The hardness was found to be gradually decreasing through TMAZ
, HAZ and the hardness profile resembles the shape of "W" .
The NZ, TMAZ
, HAZ, and based material (BM) were labelled in Figure 5(a).
Fig 11 shows the different regions of the weld metal namely the nugget zone, TMAZ
, HAZ on both the advancing and retreating sides of the weld metal.
is characterized by grains distorted in comparison to the base material.
Heat input during the process also affects the microstructure of the NZ and TMAZ
. This leads to variation in the tensile strength .
Residual stress were measured at the BM, SZ, advancing side of TMAZ
(TMAZ-AS), and retreating side of TMAZ
(TMAZ-RS) as a function of depth from the surface of the joints.
In the TMAZ
, on the other hand, the stirring slightly occurs and causes the formation and rotation of the grains.
And also it is noted that there is an appreciable variation in grain size in the stir zone region and TMAZ
. Because of the mechanical action from the processed tool, the size of the grains in TMAZ
is coarser than the stir zone region.
The hardness in the HAZ decreases towards the weld center, while the TMAZ
containing elongated grains was slightly strengthened by the intense plastic deformation as compared to the HAZ.
softened region), composed of weld nugget (WN), thermo mechanically affected zone (TMAZ
) and heat affected zone (HAZ) and thus the tensile properties of the FSW joints were lower than those of the base materials.
The microstructure of the thermomechanical affected zone (TMAZ
) was observed to confirm that the region where the hardness temporarily decreased corresponds to TMAZ
In the welding zone ,the plastic deformation in the TMAZ
and due to insufficient strain levels , the recrystallization will not occur .Figs.