Two-Step Aging Behaviors of Al-Mg-Si Alloy Extrusions
Hidenori Hatta, Shinichi Matsuda and Hideo Yoshida, Sumitomo Light Metal Industries, Ltd., Aichi, Japan
Track: EXTRUSION/DIE, PRACTICAL - Quench and Temper
ABSTRACT --- The two-step aging behaviors of various Al-Mg-Si alloy extrusions have been
mainly studied by tensile testing, Differential Scanning Calorimetry (DSC) analysis, and
electrical resistance measurements. Natural aging produces a beneficial effect on alloy extrusion
strength after artificial aging of low magnesium- and silicon-containing alloys, regardless of the
natural aging temperature. There are only a cluster and β' exothermic peaks on the DSC curve.
On the other hand, natural aging at low temperature has a negative effect on alloy extrusion
strength after artificial aging of high magnesium and silicon containing alloys, especially the
lower natural aging temperature. For these alloys the cluster, the β" and β' exothermic peaks,
were present on the DSC curves. These results suggest that the precipitation behavior of the β"
phase during artificial aging is related to the negative effect of natural aging. The final strengths
of the alloy extrusions are affected by natural aging conditions. It is important to control the
natural aging time and temperature, in order for the aluminum-magnesium-silicon (Al-Mg-Si)
alloy extrusions to obtain a homogeneous strength.
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