EP4656748A1

EP4656748A1 - Aluminum sintered member

Info

Publication number: EP4656748A1
Application number: EP23918057.3A
Authority: EP
Inventors: Takahiro Hamada; Moe MEKATA; Akira Yoshida
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2023-01-26
Filing date: 2023-01-26
Publication date: 2025-12-03
Also published as: JPWO2024157424A1; EP4656748A4; CN120548375A; WO2024157424A1

Abstract

An object of the present invention is to provide an aluminum sintered member excellent in tensile strength, stress corrosion cracking resistance, welding resistance, and fatigue strength.The present invention provides an aluminum sintered member which is a sinter-molded article of a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder, in which the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 2 to 7 mass% with a balance being Al and unavoidable impurities, an area ratio of a eutectic structure formed of the Al-Si-Mg-based alloy in a metal structure of the aluminum sintered member is 6 to 30%, and a porosity of the aluminum sintered member is 5% or less.

Description

TECHNICAL FIELD

The present invention relates to an aluminum sintered member. More specifically, the present invention relates to an aluminum sintered member excellent in tensile strength, stress corrosion cracking resistance, welding resistance, and fatigue strength.

BACKGROUND ART

A sintered member using a metal powder has a high degree of freedom in shape and component blending, has a small loss of a material by near net molding, and can reduce processing steps, and thus has attracted attention as an automobile member. Such a sintered member using a metal powder is sometimes used for a part having a complicated shape such as a bearing or a small gear in an engine part or a drive system part of an automobile, but as a general sintered member, an iron-based alloy powder is mostly used as the metal powder. In the case of a sintered member using an aluminum powder such as pure aluminum or an aluminum alloy, it is known that an oxide film to be formed on a surface inhibits sintering, and it is difficult to increase the density, and thus the sintered member is not suitable for a shaping member requiring a high strength. Meanwhile, an aluminum nitride powder and an alumina powder for sintering have also been developed, but since there is a problem in machinability, they are not suitable for automobile parts.
An additive fabricated member obtained by molding a metal powder by an additive fabrication method is also used as an automobile member, and has been increasing in recent years. As a molding method by the additive fabrication method, a method has been developed in which a raw material powder is selectively irradiated with a laser beam or an electron beam and directly sintered each time a metal powder as a raw material is laminated one by one. In a binder jet method that is a type of additive fabrication method, there is a method of injecting a liquid binding material (binder) from a nozzle to a metal powder to solidify the metal powder. In the binder jet method, high productivity is expected, but since a sintering step is required after solidification, there is no practical example in which an aluminum powder is used as a raw material similarly to the reason described above, and there is almost practical application with an iron-based powder.
However, weight reduction is required for automobile parts, application and development of aluminum are being continued, and an aluminum alloy powder to which copper is added has been proposed as an aluminum alloy powder for an aluminum sintered member (for example, JP 2009-7650 A ) .

SUMMARY OF INVENTION

However, it has been found that the sintered member using an aluminum alloy powder described JP 2009-7650 A has an insufficient strength as an automobile part, and has a problem in corrosion resistance. It has been found that weldability may not be sufficient.
Fuel saving is required for an automobile, and weight reduction is one measure for improving fuel efficiency. For this purpose, the amount of aluminum used is expected to increase in the future. The development of methods is also in progress, and it is expected that the number of parts using members manufactured using sintering or additive fabrication method will increase. In order to ensure the quality of an automobile, it is necessary to further increase the strength of these members, and a sintered member using aluminum is required to have performance such as stress corrosion cracking resistance. In particular, the conventional aluminum sintered member has a low strength, and has problems of stress corrosion cracking resistance and weldability. Therefore, an object of the present invention is to provide an aluminum sintered member excellent in tensile strength, stress corrosion cracking resistance, welding resistance, and fatigue strength.
The present inventors have conducted intensive studies in order to achieve the above object. As a result, they have found that the above object is achieved by adding a predetermined Al-Si-Mg-based alloy powder to an aluminum powder as a main component and using the resulting mixture as a raw material powder, and controlling an area ratio of a eutectic structure formed of the Al-Si-Mg-based alloy in an aluminum sintered member and a porosity of the aluminum sintered member in predetermined ranges, and have completed the present invention.
That is, the present invention is an aluminum sintered member which is a sinter-molded article of a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder, in which the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 2 to 7 mass% with a balance being Al and unavoidable impurities, an area ratio of a eutectic structure formed of the Al-Si-Mg-based alloy in a metal structure of the aluminum sintered member is 6 to 30%, and a porosity of the aluminum sintered member is 5% or less.

BRIEF DESCRIPTION OF DRAWING

Fig. 1 is an optical microscope photograph of a sample of an aluminum sintered member prepared in Example 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an aluminum sintered member according to an embodiment of the present invention will be described.

[Aluminum sintered member]

An embodiment of the present invention is an aluminum sintered member which is a sinter-molded article of a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder, in which the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 2 to 7 mass% with a balance being Al and unavoidable impurities (unavoidable impurities), an area ratio of a eutectic structure formed of the Al-Si-Mg-based alloy in a metal structure of the aluminum sintered member is 6 to 30%, and a porosity of the aluminum sintered member is 5% or less. According to the present invention, an aluminum sintered member excellent in tensile strength, stress corrosion cracking resistance, welding resistance, and fatigue strength can be obtained.
Specifically, the aluminum sintered member of the present embodiment is an aluminum sintered member obtained by mixing a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder, and sinter-molding the mixture. Here, the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 2 to 7 mass% with a balance being Al and unavoidable impurities, an area ratio of a eutectic structure formed of the Al-Si-Mg-based alloy in a metal structure of the aluminum sintered member is 6 to 30%, and a porosity of the aluminum sintered member is 5% or less.

(Raw material powder)

The aluminum sintered member of the present embodiment is produced using a raw material powder containing a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder.

(Pure aluminum powder)

The pure aluminum powder is an aluminum powder in which 99 mass% or more of the component is aluminum. A means for preparing the pure aluminum powder is not particularly limited. As pure aluminum, for example, an aluminum 1000 series material such as JIS standard A1100 or A1200 can be used. Two or more kinds of pure aluminum powders may be used in combination.

(Aluminum alloy powder except for Al-Si-Mg-based alloy)

The aluminum alloy powder except for an Al-Si-Mg-based alloy is not particularly limited as long as it is other than the Al-Si-Mg-based alloy described later, but is preferably an aluminum alloy powder having a content of Al of more than 50 mass%. Although not particularly limited, it is preferable that the contents of Si and Mg are each less than 2 mass%, and the content of Mg is larger than the content of Si. In the aluminum alloy powder, the content of Al is more preferably 80 mass% or more, still more preferably 90 mass% or more, further preferably 93 mass% or more, and further more preferably 95 mass% or more.
Note that, in the aluminum alloy powder, the content of copper that may inhibit stress corrosion cracking resistance and welding resistance is preferably less than 1 mass% and more preferably 0.5 mass% or less.
The route of obtaining the aluminum alloy powder is also not particularly limited. As the aluminum alloy, for example, aluminum 6000 series alloy such as JIS standard A6061, A6063, or A6101 can be used. The aluminum 6000 series alloy is an aluminum alloy obtained by adding Mg and Si to aluminum, and is excellent in strength and corrosion resistance. By using the aluminum 6000 series alloy, the strength of the aluminum sintered member can be further improved. Note that two or more kinds of aluminum alloy powders may be used in combination.
Here, the main component refers to a component contained in an amount of more than 50 mass% with respect to the raw material powder. The content of the pure aluminum powder or the aluminum alloy powder other than an Al-Si-Mg-based alloy (these are also referred to as aluminum powders) in the raw material powder of the aluminum sintered member of the present embodiment is not particularly limited as long as it is more than 50 mass%, and is preferably 70 to 94 mass%. As a result, the area ratio of the eutectic structure formed of the Al-Si-Mg-based alloy in the metal structure of the aluminum sintered member can be easily controlled in a predetermined range. As a result, the effect of the present invention can be more effectively obtained. When two or more kinds of aluminum powders are used in combination, the total amount thereof is preferably in the above range.

(Al-Si-Mg-based alloy powder)

The Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 2 to 7 mass% with a balance being Al and unavoidable impurities.
A problem in the sintering of the aluminum powder is that since the surface of the aluminum powder has a strong oxide film, the aluminum powder cannot be densified in the sintering step, and a sufficient strength as a sintered member cannot be obtained. In the aluminum sintered member of the present embodiment, a high-density aluminum sintered member can be provided by mixing an Al-Si-Mg-based alloy powder with a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component to promote liquid phase sintering. When Cu was added as a strengthening element, susceptibility to weld cracking and stress corrosion cracking was increased (cracking easily occurred), and thus Mg was selected as a strengthening element. Since susceptibility to weld cracking and stress corrosion cracking is increased as the amount of Mg added increased, the upper limit value of the amount of Mg was defined.

(Silicon (Si): 10 to 24 mass%)

When the content of silicon is less than 10 mass%, a sufficient strength cannot be obtained because sufficient liquid phase sintering is not performed and densification cannot be performed. When the content of silicon is more than 24 mass%, the ratio of the eutectic structure formed after sintering becomes excessively large, which causes a decrease in strength.

(Magnesium (Mg): 2 to 7 mass%)

The effect of magnesium is to have an effect of promoting liquid phase sintering as with silicon, and to reduce an oxide film on the aluminum surface to promote sintering of aluminum. When the content of magnesium is less than 2 mass%, the reduction effect of the oxide film is small, and sufficient liquid phase sintering is not performed, so that densification cannot be performed and a sufficient strength cannot be obtained. On the other hand, when the content of magnesium is more than 7 mass%, there is a problem in that the risk of stress corrosion cracking increases.

(Aluminum (Al) and unavoidable impurities: balance)

In the Al-Si-Mg-based alloy powder, the balance excluding Si and Mg is Al and unavoidable impurities. The unavoidable impurities mean those present in the raw material or inevitably mixed in the production process. The unavoidable impurities are originally unnecessary, but are contained in a very small amount, and are acceptable impurities because they do not affect the characteristics of the Al-Si-Mg-based alloy powder and the aluminum sintered member using the Al-Si-Mg-based alloy powder. The content of the unavoidable impurities is preferably less than 0.1 mass% and more preferably less than 0.01 mass% with respect to the Al-Si-Mg-based alloy powder.
Note that, in the Al-Si-Mg-based alloy powder, the content of copper that may inhibit stress corrosion cracking resistance and welding resistance is preferably less than 1 mass%, more preferably 0.5 mass% or less, still more preferably 0.1 mass% or less, and most preferably 0 mass% (copper is not contained).
The melting point of the Al-Si-Mg-based alloy powder is preferably lower than the melting point of the pure aluminum powder or the aluminum alloy powder other than an Al-Si-Mg-based alloy as a main component. As a result, liquid phase sintering can be promoted, and a high-density aluminum sintered member can be more efficiently obtained. The melting point of the Al-Si-Mg-based alloy powder is preferably, for example, about 30 to 70°C lower than the melting point of the main component. When a difference in melting point from the main component is in the above range, an aluminum sintered member which has a low porosity and is dense can be more efficiently obtained. The melting point of the Al-Si-Mg-based alloy powder can be, for example, about 590 to 630°C. The melting point of the Al-Si-Mg-based alloy powder can be controlled by adjusting the composition of the Al-Si-Mg-based alloy. For example, the content of Si or Mg is increased, the melting point tends to be increased. The melting point of the Al-Si-Mg-based alloy powder can be estimated from the phase diagram.
The content of the Al-Si-Mg-based alloy powder in the raw material powder of the aluminum sintered member of the present embodiment is not particularly limited as long as it is less than 50 mass%, and is preferably 6 to 30 mass%. As a result, the area ratio of the eutectic structure formed of the Al-Si-Mg-based alloy in the metal structure of the aluminum sintered member can be easily controlled in a predetermined range. As a result, the effect of the present invention can be more effectively obtained. When two or more kinds of Al-Si-Mg-based alloy powders are used in combination, the total amount thereof is preferably in the above range.
The total content of the aluminum powder (pure aluminum powder or aluminum alloy powder other than an Al-Si-Mg-based alloy) and the Al-Si-Mg-based alloy powder in the raw material powder of the aluminum sintered member of the present embodiment is not particularly limited, and is preferably 90 mass% or more, more preferably 95 mass% or more, still more preferably 98 mass% or more, and most preferably 100 mass% with respect to the total amount of the raw material powder. As a result, the effect of the present invention can be more remarkably obtained.
Since there are problems of stress corrosion cracking and welding as an automobile part, it is preferable that a component containing an element that inhibits corrosion resistance and weldability, such as copper, is not added to the raw material powder of the aluminum sintered member of the present embodiment.
In a preferred embodiment of the present invention, the main component of the raw material powder is a pure aluminum powder, and the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 3 to 7 mass% with a balance being Al and unavoidable impurities. According to this configuration, the effect of the present invention can be more remarkably obtained.
In another preferred embodiment of the present invention, the main component of the raw material powder is an aluminum alloy powder, and the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 2 to 7 mass% with a balance being Al and unavoidable impurities. According to this configuration, the effect of the present invention can be more remarkably obtained. In particular, the tensile strength and the fatigue strength can be further improved. At this time, when the aluminum alloy powder is an aluminum 6000 series alloy powder, a denser aluminum sintered member can be obtained, and the effect of the present invention can be more remarkably obtained.

(Elemental composition of aluminum sintered member)

The elemental composition of the aluminum sintered member according to the present embodiment can be the same as the elemental composition of the mixed powder before sinter-molding.

(Area ratio of eutectic structure formed of Al-Si-Mg-based alloy powder)

In the aluminum sintered member according to the present embodiment, the area ratio of the eutectic structure formed of the Al-Si-Mg-based alloy powder is 6 to 30%. When the area ratio of the eutectic structure is less than 6%, a sufficient strength cannot be obtained because sufficient liquid phase sintering is not performed and densification is not performed. When the area ratio of the eutectic structure is more than 30%, the eutectic structure is easily embrittled, and a sufficient strength cannot be obtained. The area ratio of the eutectic structure is preferably 6 to 24%. The area ratio of the eutectic structure can be controlled by the content of the Al-Si-Mg-based alloy powder. The area ratio of the eutectic structure can be determined by the method described in Examples described later.

(Porosity of aluminum sintered member)

The porosity of the aluminum sintered member according to the present embodiment is 5% or less. When the porosity is more than 5%, a sufficient tensile strength cannot be obtained because densification cannot be performed. Since pores are likely to serve as fatigue failure starting points, a sufficient fatigue strength cannot be obtained. The porosity of the aluminum sintered member is preferably 4% or less. Note that the lower limit value of the porosity is not particularly limited, and is, for example, 0.5% or more and preferably 1% or more. Within the above range, the effect of the present invention can be more remarkably obtained. The porosity of the aluminum sintered member can be determined by the method described in Examples described later. The porosity of the aluminum sintered member can be controlled, for example, by adjusting the type of aluminum powder as a raw material, the composition and content of the Al-Si-Mg-based alloy powder, and the pressure, temperature, time, and the like at the time of sinter-molding.

(Filling rate of aluminum sintered member)

The filling rate of the aluminum sintered member is a ratio of a portion other than pores as described in Examples described later. Therefore, from the same viewpoint as described above, the filling rate of the aluminum sintered member according to the present embodiment is 95% or more, and for example, 96% or more. The upper limit value of the filling rate is not particularly limited, and is, for example, 99.5% or less, and for example, 99% or less.

(Method for producing aluminum sintered member)

A method for producing the aluminum sintered member of the present embodiment is not particularly limited. For example, a method including a mixing step of mixing a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder to obtain a mixed powder and a sinter-molding step of sinter-molding the mixed powder can be suitably used. By this method, the aluminum sintered member of the present embodiment can be easily obtained.

(Mixing step)

In the mixing step, a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder are mixed to obtain a mixed powder.
As a mixing means, a known method can be appropriately adopted. Examples thereof include mixing using a mortar, a dry ball mill, a dynamic mill, a bead mill, a jet mill, a hammer mill, a disk mill, and a pin mill, and among them, mixing using a dry ball mill is preferable.
The mixing conditions are also not particularly limited, but the rotation speed is preferably 400 to 700 rpm. The mixing time is preferably 30 to 60 minutes.

(Sinter-molding step)

In the sinter-molding step, the mixed powder obtained in the mixing step is sinter-molded. As a result, the mixed powder is solidified to obtain an aluminum sintered member. The sinter-molding is preferably performed under vacuum, and can be performed using, for example, a vacuum hot press. The sinter-molding conditions are not particularly limited. For example, the pressure during sinter-molding is preferably 20 to 40 MPa. The temperature is preferably 500 to 580°C. The time is preferably 20 to 80 minutes. As a result, an aluminum sintered member having a predetermined area ratio of the eutectic structure and a predetermined porosity can be efficiently obtained.
The aluminum sintered member of the present embodiment is lightweight, high in strength, and excellent in stress corrosion cracking resistance and welding resistance, and therefore can be suitably used for, but is not particularly limited to, an engine part or a drive system part of an automobile.
Note that the following embodiments are also included in the scope of the present invention: the aluminum sintered member according to claim 1 having the features of claim 2; the aluminum sintered member according to claim 1 having the features of claim 3; the aluminum sintered member according to claim 1 or 3 having the features of claim 4; and the method for producing the aluminum sintered member according to any one of claims 1 to 4 having the features of claim 5.

Examples

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Examples 1 to 8 and Comparative Examples 1 to 8)

The pure aluminum powder or the aluminum alloy powder described in the following Table 1 and the Al-Si-Mg-based alloy powder having the composition described in the following Table 1 were mixed by a dry ball mill (mixing conditions: rotation speed 550 rpm, time 45 minutes), and the mixed powder was solidified by a sintering step to obtain a sintered aluminum member. A vacuum hot press was used for sintering, the sintering pressure was 30 MPa, the sintering temperature was 540°C, and the sintering time was 50 minutes.
Note that, in the following Table 1, the composition of the Al-Si-Mg-based alloy powder contains Si and Mg in the contents shown in the table with a balance being Al and unavoidable impurities. The melting point of the Al-Si-Mg-based alloy powder is a value estimated from the phase diagram. Note that in Comparative Example 7, instead of the Al-Si-Mg-based alloy powder, an Al-Cu alloy powder containing 5 mass% of Cu with a balance being Al and unavoidable impurities was used. In Comparative Example 8, instead of the Al-Si-Mg-based alloy powder, an Al-Mg alloy powder containing 5 mass% of Mg with a balance being Al and unavoidable impurities was used.

(Measurement of area ratio of eutectic structure formed of Al-Si-Mg-based alloy, porosity, and filling rate)

For samples cut out from the aluminum sintered members prepared in each of Examples and Comparative Examples, the area ratio of the eutectic structure formed of the Al-Si-Mg-based alloy (eutectic structure area ratio), the area ratio of pores of the aluminum sintered member (porosity), and the filling rate of the aluminum sintered member were measured by the following methods.
First, the sample was cut into small pieces to prepare a measurement sample. The cross section of the sample was mirror-polished and subjected to nital corrosion, and an image was taken with an optical microscope. Next, a threshold value of luminance of the image was set so that the eutectic structure can be identified, and binarization treatment was performed, and the area of the eutectic structure was measured. Then, the ratio of the area of the eutectic structure included in a range up to 100 µm in a depth direction from the surface to the total area was calculated as a percentage. Thereafter, also for the porosity, the ratio of the area was calculated as a percentage in the same manner. Note that the filling rate of the aluminum sintered member is calculated as a percentage of the area of the portion other than the pores in the measurement of the porosity. The results are shown in Table 1 below.
Fig. 1 shows an optical microscope photograph of a sample of an aluminum sintered member prepared in Example 1. As shown in Fig. 1, it is confirmed that the metal structure of the aluminum sintered member of this Example has a eutectic structure (portion appearing white) formed of the Al-Si-Mg-based alloy and pores (portion appearing black) in the α-Al phase.

(Tensile strength)

For samples cut out from the aluminum sintered members prepared in each of Examples and Comparative Examples, a tensile test was performed on the basis of JIS Z 2241:2011 to determine the tensile strength. The results are shown in Table 1 below. A tensile strength of 90 MPa or more can be suitably used.

(Stress corrosion cracking (SCC) resistance)

For samples cut out from the aluminum sintered members prepared in each of Examples and Comparative Examples, a stress corrosion cracking test was performed. As the stress corrosion cracking test, a corrosion environment evaluation in a stress load state was performed on the basis of JIS H 8711:2000. The results are shown in Table 1 below. For a specified time (1000 hours), a case where corrosion cracking did not occur was evaluated as OK, and a case where corrosion cracking occurred was evaluated as NG.

(Welding resistance)

For samples cut out from the aluminum sintered members prepared in each of Examples and Comparative Examples, two samples were welded by the MIG welding method to obtain a welding material. A test piece cut out from the welding material was subjected to a tensile test. The tensile test was performed on the basis of JIS H 8711:2000. The results are shown in Table 1 below. A case where the tensile strength of the welding material was 90% or more with respect to the tensile strength of the base material (aluminum sintered member before welding) was evaluated as OK, and a case where the tensile strength thereof was less than 90% was evaluated as NG.

(Fatigue strength)

For samples cut out from the aluminum sintered members prepared in each of Examples and Comparative Examples, a rotational bending fatigue test was performed on the basis of JIS Z 2273:1978. The results are shown in Table 1 below. The rotational bending fatigue strength was shown as a relative value when the rotational bending fatigue strength of the aluminum sintered member of Example 1 was taken as 1.0. A rotational bending fatigue strength of 0.8 or more can be suitably used.
Note that, in Table 1, in the comprehensive determination, a case where all of the tensile strength, the stress corrosion cracking resistance, the welding resistance, and the fatigue strength were suitable or OK was determined as OK, and the other cases were determined as NG.

[Table 1]

Table 1

	Raw material powder				Aluminum sintered member			Evaluation
	Main component (powder)	Al-Si-Mg-based alloy powder			Eutectic area ratio (%)	Filling rate (%)	Porosity (%)	Tensile strength (MPa)	Welding resistance	SCC resistance	Fatigue strength (relative value)	Comprehensive determination
	Main component (powder)	Composition	Melting point (°C)	Content (mass%)	Eutectic area ratio (%)	Filling rate (%)	Porosity (%)	Tensile strength (MPa)	Welding resistance	SCC resistance	Fatigue strength (relative value)	Comprehensive determination
Example 1	Pure Al	Al-Si (10 mass%)-Mg (5 mass%)	605	15	15	96.6	3.4	138	OK	OK	1.0	OK
Example 2	Pure Al	Al-Si (24 mass%)-Mg (5 mass%)	630	20	20	97.7	2.3	140	OK	OK	1.1	OK
Example 3	Pure Al	Al-Si (15 mass%)-Mg (3 mass%)	600	10	10	97.2	2.8	132	OK	OK	1.0	OK
Example 4	Pure Al	Al-Si (15 mass%)-Mg (7 mass%)	590	24	24	97.5	2.5	142	OK	OK	1.1	OK
Example 5	Pure Al	Al-Si (15 mass%)-Mg (5 mass%)	590	6	6	97.2	2.8	140	OK	OK	1.1	OK
Example 6	Pure Al	Al-Si (15 mass%)-Mg (5 mass%)	590	30	30	95.0	5.0	130	OK	OK	1.0	OK
Example 7	A6061	Al-Si (10 mass%)-Mg (2 mass%)	600	10	10	98.2	1.8	152	OK	OK	1.3	OK
Example 8	A6061	Al-Si (10 mass%)-Mg (2 mass%)	600	24	24	98.4	1.6	155	OK	OK	1.2	OK
Comparative Example 1	Pure Al	Al-Si (15 mass%)-Mg (2 mass%)	570	15	15	91.0	9.0	57	OK	OK	0.5	NG
Comparative Example 2	Pure Al	Al-Si (15 mass%)-Mg (8 mass%)	580	15	15	85.5	14.5	48	NG	NG	0.4	NG
Comparative Example 3	Pure Al	Al-Si (9 mass%)-Mg (5 mass%)	605	15	15	88.4	11.6	56	NG	OK	0.3	NG
Comparative Example 4	Pure Al	Al-Si (25 mass%)-Mg (5 mass%)	670	15	15	90.3	9.7	70	OK	OK	0.5	NG
Comparative Example 5	Pure Al	Al-Si (10 mass%)-Mg (5 mass%)	605	5	5	88.3	11.7	45	NG	OK	0.3	NG
Comparative Example 6	Pure Al	Al-Si (10 mass%)-Mg (5 mass%)	605	32	32	91.5	8.5	54	OK	OK	0.6	NG
Comparative Example 7	Pure Al	Al-Cu (5 mass%)	630	15	15	94.3	5.7	73	NG	NG	0.3	NG
Comparative Example 8	Pure Al	Al-Mg (5 mass%)	630	5	5	95.5	4.5	80	OK	OK	0.5	NG

From Table 1, it is found that the aluminum sintered members of Examples 1 to 8 in which a predetermined Al-Si-Mg-based alloy powder is used and the area ratio of the eutectic structure and the porosity are in predetermined ranges are excellent in tensile strength, stress corrosion cracking resistance, welding resistance, and fatigue strength.
On the other hand, it was found that in Comparative Examples 1 to 8 in which any of the composition of the Al-Si-Mg-based alloy powder, the area ratio of the eutectic structure, and the porosity was out of predetermined range, a sintered member excellent in tensile strength, stress corrosion cracking resistance, welding resistance, and fatigue strength was not obtained.
Although the present invention has been described above with reference to some embodiments and examples, the present invention is not limited thereto, and various modifications can be made within the scope of the gist of the present invention.
For example, the configuration described in each of the above-described embodiments and examples is not limited to each of the embodiments and examples, and for example, the composition of each of the embodiments and detailed conditions at the time of production can be changed, or the configuration of each of the embodiments and examples can be a combination other than each of the above-described embodiments and examples.

Claims

An aluminum sintered member which is a sinter-molded article of a pure aluminum powder or an aluminum alloy powder except for an Al-Si-Mg-based alloy as a main component, and an Al-Si-Mg-based alloy powder,
wherein the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 2 to 7 mass% with a balance being Al and unavoidable impurities,

an area ratio of a eutectic structure formed of the Al-Si-Mg-based alloy in a metal structure of the aluminum sintered member is 6 to 30%, and

a porosity of the aluminum sintered member is 5% or less.
The aluminum sintered member according to claim 1, wherein the main component is the pure aluminum powder, and the Al-Si-Mg-based alloy powder contains Si: 10 to 24 mass% and Mg: 3 to 7 mass% with a balance being Al and unavoidable impurities.
The aluminum sintered member according to claim 1, wherein the main component is the aluminum alloy powder.
The aluminum sintered member according to claim 3, wherein the aluminum alloy powder is an aluminum 6000 series alloy powder.
A method for producing the aluminum sintered member according to any one of claims 1 to 4, the method comprising:
a mixing step of mixing the pure aluminum powder or the aluminum alloy powder except for an Al-Si-Mg-based alloy as the main component with the Al-Si-Mg-based alloy powder to obtain a mixed powder; and

a sinter-molding step of sinter-molding the mixed powder.