EP3365472B1 - Aluminium alloy - Google Patents

Description

The invention relates to an aluminum alloy for components with increased thermal stability. The components made of the alloy are characterized by a high strength and hardness after high heat load. The aluminum alloy according to the invention is particularly suitable for the production of components of the type mentioned by means of extrusion, forging or casting in permanent molds, as well as for further processing of the components thus produced by means of thermal joining methods. The invention further relates to components which are produced by means of said alloy, and to the use of this aluminum alloy for the production of components, in particular components for the automotive industry.

Extrusion and casting are two of the most economical forming processes for aluminum alloys.

In extrusion molding, the design options are influenced and limited, above all, by the type of alloy, the available process forces and the pressing direction. Another important parameter in shaping by means of extrusion is the pressing temperature, whose height is limited by the respective alloy composition, in particular by its resistance to heat. Since it can come to a local heating of the alloy during forming, especially in the area of the tool inlet edges melting can occur, whereby the mechanical properties of the extruded product are impaired. The published application WO 2015/077880 discloses an alloy with increased thermal stability produced by extrusion.

In die casting, the design limits are mainly due to the aspired as simple as possible component geometry influenced, since the process has to do without insertable cores.

The quality of the extruded part depends not only on the machine setting and the tool design (die geometry) but also on the selected alloy system. For extruded products, in particular AlMn (Cu) and AlMgSi alloy systems are widely used ( F. OSTERMANN: "Application Technology Aluminum", 3rd ed., Pp. 456-457; Berlin 2014 ). The chemical composition and microstructure also have a crucial role in the permanent molding process, in particular in die casting, with regard to the later application technology-relevant component properties.

When forming by forging, it can also lead to an increase in temperature as a result of the forming work, in particular if the forming speeds are too high. In the process, local overheating may occur in the workpiece, impairing the microstructure and the mechanical properties. Also in this molding process, the influence of the alloy composition is essential. When designing forgings, process-related design rules must also be observed, which limit the possibilities of shaping.

As described above, the freedom of design in the mentioned molding processes (extrusion, molding, forging) limits, which may be technically or economically limited.
However, especially in the automotive industry, increasingly complex components and component groups are becoming available Application which can not or can not be economically produced by molding processes such as extrusion or molding.

As a result of the further development of suitable joining methods, in particular welding or soldering, the fields of application for components made of aluminum alloys have greatly expanded since in this way it is also possible to produce complex components and component groups.

Since in this case usually thermal joining methods such as welding or soldering are used, the reliability of the material and its stability in the thermal stress occurring essential prerequisites. The resistance of the material to short-term temperature stress is important in both accidental and intentional heating of a structure, such as soldering or welding.

In general, attention has been paid in the past to the development of aluminum alloys with pronounced high temperature strength at high processing and operating temperatures for demanding components. Especially in the automotive industry there is a demand for material stability, in particular with regard to strength and hardness, after processing by means of processes with the highest possible temperature exposure.

In this context, increasingly aluminum alloys are required, which are suitable for components which require no further heat treatment after passing through the production process in order to achieve the desired mechanical properties.

An increased resistance to thermal stress is also due to the ever-increasing operating temperatures, eg. As in engine components such as pistons, of utmost importance. Also in this field of application favorable strength properties are required at elevated temperatures, in addition to other required properties such as high wear resistance, low density, low temperature expansion and good castability. These requirements can be met only with cast alloys with relatively high Si contents and admixtures of Cu so far. However, such alloys are unsuitable for die casting due to the tendency to form air pockets.

Hot strength is generally understood to mean the strength of the material at elevated temperatures. Highest heat resistance values show u. a. the alloys of the 2xxx type (AlCu). The heat resistance is u. a. achieved by increased levels of Si, Cu, Ni or Fe, whereby, however, a deterioration of the mechanical properties (eg fracture toughness) is effected (F. OSTERMANN, supra, pp. 300-303).

At higher temperatures, it can not only lead to an irreversible change in the microstructure and thus to an irreversible reduction in strength, but also to creep, with the material or the component slowly plastically deformed. Aluminum materials with favorable creep properties are found among the alloys of the 3xxx, 5xxx and 6xxx alloy systems ( F. OSTERMANN: "Application Technology Aluminum", 3rd ed., Pp. 300-304; Berlin 2014 ). For joining techniques such as welding or soldering, aluminum alloys of type 4xxx are generally used.

Usually, the required mechanical properties, in particular high hardness, are achieved by adding copper or zinc to the alloys. In addition, these alloys are subjected to a heat treatment to achieve an improvement in the mechanical properties by the curing effects. In this case, metastable phases are formed to counteract dislocation movements under application of force. Alternatively, Al-Mn alloys are used.

The prerequisite for the solderability of an alloy is that the solidus temperature of the material is above the liquidus temperature of the solder. In brazing, the working temperature is generally 440 to 600 ° C; when soldering, the working temperature is below 440 ° C.

The temperature profile of the brazing process significantly affects the mechanical properties. If temperatures near the solidus point are used, this leads to a softening of the material. A gain in strength can only be achieved by subsequent cold or hot curing with rapid cooling of the construction.

The number of brazeable aluminum alloys is very limited. This results from the above-mentioned condition, according to which the solidus temperature of the material must be above the liquidus temperature of the brazing alloy. While common Al-Mn alloys are less susceptible to heat effects, they also show shortcomings in hardness stability at processing temperatures close to the solidus point.

Furthermore, aluminum alloys for high temperature applications are known, which additives of alloying elements from the Group of rare earth metals (eg Sc, Er). These form dispersoids in the aluminum matrix (for example of the Al ₃ Er type), which is intended to achieve an improvement in the mechanical properties at elevated operating temperatures. Out EP 2 110 452 A1 For example, such an alloy is known which has a high Cu content (1.0 to 8.0 wt%) but does not contain Zn.

In view of the above-described requirements, the present invention has for its object to provide an aluminum alloy suitable for extrusion, forging and casting in permanent molds (in particular die casting), and which is easy to cast and in the cast state and in short-term, strong heat has a high hardness. In addition, the alloy should have good joining properties, in particular good brazeability, and high corrosion resistance. In addition, the alloy should be suitable for the production of components for the automotive industry, in particular of components with increased heat resistance.

These objects are achieved with an aluminum alloy according to the main claim and by the embodiments specified in the dependent claims, as well as by the components which are produced using the aluminum alloy according to the invention, and which are further processed by means of joining methods, in particular thermal joining method.

With the alloy composition according to the invention, high heat stability can be achieved with extruded profiles, but also with forged and die-cast parts, in the production or casting state with good hardness values. The Alloy is therefore particularly suitable for the production of temperature-stressed components for the automotive industry and / or for further processing by means of joining methods, in particular thermal joining methods such as brazing or welding. (Due to the increased thermal stability of the alloy, extrusion or other forming processes can be performed at higher process speeds or higher pressures without causing local overheating in the workpiece.)

• 0,2 bis 1,8 Gew.-% Si
• 0,2 bis 1,8 Gew.-% Mg
• 0,8 bis 2,5 Gew.-% Mn
• 0,2 bis 1,5 Gew.-% Fe
• 0,05 bis 0,75 Gew.-% Zr
• 0,03 bis 0,18 Gew.-% Ti.

The alloy according to the invention has the following composition:

• 0.2 to 1.8% by weight of Si
• 0.2 to 1.8% by weight Mg
• 0.8 to 2.5% by weight of Mn
• 0.2 to 1.5% by weight Fe
• 0.05 to 0.75 wt.% Zr
• 0.03 to 0.18 wt% Ti.

• max. 0,1 Gew.-% Cr
• max. 0,05 Gew.-% Cu
• 0,2 bis 1,8 Gew.-% Zn
• 0,02 bis 0,5 Gew.-% Er.

In addition, the alloy may optionally contain one or more of the following elements in the proportions indicated below:

• Max. 0.1% by weight of Cr
• Max. 0.05% by weight of Cu
• 0.2 to 1.8% by weight of Zn
• 0.02 to 0.5% by weight of Er.

Further, the alloy may optionally contain a grain refining agent containing Ti and B in a proportion of 0.01 to 0.2% by weight. The specified composition of the alloy remains unaffected. The grain refining agent is preferred in the preparation of the alloy in the form of an aluminum master alloy containing said components.

The rest is made of aluminum and inevitable impurities. Preferably, the proportion of such impurities is max. 0.05% by weight (individually) or max. 0.15% by weight (total).

Surprisingly, it has been found that the limitation of the Cu content to a maximum of 0.05% by weight causes the solidus point of the alloy not to fall below 610 ° C. Preferably, the Cu content is limited to a maximum of 0.03 wt .-%. Further, it has been found that by setting the Mn content in the range of 0.8 to 1.5% by weight of Mn, preferably 1.2 to 1.5% by weight, high structural strength at elevated temperature is ensured can be expected, so that during demolding with very little to no delay is expected. In the case of the Mn contents used according to the invention, in addition, production by means of casting methods, in particular during die casting, prevents sticking in the mold and ensures demoldability.

Furthermore, it has surprisingly been found that by adjusting the iron / manganese ratio (based on the weight fractions) in the range of 0.5 to 0.7, in particular in the range of 0.6 to 0.7, an improvement in the castability of Alloy is effected. It is particularly advantageous if the Fe / Mn ratio is 2: 3 (= 0.67).

The preferred silicon content is 0.6 to 0.8 wt .-%, in particular 0.7 wt .-%. Regarding the Si content, it has also been found that adjustment of the Si / Mg ratio in the range of 0.9 to 1.1 has a favorable effect on the hardness of the alloy and the castability. For optimum hardness and castability, preferably a Si / Mg ratio of 1: 1 should be maintained.

The preferred zirconium content is 0.08 to 0.35 wt .-%, in particular 0.1 to 0.3 wt .-%. Regarding the Zr content, it has also been found that the heat stability and castability of the alloy can be further increased when the Ti / Zr ratio is in the range of 0.15 to 1, preferably 1: 4 (= 0.25). ,

The Fe content is 0.2 to 1.5 wt .-%, preferably 0.2 to 1.0 wt .-%, in particular 0.2 to 0.8 wt .-%. Preferably, the Fe content is adjusted depending on the Fe content, as explained above (Fe / Mn ratio).

The Mg content is in the range of 0.2 to 1.8 wt% Mg, preferably 0.2 to 1.2 wt%, more preferably 0.2 to 0.9 wt%, and is more preferably 0.7% by weight. Preferably, the Mg content is adjusted depending on the Si content, as explained above (Si / Mg ratio).

The Ti content is in the range of 0.03 to 0.18 wt .-%, preferably in the range of 0.05 to 0.1 wt .-%. The Ti content is preferably adjusted as a function of the Zr content, as explained above (Ti / Zr ratio).

Furthermore, it has surprisingly been found that the addition of erbium (Er), the thermal stability of the alloy can be additionally increased. According to a preferred embodiment, the alloy according to the invention therefore contains erbium as a further alloying element. The desired effect is achieved by addition of 0.02 to 0.5 wt .-% He. This proportion is preferably in the range from 0.02 to 0.3% by weight of Er.

Furthermore, it has surprisingly been found that the addition of zinc (Zn), the thermal stability of the alloy can be further increased. According to a preferred embodiment, the alloy according to the invention therefore contains zinc as a further alloying element. The optional Zn content is in the range of 0.2 to 1.8 wt% Zn; it is preferably 0.4 to 0.8 wt .-%, in particular 0.5 to 0.7 wt .-%. According to further embodiments, the Zn content is in the range of 0.4 to 1.2 wt .-%, preferably from 0.6 to 1.2 wt .-%, in particular 1 wt .-%.

Furthermore, it has surprisingly been found that the alloying elements Zn and Er, when used in combination, allow a further increase in thermal stability. In particular, with combined addition of 0.02 wt .-% to 0.5 wt .-% Er and 0.2 to 1.8 wt .-% Zn, preferably 0.4 to 0.8 wt .-% Zn leaves to achieve such an increase.

Grain refining is preferably performed on the alloy of the present invention using a grain refining agent containing Ti and B. The proportion of the grain refining agent in the alloy according to the invention is preferably 0.5 to 2 kg / t, particularly preferably 1.5 kg / t.

Preferably, the grain refining agent used is an aluminum master alloy containing Ti and B (balance: aluminum), and which in the preparation of the alloy in a proportion of preferably 0.5 to 2 kg / t, particularly preferably 1.5 kg / t , is added. In such Al alloying, Ti and B are substantially contained in crystalline or particulate form which can serve as nuclei (eg TiB2, Al3Ti AlTi5B1, AlTi6).

The master alloy preferably contains 2.7 to 3.2% by weight of Ti, in particular 2.9 to 3.1% by weight of Ti, and 0.6 to 1.1% by weight of B, in particular 0.8 to 0.9% by weight B; the rest is aluminum.

It is further preferred that the weight ratio Ti / B in the master alloy is 2.5 to 3.5, in particular 3: 1 (= 3.0).

The aluminum alloy according to the invention and the components produced therefrom are characterized by having a Brinell hardness of at least 55 HBW5 / 250, preferably at least 65 HBW5 / 250, more preferably at least 80 HBW5 / 250.

The aluminum alloy according to the invention and the components produced therefrom are further distinguished by a solidus temperature of ≥ 610 ° C., in particular ≥ 630 ° C.

Depending on the field of application or requirement profile, the alloy according to the invention can optionally be subjected to a heat treatment. This is preferably for a period of 2 to 42 hours, in particular 6 to 24 hours, at a temperature in the range of 325 to 425 ° C, in particular 350 to 400 ° C performed. Subsequently, an air cooling is carried out or the heat-treated alloy is quenched in a suitable gaseous (eg air or inert gas) or liquid medium (eg water or oil). The preferred heat treatment is carried out at 6-24 h and 350-400 ° C with subsequent air cooling.

The alloy according to the invention can be used to produce components for a wide variety of applications, preferably for automotive applications. The alloy according to the invention, in particular the heat-treated alloy (see above), is suitable for the production of components which have high operating temperatures - eg. Up to 250 ° C or up to 300 ° C - (eg, engine or transmission components such as pistons, cylinder heads, engine blocks, gearboxes, heat exchangers).

Furthermore, the alloy according to the invention is particularly suitable for components which are further processed by means of thermal joining methods, such as brazing (in particular brazing) or welding. The alloy according to the invention is suitable for soldering aluminum components with flux, for example in the automotive industry and air conditioning technology, as well as for processes in soldering furnaces; in particular for the production of heat exchangers.

The invention thus extends to components made of an alloy, as defined in more detail above. Preferably, the production takes place by casting in permanent molds, in particular by die casting, or by extrusion, or by forging. If necessary, the components can be produced by means of further methods, in particular thermal joining methods (eg soldering, welding) or by forging, be further processed to obtain more complex assemblies or components with complex geometries.

In general, if desired, the heat resistance of the components made of the alloy of the invention can be further increased by subjecting them to thermal aging. In addition, by such a heat treatment, an increase in the Brinell hardness can be achieved.

Surprisingly, it has been found that the high hardness already present in the state of manufacture (typically in the range from 50 to 70 HBW 5/250) can be increased even further in the case of the components produced using the alloy according to the invention by subjecting it to heat treatment at 150 to 240 ° C., preferably 180 to 220 ° C, more preferably at 200 ° C, for a period of 4 hours to 72 hours, preferably 8 to 24 hours, particularly preferably 8 to 12 hours. After such heat treatment, the components have an increased Brinell value (HBW5 / 250), which is typically 1.1 to 1.5 times the initial value (before heat treatment). An even greater increase in hardness is possible.

With a heat treatment as described above, components having a Brinell hardness (HBW5 / 250) of at least 70, preferably at least 80, can be obtained. The components produced in this way preferably have a Brinell hardness in the range from 70 to 120, in particular in the range from 75 to 95.

The alloys of the invention and the components produced therefrom are characterized by a high heat stability at high heat load, even over long periods, from. As a result, the mechanical properties, especially the hardness, are largely stable to such temperature influences.

• durch eine Wärmebeaufschlagung der Bauteile bei 150 bis 240 °C, vorzugsweise 180 bis 220 °C, besonders bevorzugt bei 200 °C, während einer Zeitdauer von 4 h bis 72 h, vorzugsweise 8 bis 24 h, besonders bevorzugt 8 bis 12 h, wird allgemein eine Zunahme der Härte bewirkt. Aufgrund der Zunahme weisen die Bauteile einen Brinell-Wert auf, der zumindest dem 1,1- bis 1,5fachen des anfänglichen Brinell-Wertes (HBW5/250) entspricht. Auch eine länger andauernde Wärmebehandlung (z. B. mehr als 3 d, bis zu 30 d oder noch länger), wie sie beispielsweise während der Verwendung oder im Betriebszustand der Bauteile vorkommen kann, hat keine nachteiligen Auswirkungen auf die Härte oder die sonstigen mechanischen Eigenschaften der Bauteile.
• wird die Wärmebeaufschlagung bei den vorstehend angegebenen Temperaturen über einen längeren Zeitraum (> 3 d, insbesondere 4 d, oder auch länger, z. B. 30 d) durchgeführt, so weisen die Bauteile danach eine Brinell-Härte auf, die zumindest dem 1- bis 1,3fachen des anfänglichen Brinell-Wertes (HBW5/250) entspricht. Vorzugsweise tritt auch bei länger andauernder Wärmebeaufschlagung (3 d oder länger, insbesondere 4 d oder länger, z. B. 30 d) bei den oben angegebenen Temperaturen keine Verschlechterung der Härte auf. Zumindest werden die anfänglich vorhandenen Härteeigenschaften im Wesentlichen beibehalten, sofern nicht - wie beschrieben - eine Steigerung der Härte bewirkt wird.
• durch eine Wärmebeaufschlagung der Bauteile bei 260 bis 350 °C, vorzugsweise 280 bis 320 °C, besonders bevorzugt bei 300 °C, während einer Zeitdauer von 4 h bis 72 h, vorzugsweise 8 bis 24 h, besonders bevorzugt 8 bis 12 h, wird lediglich eine leichte Abnahme der Härte bewirkt. Im Allgemeinen beträgt die Brinell-Härte nach einer solchen Wärmebehandlung noch 80-95% des anfänglichen Wertes (d. h. bezogen auf den Herstellungszustand). Vorzugsweise tritt auch bei länger andauernder Wärmebeaufschlagung (3 d oder länger, insbesondere 4 d oder länger, z. B. bis zu 30 d) bei den vorstehend angegebenen Temperaturen keine weitere Veränderung der Brinell-Härte auf (d. h. sie bleibt im wesentlichen konstant bei ca. 80-95% des anfänglichen Wertes).

Under the influence of elevated temperatures, the components produced from the alloy according to the invention generally exhibit the behavior described below with respect to the temperature-dependent change in hardness (Brinell hardness):

• by heat application of the components at 150 to 240 ° C, preferably 180 to 220 ° C, more preferably at 200 ° C, during a period of 4 hours to 72 hours, preferably 8 to 24 hours, particularly preferably 8 to 12 hours generally causes an increase in hardness. Due to the increase, the components have a Brinell value that is at least 1.1 to 1.5 times the initial Brinell value (HBW5 / 250). Even a prolonged heat treatment (eg more than 3 d, up to 30 d or even longer), as may occur, for example, during use or in the operating state of the components, has no adverse effects on the hardness or other mechanical properties of the components.
• If the application of heat at the abovementioned temperatures is carried out over a relatively long period of time (> 3 d, in particular 4 d or even longer, for example 30 d), the components subsequently have a Brinell hardness which is at least equal to to 1.3 times the initial Brinell value (HBW5 / 250). Preferably occurs even with prolonged heat application (3 d or longer, in particular 4 days or longer, eg B. 30 d) at the above temperatures no deterioration in hardness. At a minimum, the initial hardness properties are substantially retained unless an increase in hardness is effected, as described.
• by heat application of the components at 260 to 350 ° C, preferably 280 to 320 ° C, more preferably at 300 ° C, during a period of 4 hours to 72 hours, preferably 8 to 24 hours, particularly preferably 8 to 12 hours only causes a slight decrease in hardness. In general, the Brinell hardness after such heat treatment is still 80-95% of the initial value (ie, in terms of manufacturing state). Even with prolonged application of heat (3 d or longer, in particular 4 d or longer, eg up to 30 d), no further change in the Brinell hardness occurs at the temperatures indicated above (ie it remains essentially constant at approx 80-95% of the initial value).

Another important and advantageous feature of the alloy according to the invention is that the components produced therewith can be temporarily exposed to a temperature which is close to the solidus point, without causing a significant impairment of the hardness or other mechanical properties. This heat stability is of practical importance, since components are exposed to such a temperature load when they are further processed, for example by means of thermal joining methods (in particular brazing or welding).

The components produced with the alloy according to the invention can briefly (≤ 30 min, preferably ≤ 20 min, in particular ≤ 15 min) with a temperature of 400 to 650 ° C, preferably 400 to 620 ° C, in particular 400 to 610 ° C, are applied, without thereby causing a relevant impairment of the mechanical properties, in particular the hardness. After a temperature load, as indicated above, only a slight decrease in hardness is observed. In general, the Brinell hardness after such a short heat application is still 70-95% of the initial value (state of manufacture).

The alloy according to the invention and the components produced therefrom thus meet the requirements mentioned at the outset, in particular with regard to heat stability with high heat load.

The aluminum alloy according to the invention is particularly suitable for the production of components for the automotive industry by die-casting, forging or extrusion, wherein the components can optionally be further processed by means of joining processes, in particular by means of thermal joining processes.

The aluminum alloy of the present invention may preferably be used to manufacture such components which are exposed to elevated temperature requirements during their manufacture, further processing, or later use, such as engine or transmission components (eg, pistons, cylinder heads, engine blocks, gearboxes, etc.). , Heat exchangers, but also chassis components and body components.

The preparation of the alloy according to the invention can be carried out by methods known to the person skilled in the art, usually by producing a melt which contains a composition which corresponds to the abovementioned alloy composition according to the invention. The alloying elements Ti and B are preferably added in the form of a master alloy in the preparation of the alloy, as explained above.

The alloy according to the invention is preferably produced by the vertical continuous casting process. By prior gas treatment of the melt with inert gases, a sufficient melt quality is ensured and a low-hydrogen cast product is produced; This is also an important prerequisite for achieving a high hardness stability under heat. Methods for the treatment of molten metal with inert gases are known in the art.

According to a preferred embodiment, the alloy is subjected to an optional heat treatment after its production. This is preferably carried out for a period of 2 to 42 hours, in particular 6 to 24 hours, at a temperature in the range from 325 to 425 ° C., in particular 350 to 400 ° C. Subsequently, an air cooling is carried out or the heat-treated alloy is quenched in a suitable gaseous (eg air or inert gas) or liquid medium (eg water or oil). The preferred heat treatment is carried out at 6-24 h and 350-400 ° C with subsequent air cooling.

The production of components using the alloy according to the invention can also be carried out by means of known methods, preferably by means of extrusion molding, casting in permanent molds (in particular die casting) and / or forging. Optionally, a further processing of the components by means of joining methods (in particular brazing or welding) or by means of forming process.

According to a preferred embodiment, the components produced from an alloy according to the invention are subjected to an optional heat treatment (hot aging) for the purpose of increasing the hardness. This heat treatment is carried out at 150 to 240 ° C, preferably 180 to 220 ° C, more preferably at 200 ° C, for a period of 4 hours to 72 hours, preferably 8 to 24 hours, more preferably 8 to 12 hours ,

Examples

The starting point or comparative alloy used was an Al-Mn alloy based on EN AW-3103, which is known under the trade name "Aluman-16" (AlMnl, 6, manufacturer: Aluminum Rheinfelden GmbH). This alloy is brazeable because of its high solidification point, and it is suitable for the die casting process. The alloy is used in cooler construction and in the food industry.

The composition of this alloy is given in Table 1 (below) (first line, "V").

Due to the relatively high Mn and Fe contents, this alloy is characterized by good temperature resistance at elevated temperatures. In the new application areas described above (in particular for applications in the automotive industry), however, this alloy is reaching its limits. In particular, the hardness is no longer sufficient to meet the required component properties. Here, a clear improvement could be achieved with the alloy described in this application, as illustrated by the test results in Tables 2, 3 and 4 below. Table 1: Alloy compositions Si mg Mn Fe Zn Zr Ti Cr Cu He Solidus [° C] V 0.15 0.05 1.5 0.9 0.1 - 0.15 - 0.03 - 650 L1 0.7 0.7 1.5 0.8 - 0.1 0.1 0.06 - - 635 L2 0.7 0.7 1.2 0.8 - 0.2 0.05 0.06 - - 630 L3 0.7 0.7 1.2 0.8 - 0.3 0.05 0.06 - - 630 L5 0.7 0.7 1.2 0.8 - 0.3 0.05 0.06 - 0.05 630 L6 0.7 0.7 1.2 0.8 0.8 0.3 0.05 0.06 - - 620 L7 0.7 0.7 1.2 0.8 0.8 0.3 0.05 0.06 0.03 - 615 L4 0.7 0.7 1.2 0.8 0.6 0.3 0.08 0.06 - 0.1 625 L8 * 0.7 0.7 1.2 0.8 0.6 0.3 0.08 0.06 - 0.1 625 * Heat treated according to claim 15

All data in% by weight; Remainder: Al and unavoidable admixtures. The table lines labeled L1, L2, L3, L4, L5, L6 and L7 refer to alloy variants according to the present invention. L8 corresponds to L7 with additional heat treatment according to claim 18, and also represents an alloy according to the invention.

Seven alloys according to the invention L1, L2, L3, L4, L5, L6 and L7 were melted, the composition of which is given in Tab. L8 corresponds to L7 with additional heat treatment according to claim 18. For reference, a comparative alloy V was melted ("Aluman-16", see above), the composition of which is also given in Tab. From all eight alloys cylindrical specimens were cast (∅ 40 mm, height 30 mm).

In order to check the influence of the temperature on the change in hardness, the specimens cast from the eight alloys were subjected to different heat loads.
It was tested at three temperatures for different lengths of time. The results are given in Tables 2, 3 and 4 below.
Long-term tests were carried out at 200 ° C. (Table 2) and 300 ° C. (Table 3), each over a period of 10 hours and 100 hours.
Furthermore, a short-term test was carried out at 600 ° C and 900 s (15 min) (Table 4) in order to simulate the thermal load and the behavior of the alloys in thermal joining processes.

After heat treatment, the specimens treated under the specified temperature conditions were cooled to room temperature (about 25 ° C.) in air and then subjected to a Brinell hardness test (HBW5 / 250, tungsten carbide test ball, ball diameter 5 mm). The arithmetic mean of the measured hardness values is shown in Tables 2, 3 and 4.

The results show that all aluminum alloys according to the invention (L1 to L8) have a higher hardness than the comparative alloy V, irrespective of the duration of the heat action.

Already in the casting state (ie before the start of the test), the hardness of the alloy variants (L1 to L8) according to the invention is significantly higher than that of the comparative alloy V. In the heat treatment at 200 ° C. (10 h), the hardness could even be increased (see Tab. 2).

All other experiments show that the inventive alloy variants (L1 to L8) are superior to the comparative alloy in terms of hardness values. At higher temperatures or with a longer test duration, a decrease in hardness is observed in comparison to the cast state (see Tables 3 and 4), but the hardness values achieved are still above the hardness values of the comparative alloy.

The short-term test conducted at 600 ° C also shows a clear result. The measured hardness values of the aluminum alloys L1 to L8 according to the invention are more than 10 Brinell hardness units above the hardness value of the comparative alloy V. Table 2: Comparison of hardness (HBW5 / 250) at 200 ° C before the start of the test 10h 100h V 42 43 45 L1 72 85 74 L2 69 80 72 L3 57 83 73 L5 62 83 74 L6 65 85 72 L7 65 83 72 L4 69 81 74 L8 72 81 75 before the start of the test 10h 100h V 42 43 43 L1 72 58 58 L2 69 60 55 L3 57 55 57 L5 62 58 58 L6 65 56 55 L7 65 56 55 L4 69 60 58 L8 72 62 60 before the start of the test 900s V 42 40 L1 72 52 L2 69 54 L3 57 55 L5 62 56 L6 65 54 L7 65 51 L4 69 57 L8 72 60

Claims (15)

1. An aluminum alloy for components having increased heat stability, particularly for the production of such components by means of extrusion, forging or casting in permanent molds, the alloy having the following composition:

   0.2 to 1.8 wt% of Si

   0.2 to 1.8 wt% of Mg

   0.8 to 2.5 wt% of Mn

   0.2 to 1.5 wt% of Fe

   0.05 to 0.75 wt% of Zr

   0.03 to 0.18 wt% of Ti,

   optionally one or more of the following elements:

   max. 0.1 wt% of Cr,

   max. 0.05 wt% of Cu,

   0.2 to 1.8 wt% of Zn

   0.02 to 0.5 wt% of Er;

   and optionally 0.01 to 0.2 wt% of a grain refiner containing Ti and B;

   the balance being aluminum and inevitable impurities.
2. The aluminum alloy according to claim 1, characterized in that the Mn content is 0.8 to 1.5 wt%, preferably 1.2 to 1.5 wt%.
3. The aluminum alloy according to claim 1 or 2, characterized in that the ratio Fe/Mn is in the range of 0.5 to 0.7, preferably 2:3.
4. The aluminum alloy according to any one of the preceding claims, characterized in that the Si content is 0.6 to 0.8 wt%, preferably 0.7 wt%.
5. The aluminum alloy according to any one of the preceding claims, characterized in that the ratio Mg/Si is in the range of 0.9 to 1.1, preferably 1:1.
6. The aluminum alloy according to any one of the preceding claims, characterized in that the Zr content is from 0.08 to 0.35 wt%, preferably 0.1 to 0.3 wt%, and/or that the ratio Ti/Zr is in the range of 0.15 to 1, preferably 1:4.
7. The aluminum alloy according to any one of the preceding claims, characterized in that it comprises Cu in an amount not exceeding 0.05 wt%, preferably not exceeding 0.03 wt%.
8. The aluminum alloy according to any one of the preceding claims, characterized in that it contains Cr in an amount not exceeding 0.1 wt%, preferably not exceeding 0.08 wt%, and/or 0.02 to 0.5 wt% Er, preferably 0.02 to 0.3 wt% Er.
9. The aluminum alloy according to any one of the preceding claims, characterized in that the Zn content is 0.4 to 0.8 wt%, preferably 0.5 to 0.7 wt%.
10. The aluminum alloy according to any one of claims 1 to 8, characterized in that the Zn-content is 0.4 to 1.2 wt%, preferably 0.6 to 1.2 wt%, particularly 1 wt%.
11. The aluminum alloy according to any one of the preceding claims, characterized in that it has a Brinell hardness (HBW5/250) of at least 55, preferably at least 65, more preferably at least 80, and/or that its solidus temperature is ≥610 °C.
12. The aluminum alloy according to any one of the preceding claims, characterized in that it was heat-treated for 2 to 42 h, preferably 6 to 24 h, at 325 to 425 °C, preferably at 350 to 400 °C, followed by cooling in a gaseous or liquid medium.
13. A component, in particular for the automotive industry, made of an alloy according to any one of the preceding claims, preferably a component produced by casting in permanent molds, in particular by pressure die casting, or by forging, or by extrusion, wherein said component has optionally been further processed by means of one or more thermal joining processes, preferably by means of soldering/brazing or welding.
14. The component according to claim 13, characterized in that it is subjected to a heat treatment for 4 h to 72 h, preferably for 8 to 24 h, at 150 to 250 °C, preferably at 180 to 220 °C, wherein said component preferably has a Brinell hardness (HBW5/250) in the range of 70 to 120, in particular in the range of 75 to 95.
15. Use of an aluminum alloy according to any one of claims 1 to 12 for the manufacture of components for the automotive industry by pressure die casting, forging or extrusion, wherein the components are optionally further processed by joining processes, in particular by means of thermal joining processes.