Aluminum alloy material and method for manufacturing the same

Abstract

To provide an aluminum alloy material excellent in characteristics even when Fe or Si content is comparatively high, and a method for manufacturing the same.SOLUTION: A method for manufacturing an aluminum alloy material comprises: preparing an aluminum alloy material consisting of aluminium alloy including Si: 0.5 mass% or more and 5.0 mass% or less and Fe: 0.3 mass% or more and 3.0 mass% or less and having more than 5 μm of the maximum equivalent circle diameter of an intermetallic compound phase formed in an Al base phase; and dividing the intermetallic compound phase by introducing strain into the aluminum alloy material in a pressure of 2 GPa or more to form the maximum equivalent circle diameter of the intermetallic compound phase into 5 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an aluminum alloy material and a method for producing the same.

Background Art

[0002] Aluminum alloys utilize characteristics such as low density and high specific strength as metals, and are used in various applications such as automotive parts, aircraft parts, machine parts, and structural materials. Among these, aluminum alloys such as 5000 series alloys, 6000 series alloys, and 7000 series alloys having high strength are often used for automotive body panels and the like.

[0003] For example, in Patent Document 1, an Al-Mg-based Al alloy sheet excellent in formability is described, which has, in mass%, Mg: 3.0 to 6.0%, Si: 0.1 to 0.6%, Fe: 0.1 to 1.0%, and the balance Al as essential components, the average equivalent circle diameter of precipitates containing Fe or Si is 2 μm or less, the average aspect ratio of the precipitates is 1.8 or less, and the average crystal grain size is 30 μm or less.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, from the perspective of energy and resource conservation, the importance of technology for reusing aluminum alloy waste as a casting raw material to produce aluminum alloy materials has been increasing. However, aluminum alloy waste contains various additive elements in addition to aluminum. Among these additive elements, Fe (iron) and Si (silicon) are difficult to remove from aluminum alloys. Therefore, when aluminum alloy waste is reused as a casting raw material, there is a problem that the Fe and Si content in the recycled aluminum alloy material tends to be high. Furthermore, if the Fe and Si content in the aluminum alloy material is excessively high, coarse precipitates may form in the aluminum alloy material, potentially leading to a deterioration of the mechanical properties of the aluminum alloy material.

[0006] This invention was made in view of the above background, and aims to provide an aluminum alloy material and a method for manufacturing the same that have good properties even when the Fe and Si content is relatively high. [Means for solving the problem]

[0007] One aspect of the present invention involves preparing an aluminum alloy material having a chemical composition containing Si (silicon): 0.6% to 5.0% by mass, Fe (iron): 0.3% to 3.0% by mass, and Mg (magnesium): 0.25% to 1.2% by mass, with the remainder being Al and unavoidable impurities, wherein the maximum equivalent circle diameter of the intermetallic compound phase present in the Al matrix exceeds 5 μm. The intermetallic compound phase is broken by introducing strain into the aluminum alloy material under a pressure of 1 GPa or more. After separating the intermetallic compound phase in the aluminum alloy material, the aluminum alloy material is heated to a temperature above the solution temperature and then quenched to perform a solution treatment. The present invention relates to a method for manufacturing an aluminum alloy material in which the maximum equivalent circular diameter of the intermetallic compound phase is 5 μm or less. [Effects of the Invention]

[0008] In the manufacturing method of the above embodiment, first, an aluminum alloy material is prepared, which is an aluminum alloy in which the Si and Fe content is within the specified range. In such an aluminum alloy material, a coarse intermetallic compound phase containing Si and / or Fe is formed. By introducing strain into this aluminum alloy material under a pressure of 1 GPa or more and fragmenting the intermetallic compound phase so that the maximum equivalent circle diameter of the intermetallic compound phase in any cross-section is 5 μm or less, the influence of the coarse intermetallic compound phase on mechanical properties, etc., can be reduced. Furthermore, in the above manufacturing method, by introducing strain into the aluminum alloy material under high pressure, the crystal grains of the Al matrix in the aluminum alloy material can be refined, or the re-solubilization of additive elements in the aluminum alloy material can be promoted.

[0009] As a result, according to the manufacturing method of the above embodiment, it is possible to provide an aluminum alloy material with good properties even when the Fe and Si content is relatively high. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is an explanatory diagram of the HPT process in a reference example. [Figure 2] Figure 2 shows optical microscope images obtained by observing the HPT-processed test material B1 at various radial positions in the reference example. [Figure 3] Figure 3 is an explanatory diagram showing the stress-strain curves of test materials C1, C2, D1, and D2 in Example 1. [Modes for carrying out the invention]

[0011] In the above manufacturing method, first, an aluminum alloy material is prepared in which the Si content and Fe content are within the specified range and which contains an intermetallic compound phase. The aluminum alloy material may be, for example, an ingot or billet produced by DC casting. Alternatively, the aluminum alloy material may be a wrought material obtained by further hot working and / or cold rolling of an ingot produced by DC casting, for example. The aluminum alloy material may be subjected to heat treatment such as homogenization treatment or annealing during the manufacturing process.

[0012] The aluminum alloy material is composed of an aluminum alloy containing at least Si: 0.5% to 5.0% by mass and Fe: 0.3% to 3.0% by mass. That is, the aluminum alloy material may have a chemical composition consisting of, for example, Si: 0.5% to 5.0% by mass and Fe: 0.3% to 3.0% by mass, with the remainder being Al and unavoidable impurities. By setting the Si content and Fe content in the aluminum alloy material within the above-mentioned specific ranges, the chemical composition can be easily adjusted even when using waste aluminum alloy as a casting raw material for the aluminum alloy material.

[0013] The Si content in the aluminum alloy material is preferably more than 0.6% by mass and 5.0% by mass or less, more preferably 1.5% by mass or more and 5.0% by mass or less, and even more preferably 2.0% by mass or more and 5.0% by mass or less. In this case, the Si content can be adjusted more easily, and the range of aluminum alloy waste materials that can be used as a casting raw material for the aluminum alloy material can be broadened.

[0014] Furthermore, increasing the Si content in the aluminum alloy material allows for a larger size and greater number of intermetallic compound phases formed during casting. By introducing strain under high pressure into such an aluminum alloy material, a larger number of intermetallic compound phases can be formed in the strained aluminum alloy material. As a result, the strength of the aluminum alloy material can be further improved.

[0015] The Fe content in the aluminum alloy material is preferably 0.5% by mass or more and 3.0% by mass or less, and more preferably 1.0% by mass or more and 3.0% by mass or less. In this case, the amount of Fe can be adjusted more easily, and the range of aluminum alloy waste materials that can be used as a casting raw material for the aluminum alloy material can be broadened.

[0016] Furthermore, increasing the Fe content in the aluminum alloy material allows for larger intermetallic compound phases formed during casting, as well as an increase in the number of intermetallic compound phases. By introducing strain under high pressure into such an aluminum alloy material, a greater number of fine intermetallic compound phases can be formed in the aluminum alloy material after the strain has been introduced. As a result, the strength of the aluminum alloy material can be further improved.

[0017] The combined total of Si and Fe content in the aluminum alloy is preferably 1.0 mass% or more, more preferably 1.3 mass% or more, even more preferably 1.5 mass% or more, particularly preferably 2.5 mass% or more, and most preferably 3.5 mass% or more. By increasing the combined total of Si and Fe content in the aluminum alloy, a larger amount of intermetallic compound phase can be formed in the aluminum alloy before strain is introduced. Then, by applying strain to the aluminum alloy under high pressure and breaking up the intermetallic compound phase, the intermetallic compound phase can be finely dispersed in the final aluminum alloy. As a result, the strength of the aluminum alloy can be improved by dispersion strengthening.

[0018] In addition to Si and Fe as essential components, the aluminum alloy material may contain one or more elements selected from elements such as Mn (manganese), Mg (magnesium), Cu (copper), Zn (zinc), Cr (chromium), Zr (zirconium), Ti (titanium), B (boron) as optional components. That is, the aluminum alloy material may be any aluminum alloy of the 2000 series alloy, 3000 series alloy, 4000 series alloy, 5000 series alloy, 6000 series alloy or 7000 series alloy.

[0019] From the viewpoint of obtaining a higher-strength aluminum alloy material, it is preferable that the aluminum alloy material is composed of any aluminum alloy of the 5000 series alloy, 6000 series alloy or 7000 series alloy. The aluminum alloy made of these aluminum alloys is suitable for, for example, automobile body panels and the like.

[0020] When the aluminum alloy material is composed of a 6000 series alloy, the aluminum alloy material may have a chemical composition containing Si: more than 0.6 mass% and 5.0 mass% or less, Fe: 0.3 mass% or more and 3.0 mass% or less, and Mg: 0.25 mass% or more and 1.2 mass% or less, with the balance being Al and inevitable impurities. Further, when the aluminum alloy material is composed of a 6000 series alloy, the aluminum alloy material may further contain one or two elements selected from the group consisting of Cu: 0.05 mass% or more and 1.0 mass% or less, Mn: 0.02 mass% or more and 1.0 mass% or less, Cr: 0.01 mass% or more and 0.40 mass% or less, and Zr: 0.01 mass% or more and 0.40 mass% or less. In addition, for the purpose of refining the ingot structure, the aluminum alloy material may contain Ti (titanium): 0.01 mass% or more and 0.15 mass% or less. When 0.01 mass% or more and 0.15 mass% or less of Ti is contained in the aluminum alloy material, the aluminum alloy material may further contain B (boron): 0.0001 mass% or more and 0.05 mass% or less.

[0021] The content of Si and the content of Fe are within the specific ranges, and the aluminum alloy material before strain is introduced contains an intermetallic compound phase formed during casting. This intermetallic compound phase contains at least one of the elements Fe and Si. Also, the maximum value of the equivalent circle diameter of the intermetallic compound phase present in the aluminum alloy material exceeds 5 μm. That is, in the aluminum alloy material before the processing for introducing strain, there exists a coarse intermetallic compound phase with an equivalent circle diameter exceeding 5 μm. Here, the equivalent circle diameter of the intermetallic compound phase refers to the diameter of a circle having an area equal to the area of the intermetallic compound phase in the cross-section. Also, in the aluminum alloy material before strain is introduced, it is sufficient if the intermetallic compound phase having an equivalent circle diameter exceeding 5 μm is included in any one of various cross-sections.

[0022] Note that the aluminum alloy material before strain is introduced may contain an intermetallic compound phase with an equivalent circle diameter of 5 μm or less.

[0023] In the manufacturing method, strain is introduced into such an aluminum alloy material under a pressure of 1 GPa or more. By this processing, the coarse intermetallic compound phase existing in the aluminum alloy material before strain is introduced is divided so that the equivalent circle diameter becomes 5 μm or less in any cross-section, and the influence of the coarse intermetallic compound phase on the mechanical properties etc. of the aluminum alloy material can be reduced. Furthermore, in the manufacturing method, by introducing strain into the aluminum alloy material under high pressure, the crystal grains of the Al matrix phase in the aluminum alloy material can be refined.

[0024] In the manufacturing method, due to these effects acting synergistically, an aluminum alloy material with good properties can be obtained even when the content of Fe or Si is relatively high. Therefore, according to the manufacturing method, waste materials of aluminum alloy can be reused as casting raw materials to obtain an aluminum alloy material with good properties.

[0025] In the above-mentioned manufacturing method, various methods can be used to introduce strain into the aluminum alloy material. For example, in the above-mentioned manufacturing method, a method can be employed in which strain is introduced into the aluminum alloy material by shearing it under high pressure. One such method is HPT (High Pressure Torsion) processing, which twists the aluminum alloy material under high pressure, but the method is not limited to HPT processing, as long as it can introduce strain into the aluminum alloy material and separate the intermetallic compound phase. For example, as a method for shearing the aluminum alloy material under high pressure, HPS (High Pressure Sliding) processing, which shears the aluminum alloy material under high pressure, can be employed. Furthermore, the processing to introduce strain into the aluminum alloy material can be carried out, for example, at room temperature.

[0026] In the above manufacturing method, the aluminum alloy material subjected to strain under high pressure has a metallic structure in which the fragmented intermetallic compound phase is finely dispersed in the Al matrix, and the crystal grains of the Al matrix are refined. Therefore, the aluminum alloy material subjected to strain under high pressure has higher strength than the material before strain was introduced. Such an aluminum alloy material is particularly suitable for applications requiring high strength.

[0027] Furthermore, in the above manufacturing method, the aluminum alloy material may be tempered by performing drawing or heat treatment on the aluminum alloy material that has been strained under high pressure. For example, in the above manufacturing method, after separating the intermetallic compound phase in the aluminum alloy material, at least one of hot rolling and cold rolling may be performed on the aluminum alloy material.

[0028] Furthermore, in the above manufacturing method, the aluminum alloy material may be heated and annealed after the intermetallic compound phase in the aluminum alloy material has been broken up. In this case, the strain introduced into the aluminum alloy material can be restored, and the ductility of the aluminum alloy material can be further improved.

[0029] Furthermore, in the above manufacturing method, after separating the intermetallic compound phase in the aluminum alloy material, the aluminum alloy material can be heated to a temperature above the solution temperature and then quenched to perform solution treatment. In this case, the strain introduced into the aluminum alloy material can be restored, and the intermetallic compound phase and precipitates in the aluminum alloy material can be dissolved in the Al matrix. This makes it possible to improve the ductility and strength of the aluminum alloy material in a well-balanced manner.

[0030] If the aluminum alloy is a heat-treatable alloy, it can undergo further aging treatment after solution treatment. In this case, the strength of the aluminum alloy can be further improved while maintaining its ductility.

[0031] The aluminum alloy material obtained by the manufacturing method described above is, for example, composed of an aluminum alloy containing Si: more than 0.6 mass% and 5.0 mass% or less and Fe: more than 0.3 mass% and 3.0 mass% or less. It has a metallic structure in which an intermetallic compound phase is dispersed in an Al matrix. Furthermore, the equivalent circular diameter of the intermetallic compound phase in the aluminum alloy material is 5 μm or less.

[0032] In the aluminum alloy material produced by the above manufacturing method, the intermetallic compound phase that existed before the introduction of strain is fragmented and finely dispersed in the Al matrix. Furthermore, the introduction of strain refines the crystal grains of the Al matrix. The average crystal grain size of such an aluminum alloy material. is 2 It is 0 μm or less. Note that the average grain size of the aluminum alloy material is calculated using electron backscatter diffraction.

[0033] The aluminum alloy material may be composed of, for example, any of the following aluminum alloys: 2000 series alloy, 3000 series alloy, 4000 series alloy, 5000 series alloy, 6000 series alloy, or 7000 series alloy.

[0034] When the aluminum alloy material is composed of a 6000 series alloy, the aluminum alloy constituting the aluminum alloy material may contain Si: greater than 0.6 mass% and 5.0 mass% or less, Fe: 0.3 mass% to 3.0 mass% or less, and Mg: 0.25 mass% to 1.2 mass% or less, with the remainder being Al and unavoidable impurities. Furthermore, when the aluminum alloy material is composed of a 6000 series alloy, the aluminum alloy constituting the aluminum alloy may further contain one or two elements selected from the group consisting of Cu: 0.05 mass% to 1.0 mass%, Mn: 0.02 mass% to 1.0 mass%, Cr: 0.01 mass% to 0.40 mass%, and Zr: 0.01 mass% to 0.40 mass%. This aluminum alloy may further contain Ti: 0.01 mass% to 0.15 mass% or less. If the aluminum alloy contains Ti: 0.01% by mass or more and 0.15% by mass or less, the aluminum alloy may further contain B: 0.0001% by mass or more and 0.05% by mass or less.

[0035] As mentioned above, such aluminum alloy materials have good properties even when the Si and Fe content is relatively high, because the coarse intermetallic compound phase is broken up and the crystal grains of the Al matrix are refined during the manufacturing process. [Examples]

[0036] Examples of the aluminum alloy material and its manufacturing method described above are explained below. Note that the specific embodiments of the aluminum alloy material and its manufacturing method according to the present invention are not limited to the embodiments shown below, and the configuration can be modified as appropriate without impairing the spirit of the present invention.

[0037] (Reference example) This example describes the microstructure of an aluminum alloy material subjected to strain under high pressure. First, an ingot having the chemical composition shown in alloy symbol A1 of Table 1 is produced by DC casting. In Table 1, "Bal." indicates the remainder. The content of each element is measured using a countermeter.

[0038] Next, a disc-shaped test specimen is taken from an aluminum alloy ingot. Then, as shown in Figure 1, the test specimen 1 is sandwiched between a pair of jigs 2 (2a, 2b). In this state, the test specimen 1 is compressed in the thickness direction through the jigs 2, and one jig 2a is rotated relative to the other jig 2b, thereby torsionally deforming the test specimen 1. In this way, shear strain can be introduced into the test specimen 1.

[0039] In this example, the pressure applied to test specimen 1 is 6 GPa, and the rotation speed of jig 2a is 1 rpm. Furthermore, the process of introducing strain to test specimen 1 can be carried out at room temperature. The rotation speed of jig 2a is as shown in Table 2. As a result, test material B1 shown in Table 2 can be obtained.

[0040] The magnitude of the strain introduced into test specimen 1 is expressed as the equivalent strain. Equivalent strain ε eq Specifically, the equivalent strain can be calculated using the following formula (1), with r (in mm) being the distance from the center of specimen 1, t (in mm) being the thickness of specimen 1, and N being the number of rotations. Table 2 shows the calculated equivalent strain values ​​for each test material at positions where the distance from the center is 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm. The thickness of the specimen t is approximately 1 mm.

[0041]

number

[0042] [Table 1]

[0043] [Table 2]

[0044] Figures 2(a) to 2(f) show optical microscope images of test material B1 at positions 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm from the center, respectively. Although not shown in the figures, test material B1 before HPT processing has a metal structure in which coarse intermetallic compound phases such as Al6Fe and Al3Fe are dispersed in the Al matrix (α phase). On the other hand, as shown in Figures 2(a) to 2(f), in the metal structure of test material B1, the coarse intermetallic compound phases that were present in test material B1 before HPT processing have disappeared, and the intermetallic compound phases are finely dispersed in the Al matrix. Furthermore, from the comparison of Figures 2(a) to 2(f), it can be seen that the size of the intermetallic compound phases decreases as the amount of strain introduced into test material B1 increases.

[0045] These results demonstrate that introducing strain by torsionally deforming an aluminum alloy material under high pressure can break down coarse intermetallic compound phases such as Al6Fe and Al3Fe present in the ingot.

[0046] (Examples) This example describes an aluminum alloy material obtained by introducing strain under high pressure into an aluminum alloy rolled sheet. First, an ingot having the chemical composition shown in alloy symbol A2 in Table 1 is produced by DC casting. Hot rolling and cold rolling are performed on this ingot to produce an aluminum alloy rolled sheet. The temper of the aluminum alloy rolled sheet used in this example is H18.

[0047] Next, a disc-shaped test specimen is taken from the rolled aluminum alloy sheet. Shear strain is introduced into this specimen using the same method as in the reference example. In this example, the pressure applied to the specimen is 2 GPa, and the rotation speed of the jig is 1 rpm. The process of introducing strain into the specimen may be carried out at room temperature. The number of rotations of the jig is 1 or 10. As a result, test specimens C1 and C2 shown in Table 3 can be obtained.

[0048] Furthermore, by performing a solution treatment on test materials C1 and C2 obtained as described above, test materials D1 and D2 shown in Table 3 can be obtained. In this example, the heating temperature in the solution treatment is 550°C and the holding time is 30 minutes. Also in this example, immediately after heating is completed, the test material is immersed in water for water quenching and rapidly cooled until the temperature of the test material reaches room temperature.

[0049] In this example, tensile tests are performed using the test materials shown in Table 3 according to the method compliant with JIS Z2241:2011, thereby obtaining the stress-strain curves for each test material shown in Figure 3. The mechanical properties of each test material can be evaluated based on these stress-strain curves. Table 3 shows the tensile strength and elongation of each test material calculated based on the stress-strain curves. In Figure 3, the vertical axis represents nominal stress (unit: MPa), and the horizontal axis represents nominal strain. The tensile tests were performed at room temperature, and the initial strain rate in the tensile tests was 3.0 × 10⁻⁶. -3 s -1 Let's assume that.

[0050] Furthermore, Figure 3 shows the stress-strain curves of aluminum alloy rolled sheets (test sheets R1 and S1) that have not undergone any strain-inducing processing, for comparison with test sheets C1-C2 and D1-D2. Test sheet R1 is an aluminum alloy rolled sheet before any strain-inducing processing is applied. Test sheet S1 is an aluminum alloy rolled sheet that has been solution-treated under the conditions described above, as is done with test sheet R1.

[0051] Furthermore, the values ​​shown in the "Average Crystal Grain Size" column of Table 3 represent the average crystal grain size of the Al matrix phase in each test material, calculated by electron backscatter diffraction. The values ​​shown in the "Maximum Equivalent Circle Diameter of Intermetallic Compound Phase" column represent the maximum equivalent circle diameter of the intermetallic compound phase in each test material, calculated based on secondary electron observation images obtained by scanning electron microscopy. The symbol "-" in these columns indicates that the average crystal grain size or the maximum equivalent circle diameter of the intermetallic compound phase has not been calculated.

[0052] [Table 3]

[0053] Comparing the untreated test materials shown in Figure 3 and Table 3, test materials C1 and C2, which underwent strain-inducing processing, exhibit significantly higher tensile strength compared to test material R1, which did not undergo strain-inducing processing. Therefore, these results indicate that by applying strain-inducing processing to rolled aluminum alloy sheets under high pressure, the influence of coarse intermetallic compound phases can be reduced, resulting in aluminum alloy materials with high strength.

[0054] Furthermore, when comparing test materials that have undergone solution treatment, test materials D1 and D2, which have undergone strain-inducing processing, have higher tensile strength than test material S1, which has not undergone strain-inducing processing. In addition, test materials D1 and D2 have significantly greater elongation than test materials C1 and C2, which are manufactured using the same manufacturing method except that they have not undergone solution treatment.

[0055] Therefore, these results indicate that by subjecting an aluminum alloy rolled sheet to a process that introduces strain under high pressure, followed by solution treatment, an aluminum alloy material with excellent strength and elongation can be obtained. [Explanation of Symbols]

[0056] 1 Test specimen 2. Jig

Claims

1. An aluminum alloy material is prepared having a chemical composition containing Si: 0.6% to 5.0% by mass, Fe: 0.3% to 3.0% by mass, and Mg: 0.25% to 1.2% by mass, with the remainder being Al and unavoidable impurities, wherein the maximum equivalent circle diameter of the intermetallic compound phase formed in the Al matrix exceeds 5 μm. The intermetallic compound phase is separated by introducing strain into the aluminum alloy material under a pressure of 2 GPa or more. A method for manufacturing an aluminum alloy, comprising: breaking the intermetallic compound phase in the aluminum alloy material; then heating the aluminum alloy material to a temperature above the solution temperature and quenching it to perform a solution treatment, thereby reducing the maximum equivalent circular diameter of the intermetallic compound phase to 5 μm or less.

2. The method for producing an aluminum alloy material according to claim 1, wherein the chemical composition of the aluminum alloy material further includes one or two elements selected from the group consisting of Cu: 0.05% by mass or more and 1.0% by mass or less, Mn: 0.02% by mass or more and 1.0% by mass or less, Cr: 0.01% by mass or more and 0.40% by mass or less, and Zr: 0.01% by mass or more and 0.40% by mass or less.

3. It is an aluminum alloy having a chemical composition containing Si: more than 0.6% by mass and 5.0% by mass or less, Fe: 1.0% by mass or more and 3.0% by mass or less, and Mg: 0.25% by mass or more and 1.2% by mass or less, with the remainder being Al and unavoidable impurities. It has a metallic structure in which an intermetallic compound phase is dispersed in an Al matrix. The average crystal grain size of the Al matrix is ​​20 μm or less. An aluminum alloy material in which the maximum equivalent circular diameter of the intermetallic compound phase is 5 μm or less.

4. The aluminum alloy material according to claim 3, wherein the aluminum alloy further contains one or two elements selected from the group consisting of Cu: 0.05 mass% to 1.0 mass%, Mn: 0.02 mass% to 1.0 mass%, Cr: 0.01 mass% to 0.40 mass%, and Zr: 0.01 mass% to 0.40 mass%.

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