JPH0452235A - Method for manufacturing porous aluminum alloy - Google Patents

Abstract

PURPOSE:To obtain a porous Al alloy with high porosity having uniform and fine pores and excellent in mechanical characteristics, at the time of subjecting the green compact of Al alloy powder in which moisture is adsorbed an held on the surface to heating treatment, by vibrating the Al alloy powder in a steam-contg. atmosphere. CONSTITUTION:A vibrating apparatus 2 having a vibrating motor 1 is set in such a manner that it faces a chamber 3. Al alloy powder 5 is placed on a tray 4 on the apparatus 2, and the vibrating motor 1 is operated while a steam- contg. atmosphere is allowed to flow. In this way, moisture is largely absorbed into the Al alloy powder 5. This alloy powder is compacted by hot plastic working at 300 to 500 deg.C and is thereafter subjected to heating treatment at 400 to 600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a porous aluminum alloy.

[Conventional technology]! Hole-X aluminum (A1) alloy is used as filters, sound absorbing materials, and bearing materials because it is lighter than stainless steel, nickel alloy, etc., and has good workability.

As for the manufacturing method of these porous AJZ alloys, ■A
Method of pressurizing and sintering 1 powder■ AIL-Cu powder or metal powders such as Cu and Mg that have a eutectic reaction with A1 are partially melted and sintered in a non-oxidizing atmosphere without pressure. There are known methods of tying the knot.

However, in ■, the porosity is less than 20% because pressure is applied to destroy the oxide on the surface of the AJ2 powder to facilitate sintering, and the oxide is not sufficiently destroyed. The strength is also not that high. In case (2), high strength cannot be obtained because the liquid phase is heated to a relatively high temperature, and the bonding of the powders together is insufficient.

As an attempt to solve such problems, JP-A No. 1
-298123, 0.01 to 1.0% by weight of water was adsorbed and retained on the surface of aluminum alloy powder with an average particle size of 5 to 200 μm, and the powder was molded and solidified by hot plastic working at 200 to 500°C. After that, a method is described in which heat treatment is performed at a temperature of 400 to 600 t.

Furthermore, in Japanese Patent Publication No. 2-10842, Cu in an amount exceeding the solid solution limit at room temperature is treated as a solid solution with All.
A porous sintered sound absorbing material with excellent mechanical strength and corrosion resistance is described.

[Problems to be Solved by the Invention] However, in either method, the oxide film of about 100 to 200 A formed during powder production inhibits the bonding of the powders, so it cannot be said that the mechanical strength is high.

Moreover, the pores contained in the sintered material were not necessarily uniformly dispersed.

[1! Means for Solving the Problem] The method of the present invention applies vibration to aluminum alloy powder in a water vapor-containing atmosphere, causes the aluminum alloy powder to adsorb and retain moisture, and is formed by hot plastic working at 300 to 500°C. After solidification, it is characterized by heat treatment at a temperature of 400 to eoo°C.

[Function] When a solidified compact of A1 alloy powder that adsorbs and retains moisture on its surface is heat-treated at a temperature of 400 to 600°C, blisters are formed on the old powder grain boundaries due to the adsorbed moisture.

In the method of the present invention, a large amount of water is adsorbed by applying vibration to the water vapor powder in a water vapor-containing atmosphere. As a result, when the solidified molded body is heat-treated, a large number of pores are formed.

The reason why a large amount of water is absorbed when vibration is applied is that microscopic cracks or racks are formed in the coating layer such as hydroxide on the surface of the aluminum alloy powder due to vibration, and the coating layer falls off. increase in the specific surface area of
In addition, this is thought to be due to the gradual formation of an oxide film on the surface of the powder after it falls off.

In order to absorb moisture into the aluminum powder while applying vibration, as shown in FIG. The A1 alloy powder 5 may be placed in the chamber, and the vibration motor 1 may be operated while flowing an atmosphere containing water vapor.

There is no particular restriction on the composition of the A1 alloy to which the method of the present invention can be applied; Al-5t alloy, Al2-Fe alloy, AIL-Z
n alloy, Ni%Cu, Mg, Cr.

An alloy to which Co or the like is added can be used.

Various known methods such as extrusion, forging, hot pressing, and HIP can be employed as the hot plastic working method for compacting and solidifying the aluminum alloy powder that has absorbed water in this manner.

Heat treatment temperature for blister generation is 400-600
The reason for this is that below 400°C, blisters do not occur and no pores are formed, and above 600°C, the temperature increases rapidly. ! This is because the metal structure obtained by hardening becomes coarse and the strength decreases.

The amount of water adsorbed and retained on the surface of A1 alloy powder is 0.01
% by weight or more, especially 0.05 to 0.5% by weight is preferred.

When using 0.01% by weight, the occurrence of blisters is significantly reduced, and a porous body with high porosity cannot be obtained.
．． If it exceeds 5% by weight, on the contrary, the amount of blisters generated will be too large, resulting in poor dimensional accuracy and a risk of lowering strength.

The reason why the hot plastic working temperature for forming and solidifying A1 alloy powder was set at 300 to 500°C is that below 300°C, it is difficult to bond the powders together, and when the temperature exceeds 500°C, the adsorbed moisture will be released onto the powder surface. This is because it dissociates and scatters.

[Example] Cooling rate 102-103°C manufactured by air atomization method
/S A1 alloy powder was subjected to vibration treatment in a steam atmosphere using the apparatus shown in FIG. 1, and then '! After molding under the conditions shown in Table J1, heat treatment was performed. Table 2 shows the filling properties of the obtained porous chamber AI alloy.

Sample No. 4.5.6 according to the present invention exhibits a porosity about 1.5 times higher despite being kept in a steam atmosphere for the same treatment time. This shows that if the conditions are properly selected, it is possible to produce a molded article with even higher porosity and fine, uniform pores as shown in FIG.

The positive according to the present invention example, 1.2.3, is the positive according to the comparative example, 7
．． Compared to No. 8.9, it shows higher tensile strength despite having the same porosity. The reason for this is as shown in the example of the present invention. When vibration is applied to the AIL alloy powder, when adjacent particles rub against each other, the coating layer on the surface of the powder particles is lost, making it easier for the bare skin of the A1 alloy to come into direct contact. It is thought that this promotes sintering during heat treatment and increases the bonding strength between particles. It is also believed that this is due to the fact that the pores are more uniformly and finely dispersed in the inventive example than in the comparative example, as shown in FIG.

Table 2

[Brief explanation of drawings]

FIG. 1 is a front view of the moisture adsorption device. FIG. 2 is a schematic diagram of a micrograph showing the structure of the cross section of the molded body. 1... Vibration motor, 2... Vibration device, 3...
・Chamber, 4...Tray 5...AJZ
Alloy powder.

Claims (1)

[Claims] (1) Vibration is applied to the aluminum alloy powder in a water vapor-containing atmosphere to cause the aluminum alloy powder to adsorb and retain moisture, and after being molded and solidified by hot plastic working at 300 to 500°C, the powder is heated to a temperature of 400 to 600°C. A method for producing a porous aluminum alloy, the method comprising heating the porous aluminum alloy.