Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 36: Nano structured materials IV

MM 36.3: Talk

Thursday, March 29, 2007, 15:15–15:30, H4

Basic investigations of the precipitation behaviour of AlMgSi alloys — •Ingmar Wieler, Nelia Wanderka, and John Banhart — Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin

AlMgSi alloys are widely used in aerospace applications and in increasing quantity for car body panels. Their beneficial mechanical properties are achieved by precipitation of nanoscaled metastable precursors of Mg₂Si during heat treatment. A room temperature storage after solution heat treatment often results in a slowered and decreased hardening during subsequent artifical aging - the so called negative effect.

Two high purity alloys AlMg0,6Si0,8 and AlMg0,8Si0,6 were produced and subjected to natural as well as artificial aging with and without previous natural aging and a pre-aging step. Certain states have been characterized by hardness and in situ electrical resistivity measurements. Qualitative and quantitative TEM investigations have been made to associate the properties with the microstructural evolution.

The room temperature storage before artificial aging at 180^∘C gave rise to a distinct delay and reduction of the hardness growth especially for the Si-richer alloy. The resistivity of artificial aged samples was increased by the room temperature storage until about peak hardness was reached. The TEM investigations proved a low-density, coarse precipitate structure to be the reason for the negative effect.