JP7810963B2 - Aluminum alloy sheet for conductive member and terminal using same - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) On April 14, 2021, Yoshihito Ikeda, Jun Yamashita, Hidehiro Nakayama, and Naohiro Saruwatari published a paper titled "Effect of Added Elements on the Stress Relaxation Properties of 6000 Series Aluminum Alloy Sheets" on "Aluminum Alloy Sheets for Conductive Materials and Terminals Using Them" in the Abstracts of the 140th Spring Meeting of the Japan Institute of Light Metals. On May 16, 2021, Yoshihito Ikeda, Jun Yamashita, Hidehiro Nakayama, and Naohiro Saruwatari published a paper titled "Effect of Added Elements on the Stress Relaxation Properties of 6000 Series Aluminum Alloy Sheets" on "Aluminum Alloy Sheets for Conductive Materials and Terminals Using Them" in the Abstracts of the 140th Spring Meeting of the Japan Institute of Light Metals. (2) On April 14, 2021, Jun Yamashita, Yoshihito Ikeda, Norio Nunomura, Hidehiro Nakayama, and Naohiro Saruwatari published a paper titled "First-principles calculation of mechanical properties of intermetallic compounds in 6000-series aluminum alloys" on "Aluminum alloy sheets for conductive components and terminals using the same" in the abstracts of the 140th Spring Meeting of the Japan Institute of Light Metals. On May 16, 2021, Jun Yamashita, Norio Nunomura, Hidehiro Nakayama, and Naohiro Saruwatari published a paper titled "First-principles calculation of mechanical properties of intermetallic compounds in 6000-series aluminum alloys" on "Aluminum alloy sheets for conductive components and terminals using the same" in the abstracts of the 140th Spring Meeting of the Japan Institute of Light Metals.

The present invention relates to aluminum alloy sheets for conductive components and terminals using the same.

In recent years, with the need to reduce the weight of automobiles, the use of aluminum electric wires in vehicles has been expanding. The metal terminals connected to such aluminum electric wires are generally made of copper or copper alloys, which have excellent electrical properties. However, if the materials used are different between the conductor of the aluminum electric wire and the metal terminal, corrosion is likely to occur at the joint between the conductor and the metal terminal. Therefore, the use of aluminum alloys, which are low-cost, lightweight, and have a low risk of corrosion when exposed to aluminum electric wires, as terminal materials is being considered in place of conventional copper.

However, with terminals made from conventional aluminum alloys, stress relaxation caused by continued application of stress to the bolted joint can cause the bolt to loosen in the high-temperature environment simulated inside a vehicle. As a result, there are concerns that the electrical resistance of the bolted joint may increase.

For this reason, efforts have been made to develop aluminum alloys with excellent stress relaxation properties. Patent Document 1 discloses an aluminum alloy sheet for crimping that can be used at temperatures below 170°C without stress relaxation. Specifically, the aluminum alloy sheet contains 0.2 to 0.9 mass% Cu, 0.6 to 1.4 mass% Mg, and the remainder Al and unavoidable impurities. The unavoidable impurities are restricted to 0.8 mass% or less of Si, 0.6 mass% or less of Fe, 0.15 mass% or less of Mn, 0.3 mass% or less of Cr, 0.3 mass% or less of Zn, 0.1 mass% or less of Ti, and 0.15 mass% or less of Zr. The aluminum alloy sheet has a thickness of more than 1.0 mm but less than 3.0 mm, a grain size of 35 to 300 μm, and an electrical conductivity of 50% IACS or less.

Patent No. 4009244

However, although the aluminum alloy sheet in Patent Document 1 has improved stress relaxation properties, it has low yield strength, and is therefore susceptible to plastic deformation when a load is applied. As such, conventional aluminum alloy sheets have the problem of being unable to achieve both stress relaxation properties and yield strength while maintaining electrical conductivity.

The present invention was made in consideration of the problems inherent in the prior art. The object of the present invention is to provide an aluminum alloy sheet for conductive components that has high electrical conductivity while also exhibiting excellent stress relaxation properties and yield strength, and a terminal using such an aluminum alloy sheet for conductive components.

An aluminum alloy sheet for conductive members according to one embodiment of the present invention contains 0.16 to 0.2 mass% silicon, 0.6 to 0.9 mass% copper, 0.2 to 0.5 mass% magnesium, 2.0 to 4.2 mass% iron, and 0 to 0.2 mass% manganese, with the remainder consisting of aluminum and inevitable impurities. The aluminum alloy sheet for conductive members has a dispersed structure containing a plurality of crystallized particles and a plurality of precipitates made of intermetallic compounds containing aluminum and copper. Furthermore, the particle diameter of the crystallized particles is 1 μm or more, and the particle diameter of the precipitates is less than 1 μm.

A terminal according to another aspect of the present invention includes the aluminum alloy sheet for conductive members described above.

The present invention provides an aluminum alloy sheet for conductive components that has high conductivity while also exhibiting excellent stress relaxation properties and yield strength, as well as a terminal made from this aluminum alloy sheet for conductive components.

1 is a perspective view schematically showing a terminal using an aluminum alloy plate for conductive members according to an embodiment of the present invention. 1 is a flowchart showing the manufacturing process of aluminum alloy plates of Samples No. 1 to 5. 1 is a photograph showing the results of observing a cross section (RD-ND cross section) of an aluminum alloy plate of Sample No. 2 according to an example using a transmission electron microscope. 1 is a photograph showing the results of observing a cross section (RD-ND cross section) of an aluminum alloy plate of Sample No. 2 according to an example using a metallurgical microscope. 1 is a photograph showing the results of observing a cross section (RD-ND cross section) of an aluminum alloy plate of Sample No. 1 according to an example using a scanning electron microscope. 1 is a graph showing the relationship between the silicon content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. 1 is a graph showing the relationship between the copper content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. 1 is a graph showing the relationship between the magnesium content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. 1 is a graph showing the relationship between the iron content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. 1 is a graph showing the relationship between the manganese content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation.

The aluminum alloy sheet for conductive members according to this embodiment and the terminal using this aluminum alloy sheet for conductive members will be described in detail below with reference to the drawings. Note that the dimensional proportions in the drawings have been exaggerated for the sake of explanation and may differ from the actual proportions.

[Aluminum alloy sheet for conductive members]
The aluminum alloy sheet for conductive members according to this embodiment has an optimized aluminum alloy composition and finer crystallized particles and precipitates formed in the aluminum alloy structure, thereby improving stress relaxation characteristics and yield strength while maintaining high electrical conductivity.

The aluminum alloy plate according to this embodiment is made of an aluminum alloy having a composition containing 0.16 to 0.2 mass% silicon, 0.6 to 0.9 mass% copper, 0.2 to 0.5 mass% magnesium, 2.0 to 4.2 mass% iron, and 0 to 0.2 mass% manganese, with the remainder being aluminum and unavoidable impurities.

The aluminum used as the base material in the aluminum alloy plate is preferably pure aluminum with a purity of 99.7% by mass or higher. In other words, aluminum bullion specified in Japanese Industrial Standard JIS H2102 (Aluminum Bullion) with a purity of Al99.70 or higher can be preferably used. Specific examples include Al99.70, Al99.94, Al99.97, Al99.98, Al99.99, Al99.990, and Al99.995, each with a purity of 99.7% by mass or higher. In this way, in this embodiment, aluminum bullion can be used that is not only expensive and highly pure, such as Al99.995, but also more affordable, with a purity of 99.7% by mass or higher.

Silicon (Si) can improve the strength of aluminum alloy sheets through solid solution strengthening. However, if the silicon content exceeds 0.2 mass%, stress relaxation properties and electrical conductivity may decrease. Therefore, it is preferable that the silicon content in aluminum alloy sheets be 0.16 to 0.2 mass%, and more preferably 0.17 to 0.19 mass%.

Copper (Cu) can also improve the strength of aluminum alloy sheets through solid solution strengthening. Therefore, it is preferable that the aluminum alloy sheet contain 0.6 to 0.9 mass% copper, and more preferably 0.6 to 0.8 mass% copper.

Magnesium (Mg) is an element that can increase the strength of aluminum alloy sheets while minimizing the decrease in electrical conductivity. However, if the magnesium content exceeds 0.5% by mass, the electrical conductivity, ductility, and toughness of the resulting aluminum alloy sheet tend to decrease. Therefore, it is preferable that the magnesium content in the aluminum alloy sheet be 0.2 to 0.5% by mass, and more preferably 0.2 to 0.3% by mass.

Iron (Fe) is an element that can increase the strength of an aluminum alloy sheet while minimizing the decrease in electrical conductivity. In other words, iron has a low solid solubility limit and forms intermetallic compounds with aluminum. The dispersion of these intermetallic compounds can increase the strength of the aluminum alloy sheet. As described below, the aluminum alloy sheet of this embodiment preferably contains dispersed crystallized particles consisting of intermetallic compounds containing aluminum, iron, and copper. Dispersion of the crystallized particles within the aluminum alloy sheet makes it possible to achieve high yield strength and electrical conductivity while reducing the stress relaxation rate. Therefore, from the perspective of dispersing a large number of crystallized particles in the aluminum alloy sheet, the iron content in the aluminum alloy sheet is preferably 2.0 to 4.2 mass%, and more preferably 2.5 to 3.5 mass%.

Manganese (Mn) can improve the strength of aluminum alloy sheets through solid solution strengthening. Therefore, zinc is preferably contained in the aluminum alloy sheet at 0 to 0.2 mass%, and more preferably at 0.05 to 0.15 mass%.

Inevitable impurities that may be contained in the aluminum alloy sheet include gallium (Ga), boron (B), zinc (Zn), lead (Pb), sodium (Na), calcium (Ca), cobalt (Co), nickel (Ni), tin (Sn), and vanadium (V). These are unavoidably contained to the extent that they do not impair the effects of this embodiment and do not significantly affect the properties of the aluminum alloy sheet of this embodiment. Elements that are already contained in the pure aluminum ingot used are also included in the unavoidable impurities referred to here. The amount of unavoidable impurities in the aluminum alloy sheet is preferably 0.15% by mass or less in total, and more preferably 0.12% by mass or less.

The aluminum alloy sheet of this embodiment preferably contains crystallized particles and precipitates made of intermetallic compounds containing aluminum and copper. It is more preferable that the aluminum alloy sheet have a plurality of crystallized particles and precipitates dispersed therein. High dispersion of such crystallized particles and precipitates within the aluminum alloy sheet increases the yield strength in a high-temperature atmosphere, thereby improving stress relaxation characteristics. Furthermore, even when the aluminum alloy sheet is used as a terminal material, it is possible to suppress stress relaxation in the bolt fastening portion while suppressing plastic deformation of the terminal.

As mentioned above, the precipitates preferably consist of an intermetallic compound containing aluminum and copper. The precipitates may also contain silicon and magnesium in addition to aluminum and copper. That is, the precipitates more preferably consist of an intermetallic compound containing aluminum, copper, silicon, and magnesium. In such precipitates, the Q' phase of the AlCuSiMg quaternary system is formed as the intermetallic compound. This Q' phase is known to have the effect of slowing the progression of age hardening. Therefore, by highly dispersing the precipitates within the aluminum alloy sheet, the yield strength in a high-temperature atmosphere is increased and the stress relaxation rate can be reduced.

Increasing the barriers to dislocation movement is an effective way to improve the strength of aluminum alloy sheets. When precipitates are present in the aluminum alloy structure, dislocation lines advance while cutting through the precipitates. Therefore, for example, in hard precipitates containing copper, dislocations advance more slowly, making deformation more difficult. On the other hand, when crystallized particles with larger particle sizes than precipitates are present in the aluminum alloy structure, dislocation lines advance around the crystallized particles without cutting through them, so even if hard crystallized particles are present, their effect in making it less difficult for dislocations to advance is smaller than that of precipitates. Therefore, precipitates contribute more to improving stress relaxation properties and yield strength than crystallized particles.

The aluminum content in the precipitate is preferably 90 atomic % or more. The copper content in the precipitate is preferably 1.0 atomic % or more, and more preferably 1.5 atomic % or more. The silicon content in the precipitate is preferably 0.5 atomic % or more, and more preferably 1.0 atomic % or more. The content of each element in the precipitate can be confirmed by observing the aluminum alloy plate with a transmission electron microscope (TEM) and analyzing the precipitate with energy dispersive X-ray analysis (EDX).

The particle diameter of the precipitates dispersed in the aluminum alloy plate is less than 1 μm, and preferably 300 nm or less. A precipitate particle diameter of less than 1 μm makes it possible to achieve both high stress relaxation properties and yield strength, and to suppress strength degradation at high temperatures. In this specification, "particle diameter of precipitates" refers to the longest distance between two different points on the outline of a precipitate particle when the cross section of the aluminum alloy plate is observed under a microscope.

As described above, the precipitated crystals preferably comprise an intermetallic compound containing aluminum and copper. The precipitated crystals preferably contain 50 atomic % or more of aluminum and 1 atomic % or more of copper. Specifically, when the aluminum alloy sheet is observed with a scanning electron microscope (SEM) and the precipitated crystals are analyzed with energy dispersive X-ray spectroscopy (EDX), the aluminum content is preferably 50 atomic % or more and the copper content is preferably 0.3 atomic % or more. High dispersion of precipitated crystals with this composition within the aluminum alloy sheet increases the yield strength in a high-temperature atmosphere and reduces the stress relaxation rate. The precipitated crystals preferably contain 55 atomic % or more of aluminum, and even more preferably 60 atomic % or more. The precipitated crystals preferably contain 1.0 atomic % or more of copper.

The precipitated material may contain silicon, iron, and manganese in addition to aluminum and copper. That is, the precipitated material preferably consists of an intermetallic compound containing aluminum, copper, silicon, iron, and manganese. High dispersion of precipitated material with such a composition within the aluminum alloy sheet also increases the yield strength in a high-temperature atmosphere and reduces the stress relaxation rate. The iron content of the precipitated material is preferably 10 atomic % or more, more preferably 20 atomic % or more, and even more preferably 30 atomic % or more. The silicon content of the precipitated material is preferably 0.1 atomic % or more, and more preferably 0.4 atomic % or more. The manganese content of the precipitated material is preferably 0.2 atomic % or more, and more preferably 0.4 atomic % or more.

The particle size of the crystallized particles dispersed in the aluminum alloy plate is 1 μm or more, and preferably 5 μm or more. A crystallized particle size of 1 μm or more makes it possible to achieve both high stress relaxation properties and yield strength. These crystallized particles also make it possible to suppress strength degradation at high temperatures. There is no particular upper limit to the particle size of the crystallized particles, but it can be set to 20 μm, for example. In this specification, the "particle size of the crystallized particles" refers to the longest distance between two different points on the outline of a crystallized particle when the cross section of the aluminum alloy plate is observed under a microscope.

In the aluminum alloy plate, the number of crystallized particles is preferably 6000 particles/ ^mm2 or more. Specifically, when the aluminum alloy plate is observed with a metallurgical microscope, the number of crystallized particles per ^mm2 is preferably 6000 particles or more. This enables the aluminum alloy plate to obtain high stress relaxation properties.

The particle size of the precipitated crystals tends to increase as the iron content in the aluminum alloy plate increases. The number of precipitated crystals also tends to increase as the iron content in the aluminum alloy plate increases. Therefore, by adjusting the iron content added to the aluminum alloy plate, it is possible to control the particle size and number of precipitated crystals. However, if the amount of precipitated crystals becomes too large, it will affect the formation of precipitates that slow the progression of age hardening. Therefore, as mentioned above, it is necessary to optimize the composition of the aluminum alloy by adjusting the amount of added elements.

The aluminum alloy sheet of this embodiment preferably has a stress relaxation rate of 20% or less, and more preferably 15% or less, when heated at 150°C for 1,000 hours, as measured in accordance with JCBA T309:2004. Furthermore, the aluminum alloy sheet preferably has a 0.2% yield strength of 120 MPa or more and a conductivity of 45% IACS or more, as measured in accordance with JIS H4000:2014. By having a stress relaxation rate of 20% or less and a 0.2% yield strength of 120 MPa or more, even when used as a terminal material, it is possible to suppress stress relaxation in the bolt fastening portion while suppressing plastic deformation of the terminal. Furthermore, since the conductivity is 45% IACS or more, the aluminum alloy sheet has high conductivity, making it suitable for use as a terminal material. The stress relaxation rate can be measured in accordance with the Japan Copper and Brass Association's technical standard JCBA T309:2004 (Bending stress relaxation test method for copper and copper alloy thin plate strips). The test temperature for measuring the stress relaxation rate is 150±5°C, and the test time is 1000 hours±3%. The 0.2% yield strength and electrical conductivity can be measured in accordance with the tensile test and electrical conductivity test specified in JIS H4000:2014 (Aluminum and aluminum alloy plate and strips), respectively.

Next, we will explain the manufacturing method of the aluminum alloy sheet of this embodiment. The aluminum alloy sheet of this embodiment can be obtained by performing heat treatment under conditions equivalent to the T7 treatment of standard product A6101 specified in JIS H4000:2014.

Specifically, first, aluminum, silicon, copper, magnesium, iron, and, if necessary, manganese are melted and cast to obtain the above composition to produce an ingot. The resulting plate-shaped ingot is then preheated (pre-soaked). Preheating conditions can be, for example, 600°C for 24 hours. The preheated ingot is then subjected to a facing process, if necessary.

The preheated ingot is then subjected to homogenization heat treatment. This homogenizes the alloy components and structure, precipitates supersaturated solid-solution components, and removes internal stress. Homogenization heat treatment can be performed at 500-560°C for 4-10 hours. After homogenization heat treatment, hot rolling is performed to obtain a hot-rolled plate. The rolling reduction can be, for example, 90%. The hot-rolled plate is then cold-rolled to obtain a cold-rolled plate. The rolling reduction can be, for example, 80%.

The cold-rolled plate is then subjected to solution treatment, quenching, and aging heat treatment. Solution treatment is carried out at 520-550°C for at least 15 minutes to homogenize the alloy. The rolled plate is then rapidly cooled after solution treatment and quenched. Water, for example, can be used as a coolant during quenching. The rolled plate is then subjected to aging heat treatment. The aging heat treatment conditions can be at 190-270°C for at least 4 hours.

As described above, in this embodiment, heat treatment is performed under conditions equivalent to T7 treatment, which causes crystallized particles and precipitates to form and be highly dispersed inside the aluminum alloy sheet. This makes it possible to obtain an aluminum alloy sheet for conductive components that has excellent stress relaxation properties and yield strength.

As described above, the aluminum alloy sheet for conductive components of this embodiment contains 0.16 to 0.2 mass% silicon, 0.6 to 0.9 mass% copper, 0.2 to 0.5 mass% magnesium, 2.0 to 4.2 mass% iron, and 0 to 0.2 mass% manganese, with the remainder consisting of aluminum and unavoidable impurities. The aluminum alloy sheet also contains dispersed therein a plurality of crystallized particles and precipitates composed of intermetallic compounds containing aluminum and copper. The particle diameter of the crystallized particles is 1 μm or more, and the particle diameter of the precipitates is less than 1 μm. The aluminum alloy sheet of this embodiment contains predetermined amounts of at least silicon, copper, magnesium, and iron, and further contains highly dispersed multiple crystallized particles and precipitates. As described above, the highly dispersed crystallized particles and precipitates composed of intermetallic compounds containing at least aluminum and copper result in good 0.2% yield strength not only at room temperature but also in a high-temperature atmosphere of 150°C. Furthermore, the high dispersion of crystallized particles and precipitates can also suppress an increase in the stress relaxation rate. Furthermore, the aluminum alloy sheet of this embodiment has high stress relaxation properties and yield strength, as well as excellent conductivity, making it suitable for use in conductive components such as terminals.

[Terminal]
As described above, the aluminum alloy sheet of this embodiment has high electrical conductivity and excellent stress relaxation properties and yield strength, and therefore can be suitably used as a conductive member. The conductive member is not particularly limited, but examples thereof include terminals, bus bars, connectors, relays, switches, and lead frames. The aluminum alloy sheet of this embodiment is particularly preferably used as a terminal material. Because the aluminum alloy sheet has high stress relaxation properties, yield strength, and electrical conductivity, even if stress is continuously applied to the bolted portion, the bolt is unlikely to loosen, and electrical continuity can be ensured over a long period of time. A terminal using the aluminum alloy sheet of this embodiment will now be described.

The terminal 10 according to this embodiment includes the aluminum alloy plate for conductive materials described above. Specifically, the terminal 10 is formed by molding the aluminum alloy plate for conductive materials using a die press or the like, as shown in Figure 1(a).

The terminal 10 has a mating connection portion 11 and a wire crimping portion 12 formed integrally with the mating connection portion 11. The wire crimping portion 12 has a base portion 14, a pair of conductor crimping portions 16 extending from both side edges of the base portion 14, and a pair of insulation crimping portions 18 connected to the rear of the conductor crimping portion 16. The mating connection portion 11 has a mounting hole 13 through which, for example, a bolt is inserted, and is formed in a generally rectangular shape. The mating connection portion 11 is then connected to a mating terminal (not shown) with a bolt and nut.

As shown in Figure 1(a), the electric wire 20 has a conductor 23 made of a bundle of multiple wires 21, which are made of an aluminum alloy. The insulator layer 24 is made of an electrically insulating synthetic resin and surrounds the outer periphery of the conductor 23. At the end of the electric wire 20, the insulator layer 24 is stripped away, exposing the conductor 23. The conductor crimping portion 16 of the terminal 10 is then connected to this exposed conductor 23.

When connecting an electric wire 20 to such a terminal 10, first, the conductor 23 and the front end of the insulator layer 24 exposed at the end of the electric wire 20 are placed on the top surface of the base portion 14. Then, as shown in FIG. 1(b), the conductor crimping portion 16 is crimped to cover the conductor 23 and crimped to the conductor 23, and the coating crimping portion 18 is crimped to cover the front end of the insulator layer 24 and crimped to the insulator layer 24. In this way, the electric wire 20 can be connected to the terminal 10.

When connecting terminal 10 to a mating terminal (not shown), a bolt is inserted into mounting hole 13 and fastened with a nut. However, as mentioned above, aluminum alloy plate has excellent stress relaxation properties, so even if stress is continuously applied near mounting hole 13, stress relaxation is suppressed, making it unlikely that the bolt will loosen. This makes it possible to maintain conductivity between terminal 10 and the mating terminal for an extended period of time.

The present embodiment will be described in further detail below with reference to examples, comparative examples, and reference examples, but the present embodiment is not limited to these examples.

[Example]
(Production of aluminum alloy plate)
Sample No. 1 according to the example was prepared according to the flowchart shown in Figure 2. Specifically, aluminum, silicon, copper, magnesium, iron, and manganese were first weighed out in the proportions shown in Sample No. 1 in Table 1. Aluminum was used as Al99.7 according to JIS H2102. The weighed aluminum, silicon, copper, magnesium, iron, and manganese were then melted to prepare a molten metal, which was then poured into a mold to obtain an ingot. The ingot was in the shape of a plate with a thickness of 50 mm, a width of 145 mm, and a length of 250 mm.

The resulting ingot was then subjected to a preheating treatment (pre-soaking treatment). The preheating treatment was carried out at 600°C for 24 hours, with a temperature increase rate of 40°C/h. The surface of the preheated ingot was then chamfered to a thickness of 45 mm, width of 140 mm, and length of 200 mm.

Then, the ingot after facing was subjected to homogenization heat treatment. The homogenization heat treatment was carried out at 540°C for 4 hours, with a temperature increase rate of 40°C/h. Next, the ingot after homogenization heat treatment was hot rolled to obtain a hot-rolled plate. The obtained hot-rolled plate was in the shape of a plate with a thickness of 5 mm, a width of 200 mm, and a length of 1120 mm, meaning that the hot-rolling reduction ratio was 88.9%.

The hot-rolled plate was then cut into plates measuring 5 mm thick, 200 mm wide, and 250 mm long. The cut hot-rolled plate was then cold-rolled to obtain a cold-rolled plate. The resulting cold-rolled plate was 1 mm thick, 200 mm wide, and 250 mm long, meaning the cold-rolling reduction ratio was 80.0%. The resulting cold-rolled plate was then cleaned and straightened.

The resulting cold-rolled sheet was then subjected to solution treatment, quenching, and aging heat treatment. The solution treatment was performed at 540°C for 0.5 hours. Quenching was performed using water as a coolant. The aging heat treatment was performed at 200°C for 8 hours. This resulted in the aluminum alloy sheet of Sample No. 1 according to the example.

Furthermore, aluminum alloy sheets Nos. 2 to 5 were produced using the same manufacturing method as Sample No. 1, with the compositions shown in Table 1. Sample No. 2 is a sample according to the example, and Samples Nos. 3 to 5 are samples according to comparative examples.

(evaluation)
<Measurement of stress relaxation rate, 0.2% yield strength and electrical conductivity>
The stress relaxation rates of the aluminum alloy sheets of Samples No. 1 to 5 were measured in accordance with JCBA T309:2004. The test temperature for measuring the stress relaxation rate was 150±5°C, and the test time was 1000 hours±3%. The 0.2% yield strength and electrical conductivity of the aluminum alloy sheets of Samples No. 1 to 5 were measured in accordance with JIS H4000:2014. The 0.2% yield strength of the aluminum alloy sheets of Samples No. 1 to 5 was measured at room temperature, and the 0.2% yield strength of the aluminum alloy sheets of Samples No. 1 and 2 was also measured at 150°C. The stress relaxation rate, 0.2% yield strength at room temperature, and electrical conductivity of each sample are summarized in Table 1.

As shown in Table 1, Samples 1 and 2 according to the embodiment have a stress relaxation rate of 15% or less, a 0.2% yield strength at room temperature of 120 MPa or more, and an electrical conductivity of 45% IACS or more. Therefore, these samples are excellent in electrical conductivity, stress relaxation characteristics, and yield strength at room temperature.

As shown in Table 1, the 0.2% yield strength measured at room temperature was 130 MPa for Sample No. 1 and 133 MPa for Sample No. 2. Furthermore, the 0.2% yield strength measured at 150°C was 121 MPa for Sample No. 1 and 136 MPa for Sample No. 2. As such, the yield strength at 150°C for these samples was not significantly lower than the yield strength at room temperature, demonstrating that plastic deformation can be suppressed in these samples even at high temperatures.

In contrast, sample No. 3, a comparative example, had insufficient silicon and magnesium contents. As a result, the 0.2% yield strength fell below 120 MPa, resulting in a deterioration. Furthermore, samples No. 4 and 5, a comparative example, had insufficient silicon contents, and sample No. 5 had an excessive copper content. As a result, the stress relaxation rate exceeded 20%, resulting in a deterioration.

Note that Samples No. 6 to 15 in Table 1 correspond to Samples No. 1 to 10, respectively, described in the examples of Patent Document 1. Table 1 also shows the composition, stress relaxation rate, 0.2% yield strength, and electrical conductivity described in Patent Document 1. Table 1 indicates that the samples of Patent Document 1 have insufficient stress relaxation properties and yield strength because the silicon, copper, magnesium, and/or iron contents are outside the composition range of this embodiment. That is, while the 0.2% yield strength of copper alloys is 150 to 300 MPa, many of the samples of Patent Document 1 have a yield strength of 100 MPa or less, indicating that their yield strength is insufficient compared to copper alloys. Furthermore, samples of Patent Document 1 with a yield strength exceeding 100 MPa have a higher stress relaxation rate than copper alloys. That is, the stress relaxation rate of copper alloys is approximately 30% when evaluated at 150°C for 1,000 hours, while the sample of Patent Document 1 has a value close to 40%. Therefore, it can be seen that the samples of Patent Document 1 do not achieve both stress relaxation properties and yield strength.

Tables 2 and 3 show the composition and temper of JIS-standard aluminum alloy sheets, as well as the stress relaxation rate, electrical conductivity, and 0.2% yield strength at room temperature and 150°C. As can be seen from Tables 2 and 3, the stress relaxation rate of JIS-standard products exceeds 40% when evaluated at 150°C for 1000 hours, indicating that the stress relaxation properties are insufficient compared to copper alloys. Furthermore, the stress relaxation rates of A5052 (O temper), A6061, and A6101, which have compositions similar to the aluminum alloy sheet of this embodiment, are 41%, 42%, and 76%, respectively, indicating insufficient stress relaxation properties. In contrast, the stress relaxation rate of the aluminum alloy sheet of this embodiment is 15% or less when evaluated at 150°C for 1000 hours, indicating excellent stress relaxation properties.

<TEM-EDX Measurement of Precipitates>
The cross section of the aluminum alloy plate of Sample No. 2 according to the example was observed with a transmission electron microscope (TEM), and the precipitates were analyzed with energy dispersive X-ray spectroscopy (EDX). The elements contained in the precipitates and the concentrations of those elements were then measured. Figure 3 shows the results of TEM observation of the cross section of the aluminum alloy plate of Sample No. 2. As shown in Figure 3, numerous precipitates 5 highly dispersed throughout the aluminum alloy plate 1 were confirmed. Table 4 shows the elements contained in the precipitates and the concentrations of those elements.

As shown in Table 4, the precipitates are composed of intermetallic compounds containing at least aluminum and copper. Furthermore, the precipitates are composed of intermetallic compounds containing silicon and magnesium in addition to aluminum and copper. The intermetallic compounds are thought to be the Q' phase of the AlCuSiMg quaternary system. The aluminum content in the precipitates was 90 atomic % or more, the copper content was 1.5 atomic % or more, and the silicon content was 1.0 atomic % or more. Thus, it can be seen that the high dispersion of multiple precipitates composed of intermetallic compounds containing aluminum and copper enables the production of an aluminum alloy sheet with high electrical conductivity, excellent stress relaxation properties, and excellent yield strength.

<Metallurgical microscope observation>
In Sample No. 2 according to the example, a cross section (RD-ND cross section) formed by the rolling direction (RD) and the sheet surface normal direction (ND) was observed with a metallurgical microscope. As a result of observing the aluminum alloy sheet 1 of Sample No. 1, crystallized particles 2 were confirmed as shown in FIG. 4. It can also be seen from FIG. 4 that the crystallized particles 2 are highly dispersed throughout the aluminum alloy sheet 1. Furthermore, it can be seen that many crystallized particles 2 having a particle size of 1 μm or more are confirmed in the aluminum alloy structure, and that many large crystallized particles having a particle size exceeding 5 μm are also present. Therefore, it can be seen that the high dispersion of crystallized particles 2 having a particle size of 1 μm or more, preferably 5 μm or more, improves the stress relaxation properties and yield strength.

Here, the number of crystallized particles ² per mm2 was calculated from the metallurgical microscope image of Fig. 4, and the result was 11000 particles/ ^mm2 for Sample No. 2. Therefore, it can be seen that when the number of crystallized particles is 6000 particles/ ^mm2 or more in an aluminum alloy plate, the stress relaxation characteristics become good.

<SEM-EDX measurement of crystallized material>
The cross sections of the aluminum alloy sheets of Samples No. 1 and 2 according to the examples were observed with a scanning electron microscope (SEM), and the precipitated crystals were analyzed with energy dispersive X-ray analysis (EDX). The elements contained in the precipitated crystals and the concentrations of those elements were measured. Figure 5 shows the results of SEM observation of the cross section of the aluminum alloy sheet of Sample No. 1. Table 5 shows the elements contained in the precipitated crystals and the concentrations of those elements.

As shown in Table 5, the precipitated crystals are composed of intermetallic compounds containing at least aluminum and copper. They are also composed of intermetallic compounds containing silicon, manganese, and iron in addition to aluminum and copper. The aluminum content in the precipitated crystals was 60 atomic % or more, and the copper content was 0.3 atomic % or more. The iron content in the precipitated crystals was 30 atomic % or more, the silicon content was 0.4 atomic % or more, and the manganese content was 0.4 atomic % or more. Thus, it can be seen that the high dispersion of precipitated crystals primarily composed of aluminum, iron, and copper enables the production of an aluminum alloy sheet with high electrical conductivity, as well as excellent stress relaxation properties and yield strength.

(Simulation of composition range)
Based on the physical property data (stress relaxation rate, yield strength, electrical conductivity) of aluminum alloy sheets having various compositions that were actually measured, a simulation was performed using a data analysis method to investigate the composition range that would achieve the target physical properties, which were set as a stress relaxation rate of 20% or less, a 0.2% yield strength of 120 MPa or more, and an electrical conductivity of 45% IACS or more.

Here, nonlinear support vector regression was used to simulate the stress relaxation properties. This method makes it possible to predict the stress relaxation rate for various amounts of silicon, copper, magnesium, iron, and manganese added.

Specifically, the stress relaxation rate was used as the target variable, and the additive amounts of Si, Cu, Mg, Fe, and Mn, as well as the combined ratio of elements (e.g., the Si/Cu ratio), were listed as candidate explanatory variables. From these candidates, a combination that would maximize the model's performance was searched for. Finally, seven explanatory variables were selected. The accuracy of the model is expressed by the coefficient of determination ( ^r2 ), and the closer to 1, the smaller the difference between the predicted value and the measured value. The measured physical property data (61 samples) were then divided into training data for model creation and test data for model evaluation in an 85:15 ratio, and model creation and model performance evaluation were performed. This model creation and model performance evaluation were randomly repeated 30 times, and the average coefficient of determination for the 30 runs was 0.96. This indicates sufficient predictive accuracy of the model. Using the model created by the above method, the range within which the target physical property of stress relaxation rate could be achieved was predicted.

For the 0.2% yield strength, simulations were performed using Ridge regression based on the 0.2% yield strength measured on aluminum alloy plates manufactured with various compositions.

The method for calculating the electrical conductivity is described in the following document. The electrical conductivity was calculated based on the maximum solid solubility (wt.%) of each element (Si, Cu, Mg, Fe, Mn) in aluminum, and the average increase in resistivity (μΩ-cm) and decrease in electrical conductivity (%IACS/wt.%) when each element was added to aluminum. In other words, the electrical conductivity of the aluminum alloy was calculated from the amounts of Si, Cu, Mg, Fe, and Mn added in the aluminum alloy, as well as the maximum solid solubility, average increase in resistivity, and decrease in electrical conductivity.
Minoru Yokota, Kenichi Sato, "Aluminum Wire," Light Metals, Japan Institute of Light Metals, August 30, 1982, Vol. 32, No. 8, pp. 432-440

The simulation results are shown in Table 6 and Figures 6A, 6B, 6C, 7A, and 7B. The simulation results show that the above target physical properties can be achieved when the silicon content is in the range of 0.16 to 0.2 mass%, copper is in the range of 0.6 to 0.9 mass%, magnesium is in the range of 0.2 to 0.5 mass%, iron is in the range of 2.0 to 4.2 mass%, and manganese is in the range of 0 to 0.2 mass%.

The present embodiment has been described above, but it is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment.

REFERENCE SIGNS LIST 1 Aluminum alloy sheet for conductive member 2 Crystallized substance 5 Precipitate 10 Terminal

Claims (8)

The composition contains 0.16 to 0.2 mass% of silicon, 0.6 to 0.9 mass% of copper, 0.2 to 0.5 mass% of magnesium, 2.0 to 4.2 mass% of iron, and 0 to 0.2 mass% of manganese, with the balance being aluminum and inevitable impurities;
A plurality of crystallized particles and a plurality of precipitates made of an intermetallic compound containing aluminum and copper are dispersed,
The aluminum alloy sheet for conductive members, wherein the particle size of the crystallized particles is 1 μm or more and the particle size of the precipitates is less than 1 μm. The aluminum alloy sheet for conductive components according to claim 1, wherein the precipitates contain 90 atomic % or more of aluminum and 1.0 atomic % or more of copper. The aluminum alloy sheet for conductive components according to claim 1 or 2, wherein the precipitates are composed of intermetallic compounds containing aluminum, copper, silicon, and magnesium, and the intermetallic compounds form an AlCuSiMg quaternary Q' phase. The aluminum alloy sheet for conductive components according to claim 1 or 2, wherein the aluminum content in the crystallized product is 50 atomic % or more and the copper content is 0.3 atomic % or more. The aluminum alloy sheet for conductive members according to claim 1 or 2, wherein the number of the crystallized particles is 6000 particles/mm ² or more. The aluminum alloy sheet for conductive components according to claim 1 or 2, wherein the crystallized particles are intermetallic compounds containing aluminum, copper, silicon, manganese, and iron. The stress relaxation rate measured in accordance with JCBA T309:2004 when heated at 150°C for 1000 hours is 20% or less,
The aluminum alloy sheet for conductive members according to claim 1 or 2, having a 0.2% yield strength measured in accordance with JIS H4000:2014 of 120 MPa or more and a conductivity of 45% IACS or more. A terminal comprising the aluminum alloy sheet for conductive components according to claim 1 or 2.