阅读说明：本技术 耐晶间腐蚀的铝合金带及其制造方法 (Intergranular corrosion resistant aluminum alloy strip and method of making same ) 是由 亨克-扬·布林克曼 奥拉夫·恩格勒 托马斯·亨舍尔 于 2013-08-22 设计创作，主要内容包括：本发明涉及一种由AA5xxx类型的铝合金构成的铝合金带,该铝合金除了Al和不能够避免的杂质之外还具有至少为4重量％的Mg含量。本发明的目的在于,提出一种由AlMg合金组成的铝合金带,尽管具有高强度和至少为4重量％的Mg含量,该铝合金带对晶间腐蚀稳定,该目的按照本发明的第一教导通过一种铝合金带实现,该铝合金带具有再结晶的组织结构,其中,μm表示的组织结构的晶粒度(KG)与重量％表示的Mg含量(c_Mg)满足以下相关性：KG≥22+2×c_Mg,其中,铝合金带的铝合金具有以下组成成分(重量％)：Si≤0.2％,Fe≤0.35％,0.04％≤Cu≤0.08％,0.2％≤Mn≤0.5％,4.35％≤Mg≤4.8％,Cr≤0.1％,Zn＜0.25％,Ti≤0.1％,剩余Al和单独最大为0.05重量％,总量最大为0.15重量％的不能够避免的杂质。(The invention relates to an aluminium alloy strip consisting of an aluminium alloy of the AA5xxx type, which has a Mg content of at least 4 wt.% in addition to Al and unavoidable impurities. The object of the invention is to provide an aluminum alloy strip made of an AlMg alloy which is stable to intergranular corrosion despite high strength and a Mg content of at least 4 wt.%, which object is achieved according to the first teaching of the invention by an aluminum alloy strip having a recrystallized structure, wherein the grain size (KG) of the structure expressed in μm and the Mg content (c _ Mg) expressed in wt.% satisfy the following correlation: KG ≧ 22+2 xc _ Mg, wherein the aluminum alloy of the aluminum alloy strip has the following composition (in% by weight): si is less than or equal to 0.2 percent, Fe is less than or equal to 0.35 percent, Cu is more than or equal to 0.04 percent and less than or equal to 0.08 percent, Mn is more than or equal to 0.2 percent and less than or equal to 0.5 percent, Mg is more than or equal to 4.35 percent and less than or equal to 4.8 percent, Cr is less than or equal to 0.1 percent, Zn is less than 0.25 percent, Ti is less than or equal to 0.1 percent, the balance of Al and inevitable impurities which individually account for 0.05 percent at most and account.)

1. Method for manufacturing an aluminium alloy strip consisting of an aluminium alloy of the AA5 xxx-type having, in addition to Al and unavoidable impurities, a Mg content of at least 4 wt. -%, characterized in that the aluminium alloy strip has a recrystallized structure wherein the grain size (KG) of the structure and the Mg content in wt.% (c _ Mg) satisfy the following correlation:

KG≥22+2×c_Mg，

and a grain size of at most 45 μm, wherein the aluminium alloy of the aluminium alloy strip has the following composition in weight-%:

Si≤0.2％,

Fe≤0.35％,

0.04％≤Cu≤0.08％,

0.2％≤Mn≤0.5％,

4.35％≤Mg≤4.8％,

Cr≤0.1％,

Zn≤0.25％,

Ti≤0.1％,

residual Al and unavoidable impurities up to 0.05 wt.% alone and up to 0.15 wt.% in total, the method comprising the following process steps:

-casting a rolled ingot,

-homogenizing the rolled ingot at 480 ℃ to 550 ℃ for at least 0.5 hours,

-hot rolling the rolled ingot at a temperature of 280 ℃ to 500 ℃,

-cold rolling the aluminium alloy strip to a final gauge at a reduction ratio of less than 40%,

-soft annealing the completed cold rolled aluminium alloy strip at 300 ℃ to 500 ℃.

2. The method of claim 1, wherein the aluminum alloy strip is cold rolled to a final gauge at a maximum roll rate of 30%.

3. The method of claim 1, wherein the aluminum alloy strip is cold rolled to a final gauge at a maximum roll rate of 25%.

4. The method according to claim 1, wherein the following process steps are optionally carried out after hot rolling:

-cold rolling the hot rolled aluminium alloy strip at a minimum rolling reduction of 30%,

-intermediate annealing the aluminium alloy strip at 300 ℃ to 500 ℃,

-subsequent cold rolling to a final gauge at a reduction of less than 40%,

softening annealing the rolled aluminium alloy strip at 300 ℃ to 500 ℃.

5. The method of claim 4, wherein the hot rolled aluminum alloy strip is cold rolled at a minimum of 50% roll rate.

6. The method of claim 4, wherein the aluminum alloy strip is cold rolled to a final gauge at a maximum roll rate of 30%.

7. The method of claim 4, wherein the aluminum alloy strip is cold rolled to a final gauge at a maximum roll rate of 25%.

8. The method according to any one of claims 1 to 7, characterized in that the intermediate annealing and/or the softening annealing is carried out in a box furnace or a continuous furnace.

Technical Field

The invention relates to an aluminium alloy strip consisting of an aluminium alloy of the AA5xxx type, which has a Mg content of at least 4 wt.% in addition to Al and unavoidable impurities. In addition, the invention relates to a method for producing the aluminum alloy strip according to the invention and to a component produced from the aluminum alloy strip according to the invention.

Background

Aluminum magnesium (AlMg-) alloys of the AA5xxx type are used in the form of plates, sheets or strips for the construction of welded or scarf structures in the manufacture of ships, automobiles and aircraft. Such alloys are particularly characterized by high strength, which increases with increasing magnesium content.

For example, an aluminum alloy strip composed of an AA5182 alloy having a Mg content of 4.65 wt.% suitable for use in automotive construction is known in a paper by Zhao et al entitled "Development of double strip casting of aluminum alloys of the AA5xxx series aluminum alloys for automotive sheet".

Aluminum alloy strips of the AA5182 type with a Mg content of at least 4% by weight are likewise known from Kang et al in a paper entitled "Semi-Solid Processing of Alloys and Composites" and a Comparison of the recrystallization textures of cold-rolled DC and CC AA5182 aluminum Alloys "published by Liu et al in a paper entitled" Complex-Solid Processing of Alloys and Composites "and from US 2003/0150587A 1. An article published by Lin et al entitled "Hot Tear sensitivity and Grain refinement Effect of aluminum wrought alloys" ("Hot-Tear durability of aluminum Wroughcast alloys and the Effect of gain Refining") relates to round bars composed of AA5182 alloys.

DE 10231437 a1 relates to corrosion-resistant aluminum alloy sheets, wherein a sufficiently strong resistance to intergranular corrosion is achieved by adding a Zn content of more than 0.4 wt.%.

In addition, GB 2027621 a discloses a method of manufacturing aluminium alloy strip.

AlMg alloys of the AA5xxx type have a Mg content of greater than 3%, particularly greater than 4%, and have a tendency to continue to increase intergranular corrosion when exposed to elevated temperatures. beta-Al at a temperature of 70 ℃ to 200 DEG C₅Mg₃The phase is precipitated along the grain boundary, the beta-Al₅Mg₃The phases are called beta-particles and can be selectively dissolved in the presence of corrosive media. This has the consequence that, if the presence of corrosive media is taken into account, for example water in the form of moisture, in particular aluminium alloys of the AA55182 type (al4.5% mg0.4% Mn) having very good strength properties and very good deformability cannot be used in the heat-loaded region. This is particularly the case for automotive components, which are usually painted cathodically (KTL) and subsequently dried in a calcination process, since sensitization to intergranular corrosion can already be caused on conventional aluminum alloy belts by the calcination process. In addition, applications in the automotive field take into account deformations during the production of the component and the subsequent operating load of the component.

Susceptibility to intergranular corrosion is typically measured by a standard test according to ASTM G67, in which a sample is exposed to nitric acid and the weight loss due to beta-particle dissolution is measured. According to ASTM G67, the weight loss of the raw material which is not resistant to intergranular corrosion is greater than 15mg/cm²。

Therefore, the corresponding raw materials and aluminum alloy belts are not suitable for use in the heat load zone.

Disclosure of Invention

Starting from this, the object of the invention is to provide an aluminum alloy strip made of an AlMg alloy which, despite high strength and a Mg content of more than 4 wt.%, is resistant to intergranular corrosion, in particular after deformation and subsequent application of heat. In addition to this, a method of manufacturing is presented by which aluminium alloy strips resistant to intergranular corrosion can be manufactured. Finally, a class of intergranular corrosion resistant automotive components consisting of aluminium alloys of the AA5xxx type, such as bodywork components or bodywork fittings like doors, hoods and tailgates or other structural parts, has also been proposed.

According to a first teaching of the present invention, the above object is achieved by an aluminium alloy strip having a recrystallized structure wherein the grain size (KG) of the structure expressed in μm and the Mg content (c _ Mg) expressed in weight% satisfy the following correlation:

KG≥22+2×c_Mg。

wherein the aluminium alloy of the aluminium alloy strip has the following composition (in weight%):

Si≤0.2％,

Fe≤0.35％,

0.04％≤Cu≤0.08％,

0.2％≤Mn≤0.5％,

4.35％≤Mg≤4.8％,

Cr≤0.1％,

Zn≤0.25％,

Ti≤0.1％,

the residual Al and unavoidable impurities are individually at most 0.05% by weight and in total at most 0.15% by weight.

When the Cu content reaches 0.04 wt% to 0.08 wt%, the strength of the copper is also improved, but the intergranular corrosion resistance is not greatly reduced. In addition, by limiting the Mg range to between 4.35 wt% and 4.8 wt%, very good strength can be achieved at the appropriate grain size. Since the grain size necessary for the microstructure is always achievable in this method, the intergranular corrosion resistance can be achieved particularly reliably.

Aluminum alloy strips with a recrystallized structure can be produced by hot-rolling the strip or by soft-annealing the cold-rolled strip. Through extensive research, the crystal grain size, the magnesium content and the resistanceThere is a correlation between intergranular corrosivity. Since the grain size of the material is always present in distributed form, all the mentioned data of the grain size relate to the average grain size. The average grain size may be determined according to ASTM E1382. When the grain size is sufficiently large, that is, as long as the grain size is greater than or equal to the lower limit value of the grain size relative to the Mg content of the aluminum alloy strip according to the present invention, intergranular corrosion resistance can be achieved, whereby the weight loss is reduced to 15Mg/cm in the ASTM G67 test²The following. Thus, the corresponding aluminum alloy strip may be referred to as intergranular corrosion resistant. This has been demonstrated for the aluminium alloy strip in the undeformed state described above after a simulated cathodic dip coating cycle (KTL-Zyklus) or after a simulated cathodic dip coating cycle and including a subsequent work load of up to 500 hours at 80 ℃. The intergranular corrosion resistance of the above-described aluminium alloy strip was also demonstrated when the material was extended by 15% before the cathodic dip cycle and the working load in order to simulate deformation into a component. Thus, the aluminum alloy strip according to the invention provides higher strength and yield strength while also being resistant to intergranular corrosion due to its relatively high Mg content. In this way, the aluminum alloy strip can be used very well in the heat load region of automobile construction.

According to a further embodiment of the aluminium alloy strip according to the invention, the following condition is additionally fulfilled if the grain size:

KG＜(253/(265-50×c_Mg))²，

wherein KG units are μm and c _ Mg units are weight%,

it can be ensured that the yield limit R of the aluminium alloy strip is_p0.2Greater than 110MPa, where the tensile strength of the strip is generally above 255 MPa.

A further advantageous embodiment of the aluminum alloy strip is achieved in that the aluminum alloy of the aluminum alloy strip has the following composition in wt.%:

Si≤0.2％,

Fe≤0.35％,

0.04％≤Cu≤0.08％,

0.2％≤Mn≤0.5％,

4.45％≤Mg≤4.8％,

Cr≤0.1％,

Zn≤0.25％,

Ti≤0.1％,

the remainder being at most 0.05% by weight, Al alone, and at most 0.15% by weight in total, of unavoidable impurities. By limiting the Mg range to between 4.45 wt% and 4.8 wt%, very good strength can also be achieved at the appropriate grain size.

According to a further embodiment of the aluminium alloy strip according to the invention the grain size is at most 50 μm, since the process reliability is reduced when producing aluminium alloy strips with a grain size of more than 50 μm in aluminium alloys of the AA5xxx type with a minimum Mg content of 4 wt.%. In contrast, a grain size of at most 50 μm achieves process stability. As the grain size decreases, the process stability of the texture structure for forming a controlled grain size increases. Thus, the production of aluminium alloy strip with a grain size of at most 45 μm, preferably at most 40 μm, is associated with an improved process stability.

According to a further embodiment of the aluminium alloy strip according to the invention, the aluminium alloy strip has a thickness of 0.5mm to 5mm and is therefore particularly suitable for most applications, such as automotive construction.

In addition to this, the aluminium alloy strip according to the invention can advantageously be designed by cold rolling and subsequent soft annealing of the aluminium alloy strip. The softening annealing of the recrystallization is generally carried out at temperatures of 300-500 ℃ and this achieves the removal of the hardening produced during rolling and ensures good deformability of the aluminium alloy strip. In addition to this, cold rolled, soft annealed and thereby recrystallized aluminium alloy strip can provide a thinner final thickness than recrystallized hot rolled strip.

Finally, an aluminium alloy strip according to another design has a yield limit R of more than 120MPa_p0.2And a tensile strength R of more than 260MPa_m. The intergranular corrosion-resistant aluminum alloy strip according to the invention therefore also exceeds the strength properties required according to DIN485-2 for aluminum alloys of the AA5182 type. Here, a minimum uniform elongation A of 19%_gAnd a minimum elongation at break A of 22%_80mmAnd also far exceed the values required in DIN 485-2.

According to a second teaching of the present invention, the above object is achieved by a method for manufacturing an aluminium alloy strip comprising the process steps of:

casting a rolled ingot consisting of the composition of the aluminium alloy according to the invention,

-homogenizing the rolled ingot at 480 ℃ to 550 ℃ for at least 0.5 hours,

-hot rolling the rolled ingot at a temperature of 280 ℃ to 500 ℃,

-cold rolling the aluminium alloy strip to a final gauge at a reduction of less than 40%, preferably at a reduction of at most 30%, particularly preferably at a reduction of at most 25%,

softening annealing the rolled aluminium alloy strip at 300 ℃ to 500 ℃.

In summary, these enumerated process steps result in a grain size that can be formed after the softening anneal that satisfies the above-described correlation with Mg content, due to the low rolling rate during cold rolling of the aluminum alloy strip to final gauge. Before the softening annealing, the hardening of the aluminum alloy, which determines the grain size obtained, is adjusted by the rolling rate to the final thickness. By gradually reducing the rolling rate to less than 40% over a maximum of 30% and a maximum of 20%, different grain sizes can be adjusted which are adapted to the composition of the alloy. In this regard, aluminum alloy belts can be made that are resistant to intergranular corrosion.

According to a further embodiment of the method according to the invention, the following process steps are optionally carried out after hot rolling:

-cold rolling the hot rolled aluminium alloy strip at a minimum roll rate of 30%, preferably at a minimum roll rate of 50%,

-intermediate annealing the aluminium alloy strip at 300 ℃ to 500 ℃,

subsequent cold rolling to a final thickness at a reduction of less than 40%, preferably at a reduction of at most 30%, particularly preferably at most 25%,

softening annealing the rolled aluminium alloy strip at 300 ℃ to 500 ℃.

The common feature of the two methods listed above is that the rolling rate before the softening annealing, i.e. the rolling rate of the final thickness in the cold rolling, is limited to less than 40%, preferably to a maximum of 30%, particularly preferably to a maximum of 25%. In a second embodiment of the method according to the invention, an additional cold rolling step is carried out after the intermediate annealing at 300 ℃ to 500 ℃. During the intermediate annealing, the aluminum alloy strip that has been significantly hardened by cold rolling recrystallizes and once again transforms into a state that cannot be deformed. Subsequently, the cold rolling step at a rolling rate of less than 40%, preferably at a maximum of 30%, particularly preferably at a maximum of 25%, results in that the grain size, which is related to the Mg content of the aluminium alloy used, can be adjusted to the desired proportional relationship. Consequently, a strip having both intergranular corrosion resistance and the necessary deformation or strength properties can be produced subsequently in the soft-annealed state.

According to a further embodiment of the method according to the invention, the intermediate annealing and/or the softening annealing are carried out in a batch furnace, in particular in a box furnace or a continuous furnace. Both furnaces can lead to the formation of a sufficiently coarse grain structure ensuring resistance to intergranular corrosion. Neither batch furnaces are expensive to operate nor purchase as continuous furnaces are expensive.

According to a third teaching of the present invention, the above object is achieved by a component for a motor vehicle, which component is at least partially composed of an aluminum alloy strip according to the present invention. The component is usually painted, preferably cathodic dip-painted. Nevertheless, it is possible to use components made of the aluminum alloys according to the invention which are not painted.

As mentioned above, the aluminium alloy strip has outstanding strength, deformability and resistance to intergranular corrosion, so that, in particular during the heat treatment during painting, a calcination at approximately 185 ℃ for typically 20min has only a small effect on the resistance of the component to intergranular corrosion. The deformation of the component simulated by an elongation of 15% transverse to the initial rolling direction also had only a slight effect on the intergranular corrosion resistance of the component. Even after 15% elongation, the weight loss according to ASTM G67 is less than 15mg/cm². In addition, the operation in the heat load range, which is simulated by a heat load of 200 or 500 hours at 80 ℃, also has only a slight effect on the intergranular corrosion resistance of the component. Even after a corresponding thermal load, according to ASTM G67The weight loss value is still less than 15mg/cm²。

The component is particularly advantageously provided as a body or a body fitting of a motor vehicle. Typical body parts are parts of fenders or floor assemblies, roofs, etc. In general, doors, tailgate, etc. are referred to as body parts, which are not rigidly connected to the motor vehicle. It is preferable to produce invisible body components or body fittings from the aluminum alloy strip according to the invention. Such invisible body components or body fittings are, for example, door interior parts or interior parts of a tailgate and a floor panel. Typical thermal loads of motor vehicle components, such as door interior parts, for example, are caused by sunlight during operation of the motor vehicle. In addition to this, the body or body fittings of the motor vehicle are often exposed to moisture, for example in the form of spray or condensation water, so that the components must be resistant to intergranular corrosion. The vehicle body or vehicle body part according to the invention, which is produced from the aluminium alloy strip according to the invention, satisfies these conditions, and in addition ensures a weight advantage over the steel structures currently used.

Drawings

The invention is further explained below with the aid of a number of embodiments in conjunction with the drawing. In the drawings, there is shown in the drawings,

figure 1 shows an embodiment of a manufacturing method in a flow diagram,

fig. 2 shows the dependence of the grain size of the examples on the magnesium content in a graph, and,

fig. 3 shows a component of a motor vehicle according to a further exemplary embodiment.

Detailed Description

It was investigated with the aid of extensive tests whether there is a correlation between the grain size of an aluminium alloy strip consisting of an aluminium alloy of the AA5xxx type and the Mg content in relation to the resistance to intergranular corrosion. For this purpose, different aluminum alloys and different process parameters are used. Table 1 shows the different alloy composition components with which the relationship between grain size, intergranular corrosion resistance and yield strength was investigated. The aluminium alloys mentioned in table 1 contain, in addition to the alloying elements (given in weight%), Si, Fe, Cu, Mn, Mg, Cr, Zn and Ti, the remaining aluminium as well as impurities individually up to 0.05 weight%, in total up to 0.15 weight%.

Since the grain size is influenced by, in particular, the final softening annealing and the final cold rolling rate, the grain size measured in the respective tests varies. For example, the grain size varies from 16 μm to 61 μm, and the final rolling ratio varies from 17% to 57%. The final softening annealing may be performed in a box furnace (KO) or a continuous belt furnace (BDLO).

TABLE 1

FIG. 1 shows a flow of an embodiment for manufacturing aluminum alloy strip. The flow chart of figure 1 schematically shows the different process steps of the manufacturing process of aluminium alloy strip according to the invention.

In step 1, an aluminium alloy of the AA5xxx type with a Mg content of a minimum of 4 wt.% is cast into a rolled ingot, for example in a DC continuous casting process. Subsequently, the rolled ingot is homogenized in process step 2, which homogenization may be accomplished in one or more stages. The temperature of the rolled ingot is brought to 480 ℃ to 550 ℃ for at least 0.5h while homogenizing. Subsequently, the rolled ingot is hot rolled in process step 3, wherein a typical temperature of between 280 ℃ and 500 ℃ is reached. The final thickness of the hot-rolled strip is, for example, 2 to 12 mm. The final thickness of the hot-rolled strip is selected in such a way that only one cold rolling step 4 is carried out after the hot rolling, wherein the hot-rolled strip reduces its thickness by less than 40%, preferably by a maximum of 30%, particularly preferably by a maximum of 25%.

Subsequently, the aluminum alloy strip which has been cold rolled to a final thickness is subjected to a softening annealing. To test the correlation of box-type or continuous belt furnaces with corrosion performance, softening annealing was performed in the continuous belt furnace or the box furnace. In the example shown in table 1, the second approach uses an intermediate anneal. For this purpose, the hot strip is subjected to a cold rolling 4a after the hot rolling according to process step 3, which cold rolling has a cold reduction of more than 30% or more than 50%, so that the aluminum alloy strip is preferably completely recrystallized in a subsequent intermediate annealing. In these embodiments, the intermediate anneal may be accomplished in a continuous belt furnace at 400 ℃ to 450 ℃ or in a box furnace at 330 ℃ to 380 ℃.

This intermediate anneal is shown in fig. 1 as process step 4 b. In process step 4c according to fig. 1, the finally interannealed aluminum alloy strip is cold rolled to a final thickness, wherein the rolling reduction in process step 4c is less than 40%, preferably at most 30%, particularly preferably at most 25%. Subsequently, the aluminum alloy strip is once again transformed into a softened state by a softening annealing, wherein the softening annealing can be done in a continuous strip furnace at 400 ℃ to 450 ℃ or in a box furnace at 330 ℃ to 380 ℃. In different tests, different rolling reduction after intermediate annealing was adjusted in addition to different aluminium alloys. The values of the rolling reduction after the intermediate annealing are also shown in table 1. In addition, the grain size of each of the aluminum alloy strips which had been soft-annealed was also measured.

Determination of mechanical characteristic values, in particular yield limits R, on these correspondingly produced aluminum alloy strips_p0.2Tensile strength R_mUniform elongation A_gAnd elongation at break A_80mm. In addition, the intergranular corrosion resistance is determined according to ASTM G67, that is to say without additional heat treatment in the initial state (initial 0 h). In addition, the grain sizes calculated according to formula (1) for resistance to intergranular corrosion and formula (2) for achieving the necessary mechanical properties, in particular a sufficiently high yield limit, in addition to the mechanical characteristic values of the aluminum alloy strip measured according to EN 10002-1 or ISO 6892 are given in Table 2 in columns KG (IK) and KG (R)_p) The columns show. The grain size is measured according to ASTM E1382 and is expressed in μm.

TABLE 2

TABLE 3

In order to simulate the use in motor vehicles, the aluminum alloy strip was additionally subjected to a different heat treatment before the corrosion test. To record the KTL cycle, the first heat treatment preserved the aluminum alloy strip at 185 ℃ for 20 min. In another measurement series, the aluminium alloy strip was additionally stored at 80 ℃ for 200 hours or 500 hours and subsequently subjected to a corrosion test. Since deformation of the aluminium alloy strip or aluminium alloy sheet may also affect the corrosion resistance, aluminium alloy strip which has been extended by about 15% in another test is heat treated or kept at elevated temperature and subsequently tested for intergranular corrosion according to ASTM G67, wherein the loss of weight is determined.

There appears to be a close relationship between grain size, Mg content and intergranular corrosion resistance. Examples 11 to 19 can all be classified as intergranular corrosion resistant. Aluminum alloy belts of this type are also suitable for use in motor vehicles which are subject to thermal stress and in the presence of moisture or corrosive media. In addition, examples 12, 14, 16 and 17 show the mechanical characteristic values required according to DIN EN485-2 for aluminum alloy belts of the AA5182 type.

Fig. 2 shows the dependence of the grain size of the examples on the magnesium content (% by weight) in a graph. In addition to the measurement points, the graph also contains two curves a and B. Line A represents grain size and aluminum alloy belts higher than line A at a particular Mg content may be referred to as intergranular corrosion resistance. The grain size (KG) can be derived from the following equation:

KG＝22+2×c_Mg (1)

where c _ Mg is the Mg content given in weight%.

In contrast, curve B shows the limit value from which the aluminum alloy strip has an excessively low yield limit of less than 110MPa, so that the aluminum alloy strip is no longer considered to be an alloy of the AA5182 type according to DIN EN 485-2. The curve B is determined by the following equation:

KG＝(253/(265-50×c_Mg))² (2)

thus, all the examples to the right of curve B meet the requirement of a yield limit greater than 110 MPa.

Finally, fig. 3 schematically shows a typical motor vehicle component in the form of a door inner part. The door inner 6 is typically made of steel. However, the aluminum alloy strip produced can achieve high strength and intergranular corrosion resistance as long as the proportional relationship between grain size and Mg content is adjusted according to the present invention. The component according to fig. 3 has a significantly lower weight than comparable components made of steel and is nevertheless resistant to intergranular corrosion.