JP7849692B2 - Aluminum alloy plate for conductive materials and terminals using the 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 study on "Aluminum alloy sheets for conductive materials and terminals using the same" in the abstract collection of the 140th Spring Meeting of the Japan Institute of Light Metals, under the title "Influence of additive elements on the stress relaxation characteristics of 6000 series aluminum alloy sheets." On May 16, 2021, Yoshihito Ikeda, Jun Yamashita, Hidehiro Nakayama, and Naohiro Saruwatari published a study on "Aluminum alloy sheets for conductive materials and terminals using the same" at the 140th Spring Meeting of the Japan Institute of Light Metals, under the title "Influence of additive elements on the stress relaxation characteristics of 6000 series aluminum alloy sheets." (2) On April 14, 2021, Jun Yamashita, Yoshihito Ikeda, Norio Nunomura, Hidehiro Nakayama, and Naohiro Saruwatari published their research on "Aluminum alloy plates for conductive materials and terminals using the same" under the title "First-principles calculation of mechanical properties of intermetallic compounds in 6000 series aluminum alloys" in the abstract collection 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 their research on "Aluminum alloy plates for conductive materials and terminals using the same" under the title "First-principles calculation of mechanical properties of intermetallic compounds in 6000 series aluminum alloys" at the 140th Spring Meeting of the Japan Institute of Light Metals.

This invention relates to an aluminum alloy plate for conductive materials and a terminal using the same.

In recent years, the increasing demand for lightweight automobiles has led to a growing use of aluminum wires in vehicles. Generally, copper or copper alloys, known for their excellent electrical properties, are used as metal terminals connected to these aluminum wires. However, when the materials of the aluminum wire conductor and the metal terminal differ, corrosion is more likely to occur at the joint. Therefore, the use of aluminum alloys as terminal materials is being considered as an alternative to conventional copper, due to their lower cost, lighter weight, and reduced corrosion risk with aluminum wires.

However, with conventional aluminum alloy terminals, the bolts may loosen under high-temperature conditions, such as those found inside a vehicle, due to stress relaxation caused by continuous stress on the bolt fastening area. As a result, there are concerns that the electrical resistance of the bolt fastening area may increase.

Therefore, the development of aluminum alloys with superior stress relaxation properties has been ongoing. Patent Document 1 discloses an aluminum alloy sheet for crimping that can be used without stress relaxation even in temperature ranges below 170°C. Specifically, this aluminum alloy sheet contains Cu: 0.2 to 0.9 mass%, Mg: 0.6 to 1.4 mass%, with the remainder being Al and unavoidable impurities. The composition of the unavoidable impurities is restricted to Si: 0.8 mass% or less, Fe: 0.6 mass% or less, Mn: 0.15 mass% or less, Cr: 0.3 mass% or less, Zn: 0.3 mass% or less, Ti: 0.1 mass% or less, and Zr: 0.15 mass% or less. Furthermore, the aluminum alloy sheet has a thickness greater than 1.0 mm and 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, while the aluminum alloy sheet described in Patent Document 1 exhibits improved stress relaxation properties, its low yield strength means it may undergo plastic deformation under load. Thus, conventional aluminum alloy sheets have faced the problem of difficulty in achieving both electrical conductivity and high yield strength simultaneously.

This invention has been made in view of the problems of the prior art described above. The object of this invention is to provide an aluminum alloy plate for conductive members that has high conductivity while also possessing excellent stress relaxation characteristics and yield strength, and a terminal using said aluminum alloy plate for conductive members.

The aluminum alloy sheet for conductive members according to an embodiment of the present invention has a composition containing silicon: 0.2 to 0.45% by mass, copper: 0.5 to 1.05% by mass, magnesium: 0.15 to 1.5% by mass, zinc: 0 to 1.5% by mass, and iron: 0 to 1.1% by mass, with the remainder being aluminum and unavoidable impurities. Furthermore, the aluminum alloy sheet for conductive members contains dispersed precipitates and crystals composed of intermetallic compounds containing aluminum and copper. The particle size of the precipitates is 1 μm or larger, while the particle size of the precipitates is less than 1 μm.

Another aspect of the present invention relates to a terminal comprising the above-described aluminum alloy plate for conductive members.

According to the present invention, it is possible to provide an aluminum alloy plate for conductive members that has high conductivity while also exhibiting excellent stress relaxation characteristics and yield strength, and a terminal using said aluminum alloy plate for conductive members.

This is a schematic perspective view showing a terminal using an aluminum alloy plate for conductive members according to this embodiment. This is a flowchart showing the manufacturing process for aluminum alloy sheets, samples No. 1 to 17. This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of sample No. 4 of the example aluminum alloy plate using a transmission electron microscope. This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of sample No. 1 of the example using a metallurgical microscope. This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of sample No. 1 of the example using a scanning electron microscope. This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of sample No. 2 of the example using a scanning electron microscope. This graph shows the relationship between silicon content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. This graph shows the relationship between copper content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. This graph shows the relationship between magnesium content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. This graph shows the relationship between zinc content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. This graph shows the relationship between iron content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. This photograph shows the results of observing the cross-sections (RD-ND cross-sections) of aluminum alloy plates with iron content of 0.05 mass%, 0.4 mass%, 0.5 mass%, and 0.7 mass% using a metallurgical microscope.

The aluminum alloy plate for conductive members and the terminal using the said aluminum alloy plate for conductive members according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[Aluminum alloy sheet for conductive materials]
The aluminum alloy plate for conductive members according to this embodiment optimizes the composition of the aluminum alloy and further forms fine crystals and precipitates within the aluminum alloy structure, thereby improving stress relaxation characteristics and yield strength while maintaining high conductivity.

The aluminum alloy sheet according to this embodiment is made of an aluminum alloy having a composition containing silicon: 0.2 to 0.45% by mass, copper: 0.5 to 1.05% by mass, magnesium: 0.15 to 1.5% by mass, zinc: 0 to 1.5% by mass, and iron: 0 to 1.1% by mass, with the remainder being aluminum and unavoidable impurities.

For aluminum alloy sheets, it is preferable to use pure aluminum with a purity of 99.7% by mass or higher as the base material. Specifically, among the aluminum ingots specified in Japanese Industrial Standard JIS H2102 (Aluminum Ingots), those with a purity of Al99.70 or higher can be preferably used. More specifically, examples include Al99.70, Al99.94, Al99.97, Al99.98, Al99.99, Al99.990, and Al99.995, all with a purity of 99.7% by mass or higher. Thus, in this embodiment, not only expensive, high-purity aluminum ingots like Al99.995 can be used, but also more affordable aluminum ingots with a purity of 99.7% by mass or higher can be used.

Silicon (Si) can improve the strength of aluminum alloy sheets through solid solution strengthening. However, if the silicon content exceeds 0.45% by mass, stress relaxation properties and conductivity may decrease. Therefore, it is preferable that the silicon content in the aluminum alloy sheet be 0.2 to 0.45% by mass, and more preferably 0.2 to 0.4% by mass.

Copper (Cu) can also be added through solid solution strengthening to improve the strength of the aluminum alloy sheet. Therefore, it is preferable that the aluminum alloy sheet contains 0.5 to 1.05% by mass of copper, and more preferably 0.55 to 0.8% by mass.

Magnesium (Mg) is an element that can increase the strength of aluminum alloy sheets while minimizing the decrease in electrical conductivity. However, when the magnesium content exceeds 1.5% by mass, the electrical conductivity, ductility, and toughness of the resulting aluminum alloy sheet tend to decrease. Therefore, it is preferable that magnesium be present in the aluminum alloy sheet at a concentration of 0.15 to 1.5% by mass, and more preferably at 0.3 to 0.5% by mass.

Zinc (Zn) can improve the strength of aluminum alloy sheets through solid solution strengthening. Therefore, it is preferable that zinc be present in the aluminum alloy sheet at a concentration of 0 to 1.5% by mass, and more preferably at 0.1 to 0.5% by mass.

Iron (Fe) is an element that can increase the strength of aluminum alloy sheets while minimizing the decrease in conductivity. Specifically, iron has a low solid solubility limit and forms intermetallic compounds with aluminum. The dispersion of these intermetallic compounds increases the strength of the aluminum alloy sheet. As will be described later, it is preferable that the aluminum alloy sheet of this embodiment contains dispersed precipitates composed of intermetallic compounds containing aluminum, iron, and copper. The dispersion of precipitates within the aluminum alloy sheet allows for high yield strength and conductivity while reducing the stress relaxation rate. Therefore, from the viewpoint of dispersing a large number of precipitates in the aluminum alloy sheet, it is preferable that iron be present in the aluminum alloy sheet at 0 to 1.1% by mass, and more preferably at 0.4 to 0.8% by mass.

Aluminum alloy sheets may contain at least one of cobalt (Co) and nickel (Ni) in addition to silicon, copper, magnesium, zinc, and iron. Specifically, the aluminum alloy sheet may further contain at least one of nickel: 0.2 to 0.55 mass% and cobalt: 0.2 to 2.1 mass%. By incorporating at least one of cobalt and nickel into the aluminum alloy sheet, it is possible to further improve stress relaxation properties and yield strength.

Unavoidable impurities that may be present in the aluminum alloy sheet include gallium (Ga), boron (B), manganese (Mn), lead (Pb), sodium (Na), calcium (Ca), tin (Sn), and vanadium (V). These are inevitably present to the extent that they do not hinder the effects of this embodiment or significantly affect the properties of the aluminum alloy sheet. Elements already present in the pure aluminum ingot used are also included in these unavoidable impurities. The amount of unavoidable impurities in the aluminum alloy sheet is preferably 0.15% by mass or less, and more preferably 0.12% by mass or less.

In this embodiment, the aluminum alloy sheet preferably contains precipitates and crystalline deposits composed of intermetallic compounds containing aluminum and copper. More preferably, the aluminum alloy sheet has multiple precipitates and crystalline deposits dispersed internally. High dispersion of these precipitates and crystalline deposits within the aluminum alloy sheet increases its yield strength under high-temperature atmospheres, thereby improving stress relaxation characteristics. Furthermore, even when the aluminum alloy sheet is used as a terminal material, it becomes possible to suppress stress relaxation at the bolted connection while simultaneously suppressing plastic deformation of the terminal.

As described above, the precipitate is preferably composed of an intermetallic compound containing aluminum and copper. Furthermore, the precipitate may also contain silicon and magnesium in addition to aluminum and copper. In other words, it is more preferable that the precipitate is composed of an intermetallic compound containing aluminum, copper, silicon, and magnesium. In such a precipitate, 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 down the progression of age hardening. Therefore, by highly dispersing the precipitate within the aluminum alloy sheet, the yield strength under high-temperature atmospheres is increased, and the stress relaxation rate can be reduced.

To improve the strength of aluminum alloy sheets, increasing the barrier to dislocation movement is effective. When precipitates are present in the aluminum alloy structure, dislocation lines cut through the precipitates as they progress. Therefore, dislocations are less likely to advance through hard precipitates, such as those containing copper, making deformation more difficult. On the other hand, when crystals with larger particle sizes than precipitates are present in the aluminum alloy structure, dislocation lines curve around the crystals without cutting them. Therefore, even if hard crystals are present, their effect on preventing dislocation movement is smaller compared to precipitates. Thus, precipitates contribute more to improving stress relaxation properties and yield strength than crystals.

In the precipitate, the aluminum content is preferably 90 atomic percent or more. Furthermore, the copper content is preferably 0.1 atomic percent or more, and more preferably 0.3 atomic percent or more. Additionally, the silicon content is preferably 0.3 atomic percent or more, and more preferably 0.5 atomic percent 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 by energy-dispersive X-ray spectroscopy (EDX).

The particle size of the precipitates dispersed in the aluminum alloy plate is less than 1 μm, and preferably 300 nm or less. A particle size of less than 1 μm allows for both high stress relaxation characteristics and yield strength, and suppresses strength reduction at high temperatures. In this specification, "particle size of precipitates" refers to the longest distance between two different points on the contour of the precipitate particles when the cross-section of the aluminum alloy plate is observed under a microscope.

As described above, the precipitates are preferably composed of intermetallic compounds containing aluminum and copper. More preferably, the aluminum content in the precipitates is 50 atomic percent or more, and the copper content is 1 atomic percent or more. Specifically, when an aluminum alloy plate is observed with a scanning electron microscope (SEM) and the precipitates are analyzed by energy-dispersive X-ray spectroscopy (EDX), it is preferable that the aluminum content is 50 atomic percent or more and the copper content is 1 atomic percent or more. High dispersion of precipitates with this composition within the aluminum alloy plate increases the yield strength under high-temperature atmospheres and reduces the stress relaxation rate. Furthermore, the aluminum content in the precipitates is more preferably 55 atomic percent or more, and even more preferably 60 atomic percent or more. Also, the copper content in the precipitates is more preferably 2 atomic percent or more.

The precipitates may contain iron and silicon in addition to aluminum and copper. In other words, it is preferable that the precipitates consist of intermetallic compounds containing aluminum, copper, iron, and silicon. High dispersion of precipitates with such a composition within the aluminum alloy sheet increases the yield strength under high-temperature atmospheres and reduces the stress relaxation rate. The iron content in the precipitates is preferably 10 atomic percent or more, more preferably 15 atomic percent or more, and even more preferably 20 atomic percent or more. Furthermore, the silicon content in the precipitates is preferably 0.5 atomic percent or more, more preferably 1.5 atomic percent or more, and even more preferably 3 atomic percent or more.

Here, if the aluminum alloy sheet contains nickel, the precipitates may contain nickel in addition to aluminum, copper, iron, and silicon. In other words, when the aluminum alloy sheet contains nickel, it is preferable that the precipitates consist of intermetallic compounds containing aluminum, copper, iron, silicon, and nickel. High dispersion of precipitates with such a composition within the aluminum alloy sheet increases the yield strength under high-temperature atmospheres and reduces the stress relaxation rate. It is preferable that the nickel content in the precipitates be 5 atomic percent or more, and more preferably 10 atomic percent or more.

The particle size of the precipitates dispersed in the aluminum alloy plate is 1 μm or larger, preferably 5 μm or larger. A particle size of 1 μm or larger allows for both high stress relaxation characteristics and yield strength. Furthermore, these precipitates help suppress strength reduction at high temperatures. While there is no particular upper limit to the particle size of the precipitates, it can be, for example, 20 μm. In this specification, "particle size of precipitates" refers to the longest distance between two different points on the contour of the precipitate particles when the cross-section of the aluminum alloy plate is observed under a microscope.

In aluminum alloy sheets, it is preferable that the number of precipitates is 6,000 or more per ^mm² . Specifically, when the aluminum alloy sheet is observed with a metallurgical microscope, it is preferable that the number of precipitates per 1 ^mm² is 6,000 or more. This makes it possible for the aluminum alloy sheet to obtain high stress relaxation characteristics.

Furthermore, the particle size of precipitates tends to increase as the iron content in the aluminum alloy sheet increases. Similarly, the number of precipitates also tends to increase with higher iron content. Therefore, by adjusting the iron content added to the aluminum alloy sheet, it is possible to control both the particle size and number of precipitates. However, if the amount of precipitates becomes too high, it can affect the formation of precipitates that slow down age hardening. Therefore, as mentioned above, it is necessary to optimize the composition of the aluminum alloy by adjusting the amount of added elements.

In this embodiment, the aluminum alloy sheet preferably has a stress relaxation rate of 30% or less when heated at 150°C for 1000 hours, as measured in accordance with JCBA T309:2004. Furthermore, the aluminum alloy sheet preferably has a 0.2% yield strength of 150 MPa or more and an electrical conductivity of 45% IACS or more, as measured in accordance with JIS H4000:2014. The stress relaxation rate of 30% or less and the 0.2% yield strength of 150 MPa or more make it possible to suppress plastic deformation of the terminal while suppressing stress relaxation at the bolt fastening portion, even when the aluminum alloy sheet is used as a terminal material. Additionally, the high electrical conductivity of 45% IACS or more makes the aluminum alloy sheet suitable for use as a terminal material. The stress relaxation rate can be measured in accordance with the Japan Copper and Brass Association Technical Standard JCBA T309:2004 (Stress Relaxation Test Method for Bending Thin Sheets and Strips of Copper and Copper Alloys). The test temperature for measuring the stress relaxation rate shall be 150 ± 5°C, and the test duration shall be 1000 hours ± 3%. Furthermore, the 0.2% proof stress and conductivity can be measured in accordance with the tensile and conductivity tests specified in JIS H4000:2014 (Aluminum and aluminum alloy plates and strips), respectively.

Next, the manufacturing method of the aluminum alloy sheet of this embodiment will be described. 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, an ingot is produced by melting and casting aluminum, silicon, copper, and magnesium, and optionally iron, zinc, nickel, and cobalt, to the above composition. Next, the resulting plate-shaped ingot is preheated (pre-soaked). For example, the preheating conditions can be 600°C for 24 hours. Then, the preheated ingot is subjected to surface machining as needed.

Next, the ingot, after preheating, undergoes a homogenization heat treatment. This treatment homogenizes the alloy components and microstructure, precipitates supersaturated dissolved components, and removes internal stresses. The homogenization heat treatment can be performed at 500-560°C for 4-10 hours. After the homogenization heat treatment, hot rolling is performed to obtain a hot-rolled sheet. The rolling ratio can be, for example, 90%. Then, the hot-rolled sheet is cold-rolled to obtain a cold-rolled sheet. The rolling ratio can be, for example, 80%.

Next, the cold-rolled sheet undergoes solution treatment, quenching, and aging heat treatment. The solution treatment is performed at 520-550°C for 15 minutes or more to homogenize the alloy. Following this, the rolled sheet is rapidly cooled and quenched. Water, for example, can be used as a coolant during quenching. Afterward, the rolled sheet undergoes aging heat treatment. The aging heat treatment can be performed at 190-270°C for 4 hours or more.

As described above, in this embodiment, by performing heat treatment under conditions equivalent to the T7 treatment of A6101, crystals and precipitates are formed and highly dispersed within the aluminum alloy sheet. Therefore, an aluminum alloy sheet for conductive members with excellent stress relaxation properties and yield strength can be obtained.

As described above, the aluminum alloy plate for conductive members of this embodiment has a composition containing silicon: 0.2 to 0.45 mass%, copper: 0.5 to 1.05 mass%, magnesium: 0.15 to 1.5 mass%, zinc: 0 to 1.5 mass%, and iron: 0 to 1.1 mass%, with the remainder being aluminum and unavoidable impurities. Furthermore, the aluminum alloy plate contains dispersed precipitates and crystals made of intermetallic compounds containing aluminum and copper. The particle size of the precipitates is 1 μm or larger, and the particle size of the precipitates is less than 1 μm. The aluminum alloy plate of this embodiment contains predetermined amounts of at least silicon, copper, and magnesium, and furthermore, the precipitates and crystals are highly dispersed. In this way, the high dispersion of precipitates and crystals made of intermetallic compounds containing at least aluminum and copper results in good 0.2% proof stress not only at room temperature but also under high temperature conditions of 150°C. Furthermore, the high dispersion of crystals and precipitates suppresses the increase in the stress relaxation rate. Moreover, the aluminum alloy plate of this embodiment possesses high stress relaxation characteristics and yield strength, while also exhibiting excellent conductivity, making it suitable for use in conductive components such as terminals.

[Terminals]
As described above, the aluminum alloy plate of this embodiment has high conductivity while also possessing excellent stress relaxation characteristics and yield strength, making it suitable for use as a conductive member. The conductive member is not particularly limited, but examples include terminals, busbars, connectors, relays, switches, and lead frames. In particular, the aluminum alloy plate of this embodiment is preferably used as a terminal material. Because the aluminum alloy plate has high stress relaxation characteristics, yield strength, and conductivity, there is a low possibility that the bolts will loosen even if stress is continuously applied to the bolt fastening part, and conductivity can be ensured over a long period of time. The terminal using the aluminum alloy plate of this embodiment will be described below.

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

Terminal 10 has a mating connector 11 and a wire crimping section 12 integrally formed on the mating connector 11. The wire crimping section 12 has a base 14, a pair of conductor crimping sections 16 extending from both side edges of the base 14, and a pair of insulation crimping sections 18 connected to the rear of the conductor crimping sections 16. The mating connector 11 has a mounting hole 13 through which, for example, a bolt is inserted, and is formed in a substantially rectangular shape. The mating connector 11 is connected to a mating terminal (not shown) by a bolt and nut.

As shown in Figure 1(a), the electric wire 20 has a conductor 23 made up of bundled strands 21, and the strands 21 are made of an aluminum alloy. The insulating layer 24 is made of an electrically insulating synthetic resin and surrounds the outer circumference of the conductor 23. At the end of the electric wire 20, the insulating layer 24 is peeled off, 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 exposed conductor 23 and the front end of the insulating layer 24 at the end of the electric wire 20 are placed on the upper surface of the base portion 14. Then, as shown in Figure 1(b), the conductor crimping portion 16 is crimped to cover the conductor 23 and pressed against it, while the covering crimping portion 18 is crimped to cover the front end of the insulating layer 24 and pressed against it. In this way, the electric wire 20 can be connected to the terminal 10.

Here, when connecting terminal 10 to a mating terminal (not shown), a bolt is inserted into the mounting hole 13 and fastened with a nut. However, as mentioned above, since the aluminum alloy plate has excellent stress relaxation properties, stress relaxation is suppressed even if stress continues to be applied near the mounting hole 13, making it unlikely that the bolt will loosen. Therefore, it is possible to maintain electrical conductivity between terminal 10 and the mating terminal for a long period of time.

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

[Examples]
(Fabrication of aluminum alloy plates)
Sample No. 1 according to the example was prepared according to the flowchart shown in Figure 2. Specifically, aluminum, silicon, copper, magnesium, zinc, and iron were weighed in the proportions shown for Sample No. 1 in Table 1. In this case, JIS H2102 Al99.7 was used for the aluminum. Then, the weighed aluminum, silicon, copper, magnesium, zinc, and iron were melted to prepare molten metal, which was then poured into a mold to obtain an ingot. This ingot was made into a plate shape with a thickness of 50 mm, a width of 145 mm, and a length of 250 mm.

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

Next, the ingot after surface machining was subjected to a homogenization heat treatment. The homogenization heat treatment was carried out at 540°C for 4 hours, with a heating rate of 40°C/h. Subsequently, the ingot after the homogenization heat treatment was hot-rolled to obtain a hot-rolled sheet. The resulting hot-rolled sheet was 5 mm thick, 200 mm wide, and 1120 mm long, indicating a rolling ratio of 88.9%.

Next, the hot-rolled sheet was cut into plates with a thickness of 5 mm, a width of 200 mm, and a length of 250 mm. Then, the cut hot-rolled sheets were cold-rolled to obtain cold-rolled sheets. The resulting cold-rolled sheets were 1 mm thick, 200 mm wide, and 250 mm long, indicating a rolling ratio of 80.0%. Furthermore, the obtained cold-rolled sheets were washed and straightened.

Next, the obtained cold-rolled sheet was 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 yielded Sample No. 1 of the example aluminum alloy sheet.

Furthermore, aluminum alloy plates No. 2 to 17, with the compositions shown in Table 1, were prepared using the same manufacturing method as Sample No. 1. Samples No. 2 to 4 are examples, while samples No. 5 to 17 are comparative examples.

(evaluation)
<Measurement of stress relaxation rate, 0.2% proof stress, and electrical conductivity>
The stress relaxation rate of aluminum alloy plates No. 1 to 17 was 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%. In addition, the 0.2% yield strength and conductivity of aluminum alloy plates No. 1 to 17 were measured in accordance with JIS H4000:2014. The 0.2% yield strength of aluminum alloy plates No. 1 to 17 was measured at room temperature, and the 0.2% yield strength of aluminum alloy plates No. 1, 3, and 4 was also measured at 150°C. The stress relaxation rate, 0.2% yield strength at room temperature, and conductivity of each sample are summarized in Table 1.

As shown in Table 1, samples No. 1 to 4 in the examples have a stress relaxation rate of 30% or less, a 0.2% yield strength at room temperature of 150 MPa or more, and an electrical conductivity of 45% IACS or more. Therefore, these samples demonstrate excellent 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 157 MPa for sample No. 1, 169 MPa for sample No. 2, 161 MPa for sample No. 3, and 155 MPa for sample No. 4. Furthermore, the 0.2% yield strength measured at 150°C was 150 MPa for sample No. 1, 155 MPa for sample No. 3, and 138 MPa for sample No. 4. Thus, since the yield strength at 150°C for these samples did not decrease significantly from the yield strength at room temperature, it can be seen that these samples can suppress plastic deformation even at high temperatures. Also, since the 0.2% yield strength of copper alloys is typically 150-300 MPa, it can be seen that samples No. 1-4 have yield strength equivalent to that of copper alloys.

In contrast, samples No. 5-8 in the comparative examples had insufficient copper content, and sample No. 7 had zinc outside the compositional range of this embodiment. As a result, the stress relaxation rate deteriorated, exceeding 30%. Furthermore, samples No. 9-13 in the comparative examples had insufficient silicon content and excessive iron content. As a result, the 0.2% yield strength deteriorated, falling below 150 MPa. Additionally, samples No. 14-17 in the comparative examples had silicon, copper, and/or iron content outside the compositional range of this embodiment. Therefore, the stress relaxation rate deteriorated, exceeding 30%.

Furthermore, samples No. 18-27 in Table 1 correspond to samples No. 1-10 described in the examples of Patent Document 1. Table 1 shows the composition, stress relaxation rate, 0.2% yield strength, and conductivity described in Patent Document 1. From Table 1, it can be seen that the samples in Patent Document 1 have insufficient yield strength because their silicon content is outside the compositional range of this embodiment. Specifically, while the 0.2% yield strength of copper alloys is 150-300 MPa, most of the samples in Patent Document 1 have a yield strength of 100 MPa or less, indicating insufficient yield strength compared to copper alloys. Additionally, for samples in Patent Document 1 with a yield strength exceeding 100 MPa, the stress relaxation rate is higher than that of copper alloys. Specifically, while the stress relaxation rate of copper alloys is approximately 30% at 150°C and 1000 hours, the samples in Patent Document 1 have a value close to 40%. Therefore, it can be seen that the samples in Patent Document 1 do not achieve a balance between stress relaxation characteristics and yield strength.

Tables 2 and 3 show the composition and tempering of JIS standard aluminum alloy sheets, as well as their stress relaxation rate, 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 the JIS standard product exceeds 40% in the evaluation at 150°C for 1000 hours, indicating insufficient stress relaxation characteristics compared to copper alloys. Furthermore, the stress relaxation rates of A6061 and A6101, which have similar compositions to the aluminum alloy sheet of this embodiment, are 42% and 76%, respectively, indicating insufficient stress relaxation characteristics. In contrast, the stress relaxation rate of the aluminum alloy sheet according to this embodiment is 30% or less in the evaluation at 150°C for 1000 hours, demonstrating superior stress relaxation characteristics.

<TEM-EDX measurement of precipitates>
The cross-section of sample No. 4 of the aluminum alloy plate in the example was observed using a transmission electron microscope (TEM), and the precipitates were analyzed by energy-dispersive X-ray spectroscopy (EDX). The elements contained in the precipitates and their concentrations were then measured. Figure 3 shows the results of TEM observation of the cross-section of sample No. 4 of the aluminum alloy plate. As shown in Figure 3, numerous precipitates 5 highly dispersed throughout the aluminum alloy plate 1 were observed. Table 4 shows the elements contained in the precipitates and their concentrations.

As shown in Table 4, the precipitates consist of intermetallic compounds containing at least aluminum and copper. Furthermore, the precipitates also consist of intermetallic compounds containing silicon and magnesium in addition to aluminum and copper. It is believed that the Q' phase of the AlCuSiMg quaternary system is formed as the intermetallic compound. In the precipitates, the aluminum content was 90 atomic percent or more, the copper content was 0.3 atomic percent or more, and the silicon content was 0.5 atomic percent or more. Thus, it can be seen that the high dispersion of multiple precipitates consisting of intermetallic compounds containing aluminum and copper results in an aluminum alloy sheet with high conductivity while exhibiting excellent stress relaxation properties and yield strength.

<Metal Microscope Observation>
The cross-section (RD-ND cross-section) formed by the rolling direction (RD) and the direction normal to the plate surface (ND) of sample No. 1 in the example was observed using a metallurgical microscope. As a result of observing the aluminum alloy plate 1 of sample No. 1, precipitates 2 and crystal grains 3 could be confirmed, as shown in Figure 4. Furthermore, from Figure 4, it can be seen that the precipitates 2 are highly dispersed throughout the aluminum alloy plate 1. In addition, it can be seen that many precipitates 2 with a particle size of 1 μm or more were confirmed in the aluminum alloy structure, and that there are many large precipitates with a particle size exceeding 5 μm. Therefore, it can be seen that the stress relaxation characteristics and yield strength are good due to the high dispersion of precipitates 2 with a particle size of 1 μm or more, preferably 5 μm or more.

Here, from the metal microscope image in Figure 4, the number of precipitates per 1 ^mm² was calculated to be 12,000 particles/ ^mm² for sample No. 1. As will be described later, in aluminum alloy plates, a number of precipitates of 6,000 particles/ ^mm² or more results in high dispersion of the precipitates internally, leading to good stress relaxation characteristics.

<SEM-EDX measurement of crystallized material>
Cross-sections of aluminum alloy plates No. 1 to No. 4 in the example were observed using a scanning electron microscope (SEM), and the precipitates were analyzed by energy-dispersive X-ray spectroscopy (EDX). The elements contained in the precipitates and their concentrations were then measured. Figure 5 shows the results of SEM observation of the cross-section of aluminum alloy plate No. 1, and Figure 6 shows the results of SEM observation of the cross-section of aluminum alloy plate No. 2. Table 5 shows the elements contained in the precipitates and their concentrations.

As shown in Table 5, the precipitates consist of intermetallic compounds containing at least aluminum and copper. Furthermore, the precipitates also consist of intermetallic compounds containing iron and silicon in addition to aluminum and copper. In the precipitates, the aluminum content was 60 atomic percent or more, the copper content was 1 atomic percent or more, the iron content was 10 atomic percent or more, and the silicon content was 0.5 atomic percent or more. Thus, it can be seen that by highly dispersing precipitates mainly composed of aluminum, iron, and copper, an aluminum alloy sheet with high conductivity, as well as excellent stress relaxation properties and yield strength, can be obtained.

Furthermore, as shown in Sample No. 2, when nickel is present in an aluminum alloy plate, the precipitates consist of intermetallic compounds containing aluminum, iron, copper, silicon, and nickel. The nickel content in the precipitates was 10 atomic percent or more. Thus, even though the precipitates are primarily composed of aluminum, iron, and copper, the inclusion of nickel makes it possible to further enhance the stress relaxation rate and yield strength.

(Simulation of composition range)
Based on physical property data (stress relaxation rate, yield strength, and conductivity) obtained by fabricating aluminum alloy plates with various compositions, simulations using data analysis methods were conducted to investigate the composition range that achieves the target physical properties. The target physical properties were set as a stress relaxation rate of 30% or less, a 0.2% yield strength of 150 MPa or more, and an conductivity of 45% IACS or more.

Here, "nonlinear support vector regression" was used to simulate the stress relaxation characteristics. This method allows for the prediction of the stress relaxation rate for different amounts of silicon, copper, magnesium, zinc, iron, and manganese added.

Specifically, with the stress relaxation rate as the target variable, candidate explanatory variables included the amounts of Si, Cu, Mg, Zn, Fe, and Mn added, as well as the ratio of elemental combinations (e.g., Si/Cu ratio). The combination that yielded the highest model performance was then searched for. Ultimately, seven explanatory variables were selected. Model accuracy is represented by the coefficient of determination ( ^R² ), where a value closer to 1 indicates a smaller difference between predicted and measured values. The measured material property data (61 samples) was then divided into training data for model creation and test data for model evaluation in an 85:15 ratio, and model creation and performance evaluation were performed. This model creation and performance evaluation process was repeated randomly 30 times, and the average R² over 30 trials was 0.75. This indicates sufficient predictive accuracy for the model. Using the model created using the above method, the range within which the target material property of stress relaxation rate can be achieved was predicted.

For the 0.2% proof stress, simulations were performed using Ridge regression based on the measured 0.2% proof stress of aluminum alloy plates with various compositions.

The conductivity was calculated based on the maximum solid solubility (wt.%) of each element (Si, Cu, Mg, Zn, Fe, Mn) in aluminum, as well as the average increase in resistivity (μΩ-cm) and decrease in conductivity (%IACS/wt.%) when each element is added to aluminum, as described in the following literature. In other words, the conductivity of the aluminum alloy was calculated from the amount of Si, Cu, Mg, Zn, Fe, Mn added to the aluminum alloy, as well as the above-mentioned maximum solid solubility, average increase in resistivity, and decrease in conductivity.
Minoru Yokota, Kenichi Sato, "Aluminum Wire," Light Metals, The 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 7A, 7B, 7C, 8A, and 8B. The simulation results show that the target physical properties described above can be achieved when the silicon content is in the range of 0.2–0.45 mass%, copper in the range of 0.5–1.05 mass%, magnesium in the range of 0.15–1.5 mass%, zinc in the range of 0–1.5 mass%, and iron in the range of 0–1.1 mass%.

[Reference example]
Aluminum alloy plates with different iron content were fabricated according to the flowchart shown in Figure 2. Specifically, first, each element was weighed so that the amount of silicon added was 0.22 to 0.58 mass%, the amount of copper added was 0 to 0.60 mass%, the amount of magnesium added was 0.34 to 1.02 mass%, and the amount of zinc added was 0 to 0.70 mass%. Furthermore, the amount of iron added was weighed so that it was 0.05 mass%, 0.4 mass%, 0.5 mass%, and 0.7 mass%, respectively. Then, following the flowchart shown in Figure 2, aluminum alloy plates with iron content of 0.05 mass%, 0.4 mass%, 0.5 mass%, and 0.7 mass%, respectively, were obtained.

Next, the number of precipitates per 1 ^mm² in the obtained aluminum alloy plates was calculated. Specifically, the cross-sections of the aluminum alloy plates were first observed using a metallurgical microscope. Figure 9 shows the observation results of the cross-sections of each aluminum alloy plate. Next, the number of precipitates present in a predetermined area (0.14 ^mm² ) in each image was counted, and the number of precipitates per 1 ^mm² was calculated. The number of precipitates in each aluminum alloy plate is summarized in Table 7.

As shown in Figure 9 and Table 7, it can be seen that the number of precipitates formed increases as the amount of iron added to the aluminum alloy sheet increases. Furthermore, from Figure 9, it can be seen that when the iron content is 0.05 mass%, the particle size of the precipitates is small, but as the iron content increases, the number of precipitates with larger particle sizes increases. As mentioned above, it is presumed that highly dispersed precipitates contribute to the improvement of stress relaxation characteristics and yield strength. Furthermore, it can be seen that in order to have 6000 precipitates/ ^mm² or more in the aluminum alloy sheet, it is preferable to add 0.4 mass% or more of iron.

Although this embodiment has been described above, it is not limited to these examples, and various modifications are possible within the scope of the gist of this embodiment.

1. Aluminum alloy plate for conductive components 2. Crystallized material 5. Precipitated material 10. Terminal

Claims (6)

It has a composition containing silicon: 0.2 to 0.45 mass%, copper: 0.5 to 1.05 mass%, magnesium: 0.15 to 1.5 mass%, zinc: 0 to 1.5 mass%, and iron: 0.4 to 1.1 mass%, with the remainder being aluminum and unavoidable impurities.
It further contains at least one of nickel: 0.2 to 0.55 mass% and cobalt: 0.2 to 2.1 mass%.
Multiple precipitates consisting of intermetallic compounds containing aluminum and copper are dispersed,
An aluminum alloy plate for conductive materials, wherein the particle size of the precipitated material is 1 μm or larger. The aluminum alloy plate for conductive members according to claim 1 , wherein the precipitate contains 50 atomic percent or more of aluminum and 1 atomic percent or more of copper. The aluminum alloy plate for conductive members according to claim 1 or 2, wherein the number of precipitates is 6,000 or more per ^mm² . The aluminum alloy plate for conductive members according to claim 1 or 2, wherein the precipitated product consists of an intermetallic compound containing aluminum, iron, copper, and silicon. The stress relaxation rate after heating at 150°C for 1000 hours, as measured in accordance with JCBA T309:2004, is 30% or less.
An aluminum alloy plate for conductive members according to claim 1 or 2, wherein the 0.2% yield strength measured in accordance with JIS H4000:2014 is 150 MPa or more, and the electrical conductivity is 45% IACS or more. A terminal comprising an aluminum alloy plate for conductive members as described in claim 1 or 2.