**2.1.3 Thermo-mechanically affected zone**

In FSW a Thermo-Mechanically Affected Zone (TMAZ) is formed between the parent metal and the nugget zone, as shown in Figure 10b. The TMAZ experiences both temperature and deformation during welding process. The TMAZ is characterized by a highly deformed structure. Although the TMAZ underwent plastic deformation, recrystallization does not occur in this zone due to insufficient deformation strain. However, dissolution of some precipitates is observed, due to the high-temperature. The extent of dissolution depends on the thermal cycle experienced by TMAZ.
