Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/09—Mixtures of metallic powders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/14—Both compacting and sintering simultaneously
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0408—Light metal alloys
  • C22C1/0416—Aluminium-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

• the present invention relates to an aluminum sintered member. More specifically, the present invention relates to an aluminum sintered member that has excellent tensile strength, stress corrosion cracking resistance, weldability, and fatigue strength.
• Sintered parts made from metal powders are attracting attention as automotive parts because they offer a high degree of freedom in terms of shape and composition, and because near-net forming reduces material loss and processing steps. Sintered parts made from such metal powders are sometimes used for parts with complex shapes such as bearings and small gears in automotive engine and drive system parts, but most sintered parts generally use iron-based alloy powder as the metal powder.
• sintered parts made from aluminum powder such as pure aluminum or aluminum alloy
• development of aluminum nitride powder and alumina powder for sintering is also underway, but they have problems with machinability and are therefore unsuitable for automotive parts.
• additive manufacturing components obtained by forming metal powder using additive manufacturing methods are also being used as automotive components, and their use has been increasing in recent years.
• a molding method using additive manufacturing a method has been developed in which the raw metal powder is selectively irradiated with a laser beam or electron beam and directly sintered as each layer of the raw metal powder is stacked.
• the binder jet method which is one type of additive manufacturing method, involves spraying a liquid binder from a nozzle onto metal powder to solidify it.
• the binder jet method is expected to be highly productive, it requires a sintering process after solidification, and for the same reasons as mentioned above, there are no practical examples of using aluminum powder as the raw material, and most practical applications have been with iron-based powder.
• Aluminum alloy powder with added copper has been proposed as an aluminum alloy powder for aluminum sintered components (for example, JP 2009-7650 A).
• Automobiles are required to be fuel efficient, and weight reduction is one way to improve fuel efficiency. To achieve this, the amount of aluminum used is expected to continue to increase. Furthermore, the development of manufacturing methods is also progressing, and it is expected that the number of parts using materials manufactured using sintering and additive manufacturing methods will increase. To ensure the quality of automobiles, these components need to be further strengthened, and sintered components using aluminum are required to have performance such as stress corrosion cracking resistance. In particular, conventional aluminum sintered components have low strength, and there are also issues with stress corrosion cracking resistance and weldability. Therefore, the object of the present invention is to provide an aluminum sintered component that has excellent tensile strength, stress corrosion cracking resistance, weldability, and fatigue strength.
• the present invention is an aluminum sintered member that is a sintered product of pure aluminum powder or aluminum alloy powder other than Al-Si-Mg alloy as the main component and Al-Si-Mg alloy powder, the Al-Si-Mg alloy powder contains 10-24 mass% Si and 2-7 mass% Mg, with the remainder being Al and unavoidable impurities, the area ratio of the eutectic structure formed of the Al-Si-Mg alloy in the metal structure of the aluminum sintered member is 6-30%, and the porosity of the aluminum sintered member is 5% or less.
• FIG. 1 is an optical microscope photograph of a sample of the aluminum sintered member produced in Example 1.
• One embodiment of the present invention is an aluminum sintered member which is a sintered product of pure aluminum powder or aluminum alloy powder other than Al-Si-Mg alloy as a main component and Al-Si-Mg alloy powder, the Al-Si-Mg alloy powder containing 10-24 mass % Si and 2-7 mass % Mg with the balance being Al and unavoidable impurities (unavoidable impurities), the area ratio of the eutectic structure formed of the Al-Si-Mg alloy in the metal structure of the aluminum sintered member is 6-30%, and the 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, weldability and fatigue strength can be obtained.
• the aluminum sintered member of this embodiment is an aluminum sintered member that is formed by mixing and sintering pure aluminum powder or aluminum alloy powder other than Al-Si-Mg alloy as the main component with Al-Si-Mg alloy powder.
• the Al-Si-Mg alloy powder contains 10-24 mass% Si and 2-7 mass% Mg, with the remainder being Al and unavoidable impurities, and in the metal structure of the aluminum sintered member, the area ratio of the eutectic structure formed by the Al-Si-Mg alloy is 6-30%, and the porosity of the aluminum sintered member is 5% or less.
• the aluminum sintered member of this embodiment is manufactured using raw material powder containing, as a main component, pure aluminum powder or aluminum alloy powder other than Al-Si-Mg alloy, and Al-Si-Mg alloy powder.
• the pure aluminum powder is an aluminum powder in which 99% by mass or more of the components are aluminum.
• the means for preparing the pure aluminum powder is not particularly limited.
• As the pure aluminum for example, aluminum 1000 series materials such as JIS standard A1100 and A1200 can be used. Two or more types of pure aluminum powders may be used in combination.
• the aluminum alloy powder other than the Al-Si-Mg alloy is not particularly limited as long as it is other than the Al-Si-Mg alloy described below, but is preferably an aluminum alloy powder having an Al content of more than 50 mass%. Also, although not particularly limited, it is preferable that the Si and Mg contents are each less than 2 mass%, and the Mg content is greater than the Si content.
• the aluminum alloy powder preferably has an Al content of 80 mass% or more, more preferably 90 mass% or more, even more preferably 93 mass% or more, and even more preferably 95 mass% or more.
• the aluminum alloy powder preferably contains less than 1 mass % copper, which may impair stress corrosion cracking resistance and weldability, and more preferably contains 0.5 mass % or less copper.
• the source of the aluminum alloy powder is not particularly limited.
• aluminum 6000 series alloys such as JIS standards A6061, A6063, and A6101 can be used as the aluminum alloy.
• Aluminum 6000 series alloys are aluminum alloys to which Mg and Si have been added, and have excellent strength and corrosion resistance.
• the strength of the aluminum sintered member can be further improved by using an aluminum 6000 series alloy.
• Two or more types of aluminum alloy powders may be used in combination.
• the term "main component” refers to a component that is contained in an amount of more than 50% by mass in the raw material powder.
• the content of pure aluminum powder or aluminum alloy powder other than Al-Si-Mg alloy (also referred to as aluminum powder) in the raw material powder of the aluminum sintered member of this embodiment is not particularly limited as long as it is more than 50% by mass, but it is preferably 70 to 94% by mass. This makes it possible to easily control the area ratio of the eutectic structure formed by the Al-Si-Mg alloy in the metal structure of the aluminum sintered member to within a specified range. As a result, the effects of the present invention can be obtained more effectively. When two or more types of aluminum powder are used in combination, it is preferable that the total amount is within the above range.
• Al-Si-Mg alloy powder contains 10 to 24 mass % Si, 2 to 7 mass % Mg, and the remainder being Al and unavoidable impurities.
• the problem with sintering aluminum powder is that the aluminum powder has a strong oxide film on its surface, which means that it cannot be densified during the sintering process, and therefore the sintered part cannot have sufficient strength.
• this form of sintered aluminum part it is possible to provide a high-density sintered aluminum part by mixing Al-Si-Mg alloy powder with the main component pure aluminum powder or aluminum alloy powder other than Al-Si-Mg alloy to promote liquid phase sintering.
• Cu is added as a strengthening element, the susceptibility to weld cracking and stress corrosion cracking increases (cracks become more likely to occur), so Mg was selected as the strengthening element.
• the susceptibility to weld cracking and stress corrosion cracking increases with the amount of Mg added, so an upper limit for the amount of Mg is specified.
• Magneium (Mg): 2 to 7% by mass The effect of magnesium is to promote liquid phase sintering like silicon, and to reduce the oxide film present on the aluminum surface and promote sintering of aluminum. If the magnesium content is less than 2 mass%, the reduction effect of the oxide film is small and sufficient liquid phase sintering is not performed, so densification is not possible and sufficient strength cannot be obtained. On the other hand, if the magnesium content exceeds 7 mass%, there is a problem that the risk of stress corrosion cracking increases.
• the Al-Si-Mg alloy powder is composed of Al and inevitable impurities, excluding Si and Mg.
• the inevitable impurities refer to those that are present in the raw materials or that are inevitably mixed in during the manufacturing process. Although the inevitable impurities are essentially unnecessary, they are permitted because they are present in trace amounts and do not affect the properties of the Al-Si-Mg alloy powder or the aluminum sintered member using the same.
• the content of the inevitable impurities is preferably less than 0.1 mass % of the Al-Si-Mg alloy powder, and more preferably less than 0.01 mass %.
• the Al-Si-Mg alloy powder preferably contains less than 1 mass% copper, which may impair stress corrosion cracking resistance and weldability, more preferably 0.5 mass% or less, even more preferably 0.1 mass% or less, and most preferably 0 mass% (no copper).
• the melting point of the Al-Si-Mg alloy powder is preferably lower than that of the main component, pure aluminum powder, or aluminum alloy powder other than the Al-Si-Mg alloy. This can promote liquid phase sintering, and a high-density aluminum sintered member can be obtained more efficiently.
• the melting point of the Al-Si-Mg alloy powder is preferably, for example, about 30 to 70°C lower than that of the main component. If the difference in melting point with the main component is within the above range, a dense aluminum sintered member with low porosity can be obtained more efficiently.
• the melting point of the Al-Si-Mg alloy powder can be, for example, about 590 to 630°C.
• the melting point of the Al-Si-Mg alloy powder can be controlled by adjusting the composition of the Al-Si-Mg alloy. For example, the melting point tends to be higher when the content of Si or Mg is increased.
• the melting point of the Al-Si-Mg alloy powder can be estimated from a phase diagram.
• the content of Al-Si-Mg alloy powder in the raw powder of the aluminum sintered member of this embodiment is not particularly limited as long as it is less than 50 mass%, but it is preferably 6 to 30 mass%. This makes it possible to easily control the area ratio of the eutectic structure formed by the Al-Si-Mg alloy in the metal structure of the aluminum sintered member within a predetermined range. As a result, the effects of the present invention can be obtained more effectively. When two or more types of Al-Si-Mg alloy powders are used in combination, it is preferable that the total amount is within the above range.
• the total content of aluminum powder (pure aluminum powder or aluminum alloy powder other than Al-Si-Mg alloy) and Al-Si-Mg alloy powder in the raw material powder of the aluminum sintered member of this embodiment is not particularly limited, but is preferably 90 mass% or more, more preferably 95 mass% or more, and even more preferably 98 mass% or more, based on the total amount of raw material powder. 100 mass% is most preferable. This allows the effects of the present invention to be obtained more significantly.
• the main component of the raw material powder is pure aluminum powder, and the Al-Si-Mg alloy powder contains 10-24 mass% Si and 3-7 mass% Mg, with the remainder being Al and unavoidable impurities.
• the main component of the raw material powder is an aluminum alloy powder
• the Al-Si-Mg alloy powder contains 10-24 mass% Si and 2-7 mass% Mg, with the remainder being Al and unavoidable impurities.
• the elemental composition of the aluminum sintered member according to this embodiment can be the same as the elemental composition of the mixed powder before sintering and compacting.
• the area ratio of the eutectic structure formed by the Al-Si-Mg alloy powder is 6 to 30%.
• the area ratio of the eutectic structure is less than 6%, the liquid phase sintering is not performed sufficiently, and the densification is not performed, so that sufficient strength cannot be obtained.
• the area ratio of the eutectic structure exceeds 30%, the eutectic structure is easily embrittled, and 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 alloy powder.
• the area ratio of the eutectic structure can be obtained by the method described in the examples below.
• the porosity of the aluminum sintered member according to this embodiment is 5% or less. If the porosity exceeds 5%, sufficient tensile strength cannot be obtained because the densification is not achieved. In addition, since the pores tend to become the starting points of fatigue failure, sufficient fatigue strength cannot be obtained.
• the porosity of the aluminum sintered member is preferably 4% or less.
• the lower limit of the porosity is not particularly limited, but is, for example, 0.5% or more, and preferably 1% or more. If it is within the above range, the effect of the present invention can be obtained more significantly.
• the porosity of the aluminum sintered member can be determined by the method described in the examples below.
• the porosity of the aluminum sintered member can be controlled, for example, by adjusting the type of aluminum powder as the raw material, the composition and content of the Al-Si-Mg alloy powder, and the pressure, temperature, and time during sintering.
• the filling rate of the sintered aluminum member is the ratio of the portion other than the pores, as described in the examples below. From the same viewpoint as above, the filling rate of the sintered aluminum member according to this embodiment is 95% or more, for example, 96% or more.
• the upper limit of the filling rate is not particularly limited, but is, for example, 99.5% or less, for example, 99% or less.
• the method for producing the aluminum sintered member of this embodiment is not particularly limited.
• a method including a mixing step of mixing a pure aluminum powder or an aluminum alloy powder other than an Al-Si-Mg alloy as a main component with an Al-Si-Mg alloy powder to obtain a mixed powder, and a sintering and molding step of sintering and molding the mixed powder can be preferably used.
• the aluminum sintered member of this embodiment can be easily obtained.
• any known method can be used as appropriate. For example, mixing using a mortar, dry ball mill, dynamic mill, bead mill, jet mill, hammer mill, disk mill, or pin mill can be used, and among these, mixing using a dry ball mill is preferred.
• the rotation speed is preferably 400 to 700 rpm.
• the mixing time is preferably 30 to 60 minutes.
• the mixed powder obtained in the mixing step is sintered and formed. This solidifies the mixed powder to obtain an aluminum sintered member.
• the sintering and forming is preferably performed in a vacuum, for example, using a vacuum hot press.
• the conditions for the sintering and forming are not particularly limited.
• the pressure during the sintering and forming is preferably 20 to 40 MPa.
• the temperature is preferably 500 to 580°C.
• the time is preferably 20 to 80 minutes. This makes it possible to efficiently obtain an aluminum sintered member having a predetermined eutectic structure area ratio and a predetermined porosity.
• the aluminum sintered component of this embodiment is lightweight, has high strength, and has excellent resistance to stress corrosion cracking and welding, and is therefore suitable for use in automobile engine parts and drivetrain parts, although there are no particular limitations.
• the aluminum sintered member according to claim 1 having the characteristics of claim 2; the aluminum sintered member according to claim 1 having the characteristics of claim 3; the aluminum sintered member according to claim 1 or 3 having the characteristics of claim 4; and the method for manufacturing an aluminum sintered member according to any one of claims 1 to 4 having the characteristics of claim 5.
• Example 1 Pure aluminum powder or aluminum alloy powder shown in Table 1 below was mixed with Al-Si-Mg alloy powder having the composition shown in Table 1 below in a dry ball mill (mixing conditions: rotation speed 550 rpm, time 45 minutes), and the mixed powder was solidified by a sintering process to obtain a sintered aluminum member.
• Sintering was performed using a vacuum hot press under a sintering pressure of 30 MPa at a sintering temperature of 540°C for a sintering time of 50 minutes.
• the composition of the Al-Si-Mg alloy powder contains the Si and Mg contents shown in the table, with the remainder being Al and unavoidable impurities.
• the melting point of the Al-Si-Mg alloy powder is a value estimated from a phase diagram.
• Comparative Example 7 instead of the Al-Si-Mg alloy powder, an Al-Cu alloy powder containing 5 mass% Cu with the remainder being Al and unavoidable impurities was used.
• Comparative Example 8 instead of the Al-Si-Mg alloy powder, an Al-Mg alloy powder containing 5 mass% Mg with the remainder being Al and unavoidable impurities was used.
• the sample was cut into small pieces to prepare the specimen for measurement.
• the cross section of the sample was mirror-polished, etched with nital, and an image was taken with an optical microscope.
• a threshold was set for the brightness of the image so that the eutectic structure could be identified, and a binarization process was performed to measure the area of the eutectic structure.
• the ratio of the area of the eutectic structure contained in the range from the surface to 100 ⁇ m in the depth direction was calculated as a percentage.
• the porosity was then calculated as a percentage of the area using the same method.
• the filling rate of the aluminum sintered component was calculated as the ratio of the area of the parts other than the pores in the above porosity measurement. The results are shown in Table 1 below.
• Figure 1 shows an optical microscope photograph of the sample of the aluminum sintered part produced in Example 1.
• the metal structure of the aluminum sintered part of this example is confirmed to have a eutectic structure (white parts) and voids (black parts) formed of an Al-Si-Mg alloy in the ⁇ -Al phase.
• Stress corrosion cracking (SCC) resistance Stress corrosion cracking tests were carried out on samples cut out from the aluminum sintered members produced in each of the Examples and Comparative Examples. In the stress corrosion cracking tests, a corrosive environment evaluation was carried out under stress load based on JIS H 8711:2000. The results are shown in Table 1 below. If no corrosion cracking occurred within the specified time (1000 hours), it was judged as OK, and if corrosion cracking occurred, it was judged as NG.
• Table 1 shows that the aluminum sintered parts of Examples 1 to 8, which use a specified Al-Si-Mg alloy powder and have a eutectic structure area ratio and porosity within the specified range, have excellent tensile strength, stress corrosion cracking resistance, weldability, and fatigue strength.
• Comparative Examples 1 to 8 in which either the composition of the Al-Si-Mg alloy powder, the area ratio of the eutectic structure, or the porosity was outside the specified range, it was found that sintered components with excellent tensile strength, stress corrosion cracking resistance, weldability, and fatigue strength were not obtained.
• the configurations described in the above-mentioned embodiments and examples are not limited to each embodiment or example, and for example, the composition of each embodiment or the detailed conditions for manufacturing can be changed, or the configurations of each embodiment or example can be combined in a way other than the above-mentioned embodiments or examples.

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• 2023
  • 2023-01-26 JP JP2024572758A patent/JPWO2024157424A1/ja active Pending
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