J. Österreicher, M. Kumar, A. Schiffl, S. Schwarz, G. Bourret:
"Secondary precipitation during homogenization of Al-Mg-Si alloys: Influence on high temperature flow stress";
Materials Science and Engineering A, 687 (2017), S. 175 - 180.

Kurzfassung englisch:
In the automotive industry Al-Mg-Si alloys are often chosen for high strength extruded profiles. However, the
production of such profiles can be challenging for high alloy contents. Among several processing steps, the
homogenization heat treatment before extrusion is readily accessible to modifications to improve high
temperature formability. In this work, the influence of five different homogenization variants on the flow stress
of AA6082 at elevated temperatures was assessed by compression testing in a deformation dilatometer at
450 °C, 480 °C, and 510 °C. The observed differences in flow stress were interpreted with regards to the
microstructure. Samples from billets homogenized at higher soak temperatures exhibited lower hot flow stresses
in subsequent dilatometer testing, indicating better processability. Since the decrease in flow stress is
approximately constant at all test temperatures, it is suggested that it is due to a lower number density of
relatively temperature-stable α-Al(Mn,Fe)Si dispersoids formed during homogenization at higher temperatures;
these dispersoids are stable at all three test temperatures. In contrast, the influence of a cooling rate variation
was relatively minor and diminishes at higher test temperatures since Mg-Si precipitates - whose size and
number density is affected by changes of the cooling rate - are less stable at the higher test temperatures.

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