Aluminum alloy material for a vehicular component, a vehicular component manufactured thereof, and a method of manufacturing a vehicular component

Abstract

An aluminum alloy material for a vehicular component is provided. The aluminum alloy material includes 0.1 wt % or less of Si, 0.1 wt % or less of Fe, 0.1 to 0.4 wt % of Cu, 1.0 to 1.5 wt % of Mg, 4.5 to 5.5 wt % of Zn, 0.04 wt % of Ti, 0.2 wt % of Zr, and the balance being Al on the wt % basis. This aluminum alloy material exhibits improved properties in terms of yield strength, tensile strength, and elongation ratio, all of which contribute to the lightweighting of a vehicle.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Korean Patent Application No. 10-2023-0100719, filed on Aug. 1, 2023, which is incorporated herein by reference in its entirety.BACKGROUNDField of the Disclosure

[0002] The present disclosure relates to an aluminum alloy material for a vehicular component, such as a seat cross member.Description of Related Art

[0003] To address the lightweighting challenges posed by vehicular electrification, there is an increasing demand for extrudates for vehicular components. Accordingly, there is also an increasing need to develop high-strength aluminum alloys that allow for the thinning of these extrudates.

[0004] Korean Patent Application Publication No. 10-2008-0109347 discloses a technology related to the strength of a component, such as a seat cross member, which is used in a vehicular center floor.

[0005] A comparatively high-strength aluminum extrudate in the related art has a yield strength of 320 MPa, a tensile strength of 370 MPa, and an elongation ratio of 13% or higher.

[0006] However, a reduction in the weights of the vehicular component requires the continuous development of higher-strength materials.

[0007] The matters described above are intended to help an understanding of the background of the present disclosure and may include matters that, although not referred to as the related art, are known to a person of ordinary skill in the art to which the present disclosure pertains.SUMMARY

[0008] An object of the present disclosure, which is contrived to find a solution to the above-mentioned problem, is to provide an aluminum alloy material for a vehicle component, a vehicular component manufactured of the aluminum alloy material, and a method of manufacturing the vehicular component. The aluminum alloy material is capable of having improved properties in terms of yield strength, tensile strength, elongation ratio, and the like, all of which contribute to the lightweighting of a vehicle.

[0009] According to an aspect of the present disclosure, an aluminum alloy material for a vehicular component is provided, wherein the material includes: 0.1 wt % or less of silicon (Si); 0.1 wt % or less of iron (Fe); 0.1 to 0.4 wt % of copper (Cu); 1.0 to 1.5 wt % of magnesium (Mg); 4.5 to 5.5 wt % of zinc (Zn); 0.04 wt % or less of titanium (Ti); 0.2 wt % or less of zirconium (Zr); and the balance being aluminum (Al).

[0010] According to another aspect of the present disclosure, there is provided a vehicular component manufactured by extruding the aluminum alloy material and then performing a two-step heat treatment on an extrudate resulting from the extrusion.

[0011] In the vehicular component, the two-step heat treatment may be performed on the extrudate: primarily at a temperature of ranging from 80° C. to 120° C. for 3 to 6 hours, and secondarily at a temperature of ranging from 130° C. to 180° C. for 8 to 15 hours.

[0012] In the vehicular component, the aluminum alloy material may have a yield strength of 401 MPa or more.

[0013] In the vehicular component, the aluminum alloy material may have a tensile strength of 436 MPa or more.

[0014] In the vehicular component, the aluminum alloy material may have an elongation ratio of 16.3% or higher.

[0015] According to still another aspect of the present disclosure, there is provided a method of manufacturing a vehicular component, the method including: extruding the aluminum alloy material; and performing a two-step heat treatment on an extrudate resulting from the extrusion.

[0016] In the method, the performing of the two-step heat treatment may include: primarily performing a heat treatment on the extrudate at a temperature ranging from 80° C. to 120° C. for 3 to 6 hours; and secondarily performing a heat treatment on the extrudate at a temperature ranging from 130° C. to 180° C. for 8 to 15 hours.

[0017] The aluminum alloy material according to the present disclosure has the properties, including a yield strength of 401 MPa or more, a tensile strength of 436 MPa or more, and an elongation ratio of 16.3% or higher. The vehicular component manufactured of the aluminum alloy material can contribute to the lightweighting of a vehicle.

[0018] In addition, the aluminum alloy material has a uniform microstructure, and the corrosion resistance thereof is increased. The vehicular component, which has demonstrated high performance in corrosion evaluation, can be manufactured.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 depicts images of examples of an aluminum alloy material according to the present disclosure that are captured by an electron microscope.

[0020] FIG. 2 depicts a graph showing an average magnitude of grains of examples of the aluminum alloy material according to the present disclosure.

[0021] FIG. 3 depicts images of a microstructure of an example of an aluminum alloy material as the reference for comparison that are captured by the electron microscope.

[0022] FIG. 4 depicts a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison.

[0023] FIG. 5 depicts a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison.

[0024] FIG. 6 depicts an image of a microstructure of an example of the aluminum alloy material according to the present disclosure that is captured by an optical microscope.

[0025] FIG. 7 depicts an image of a microstructure of an example of the aluminum alloy material as the reference for comparison that is captured by the optical microscope.

[0026] FIG. 8 depicts a view illustrating a state where a seat cross member formed of the aluminum alloy material according to the present disclosure and a center floor panel are welded to each other.

[0027] FIGS. 9 and 10 depict photographs each showing a state where the seat cross member manufactured according to the present disclosure and the center floor panel are welded to each other.

[0028] FIG. 11 depicts a graph showing fracture strengths of base materials and fracture strengths of welded portions.

[0029] FIG. 12 depicts an image of an example of a microstructure of an A6082 alloy material.

[0030] FIG. 13 depicts an image of an example of a microstructure of the aluminum alloy material as the reference for comparison.

[0031] FIG. 14 depicts an image of an example of a microstructure of the aluminum alloy material according to the present disclosure.

[0032] FIG. 15 depicts a graph showing the results of the corrosion experiment in terms of the microstructures in FIGS. 12 to 14.DETAILED DESCRIPTION

[0033] To gain a comprehensive understanding of the present disclosure, its operational advantages, and its object that is accomplished by its embodiments, reference should be made to the accompanying drawings in which its embodiments are illustrated and the contents of the drawings.

[0034] A description of a well-known technology associated with the embodiments of the present disclosure, when it makes the nature and gist of the present disclosure unnecessarily obfuscated, is shortened or omitted.

[0035] An aluminum alloy material according to the present disclosure is an alloy material for manufacturing a vehicular component, such as a seat cross member that is used in a center floor panel. The vehicular component according to the present disclosure is manufactured by extruding the aluminum alloy material according to the present disclosure and performing a heat treatment on an extrudate that results from the extrusion. The aluminum alloy material according to the present disclosure that has more improved yield strength, tensile strength, and elongation than an aluminum alloy material in the related art is provided.

[0036] The aluminum alloy material according to the present disclosure is an alloy composition for obtaining such a high-strength extrudate. That is, the aluminum alloy material is an aluminum extrudate that is obtained by adding copper (Cu) and zirconium (Zr), but not adding chromium (Cr) and manganese (Mn), to an Al—Zn—Mg aluminum alloy as a base composition.

[0037] A composition of the aluminum alloy material according to the present disclosure and the composition and properties of a reference for comparison are shown in the following Table 1.TABLE 1Mechanical PropertiesYieldTensileComposition (wt %)StrengthStrengthElongationElementSiFeCuMnMgCrZnTiZr(MPa)(MPa)Ratio (%)Alloy0.1 or0.1 or0.1 to01.0 to04.5 to0.04 or0.20 or401 or436 or16.3 oraccording tolessless0.41.55.5lesslessmoremoremorethe PresentDisclosureAlloy as0.1 or0.2 or0.45 to0.1 to1.3 to0.1 or4.5 to0.04 or0.08 to37140415Reference forlessless0.600.21.5less5.1less0.12Comparison(0.046)(0.078)(0.60)(0.147)(1.356)(0.001)(4.89)(0.034)(0.115)

[0038] The properties of the reference for comparison in Table 1 are the results of comparison with a comparative example shown in parentheses.

[0039] As shown in Table 1, the feature of the aluminum alloy material according to the present disclosure is that it does not include Cr and Mn, with a Cu alloy being limited to 0.4 wt % or less.

[0040] In order to obtain the effect of recrystallization inhibition, Cr and Mn are consistently added to an aluminum extrudate, regardless of whether this aluminum extrudate is formed of 6xxx series alloys or 7xxx series alloys.

[0041] The absence of Cr and Mn in the aluminum alloy material according to the present disclosure demonstrates that the aluminum alloy material has high strength properties without abnormal crystal grains being generated at the microstructural level. Furthermore, the reason for limiting a Cu content to 0.4 wt % or less is because this content provides sufficient corrosion resistance when compared with an amount of Cu added in another alloy.

[0042] Cr and Mn have the effect of inhibiting recrystallization at the microstructural level after extrusion. This effect also causes a difference in recrystallization energy between the surface and the inside of an aluminum extrudate, resulting in generating abnormal crystal grains. However, according to the present disclosure, Cr and Mn are not added to prevent the effect of recrystallization inhibition.

[0043] In the case of the 7xxx series alloys, stress corrosion cracking (SCC) occurs. Accordingly, the Cu content is increased, or a two-step heat treatment is performed in order to prevent the stress corrosion cracking. According to the present disclosure, the Cu content is limited to 0.4 wt % or less to obtain the effect of having sufficient corrosion resistance.

[0044] Thus, the composition of the aluminum alloy material according to present disclosure is limited as follows: Cr and Mn: 0 wt %, Cu: 0.1 to 0.4 wt %, Si: 0.1 wt % or less, Fe: 0.1 wt % or less, Mg: 1.0 to 1.5 wt %, Zn: 4.5 to 5.5 wt %, Ti: 0.04 wt % or less, Zr: 0.2 wt % or less, and the balance being Al.

[0045] FIG. 1 depicts images of the aluminum alloy material according to the present disclosure that are captured by an electron microscope. FIG. 2 depicts a graph showing an average magnitude of grains of the aluminum alloy material according to the present disclosure. FIG. 3 depicts images of a microstructure of an aluminum alloy material as the reference for comparison that are captured by the electron microscope. FIG. 4 depicts a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison. FIG. depicts is a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison.

[0046] Extrusion direction (ED) of the extrudate was analyzed in an electron backscatter diffraction (EBSD) technique using the electron microscope. The results of the analysis show a difference in microstructure between the aluminum alloy material according to the present disclosure and the aluminum alloy material as the reference for comparison. As described above, the extrudate formed of the aluminum alloy material according to the present disclosure exhibits a uniform magnitude of crystal grains across regions thereof, while a surface region (FIG. 4) and a central region (FIG. 5) of the extrudate formed of the aluminum alloy material as of the reference for comparison exhibit different magnitudes of crystal grains. That is, abnormal crystal grains are present on a surface of the extrudate formed of the aluminum of the reference for comparison.

[0047] The abnormal crystal grains exhibit a different magnitude from regular crystal grains. As shown in FIG. 2, the extrudate formed of the aluminum alloy material according to the present disclosure exhibits an average magnitude of 162.5 micrometers (μm). The extrudate formed of the aluminum alloy material as the reference for comparison exhibits an average magnitude of crystal grains, measuring 237.6 μm (FIG. 4), across the surface region thereof. The extrudate formed of the aluminum alloy material as the reference for comparison exhibits an average magnitude of crystal grains, measuring 36.8 μm (FIG. 5), across the central region thereof. This difference is determined to be due to an influence of Cr and Mn as described above.

[0048] FIG. 6 depicts an image of a microstructure of the aluminum alloy material according to the present disclosure that is captured by an optical microscope. FIG. 7 depicts an image of a microstructure of the aluminum alloy material as the reference for comparison that is captured by the optical microscope.

[0049] The microstructures that are observed in the EBSD technique using the optical microscope exhibit a difference.

[0050] The aluminum alloy material according to the present disclosure and the aluminum alloy material as the reference for comparison were used for the seat cross member, which is a vehicular underbody component. The aluminum alloy materials were extruded, and samples for tension testing were collected from upper end portions, respectively, of the resulting extrudate.

[0051] Implementation examples and comparative examples are shown in the following Tables 2 and 3. An optimized two-step heat treatment was performed on each of the extrudates. In order to suppress the SCC, instead of single heat treatment, the two-step heat treatment may be performed on 7xxx series aluminum extrudates. From the results of comparison in strength and elongation ratio, it can be seen that the extrudate formed of the aluminum alloy material according to the present disclosure has more excellent properties than the extrudate formed of the aluminum alloy material as the reference for comparison.

[0052] In other words, according to the present disclosure, the two-step heat treatment may be performed on the aluminum extrudate: primarily at a temperature ranging from 80° C. to 120° C. for 3 to 6 hours, and secondarily at a temperature ranging from 130° C. to 180° C. for 8 to 15 hours, resulting in an aluminum extrudate.TABLE 2Mechanical PropertiesYield Tensile Heat Treatment Strength Strength Elongation CategorizationConditions(MPa)(MPa)(%)Implementation 100° C., 3 hrs + 40143617.0Example 1150° C., 12 hrsImplementation 100° C., 3 hrs + 41144317.0Example 2150° C., 12 hrsImplementation 100° C., 3 hrs + 40243617.0Example 3150° C., 12 hrsImplementation 100° C., 3 hrs + 41144217.4Example 4150° C., 12 hrsImplementation 100° C., 3 hrs + 42345317.3Example 5150° C., 12 hrsImplementation 100° C., 3 hrs + 40844116.8Example 6150° C., 12 hrsImplementation 100° C., 3 hrs + 40744016.3Example 7150° C., 12 hrsImplementation 100° C., 3 hrs + 40443917.5Example 8150° C., 12 hrsImplementation 100° C., 3 hrs + 40944216.4Example 9150° C., 12 hrsTABLE 3Mechanical PropertiesYield Tensile Heat Treatment Strength Strength Elongation CategorizationConditions(MPa)(MPa)(%)Comparative 124° C., 20 hrs + 33337016.3Example 1175° C., 1.5 hrsComparative 124° C., 20 hrs + 31635516.9Example 2175° C., 1.5 hrsComparative 124° C., 20 hrs + 32636518.1Example 3175° C., 1.5 hrsComparative 124° C., 20 hrs + 32035915.6Example 4175° C., 1.5 hrsComparative 124° C., 20 hrs + 32536211.9Example 5175° C., 1.5 hrsComparative 124° C., 20 hrs + 34638716.5Example 6175° C., 1.5 hrsComparative 124° C., 20 hrs + 35939615.2Example 7175° C., 1.5 hrsComparative 124° C., 20 hrs + 35138914.9Example 8175° C., 1.5 hrsAn example of the extrudate that, as described above, is obtained by extruding and heat-treating the aluminum alloy material according to the present disclosure is a seat cross member 10 illustrated in FIG. 8. The seat cross member 10 may be manufactured in such a manner that it is coupled, by welding, to an object, like a floor panel 20, that anchors a seat.

[0054] For example, the seat cross member 10 may have a thickness of 3.0 t, and the center floor panel 20 may have a thickness of 1.1 t.

[0055] FIG. 8 illustrates the result of laser-welding the seat cross member 10 formed of an A70231 material and the center floor panel 20 to each other.

[0056] FIGS. 9 and 10 each show the result of laser-welding the seat cross member 10 manufactured according to the present disclosure and the center floor panel 20 to each other. FIG. 11 is a graph showing fracture strengths of base materials and fracture strengths of welded portions.

[0057] In FIGS. 9 and 10, the seat cross member 10 formed of the aluminum alloy material according to the present disclosure, which serves as an upper plate, may have a thickness of 3.0 t. In FIG. 9, the center floor panel 20 formed of an A6451 alloy, which serves as a lower plate, has a thickness of 1.1 t. In FIG. 10, the center floor panel 20 formed of an A6063 alloy, which serves as a lower plate, has a thickness of 3.0 t.

[0058] From FIGS. 9 and 10, it can be seen that the quality of the sample is excellent (no bubbles and no defects) when viewed in a cross-sectional state and that the welding depth is appropriate.

[0059] From the results of fracturing the laser-welded sample, it can be seen that, as illustrated in FIG. 11, a fracture strength of the laser-welded sample is approximately 50% of the fracture strength of the base material. Despite this, the fracture strength of the laser-welded sample remains impressive when using an aluminum fusion welding, compared to the base material.

[0060] Next, a corrosion experiment was conducted on an A6082 alloy material, the aluminum alloy material as the reference for comparison in Table 1, and the aluminum alloy material according to the present disclosure. Subsequently, the results of the experiment were compared. FIG. 12 is an image of a microstructure of the A6082 alloy material. FIG. 13 is an image of the microstructure of the aluminum alloy material as the reference for comparison. FIG. 14 is an image of the microstructure of the aluminum alloy material according to the present disclosure.TABLE 4Electrochemical TestCorrosionCorrosionRepassivationPittingCu ContentPotential,Current,Potential,Susceptibility,Alloy(%)Aging ConditionG47Ecorr (V)Icorr (μA / cm2)Er (V)Er-Ecorr (V)A6082—180° C., 8 h—−0.8194.59−0.7890.029Alloy as Reference for0.547124° C., 20 h + 170° C.,40 days−1.2182.65−0.7020.516Comparison5 h(PASS)Alloy according to the0.203100° C., 3 h + 150° C.,40 days−1.1871.91−0.8670.320Present Disclosure12 h(PASS)

[0061] Corrosion evaluation was made based on the ASTM G47 method (40-day corrosion test). In this case, the results of the corrosion evaluation showed that the aluminum alloy material as the reference for comparison and the aluminum alloy material according to the present disclosure passed the test. However, as shown in FIG. 15, the corrosion evaluation that used the amended ASTM G47 method showed different results. That is, cracks did not occur in the extrudate formed of the aluminum alloy material according to the present disclosure. However, cracks that corresponded to 74% occurred in the extrudate formed of the aluminum alloy material as the reference for comparison. In addition, the results of the electrochemical corrosion evaluation showed that the aluminum alloy material had an electric current value of 1.91 μA / cm2, while the aluminum alloy material as the reference for comparison had an electric current value of 2.65 μA / cm2. This indicates that the aluminum alloy material as the reference for comparison is more vulnerable to corrosion than the aluminum alloy material according to the present disclosure.

[0062] As described above, the aluminum alloy material according to the present disclosure has excellent properties, including a yield strength of 401 Mpa, a tensile strength of 436 Mpa, and an elongation ratio of 16.3% or higher. The aluminum alloy material is used to manufacture vehicular components, contributing to the lightweighting of a vehicle.

[0063] The embodiments of the present disclosure are described above with reference to the accompanying drawings. However, the present disclosure is not limited to the disclosed embodiments. It would be apparent to a person of ordinary skill in the art that various modifications and alterations of the embodiments may possibly be made within the scope that does not depart from the nature and gist of the present disclosure. The resulting modification or alteration examples should fall within the scope of the claims of the present disclosure. The scope of the present disclosure should be defined by the claims.

Examples

Embodiment Construction

[0033]To gain a comprehensive understanding of the present disclosure, its operational advantages, and its object that is accomplished by its embodiments, reference should be made to the accompanying drawings in which its embodiments are illustrated and the contents of the drawings.

[0034]A description of a well-known technology associated with the embodiments of the present disclosure, when it makes the nature and gist of the present disclosure unnecessarily obfuscated, is shortened or omitted.

[0035]An aluminum alloy material according to the present disclosure is an alloy material for manufacturing a vehicular component, such as a seat cross member that is used in a center floor panel. The vehicular component according to the present disclosure is manufactured by extruding the aluminum alloy material according to the present disclosure and performing a heat treatment on an extrudate that results from the extrusion. The aluminum alloy material according to the present disclosure tha...

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Korean Patent Application No. 10-2023-0100719, filed on Aug. 1, 2023, which is incorporated herein by reference in its entirety.BACKGROUNDField of the Disclosure

[0002] The present disclosure relates to an aluminum alloy material for a vehicular component, such as a seat cross member.Description of Related Art

[0003] To address the lightweighting challenges posed by vehicular electrification, there is an increasing demand for extrudates for vehicular components. Accordingly, there is also an increasing need to develop high-strength aluminum alloys that allow for the thinning of these extrudates.

[0004] Korean Patent Application Publication No. 10-2008-0109347 discloses a technology related to the strength of a component, such as a seat cross member, which is used in a vehicular center floor.

[0005] A comparatively high-strength aluminum extrudate in the related art has a yield strength of 320 MPa, a tensile strength of 370 MPa, and an elongation ratio of 13% or higher.

[0006] However, a reduction in the weights of the vehicular component requires the continuous development of higher-strength materials.

[0007] The matters described above are intended to help an understanding of the background of the present disclosure and may include matters that, although not referred to as the related art, are known to a person of ordinary skill in the art to which the present disclosure pertains.SUMMARY

[0008] An object of the present disclosure, which is contrived to find a solution to the above-mentioned problem, is to provide an aluminum alloy material for a vehicle component, a vehicular component manufactured of the aluminum alloy material, and a method of manufacturing the vehicular component. The aluminum alloy material is capable of having improved properties in terms of yield strength, tensile strength, elongation ratio, and the like, all of which contribute to the lightweighting of a vehicle.

[0009] According to an aspect of the present disclosure, an aluminum alloy material for a vehicular component is provided, wherein the material includes: 0.1 wt % or less of silicon (Si); 0.1 wt % or less of iron (Fe); 0.1 to 0.4 wt % of copper (Cu); 1.0 to 1.5 wt % of magnesium (Mg); 4.5 to 5.5 wt % of zinc (Zn); 0.04 wt % or less of titanium (Ti); 0.2 wt % or less of zirconium (Zr); and the balance being aluminum (Al).

[0010] According to another aspect of the present disclosure, there is provided a vehicular component manufactured by extruding the aluminum alloy material and then performing a two-step heat treatment on an extrudate resulting from the extrusion.

[0011] In the vehicular component, the two-step heat treatment may be performed on the extrudate: primarily at a temperature of ranging from 80° C. to 120° C. for 3 to 6 hours, and secondarily at a temperature of ranging from 130° C. to 180° C. for 8 to 15 hours.

[0012] In the vehicular component, the aluminum alloy material may have a yield strength of 401 MPa or more.

[0013] In the vehicular component, the aluminum alloy material may have a tensile strength of 436 MPa or more.

[0014] In the vehicular component, the aluminum alloy material may have an elongation ratio of 16.3% or higher.

[0015] According to still another aspect of the present disclosure, there is provided a method of manufacturing a vehicular component, the method including: extruding the aluminum alloy material; and performing a two-step heat treatment on an extrudate resulting from the extrusion.

[0016] In the method, the performing of the two-step heat treatment may include: primarily performing a heat treatment on the extrudate at a temperature ranging from 80° C. to 120° C. for 3 to 6 hours; and secondarily performing a heat treatment on the extrudate at a temperature ranging from 130° C. to 180° C. for 8 to 15 hours.

[0017] The aluminum alloy material according to the present disclosure has the properties, including a yield strength of 401 MPa or more, a tensile strength of 436 MPa or more, and an elongation ratio of 16.3% or higher. The vehicular component manufactured of the aluminum alloy material can contribute to the lightweighting of a vehicle.

[0018] In addition, the aluminum alloy material has a uniform microstructure, and the corrosion resistance thereof is increased. The vehicular component, which has demonstrated high performance in corrosion evaluation, can be manufactured.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 depicts images of examples of an aluminum alloy material according to the present disclosure that are captured by an electron microscope.

[0020] FIG. 2 depicts a graph showing an average magnitude of grains of examples of the aluminum alloy material according to the present disclosure.

[0021] FIG. 3 depicts images of a microstructure of an example of an aluminum alloy material as the reference for comparison that are captured by the electron microscope.

[0022] FIG. 4 depicts a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison.

[0023] FIG. 5 depicts a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison.

[0024] FIG. 6 depicts an image of a microstructure of an example of the aluminum alloy material according to the present disclosure that is captured by an optical microscope.

[0025] FIG. 7 depicts an image of a microstructure of an example of the aluminum alloy material as the reference for comparison that is captured by the optical microscope.

[0026] FIG. 8 depicts a view illustrating a state where a seat cross member formed of the aluminum alloy material according to the present disclosure and a center floor panel are welded to each other.

[0027] FIGS. 9 and 10 depict photographs each showing a state where the seat cross member manufactured according to the present disclosure and the center floor panel are welded to each other.

[0028] FIG. 11 depicts a graph showing fracture strengths of base materials and fracture strengths of welded portions.

[0029] FIG. 12 depicts an image of an example of a microstructure of an A6082 alloy material.

[0030] FIG. 13 depicts an image of an example of a microstructure of the aluminum alloy material as the reference for comparison.

[0031] FIG. 14 depicts an image of an example of a microstructure of the aluminum alloy material according to the present disclosure.

[0032] FIG. 15 depicts a graph showing the results of the corrosion experiment in terms of the microstructures in FIGS. 12 to 14.DETAILED DESCRIPTION

[0033] To gain a comprehensive understanding of the present disclosure, its operational advantages, and its object that is accomplished by its embodiments, reference should be made to the accompanying drawings in which its embodiments are illustrated and the contents of the drawings.

[0034] A description of a well-known technology associated with the embodiments of the present disclosure, when it makes the nature and gist of the present disclosure unnecessarily obfuscated, is shortened or omitted.

[0035] An aluminum alloy material according to the present disclosure is an alloy material for manufacturing a vehicular component, such as a seat cross member that is used in a center floor panel. The vehicular component according to the present disclosure is manufactured by extruding the aluminum alloy material according to the present disclosure and performing a heat treatment on an extrudate that results from the extrusion. The aluminum alloy material according to the present disclosure that has more improved yield strength, tensile strength, and elongation than an aluminum alloy material in the related art is provided.

[0036] The aluminum alloy material according to the present disclosure is an alloy composition for obtaining such a high-strength extrudate. That is, the aluminum alloy material is an aluminum extrudate that is obtained by adding copper (Cu) and zirconium (Zr), but not adding chromium (Cr) and manganese (Mn), to an Al—Zn—Mg aluminum alloy as a base composition.

[0037] A composition of the aluminum alloy material according to the present disclosure and the composition and properties of a reference for comparison are shown in the following Table 1.TABLE 1Mechanical PropertiesYieldTensileComposition (wt %)StrengthStrengthElongationElementSiFeCuMnMgCrZnTiZr(MPa)(MPa)Ratio (%)Alloy0.1 or0.1 or0.1 to01.0 to04.5 to0.04 or0.20 or401 or436 or16.3 oraccording tolessless0.41.55.5lesslessmoremoremorethe PresentDisclosureAlloy as0.1 or0.2 or0.45 to0.1 to1.3 to0.1 or4.5 to0.04 or0.08 to37140415Reference forlessless0.600.21.5less5.1less0.12Comparison(0.046)(0.078)(0.60)(0.147)(1.356)(0.001)(4.89)(0.034)(0.115)

[0038] The properties of the reference for comparison in Table 1 are the results of comparison with a comparative example shown in parentheses.

[0039] As shown in Table 1, the feature of the aluminum alloy material according to the present disclosure is that it does not include Cr and Mn, with a Cu alloy being limited to 0.4 wt % or less.

[0040] In order to obtain the effect of recrystallization inhibition, Cr and Mn are consistently added to an aluminum extrudate, regardless of whether this aluminum extrudate is formed of 6xxx series alloys or 7xxx series alloys.

[0041] The absence of Cr and Mn in the aluminum alloy material according to the present disclosure demonstrates that the aluminum alloy material has high strength properties without abnormal crystal grains being generated at the microstructural level. Furthermore, the reason for limiting a Cu content to 0.4 wt % or less is because this content provides sufficient corrosion resistance when compared with an amount of Cu added in another alloy.

[0042] Cr and Mn have the effect of inhibiting recrystallization at the microstructural level after extrusion. This effect also causes a difference in recrystallization energy between the surface and the inside of an aluminum extrudate, resulting in generating abnormal crystal grains. However, according to the present disclosure, Cr and Mn are not added to prevent the effect of recrystallization inhibition.

[0043] In the case of the 7xxx series alloys, stress corrosion cracking (SCC) occurs. Accordingly, the Cu content is increased, or a two-step heat treatment is performed in order to prevent the stress corrosion cracking. According to the present disclosure, the Cu content is limited to 0.4 wt % or less to obtain the effect of having sufficient corrosion resistance.

[0044] Thus, the composition of the aluminum alloy material according to present disclosure is limited as follows: Cr and Mn: 0 wt %, Cu: 0.1 to 0.4 wt %, Si: 0.1 wt % or less, Fe: 0.1 wt % or less, Mg: 1.0 to 1.5 wt %, Zn: 4.5 to 5.5 wt %, Ti: 0.04 wt % or less, Zr: 0.2 wt % or less, and the balance being Al.

[0045] FIG. 1 depicts images of the aluminum alloy material according to the present disclosure that are captured by an electron microscope. FIG. 2 depicts a graph showing an average magnitude of grains of the aluminum alloy material according to the present disclosure. FIG. 3 depicts images of a microstructure of an aluminum alloy material as the reference for comparison that are captured by the electron microscope. FIG. 4 depicts a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison. FIG. depicts is a region-based image of the aluminum alloy material as the reference for comparison that is captured by the electron microscope and a graph showing a region-based average magnitude of grains of the aluminum alloy material as the reference for comparison.

[0046] Extrusion direction (ED) of the extrudate was analyzed in an electron backscatter diffraction (EBSD) technique using the electron microscope. The results of the analysis show a difference in microstructure between the aluminum alloy material according to the present disclosure and the aluminum alloy material as the reference for comparison. As described above, the extrudate formed of the aluminum alloy material according to the present disclosure exhibits a uniform magnitude of crystal grains across regions thereof, while a surface region (FIG. 4) and a central region (FIG. 5) of the extrudate formed of the aluminum alloy material as of the reference for comparison exhibit different magnitudes of crystal grains. That is, abnormal crystal grains are present on a surface of the extrudate formed of the aluminum of the reference for comparison.

[0047] The abnormal crystal grains exhibit a different magnitude from regular crystal grains. As shown in FIG. 2, the extrudate formed of the aluminum alloy material according to the present disclosure exhibits an average magnitude of 162.5 micrometers (μm). The extrudate formed of the aluminum alloy material as the reference for comparison exhibits an average magnitude of crystal grains, measuring 237.6 μm (FIG. 4), across the surface region thereof. The extrudate formed of the aluminum alloy material as the reference for comparison exhibits an average magnitude of crystal grains, measuring 36.8 μm (FIG. 5), across the central region thereof. This difference is determined to be due to an influence of Cr and Mn as described above.

[0048] FIG. 6 depicts an image of a microstructure of the aluminum alloy material according to the present disclosure that is captured by an optical microscope. FIG. 7 depicts an image of a microstructure of the aluminum alloy material as the reference for comparison that is captured by the optical microscope.

[0049] The microstructures that are observed in the EBSD technique using the optical microscope exhibit a difference.

[0050] The aluminum alloy material according to the present disclosure and the aluminum alloy material as the reference for comparison were used for the seat cross member, which is a vehicular underbody component. The aluminum alloy materials were extruded, and samples for tension testing were collected from upper end portions, respectively, of the resulting extrudate.

[0051] Implementation examples and comparative examples are shown in the following Tables 2 and 3. An optimized two-step heat treatment was performed on each of the extrudates. In order to suppress the SCC, instead of single heat treatment, the two-step heat treatment may be performed on 7xxx series aluminum extrudates. From the results of comparison in strength and elongation ratio, it can be seen that the extrudate formed of the aluminum alloy material according to the present disclosure has more excellent properties than the extrudate formed of the aluminum alloy material as the reference for comparison.

[0052] In other words, according to the present disclosure, the two-step heat treatment may be performed on the aluminum extrudate: primarily at a temperature ranging from 80° C. to 120° C. for 3 to 6 hours, and secondarily at a temperature ranging from 130° C. to 180° C. for 8 to 15 hours, resulting in an aluminum extrudate.TABLE 2Mechanical PropertiesYield Tensile Heat Treatment Strength Strength Elongation CategorizationConditions(MPa)(MPa)(%)Implementation 100° C., 3 hrs + 40143617.0Example 1150° C., 12 hrsImplementation 100° C., 3 hrs + 41144317.0Example 2150° C., 12 hrsImplementation 100° C., 3 hrs + 40243617.0Example 3150° C., 12 hrsImplementation 100° C., 3 hrs + 41144217.4Example 4150° C., 12 hrsImplementation 100° C., 3 hrs + 42345317.3Example 5150° C., 12 hrsImplementation 100° C., 3 hrs + 40844116.8Example 6150° C., 12 hrsImplementation 100° C., 3 hrs + 40744016.3Example 7150° C., 12 hrsImplementation 100° C., 3 hrs + 40443917.5Example 8150° C., 12 hrsImplementation 100° C., 3 hrs + 40944216.4Example 9150° C., 12 hrsTABLE 3Mechanical PropertiesYield Tensile Heat Treatment Strength Strength Elongation CategorizationConditions(MPa)(MPa)(%)Comparative 124° C., 20 hrs + 33337016.3Example 1175° C., 1.5 hrsComparative 124° C., 20 hrs + 31635516.9Example 2175° C., 1.5 hrsComparative 124° C., 20 hrs + 32636518.1Example 3175° C., 1.5 hrsComparative 124° C., 20 hrs + 32035915.6Example 4175° C., 1.5 hrsComparative 124° C., 20 hrs + 32536211.9Example 5175° C., 1.5 hrsComparative 124° C., 20 hrs + 34638716.5Example 6175° C., 1.5 hrsComparative 124° C., 20 hrs + 35939615.2Example 7175° C., 1.5 hrsComparative 124° C., 20 hrs + 35138914.9Example 8175° C., 1.5 hrsAn example of the extrudate that, as described above, is obtained by extruding and heat-treating the aluminum alloy material according to the present disclosure is a seat cross member 10 illustrated in FIG. 8. The seat cross member 10 may be manufactured in such a manner that it is coupled, by welding, to an object, like a floor panel 20, that anchors a seat.

[0054] For example, the seat cross member 10 may have a thickness of 3.0 t, and the center floor panel 20 may have a thickness of 1.1 t.

[0055] FIG. 8 illustrates the result of laser-welding the seat cross member 10 formed of an A70231 material and the center floor panel 20 to each other.

[0056] FIGS. 9 and 10 each show the result of laser-welding the seat cross member 10 manufactured according to the present disclosure and the center floor panel 20 to each other. FIG. 11 is a graph showing fracture strengths of base materials and fracture strengths of welded portions.

[0057] In FIGS. 9 and 10, the seat cross member 10 formed of the aluminum alloy material according to the present disclosure, which serves as an upper plate, may have a thickness of 3.0 t. In FIG. 9, the center floor panel 20 formed of an A6451 alloy, which serves as a lower plate, has a thickness of 1.1 t. In FIG. 10, the center floor panel 20 formed of an A6063 alloy, which serves as a lower plate, has a thickness of 3.0 t.

[0058] From FIGS. 9 and 10, it can be seen that the quality of the sample is excellent (no bubbles and no defects) when viewed in a cross-sectional state and that the welding depth is appropriate.

[0059] From the results of fracturing the laser-welded sample, it can be seen that, as illustrated in FIG. 11, a fracture strength of the laser-welded sample is approximately 50% of the fracture strength of the base material. Despite this, the fracture strength of the laser-welded sample remains impressive when using an aluminum fusion welding, compared to the base material.

[0060] Next, a corrosion experiment was conducted on an A6082 alloy material, the aluminum alloy material as the reference for comparison in Table 1, and the aluminum alloy material according to the present disclosure. Subsequently, the results of the experiment were compared. FIG. 12 is an image of a microstructure of the A6082 alloy material. FIG. 13 is an image of the microstructure of the aluminum alloy material as the reference for comparison. FIG. 14 is an image of the microstructure of the aluminum alloy material according to the present disclosure.TABLE 4Electrochemical TestCorrosionCorrosionRepassivationPittingCu ContentPotential,Current,Potential,Susceptibility,Alloy(%)Aging ConditionG47Ecorr (V)Icorr (μA / cm2)Er (V)Er-Ecorr (V)A6082—180° C., 8 h—−0.8194.59−0.7890.029Alloy as Reference for0.547124° C., 20 h + 170° C.,40 days−1.2182.65−0.7020.516Comparison5 h(PASS)Alloy according to the0.203100° C., 3 h + 150° C.,40 days−1.1871.91−0.8670.320Present Disclosure12 h(PASS)

[0061] Corrosion evaluation was made based on the ASTM G47 method (40-day corrosion test). In this case, the results of the corrosion evaluation showed that the aluminum alloy material as the reference for comparison and the aluminum alloy material according to the present disclosure passed the test. However, as shown in FIG. 15, the corrosion evaluation that used the amended ASTM G47 method showed different results. That is, cracks did not occur in the extrudate formed of the aluminum alloy material according to the present disclosure. However, cracks that corresponded to 74% occurred in the extrudate formed of the aluminum alloy material as the reference for comparison. In addition, the results of the electrochemical corrosion evaluation showed that the aluminum alloy material had an electric current value of 1.91 μA / cm2, while the aluminum alloy material as the reference for comparison had an electric current value of 2.65 μA / cm2. This indicates that the aluminum alloy material as the reference for comparison is more vulnerable to corrosion than the aluminum alloy material according to the present disclosure.

[0062] As described above, the aluminum alloy material according to the present disclosure has excellent properties, including a yield strength of 401 Mpa, a tensile strength of 436 Mpa, and an elongation ratio of 16.3% or higher. The aluminum alloy material is used to manufacture vehicular components, contributing to the lightweighting of a vehicle.

[0063] The embodiments of the present disclosure are described above with reference to the accompanying drawings. However, the present disclosure is not limited to the disclosed embodiments. It would be apparent to a person of ordinary skill in the art that various modifications and alterations of the embodiments may possibly be made within the scope that does not depart from the nature and gist of the present disclosure. The resulting modification or alteration examples should fall within the scope of the claims of the present disclosure. The scope of the present disclosure should be defined by the claims.

Examples

Embodiment Construction

[0033]To gain a comprehensive understanding of the present disclosure, its operational advantages, and its object that is accomplished by its embodiments, reference should be made to the accompanying drawings in which its embodiments are illustrated and the contents of the drawings.

[0034]A description of a well-known technology associated with the embodiments of the present disclosure, when it makes the nature and gist of the present disclosure unnecessarily obfuscated, is shortened or omitted.

[0035]An aluminum alloy material according to the present disclosure is an alloy material for manufacturing a vehicular component, such as a seat cross member that is used in a center floor panel. The vehicular component according to the present disclosure is manufactured by extruding the aluminum alloy material according to the present disclosure and performing a heat treatment on an extrudate that results from the extrusion. The aluminum alloy material according to the present disclosure tha...

Claims

1. An aluminum alloy material for a vehicular component, the aluminum alloy material comprising:0.1 wt % or less of Si;0.1 wt % or less of Fe;0.1 to 0.4 wt % of Cu;1.0 to 1.5 wt % of Mg;4.5 to 5.5 wt % of Zn;0.04 wt % or less of Ti;0.2 wt % or less of Zr; anda balance of Al.

2. The aluminum alloy material of claim 1, wherein the aluminum alloy material contains no chromium or manganese.

3. A vehicular component comprising:an extruded, heat-treated aluminum alloy material having:0.1 wt % or less of Si;0.1 wt % or less of Fe;0.1 to 0.4 wt % of Cu;1.0 to 1.5 wt % of Mg;4.5 to 5.5 wt % of Zn;0.04 wt % or less of Ti;0.2 wt % or less of Zr; anda balance of Al.

4. The vehicular component of claim 3, wherein the extruded, heat-treated aluminum alloy material has been extruded and subsequently subjected to a two-step heat treatment comprising: primarily heating the aluminum alloy material at a temperature ranging from 80° C. to 120° C. for 3 to 6 hours, and secondarily heating the aluminum alloy material at a temperature ranging from 130° C. to 180° C. for 8 to 15 hours.

5. The vehicular component of claim 3, wherein the extruded, heat-treated aluminum alloy material has a yield strength of 401 MPa or more.

6. The vehicular component of claim 3, wherein the extruded, heat-treated aluminum alloy material has a tensile strength of 436 MPa or more.

7. The vehicular component of claim 3, wherein the extruded, heat-treated aluminum alloy material has an elongation ratio of 16.3% or higher.

8. The vehicular component of claim 3, wherein the aluminum alloy material contains no chromium or manganese.

9. A method of manufacturing a vehicular component, the method comprising:extruding an aluminum alloy material to provide an extrudate; andperforming a two-step heat treatment on the extrudate to provide the vehicular component.

10. The method of claim 9, wherein the aluminum alloy material comprises:0.1 wt % or less of Si;0.1 wt % or less of Fe;0.1 to 0.4 wt % of Cu;1.0 to 1.5 wt % of Mg;4.5 to 5.5 wt % of Zn;0.04 wt % or less of Ti;0.2 wt % or less of Zr; anda balance of Al.

11. The method of claim 10, wherein the aluminum alloy material contains no chromium or manganese.

12. The method of claim 9, wherein the performing of the two-step heat treatment comprises:primarily performing a heat treatment on the extrudate at a temperature in a range of 80° C. to 120° C. for 3 to 6 hours; andsecondarily performing a heat treatment on the extrudate at a temperature in a range of 130° C. to 180° C. for 8 to 15 hours.

Images