Aluminum alloy with improved strength and ductility

Abstract

The present disclosure relates to aluminum alloys with improved strength and ductility. The aluminum alloy composition achieves an excellent combination of strength / ductility as compared to existing Al-Mg-Si alloys. The aluminum alloy may be particularly suitable for applications that require a yield strength of more than 240 MPa. The aluminum alloy, by weight percent, contains 0.41 to 0.59 Si; ≤0.3 Fe; 0.08 to 0.30 Cu; 0.45 to 0.55 Mg; 0.08 to 0.20 Mn; and the balance aluminum and unavoidable impurities. Mn may be substituted with Cr up to an equivalent ratio of Mn to Cr of Mn = 1.6Cr, in which case Mn + 1.6Cr + Cu ≥ 0.25.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 364,890, filed on May 18, 2022, the entire content of which is incorporated herein by reference.

[0002] This disclosure relates to the field of aluminum alloys, such as Al - Mg - Si alloys, particularly aluminum alloys useful in the automotive industry.

Background Art

[0003] Aluminum alloys are used in the automotive industry because they have desirable mechanical properties suitable for the automotive industry. In automotive extrusion applications, it is desirable to increase strength to enhance energy absorption and to reduce the wall thickness of parts to reduce the vehicle weight of the automobile. Good ductility is also required to accommodate plastic deformation during part forming operations and to withstand severe plastic deformation during collisions without generating cracks that could limit energy absorption. In existing Al - Mg - Si extrusion alloys, strength can be increased by increasing the concentrations of the major elements Mg and Si, but generally, increasing strength always comes with a loss of ductility measured by bend tests or fracture strain.

Summary of the Invention

[0004] It is desirable to produce aluminum alloys with increased strength without sacrificing ductility, particularly for use in the automotive industry. In one aspect, by weight percentage, 0.41 to 0.59 Si; ≤ 0.3 Fe; 0.08 to 0.30 Cu; 0.45 to 0.55 Mg; 0.08 to 0.20 Mn, or Mn is replaced by Cr up to the equivalent ratio of Mn and Cr of Mn = 1.6Cr, and the balance of aluminum and unavoidable impurities, an aluminum alloy is provided with Mn + 1.6Cr + Cu ≥ 0.25. In some embodiments, the aluminum alloy contains up to 0.12 wt% Cr. In some embodiments, the unavoidable impurities constitute less than 0.1 wt% of the aluminum alloy, and each unavoidable impurity is present at a maximum of 0.05 wt%. In some embodiments, the unavoidable impurities contain ≤ 0.05 wt% Ni. In some embodiments, the unavoidable impurities contain ≤ 0.05 wt% Zn. In some embodiments, the unavoidable impurities contain ≤ 0.05 wt% Ti. In some embodiments, the unavoidable impurities contain ≤ 0.05 wt% B. In some embodiments, the unavoidable impurities contain ≤ 0.05 wt% V. In some embodiments, the alloy contains 0.43 to 0.55 Si. In some embodiments, the alloy contains ≤ 0.25 Fe. In some embodiments, the alloy contains 0.10 to 0.30 Cu. In some embodiments, the alloy contains 0.47 to 0.53 Mg. In some embodiments, the alloy contains 0.10 to 0.20 Mn. In some embodiments, the alloy contains at least 0.10 Fe. In some embodiments, the alloy contains up to 0.10 Cr. In some embodiments, the alloy contains 0.48 to 0.52 Mg. In some embodiments, the alloy further contains a grain refiner.

[0005] In one aspect, an aluminum alloy is provided that contains, by weight percent, 0.41 to 0.59 Si; ≤0.3 Fe; 0.08 to 0.30 Cu; 0.45 to 0.55 Mg; up to 0.20 Mn; up to 0.12 Cr, and the balance aluminum and unavoidable impurities. In some embodiments, the unavoidable impurities constitute less than 0.1 weight percent of the aluminum alloy, and each unavoidable impurity is present at up to 0.05 weight percent. In some embodiments, the unavoidable impurities include ≤0.05 weight percent Ni. In some embodiments, the unavoidable impurities include ≤0.05 weight percent Zn. In some embodiments, the unavoidable impurities include ≤0.05 weight percent Ti. In some embodiments, the unavoidable impurities include ≤0.05 weight percent B. In some embodiments, the unavoidable impurities include ≤0.05 weight percent V. In some embodiments, the alloy contains 0.43 to 0.55 Si. In some embodiments, the alloy contains ≤0.25 Fe. In some embodiments, the alloy contains 0.10 to 0.30 Cu. In some embodiments, the alloy contains 0.47 to 0.53 Mg. In some embodiments, the alloy contains 0.08 to 0.20 Mn. In some embodiments, the alloy contains at least 0.10 Fe. In some embodiments, the alloy contains up to 0.10 Cr. In some embodiments, the alloy contains 0.48 to 0.52 Mg. In some embodiments, the alloy further contains a grain refiner. In some embodiments, the aluminum alloy contains a combination of Cu, Mn, and Cr with a concentration, by weight percent, of Cu + Mn + 1.6Cr ≥ 0.25. In some embodiments, the aluminum alloy contains Cu + Mn ≥ 0.25 or Cu + 1.6Cr ≥ 0.25. In some embodiments, the aluminum alloy contains a combination of Mn and Cr with a concentration, by weight percent, of up to 1.6Cr.

[0006] In one aspect, an aluminum product containing the aluminum alloy of the present disclosure is provided. The aluminum product may have a recrystallized grain structure. The aluminum product may be a billet for extrusion. The aluminum product may be an automotive part.

[0007] Also provided is a method for manufacturing an aluminum product, including a step of casting an aluminum alloy described in this specification to manufacture a cast aluminum product, a step of extruding the cast aluminum product to manufacture an extruded aluminum product, and a step of cooling the extruded aluminum product.

[0008] In one embodiment, the aluminum alloy is cast by direct chill casting, continuous casting, and / or semi-continuous casting. Preferably, the aluminum alloy is cast using a propeller continuous caster, a twin roll caster, or a block caster. In another embodiment, the extruded aluminum product is cooled using a cooling fan, water spray, or water cooling. In one embodiment, the cast aluminum product is extruded by hollow extrusion. In a further embodiment, the method described in this specification further includes a step of heat-treating or homogenizing the cast aluminum product before extrusion.

[0009] Those skilled in the art will, by reading this disclosure, become aware of many further features and combinations thereof related to the improvement of the present invention.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0011] The present disclosure relates to aluminum alloys with improved strength and ductility. The aluminum alloy compositions of the present disclosure achieve an excellent combination of strength / ductility compared to existing Al-Mg-Si alloys. In some embodiments, the aluminum alloy is particularly suitable for applications that require a yield strength of more than 240 MPa. The Al-Mg-Si alloys of the present disclosure surprisingly achieve a combination of improved strength and ductility by the controlled addition of 0.08 to 0.30 Cu and 0.08 to 0.20 Mn. The improved strength and ductility can be measured, for example, by comparison with conventional 6XXX aluminum alloys for automotive extrusion (e.g., AA6060 and AA6063). More specifically, the aluminum alloy of the present disclosure, in some embodiments, contains, by weight percent, 0.41 to 0.59 Si, ≤0.3 Fe, 0.08 to 0.30 Cu, 0.45 to 0.55 Mg, optionally up to 0.12 Cr and 0.08 to 0.20 Mn, and the balance aluminum and unavoidable impurities. It is included that the content of Mn and Cr is in the ratio of Mn:1.6Cr and Cu is at least 0.25 wt%. The alloys included herein can be cast as billets for extrusion and extruded into products such as extruded profiles for automotive applications.

[0012] The aluminum alloy of the present disclosure has a Si content of 0.41 to 0.59, 0.42 to 0.59, 0.43 to 0.59, 0.44 to 0.59, 0.41 to 0.58, 0.41 to 0.57, 0.41 to 0.56, 0.41 to 0.55, 0.41 to 0.54, 0.41 to 0.53, 0.41 to 0.52, 0.41 to 0.51, 0.41 to 0.50, 0.41 to 0.49, 0.41 to 0.48, 0.41 to 0.47, 0.41 to 0.46, 0.41 to 0.45, 0.42 to 0.50, 0.43 to 0.50, 0.42 to 0.48, 0.43 to 0.47, or 0.43 to 0.45, by weight percent based on the total weight of the aluminum alloy. Silicon improves the strength of the Al alloy by combining with Mg and Cu to bring about precipitation hardening, and also promotes the formation of Al-Mn-Fe-Si dispersion particles that can prevent the localization of slip.

[0013] The aluminum used to produce the alloys described herein may be primary aluminum alloys or recycled materials. Iron is a natural impurity in primary aluminum and can also be found at increased levels in recycled materials, and the claims reflect the use of materials from these two sources. The aluminum alloys of the present disclosure have an Fe content, by weight percent relative to the total weight of the aluminum alloy, of up to 0.3, up to 0.25, up to 0.22, up to 0.21, up to 0.20, 0.10 - 0.30, 0.10 - 0.25, 0.10 - 0.22, 0.10 - 0.20, 0.12 - 0.25, 0.13 - 0.24, 0.14 - 0.23, or 0.15 - 0.22. The amount of Fe is limited to up to 0.3, preferably up to 0.25, more preferably up to 0.22, in order to avoid any adverse effects on the mechanical properties of the aluminum alloy. Fe has low solubility in aluminum and typically forms Al-Fe-Si type intermetallic compounds or constituent particles during the casting and homogenization processes, which can be detrimental to the surface finish of the profile and, when present at high concentrations, can be detrimental to ductility. For this reason, an upper limit on the Fe content, as described herein, is desirably, for example, up to 0.3, up to 0.25, or up to 0.2.

[0014] The aluminum alloy of the present disclosure has a Cu content of 0.08 - 0.30, 0.09 - 0.30, 0.10 - 0.30, 0.11 - 0.30, 0.12 - 0.30, 0.13 - 0.30, 0.14 - 0.30, 0.15 - 0.30, 0.16 - 0.30, 0.17 - 0.30, 0.18 - 0.30, 0.19 - 0.30, 0.08 - 0.29, 0.08 - 0.28, 0.08 - 0.27, 0.08 - 0.26, 0.08 - 0.25, 0.08 - 0.24, 0.08 - 0.23, 0.08 - 0.22, 0.08 - 0.21, 0.08 - 0.20, 0.10 - 0.29, 0.10 - 0.28, 0.10 - 0.27, 0.10 - 0.26, 0.10 - 0.25, 0.10 - 0.24, 0.10 - 0.23, 0.10 - 0.22, 0.10 - 0.21, 0.10 - 0.20, 0.11 - 0.19, 0.12 - 0.18, or 0.13 - 0.17, by weight percent based on the total weight of the aluminum alloy. In addition to the normal MgSi precipitates, Cu promotes the formation of Al-Mg-Si-Cu age precipitates such as Q" or Q' that can improve the dispersion of slip during plastic deformation.

[0015] The aluminum alloy of the present disclosure has a Mg content of 0.45 - 0.55, 0.45 - 0.54, 0.45 - 0.53, 0.45 - 0.52, 0.45 - 0.51, 0.45 - 0.50, 0.46 - 0.55, 0.47 - 0.55, 0.48 - 0.55, 0.49 - 0.55, 0.50 - 0.55, 0.46 - 54, 0.47 - 0.54, 0.48 - 0.54, 0.47 - 0.53, or 0.48 - 0.52, by weight percent based on the total weight of the aluminum alloy. Magnesium contributes to solid-solution strengthening. The main role of magnesium is to bring about precipitation hardening in combination with Si and Cu.

[0016] The aluminum alloy of the present disclosure has an Mn content of up to 0.20, up to 0.19, up to 0.18, up to 0.17, up to 0.16, up to 0.15, 0.08 - 0.20, 0.08 - 0.19, 0.08 - 0.18, 0.08 - 0.17, 0.08 - 0.16, 0.08 - 0.15, 0.08 - 0.14, 0.09 - 0.20, 0.09 - 0.19, 0.09 - 0.18, 0.09 - 0.17, 0.09 - 0.16, 0.09 - 0.15, 0.09 - 0.14, 0.10 - 0.20, 0.10 - 0.19, 0.10 - 0.18, 0.10 - 0.17, 0.10 - 0.16, 0.10 - 0.15, 0.10 - 0.14, 0.11 - 0.16, or 0.12 - 0.15, by weight percentage based on the total weight of the aluminum alloy. Mn can contribute to the strength of the Al alloy by dispersion particle strengthening and solid solution hardening. Mn promotes the formation of Al-Mn-Fe-Si submicron dispersion particles during the homogenization process. These dispersion particles act to disperse slip during the plastic deformation process, thereby delaying the occurrence of internal stress concentration and fracture phenomena. Mn also improves the extrusion formability by promoting the transformation of the β component phase Al-(Fe,Mn)Si to the α phase. However, an excessive amount of dispersion particles may increase the flow stress of the alloy at the extrusion forming temperature, affect the extrusion forming speed, and inhibit recrystallization, potentially forming a coarse recrystallized grain structure or a non-recrystallized grain structure.

[0017] In some embodiments, the aluminum alloy of the present disclosure has a combined content of Cu and Mn of at least 0.25, at least 0.26, at least 0.27, at least 0.28, or at least 0.29 weight percent. In some examples, the combined content of Cu and Mn has at least 0.05 Mn, at least 0.06 Mn, at least 0.07 Mn, or at least 0.08 Mn, in weight percent. In further examples, the combination of Cu and Mn has at least 0.08 Mn. Indeed, it has been surprisingly found that by combining Cu and Mn within the specified individual and combined minimum ranges, the strength of the aluminum alloy is improved while advantageously maintaining or improving ductility. This is demonstrated in the Examples section below.

[0018] In some embodiments, Cr can act to replace Mn or complement Mn. In fact, the dispersive particles formed by the addition of Cr and Mn have a similar cubic crystal structure with similar lattice constants and dissolve in each other to such an extent that the two elements are exchangeable to some degree. Accordingly, the aluminum alloy of the present disclosure can have a Cr content of up to 0.12, up to 0.11, up to 0.10, up to 0.09, up to 0.08, up to 0.07, up to 0.06, 0.03 to 0.12, 0.03 to 0.11, 0.03 to 0.10, 0.03 to 0.09, 0.05 to 0.12, 0.05 to 0.11, 0.05 to 0.10, 0.05 to 0.09, 0.06 to 0.12, 0.06 to 0.11, 0.06 to 0.10, 0.06 to 0.09, or 0.07 to 0.08 in weight percent based on the total weight of the aluminum alloy. In some embodiments, the minimum content of Cr is at least 0.03 wt%, at least 0.04 wt%, at least 0.05 wt%, or more than 0.05 wt%. In other embodiments, Cr may not be included in the alloy, and accordingly, the aluminum alloy will contain less than 0.05 wt%, less than 0.03 wt%, or less than 0.01 wt% of Cr. In some embodiments, Cr may be used instead of Mn, and vice versa. In one embodiment, Mn is replaced by Cr up to an equivalent ratio of Mn and Cr of Mn = 1.6Cr. In other embodiments, when Mn is at least 0.1 wt%, the alloy does not contain Cr.

[0019] Since Mn and Cr are exchangeable, only a part of Mn can be replaced by Cr (and vice versa). Accordingly, the total content of Mn, Cr, and Cu in the alloy of the present invention can be set as follows: Mn + 1.6Cr + Cu ≥ 0.25 wt%. In some embodiments, the concentration of Mn + 1.6Cr + Cu can be at least 0.26 wt%, at least 0.27 wt%, at least 0.28 wt%, or at least 0.29 wt%. In such embodiments, the total content of Mn and Cr is defined as follows: Mn + 1.6Cr ≤ 0.20.

[0020] Since Mn and Cr can be exchangeable, in some embodiments, the aluminum alloy of the present disclosure can have a combined content of Cr and Cu defined as follows: Cu + 1.6Cr ≥ 0.25. In such embodiments, Cr may completely replace Mn. In some embodiments, Cu + 1.6Cr can be at least 0.26, at least 0.27, at least 0.28, or at least 0.29. Thus, in some embodiments, the aluminum alloy can be defined as having Cu + 1.6Cr ≥ 0.25 with Mn < 0.05 wt%, or as having Mn + Cu ≥ 0.25 with Cr < 0.05 wt%.

[0021] The weight percent concentrations in the aluminum alloy are provided assuming the balance is aluminum and unavoidable impurities. In some embodiments, each of the unavoidable impurities is present at a maximum of 0.05 (0.03 in some embodiments), and the total of the unavoidable impurities constitutes less than 0.10. In some embodiments, herein, the term "unavoidable impurities" is to be understood to mean those that are not intentionally added.

[0022] In some embodiments, the unavoidable impurities include Ni at a concentration of 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less. Ni has a very low solubility in aluminum and forms undesirable constituent particles. Ni can be present as an impurity from the anode in the reduction process.

[0023] In some embodiments, the unavoidable impurities include Zn at a concentration of 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less. The presence of Zn can have an adverse effect on the corrosion performance of the alloy.

[0024] In some embodiments, the unavoidable impurities include Ti at a concentration of 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less. In some embodiments, the inevitable impurities contain B at a concentration of 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less.

[0025] In some embodiments, the inevitable impurities contain V at a concentration of 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less. V is harmful to the extrusion formability of the aluminum alloy and is generally an impurity caused only by the reduction process.

[0026] In some embodiments, the inevitable impurities contain Zr at a concentration of 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less. In some embodiments, the aluminum alloy of the present disclosure contains, consists essentially of, or consists of any combination of the concentration ranges described above for Si, Fe, Cu, Mg, Mn, Cu + Mn, Cr, and inevitable impurities.

[0027] In some embodiments, the aluminum alloy further contains a crystal refiner such as titanium, titanium boride, or titanium carbide, as desired, to solidify the aluminum alloy. In one embodiment, the crystal refiner is in the form of Ti, TiB, or TiC. When TiB is used as the crystal refiner, as a result, the B content in the alloy can be up to 0.05 wt%. When TiC is used as the crystal refiner, as a result, the C content in the alloy can be up to 0.01 wt%. Ti dissolved in the molten aluminum is TiB 2 / The formation of the interfacial TiAl layer at the melt interface 3 can be promoted, which subsequently promotes the nucleation of Al crystal grains.

[0028] The present disclosure also provides a method for manufacturing high-strength aluminum products using the aluminum alloys of the present disclosure. In a first step, the method includes casting an aluminum alloy of the present disclosure to obtain a cast aluminum product. The casting step may include, for example, direct chill casting, continuous casting, and / or semi-continuous casting. A direct chill continuous casting may be used, which may be a wheel-belt casting process or a track-belt casting. The track-belt process replaces the casting wheel with a plurality of copper blocks. Other options including a twin-roll caster may be used. The twin-roll caster has two rolls that rotate to continuously advance the formed article. The rolls may be cooled to assist in the solidification of the molten aluminum alloy. As a further option, a block caster having blocks configured to function as a belt may be mentioned. The blocks may be cooled to assist in the solidification of the molten aluminum alloy.

[0029] In a second step, the cast aluminum product is extruded to form an extruded aluminum product. During the extrusion process, the aluminum alloy is heated to a temperature at which the alloy becomes malleable. A press container may be used prior to the die orifice. Pressure may be applied using a hydraulic ram to push the aluminum alloy to fill the container and through the die to the desired shape. After hot deformation (i.e., extrusion or direct chill hot rolling), the aluminum alloy may be actively cooled by the use of cooling fans and / or water spray or full water quench. In a preferred embodiment, a cooling rate of 20 °C / second from 500 to 300 °C is used. Most automotive extrusions are hollow to improve stiffness and crush performance. Thus, in some embodiments, the extruded product is a hollow extruded product such as a hollow automotive extrusion. Water cooling at the press exit, which is usually spray cooling, is generally beneficial for ductility compared to, for example, air cooling and is thus preferred. The improvement with water cooling compared to air cooling may be related to changes in the microstructure at the grain boundaries.

[0030] A fully recrystallized grain structure provides advantages in automotive applications compared to a non-recrystallized grain structure (typically with a coarse recrystallized grain surface). These include a reduced sensitivity of strength to the press cooling rate, no occurrence of surface orange peel that can be a starting point for fatigue and corrosion, and local extrusion weld line ductility. Additionally, when the levels of dispersion particle-forming elements such as Mn and Cr required to produce a non-recrystallized grain structure are high, typically, the extrusion formability and strength cooling sensitivity can be inferior. In some embodiments, the aluminum alloy of the present invention achieves a fully recrystallized grain structure to benefit from these advantages, and the fully recrystallized structure is a feature of the product.

[0031] In one embodiment, the method further includes heat-treating or homogenizing the cast aluminum product after casting and before extrusion. The heat-treatment conditions can be a duration of at least about 1 hour, at least about 2 hours, at least about 3 hours, at least about 4 hours, or at least about 5 hours at a temperature of about 450 to about 600 °C, about 500 to about 600 °C, about 550 to about 590 °C, or about 560 to about 580 °C. In some embodiments, the aluminum product is a billet for extrusion.

[0032] The strength and ductility of an aluminum alloy can be specified in various suitable ways. However, the elongation to failure in a tensile test is not a useful parameter for predicting impact performance. On the other hand, the ductility of an extruded product can be evaluated by the bending test (VDA 238-100) of the German Automobile Industry Association in the extrusion direction or in the direction transverse to the extrusion direction. In such a bending test, the bending applied during bending in axial or lateral crush, or the strain applied during mechanical joining such as self-piercing rivets, can be simulated. The true fracture strain (Ln(initial cross-sectional area / final fracture area)) measured in a tensile test is a useful measure of ductility in such applications.

[0033] In some embodiments, the aluminum products of the present disclosure have a tensile strength (UTS) of at least 250 MPa, at least 255 MPa, at least 259 MPa, or at least 265 MPa. In some embodiments, the aluminum products of the present disclosure have a yield strength of at least 230 MPa, at least 235 MPa, at least 240 MPa, greater than 240 MPa, at least 245 MPa, at least 250 MPa, or at least 255 MPa. In some embodiments, the aluminum products of the present disclosure have a longitudinal VDA bend angle of at least 105°, at least 109°, at least 115°, or at least 119° for a thickness of 2.5 mm. In some embodiments, the aluminum products of the present disclosure have a transverse VDA bend angle of at least 58°, 59°, 60°, 61°, 62°, 63°, 64°, or 65°. In some embodiments, the aluminum products of the present disclosure have a true fracture strain of at least 0.65, at least 0.66, at least 0.67, at least 0.68, at least 0.69, at least 0.70, at least 0.71, at least 0.72, at least 0.73, at least 0.73, at least 0.74, at least 0.75, or at least 0.75 when the aluminum product has a thickness of 2.5 mm.

[0034] Examples The alloy composition listed in Table 1 was directly chill cast (DC cast) as a billet with a diameter of 101 mm. Before casting, a 5% Ti-1% B crystal refiner was added. After homogenizing the billet at 580 °C for 2 hours, forced air cooling was performed at 450 °C / hour from 500 to 200 °C. These were extruded into a 50×20×2.5 mm hollow box profile at an extrusion exit speed of 13 m / min using a billet preheating temperature of 500 °C. The die was constructed such that the extrusion welding part was located on the 20 mm surface of the profile so that the characteristics could be evaluated on a 50 mm wide surface away from the extrusion welding part. After discharging from the die, the profile was water spray cooled from 500 to 300 °C at a rate of 150 °C / second. The cooling rate was measured using a clip-on contact thermocouple attached to a high-frequency logger with a WiFi transmitter. The cooled profile was stretched to impart a 0.5% permanent strain, and after a 24-hour delay at room temperature, it was aged at 177 °C for 8 hours. The tensile test was performed longitudinally in accordance with ASTM E8, and the fracture cross-sectional area projected in the tensile direction was measured using image analysis technology so that the true fracture strain could be calculated using the formula Ln(initial cross-sectional area / final fracture cross-sectional area). The larger the value of the fracture strain, the better the bendability. The VDA bend test was performed longitudinally (the bending axis is perpendicular to the extrusion direction) and transversely (the bending axis is parallel to the extrusion direction) with a punch radius of 0.4 mm, a roller spacing of twice the material thickness, i.e., 5 mm, and a load drop of 60 N. After removing the load, the complementary angle of the bending angle was measured, indicating that the larger the bending angle, the better the ductility or bendability.

[0035]

Table 1

[0036] Alloy A represents a typical commercially available AA6063 alloy used in automobiles and other applications, and Alloy K represents a typical commercially available high-strength AA6063 with an increased silicon level. To these types of alloys, 0.02 - 0.08 wt% of Mn was added to promote the transformation of the β-phase Al-(Fe,Mn)Si to the α-phase, thereby improving the extrudability. Compositions B - J and L represent the addition of Mn and Cu separately and combined with a gradual increase.

[0037] Table 2 shows the results of the mechanical properties of each composition. In the table, VDA-L is the longitudinal bending angle test, VDA-T is the transverse bending angle test, El is the elongation, Ef is the true fracture strain, YS is the yield strength, and UTS is the tensile strength.

[0038]

Table 2

[0039] The microstructure of the extruded product was evaluated metallographically. All microstructures exhibited a fully recrystallized grain structure, which is desirable in this type of product to improve bulk ductility and local ductility at the extrusion weld line. Aluminum alloys generally showed a tendency for ductility (measured by VDA bend angle or fracture strain) to decrease as yield strength increased, which was mainly due to the earlier onset of fracture events as the stress level applied to the microstructure increased. Figure 1 is a plot of the longitudinal VDA bend angle versus yield strength after artificial aging. The data points are labeled with the alloy IDs from Table 1. The baseline alloys A and K are included in the band together with alloys J, H, B, and L with gradually increasing additions of Mn, and alloy C with additions of 0.08 wt% Mn and 0.08 wt% Cu. The addition of Mn to alloy A slightly increased the bend angle but also caused an undesirable decrease in strength. Adding 0.20 wt% Mn to the baseline alloy K slightly increased the bend angle instead of slightly decreasing the yield strength. However, alloys D, E, F, G, and I of the present invention with combined additions of Mn and Cu had improved strength compared to the baseline alloy A with the same ductility, or had significantly improved ductility to obtain a high strength equivalent to the baseline alloy K. Figures 2 and 3 show the transverse VDA bend angle and true fracture strain, which are other measures of ductility, also plotted against the yield strength. The trends are very similar to those in Figure 1, and alloys D, E, F, G, and I provide an excellent combination of strength and ductility. As shown by the comparison between Figures 1 and 2, the bend angle measured transverse to the extrusion direction is typically smaller than the bend angle measured longitudinally.

[0040] Figure 4 is a plot of the Mn content versus the Cu content of the experimental alloys, separating the compositions in the same way as shown in Figures 1 - 3. Compositions exhibiting improved strength and ductility (black dots) can be distinguished from compositions showing baseline strength and ductility by a line corresponding to Mn + Cu > 0.20 wt%, preferably Mn + Cu ≧ 0.25 wt%, where the effective Mn is calculated using Mn + 1.6Cr.

[0041] All test materials were cooled by water spraying after extrusion molding, which was a necessary process to achieve high ductility. In fact, a significant improvement in ductility can be obtained by increasing the cooling rate associated with this type of cooling.

[0042] The alloy compositions in Table 3 were DC cast as billets with a diameter of 101 mm. Before casting, a 5% Ti - 1% B grain refiner was added. After homogenizing the billets at 580 °C for 2 hours, forced air cooling was carried out from 500 to 200 °C at a rate of 450 °C / hour. These were extruded into a 50×20×2.5 mm hollow box profile at an extrusion exit speed of 13 m / min using a billet preheating temperature of 500 °C. This profile was spray cooled at a rate of 150 °C / second at the die exit. The cooled profile was stretched to impart a 0.5% permanent plastic extension, and after a 24 - hour delay at room temperature, it was solution - treated at 177 °C for 8 hours. Mechanical tests including tensile tests and VDA bending tests were carried out in the same manner as in the previous examples.

[0043]

Table 3

[0044] Alloy M is a repeated casting of alloy G that, in the examples reported herein, resulted in improved ductility as measured by VDA for a given yield strength. To evaluate the effect of partial and complete substitution of Mn by Cr, alloys N and O were produced while maintaining the contents of Mg, Si, and Cu constant. As shown herein, in the sub - micron dispersion particles formed during homogenization, these two elements, Mn and Cr, can be exchangeable.

[0045] Table 4 shows the results of the mechanical properties of the three compositions described in Table 3. The tensile properties and ductility values as measured by the VDA bend angle are approximately the same, indicating that partial and complete substitution of Mn by Cr is effective in maintaining excellent strength and ductility.

[0046]

Table 4

[0047] The yield strength and VDA bending angles of the tested compositions are shown in Fig. 1 (longitudinal VDA) and Fig. 2 (transverse VDA). In Fig. 1, alloys M, N, and O showed yield strength values similar to those of the original alloy G, but the longitudinal bending angles were slightly lower. This can be explained by slight variations in the test conditions during the extrusion test. However, all three compositions showed performance superior to the baseline alloy band, indicating that Mn can be replaced by Cr, as exemplified herein. In Fig. 2, a similar trend was seen for the transverse bending angle. The results for the three compositions M and N fell within the range of an improved strength / ductility band compared to the baseline strength and ductility.

[0048] As demonstrated, Cr can be used to partially or fully replace Mn as a dispersion particle-forming element. Although the present disclosure has been described in connection with its specific embodiments, the present disclosure is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the present disclosure that fall within the scope of known or customary practice in the art and that depart from the present disclosure as set forth in the foregoing description and as defined by the following appended claims.

Claims

1. In weight percentage, Si between 0.41 and 0.59; Fe ≤ 0.3; Cu between 0.08 and 0.30; 0.45–0.55 mg; Mn in amounts of 0.08 to 0.20, or Mn is substituted with Cr up to the equivalent ratio of Mn to Cr of Mn = 1.6Cr, in which case Mn + 1.6Cr + Cu ≥ 0.25; and Remaining aluminum and unavoidable impurities, Aluminum alloys, including aluminum alloys.

2. The aluminum alloy according to claim 1, comprising 0.08 to 0.20 units of Mn.

3. The aluminum alloy according to claim 1, wherein Mn is replaced with Cr in the alloy up to an equivalent ratio of Mn = 1.6Cr.

4. The aluminum alloy according to any one of claims 1 to 3, wherein the aforementioned unavoidable impurities constitute less than 0.1% by weight of the aluminum alloy, and each unavoidable impurity is present in a maximum of 0.05% by weight.

5. The aluminum alloy according to any one of claims 1 to 3, wherein the aforementioned unavoidable impurities include ≤0.05% by weight of Ni.

6. The aluminum alloy according to any one of claims 1 to 3, wherein the aforementioned unavoidable impurity contains ≤0.05% by weight of Zn.

7. The aluminum alloy according to any one of claims 1 to 3, wherein the aforementioned unavoidable impurities contain ≤0.05% by weight of Ti.

8. The aluminum alloy according to any one of claims 1 to 3, wherein the aforementioned unavoidable impurity contains ≤0.05% by weight of B.

9. The aluminum alloy according to any one of claims 1 to 3, wherein the aforementioned unavoidable impurity contains ≤0.05% by weight of V.

10. An aluminum alloy according to any one of claims 1 to 3, comprising 0.43 to 0.55% by weight of Si.

11. An aluminum alloy according to any one of claims 1 to 3, comprising ≤0.25% by weight of Fe.

12. An aluminum alloy according to any one of claims 1 to 3, comprising 0.10 to 0.30% by weight of Cu.

13. An aluminum alloy according to any one of claims 1 to 3, comprising 0.47 to 0.53% by weight of Mg.

14. An aluminum alloy according to any one of claims 1 to 3, comprising 0.10 to 0.20% by weight of Mn.

15. An aluminum alloy according to any one of claims 1 to 3, comprising at least 0.10% by weight of Fe.

16. An aluminum alloy according to any one of claims 1 to 3, comprising up to 0.10% by weight of Cr.

17. The aluminum alloy according to any one of claims 1 to 3, further comprising a crystal refiner.

18. An aluminum product comprising the aluminum alloy described in any one of claims 1 to 3.

19. The aluminum product according to claim 18, having a recrystallized grain structure.

20. The aluminum product according to claim 18, which is a billet for extrusion molding.

21. The aluminum product according to claim 18, which is an automotive part.

22. A method for manufacturing aluminum products, a) A step of manufacturing a cast aluminum product by casting an aluminum alloy according to any one of claims 1 to 3, b) A step of manufacturing an extruded aluminum product by extruding the cast aluminum product, and c) A step of cooling the extruded aluminum product, Methods that include...

23. The method according to claim 22, wherein the aluminum alloy is cast by direct chill casting, continuous casting, and / or semi-continuous casting.

24. The method according to claim 22, wherein the aluminum alloy is cast using propelch continuous casting, twin-roll caster, or block caster.

25. The method according to claim 22, wherein the extruded aluminum product is cooled using a cooling fan, water spray, or water cooling.

26. The method according to claim 22, wherein the cast aluminum product is extruded by hollow extrusion molding.

27. The method according to claim 22, further comprising the step of heat-treating or homogenizing the cast aluminum product before extrusion molding.

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