TWI718319B - Aluminum alloy plastically worked part and production method thereof - Google Patents

Abstract

Provides aluminum alloy plastic working materials with low Young's modulus and excellent endurance and an efficient manufacturing method.

An aluminum alloy plastic processing material, characterized in that it contains 5.0 to 10.0wt% Ca, the remainder is made of aluminum and inevitable impurities, _{the volume ratio of the Al 4} Ca phase as the dispersed phase is more than 25%, and the Al ₄ Ca phase the system consists of Al ₄ Ca tetragonal Al ₄ Ca phase and monoclinic phase, obtained by X-ray diffraction measurement of the maximum diffraction peak (I ₁₎ due to the sky tetragonal, monoclinic and by the maximum diffraction peak intensity of the sky (I ₂₎ ratio (I ₁ / I ₂₎ of 1 or less.

Description

Aluminum alloy plastic processing material and manufacturing method thereof

The present invention relates to an aluminum alloy plastic working material having a low Young's modulus and excellent endurance, and a method for manufacturing the same.

Aluminum has many excellent properties such as corrosion resistance, electrical conductivity, thermal conductivity, light weight, brilliance, and machinability, and is used in various applications. In addition, since plastic deformation resistance is small, it can be given various shapes, and it is also mostly used in members subjected to plastic processing such as bending processing.

Here, if the rigidity of the aluminum alloy is high, the amount of springback increases when plastic working such as bending is performed, and there is a problem that it is difficult to obtain dimensional accuracy. Under the conditions shown above, an aluminum alloy material with a low Young's modulus is urgently desired, and a method for lowering the Young's modulus of the aluminum alloy material is studied.

For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-105982), an aluminum alloy has been proposed, which is an aluminum alloy containing an Al phase and an Al ₄ Ca phase, and is characterized in that the Al ₄ Ca phase contains Al ₄ Ca crystals, and the _{average value of the long sides of the Al 4} Ca crystals is 50 μm or less.

In the aluminum alloy disclosed in Patent Document 1, since _{the movement of Al 4} Ca crystallized dislocations in the matrix becomes easier, the rolling workability of the aluminum alloy can be significantly improved.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2011-105982 A

However, for example, as represented by terminals of electrical equipment, the requirements for dimensional accuracy of aluminum alloy products have been strict year by year, and an aluminum alloy that has lower rigidity while maintaining endurance is sought. Under the background shown above, it is a present situation that the aluminum alloy of Patent Document 1 mentioned above cannot sufficiently satisfy this requirement.

In view of the problems of the conventional technology as shown above, the object of the present invention is to provide an aluminum alloy plastic working material with a lower Young's modulus and excellent endurance and an efficient manufacturing method thereof.

In order to achieve the above-mentioned object, the inventors of the present invention have conducted intensive studies on aluminum alloy plastic working materials and manufacturing methods, and found that it is extremely effective to _{use Al 4} Ca phase as a dispersed phase and appropriately control the _{crystal structure of the Al 4 Ca phase.} Reach the present invention.

That is, the present invention provides an aluminum alloy plastic working material, which is characterized in that it contains 5.0 to 10.0 wt% Ca, the remainder is made of aluminum and inevitable impurities, and the volume ratio _{of the Al 4 Ca phase as the dispersed phase is 25} % Or more, the aforementioned Al ₄ Ca phase is composed of tetragonal Al ₄ Ca phase and monoclinic Al ₄ Ca phase. The maximum diffraction peak due to the aforementioned tetragonal crystal obtained by X-ray diffraction measurement ( I ₁ ), and the intensity ratio (I ₁ /I ₂ ) of the maximum diffraction peak (I ₂ ) due to the aforementioned monoclinic crystal is 1 or less.

By adding Ca, a _{compound of Al 4} Ca is formed, which has the effect of lowering the Young's modulus of the aluminum alloy. This effect is more pronounced if the Ca content is 5.0% or more. Conversely, if it is added more than 10.0%, the castability will be reduced. In particular, casting by continuous casting such as DC casting becomes more difficult, so it is derived It is necessary to manufacture by high-cost manufacturing methods such as powder metallurgy. If it is manufactured by powder metallurgy, the oxide formed on the surface of the alloy powder is mixed into the product, which may reduce the endurance.

In the aluminum alloy plastic processing of the present invention, _{the crystal structure of the Al 4} Ca phase used as the dispersed phase is basically a tetragonal crystal. However, after careful research by the inventors of the present invention, it is clear that if crystals exist _{in the Al 4 Ca phase} If the structure is monoclinic, the endurance is unlikely to decrease. On the other hand, the Young's modulus is greatly reduced. Here, if _{the volume ratio of the Al 4} Ca phase is set to 25% or more, the maximum diffraction peak (I ₁ ) due to the aforementioned tetragonal crystal obtained by X-ray diffraction measurement is different from that due to the aforementioned monoclinic crystal. The intensity ratio (I ₁ /I ₂ ) of the maximum diffraction peak (I ₂ ) of the initial peak is 1 or less, and the Young's modulus can be greatly reduced while maintaining endurance.

In addition, in the aluminum alloy plastic working material of the present invention, it is preferable to additionally include any one or more of Fe: 0.05 to 1.0 wt% and Ti: 0.005 to 0.05 wt%.

By making the aluminum alloy contain Fe, the solidification temperature range (solid-liquid coexistence area) is enlarged, thereby improving the castability and improving the casting surface of the ingot. In addition, it also has the effect of making the eutectic structure uniform by the dispersed crystals of Fe. This effect is more pronounced if the Fe content is 0.05 wt% or more. Conversely, if the Fe content exceeds 1.0 wt%, the eutectic structure becomes coarse, which may reduce the endurance.

The Ti-based material functions as a finer material for the casting structure, and plays a role in improving the castability, extrudability, and ductility. This effect is more pronounced if the Ti content is 0.005wt% or more. On the contrary, even if it is added more than 0.05wt%, it cannot be expected to increase the effect of making the cast structure finer. Instead, coarse intermetallic compounds that become the starting point of failure are formed The fear. When Ti is cast, it is better to use a rod hardener (Al-Ti-B alloy) to add. Among them, B added together with Ti is allowed as a rod hardener at this time.

In addition, in the aluminum alloy plastic working of the present invention, it is preferable that the average crystal grain size of the _{Al 4 Ca phase is 1.5 μm or less.} If _{the average particle size of the Al 4} Ca phase is too large, the durability of the aluminum alloy will decrease, but by making the average particle size 1.5 μm or less, the decrease in the durability can be suppressed.

In addition, the present invention also provides a method for manufacturing aluminum alloy plastic processing materials, which is characterized by: having: the first process, which is to perform plastic processing on aluminum alloy ingots, and the aluminum alloy ingots contain 5.0 to 10.0 wt% Ca, the remnant is made of aluminum and inevitable impurities, and _{the volume ratio of the Al 4} Ca phase as the dispersed phase is more than 25%; and the second process, which is a heat treatment in the temperature range of 100 to 300 ℃.

In the plastic processing of aluminum alloy ingots, the aluminum alloy ingots contain 5.0 to 10.0wt% Ca, and the remaining part is made of aluminum and inevitable impurities. _{The volume ratio of the Al 4} Ca phase as the dispersed phase is more than 25% After the first step, heat treatment (second step) is performed in the temperature range of 100 to 300°C, thereby _{changing part of the Al 4} Ca phase whose crystal structure is tetragonal to monoclinic.

If the holding temperature in the second process is set to less than 100°C, the change from tetragonal crystal to monoclinic crystal is unlikely to occur. If the holding temperature is set to 300°C or higher, recrystallization of the aluminum base material may occur, which may reduce endurance. . Among them, the better temperature range for heat treatment is 160~240°C. In addition, the appropriate heat treatment time varies depending on the size and shape of the aluminum alloy material, but it is preferable that at least the temperature of the aluminum alloy material itself be maintained at the holding temperature for 1 hour or more.

In addition, in the method for manufacturing an aluminum alloy plastic working material of the present invention, it is preferable that the aluminum alloy ingot contains at least one of Fe: 0.05 to 1.0 wt% and Ti: 0.005 to 0.05 wt%.

By making the aluminum alloy contain Fe, the solidification temperature range (solid-liquid coexistence area) is enlarged, thereby improving the castability and improving the casting surface of the ingot. In addition, it also has the effect of making the eutectic structure uniform by the dispersed crystals of Fe. This effect is more pronounced if the Fe content is 0.05 wt% or more. Conversely, if the Fe content exceeds 1.0 wt%, the eutectic structure becomes coarse, which may reduce the endurance.

The Ti-based material functions as a finer material for the casting structure, and plays a role in improving the castability, extrudability, and ductility. This effect is more pronounced if the Ti content is 0.005wt% or more. On the contrary, even if it is added more than 0.05wt%, it cannot be expected to increase the effect of making the cast structure finer. Instead, coarse intermetallic compounds that become the starting point of failure are formed The fear. When Ti is cast, it is better to add rod hardener (Al-Ti-B alloy). Among them, B added together with Ti is allowed as a rod hardener at this time.

In addition, in the manufacturing method of the aluminum alloy plastic working material of the present invention, it is preferable that the heat treatment maintained at a temperature of 400° C. or higher is not performed before the aforementioned first step.

Generally speaking, in the manufacture of aluminum alloys, the ingot is subjected to a homogenization treatment that is kept between 400 and 600°C before plastic working. However, if this homogenization treatment is performed, the Al ₄ Ca phase contained in the aluminum alloy is It is easy to become larger, and the average particle size will be greater than 1.5μm. The endurance decreases due to the increase in the average particle size, and therefore, it is preferable not to perform the homogenization treatment at the holding temperature of 400°C or higher.

With the present invention, it is possible to provide an aluminum alloy plastic working material with both excellent endurance and low Young's modulus and an efficient manufacturing method thereof.

Fig. 1 is an engineering drawing relating to the manufacturing method of the aluminum alloy plastic working material of the present invention.

Figure 2 is the X-ray diffraction pattern of the aluminum alloy plastic working material.

FIG. 3 is a photograph of the structure of the aluminum alloy plastic working material 3.

Fig. 4 is a photo of the structure of the comparative aluminum alloy plastic working material 8.

Hereinafter, while referring to the drawings, the aluminum alloy plastic processing material and the manufacturing method thereof of the present invention will be described in detail, but the present invention is not limited to these.

1. Aluminum alloy plastic processing material

(1) Composition

The aluminum alloy plastic processing material of the present invention contains 5.0-10.0wt% Ca, and the remaining part is made of aluminum and unavoidable impurities. In addition, it is preferable to additionally contain at least one of Fe: 0.05 to 1.0 wt% and Ti: 0.005 to 0.05 wt%.

Each component element is described below.

Ca: 5.0~10.0wt% (preferably 6.0~8.0wt%)

The Ca-based _{compound forms Al 4} Ca and has the effect of lowering the Young's modulus of the aluminum alloy. This effect is more pronounced at 5.0% or more. On the contrary, if it is added at more than 10.0%, the castability will be reduced. In particular, casting by continuous casting such as DC casting becomes more difficult. Therefore, manufacturing costs such as powder metallurgy are derived. Necessity of high method. If it is manufactured by powder metallurgy, the oxide formed on the surface of the alloy powder is mixed into the product, which may reduce the endurance.

Fe: 0.05~1.0wt%

By containing Fe, the solidification temperature range (solid-liquid coexistence area) is enlarged, the castability is improved, and the casting surface of the ingot is improved. In addition, it also has the effect of making the eutectic structure uniform by the dispersed crystals of Fe. This effect is more pronounced at 0.05 wt% or more. Conversely, if the content exceeds 1.0 wt%, the eutectic structure becomes coarse, which may reduce the endurance.

Ti: 0.005~0.05wt%

The Ti-based material functions as a finer material for the casting structure, and plays a role in improving the castability, extrudability, and ductility. This effect is more pronounced at 0.005 wt% or more. On the contrary, even if the addition exceeds 0.05 wt%, the effect of making the cast structure finer cannot be expected to increase, and instead, there is a possibility that a coarse intermetallic compound that becomes the starting point of failure may be generated. When Ti is cast, it is better to add rod hardener (Al-Ti-B alloy). Among them, at this time, B added together with Ti is allowed as a rod hardener.

Other ingredients

As long as the effect of the present invention is not impaired, other elements are allowed.

(2) Organization

The aluminum alloy plastic working material system of the present invention has _{a volume ratio of the Al 4} Ca phase as the dispersed phase of 25% or more. The Al ₄ Ca phase is composed of a tetragonal Al ₄ Ca phase and a monoclinic Al ₄ Ca phase. obtained by X-ray diffraction measurement result of tetragonal sky maximum diffraction peak (I _1), the maximum intensity of the diffraction peaks due to monoclinic sky (I ₂₎ ratio (I ₁ / I ₂₎ Is less than 1.

In the Al ₄ Ca phase system is present as a dispersed phase of Al ₄ Ca tetragonal phase and the monoclinic phase of Al ₄ Ca, etc. However, the total of the Al ₄ Ca phase volume ratio becomes 25% or more. By setting _{the volume ratio of the Al 4} Ca phase to 25% or more, it is possible to impart excellent durability to the aluminum alloy plastic working material.

In addition, it is preferable that the average crystal grain size of the _{Al 4 Ca phase is 1.5 μm or less regardless of the crystal structure.} If the average particle size exceeds 1.5 μm, the durability of the aluminum alloy plastic working material may decrease.

The crystalline structure of the Al ₄ Ca phase is usually tetragonal. However, after careful research by the inventor of this case, it was found that if _{there is a monoclinic crystal in the Al 4} Ca phase, the endurance will hardly decrease, but the Young’s The modulus is greatly reduced. Among them, it is not necessary that all of the Al ₄ Ca phase has a monoclinic crystal structure, and it may be in a mixed state with a tetragonal crystal. There is an Al ₄ Ca phase with a monoclinic crystal structure, and it can be specified by measuring the diffraction peak using an X-ray diffraction method, for example.

About Al ₄ Ca phase, tetragonal sky because the maximum diffraction peak (I _1), and because the maximum diffraction peak of monoclinic sky (I ₂₎ intensity ratio (I ₁ / I ₂₎ based may by It is obtained by general X-ray diffraction measurement using Cu-Kα line source. Among them, _{the lattice constants of tetragonal Al 4} Ca are a=0.4354, c=1.118, and _{the lattice constants of orthorhombic Al 4} Ca are a=0.6158, b=0.6175, c=1.118, and β=88.9°.

2. Manufacturing method of aluminum alloy plastic processing material

The engineering drawing of the aluminum alloy plastic working material of the present invention is shown in FIG. 1. The manufacturing method of the aluminum alloy plastic working material of the present invention includes: a first process (S01) of plastic processing an aluminum alloy ingot, and a second process (S02) of performing a heat treatment. The following describes each project.

(1) Casting

After the molten metal of the aluminum alloy having the composition of the aluminum alloy plastic processing material of the present invention described above is subjected to a conventionally known molten metal cleaning treatment such as slagging treatment, degassing treatment, and filtration treatment, it can be cast into a predetermined Shape, and made ingots.

The casting method is not particularly limited, and various conventionally known casting methods can be used. For example, a continuous casting method such as DC casting is preferably used to facilitate the plastic processing (extrusion, rolling, forging, etc.) of the first process (S01). The shape of) is better. Among them, a rod hardener (Al-Ti-B) may be added during casting to improve castability.

Generally, in the production of aluminum alloys, the ingot is subjected to a homogenization treatment that is maintained at 400 to 600°C before plastic working. However, if the homogenization treatment is performed, the Al ₄ Ca phase tends to become larger (larger than the average particle size of 1.5 μm). The endurance of aluminum alloy is reduced, and therefore, in the method for manufacturing an aluminum alloy plastic working material of the present invention, it is preferable not to perform the homogenization treatment.

(2) The first project (S01)

The first process (S01) is a process in which the aluminum alloy ingot obtained in (1) is subjected to plastic processing to form the desired shape.

For plastic processing systems such as extrusion, rolling, and forging, either hot processing or cold processing may be used, and plural of these may be combined. By performing this plastic working, the aluminum alloy is formed into a working structure, and endurance is improved. Among them, at the stage of plastic working, most of the Al ₄ Ca phase system crystal structure contained in the aluminum alloy is tetragonal.

(3) The second project (S02)

The second process (S02) is a process of performing heat treatment on the aluminum alloy plastic working material obtained in the first process (S01).

_{A part of the Al 4} Ca phase whose crystal structure is a tetragonal crystal can be formed into a monoclinic crystal by performing a heat treatment that keeps the aluminum alloy plastic-worked material after plastic working in the first process (S01) at 100 to 300°C. . If the holding temperature is less than 100°C, the change from the tetragonal crystal to the monoclinic crystal is not easy to occur. On the other hand, if the holding temperature is above 300°C, the aluminum base material will recrystallize and the endurance may be reduced. Therefore, the holding temperature of the heat treatment is preferably 100~300°C, more preferably 160~240°C .

In addition, the optimal heat treatment time varies depending on the size or shape of the aluminum alloy plastic processed material to be processed, but it is preferable that at least the temperature of the aluminum alloy plastic processed material be maintained at the aforementioned holding temperature for 1 hour or more.

The representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design changes are possible, and these design changes are all included in the technical scope of the present invention.

[Example]

≪Examples≫

After the aluminum alloy with the composition shown in Table 1 is cast into a Φ8-inch ingot (cast billet) by the DC casting method, it is plastically processed at an extrusion temperature of 500°C into a Φ8-inch ingot (slab). Flat-shaped. After that, after cold rolling to a thickness of 5 mm, heat treatment was performed at 200° C. for 4 hr to obtain an aluminum alloy plastic-worked material.

The obtained aluminum alloy plastically worked material 3 was subjected to X-ray diffraction, and the peak position _{of the Al 4 Ca phase was measured.} Among them, the X-ray diffraction method is to cut out a 20mm×20mm sample from a plate-shaped aluminum alloy plastic working material, cut the surface portion about 500 μm, and then measure θ-2θ with a Cu-Kα line source. The results obtained are shown in Figure 2. Wherein, after obtaining the maximum diffraction peak of tetragonal because the sky (I _1), due to the intensity of the monoclinic sky maximum diffraction peak (I ₂₎ ratio (I ₁ / I _2), the result is 0.956 .

In addition, JIS-14B test pieces were cut out of aluminum alloy plastic processed materials 1 to 5, and the Young's modulus and endurance were measured by a tensile test. The results obtained are shown in Table 2. _{In addition, the volume ratio of the dispersed phase (Al 4} Ca phase) calculated from the structure observation result obtained by the optical microscope is also shown in Table 2.

Except that the temperature of the heat treatment was set to any one of 100° C., 160° C., 240° C., and 300° C., similarly to the case of the aluminum alloy plastic working material 3, aluminum alloy plastic working materials 6 to 9 were obtained. In addition, the Young's modulus and endurance were measured by a tensile test similarly to the case where aluminum alloy plastic working materials 1 to 5 were implemented. The results obtained are shown in Table 3.

≪Comparative example≫

After the aluminum alloy with the composition shown in Table 1 is cast into a Φ8-inch ingot (cast billet) by the DC casting method, it is plastically processed at an extrusion temperature of 500°C into a Φ8-inch ingot (slab). Flat-shaped. After that, it was cold rolled to a thickness of 5 mm to obtain comparative aluminum alloy plastic working materials 1 to 5 (without heat treatment).

X-ray diffraction was performed on the obtained comparative aluminum alloy plastic working material 3, and the peak position _{of the Al 4 Ca phase was measured.} Among them, the X-ray diffraction method is to cut out a 20mm×20mm sample from a plate-shaped aluminum alloy plastic working material, cut the surface portion about 500 μm, and then measure θ-2θ with a Cu-Kα line source. The results obtained are shown in Figure 2. Wherein, after obtaining the maximum diffraction peak of tetragonal because the sky (I _1), due to the intensity of the monoclinic sky maximum diffraction peak (I ₂₎ ratio (I ₁ / I _2), the result is 1.375 .

In addition, JIS-14B test pieces were cut out from comparative aluminum alloy plastic working materials 1 to 5, and the Young's modulus and endurance were measured by a tensile test. The results obtained are shown in Table 2.

Except that the temperature of the heat treatment was set to either 90°C or 310°C, the comparative aluminum alloy plastic working materials 6 and 7 were obtained in the same manner as in the case where the aluminum alloy plastic working material 3 was applied. In addition, the Young's modulus and endurance were measured by a tensile test as in the case of the comparative aluminum alloy plastic working materials 1 to 5. The results obtained are shown in Table 3.

Except that after casting into an ingot (slab), a homogenization treatment maintained at 550°C was performed, similarly to the aluminum alloy plastic working material 3, a comparative aluminum alloy plastic working material 8 was obtained. In addition, a JIS-14B test piece was cut out from the comparative aluminum alloy plastic working material 8, and the Young's modulus and endurance were measured by a tensile test. The results obtained are shown in Table 4. Among them, in terms of comparative data, Table 4 also shows the Young's modulus and endurance of the aluminum alloy plastic working material 3 that is different in the presence or absence of homogenization treatment.

From the results in Table 2, it can be seen that if the aluminum alloy plastic-worked materials with the same composition are compared with the comparative aluminum alloy plastic-worked materials, the aluminum alloy plastic-worked materials of the present invention (the aluminum alloy plastic-worked materials 1 to 5) are Compared with the Young's modulus of comparative aluminum alloy plastic working materials 1 to 5 without heat treatment, the Young's modulus is greatly reduced. On the other hand, the endurance and tensile strength of the aluminum alloy plastic processed materials 1 to 5 are not significantly lower than those of the comparative aluminum alloy plastic processed materials 1 to 5. _{Among them, the volume ratio of the dispersed phase (Al 4} Ca phase) in the aluminum alloy plastic working material of the present invention is 25% or more.

From the results of Table 3, if the holding temperature of the heat treatment is 90°C (comparative aluminum alloy plastic working material 6), the Young's modulus shows a high value (almost no decrease). In addition, if the holding temperature of the heat treatment is 310°C (compared to aluminum alloy plastic working material 7), it is found that the Young's modulus is lowered, but the endurance and tensile strength are also lowered. From this result, if the holding temperature of the heat treatment is 310°C, it is considered that the recrystallization of the plastic working structure has progressed.

In FIGS. 3 and 4, the microstructure pictures obtained by the optical microscope of the aluminum alloy plastic working material 3 and the comparative aluminum alloy plastic working material 8 are respectively shown. In this microstructure photograph, the black area is the Al ₄ Ca phase, and the average crystal grain size _{of the Al 4} Ca phase is measured by image analysis. The results obtained are shown in Table 4.

From the results of Table 4, if the homogenization treatment maintained at 550°C (comparative aluminum alloy plastic working material 8) was performed, it was found that the endurance and tensile strength were reduced. Here, by the homogenization treatment, _{the average crystal grain size of the Al 4} Ca phase was increased to 1.56 μm. It is considered that the increase in the average crystal grain size reduces the endurance and tensile strength.

Claims (4)

An aluminum alloy plastic processing material, characterized in that it contains 5.0~10.0wt% of Ca, Fe: 0.05~1.0wt%, and Ti: 0.005~0.05wt%, and the residual part is made of aluminum and inevitable impurities as the dispersed phase The volume ratio of the Al ₄ Ca phase is 25% or more. The Al ₄ Ca phase is composed of a tetragonal Al ₄ Ca phase and a monoclinic Al ₄ Ca phase. The result is determined by X-ray diffraction measurement. tetragonal sky maximum diffraction peak (I _1), due to the intensity of the monoclinic sky maximum diffraction peak (I ₂₎ ratio (I ₁ / I ₂₎ of 1 or less. For example, the aluminum alloy plastic working material of the first item in the scope of the patent application, wherein _{the average crystal grain size of the aforementioned Al 4} Ca phase is 1.5 μm or less. A manufacturing method of aluminum alloy plastic processing material, which is characterized by: having: the first project, which is to perform plastic processing on aluminum alloy ingots, and the aluminum alloy ingots contain 5.0~10.0wt% of Ca and Fe: 0.05~ 1.0wt%, and Ti: 0.005~0.05wt%, the residue is made of aluminum and unavoidable impurities, _{the volume ratio of the Al 4} Ca phase as the dispersed phase is more than 25%; and the second project, which is 100~300 Heat treatment is performed in the temperature range of ℃. For example, the manufacturing method of aluminum alloy plastic working material in the scope of patent application 3, wherein, before the aforementioned first process, the heat treatment to maintain a temperature of 400° C. or more is not performed.

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