JPS61221307A - Porous al sintered material - Google Patents

Abstract

PURPOSE:To produce a porous Al sintered material having excellent strength, sound absorbing characteristic and corrosion resistance by subjecting a sintered body which is obtd. by sintering a powder mixture composed of Al added with Cu in a non-oxidizing atmosphere under no pressure to a soln. heat treatment. CONSTITUTION:The powder mixture which consists essentially of Al and contains Cu as an additive component is sintered in the non-oxidizing atmosphere under no pressure in a vessel consisting of graphite or the like which does not react with Al at the liquid phase generating temp. of Cu or above and the m.p. of Al or below, by which the porous sintered body having 30-60% porosity is obtd. the sintered body is then subjected to the soln. heat treatment. The CuAl2 phase is thoroughly diffused into the base by such treatment and the porous Al sintered material having the excellent mechanical strength, sound absorbing characteristic and corrosion resistance is obtd.

Description

[Detailed Description of the Invention] <Object of the Invention> Industrial Field of Application The present invention relates to a porous Al-based sintered material, and more specifically, it relates to a porous Al-based sintered material, which has excellent sound absorption characteristics such as noise and noise, and excellent corrosion resistance. It concerns a porous Al-based sintered material.

Conventional technology Porous At-based sintered materials have (1) lower specific gravity than Cu- or Fe-based porous sintered materials;

(2) Since it has good malleability, bending is relatively easy.

(3) The sintering temperature is low and it can be manufactured at relatively low cost.

Since it has the following advantages, its development has been actively promoted.

However, in the early days, Tokuko No. 43-20884, 4
No. 5-24206, No. 45-24007, No. 47-321
As shown in the publications of 63@, since the development was mainly aimed at oil-impregnated bearings for mechanical parts, the strength of porous sintered materials was required, and sinterability was inevitably required as a sintered component. Many sintered materials contain Cu, which is easy to obtain good strength, and technically speaking, the common method was to press the surface oxide film that inhibits sintering to break it and allow sintering to proceed. The porosity of the resulting sintered material is at most 10
It was ~20%.

Then, in Japanese Patent Publication No. 5G-11373, a method was developed to obtain a porous Al-based sintered material with a porosity of 40 to 50% by sintering in a non-pressure and non-oxidizing atmosphere. It has come to be widely applied to overfill materials, etc., but the mechanical strength,
Al--Cu based sintered materials have been mainly used from the viewpoint of weather resistance and sound absorption properties.

However, conventional porous AJ-based sintered materials containing Cu have the disadvantage that their use is limited in applications and locations that require corrosion resistance, and their use in applications that require corrosion resistance is problematic. was there.

Problems to be Solved by the Invention The present invention aims to solve these problems, and specifically aims to provide a porous Al-based sintered material that is highly corrosion resistant.

<Structure of the Invention> Means for Solving the Problems and Their Effects The present invention provides a non-pressurized, non-oxidizing method for preparing a mixed powder containing Al as a main component and Cu as an additive component in a container that does not react with Al. It is characterized in that a sintered body having a porosity of 30 to 60% is sintered in an atmosphere and subjected to a solution stratification treatment.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram of an example of a manufacturing process for manufacturing a porous Al-based sintered material according to the present invention, and FIG.
It is a Cu system phase diagram.

In FIG. 1, a raw material powder 1 containing Al as a main component is uniformly spread to a predetermined thickness from a hopper 2 into a container 3 (for example, a graphite container) that does not react with Al. The thickness of the spray at this time is adjusted depending on the depth of the container. Containers 3 naturally filled with raw material powder are stacked in layers, and NH3 decomposition gas and N
After being sintered in a sintering furnace 4 maintained in a two-gas atmosphere and cooled in a cooling zone 6, the porous Al-based sintered material 7 is obtained by removing it from the container 3.

As described above, in the present invention, the raw material powder 1 containing Al as a main component in the container 3 is in a naturally filled state, and the surface oxide film that inhibits sintering in a normal sintering method is destroyed by pressing. On the other hand, during sintering, the aluminum powder particles are destroyed due to the difference in thermal expansion coefficient between the inside of the particles and the oxide film, and sintering progresses through this destroyed portion. At this time, the destroyed and exposed metallic parts and the generated liquid phase parts are easily oxidized, so the atmosphere in the sintering furnace must be controlled to have a low partial pressure of oxygen, and the sintering furnace must be sintered in an atmosphere with a dew point of 130°C or less. tied. Further, the sintering temperature is higher than the liquid phase generation temperature of the additive component powder and lower than the melting point of Al.

The resulting porous Al-based sintered material can have a porosity of 60% or more by using fine-grained powder and controlling the liquid phase amount of the additive components to a small value. The material is not practical because it has low strength and tends to become unsintered.

In addition, by controlling the sintering temperature and additive components, the porosity can be reduced to 30.
It is possible to obtain a sintered material with a porosity of 30% or less, but when the porosity is 30% or less, independent pores increase locally and the temperature control limit is exceeded, which tends to result in metallic sintering. Therefore,
The porosity is preferably 30 to 60%.

In general, alloys consisting of two or more different phases are more susceptible to corrosion than single-phase alloys due to the electrochemical action between the different phases. Since the surface area is much larger and the strength is lower, the influence of corrosion is very large, and improving corrosion resistance is an important issue. An important factor when aiming for corrosion resistance is the electrode potential, and the electrode potential of the solid solution or intermetallic compound with Al as an additive component is
It is necessary to select one close to the electric bridge potential of l.

Table 1 shows 8 types of metals! This figure shows the bridge potential of solid solutions with and intermetallic compounds.

Table 1: However, NaCJ: 53g and H2O2 in 11 solutions:
Measurement in an aqueous solution containing 3(l) As mentioned above, 1-Cu-based porous sintered materials have excellent mechanical strength and sound absorption properties, but they have poor corrosion resistance, making them difficult to use in applications and places where corrosion resistance is required. Since its use is restricted, improving the corrosion resistance of Al-Cu based porous sintered materials is a major challenge.

Considering the cause of poor corrosion resistance from the electrode potential, as shown in Table 1, the electrode potential of the Ai-cu solid solution -〇, 69V, 1i14Allf7) -0,85V is not a large difference. However, its intermetallic compound CuAl
The electric potential wA of No. 2 is quite significantly different from -0.53V.

Therefore, if the amount of Cu added is small and within the solid solubility limit, it will not be harmful, but if it exceeds the solid solubility limit and CuAl2 phase precipitates, it will be harmful and the corrosion resistance will be significantly reduced. I understand. Therefore, the present invention was born from the knowledge that it is important to prevent the precipitation of CuAl2 in order to improve the corrosion resistance of At-Cu based porous sintered materials.

That is, by introducing the solution stratification treatment adopted in high-strength At alloys to porous 'RA1-based sintered materials,
The material was successfully improved in corrosion resistance, and specifically, the Al-CIJ porous sintered material obtained as described above was
The α phase of the Al-Cu system phase diagram shown in the figure is heated up (for example, 5
00° C.) and then rapidly cooled to improve corrosion resistance. Microscopic observation of the structure after this treatment shows that the CuAl2 phase at the grain boundaries has completely disappeared and has been diffused into the fabric.

Example Examples will be further described below.

Example 1 A porous sintered plate of 13% Cu was held at a temperature of 580°C for 1 hour, and after being rapidly cooled in water with a water temperature of 18°C, the microscopic structure and tensile strength before and after the treatment were measured. The CuAl2 phase at the grain boundaries had completely disappeared. Moreover, the tensile strength increased from an average of 1.95 kG/CI2 before treatment to an average of 2.85 klJ/CI2 by treatment.

<Effects of the Invention> As explained above, the present invention has a porosity of 30 to 60%.
By solution treatment of t-Cu based porous sintered material, we succeeded in improving the corrosion resistance, which was a drawback of conventional Al-Cu based porous sintered material, and improved mechanical strength, sound absorption properties and corrosion resistance. A new porous Al-based sintered material has been obtained, which can now be used satisfactorily in applications and places that require corrosion resistance.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of the manufacturing process of a porous At-based sintered material according to the present invention, and FIG. 2 is an Al-Cu-based phase diagram. Code 1... Raw material powder 2... Hopper 3... Container 4... Sintering furnace 5... Sintering zone G... ... Cooling zone 7 ... Porous Al-based sintered material patent applicant KonuDC Co., Ltd. Representative Patent attorney Yoshikatsu Matsushita Attorney 01 Fumi Yu Shima

Claims (1)

[Claims] A sintered body with a porosity of 30 to 60% is made by sintering a mixed powder containing Al as the main component and Cu as an additive component in a container that does not react with Al without pressure and in a non-oxidizing atmosphere. Porous Al-based sintered material made by processing.