JP2885393B2 - Manufacturing method of aluminum sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to aluminum (hereinafter referred to as Al).
The present invention relates to a method for producing a sintered body.

[0002]

2. Description of the Related Art A powder metallurgy method in which a metal powder or an alloy powder is compacted and heated at a temperature lower than the melting point and sintered is used. Such a powder metallurgy method has an advantage that a product can be obtained from a powder without performing a cutting process or the like, and a product having a complicated shape can be manufactured.

Although the powder metallurgy method has the above-mentioned advantages, it cannot be applied to any metal powder. Particularly, when sintering Al powder or Al alloy powder, these powder particles are used. Since the surface is covered with a strong oxide film (Al ₂ O ₃ ), Al metal atoms cannot be firmly bonded to each other by sintering.

Regarding the sintering of Al alloy powder,
Prior arts are disclosed in JP-A-33164 and JP-A-6-57363. Japanese Patent Application Laid-Open No. Hei 6-33164 discloses that Al powder is heated in a nitrogen atmosphere to form nitride (AlN) on the surface of Al powder, and then hot-worked to form nitride (AlN). Is destroyed and dispersed in the Al alloy. Japanese Patent Application Laid-Open No. 6-57363 discloses that an Al alloy powder containing Mg is prepared by a rapid solidification method, and the surface of the fine Al alloy powder is heated in a nitrogen atmosphere to obtain a surface of the Al powder. (AlN) is formed on the substrate, and thereafter sintering is performed.

[0005]

[0007] The prior art described above by forming the both nitride Al powder surface (AlN), but so as to enhance the bond strength, Al ₂ on the surface O
_{Although the} bonding strength is improved as compared with the case where ₃ exists, it cannot be said that it is sufficient.

[0006]

According to the present invention, in order to solve the above-mentioned problems, Mg or an Mg alloy is put in a crucible or the like and set in a furnace in addition to a compact formed from an Al powder or an Al alloy powder. By heating the furnace in a rare gas atmosphere, more preferably under reduced pressure, to sublime magnesium from magnesium or a magnesium alloy, and then introducing nitrogen gas into the furnace and reacting with the sublimated magnesium to produce magnesium nitride. (Mg ₃ N ₂ ) was produced, and this magnesium nitride was brought into contact with aluminum oxide (Al ₂ O ₃ ) on the surface of the powder and reduced to expose aluminum metal atoms and to sinter the powder.

[0007]

[Function] The Al ₂ O ₃ coating covering the surface of the Al powder particles has M
When g ₃ N ₂ comes into contact, oxygen constituting Al ₂ O ₃ is combined with Mg, and Al metal atoms are exposed on the surface of the powder particles.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view of a sintering furnace for carrying out the method for manufacturing an aluminum sintered body according to the present invention. In the sintering furnace, a heater 2 is provided around a furnace body 1 and a furnace body 1 is provided. At one side, an atmosphere gas supply port 3 and an atmosphere gas discharge port 4 are provided.
Ar gas or N ₂ gas can be selectively supplied into the furnace, and the pressure in the furnace body 1 is reduced by driving the pump 6. The pump 6 is turned on and off by a sensor 7 for detecting the pressure in the furnace 1 and a manual switch 8.

A table 9 and a crucible 10 are installed in the furnace 1, a green compact W is set on the table 9, and Mg or Mg alloy M is put in the crucible 10. Here, as the Mg alloy, for example, Al-Mg having a Mg content of 30 wt% or more is used.
Alloys and the like are suitable. Further, the green compact W does not contain Mg, or when it contains Mg, the content is 0.3 wt% or less. When the content ratio of Mg in the green compact W is large, it is not necessary to put the crucible 10 containing Mg or Mg alloy M into the furnace body 1.

As described above, in order to sinter the green compact W, first, as shown in the graph of the processing pattern in FIG.
And heat (1 atm) for 90 minutes. By this heat treatment, the lubricant (wax) in the green compact W is removed.
FIG. 3 is a schematic view showing the particle structure of the green compact W. At this stage, Al ₂ O _{3 in} which Al atoms and O atoms are strongly bonded is formed on the surface of the Al alloy powder particles. I have.
The atmosphere may be changed to a rare gas atmosphere when Mg, which will be described later, sublimes.

Thereafter, the pressure in the sintering furnace is reduced to 10 Torr or less, preferably about 0.1 Torr, and the sintering furnace is heated at 500 ° C. for 5 minutes in a rare gas atmosphere. By this treatment, Mg or Mg alloy M in the crucible 10 is sublimated, and the sublimated (gasified) Mg does not react with Ar inside the furnace 1,
Furthermore, it is uniformly diffused on the surface of the green compact W and inside the green compact W. In addition, as a rare gas, there are He (helium), Ne (neon), Kr (krypton), Xe (xenon), and Rn (radon) in addition to Ar.

Next, N ₂ gas is introduced into the sintering furnace at once, and the temperature is raised to 540 ° C. (below the melting point of Al). Mg sublimated by introducing N ₂ gas
Gas and N ₂ to form magnesium nitride, as shown in FIG. 4 in response (Mg ₃ N _2).

The magnesium nitride (Mg ₃ N ₂ ) comes into contact with aluminum oxide (Al ₂ O ₃ ) on the surface of the Al powder particles,
Performs a reducing action. That is, as shown in FIG. 5, the O atom of Al ₂ O ₃ and Mg are combined to form MgO, the O atom is released from Al ₂ O _3, and the Al metal atom is exposed on the particle surface.

The reaction formula in the sintering furnace is shown below. _{3Mg (gas) + N 2 =} Mg 3 N 2 2Mg 3 N 2 + 2Al 2 O 3 = 2AlN + 6MgO + 2Al + N 2 Mg 3 N 2 + 2Al 2 O 3 + 3Mg = 2AlN + 6MgO + 2Al ( standard formation energy of Gibbs) .DELTA.G of these equations is negative, since the reaction proceeds to the right, Al ₂ in the presence of Mg ₃ N ₂
O atoms are eliminated from O ₃ .

The following (Table 1) compares the properties of the sintered products manufactured by the method of the present invention and those manufactured by other methods. The conditions of each method are as follows. (Sintering: the present invention) (Al-10Si-4C)
u) was prepared. As specific elementary powders for obtaining the component system, 33.3 wt% of Al-30% Si and 20 wt% of Al-20% Cu are used.
%, The wax content is 0.5 to 2 wt%, and the rest is pure Al. The above material powder (100 mesh or less) is mixed with a V-type mixer for 30
After mixing for minutes, compact the powder. The pressure at the time of compacting is set to 4 to 6 ton / cm ² so that the density of the compact is within 60 to 85%. By setting the density of the compact to 60 to 85% in this way, Mg ₃ N ₂ can be uniformly diffused into the inside of the compact. Heating conditions, the heating of the first stage to minutes 400 ° C. × 90 in an Ar atmosphere, the second in an N ₂ atmosphere
The stage heating was 540 ° C. × 60 minutes. Further, Mg having a purity of 100% was put in the crucible. (Forging) Forging was performed under the conditions of a mold temperature of 400 ° C., a billet temperature of 450 ° C., and a pressing rate of 40%. (Heat Treatment) The heat treatment was 490 ° C. for the soaking treatment and 190 ° C. × 3 hours for the aging treatment.

[0016]

[Table 1]

From this (Table 1), it can be seen that the product manufactured by the method of the present invention exhibits high yield strength and strength and has a large elongation. FIG. 6 is a graph showing the relationship between the addition amount (%) of Mg and the proof stress (MPa) and strength (MPa). From this graph, the proof stress (MPa) starts at the 0.3% addition amount of Mg. It can be seen that the strength (MPa) sharply improved. Therefore, the addition amount of Mg is preferably 0.3% or more.

[0018] Incidentally, experiments employing the sublimation of Mg in an N ₂ gas atmosphere, i.e. although experiments with N ₂ gas atmosphere was carried out from the beginning without sublimation of Mg in rare gas atmosphere such as argon,
In this case, Mg (gas) sublimated from the crucible immediately
₂ combine with it generates Mg ₃ N ₂ around the crucible, Mg ₃ N ₂ does not reach the powder compact.

[0019]

According to the present invention as described above,
In addition to the green compact made of Al powder or Al alloy powder, M
g or Mg alloy is placed in a crucible or the like and set in a furnace. The furnace is heated in a rare gas atmosphere such as Ar under reduced pressure to sublimate Mg. Thereafter, nitrogen gas is introduced into the furnace. It reacts with the sublimated Mg to produce magnesium nitride (Mg ₃ N ₂ ), and the magnesium nitride is brought into contact with aluminum oxide (Al ₂ O ₃ ) on the surface of the powder to reduce it, exposing aluminum metal atoms and burning. I decided to tie
The bonding strength of Al particles or Al alloy particles can be increased while taking advantage of sintering.

[Brief description of the drawings]

FIG. 1 is a sectional view of a sintering furnace for implementing a method for manufacturing an aluminum sintered body according to the present invention.

FIG. 2 is a graph showing a processing pattern in a sintering furnace.

FIG. 3 is a schematic view of the atomic arrangement of Al powder particles before Mg sublimates.

FIG. 4 is a schematic view showing a state where sublimated Mg and N are combined.

FIG. 5 is a schematic view showing a state in which Mg and O are bonded and Al is exposed.

FIG. 6 is a graph showing the relationship between the amount of Mg added and proof stress and strength.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Furnace body, 2 ... Heater, 3 ... Atmosphere gas supply port, 4 ...
Atmospheric gas discharge port, 5: switching valve, 9: table, W: green compact.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22C 1 / 04,1 / 10 B22F 3/00-3/26

Claims (3)

(57) [Claims] 1. A green compact comprising an aluminum powder or an aluminum alloy powder and magnesium or a magnesium alloy are set in a furnace, and the furnace is heated in a rare gas atmosphere to sublime magnesium, and then melt at a melting temperature. In sintering at the following temperature, nitrogen gas is introduced into the furnace to react with sublimated magnesium to produce magnesium nitride (Mg ₃ N ₂ ), and this magnesium nitride is oxidized on the surface of aluminum powder or aluminum alloy powder. A method for producing an aluminum sintered body, characterized in that aluminum metal atoms are exposed and reduced by contact with aluminum (Al ₂ O ₃ ) for reduction and sintering. 2. The method for producing an aluminum sintered body according to claim 1, wherein the sublimation of the magnesium is performed under a rare gas atmosphere and under reduced pressure. 3. The method for producing an aluminum sintered body according to claim 1, wherein the content ratio of said magnesium is 0.3 wt% or less.