Aluminum alloy and aluminum alloy material

Abstract

[Problem] Provided are: an aluminum alloy material having high strength, favorable moldability, and high thermal conductivity and having gradual strength reduction due to annealing; and an aluminum alloy for obtaining said aluminum alloy material. [Solution] This aluminum alloy is characterized by comprising 0.5-2.5 mass% of Fe and 0.5-2.5 mass% of Ni, with the remainder consisting of Al and inevitable impurities, wherein: the Ni content (mass%) / Fe content (mass%) is 0.3-4.0; and the total of the Fe content (mass%) and the Ni content (mass%) is 1.5-5.0 mass%.

Description

Aluminum alloys and aluminum alloy materials

[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 suitable for use in battery cases and lids.

[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 material that has been work-hardened by H24 or H14 tempering, but its strength drops sharply when maintained at temperatures above 350° C. Charge and discharge temperatures have risen in recent years as the capacity of batteries has increased, and if a work-hardened material is used, there is a risk that the material will soften during use and will not 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 response to this, the present inventors have reported in Patent Document 1 (JP 2020-50889 A) that a ferrite alloy contains 0.85 to 1.50 mass% Fe, 0.30 to 0.70 mass% Mn, 0.002 to 0.15 mass% Ti, and less than 0.05 mass% B, with the balance being Al and impurities, the Fe / Mn ratio is regulated to 1.8 to 3.5, and the impurities of Si are less than 0.40 mass% and Cu are less than 0.03 mass%. The present invention discloses an aluminum alloy sheet for battery lids for forming one-piece explosion-proof valves, characterized in that the aluminum alloy sheet has a component composition in which Mg is restricted to less than 0.05 mass% and V is restricted to less than 0.03 mass%, 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, has a recrystallized structure, and has an elongation value of 6.5% or more after cold rolling at a reduction ratio 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.

[0008] Japanese Patent Application Laid-Open No. 2020-50889

[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.

[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, and as a result, 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 an aluminum alloy characterized by containing: Fe: 0.5 to 2.5% by mass; Ni: 0.5 to 2.5% by mass; the balance consisting of Al and inevitable impurities; the Ni content (% by mass) / Fe content (% by mass) is 0.3 to 4.0; and the sum of the Fe content (% by mass) and the Ni content (% by mass) is 1.5 to 5.0% by mass.

[0013] In the aluminum alloy of the present invention, by adding Ni to the aluminum alloy containing Fe, the precipitates are Al. ３ Fe to Al ９ As a result, fine crystallized particles (Al ９ The addition of Ni to the Al matrix promotes recovery in large strain processing at room temperature, so that recrystallization is unlikely 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 having excellent ductility can be obtained, and in particular, the 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, Ni is an element that is hardly dissolved in the Al matrix, and Fe is an element that is hardly dissolved in the Al matrix. ９ Since it is discharged from the matrix as FeNi, it can impart high thermal conductivity to the aluminum alloy material.

[0015] In the aluminum alloy of the present invention, the Ni content (mass%) / Fe content (mass%) is 0.3 to 4.0. When the Ni content (mass%) / Fe content (mass%) 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%) 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%) is 4.0.

[0016] 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 making the total of the Fe content (mass%) and the Ni content (mass%) 1.5 mass% or more, a sufficient number of Al atoms can be contained to increase the strength of the aluminum alloy material. ９ On the other hand, even if the total of the Fe content (mass%) and the Ni content (mass%) exceeds 5.0 mass%, the Al content can be dispersed. ９ Further strengthening of the aluminum alloy material due to the dispersion of FeNi 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 content of Fe (% by mass) and Ni (% by mass) is set to 5.0% by mass.

[0017] Furthermore, the aluminum alloy of the present invention preferably further contains, as an optional additional element, Mn: more than 0 mass % to 1.5 mass % or less. 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 % and 1.0 mass % or less 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 generated, 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 member can be obtained.

[0023] In addition, 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 member can be obtained.

[0024] In addition, in the aluminum alloy material of the present invention, it is preferable that the average circle-equivalent diameter of the compound particles is 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. 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 setting the absolute maximum diameter of the compound particles to 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 The particle number surface density of the compound particles is preferably 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.

[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.

[0028] 1 is a graph showing the relationship between electrical conductivity and thermal conductivity of a metal material. FIG. 1 is a stress-strain curve in Example 3. FIG. 2 is a stress-strain curve in Comparative Example 1. FIG. 3 is a stress-strain curve in Comparative Example 2. FIG. 4 is a graph showing the relationship between 0.2% proof stress and annealing temperature of an aluminum alloy material. FIG. 5 is an optical microscope observation result of an aluminum alloy material obtained in Example 3. FIG. 6 is an optical microscope observation result of an aluminum alloy material obtained in Example 4. FIG. 7 is an optical microscope observation result of an aluminum alloy material obtained in Comparative Example 1. FIG. 8 is an optical microscope observation result of an aluminum alloy material obtained in Comparative Example 3. FIG. 9 is a structural observation result of an aluminum alloy material obtained in Example 3. FIG. 10 is a structural observation result of an aluminum alloy material obtained in Example 4. FIG. 11 is a structural observation result of an aluminum alloy material obtained in Comparative Example 2. FIG.

[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 Additional Elements Fe: 0.5 to 2.5% by mass The Fe content is 0.5 to 2.5% by mass. In an aluminum alloy containing an appropriate amount of Ni, by setting the Fe content to 0.5 wt% or more, the formation of Al-Fe-Ni compounds can be formed, thereby increasing the strength of the aluminum alloy material. Furthermore, by setting the Fe content to 2.5% by 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% by mass, and more preferably 1.2 to 1.8% by mass.

[0032] Ni: 0.5 to 2.5 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, the aluminum alloy material can be strengthened by forming Al-Fe-Ni compounds. 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 an aluminum alloy containing Ni is 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 an aluminum alloy material obtained by cold rolling is annealed. More specifically, even when final annealing is performed at 450°C, an unrecrystallized structure is obtained, and the decrease in strength can be suppressed.

[0034] Ni content (mass%) / Fe content (mass%): 0.3 to 4.0 The Ni content (mass%) / Fe content (mass%) is 0.3 to 4.0. When the Ni content (mass%) / Fe content (mass%) 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%) exceeds 4.0, the effect of adding Ni cannot be significantly improved, and since Ni is an expensive element, the upper limit of the Ni content (mass%) / Fe content (mass%) is 4.0. The Ni content (mass%) / Fe content (mass%) is preferably 0.5 to 3.5, and more preferably 1.0 to 2.0. Here, the value of the Ni content (mass%) / Fe content (mass%) in the aluminum alloy of the present invention is a value obtained by rounding the value obtained by calculating the Ni content (mass%) / Fe content (mass%) to one decimal place.

[0035] Sum of Fe content (mass%) and Ni content (mass%): 1.5 to 5.0 mass% The sum of the Fe content (mass%) and Ni content (mass%) is 1.5 to 5.0 mass%. By making the sum of the Fe content (mass%) and Ni content (mass%) 1.5 mass% or more, a sufficient number of Al atoms are present to increase the strength of the aluminum alloy material. ９ On the other hand, even if the total of the Fe content (mass%) and the Ni content (mass%) exceeds 5.0 mass%, the Al content can be dispersed. ９Further strengthening of the aluminum alloy material due to the dispersion of FeNi 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%. The total of the Fe content (mass%) and the Ni content (mass%) is preferably 2.0 to 4.5 mass%, and more preferably 2.5 to 4.0 mass%.

[0036] (2) Optional Added Element Mn: More than 0% by mass and 1.5% by mass or less By adding more than 0% by mass and 1.5% by mass or less of 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% by 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% by mass.

[0037] Si: More than 0% by mass and 1.0% by mass or less By adding more than 0% by mass and 1.0% by mass or less 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 generated, which can efficiently increase the strength of the aluminum alloy material. On the other hand, if the amount of Si added exceeds 1.0% by mass, eutectic Si particles are generated, which makes it easy for recrystallization to occur during final annealing, thereby decreasing the strength of the aluminum alloy material. The amount of Si added is preferably 0.05 to 0.5% by mass, and more preferably 0.07 to 0.3% by mass.

[0038] (3) Inevitable Impurities Specific examples of inevitable 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, copper (Cu) is preferably strictly excluded. Even a small amount of copper (Cu) reduces the thermal conductivity of the aluminum alloy material, making it more susceptible to intergranular corrosion and making it difficult to use as a battery material (case and lid), 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 refinement elements 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) Structure 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 prevent 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 number 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 number density of the compound particles to 50,000 particles / mm, the compound particles effectively prevent dislocation movement, and the aluminum alloy material can be provided with high strength. In addition, Fe and Ni are sufficiently discharged from the Al matrix, and the aluminum alloy material can be provided with high electrical conductivity. ２ More preferably, it is 60,000 pieces / mm or more. 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 In a tensile test at room temperature, 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. 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 has 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, the "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 may be calculated by conversion 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. Method for producing 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, but 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 the cast material is hot-rolled and cold-rolled to form an aluminum alloy plate having a desired plate thickness, and then final annealed 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.

[0054] Examples: 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 value of Ni content (mass%) / Fe content (mass%) is expressed as a value 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, the aluminum alloys according to the examples had a Ni content (mass%) / Fe content (mass%) ratio of 0.3 to 4.0, and a total of Fe content (mass%) and Ni content (mass%) of 1.5 to 5.0% by mass.

[0055]

[0056] Next, the obtained cast material was subjected to a 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 a final annealing (O treatment) at 450°C for 3 hours to obtain an aluminum alloy material according to an example of the present invention.

[0057] The microstructure of an arbitrary cross section of each of the obtained aluminum alloy materials 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]

[0059] Tensile test specimens (JIS Z2201 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 Z2241. The tensile test specimens were tensile in the 0° direction (L direction), 45° direction, and 90° direction (LT direction) 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. The electrical conductivity was measured using a digital conductivity meter (AutoSigma 3000 / DL) manufactured by Hocking, and the 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 Examples Aluminum alloy materials were obtained in the same manner as in the Examples, except that a cast aluminum alloy material having a composition shown as a comparative example in Table 1 was 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%) was 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%) was less than 1.5 mass%.

[0063] The obtained aluminum alloy materials were evaluated in the same manner as in the examples. The obtained 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 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 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 of 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] 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 in Comparative Examples 7 and 9, the compound particle number areal density is small, resulting in a 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 generated, 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 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, which have a low Ni content, and Comparative Example 10, which has a low Fe content, 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 suppress the decrease in strength due to annealing. This means that the aluminum alloy material of the present invention suppresses the decrease in strength and hardness in the heat-affected zone during welding.

[0069] 6, 7, 8 and 9 show 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. 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 etching treatment. In Examples 3 and 4, the non-recrystallized structure was maintained even after O treatment. In contrast, in Comparative Examples 2, 3, and 7, it was found that recrystallization progressed due to O treatment.

[0071] From the above results, it is clear that in order to obtain an aluminum alloy material that has high strength, good formability, and high thermal conductivity and that is subject to a gradual decrease in strength due to annealing, it is effective to optimize the contents of Ni and Fe and to perform O treatment.

Claims

1. An aluminum alloy comprising: 0.5 to 2.5 mass% Fe; 0.5 to 2.5 mass% Ni; the remainder consisting of Al and inevitable impurities; the Ni content (mass%) / Fe content (mass%) ratio is 0.3 to 4.0; and the sum of the Fe content (mass%) and the Ni content (mass%) is 1.5 to 5.0 mass%.

2. The aluminum alloy according to claim 1, further comprising, as an optional added element, Mn: more than 0 mass % and not more than 1.5 mass %.

3. An aluminum alloy according to claim 1 or 2, further comprising, as an optional added element, Si: more than 0 mass % and not more than 1.0 mass %.

4. An aluminum alloy material characterized by being made of the aluminum alloy according to claim 1 or 2.

5. The aluminum alloy material according to claim 4, characterized in that the thermal conductivity at room temperature is 200 W / m·k or more.

6. The aluminum alloy material according to claim 4, characterized in that in a tensile test at room temperature, the tensile strength is 100 MPa or more, the 0.2% yield strength is 50 MPa or more, and the total elongation is 25% or more.

7. The aluminum alloy material according to claim 6, characterized in that the uniform elongation is 15% or more in a tensile test at room temperature.

8. The aluminum alloy material according to claim 6, wherein in a tensile test at room temperature, the difference in the uniform elongation in the 0°, 45°, and 90° directions relative to the rolling direction is within 4%.

9. The aluminum alloy material according to claim 4, wherein the compound particles have an average equivalent circle diameter of 1.5 μm or less.

10. The aluminum alloy material according to claim 4, wherein the compound particles have an absolute maximum diameter of 15 μm or less.

11. The particle number surface density of the compound particles is 40,000 particles / mm ２ The aluminum alloy material according to claim 4, wherein:

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