EP3196324B1 - Curable aluminium alloy on an al-mg-si-basis - Google Patents

Description

The invention relates to a hardenable aluminum alloy based on Al-Mg-Si.

In order to improve the thermosetting ability of a room-temperature cold-cured A6061 Al-Mg-Si based aluminum alloy, U.S. Pat WO2013 / 124472A1 to add to the solid solution of the aluminum alloy a vacancy active trace element, namely tin (Sn) and / or indium (In).

Comparable alloys of the type 6xxx are moreover from the WO 2015/034024 A1 known.

In addition, it is known ("Statistical and thermodynamic optimization of trace-element modified Al-Mg-Si-Cu Alloys", Stefan Pogatscher et al.) That certain main and minor alloying elements of the A6061 aluminum alloy solubility of tin or indium in of the aluminum alloy, which negatively affects the storage stability at room temperature of the 6xxx aluminum alloys. For example, an increased content of Mg, Si, Cu or Zn in the 6xxx aluminum alloy is believed to reduce solubility, whereas an increased content of Fe, Ti and Mn increases solubility. In addition, interaction effects, for example, between Si and Mg and / or between Cu and Mg, also play an important role in the solubility of Sn in the aluminum alloy.

However, the main and minor alloying elements can not be arbitrarily varied in their content in the aluminum alloy, because in addition to a desirable high age hardening ability other mechanical and / or chemical requirements - such as formability, strength, ductility and / or corrosion resistance - are met. This requires, for example, high concentrations of main alloying elements in the aluminum alloy in order to form certain hot excretions.

In the setting of the composition of an aluminum alloy based on Al-Mg-Si, countercurrent proportions are usually required in the case of the main and minor alloying elements - on the one hand, those proportions which are beneficial for the solubility of Sn in the aluminum alloy, ensuring a high storage stability Room temperature to allow, and on the other hand those proportions that provide high mechanical and / or chemical characteristics or properties of the aluminum alloy, but usually have a negative effect on the solubility of Sn.

It is therefore an object of the invention to modify a curable aluminum alloy based on Al-Mg-Si with Sn as a trace element in the composition such that a high mechanical and chemical properties of the aluminum alloy are combined after hot curing with a high storage stability at room temperature can. In addition, the aluminum alloy should be particularly suitable for the use of secondary aluminum.

The invention achieves the stated object in that the aluminum alloy contains from 0.6 to 1% by weight of magnesium (Mg), from 0.2 to 0.7% by weight of silicon (Si), from 0.16 to 0, 7 wt .-% iron (Fe), from 0.05 to 0.4 wt .-% copper (Cu), at most 0.15 wt .-% (or from 0 to 0.15 wt .-%) manganese (Mn), at most 0.35 wt .-% (or from 0 to 0.35 wt .-%) chromium (Cr), at most 0.2 wt .-% (or from 0 to 0.2 wt. -%) zirconium (Zr), at most 0.25 wt .-% (or from 0 to 0.25 wt .-%) zinc (Zn), at most 0.15 wt .-% (or from 0 to 0 , 15% by weight) of titanium (Ti), 0.005 to 0.075% by weight of tin (Sn) and / or indium (In) and the remainder being aluminum as well as unavoidable impurities due to production, the ratio of the weight percent of Si / Fe being less than 2 , 5 and the content of Si is in accordance with the equation wt .-% Si = A + [0.3 * (wt .-% Fe)] with the parameter A in the range of 0.17 to 0.4 wt. % certainly.

By the rule of restricting the Si content to 0.2 to 0.7 wt .-% and the Fe content to 0.16 to 0.7 wt .-% and the vote of the Si content with The Fe content can be influenced to a particularly great extent on the storage stability and heat-hardening ability of the Al-Mg-Si-aluminum alloy if this coordination both the ratio of the weight percent of Si / Fe less than 2.5 and the equation wt. % Si = A + [0.3 * (wt% Fe)] satisfies the parameter A in the range of 0.17 to 0.4 wt%.
Such a closely matched in Si and Fe content aluminum alloy, which vote, for example, the hatched area in Fig. 1 can be seen, namely, due to the upper limit of that provision for a sufficient solubility of tin and / or indium in the solid solution of the aluminum alloy, which slows the precipitation behavior during cold curing and thus the storage stability of the aluminum alloy is conducive. In addition, due to the lower limit in the tuning, a sufficient precipitation behavior in the thermosetting is to be expected - whereby high strength values can be achieved in the thermosetting and the aluminum alloy itself can achieve or improve those mechanical and chemical properties of 6xxx aluminum alloy with a higher content of main and Secondary alloy elements are known.
Surprisingly, however, it has been found that, compared with known 6xxx aluminum alloys, comprising Sn to suppress cold hardening, this method can be used to observe a much slower precipitation behavior at room temperature. Although it is known that a comparatively low Si content may be responsible for delayed cold curing, the tuning of the Si content according to the invention, however, leads far beyond these known effects and shows an unusually high storage stability of the aluminum alloys.
According to the invention, therefore, the advantages of a particularly high storage stability at room temperature and good heat-setting ability of the aluminum alloy can be combined.
In addition, this composition of the invention can also be particularly suitable for the use of secondary aluminum for this purpose due to the comparatively high Fe content.

In general, it is mentioned that in the Al-Mg-Si-aluminum alloy, impurities each having a maximum of 0.05 wt% and a total of at most 0.15 wt% may occur. In addition, it is generally mentioned that maximum weight percentages, such as those found with Mn, Cr, Zr, Zn or titanium, for example, can be considered as starting from 0.
For the sake of completeness, it is further mentioned that aluminum or an aluminum alloy, obtained from aluminum scrap, can be understood as the secondary aluminum.

The storage stability and the thermosetting ability of the aluminum alloy can be further improved when the parameter A is in the range of 0.26 to 0.34 wt%. By this rule, namely, the solubility of Sn can be relatively large and Si exercise only a small impact on cold curing. This allows an unexpectedly high stability at room temperature. In addition, it can be shown that this alloy set in this way can attain surprisingly high strength after hot curing, for example by means of heat aging, although this alloy has a comparatively low Si content.

An optimum of storage stability and thermosetting ability may be exhibited when the parameter A is 0.3% by weight.

If the content of Si is determined by the equation wt% Si = A + [0.3 * (wt% Fe)] -% by weight of Ti, the components affecting the solubility of Sn can be further improved on each other be matched. In particular, Ti can form phases with Si, which can have a positive influence on the solubility of Sn. The storage stability of the aluminum alloy is thus further improved.

If the ratio of the weight percent of Si / Fe is less than 2, by increasing the setting of Si by Fe, the content of dissolved Si in the aluminum alloy can be significantly reduced. Thus, the solubility of tin and / or indium in the solid solution of the Al-Mg-Si-aluminum alloy can be improved, which can further increase the storage stability.

A comparatively high solubility of tin and / or indium in the solid solution of the Al-Mg-Si-aluminum alloy can be achieved when the ratio of the weight percent of Si / Mg is in the range of 0.3 to 0.9.

If the aluminum alloy has at least 0.25% by weight of copper (Cu), on the basis of this comparatively high content of Cu, it can compensate for the adverse effects of Mg and Si on the solubility of Sn in the solid solution of Al-Mg-Si Aluminum alloy are intervened.

An excellent storage stability of the aluminum alloy can be achieved if it has in the range of 0.005 to 0.05 wt .-% tin (Sn) in solid solution in the aluminum mixed crystal. In general, it is mentioned that the term "solid solution" may denote a state in which an alloying element is distributed in a solid matrix.

Preferably, the aluminum alloy belongs to the 6xxx series. Preferably, the aluminum alloy is an EN AW-6061 aluminum alloy.

If the aluminum alloy has at most 0.05% by weight of chromium (Cr) and more than 0.05% by weight of zirconium (Zr), the quenching sensitivity for Sn can be reduced and Sn can be kept in solid solution in the mixed aluminum crystal even at comparatively low quenching rates become. In addition, it is thus possible, even with heavy plates, to achieve optimum storage stability and heat-hardening capability.

The aluminum alloy may have at least 0.02 wt% chromium (Cr) to eventually improve the corrosion performance.

To demonstrate the effects achieved, thin sheets of various aluminum alloys based on Al-Mg-Si (6xxx series) were produced. The compositions of the alloys studied are listed in Table 1. Table 1: Overview of the investigated alloys in% by weight alloys sn mg Si Cu Fe Mn Cr Zn Ti 1 0.04 0.8 0.64 0.22 0.47 0.11 0.16 0.05 0.05 2 0.04 0.78 0.43 0.36 0.46 0.11 0.14 0.05 0.06

The aluminum alloy 1 of Table 1 essentially corresponds to a standard alloy AA6061 after addition of the trace element Sn, it being conceivable instead of tin to use indium or a combination of Sn and In. Alloy 2 represents the composition according to the invention of the 6xxx series and is relatively recycling-friendly due to the comparatively high Fe content.
The aluminum alloy 1 is well outside the inventively tuned Si / Fe content, this is for example in the Fig. 1 can be seen. The aluminum alloy 2 is placed substantially centrally in this tuned Si / Fe content.

Both aluminum alloys 1 and 2 were solution-annealed in solid solution, quenched, and cold-cured by aging at room temperature and then thermoset. Solution heat treatment was carried out at a temperature greater than 530 degrees Celsius - quenching at a quench rate greater than 20 degrees Celsius / second. Both alloys 1 and 2 were subjected to a storage time or cold curing of 180 days [d] and a 30-minute thermosetting at different temperatures. Brinell hardness [HBW] was determined during cold aging and after hot aging.

In terms of storage stability is after Fig. 2 to recognize that the Alloy 1 already after 14 days of a comparatively strong rising cold curing under storage at room temperature - which over a longer storage time disadvantageously leads to comparatively high and increasing Brinellhärte and adversely affects forming before hot curing.
In contrast, in the case of alloy 2, initial cold hardening does not become apparent until after about 180 days, as a result of which alloy 2 according to the invention is considered to be particularly stable in storage. Such a surprisingly high storage stability has not yet been observed with any 6xxx alloy. This leads to an unexpected, enormous gain in the manipulation time of the alloy after quenching in the soft state.

In the subsequent hot curing is in comparison of the two alloys after Fig. 3 to recognize that the alloy 2 lags at lower Auslagerungstemperaturen in the Brinellhärte first alloy 1. At higher aging temperatures, the Brinell hardness of the alloy 1 can be significantly exceeded.

Claims (10)

1. A hardenable AI-Mg-Si-based aluminum alloy, comprising
   from 0.6 to 1% by weight of magnesium (Mg),
   from 0.2 to 0.7% by weight of silicon (Si),
   from 0.16 to 0.7% by weight of iron (Fe),
   from 0.05 to 0.4% by weight of copper (Cu),
   a maximum of 0.15% by weight of manganese (Mn),
   a maximum of 0.35% by weight of chromium (Cr),
   a maximum of 0.2% by weight of zirconium (Zr),
   a maximum of 0.25% by weight of zinc (Zn),
   a maximum of 0.15% by weight of titanium (Ti),
   0.005 to 0.075% by weight of tin (Sn) and/or indium (In),
   and the aluminum as the remainder as well as production-related unavoidable impurities, wherein
   the ratio of the weight percentages of Si/Fe is less than 2.5
   and the content of Si is determined according to the equation $$\mathrm{wt}.\%\mathrm{Si}=\mathrm{A}+\left[0.3*\left(\mathrm{wt}.\%\mathrm{Fe}\right)\right],$$

   

   with the parameter A being in the range of 0.17 to 0.4% by weight.
2. Aluminum alloy according to claim 1, characterized in that the parameter A is in the range of 0.26 to 0.34% by weight.
3. Aluminum alloy according to claim 1 or 2, characterized in that the parameter A is 0.3% by weight.
4. Aluminum alloy according to claim 1, 2 or 3, characterized in that the content of Si is determined according to the equation $$\mathrm{wt}.\%\mathrm{Si}=\mathrm{A}+\left[0.3*\left(\mathrm{wt}.\%\mathrm{Fe}\right)\right]-\mathrm{wt}.\%\mathrm{Ti}.$$

   
5. Aluminum alloy according to one of claims 1 to 4, characterized in that the ratio of the weight percent of Si/Fe is less than 2.
6. Aluminum alloy according to one of claims 1 to 5, characterized in that the ratio of the weight percentages of Si/Mg is in the range of 0.3 to 0.9.
7. Aluminum alloy according to one of claims 1 to 6, characterized in that the aluminum alloy has at least 0.25% by weight of copper (Cu).
8. Aluminum alloy according to one of claims 1 to 7, characterized in that the aluminum alloy comprises tin (Sn) in the range of 0.005 to 0.05% by weight in solid solution in the aluminum mixed crystal.
9. Aluminum alloy according to one of claims 1 to 8, characterized in that the aluminum alloy has a maximum of 0.05% by weight of chromium (Cr) and more than 0.05% by weight of zirconium (Zr).
10. Aluminum alloy according to one of claims 1 to 9, characterized in that the aluminum alloy has at least 0.02% by weight of chromium (Cr).

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