Aluminum alloy sheet for conductive member and terminal using same

Abstract

To provide an aluminum alloy plate for conductive member which has high conductivity, and has excellent stress relaxation properties and proof stress, and a terminal using the aluminum alloy plate for conductive member.SOLUTION: An aluminum alloy plate 1 for conductive member, comprises: 0.16-0.2 mass% of silicon; 0.6-0.9 mass% of copper; 0.2-0.5 mass% of magnesium; 2.0-4.2 mass% of iron; and 0-0.2 mass% of manganese, with the remainder formed of aluminum and inevitable impurities. There are dispersed a plurality of crystallized objects 2 and a plurality of precipitated objects 5 which are formed of intermetallic compounds including aluminum and copper, a particle diameter of the crystallized object 2 is 1 μm or greater, and a particle diameter of the precipitated object 5 is less than 1 μm, and the terminal 10 has the aluminum alloy plate 1 for conductive member.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy sheet for conductive members and a terminal using the same. [Background technology]

[0002] In recent years, the need for lighter automobiles has led to an increasing use of aluminum electric wires in vehicles. Metal terminals connected to such aluminum electric wires are generally made of copper or copper alloys, which have excellent electrical properties. However, if the conductor of an aluminum electric wire and the metal terminal are made of different materials, corrosion is likely to occur at the joint between the conductor and the metal terminal. Therefore, the use of aluminum alloys, which are low-cost, lightweight, and have a low risk of corrosion when combined with aluminum electric wires, as terminal materials has been considered in place of conventional copper.

[0003] However, with terminals made of conventional aluminum alloys, stress relaxation caused by continuous application of stress to the bolted joint can cause the bolt to loosen in the high-temperature environment simulated inside a vehicle, raising concerns that this could result in an increase in electrical resistance at the bolted joint.

[0004] For this reason, development of aluminum alloys with excellent stress relaxation properties has been underway. Patent Document 1 discloses an aluminum alloy sheet for crimping that can be used at temperatures below 170°C without stress relaxation. Specifically, the aluminum alloy sheet contains 0.2 to 0.9 mass% Cu, 0.6 to 1.4 mass% Mg, and the remainder Al and unavoidable impurities, with the unavoidable impurities being regulated to 0.8 mass% or less of Si, 0.6 mass% or less of Fe, 0.15 mass% or less of Mn, 0.3 mass% or less of Cr, 0.3 mass% or less of Zn, 0.1 mass% or less of Ti, and 0.15 mass% or less of Zr. The aluminum alloy sheet has a thickness of more than 1.0 mm 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 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the aluminum alloy sheet of Patent Document 1 has improved stress relaxation properties, it has low yield strength and is therefore susceptible to plastic deformation when a load is applied. Thus, conventional aluminum alloy sheets have had the problem that it is difficult to achieve both stress relaxation properties and yield strength while ensuring electrical conductivity.

[0007] The present invention has been made in view of the problems inherent in the prior art, and an object of the present invention is to provide an aluminum alloy sheet for conductive members that has high electrical conductivity and also has excellent stress relaxation properties and yield strength, and a terminal using the aluminum alloy sheet for conductive members. [Means for solving the problem]

[0008] An aluminum alloy sheet for conductive materials according to an embodiment of the present invention has a composition containing 0.16 to 0.2 mass% silicon, 0.6 to 0.9 mass% copper, 0.2 to 0.5 mass% magnesium, 2.0 to 4.2 mass% iron, and 0 to 0.2 mass% manganese, with the remainder being aluminum and unavoidable impurities. The aluminum alloy sheet for conductive materials has dispersed therein a plurality of crystallized particles and a plurality of precipitates each composed of an intermetallic compound containing aluminum and copper. The particle diameter of the crystallized particles is 1 μm or more, and the particle diameter of the precipitates is less than 1 μm.

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

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

[0011] [Figure 1] 1 is a perspective view schematically showing a terminal using an aluminum alloy plate for conductive members according to an embodiment of the present invention. [Figure 2] 1 is a flowchart showing the manufacturing process of the aluminum alloy sheets of Samples Nos. 1 to 5. [Figure 3] 1 is a photograph showing the results of observation of a cross section (RD-ND cross section) of an aluminum alloy plate of Sample No. 2 according to an example using a transmission electron microscope. [Figure 4] 1 is a photograph showing the results of observing a cross section (RD-ND cross section) of an aluminum alloy plate of Sample No. 2 according to an example using a metallurgical microscope. [Figure 5] 1 is a photograph showing the results of observing a cross section (RD-ND cross section) of an aluminum alloy plate of Sample No. 1 according to an example using a scanning electron microscope. [Figure 6A] 1 is a graph showing the relationship between the silicon content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. [Figure 6B] 1 is a graph showing the relationship between the copper content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. [Figure 6C] 1 is a graph showing the relationship between the magnesium content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. [Figure 7A] 1 is a graph showing the relationship between the iron content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. [Figure 7B] 1 is a graph showing the relationship between the manganese content and the stress relaxation rate in an aluminum alloy plate, obtained by simulation. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] [Aluminum alloy sheets for conductive materials] The aluminum alloy sheet for conductive members according to this embodiment has an optimized aluminum alloy composition and finer crystallized particles and precipitates formed in the aluminum alloy structure, thereby improving stress relaxation characteristics and yield strength while maintaining high electrical conductivity.

[0014] The aluminum alloy plate according to this embodiment is made of an aluminum alloy having a composition containing 0.16 to 0.2 mass% silicon, 0.6 to 0.9 mass% copper, 0.2 to 0.5 mass% magnesium, 2.0 to 4.2 mass% iron, and 0 to 0.2 mass% manganese, with the remainder being aluminum and unavoidable impurities.

[0015] The aluminum used as the base material in the aluminum alloy plate is preferably pure aluminum with a purity of 99.7% by mass or more. That is, among the aluminum ingots specified in Japanese Industrial Standard JIS H2102 (aluminum ingots), those with a purity of Al99.70 or more can be preferably used. Specific examples include Al99.70, Al99.94, Al99.97, Al99.98, Al99.99, Al99.990, and Al99.995, each with a purity of 99.7% by mass or more. In this way, in this embodiment, not only expensive, high-purity aluminum such as Al99.995 can be used as the aluminum ingot, but also affordable aluminum ingots with a purity of 99.7% by mass or more can be used.

[0016] Silicon (Si) can improve the strength of aluminum alloy sheets by solid solution strengthening. However, if the silicon content exceeds 0.2 mass%, stress relaxation properties and electrical conductivity may be reduced. Therefore, the silicon content in the aluminum alloy sheets is preferably 0.16 to 0.2 mass%, and more preferably 0.17 to 0.19 mass%.

[0017] Copper (Cu) can also improve the strength of the aluminum alloy sheet through solid solution strengthening, so the aluminum alloy sheet preferably contains 0.6 to 0.9 mass %, more preferably 0.6 to 0.8 mass % of copper.

[0018] Magnesium (Mg) is an element that can increase the strength of an aluminum alloy sheet while minimizing the decrease in electrical conductivity. However, if the magnesium content exceeds 0.5 mass%, the electrical conductivity, ductility, and toughness of the resulting aluminum alloy sheet tend to decrease. Therefore, the magnesium content in the aluminum alloy sheet is preferably 0.2 to 0.5 mass%, and more preferably 0.2 to 0.3 mass%.

[0019] Iron (Fe) is an element that can increase the strength of an aluminum alloy sheet while minimizing a decrease in electrical conductivity. That is, iron has a low solid solubility limit and forms an intermetallic compound with aluminum. The dispersion of the intermetallic compound can increase the strength of the aluminum alloy sheet. As will be described later, the aluminum alloy sheet of this embodiment preferably has dispersed therein crystallized particles composed of an intermetallic compound containing aluminum, iron, and copper. The dispersion of the crystallized particles inside the aluminum alloy sheet makes it possible to obtain high yield strength and electrical conductivity while reducing the stress relaxation rate. Therefore, from the viewpoint of dispersing a large number of crystallized particles in the aluminum alloy sheet, the content of iron in the aluminum alloy sheet is preferably 2.0 to 4.2 mass%, more preferably 2.5 to 3.5 mass%.

[0020] Manganese (Mn) can improve the strength of the aluminum alloy sheet by solid solution strengthening, so the aluminum alloy sheet preferably contains 0 to 0.2 mass % of zinc, and more preferably 0.05 to 0.15 mass % of zinc.

[0021] Examples of unavoidable impurities that may be contained in the aluminum alloy sheet include gallium (Ga), boron (B), zinc (Zn), lead (Pb), sodium (Na), calcium (Ca), cobalt (Co), nickel (Ni), tin (Sn), and vanadium (V). These are unavoidably contained to the extent that they do not impair the effects of this embodiment and do not significantly affect the properties of the aluminum alloy sheet of this embodiment. Elements that are already contained in the pure aluminum ingot used are also included in the unavoidable impurities referred to here. The amount of unavoidable impurities in the aluminum alloy sheet is preferably 0.15% by mass or less in total, and more preferably 0.12% by mass or less.

[0022] The aluminum alloy sheet of this embodiment preferably contains crystallized particles and precipitates made of intermetallic compounds containing aluminum and copper. Furthermore, the aluminum alloy sheet more preferably has a plurality of crystallized particles and precipitates dispersed therein. High dispersion of such crystallized particles and precipitates within the aluminum alloy sheet increases the yield strength in a high-temperature atmosphere, thereby improving stress relaxation characteristics. Furthermore, even when the aluminum alloy sheet is used as a terminal material, it is possible to suppress plastic deformation of the terminal while suppressing stress relaxation in the bolt-fastened portion.

[0023] As described above, the precipitates are preferably composed of an intermetallic compound containing aluminum and copper. The precipitates may contain silicon and magnesium in addition to aluminum and copper. That is, the precipitates are more preferably composed of an intermetallic compound containing aluminum, copper, silicon, and magnesium. In such precipitates, the Q' phase of an AlCuSiMg quaternary system is formed as the intermetallic compound. This Q' phase is known to have the effect of slowing the progression of age hardening. Therefore, by highly dispersing the precipitates inside the aluminum alloy sheet, the yield strength in a high-temperature atmosphere can be increased and the stress relaxation rate can be reduced.

[0024] In order to improve the strength of an aluminum alloy sheet, it is effective to increase the barrier to dislocation movement. When precipitates are present in the aluminum alloy structure, dislocation lines advance while cutting through the precipitates. Therefore, for example, in hard precipitates containing copper, dislocations are less likely to advance and deformation is less likely. On the other hand, when precipitates with larger particle sizes than precipitates are present in the aluminum alloy structure, dislocation lines advance around the precipitates without cutting them, so even if hard precipitates are present, their effect of making it less likely for dislocations to advance is smaller than that of precipitates. Therefore, precipitates contribute more to improving stress relaxation properties and yield strength than precipitates.

[0025] In the precipitate, the aluminum content is preferably 90 atomic % or more. In addition, in the precipitate, the copper content is preferably 1.0 atomic % or more, and more preferably 1.5 atomic % or more. Furthermore, in the precipitate, the silicon content is preferably 0.5 atomic % or more, and more preferably 1.0 atomic % or more. The content of each element in the precipitate can be confirmed by observing the aluminum alloy plate with a transmission electron microscope (TEM) and analyzing the precipitate with energy dispersive X-ray analysis (EDX).

[0026] The particle diameter of the precipitates dispersed in the aluminum alloy sheet is less than 1 μm, and preferably 300 nm or less. A precipitate particle diameter of less than 1 μm makes it possible to achieve both high stress relaxation properties and high yield strength, and to suppress strength degradation at high temperatures. In this specification, the "particle diameter of the precipitates" refers to the longest distance between two different points on the outline of a precipitate particle when a cross section of the aluminum alloy sheet is observed under a microscope.

[0027] As described above, the precipitated material preferably comprises an intermetallic compound containing aluminum and copper. The precipitated material preferably contains 50 atomic % or more of aluminum and 1 atomic % or more of copper. Specifically, the aluminum alloy sheet is observed with a scanning electron microscope (SEM) and the precipitated material is analyzed with energy dispersive X-ray spectroscopy (EDX), and the aluminum content is preferably 50 atomic % or more and the copper content is preferably 0.3 atomic % or more. High dispersion of precipitated material with such a composition within the aluminum alloy sheet increases the yield strength in a high-temperature atmosphere and reduces the stress relaxation rate. The precipitated material preferably contains 55 atomic % or more of aluminum, more preferably 60 atomic % or more. The precipitated material preferably contains 1.0 atomic % or more of copper.

[0028] The precipitated material may contain silicon, iron, and manganese in addition to aluminum and copper. That is, the precipitated material is preferably composed of an intermetallic compound containing aluminum, copper, silicon, iron, and manganese. High dispersion of precipitated material with such a composition within the aluminum alloy sheet also increases the yield strength in a high-temperature atmosphere and reduces the stress relaxation rate. The iron content of the precipitated material is preferably 10 atomic % or more, more preferably 20 atomic % or more, and even more preferably 30 atomic % or more. The silicon content of the precipitated material is preferably 0.1 atomic % or more, and more preferably 0.4 atomic % or more. The manganese content of the precipitated material is preferably 0.2 atomic % or more, and more preferably 0.4 atomic % or more.

[0029] The particle size of the precipitated crystals dispersed in the aluminum alloy sheet is 1 μm or more, and preferably 5 μm or more. A particle size of 1 μm or more of the precipitated crystals makes it possible to achieve both high stress relaxation properties and high yield strength. Furthermore, these precipitated crystals make it possible to suppress a decrease in strength at high temperatures. The upper limit of the particle size of the precipitated crystals is not particularly limited, but can be, for example, 20 μm. In this specification, the "particle size of the precipitated crystals" refers to the longest distance between two different points on the contour of a precipitated crystal particle when the cross section of the aluminum alloy sheet is observed under a microscope.

[0030] In aluminum alloy plates, the number of crystallized particles is 6000 / mm 2 Specifically, when the aluminum alloy plate is observed with a metallurgical microscope, it is preferable that the thickness is 1 mm or more. 2 It is preferable that the number of crystallized particles per unit area is 6000 or more, which enables the aluminum alloy sheet to have high stress relaxation properties.

[0031] The particle size of the precipitated crystals tends to increase as the iron content in the aluminum alloy sheet increases. The number of precipitated crystals 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 the particle size and number of precipitated crystals. However, if the amount of precipitated crystals becomes too large, it also affects the formation of precipitates that delay the progress of age hardening. Therefore, as described above, it is necessary to optimize the composition of the aluminum alloy by adjusting the amount of added elements.

[0032] The aluminum alloy sheet of this embodiment preferably has a stress relaxation rate of 20% or less, more preferably 15% 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 120 MPa or more and an electrical conductivity of 45% IACS or more, as measured in accordance with JIS H4000:2014. Having a stress relaxation rate of 20% or less and a 0.2% yield strength of 120 MPa or more enables the suppression of stress relaxation in bolted joints and plastic deformation of terminals, even when used as a terminal material. Furthermore, an electrical conductivity of 45% IACS or more provides high electrical conductivity, making the aluminum alloy sheet suitable for use as a terminal material. The stress relaxation rate can be measured in accordance with JCBA T309:2004 (Bending stress relaxation test method for copper and copper alloy thin sheet strips) technical standard of the Japan Copper and Brass Association. The test temperature for measuring the stress relaxation rate is 150±5°C, and the test time is 1000 hours±3%. The 0.2% yield strength and electrical conductivity can be measured in accordance with the tensile test and electrical conductivity test specified in JIS H4000:2014 (Aluminum and aluminum alloy plates and strips), respectively.

[0033] Next, a method for manufacturing the aluminum alloy sheet of this embodiment will be described. The aluminum alloy sheet of this embodiment can be obtained by carrying out heat treatment under conditions equivalent to the T7 treatment of standard product A6101 specified in JIS H4000:2014.

[0034] Specifically, aluminum, silicon, copper, magnesium, iron, and optionally manganese are melted and cast to produce an ingot having the above composition. The resulting plate-shaped ingot is then preheated (pre-soaked). The preheating conditions can be, for example, 600°C for 24 hours. The preheated ingot is then subjected to a facing process as needed.

[0035] The preheated ingot is then subjected to a homogenization heat treatment. The homogenization heat treatment homogenizes the alloy components and structure, precipitates supersaturated solid-solution components, and removes internal stress. The homogenization heat treatment conditions can be 500 to 560°C for 4 to 10 hours. After the homogenization heat treatment, hot rolling is performed to obtain a hot-rolled sheet. In this case, the rolling reduction can be, for example, 90%. Next, the hot-rolled sheet is cold-rolled to obtain a cold-rolled sheet. In this case, the rolling reduction can be, for example, 80%.

[0036] Next, the cold-rolled sheet is subjected to solution treatment, quenching, and aging heat treatment. The solution treatment is performed at 520 to 550°C for 15 minutes or more to make the alloy uniform. Next, the rolled sheet after the solution treatment is quenched and quenched. Water, for example, can be used as a coolant during quenching. Thereafter, the rolled sheet is subjected to aging heat treatment. The aging heat treatment conditions can be 190 to 270°C for 4 hours or more.

[0037] As described above, in this embodiment, by performing heat treatment under conditions equivalent to those of T7 treatment, crystallized substances and precipitates are formed and highly dispersed inside the aluminum alloy sheet, and therefore, an aluminum alloy sheet for conductive members having excellent stress relaxation properties and yield strength can be obtained.

[0038] As described above, the aluminum alloy sheet for conductive materials of this embodiment contains 0.16 to 0.2 mass% silicon, 0.6 to 0.9 mass% copper, 0.2 to 0.5 mass% magnesium, 2.0 to 4.2 mass% iron, and 0 to 0.2 mass% manganese, with the remainder being aluminum and unavoidable impurities. The aluminum alloy sheet has a plurality of crystallized particles and precipitates dispersed therein, each composed of an intermetallic compound containing aluminum and copper. The crystallized particles have a particle size of 1 μm or more, and the precipitates have a particle size of less than 1 μm. The aluminum alloy sheet of this embodiment contains at least silicon, copper, magnesium, and iron in predetermined amounts, and a plurality of crystallized particles and precipitates are highly dispersed therein. The high dispersion of the crystallized particles and precipitates composed of an intermetallic compound containing at least aluminum and copper improves the 0.2% proof stress not only at room temperature but also in a high-temperature atmosphere at 150°C. Furthermore, since the crystallized substances and precipitates are highly dispersed, an increase in the stress relaxation rate can be suppressed. Furthermore, the aluminum alloy sheet of the present embodiment has high stress relaxation properties and yield strength, and also has excellent electrical conductivity, so that it can be suitably used for conductive members such as terminals.

[0039] Terminal As described above, the aluminum alloy sheet of this embodiment has high electrical conductivity and excellent stress relaxation properties and yield strength, and therefore can be suitably used as a conductive member. The conductive member is not particularly limited, but examples thereof include terminals, bus bars, connectors, relays, switches, and lead frames. The aluminum alloy sheet of this embodiment is particularly preferably used as a terminal material. Because the aluminum alloy sheet has high stress relaxation properties, yield strength, and electrical conductivity, even if stress is continuously applied to the bolted portion, the bolt is unlikely to loosen, and electrical continuity can be ensured over a long period of time. A terminal using the aluminum alloy sheet of this embodiment will now be described.

[0040] The terminal 10 according to this embodiment includes the aluminum alloy plate for conductive material described above. Specifically, the terminal 10 is formed by shaping the aluminum alloy plate for conductive material by die pressing or the like, as shown in Fig. 1(a).

[0041] The terminal 10 has a mating connection portion 11 and a wire crimping portion 12 formed integrally with the mating connection portion 11. The wire crimping portion 12 has a base portion 14, a pair of conductor crimping portions 16 extending from both side edges of the base portion 14, and a pair of insulation crimping portions 18 continuing to the rear of the conductor crimping portion 16. The mating connection portion 11 has a mounting hole 13 through which a bolt, for example, is inserted, and is formed in a substantially rectangular shape. The mating connection portion 11 is connected to a mating terminal (not shown) with a bolt and a nut.

[0042] 1(a), the electric wire 20 has a conductor 23 formed by bundling a plurality of element wires 21, and the element wires 21 are made of an aluminum alloy. An insulator layer 24 is made of an electrically insulating synthetic resin and surrounds the outer periphery of the conductor 23. At the end of the electric wire 20, the insulator layer 24 is stripped away to expose the conductor 23. The conductor crimping portion 16 of the terminal 10 is then connected to this exposed conductor 23.

[0043] When connecting an electric wire 20 to such a terminal 10, first, the front ends of the conductor 23 and the insulator layer 24 exposed at the end of the electric wire 20 are placed on the upper surface of the base portion 14. Then, as shown in FIG. 1(b), the conductor crimping portion 16 is crimped to cover the conductor 23 and is crimped to the conductor 23, and the coating crimping portion 18 is crimped to cover the front end of the insulator layer 24 and is crimped to the insulator layer 24. In this manner, the electric wire 20 can be connected to the terminal 10.

[0044] When connecting terminal 10 to a mating terminal (not shown), a bolt is inserted into mounting hole 13 and fastened with a nut. However, as mentioned above, aluminum alloy plate has excellent stress relaxation properties, so even if stress is continuously applied near mounting hole 13, stress relaxation is suppressed, making it unlikely that the bolt will loosen. This makes it possible to maintain conductivity between terminal 10 and the mating terminal for a long period of time. [Example]

[0045] Hereinafter, the present embodiment will be described in more detail with reference to examples, comparative examples and reference examples, but the present embodiment is not limited to these examples.

[0046] [Example] (Production of aluminum alloy plates) Sample No. 1 according to the example was produced according to the flowchart shown in FIG. 2. Specifically, aluminum, silicon, copper, magnesium, iron, and manganese were first weighed out in the proportions shown in Sample No. 1 in Table 1. The aluminum used was Al99.7 according to JIS H2102. The weighed aluminum, silicon, copper, magnesium, iron, and manganese were then melted to prepare a molten metal, which was then poured into a mold to obtain an ingot. The ingot was in the shape of a plate with a thickness of 50 mm, a width of 145 mm, and a length of 250 mm.

[0047] The resulting ingot was then subjected to a preheating treatment (pre-soaking treatment). The preheating treatment was carried out at 600°C for 24 hours with a temperature increase rate of 40°C / h. The surface of the preheated ingot was then chamfered to a thickness of 45 mm, a width of 140 mm, and a length of 200 mm.

[0048] The ingot after facing was then subjected to a homogenization heat treatment. The homogenization heat treatment was carried out at 540°C for 4 hours, with a temperature increase rate of 40°C / h. Next, the ingot after the homogenization heat treatment was hot rolled to obtain a hot-rolled plate. The obtained hot-rolled plate had a plate shape with a thickness of 5 mm, a width of 200 mm, and a length of 1120 mm, and the hot-rolling reduction ratio was 88.9%.

[0049] Next, the hot-rolled plate was cut into a plate shape with a thickness of 5 mm, a width of 200 mm, and a length of 250 mm. The cut hot-rolled plate was then cold-rolled to obtain a cold-rolled plate. The obtained cold-rolled plate had a thickness of 1 mm, a width of 200 mm, and a length of 250 mm, so the cold-rolling reduction ratio was 80.0%. Furthermore, the obtained cold-rolled plate was subjected to cleaning and straightening.

[0050] 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. The quenching was performed using water as a coolant. The aging heat treatment was performed at 200°C for 8 hours. In this way, an aluminum alloy sheet of Sample No. 1 according to the example was obtained.

[0051] Furthermore, aluminum alloy sheets of Samples Nos. 2 to 5 having the compositions shown in Table 1 were produced by the same manufacturing method as Sample No. 1. Sample No. 2 is a sample according to the example, and Samples Nos. 3 to 5 are samples according to comparative examples.

[0052] [Table 1]

[0053] (evaluation) <Measurement of stress relaxation rate, 0.2% yield strength and electrical conductivity> The stress relaxation rates of the aluminum alloy sheets of Samples No. 1 to No. 5 were measured in accordance with JCBA T309:2004. The test temperature for measuring the stress relaxation rate was 150±5°C, and the test time was 1000 hours±3°C. The 0.2% yield strength and electrical conductivity of the aluminum alloy sheets of Samples No. 1 to No. 5 were measured in accordance with JIS H4000:2014. The 0.2% yield strength of the aluminum alloy sheets of Samples No. 1 to No. 5 was measured at room temperature, and the 0.2% yield strength of the aluminum alloy sheets of Samples No. 1 and No. 2 was also measured at 150°C. The stress relaxation rate, 0.2% yield strength at room temperature, and electrical conductivity of each sample are summarized in Table 1.

[0054] As shown in Table 1, Samples No. 1 and 2 according to the embodiment have a stress relaxation rate of 15% or less, a 0.2% yield strength at room temperature of 120 MPa or more, and an electrical conductivity of 45% IACS or more. Therefore, it can be seen that these samples are excellent in all of electrical conductivity, stress relaxation characteristics, and yield strength at room temperature.

[0055] As shown in Table 1, the 0.2% yield strength measured at room temperature was 130 MPa for Sample No. 1 and 133 MPa for Sample No. 2. The 0.2% yield strength measured at 150°C was 121 MPa for Sample No. 1 and 136 MPa for Sample No. 2. As such, the yield strength at 150°C for these samples was not significantly lower than the yield strength at room temperature, which indicates that plastic deformation can be suppressed in these samples even at high temperatures.

[0056] In contrast, the silicon and magnesium contents of sample No. 3 according to the comparative example were too low. As a result, the 0.2% proof stress fell below 120 MPa, resulting in a deterioration. Furthermore, the silicon contents of samples Nos. 4 and 5 according to the comparative examples were too low, and the copper content of sample No. 5 was excessive. As a result, the stress relaxation rate exceeded 20%, resulting in a deterioration.

[0057] Samples Nos. 6 to 15 in Table 1 correspond to samples Nos. 1 to 10, respectively, described in the examples of Patent Document 1. Table 1 also shows the compositions, stress relaxation rates, 0.2% yield strengths, and electrical conductivities described in Patent Document 1. Table 1 reveals that the samples of Patent Document 1 have insufficient stress relaxation properties and yield strength because the silicon, copper, magnesium, and / or iron contents are outside the composition range of the present embodiment. That is, while the 0.2% yield strength of copper alloys is 150 to 300 MPa, most of the samples of Patent Document 1 have a yield strength of 100 MPa or less, indicating that the yield strength is insufficient compared to copper alloys. Furthermore, samples of Patent Document 1 with a yield strength exceeding 100 MPa have a higher stress relaxation rate than copper alloys. That is, the stress relaxation rate of copper alloys is approximately 30% when evaluated at 150°C for 1,000 hours, while the stress relaxation rate of the samples of Patent Document 1 is close to 40%. Therefore, it can be seen that the samples of Patent Document 1 do not achieve both stress relaxation properties and yield strength.

[0058] Tables 2 and 3 show the composition and temper of JIS-standard aluminum alloy sheets, as well as the stress relaxation rate, electrical conductivity, and 0.2% yield strength at room temperature and 150°C. As can be seen from Tables 2 and 3, the stress relaxation rate of the JIS-standard products exceeds 40% when evaluated at 150°C for 1000 hours, indicating that the stress relaxation properties are insufficient compared to copper alloys. Furthermore, the stress relaxation rates of A5052 (tempered O), A6061, and A6101, which have compositions similar to those of the aluminum alloy sheet of this embodiment, are 41%, 42%, and 76%, respectively, indicating that the stress relaxation properties are insufficient. In contrast, the stress relaxation rate of the aluminum alloy sheet of this embodiment is 15% or less when evaluated at 150°C for 1000 hours, indicating that the aluminum alloy sheet of this embodiment has excellent stress relaxation properties.

[0059] [Table 2]

[0060] [Table 3]

[0061] <TEM-EDX measurement of precipitates> The cross section of the aluminum alloy sheet of Sample No. 2 according to the example was observed with a transmission electron microscope (TEM), and the precipitates were analyzed with energy dispersive X-ray spectroscopy (EDX). The elements contained in the precipitates and the concentrations of the elements were measured. Figure 3 shows the results of TEM observation of the cross section of the aluminum alloy sheet of Sample No. 2. As shown in Figure 3, a large number of highly dispersed precipitates 5 were confirmed throughout the aluminum alloy sheet 1. Table 4 shows the elements contained in the precipitates and the concentrations of the elements.

[0062] [Table 4]

[0063] As shown in Table 4, it can be seen that the precipitates consist of intermetallic compounds containing at least aluminum and copper. It can also be seen that the precipitates consist of intermetallic compounds containing silicon and magnesium in addition to aluminum and copper. It is believed that the intermetallic compound is the Q' phase of an AlCuSiMg quaternary system. The aluminum content in the precipitates was 90 atomic % or more, the copper content was 1.5 atomic % or more, and the silicon content was 1.0 atomic % or more. It can be seen that the high dispersion of multiple precipitates consisting of intermetallic compounds containing aluminum and copper allows for the production of an aluminum alloy sheet that has high electrical conductivity, as well as excellent stress relaxation properties and yield strength.

[0064] <Metallurgical microscope observation> A cross section (RD-ND cross section) formed by the rolling direction (RD) and the sheet surface normal direction (ND) of Sample No. 2 according to the example was observed using a metallurgical microscope. As a result of observing the aluminum alloy sheet 1 of Sample No. 1, crystallized particles 2 were confirmed as shown in FIG. 4. FIG. 4 also shows that the crystallized particles 2 are highly dispersed throughout the aluminum alloy sheet 1. Furthermore, many crystallized particles 2 having a particle size of 1 μm or more were confirmed in the aluminum alloy structure, and many large crystallized particles having a particle size exceeding 5 μm were also present. Therefore, it can be seen that the high dispersion of crystallized particles 2 having a particle size of 1 μm or more, preferably 5 μm or more, results in good stress relaxation properties and yield strength.

[0065] Here, from the metallurgical microscope image in Figure 4, 2 The number of crystallized particles 2 per square millimeter was calculated, and the number was 11,000 particles / mm for sample No. 2. 2 Therefore, the number of crystallized particles in the aluminum alloy plate was 6000 / mm 2 It can be seen that the above results in good stress relaxation properties.

[0066] <SEM-EDX measurement of crystallized material> The cross sections of the aluminum alloy sheets of Samples No. 1 and 2 according to the examples were observed with a scanning electron microscope (SEM), and the precipitated crystals were analyzed with energy dispersive X-ray spectroscopy (EDX). The elements contained in the precipitated crystals and the concentrations of the elements were measured. Figure 5 shows the results of SEM observation of the cross section of the aluminum alloy sheet of Sample No. 1. Table 5 shows the elements contained in the precipitated crystals and the concentrations of the elements.

[0067] [Table 5]

[0068] As shown in Table 5, it can be seen that the precipitates are composed of intermetallic compounds containing at least aluminum and copper. It can also be seen that the precipitates are composed of intermetallic compounds containing silicon, manganese, and iron in addition to aluminum and copper. The aluminum content in the precipitates was 60 atomic % or more, and the copper content was 0.3 atomic % or more. The iron content in the precipitates was 30 atomic % or more, the silicon content was 0.4 atomic % or more, and the manganese content was 0.4 atomic % or more. Thus, it can be seen that by highly dispersing the precipitates primarily composed of aluminum, iron, and copper, an aluminum alloy sheet can be obtained that has high electrical conductivity, as well as excellent stress relaxation properties and yield strength.

[0069] (Simulation of composition range) Based on the physical property data (stress relaxation rate, yield strength, electrical conductivity) of aluminum alloy sheets with various compositions that were actually measured, simulations were performed using data analysis techniques to determine the composition range that would achieve the target physical properties. The target physical properties were set as a stress relaxation rate of 20% or less, a 0.2% yield strength of 120 MPa or more, and an electrical conductivity of 45% IACS or more.

[0070] Here, the stress relaxation properties were simulated using nonlinear support vector regression, which allows prediction of the stress relaxation rate for the amount of silicon, copper, magnesium, iron, and manganese added.

[0071] Specifically, the stress relaxation rate was set as the target variable, and the amount of added Si, Cu, Mg, Fe, and Mn, as well as the combined ratio of elements (for example, the Si / Cu ratio), were listed as candidates for explanatory variables, and a search was conducted to find the combination that would give the best model performance. Ultimately, seven explanatory variables were selected. The accuracy of the model was evaluated using the coefficient of determination (r 2), and the closer it is to 1, the smaller the difference between the predicted value and the actual measured value. The measured physical property data (61 samples) was then divided into training data for model creation and test data for model evaluation in a ratio of 85:15, and model creation and model performance evaluation were carried out. This model creation and model performance evaluation were repeated randomly 30 times, and the average coefficient of determination for the 30 times was 0.96, indicating that the model has sufficient predictive accuracy. Using the model created using the above method, the range in which the target physical property of stress relaxation rate can be achieved was predicted.

[0072] The 0.2% yield strength was simulated using Ridge regression based on the 0.2% yield strength measured on aluminum alloy sheets having various compositions.

[0073] The method for calculating electrical conductivity is described in the following document. The electrical conductivity was calculated based on the maximum solid solubility (wt.%) of each element (Si, Cu, Mg, Fe, Mn) in aluminum, and the average increase in resistivity (μΩ-cm) and decrease in electrical conductivity (%IACS / wt.%) when each element was added to aluminum. In other words, the electrical conductivity of the aluminum alloy was calculated from the amounts of Si, Cu, Mg, Fe, and Mn added in the aluminum alloy, as well as the maximum solid solubility, average increase in resistivity, and decrease in electrical conductivity. Minoru Yokota and Kenichi Sato, "Aluminum Wire," Light Metals, Japan Institute of Light Metals, August 30, 1982, Vol. 32, No. 8, pp. 432-440

[0074] The simulation results are shown in Table 6 and Figures 6A, 6B, 6C, 7A, and 7B. The simulation results show that the above-mentioned target physical properties can be achieved when the silicon content is in the range of 0.16 to 0.2 mass%, copper content is in the range of 0.6 to 0.9 mass%, magnesium content is in the range of 0.2 to 0.5 mass%, iron content is in the range of 2.0 to 4.2 mass%, and manganese content is in the range of 0 to 0.2 mass%.

[0075] [Table 6]

[0076] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0077] 1. Aluminum alloy sheet for conductive materials 2 Crystallized matter 5 Precipitate 10 terminals

Claims

1. The composition contains 0.16 to 0.2 mass% of silicon, 0.6 to 0.9 mass% of copper, 0.2 to 0.5 mass% of magnesium, 2.0 to 4.2 mass% of iron, and 0 to 0.2 mass% of manganese, with the balance being aluminum and inevitable impurities; A plurality of crystallized particles and a plurality of precipitates made of an intermetallic compound containing aluminum and copper are dispersed, The aluminum alloy sheet for conductive members, wherein the particle size of the crystallized particles is 1 μm or more and the particle size of the precipitates is less than 1 μm.

2. 2. The aluminum alloy sheet for conductive members according to claim 1, wherein the precipitates have an aluminum content of 90 atomic % or more and a copper content of 1.0 atomic % or more.

3. 3. The aluminum alloy sheet for conductive members according to claim 1, wherein the precipitates are composed of intermetallic compounds containing aluminum, copper, silicon, and magnesium, and an AlCuSiMg quaternary Q' phase is formed as the intermetallic compound.

4. 3. The aluminum alloy sheet for conductive members according to claim 1, wherein the aluminum content in the crystallized product is 50 atomic % or more and the copper content is 0.3 atomic % or more.

5. The number of crystallized particles is 6,000 / mm ２ The aluminum alloy sheet for conductive members according to claim 1 or 2, wherein

6. 3. The aluminum alloy sheet for use as a conductive member according to claim 1, wherein the precipitated particles are intermetallic compounds containing aluminum, copper, silicon, manganese, and iron.

7. The stress relaxation rate measured in accordance with JCBA T309:2004 when heated at 150°C for 1000 hours is 20% or less, The aluminum alloy sheet for conductive members according to claim 1 or 2, having a 0.2% yield strength measured in accordance with JIS H4000:2014 of 120 MPa or more and a conductivity of 45% IACS or more.

8. A terminal comprising the aluminum alloy sheet for conductive members according to claim 1 or 2.

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