JP2023083155A - Aluminum alloy forged article - Google Patents

Abstract

To provide an aluminum alloy forged article having better mechanical characteristics than a conventional aluminum alloy forged article.SOLUTION: An aluminum alloy forged article according to the present invention is composed of an aluminum alloy comprising 0.2-0.5 mass% Cu, 0.6-1.2 mass% Mg, 0.4-1.25 mass% Si, 0.4-0.6 mass% Mn, 0.15-0.70 mass% Fe, 0.09-0.25 mass% Cr, 0.012-0.035 mass% Ti, with the balance consisting of Al and inevitable impurities, and contains a substance which contains any two or more elements of Mg, Si, Al and Cu in a chemical composition as precipitates composed of intermetallic compounds observed when an Al base phase is observed on <100>incidence by a transmission electron microscope, has a plurality of Cu atom rows on the outer periphery of the precipitates, and has an average interval between the Cu atom rows arranged on the outer periphery of 10 nm or less.SELECTED DRAWING: Figure 5

Description

The present invention relates to aluminum alloy forgings.

Since 6000 series aluminum alloys have good strength and corrosion resistance, they are suitably used as materials for structures such as ships, vehicles, land structures, buildings, guardrails, home appliances, busbars, electric wires, machines, and automobile parts. there is 2. Description of the Related Art In recent years, there has been a strong demand for weight reduction of aluminum alloy forged materials for automobiles, such as automobiles and automobile parts, for reasons such as reducing vehicle weight and improving fuel efficiency. In order to reduce the weight, it is necessary to increase the strength of the material itself, and the development of such a material has been strongly desired.

Among commonly known metal strengthening mechanisms, precipitation strengthening plays a major role in the case of 6000 series aluminum alloys. After solution treatment, a supersaturated solid solution is formed, and then low-temperature tempering (artificial aging treatment) is performed to finely precipitate nano-sized compound particles in the matrix. is strengthened. The addition of Cu is well known as a technique for further enhancing the precipitation strengthening of 6000 series aluminum alloys, and it is known that the inclusion of Cu in the precipitates contributes to the fine dispersion of the precipitates (non-patent literature 1).

In addition, in the Cu-added 6000 series aluminum alloy, it has been clarified that various metastable phases such as the Q' phase and the C phase appear in the process of artificial aging (Non-Patent Document 2). Various efforts have been made to improve base material strength and corrosion resistance by highly controlling the atomic structure and dispersion state of these precipitates (for example, Patent Publication 1).

Japanese Patent No. 5901738

Haruhiko Abe, Shinya Komatsu, Katsuhiko Ikeda, Takeo Sakurai: "Study of the effect of copper addition on 473 K aging behavior of Al-1%Mg2Si alloy by resistivity method", Keikinzoku, 52 (2002), 179-184. Takeshi Saito, Eva A. Mortsell, Sigurd Wenner, Calin D. Marioara, Sigmund J. Andersen, Jesper Friis, Kenji Matsuda, and Randi Holmestad: “Atomic Structures of Precipitates in Al-Mg-Si Alloys with Small Additions of Other Elements” , Advanced Engineering Materials, 20 (2018), 1800125.

The present invention has been made in view of the above circumstances, and an aluminum alloy forging having better mechanical properties by controlling the structure of precipitates formed by artificial aging treatment to a higher degree than before. intended to provide

In order to solve the above problems, the present invention provides the following means.

The aluminum alloy forged product according to the first aspect of the present invention has Cu: 0.2 mass% to 0.5 mass%, Mg: 0.6 mass% to 1.2 mass%, Si: 0.4 mass% to 1.25% by mass, Mn: 0.4% by mass to 0.6% by mass or less, Fe: 0.15% by mass to 0.70% by mass, Cr: 0.09% by mass to 0.25% by mass or less, Ti: 0.012% by mass to 0.035% by mass, the balance being an aluminum alloy forged product composed of an aluminum alloy consisting of Al and inevitable impurities, <100> with respect to the Al matrix phase by a transmission electron microscope As a precipitate composed of an intermetallic compound observed when observed under incident light, the chemical composition contains at least two elements selected from among Mg, Si, Al and Cu, and a plurality of Those having Cu atomic rows and having an average spacing between the Cu atomic rows arranged on the outer periphery of 10 nm or less are included.

In the aluminum alloy forged product according to _the above aspect, the ratio ( _{N i / ni} ) may be 1 or more.

In the aluminum alloy forged product according to the above aspect, 70% or more of the Cu atomic arrays arranged on the outer periphery of the precipitates may coincide with the Al atomic array positions of the Al matrix.

The aluminum alloy forged product according to the above aspect may further contain 0.0001% by mass to 0.03% by mass of B.

According to the aluminum alloy forged product of the present invention, it is possible to provide an aluminum alloy forged product having better mechanical properties than conventional products.

FIG. 2 is a schematic perspective view showing the arrangement of Cu atomic rows in a part of the aluminum alloy forged product according to the present embodiment. 1 is a cross-sectional view showing an example of the vicinity of a mold of a horizontal continuous casting apparatus for producing an aluminum alloy ingot. FIG. FIG. 3 is an enlarged cross-sectional view of a main part showing the vicinity of a cooling water cavity in FIG. 2; It is an explanatory view explaining heat flux of a cooling wall part of a horizontal continuous casting device. FIG. 2 is a schematic plan view schematically showing the typical shape of precipitates and their atomic array arrangement in a TEM image. 1 is a schematic perspective view of an aluminum alloy forged product produced in an example. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, aluminum alloy forged products according to embodiments of the present invention will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, characteristic parts may be shown enlarged for convenience in order to make the characteristics easier to understand, and the dimensional ratio of each component may differ from the actual one. The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited to them, and can be implemented with appropriate changes within the scope of the present invention.

[Aluminum alloy forgings]
FIG. 1 is a schematic perspective view showing the arrangement of Cu atomic rows in a part of the aluminum alloy forged product according to the present embodiment. Each circle in the drawing corresponds to a Cu atom, and rows of Cu atoms aligned in the <100> direction are Cu atom rows, and FIG. 1 shows 10 Cu atom rows. In FIG. 1, the Cu atoms arranged on the (100) plane, which is the observation plane, are patterned.

The aluminum alloy forged product according to the present embodiment has Cu: 0.2 mass% to 0.5 mass%, Mg: 0.6 mass% to 1.2 mass%, Si: 0.4 mass% to 1.25. % by mass, Mn: 0.4% by mass to 0.6% by mass, Fe: 0.15% by mass to 0.70% by mass, Cr: 0.09% by mass to 0.25% by mass, Ti: 0.012 It is composed of an aluminum alloy composed of mass % to 0.035 mass %, the balance being Al and unavoidable impurities.
Impurity elements that may inevitably be mixed into the aluminum alloy may be contained within a range that does not affect product characteristics. For example, typical elements include Zn, and transition elements include Zr. Furthermore, for the purpose of controlling the crystal grain size during casting, refiners such as Al--Ti--B rods are often added. Additions may be made.

The aluminum alloy forged product according to the present embodiment has a chemical composition of Mg, Si , Al and Cu, and having a plurality of Cu atomic rows on the outer circumference of the precipitate Seg, with an average spacing between the Cu atomic rows arranged on the outer circumference being 10 nm or less. It is included.
Here, in this specification, the term "transmission electron microscope" also includes a scanning transmission electron microscope (STEM).

In the aluminum alloy forged product according to the present embodiment, the C phase precipitates in the intermetallic compound precipitates Seg observed when observing the Al parent phase with <100> incidence with a transmission electron microscope. and β″ phase precipitates.
For example, it is preferable that the precipitates of the C phase have a plurality of Cu atomic arrays on the outer circumference thereof, and the average spacing between the Cu atomic arrays arranged on the outer circumference is 10 nm or less.

It is preferable that 10% or more of C-phase precipitates are contained in the precipitates Seg. This is because the examples suggest that the precipitates of the C phase improve the tensile strength and the 0.2% yield strength, as will be described later.
Further, it is more preferable that 20% or more of the precipitates Seg are C-phase precipitates. More preferably, 30% or more of C-phase precipitates are contained in the precipitates Seg. More preferably, 40% or more of the precipitates Seg are C-phase precipitates. More preferably, 50% or more of the precipitates Seg are C-phase precipitates. More preferably, 60% or more of the precipitates Seg are C-phase precipitates. More preferably, 70% or more of the precipitates Seg are C-phase precipitates.

In this specification, the range of the "precipitate" (the boundary between the atomic rows contained inside and outside the precipitate and the atomic rows not contained) is, for example, a TEM image obtained by transmission electron microscopy (TEM) can be determined by Al matrix In addition to TEM, a HAADF-STEM image (hereinafter simply referred to as "STEM image") obtained by a high-angle scattering annular dark field method (HAADF-STEM) that can obtain a contrast depending on the atomic number (Z) ), or elemental mapping obtained by combining electron beam scanning in STEM with energy dispersive X-ray spectroscopy (EDS).
In addition, in this specification, the “periphery of the precipitate” refers to a shape formed by connecting the centers of bright spots corresponding to each atomic row that constitutes the precipitate in a TEM image, STEM image, or elemental mapping (Fig. 1, dotted line P). The atomic arrays forming the "periphery of the precipitate" are the atomic arrays arranged on the "periphery of the precipitate". In the TEM image or STEM image, the image of the atomic row arranged on the "periphery of the precipitate" is broken in the continuity of the lattice in which the images of the atomic rows of the Al matrix are arranged, so that the "periphery of the precipitate" Atom columns to be placed can be determined. This allows the extent of the "precipitate" to be established. Further, in the elemental mapping, it is possible to determine the range of the "precipitate" by determining the atomic array to be arranged on the "periphery of the precipitate" according to the element species in the image of the atomic array. Among the atomic arrays belonging to the range of the "precipitate", the atomic arrays other than the atomic arrays arranged on the "periphery of the precipitate" are the atomic arrays "included inside the precipitate".
In addition, in this specification, the “average spacing between Cu atomic rows arranged on the outer periphery” is a circle having an area equal to the area S ₀ of the shape surrounded by the “periphery of the precipitate” (equivalent circle). It is the distance between adjacent Cu atomic arrays when the Cu atomic arrays are evenly arranged on the circumference. That is, when the equivalent circle diameter is R and the number of Cu atomic rows arranged on the outer periphery of the precipitate is N _i , the “average spacing between the Cu atomic rows arranged on the outer periphery” l _Cu = 2πr (peripheral length of the equivalent circle )/N _i (the number of Cu atomic rows arranged on the periphery of the precipitate).

In addition, the aluminum alloy forged product according to _the present embodiment has a ratio ( _{N i / ni} ) is preferably 1 or more. This is because the Cu atomic arrays arranged on the periphery of the precipitate serve as a barrier when the precipitate coarsens, leading to fine dispersion of the precipitate.
In the present specification, "the number of Cu atomic rows contained inside the precipitate" means, among the Cu atomic rows contained in the precipitate, the number of Cu atomic rows excluding the Cu atomic rows arranged on the periphery of the precipitate. is a number.

Further, in the aluminum alloy forged product according to the present embodiment, it is preferable that 70% or more of the Cu atomic arrays arranged on the outer circumference of the precipitates coincide with the Al atomic array positions of the Al matrix. This is because the Cu atomic arrays arranged at positions corresponding to the Al atomic array positions of the Al matrix phase can stably exist, so that coarsening of the precipitates is suppressed, leading to fine dispersion of the precipitates.
In the present specification, "matching the Al atomic row position of the Al matrix" means that in the TEM image or the STEM image, if there are no precipitates, it matches the position where the Al atomic row of the Al matrix is arranged. It means that

(Cu: 0.2% by mass to 0.5% by mass)
Cu has the effect of finely dispersing the Mg—Si-based compound in the aluminum alloy, and the effect of improving the tensile strength of the aluminum alloy by precipitating as an Al—Cu—Mg—Si-based compound including the Q phase. have When the Cu content is within the above range, the tensile strength of the aluminum alloy can be improved.

(Mg: 0.6% by mass to 1.2% by mass)
Mg has the effect of improving the tensile strength of the aluminum alloy. Strengthening of aluminum alloys by solid-solution of Mg into the aluminum matrix phase, or precipitation as Mg-Si compounds such as the β'' phase, or Al-Cu-Mg-Si compounds such as the Q phase. contribute to By keeping the Mg content within the above range, the tensile strength of the aluminum alloy can be improved.

(Si: 0.4% by mass to 1.25% by mass)
Si has the effect of improving the tensile strength of the aluminum alloy. However, if Si is excessively added to the aluminum alloy, the tensile strength of the aluminum alloy may decrease due to crystallization of coarse primary crystal Si grains. When the content of Si is within the above range, it is possible to improve the tensile strength of the aluminum alloy while suppressing the crystallization of primary crystal Si.

(Mn: 0.4% by mass to 0.6% by mass)
Mn forms fine granular crystallized substances containing intermetallic compounds such as Al-Mn-Fe-Si and Al-Mn-Cr-Fe-Si in the aluminum alloy, thereby increasing the tensile strength of the aluminum alloy. It has the effect of improving When the Mn content is within the above range, the tensile strength of the aluminum alloy can be improved.

(Fe: 0.15% by mass to 0.70% by mass)
Fe is contained in fine particles including intermetallic compounds such as Al--Mn--Fe--Si, Al--Mn--Cr--Fe--Si, Al--Fe--Si, Al--Cu--Fe, and Al--Mn--Fe in aluminum alloys. By crystallizing as a crystallized product, it has the effect of improving the tensile strength of the aluminum alloy. When the Fe content is within the above range, the tensile strength of the aluminum alloy can be improved.

(Cr: 0.09% by mass to 0.25% by mass)
Cr improves the tensile strength of aluminum alloys by forming fine granular crystallized substances containing intermetallic compounds such as Al-Mn-Cr-Fe-Si and Al-Fe-Cr in aluminum alloys. It has the effect of causing When the Cr content is within the above range, the tensile strength of the aluminum alloy can be improved.

(Ti: 0.012% by mass to 0.035% by mass)
Ti has the effect of refining the crystal grains of the aluminum alloy forged product and improving the drawing workability. If the Ti content is less than 0.012% by mass, the effect of refining crystal grains may not be sufficiently obtained. On the other hand, if the Ti content exceeds 0.035% by mass, coarse crystallized substances may be formed and the drawability may deteriorate. Further, if a large amount of coarse crystallized substances containing Ti are mixed into the final product of the aluminum alloy, the toughness may be lowered. Therefore, the Ti content should be in the range of 0.012% by mass to 0.035% by mass. The Ti content is preferably in the range of 0.015% by mass to 0.030% by mass.

(B: 0.0001% by mass to 0.03% by mass)
B has the effect of refining the crystal grains of the aluminum alloy forged product and improving the drawing workability. By further adding B to the aluminum alloy together with Ti, the grain refinement effect is improved. If the content of B is less than 0.001% by mass, there is a possibility that a sufficient grain refining effect cannot be obtained. On the other hand, if the content of B exceeds 0.03% by mass, coarse crystallized substances may be formed and mixed into the final aluminum alloy product as inclusions. In addition, if a large amount of coarse crystallized substances containing B are mixed into the final product of the aluminum alloy, the toughness may be lowered. Therefore, the B content should be in the range of 0.0001% by mass or more and 0.03% by mass or less. The content of B is preferably in the range of 0.005% by mass or more and 0.025% by mass or less.

(Inevitable impurities)
The unavoidable impurities are impurities that are unavoidably mixed into the aluminum alloy from the raw material of the aluminum alloy or the manufacturing process. Examples of unavoidable impurities include Zn, Ni, Zr, Sn, and Be. The content of these unavoidable impurities preferably does not exceed 0.1% by mass.

Next, a method for manufacturing the aluminum alloy forged product of the present embodiment will be described.
The aluminum alloy forged product of the present embodiment can be manufactured by a method including, for example, a molten metal forming step, a casting step, a homogenization heat treatment step, a forging step, a solution treatment step, a quenching treatment step, and an aging treatment step.

(Molten metal forming process)
The molten metal forming step is a step of melting raw materials to obtain aluminum alloy molten metal having an adjusted composition. The composition of the molten aluminum alloy is the same as the composition of the aluminum alloy forged product. A molten aluminum alloy can be obtained by heating and melting an aluminum alloy. Impurity elements that may inevitably be mixed into the aluminum alloy may be contained within a range that does not affect product characteristics. For example, typical elements include Zn, and transition elements include Zr. Furthermore, for the purpose of controlling the crystal grain size during casting, refiners such as Al--Ti--B rods are often added. Addition may be performed.

(Casting process)
In the casting process, a molten aluminum alloy (liquid phase) is cooled and solidified into a solid (solid phase) to obtain an aluminum alloy casting. The casting process is not particularly limited, and any known continuous casting method such as a horizontal continuous casting method or a vertical continuous casting method may be used. Further, in order to improve the reliability of the final product, the molten metal may be appropriately subjected to degassing treatment or filtering treatment.
FIG. 2 is a cross-sectional view showing an example of a horizontal continuous casting apparatus that can be used to manufacture the aluminum alloy casting product of the present embodiment. It is a sectional view.

A horizontal continuous casting apparatus 10 shown in FIGS. 2 and 3 is arranged between a molten metal receiver (tundish) 11, a hollow cylindrical mold 12, and one end 12a of the mold 12 and the molten metal receiver 11. and a refractory plate (heat insulating member) 13.

The molten metal receiving portion 11 is composed of a molten metal inlet portion 11a for receiving the aluminum alloy molten metal M obtained in the molten metal forming step, a molten metal holding portion 11b, and an outlet portion 11c to the hollow portion 21 of the mold 12. The molten metal receiving part 11 maintains the level of the upper liquid level of the aluminum alloy molten metal M at a position higher than the upper surface of the hollow part 21 of the mold 12, and in the case of multiple casting, each mold 12 has an aluminum alloy The molten metal M is stably distributed.

The molten aluminum alloy M held in the molten metal holding portion 11b in the molten metal receiving portion 11 is poured into the hollow portion 21 of the mold 12 from the pouring passage 13a provided in the refractory plate 13. Then, the molten aluminum alloy M supplied into the hollow portion 21 is cooled and solidified by a cooling device 23, which will be described later, and is pulled out from the other end side 12b of the mold 12 as an aluminum alloy rod B, which is a solidified ingot.

At the other end 12b of the mold 12, a drawer driving device (not shown) for drawing out the cast aluminum alloy rod B at a constant speed may be installed. Moreover, it is also preferable to install a synchronous cutting machine (not shown) for cutting the continuously drawn aluminum alloy rod B to an arbitrary length.

The refractory plate-like body 13 is a member that blocks heat transfer between the molten metal receiving portion 11 and the mold 12, and is, for example, calcium silicate, alumina, silica, a mixture of alumina and silica, silicon nitride, and silicon carbide. , graphite or the like. Such a refractory plate-like body 13 can also be composed of a plurality of layers of different constituent materials.

The mold 12 is a hollow cylindrical member in this embodiment, and is made of, for example, one or a combination of two or more materials selected from aluminum, copper, or alloys thereof. Materials for the mold 12 may be selected in an optimum combination from the viewpoints of thermal conductivity, heat resistance, and mechanical strength.

A hollow portion 21 of the mold 12 is formed to have a circular cross section in order to form the aluminum alloy rod B to be cast into a cylindrical rod shape, and a mold center axis (central axis) C passing through the center of the hollow portion 21 extends substantially horizontally. A mold 12 is held along it.

The inner peripheral surface 21a of the hollow portion 21 of the mold 12 is 0 to 3 degrees (more preferably 0 to 1 degree) with respect to the mold central axis C toward the casting direction of the aluminum alloy rod B (see FIG. 5). ) is formed at an elevation angle of That is, the inner peripheral surface 21a is formed in a tapered shape that opens in a cone shape in the casting direction. The angle formed by the taper is the elevation angle.

If the angle of elevation is less than 0 degree, casting may become difficult because the aluminum alloy rod B receives resistance at the other end 12b, which is the exit of the mold, when pulled out from the mold 12. On the other hand, if the angle of elevation exceeds 3 degrees, the contact of the inner peripheral surface 21a with the molten aluminum alloy M becomes insufficient, and the effect of removing heat from the molten aluminum alloy M and the solidified shell obtained by cooling and solidifying it to the mold 12 decreases. This may result in insufficient coagulation. As a result, re-melting texture may occur on the surface of the aluminum alloy rod B, or unsolidified molten aluminum alloy M may spout out from the end of the aluminum alloy rod B, which may lead to casting troubles, which is not preferable.

In addition, the cross-sectional shape of the hollow portion 21 of the mold 12 (the planar shape when the hollow portion 21 of the mold 12 is viewed from the other end side 21b) may be, for example, a triangular or rectangular cross-sectional shape other than the circular shape of the present embodiment. It may be selected according to the shape of the aluminum alloy rod to be cast, such as polygonal, semicircular, elliptical, or a shape having a modified cross-sectional shape with no axis of symmetry or plane of symmetry.

A fluid supply pipe 22 for supplying lubricating fluid into the hollow portion 21 of the mold 12 is arranged on one end side 12 a of the mold 12 . As the lubricating fluid supplied from the fluid supply pipe 22, one or more lubricating fluids selected from gas lubricating materials and liquid lubricating materials can be used. When supplying both the gas lubricant and the liquid lubricant, it is preferable to provide separate fluid supply pipes for each. The lubricating fluid supplied under pressure from the fluid supply pipe 22 is supplied into the hollow portion 21 of the mold 12 through the annular lubricant supply port 22a.

In this embodiment, the pumped lubricating fluid is supplied to the inner peripheral surface 21a of the mold 12 from the lubricant supply port 22a. It should be noted that the liquid lubricant may be heated to become a decomposed gas and supplied to the inner peripheral surface 21 a of the mold 12 . Alternatively, a porous material may be arranged in the lubricant supply port 22a, and the lubricating fluid may be exuded to the inner peripheral surface 21a of the mold 12 through the porous material.

Inside the mold 12, a cooling device 23, which is cooling means for cooling and solidifying the molten alloy M, is formed. The cooling device 23 of this embodiment includes a cooling water cavity 24 containing cooling water W for cooling the inner peripheral surface 21a of the hollow portion 21 of the mold 12, and the cooling water cavity 24 and the hollow portion 21 of the mold 12. It has a cooling water injection passage 25 that communicates with.

The cooling water cavity 24 is formed annularly so as to surround the hollow portion 21 outside the inner peripheral surface 21 a of the hollow portion 21 inside the mold 12 , and is supplied with cooling water W through a cooling water supply pipe 26 . be.
The inner peripheral surface 21a of the mold 12 is cooled by the cooling water W contained in the cooling water cavity 24, so that the heat of the molten alloy M filling the hollow portion 21 of the mold 12 is transferred to the inner peripheral surface 21a of the mold 12. to form a solidified shell on the surface of the molten alloy M.

The cooling water injection passage 25 cools the aluminum alloy rod B by applying cooling water directly from the shower opening 25 a facing the hollow portion 21 toward the aluminum alloy rod B at the other end side 12 b of the mold 12 . The longitudinal cross-sectional shape of the cooling water injection passage 25 may be, for example, semicircular, pear-shaped, or horseshoe-shaped, in addition to the circular shape of the present embodiment.

In this embodiment, the cooling water W supplied through the cooling water supply pipe 26 is first accommodated in the cooling water cavity 24 to cool the inner peripheral surface 21a of the hollow portion 21 of the mold 12, and then the cooling water The cooling water W in the cavity 24 is injected from the cooling water injection passage 25 toward the aluminum alloy rod B, but it is also possible to supply these through separate cooling water supply pipes.

The length from the position where the extension of the central axis of the shower opening 25a of the cooling water injection passage 25 hits the surface of the cast aluminum alloy rod B to the contact surface between the mold 12 and the refractory plate 13 This effective mold length L is called an effective mold length L, and is preferably, for example, 10 mm or more and 40 mm or less. When the effective mold length L is less than 10 mm, casting is not possible because a good film is not formed. The contact resistance with the molten alloy M or the aluminum alloy rod B increases, and the casting surface may be cracked, or the casting may be torn inside the mold, resulting in unstable casting.

The supply of cooling water to the cooling water cavity 24 and the injection of cooling water from the shower opening 25a of the cooling water injection passage 25 are preferably controlled by control signals from a control device (not shown).

The cooling water cavity 24 is formed such that the inner bottom surface 24a near the hollow portion 21 of the mold 12 is parallel to the inner peripheral surface 21a of the hollow portion 21 of the mold 12 . The term “parallel” here means that the inner peripheral surface 21a of the hollow portion 21 of the mold 12 is formed at an elevation angle of 0 to 3 degrees with respect to the inner bottom surface 24a of the cooling water cavity 24. A case in which the bottom surface 24a is inclined more than 0 degrees and up to 3 degrees with respect to the inner peripheral surface 21a is also included.

As shown in FIG. 3, the cooling wall portion 27 of the mold 12, which is the portion where the inner bottom surface 24a of the cooling water cavity 24 and the inner peripheral surface 21a of the hollow portion 21 of the mold 12 face each other, is the molten alloy in the hollow portion 21. It is formed so that the heat flux value per unit area from M toward the cooling water W of the cooling water cavity 24 is in the range of 10×10 ⁵ W/m ² or more and 50×10 ⁵ W/m ² or less. .

The thickness t of the cooling wall portion 27 of the mold 12, that is, the distance between the inner bottom surface 24a of the cooling water cavity 24 and the inner peripheral surface 21a of the hollow portion 21 of the mold 12 is, for example, 0.5 mm or more and 3.0 mm or less, preferably It is sufficient that the mold 12 is formed so that the diameter is within the range of 0.5 mm or more and 2.5 mm or less. Moreover, the material for forming the mold 12 may be selected so that at least the cooling wall portion 27 of the mold 12 has a thermal conductivity within the range of 100 W/m·K or more and 400 W/m·K or less.

In FIG. 3, the molten alloy M in the molten metal receiving portion 11 is supplied from one end side 12a of the mold 12 held so that the mold central axis C is substantially horizontal through the refractory plate-shaped body 13, and the mold 12 is forcibly cooled at the other end side 12b of the aluminum alloy rod B. Since the aluminum alloy rod B is pulled out at a constant speed by a pull-out driving device (not shown) installed near the other end 12b of the mold 12, it is continuously cast to form a long aluminum alloy rod B. The pulled-out aluminum alloy rod B is cut to a desired length by, for example, a synchronized cutting machine (not shown).

The composition ratio of the cast aluminum alloy rod B can be confirmed, for example, by a method using a photoelectric photometric emission spectrometer (device example: PDA-5500 manufactured by Shimadzu Corporation, Japan) as described in JIS H 1305. .

The difference in height between the liquid level of the molten alloy M stored in the molten metal receiving portion 11 and the upper inner peripheral surface 21a of the mold 12 is 0 mm to 250 mm (more preferably 50 mm to 170 mm). preferably. With this range, the pressure of the molten alloy M supplied into the mold 12 and the lubricating oil and the vaporized gas of the lubricating oil are well balanced, so that castability is stabilized.

A vegetable oil, which is a lubricating oil, can be used as the liquid lubricant. Examples include rapeseed oil, castor oil, and salad oil. These are preferred because they have little adverse effect on the environment.

The lubricating oil supply rate is preferably 0.05 mL/min to 5 mL/min (more preferably 0.1 mL/min or more and 1 mL/min or less). If the supply amount is too small, the molten alloy of the aluminum alloy rod B may leak from the mold without solidifying due to insufficient lubrication. If the amount supplied is excessive, there is a risk that the surplus will be mixed into the aluminum alloy rod B and cause internal defects.

The casting speed, which is the speed at which the aluminum alloy rod B is drawn out of the mold 12, is preferably 200 mm/min or more and 1500 mm/min or less (more preferably 400 mm/min or more and 1000 mm/min or less). This is because if the casting speed is within this range, the network structure of crystallized substances formed by casting becomes uniform and fine, the resistance to deformation of the aluminum material at high temperatures increases, and the high-temperature mechanical strength improves. be.

The amount of cooling water injected from the shower opening 25a of the cooling water injection passage 25 is preferably 10 L/min or more and 50 L/min or less (more preferably 25 L/min or more and 40 L/min or less) per mold. If the amount of cooling water is less than this, the molten alloy may not solidify and may leak from the mold. In addition, the surface of the cast aluminum alloy rod B may be remelted to form a non-uniform structure, which may remain as internal defects. On the other hand, if the amount of cooling water is more than this range, there is a possibility that the mold 12 may solidify due to excessive heat removal.

The average temperature of the molten alloy M flowing into the mold 12 from the molten metal receiving part 11 is preferably, for example, 650° C. or higher and 750° C. or lower (more preferably 680° C. or higher and 720° C. or lower). If the temperature of the molten alloy M is too low, coarse crystallized substances may be formed in the mold 12 and in front of it, and may be incorporated into the aluminum alloy rod B as internal defects. On the other hand, if the temperature of the molten alloy M is too high, a large amount of hydrogen gas is likely to be taken into the molten alloy 255, and may be taken into the aluminum alloy rod B as porosity, resulting in internal cavities.

In the cooling wall portion 27 of the mold 12, the heat flux value per unit area from the molten alloy M in the hollow portion 21 toward the cooling water W in the cooling water cavity 24 is 10×10 ⁵ W/m ² or more and 50×10 By keeping it within the range of ⁵ W/m ² or less, it is possible to prevent the occurrence of seizure of the aluminum alloy rod B.

The cooling wall portion 27 of the mold 12 receives heat from the molten alloy M, and the heat is cooled by the cooling water W contained in the cooling water cavity 24 for heat exchange. Regarding the state of exchange, attention was focused on the heat flux per unit area, as shown in the explanatory diagram of FIG. The heat flux per unit area is represented by the following formula (1) according to Fourier's law.
Q=-k×(T1-T2)/L (1)
Q: heat flux k: thermal conductivity (W/m K) of a portion through which heat passes (cooling wall portion 27 of mold 12 in this embodiment)
T1: Low-temperature side temperature of a portion through which heat passes (in this embodiment, the inner bottom surface 24a of the cooling water cavity 24)
T2: High-temperature side temperature of a portion through which heat passes (in this embodiment, the inner peripheral surface 21a of the hollow portion 21 of the mold 12)
L: Section length (mm) where heat passes (thickness t of cooling wall portion 27 of mold 12 in this embodiment)

Based on the mold material, thickness, and temperature measurement data that gave good results even when the amount of lubricating oil was reduced during casting, the mold was adjusted so that the heat flux value per unit area was 10 × 10 ⁵ W / m ² or more. By forming the twelve cooling wall portions 27, seizure of the cast aluminum alloy rod B can be prevented. Also, the heat flux value per unit area is preferably 50×10 ⁵ W/m ² or less.

In order to bring the cooling wall portion 27 of the mold 12 into such a range of heat flux values, the mold 12 is set so that the thickness t of the cooling wall portion 27 of the mold 12 is in the range of, for example, 0.5 mm or more and 3.0 mm or less. should be formed. In addition, the thermal conductivity of at least the cooling wall portion 27 of the mold 12 should be in the range of 100 W/m·K or more and 400 W/m·K or less.

When manufacturing the aluminum alloy rod of the present embodiment, the above-described horizontal continuous casting apparatus 10 is used to cast the molten alloy M stored in the molten metal receiving portion 11 from one end side 12a of the mold 12 into the hollow portion 21. supply continuously to In addition, cooling water W is supplied to the cooling water cavity 24 and lubricating fluid such as lubricating oil is supplied from the fluid supply pipe 22 .

Then, the molten alloy M supplied into the hollow portion 21 is cooled and solidified under the condition that the heat flux value per unit area in the cooling wall portion 27 is 10×10 ⁵ W/m ² or more, and the aluminum alloy rod B is obtained. to cast. Further, when casting the aluminum alloy rod B, it is preferable to set the wall surface temperature of the cooling wall portion 27 of the mold 12 cooled by the cooling water W to 100° C. or less.

The aluminum alloy rod B obtained in this way is cooled and solidified under the condition that the heat flux value per unit area in the cooling wall portion 27 is 10×10 ⁵ W/m ² or more, thereby forming the gas of the lubricating oil and the molten alloy M. adhesion of reaction products, such as carbides, caused by contact with the As a result, there is no need to remove carbides and the like from the surfaces of the aluminum alloy rods B by cutting, and the aluminum alloy rods B can be produced at a high yield.

The casting process for obtaining cast products from molten aluminum alloy is not limited to the horizontal continuous casting method described above, and known continuous casting methods such as a vertical continuous casting method can be used. The vertical continuous casting method is classified into the float method and the hot top method depending on the method of supplying the molten aluminum alloy to the mold, and the hot top method will be briefly described below. A casting apparatus used in the hot top method is equipped with a mold, a molten metal receiver (header), and the like. The molten metal supplied to the molten metal receiving part passes through the outlet port and the header to adjust the flow velocity, and enters the cylindrical mold installed almost horizontally, where it is forcedly cooled to form a solidified shell on the outer surface of the molten metal. is formed. Furthermore, the cooling water is directly radiated to the cast product drawn out from the mold, and the cast product is continuously drawn out while solidification of the metal progresses to the inside of the cast product. Generally, the mold is made of a metal member with good thermal conductivity and has a hollow structure for introducing a coolant inside. The refrigerant to be used may be appropriately selected from industrially available refrigerants, but water is recommended from the viewpoint of ease of use. The mold used in this embodiment is appropriately selected from metals such as copper and aluminum, and graphite from the viewpoint of heat transfer performance and durability at the contact portion with the molten metal. The header, generally made of refractory material, is placed on the upper side of the mold. The material and size of the header may be appropriately selected according to the composition range of the alloy to be cast and the dimensions of the cast product, and are not particularly limited. The average cooling rate during casting may be appropriately selected from a generally recommended range such as 10 to 300° C./sec. The casting speed may be appropriately selected from a general range in horizontal continuous casting, for example, from a range of 200 to 600 mm/min. By the casting method described above, it is possible to obtain a uniform metal structure even for medium-sized to large-sized castings. The diameter of the target casting is not particularly limited, and it is preferably used for bars with a diameter of 30 to 100 mm.

(Homogenization heat treatment step)
In the homogenization heat treatment process, the aluminum alloy casting obtained in the casting process is subjected to homogenization heat treatment to homogenize microsegregation caused by solidification, precipitate supersaturated solid solution elements, and metastable equilibrium phases. It is a process to change to
In this embodiment, the aluminum alloy casting obtained in the casting process is subjected to homogenization heat treatment at a temperature of 370° C. or more and 560° C. or less for 4 to 10 hours. Homogenization heat treatment within this temperature range homogenizes the cast aluminum alloy and causes the solute atoms to fully dissolve into solid solution. Become.

(Forging process)
In the forging process, the aluminum alloy casting after the homogenization heat treatment process is formed into a predetermined size to obtain a forging material, the obtained forging material is heated to a predetermined temperature, and then pressure is applied with a press. It is a process of forging.
In this embodiment, it is preferable to heat the forging material to a temperature of 450° C. or higher and 560° C. or lower, and then start forging to obtain a forged product (such as an automobile suspension arm component). If the forging start temperature is less than 450°C, the deformation resistance may increase and sufficient processing may not be possible. It may easily occur.

(Solution treatment process)
The solution treatment step is a step of heating the forged product obtained in the forging step to cause the forged product to be solutionized, thereby relaxing the strain introduced into the cast product and causing the solute elements to form a solid solution.
In this embodiment, the solution treatment is preferably performed by holding the forged product at a treatment temperature of 530° C. or higher and 560° C. or lower for 0.3 to 3 hours. The heating rate from room temperature to the above treatment temperature is preferably 5.0° C./min or more. If the heating rate is less than 5° C./min, the Mg—Si-based compound is coarsely precipitated, and Mg and Si that contribute to the formation of precipitates are reduced. If the treatment temperature is less than 530° C., the solutionization does not proceed, and high strength due to aging precipitation cannot be achieved. If the treatment temperature exceeds 560° C., solid solution of the solute element is further promoted, but eutectic melting and recrystallization tend to occur.

(Quenching treatment process)
The quenching treatment step is a step of rapidly cooling the solid solution forging obtained by the solution treatment step to form a supersaturated solid solution.
Within 5 to 60 seconds after the solution treatment, the forging is quenched by placing it in a quenching water bath so that all surfaces are in contact with the quenching water, thereby forming a supersaturated solid solution. It is preferable that the holding time in the quenching water is 5 minutes to 40 minutes. Holding in water for more than 5 minutes allows the entire forging to cool and form a uniform supersaturated solid solution. In addition, if the retention in water exceeds 40 minutes, Cluster I (Si-rich), which is known to cause negative effects of natural aging, grows, resulting in a decrease in strength after artificial aging treatment. Therefore, it is desirable that the retention time in water exceeds 5 minutes and is within 40 minutes. The water temperature used in the quenching treatment is in the range of 45 to 95 ° C., making it difficult for cluster I to occur, making cluster II (GP zone) more likely to occur in the subsequent artificial aging treatment, and suppressing bending of the forged product during quenching. A temperature range of 55 to 65°C is desirable. Furthermore, the temperature drop from the quenching temperature is suppressed by controlling the time from the end of the quenching treatment to the start of the artificial aging treatment to 60 seconds or less. As a result, for example, an aluminum alloy forging that has been quenched at 60°C is quickly heated from 60°C to the artificial aging treatment temperature, and the growth of cluster II that contributes to strengthening the base material and the atomic structure of precipitates can be stabilized. . The temperature from the end of the quenching treatment to the start of artificial aging is desirably controlled so as to be kept within the range of 55 to 65° C. from the viewpoint of making Cluster I less likely to occur.

(Artificial aging treatment process)
As the artificial aging treatment for the forged product that has undergone the quenching treatment process, the temperature is maintained at 170 to 190° C. for 4.5 to 6.5 hours. As a result, Cu atomic arrays can be formed at sufficiently dense intervals around the precipitates composed of Mg, Si, and Al, and serve as a barrier to the coarsening of the precipitates, thereby realizing a fine and uniform precipitate distribution. can be done. Here, the crystal phase of the formed precipitate includes a β''-MgSi phase (hereinafter simply referred to as β'' phase) and a C-AlCuMgSi phase (hereinafter simply referred to as C phase). These crystal phases are known to be formed early in the artificial aging process of Cu-added 6000 series aluminum alloys. It has been reported that all of them have an interface consistent with the Al matrix phase, and the strain field induced by the precipitates themselves or lattice mismatch functions as an obstacle to dislocation movement, contributing to the strengthening of the matrix. can be done. When the treatment temperature is less than 170° C. or the treatment time is less than 4.5 hours, the number density of precipitates does not reach a range sufficient for strength improvement. In addition, when the treatment temperature exceeds 190 ° C. or the treatment time is longer than 6.5 hours, the structure transition of the precipitate progresses so that the Cu atomic row is not included around the precipitate (representative In practice, it becomes a Q'-AlCuMgSi phase, hereinafter simply referred to as the Q phase), and the effect of improving the strength of the base material by the precipitates is reduced. Although there are a certain number of precipitates (β″ phase) that do not contain Cu atomic rows, it is desirable that the observed precipitates be 10% or less, and more preferably 5% or less. desired.

<Observation method>
In order to observe the atomic structure around the precipitate, a technique capable of observation at atomic resolution such as transmission electron microscopy (TEM) is used. Among them, the observation by the high-angle annular dark-field spectroscopy (HAADF-STEM), which can obtain the (Z) contrast depending on the atomic number, is suitable. In addition to the intensity information of STEM images, energy dispersive X-ray spectroscopy (EDS) is used to clarify in detail the element species of the atomic arrays that make up the precipitates and the atomic arrays that make up the periphery of the precipitates. By obtaining an elemental mapping for each atomic column, it is possible to easily grasp the element species and the number of atomic columns in the periphery of the precipitate. In addition, in order to observe the interface structure around the precipitate with high resolution, it is desirable to use an electron microscope that can focus the irradiated electron beam to the size of one atom or less by the spherical aberration correction function.

A specific procedure for observing the precipitate at atomic resolution will now be described. The acceleration voltage of the incident electron beam may be selected from a range that allows sufficient transmission through the thin film sample and does not damage the sample more than necessary. In order to observe the atomic structure of the precipitates of the 6000 series aluminum alloy in detail, the incident direction of the electron beam should be the <100> or <310> orientation of the Al matrix phase, where the precipitates including the β'' phase can be easily observed. The orientation is preferable, and the <100> orientation is more preferable so that the correspondence with the lattice arrangement of the Al matrix phase can be easily interpreted. For example, a field containing a large number of precipitates is selected from an observation field with a magnification of 500,000 times, and five of them with different shapes and crystal structures are extracted. Measure the equivalent circle radius r _i of each precipitate and the number N _i of Cu atomic rows on the outer circumference, and use these measurement results to calculate the average spacing of Cu atomic rows on the outer circumference of the precipitate according to the following formula. (See FIGS. 1 and 5).

Here, L _i is the circumferential length calculated from the equivalent circle radius of the precipitate i.
Furthermore, by using the number of Cu atomic rows n _i contained inside the precipitate, the ratio of the number of Cu atomic rows on the periphery of the precipitate to the number of Cu atomic rows contained inside the precipitate is obtained by N _i / _ni . can be done.
Further, whether or not the Cu atomic row coincides with the lattice point of the (100) plane of the Al matrix can be determined by setting the incident direction of the electron beam to the <100> direction of the Al matrix using a TEM image or a STEM image. Fully readable from above. There are no particular restrictions on the method of analyzing grid point positions, and image analysis software may be used.

FIG. 5 is a schematic plan view schematically showing a typical shape (left figure) of a precipitate in a TEM image and its atomic array arrangement.
The arrangement of atomic array images schematically shown in the precipitate 3 in the figure reproduces an actual STEM image. It has been observed that needle-shaped precipitates have regularly arranged Cu atomic rows on the outer circumference, and the Cu atomic rows inside the precipitate are also regularly arranged so as to correspond to the regular Cu atomic rows on the outer circumference. there is
In the precipitate 3 in the figure, the straight lines of "lattice _x (Cu)" and "lattice _y (Cu)" indicated by dotted lines are arranged in Cu atomic rows on the Al matrix Al atomic row lattice, That is, it indicates that the Cu atomic array matches the Al atomic array position of the Al matrix.

Next, specific examples of the present invention will be described. However, the present invention is not limited to these examples.

(Sample creation)
An aluminum alloy having the alloy composition shown in Table 1 was cast by a hot-top horizontal continuous casting method to produce a long rod-shaped continuous cast product having a circular cross section with a diameter of 49 mm.

The obtained continuous cast product was subjected to homogenization heat treatment, forging, solution treatment, quenching treatment, and artificial aging treatment in this order. In the hot forging, after preheating under the conditions shown in Table 2 (Table 2A, Table 2B), it is formed into a simulated shape of an automobile suspension arm as shown in FIG. 6, and then allowed to cool in the atmosphere. to produce an aluminum alloy forged product 100 as a simulated forged product. The conditions for each step of homogenization heat treatment, forging, solution treatment, quenching, and artificial aging are shown in Table 2 (Table 2A, Table 2B) below. For the continuous cast product having the composition indicated by Alloy 1 in Table 1, an aluminum alloy forged product 100 was produced under three types of conditions 1 to 3. In addition, an aluminum alloy forged product 100 was produced under condition 1 for the continuous cast product having the composition indicated by alloy 2. Conditions 1 to 3 differ only in the conditions of the quenching process.
For the aluminum alloy forgings of "alloy 1 + condition 1" and "alloy 2 + condition 1", structural analysis by transmission electron microscope observation and mechanical property evaluation by tensile test were performed. Furthermore, the mechanical properties of the aluminum alloy forgings of "alloy 1 + condition 2" and the aluminum alloy forgings of "alloy 1 + condition 3" are evaluated, and the mechanical characteristics of the difference in the conditions of the quenching process are evaluated. investigated the effects of

(evaluation)
HAADF-STEM observation was performed on the aluminum alloy forgings of "alloy 1 + condition 1" (example) and the aluminum alloy forgings of "alloy 2 + condition 1" (comparative example), and five precipitate atoms Analyzing the structure, the average spacing of Cu atomic rows on the outer periphery of the precipitate, the ratio of the number of Cu atomic rows on the outer periphery to the number of Cu atomic rows inside, and the Cu atomic rows that match the atomic row positions of the Al matrix We asked for the ratio of Table 3 shows the results. In selecting the precipitates, from the viewpoint of selecting a field containing many precipitates in the observation field with a magnification of 500,000 times, and selecting precipitates with typical shapes and crystal structures from among them, five precipitates. selected things. Also, the mechanical properties were evaluated by the procedure described later.

<Transmission electron microscope observation>
A JEM-ARM200F (manufactured by JEOL Ltd.) was used to observe precipitates contained in each aluminum alloy forged product, and aberration correction was performed by a spherical aberration corrector (manufactured by JEOL Ltd.) installed in the irradiation system. gone. A cubic sample with a side of 10 mm cut out from the portion shown in FIG. , TEM observation samples were obtained. The acceleration voltage of the incident electron beam was set to 200 kV, and the viewing direction was set to <100> direction incidence of the Al matrix phase. HAADF-STEM observation was carried out by setting the observation magnification to 20,000,000 times and using wide-angle scattered electrons for image formation. Note that the observation area was the area where the number density of precipitates was a representative value. Furthermore, an EELS spectrum was obtained using electron energy loss spectroscopy (EELS), and the thickness of the sample was obtained from the intensity ratio of the zero-loss peak and the plasmon peak.
The average spacing between Cu atomic rows can be calculated to be 3.1 nm in the example and 10.5 nm in the comparative example. Similarly, the ratio of the number of Cu atomic rows on the outer circumference to the number of Cu atomic rows on the inside can be calculated as 1.0 in the example and 0.8 in the comparative example. Note that the Cu atomic arrays observed on the periphery of the precipitates were all consistent with the Al matrix.
The crystal phases of the five precipitates (Nos. 1 to 5) each belonged to the metastable phases shown in Table 3. In the example, three types of metastable phases, β″ phase, Q′ phase, and C phase, were observed, whereas in the comparative example, the C phase could not be found, and the β″ phase and Q Only two metastable phases of the ' phase could be observed. In the embodiment, the above-mentioned No. Of the 578 precipitates in the field of observation containing 1 to 5 precipitates, the proportions of β'' phase, Q' phase, and C phase were 8%, 18%, and 74%, respectively. On the other hand, in the comparative example, precipitates were also observed, but the C phase could not be found. Considering that the number density of precipitates in this observation field is obtained from a representative field, it is inferred that the C phase is 5% or less in the comparative example. As described above, the proportion of the C phase in the precipitates of the metastable phase was significantly different between the examples and the comparative examples. As will be described later, the examples have superior tensile strength and 0.2% yield strength to the comparative examples. It is speculated that these differences in mechanical properties are highly likely due to the large difference in the ratio of the C phase.
In Table 3, the precipitates having two types of metastable phases had the characteristics of both types.

<Mechanical property evaluation>
The mechanical properties of Examples and Comparative Examples were evaluated by performing a tensile test. That is, from the aluminum alloy forging after artificial aging treatment, a test piece having a gauge length of 25.4 mm and a parallel part diameter of 6.4 mm was taken at the position shown in FIG. Various tensile properties were measured by performing tensile tests at speed. Table 4 shows the results. Table 4 also shows measurement results of various tensile properties of the aluminum alloy forgings of "alloy 1 + condition 2" and the aluminum alloy forgings of "alloy 1 + condition 3".

As is clear from Table 4, it was confirmed that the aluminum alloy forgings having the precipitate composition of the present invention had superior tensile strength and 0.2% yield strength to those of the comparative examples. That is, the manufacturing method of the present invention makes it possible to obtain an aluminum alloy forged product with excellent mechanical properties.
It is believed that this excellent mechanical property is due to the atomic scale crystal structure of the precipitate. That is, the average spacing between the Cu atomic rows arranged on the outer periphery of the precipitate is narrower in the example than in the comparative example, that is, the precipitates are more finely dispersed by arranging them more densely on the outer periphery. and that the ratio of Cu atomic rows arranged at the atomic row positions of the Al matrix (lattice matrix positions) is higher in the example than in the comparative example, that is, the Cu atomic rows are more stable. This is thought to be due to the placement of the
The present invention provides an aluminum alloy forging having excellent mechanical properties by controlling the atomic scale crystal structure of precipitates.

From the measurement results of various tensile properties of the aluminum alloy forgings of "alloy 1 + condition 2" and "alloy 1 + condition 3", the artificial aging treatment is started from the time of submersion in the quenching treatment process and the end of quenching treatment. It has been found that the waiting time until the time is reached is an important parameter for improving tensile strength and improving 0.2% yield strength.

From the above results, in order to manufacture the aluminum alloy forged product according to the present invention, it is necessary to perform the composition of Cu, the water immersion time in the quenching treatment process, and the waiting time before artificial aging treatment under predetermined conditions. I found out.

10... Horizontal continuous casting device 11... Molten metal receiving part (tundish)
DESCRIPTION OF SYMBOLS 11a... Molten-metal inflow part 11b... Molten-metal holding part 11c... Outflow part 12... Mold 12a... One end side 12b... The other end side 13... Refractory plate-shaped body (insulation member)
DESCRIPTION OF SYMBOLS 13a... Pouring passage 21... Hollow part 21a... Inner peripheral surface 21b... Other end side 22... Fluid supply pipe 22a... Lubricant supply port 23... Cooling device 24... Cooling water cavity 24a... Inner bottom surface 25... Cooling water injection passage 25a... Shower opening 26... Cooling water supply pipe 27... Cooling wall portion B... Aluminum alloy rod M... Molten alloy W... Cooling water 100... Aluminum alloy forged product

Claims (4)

Cu: 0.2% to 0.5% by mass, Mg: 0.6% to 1.2% by mass, Si: 0.4% to 1.25% by mass, Mn: 0.4% by mass to 0.6% by mass or less, Fe: 0.15% by mass to 0.70% by mass, Cr: 0.09% by mass to 0.25% by mass or less, Ti: 0.012% by mass to 0.035% by mass, An aluminum alloy forged product composed of an aluminum alloy whose balance is Al and inevitable impurities,
Two or more of Mg, Si, Al, and Cu in the chemical composition as precipitates composed of intermetallic compounds observed when observing the Al matrix phase with <100> incidence with a transmission electron microscope. and having a plurality of Cu atomic rows on the outer periphery of the precipitate, and an aluminum alloy forged product having an average spacing between the Cu atomic rows arranged on the outer periphery of 10 nm or less. . 2. A ratio (N _i /n _i ) of the number of Cu atomic rows (N _i ) arranged in the outer periphery to the number of Cu atomic rows (n _i ) contained inside the precipitate is 1 or more. The aluminum alloy forged product described in . 3. The aluminum alloy forged product according to claim 1 or 2, wherein 70% or more of the Cu atomic arrays arranged on the outer periphery of the precipitates coincide with the Al atomic array positions of the Al matrix. . The aluminum alloy forged product according to any one of claims 1 to 3, further containing 0.0001 mass% to 0.03 mass% of B.

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