powder mixture collapses occurs.

Further, in the conventional method, in order to prepare a powder mixture having a desired gradient composition, the powder uniform mixing / laminating step is repeated several times, and vibration is forcedly applied, so that a great cost is required. It was hanging.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present inventors have conducted extensive studies and developed the following method for producing a gradient composition material. In a method for producing a gradient composition material by sintering a homogeneous mixture of two or more kinds of powders having different melting points and specific gravities, the powder mixture is first heated to a temperature not higher than the melting point of the high melting point powder and higher than the melting point of the low melting point powder. The powder having a low melting point then forms a liquid phase, and while the powder having a high melting point is a solid phase, a gradient composition is generated by the difference in specific gravity between them and the powder is sintered as it is. Method of manufacturing gradient composition material.

[0010]

[Operation] FIG. 1 schematically shows an example of a method for producing a gradient composition material of the present invention. Fig. 1 (a) shows 2 with different melting points and specific gravities.
The figure shows a state in which the powders of different types are simply mixed uniformly. Figure 1
(B) is heating the powder mixture at a temperature not higher than the melting point of the powder having a high melting point (first phase) and not lower than the melting point of the powder having a low melting point (second phase) to liquefy the second phase, Furthermore, the gradient composition material is produced by the difference in specific gravity between the liquid phase-deposited second phase (large specific gravity) and the solid phase first phase (small specific gravity), and the state is shown as it is as it is sintered. FIG. 1 (c) shows a graded composition material.

In the present invention, the sintering temperature is set to be equal to or lower than the melting point of the powder having a high melting point and equal to or higher than the melting point of the powder having a low melting point, because the difference in melting point between the two types of powder causes the powder having a low melting point to become a liquid phase. This is because the powder easily flows, and due to the difference in specific gravity, the powder having a low melting point and the powder having a high melting point, which have become liquid phases, flow upward and downward to generate the gradient composition material.

When a gradient composition material is produced by the method of the present invention, the powder having a large melting point difference and specific gravity difference and the longer the sintering temperature holding time is, the powder having a lower melting point in a liquid phase,
The ratio of the powder having a high melting point to the upper and lower parts is increased, and the thickness of the produced gradient composition is reduced. Therefore, the thickness of the graded composition can be controlled by appropriately selecting the difference in melting point of the powder used, the difference in specific gravity, the thickness of the powder mixture mixed appropriately before sintering, and the sintering temperature holding time.

Further, according to the present invention, it is not necessary to pre-mix the powder to be used with a desired gradient composition in the preparation of the powder mixture before sintering, and it is possible to simply mix the powders, which results in a significant cost reduction. It will be possible.

[0014]

EXAMPLE A gradient composition material was prepared using Cu (pure copper) powder (particle size 160 μm or less) and ZrO ₂ (partially stabilized zirconia) powder (average particle size 0.3 μm). The melting point of Cu powder is 1083 ° C., and the commonly used sintering temperature is 80.
It is 0 to 1000 ° C. The melting point of ZrO ₂ powder is 2700
C., the commonly used sintering temperature is 1300 to 1500.degree. ZrO ₂ powder and Cu powder were mixed, and the volume ratio of each powder was ZrO ₂ : 100%, ZrO ₂ : 75%, Cu: 25
%, ZrO ₂ : 25%, Cu: 75%, Cu: 100%
A powder mixture having a graded composition was prepared by stacking four-stage uniform mixed powders as follows, and was sintered at 1000 ° C. according to a conventional sintering method.

However, the sintering temperature (1000 ° C.) is the normally used sintering temperature of ZrO ₂ (1300-150).
(0 ° C), the ZrO ₂ powder does not sinter sufficiently, and ZrO ₂ is contained in the ZrO ₂ volume ratio of 75% or more.
The O ₂ powder remained as it was, and a gradient composition material of Cu / ZrO ₂ could not be prepared.

On the other hand, the same volume of Cu / ZrO _{2 was} previously prepared.
The powder was mixed uniformly, filled into a mild steel capsule of the shape shown in FIG.
G-weld to obtain a powder mixture. Next, this powder mixture was sintered by HIP under conditions of 1300 ° C., 2000 Atm, Ar (argon) atmosphere for 1 hour.
Since Cu becomes a liquid phase during sintering, Cu and ZrO ₂
Of specific gravity of Cu (Cu: 8.6, ZrO ₂ : 6.1)
(Liquid phase) flowed downward, and a gradient composition material of Cu / ZrO ₂ was obtained. This graded composition material had a region of graded composition with a thickness of 5 mm. Therefore, according to the method of the present invention, Cu
/ ZrO ₂ system functionally graded material can be created.

[0017]

By using the method of the present invention, first of all, it becomes possible to prepare a gradient composition material even if two kinds of powders having significantly different melting points are used, and the restrictions on the combination of powders are greatly restricted. Be improved. Next, there is no need to create a powder mixture having a gradient composition in advance,
Since the process related to this can be omitted, the manufacturing cost of the gradient composition material is significantly reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an outline of a manufacturing process of a gradient composition material according to the method of the present invention.

FIG. 2 is an explanatory view schematically showing a cross section of a gradient composition material.

FIG. 3 is an explanatory view showing an outline of a manufacturing process of a gradient composition material by a conventional thin film laminating method.

FIG. 4 is an explanatory diagram showing an outline of an experimental apparatus for producing a gradient composition material by a conventional vibration mixing method.

FIG. 5 is an explanatory view showing the shape of the mild steel capsule used in the example of the method of the present invention.

Claims (1)

[Claims] 1. A method for producing a gradient composition material by sintering a homogeneous mixture of two or more kinds of powders having different melting points and specific gravities, wherein the powder mixture is a powder having a melting point lower than or equal to that of the powder having a higher melting point and a powder having a lower melting point. The powder having a lower melting point forms a liquid phase, and the powder having a higher melting point forms a liquid phase, while the powder having a higher melting point forms a gradient composition due to the difference in specific gravity between them, and is sintered as it is. A method of manufacturing a gradient composition material, comprising: