Al-Mg-Si-Ni alloys and Al-Mg-Si-Ni alloy materials

Abstract

Provided are a high-strength 6000 series aluminum alloy having exceptional plastic workability even when the Fe content is increased in association with recycling of scrap material, and an aluminum alloy material composed of said aluminum alloy. The present invention relates to an Al-Mg-Si-Ni alloy characterized by containing more than 0 to 2.0 wt% of Fe and containing Ni such that 0.7≤Ni (wt%) / Fe (wt%)≤3.5. The alloy preferably contains 0.5-1.4 wt% of Si, 0.6-1.7 wt% of Mg, 0.1-2.5 wt% of Ni, and 0.1-2.0 wt% of Fe, the balance being Al and inevitable impurities.

Description

[Technical Field]

[0001] This invention relates to a high-strength aluminum alloy material with excellent plasticity, and more particularly to an aluminum alloy and aluminum alloy material suitable for recycling using scrap materials. [Background technology]

[0002] 6000 series aluminum alloy is one of the most widely used heat-treatable aluminum alloys. It is primarily an Al-Mg-Si alloy with added Mg and Si, exhibiting excellent formability and corrosion resistance, as well as moderate age hardening and good strength. It is widely used as a structural component in transportation equipment, including automobiles.

[0003] However, in recent years, there has been a growing demand for lighter transportation equipment to improve fuel efficiency and reduce CO2 emissions, and there is a strong need for higher strength and toughness in 6000 series aluminum alloy materials. In response to this, for example, Patent Document 1 (Japanese Patent Application Publication No. 2017-155251) describes an aluminum alloy forging material containing, by mass%, Si: 0.7~1.5%, Mg: 0.6~1.2%, Fe: 0.01~0.5%, and further containing one or more of Mn: 0.05~1.0%, Cr: 0.01~0.5%, and Zr: 0.01~0.2%, with the remainder being Al and unavoidable impurities, and the microstructure of the observation surface at the center of the thickness of the thickest part of this forging material has an average dislocation density of 1.0 × 10⁻⁶ as measured by X-ray diffraction. 14 ~5.0×10 16 / m 2 The range is such that, as measured by SEM-EBSD, the average proportion of small-angle grain boundaries with an inclination angle of 2-15° for crystal grains with an orientation difference of 2° or more is 50% or more, and the average number density of precipitates measurable by TEM at a magnification of 300,000x is 5.0 × 10⁻⁶. 2 pieces / μm 3 An aluminum alloy forged material with excellent strength and ductility, characterized by the above, is disclosed.

[0004] In the aluminum alloy forging member described in Patent Document 1 above, in the case of a 6000-series aluminum alloy forging material, when a working strain is imparted by warm working to the forging material that has been solutionized and quenched, and then artificial aging treatment is performed, both the strength and the ductility are improved (strengthened and highly ductile) compared to the normal case where no working strain is imparted. Therefore, in order to exhibit or guarantee such an effect, as the structure at the center of the thickness of the thickest part of the forging material after artificial aging treatment, the average dislocation density, the average ratio of small-angle grain boundaries, and the average number density of precipitates are each defined.

[0005] Among 6000-series aluminum alloys, Al-Mg-Si-Cu-based hypereutectic Si alloys have high strength and low deformation resistance, and thus are used for plastic processed materials such as extruded materials, rolled materials, and forging materials that require high strength.

[0006] In Patent Document 2 (Japanese Patent Application Laid-Open No. 2020-164946), the present inventors defined the tensile strength of a test piece with the L direction as the longitudinal direction as UTS L and defined the Charpy value of a test piece with the L direction as the longitudinal direction as S L After performing a solution treatment at 550°C for 5 minutes and further performing an artificial aging treatment at 17�°C for 14 hours, the UTS L is 340 MPa or more, and the S L is 16.0 J / cm 2 or more, and disclosed an Al-Mg-Si-based aluminum alloy cold-rolled sheet.

[0007] In the cold-rolled aluminum alloy sheet described in Patent Document 2 above, by limiting the Si / Mg ratio of the Al-Mg-Si aluminum alloy to the range of 0.4 to 0.9 and reducing the amount of excess Si and excess Mg, the width of the PFZ generated during artificial aging can be reduced, and the growth of intermetallic compounds such as β" and β' that precipitate as intermediate phases at the grain boundaries can be suppressed. As a result, the aluminum alloy after solution treatment and aging can be made to have excellent impact resistance. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-155251 [Patent Document 2] Japanese Patent Publication No. 2020-164946 [Overview of the project] [Problems that the invention aims to solve]

[0009] Because aluminum smelting consumes a large amount of electricity, there has been a growing demand in recent years for recycling aluminum scrap, driven by environmental concerns such as global warming. However, aluminum inevitably tends to become contaminated with iron (Fe), and this tendency becomes more pronounced as the proportion of scrap material used as raw material increases.

[0010] While Fe also has the effect of increasing the strength of aluminum, in aluminum alloys containing Si, it forms Al-Fe-Si precipitates. However, in this case, Si, a constituent element of Mg2Si that precipitates during aging and contributes to improving the strength of the aluminum alloy, is consumed by the formation of Al-(Fe,M)Si precipitates, so precipitation strengthening may not be sufficiently achieved.

[0011] Furthermore, when the Fe content in an aluminum alloy is high, Al-Fe-Si precipitates tend to become coarser. Since these coarse precipitates become the starting points for fracture, it becomes impossible to impart excellent ductility and toughness to the aluminum alloy, and good plastic workability cannot be obtained.

[0012] In contrast, the aluminum alloy forged material described in Patent Document 1 and the aluminum alloy cold-rolled sheet described in Patent Document 2 do not take into consideration the effects of Fe, which is inevitably mixed in, and therefore the proportion of scrap material in the raw materials cannot be sufficiently increased.

[0013] In view of the problems of the prior art described above, the object of the present invention is to provide a high-strength 600-series aluminum alloy and an aluminum alloy material made from said aluminum alloy that have excellent plastic workability even when the Fe content increases due to the recycling of scrap material. [Means for solving the problem]

[0014] In order to achieve the above objective, the inventors diligently researched the relationship between the composition, structure, and mechanical properties of Fe-containing 6000 series aluminum alloy materials. As a result, they discovered that in order to obtain a high-strength 6000 series aluminum alloy material with excellent plastic workability, it is extremely effective to preferentially crystallize Al-Fe-Ni compounds over Al-Fe-Si compounds by adding Ni, and thus arrived at the present invention.

[0015] In other words, the present invention is Fe greater than 0 and less than 2.0 wt%, It contains Ni such that 0.7 ≤ Ni(wt%) / Fe(wt%) ≤ 3.5. We provide an Al-Mg-Si-Ni alloy characterized by the following:

[0016] The Al-Mg-Si-Ni alloy of the present invention contains Fe in an amount exceeding 0 and not exceeding 2.0 wt%. However, due to the addition of an appropriate amount of Ni, Al-Fe-Ni compounds preferentially crystallize, and the amount of Si crystallizing as Al-Fe-Si compounds decreases, effectively suppressing the decrease in the amount of Si dissolved in the matrix phase. As a result, a sufficient amount of Mg-Si compounds can be precipitated by aging treatment, and high strength can be exhibited in the aluminum alloy by precipitation strengthening. The action effect can be surely obtained by setting Ni(wt%) / Fe(wt%) to 0.7 or more, but no further improvement can be obtained even if Ni with Ni(wt%) / Fe(wt%) of 3.5 or more is added.

[0017] In addition, the Al-Mg-Si-Ni alloy of the present invention Si: 0.5 to 1.4 wt%, Mg: 0.6 to 1.7 wt%, Ni: 0.1 to 2.5 wt%, Fe: 0.1 to 2.0 wt%, and it is preferable that the balance consists of Al and inevitable impurities.

[0018] By setting the content of Si to 0.5 wt% or more, solid solution strengthening and age hardening can be sufficiently exhibited, and by setting it to 1.4 wt% or less, a decrease in corrosion resistance and a decrease in ductility due to coarsening of crystallized substances and precipitates can be suppressed. Further, by setting the content of Si to 0.6 to 0.8 wt%, these effects can be more surely obtained.

[0019] In addition, by setting the content of Mg to 0.6 wt% or more, a sufficient amount of Mg-Si precipitates can be formed, enhancing strength and fatigue characteristics, and by setting the content of Mg to 1.7 wt% or less, the formation of coarse compounds that become the starting point of fracture can be suppressed. By setting the content of Mg to 1.0 to 1.4 wt%, these effects can be more surely obtained.

[0020] In addition, the Al-Mg-Si-Ni alloy of the present invention Cu: 0.2 to 1.0 wt%, Mn: 0.1~0.8 wt%, It is preferable that the material contains one or more of the following: Cr: 0.1 to 0.8 wt%.

[0021] By adding 0.2 to 1.0 wt% Cu, the mechanical strength and fatigue strength can be increased by forming precipitates (Q phase or Q' phase). Furthermore, by adding 0.1 to 0.8 wt% Mn or 0.1 to 0.8 wt% Cr, the strength of the aluminum alloy can be increased by forming Al-(Fe,Mn,Cr)-Si compounds.

[0022] Furthermore, the Al-Mg-Si-Ni alloy of the present invention is Zr: 0.05~0.20 wt%, V: 0.05~0.20 wt%, Ti: 0.01~0.15 wt%, It is preferable that the material contains one or more of the following: B: 0.001 to 0.05 wt%.

[0023] By including an appropriate amount of one or more of Zr, V, Ti, and B, it is possible to achieve micronization of the structure and stabilization of the processed structure.

[0024] Furthermore, it is preferable that the Al-Mg-Si-Ni alloy of the present invention has a Mg(wt%) / Si(wt%) ratio of 1.73 or higher. By setting the Mg(wt%) / Si(wt%) ratio to 1.73 or higher, a sufficient amount of Mg-Si compounds can be precipitated by aging treatment, and high strength can be achieved in the aluminum alloy material through precipitation strengthening.

[0025] Furthermore, the present invention also provides an Al-Mg-Si-Ni alloy material characterized by being made of the Al-Mg-Si-Ni alloy of the present invention and having an Al-Fe-Ni compound dispersed in it.

[0026] The Al-Mg-Si-Ni alloy material of the present invention has Fe rendered harmless by the addition of an appropriate amount of Ni, resulting in an aluminum alloy material with excellent plastic workability and high strength. Since Al-Fe-Ni compounds are less prone to coarsening than Al-Fe-Si compounds, the formation of coarse compounds that become fracture initiation points when stress is applied is suppressed. As a result, fine Al-Fe-Ni compounds are dispersed and crystallized, which imparts excellent plastic workability and toughness to the aluminum alloy.

[0027] In the Al-Mg-Si-Ni alloy material of the present invention, it is preferable that it has tensile properties of a 0.2% yield strength of 300 MPa or more and an elongation at break of 12% or more. Because the Al-Mg-Si-Ni alloy material has a 0.2% yield strength of 300 MPa or more and an elongation of 12% or more, it can be suitably used in structural members where high reliability is required. Furthermore, since sufficient ductility is ensured and it has excellent plastic workability, it can be used as a plastically deformable material such as an extruded material, a rolled material, and a forged material.

[0028] Furthermore, it is preferable that the Al-Mg-Si-Ni alloy material of the present invention has a limiting bending angle of 50° or more in the VDA bending test specified in VDA238-100. Having a limiting bending angle of 50° or more in the VDA bending test of the Al-Mg-Si-Ni alloy material allows for processing steps that require large plastic deformation. [Effects of the Invention]

[0029] According to the present invention, even when the Fe content increases due to the recycling of scrap materials, it is possible to provide a high-strength 600-series aluminum alloy with excellent plastic workability and an aluminum alloy material made from said aluminum alloy. [Brief explanation of the drawing]

[0030] [Figure 1] This is the X-ray diffraction pattern of an actual aluminum alloy material having the composition of Example 4. [Figure 2]This is the X-ray diffraction pattern of an actual aluminum alloy material having the composition of Example 8. [Figure 3] This is an optical microscope image of an actual aluminum alloy material having the composition of Example 4. [Figure 4] This is an optical microscope image of an actual aluminum alloy material having the composition of Example 8. [Figure 5] This is an optical microscope image of an actual aluminum alloy material having the composition of Example 9. [Figure 6] This is the X-ray diffraction pattern of a comparative aluminum alloy material having the composition of Comparative Example 4. [Figure 7] This is an optical microscope image of a comparative aluminum alloy material having the composition of Comparative Example 4. [Figure 8] This is an optical microscope image of a comparative aluminum alloy material having the composition of Comparative Example 8. [Figure 9] This is a photograph of the appearance of a comparative aluminum alloy material having the composition of Comparative Example 11. [Figure 10] This is an optical microscope image of a comparative aluminum alloy material having the composition of Comparative Example 9. [Figure 11] This is an optical microscope image of a comparative aluminum alloy material having the composition of Comparative Example 10. [Figure 12] This is an optical microscope image of a comparative aluminum alloy material having the composition of Comparative Example 11. [Modes for carrying out the invention]

[0031] Hereinafter, representative embodiments of the Al-Mg-Si-Ni alloy and Al-Mg-Si-Ni alloy material of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these embodiments.

[0032] 1.Al-Mg-Si-Ni alloy The Al-Mg-Si-Ni alloy of the present invention is characterized by the addition of Ni to a 6000 series aluminum alloy in order to preferentially crystallize Al-Fe-Ni compounds over Al-Fe-Si compounds to detoxify Fe, and to utilize dispersion strengthening by Al-Fe-Ni compounds. Each component will be described in detail below.

[0033] (1) Essential additive elements Si: 0.5~1.4 wt% The Si content is preferably 0.5 to 1.4 wt%. A Si content of 0.5 wt% or more allows for sufficient solid solution strengthening and age hardening, while a Si content of 1.4 wt% or less suppresses a decrease in corrosion resistance and a decrease in ductility due to the coarsening of crystals and precipitates. A more preferable Si content is 0.6 to 0.8 wt%. These effects can be more reliably obtained by having a Si content of 0.6 to 0.8 wt%.

[0034] Mg: 0.6~1.7 wt% The Mg content is preferably 0.6 to 1.7 wt%. A Mg content of 0.6 wt% or more allows for the formation of a sufficient amount of Mg-Si precipitates, improving strength and fatigue properties. A Mg content of 1.7 wt% or less suppresses the formation of coarse compounds that can trigger fracture. A more preferable Mg content is 1.0 to 1.4 wt%. These effects can be more reliably obtained by setting the Mg content to 1.0 to 1.4 wt%.

[0035] Ni: 0.1~2.5 wt% The Ni content is preferably 0.1 to 2.5 wt%, assuming a Ni(wt%) / Fe(wt%) ratio of 0.7 to 3.5. A Ni content of 0.1 wt% or more allows for the crystallization of Al-Fe-Ni compounds. Furthermore, a Ni content of 2.5 wt% or less helps to suppress the increase in raw material costs due to excessive Ni addition. A Ni content of 0.2 to 1.1 wt% is more preferable, and 0.3 to 1.0 wt% is most preferable.

[0036] Fe: 0.1~2.0 wt% The Fe content is preferably 0.1 to 2.0 wt%. Allowing a Fe content of 0.1 to 2.0 wt% allows for the suitable use of scrap material as a raw material. Furthermore, with a Fe content of 0.1 to 2.0 wt%, the effects of the Fe can be reliably neutralized by the addition of Ni. A Fe content of 0.15 to 1.1 wt% is more preferable.

[0037] In the Al-Mg-Si-Ni alloy of the present invention, the Ni(wt%) / Fe(wt%) value is 0.7 to 3.5. By setting the Ni(wt%) / Fe(wt%) value to 0.7 to 3.5, Al-Fe-Ni compounds can be preferentially crystallized without adding excess Ni, reducing the amount of Si crystallized as Al-Fe-Si compounds and effectively suppressing the decrease in the amount of Si solid solution in the matrix. As a result, a sufficient amount of MgSi compounds can be precipitated by aging treatment, and high strength can be achieved in the aluminum alloy through precipitation strengthening. A more preferable range for Ni(wt%) / Fe(wt%) is 1.0 to 3.0, and the most preferable range is 1.1 to 2.0.

[0038] Furthermore, it is preferable that the Mg(wt%) / Si(wt%) ratio is 1.73 or higher. By setting the Mg(wt%) / Si(wt%) ratio to 1.73 or higher, a sufficient amount of MgSi-based compounds can be precipitated by aging treatment, and high strength can be achieved in the aluminum alloy through precipitation strengthening. A more preferable range for Mg(wt%) / Si(wt%) is 1.73 to 2.00, and the most preferable range is 1.75 to 1.95.

[0039] (2) Any additive element Cu: 0.2~1.0 wt% The Cu content is preferably 0.2 to 1.0 wt%. Cu enhances mechanical strength and fatigue strength by forming Al, Mg, Si, Cu-based quaternary precipitates (Q phase or Q' phase). These effects cannot be fully obtained if the Cu content is less than 0.2 wt%. On the other hand, if the Cu content exceeds 1.0 wt%, there is a risk of reducing corrosion resistance.

[0040] Mn: 0.1~0.8wt% The Mn content is preferably 0.1 to 0.8 wt%. By setting the Mn content to 0.1 wt% or more, the aluminum alloy can be strengthened by the formation of Al-(Fe,Mn,Cr)-Si compounds. Conversely, by setting the Mn content to 0.8 wt% or less, the formation of coarse Al-(Fe,Mn,Cr)-Si compounds, which reduce toughness and ductility, can be suppressed.

[0041] Cr: 0.1~0.8 wt% The Cr content is preferably 0.1 to 0.8 wt%. By setting the Cr content to 0.1 wt% or more, the aluminum alloy can be strengthened by the formation of Al-(Fe,Mn,Cr)-Si compounds. Conversely, by setting the Cr content to 0.8 wt% or less, the formation of coarse Al-(Fe,Mn,Cr)-Si compounds that reduce toughness and ductility can be suppressed.

[0042] Zr: 0.05~0.20 wt% Zr has the effect of suppressing recrystallization and stabilizing the processed structure by pinning the compound. This effect can be fully exhibited by having a content of 0.05 wt% or more, and the decrease in ductility due to the coarsening of the compound can be suppressed by having a content of 0.20 wt% or less.

[0043] V: 0.05~0.20 wt% By adding 0.05 wt% or more of V, Al-V dispersed particles are formed, which suppress grain boundary movement and recrystallization, exhibiting a so-called pinning effect and contributing to strength. Furthermore, by limiting the amount of V added to 0.20 wt% or less, the decrease in ductility associated with the coarsening of Al-V dispersed particles can be suppressed.

[0044] Ti: 0.01~0.15 wt% When Ti is added in combination with B, it forms Al-Ti and Ti-B compounds, which refine the cast structure, prevent casting cracks, and promote the homogenization of the added elements. These effects are insufficient at amounts less than 0.01 wt%, and adding amounts exceeding 0.15 wt% not only saturates the effect but also forms coarse Al-Ti precipitates, reducing toughness. Furthermore, by solid-solving Ti in Al, the growth of reinforcing phases such as Al2Cu and Al2CuMg precipitates at high temperatures is suppressed, allowing for stable acquisition of high strength.

[0045] B: 0.001~0.05 wt% The addition of B can refine the microstructure of the casting. This refinement effect can be fully achieved by using a B content of 0.001 wt% or more, and by using a B content of 0.05 wt% or less, the decrease in ductility caused by the formation of coarse compounds can be suppressed. In order to obtain the effect of refining the microstructure of the casting, it is preferable to add B to the molten alloy immediately before casting.

[0046] 2.Al-Mg-Si-Ni alloy material The Al-Mg-Si-Ni alloy material of the present invention is an aluminum alloy material made from the Al-Mg-Si-Ni alloy of the present invention. The microstructure and mechanical properties of the Al-Mg-Si-Ni alloy material will be described in detail below.

[0047] (1) Organization The Al-Mg-Si-Ni alloy material of the present invention is characterized by the dispersion of fine Al-Fe-Ni compounds.

[0048] Since the formation energy of Al-Fe-Ni compounds is lower than that of Al-Fe-Si compounds, adding a small amount of Ni to an Al-Mg-Si alloy allows for the fine crystallization of Al-Fe-Ni compounds before the crystallization of Al-Fe-Si compounds. Here, the formation energy of Al2FeNi is -0.52 eV, while the formation energy of Al2(FeSi)3 is -0.481 eV, the formation energy of AlFe2Si is -0.46 eV, and the formation energy of Al2Fe3Si4 is -0.431 eV.

[0049] Furthermore, Al-Fe-Ni compounds can be crystallized more finely than Al-Fe-Si compounds. The uniform dispersion of these fine Al-Fe-Ni compounds allows for highly effective dispersion strengthening; therefore, when the Fe and Ni content is high, this dispersion strengthening can be used to increase the strength of the aluminum alloy. Even with high Fe and Ni content, the Al-Fe-Ni compounds do not become coarser; rather, their number can be increased.

[0050] By allowing the Al-Fe-Ni compound to crystallize finely before the Al-Fe-Si compound crystallizes, a sufficient amount of Si solid solution can be secured after solution treatment. This allows for increased strength while maintaining high toughness during subsequent heat treatment. In other words, even with aluminum alloys made from scrap material and containing a relatively large amount of Fe, excellent toughness and high strength can be simultaneously imparted.

[0051] The average particle size of the Al-Fe-Ni compound dispersed in the Al-Mg-Si-Ni alloy material is preferably 15 μm or less, more preferably 10 μm or less, and most preferably 5 μm or less. By setting the average particle size of the Al-Fe-Ni compound to these values, the decrease in toughness and ductility caused by the Al-Fe-Ni compound can be suppressed, and dispersion strengthening can be utilized. The method for determining the average particle size of the Al-Fe-Ni compound is not particularly limited; for example, the average particle size of the Ni-containing compound can be determined from optical microscope images, SEM-EDS mapping, or EPMA mapping of the cross-section of the Al-Mg-Si-Ni alloy material.

[0052] Furthermore, it is preferable that 80% or more of the precipitates dispersed in the Al-Mg-Si-Ni alloy material are Al-Fe-Ni compounds. A more preferable proportion of Al-Fe-Ni compounds is 85% or more, and the most preferable proportion of Al-Fe-Ni compounds is 90% or more. The method for determining the proportion of Al-Fe-Ni compounds is not particularly limited; for example, the proportion of Ni-containing compounds can be determined from SEM-EDS mapping or EPMA mapping of the cross-section of the Al-Mg-Si-Ni alloy material. Alternatively, quantitative values ​​from various elemental analyses may be used, or it may be calculated from the peak intensity of the diffraction pattern obtained by XRD measurement.

[0053] (2) Mechanical properties The 0.2% yield strength of Al-Mg-Si-Ni alloy materials is preferably 300 MPa or higher, more preferably 330 MPa or higher, and most preferably 360 MPa or higher. Furthermore, the elongation at break of Al-Mg-Si-Ni alloy materials is preferably 12% or higher, more preferably 13% or higher, and most preferably 14% or higher. Because Al-Mg-Si-Ni alloy materials possess these tensile properties, they can be suitably used in structural members where high reliability is required. In addition, since sufficient ductility is ensured and they have excellent plastic workability, they can be used as plastically deformed materials such as extruded materials, rolled materials, and forged materials.

[0054] Furthermore, for Al-Mg-Si-Ni alloy materials, it is preferable that the limit bending angle of the VDA bending test specified in VDA238-100 is 50° or higher. A more preferable limit bending angle is 60° or higher, and the most preferable limit bending angle is 70° or higher. Having a limit bending angle of these values ​​or higher in the VDA bending test for Al-Mg-Si-Ni alloy materials allows for processing steps that require large plastic deformation.

[0055] VDA is a German Association of the Automotive Industry standard (Verband der Automobilindustrie), and VDA238-100 is specified as a plate bending test aimed at evaluating the cracking behavior during material crushing.

[0056] The method for manufacturing the Al-Mg-Si-Ni alloy material is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known methods for manufacturing aluminum alloy materials can be used with the Al-Mg-Si-Ni alloy of the present invention.

[0057] Although typical embodiments of the present invention have been described above, the present invention is not limited to these, and various design modifications are possible, all of which fall within the technical scope of the present invention. [Examples]

[0058] Examples Aluminum alloy slabs with a thickness of 70 mm were obtained by DC continuous casting, having the compositions shown as examples in Table 1. The components in Table 1 are shown in wt%. Table 1 also shows the Ni(wt%) / Fe(wt%) and Mg(wt%) / Si(wt%) values. For all compositions shown as examples, the Ni(wt%) / Fe(wt%) value is within the range of 0.7 to 3.5.

[0059] Next, the obtained slab was homogenized at 540°C for 6 hours and then hot-rolled to a thickness of 6 mm. Subsequently, it was cold-rolled to a thickness of 2 mm and then subjected to T6 heat treatment to obtain the aluminum alloy material of the present invention. The T6 heat treatment involved holding at 557°C for 2 hours, followed by water cooling and aging treatment at 175°C.

[0060] [Table 1]

[0061] The obtained aluminum alloy material was cut and mirror-polished to prepare a cross-sectional sample. Next, X-ray diffraction patterns were obtained from the cross-section using X-ray diffraction, and the compounds were identified. The X-ray diffraction patterns of the aluminum alloy materials having the compositions of Example 4 and Example 8 are shown in Figures 1 and 2, respectively. In the aluminum alloy material having the composition of Example 4, only peaks attributable to Al, Al9(FeNi)2, and Mg2Si were clearly observed. In the aluminum alloy material having the composition of Example 8, peaks attributable to Al, Al9(FeNi)2, and Mg2Si were clearly observed, and a small peak attributable to α-Al(Fe·M)Si was also confirmed. From these results, it can be seen that most of the compounds formed are Al-Fe-Ni compounds.

[0062] Furthermore, the obtained aluminum alloy material was cut and mirror-polished to prepare cross-sectional observation samples, and the microstructure was observed using an optical microscope. Optical microscope images of the aluminum alloy materials having the compositions of Examples 4, 8, and 9 are shown in Figures 3, 4, and 5, respectively.

[0063] A large number of fine Al-Fe-Ni compounds are dispersed, and no Al-Fe-Ni compounds with a particle size of 10 μm or larger are observed. Furthermore, even when the amount of Fe and Ni added is high (Example 9), the Al-Fe-Ni compounds do not become coarser, and it can be seen that the number of dispersed Al-Fe-Ni compounds has increased significantly.

[0064] Table 2 shows the tensile properties of each of the experimental aluminum alloy materials obtained. The tensile test specimens used were No. 14A specimens as described in JIS Z 2241, and the tensile speed was set in accordance with JIS Z 2241, at 2 mm / min up to the 0.2% yield strength and 5 mm / min thereafter. As shown in Table 2, the experimental aluminum alloy material of the present invention possesses both a 0.2% yield strength at 300 MPa and an elongation of 12% or more.

[0065] [Table 2]

[0066] Furthermore, a VDA bending test, as specified in VDA238-100, was performed on each of the obtained aluminum alloy materials to evaluate the limit bending angle. The obtained limit bending angles are shown in Table 2. The limit bending angle was evaluated in both the L direction (rolling direction) and the LT direction (direction perpendicular to the rolling direction), and all of the obtained aluminum alloy materials showed a value of 50° or higher.

[0067] ≪Comparative Example≫ A comparative aluminum alloy material was obtained in the same manner as in the examples, except that an aluminum alloy slab having the composition shown as a comparative example in Table 1 was used. The obtained comparative aluminum alloy material was also evaluated in the same manner as in the examples.

[0068] Figure 6 shows the X-ray diffraction pattern of the comparative aluminum alloy material having the composition of Comparative Example 4. When the compounds formed on the comparative aluminum alloy material having the composition of Comparative Example 4 were identified by X-ray diffraction, peaks originating from Al and α-Al(Fe·M)Si were clearly observed.

[0069] Optical microscope images of comparative aluminum alloy materials having the compositions of Comparative Example 4 and Comparative Example 8 are shown in Figures 7 and 8, respectively. Comparing the microstructures of Comparative Example 4 and Example 8, whose main difference is the presence or absence of Ni addition, it can be seen that the compound of Comparative Example 4 is coarser. This result indicates that the compound is refined by the addition of Ni.

[0070] When comparing the microstructures of Comparative Example 8 and Example 9, where the main difference is the presence or absence of Ni addition, in the case of a high Fe content (approximately 1 wt%), it can be seen that the compound in Comparative Example 8 is coarser. This result indicates that even with a high Fe content, the compound is refined by the addition of Ni.

[0071] Table 2 shows the tensile properties and limiting bending angles of each comparative aluminum alloy material obtained. None of the comparative aluminum alloy materials met all of the following criteria: 0.2% yield strength of 300 MPa or higher, elongation of 12% or higher, and limiting bending angle of 50° or higher.

[0072] For example, comparing the mechanical properties of Comparative Example 4 and Example 8, where the main difference is the presence or absence of Ni addition, Comparative Example 4 does not reach a limiting bending angle of 50° in the L direction, and therefore cannot exhibit sufficient plastic workability. Furthermore, comparing Comparative Example 8, which has a high Fe content, with Example 9, Comparative Example 8 does not reach a 0.2% yield strength of 300 MPa, and therefore cannot be used as a high-strength member.

[0073] Furthermore, in Comparative Examples 9 and 10, which contained a large amount of Fe and no Ni, precipitation strengthening by Mg2Si could not be sufficiently achieved, resulting in low 0.2% proof stress values. In particular, Comparative Example 10, which had a higher Fe content, had an extremely low 0.2% proof stress of 211 MPa.

[0074] In Comparative Example 11, Ni was added to the composition of Comparative Example 10. However, when the Fe content was too high, coarse Fe-based primary crystals were formed, and a good sheet material could not be obtained. Figure 9 shows a photograph of the appearance of the aluminum alloy material in Comparative Example 11, and it can be seen that many cracks occurred and a smooth surface was not obtained.

[0075] Optical microscope images of comparative aluminum alloy materials having the compositions of Comparative Examples 9, 10, and 11 are shown in Figures 10, 11, and 12, respectively. In Comparative Example 10, which has a high Fe content, the formation of coarse Fe-based primary crystals is observed. In Comparative Example 11, which has Ni added, the width of the iron-based primary crystals is thinner, but when the Fe content is too high, the coarsening cannot be completely suppressed.

[0076] From the above results, it can be seen that by using the Al-Mg-Si-Ni alloy of the present invention, even when the Fe content is increased, a high-strength aluminum alloy material with excellent plastic workability can be obtained as long as the Fe content is 2.0 wt% or less.

Claims

1. Ni such that 0.7 ≤ Ni (wt%) / Fe (wt%) ≤ 3.5, Si: 0.5-1.4wt%, Mg: 0.6 to 1.7 wt%, Ni: 0.1 to 2.5 wt%, It contains Fe: 0.1 to 2.0 wt%, The remainder consists of Al and unavoidable impurities. Al-Fe-Ni compounds are dispersed, It has tensile properties such as a 0.2% yield strength of 300 MPa or more and an elongation at break of 12% or more. The limit bending angle for the VDA bending test specified in VDA238-100 must be 50° or greater. An Al-Mg-Si-Ni alloy material characterized by the following features.

2. Cu: 0.2 to 1.0 wt%, Mn: 0.1 to 0.8 wt%, Cr: Contains one or more of the following: 0.1 to 0.8 wt%, The Al-Mg-Si-Ni alloy material according to claim 1, characterized by the above.

3. Zr: 0.05 to 0.20 wt%, V: 0.05-0.20wt%, Ti: 0.01-0.15wt%, B: Contains one or more of the following in an amount of 0.001 to 0.05 wt%, The Al-Mg-Si-Ni alloy material according to claim 1 or 2, characterized by the above.

4. The ratio of Mg (wt%) to Si (wt%) is 1.73 or more. The Al-Mg-Si-Ni alloy material according to claim 1 or 2, characterized by the above.

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