The microstructure of the stir zone weld that the weld contains fine structure and includes Mg2Si particles in the
mixture of aluminum matrix dispersion regularly throughout the area. In the stir zone (SZ), the globular and eutectic
phases disappeared. The Mg2Si particles are uniformly dispersed throughout the stir zone. This is due to the friction
between the shoulder and the pin to the base metal being welded. Cracks were observed in the stir zone of WT and
TWT which is influenced by heat treatment. Moreover, the SWA and WA revealed no crack in the stir zone.
The hardness values across the joint of each sample vary depending on the heat treatment. In short, the highest
hardness of the stir zone was from WT (1000) at the value of 95.5 HV and the lowest hardness of the stir zone was
from AW (710) at the value of 48.6 HV.