The influence of multi-pass friction stir processing on the microstructural and mechanical properties of Aluminum Alloy 6082.
El-Danaf, Magdy M. El-Rayes, Ehab A. . 2012
Samples with one through three passes with 100% overlap were created using friction stir processing
(FSP) in order to locally modify the microstructural and mechanical properties of 6082-T6 Aluminum
Alloy. A constant rotational speed and three different traverse speeds were used for processing. In this
article, the microstructural properties in terms of grain structure and second phase particles distribution,
and also the mechanical properties in terms of hardness and tensile strength of the processed zone were
addressed with respect to the number of passes and traverse speeds. The parameter combination which
resulted in highest ultimate tensile strength was further compared with additional two rotation speeds.
FSP caused dynamic recrystallization of the stir zone leading to equiaxed grains with high angle grain
boundaries which increased with increasing the number of passes. The accumulated heat accompanying
multiple passes resulted in increase in the grain size, dissolution of precipitates and fragmentation of
second phase particles. Increasing the traverse speed on the other hand did not affect the grain size, yet
reduced the particles size as well as increased the particle area fraction. Hardness and tensile test results
of the stir zone were in good agreement where increasing the number of passes caused softening and
reduction of the ultimate tensile strength, whereas, increasing the traverse speed increased the strength
and hardness. Increasing the tool rotational speed did not have a significant influence on particle mean
diameter, ultimate tensile strength and hardness values of the stir zone, whereas, it caused an increase
in mean grain size as well as particle area fraction.
