Hot-and cold-formed aluminum alloy

Abstract

A component or semi-finished piece is made from a hot-form aluminium alloy of the following composition in wt. %: silicon 0.9-1.3, magnesium 0.7-1.2, manganese 0.5-1.0, copper less than 0.1, iron less than 0.5, chromium less than 0.25, titanium less than 0.1, zinc less than 0.2, zirconium and / or hafnium 0.05-0.2 and further unavoidable impurities, whereby the total amount of chromium and manganese and zirconium and / or hafnium is at least 0.4 by weight. The aluminium / silicon mixed crystals are present in addition to magnesium silicide precipitates.

Description

[0001] This is a divisional of U.S. patent Ser. No. 10 / 499,755, filed Jun. 18, 2004, which claims priority to German Patent Application No. 101 63 039, filed Dec. 21, 2001 through International Patent Application Serial No. PCT / EP02 / 14452, filed Dec. 18, 2002.[0002] The present invention relates to a hot- and cold-workable aluminum alloy and to a method for manufacturing an aluminum component. BACKGROUND [0003] High-strength Cu- (for example, Al Mg Si 1 Cu 0.5) or Zn-containing, heat-treated Al semi-finished products and Al forgings do have high static strength levels, but their elongation at break is low. Therefore, in the case of a notch effect (for example, stone impact), this results in a low dynamic strength. Moreover, these alloys are susceptible to corrosion so that expensive corrosion protection is required to avoid corrosion pits having a notch effect. Since, for example, highly stressed, forged Al suspension components are always exposed to stone impact (notching) and corr...

AI Technical Summary

Benefits of technology

[0007] It is an object of the present invention to provide a component and a method for manufacturing a component whose recrystallization-inhibiting activity is improved over the prior art and which lead to higher strength and corrosion resistance of the components.

[0022] The forming temperatures according to the present invention, which at the same time imply a solution treatment, are higher than the usual forming temperatures, which results in a lower work hardening and thus in less formation of recrystallization nuclei in the grain structure. Thus, recrystallization is effectively suppressed, resulting in higher strength levels and, above all, in a significantly higher elongation at break in highly worked areas.

Problems solved by technology

Therefore, in the case of a notch effect (for example, stone impact), this results in a low dynamic strength.

Moreover, these alloys are susceptible to corrosion so that expensive corrosion protection is required to avoid corrosion pits having a notch effect.

Al Mg Si 1 alloys with higher ductility or lower notch sensitivity, such as EN-AW 6082, are, in fact, corrosion-resistant because of their low Cu- and Zn-content; however, these alloys do not reach adequate strength levels.

Another disadvantage of such alloys is that during forming and subsequent heat treatment, highly worked zones of forgings and semi-finished products recrystallize, forming coarse grains.

A coarse-grained or brittle and less stable grain structure leads to premature failure of the Al component.

Even more problematic is the recrystallization behavior of cold-formed Al semi-finished products that are subsequently heat-treated.

During subsequent heat treatment, the grain structure is therefore highly susceptible to recrystallization.

Unexamined German Laid-Open Patent Applications DE-OS 2 103 614 and DE OS 2 213 136 each describe an aluminum-silicon-magnesium alloy that reacts in a recrystallization-inhibiting manner; however, these alloys have insufficient strength, and the tendency of this alloy to recrystallize is still too high for cold-formed components or components undergoing multiple forming operations.

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