Aluminum alloy plate for conductive materials and terminals using the same

Abstract

To provide an aluminum alloy sheet for conductive members that has excellent stress relaxation properties and proof stress while having high conductivity, and a terminal using the aluminum alloy sheet for conductive members.SOLUTION: An aluminum alloy sheet 1 for conductive members contains: silicon: 0.2-0.45 mass%, copper: 0.5-1.05 mass%, magnesium: 0.15-1.5 mass%, zinc: 0-1.5 mass%, and iron: 0-1.1 mass% with the balance being aluminum and unavoidable impurities. A plurality of crystallized substances 2 composed of intermetallic compounds containing aluminum and copper and a plurality of precipitates 5 are dispersed herein. The crystallized substances 2 have a particle size of 1 μm or more and the precipitates 5 have a particle size of less than 1 μm. A terminal 10 comprises the aluminum alloy sheet 1 for conductive members.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to an aluminum alloy plate for conductive materials and a terminal using the same. [Background technology]

[0002] In recent years, the increasing demand for lighter automobiles has led to a growing use of aluminum wires in vehicles. Generally, copper or copper alloys, which have 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 between the conductor and the terminal. 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.

[0003] However, with conventional aluminum alloy terminals, the bolts may loosen in high-temperature environments such as those 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.

[0004] Therefore, the development of aluminum alloys with superior stress relaxation properties has been underway. Patent Document 1 discloses an aluminum alloy sheet for crimping that can be used without stress relaxation even in a temperature range of 170°C or below. Specifically, the 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. Among the unavoidable impurities, the composition 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. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4009244 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, although the aluminum alloy sheet described in Patent Document 1 has improved stress relaxation properties, its yield strength is low, and there is a risk of plastic deformation when a load is applied. Thus, conventional aluminum alloy sheets have the problem of being difficult to achieve both stress relaxation properties and yield strength while ensuring conductivity.

[0007] This invention has been made in view of the problems of the prior art. The object of this invention is to provide an aluminum alloy plate for conductive members that has high conductivity while also having excellent stress relaxation characteristics and yield strength, and a terminal using the aluminum alloy plate for conductive members. [Means for solving the problem]

[0008] 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 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. 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, and the particle size of the precipitates is less than 1 μm.

[0009] A terminal according to another aspect of the present invention comprises the above-described aluminum alloy plate for conductive members. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an aluminum alloy plate for conductive members that has high conductivity while also having excellent stress relaxation characteristics and yield strength, and a terminal using the aluminum alloy plate for conductive members. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic perspective view showing a terminal using an aluminum alloy plate for conductive members according to this embodiment. [Figure 2] This is a flowchart showing the manufacturing process for aluminum alloy sheets of samples No. 1 to 17. [Figure 3] This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of the aluminum alloy plate sample No. 4 in the example using a transmission electron microscope. [Figure 4] This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of the aluminum alloy plate sample No. 1 in the example using a metallurgical microscope. [Figure 5] This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of the aluminum alloy plate sample No. 1 in the example using a scanning electron microscope. [Figure 6] This is a photograph showing the results of observing the cross-section (RD-ND cross-section) of the aluminum alloy plate of sample No. 2 in the example using a scanning electron microscope. [Figure 7A] This graph shows the relationship between silicon content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. [Figure 7B] This graph shows the relationship between copper content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. [Figure 7C] This graph shows the relationship between magnesium content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. [Figure 8A] This graph shows the relationship between zinc content and stress relaxation rate in an aluminum alloy sheet, as determined by simulation. [Figure 8B]A graph showing the relationship between the iron content and the stress relaxation rate in an aluminum alloy plate obtained by simulation. [Figure 9] A photograph showing the results of observing the cross-sections (RD-ND cross-sections) of aluminum alloy plates with iron contents of 0.05 mass%, 0.4 mass%, 0.5 mass%, and 0.7 mass% using a metallurgical microscope.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the aluminum alloy plate for a conductive member according to the present embodiment and a terminal using the aluminum alloy plate for a conductive member will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

[0013] [Aluminum Alloy Plate for Conductive Member] The aluminum alloy plate for a conductive member according to the present embodiment optimizes the composition of the aluminum alloy and further forms finer crystallites and precipitates in the aluminum alloy structure, thereby having high conductivity while improving stress relaxation characteristics and yield strength.

[0014] The aluminum alloy plate according to the present embodiment is made of an aluminum alloy having 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 balance being aluminum and unavoidable impurities.

[0015] 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. That is, among the aluminum ingots specified in the Japanese Industrial Standard JIS H2102 (Aluminum Ingots), those with a purity of Al99.70 or higher can be preferably used. 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 and high-purity aluminum ingots such as Al99.995 can be used, but also reasonably priced aluminum ingots with a purity of 99.7% by mass or higher can be used.

[0016] Silicon (Si) can improve the strength of aluminum alloy sheets through solid solution strengthening. However, if the silicon content exceeds 0.45% by mass, the 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.

[0017] 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.

[0018] Magnesium (Mg) is an element that can increase the strength of aluminum alloy sheets while minimizing the decrease in conductivity. However, when the magnesium content exceeds 1.5 mass%, the conductivity, ductility, and toughness of the resulting aluminum alloy sheet tend to decrease. Therefore, it is preferable that magnesium be included in the aluminum alloy sheet at a concentration of 0.15 to 1.5 mass%, and more preferably at a concentration of 0.3 to 0.5 mass%.

[0019] Zinc (Zn) can improve the strength of aluminum alloy sheets through solid solution strengthening. Therefore, it is preferable that zinc be included in the aluminum alloy sheet at a concentration of 0 to 1.5% by mass, and more preferably at a concentration of 0.1 to 0.5% by mass.

[0020] Iron (Fe) is an element that can increase the strength of an aluminum alloy sheet while minimizing the decrease in conductivity. In other words, 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 consisting of intermetallic compounds containing aluminum, iron, and copper. The dispersion of precipitates within the aluminum alloy sheet makes it possible to obtain 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 contained in the aluminum alloy sheet at a concentration of 0 to 1.1 mass%, and more preferably at a concentration of 0.4 to 0.8 mass%.

[0021] In addition to silicon, copper, magnesium, zinc, and iron, aluminum alloy sheets may contain at least one of cobalt (Co) and nickel (Ni). Specifically, aluminum alloy sheets may further contain at least one of nickel: 0.2 to 0.55 mass% and cobalt: 0.2 to 2.1 mass%. By including at least one of cobalt and nickel in aluminum alloy sheets, it is possible to further improve stress relaxation properties and yield strength.

[0022] 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 and do not particularly affect the properties of the aluminum alloy sheet of this embodiment. Elements that are already present in the pure aluminum ingot used are also included in these unavoidable impurities. Preferably, the total amount of unavoidable impurities in the aluminum alloy sheet is 0.15% by mass or less, and more preferably 0.12% by mass or less.

[0023] The aluminum alloy sheet of this embodiment preferably contains precipitates and crystalline deposits made of intermetallic compounds containing aluminum and copper. More preferably, the aluminum alloy sheet has multiple precipitates and crystalline deposits dispersed internally. High dispersion of such 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 is possible to suppress plastic deformation of the terminal while suppressing stress relaxation at the bolt fastening portion.

[0024] As described above, the precipitate is preferably composed of an intermetallic compound containing aluminum and copper. In addition to aluminum and copper, the precipitate may also contain silicon and magnesium. 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 inside the aluminum alloy sheet, the yield strength under high-temperature atmospheres is increased and the stress relaxation rate can be reduced.

[0025] To improve the strength of aluminum alloy sheets, it is effective to increase the barrier to dislocation movement. When precipitates are present in the aluminum alloy structure, dislocation lines cut through the precipitates as they progress. For example, dislocations have difficulty progressing through hard precipitates such as copper, making deformation 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, the effect of hindering dislocation movement is smaller compared to precipitates. Thus, precipitates contribute more to improving stress relaxation properties and yield strength than crystals.

[0026] In the precipitate, the aluminum content is preferably 90 atomic percent or more. Furthermore, the copper content in the precipitate is preferably 0.1 atomic percent or more, and more preferably 0.3 atomic percent or more. In addition, the silicon content in the precipitate 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).

[0027] 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 makes it possible to achieve both high stress relaxation characteristics and yield strength, and to suppress 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.

[0028] As described above, the precipitates preferably consist 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 such a composition within the aluminum alloy plate increases the yield strength under high-temperature atmospheres and reduces the stress relaxation rate. More preferably, the aluminum content in the precipitates is 55 atomic percent or more, and even more preferably 60 atomic percent or more. Furthermore, it is more preferable that the copper content in the precipitates is 2 atomic percent or more.

[0029] 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 plate can increase the yield strength under high-temperature atmospheres and reduce 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. 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.

[0030] In this case, if the aluminum alloy sheet contains nickel, the precipitates may contain nickel in addition to aluminum, copper, iron, and silicon. In other words, if the aluminum alloy sheet contains nickel, it is preferable that the precipitates consist of an intermetallic compound containing aluminum, copper, iron, silicon, and nickel. High dispersion of precipitates with such a composition within the aluminum alloy sheet can increase the yield strength under high-temperature atmospheres and reduce the stress relaxation rate. In the precipitates, the nickel content is preferably 5 atomic percent or more, and more preferably 10 atomic percent or more.

[0031] 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 makes it possible to achieve 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.

[0032] In aluminum alloy sheets, the number of precipitates is 6000 per mm². 2 It is preferable that the above is true. Specifically, when an aluminum alloy plate is observed with a metallurgical microscope, 1 mm 2 It is preferable that the number of crystals per unit area be 6,000 or more. This makes it possible for the aluminum alloy sheet to obtain high stress relaxation properties.

[0033] 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 as the iron content in the aluminum alloy sheet increases. 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 large, 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.

[0034] 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 higher and an electrical conductivity of 45% IACS or higher, 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 higher make it possible to suppress stress relaxation at the bolted fastening portion and reduce plastic deformation of the terminal, even when the aluminum alloy sheet is used as a terminal material. Additionally, the high electrical conductivity of 45% IACS or higher 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 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.

[0035] Next, the method for manufacturing 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.

[0036] 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 subjected to preheating (pre-soaking). The preheating conditions can be, for example, 600°C for 24 hours. Then, the ingot after preheating is subjected to surface machining as needed.

[0037] Next, the ingot, after preheating, is subjected to a homogenization heat treatment. This treatment homogenizes the alloy components and structure, precipitates supersaturated dissolved components, and removes internal stresses. The conditions for the homogenization heat treatment can be 500-560°C for 4-10 hours. After the homogenization heat treatment, hot rolling is performed to obtain a hot-rolled sheet. At this stage, the rolling ratio can be, for example, 90%. Subsequently, the hot-rolled sheet is cold-rolled to obtain a cold-rolled sheet. At this stage, the rolling ratio can be, for example, 80%.

[0038] Next, the cold-rolled sheet is subjected to 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. Then, the rolled sheet is rapidly cooled after the solution treatment and quenched. Water can be used as a coolant during quenching. After that, the rolled sheet is subjected to aging heat treatment. The conditions for aging heat treatment can be 190-270°C for 4 hours or more.

[0039] 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.

[0040] As described above, the aluminum alloy plate for conductive members of this embodiment has a composition containing silicon: 0.2-0.45 mass%, copper: 0.5-1.05 mass%, magnesium: 0.15-1.5 mass%, zinc: 0-1.5 mass%, and iron: 0-1.1 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. As a result of this high dispersion of precipitates and crystals made of intermetallic compounds containing at least aluminum and copper, the 0.2% proof stress is good not only at room temperature but also in a high-temperature atmosphere of 150°C. Furthermore, the high dispersion of crystals and precipitates can suppress the increase in the stress relaxation rate. Moreover, the aluminum alloy plate of this embodiment has high stress relaxation characteristics and yield strength, as well as excellent conductivity, making it suitable for use in conductive members such as terminals.

[0041] [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.

[0042] The terminal 10 according to this embodiment includes the above-mentioned aluminum alloy plate for conductive members. Specifically, the terminal 10 is formed by molding the aluminum alloy plate for conductive members by die press working or the like, as shown in Figure 1(a).

[0043] Terminal 10 has a mating connector 11 and a wire crimping section 12 integrally formed with 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.

[0044] 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 and the conductor 23 is exposed. The conductor crimping portion 16 of the terminal 10 is then connected to this exposed conductor 23.

[0045] 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 14. Then, as shown in Figure 1(b), the conductor crimping portion 16 is crimped to cover the conductor 23 and pressed against the conductor 23, and the covering crimping portion 18 is crimped to cover the front end of the insulating layer 24 and pressed against the insulating layer 24. In this way, the electric wire 20 can be connected to the terminal 10.

[0046] 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 aluminum alloy plates have 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. [Examples]

[0047] The embodiment will be described in more detail below with reference to examples, comparative examples, and reference examples, but the embodiment is not limited to these examples.

[0048] [Examples] (Fabrication of aluminum alloy sheets) Sample No. 1 for the embodiment 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, Al99.7 of JIS H2102 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.

[0049] 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.

[0050] Next, the ingot after surface machining was subjected to 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 homogenization heat treatment was hot-rolled to obtain a hot-rolled sheet. The obtained hot-rolled sheet was 5 mm thick, 200 mm wide, and 1120 mm long, indicating a rolling ratio of 88.9%.

[0051] 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.

[0052] Next, the obtained cold-rolled sheet was subjected to solution treatment, quenching, and aging heat treatment. The solution treatment was carried out at 540°C for 0.5 hours. Quenching was performed using water as a coolant. The aging heat treatment was carried out at 200°C for 8 hours. This yielded the aluminum alloy sheet No. 1 according to the example.

[0053] 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.

[0054] [Table 1]

[0055] (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.

[0056] 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, it can be seen that these samples are excellent in terms of electrical conductivity, stress relaxation characteristics, and yield strength at room temperature.

[0057] 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.

[0058] In contrast, samples No. 5 to 8 in the comparative examples had insufficient copper content, and sample No. 7 had zinc outside the composition range of this embodiment. As a result, the stress relaxation rate worsened, exceeding 30%. Furthermore, samples No. 9 to 13 in the comparative examples had insufficient silicon content and excessive iron content. As a result, the 0.2% yield strength worsened, falling below 150 MPa. Furthermore, samples No. 14 to 17 in the comparative examples had silicon, copper, and / or iron content outside the composition range of this embodiment. As a result, the stress relaxation rate worsened, exceeding 30%.

[0059] 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 composition range of this embodiment. In other words, while the 0.2% yield strength of copper alloys is 150-300 MPa, most of the samples in Patent Document 1 are below 100 MPa, indicating that their yield strength is insufficient compared to copper alloys. Furthermore, for the samples in Patent Document 1 with a yield strength exceeding 100 MPa, the stress relaxation rate is higher than that of copper alloys. In other words, the stress relaxation rate of copper alloys is about 30% when evaluated at 150°C for 1000 hours, while the samples in Patent Document 1 are 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.

[0060] Tables 2 and 3 show the composition and tempering of JIS standard aluminum alloy sheets, as well as the 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 JIS standard products exceeds 40% in the evaluation at 150°C for 1000 hours, indicating that the stress relaxation characteristics are insufficient 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, indicating superior stress relaxation characteristics.

[0061] [Table 2]

[0062] [Table 3]

[0063] <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 observing the cross-section of sample No. 4 of the aluminum alloy plate with a TEM. 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.

[0064] [Table 4]

[0065] As shown in Table 4, the precipitates consist of intermetallic compounds containing at least aluminum and copper. Furthermore, the precipitates 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% or more, the copper content was 0.3 atomic% or more, and the silicon content was 0.5 atomic% or more. Thus, it can be seen that by highly dispersing multiple precipitates consisting of intermetallic compounds containing aluminum and copper, an aluminum alloy sheet with high conductivity, as well as excellent stress relaxation properties and yield strength, can be obtained.

[0066] <Metallurgical Microscope Observation> The cross-section (RD-ND cross-section) of Sample No. 1 in the example, formed by the rolling direction (RD) and the direction normal to the plate surface (ND), was observed using a metallurgical microscope. Observation of the aluminum alloy plate 1 of Sample No. 1 revealed the presence of precipitates 2 and crystal grains 3, as shown in Figure 4. Furthermore, Figure 4 shows that the precipitates 2 are highly dispersed throughout the aluminum alloy plate 1. In addition, numerous precipitates 2 with a particle size of 1 μm or more were observed in the aluminum alloy structure, and many large precipitates with a particle size exceeding 5 μm were also present. Therefore, it can be seen that the high dispersion of precipitates 2 with a particle size of 1 μm or more, preferably 5 μm or more, results in good stress relaxation properties and yield strength.

[0067] Here, from the metal microscope image in Figure 4, 1 mm 2 The number of crystallized particles per square millimeter was calculated, and in sample No. 1, it was 12,000 particles / mm². 2 And, as will be described later, in the aluminum alloy plate, the number of crystals was 6000 / mm 2 As a result of the above, the precipitates are highly dispersed internally, leading to good stress relaxation properties.

[0068] <SEM-EDX measurement of crystallized material> Cross-sections of aluminum alloy plates No. 1 to No. 4 in the examples 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.

[0069] [Table 5]

[0070] As shown in Table 5, the precipitates consist of intermetallic compounds containing at least aluminum and copper. Furthermore, the precipitates consist of intermetallic compounds containing iron and silicon in addition to aluminum and copper. In the precipitates, the aluminum content was 60 atomic% or more, the copper content was 1 atomic% or more, the iron content was 10 atomic% or more, and the silicon content was 0.5 atomic% 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.

[0071] 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 mainly composed of aluminum, iron, and copper, the inclusion of nickel makes it possible to further increase the stress relaxation rate and yield strength.

[0072] (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 higher.

[0073] Here, "nonlinear support vector regression" was used to simulate the stress relaxation characteristics. This method makes it possible to predict the stress relaxation rate for different amounts of silicon, copper, magnesium, zinc, iron, and manganese added.

[0074] Specifically, the stress relaxation rate was used as the target variable, and 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. The accuracy of the model was measured by the coefficient of determination (R). 2 This is represented by the coefficient of determination, and the closer it is to 1, the smaller the difference between the predicted value and the measured value. 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 model performance evaluation were performed. This model creation and model performance evaluation was repeated randomly 30 times, and the average coefficient of determination for the 30 trials was 0.75. This indicates that the model has sufficient predictive accuracy. Using the model created using the above method, the range in which the target material property of stress relaxation rate can be achieved was predicted.

[0075] For the 0.2% yield strength, simulations were performed using Ridge regression based on the measured 0.2% yield strength of aluminum alloy plates with various compositions.

[0076] 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.

[0077] The results of the simulation are shown in Table 6 and FIGS. 7A, 7B, 7C, 8A, and 8B. From the simulation results, it was found that the above-mentioned target physical properties can be achieved when silicon is in the range of 0.2 to 0.45% by mass, copper is in the range of 0.5 to 1.05% by mass, magnesium is in the range of 0.15 to 1.5% by mass, zinc is in the range of 0 to 1.5% by mass, and iron is in the range of 0 to 1.1% by mass.

[0078] [Table 6]

[0079] [Reference Example] Aluminum alloy plates with different iron contents were produced along the flowchart shown in FIG. 2. Specifically, first, each element was weighed so that the addition amount of silicon was 0.22 to 0.58% by mass, the addition amount of copper was 0 to 0.60% by mass, the addition amount of magnesium was 0.34 to 1.02% by mass, and the addition amount of zinc was 0 to 0.70% by mass. Further, the addition amounts of iron were weighed to be 0.05% by mass, 0.4% by mass, 0.5% by mass, and 0.7% by mass, respectively. Then, along the flowchart shown in FIG. 2, aluminum alloy plates with iron contents of 0.05% by mass, 0.4% by mass, 0.5% by mass, and 0.7% by mass were obtained.

[0080] Next, the number of precipitates 2 per 1 mm 2 in the obtained aluminum alloy plate was calculated. Specifically, first, the cross-section of the aluminum alloy plate was observed with a metallurgical microscope. FIG. 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 mm 2 ) in each image was counted, and the number of precipitates per 1 mm 2 was calculated. The number of precipitates in each aluminum alloy plate is summarized in Table 7.

[0081] [Table 7]

[0082] 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. And, as mentioned above, it is presumed that the highly dispersed precipitates contribute to the improvement of stress relaxation properties and yield strength. Furthermore, in the aluminum alloy sheet, the number of precipitates is 6000 particles / mm 2 To achieve the above, it is preferable to add 0.4% by mass or more of iron.

[0083] Although this embodiment has been described above, this embodiment is not limited to these, and various modifications are possible within the scope of the gist of this embodiment. [Explanation of Symbols]

[0084] 1. Aluminum alloy plate for conductive components 2 Crystallized matter 5 Precipitate 10 terminals

Claims

1. 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.

2. 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.

3. The number of crystals is 6000 / mm². ２ The aluminum alloy plate for conductive members according to claim 1 or 2.

4. The aluminum alloy plate for conductive members according to claim 1 or 2, wherein the precipitate consists of an intermetallic compound containing aluminum, iron, copper, and silicon.

5. 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.

6. A terminal comprising an aluminum alloy plate for conductive members as described in claim 1 or 2.

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