Aluminum alloys and aluminum alloy materials

Abstract

Provided are an aluminum alloy material that combines high strength, good formability, and high thermal conductivity and that undergoes gradual reduction in strength due to annealing, and an aluminum alloy for producing said aluminum alloy material. [Solution] An aluminum alloy characterized by containing 0.5 to 2.5 mass% Fe, 0.5 to 2.5 mass% Ni, with the remainder consisting of Al and unavoidable impurities, the Ni content (mass%) / Fe content (mass%) being 0.3 to 4.0, and the sum of the Fe content (mass%) and the Ni content (mass%) being 1.5 to 5.0 mass%.

Description

[Technical Field]

[0001] The present invention relates to an Al-Fe-Ni based aluminum alloy and aluminum alloy material, and more particularly to an aluminum alloy plate that can be suitably used for battery cases and lids. [Background technology]

[0002] Aluminum alloy materials are lightweight and have excellent workability, and are used for a variety of components, including general utensils, building materials, ship materials, fin materials, various containers, etc. For example, JIS-3003 (Al-Mn) alloy materials, which have improved strength through work hardening, are used for battery cases and lids, which require excellent heat dissipation properties.

[0003] More specifically, the battery case and lid are made of 3000-series cold-rolled aluminum alloy that has been work-hardened using H24 or H14 tempering, but its strength drops sharply when maintained at temperatures above 350°C. With the recent increase in battery capacity, charge and discharge temperatures have risen, and if work-hardened materials are used, there is a risk that they will soften during battery use and will no longer be able to maintain sufficient strength.

[0004] In addition, welding is often performed when manufacturing an aluminum alloy structure, and the heat-affected zone of the work-hardened aluminum alloy material is significantly softened, so that the strength of the aluminum alloy structure is determined by the heat-affected zone, which means that the inherent strength and reliability of the aluminum alloy material cannot be fully utilized.

[0005] Furthermore, work-hardened aluminum alloys are known to have poor ductility, particularly low uniform elongation. It is also difficult to achieve isotropic ductility, and the influence of the tensile direction on uniform elongation is significant. Therefore, work-hardened aluminum alloys are difficult to use as aluminum alloy parts that require high quality or have complex shapes.

[0006] In contrast, the present inventors have disclosed in Patent Document 1 (JP 2020-50889 A) an aluminum alloy sheet for battery lids for forming an integral explosion-proof valve, which contains 0.85 to 1.50% by mass of Fe, 0.30 to 0.70% by mass of Mn, 0.002 to 0.15% by mass of Ti, and less than 0.05% by mass of B, with the balance being Al and impurities, and the Fe / Mn ratio is regulated to 1.8 to 3.5. The impurities Si is less than 0.40% by mass, Cu is less than 0.03% by mass, Mg is less than 0.05% by mass, and V is less than 0.03% by mass. The aluminum alloy sheet has a tensile strength of 95 MPa or more, a 0.2% proof stress of 40 MPa or more, an elongation value of 40% or more, a recrystallized structure, and an elongation value of 6.5% or more after cold rolling at a rolling reduction of 80%.

[0007] The aluminum alloy plate for battery lids described in Patent Document 1 has a tensile strength of 95 MPa or more, a 0.2% yield strength of 40 MPa or more, an elongation value of 40% or more, and a recrystallized structure. In addition, the elongation value after cold rolling at a reduction ratio of 80% is 6.5% or more. Therefore, the aluminum alloy plate has appropriate strength, excellent deformation resistance, and formability. Furthermore, the explosion-proof valve formed integrally with the plate has little variation in operating pressure and excellent cyclic fatigue resistance. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-50889 Summary of the Invention [Problem to be solved by the invention]

[0009] The aluminum alloy sheet for battery lids described in Patent Document 1 has good ductility and formability, and the decrease in strength due to an increase in temperature is suppressed. However, the tensile strength is about 95 MPa, which is not sufficient for various applications.

[0010] In view of the above-mentioned problems in the conventional art, an object of the present invention is to provide an aluminum alloy material which has high strength, good formability and high thermal conductivity and which is subject to gradual reduction in strength due to annealing, and an aluminum alloy for obtaining the aluminum alloy material. [Means for solving the problem]

[0011] In order to achieve the above object, the present inventors have conducted extensive research into the relationship between the composition of an aluminum alloy material and the mechanical properties and thermal conductivity. As a result, they have found that adding appropriate amounts of Fe and Ni to an aluminum alloy material is extremely effective, and have arrived at the present invention.

[0012] That is, the present invention provides: Fe: 0.5~2.5% by mass, Ni: 0.5 to 2.5 mass %, The balance is Al and unavoidable impurities, the Ni content (mass%) / Fe content (mass%) is 0.3 to 4.0, the total of the Fe content (mass%) and the Ni content (mass%) is 1.5 to 5.0 mass%; The present invention provides an aluminum alloy characterized by:

[0013] In the aluminum alloy of the present invention, by adding Ni to an aluminum alloy containing Fe, the crystallized particles change from Al3Fe to Al9FeNi, and the crystallization temperature decreases. As a result, fine crystallized particles (Al9FeNi) are dispersed uniformly in large quantities in the Al matrix, increasing the strength of the aluminum alloy material and suppressing strength reduction in the heat-affected zone. In addition, the addition of Ni to the Al matrix promotes recovery during severe strain processing at room temperature, making it difficult for recrystallization to occur even when the aluminum alloy material obtained by cold rolling is annealed, and even an annealed O material can maintain high strength.

[0014] Furthermore, in the aluminum alloy of the present invention, since the aluminum alloy material can be strengthened without using work hardening, an aluminum alloy material with excellent ductility can be obtained, and in particular, uniform elongation can be increased. In addition, the anisotropy of ductility is reduced compared to work hardened materials, and good formability can be imparted to the aluminum alloy material. In addition, since Ni is an element that is hardly dissolved in the Al matrix, and Fe is expelled from the matrix as Al9FeNi, high thermal conductivity can be imparted to the aluminum alloy material.

[0015] In the aluminum alloy of the present invention, the Ni content (mass%) / Fe content (mass%) ratio is 0.3 to 4.0. When the Ni content (mass%) / Fe content (mass%) ratio is 0.3 or more, the effect of adding Ni can be fully exhibited. On the other hand, even if the Ni content (mass%) / Fe content (mass%) ratio exceeds 4.0, the effect of adding Ni cannot be significantly improved, and Ni is an expensive element, so the upper limit of the Ni content (mass%) / Fe content (mass%) ratio is 4.0.

[0016] Furthermore, in the aluminum alloy of the present invention, the total of the Fe content (mass%) and the Ni content (mass%) is 1.5 to 5.0 mass%. By setting the total of the Fe content (mass%) and the Ni content (mass%) to 1.5 mass% or more, a sufficient number of Al9FeNi particles can be dispersed to increase the strength of the aluminum alloy material. On the other hand, even if the total of the Fe content (mass%) and the Ni content (mass%) exceeds 5.0 mass%, further increase in the strength of the aluminum alloy material due to the dispersion of Al9FeNi cannot be expected, and there is a risk of a decrease in toughness. Furthermore, since Ni is an expensive element, the upper limit of the total of the Fe content (mass%) and the Ni content (mass%) is set to 5.0 mass%.

[0017] Furthermore, the aluminum alloy of the present invention preferably further contains, as an optional additive element, more than 0 mass % and 1.5 mass % or less of Mn. By adding an appropriate amount of Mn, it is possible to increase the strength of the aluminum alloy material while minimizing the decrease in thermal conductivity.

[0018] Furthermore, the aluminum alloy of the present invention preferably further contains, as an optional additive element, more than 0 mass% but not more than 1.0 mass% of Si. By adding an appropriate amount of Si, it is possible to increase the strength of the aluminum alloy material while minimizing the decrease in thermal conductivity. In particular, by adding Si together with Mn, Al-Si-Mn compounds are formed, which allows the aluminum alloy material to be efficiently increased in strength.

[0019] The present invention also provides an aluminum alloy material comprising the aluminum alloy of the present invention. Since the aluminum alloy material of the present invention is made of the aluminum alloy of the present invention, it has the characteristics of having high strength, good formability, and high thermal conductivity, and of having a gradual decrease in strength due to annealing.

[0020] The aluminum alloy material of the present invention preferably has a thermal conductivity of 200 W / m·k or more at room temperature. Having a thermal conductivity of 200 W / m·k or more makes it suitable for use as battery materials (cases and lids) and the like.

[0021] Furthermore, the aluminum alloy material of the present invention preferably has a tensile strength of 100 MPa or more, a 0.2% yield strength of 50 MPa or more, and a total elongation of 25% or more in a tensile test at room temperature. Because the aluminum alloy material has such tensile properties, it can be suitably used as a member that requires high strength and reliability.

[0022] Furthermore, the aluminum alloy material of the present invention preferably has a uniform elongation of 15% or more in a tensile test at room temperature. When the aluminum alloy material exhibits a uniform elongation of 15% or more, a good formed part can be obtained.

[0023] Furthermore, it is preferable that the aluminum alloy material of the present invention has a difference in uniform elongation of 4% or less in the directions of 0°, 45°, and 90° relative to the rolling direction in a tensile test at room temperature. When the aluminum alloy material has isotropic uniform elongation, a good formed product can be obtained.

[0024] In addition, in the aluminum alloy material of the present invention, it is preferable that the compound particles have an average circle-equivalent diameter of 1.5 μm or less. When the compound particles have an average circle-equivalent diameter of 1.5 μm or less, a sufficient number of compound particles can be dispersed in the Al matrix, and the intervals between the compound particles can be narrowed. As a result, the compound particles effectively hinder the movement of dislocations, and high strength can be imparted to the aluminum alloy material. Here, the compound particles in the aluminum alloy material of the present invention are Al-Fe-Ni-based compounds or Al-Si-Mn-based compounds.

[0025] In the aluminum alloy material of the present invention, the compound particles preferably have an absolute maximum diameter of 15 μm or less. By making the compound particles have an absolute maximum diameter of 15 μm or less, fracture originating from the compound particles or the compound particle / Al matrix interface can be suppressed.

[0026] Furthermore, in the aluminum alloy material of the present invention, the particle number surface density of the compound particles is 40,000 particles / mm 2 It is preferable that the particle number surface density of the compound particles is 40,000 particles / mm 2 By doing so, the compound particles can effectively hinder the movement of dislocations, imparting high strength to the aluminum alloy material, and in addition, Fe and Ni are sufficiently discharged from the Al matrix, imparting high electrical conductivity to the aluminum alloy material. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide an aluminum alloy material that has high strength, good formability, and high thermal conductivity and that undergoes gradual reduction in strength due to annealing, and an aluminum alloy for obtaining the aluminum alloy material. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a graph showing the relationship between the electrical conductivity and thermal conductivity of a metal material. [Figure 2] 10 is a stress-strain curve in Example 3. [Figure 3] 1 is a stress-strain curve in Comparative Example 1. [Figure 4] 10 is a stress-strain curve in Comparative Example 2. [Figure 5] 1 is a graph showing the relationship between 0.2% proof stress and annealing temperature of an aluminum alloy material. [Figure 6] 1 shows the results of optical microscope observation of the aluminum alloy material obtained in Example 3. [Figure 7] 1 shows the results of optical microscope observation of the aluminum alloy material obtained in Example 4. [Figure 8] 1 shows the results of optical microscope observation of the aluminum alloy material obtained in Comparative Example 1. [Figure 9] 1 shows the results of optical microscope observation of the aluminum alloy material obtained in Comparative Example 3. [Figure 10] 1 shows the results of observing the structure of the aluminum alloy material obtained in Example 3. [Figure 11] 1 shows the results of observing the structure of the aluminum alloy material obtained in Example 4. [Figure 12] 1 shows the results of observing the structure of the aluminum alloy material obtained in Comparative Example 2. [Figure 13] 1 shows the results of observing the structure of the aluminum alloy material obtained in Comparative Example 3. [Figure 14] 1 shows the results of observation of the structure of the aluminum alloy material obtained in Comparative Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0029] Representative embodiments of the aluminum alloy and aluminum alloy material of the present invention will be described in detail below, but the present invention is not limited to these.

[0030] 1. Aluminum alloy The aluminum alloy of the present invention has an optimized content of Fe and Ni, in particular, to impart high strength, good formability, and high thermal conductivity to the aluminum alloy material and to suppress a decrease in strength due to annealing. Each of the component elements of the aluminum alloy of the present invention will be described below.

[0031] (1) Essential additive elements Fe:0.5~2.5% by mass The Fe content is 0.5 to 2.5 mass%. In an aluminum alloy containing an appropriate amount of Ni, by setting the Fe content to 0.5 wt% or more, Al-Fe-Ni compounds are formed, thereby increasing the strength of the aluminum alloy material. Furthermore, by setting the Fe content to 2.5 mass% or less, the formation of coarse Al-Fe-Ni compounds that reduce toughness and ductility can be suppressed. The Fe content is preferably 1.0 to 2.0 mass%, and more preferably 1.2 to 1.8 mass%.

[0032] Ni: 0.5~2.5% by mass The Ni content is 0.5 to 2.5 mass%. In an aluminum alloy containing an appropriate amount of Fe, by setting the Ni content to 0.5 wt% or more, Al-Fe-Ni compounds are formed, thereby increasing the strength of the aluminum alloy material. Furthermore, by setting the Ni content to 2.5 mass% or less, the formation of coarse Al-Fe-Ni compounds that reduce toughness and ductility can be suppressed. The Ni content is preferably 1.0 to 2.0 mass%, and more preferably 1.2 to 1.8 mass%.

[0033] Ni is an element that is hardly dissolved in the Al matrix at room temperature, and when Ni-added aluminum alloys are subjected to large strain processing at room temperature, a phenomenon occurs in which strength decreases. This is due to the progress of recovery associated with processing in the large strain range. By utilizing this phenomenon, an unrecrystallized structure can be obtained even when annealing aluminum alloy materials obtained by cold rolling. More specifically, even when final annealing is performed at 450°C, an unrecrystallized structure is obtained, and strength loss can be suppressed.

[0034] Ni content (mass%) / Fe content (mass%): 0.3 to 4.0 The Ni content (mass%) / Fe content (mass%) ratio is 0.3 to 4.0. When the Ni content (mass%) / Fe content (mass%) ratio is 0.3 or more, the effect of Ni addition can be fully exhibited. On the other hand, even if the Ni content (mass%) / Fe content (mass%) ratio exceeds 4.0, the effect of Ni addition cannot be significantly improved, and Ni is an expensive element, so the upper limit of the Ni content (mass%) / Fe content (mass%) ratio is 4.0. The Ni content (mass%) / Fe content (mass%) ratio is preferably 0.5 to 3.5, and more preferably 1.0 to 2.0. Here, the Ni content (mass%) / Fe content (mass%) ratio in the aluminum alloy of the present invention is calculated by rounding the value obtained by the calculation of the Ni content (mass%) / Fe content (mass%) to one decimal place.

[0035] Total of Fe content (mass%) and Ni content (mass%): 1.5 to 5.0 mass% The total of the Fe content (mass%) and the Ni content (mass%) is 1.5 to 5.0 mass%. By setting the total of the Fe content (mass%) and the Ni content (mass%) to 1.5 mass% or more, a sufficient number of Al9FeNi particles can be dispersed to increase the strength of the aluminum alloy material. On the other hand, even if the total of the Fe content (mass%) and the Ni content (mass%) exceeds 5.0 mass%, further increase in the strength of the aluminum alloy material due to the dispersion of Al9FeNi cannot be expected, and there is a risk of a decrease in toughness. In addition, since Ni is an expensive element, the upper limit of the total of the Fe content (mass%) and the Ni content (mass%) is 5.0 mass%. The total of the Fe content (mass%) and the Ni content (mass%) is preferably 2.0 to 4.5 mass%, more preferably 2.5 to 4.0 mass%.

[0036] (2) Optional additive elements Mn: More than 0% by mass and 1.5% by mass or less By adding more than 0 mass% and not more than 1.5 mass% Mn, it is possible to increase the strength of the aluminum alloy material while minimizing the decrease in thermal conductivity. On the other hand, if the amount of Mn added exceeds 1.5 mass%, the thermal conductivity of the aluminum alloy material will be less than 200 W / m·k. The amount of Mn added is preferably 0.5 to 1.0 mass%.

[0037] Si: More than 0 mass% and 1.0 mass% or less By adding Si in an amount of more than 0 mass% and not more than 1.0 mass%, it is possible to increase the strength of the aluminum alloy material while minimizing the decrease in thermal conductivity. In particular, by adding Si together with Mn, Al-Si-Mn compounds are formed, which can efficiently increase the strength of the aluminum alloy material. On the other hand, if the amount of Si added exceeds 1.0 mass%, eutectic Si particles are formed, which are likely to recrystallize during final annealing, thereby decreasing the strength of the aluminum alloy material. The amount of Si added is preferably 0.05 to 0.5 mass%, and more preferably 0.07 to 0.3 mass%.

[0038] (3) Inevitable impurities Specific examples of unavoidable impurity elements include magnesium (Mg), copper (Cu), zinc (Zn), lithium (Li), nickel (Ni), titanium (Ti), calcium (Ca), sodium (Na), strontium (Sr), yttrium (Y), niobium (Nb), molybdenum (Mo), tungsten (W), antimony (Sb), beryllium (Be), phosphorus (P), vanadium (V), tin (Sn), lead (Pb), bismuth (Bi), cobalt (Co), silver (Ag), gallium (Ga), scandium (Sc), cerium (Ce), boron (B), carbon (C), nitrogen (N), and oxygen (O). However, it is preferable to strictly exclude copper (Cu). Even a small amount of copper (Cu) reduces the thermal conductivity of aluminum alloy materials and makes them susceptible to intergranular corrosion, making them difficult to use as battery materials (cases and lids), etc.

[0039] These inevitable impurity elements may be present inevitably in aluminum ingots, may be mixed inevitably during the production of aluminum alloys, or may be modifier elements when grain refiners such as titanium, boron, and zirconium are intentionally added. The content of these inevitable impurity elements is not particularly limited as long as it does not impair the effects of the present invention, but each element is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and particularly preferably 0.2% by mass or less. The content of each element can be measured by ICP atomic emission spectroscopy, inert gas fusion-infrared absorption spectroscopy, or the like.

[0040] 2. Aluminum alloy material The aluminum alloy material of the present invention has high strength, good formability, and high thermal conductivity, and is suppressed from decreasing in strength due to annealing. The structure and each feature of the aluminum alloy material of the present invention will be described below.

[0041] (1) Organization The aluminum alloy material of the present invention has a structure in which compound particles (second phase particles) such as Al-Fe-Ni based compounds and Al-Si-Mn based compounds are dispersed in an Al matrix.

[0042] The average circle-equivalent diameter of the compound particles is preferably 1.5 μm or less. By making the average circle-equivalent diameter of the compound particles 1.5 μm or less, a sufficient number of compound particles can be dispersed in the Al matrix, and the intervals between the compound particles can be narrowed. As a result, the compound particles effectively hinder the movement of dislocations, and high strength can be imparted to the aluminum alloy material. The average circle-equivalent diameter of the compound particles is more preferably 1.0 μm or less.

[0043] The absolute maximum diameter of the compound particles is preferably 15 μm or less. By setting the absolute maximum diameter of the compound particles to 15 μm or less, it is possible to suppress fracture originating from the compound particles or the compound particle / Al matrix interface. The absolute maximum diameter of the compound particles is more preferably 10 μm or less, and most preferably 8 μm or less.

[0044] The particle surface density of the compound particles is 40,000 particles / mm 2 The particle number surface density of the compound particles is preferably 40,000 particles / mm 2 By setting the particle density to the above, the compound particles can effectively prevent dislocation movement, and high strength can be imparted to the aluminum alloy material. In addition, Fe and Ni are sufficiently discharged from the Al matrix, and high electrical conductivity can be imparted to the aluminum alloy material. The particle number surface density of the compound particles is 50,000 particles / mm 2 More preferably, it is 60,000 pieces / mm 2 More preferably, it is equal to or greater than this.

[0045] The method for determining the average circle-equivalent diameter, absolute maximum diameter, and particle number areal density of the compound particles is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known methods may be used. For example, the aluminum alloy material may be cut at an arbitrary cross section, and the resulting cross-sectional sample may be observed using an optical microscope or a scanning electron microscope. Here, information about the compound particles can be extracted simply and efficiently by binarizing the obtained microstructure photograph using image processing. Depending on the observation method, the cross-sectional sample may be subjected to mechanical polishing, buffing, electrolytic polishing, etching, or the like.

[0046] (2) Tensile properties The aluminum alloy material of the present invention preferably has a tensile strength of 100 MPa or more, a 0.2% yield strength of 50 MPa or more, and a total elongation of 25% or more in a tensile test at room temperature. Because the aluminum alloy material has such tensile properties, it can be suitably used as a component requiring high strength and reliability. The tensile strength is more preferably 120 MPa or more, and most preferably 140 MPa or more. The 0.2% yield strength is more preferably 60 MPa or more, and most preferably 70 MPa or more. The total elongation is more preferably 30% or more, and most preferably 35% or more.

[0047] Furthermore, the aluminum alloy material of the present invention preferably has a uniform elongation of 15% or more in a tensile test at room temperature. When the aluminum alloy material exhibits a uniform elongation of 15% or more, a good formed part can be obtained. The uniform elongation is more preferably 18% or more, and most preferably 20% or more.

[0048] Furthermore, in a tensile test at room temperature, the aluminum alloy material of the present invention preferably exhibits a difference in uniform elongation of 4% or less in the 0°, 45°, and 90° directions relative to the rolling direction. The aluminum alloy material has isotropic uniform elongation, which allows for the production of a good formed part. Here, "difference in uniform elongation" refers to the difference in absolute values ​​measured for tensile test specimens taken so that the tensile direction is 0°, 45°, and 90° relative to the rolling direction. The difference in uniform elongation is more preferably 3% or less, and most preferably 2% or less.

[0049] (3) Thermal conductivity The aluminum alloy material of the present invention preferably has a thermal conductivity of 200 W / m·k or more at room temperature. Having a thermal conductivity of 200 W / m·k or more allows it to be suitably used as a battery material (case and lid). The thermal conductivity is more preferably 220 W / m·k or more, and most preferably 240 W / m·k or more.

[0050] The method for measuring the thermal conductivity of an aluminum alloy material is not particularly limited, and can be measured by various conventionally known methods such as the flash method or the temperature gradient method. Alternatively, the thermal conductivity can be calculated from the electrical conductivity. It is known that the electrical conductivity and thermal conductivity of a metal material have a relationship according to the Wiedemann-Franz law, as shown in Figure 1 (Kobe Steel Technical Report, Vol. 71, No. 2, June 2022, p. 29).

[0051] 3. Manufacturing method of aluminum alloy material The method for producing the aluminum alloy material of the present invention is not particularly limited as long as the effects of the present invention are not impaired. However, by using the aluminum alloy of the present invention and performing O treatment as final annealing, it is possible to obtain an aluminum alloy material that has uniform tensile properties and good ductility, and that exhibits good formability and high thermal conductivity.

[0052] More specifically, for example, a cast material made of the aluminum alloy of the present invention is subjected to a homogenization treatment, and then hot-rolled and cold-rolled to form an aluminum alloy plate having a desired thickness, followed by final annealing at 300 to 500°C, thereby obtaining the aluminum alloy material of the present invention.

[0053] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. [Example]

[0054] Example Cast aluminum alloys having the compositions shown in Table 1 were obtained by DC continuous casting. Table 1 also lists the values ​​of "Ni content (mass%) / Fe content (mass%)" and "total of Fe content (mass%) and Ni content (mass%)." The Ni content (mass%) / Fe content (mass%) values ​​are expressed as values ​​up to one decimal place, obtained by rounding the value obtained by calculating Ni content (mass%) / Fe content (mass%) to one decimal place. In all cases of the aluminum alloys according to the examples, the Ni content (mass%) / Fe content (mass%) ratio was 0.3 to 4.0, and the total of the Fe content (mass%) and Ni content (mass%) was 1.5 to 5.0 mass%.

[0055] [Table 1]

[0056] Next, the obtained cast material was subjected to homogenization treatment at 560°C for 6 hours, and then hot-rolled to a plate thickness of 7 mm, and cold-rolled to a final plate thickness of 1 mm, and then subjected to final annealing (O treatment) at 450°C for 3 hours to obtain an aluminum alloy material as an example of the present invention.

[0057] The microstructure of an arbitrary cross section of each aluminum alloy material obtained was observed using an optical microscope. The obtained microstructure photographs were binarized using commercially available image processing software, and compound particles dispersed in the Al matrix were extracted. In addition, the circle-equivalent mean diameter, absolute maximum diameter, and particle number surface density of the extracted compound particles were determined. Here, the circle-equivalent diameter is the diameter of a circle equivalent to the area of ​​each extracted compound particle, and the absolute maximum diameter is the largest value among the diameters passing through the center of gravity of the compound particle and connecting two points on the periphery of the compound particle. The obtained values ​​are shown in Table 2.

[0058] [Table 2]

[0059] Tensile test specimens (JIS Z 2201 14B test specimens) were taken from each aluminum alloy material, and the tensile properties were evaluated at room temperature according to the tensile test method of JIS Z 2241. The tensile test specimens were tensile in the 0° (L direction), 45°, and 90° (LT direction) directions relative to the rolling direction. Total elongation and uniform elongation were measured. The obtained tensile properties are shown in Table 2.

[0060] Next, the electrical conductivity of each aluminum alloy material was measured, and the obtained electrical conductivity was converted to thermal conductivity. A digital conductivity meter (AutoSigma 3000 / DL) manufactured by Hocking was used to measure the electrical conductivity, and thermal conductivity was calculated as four times the electrical conductivity using the relationship shown in Figure 1. The obtained electrical conductivity and thermal conductivity are shown in Table 2.

[0061] Comparative Example Aluminum alloy materials were obtained in the same manner as in the Examples, except that cast aluminum alloy materials having the compositions shown as Comparative Examples in Table 1 were used. Here, only Comparative Example 1 was subjected to H24 treatment instead of O treatment. The H24 treatment conditions were 280°C for 3 hours.

[0062] Here, in Comparative Examples 1 to 3, the Ni content (mass%) / Fe content (mass%) ratio is less than 0.3, and in Comparative Examples 1 to 6, 9, and 11, the sum of the Fe content (mass%) and the Ni content (mass%) is less than 1.5 mass%.

[0063] The obtained aluminum alloy materials were evaluated in the same manner as in the examples. The evaluation results are shown in Table 2. As shown in Table 2, the example aluminum alloy materials had a tensile strength of 100 MPa or more, a 0.2% proof stress of 50 MPa or more, and a total elongation of 25% or more for all compositions and in all tensile directions. Although the example aluminum alloy materials were subjected to O treatment, the strength reduction due to annealing was gradual, so a tensile strength of 100 MPa or more was maintained. Furthermore, the example aluminum alloy materials had a uniform elongation of 15% or more for all compositions and in all tensile directions, and the difference in uniform elongation in the 0°, 45°, and 90° directions relative to the rolling direction was within 4%.

[0064] In contrast, in Comparative Example 1, which was work-hardened by H24 treatment, both the total elongation and uniform elongation were low, and in addition, the differences in elongation in the 0°, 45°, and 90° directions relative to the rolling direction were extremely large. Furthermore, in Comparative Example 2, in which an aluminum alloy material with the same composition as Comparative Example 1 was subjected to O treatment, the total elongation and uniform elongation were improved, but the 0.2% proof stress was low, and the differences in uniform elongation in the 0°, 45°, and 90° directions relative to the rolling direction exceeded 4%. As representative examples, the stress-strain curves of Example 3, Comparative Example 1, and Comparative Example 2 are shown in Figures 2, 3, and 4, respectively. It can be seen that the aluminum alloy material of Example 3 has isotropic tensile properties compared to the aluminum alloy materials of Comparative Examples 1 and 2.

[0065] Furthermore, for example, in the aluminum alloy materials of Comparative Examples 7 to 9, the difference in uniform elongation in the 0°, 45°, and 90° directions relative to the rolling direction is small, but the compound particle number areal density is small in Comparative Examples 7 and 9, resulting in low 0.2% yield strength. Furthermore, since Comparative Example 7 contains 2 mass% Si, eutectic Si (compound particle circle-equivalent mean diameter: 1.7 μm, absolute maximum diameter: 17.7 μm) is formed, which recrystallizes after final annealing at 450°C, resulting in a decrease in strength. In Comparative Example 8, coarse compound particles are formed, resulting in a low thermal conductivity. Comparative Example 11, which contains a small amount of Ni, also has a thermal conductivity of less than 200 W / m·k.

[0066] Furthermore, in Comparative Examples 3 to 6 in which the Ni content is low and Comparative Example 10 in which the Fe content is low, the 0.2% yield strength of the aluminum alloy material is low.

[0067] In order to evaluate the decrease in strength of the aluminum alloy material due to the annealing treatment, the aluminum alloy materials obtained in Example 3, Example 4, Comparative Example 1, and Comparative Example 3 were additionally annealed, and tensile tests in the rolling direction were carried out in the same manner as above. The annealing temperatures were 300°C, 350°C, 400°C, 450°C, and 500°C, and the holding time was 3 hours. The relationship between the obtained 0.2% proof stress and the annealing temperature is shown in Figure 5.

[0068] The work-hardened aluminum alloy material of Comparative Example 1 has high strength at room temperature, but when annealed at a temperature of 350°C or higher, the 0.2% proof stress is significantly reduced. On the other hand, the aluminum alloy material of Comparative Example 3, which was subjected to O treatment, shows a small decrease in strength due to annealing, but the absolute value of the 0.2% proof stress is low. In contrast, the aluminum alloy materials obtained in Examples 3 and 4 not only have high strength at room temperature, but also show a suppressed decrease in strength due to annealing. This means that the aluminum alloy material of the present invention suppresses a decrease in strength and hardness in the heat-affected zone during welding.

[0069] The results of optical microscope observation of the cross sections of the aluminum alloy materials obtained in Example 3, Example 4, Comparative Example 1 and Comparative Example 3 are shown in Figures 6, 7, 8 and 9, respectively. Compared with Comparative Example 1 and Comparative Example 3, it can be seen that a large number of fine compound particles are dispersed in Examples 3 and 4.

[0070] The results of structural observation of the cross sections of Example 3, Example 4, Comparative Example 2, Comparative Example 3, and Comparative Example 7 are shown in Figures 10, 11, 12, 13, and 14, respectively. The cross sections were subjected to an etching treatment. In Examples 3 and 4, the non-recrystallized structure was maintained even after the O treatment. In contrast, in Comparative Examples 2, 3, and 7, it was found that recrystallization progressed due to the O treatment.

[0071] From the above results, it is clear that optimizing the Ni and Fe contents and performing O treatment are effective in obtaining an aluminum alloy material that combines high strength, good formability, and high thermal conductivity and that undergoes gradual strength degradation due to annealing.

Claims

1. Fe: 0.5 to 2.5% by mass, Ni: 0.5 to 2.5% by mass, Contains Si: more than 0% by mass and 1.0% by mass or less, the balance being Al and inevitable impurities, The Ni content (mass%) / Fe content (mass%) is 0.3 to 4.0, The aluminum alloy has a total content (mass%) of the Fe and the Ni (mass%) of 1.5 to 5.0 mass%, The compound particles have an average equivalent circle diameter of 1.5 μm or less, the compound particles have a particle number surface density of 40,000 particles / mm 2 or more; The thermal conductivity at room temperature is 200 W / m·k or more, In tensile tests at room temperature in the 0° direction, 45° direction, and 90° direction relative to the rolling direction, the tensile strength is 100 MPa or more, the 0.2% proof stress is 50 MPa or more, and the total elongation is 25% or more, To be used for battery cases and battery covers; An aluminum alloy rolled material characterized by:

2. The aluminum alloy contains more than 0 mass% and not more than 1.5 mass% Mn, The rolled aluminum alloy material according to claim 1,

3. In the tensile test, the uniform elongation is 15% or more, 3. The rolled aluminum alloy material according to claim 1 or 2,

4. In the tensile test, the difference in uniform elongation is within 4%. The rolled aluminum alloy material according to claim 3,

5. The absolute maximum diameter of the compound particles is 15 μm or less.

3. The rolled aluminum alloy material according to claim 1 or 2,

Images