Aluminum alloy, use of aluminum alloy, structural component for motor vehicle, and motor vehicle having structural component

Abstract

The present invention relates to an aluminum alloy with enhanced ductility for structural casting, the aluminum alloy comprising: 7.5 to 11.5 weight percent of silicon; a maximum of 0.24 weight percent manganese; 0.08 to 0.5 weight percent of chromium; 0.04 to 0.095 weight percent of magnesium, in particular 0.06 to 0.095 weight percent of magnesium; 0.205 to 0.5 weight percent of iron, in particular 0.22 to 0.5 weight percent of iron, in particular 0.255 to 0.5 weight percent of iron; 0.01 to 0.5 weight percent of copper, in particular 0.205 to 0.5 weight percent of copper, in particular 0.22 to 0.5 weight percent of copper; a maximum of 0.35 weight percent of zinc; 0.004 to 0.15 weight percent of titanium; and aluminum and unavoidable impurities as the remainder.

Description

Technical Field

[0001] The present invention relates to an aluminum alloy with enhanced ductility for structural casting, the application of the aluminum alloy in die-cast structural components, structural components made of the aluminum alloy for motor vehicles, and motor vehicles having structural components. Background Technology

[0002] For high-load die-cast components in vehicle structures, solution-annealed alloys are primarily used. This is because solution annealing advantageously alters the structure, thereby achieving high ductility in addition to high strength, which is beneficial for component performance and the joining process.

[0003] On the other hand, using recycled aluminum can reduce costs, decrease energy input and thus reduce CO2 emissions (CO2 footprint) in vehicle manufacturing, and improve the durability of the aluminum used. Therefore, the use of recycled aluminum alloys is advantageous in terms of durability and climate protection. This is because using recycled alloys instead of virgin aluminum alloys to manufacture components can achieve CO2 emission reductions ranging from approximately 5 to 17 tons of CO2 equivalent per ton of aluminum alloy.

[0004] However, when using recycled aluminum or utilizing recycled waste to manufacture aluminum components, "impurity elements" are typically present in the alloy. Impurity elements refer to elements that are not essential for achieving the desired performance but are detrimental instead, yet cannot be avoided during the recycling process and are therefore present in the final product of the recycling process. Typical impurity elements are iron, copper, zinc, and titanium. A high proportion of recycled aluminum is chosen, which is associated with an increased proportion of these impurity elements in the alloy.

[0005] Furthermore, it is advantageous to use AlSi9Mn-type naturally hardening alloys, which do not harden due to their very low magnesium content, thus eliminating the need for subsequent heat treatment and, consequently, solution annealing. Therefore, components made from such alloys can be produced cost-effectively due to the lack of unnecessary heat treatment, and these alloys also enable the manufacture of very large, one-piece die-cast components. This trend makes it possible to manufacture vehicle bodies with the smallest possible body manufacturing area and equipment investment.

[0006] For example, document EP 1 443 122 A1 describes an aluminum alloy suitable for die-casting components with high elongation in the as-cast state, the aluminum alloy comprising: 8.5 to 10.5 wt% silicon; 0.3 to 0.8 wt% manganese; up to 0.06 wt% magnesium; up to 0.15 wt% iron; up to 0.03 wt% copper; up to 0.10 wt% zinc; up to 0.15 wt% titanium; 0.05 to 0.5 wt% molybdenum; 30 to 300 ppm strontium; or 5 to 30 ppm sodium; and / or 1 to 30 ppm calcium for continuous refining processes. Optionally, the alloy also contains: 0.05 to 0.3 wt% zirconium; gallium phosphide and / or indium phosphide in a content corresponding to 1 to 250 ppm phosphorus for grain refinement; titanium and boron, added by means of an aluminum master alloy comprising 1 to 2 wt% Ti and 1 to 2 wt% B for grain refinement; aluminum as the remainder and unavoidable impurities.

[0007] Furthermore, document EP 3 825 428 A1 describes a method for manufacturing die-cast components and die-cast components manufactured by the method, wherein excellent riveting capability is achieved when the die-cast component has an age-hardening aluminum alloy comprising the following alloy components: 5.0 to 9.0 wt% silicon; 0.25 to 0.5 wt% magnesium; aluminum as the remainder; and unavoidable impurities due to manufacturing, said impurities being at most 0.05 wt% and at most 0.15 wt% in total, wherein the die-cast component has a yield strength (Rp0.2) greater than 190 MPa and an elongation at break (A5) greater than or equal to 7%, and the uniform elongation (Ag) and reduction of area (Az) satisfy the condition Az ≥ Ag / 2.

[0008] Furthermore, document EP 3 775 309 B1 (WO 2020 / 207 708 A1) describes an aluminum die-casting alloy having the following alloy composition: 7.5 to 11.5 wt% silicon; 0.25 to 0.6 wt% manganese; 0.03 to 0.06 wt% chromium; 0.001 to 0.048 wt%, particularly 0.001 to 0.043 wt%, particularly 0.024 to 0.043 wt% molybdenum; 0.001 to 0.08 wt% magnesium; optionally 0.001 to 0.15 wt% iron; optionally 0.004 to 0.15 wt% titanium; optionally 0.01 to 0.2 wt% zirconium; optionally 0.008 to 0.02 wt% strontium; optionally 0.001 to 0.1 wt% strontium. Vanadium by weight percentage; aluminum as the remainder and unavoidable impurities. Summary of the Invention

[0009] Therefore, the purpose of this invention is to provide a naturally hardened aluminum casting alloy that does not require subsequent heat treatment after casting, has good mechanical properties, and can reduce costs and CO2 footprint.

[0010] According to the invention, the objective is achieved by an aluminum alloy for structural casting having the features described in claim 1, which has enhanced ductility. Furthermore, the objective is achieved by the application of this aluminum alloy, as described in another independent claim, to die-cast structural components, structural components for motor vehicles made from this aluminum alloy, and motor vehicles having structural components. Advantageous improvements of the invention are given in the dependent claims.

[0011] The present invention is based on the following basic idea: to provide an aluminum alloy that can use a high proportion of recycled aluminum without degrading the mechanical properties of the aluminum alloy.

[0012] According to a first aspect, this disclosure provides an aluminum alloy with enhanced ductility for structural casting, the aluminum alloy comprising: 7.5 to 11.5 wt% silicon; up to 0.24 wt% manganese; 0.08 to 0.5 wt% chromium; 0.04 to 0.095 wt% magnesium, particularly 0.06 to 0.095 wt% magnesium; 0.205 to 0.5 wt% iron, particularly 0.22 to 0.5 wt% iron, particularly 0.255 to 0.5 wt% iron; 0.01 to 0.5 wt% copper, particularly 0.205 to 0.5 wt% copper, particularly 0.22 to 0.5 wt% copper; up to 0.35 wt% zinc; 0.004 to 0.15 wt% titanium; aluminum as the remainder; and unavoidable impurities.

[0013] It should be noted that there is a conflict of objectives when using aluminum die-cast components. Silicon-containing alloys are advantageous in aluminum die-cast components due to their casting properties. However, in applications where no heat treatment is performed, they are relatively brittle compared to solution-annealed alloys because the absence of a solution annealing process restricts deformation capacity and promotes crack susceptibility in the brittle phases.

[0014] Here, solution annealing of alloys can often achieve better mechanical properties; however, it requires costly subsequent heat treatment processes. Due to these heat treatments, the size of the possible components is severely limited, or is only possible with high cost and investment, due to high space requirements, high energy consumption, and long heating and cooling times.

[0015] Naturally hardened alloys do not have this limitation and do not require costly subsequent processes, thus reducing the manufacturing cost of body components when using them. However, they are also relatively brittle.

[0016] Here, natural hardening refers to the situation where the required strength increase can only be achieved through solid solution strengthening and work hardening, without precipitation hardening. Therefore, naturally hardening alloys are also known as non-heat-treatable alloys. Conversely, the strength increase of heat-treatable alloys is achieved through precipitation hardening (a special heat treatment). For example, some silicon-containing aluminum alloys (AlSi alloys) are naturally hardening alloys.

[0017] The ever-increasing size of components necessitates the use of naturally hardened alloys that do not require heat treatment, as this makes it easier to meet the tolerance requirements of the vehicle body and avoids high manufacturing costs.

[0018] By skillfully selecting alloying elements, a naturally hardened alloy can be created. Although this alloy is a naturally hardened, unannealed alloy, it still possesses good casting properties, excellent mechanical properties, and high elongation.

[0019] Here, a silicon content within the range of 7.5 to 11.5 wt% ensures a good balance between ductility and casting performance for different component sizes. Silicon expands upon solidification, thus compensating for shrinkage during the solidification process of the cast component. Furthermore, compared to other elements, silicon releases a very large amount of energy upon solidification; therefore, a high silicon content ensures good fluidity, resulting in excellent casting properties of the alloy. If the selected silicon content is below 7.5 wt%, good fluidity cannot be achieved, therefore a silicon content below 7.5 wt% is not preferred. On the other hand, aluminum with a silicon content above 11.5 wt% tends to become brittle, therefore a silicon content above 11.5 wt% is also not preferred.

[0020] In alloys known from existing technology, manganese is partially added to reduce the adhesion tendency of die-casting molds, thereby improving the demolding performance of the resulting castings. Here, the manganese content is typically between 0.3 and 0.8% by weight. If the manganese content is below 0.3% by weight, it tends to exacerbate the adhesion tendency, and complex castings may no longer be able to be demolded from the mold.

[0021] However, the disclosed alloy achieves a very low manganese content of less than 0.24 wt% in die casting compared to existing technologies, while the use of chromium allows for problem-free demolding. Furthermore, an advantageous manganese content is at most 0.20 wt%, preferably at most 0.15 wt%, and more preferably at most 0.10 wt%.

[0022] This ensures a virtually defect-free production process while achieving significantly superior mechanical properties compared to naturally hardened alloys with high manganese content commonly found in current technologies. Despite being in an unannealed state, the disclosed alloy exhibits remarkably high elongation at break. In contrast, alloys with manganese content exceeding 0.24% by weight tend to form coarse intermetallic precipitates, which can lead to material embrittlement and consequently, a decrease in ductility and deformability.

[0023] The upper limit of 0.095 wt% for magnesium allows for the use of high proportions of recycled aluminum, while maintaining the natural hardening properties of the alloys disclosed herein. Increasing the magnesium proportion further beyond 0.095 wt% may lead to age hardening over time, resulting in an unfavorable unstable strength state. Conversely, below 0.04 wt%, the hardening effect of solid solution strengthening is lost, potentially leading to lower alloy strength. Significant solid solution strengthening, preventing age hardening, and achieving a thermally stable state are only observed within the aforementioned range of 0.04 to 0.095 wt% magnesium, particularly 0.06 to 0.095 wt%.

[0024] Furthermore, it is advantageous that the yield strength does not exceed 160 MPa and / or the increase in yield strength does not exceed 30 MPa after the coating process, including heat treatment, because such an increase indicates thermal instability.

[0025] Furthermore, it is advantageous that after the coating process, including heat treatment, the yield strength does not exceed 160 MPa and / or the increase in yield strength does not exceed 30 MPa (the increase in yield strength does not exceed 30 MPa), because such an increase indicates thermal instability. For example, in such a coating process, it may be set to continue at 80°C to 250°C for 10 to 120 minutes, particularly at 150°C to 250°C for 25 to 120 minutes.

[0026] In other words, in heat treatment simulating the coating process, or in heat treatment simulating temperature stress during the service life of a component (e.g., by heat treatment with a temperature load of 150°C for 1000 hours), the yield strength should not exceed 160 MPa and / or the increase in yield strength should not exceed 30 MPa; otherwise, thermal instability is indicated. Furthermore, excessively low yield strength values ​​may lead to fatigue strength problems.

[0027] The proportions of iron, copper, zinc, and titanium in the alloy disclosed herein allow the alloy to be made from a mixture of primary and recycled aluminum, wherein the content of recycled aluminum is maintained at a high level. On the other hand, according to the invention, the contents are selected such that even if the contents of iron, copper, zinc, and titanium are increased, coarser phase aggregates are not formed, thereby avoiding adverse effects on mechanical properties. From the perspective of corrosion resistance, unfavorable properties (which may be mainly caused by the presence of copper) can be kept within a limited range by the given weight proportions. For the purpose of manufacturing components with high ductility and good corrosion resistance or low corrosion susceptibility from the obtained aluminum alloy, it is advantageous to select copper and iron contents that are not too high.

[0028] The alloy according to the invention comprises 0.205 to 0.5 weight percent iron, preferably 0.22 to 0.5 weight percent iron, more preferably 0.255 to 0.5 weight percent iron, and even more preferably 0.28 to 0.5 weight percent iron.

[0029] The reason is that an iron content exceeding 0.205% can suppress the formation of the undesirable copper phase, thereby significantly improving corrosion resistance. Simultaneously, a particularly favorable phase formation and consequently high ductility can be achieved when the iron content exceeds 0.205%. For this purpose, high compositional supercooling may be advantageous. This compositional supercooling can be achieved by a combination of chromium and molybdenum by increasing the liquidus temperature of the Al(Fe,Cr,Mo)Si phase.

[0030] Furthermore, the alloy according to the invention comprises 0.001 to 0.5 weight percent copper, preferably 0.01 to 0.5 weight percent copper, more preferably 0.205 to 0.5 weight percent copper, and even more preferably 0.22 to 0.5 weight percent copper.

[0031] Furthermore, copper is preferably used in amounts of 0.001 to 0.40 by weight, more preferably in amounts of 0.001 to 0.35 by weight, even more preferably in amounts of 0.001 to 0.30 by weight, and even more preferably in amounts of 0.001 to 0.25 by weight.

[0032] Compared to some alloys in the prior art, a high copper content is acceptable due to the very limited magnesium content. In this way, the alloy achieves its advantageous corrosion resistance. Since copper can also cause age hardening, it is advantageous to use a low Mg content, thereby further improving thermal stability.

[0033] Furthermore, the alloy according to the invention comprises up to 0.35% by weight of zinc, preferably up to 0.30% by weight of zinc, preferably up to 0.25% by weight of zinc, more preferably up to 0.20% by weight of zinc, and even more preferably up to 0.15% by weight of zinc. High zinc content may lead to surface corrosion and thus adhesive leakage, potentially limiting the alloy's application range.

[0034] In particular, this can significantly reduce the CO2 footprint in demanding fields such as structural casting, i.e., manufacturing structural components such as thin-walled car body parts. For example, producing one kilogram of aluminum alloy can achieve a CO2 emission reduction of more than 6 kilograms of CO2 equivalent. This is extremely beneficial for reducing the CO2 footprint.

[0035] Furthermore, iron, for example, is almost insoluble in aluminum alloys, and therefore precipitates almost entirely as a coarse intermetallic phase. In silicon-containing aluminum alloys, the β-Al₅FeSi phase is particularly unfavorable because it is needle-like. This needle-like iron-containing phase reduces the ductility of components obtained from the aluminum alloy. Moreover, this iron-containing intermetallic phase is very brittle and prone to aggregation. When the iron content in the aluminum alloy is high, these needle-like iron-containing phases can become very large.

[0036] In particular, these large intermetallic ferrous phases have a strong tendency to initiate cracks and thus often lead to premature failure of components under mechanical stress. This is especially attributed to the low ductility of the component material due to the presence of acicular ferrous phases.

[0037] By adding manganese and / or molybdenum and / or chromium and / or vanadium, the formation of the unfavorable β-Al5FeSi phase can be particularly suppressed, and an iron-containing α phase is formed instead. This α phase, containing manganese and / or molybdenum and / or chromium and / or vanadium in addition to iron and aluminum, ensures a more favorable morphology for the phases containing these additives. In particular, it prevents the formation of large, acicular iron-containing phases. This can lead to improved mechanical properties of components made from the obtained aluminum alloy. Specifically, the ductility of components formed from the obtained aluminum alloy can be significantly improved in this way.

[0038] The alloys according to the invention comprise 0.08 to 0.5% by weight of chromium, preferably 0.08 to 0.36% by weight of chromium, because a higher chromium content may lead to the formation of coarse sludge phases, thereby potentially causing a rapid decrease in ductility.

[0039] Furthermore, the present invention includes improvements that provide additional advantages.

[0040] In an advantageous refinement of the invention, the alloy may further comprise 0.001 to 0.095 weight percent of molybdenum. When added to the α-AlFeSi phase, molybdenum may make the phase more spherical, which is advantageous for elongation at break or ductility. This effect does not occur or only decreases when molybdenum is insufficient, thus a molybdenum content greater than 0.001 weight percent is advantageous. Conversely, if the molybdenum content is greater than 0.095 weight percent (particularly associated with high Cr content), coarser agglomerates (so-called sludge phases) may occur, which may be detrimental to ductility and may significantly reduce the ductility of parts made from the alloy. Therefore, the molybdenum content is preferably no more than 0.095 weight percent (inclusive of this critical value).

[0041] In an advantageous improvement of the invention, the alloy may further comprise 0.01 to 0.2 weight percent zirconium. This improvement allows for an increase in the yield strength of the alloy without heat treatment. Zirconium forms a so-called aluminate, or Al3Zr phase, which has a grain-refining effect and also increases strength. This effect cannot be determined at very low content levels; therefore, a lower limit of 0.01 weight percent is preferred. On the other hand, if the content is too high, exceeding 0.2%, coarser Al3Zr acicular phases are formed, which in turn leads to a decrease in ductility.

[0042] In an advantageous improvement of the invention, the alloy may further comprise 0.001 to 0.1 weight percent vanadium. This improvement allows for an increase in the yield strength of the alloy without heat treatment. Furthermore, the vanadium content enables the easy use of recycled aluminum. Similar to manganese, vanadium can also suppress or reduce β-AlFeSi by adding it to α-AlFeSi. At lower vanadium contents, the beneficial effects of vanadium can no longer be determined. If the vanadium content is increased above the given limit of 0.1 weight percent, a coarse phase can be formed again, resulting in poor ductility.

[0043] In an advantageous improvement of the invention, the alloy may further comprise 0.002 to 0.030 weight percent of strontium. This improvement allows for an increase in the yield strength of the alloy without heat treatment. Strontium can modify the silicon phase, causing it to form a fine network structure. If the selected strontium proportion is too low, this effect cannot be determined. However, if the selected strontium proportion is too high, so-called over-modification occurs, leading to a re-coarsening of the silicon phase and a further decrease in ductility. Furthermore, when the strontium content exceeds 0.03 weight percent, the hydrogen content of the melt may increase, thereby reducing the quality of the casting.

[0044] In an advantageous embodiment of the invention, the aluminum alloy may be specified to comprise 25% by weight or more of recycled aluminum, and / or 10% by weight or more of post-consumer recycled aluminum. This embodiment offers the advantage that a reduction in CO2 footprint can be achieved in a simple manner with this composition.

[0045] In an advantageous improvement of the invention, it can be specified that after a temperature loading of 80°C to 250°C for 10 to 120 minutes, particularly after a temperature loading of 150°C to 250°C for 25 to 120 minutes, the yield strength is less than 160 MPa and the increase in yield strength is less than 30 MPa, and / or after a temperature loading of 150°C for 1000 hours, the yield strength is less than 160 MPa and the increase in yield strength is less than 30 MPa.

[0046] On the other hand, if the yield strength increases to above 160 MPa and / or by 30 MPa or more after loading at such a temperature, precipitation hardening has occurred, indicating the presence of thermal instability. This thermal instability is undesirable because it can lead to a decrease in elongation at break and thus reduce the load-bearing capacity of the component, or weaken its ability to absorb deformation energy in the event of an accident in a motor vehicle. An excessively low elongation at break can also cause problems with fatigue strength.

[0047] On the one hand, the heat treatment values ​​defined above are based on the fact that, advantageously, after a coating process including heat treatment, the yield strength does not exceed 160 MPa and / or the increase in yield strength does not exceed 30 MPa (an increase in yield strength not exceeding 30 MPa), because such an increase indicates thermal instability. For example, in such a coating process, it may be set to continue at 80°C to 250°C for 10 to 120 minutes, particularly at 150°C to 250°C for 25 to 120 minutes.

[0048] On the other hand, after heat treatment to simulate temperature stress during the service life of the component (e.g., by heat treatment with a temperature loading of 150°C for 1000 hours), the yield strength should not exceed 160 MPa and / or the increase in yield strength should not exceed 30 MPa (compared to the as-cast state), as this also indicates thermal instability.

[0049] Furthermore, according to one aspect of the invention, the above-described aluminum alloy is provided for use in die-casting structural components, particularly for die-casting structural components in automobile manufacturing. In other words, the above-described aluminum alloy can be used to manufacture structural components by means of die casting, which can be used, for example, as body components in automobile manufacturing.

[0050] Furthermore, according to one aspect of the invention, a structural member for a motor vehicle is provided, the structural member being made of an aluminum alloy according to the invention.

[0051] This type of structural component can be used for a variety of different applications in motor vehicles because it possesses not only the required strength but also sufficiently high ductility and good mold release properties. High strength is advantageous because it allows for the manufacture of motor vehicles with thin-walled structural components, which in turn reduces the vehicle's weight. Sufficiently high ductility ensures, for example, that crack-free and fracture-free riveting connections can be formed during stamping and riveting. Good mold release properties are advantageous, for example, in manufacturing processes such as the die casting of structural components.

[0052] The aluminum alloy according to the invention is particularly suitable for such structural components; however, the aluminum alloy can also be used for other components. By eliminating the need for heat treatment of the structural components, geometric deformation of the structural components can be avoided, thereby achieving high geometric or shape accuracy of the structural components.

[0053] Furthermore, according to another aspect of the invention, a motor vehicle having the aforementioned structural member is provided. In addition to the advantages described above, the use of the structural member eliminates the need for costly heat treatment, thus particularly achieving advantages in terms of cost and manufacturing time. Furthermore, if deformation due to heat treatment can be avoided, the dimensional stability of the motor vehicle according to the invention can be improved. Moreover, by using recycled aluminum, CO2 emissions during the manufacture of the motor vehicle according to the invention can be reduced, thus further reducing costs and improving durability. The motor vehicle according to the invention is preferably designed as an automobile, particularly as a passenger car or commercial vehicle, or as a bus or motorcycle.

[0054] The present invention also includes feature combinations of the described embodiments. Therefore, the present invention also includes the following implementations, each having a plurality of feature combinations of the described embodiments, provided that these implementations are not described as mutually exclusive. Attached Figure Description

[0055] Embodiments of the present invention are described below. This is illustrated in the following:

[0056] Figure 1 A schematic diagram showing the relationship between yield strength and magnesium content.

[0057] List of reference numerals in the attached diagram:

[0058] 100 Yield Strength

[0059] 102. No solution hardening range.

[0060] 104. Scope of solid solution hardening

[0061] 106 Range of thermal instability

[0062] 108 x-axis

[0063] 110 y-axis

[0064] 112 Lower limit

[0065] 114 upper limit Detailed Implementation

[0066] Figure 1 A schematic diagram showing the relationship between the yield strength 100 of an aluminum alloy and its magnesium content.

[0067] The Mg content, expressed as a weight percentage, is recorded on the x-axis (108), while the yield strength Rp0.2, expressed in MPa, is recorded on the y-axis (110). Here, 0.2% yield strength Rp0.2 refers to a (uniaxial) mechanical stress such that, after unloading, the permanent elongation (i.e., plastic deformation, hence with a subscript) relative to the initial length of the specimen reaches 0.2%.

[0068] from Figure 1 As can be seen, the Mg content range of 104 selected in this disclosure is optimal, ranging from the lower limit of 0.04 wt% (112) to the upper limit of 0.095 wt% (114). Only within the lower limit of 112 and the upper limit of 114 can both the strengthening effect brought about by solid solution strengthening and the thermally stable state be achieved.

[0069] When the Mg content is less than 0.04% by weight, the strength of the aluminum alloy is very low (range 102); however, when the magnesium content is high (range 106), that is, exceeding the upper limit of 114, age hardening will occur over time, resulting in unfavorable thermal instability.

[0070] The composition of various alloys is further shown in Table 1 below, and their properties are listed in Table 2 below.

[0071] Table 1: Composition of various aluminum alloys

[0072]

[0073] Table 2: Properties of Various Aluminum Alloys

[0074]

[0075] The first column of Table 1 lists the various chemical elements, and their contents in the given alloys are listed in Table 1 as a weight percentage.

[0076] Reference alloy 1 is taken from document EP 1 443 122 B1, reference alloy 2 is taken from document EP 3 825 428 B1, and reference alloy 3 is taken from document EP 3 775 309 B1. Furthermore, alloys according to the invention are listed in the fifth column of Tables 1 and 2.

[0077] Here, 0.2% yield strength R p0.2 This refers to a uniaxial mechanical stress such that, after unloading, the permanent elongation (i.e., the subscript p indicates plastic deformation) calculated relative to the initial length of the specimen reaches 0.2%. Furthermore, R is used here... p0.2 (F) represents the 0.2% yield strength in MPa at as-cast F without further heat treatment, and A(F) represents the elongation at break in % at as-cast F without further heat treatment. Furthermore, R is used here. p0.2 (T5) represents the 0.2% yield strength in MPa after heat treatment at 150°C for 1000 hours, while A(T5) represents the elongation at break in % after heat treatment at 150°C for 1000 hours.

[0078] Here, a larger value is preferred for the 0.2% yield strength of the aluminum alloy in the as-cast state, because this allows for a smaller wall thickness of the component, which helps to reduce the weight of the component.

[0079] Elongation at break here refers to the permanent elongation of a tensile specimen after fracture in a fracture test, which is calculated relative to the initial length of the tensile specimen. It characterizes the material's deformability or ductility. Preferably, aluminum alloys have a high elongation at break because this enables good riveting and stitching connections.

[0080] The descriptions of thermal stability, riveting connection, and corrosion resistance involve testing the alloy, whereby the alloy is evaluated relative to a pre-defined standard catalog. For example, thermal stability is tested by measuring the 0.2% yield strength and elongation at break on predefined samples, one hand without heat treatment and the other after heat treatment at 150°C for 1000 hours. If R... p0.2 If the increase exceeds 30 MPa, thermal stability cannot be guaranteed.

[0081] Regarding the stamping and riveting joint performance, the experimental design involved inserting a stamped rivet (5.3 mm in diameter) into a specimen. The specimen consisted of a 2 mm thick 6000 series sheet on the stamping side, while the mating parts on the die side comprised a 3 mm thick sheet of die-cast alloy to be inspected. Following the stamping and riveting connection, the resulting rivet joints were inspected for cracks and anomalies, and the results were evaluated according to a pre-defined standard catalog.

[0082] In addition, corrosion resistance is evaluated in corrosion change tests according to a standardized testing procedure. This testing procedure involves cyclical alternation of different climatic loads and / or corrosion loads. One test cycle includes:

[0083] – 4-hour salt spray test, according to test method NSS of DIN EN ISO 9227;

[0084] – 4 hours of storage under standard climate conditions; and

[0085] – 16 hours of humid heat storage, tested according to the DIN EN ISO 6270-2 climate (CH).

[0086] After every 5 cycles, a 2-day resting phase is performed under standard climatic conditions. Therefore, the 15-cycle test lasts a total of 3 weeks. These test methods allow for the evaluation of corrosion behavior under static loads comprised of salt, humidity, and temperature.

[0087] High thermal stability, good riveting connection properties, and high corrosion resistance are preferred here to ensure the wide applicability of the aluminum alloy. High yield strength, high elongation at break, high thermal stability, good riveting connection properties, and high corrosion resistance are also referred to here as good mechanical properties.

[0088] The recycling rate indicates the percentage by weight of recycled aluminum in the entire alloy. Additionally, the post-consumer waste ratio indicates the proportion of recycled aluminum that has been used by the end user and then re-enters the recycling cycle. High recycling rates and high post-consumer waste ratios contribute to improved durability of the aluminum alloys used.

[0089] Comparative alloys 1 and 3 have low magnesium content and are therefore naturally hardened. They possess good mechanical, physical, and thermal properties, but due to their low Fe, Cu, Mg, and Zn content, they can only be manufactured from recycled materials to a limited extent. This can be derived from the recovery rate values ​​in Table 2. These values ​​are calculated from or derived from the iron and copper contents given in the literature.

[0090] As can be seen from the table, due to the extremely low tolerance limits for impurity metals in alloys 1 and 3, post-consumer waste can only be used in a very limited manner.

[0091] Control Alloy 2 achieved a very high recovery rate and utilized an increased chromium content in addition to manganese. However, compared to Control Alloys 1 and 3, Control Alloy 2 exhibits only very limited mechanical and physical properties, primarily due to its still high manganese content of 0.61 wt% and, particularly, its high magnesium content of 0.35 wt%. This is evident from the poorer evaluation of thermal stability and riveting joinability according to Table 2. Furthermore, due to the increased magnesium and zinc content, Control Alloy 2 lacks natural hardening properties and therefore cannot maintain thermal stability.

[0092] The increased magnesium and zinc content compared to control alloys 1 and 3 slightly improves the possibility of using control alloy 2 to manufacture recycled aluminum (recycled material); however, this possibility is very limited by the limited iron and copper content.

[0093] The alloy according to the invention is the only alloy in this comparison that combines all the advantages. By selecting the range of Fe, Cu, Zn, and Mg contents, an alloy according to the invention with a high proportion of recycled aluminum can be achieved. This alloy achieves a recovery rate of 91% and a post-consumer waste ratio of 40%, which even exceeds the recovery rates of the aforementioned control alloys 1, 2, and 3.

[0094] Furthermore, by skillfully adjusting the element content in the alloy and the appropriate proportions between them, the alloy according to the invention is an alloy that is thermally stable on the one hand, has a high elongation on the other hand, and is also capable of achieving a high recycling rate.

[0095] The practice of allowing increased impurity element content enables extremely high recovery rates. Furthermore, by setting specific element content boundary conditions, the following comprehensive performance can be achieved: even with an increased proportion of impurity elements, better elongation properties (0.2% yield strength and elongation at break) than control alloys 1 and 3 with low recovery rates. Surprisingly, the elongation properties of the alloy according to the invention even surpass those of conventional naturally hardened alloys containing primary aluminum. Thus, the performance disadvantages of naturally hardened alloys compared to annealed alloys are partially compensated for or even overcome.

[0096] Overall, the examples demonstrate how to provide an aluminum alloy with enhanced ductility for structural casting, the application of the aluminum alloy in die-cast structural components, structural components made of the aluminum alloy for motor vehicles, and motor vehicles having the structural components.

Claims

1. An aluminum alloy with enhanced ductility for structural casting, the aluminum alloy comprising: - 7.5 to 11.5% by weight of silicon; - Up to 0.24% by weight of manganese; - 0.08 to 0.5% by weight of chromium; - 0.04 to 0.095% by weight of magnesium, particularly 0.06 to 0.095% by weight of magnesium; - 0.205 to 0.5% by weight of iron, particularly 0.22 to 0.5% by weight of iron, particularly 0.255 to 0.5% by weight of iron; - 0.001 to 0.5% copper by weight, particularly 0.205 to 0.5% copper by weight, particularly 0.22 to 0.5% copper by weight; - Up to 0.35% by weight of zinc; - 0.004 to 0.15% by weight of titanium; - As a surplus of aluminum and unavoidable impurities.

2. The aluminum alloy according to claim 1, Its features are, The aluminum alloy comprises 0.001 to 0.095 weight percent molybdenum.

3. The aluminum alloy according to claim 1 or 2, Its features are, The aluminum alloy includes 0.01 to 0.2% by weight zirconium.

4. The aluminum alloy according to any one of the preceding claims, Its features are, The aluminum alloy comprises 0.001 to 0.1% by weight of vanadium.

5. The aluminum alloy according to any one of the preceding claims, Its features are, The aluminum alloy comprises 0.002 to 0.030 wt% strontium.

6. The aluminum alloy according to any one of the preceding claims, Its features are, The aluminum alloy comprises 25% by weight or more recycled aluminum content, and / or 10% by weight or more post-consumer recycled aluminum content.

7. The aluminum alloy according to any one of the preceding claims, Its features are, - After being subjected to temperature loading at 80°C to 250°C for 10 to 120 minutes, especially after being subjected to temperature loading at 150°C to 250°C for 25 to 120 minutes, the yield strength is less than 160 MPa and the increase in yield strength is less than 30 MPa, and / or - After being subjected to temperature loading at 150°C for 1000 hours, the yield strength is less than 160 MPa and the increase in yield strength is less than 30 MPa.

8. The application of the aluminum alloy according to any one of the preceding claims for die-cast structural components, particularly for die-cast structural components in automobile manufacturing.

9. A structural member for a motor vehicle made of an aluminum alloy according to any one of claims 1 to 8.

10. A motor vehicle having the structural member according to claim 9.

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